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Forests, Volume 9, Issue 12 (December 2018)

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Cover Story (view full-size image) The provision of enhanced operational intelligence arising from in-forest forecasts of end-product [...] Read more.
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Open AccessArticle Different Nitrate and Ammonium Ratios Affect Growth and Physiological Characteristics of Camellia oleifera Abel. Seedlings
Forests 2018, 9(12), 784; https://doi.org/10.3390/f9120784
Received: 31 October 2018 / Revised: 5 December 2018 / Accepted: 17 December 2018 / Published: 19 December 2018
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Abstract
Camellia oleifera Abel., is an important woody plant, and its fruit contains high-quality edible oil. Production of C. oleifera has significantly expanded over the last 20 years in China. Due to the lack of appropriate information on nutrient management, its production has encountered [...] Read more.
Camellia oleifera Abel., is an important woody plant, and its fruit contains high-quality edible oil. Production of C. oleifera has significantly expanded over the last 20 years in China. Due to the lack of appropriate information on nutrient management, its production has encountered low yield and low oil quality problems. As nitrogen (N) is an essential nutrient and the most abundant in C. oleifera tissues, the present study investigated effects of different ratios of nitrate (NO3) and ammonium (NH4+) on the growth of a cultivar Xianglin 27 at the seedling stage. Uniform seedlings were grown in a soil-based substrate in containers and fertigated with solutions composed of six ratios of NO3 and NH4+, respectively for five months. Results showed that C. oleifera prefers both NO3 and NH4+ at a ratio of 1:1. Seedlings receiving this solution had the highest total N in leaves and total dry weight; elevated chrolophyll, soluble saccharide and protein contents as well as higher activities of peroxidase (POD), superoxide dismutase (SOD), nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT). Our study shows for the first time that N supply for producing C. oleifera should be an equal ratio of NO3 and NH4+. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Morphological Characteristics and Allometric Relationships of Shoot in Two Undergrowth Plants: Polygonatum odoratum and Polygonatum multiflorum
Forests 2018, 9(12), 783; https://doi.org/10.3390/f9120783
Received: 16 November 2018 / Revised: 14 December 2018 / Accepted: 17 December 2018 / Published: 19 December 2018
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Abstract
The main purpose of this investigation was to describe the spatial arrangement of shoot tissues, as seen in transverse section, and allometric relationships in two contrasting species of Polygonatum i.e., Polygonatum odoratum which commonly grows in mixed pine-oak forest with shoots rectangular in [...] Read more.
The main purpose of this investigation was to describe the spatial arrangement of shoot tissues, as seen in transverse section, and allometric relationships in two contrasting species of Polygonatum i.e., Polygonatum odoratum which commonly grows in mixed pine-oak forest with shoots rectangular in shape, and Polygonatum multiflorum found in oak-hornbeam forest with cylindrical shoots. The mass and length of the aerial shoots of each individual plant were measured. The shoot regions of each plant were then categorized as basal (b), central (c) or apical (a). Transverse sections of these shoot regions were subsequently cut, and the following parameters were measured: (1) Diameter of shoots, (2) thickness of the outer and inner zones of parenchyma and (3) thickness of the sclerenchyma zone. Additional allometric relationships between the various measurements were computed and determined as Pearson’s correlation coefficients (r). Both species of Polygonatum differed significantly with respect to the length, diameter and thickness of the outer zone of parenchyma. Shoots of P. multiflorum were taller but narrower than those of P. odoratum, which had a significantly wider zone of outer parenchyma. Allometric relationships were stronger for P. multiflorum, and for both species, they were generally stronger in the basal part of the shoot. We conclude that in P. multiflorum, the strong correlation between the diameter and length of the shoot seems to be important to the growth in shaded environments. Full article
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Open AccessArticle Calcium and Potassium Imbalance Favours Leaf Blight and Defoliation Caused by Calonectria pteridis in Eucalyptus Plants
Forests 2018, 9(12), 782; https://doi.org/10.3390/f9120782
Received: 26 October 2018 / Revised: 30 November 2018 / Accepted: 13 December 2018 / Published: 18 December 2018
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Abstract
The supply of nutrients in balanced proportions leads to greater crop yields and represents an alternative practice for the management of plant diseases. Accordingly, we investigated the effect of the doses of and the nutritional balance between calcium (Ca) and potassium (K) on [...] Read more.
The supply of nutrients in balanced proportions leads to greater crop yields and represents an alternative practice for the management of plant diseases. Accordingly, we investigated the effect of the doses of and the nutritional balance between calcium (Ca) and potassium (K) on the severity of leaf spot and defoliation caused by the fungus Calonectria pteridis. Moreover, the effect of the treatments on the growth of interspecific hybrid eucalyptus clone seedlings (Eucalyptus grandis Hill ex Maiden × E. urophylla S.T. Blake), which are highly susceptible to the disease, was evaluated. The 25 treatments comprised combinations of one of five doses of Ca (1.2, 3.0, 6.0, 9.0 and 12.0 mmol L−1) with one of five doses of K (0.8, 2.0, 4.0, 8.0 and 12.0 mmol L−1) and five replicates of each treatment were included in the study. The supply of high concentrations of K favoured C. pteridis infection and resulted in high disease severity, although defoliation was not observed. However, the supply of both nutrients in excess (12.0 mmol L−1 Ca × 9.0 mmol L−1 K) resulted in a higher disease severity and an increased defoliation percentage (82 and 64%, respectively). Defoliation not associated with Calonectria leaf blight disease was observed with the imbalanced treatments, that is, the treatments combining a low concentration of one nutrient and an excess concentration of the other nutrient. The supply of K at a level near the standard dose (6 mmol L−1) and of Ca at a dose above 4 mmol L−1 (standard dose) ensured high mean values for the morphological variables root and shoot biomass, plant height and chlorophyll a and b contents. These treatments also resulted in low disease severity and defoliation percentages, indicating that a balanced supply of Ca and K ensures reductions in disease severity and defoliation and contributes to higher growth. Full article
(This article belongs to the Special Issue Impacts, Monitoring and Management of Forest Pests and Diseases)
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Open AccessArticle Assessing the Trade-Offs of SPOT7 Imagery for Monitoring Natural Forest Canopy Intactness
Forests 2018, 9(12), 781; https://doi.org/10.3390/f9120781
Received: 30 October 2018 / Revised: 5 December 2018 / Accepted: 7 December 2018 / Published: 18 December 2018
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Abstract
Natural and human-induced disturbances influence the biodiversity and functionality of forest ecosystems. Regular, repeated assessments of canopy intactness are essential to map site-specific forest disturbance and recovery patterns, an essential requirement for forest monitoring and management. However, accessibility to images required for this [...] Read more.
