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Forest Ecology and Management
Elsevier Science
Forest Ecology and Management

Elsevier Science

0378-1127

Forest Ecology and Management/Journal Forest Ecology and ManagementSCIISTPEIAHCI
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    Fine root nutrient foraging ability in relation to carbon availability along a chronosequence of Chinese fir plantations

    Zhu, LiqinSun, JieYao, XiaodongWang, Xiaohong...
    10页
    查看更多>>摘要：In the quest to reveal the mechanisms of yield decline during the late growth stage of tree plantations, there remains a knowledge gap regarding the changes of the fine root nutrient foraging strategies during stand development and their underlying mechanisms. Fine root traits were studied using the soil core method in a typical chronosequence of six first-generation Chinese fir plantations: 2- (recently planted), 7- (sapling), 16- (middle-aged), 21- (pre-mature), 40- (mature), and 88-year-old (over-mature) stands. For the fine roots of the 0-1 mm diameter class, the specific root length (SRL), specific root area (SRA), and specific root tip density (SRT) decreased with stand age, indicating that the fine root nutrient foraging ability decreased in older stands. Fine root nitrogen (N) concentration decreased with stand age, but it significantly increased by the over-mature stage, likely as a result of physiological compensation for the decline in nutrient foraging ability. The concentrations of non-structural carbohydrates (NSCs), their components, and the NSC : N ratio (R-NN) were lower in older stands, but the ratio of soluble sugar concentration to starch concentration (R-SS) and the root delta C-13 values were higher. This reflected decreased carbon (C) availability and increased utilization of C reserves in the fine roots during late stand development. The root NSC concentration was positively correlated with SRL, SRT, and N concentration, indicating a positive effect of root C availability on nutrient foraging ability. The root delta C-13 value was positively correlated with the R-SS and negatively correlated with the R-NN, indicating that delta C-13 can accurately reflect the balance of carbohydrate supply and demand in fine roots. It was concluded that fine root nutrient foraging ability decreased in older stands, likely due to increasing fine root C limitation. These results provide a new perspective for understanding the mechanism of age-related yield decline in tree plantations.
      原文链接:
    • NSTL
    • Elsevier

    Effect of forest logging on food availability, suitable nesting habitat, nest density and spatial pattern of a Neotropical parrot

    Rivera, L.Politi, N.Bucher, E. H.Pidgeon, A....
    9页
    查看更多>>摘要：Secondary cavity nesters, bird species that rely on the presence of existing cavities, are highly vulnerable to anthropogenic and stochastic processes that reduce the availability of cavity bearing trees. The most common logging practice in Neotropical forests is selective logging, where a few valuable tree species are logged, primarily old, large trees that are the most prone to develop cavities and produce larger amounts of fruits and seeds. Tucuman Amazon, Amazona tucumana, is a threatened parrot that relies on the tree-cavities and food provided by large, old trees. Our objective was to evaluate how logging affects 1) stand and nest plot forest structure, 2) nesting site selection, 3) food availability, 4) density of suitable cavities, 5) nest density, and 6) nest spatial pattern of Tucuman Amazon by comparing a mature undisturbed forest in a National Park (NP) vs a logged forest (LF). We determined the availability of suitable cavities and food resources consumed by Tucuman Amazon, and we compared nest density and spatial pattern of nests between NP vs LF. The Index of food availability for all tree species consumed by Tucuman Amazon and for P. parlatorei were significantly higher in NP than in LF (34.5 +/- 13.3 m ha(-1) vs. 3.5 +/- 1.0 m ha(-1) and 5.6 +/- 2.3 m ha(-1) vs. 1.2 +/- 1.0 m ha(-1), respectively). Density of suitable cavities for nesting in the NP was significantly higher than in the LF: 4.6 cavities ha(-1) [C.I. 95 %: 3.07 - 7.04 cavities ha(-1)] vs. 1.1 cavities ha(-1) [C.I. 95 %: 0.73 - 1.66 cavities ha(-1)], respectively. Mean density of Tucuman Amazon nests was significantly higher in the NP than in LF (0.25 +/- 0.04 vs. 0.06 +/- 0.04 nest ha(-1), respectively). Food availability is an important factor that affects Tucuman Amazon populations and when food is not limiting, the availability of suitable cavities and territorial behavior could play a role in regulating nest density. When evaluating the limiting factors for secondary cavity-nesting species of conservation concern it is important to evaluate the interplay of a set of potential limiting factors to propose sound forest management recommendations.
      原文链接:
    • NSTL
    • Elsevier

