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Forests, Volume 9, Issue 7 (July 2018)

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Open AccessArticle What Can We Learn from an Early Test on the Adaptation of Silver Fir Populations to Marginal Environments?
Forests 2018, 9(7), 441; https://doi.org/10.3390/f9070441
Received: 21 June 2018 / Revised: 16 July 2018 / Accepted: 19 July 2018 / Published: 23 July 2018
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Abstract
In order to determine the adaptive potential of silver fir in the southeast of Poland, the stability of the height of its five-year-old progeny was analyzed. The study was conducted in two different population groups in a total of four environments, including one
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In order to determine the adaptive potential of silver fir in the southeast of Poland, the stability of the height of its five-year-old progeny was analyzed. The study was conducted in two different population groups in a total of four environments, including one ecologically marginal environment. The linear mixed model was used to evaluate the differentiation of populations in terms of height growth. The genotype and genotype-by-environment interaction biplot (GGE) were used to verify the stability of height. The climate of populations origin, in relation to actual fir distribution in Poland, was verified based on principal components analysis (PCA) of bioclimatic parameters. The highest total variability was explained by the genotype-environment interaction effect (GE) (54.50%), while the genotype effect (G) explained 41.27% and only 4.23% was explained by the site effect. The result of height growth variations revealed the Komańcza site as the most representative among study sites, while the Lesko site characterized the highest discriminating ability. The progeny occurring in climatic conditions most different from the average testing conditions showed a heterogeneous growth reaction, only adapting to the marginal environment, while the progeny of the second population in this region as well as the northernmost one was characterized by a mean but stable growth. The westernmost population revealed maladaptation. The assessment of the adaptability of silver fir depends on the broad spectrum of test conditions considering the ecologically marginal environments. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Growth of Pinus cembroides Zucc. in Response to Hydroclimatic Variability in Four Sites Forming the Species Latitudinal and Longitudinal Distribution Limits
Forests 2018, 9(7), 440; https://doi.org/10.3390/f9070440
Received: 5 June 2018 / Revised: 11 July 2018 / Accepted: 16 July 2018 / Published: 22 July 2018
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Abstract
Climate change modifies the distribution and dominance of forest tree species, particularly near their distribution limits. This study used tree-ring width data for Pinus cembroides Zucc. at its distribution limits in Mexico and the SW USA to assess how tree populations responded to
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Climate change modifies the distribution and dominance of forest tree species, particularly near their distribution limits. This study used tree-ring width data for Pinus cembroides Zucc. at its distribution limits in Mexico and the SW USA to assess how tree populations responded to hydroclimatic variability. Indexed ring-width chronologies were built and correlated with climate and drought records at four marginal stands. We found that P. cembroides responds differently to climatic conditions depending on the bioclimatic and biogeographic conditions, with the forests situated in the driest area (Nuevo León) presenting the highest growth association to maximum temperatures and drought, while the forest situated in the wettest area (Puebla) was the least correlated to these hydroclimatic factors. In particular, dry and hot conditions, during the prior autumn and winter, reduced radial growth. Drought conditions could result in more vulnerable forests at the driest sites. These results advance our understanding of the radial growth responses of P. cembroides and similar widely distributed trees to climatic change near their biogeographical limits. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Urban Park Systems to Support Sustainability: The Role of Urban Park Systems in Hot Arid Urban Climates
Forests 2018, 9(7), 439; https://doi.org/10.3390/f9070439
Received: 18 June 2018 / Revised: 12 July 2018 / Accepted: 20 July 2018 / Published: 22 July 2018
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Abstract
Quantifying ecosystem services in urban areas is complex. However, existing ecosystem service typologies and ecosystem modeling can provide a means towards understanding some key biophysical links between urban forests and ecosystem services. This project addresses broader concepts of sustainability by assessing the urban
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Quantifying ecosystem services in urban areas is complex. However, existing ecosystem service typologies and ecosystem modeling can provide a means towards understanding some key biophysical links between urban forests and ecosystem services. This project addresses broader concepts of sustainability by assessing the urban park system in Phoenix, Arizona’s hot urban climate. This project aims to quantify and demonstrate the multiple ecosystem services provided by Phoenix’s green infrastructure (i.e., urban park system), including its air pollution removal values, carbon sequestration and storage, avoided runoff, structural value, and the energy savings it provides for city residents. Modeling of ecosystem services of the urban park system revealed around 517,000 trees within the system, representing a 7.20% tree cover. These trees remove about 3630 tons (t) of carbon (at an associated value of $285,000) and about 272 t of air pollutants (at an associated value of $1.16 million) every year. Trees within Phoenix’s urban park system are estimated to reduce annual residential energy costs by $106,000 and their structural value is estimated at $692 million. The findings of this research will increase our knowledge of the value of green infrastructure services provided by different types of urban vegetation and assist in the future design, planning and management of green infrastructure in cities. Thus, this study has implications for both policy and practice, contributing to a better understanding of the multiple benefits of green infrastructure and improving the design of green spaces in hot arid urban climates around the globe. Full article
(This article belongs to the Special Issue Growth and Ecosystem Services of Urban Trees)
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Open AccessArticle Combining Decision Support Approaches for Optimizing the Selection of Bundles of Ecosystem Services
Forests 2018, 9(7), 438; https://doi.org/10.3390/f9070438
Received: 24 May 2018 / Revised: 18 July 2018 / Accepted: 19 July 2018 / Published: 21 July 2018
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Abstract
This study examines the potential of combining decision support approaches to identify optimal bundles of ecosystem services in a framework characterized by multiple decision-makers. A forested landscape, Zona de Intervenção Florestal of Paiva and Entre-Douro and Sousa (ZIF_VS) in Portugal, is used to
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This study examines the potential of combining decision support approaches to identify optimal bundles of ecosystem services in a framework characterized by multiple decision-makers. A forested landscape, Zona de Intervenção Florestal of Paiva and Entre-Douro and Sousa (ZIF_VS) in Portugal, is used to test and demonstrate this potential. The landscape extends over 14,388 ha, representing 1976 stands. The property is fragmented into 376 holdings. The overall analysis was performed in three steps. First, we selected six alternative solutions (A to F) in a Pareto frontier generated by a multiple-criteria method within a web-based decision support system (SADfLOR) for subsequent analysis. Next, an aspatial strategic multicriteria decision analysis (MCDA) was performed with the Criterium DecisionPlus (CDP) component of the Ecosystem Management Decision Support (EMDS) system to assess the aggregate performance of solutions A to F for the entire forested landscape with respect to their utility for delivery of ecosystem services. For the CDP analysis, SADfLOR data inputs were grouped into two sets of primary criteria: Wood Harvested and Other Ecosystem Services. Finally, a spatial logic-based assessment of solutions A to F for individual stands of the study area was performed with the NetWeaver component of EMDS. The NetWeaver model was structurally and computationally equivalent to the CDP model, but the key NetWeaver metric is a measure of the strength of evidence that solutions for specific stands were optimal for the unit. We conclude with a discussion of how the combination of decision support approaches encapsulated in the two systems could be further automated in order to rank several efficient solutions in a Pareto frontier and generate a consensual solution. Full article