Natural and human-induced disturbances influence the biodiversity and functionality of forest ecosystems. Regular, repeated assessments of canopy intactness are essential to map site-specific forest disturbance and recovery patterns, an essential requirement for forest monitoring and management. However, accessibility to images required for this practice, uncertainty around the levels of accuracy achieved with images of different resolution, and the affordability of the practice challenges its application in many developing regions. This study aimed to compare the accuracy of forest gap detection (in subtropical forests) achieved with lower-resolution (SPOT7 5 m) and higher-resolution (SPOT7 1.5 m) pan-sharpened imagery. Additionally, the Normalised Difference Vegetation Index (NDVI) and Synthetic Aperture Radar (SAR) were compared in terms of their ability to increase the accuracy of this detection when used in conjunction with both high and low resolution imagery. Results indicate that the SPOT7 1.5 m imagery produced an overall accuracy of 77.78% and a ϰ coefficient of 0.66 compared with the 69.44% accuracy and the 0.59 ϰ coefficient achieved with the SPOT7 5 m imagery. Computing image texture analysis within the Random Forest classifier (RF) framework increased classification accuracies to 75.00% for the SPOT 5 m and 86.11% for the SPOT7 1.5 m imagery, validating the usefulness of texture analysis. Variable importance was used to identify wavebands and texture-derived variables that were the most effective in discriminating canopy gaps from intact canopy. In this regard, near infrared, NDVI, SAR, contrast, mean, entropy and second moment were the most important. Collectively the results indicate that the approach adopted in this study, i.e., the use of SPOT7 1.5 m imagery in conjunction with image texture analysis and variable importance, can be used to accurately discriminate between canopy gaps and intact canopy, making it a cost-effective spatial approach for monitoring and managing natural forests. Full article
(This article belongs to the Special Issue Mapping Forest Health Using Moderate Resolution Satellites)
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Open AccessArticle Spoil Type Influences Soil Genesis and Forest Development on an Appalachian Surface Coal Mine Ten Years after Placement
Forests 2018, 9(12), 780; https://doi.org/10.3390/f9120780
Received: 15 November 2018 / Revised: 13 December 2018 / Accepted: 16 December 2018 / Published: 18 December 2018
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Abstract
Surface mining for coal (or other mineral resources) is a major driver of land-use change around the world and especially in the Appalachian region of the United States. Intentional and well-informed reclamation of surface-mined land is critical for the restoration of healthy ecosystems [...] Read more.
Surface mining for coal (or other mineral resources) is a major driver of land-use change around the world and especially in the Appalachian region of the United States. Intentional and well-informed reclamation of surface-mined land is critical for the restoration of healthy ecosystems on these disturbed sites. In Appalachia, the pre-mining land cover is predominately mixed hardwood forest, with rich species diversity. In recent years, Appalachian mine reforestation has become an issue of concern, prompting the development of the Forestry Reclamation Approach, a series of mine reforestation recommendations. One of these recommendations is to use the best available soil substitute; however, the characteristics of the “best” soil substitute have been an issue. This study was initiated to compare the suitability of several types of mine spoil common in the Appalachian region: brown sandstone (Brown), gray sandstone (Gray), mixed spoils (Mixed), and shale (Shale). Experimental plots were established in 2007 with each spoil type replicated three times. These plots were planted with a mix of native hardwood species. Ten years after plot construction and planting, tree growth and canopy cover were highest in Brown, followed by Shale, Mixed, and Gray. Soil conditions (particularly pH) in Brown and Shale were more favorable for native tree growth than Mixed or Gray, largely explaining these differences in tree growth and canopy cover. However, soil chemistry did not clearly explain differences in tree growth between Brown and Shale. These differences were more likely related to differences in near-surface soil temperature, which is related to soil color and available shade. Full article
(This article belongs to the Special Issue Monitoring and Management of Forest Recovery)
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Open AccessArticle Genomic Prediction of Growth and Stem Quality Traits in Eucalyptus globulus Labill. at Its Southernmost Distribution Limit in Chile
Forests 2018, 9(12), 779; https://doi.org/10.3390/f9120779
Received: 4 October 2018 / Revised: 5 November 2018 / Accepted: 14 December 2018 / Published: 18 December 2018
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Abstract
The present study was undertaken to examine the ability of different genomic selection (GS) models to predict growth traits (diameter at breast height, tree height and wood volume), stem straightness and branching quality of Eucalyptus globulus Labill. trees using a genome-wide Single Nucleotide [...] Read more.
The present study was undertaken to examine the ability of different genomic selection (GS) models to predict growth traits (diameter at breast height, tree height and wood volume), stem straightness and branching quality of Eucalyptus globulus Labill. trees using a genome-wide Single Nucleotide Polymorphism (SNP) chip (60 K), in one of the southernmost progeny trials of the species, close to its southern distribution limit in Chile. The GS methods examined were Ridge Regression-BLUP (RRBLUP), Bayes-A, Bayes-B, Bayesian least absolute shrinkage and selection operator (BLASSO), principal component regression (PCR), supervised PCR and a variant of the RRBLUP method that involves the previous selection of predictor variables (RRBLUP-B). RRBLUP-B and supervised PCR models presented the greatest predictive ability (PA), followed by the PCR method, for most of the traits studied. The highest PA was obtained for the branching quality (~0.7). For the growth traits, the maximum values of PA varied from 0.43 to 0.54, while for stem straightness, the maximum value of PA reached 0.62 (supervised PCR). The study population presented a more extended linkage disequilibrium (LD) than other populations of E. globulus previously studied. The genome-wide LD decayed rapidly within 0.76 Mbp (threshold value of r2 = 0.1). The average LD on all chromosomes was r2 = 0.09. In addition, the 0.15% of total pairs of linked SNPs were in a complete LD (r2 = 1), and the 3% had an r2 value >0.5. Genomic prediction, which is based on the reduction in dimensionality and variable selection may be a promising method, considering the early growth of the trees and the low-to-moderate values of heritability found in the traits evaluated. These findings provide new understanding of how develop novel breeding strategies for tree improvement of E. globulus at its southernmost range limit in Chile, which could represent new opportunities for forest planting that can benefit the local economy. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Spatiotemporal Variations of Aboveground Biomass under Different Terrain Conditions
Forests 2018, 9(12), 778; https://doi.org/10.3390/f9120778
Received: 30 October 2018 / Revised: 3 December 2018 / Accepted: 13 December 2018 / Published: 17 December 2018
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Abstract
Biomass is a key biophysical parameter used to estimate carbon storage and forest productivity. Spatially-explicit estimation of biomass provides invaluable information for carbon stock calculation and scientific forest management. Nevertheless, there still exists large uncertainty concerning the relationship between biomass and influential factors. [...] Read more.
Biomass is a key biophysical parameter used to estimate carbon storage and forest productivity. Spatially-explicit estimation of biomass provides invaluable information for carbon stock calculation and scientific forest management. Nevertheless, there still exists large uncertainty concerning the relationship between biomass and influential factors. In this study, aboveground biomass (AGB) was estimated using the random forest algorithm based on remote sensing imagery (Landsat) and field data for three regions with different topographic conditions in Zhejiang Province, China. AGB distribution and change combined with stratified terrain classifications were analyzed to investigate the relations between AGB and topography conditions. The results indicated that AGB in three regions increased from 2010 to 2015 and the magnitude of growth varied with elevation, slope, and aspect. In the basin region, slope had a greater influence on AGB, and we attributed this negative AGB-elevation relationship to ecological forest construction. In the mountain area, terrain features, especially elevation, showed significant relations with AGB. Moreover, AGB and its growth showed positive relations with elevation and slope. In the island region, slope also played a relatively more important role in explaining the relationship. These results demonstrate that AGB varies with terrain conditions and its change is a consequence of interactions between the natural environment and anthropogenic behavior, implying that biomass retrieval based on Landsat imagery could provide considerable important information related to regional heterogeneity investigations. Full article
(This article belongs to the Special Issue Remote Sensing Technology Applications in Forestry and REDD+)
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Open AccessArticle Hierarchical Environmental Factors Affecting the Distribution of Abies koreana on the Korean Peninsula
Forests 2018, 9(12), 777; https://doi.org/10.3390/f9120777
Received: 22 October 2018 / Revised: 10 December 2018 / Accepted: 11 December 2018 / Published: 16 December 2018
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Abstract
A regional decline in the Korean fir (Abies koreana) has been observed since the 1980s in the subalpine region. To explain this decline, it is important to investigate the degree to which environmental factors have contributed to plant distributions on diverse [...] Read more.
