Role Of Forest Structure Research Articles

Scaling up tree growth to assess forest resilience under increasing aridity: the case of Iberian dry-edge pine forests

ContextMediterranean managed dry-edge pine forests maintain biodiversity and supply key ecosystem services but are threatened by climate change and are highly vulnerable to desertification. Forest management through its effect on stand structure can play a key role on forest stability in response to increasing aridity, but the role of forest structure on drought resilience remains little explored.ObjectivesTo investigate the role of tree growth and forest structure on forest resilience under increasing aridity and two contrasting policy-management regimes. We compared three management scenarios; (i) “business as usual”-based on the current harvesting regime and increasing aridity—and two scenarios that differ in the target forest function; (ii) a “conservation scenario”, oriented to preserve forest stock under increasing aridity; and (iii), a “productivity scenario” oriented to maintain forest yield under increasingly arid conditions.MethodsThe study site is part of a large-homogeneous pine-covered landscape covering sandy flatlands in Central Spain. The site is a dry-edge forest characterized by a lower productivity and tree density relative to most Iberian Pinus pinaster forests. We parameterized and tested an analytical size-structured forest dynamics model with last century tree growth and forest structure historical management records.ResultsUnder current management (Scenario-i), increasing aridity resulted in a reduction of stock, productivity, and maximum mean tree size. Resilience boundaries differed among Scenario-ii and -Scenario-iii, revealing a strong control of the management regime on resilience via forest structure. We identified a trade-off between tree harvest size and harvesting rate, along which there were various possible resilient forest structures and management regimes. Resilience boundaries for a yield-oriented management (Scenario-iii) were much more restrictive than for a stock-oriented management (Scenario-ii), requiring a drastic decrease in both tree harvest size and thinning rates. In contrast, stock preservation was feasible under moderate thinning rates and a moderate reduction in tree harvest size.ConclusionsForest structure is a key component of forest resilience to drought. Adequate forest management can play a key role in reducing forest vulnerability while ensuring a long-term sustainable resource supply. Analytical tractable models of forest dynamics can help to identify key mechanisms underlying drought resilience and to design management options that preclude these social-ecological systems from crossing a tipping point over a degraded alternate state.

Ranging ecology and resource selection of white-lipped peccaries (Tayassu pecari) in the world's largest tropical agricultural frontier.

Agricultural commodity production is one the main drivers of deforestation in Legal Brazilian Amazonia resulting in a deforested and/or fragmented landscape formed by forest remnants of different sizes and shape embedded within the agricultural matrix. As an ecosystem engineer and a crucial seed predator, white-lipped peccaries (Tayassu pecari) play a pivotal role in forest structure, biodiversity, and nutrient cycling. However, they are highly sensitive to habitat fragmentation and hunting pressure. White-lipped peccaries are, therefore, a wide-ranging "landscape species," the spatial and ecological requirements of which can be used to guide conservation planning in human-modified landscapes. Using data from GPS-tracked individuals in large-scale mechanized agriculture landscapes in the state of Mato Grosso, Brazil's largest soybean and maize producer, we investiated the home range size and resource selection during both the crop and non-crop season. We observed a seasonal variation in home range size and an increased selection for croplands during the crop season. White-lipped peccaries favored native vegetation patches and also exhibited avoidance of locations distant from perennial water bodies and distant cropland locations far from forest remmants. This study can contribute to inform effective conservation strategies and land management practices aimed at preserving suitable habitats and promoting wildlife coexistence with working agricultural landscapes.

Multidimensional beta-diversity across local and regional scales in a Chinese subtropical forest: The role of forest structure.