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Open AccessArticle Modeling Burned Areas in Indonesia: The FLAM Approach
Forests 2018, 9(7), 437; https://doi.org/10.3390/f9070437
Received: 20 June 2018 / Revised: 16 July 2018 / Accepted: 18 July 2018 / Published: 20 July 2018
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Abstract
Large-scale wildfires affect millions of hectares of land in Indonesia annually and produce severe smoke haze pollution and carbon emissions, with negative impacts on climate change, health, the economy and biodiversity. In this study, we apply a mechanistic fire model to estimate burned
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Large-scale wildfires affect millions of hectares of land in Indonesia annually and produce severe smoke haze pollution and carbon emissions, with negative impacts on climate change, health, the economy and biodiversity. In this study, we apply a mechanistic fire model to estimate burned area in Indonesia for the first time. We use the Wildfire Climate Impacts and Adaptation Model (FLAM) that operates with a daily time step on the grid cell of 0.25 arc degrees, the same spatio-temporal resolution as in the Global Fire Emissions Database v4 (GFED). GFED data accumulated from 2000–2009 are used for calibrating spatially-explicit suppression efficiency in FLAM. Very low suppression levels are found in peatland of Kalimantan and Sumatra, where individual fires can burn for very long periods of time despite extensive rains and fire-fighting attempts. For 2010–2016, we validate FLAM estimated burned area temporally and spatially using annual GFED observations. From the validation for burned areas aggregated over Indonesia, we obtain Pearson’s correlation coefficient separately for wildfires and peat fires, which equals 0.988 in both cases. Spatial correlation analysis shows that in areas where around 70% is burned, the correlation coefficients are above 0.6, and in those where 30% is burned, above 0.9. Full article
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Open AccessArticle Understory Plants Regulate Soil Respiration through Changes in Soil Enzyme Activity and Microbial C, N, and P Stoichiometry Following Afforestation
Forests 2018, 9(7), 436; https://doi.org/10.3390/f9070436
Received: 18 June 2018 / Revised: 8 July 2018 / Accepted: 18 July 2018 / Published: 20 July 2018
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Abstract
Soil respiration (SR) is an important process in the carbon cycle. However, the means by which changes in understory plant community traits affect this ecosystem process is still poorly understood. In this study, plant species surveys were conducted and soil samples were collected
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Soil respiration (SR) is an important process in the carbon cycle. However, the means by which changes in understory plant community traits affect this ecosystem process is still poorly understood. In this study, plant species surveys were conducted and soil samples were collected from forests dominated by black locust (Robinia pseudoacacia L.), with a chronosequence of 15, 25, and 40 years (RP15, RP25, and RP40, respectively), and farmland (FL). Understory plant coverage, evenness, diversity, and richness were determined. We investigated soil microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), and stoichiometry (MBC:MBN, MBC:MBP, and MBN:MBP). Soil enzyme assays (catalase, saccharase, urease, and alkaline phosphatase), heterotrophic respiration (HR), and autotrophic respiration (AR) were measured. The results showed that plant coverage, plant richness index (R), evenness, and Shannon-Wiener diversity were higher in RP25 and RP40 than in RP15. SR, HR, and AR were significantly higher in the forested sites than in farmland, especially for SR, which was on average 360.7%, 249.6%, and 248.2% higher in RP40, RP25, and RP15, respectively. Meanwhile, catalase, saccharase, urease, and alkaline phosphatase activities and soil microbial C, N, P, and its stoichiometry were also higher after afforestation. Moreover, significant Pearson linear correlations between understory plants (coverage, evenness, diversity, and richness) and SR, HR, and AR were observed, with the strongest correlation observed between plant coverage and SR. This correlation largely depended on soil enzymes (i.e., catalase, saccharase, urease, and alkaline phosphatase), and soil microbial biomass C, N, and P contents and its stoichiometry, particularly urease activity and the MBC:MBP ratio. Therefore, we conclude that plant communities are drivers of soil respiration, and that changes in soil respiration are associated with shifts in soil enzyme activities and nutrient stoichiometry. Full article
(This article belongs to the Special Issue Afforestation and Reforestation: Drivers, Dynamics, and Impacts)
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Open AccessArticle Carbon Pools in a Hemiboreal Over-Mature Norway Spruce Stands
Forests 2018, 9(7), 435; https://doi.org/10.3390/f9070435
Received: 21 June 2018 / Revised: 9 July 2018 / Accepted: 19 July 2018 / Published: 20 July 2018
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Abstract
Old unmanaged forests are commonly assumed to be carbon neutral; however, there is still a lack of reference studies available to increase the recognition of carbon stock changes in these forests. Studies of old forest carbon storage from hemiboreal regions are very rare
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Old unmanaged forests are commonly assumed to be carbon neutral; however, there is still a lack of reference studies available to increase the recognition of carbon stock changes in these forests. Studies of old forest carbon storage from hemiboreal regions are very rare compared to temperate and boreal forests in Europe; therefore, the aim of this study was to quantify the carbon stock in hemiboreal over-mature (167–213 years) Norway spruce (Picea abies (L.) Karst.) stands. To explore the total ecosystem carbon pool, the carbon stock of tree biomass, deadwood, and soil in unmanaged (for at least the last 40 years) spruce stands was calculated and compared between different forest site types on dry, wet, and drained mineral soils. Total carbon stock of hemiboreal over-mature spruce stands ranged from 164.8 Mg C ha−1 to 386.7 Mg C ha−1, and 238.5 Mg C ha−1 on average, with no significant differences (p > 0.05) between the forest site types. The carbon stock of tree biomass was significantly affected by the basal area of the upper tree layer (p < 0.0001) and the interaction between the forest site type and proportion of spruce in the stand composition (p = 0.002). Tree biomass was the dominant carbon pool, followed by soil and deadwood in over-mature spruce stands. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Using a Marginal Value Approach to Integrate Ecological and Economic Objectives across the Minnesota Landscape
Forests 2018, 9(7), 434; https://doi.org/10.3390/f9070434
Received: 22 June 2018 / Revised: 14 July 2018 / Accepted: 17 July 2018 / Published: 19 July 2018
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Abstract
Forest management situations are intrinsically challenging due to the nature of being an interconnected and multi-faceted problem. Integrating ecological, social, and economic objectives is one of the biggest hurdles for forest planners. Often, decisions made with the interest of producing a specific ecosystem
[...] Read more.