A regional decline in the Korean fir (Abies koreana) has been observed since the 1980s in the subalpine region. To explain this decline, it is important to investigate the degree to which environmental factors have contributed to plant distributions on diverse spatial scales. We applied a hierarchical regression model to determine quantitatively the relationship between the abundance of Korean fir (seedlings) and diverse environmental factors across two different ecological scales. We measured Korean fir density and the occurrence of its seedlings in 102 (84) plots nested at five sites and collected a range of environmental factors at the same plots. Our model included hierarchical explanatory variables at both site-level (weather conditions) and plot-level (micro-topographic factors, soil properties, and competing species). The occurrence of Korean fir seedlings was positively associated with moss cover and rock cover but negatively related to dwarf bamboo cover. At the site level, winter precipitation was significantly and positively related to the occurrence of seedlings. A hierarchical Poisson regression model revealed that Korean fir density was negatively associated with slope aspect, topographic position index, Quercus mongolica cover, and mean summer temperature. Our results suggest that rising temperature, drought, and competition with other species are factors that impede the survival of the Korean fir. We can predict that the population of Korean fir will continue to decline in the subalpine, and only a few Korean fir will survive on northern slopes or valleys due to climate change. Full article
(This article belongs to the Special Issue Influence of Climate Change on Tree Growth and Forest Ecosystems)
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Open AccessArticle Nondestructive Characterization of Dry Heat-Treated Fir (Abies Alba Mill.) Timber in View of Possible Structural Use
Forests 2018, 9(12), 776; https://doi.org/10.3390/f9120776
Received: 14 November 2018 / Revised: 4 December 2018 / Accepted: 11 December 2018 / Published: 15 December 2018
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Abstract
The use of heat-treated timber for building with wood is of increasing interest. Heat treatment improves the durability and dimensional stability of wood; however, it needs to be optimized to keep wood’s mechanical properties in view of the possible structural use of timber. [...] Read more.
The use of heat-treated timber for building with wood is of increasing interest. Heat treatment improves the durability and dimensional stability of wood; however, it needs to be optimized to keep wood’s mechanical properties in view of the possible structural use of timber. Therefore, dry vacuum heat treatment varying the maximum temperature between 170 °C and 230 °C was used on fir (Abies alba Mill.) structural timber, visually top graded according to EN 338, to analyze its final weight loss, hygroscopicity, CIELAB color, and dynamic elastomechanical properties. It turned out that weight loss and total color difference of wood positively correlates with the increasing intensity of the heat treatment. The maximum 40% reduction of the hygroscopicity of wood was already reached at 210 °C treatment temperature. The moduli of elasticity in longitudinal and radial direction of wood, determined by ultrasound velocity, increased initially up to the treatment temperature of 210 °C, and decreased at higher treatment temperature. Equally, the Euler-Bernoulli modulus of elasticity from free-free flexural vibration of boards in all five vibration modes increased with the rising treatment temperature up to 190 °C, and decreased under more intensive treatment conditions. The Euler-Bernoulli model was found to be valid only in the 1st vibration mode of heat-treated structural timber due to the unsteady decrease in the evaluated moduli of elasticity related to the increasing mode number. Full article
(This article belongs to the Special Issue Wood Properties and Processing)
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Open AccessArticle Environmental Conditions and Species Identity Drive Metabolite Levels in Green Leaves and Leaf Litter of 14 Temperate Woody Species
Forests 2018, 9(12), 775; https://doi.org/10.3390/f9120775
Received: 30 October 2018 / Revised: 30 November 2018 / Accepted: 11 December 2018 / Published: 15 December 2018
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Abstract
Research Highlights: Leaf chemistry is a key driver of litter decomposition; however, studies directly comparing metabolites that are important for tree growth and defence across different woody species are scarce. Background and Objectives: Choosing 14 temperate woody species differing in their growth rates, [...] Read more.
Research Highlights: Leaf chemistry is a key driver of litter decomposition; however, studies directly comparing metabolites that are important for tree growth and defence across different woody species are scarce. Background and Objectives: Choosing 14 temperate woody species differing in their growth rates, nutrient demand, shade tolerance, and drought sensitivity, we hypothesized that the species would group according to their metabolite profiles based on their ecological background. Materials and Methods: We analysed total N and C, soluble amino acid, protein, and phenolic levels in green leaves and leaf litter of these species, each in two consecutive years. Results: Metabolite levels varied significantly across species and between the sampling years which differed in temperature and precipitation (i.e., colder/drier vs warmer/ wetter). Conclusions: The 14 woody species could not be grouped according to their green leaf or leaf litter metabolite profiles. In litter leaves, most of the variation was explained by total phenolics and total nitrogen levels, and in green leaves by total phenolics and total soluble amino acid levels. Local climate variation between the two consecutive years for green leaves or leaf litter led to significant differences in metabolite levels, although some of them were species-specific. Full article
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Open AccessArticle Spatial Pattern and Competitive Relationships of Moso Bamboo in a Native Subtropical Rainforest Community
Forests 2018, 9(12), 774; https://doi.org/10.3390/f9120774
Received: 10 November 2018 / Revised: 6 December 2018 / Accepted: 11 December 2018 / Published: 14 December 2018
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Abstract
Bamboo has invaded native forests worldwide, and its aggressive spread by rhizomes facilitates patch expansion and the eventual replacement of adjacent forests. However, fine-scale studies of the spatial pattern and competitive relationships of bamboo in native forests are still lacking. We obtained data [...] Read more.
Bamboo has invaded native forests worldwide, and its aggressive spread by rhizomes facilitates patch expansion and the eventual replacement of adjacent forests. However, fine-scale studies of the spatial pattern and competitive relationships of bamboo in native forests are still lacking. We obtained data from nine plots in a native south subtropical rainforest in Guizhou Province, northwest China. Pair-correlation functions indicated that competition caused by bamboo expansion has not led to large-scale regular spatial distributions in bamboo forest and negative density-related dependence mechanisms regulating the spatial pattern of the native forest community. Marked correlation functions indicated small bamboo in clusters form colony patches that grow around the larger mature trees, resulting in patch expansion in the native forest community. Mark variogram functions identified significant positive spatial autocorrelation of moso bamboo caused by interactions with similar-sized trees within colony patches. This study showed that moso bamboo has colonized and expanded within the native forest community. Compared to the native forest species, the strategy of patch expansion and equal tree sizes in colony patches of moso bamboo could prevent regular distribution trend and size-asymmetric competition between nearby bamboo for the asymmetric and limited sources (i.e., light) in the forest, enhancing the persistence of moso bamboo in the native forest in our study stand located in a south subtropical rainforest in a river valley. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Allelopathy of Wild Mushrooms—An Important Factor for Assessing Forest Ecosystems in Japan
Forests 2018, 9(12), 773; https://doi.org/10.3390/f9120773
Received: 7 November 2018 / Revised: 6 December 2018 / Accepted: 11 December 2018 / Published: 14 December 2018
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Abstract
Research Highlights: Some organisms such as plants and fungi release certain secondary metabolites, generally called allelochemicals, which can influence the organisms around them. Some of the secondary metabolites released by mushrooms may have certain effects on the growth and development of neighboring plants. [...] Read more.
