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Forests, Volume 10, Issue 2 (February 2019)

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Cover Story (view full-size image) Natural forests that have not been disturbed for many decades are called old-growth forest (OGF.) [...] Read more.
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Open AccessArticle Thermal Insulating and Mechanical Properties of Cellulose Nanofibrils Modified Polyurethane Foam Composite as Structural Insulated Material
Forests 2019, 10(2), 200; https://doi.org/10.3390/f10020200
Received: 3 February 2019 / Revised: 19 February 2019 / Accepted: 19 February 2019 / Published: 25 February 2019
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Abstract
Cellulose nanofibrils (CNF) modified polyurethane foam (PUF) has great potential as a structural insulated material in wood construction industry. In this study, PUF modified with spray-dried CNF was fabricated and the physical and mechanical performance were studied. Results showed that CNF had an [...] Read more.
Cellulose nanofibrils (CNF) modified polyurethane foam (PUF) has great potential as a structural insulated material in wood construction industry. In this study, PUF modified with spray-dried CNF was fabricated and the physical and mechanical performance were studied. Results showed that CNF had an impact on the foam microstructure by increasing the precursor viscosity and imposing resistant strength upon foaming. In addition, the intrinsic high mechanical strength of CNF imparted an extra resistant force against cells expansion during the foaming process and formed smaller cells which reduced the chance of creating defective cells. The mechanical performance of the foam composite was significantly improved by introducing CNF into the PUF matrix. Compared with the PUF control, the specific bending strength, specific tensile strength, and specific compression strength increased up to three-fold for the CNF modified PUF. The thermal conductivity of PUF composite was mainly influenced by the closed cell size. The introduction of CNF improved thermal insulating performance, with a decreased thermal conductivity from 0.0439 W/mK to 0.02724 W/mK. Full article
(This article belongs to the Special Issue Wood Productions and Renewable Materials)
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Open AccessArticle The Impact of Anatomical Characteristics on the Structural Integrity of Wood
Forests 2019, 10(2), 199; https://doi.org/10.3390/f10020199
Received: 8 February 2019 / Revised: 19 February 2019 / Accepted: 21 February 2019 / Published: 24 February 2019
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Abstract
The structural integrity of wood is closely related to its brittleness and thus to its suitability for numerous applications where dynamic loads, wear and abrasion occur. The structural integrity of wood is only vaguely correlated with its density, but affected by different chemical, [...] Read more.
The structural integrity of wood is closely related to its brittleness and thus to its suitability for numerous applications where dynamic loads, wear and abrasion occur. The structural integrity of wood is only vaguely correlated with its density, but affected by different chemical, physico-structural and anatomical characteristics, which are difficult to encompass as a whole. This study aimed to analyze the results from High-Energy Multiple Impact (HEMI) tests of a wide range of softwood and hardwood species with an average oven-dry wood density in a range between 0.25 and 0.99 g/cm³ and multifaceted anatomical features. Therefore, small clear specimens from a total of 40 different soft- and hardwood species were crushed in a heavy vibratory ball mill. The obtained particles were fractionated and used to calculate the ‘Resistance to Impact Milling (RIM)’ as a measure of the wood structural integrity. The differences in structural integrity and thus in brittleness were predominantly affected by anatomical characteristics. The size, density and distribution of vessels as well as the ray density of wood were found to have a significant impact on the structural integrity of hardwoods. The structural integrity of softwood was rather affected by the number of growth ring borders and the occurrence of resin canals. The density affected the Resistance to Impact Milling (RIM) of neither the softwoods nor the hardwoods. Full article
(This article belongs to the Special Issue Wood Properties and Processing)
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Open AccessArticle Modelling the Incursion and Spread of a Forestry Pest: Case Study of Monochamus alternatus Hope (Coleoptera: Cerambycidae) in Victoria
Forests 2019, 10(2), 198; https://doi.org/10.3390/f10020198
Received: 22 January 2019 / Revised: 15 February 2019 / Accepted: 20 February 2019 / Published: 22 February 2019
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Abstract
Effective and efficient systems for surveillance, eradication, containment and management of biosecurity threats require methods to predict the establishment, population growth and spread of organisms that pose a potential biosecurity risk. To support Victorian forest biosecurity operations, Agriculture Victoria has developed a landscape-scale, [...] Read more.
Effective and efficient systems for surveillance, eradication, containment and management of biosecurity threats require methods to predict the establishment, population growth and spread of organisms that pose a potential biosecurity risk. To support Victorian forest biosecurity operations, Agriculture Victoria has developed a landscape-scale, spatially explicit, spatio-temporal population growth and dispersal model of a generic pest pine beetle. The model can be used to simulate the incursion of a forestry pest from a nominated location(s), such as an importation business site (approved arrangement, AA), into the surrounding environment. The model provides both illustrative and quantitative data on population dynamics and spread of a forestry pest species. Flexibility built into the model design enables a range of spatial extents to be modelled, from user-defined study areas to the Victoria-wide area. The spatial resolution of the model (size of grid cells) can be altered from 100 m to greater than 1 km. The model allows core parameters to be altered by the user, enabling the spread of a variety of windborne insect species and pathogens to be investigated. We verified the model and its parameters by simulating and comparing the outputs with the 1999/2000 Melbourne incursion, but no establishment of a forestry pest beetle was believed to be Monochamus alternatus Hope (Coleoptera: Cerambycidae). The model accurately predicts the distance and direction of the historic incursion, and the subsequent failure to establish is due to low overall population density of the pest species. Full article
(This article belongs to the Special Issue Exotic Forest Pest and Pathogen Risks)
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Open AccessArticle Biomass Accumulation and Carbon Sequestration in an Age-Sequence of Mongolian Pine Plantations in Horqin Sandy Land, China
Forests 2019, 10(2), 197; https://doi.org/10.3390/f10020197
Received: 24 January 2019 / Revised: 13 February 2019 / Accepted: 20 February 2019 / Published: 22 February 2019
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Abstract
The Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) was first introduced to the southeastern Horqin sandy land in the mid-1950s. Since then, it has been widely planted and has become the most important conifer species in Northern China, providing significant ecological, [...] Read more.
The Mongolian pine (Pinus sylvestris L. var. mongolica Litv.) was first introduced to the southeastern Horqin sandy land in the mid-1950s. Since then, it has been widely planted and has become the most important conifer species in Northern China, providing significant ecological, economic and social benefits. However, its function in sequestering carbon at different developmental stages has been little studied. In this study, twenty plots inventory and destructive sampling of eight trees were conducted in 12-, 19-, 34-, 48- and 58-year-old Mongolian pine stands of China. Allometric biomass equations (ABEs) for tree components were established and used to determine the magnitude and distribution of tree biomass and carbon density. The carbon density of the understory, forest floor and soil was also determined. The ABEs with age as the second variable could simply and accurately determine the biomass of plantation tree branches, foliage and fruit, which were considerably influenced by age. With increasing stand age, the proportion of stem biomass to total tree biomass increased from 22.2% in the 12-year-old stand to 54.2% in the 58-year-old stand, and the proportion of understory biomass to total ecosystem biomass decreased, with values of 7.5%, 4.6%, 4.4%, 4.1% and 3.0% in the five stands. The biomass of the forest floor was 0.00, 1.12, 2.04, 6.69 and 3.65 Mg ha−1 in the five stands. The ecosystem carbon density was 40.2, 73.4, 92.9, 89.9 and 87.3 Mg ha−1 in the 12-, 19-, 34-, 48-, and 58-year-old stands, in which soil carbon density accounted for the largest proportion, with values of 67.4%, 76.8%, 73.2%, 63.4%, and 57.7% respectively. The Mongolian pine had the potential for carbon sequestration during its development, especially in the early stages, however, in the later growth stage, the ecosystem carbon density decreased slightly. Full article
(This article belongs to the Special Issue Forest Stand Management and Biomass Growth)
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Open AccessArticle The Cumulative Effects of Forest Disturbance and Climate Variability on Streamflow in the Deadman River Watershed
Forests 2019, 10(2), 196; https://doi.org/10.3390/f10020196
Received: 11 January 2019 / Revised: 13 February 2019 / Accepted: 20 February 2019 / Published: 22 February 2019
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Abstract
Climatic variability and cumulative forest cover change are the two dominant factors affecting hydrological variability in forested watersheds. Separating the relative effects of each factor on streamflow is gaining increasing attention. This study adds to the body of literature by quantifying the relative [...] Read more.