Beta-diversity, or the spatio-temporal variation in community composition, can be partitioned into turnover and nestedness components in a multidimensional framework. Forest structure, including comprehensive characteristics of vertical and horizontal complexity, strongly affects species composition and its spatial variation. However, the effects of forest structure on beta-diversity patterns in multidimensional and multiple-scale contexts are poorly understood. Here, we assessed beta-diversity at local (a 20-ha forest dynamics plot) and regional (a plot network composed of 19 1-ha plots) scales in a Chinese subtropical evergreen broad-leaved forest. We then evaluated the relative importance of forest structure, topography, and spatial structure on beta-diversity and its turnover and nestedness components in taxonomic, functional, and phylogenetic dimensions at local and regional scales. We derived forest structural parameters from both unmanned aerial vehicle light detection and ranging (UAV LiDAR) data and plot inventory data. Turnover component dominated total beta-diversity for all dimensions at the two scales. With the exception of some components (taxonomic and functional turnover at the local scale; functional nestedness at the regional scale), environmental factors (i.e., topography and forest structure) contributed more than pure spatial variation. Explanations of forest structure for beta-diversity and its component patterns at the local scale were higher than those at the regional scale. The joint effects of spatial structure and forest structure influenced component patterns in all dimensions (except for functional turnover) to some extent at the local scale, while pure forest structure influenced taxonomic and phylogenetic nestedness patterns to some extent at the regional scale. Our results highlight the importance and scale dependence of forest structure in shaping multidimensional beta-diversity and its component patterns. Clearly, further studies need to link forest structure directly to ecological processes (e.g., asymmetric light competition and disturbance dynamics) and explore its roles in biodiversity maintenance.

Structural complexity and primary production resistance are coupled in a temperate forest

The capacity of forests to resist structural change and retain material legacies–the biotic and abiotic resources that persist through disturbance–is crucial to sustaining ecosystem function after disturbance. However, the role of forest structure as both a material legacy and feature supporting carbon (C) cycling stability following disturbance has not been widely investigated. We used a large-scale disturbance manipulation to ask whether legacies of lidar-derived canopy structures drive 3-year primary production responses to disturbance. As part of the Forest Resilience Threshold Experiment (FoRTE) in northern Michigan, USA we simulated phloem-disrupting disturbances producing a range of severities and affecting canopy trees of different sizes. We quantified the legacies of forest structure using two approaches: one measuring the change in structure and primary production from pre-to post-disturbance and the second estimating resistance as log transformed ratios of control and treatment values. We found that total aboveground wood net primary production (ANPPw) was similar across disturbance severities as legacy trees rapidly increased rates of primary production. Experiment-wide, the disturbance had limited effects on change in mean structural complexity values; however, high variance underscored large differences in the magnitude and direction of complexity's response at the plot-scale. Plot-scale structural complexity, but not vegetation area index (VAI), resistance strongly predicted ANPPw resistance while temporal VAI and structural complexity changes did not. We conclude that the presence of material legacies in the form of forest structure may affect primary production stability following disturbance and that how legacies are quantified may affect the interpretation of disturbance response.

The role of forest structure and composition in driving the distribution of bats in Mediterranean regions

Forests are key native habitats in temperate environments. While their structure and composition contribute to shaping local-scale community assembly, their role in driving larger-scale species distributions is understudied. We used detailed forest inventory data, an extensive dataset of occurrence records, and species distribution models integrated with a functional approach, to disentangle mechanistically how species-forest dependency processes drive the regional-scale distributions of nine forest specialist bats in a Mediterranean region in the south of Spain. The regional distribution patterns of forest bats were driven primarily by forest composition and structure rather than by climate. Bat roosting ecology was a key trait explaining the strength of the bat-forest dependency relationships. Tree roosting bats were strongly associated with mature and heterogeneous forest with large trees (diameters > 425 mm). Conversely, and contrary to what local-scale studies show, our results did not support that flight-related traits (wing loading and aspect ratio) drive species distributional patterns. Mediterranean forests are expected to be severely impacted by climate change. This study highlights the utility of disentangling species-environment relationships mechanistically and stresses the need to account for species-forest dependency relationships when assessing the vulnerability of forest specialists towards climate change.