    Does natural stand dynamics generate an aggregated pattern of canopy openness? A case study in Abies-Picea-Fagus old-growth forests

    Paluch, J.Jastrzebski, R.
    13页
    查看更多>>摘要：The action of many agents causing the mortality of overstory trees may potentially induce the formation of an aggregated distribution of canopy gaps. In this study we tested the hypothesis that natural stand dynamics generates an aggregated pattern of canopy openness in old-growth forests formed by Fagus sylvatica L., Abies alba Mill. and Picea abies (L.) H. Karst. We compared canopy openness and its spatial heterogeneity in five stands in the Western Carpathians (Central Europe) and three stands in the Dinaric Mountains (Southeast Europe). The stands were between 4.48 and 9.24 ha in size. In each stand we took hemispheric photographs in a regular 20 x 20 m grid in the leafless period to minimize coverage by the understory. Tree species and the dbh of live trees of dbh >= 7 cm were recorded on circular plots with a radius of 7 m centered at the grid points. At the stage of picture processing, understory trees of dbh <25 cm and polar coordinates recorded during field measurements were removed from the pictures, and for every grid point the local canopy openness of the overstory layer was determined in the sky region defined by a zenith angle of 15 degrees. We characterized the spatial pattern of canopy openness by using variograms and Morans I coefficients and tested the spatial dependence in the distribution patterns of grid points characterized by different levels of canopy openness. Depending on the stand, mean canopy openness varied between 17.5 and 41.0%, with the greatest values recorded in the Carpathian stands with a considerable proportion of Norway spruce and a more severe disturbance regime. Relationships between canopy openness and the overall number, basal area or volume of trees forming the overstory were strongly modified by variation in the density and species percentage in the mid-canopy zone. In all the stands small-scale variation determined for inter-point distances of 20 m accounted for the majority of the total variation in canopy heterogeneity and ranged between 61 and 100%. We found a tendency to form random patterns of canopy openness in the Dinaric stands, which were characterized by a greater basal area and probably also lower frequency of severe disturbances, and aggregated patterns in the Carpathian stands, which were characterized by a smaller basal area driven by more severe disturbances. The revealed spatial dependence in canopy openness may suggest that in the studied ecosystem canopy gaps are not only a legacy of the mortality of canopy trees but also self-organizing structural elements which, under a more severe disturbance regime, can affect the mortality rate in their neighbourhood. Nonetheless, the percentage of spatially structured variability in canopy openness observable at scales larger than the grid spacing used in our study was insignificant (83% on average). The close-to-random pattern of canopy heterogeneity may weaken the spatio-temporal synchronization of the juvenile growth, maturation and senescence of neighbouring trees and counteract the formation of coarse-grained patch mosaics.
      原文链接:
    • NSTL
    • Elsevier

    Analysis of various crown variables on stem form for Cunninghamia lanceolata based on ANN and taper function

    Liang, RuitingSun, YujunZhou, LaiWang, Yifu...
    10页
    查看更多>>摘要：Crown, with many dimensions greatly influences the stem taper of a tree. However, few taper models have accounted for its impact on diameter estimation. In order to investigate and quantify the effects of various crown factors on stem taper and develop new taper models incorporating crown information for Cunninghamia lanceolata in Southeast China, a sample data of 1100 taper measurements from 108 trees and two different modeling methods were utilized. A set of traditional non-linear regression (NLR) models with linear and non-linear functions composed of crown factors introduced respectively, were developed for stem diameter prediction, as well as artificial neural network (ANN) models based on different input variables. ANN technology was applied to variable screening prior to developing models, and the evaluation statistics and graphics were used to assess the models. The results showed that crown length (CL) and height to live crown base (HCB) had larger influence on the model accuracy than other crown variables, demonstrating that variables screening based on ANN is feasible and efficient when numerous potential variables are available. The accuracy of taper model was improved when incorporating different crown variables or their combinations in terms of higher R-2 and lower RMSE, however, the degree of improvement varied, depending on the variables added and the modelling approach. The inclusion of CR and HCB presented the highest improvement, whether using ANN or NLR modelling methods. The ANN model decreased 13.96 % in RMSE and 17.00 % in MAE. Similarly, the NLR model reduced 2.1 % in RMSE and 1.78 % in MAE. This study indicated that the refined models with crown variables included were more in line with the biological logic of nature and the accuracy has been improved, although the improvement of nonlinear regression models was not as significant as expected. In addition, it also suggested that in forest resource inventory, ANN was a recommended technique for variable screening and an alternative method for model development.
      原文链接:
    • NSTL
    • Elsevier