Climatic variability and cumulative forest cover change are the two dominant factors affecting hydrological variability in forested watersheds. Separating the relative effects of each factor on streamflow is gaining increasing attention. This study adds to the body of literature by quantifying the relative contributions of those two drivers to the changes in annual mean flow, low flow, and high flow in a large forested snow dominated watershed, the Deadman River watershed (878 km2) in the Southern Interior of British Columbia, Canada. Over the study period of 1962 to 2012, the cumulative effects of forest disturbance significantly affected the annual mean streamflow. The effects became statistically significant in 1989 at the cumulative forest disturbance level of 12.4% of the watershed area. The modified double mass curve and sensitivity-based methods consistently revealed that forest disturbance and climate variability both increased annual mean streamflow during the disturbance period (1989–2012), with an average increment of 14 mm and 6 mm, respectively. The paired-year approach was used to further investigate the relative contributions to low and high flows. Our analysis showed that low and high flow increased significantly by 19% and 58%, respectively over the disturbance period (p < 0.05). We conclude that forest disturbance and climate variability have significantly increased annual mean flow, low flow and high flow over the last 50 years in a cumulative and additive manner in the Deadman River watershed. Full article
(This article belongs to the Special Issue Forest Hydrology and Watershed)
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Open AccessArticle Spatial Autocorrelation Analysis of Multi-Scale Damaged Vegetation in the Wenchuan Earthquake-Affected Area, Southwest China
Forests 2019, 10(2), 195; https://doi.org/10.3390/f10020195
Received: 17 January 2019 / Revised: 14 February 2019 / Accepted: 19 February 2019 / Published: 21 February 2019
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Abstract
Major earthquakes can cause serious vegetation destruction in affected areas. However, little is known about the spatial patterns of damaged vegetation and its influencing factors. Elucidating the main influencing factors and finding out the key vegetation type to reflect spatial patterns of damaged [...] Read more.
Major earthquakes can cause serious vegetation destruction in affected areas. However, little is known about the spatial patterns of damaged vegetation and its influencing factors. Elucidating the main influencing factors and finding out the key vegetation type to reflect spatial patterns of damaged vegetation are of great interest in order to improve the assessment of vegetation loss and the prediction of the spatial distribution of damaged vegetation caused by earthquakes. In this study, we used Moran’s I correlograms to study the spatial autocorrelation of damaged vegetation and its potential driving factors in the nine worst-hit Wenchuan earthquake-affected cities and counties. Both dependent and independent variables showed a positive spatial autocorrelation but with great differences at four aggregation levels (625 × 625 m, 1250 × 1250 m, 2500 × 2500 m, and 5000 × 5000 m). Shrubs can represent the characteristics of all damaged vegetation due to the significant linear relationship between their Moran’s I at the four aggregation levels. Clustering of similar high coverage of damaged vegetation occurred in the study area. The residuals of the standard linear regression model also show a significantly positive autocorrelation, indicating that the standard linear regression model cannot explain all the spatial patterns in damaged vegetation. Spatial autoregressive models without spatially autocorrelated residuals had the better goodness-of-fit to deal with damaged vegetation. The aggregation level 8 × 8 is a scale threshold for spatial autocorrelation. There are other environmental factors affecting vegetation destruction. Our study provides useful information for the countermeasures of vegetation protection and conservation, as well as the prediction of the spatial distribution of damaged vegetation, to improve vegetation restoration in earthquake-affected areas. Full article
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Open AccessArticle Characterisation of Physical and Mechanical Properties of Unthinned and Unpruned Plantation-Grown Eucalyptus nitens H.Deane & Maiden Lumber
Forests 2019, 10(2), 194; https://doi.org/10.3390/f10020194
Received: 22 January 2019 / Revised: 4 February 2019 / Accepted: 20 February 2019 / Published: 21 February 2019
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Abstract
The use of fast-growing plantation eucalypt (i.e., pulpwood eucalypt) in the construction of high-value structural products has received special attention from the timber industry in Australia and worldwide. There is still, however, a significant lack of knowledge regarding the physical and mechanical properties [...] Read more.
The use of fast-growing plantation eucalypt (i.e., pulpwood eucalypt) in the construction of high-value structural products has received special attention from the timber industry in Australia and worldwide. There is still, however, a significant lack of knowledge regarding the physical and mechanical properties of the lumber from such plantation resources as they are mainly being managed to produce woodchips. In this study, the physical and mechanical properties of lumber from a 16-year-old pulpwood Eucalyptus nitens H.Deane & Maiden resource from the northeast of Tasmania, Australia was evaluated. The tests were conducted on 318 small wood samples obtained from different logs harvested from the study site. The tested mechanical properties included bending modulus of elasticity (10,377.7 MPa) and modulus of rupture (53 MPa), shear strength parallel (5.5 MPa) and perpendicular to the grain (8.5 MPa), compressive strength parallel (42.8 MPa) and perpendicular to the grain (4.1 MPa), tensile strength perpendicular to the grain (3.4 MPa), impact bending (23.6 J/cm2), cleavage (1.6 kN) and Janka hardness (23.2 MPa). Simple linear regression models were developed using density and moisture content to predict the mechanical properties. The variations in the moisture content after conventional kiln drying within randomly selected samples in each test treatment were not high enough to significantly influence the mechanical properties. A relatively high variation in the density values was observed that showed significant correlations with the changes in the mechanical properties. The presence of knots increased the shear strength both parallel and perpendicular to the grain and significantly decreased the tensile strength of the lumber. The results of this study created a profile of material properties for the pulpwood E. nitens lumber that can be used for numerical modelling of any potential structural product from such a plantation resource. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Expression Patterns of MYB (V-myb Myeloblastosis Viral Oncogene Homolog) Gene Family in Resistant and Susceptible Tung Trees Responding to Fusarium Wilt Disease
Forests 2019, 10(2), 193; https://doi.org/10.3390/f10020193
Received: 3 January 2019 / Revised: 13 February 2019 / Accepted: 15 February 2019 / Published: 21 February 2019
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Abstract
Vernicia fordii (tung oil tree) is famous in the world for its production of tung oil. Unfortunately, it was infected by the soil-borne fungus Fusarium oxysporum f. sp. fordii 1 (Fof-1) and suffered serious wilt disease. Conversely, its sister species V. [...] Read more.