Forest management situations are intrinsically challenging due to the nature of being an interconnected and multi-faceted problem. Integrating ecological, social, and economic objectives is one of the biggest hurdles for forest planners. Often, decisions made with the interest of producing a specific ecosystem service may affect the production of other forest ecosystem services. We present a forest management scheduling model that involves multiple ownerships and addresses the joint production of two ecosystem services: timber and upland hardwood old forest. We use a marginal value approach to evaluate old forest. We analyze the impacts of considering different management options, shapes and levels of marginal value functions for old forest, and potential benefits of rewarding the major forest land ownership groups to produce old forest. Results show the downward-sloping marginal value function as a compromise strategy and the benefits of applying it over approaches using either fixed values or targets for addressing ecosystem services. A decomposition model was useful for recognizing important stand-level detail. A broad landscape and multiple ownership approach helped identify interconnections between forest cover types and between landowner groups. Full article
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Open AccessArticle Evaluation of the Water-Storage Capacity of Bryophytes along an Altitudinal Gradient from Temperate Forests to the Alpine Zone
Forests 2018, 9(7), 433; https://doi.org/10.3390/f9070433
Received: 10 May 2018 / Revised: 13 July 2018 / Accepted: 16 July 2018 / Published: 18 July 2018
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Abstract
Forests play crucial roles in regulating the amount and timing of streamflow through the water storage function. Bryophytes contribute to this increase in water storage owing to their high water-holding capacity; however, they might be severely damaged by climate warming. This study examined
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Forests play crucial roles in regulating the amount and timing of streamflow through the water storage function. Bryophytes contribute to this increase in water storage owing to their high water-holding capacity; however, they might be severely damaged by climate warming. This study examined the water storage capacity (WSC) of bryophytes in forests in the mountainous areas of Japan. Sampling plots (100 m2) were established along two mountainous trails at 200-m altitude intervals. Bryophytes were sampled in these plots using 100-cm2 quadrats, and their WSC was evaluated according to the maximum amount of water retained in them (WSC-quadrat). The total amount of water in bryophytes within each plot (WSC-plot) was then calculated. The WSC-quadrat was affected by the forms of bryophyte communities (life forms) and their interactions, further influencing soil moisture. The WSC-quadrat did not show any significant trend with altitude, whereas, the highest WSC-plot values were obtained in subalpine forests. These changes to WSC-plot were explained by large differences in bryophyte cover with altitude. As the WSC controlled by the life forms might be vulnerable to climate warming, it can provide an early indicator of how bryophyte WCS and associated biological activities are influenced. Full article
(This article belongs to the Special Issue Forest Hydrology and Watershed)
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Open AccessArticle Detection of Coniferous Seedlings in UAV Imagery
Forests 2018, 9(7), 432; https://doi.org/10.3390/f9070432
Received: 26 June 2018 / Revised: 13 July 2018 / Accepted: 16 July 2018 / Published: 18 July 2018
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Abstract
Rapid assessment of forest regeneration using unmanned aerial vehicles (UAVs) is likely to decrease the cost of establishment surveys in a variety of resource industries. This research tests the feasibility of using UAVs to rapidly identify coniferous seedlings in replanted forest-harvest areas in
[...] Read more.
Rapid assessment of forest regeneration using unmanned aerial vehicles (UAVs) is likely to decrease the cost of establishment surveys in a variety of resource industries. This research tests the feasibility of using UAVs to rapidly identify coniferous seedlings in replanted forest-harvest areas in Alberta, Canada. In developing our protocols, we gave special consideration to creating a workflow that could perform in an operational context, avoiding comprehensive wall-to-wall surveys and complex photogrammetric processing in favor of an efficient sampling-based approach, consumer-grade cameras, and straightforward image handling. Using simple spectral decision rules from a red, green, and blue (RGB) camera, we documented a seedling detection rate of 75.8 % (n = 149), on the basis of independent test data. While moderate imbalances between the omission and commission errors suggest that our workflow has a tendency to underestimate the seedling density in a harvest block, the plot-level associations with ground surveys were very high (Pearson’s r = 0.98; n = 14). Our results were promising enough to suggest that UAVs can be used to detect coniferous seedlings in an operational capacity with standard RGB cameras alone, although our workflow relies on seasonal leaf-off windows where seedlings are visible and spectrally distinct from their surroundings. In addition, the differential errors between the pine seedlings and spruce seedlings suggest that operational workflows could benefit from multiple decision rules designed to handle diversity in species and other sources of spectral variability. Full article
(This article belongs to the Special Issue Forestry Applications of Unmanned Aerial Vehicles (UAVs))
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Open AccessArticle Impact of Non-Timber Forest Product Use on the Tree Community in North-Western Vietnam
Forests 2018, 9(7), 431; https://doi.org/10.3390/f9070431
Received: 18 May 2018 / Revised: 11 July 2018 / Accepted: 16 July 2018 / Published: 18 July 2018
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Abstract
Trees providing non-timber forest products (NTFPs) are valuable forest resources, and their management can support conservation objectives. We analyzed the abundance of tree species providing NTFPs, recognized by local H’mong people, in both the strictly protected core zone and the low-intensity forest use
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Trees providing non-timber forest products (NTFPs) are valuable forest resources, and their management can support conservation objectives. We analyzed the abundance of tree species providing NTFPs, recognized by local H’mong people, in both the strictly protected core zone and the low-intensity forest use buffer zone in north-western Vietnam. We identified 249 tree species, of which 48% were classified as NTFP species. The abundance of 35% of the NTFP tree species was significantly correlated with footpaths, indicating an influence of human activity. A multiple logistic regression model indicates that using NTFP trees for food, medicine, and root harvesting, increases the probability of an NTFP tree absence in the buffer zone. In contrast, the high density of species, and collections of fruit, leaf, and resin decrease the probability of an NTFP tree absence in the buffer zone. Further assessment with a logistic model indicated that NTFP use has lower impacts on the tree community than timber use. We think that the parameterized models will enable comparisons of different situations and forest types and be particularly helpful in evaluating potential changes in tree communities over time. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Variation in Carbon Fraction, Density, and Carbon Density in Conifer Tree Tissues
Forests 2018, 9(7), 430; https://doi.org/10.3390/f9070430
Received: 16 June 2018 / Revised: 9 July 2018 / Accepted: 13 July 2018 / Published: 18 July 2018
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Abstract
We analyzed variations in three tree properties: tissue density, carbon fraction, and carbon density within bole tissues of nine Californian conifer species. Model performance for all three tree properties was significantly improved with the addition of covariates related to crown characteristics and position