Research Highlights: Some organisms such as plants and fungi release certain secondary metabolites, generally called allelochemicals, which can influence the organisms around them. Some of the secondary metabolites released by mushrooms may have certain effects on the growth and development of neighboring plants. Background Objectives: The purpose of the present study was to investigate the allelopathic potential of mushrooms in a forest ecosystem. To this end, 289 Japanese mushroom species were collected from the wild and tested using a modified sandwich method, which is a quick and effective bioassay technique. Materials and Methods: The collected specimens were prepared for bioassay as dried samples, and 10 mg/well (10 cm2) was added to a 6-well multidish according to the mycelia biomass, which was estimated at 700−900 kg ha−1 year−1 (7–9 mg 10 cm−2) in coniferous forests. Results: Of the screened mushroom species, 74% inhibited more than 50% of the radicle elongation in lettuce (Lactuca sativa var. Great Lakes 366) seedlings, while the average of all species was 41.1%. This result suggests that wild mushrooms have a significant regulatory effect on lettuce growth. According to our standard deviation variance analysis, 54 out of 289 species showed significant allelopathic activity. Among these species, Xeromphalina tenuipes, Cortinarius violaceus, and Clavaria miyabeana exhibited the strongest growth inhibitory activity, with radicle elongation of 5.1%, 4.3%, and 7.6% of the control, respectively. In contrast, Ischnoderma resinosum stimulated the length of radicle and hypocotyl growth by 30.6% and 42.0%, respectively. These results suggest that these species may play important roles in ecosystems. In addition, the wide range of allelopathic activities observed in mushrooms indicates that various amounts of diverse secondary metabolites from these species are involved in mushroom allelopathy. Conclusions: Our study reveals the importance of evaluating mushroom allelopathy to understand the wider ecological structures within complex ecosystems. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Variation in Climate Signals in Teak Tree-Ring Chronologies in Two Different Growth Areas
Forests 2018, 9(12), 772; https://doi.org/10.3390/f9120772
Received: 30 November 2018 / Accepted: 11 December 2018 / Published: 14 December 2018
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Abstract
We developed two tree-ring chronologies of teak (Tectona grandis L.f.) from Mae Tuen (462-year, 1555–2016) and Umphang (165-year, 1852–2016) in Tak province, northwestern Thailand. The chronologies were based on 67 and 71 living teak trees, respectively. We used crossdating methods to check [...] Read more.
We developed two tree-ring chronologies of teak (Tectona grandis L.f.) from Mae Tuen (462-year, 1555–2016) and Umphang (165-year, 1852–2016) in Tak province, northwestern Thailand. The chronologies were based on 67 and 71 living teak trees, respectively. We used crossdating methods to check and verify the tree-ring width data and tree-ring chronology construction using the ARSTAN program. In this study, the two teak tree-ring chronologies from two different growth areas could not be crossdated. The relationship among these chronologies is, thus, relatively low (r = 0.33, n = 165, p < 0.01). This result shows that the growth of tree-ring structure from two sites can be affected by a variety of non-climatic patterns due to site variation, such as topography, nutrient, light, and internal factors. However, these chronologies have a significant positive correlation with rainfall, during the pre-monsoon season (April to May). As demonstrated by the spatial correlation patterns, these chronologies represent April to May rainfall, which was a limiting factor of teak growth from northwestern Thailand. While the difference in surface temperatures of the Indian Ocean Dipole (IOD) might not be affected by rainfall, its unstable relationship with the El Niño-Southern Oscillation (ENSO) was noted to have occurred. Full article
(This article belongs to the Special Issue Wood Science and Tropical Forest Ecology)
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Open AccessArticle Leaf Nitrogen and Phosphorus Stoichiometry of Cyclocarya paliurus across China
Forests 2018, 9(12), 771; https://doi.org/10.3390/f9120771
Received: 16 November 2018 / Revised: 11 December 2018 / Accepted: 13 December 2018 / Published: 13 December 2018
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Abstract
Leaf stoichiometry (nitrogen (N), phosphorus (P) and N:P ratio) is not only important for studying nutrient composition in forests, but also reflects plant biochemical adaptation to geographic and climate conditions. However, patterns of leaf stoichiometry and controlling factors are still unclear for most [...] Read more.
Leaf stoichiometry (nitrogen (N), phosphorus (P) and N:P ratio) is not only important for studying nutrient composition in forests, but also reflects plant biochemical adaptation to geographic and climate conditions. However, patterns of leaf stoichiometry and controlling factors are still unclear for most species. In this study, we determined leaf N and P stoichiometry and their relationship with soil properties, geographic and climate variables for Cyclocarya paliurus based on a nation-wide dataset from 30 natural populations in China. The mean values of N and P concentrations and N:P ratios were 9.57 mg g−1, 0.91 mg g−1 and 10.51, respectively, indicating that both leaf N and P concentrations in C. paliurus forests were lower than those of China and the global flora, and almost all populations were limited in N concentration. We found significant differences in leaf N and P concentrations and N:P ratios among the sampled C. paliurus populations. However, there were no significant correlations between soil properties (including organic C, total N and P concentrations) and leaf stoichiometry. The pattern of variation in leaf N concentration across the populations was positively correlated with latitude (24.46° N–32.42° N), but negatively correlated with mean annual temperature (MAT); meanwhile, leaf N concentration and N:P ratios were negatively correlated with mean temperature in January (MTmin) and mean annual frost-free period (MAF). Together, these results suggested that temperature-physiological stoichiometry with a latitudinal trend hold true at both global and regional levels. In addition, the relationships between leaf stoichiometry and climate variables provided information on how leaf stoichiometry of this species may respond to climate change. Full article
(This article belongs to the Special Issue Nutrient Cycling in Forest Ecosystems)
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Open AccessArticle Stand Volume Production in the Subsequent Stand during Three Decades Remains Unaffected by Slash and Stump Harvest in Nordic Forests
Forests 2018, 9(12), 770; https://doi.org/10.3390/f9120770
Received: 8 October 2018 / Revised: 10 December 2018 / Accepted: 12 December 2018 / Published: 13 December 2018
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Abstract
The renewable energy policies of the European Union rely on forest biomass in achieving climate mitigation targets. In Sweden, where secondary residues from the forest industries are fully utilized, primary residues following harvest such as stumps and slash offer a potential as an [...] Read more.
The renewable energy policies of the European Union rely on forest biomass in achieving climate mitigation targets. In Sweden, where secondary residues from the forest industries are fully utilized, primary residues following harvest such as stumps and slash offer a potential as an additional biomass source. Stump and slash harvest may, however, have adverse effects on site productivity due to increased nutrient loss from the site which could negatively impact the stand volume production of the subsequent stand. Stand volume production is also affected by seedling survival, seedling input from natural regeneration and management of the regenerated stand. In this study, we evaluate the effects of stump and slash harvest on stand volume production of the subsequent stand based on data from eight experimental sites across Sweden planted with Scots pine (Pinus sylvestris L.) or Norway spruce (Picea abies (L.) Karst.) over period of 31–34 years after clearcut with (1) traditional stem-only harvest; (2) stem and stump harvest; (3) stem and slash harvest; and (4) stem, stump and slash harvest. With the goal to explain treatment differences in stand volume production, treatment effects on site productivity estimated through initial height growth (10–19 years after planting), seedling survival, and input of seedlings through natural regeneration were also analyzed. We found that stand volume production was higher following stump harvest as compared to slash harvest, but stand volume production for the more intense harvest treatments (2)–(4) did not differ from stem-only harvest (1). Initial height growth (i.e., site productivity) did not differ between treatments, but followed the trend in stand volume production with (2) > (4) > (3) > (1). Survival of planted seedlings was not affected by the treatments, whereas natural regeneration after 5 years was significantly increased after both treatments including slash harvest (3) and (4) in comparison to stem-only harvest. However, since most of that natural regeneration was removed in subsequent pre-commercial thinnings, this initial increase did not affect stand volume production. The absence of a significant interaction between treatment and species planted for all independent variables tested suggests that there were no species related response differences. Since the experimental design did not allow for site-level analyses, we cannot exclude the possibility that site-specific harvest treatment effects might have masked general effects across all sites. Thus, slash and stump harvest effects at the site level need to be further studied. These results suggest, at least over a 3-decade perspective, that logging residues like stumps and slash can provide an additional renewable energy source to help achieving climate change mitigation goals in the Nordic countries without depleting the future forest biomass resource. Full article
(This article belongs to the Special Issue Forest Biomass Production and Transport Planning)
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Open AccessArticle High-Efficiency Somatic Embryogenesis from Seedlings of Koelreuteria paniculata Laxm.