Vernicia fordii (tung oil tree) is famous in the world for its production of tung oil. Unfortunately, it was infected by the soil-borne fungus Fusarium oxysporum f. sp. fordii 1 (Fof-1) and suffered serious wilt disease. Conversely, its sister species V. montana is highly resistant to Fof-1. The MYB (v-myb myeloblastosis viral oncogene homolog) transcription factors were activated during the pathogen Fof-1 infection according to our previous comparative transcriptomic results. Depending on whether the sequence has a complete MYB-DNA-binding domain, a total of 75 VfMYB and 77 VmMYB genes were identified in susceptible V. fordii and resistant V. montana, respectively. In addition, we detected 49 pairs of one-to-one orthologous Vf/VmMYB genes with the reciprocal-best BLAST-hits (RBH)method. In order to investigate the expression modes and the internal network of MYB transcription factors in the two species responding to Fusarium wilt disease, the expressions of Vf/VmMYBs were then investigated and we found that most orthologous Vf/VmMYB genes exhibited similar expression patterns during the Fof-1 infection. However, four pairs of Vf/VmMYB genes, annotated as unknown proteins and mediator of root architecture, demonstrated absolute opposite expression patterns in the two Vernicia species responding to Fof-1. The interaction network of VmMYB genes were further constructed using weighted gene co-expression network analysis (WGCNA) method and four hub genes showing extremely high interaction with the other 1157 genes were identified. RT-qPCR result verified the opposite expression pattern of the hub gene VmMYB011 and VmMYB041 in two Vernicia species. In summary, co-expression network of the Vf/VmMYBs and significantly opposite related pairs of genes in resistant and susceptible Vernicia species provided knowledge for understanding the molecular basis of Vernicia responding to Fusarium wilt disease. Full article
(This article belongs to the Special Issue Functional and Phylogenetic Signals of Forest Tree Communities)
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Open AccessArticle Forest Soil Profile Inversion and Mixing Change the Vertical Stratification of Soil CO2 Concentration without Altering Soil Surface CO2 Flux
Forests 2019, 10(2), 192; https://doi.org/10.3390/f10020192
Received: 28 December 2018 / Revised: 15 February 2019 / Accepted: 19 February 2019 / Published: 21 February 2019
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Abstract
In order to gain more detailed knowledge of the CO2 concentration gradient in forest soil profiles and to better understand the factors that control CO2 concentration along forest soil profiles, we examined the soil surface CO2 flux, soil properties and [...] Read more.
In order to gain more detailed knowledge of the CO2 concentration gradient in forest soil profiles and to better understand the factors that control CO2 concentration along forest soil profiles, we examined the soil surface CO2 flux, soil properties and soil profile CO2 concentration in upright (CK), inverted and mixed soil columns with a depth of 60 cm in two subtropical forests in China from May 2008 to December 2009. The results showed that: (1) The SOC (soil organic carbon), TN (total N) and microbial biomass were higher in the deeper layers in the inverted soil column, which was consistent with an increase in CO2 concentration in the deeper soil layer. Furthermore, the biogeochemical properties were homogenous among soil layers in the mixed soil column. (2) CO2 concentration in the soil profile increased with depth in CK while soil column inversion significantly intensified this vertical stratification as the most active layer (surface soil) was now at the bottom. The stratification of CO2 concentration along the soil profile in the mixed soil column was similar to that in CK but it was not intensified after soil was mixed. (3) The soil surface CO2 flux did not significantly change after the soil column was inverted. The surface CO2 flux rate of the mixed soil column was higher compared to that of the inverted soil column but was not significantly different from CK. Our results indicated that the profile soil CO2 production was jointly controlled by soil properties related to CO2 production (e.g., SOC content and soil microbial biomass) and those related to gas diffusion (e.g., soil bulk density and gas molecular weight), but the soil surface CO2 flux was mainly determined by soil surface temperature and may be affected by the intensity of soil disturbance. Full article
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Open AccessArticle Profile, Level of Vulnerability and Spatial Pattern of Deforestation in Sulawesi Period of 1990 to 2018
Forests 2019, 10(2), 191; https://doi.org/10.3390/f10020191
Received: 24 November 2018 / Revised: 6 February 2019 / Accepted: 10 February 2019 / Published: 20 February 2019
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Abstract
Deforestation is an event of loss of forest cover to another cover. Sulawesi forests have the potential to be deforested as with Sumatra and Kalimantan. This study aims to provide information on deforestation events in Sulawesi from 1990 to 2018. The data used [...] Read more.
Deforestation is an event of loss of forest cover to another cover. Sulawesi forests have the potential to be deforested as with Sumatra and Kalimantan. This study aims to provide information on deforestation events in Sulawesi from 1990 to 2018. The data used in this study are (1) land cover in 1990, 2000, 2010; (2) Landsat 8 imagery in 2018; (3) administrative map of BIG in 2018. The methods used are (1) image classification with on-screen digitation techniques following the PPIK land cover classification guidelines, Forestry Planning Agency (2008) using ArcGIS Desktop 10.6 from ESRI; (2) overlapping maps; (3) analysis of deforestation; (4) analysis of deforestation profiles, (5) vulnerability analysis; and (6) analysis of distribution patterns of deforestation. The results showed that the profile of deforestation occurring on Sulawesi Island in the 1990–2018 observation period was dominated by profile 3-1-1 (the proportion of large forest area, the highest incidence of deforestation early stage at the beginning, at a low rate) in 13 districts. The level of vulnerability to deforestation is a non-vulnerable category (37 districts) which is directed to become a priority in handling deforestation in Sulawesi. Spatial patterns of the deforestation that occurred randomly and were scattered are dominated by shrubs, dryland agricultural activities, and small-scale plantations. Full article
(This article belongs to the Special Issue Impact of Land Use Change on Forest Biodiversity)
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Open AccessArticle Predicting the Potential Distribution of Paeonia veitchii (Paeoniaceae) in China by Incorporating Climate Change into a Maxent Model
Forests 2019, 10(2), 190; https://doi.org/10.3390/f10020190
Received: 14 January 2019 / Revised: 14 February 2019 / Accepted: 19 February 2019 / Published: 20 February 2019
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Abstract
A detailed understanding of species distribution is usually a prerequisite for the rehabilitation and utilization of species in an ecosystem. Paeonia veitchii (Paeoniaceae), which is an endemic species of China, is an ornamental and medicinal plant that features high economic and ecological values. [...] Read more.
A detailed understanding of species distribution is usually a prerequisite for the rehabilitation and utilization of species in an ecosystem. Paeonia veitchii (Paeoniaceae), which is an endemic species of China, is an ornamental and medicinal plant that features high economic and ecological values. With the decrease of its population in recent decades, it has become a locally endangered species. In present study, we modeled the potential distribution of P. veitchii under current and future conditions, and evaluated the importance of the factors that shape its distribution. The results revealed a highly and moderately suitable habitat for P. veitchii that encompassed ca. 605,114 km2. The central area lies in northwest Sichuan Province. Elevation, temperature seasonality, annual mean precipitation, and precipitation seasonality were identified as the most important factors shaping the distribution of P. veitchii. Under the scenario with a low concentration of greenhouse gas emissions (RCP 2.6), we predicted an overall expansion of the potential distribution by 2050, followed by a slight contraction in 2070. However, with the scenario featuring intense greenhouse gas emissions (RCP 8.5), the range of suitable habitat should increase with the increasing intensity of global warming. The information that was obtained in the present study can provide background information related to the long-term conservation of this species. Full article
(This article belongs to the Special Issue Geographic Information Systems and Their Applications in Forests)
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Open AccessArticle Influence of Site Conditions and Quality of Birch Wood on Its Properties and Utilization after Heat Treatment. Part I—Elastic and Strength Properties, Relationship to Water and Dimensional Stability
Forests 2019, 10(2), 189; https://doi.org/10.3390/f10020189
Received: 22 January 2019 / Revised: 7 February 2019 / Accepted: 20 February 2019 / Published: 20 February 2019
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Abstract
This work deals with the quality of birch (Betula pendula) wood from different sites and the impact of heat treatment on it. Two degrees of heat treatment were used, 170 °C and 190 °C. The resulting property values were compared with [...] Read more.