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We analyzed variations in three tree properties: tissue density, carbon fraction, and carbon density within bole tissues of nine Californian conifer species. Model performance for all three tree properties was significantly improved with the addition of covariates related to crown characteristics and position within the tree. This suggests that biomass and carbon mass estimates that rely on fixed wood density and carbon fraction may be inaccurate across tree sizes. We found a significant negative relationship between tissue density and carbon fraction within tree bole tissues, indicating that multiplying biomass by an average carbon fraction to obtain carbon mass is likely to lead to inaccurate estimates. Measured carbon fractions in tree tissues deviated from the widely used 0.5 value from a low of 1.4% to a high of 17.6%. Carbon fraction model parameters indicate the potential for an additional deviation from this 0.5 value of up to 2.7% due to the interaction between relative height and wood density. Applying measured carbon fractions to whole bole biomasses resulted in carbon mass estimates as much as 10.6% greater than estimates derived using the 0.5 value. We also found a significant, though modest, improvement in carbon fraction model estimates by assigning trees to groups based on tree bark characteristics. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Consumption Rates and Use Patterns of Firewood and Charcoal in Urban and Rural Communities in Yedashe Township, Myanmar
Forests 2018, 9(7), 429; https://doi.org/10.3390/f9070429
Received: 12 June 2018 / Revised: 13 July 2018 / Accepted: 16 July 2018 / Published: 17 July 2018
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Abstract
There is concern over the environmental impact of charcoal use for cooking in urban areas; however, studies have mainly been limited to Africa and South Asia. This investigation aimed to evaluate woodfuel consumption rates and patterns in an urban area in Yedashe Township,
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There is concern over the environmental impact of charcoal use for cooking in urban areas; however, studies have mainly been limited to Africa and South Asia. This investigation aimed to evaluate woodfuel consumption rates and patterns in an urban area in Yedashe Township, Myanmar and compared them with results from a rural area in the same township. From interviews with 66 urban households, it was evident that firewood and charcoal consumption rates in the urban area were about one-third and one-fourth, respectively, of those in the rural area. These low consumption rates were because of multiple-fuel use (mainly woodfuel and electricity) in the urban area in contrast to single-fuel use in the rural area. We estimated the forest area required to meet woodfuel demand of the whole township to be 3738 ha; that could decrease by almost 40% (1592 ha) if the single-fuel use in the rural area switched to the multiple-fuel methods used in the urban area. This study confirms that urbanization with an “energy stack” in multiple-fuel use, rather than an “energy ladder” from firewood to charcoal, could largely reduce the environmental impact on forests. Full article
(This article belongs to the Section Forest Economics and Human Dimensions)
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Open AccessArticle A Probabilistic Method Predicting Forest Fire Occurrence Combining Firebrands and the Weather-Fuel Complex in the Northern Part of the Daxinganling Region, China
Forests 2018, 9(7), 428; https://doi.org/10.3390/f9070428
Received: 16 June 2018 / Revised: 11 July 2018 / Accepted: 16 July 2018 / Published: 17 July 2018
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Abstract
The fire danger rating method currently used in the northern part of the Daxinganling Region with the most severe forest fires in China only uses weather variables without considering firebrands. The discrepancy between fire occurrence and fire risk by FFDWR (Forest Fire-Danger Weather
[...] Read more.
The fire danger rating method currently used in the northern part of the Daxinganling Region with the most severe forest fires in China only uses weather variables without considering firebrands. The discrepancy between fire occurrence and fire risk by FFDWR (Forest Fire-Danger Weather Rating, a method issued by the National Meteorological Bureau, that is used to predict forest fire probability through links between forest fire occurrence and weather variables) in the northern part is more obvious than that in the southern part. Great discrepancy has emerged between fire danger predicted by the method and actual fire occurrence in recent years since a strict firebrand prohibition policy has significantly reduced firebrands in the region. A probabilistic method predicting fire probability by introducing an Ignition Component (IC) in the National Fire Danger Rating System (NFDRS) adopted in the United States to depict effects of both firebrand and weather-fuel complex on fire occurrence is developed to solve the problem. The suitability and accuracy of the new method in the region were assessed. Results show that the method is suitable in the region. IC or the modified IC can be adopted to depict the effect of the weather-fuel complex on fire occurrence and to rate fire danger for periods with fewer firebrands. Fire risk classes and corresponding preparedness level can be determined from IC in the region. Methods of the same principle could be established to diminish similar discrepancy between actual fire occurrence and fire danger in other countries. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Composite Estimators for Growth Derived from Repeated Plot Measurements of Positively-Asymmetric Interval Lengths
Forests 2018, 9(7), 427; https://doi.org/10.3390/f9070427
Received: 5 June 2018 / Revised: 11 July 2018 / Accepted: 16 July 2018 / Published: 17 July 2018
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Abstract
The statistical properties of candidate methods to adjust for the bias in growth estimates obtained from observations on increasing interval lengths are compared and contrasted against a standard set of estimands. This standard set of estimands is offered here as a solution to
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The statistical properties of candidate methods to adjust for the bias in growth estimates obtained from observations on increasing interval lengths are compared and contrasted against a standard set of estimands. This standard set of estimands is offered here as a solution to a varying set of user expectations that can arise from the jargon surrounding a particular data aggregation procedure developed within the USDA’s Forest Inventory and Analysis Program, specifically the term “average annual” growth. The definition of a standard set of estimands also allows estimators to be defined and the statistical properties of those estimators to be evaluated. The estimators are evaluated in a simulation for their effectiveness in the presence of a simple distribution of positively-asymmetric measurement intervals, such as what might arise subsequent to a reduction in budget being applied to a national forest inventory. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessFeature PaperReview Water Balance of Mediterranean Quercus ilex L. and Pinus halepensis Mill. Forests in Semiarid Climates: A Review in A Climate Change Context
Forests 2018, 9(7), 426; https://doi.org/10.3390/f9070426
Received: 5 June 2018 / Revised: 11 July 2018 / Accepted: 12 July 2018 / Published: 16 July 2018
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Abstract
Forests provide many environmental services, especially those related to the water cycle. In semiarid areas where water is a limiting factor for ecosystem functioning, forested areas can have a strong impact on ground water recharge. In these areas, proper knowledge of forests’ water