    Hardwood mixtures facilitate leaf litter decomposition and soil nitrogen mineralization in conifer plantations

    Masaka, KazuhikoMorikawa, YumenaSuzuki, MasanoriTada, Chika...
    10页
    查看更多>>摘要：Productivity in conifer plantations can be increased by hardwood mixture. However, the underlying mechanisms that govern the relationship between hardwood mixture and productivity remain poorly understood, particularly with respect to nutrient cycling. We investigated how and to what extent hardwood mixtures alter nitrogen amounts in leaf litterfall, leaf litter decomposition rates, and soil nitrogen mineralization rates in an experiment that used different thinning intensities (i.e., a non-thinned "control" group with few hardwoods, a 33%-thinned "weak" group with a small amount of hardwoods, and a 67%-thinned "intensive" group with abundant hardwoods) in a conifer Cryptomeria japonica plantation (38-year old). Most of the hardwoods were 15-year old trees that have been regenerated after the first thinning. The annual leaf litterfall amount for the conifer was highest in the control group and lowest in the intensive group, whereas the reverse was true for hardwoods, although the hardwoods' annual leaf litterfall amount was approximately half that of conifers, even in the intensive group. Consequently, the annual amount of leaf litterfall of hardwoods and conifers combined was lowest in the intensive group. However, the total amount of nitrogen in the annual leaf litterfall of hardwoods and conifers combined did not differ according to thinning intensity, because the mass-based nitrogen concentration in the leaf litterfall of hardwoods was twice that of conifers. The leaf litter decomposition rate in hardwoods was approximately three times faster than that in conifers irrespective of thinning intensity, mainly due to the lower carbon-to-nitrogen (C:N) ratio. Thus, the total amount of nitrogen in the decomposed leaves of hardwoods and conifers combined, calculated by multiplying the total amount of nitrogen in the annual leaf litterfall of hardwoods and conifers by the decomposition rate and summing the results, was highest in the intensive group. In soil from shallow depths (0-10 cm), the nitrogen mineralization rate increased in the order of control, weak, and intensive, attributable primarily to the C:N ratio, which decreased in the same order. The results indicated that increasing the hardwood content by intensive thinning significantly enhances the availability of soil inorganic nitrogen in conifer plantations, by facilitating leaf litter decomposition and soil nitrogen mineralization. These findings indicate that hardwood mixtures can increase forest productivity by enhancing nitrogen cycling.
      原文链接:
    • NSTL
    • Elsevier

    One of the world's largest regreening programs promotes healthy tree growth and nutrient accumulation up to 40-years post restoration

    Galarza, JessicaLevasseur, Patrick A.Watmough, Shaun A.
    10页
    查看更多>>摘要：Mining and smelting degraded landscapes are characterised by heavily eroded, acidic soils that are contaminated with toxic metals and depleted of essential nutrients. Increasing forest cover through regreening of degraded landscapes has been highlighted to support carbon (C) mitigation measures and protect biodiversity. One of the worlds largest regreening programs in the City of Greater Sudbury, Ontario has been ongoing since 1978 and involves the liming and fertilization of selected areas followed by planting of primarily coniferous trees. In this study, we assessed how aboveground biomass (AGB) and aboveground nutrient (calcium (Ca), magnesium (Mg), nitrogen (N), phosphorous (P), potassium (K), and C) pools changed using a space-for-time approach. We established a series of sites ranging from 15 to 42 years since treatment. To determine the potential effects of erosion on AGB and AGB nutrient pools, each site was categorized as "stable" (<10% bedrock cover) or "eroded" (greater than 30% bedrock cover). Both AGB and AGB nutrient pools increased with time since regreening at rates similar to conifer plantations grown in undisturbed regions. Individual tree growth and nutrient accumulation did not differ between stable and eroded sites; however, stable sites had a higher stem density leading to overall higher per hectare AGB and AGB nutrient pools. Future N limitation of the regreening forests does not appear to be a concern as aboveground N pools were six times larger than applied N. Conversely, aboveground P concentrations decreased with time since tree planting and the 40-year-old study sites had aboveground P concentrations below values for "healthy" trees. This study shows that the regreening efforts have led to a massive addition of 1,144,588 Mg of AGB (550,547 Mg C) onto the landscape, and capable of sustaining healthy tree growth up to 40-years post regreening. However, as the regreening stands age, nutrient limitation may impact future tree growth and warrants further study.
      原文链接:
    • NSTL
    • Elsevier