This work deals with the quality of birch (Betula pendula) wood from different sites and the impact of heat treatment on it. Two degrees of heat treatment were used, 170 °C and 190 °C. The resulting property values were compared with reference to untreated wood samples. These values were wood density, compressive strength, modulus of elasticity (MOE), bending strength (MOR), impact bending strength (toughness), hardness, swelling, limit of hygroscopicity, moisture content and color change. It was supposed that an increase in heat-treatment temperature could reduce strength properties and, adversely, lead to better shape and dimensional stability, which was confirmed by experiments. It was also shown that the properties of the wood before treatment affected their condition after heat treatment, and that the characteristic values and variability of birch properties from 4 sites, 8 stems totally, were reflected in the properties of the heat-treated wood. Values of static MOR were the exception, where the quality of the input wood was less significant at a higher temperature, and this was even more significant in impact bending strength, where it manifested at a lower temperature degree. Impact bending strength also proved to be significantly negatively affected by heat treatment, about 48% at 170 °C, and up to 67% at 190 °C. On the contrary, the most positive results were the MOE and hardness increases at 170 °C by about 30% and about 21%, respectively, with a decrease in swelling at 190 °C by about 31%. On the basis of color change and other ascertained properties, there is a possibility that, after suitable heat treatment, birch could replace other woods (e.g., beech) for certain specific purposes, particularly in the furniture industry. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Variability of Aboveground Litter Inputs Alters Soil Carbon and Nitrogen in a Coniferous–Broadleaf Mixed Forest of Central China
Forests 2019, 10(2), 188; https://doi.org/10.3390/f10020188
Received: 26 January 2019 / Revised: 19 February 2019 / Accepted: 20 February 2019 / Published: 20 February 2019
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Abstract
Global changes and human disturbances can strongly affect the quantity of aboveground litter entering soils, which could result in substantial cascading effects on soil biogeochemical processes in forests. Despite extensive reports, it is unclear how the variations in litter depth affect soil carbon [...] Read more.
Global changes and human disturbances can strongly affect the quantity of aboveground litter entering soils, which could result in substantial cascading effects on soil biogeochemical processes in forests. Despite extensive reports, it is unclear how the variations in litter depth affect soil carbon and nitrogen cycling. The responses of soil carbon and nitrogen to the variability of litter inputs were examined in a coniferous–broadleaf mixed forest of Central China. The litter input manipulation included five treatments: no litter input, natural litter, double litter, triple litter, and quadruple litter. Multifold litter additions decreased soil temperature but did not affect soil moisture after 2.5 years. Reductions in soil pH under litter additions were larger than increases under no litter input. Litter quantity did not affect soil total organic carbon, whereas litter addition stimulated soil dissolved organic carbon more strongly than no litter input suppressed it. The triggering priming effect of litter manipulation on soil respiration requires a substantial litter quantity, and the impacts of a slight litter change on soil respiration are negligible. Litter quantity did not impact soil total nitrogen, and only strong litter fluctuations changed the content of soil available nitrogen (nitrate nitrogen and ammonium nitrogen). Litter addition enhanced soil microbial biomass carbon and nitrogen more strongly than no litter input. Our results imply that the impacts of multifold litter inputs on soil carbon and nitrogen are different with a single litter treatment. These findings suggest that variability in aboveground litter inputs resulting from environmental change and human disturbances have great potential to change soil carbon and nitrogen in forest ecosystems. The variability of aboveground litter inputs needs to be taken into account to predict the responses of terrestrial soil carbon and nitrogen cycling to environmental changes and forest management. Full article
(This article belongs to the Special Issue Forest Carbon Dynamics under Changing Climate and Disturbance Regimes)
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Open AccessArticle Individual Tree Diameter Growth Models of Larch–Spruce–Fir Mixed Forests Based on Machine Learning Algorithms
Forests 2019, 10(2), 187; https://doi.org/10.3390/f10020187
Received: 20 December 2018 / Revised: 15 February 2019 / Accepted: 18 February 2019 / Published: 20 February 2019
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Abstract
Individual tree growth models are flexible and commonly used to represent growth dynamics for heterogeneous and structurally complex uneven-aged stands. Besides traditional statistical models, the rapid development of nonparametric and nonlinear machine learning methods, such as random forest (RF), boosted regression tree (BRT), [...] Read more.
Individual tree growth models are flexible and commonly used to represent growth dynamics for heterogeneous and structurally complex uneven-aged stands. Besides traditional statistical models, the rapid development of nonparametric and nonlinear machine learning methods, such as random forest (RF), boosted regression tree (BRT), cubist (Cubist) and multivariate adaptive regression splines (MARS), provides a new way for predicting individual tree growth. However, the application of these approaches to individual tree growth modelling is still limited and short of a comparison of their performance. The objectives of this study were to compare and evaluate the performance of the RF, BRT, Cubist and MARS models for modelling the individual tree diameter growth based on tree size, competition, site condition and climate factors for larch–spruce–fir mixed forests in northeast China. Totally, 16,619 observations from long-term sample plots were used. Based on tenfold cross-validation, we found that the RF, BRT and Cubist models had a distinct advantage over the MARS model in predicting individual tree diameter growth. The Cubist model ranked the highest in terms of model performance (RMSEcv [0.1351 cm], MAEcv [0.0972 cm] and R2cv [0.5734]), followed by BRT and RF models, whereas the MARS ranked the lowest (RMSEcv [0.1462 cm], MAEcv [0.1086 cm] and R2cv [0.4993]). Relative importance of predictors determined from the RF and BRT models demonstrated that the competition and tree size were the main drivers to diameter growth, and climate had limited capacity in explaining the variation in tree diameter growth at local scale. In general, the RF, BRT and Cubist models are effective and powerful modelling methods for predicting the individual tree diameter growth. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Effects of Arbuscular Mycorrhizal Fungi on Growth, Photosynthesis, and Nutrient Uptake of Zelkova serrata (Thunb.) Makino Seedlings under Salt Stress
Forests 2019, 10(2), 186; https://doi.org/10.3390/f10020186
Received: 31 January 2019 / Revised: 15 February 2019 / Accepted: 15 February 2019 / Published: 20 February 2019
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Abstract
Salinity is the primary restriction factor for vegetation conservation and the rehabilitation of coastal areas in Eastern China. Arbuscular mycorrhizal fungi (AMF) have been proved to have the ability to alleviate salt stress in plants. However, the role of AMF in relieving salt [...] Read more.
Salinity is the primary restriction factor for vegetation conservation and the rehabilitation of coastal areas in Eastern China. Arbuscular mycorrhizal fungi (AMF) have been proved to have the ability to alleviate salt stress in plants. However, the role of AMF in relieving salt stress among indigenous trees species is less well known, limiting the application of AMF in the afforestation of local area. In this study, a salt-stress pot experiment was conducted to evaluate the effects of AMF on Zelkova serrata (Thunb.) Makino, a tree species with significant potential for afforestation of coastal area. The Z. serrata seedlings inoculated with three AMF strains (Funneliformis mosseae 1, Funneliformis mosseae 2, and Diversispora tortuosa) were subjected to two salt treatments (0 and 100 mM NaCl) under greenhouse conditions. The results showed that the three AMF strains had positive effects, to a certain extent, on plant growth and photosynthesis under normal condition. However, only F. mosseae 1 and F. mosseae 2 alleviated the inhibition of growth, photosynthesis, and nutrient uptake of Z. serrata seedlings under salt stress. The two AMF strains mitigated salt-induced adverse effects on seedlings mainly by increasing the leaf photosynthetic ability and biomass accumulation by reducing Na+ content, increasing P, K+, and Mg2+ content, as well as by enhancing photosynthetic pigments content and the stomatal conductance of leaves. These results indicated that AMF inoculation is a promising strategy for the afforestation of coastal areas in Eastern China. Full article
(This article belongs to the Special Issue Ecto- and Endomycorrhizal Relationships in Forest Trees)
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Open AccessArticle Caribou Conservation: Restoring Trees on Seismic Lines in Alberta, Canada
Forests 2019, 10(2), 185; https://doi.org/10.3390/f10020185
Received: 22 December 2018 / Revised: 15 February 2019 / Accepted: 18 February 2019 / Published: 20 February 2019
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Abstract
Seismic lines are narrow linear (~3–8 m wide) forest clearings that are used for petroleum exploration in Alberta’s boreal forest. Many seismic lines have experienced poor tree regeneration since initial disturbance, with most failures occurring in treed peatlands that are used by the [...] Read more.