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Forests provide many environmental services, especially those related to the water cycle. In semiarid areas where water is a limiting factor for ecosystem functioning, forested areas can have a strong impact on ground water recharge. In these areas, proper knowledge of forests’ water balance is necessary to promote management practices that may ensure ecosystem properties and environmental services like water or carbon fixation. In this article, we review several ecohydrology topics within the framework of Mediterranean water-limited environments in two representative ecosystems: Kermes oak (Quercus ilex L.) and Aleppo pine (Pinus halepensis Mill.) forests. Both are the commonest species in countries that surround the Western Mediterranean Basin. We analysed the Blue and Green water components, i.e., green water is the water demand of forests, represented by evapotranspiration and interception; while blue water is the part of the balance involving runoff and deep percolation, which can be regarded as water directly usable by society. In general, different studies conducted in Mediterranean areas have pointed out that the water balances of Q. ilex and P. halepensis forests have low values for the Blue to Green water (B/G) ratios. Adaptive forest management like forest thinning can compensate for these ratios. Thinning has demonstrated to reduce losses by interception, but at same time, it can also increase individual tree transpiration and evaporation rates. However, these practices lead to higher B/G ratios when considering the whole stand. In future global change scenarios, in which drought conditions are expected to intensify, management practices can improve the water balance in these ecosystems by minimizing the risk of plant mortality and species replacement due to intense competence by water resources. Full article
(This article belongs to the Special Issue Water and Gas Exchanges in Forests)
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Open AccessArticle Forest Management Certification in Romania: Motivations and Perceptions
Forests 2018, 9(7), 425; https://doi.org/10.3390/f9070425
Received: 31 May 2018 / Revised: 27 June 2018 / Accepted: 13 July 2018 / Published: 15 July 2018
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Abstract
Forestland privatization and transition to a market economy triggered important changes in the Romanian forest sector, imposing challenges for forest management structures. Voluntary forest management certification has been considered a possible solution; therefore, the certified forest area has increased rapidly regardless of the
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Forestland privatization and transition to a market economy triggered important changes in the Romanian forest sector, imposing challenges for forest management structures. Voluntary forest management certification has been considered a possible solution; therefore, the certified forest area has increased rapidly regardless of the land owner. The purpose of this study is to provide an insight into the certification process. It presents the result of a survey applied to 417 forest management structures in Romania, which was intended to identify the perception of their managers regarding the reasons to adopt certification, the changes determined by the certification, the problems during the process, and the benefits. The study reveals the difference in perception among different types of forest management structures. Non-state management structures voluntarily adopted FSC certification, mainly aiming to obtain economic advantages. Most of the respondents indicated important changes in the consultation with stakeholders including local communities, transparency and clear records, the use of chemicals, and biodiversity protection. Although the FSC certification was not perceived as solving issues like illegal logging, there is a general perception that it improved forest management. The study concludes that the FSC certification proves the willingness of the Romanian forest management sector to cope with the market and trends and clarify its position in society. Full article
(This article belongs to the Special Issue Policies Affecting Development and Forest Conservation)
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Open AccessArticle Exploring the Use of Harvesters in Large-Diameter Hardwood-Dominated Stands
Forests 2018, 9(7), 424; https://doi.org/10.3390/f9070424
Received: 21 June 2018 / Revised: 6 July 2018 / Accepted: 11 July 2018 / Published: 15 July 2018
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Abstract
The use of fully-mechanized operations, normally targeted at coniferous species, has also been on the rise in mixed-species and continuous-cover forests comprised of a strong share of deciduous species. With special form characteristics (complex crowns, large-diameter branches, forks and sweeps, high wood density,
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The use of fully-mechanized operations, normally targeted at coniferous species, has also been on the rise in mixed-species and continuous-cover forests comprised of a strong share of deciduous species. With special form characteristics (complex crowns, large-diameter branches, forks and sweeps, high wood density, etc.), deciduous trees can lead to wide-ranging harvesting productivities, often divergent from those originally derived from coniferous species. Due to the importance and growing interest in mechanizing operations in close-to-nature mixedwood and deciduous stands, obtaining insight on harvesting productivity in large-diameter deciduous trees was of interest. This study located in Bavaria, Germany, monitored four harvesters (two wheeled and two tracked machines) operated in four distinct harvest blocks (case studies), all of which had a high percentage of large-diameter European beech and oak trees. Harvesting productivity and volume recovery was assessed and quantified. Based on the field inventory of European beech and oak trees and continuous time-and-motion study, average harvesting productivity ranged from 29 to 43 m3/PMH0 (productive machine hours without delay), whereas volume recovery fluctuated between 73% and 85% for trees that were completely felled and processed by machines. Because of the rather limited sample size and the variable conditions between case studies, results should only be used as general orientation on the performance of the tested machines and additional research is suggested to further understand the influence of tree form characteristics on impediments to mechanized processing. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Fire Season, Overstory Density and Groundcover Composition Affect Understory Hardwood Sprout Demography in Longleaf Pine Woodlands
Forests 2018, 9(7), 423; https://doi.org/10.3390/f9070423
Received: 10 May 2018 / Revised: 13 June 2018 / Accepted: 13 July 2018 / Published: 14 July 2018
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Abstract
Seasonal timing of prescribed fire and alterations to the structure and composition of fuels in savannas and woodlands can release understory hardwoods, potentially resulting in a global increase of closed-canopy forest and a loss of biodiversity. We hypothesized that growing-season fire, high overstory
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Seasonal timing of prescribed fire and alterations to the structure and composition of fuels in savannas and woodlands can release understory hardwoods, potentially resulting in a global increase of closed-canopy forest and a loss of biodiversity. We hypothesized that growing-season fire, high overstory density, and wiregrass presence in longleaf pine woodlands would reduce the number and stature of understory hardwoods, and that because evergreen hardwoods retain live leaves, dormant-season fire would reduce performance and survival of evergreen more than deciduous hardwoods. Understory hardwood survival and height were monitored over seven years in longleaf pine woodlands in southwest Georgia with a range of overstory density, groundcover composition, and season of application of prescribed fire. Hardwood stem survival decreased with increasing overstory density, and deciduous hardwoods were more abundant in the absence of wiregrass. Contrary to expectations, evergreen hardwood growth increased following dormant-season fire. Differences in hardwood stem survival and height suggest that low fire intensity in areas with low overstory density increase the risk that hardwoods will grow out of the understory. These results indicate a need for focused research into the effects of groundcover composition on hardwood stem dynamics and emphasize that adequate overstory density is important in longleaf ecosystem management. Full article
(This article belongs to the Special Issue Longleaf Pine)
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Open AccessFeature PaperArticle Toward Sustainable Cultivation of Pinus occidentalis Swartz in Haiti: Effects of Alternative Growing Media and Containers on Seedling Growth and Foliar Chemistry
Forests 2018, 9(7), 422; https://doi.org/10.3390/f9070422