Forests 2018, 9(12), 769; https://doi.org/10.3390/f9120769
Received: 12 November 2018 / Revised: 4 December 2018 / Accepted: 11 December 2018 / Published: 13 December 2018
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Abstract
Research Highlights: In the current study, we established a method for plant regeneration via somatic embryogenesis (SE) in Koelreuteria paniculata Laxm. for the first time. Background and Objectives: K. paniculata is an important ornamental and medicinal plant in China. However, the plant has [...] Read more.
Research Highlights: In the current study, we established a method for plant regeneration via somatic embryogenesis (SE) in Koelreuteria paniculata Laxm. for the first time. Background and Objectives: K. paniculata is an important ornamental and medicinal plant in China. However, the plant has difficulty with asexual reproduction, which imposes a limitation on large-scale propagation. Materials and Methods: Embryogenic calluses were induced from stems of aseptic seedlings on induction media. The effects of different media types and concentrations of N6-benzyladenine (BA), α-naphthaleneacetic acid (NAA), and 2,4-dichlorophenoxyacetic acid (2,4-D) on callus induction were examined. Embryogenic calluses were then transferred to Driver-Kuniyuki Walnut (DKW) media containing NAA (0.1–0.2 mg L−1) or 2,4-D (0.5–2.0 mg L−1) to develop somatic embryos. Cotyledon embryos were cultured on DKW media containing NAA (0.1–0.2 mg L−1) until maturation, and were then transferred to 1/2 DKW medium supplemented with 1.0 mg L−1 indole-3-butyric acid (IBA) to produce complete plants. The effects of IBA and NAA on rhizogenesis were then examined by clonal culture. Results: The maximum callus induction frequency (80.25%) was obtained on DKW medium supplemented by 0.5 mg L−1 BA, 0.25 mg L−1 NAA, and 1.5 mg L−1 2,4-D. NAA had a more pronounced effect on somatic embryo growth than did 2,4-D, with a maximum SE frequency (54.75%) observed with 0.1 mg L−1 NAA added to DKW medium. For clonal culture, the highest rooting rate (52%) was observed on 1/4 DKW medium containing 1.5 mg L−1 IBA. Histology studies confirmed the presence of embryogenic calluses and somatic embryos in different stages. Conclusions: This protocol provides a novel method for large-scale propagation of K. paniculata, and creates opportunities for genetic engineering in this species. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Spatial Segregation Facilitates the Coexistence of Tree Species in Temperate Forests
Forests 2018, 9(12), 768; https://doi.org/10.3390/f9120768
Received: 26 October 2018 / Revised: 6 December 2018 / Accepted: 11 December 2018 / Published: 13 December 2018
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Abstract
Competition between plants has an important role during the natural succession of forest communities. Niche separation between plants can reduce such interspecific competition and enable multispecies plant to achieve coexistence, although this proposition has rarely been supported in experiments. Plant competition can be [...] Read more.
Competition between plants has an important role during the natural succession of forest communities. Niche separation between plants can reduce such interspecific competition and enable multispecies plant to achieve coexistence, although this proposition has rarely been supported in experiments. Plant competition can be captured by spatial segregation of the competing species to avoid fierce direct conflicts for nutrients and light. We investigated a site of 400 m × 1000 m in Beijing Pine Mountain National Nature Reserve that was established for protecting Chinese pine and some rare fungi. Six dominant tree species (Fraxinus chinensis Roxb., Syringa reticulata (Blume) H. Hara var. amurensis (Rupr.) J. S. Pringle, Quercus mongolica Fisch. ex Ledeb., Armeniaca sibirica (L.) Lam., Pinus tabuliformis Carrière, and Ulmus pumila L.) were individually marked. Metrics of spatial segregation, based on the theory of spatial point process, were calculated to detect spatial competition. The corresponding type (species)-specific probabilities and the p-values from a spatially implicit test revealed significant overall spatial segregation between the six tree species. We further used the cross-type L-function to check the spatial correlation between Chinese pine and the other tree species, and detected a significant spatial repulsion relationship with four other tree species. Our study shows that each of the six dominant tree species occupies a different subarea in the landscape to effectively reduce direct spatial competition. We thus argue that patchy distributions of different tree species could be common in late forest community succession, and the coexistence of plants could be maintained over a large spatial scale. Management intervention, such as thinning the densities of dominant tree species, could be used to foster species coexistence and ensure the productivity of commercial stands. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Current and Potential Spatial Distribution of Six Endangered Pine Species of Mexico: Towards a Conservation Strategy
Forests 2018, 9(12), 767; https://doi.org/10.3390/f9120767
Received: 24 October 2018 / Revised: 30 November 2018 / Accepted: 6 December 2018 / Published: 12 December 2018
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Abstract
Mexico is home to the highest species diversity of pines: 46 species out of 113 reported around the world. Within the great diversity of pines in Mexico, Pinus culminicola Andresen et Beaman, P. jaliscana Perez de la Rosa, P. maximartinenzii Rzed., P. nelsonii [...] Read more.
Mexico is home to the highest species diversity of pines: 46 species out of 113 reported around the world. Within the great diversity of pines in Mexico, Pinus culminicola Andresen et Beaman, P. jaliscana Perez de la Rosa, P. maximartinenzii Rzed., P. nelsonii Shaw, P. pinceana Gordon, and P. rzedowskii Madrigal et M. Caball. are six catalogued as threatened or endangered due to their restricted distribution and low population density. Therefore, they are of special interest for forest conservation purposes. In this paper, we aim to provide up-to-date information on the spatial distribution of these six pine species according to different historical registers coming from different herbaria distributed around the country by using spatial modeling. Therefore, we recovered historical observations of the natural distribution of each species and modelled suitable areas of distribution according to environmental requirements. Finally, we evaluated the distributions by contrasting changes of vegetation in the period 1991–2016. The results highlight areas of distribution for each pine species in the northeast, west, and central parts of Mexico. The results of this study are intended to be the basis of in situ and ex situ conservation strategies for the endangered Mexican pines. Full article
(This article belongs to the Section Forest Inventory, Quantitative Methods and Remote Sensing)
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Open AccessArticle Litter Inhibitory Effects on Soil Microbial Biomass, Activity, and Catabolic Diversity in Two Paired Stands of Robinia pseudoacacia L. and Pinus nigra Arn.
Forests 2018, 9(12), 766; https://doi.org/10.3390/f9120766
Received: 23 October 2018 / Revised: 30 November 2018 / Accepted: 10 December 2018 / Published: 12 December 2018
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Abstract
Research Highlights: Plant cover drives the activity of the microbial decomposer community and affects carbon (C) sequestration in the soil. Despite the relationship between microbial activity and C sequestration in the soil, potential inhibition of soil microbial activity by plant cover has received [...] Read more.