Seismic lines are narrow linear (~3–8 m wide) forest clearings that are used for petroleum exploration in Alberta’s boreal forest. Many seismic lines have experienced poor tree regeneration since initial disturbance, with most failures occurring in treed peatlands that are used by the threatened woodland caribou (Rangifer tarandus caribou). Extensive networks of seismic lines, which often reach densities of 40 km/km2, are thought to have contributed to declines in caribou. The reforestation of seismic lines is therefore a focus of conservation. Methods to reforest seismic lines are expensive (averaging $12,500 per km) with uncertainty of which seismic lines need which treatments, if any, resulting in inefficiencies in restoration actions. Here, we monitored the effectiveness of treatments on seismic lines as compared to untreated seismic lines and adjacent undisturbed reference stands for treed peatlands in northeast Alberta, Canada. Mechanical site preparation (mounding and ripping) increased tree density when compared to untreated lines, despite averaging 3.8-years since treatment (vs. 22 years since disturbance for untreated). Specifically, treated lines had, on average, 12,290 regenerating tree stems/ha, which is 1.6-times more than untreated lines (7680 stems/ha) and 1.5-times more than the adjacent undisturbed forest (8240 stems/ha). Using only mechanical site preparation, treated seismic lines consistently have more regenerating trees across all four ecosites, although the higher amounts of stems that were observed on treated poor fens are not significant when compared to untreated or adjacent undisturbed reference stands. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle Attribution Analysis for Runoff Change on Multiple Scales in a Humid Subtropical Basin Dominated by Forest, East China
Forests 2019, 10(2), 184; https://doi.org/10.3390/f10020184
Received: 12 January 2019 / Revised: 15 February 2019 / Accepted: 19 February 2019 / Published: 20 February 2019
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Abstract
Attributing runoff change to different drivers is vital in order to better understand how and why runoff varies, and to further support decision makers on water resources planning and management. Most previous works attributed runoff change in the arid or semi-arid areas to [...] Read more.
Attributing runoff change to different drivers is vital in order to better understand how and why runoff varies, and to further support decision makers on water resources planning and management. Most previous works attributed runoff change in the arid or semi-arid areas to climate variability and human activity on an annual scale. However, attribution results may differ greatly according to different climatic zones, decades, temporal scales, and different contributors. This study aims to quantitatively attribute runoff change in a humid subtropical basin (the Qingliu River basin, East China) to climate variability, land-use change, and human activity on multiple scales over different periods by using the Soil and Water Assessment Tool (SWAT) model. The results show that runoff increased during 1960–2012 with an abrupt change occurring in 1984. Annual runoff in the post-change period (1985–2012) increased by 16.05% (38.05 mm) relative to the pre-change period (1960–1984), most of which occurred in the winter and early spring (March). On the annual scale, climate variability, human activity, and land-use change (mainly for forest cover decrease) contributed 95.36%, 4.64%, and 12.23% to runoff increase during 1985–2012, respectively. On the seasonal scale, human activity dominated runoff change (accounting for 72.11%) in the dry season during 1985–2012, while climate variability contributed the most to runoff change in the wet season. On the monthly scale, human activity was the dominant contributor to runoff variation in all of the months except for January, May, July, and August during 1985–2012. Impacts of climate variability and human activity on runoff during 2001–2012 both became stronger than those during 1985–2000, but counteracted each other. The findings should help understandings of runoff behavior in the Qingliu River and provide scientific support for local water resources management. Full article
(This article belongs to the Special Issue Forest Hydrology and Watershed)
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Open AccessArticle Experimental Data on Maximum Rainfall Retention on Crowns of Deciduous Tree Species of the Middle Ural (Russia)
Forests 2019, 10(2), 183; https://doi.org/10.3390/f10020183
Received: 23 January 2019 / Revised: 15 February 2019 / Accepted: 17 February 2019 / Published: 20 February 2019
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Abstract
Metering of actual volume of rainfall flowing under deciduous stock canopy is essential for correct calculation of the water balance of forest watersheds of small rivers. This article includes the results of a physical (experimental) simulation of maximum rainfall retention on the laminae [...] Read more.
Metering of actual volume of rainfall flowing under deciduous stock canopy is essential for correct calculation of the water balance of forest watersheds of small rivers. This article includes the results of a physical (experimental) simulation of maximum rainfall retention on the laminae of deciduous tree species. The authors developed the experimental methodology, assembled the testing machine, assessed results, and suggested ways of interpreting the obtained results in calculations of flood runoff. According to experimental data, rainfall is retained on laminae both in film and drip form. Specific retention value per unit area of leaf surface is mostly determined by the level of physical roughness of a leaf, which, in turn, depends on the type of venation, typical for different types of analyzed trees. The value of complete raindrops retention by crowns of deciduous species is determined by the leaf surface area and rainfall intensity. Dependencies of the maximum mass of the retained moisture on the leaf surface area, which are characterized by the correlation coefficient of 0.98, were obtained on the basis of branch sprinkling experiments. The maximum mass of water retention on crowns of single deciduous trees can reach up to 77 kg, or 3.0–4.0 mm per projection area of a crown. This is significantly less than the maximum mass of water retention on crowns of coniferous species (for comparison, larch retains up to 150 kg of rain moisture or 5.9 mm of layer). Evaporation from crowns, as well as wind oscillations of laminae, result in larger volumes of interception as compared to the results obtained from experiments. Metering of irrecoverable losses values has great practical value in the assessment of the water balance of forest lands, moisture balance in soil layer under the forest canopy, as well as the flood runoff of small watersheds of forest zones. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle The First Record of a North American Poplar Leaf Rust Fungus, Melampsora medusae, in China
Forests 2019, 10(2), 182; https://doi.org/10.3390/f10020182
Received: 5 January 2019 / Revised: 15 February 2019 / Accepted: 19 February 2019 / Published: 20 February 2019
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Abstract
A wide range of species and hybrids of black and balsam poplars or cottonwoods (Populus L., sections Aigeiros and Tacamahaca) grow naturally, or have been introduced to grow in plantations in China. Many species of Melampsora can cause poplar leaf rust [...] Read more.