Analyzing the effect of silvicultural management on the trade-off between stand structural heterogeneity and productivity over time

This study combined an empirically based simulation with an analysis of the trade-off between structural heterogeneity and stand productivity depending on time, spatial scale, and silvicultural management, whereas volume growth and tree species diversity have been examined in detail, the role of forest structure and its interdependencies with stand productivity has only lately become a stronger research focus. We used the growth simulator SILVA to examine the development of stand structural heterogeneity and its trade-off with stand productivity in age-class versus uneven-aged pure and mixed spruce and beech stands at different spatial scales over 100 years. Those stands were based on typical forest types in Bavaria and were representative of forests in Central Europe. We examined how stand structure and its trade-off with productivity were modified by a multifunctional, a production-oriented, and a set-aside management scenario. The production-oriented management scenario applied to uneven-aged stands led to a reduction in structural heterogeneity per unit of productivity over time. In age-class stands, the production-oriented scenario was able to maintain the initial structural heterogeneity. The structural heterogeneity per unit of productivity increased more strongly with increasing spatial scale in age-class stands compared to uneven-aged stands. Combining forest stand simulation with scenario analyses is an exemplary method for testing the effect of silvicultural management alternatives on forest structure. This approach can later be connected to climate models considering long-term changes in growing conditions and support the planning of multifunctional forests.

Fruit Bat Assemblage in Different Lowland Forest Types in the Northern Sierra Madre Mountains, Philippines

Prior studies of species assemblages of fruit bats in the Philippines have focused on primary and disturbed habitats as the point of comparison. No studies to date have been conducted on assemblages of fruit bats within primary lowland forest vegetation types. This study aimed to determine the fruit bat assemblage in dipterocarp, mangrove and lowland ultramafic forest and their association with these vegetation types. We hypothesize that difference in the diversity and abundance of fruit-producing plants in these habitat types would influence the abundance and diversity of bats. The study was conducted in the Northern Sierra Madre Natural Park, Philippines from April to October 2017. Eleven species of fruit bats were captured during the study, in order of decreasing abundance: Rousettus amplexicaudatus, Ptenochirus jagori, Cynopterus brachyotis, Macroglossus minimus, Haplonycteris fischeri, Eonycteris robusta, Desmalopex leucopterus, Eonycteris spelaea, Pteropus vampyrus, Acerodon jubatus and Pteropus hypomelanus. Species richness was highest in dipterocarp forest (11 species), and lowest in the mangrove area (seven species), but species diversity was highest in the lowland ultramafic forest. The study suggests that species diversity and abundance of fruit bats in the different lowland vegetation habitats can be linked to their diet and morphology. Frugivores were strongly associated with dipterocarp forest and lowland ultramafic forest where fruit-producing plant diversity is high. Haplonycteris fischeri, C. brachyotis and P. jagori were more abundant in the dipterocarp than in the ultramafic forest. The abundance of nectarivores varied between vegetation types. Macroglossus minimus was more abundant in the mangrove while E. robusta and R. amplexicaudatus were more abundant in the dipterocarp and ultramafic forest. The difference in plant species composition and abundance may explain the variation in frugivore and nectarivore abundance between vegetation types. No pattern could be discerned for the large flying foxes (A. jubatus, P. hypomelanus, and P. vampyrus) because of few captures in each habitat, except for D. leucopterus, which was frequently captured in lowland ultramafic forest. The low captures of flying foxes may be attributed to the difficulty of capturing high-flying bats. Further research on foraging behavior, fruit selection by bats and the role of forest structure in determining the abundance and distribution of fruit bats is needed.

Spatial pattern dynamics among co-dominant populations in early secondary forests in Southwest China

The canopy of subtropical natural forests usually consists of several co-dominant populations (CDPs), which play a crucial role in forest structure, formation of the forest environment, and ecological function. However, little attention has been given to changes in spatial patterns in CDPs during natural succession. Cyclobalanopsis glauca (Thunb.) Oerst., Quercus variabilis Blume, and Pinus yunnanensis var. tenuifolia W.C. Cheng & Y.W. Law are canopy species that form CDPs in zonal forests along the Nanpan River in southwest China. We used the g(r) function and its bivariate distribution model, g12(r), which is based on distances between pairs of points, to explore the dynamics of the three CDP species with respect to distribution patterns and spatial correlations in two secondary forests (one 30-year-old forest [30-YF] and one 57-year-old forest [57-YF]). The following key results were obtained: (1) there was a clumped pattern in the 30-YF, but the intensity of aggregation varied among populations and life stages. The distribution pattern gradually shifted to become random with longer succession time (i.e., 30-YF vs. 57-YF), expansion of the observation scale (r = 0–20 m), and at later life stages. (2) Aside from the mid-sized C. glauca trees and large P. yunnanensis trees, the trees repulsed each other at certain scales (r = 0–2, 5–6, 11–12, 14–16 m) in the 30-YF. Almost all of the life stages in the CDPs were independently correlated. This independent correlation was exacerbated by a longer succession time. (3) An increase in life stages and longer succession also promoted independent changes in intraspecific correlations. (4) Intraspecific correlations were stronger than interspecific correlations. Our results showed that reducing exclusive competition is essential to coexistence in CDPs. Inter- and intra-specific repulsion may occur at the same time, but intraspecific repulsion was the main driving force behind the random distributions and independent correlations.