    Assessing the effects of large herbivores on the three-dimensional structure of temperate forests using terrestrial laser scanning

    Ge, JianpingWang, TianmingLi, ShunHou, Zhengyang...
    11页
    查看更多>>摘要：Three-dimensional (3D) vegetation structure is vital in maintaining the functions of forest ecosystems and species diversity. Temperate forests of Northeast Asia support a variety of fauna but is also affected by large herbivore disturbances or management practice (e.g., livestock grazing), resulting in varying degrees of habitat degradation and fragmentation in many areas. However, traditional methods lack the quantification of 3D vegetation structure at a fine scale, which makes it difficult to obtain complete and accurate detailed data on the multi-level structure below the canopy and limits our understanding of the impact of disturbance on habitat quality and species diversity. In this study, terrestrial laser scanning (TLS) data were used to quantify the 3D habitat structural characteristics of different stand types affected by forest management or large herbivore activities (deer-browsed forest, livestock-grazed forest, secondary forest, and mixed forest) in Northeast China. TLSderived parameters in this study revealed the subtle changes of habitat structures below the canopy: 1) livestock-grazed forest had a much lower canopy height, tree number, and stem volume than that of the other stand types; 2) the vegetation area index (VAI) of low canopy height (0-5 m) in livestock-grazed forest and deerbrowsed forest were significantly lower than those in secondary and mixed forest with less disturbance; 3) intensive large herbivores activities led to the larger understory gaps and visibility in livestock-grazed and deerbrowsed forest. TLS-derived parameters in this study are implicated in wildlife habitat selection and fitness, which contribute to revealing fine scale habitat structure-species diversity relationships. In forest management, it is proposed to use TLS to quantify the structural and functional attributes of habitats from a new perspective, thus guiding conservation practices at local scale to balance the relationship between plants and animals.
      原文链接:
    • NSTL
    • Elsevier

    Does forest management affect the magnitude and direction of the afforestation effect on soil methane fluxes? A meta-analysis

    Gatica, GabrielFernandez, Ma. ElenaJuliarena, Ma PaulaGyenge, Javier...
    10页
    查看更多>>摘要：Evidence suggests that tree plantations change soil methane (CH4) fluxes (magnitude and/or direction of the fluxes) compared to herbaceous land (i.e. afforestation effect) due to the effect of trees increasing methanotroph bacteria abundance and enhancing soil gas diffusivity. However, the magnitude of this afforestation effect is highly variable across studies. Here, we evaluated whether the variation in the afforestation effect depends on forestry management strategies, described by stand age and density, as well as taxonomic identity of the tree species, and the interaction with climatic conditions. To this end, we conducted a meta-analysis using 47 paired samples of afforested and contiguous herbaceous land from 14 studies located in different biomes worldwide. We found that afforestation predominantly increases the capacity of soil net CH4 uptake (i.e. more negative fluxes) compared to herbaceous land, but the magnitude of this effect was highly heterogeneous across paired samples. This heterogeneity was explained by environmental conditions, but significant effects of forest stand age and density were also found proving the importance of forest management on this ecological service. Soil net CH4 uptake following afforestation increases with increasing stand age. Although the stand stocking effect could be tested with a limited number of studies (24 out of the 47 paired samples), the results suggest that net CH4 uptake decreases with tree stocking (stand density) in the range of values up to 1500 individuals per ha. No change in CH4 fluxes was observed above this high stand density. Contrary to our expectations, no effect of taxonomic identity of the trees considering the most planted genera (Pinus and Eucalyptus) was observed in the average soil CH4 fluxes. Furthermore, a significant correlation between the afforestation effect on soil water content and CH4 flux suggests that the most plausible cause of the increased soil net CH4 uptake is driven by the forest impact on soil desiccation, which in turn increases in sites with higher water limitation (i.e. higher potential evapotranspiration and high temporal rainfalls variations within the ranges of the available studies). Finally, our study provides evidence that by modifying rotation time and stand stocking, afforested land may increase its environmental service as a sink of atmospheric CH4.
      原文链接:
    • NSTL
    • Elsevier