A wide range of species and hybrids of black and balsam poplars or cottonwoods (Populus L., sections Aigeiros and Tacamahaca) grow naturally, or have been introduced to grow in plantations in China. Many species of Melampsora can cause poplar leaf rust in China, and their distributions and host specificities are not entirely known. This study was prompted by the new susceptibility of a previously resistant cultivar, cv. ‘Zhonghua hongye’ of Populus deltoides (section Aigeiros), as well as by the need to know more about the broader context of poplar leaf rust in China. Rust surveys from 2015 through 2018 in Shaanxi, Sichuan, Gansu, Henan, Shanxi, Qinghai, Beijing, and Inner Mongolia revealed some samples with urediniospores with the echinulation pattern of M. medusae. The morphological characteristics of urediniospores and teliospores from poplar species of the region were further examined with light and scanning electron microscopy. Phylogenetic analysis based on sequences of the rDNA ITS region (ITS1, 5.8S rRNA gene, and ITS2) and the nuclear large subunit rDNA (D1/D2) was used to further confirm morphology-based identification. Based on combined analyses, five of the fifteen fully characterized samples were identified as Melampsora medusae: one from Shaanxi and four from Sichuan. Two of the five were from Populus deltoides cv. ‘Zhonghua hongye’. Three others were identified on Populus szechuanica, P. simonii, and P. yunnanensis. Additional samples of M. medusae were collected in Shaanxi in 2017 and 2018, and from Henan in 2015 through 2018. Altogether these findings show that this introduced pathogen is widespread and persistent from year to year in China. This is the first report of this North American poplar leaf rust species, Melampsora medusae, in China. It has previously been reported outside North America in Argentina, Europe, Australia, New Zealand, Japan, and Russia. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Within-Site Variation in Seedling Survival in Norway Spruce Plantations
Forests 2019, 10(2), 181; https://doi.org/10.3390/f10020181
Received: 23 December 2018 / Revised: 12 February 2019 / Accepted: 18 February 2019 / Published: 19 February 2019
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Abstract
Seedling survival was evaluated from inventories of a large set of Norway spruce plantations in privately owned forests in southern Sweden. The inventories were conducted at the time of planting and a subset was re-inventoried three years later. This enabled comparison of regeneration [...] Read more.
Seedling survival was evaluated from inventories of a large set of Norway spruce plantations in privately owned forests in southern Sweden. The inventories were conducted at the time of planting and a subset was re-inventoried three years later. This enabled comparison of regeneration success after soil scarification and planting. The acquired data enabled evaluation of annual and climatic variation of seedling mortality since inventories were made on newly established clearcuts distributed spatially throughout three regions in southern Sweden and repeated in five consecutive years. Within-site variation was also captured via the use of a large number of sample plots on each clearcut. To do so, thirty sample plots were established within weeks of planting on 150 clearcuts. Small- and large-scale site and management variables were recorded as well as the numbers of suitable planting spots and planted seedlings. Three years later, 60 of the initially surveyed clearcuts were revisited and the numbers of both planted and naturally regenerated seedlings counted. On average, 2000 seedlings ha−1 were planted and 1500 seedlings ha−1 had survived after three years. However, there was high variation, and in 42% of the revisited sample plots no mortality was recorded. Important variables for seedling survival identified by linear regression analysis included the number of suitable planting spots, soil moisture conditions and annual variation in available soil water. Full article
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Open AccessArticle A Forest Model Intercomparison Framework and Application at Two Temperate Forests Along the East Coast of the United States
Forests 2019, 10(2), 180; https://doi.org/10.3390/f10020180
Received: 24 December 2018 / Revised: 7 February 2019 / Accepted: 13 February 2019 / Published: 19 February 2019
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Abstract
State-of-the-art forest models are often complex, analytically intractable, and computationally expensive, due to the explicit representation of detailed biogeochemical and ecological processes. Different models often produce distinct results while predictions from the same model vary with parameter values. In this project, we developed [...] Read more.
State-of-the-art forest models are often complex, analytically intractable, and computationally expensive, due to the explicit representation of detailed biogeochemical and ecological processes. Different models often produce distinct results while predictions from the same model vary with parameter values. In this project, we developed a rigorous quantitative approach for conducting model intercomparisons and assessing model performance. We have applied our original methodology to compare two forest biogeochemistry models, the Perfect Plasticity Approximation with Simple Biogeochemistry (PPA-SiBGC) and Landscape Disturbance and Succession with Net Ecosystem Carbon and Nitrogen (LANDIS-II NECN). We simulated past-decade conditions at flux tower sites located within Harvard Forest, MA, USA (HF-EMS) and Jones Ecological Research Center, GA, USA (JERC-RD). We mined field data available from both sites to perform model parameterization, validation, and intercomparison. We assessed model performance using the following time-series metrics: Net ecosystem exchange, aboveground net primary production, aboveground biomass, C, and N, belowground biomass, C, and N, soil respiration, and species total biomass and relative abundance. We also assessed static observations of soil organic C and N, and concluded with an assessment of general model usability, performance, and transferability. Despite substantial differences in design, both models achieved good accuracy across the range of pool metrics. While LANDIS-II NECN showed better fidelity to interannual NEE fluxes, PPA-SiBGC indicated better overall performance for both sites across the 11 temporal and two static metrics tested (HF-EMS R 2 ¯ = 0.73 , + 0.07 , R M S E ¯ = 4.68 , 9.96 ; JERC-RD R 2 ¯ = 0.73 , + 0.01 , R M S E ¯ = 2.18 , 1.64 ). To facilitate further testing of forest models at the two sites, we provide pre-processed datasets and original software written in the R language of statistical computing. In addition to model intercomparisons, our approach may be employed to test modifications to forest models and their sensitivity to different parameterizations. Full article
(This article belongs to the Section Forest Inventory, Quantitative Methods and Remote Sensing)
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Open AccessArticle Evaluation of Anti-Tyrosinase and Antioxidant Properties of Four Fern Species for Potential Cosmetic Applications
Forests 2019, 10(2), 179; https://doi.org/10.3390/f10020179
Received: 4 January 2019 / Revised: 6 February 2019 / Accepted: 11 February 2019 / Published: 19 February 2019
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Abstract
Ferns are poorly explored species from a pharmaceutical perspective compared to other terrestrial plants. In this work, the antioxidant and tyrosinase inhibitory activities of hydrophilic and lipophilic extracts, together with total polyphenol content, were evaluated in order to explore the potential cosmetic applications [...] Read more.
Ferns are poorly explored species from a pharmaceutical perspective compared to other terrestrial plants. In this work, the antioxidant and tyrosinase inhibitory activities of hydrophilic and lipophilic extracts, together with total polyphenol content, were evaluated in order to explore the potential cosmetic applications of four Spanish ferns collected in the Prades Mountains (Polypodium vulgare L., Asplenium adiantum-nigrum L., Asplenium trichomanes L., and Ceterach officinarum Willd). The antioxidant activity was evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, oxygen radical absorbance capacity (ORAC) and xanthine/xanthine oxidase (X/XO) assays. The potential to avoid skin hyperpigmentation was tested by inhibiting the tyrosinase enzyme, as this causes melanin synthesis in the epidermis. All ferns were confirmed as antioxidant and anti-tyrosinase agents, but interestingly hydrophilic extracts (obtained with methanol) were more potent and effective compared to lipophilic extracts (obtained with hexane). Polypodium vulgare, Asplenium adiantum-nigrum, and Ceterach officinarum methanolic extracts performed the best as antioxidants. Polypodium vulgare methanolic extract also showed the highest activity as a tyrosinase inhibitor. Full article
(This article belongs to the Special Issue Forest, Foods and Nutrition)
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Open AccessArticle Proportional Relationship between Leaf Area and the Product of Leaf Length and Width of Four Types of Special Leaf Shapes
Forests 2019, 10(2), 178; https://doi.org/10.3390/f10020178
Received: 22 December 2018 / Revised: 12 February 2019 / Accepted: 18 February 2019 / Published: 19 February 2019
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Abstract
The leaf area, as an important leaf functional trait, is thought to be related to leaf length and width. Our recent study showed that the Montgomery equation, which assumes that leaf area is proportional to the product of leaf length and width, applied [...] Read more.