Received: 8 June 2018 / Revised: 10 July 2018 / Accepted: 10 July 2018 / Published: 13 July 2018
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Abstract
Haiti has suffered great losses from deforestation, with little forest cover remaining today. Current reforestation efforts focus on seedling quantity rather than quality. This study examined limitations to the production of high-quality seedlings of the endemic Hispaniolan pine (Pinus occidentalis Swartz). Recognizing
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Haiti has suffered great losses from deforestation, with little forest cover remaining today. Current reforestation efforts focus on seedling quantity rather than quality. This study examined limitations to the production of high-quality seedlings of the endemic Hispaniolan pine (Pinus occidentalis Swartz). Recognizing the importance of applying sustainable development principles to pine forest restoration, the effects of growing media and container types on seedling growth were evaluated with the goal of developing a propagation protocol to produce high-quality seedlings using economically feasible nursery practices. With regard to growing media, seedlings grew best in compost-based media amended with sand. Topsoil, widely used in nurseries throughout Haiti, produced the smallest seedlings overall. Despite a low water holding capacity and limited manganese, compost-based media provided adequate levels of essential mineral nutrients (particularly nitrogen), which allowed for sufficient seedling nutrition. Seedling shoot and root growth, as well as the ratio of shoot biomass to root biomass, were greater in polybags relative to D40s. Results indicate that economically feasible improvements to existing nursery practices in Haiti can improve the early growth rates of P. occidentalis seedlings. Full article
(This article belongs to the Special Issue Ecological Management of Pine Forests)
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Open AccessArticle Application of Trichoderma spp. Complex and Biofumigation to Control Damping-Off of Pinus radiata D. Don Caused by Fusarium circinatum Nirenberg and O’Donnell
Forests 2018, 9(7), 421; https://doi.org/10.3390/f9070421
Received: 1 June 2018 / Revised: 3 July 2018 / Accepted: 11 July 2018 / Published: 12 July 2018
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Abstract
The damping-off of Pinus radiata D.Don by Fusarium circinatum Nirenberg and O’Donnell represents a limiting factor in nursery production, while seed contamination with the pathogen is one of the main pathways of the pathogen movement between areas. Chemical and physical treatments have been
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The damping-off of Pinus radiata D.Don by Fusarium circinatum Nirenberg and O’Donnell represents a limiting factor in nursery production, while seed contamination with the pathogen is one of the main pathways of the pathogen movement between areas. Chemical and physical treatments have been applied with encouraging results and some limitations. In the present study, biocontrol of damping-off by F. circinatum is proposed with Trichoderma spp. complex showing complementary antagonism and biofumigation with commercial Brassica carinata A. Braun pellets with biocidal effect. Experiments were conducted in vitro and in vivo using batches of P. radiata seeds and two F. circinatum isolates. Results were highly positive, showing an excellent efficacy of a combination of Trichoderma spp. in a single preparation to reduce significantly the mortality of P. radiata seedlings in seeds bed experiment. Biofumigation with B. carinata pellets also showed efficacy in controlling the F. circinatum inoculum and reducing seed mortality in inoculated seed batches although showing some phytotoxic effect. Full article
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Open AccessArticle Responses of Soil Labile Organic Carbon to a Simulated Hurricane Disturbance in a Tropical Wet Forest
Forests 2018, 9(7), 420; https://doi.org/10.3390/f9070420
Received: 12 June 2018 / Revised: 7 July 2018 / Accepted: 9 July 2018 / Published: 12 July 2018
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Abstract
Hurricanes are an important disturbance in the tropics that can alter forest ecosystem properties and processes. To understand the immediate influence of hurricane disturbance on carbon cycling, we examined soil labile organic carbon (LOC) in a Canopy Trimming Experiment (CTE) located in the
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Hurricanes are an important disturbance in the tropics that can alter forest ecosystem properties and processes. To understand the immediate influence of hurricane disturbance on carbon cycling, we examined soil labile organic carbon (LOC) in a Canopy Trimming Experiment (CTE) located in the Luquillo Experimental Forest of Puerto Rico. We trimmed tree canopy and deposited debris (CTDD) on the forest ground of the treatment plots in December 2014, and collected floor mass samples and 0–10 cm soil samples three weeks before the treatment, as well as at scheduled intervals for 120 weeks after the treatment. Within the first week following the CTDD treatment, the mean soil microbial biomass carbon (MBC) and soil LOC in the CTDD plots were significantly greater than in the control plots (soil MBC: 2.56 g/kg versus 1.98 g/kg, soil LOC: 9.16 g/kg versus 6.44 g/kg, respectively), and the mean turnover rates of soil LOC in the CTDD plots were significantly faster than in the control plots. The measured indices fluctuated temporally more in the CTDD plots than in the control plots, especially between the 12th and 84th week after the CTDD treatment. The treatment effect on soil LOC and its turnover rate gradually disappeared after the 84th week following the treatment, while higher levels of soil MBC in the CTDD plots than in the control plots remained high, even at the 120th week. Our data suggest that hurricane disturbance can accelerate the cycling of soil LOC on a short temporal scale of less than two years, but might have a longer lasting effect on soil MBC in a tropical wet forest. Full article
(This article belongs to the Special Issue Forest Responses to Large-Scale Wind Disturbance)
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Open AccessArticle Simulating Climate Change Impacts on Hybrid-Poplar and Black Locust Short Rotation Coppices
Forests 2018, 9(7), 419; https://doi.org/10.3390/f9070419
Received: 20 June 2018 / Revised: 8 July 2018 / Accepted: 9 July 2018 / Published: 12 July 2018
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Abstract
In Brandenburg, north-eastern Germany, climate change is associated with increasing annual temperatures and decreasing summer precipitation. Appraising short rotation coppices (SRCs), given their long-time planning horizon demands for systematic assessments of woody biomass production under a considerable spectrum of climate change prospects. This
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In Brandenburg, north-eastern Germany, climate change is associated with increasing annual temperatures and decreasing summer precipitation. Appraising short rotation coppices (SRCs), given their long-time planning horizon demands for systematic assessments of woody biomass production under a considerable spectrum of climate change prospects. This paper investigates the prospective growth sensitivity of poplar and black locust SRCs, established in Brandenburg to a variety of weather conditions and long-term climate change, from 2015 to 2054, by a combined experimental and simulation study. The analysis employed (i) a biophysical, process-based model to simulate the daily tree growth and (ii) 100 realisations of the statistical regional climate model STAR 2K. In the last growing period, the simulations showed that the assumed climate change could lead to a decrease in the woody biomass of about 5 Mg ha−1 (18%) for poplar and a decrease of about 1.7 Mg ha−1 (11%) for black locust trees with respect to the median observed in the reference period. The findings corroborate the potential tree growth vulnerability to prospective climatic changes, particularly to changes in water availability and underline the importance of coping management strategies in SRCs for forthcoming risk assessments and adaptation scenarios. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle High Throughput Screening of Elite Loblolly Pine Families for Chemical and Bioenergy Traits with Near Infrared Spectroscopy