    Operational resilience in western US frequent-fire forests

    North, Malcolm P.Tompkins, Ryan E.Bernal, Alexis A.Collins, Brandon M....
    9页
    查看更多>>摘要：With the increasing frequency and severity of altered disturbance regimes in dry, western U.S. forests, treatments promoting resilience have become a management objective but have been difficult to define or operationalize. Many reconstruction studies of these forests when they had active fire regimes have documented very low tree densities before the onset of fire suppression. Building on ecological theory and recent studies, we suggest that this historic forest structure promoted resilience by minimizing competition which in turn supported vigorous tree growth. To assess these historic conditions for management practices, we calculated a widely-used measure of competition, relative stand density index (SDI), for two extensive historical datasets and compared those to contemporary forest conditions. Between 1911 and 2011, tree densities on average increased by six to seven fold while average tree size was reduced by 50%. Relative SDI for historical forests was 23-28% of maximum, in the ranges considered 'free of' (<25%) to 'low' competition (25-34%). In contrast, most (82-95%) contemporary stands were in the range of 'full competition' (35-59%) or 'imminent mortality' (>= 60%). Historical relative SDI values suggest that treatments for restoring forest resilience may need to be much more intensive then the current focus on fuels reduction. With the contemporary increase in compounding stresses such as drought, bark beetles, and high-severity wildfire, resilience in frequent-fire forests may hinge on creating stands with significantly lower densities and minimal competition. Current management practices often prescribe conditions that maintain full competition to guide development of desired forest conditions. Creating stands largely free of competition would require a fundamental rethinking of how frequent-fire forests can be managed for resilience.
      原文链接:
    • NSTL
    • Elsevier

    An introduced pine shapes gastropod assemblages in the Central European broadleaved forest

    Jankowiak, AnnaGoldyn, BartlomiejRawlik, MateuszBernard, Rafal...
    13页
    查看更多>>摘要：The aim of this study was to determine the impact of the introduction of Pinus sylvestris on the mesofauna of the forest floor in the Central European oak-hornbeam forest, using gastropods as a model group. Data on terrestrial gastropods and environmental variables were collected in 2012-2014 from 25 study plots (14 without pine and 11 with pine) at 14 localities scattered across Wielkopolska province in mid-western Poland. Forty-two species (34 of snails and 8 of slugs) were recorded, with significantly lower numbers of individuals and species in plots with pine. The negative effect of the presence of pine trees was most evident at the level of gastropod abundance. The species composition of gastropod assemblage was also significantly different between plots with and without pine. The symptoms of the assemblages reduction, impoverishment and trivialization thus suggested a long-term effect of the introduced pine on natural mesofauna. However, gastropod assemblage was shaped not by one dominating factor, but by a multifactorial combination of interacting variables, particularly related to herbaceous vegetation and to the tree- and shrub layer. Herb layer cover, moisture (reflected in the herbs), fertility (reflected in the herbs), and locally also the amount of calcium in the soil and insolation were found to be significant for the structure of gastropod assemblages. More environmental variables were significant at the sample level (i.e. within forest) than at the plot level (i.e. between forests), which is likely to be due to greater variation in the conditions within a rich forest as opposed to lower variation between forests. This highlighted the importance of using a two-scale approach to understand the conditions affecting gastropod assemblage structure in a habitat that is seemingly homogenous on the macro scale, but diversified and mosaic in the micro scale. The negative effects of pine introduction and the positive significance of the multifactorial combination of habitat factors at the macro- and micro level appear as important guidelines for favourable biodiversity management in the Central European oak-hornbeam forest and in other broadleaved forests.
      原文链接:
    • NSTL
    • Elsevier