The leaf area, as an important leaf functional trait, is thought to be related to leaf length and width. Our recent study showed that the Montgomery equation, which assumes that leaf area is proportional to the product of leaf length and width, applied to different leaf shapes, and the coefficient of proportionality (namely the Montgomery parameter) range from 1/2 to π/4. However, no relevant geometrical evidence has previously been provided to support the above findings. Here, four types of representative leaf shapes (the elliptical, sectorial, linear, and triangular shapes) were studied. We derived the range of the estimate of the Montgomery parameter for every type. For the elliptical and triangular leaf shapes, the estimates are π/4 and 1/2, respectively; for the linear leaf shape, especially for the plants of Poaceae that can be described by the simplified Gielis equation, the estimate ranges from 0.6795 to π/4; for the sectorial leaf shape, the estimate ranges from 1/2 to π/4. The estimates based on the observations of actual leaves support the above theoretical results. The results obtained here show that the coefficient of proportionality of leaf area versus the product of leaf length and width only varies in a small range, maintaining the allometric relationship for leaf area and thereby suggesting that the proportional relationship between leaf area and the product of leaf length and width broadly remains stable during leaf evolution. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Abundance and Impacts of Competing Species on Conifer Regeneration Following Careful Logging in the Eastern Canadian Boreal Forest
Forests 2019, 10(2), 177; https://doi.org/10.3390/f10020177
Received: 4 February 2019 / Revised: 13 February 2019 / Accepted: 18 February 2019 / Published: 19 February 2019
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Abstract
Managing competing vegetation is crucial in stand establishment strategies; forecasting the abundance, composition, and impact of competing vegetation after harvesting is needed to optimize silviculture scenarios and maintain long-term site productivity. Our main objective was to identify factors influencing the short-term abundance and [...] Read more.
Managing competing vegetation is crucial in stand establishment strategies; forecasting the abundance, composition, and impact of competing vegetation after harvesting is needed to optimize silviculture scenarios and maintain long-term site productivity. Our main objective was to identify factors influencing the short-term abundance and composition of competing vegetation over a large area of the Canadian boreal forest. Our second objective was to better understand the mid-term evolution of the regeneration/competing vegetation complex in cases of marginal regeneration conditions. We used operational regeneration surveys of 4471 transects sampled ≈5 years after harvesting that contained data on regeneration, competing vegetation, elevation, ecological classification, soil attributes, and pre-harvest forest stands. We performed a redundancy analysis to identify the relationships between competing vegetation, harvesting and biophysical variables. We then estimated the probability of observing a given competing species cover based on these variables. In 2015, we re-sampled a portion of the sites, where conifer regeneration was marginal early after harvesting, to assess the temporal impact of different competing levels and species groups on the free-to-grow stocking, vigour and basal area of softwood regeneration. Results from the first inventory showed that, after careful logging around advance growth, ericaceous shrubs and hardwoods were not associated with the same sets of site attributes. Ericaceous shrubs were mainly found on low fertility sites associated with black spruce (Picea mariana (Mill.) BSP) or jack pine (Pinus banksiana Lamb.). The distinction between suitable environments for commercial shade-intolerant hardwoods and non-commercial hardwoods was less clear, as they responded similarly to many variables. Analysis of data from the second inventory showed a significant improvement in conifer free-to-grow stocking when commercial shade-intolerant hardwood competing levels were low (stocking 0%–40%) and when ericaceous shrubs competing levels were moderate (percent cover 26%–75%). In these conditions of marginal regeneration, the different types and intensities of competition did not affect the vigour or basal area of softwood regeneration, 9–14 years after harvesting. Full article
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Open AccessArticle Assessing Hydrological Ecosystem Services in a Rubber-Dominated Watershed under Scenarios of Land Use and Climate Change
Forests 2019, 10(2), 176; https://doi.org/10.3390/f10020176
Received: 30 December 2018 / Revised: 7 February 2019 / Accepted: 15 February 2019 / Published: 19 February 2019
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Abstract
Land use and climate change exert pressure on ecosystems and threaten the sustainable supply of ecosystem services (ESS). In Southeast-Asia, the shift from swidden farming to permanent cash crop systems has led to a wide range of impacts on ESS. Our study area, [...] Read more.
Land use and climate change exert pressure on ecosystems and threaten the sustainable supply of ecosystem services (ESS). In Southeast-Asia, the shift from swidden farming to permanent cash crop systems has led to a wide range of impacts on ESS. Our study area, the Nabanhe Reserve in Yunnan province (PR China), saw the loss of extensive forest areas and the expansion of rubber (Hevea brasiliensis Müll. Arg.) plantations. In this study, we model water yield and sediment export for a rubber-dominated watershed under multiple scenarios of land use and climate change in order to assess how both drivers influence the supply of these ESS. For this we use three stakeholder-validated land use scenarios, varying in their degree of rubber expansion and land management rules. As projected climate change varies remarkably between different climate models, we combined the land use scenarios with datasets of temperature and precipitation changes, derived from nine General Circulation Models (GCMs) of the Fifth Assessment Report of the IPCC (Intergovernmental Panel on Climate Change) in order to model water yield and sediment export with InVEST (Integrated Valuation of Ecosystem Services and Trade-offs). Simulation results show that the effect of land use and land management decisions on water yield in Nabanhe Reserve are relatively minor (4% difference in water yield between land use scenarios), when compared to the effects that future climate change will exert on water yield (up to 15% increase or 13% decrease in water yield compared to the baseline climate). Changes in sediment export were more sensitive to land use change (15% increase or 64% decrease) in comparison to the effects of climate change (up to 10% increase). We conclude that in the future, particularly dry years may have a more pronounced effect on the water balance as the higher potential evapotranspiration increases the probability for periods of water scarcity, especially in the dry season. The method we applied can easily be transferred to regions facing comparable land use situations, as InVEST and the IPCC data are freely available. Full article
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Open AccessArticle Effects of Prescribed Fire, Site Factors, and Seed Sources on the Spread of Invasive Triadica sebifera in a Fire-Managed Coastal Landscape in Southeastern Mississippi, USA
Forests 2019, 10(2), 175; https://doi.org/10.3390/f10020175
Received: 27 January 2019 / Revised: 15 February 2019 / Accepted: 15 February 2019 / Published: 19 February 2019
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Abstract
In the Gulf of Mexico coastal region, prescribed fire has been increasingly used as a management tool to restore declining native ecosystems, but it also increases the threat posed by biological invasion, since the treated sites are more susceptible to invasive species such [...] Read more.
In the Gulf of Mexico coastal region, prescribed fire has been increasingly used as a management tool to restore declining native ecosystems, but it also increases the threat posed by biological invasion, since the treated sites are more susceptible to invasive species such as Chinese tallow (Triadica sebifera). We chose Mississippi Sandhill Crane National Wildlife Refuge (MSCNWR), a fire-managed landscape, to examine the potential effect of prescribed fire and landscape/community features on tallow invasion and spread. We took a complete survey of roadways and fire lines for tallow and measured a systematic sample of 144 10 × 3 m2 rectangular plots along two selected roadways and a simple random sample of 56 0.04-ha circular plots across burn units. We used pair correlation function for marked point pattern data, zero-inflated negative binomial models for count data, as well as multivariate Hotelling’s T2 test, to analyze the effect of prescribed fire and landscape/community characteristics on tallow invasion and spread along habitat edges and into interiors. Our results show that tallow spread along habitat edges and into interiors in a spatially clustered pattern. Tallow invasion risk decreases with the distance to seed trees and shrub coverage, and with the time since last fire if seed trees are outside the effective seed dispersal range (~300 m), but increases with the time since last fire if seed trees are within the effective seed dispersal range. Tallow seedling (≤2 years old) densities increase with the time since last fire and with increasing overstory tree basal area, but decrease with the distance to seed trees. Tallow-invaded interior plots have significantly shorter mean fire return intervals (2.7 years), lower shrub coverage (8.6%), and are closer to edges (20.3 m) than non-invaded plots (4.3 years, 18.4%, 167.6 m, respectively). Full article
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Open AccessArticle Torreya jackii (Taxaceae): A Special Species that is Genetically Admixed, Morphologically Distinct, and Geographically Sympatric with Parent Species
Forests 2019, 10(2), 174; https://doi.org/10.3390/f10020174
Received: 14 December 2018 / Revised: 25 January 2019 / Accepted: 18 February 2019 / Published: 19 February 2019
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Torreya jackii Chun is an endangered species (Taxaceae) confined to a few localities in China. However, the species status of T. jackii within Torreya Arn. has not been clearly elucidated under a phylogenetic context. In this study, phylogenetic analyses based on the nuclear [...] Read more.