Effects of habitat features and season on vertebrate communities in Southern Georgia, U.S.A.

ABSTRACTAlthough the southeastern U.S.A. contains a high diversity of species and habitats, this region is also experiencing rapid human development. Humans are modifying ecosystems in complex ways, and these changes often result in shifts in biodiversity. Therefore, examining habitat use in human-altered ecosystems gives insight into how animals will continue to respond to their rapidly changing environments. Biodiversity and abundance can be influenced by several factors, including habitat structure and seasonal variation. Understanding how these factors influence biodiversity is particularly important in areas that are experiencing high levels of human activity. Thus, we surveyed artificial cover objects to examine the effects of forest structure and season on several indices of diversity in vertebrates (mammals, reptiles, and amphibians) in forested sites in the southeastern U.S.A., a region characterised by rapid human population growth. Vertebrate abundance varied by season where abundance in the fall and winter were lower than in the spring and summer. The proximity to roads affected vertebrate abundance where abundance was higher under cover objects farther from roads. Our results provide evidence that anthropogenic, biotic, and temporal factors can influence vertebrate abundance and biodiversity. We also provide insight into the role of forest structure in vertebrate biodiversity, and we encourage future efforts focusing on the role of structural variation across different ecosystems.

Fire and lichen dynamics in the Taiga Shield of the Northwest Territories and implications for barren‐ground caribou winter forage

AbstractQuestionsFire is the main disturbance agent in boreal forests and has profound effects on vegetation composition and structure, including terrestrial lichens that provide critical winter forage for barren‐ground caribou. What is the influence of fire on forest structure and the distribution and species assemblage of forage lichens? What is the current or potential effect of climate change on forage lichen in the boreal forest?LocationHigh Boreal, Low Subarctic, and High Subarctic ecoregions of the Taiga Shield Ecozone in the Northwest Territories, Canada.MethodsWe used fire history data, satellite and air photo images, and field sampling to determine fire history and severity, and subsequent effects on tree and lichen species composition, in a 880,000 ha study area in the winter range of the Bathurst caribou herd.ResultsWe found that low‐ and mixed‐severity fires were more common than high‐severity fires, and that forest fire severity increased with distance to treeline. Forest structure and composition were more important drivers of lichen cover than fire severity or time since fire.ConclusionsWhile fire had a dominant role in forest structure and composition, the effects on lichen availability were due more to variation in tree growth. We found little evidence of changes in fire regime over the length of our reconstructions (approximately 200 years); however, increases in temperature and the positive relationship between temperature and fire frequency may lead to shortened fire cycles causing a reduction in the availability of forage lichens through burning.

Forest structure along a 600 km transect of natural disturbances and seasonality gradients in central‐southern Amazonia