Research Highlights: Plant cover drives the activity of the microbial decomposer community and affects carbon (C) sequestration in the soil. Despite the relationship between microbial activity and C sequestration in the soil, potential inhibition of soil microbial activity by plant cover has received little attention to date. Background and Objectives: Differences in soil microbial activity between two paired stands on soil at a very early stage of formation and a common story until afforestation, can be traced back to the plant cover. We hypothesized that in a black locust (Robinia pseudoacacia L.) stand the high-quality leaf litter of the tree, and that of the blackberry (Rubus fruticosus L.) understory had an inhibitory effect on soil microbial community resulting in lower mineralization of soil organic matter compared to the paired black pine (Pinus nigra Arn.) stand. Materials and Methods: We estimated potential mineralization rates (MR), microbial (MB), and active fungal biomass (AFB) of newly-shed litter, forest floor, and mineral soil. We tested the effects of litters’ water extracts on soil MR, MB, AFB and its catabolic response profile (CRP). Results: Newly-shed litter of black locust had higher MR than that of blackberry and black pine; MR, MB, and AFB were higher in forest floor and in mineral soil under black pine than under black locust. Water extracts of black locust and blackberry litter had a negative effect on the amount, activity of microorganisms, and CRP. Conclusions: The results demonstrate the potential for black locust and blackberry litter to have a marked inhibitory effect on decomposer microorganisms that, in turn, reduce organic matter mineralization with possible consequences at the ecosystem level, by increasing C sequestration in mineral soil. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Single-Molecule Long-Read Sequencing of Zanthoxylum bungeanum Maxim. Transcriptome: Identification of Aroma-Related Genes
Forests 2018, 9(12), 765; https://doi.org/10.3390/f9120765
Received: 12 November 2018 / Revised: 7 December 2018 / Accepted: 9 December 2018 / Published: 12 December 2018
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Abstract
Zanthoxylum bungeanum Maxim. is an economically important tree species that is resistant to drought and infertility, and has potential medicinal and edible value. However, comprehensive genomic data are not yet available for this species, limiting its potential utility for medicinal use, breeding programs, [...] Read more.
Zanthoxylum bungeanum Maxim. is an economically important tree species that is resistant to drought and infertility, and has potential medicinal and edible value. However, comprehensive genomic data are not yet available for this species, limiting its potential utility for medicinal use, breeding programs, and cultivation. Transcriptome sequencing provides an effective approach to remedying this shortcoming. Herein, single-molecule long-read sequencing and next-generation sequencing approaches were used in parallel to obtain transcript isoform structure and gene functional information in Z. bungeanum. In total, 282,101 reads of inserts (ROIs) were identified, including 134,074 full-length non-chimeric reads, among which 65,711 open reading frames (ORFs), 50,135 simple sequence repeats (SSRs), and 1492 long non-coding RNAs (lncRNAs) were detected. Functional annotation revealed metabolic pathways related to aroma components and color characteristics in Z. bungeanum. Unexpectedly, 30 transcripts were annotated as genes involved in regulating the pathogenesis of breast and colorectal cancers. This work provides a comprehensive transcriptome resource for Z. bungeanum, and lays a foundation for the further investigation and utilization of Zanthoxylum resources. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Eddy Covariance vs. Biometric Based Estimates of Net Primary Productivity of Pedunculate Oak (Quercus robur L.) Forest in Croatia during Ten Years
Forests 2018, 9(12), 764; https://doi.org/10.3390/f9120764
Received: 21 November 2018 / Revised: 5 December 2018 / Accepted: 6 December 2018 / Published: 11 December 2018
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Abstract
We analysed 10 years (2008–2017) of continuous eddy covariance (EC) CO2 flux measurements of net ecosystem exchange (NEE) in a young pedunculate oak forest in Croatia. Measured NEE was gap-filled and partitioned into gross primary productivity (GPP) and [...] Read more.
We analysed 10 years (2008–2017) of continuous eddy covariance (EC) CO2 flux measurements of net ecosystem exchange (NEE) in a young pedunculate oak forest in Croatia. Measured NEE was gap-filled and partitioned into gross primary productivity (GPP) and ecosystem reparation (RECO) using the online tool by Max Planck Institute for Biogeochemistry in Jena, Germany. Annual NEE, GPP, and RECO were correlated with main environmental drivers. Net primary productivity was estimated from EC (NPPEC), as a sum of −NEE and Rh obtained using a constant Rh:RECO ratio, and from independent periodic biometric measurements (NPPBM). For comparing the NPP at the seasonal level, we propose a simple model that aimed at accounting for late-summer and autumn carbon storage in the non-structural carbohydrate pool. Over the study period, Jastrebarsko forest acted as a carbon sink, with an average (±std. dev.) annual NEE of −319 (±94) gC m−2 year−1, GPP of 1594 (±109) gC m−2 year−1, and RECO of 1275 (±94) gC m−2 year−1. Annual NEE showed high inter-annual variability and poor correlation with annual average global radiation, air temperature, and total precipitation, but significant (R2 = 0.501, p = 0.02) correlation with the change in soil water content between May and September. Comparison of annual NPPEC and NPPBM showed a good overall agreement (R2 = 0.463, p = 0.03), although in all years NPPBM was lower than NPPEC, with averages of 680 (±88) gC m−2 year−1 and 819 (±89) gC m−2 year−1, respectively. Lower values of NPPBM indicate that fine roots and grasses contributions to NPP, which were not measured in the study period, could have an important contribution to the overall ecosystem NPP. At a seasonal level, two NPP estimates showed differences in their dynamic, but the application of the proposed model greatly improved the agreement in the second part of the growing season. Further research is needed on the respiration partitioning and mechanisms of carbon allocation. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Wood Density Profiles and Their Corresponding Tissue Fractions in Tropical Angiosperm Trees
Forests 2018, 9(12), 763; https://doi.org/10.3390/f9120763
Received: 12 October 2018 / Revised: 22 November 2018 / Accepted: 27 November 2018 / Published: 7 December 2018
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Abstract
Wood density profiles reveal a tree’s life strategy and growth. Density profiles are, however, rarely defined in terms of tissue fractions for wood of tropical angiosperm trees. Here, we aim at linking these fractions to corresponding density profiles of tropical trees from the [...] Read more.
Wood density profiles reveal a tree’s life strategy and growth. Density profiles are, however, rarely defined in terms of tissue fractions for wood of tropical angiosperm trees. Here, we aim at linking these fractions to corresponding density profiles of tropical trees from the Congo Basin. Cores of 8 tree species were scanned with X-ray Computed Tomography to calculate density profiles. Then, cores were sanded and the outermost 3 cm were used to semi-automatically measure vessel lumen, parenchyma and fibre fractions using the Weka segmentation tool in ImageJ. Fibre wall and lumen widths were measured using a newly developed semi-automated method. An assessment of density variation in function of growth ring boundary detection is done. A mixed regression model estimated the relative contribution of each trait to the density, with a species effect on slope and intercept of the regression. Position-dependent correlations were made between the fractions and the corresponding wood density profile. On average, density profile variation mostly reflects variations in fibre lumen and wall fractions, but these are species- and position-dependent: on some positions, parenchyma and vessels have a more pronounced effect on density. The model linking density to traits explains 92% of the variation, with 65% of the density profile variation attributed to the three measured traits. The remaining 27% is explained by species as a random effect. There is a clear variation between trees and within trees that have implications for interpreting density profiles in angiosperm trees: the exact driving anatomical fraction behind every density value will depend on the position within the core. The underlying function of density will thus vary accordingly. Full article
(This article belongs to the Special Issue Wood Science and Tropical Forest Ecology)
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Open AccessArticle Investigation of Bamboo Grid Packing Properties Used in Cooling Tower
Forests 2018, 9(12), 762; https://doi.org/10.3390/f9120762
Received: 1 November 2018 / Revised: 2 December 2018 / Accepted: 5 December 2018 / Published: 7 December 2018
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Abstract
Due to its advantages of good heat-resistance, environmental-friendliness, and low cost, bamboo grid packing (BGP) has become a promising new type of cooling packing. It is being increasingly used in Chinese industrial cooling towers to replace cooling packings made of polyvinyl chloride, cement, [...] Read more.