Forests 2018, 9(7), 418; https://doi.org/10.3390/f9070418
Received: 30 May 2018 / Revised: 7 July 2018 / Accepted: 9 July 2018 / Published: 12 July 2018
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Abstract
Pinus taeda L. (loblolly pine) dominates 13.4 million ha of US southeastern forests and contributes over $30 billion to the economy of the region. The species will also form an important component of the renewable energy portfolio as the United States seeks national
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Pinus taeda L. (loblolly pine) dominates 13.4 million ha of US southeastern forests and contributes over $30 billion to the economy of the region. The species will also form an important component of the renewable energy portfolio as the United States seeks national and energy security as well as environmental sustainability. This study employed NIR-based chemometric models as a high throughput screening tool to estimate the chemical traits and bioenergy potential of 351 standing loblolly pine trees representing 14 elite genetic families planted on two forest sites. The genotype of loblolly pine families affected the chemical, proximate and energy traits studied. With a range of 36.7% to 42.0%, the largest genetic variation (p-value < 0.0001) was detected in the cellulose content. Furthermore, although family by site interactions were significant for all traits, cellulose was the most stable across the two sites. Considering that cellulose content has strong correlations with other properties, selecting and breeding for cellulose could generate some gains. Full article
(This article belongs to the Special Issue Forest Bioenergy and Bioproducts)
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Open AccessArticle Synergies and Trade-Offs in the Production of NWFPs Predicted in Boreal Forests
Forests 2018, 9(7), 417; https://doi.org/10.3390/f9070417
Received: 4 June 2018 / Revised: 6 July 2018 / Accepted: 9 July 2018 / Published: 11 July 2018
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Abstract
The global growth of the consumption of non-wood forest products (NWFPs) is evident due to the current trends in lifestyle and consumption. Alongside the increased popularity and commercial use of NWFPs, their yields are also more often taken into account in forest management
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The global growth of the consumption of non-wood forest products (NWFPs) is evident due to the current trends in lifestyle and consumption. Alongside the increased popularity and commercial use of NWFPs, their yields are also more often taken into account in forest management planning. Empirical yield models recently developed for different NWFPs enable forest managers to include their predicted yields in multi-objective optimization. However, knowledge on the synergies and trade-offs between timber production and different NWFPs is scanty. In this study, we analyzed these relationships through correlation matrices and production possibility frontiers in two case study forest holdings from Finland. A large number of Pareto optimal forest holding level plans were produced by multi-objective optimization and used to analyze trade-offs and synergies. Empirical yield models for 12 NWFPs, representing different berries, mushrooms, and tree-based products, were utilized in the analyses. The results revealed synergies and possibilities for joint-production for NWFPs, but also trade-offs between NWFPs and timber production. NWFPs often had a negative correlation with cutting removals, with the only exception being cowberry. Despite the overall negative correlation, the maximum yields of NWFPs called for some cuttings. Negative correlations with the net present value of timber production were weaker. The results are valuable when the aim is to diversify the use of boreal forests and open avenues for truly multi-objective decision support services to facilitate the decision making of forest owners. Full article
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Open AccessArticle Contrasting Patterns of Tree Growth of Mediterranean Pine Species in the Iberian Peninsula
Forests 2018, 9(7), 416; https://doi.org/10.3390/f9070416
Received: 6 June 2018 / Revised: 9 July 2018 / Accepted: 10 July 2018 / Published: 11 July 2018
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Abstract
Wood formation is the primary biological process through which carbon is durably sequestered in woody plants, and is thus a major contributor to mitigate climate change. We analyzed the tree growth patterns of four conifer species across the Iberian Peninsula (IP) based on
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Wood formation is the primary biological process through which carbon is durably sequestered in woody plants, and is thus a major contributor to mitigate climate change. We analyzed the tree growth patterns of four conifer species across the Iberian Peninsula (IP) based on a dense dendrochronological network (179 sites) combined with a high resolution climate dataset. Generalized linear-mixed models were used to predict the potential tree growth of different pine species under different climate conditions considering different age classes. We found a strong age dependency of tree growth, significant variations across the climate gradients, and a significant interaction of both age and climate effects on the four species considered. Overall, Pinus halepensis was the species with the highest climate sensitivity and the highest growth rates in all age classes and across its distribution area. Due to its stronger plastic character and its potential adaptability, Pinus halepensis was demonstrated to be the most suitable species in terms of tree growth and potentiality to enhance carbon sequestration in the IP. Since its potential distribution largely exceeds its actual distribution, P. halepensis arises as a key species to cope with future climate conditions and to keep fixing carbon regardless of the climatic circumstances. Full article
(This article belongs to the Special Issue Water and Gas Exchanges in Forests)
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Open AccessReview Annotated Bibliography of the Global Literature on the Secondary Transportation of Raw and Comminuted Forest Products (2000–2015)
Forests 2018, 9(7), 415; https://doi.org/10.3390/f9070415
Received: 10 June 2018 / Revised: 2 July 2018 / Accepted: 9 July 2018 / Published: 10 July 2018
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Abstract
Secondary transportation of raw and comminuted forest products is a major component in forest harvesting operations in terms of economics, public perception, and safety. Consequently, there is a substantial amount of literature on this topic. The existing literature has dealt with many of
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Secondary transportation of raw and comminuted forest products is a major component in forest harvesting operations in terms of economics, public perception, and safety. Consequently, there is a substantial amount of literature on this topic. The existing literature has dealt with many of the technical aspects of transportation with a majority of them focusing on improving supply chain issues; however, there are only few specific to secondary transportation issues in general. This annotated bibliography will help practitioners, researchers, and stakeholders gain a better understanding of the existing literature from 2000 to 2015. To this end, we began by classifying the selected literature into six themes: cost, roads and routes, trucking, efficiency and safety, other modes of transportation, and supply chain and optimization. Woody biomass for bioenergy production was the most researched forest product with respect to transportation. About one-third of the articles were presented in the context of supply chain modeling and optimization. More than half of the studies originated from Europe while the United States had the most publications for any given country. Most articles (16) were published in 2013. Biomass and Bioenergy published the highest number of articles (29) during the timeframe. Full article
(This article belongs to the Special Issue Forest Operations: Planning, Innovation and Sustainability)
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Open AccessArticle Recent Drought-Induced Vitality Decline of Black Pine (Pinus nigra Arn.) in South-West Hungary—Is This Drought-Resistant Species under Threat by Climate Change?