Torreya jackii Chun is an endangered species (Taxaceae) confined to a few localities in China. However, the species status of T. jackii within Torreya Arn. has not been clearly elucidated under a phylogenetic context. In this study, phylogenetic analyses based on the nuclear internal transcribed spacer (ITS) and amplified fragment length polymorphism (AFLP) indicated that T. jackii is closely related with a sympatric species T. grandis Fort. ex Lindl. that is present due to cultivation. However, analysis based on the concatenated sequences of seven chloroplast loci resolved T. jackii as the first branch within the genus. Given their overlapping distribution and synchronous blooming, we suggest that the plastid-nuclear incongruence was derived from the dilution of the nuclear genome of T. jackii by T. grandis via pollen-mediated introgression hybridization when the two species met due to cultivation. Introgressive hybridization is fairly common in plants but few cases have been recognized as independent species. Our study highlights the complexity of protecting endangered species and the need for caution to prevent the unreasonable expansion of economic crops into the distribution ranges of their wild relatives. Full article
(This article belongs to the Section Forest Ecology and Management)
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Open AccessArticle The Effects of DNA Methylation Inhibition on Flower Development in the Dioecious Plant Salix Viminalis
Forests 2019, 10(2), 173; https://doi.org/10.3390/f10020173
Received: 25 January 2019 / Revised: 14 February 2019 / Accepted: 16 February 2019 / Published: 18 February 2019
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Abstract
DNA methylation, an important epigenetic modification, regulates the expression of genes and is therefore involved in the transitions between floral developmental stages in flowering plants. To explore whether DNA methylation plays different roles in the floral development of individual male and female dioecious [...] Read more.
DNA methylation, an important epigenetic modification, regulates the expression of genes and is therefore involved in the transitions between floral developmental stages in flowering plants. To explore whether DNA methylation plays different roles in the floral development of individual male and female dioecious plants, we injected 5-azacytidine (5-azaC), a DNA methylation inhibitor, into the trunks of female and male basket willow (Salix viminalis L.) trees before flower bud initiation. As expected, 5-azaC decreased the level of DNA methylation in the leaves of both male and female trees during floral development; however, it increased DNA methylation in the leaves of male trees at the flower transition stage. Furthermore, 5-azaC increased the number, length and diameter of flower buds in the female trees but decreased these parameters in the male trees. The 5-azaC treatment also decreased the contents of soluble sugars, starch and reducing sugars in the leaves of the female plants, while increasing them in the male plants at the flower transition stage; however, this situation was largely reversed at the flower development stage. In addition, 5-azaC treatment decreased the contents of auxin indoleacetic acid (IAA) in both male and female trees at the flower transition stage. These results indicate that hypomethylation in leaves at the flower transition stage promotes the initiation of flowering and subsequent floral growth in Salix viminalis, suggesting that DNA methylation plays a similar role in vegetative–reproductive transition and early floral development. Furthermore, methylation changes during the vegetative–reproductive transition and floral development were closely associated with the biosynthesis, metabolism and transportation of carbohydrates and IAA. These results provide insight into the epigenetic regulation of carbohydrate accumulation. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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Open AccessArticle Seasonal Variations and Thinning Effects on Soil Phosphorus Fractions in Larix principis-rupprechtii Mayr. Plantations
Forests 2019, 10(2), 172; https://doi.org/10.3390/f10020172
Received: 16 December 2018 / Revised: 5 February 2019 / Accepted: 14 February 2019 / Published: 18 February 2019
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Abstract
Thinning is a common management practice in forest ecosystems. However, understanding whether thinning treatment will change the availability of phosphorus (P) in soils, and the effect of thinning on the seasonal dynamics of soil P fractions, are still limited. The objective of the [...] Read more.
Thinning is a common management practice in forest ecosystems. However, understanding whether thinning treatment will change the availability of phosphorus (P) in soils, and the effect of thinning on the seasonal dynamics of soil P fractions, are still limited. The objective of the present study was to assess seasonal variations in soil P fractions under different forest thinning management strategies in a Larch (Larix spp.) plantation in northern China. To accomplish this, we examined soil P fractions, soil physical–chemical properties, and litter biomass under control (CK), light (LT), moderate (MT) and high thinning (HT) treatments. Data were collected during the growing season of 2017. We found that most P fractions varied seasonally at different soil depths, with the highest values occurring in the summer and autumn. When compared to CK, MT enhanced the inorganic P (Pi) concentration extracted by resin strip (R-Pi). Labile organic P (Labile Po), moderately labile P and total P (TP) also increased in both MT and HT treatments irrespective of season. In contrast, less-labile Pi and Po fractions were lower in LT than in CK, especially when examining deeper soil layers. Our results suggest that LT leads to a strong ability to utilize Po and less-labile Pi. Moreover, the effect of thinning did not tend to increase with thinning intensity, P availability was maximized at the MT. Ultimately, we show that MT can improve soil P bioavailability and is recommended in Larix principis-rupprechtii Mayr. plantations of North China. Our results emphasize that the effect of thinning management on soil microenvironment is an important basis for evaluating soil nutrients such as soil P bioavailability. Full article
(This article belongs to the Special Issue Organic Matter Production and Decomposition in Forest Soils)
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Open AccessArticle Effects of Invasive Spartina alterniflora Loisel. and Subsequent Ecological Replacement by Sonneratia apetala Buch.-Ham. on Soil Organic Carbon Fractions and Stock
Forests 2019, 10(2), 171; https://doi.org/10.3390/f10020171
Received: 29 December 2018 / Revised: 12 February 2019 / Accepted: 14 February 2019 / Published: 17 February 2019
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Abstract
Background and Objectives: The rapid spread of invasive Spartina alterniflora Loisel. in the mangrove ecosystems of China was reduced using Sonneratia apetala Buch.-Ham. as an ecological replacement. Here, we studied the effects of invasion and ecological replacement using S. apetala on soil organic [...] Read more.
Background and Objectives: The rapid spread of invasive Spartina alterniflora Loisel. in the mangrove ecosystems of China was reduced using Sonneratia apetala Buch.-Ham. as an ecological replacement. Here, we studied the effects of invasion and ecological replacement using S. apetala on soil organic carbon fractions and stock on Qi’ao Island. Materials and Methods: Seven sites, including unvegetated mudflat and S. alterniflora, rehabilitated mangroves with different ages (one, six, and 10 years) and mature native Kandelia obovata Sheue, Liu, and Yong areas were selected in this study. Samples in the top 50 cm of soil were collected and then different fractions of organic carbon, including the total organic carbon (TOC), particulate organic carbon (POC), soil water dissolved carbon (DOC) and microbial biomass carbon (MBC), and the total carbon stock were measured and calculated. Results: The growth of S. alterniflora and mangroves significantly increased the soil TOC, POC, and MBC levels when compared to the mudflat. S. alterniflora had the highest soil DOC contents at 0–10 cm and 20–30 cm and the one-year restored mangroves had the highest MBC content. S. alterniflora and mangroves both had higher soil total carbon pools than the mudflat. Conclusions: The invasive S. alterniflora and young S. apetala forests had significantly lower soil TOC and POC contents and total organic carbon than the mature K. obovata on Qi’ao Island. These results indicate that ecological replacement methods can enhance long term carbon storage in Spartina-invaded ecosystems and native mangrove species are recommended. Full article
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