Due to its advantages of good heat-resistance, environmental-friendliness, and low cost, bamboo grid packing (BGP) has become a promising new type of cooling packing. It is being increasingly used in Chinese industrial cooling towers to replace cooling packings made of polyvinyl chloride, cement, and glass fiber reinforced plastic. However, mechanical properties and fungal resistance are a concern for all bamboo applications. In this study, the modulus of rupture (MOR), modulus of elasticity (MOE), density, crystallinity, and environment scanning electron microscope (ESEM) properties were compared between fresh BGPs and those that had been in service for nine years in the cooling towers. The results showed that the MOR, MOE, density, crystallinity, and the crystal size of the used BGPs decreased to some extent, but still met the requirements for normal use in a cooling tower. The ESEM observation showed that the used BGPs were not infected by fungi. The decrease in mechanical properties could be caused by the decrease of density, crystallinity, and the decomposition of the chemical components of bamboo, but not by fungal infection. Full article
(This article belongs to the Special Issue Wood Properties and Processing)
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Open AccessArticle Changes in Sensitivity of Tree-Ring Widths to Climate in a Tropical Moist Forest Tree in Bangladesh
Forests 2018, 9(12), 761; https://doi.org/10.3390/f9120761
Received: 8 November 2018 / Revised: 28 November 2018 / Accepted: 2 December 2018 / Published: 6 December 2018
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Abstract
Tree growth in the tropics is strongly influenced by climate. However, reported tree growth responses to climate are largely inconsistent, varying with geographic location, forest type, and tree species. It is thus important to study the growth responses of tropical trees in sites [...] Read more.
Tree growth in the tropics is strongly influenced by climate. However, reported tree growth responses to climate are largely inconsistent, varying with geographic location, forest type, and tree species. It is thus important to study the growth responses of tropical trees in sites and species that are under-represented so far. Bangladesh, a country influenced by the Asian monsoon climate, is understudied in terms of tree growth response to climate. In the present study, we developed a 121-year-long regional ring-width index chronology of Chukrasia tabularis A. Juss. sampled in two moist forest sites in Bangladesh to investigate tree growth responses to climate in monsoon South Asia. Standard dendrochronological methods were used to produce the ring-width chronologies. The climate sensitivity of C. tabularis was assessed through bootstrap correlation analysis and the stationarity and consistency of climate–growth relationships was evaluated using moving correlation functions and comparing the regression slopes of two sub-periods (1950–1985 and 1986–2015). Tree growth was negatively correlated with the mean, minimum, and maximum temperatures, particularly during the early growing season (March). Likewise, precipitation negatively influenced tree growth in the later growing season (October). Besides, radial growth of Chukrasia sharply ceased in years following strong and moderate El Niño events. In parallel with a significant positive trend in local temperatures, tree growth sensitivity to early growing season (March–April) mean temperatures and July minimum temperatures increased in recent decades. Tree growth sensitivity to October precipitation and April vapor pressure deficit also increased. Overall, climate–growth relationships were stronger during the period 1986–2015 than during 1950–1985. Changes in climate sensitivity might be linked to a warming trend that induced an increase in the dry season length during recent decades. With a further predicted temperature increase at our study sites, our results suggest that radial growth of C. tabularis will further decline in response to climate warming. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Stand Characteristics and Soil Properties Affecting the Occurrence of Kunyushan Web-Spinning Sawfly (Cephalcia kunyushanica Xiao) in Japanese Red Pine (Pinus densiflora) Pure Forests in the Kunyushan Mountains, China
Forests 2018, 9(12), 760; https://doi.org/10.3390/f9120760
Received: 31 October 2018 / Revised: 1 December 2018 / Accepted: 3 December 2018 / Published: 5 December 2018
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Abstract
The Kunyushan web-spinning sawfly (Cephalcia kunyushanica) is a major pest in the Japanese red pine (JRP, Pinus densiflora) pure forests in the Kunyushan Mountains of China. In this study, four stand types (ST1–4) were identified in plots of JRP pure [...] Read more.
The Kunyushan web-spinning sawfly (Cephalcia kunyushanica) is a major pest in the Japanese red pine (JRP, Pinus densiflora) pure forests in the Kunyushan Mountains of China. In this study, four stand types (ST1–4) were identified in plots of JRP pure forests, based on the pest severity index (PSI; ranging from 0–100). The order of infestation ratio in the four type stands was as follows: ST4 > ST3 > ST2 > ST1. We investigated the correlation of C. kunyushanica occurrence with stand characteristics and soil physicochemical properties in the four stand types. The results showed that all stand characteristics were different among the four stand types. Compared with infested plots, healthy (ST1) plots had a higher soil bulk density, and the differences among the groups were significant. Differences in soil water content, non-capillary porosity, and total porosity were significant among the four ST groups. The average organic matter content, total nitrogen (N), and available N were lower in ST1 plots, whereas total potassium (K) was higher compared with other ST groups. In addition, a redundancy analysis suggested that seven (total N, diameter at breast height (DBH), soil water content, bulk density, available K, zinc ion (Zn2+), and stem density) of 24 environmental variables were significantly correlated with the ordinations of C. kunyushanica occurrence. The results provide theoretical guidance for the ecological control of C. kunyushanica, and are also useful for the management of forests in areas where C. kunyushanica is a major pest and where site and stand conditions are similar. Full article
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Open AccessArticle Improving Individual Tree Crown Delineation and Attributes Estimation of Tropical Forests Using Airborne LiDAR Data
Forests 2018, 9(12), 759; https://doi.org/10.3390/f9120759
Received: 9 August 2018 / Revised: 28 November 2018 / Accepted: 29 November 2018 / Published: 5 December 2018
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Abstract
Individual tree crown (ITC) segmentation is an approach to isolate individual tree from the background vegetation and delineate precisely the crown boundaries for forest management and inventory purposes. ITC detection and delineation have been commonly generated from canopy height model (CHM) derived from [...] Read more.
Individual tree crown (ITC) segmentation is an approach to isolate individual tree from the background vegetation and delineate precisely the crown boundaries for forest management and inventory purposes. ITC detection and delineation have been commonly generated from canopy height model (CHM) derived from light detection and ranging (LiDAR) data. Existing ITC segmentation methods, however, are limited in their efficiency for characterizing closed canopies, especially in tropical forests, due to the overlapping structure and irregular shape of tree crowns. Furthermore, the potential of 3-dimensional (3D) LiDAR data is not fully realized by existing CHM-based methods. Thus, the aim of this study was to develop an efficient framework for ITC segmentation in tropical forests using LiDAR-derived CHM and 3D point cloud data in order to accurately estimate tree attributes such as the tree height, mean crown width and aboveground biomass (AGB). The proposed framework entails five major steps: (1) automatically identifying dominant tree crowns by implementing semi-variogram statistics and morphological analysis; (2) generating initial tree segments using a watershed algorithm based on mathematical morphology; (3) identifying “problematic” segments based on predetermined set of rules; (4) tuning the problematic segments using a modified distance-based algorithm (DBA); and (5) segmenting and counting the number of individual trees based on the 3D LiDAR point clouds within each of the identified segment. This approach was developed in a way such that the 3D LiDAR points were only examined on problematic segments identified for further evaluations. 209 reference trees with diameter at breast height (DBH) ≥ 10 cm were selected in the field in two study areas in order to validate ITC detection and delineation results of the proposed framework. We computed tree crown metrics (e.g., maximum crown height and mean crown width) to estimate aboveground biomass (AGB) at tree level using previously published allometric equations. Accuracy assessment was performed to calculate percentage of correctly detected trees, omission and commission errors. Our method correctly identified individual tree crowns with detection accuracy exceeding 80 percent at both forest sites. Also, our results showed high agreement (R2 > 0.64) in terms of AGB estimates using 3D LiDAR metrics and variables measured in the field, for both sites. The findings from our study demonstrate the efficacy of the proposed framework in delineating tree crowns, even in high canopy density areas such as tropical rainforests, where, usually the traditional algorithms are limited in their performances. Moreover, the high tree delineation accuracy in the two study areas emphasizes the potential robustness and transferability of our approach to other densely forested areas across the globe. Full article
(This article belongs to the Section Forest Inventory, Quantitative Methods and Remote Sensing)
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Open AccessArticle Tree-Lists Estimation for Chinese Boreal Forests by Integrating Weibull Diameter Distributions with MODIS-Based Forest Attributes from kNN Imputation
Forests 2018, 9(12), 758; https://doi.org/10.3390/f9120758
Received: 16 October 2018 / Revised: 24 November 2018 / Accepted: 30 November 2018 / Published: 5 December 2018
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Abstract
Wall-to-wall tree-lists information (lists of species and diameter for every tree) at a regional scale is required for managers to assess forest sustainability and design effective forest management strategies. Currently, the k-nearest neighbors (kNN) method and the Weibull diameter distribution function have been [...] Read more.