Forests 2018, 9(7), 414; https://doi.org/10.3390/f9070414
Received: 12 June 2018 / Revised: 29 June 2018 / Accepted: 3 July 2018 / Published: 10 July 2018
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Abstract
This paper analyses the recent recurring dieback and growth decline of Black pine (P. nigra Arn. var austriaca) in the Keszthely mountains of south-west Hungary, and their relations to water deficits due to droughts. These relations were studied in five stands
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This paper analyses the recent recurring dieback and growth decline of Black pine (P. nigra Arn. var austriaca) in the Keszthely mountains of south-west Hungary, and their relations to water deficits due to droughts. These relations were studied in five stands with low soil water storage capacity for the period 1981–2016. The vitality was assessed using 60 tree-ring samples and changes in remotely sensed vegetation activity indices, i.e., the normalized difference vegetation index (NDVI) and the normalized difference infrared index (NDII). Water deficit was estimated by using meteorological drought indices such the standardized precipitation–evapotranspiration index (SPEI) and the forestry aridity index (FAI), as well as the relative extractable water (REW), calculated by the Brook90 hydrological model. Results revealed a strong dependency of annual tree ring width on the amount of water deficit as measured by all the above estimators, with the highest correlation shown by the summer REW. Droughts also showed a long-term superimposed effect on tree growth. NDII seemed to be more sensitive to drought conditions than NDVI. The robust dependency of tree growth on the summer water availability combined with the projected increasing aridity might lead to decreasing growth of Black pine in Hungary towards the end of the century. We thus argue that the suggestion by several papers that Black pine can be a possible substitute species in the Alpine and Mediterranean region in the future should be revisited. Full article
(This article belongs to the Special Issue Remotely Sensing of Drought-Induced Forest Change and Recovery)
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Open AccessArticle Effects of Biochar and Sludge on Carbon Storage of Urban Green Roofs
Forests 2018, 9(7), 413; https://doi.org/10.3390/f9070413
Received: 10 May 2018 / Revised: 3 July 2018 / Accepted: 4 July 2018 / Published: 10 July 2018
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Abstract
Green roofs can improve urban ecological conditions by mitigating the heat island effect and absorbing harmful gases. Soil additives can improve roof soil properties and promote the stability of the urban ecosystem. As soil additives, biochar and sludge are widely used in the
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Green roofs can improve urban ecological conditions by mitigating the heat island effect and absorbing harmful gases. Soil additives can improve roof soil properties and promote the stability of the urban ecosystem. As soil additives, biochar and sludge are widely used in the ground, but their application on roofs is still scarce. This study examined the carbon storage potential of green roofs amended with sludge and biochar. The roof soil was composed of soil and varying proportions of the additives (0%, 5%, 10%, 15%, and 20%, v/v); Sedum lineare was then planted. The carbon contents of the soils and plants were measured for one year. The influence of biochar or sludge on the carbon content of the roof soil and the factors affecting the roof carbon storage potential were analyzed. The results showed that the carbon storage potential of a biochar green roof (9.3 kg C m−2) was significantly higher than that of a sludge green roof (7.9 kg C m−2). Biochar increased the carbon content of the green roof by improving the physical properties of the roof soil and promoting plant growth, whereas sludge increased the carbon content of the green roof by improving the chemical properties of the roof soil. Moreover, biochar could not only store large amounts of stable carbon, but also reduce the weight of the green roof, improve soil moisture, and provide a resourceful utilization of municipal sludge. Thus, biochar can be considered a material for promoting carbon storage on green roofs. Full article
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Open AccessArticle Different Influences of Vegetation Greening on Regional Water-Energy Balance under Different Climatic Conditions
Forests 2018, 9(7), 412; https://doi.org/10.3390/f9070412
Received: 4 June 2018 / Revised: 4 July 2018 / Accepted: 5 July 2018 / Published: 9 July 2018
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Abstract
Vegetation serves as a key element in the land-atmospheric system, and changes in vegetation can impact the regional water-energy balance via several biophysical processes. This study proposes a new water-energy balance index that estimates the available-water-to-available-energy ratio (WER) by improving upon the Budyko
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Vegetation serves as a key element in the land-atmospheric system, and changes in vegetation can impact the regional water-energy balance via several biophysical processes. This study proposes a new water-energy balance index that estimates the available-water-to-available-energy ratio (WER) by improving upon the Budyko framework, which evaluates climate variation and vegetation change. Moreover, the impact of vegetation greening on WER is quantified in 34 catchments under different climatic conditions. The results show that the normalized difference vegetation index (NDVI) increased at all the catchments, which indicates that there was a vegetation greening trend in the study area. There are negative relationships between the NDVI and runoff at both water-limited and energy-limited catchments, which demonstrates that both types of catchments became drier due to vegetation greening. Four numerical experiments were executed to quantify the contribution of vegetation greening and climate variations to WER changes. The results show that the calculated WER trends by numerical tests fit well with the observed WER trends (R2 = 0.96). Vegetation greening has positive influences on WER changes under energy-limited conditions, which indicates that residual energy decreases faster than water availability, resulting in less energy for sensible heat, i.e., a cooling effect. Nevertheless, vegetation greening has negative influences on WER under water-limited conditions, which indicates that water availability decreases faster than residual energy, resulting in more energy for sensible heat. Notably, the WER decrease in water-limited catchments is dominated by potential evapotranspiration and NDVI variation, whereas the WER change in energy-limited catchments is dominated by climate variation. This study provides a comprehensive understanding of the relationships among water, energy and vegetation greening under different climatic conditions, which is important for land-atmosphere-vegetation modeling and designing strategies for ecological conservation and local water resource management. Full article
(This article belongs to the Special Issue Afforestation and Reforestation: Drivers, Dynamics, and Impacts)
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