Wall-to-wall tree-lists information (lists of species and diameter for every tree) at a regional scale is required for managers to assess forest sustainability and design effective forest management strategies. Currently, the k-nearest neighbors (kNN) method and the Weibull diameter distribution function have been widely used for estimating tree lists. However, the kNN method usually relies on a large number of field inventory plots to impute tree lists, whereas the Weibull function relies on strong correlations between stand attributes and diameter distribution across large regions. In this study, we developed a framework to estimate wall-to-wall tree lists over large areas based on a limited number of forest inventory plots. This framework integrates the ability of extrapolating diameter distribution from Weibull and kNN imputation of wall-to-wall forest stand attributes from Moderate Resolution Imaging Spectroradiometer (MODIS). We estimated tree lists using this framework in Chinese boreal forests (Great Xing’an Mountains) and evaluated the accuracy of this framework. The results showed that the passing rate of the Kolmogorov–Smirnov (KS) test for Weibull diameter distribution by species was from 52% to 88.16%, which means that Weibull distribution could describe the diameter distribution by species well. The imputed stand attributes (diameter at breast height (DBH), height, and age) from the kNN method showed comparable accuracy with the previous studies for all species. There was no significant difference in the tree density between the estimated and observed tree-lists. Results suggest that this framework is well-suited to estimating the tree-lists in a large area. Our results were also ecologically realistic, capturing dominant ecological patterns and processes. Full article
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Open AccessArticle A Levenberg–Marquardt Backpropagation Neural Network for Predicting Forest Growing Stock Based on the Least-Squares Equation Fitting Parameters
Forests 2018, 9(12), 757; https://doi.org/10.3390/f9120757
Received: 26 October 2018 / Revised: 1 December 2018 / Accepted: 3 December 2018 / Published: 5 December 2018
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Abstract
Traditional field surveys are expensive, time-consuming, laborious, and difficult to perform, especially in mountainous and dense forests, which imposes a burden on forest management personnel and researchers. This study focuses on predicting forest growing stock, one of the most significant parameters of a [...] Read more.
Traditional field surveys are expensive, time-consuming, laborious, and difficult to perform, especially in mountainous and dense forests, which imposes a burden on forest management personnel and researchers. This study focuses on predicting forest growing stock, one of the most significant parameters of a forest resource assessment. First, three schemes were designed—Scheme 1, based on the study samples with mixed tree species; Scheme 2, based on the study samples divided into dominant tree species groups; and Scheme 3, based on the study samples divided by dominant tree species groups—the evaluation factors are fitted by least-squares equations, and the non-significant fitted-factors are removed. Second, an overall evaluation indicator system with 17 factors was established. Third, remote sensing images of Landsat Thematic Mapper, digital elevation model, and the inventory for forest management planning and design were integrated in the same database. Lastly, a backpropagation neural network based on the Levenberg–Marquardt algorithm was used to predict the forest growing stock. The results showed that the group estimation precision exceeded 90%, which is the highest standard of total sampling precision of inventory for forest management planning and design in China. The prediction results for distinguishing dominant tree species were better than for mixed dominant tree species. The results also showed that the performance metrics for prediction could be improved by least-squares equation fitting and significance filtering of the evaluation factors. Full article
(This article belongs to the Special Issue Defining, Quantifying, Observing and Modeling Forest Canopy Traits)
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Open AccessArticle Topographic Controls on Vegetation Changes in Alpine Tundra of the Changbai Mountains
Forests 2018, 9(12), 756; https://doi.org/10.3390/f9120756
Received: 20 October 2018 / Revised: 28 November 2018 / Accepted: 30 November 2018 / Published: 5 December 2018
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Abstract
The vegetation of alpine tundra is undergoing significant changes and topography has played a significant role in mediating such changes. The roles of topography varied at different scales. In this study, we intended to identify topographic controls on tundra vegetation changes within the [...] Read more.
The vegetation of alpine tundra is undergoing significant changes and topography has played a significant role in mediating such changes. The roles of topography varied at different scales. In this study, we intended to identify topographic controls on tundra vegetation changes within the Changbai Mountains of Northeast China and reveal the scale effects. We delineated the vegetation changes of the last three decades using the normalized difference vegetation index (NDVI) time series. We conducted a trend analysis for each pixel to reveal the spatial change and used binary logistic regression models to analyze the relationship between topographic controls at different scales and vegetation changes. Results showed that about 30% of tundra vegetation experienced a significant (p < 0.05) change in the NDVI, with 21.3% attributable to the encroachment of low-altitude plants resulting in a decrease in the NDVI, and 8.7% attributable to the expansion of tundra endemic plants resulting in an increase in the NDVI. Plant encroachment occurred more severely in low altitude than in high altitude, whereas plant expansion mostly occurred near volcanic ash fields at high altitude. We found that plant encroachment tended to occur in complex terrains and the broad-scale mountain aspect had a greater effect on plant encroachment than the fine-scale local aspect. Our results suggest that it is important to include the mountain aspect in mountain vegetation change studies, as most such studies only use the local aspect. Full article
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Open AccessArticle Physical and Mechanical Properties of Particleboard Made from Palm Tree Prunings
Forests 2018, 9(12), 755; https://doi.org/10.3390/f9120755
Received: 30 October 2018 / Revised: 29 November 2018 / Accepted: 3 December 2018 / Published: 5 December 2018
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Abstract
Palm trees are very fast-growing species. Their management produces annually a large amount of biomass that traditionally has been either disposed of at dumping sites or has been burnt onsite. This paper presents an experimental study to obtain particleboard using this biomass in [...] Read more.
Palm trees are very fast-growing species. Their management produces annually a large amount of biomass that traditionally has been either disposed of at dumping sites or has been burnt onsite. This paper presents an experimental study to obtain particleboard using this biomass in a low energy process (short pressing time and low pressing temperature), using particles of different sizes from the rachis (midrib) of the three palm species most representative of urban gardening in Spain: canary palm (Phoenix canariensis hort. ex Chabaud), date palm (Phoenix dactylifera L.) and washingtonia palm (Washingtonia robusta H. Wendl). Their physical and mechanical properties were tested, and the feasibility of their use as a construction material was evaluated. The results showed that the manufactured particleboard had similar performance to conventional wood particleboard and good thermal insulation properties. Boards made with the canary species showed better mechanical performance. The properties of the particleboard depended on the particle size and species. The use of the pruning waste of palm trees to produce durable materials such as particleboard could be beneficial to the environment since it is a method of carbon fixation, helping to decrease atmospheric pollution and reducing the amount of waste that ends in dumping sites. Full article
(This article belongs to the Section Forest Ecology and Management)
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