Summary A negative relationship between stand biomass and the density of stems is expected to develop during the self‐thinning process in resource‐limited forests; this leads to a large proportion of the total biomass occurring in large trees. Nevertheless, frequent disturbance regimes can reduce self‐thinning and the accumulation of large trees. We investigated size–density relationships and the contribution of large trees (dbh ≥ 70 cm) to stand biomass in 55 1‐ha plots along a 600 km transect in central‐southern Amazonia. The effects of natural‐disturbance gradients (frequency of storms and soil characteristics) and seasonality on forest‐structure components (density of stems and mean individual mass) and stand biomass were examined. Contrary to self‐thinning predictions, stand biomass increased in forests with higher stem densities. Large trees contained only an average of 5% of stand biomass, and half of the stand biomass was represented by small trees with diameters < 27 cm. These findings indicate that persistent or strong disturbance plays a critical role in forest structure and biomass in the central‐southern Amazon. Frequent storms were identified as an important source of disturbance in the region. Forests under higher frequency of storms had trees with lower individual mass and higher stem packing. More physically restrictive soils seem to magnify the effects of exogenous disturbances limiting individual tree size. Forests in areas with longer dry seasons had lower stem densities; however, individual mass was higher in these areas. These structural components of biomass seem to counterbalance each other in generating total stand biomass. Seasonality affected forest structural components but not stand biomass. Synthesis. Forests of central‐southern Amazonia are not resource limited and accumulate most part of their biomass in small‐ to mid‐sized trees. The effects of environmental gradients on specific structural components of stand biomass differ such that strong positive effects on one component can mitigate strong negative effects on other component. Future work on the determinants of stand biomass should investigate forest structure and the contributions of individual components to stand biomass.

The role of forest structure and human occupation in structuring mammal assemblages in oligotrophic ecosystems ofCentralAmazonia

AbstractLarge mammals are vulnerable to extinction, and respond directly to ecological gradients within the forest and to the intensity of forest product use by humans. In this study, we evaluated the effects of differences in forest structure and human occupation history on the composition of medium and large‐sized mammal assemblages of theterra‐firmeforests of theAnavilhanasNationalPark, one of the most oligotrophicAmazonian ecosystems. Mammal surveys were conducted along 11 linear transects of 4 km, six of which were located in areas once inhabited by people and managed until the year that the park was created (over 30 years ago), and five in areas that were not inhabited at that time. We detected 469 individuals of 26 species during diurnal and nocturnal sampling, and 11 additional species outside transects. Human occupation history was strongly related to forest structure components. Fruit biomass, canopy cover and tree size were strongly associated with uninhabited areas, and influenced the structure of mammal assemblages. A direct relationship between diet category and species size was observed. Large frugivore‐herbivores and carnivores were more closely associated with areas with more fruit, larger trees and greater canopy cover. In contrast, small arboreal frugivore‐omnivores associated more closely with open canopy and smaller trees. Our study indicated that the effects of human occupation history on forest structure are still evident three decades after the removal of local people from the park. This long‐term effect can be explained by the low resilience of theAnavilhanas environments, demonstrating the fragility of mammal assemblages in face of anthropogenic variation in forest structure in the oligotrophic ecosystems of theNegroRiver basin.

天目山近自然毛竹林空间结构与胸径的关系

PDF HTML阅读 XML下载 导出引用 引用提醒 天目山近自然毛竹林空间结构与胸径的关系 DOI: 10.5846/stxb201308252154 作者: 作者单位: 浙江农林大学环境与资源学院 临安,浙江农林大学环境与资源学院 临安,浙江农林大学环境与资源学院 临安,浙江农林大学环境与资源学院 临安,天目山国家级自然保护区管理局 临安 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31170595); 国家"十二五"科技支撑计划(2012BAD22B0503); 浙江省重点科技创新团队(2010R50030); 教育部留学回国人员科研启动金项目(20101561); 国家林业局造林司委托项目(SFA2130218-2) The relationship between spatial structure and DBH of close-to-nature Phyllostachys edulis stands in Tianmu Mountain Author: Affiliation: School of Environment and Resource,Zhejiang A F University,School of Environment and Resource,Zhejiang A F University,School of Environment and Resource,Zhejiang A F University,School of Environment and Resource,Zhejiang A F University,Management Office,National Nature Reserve of Tianmu Mountain,Linan Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以浙江省天目山国家级自然保护区内的近自然毛竹林为研究对象,设置1块100m×100m的固定标准地,采用相邻网格调查法划分为100个调查单元,通过全站仪精确定位毛竹基部的三维坐标(X, Y, Z),利用角尺度、大小比数和年龄隔离度3个林分空间结构指数,并按毛竹胸径大小划分为Ⅰ(DBH < 7cm) 、Ⅱ(7cm ≤ DBH<13cm)、Ⅲ(DBH ≥ 13cm)3个径级,分析近自然毛竹林空间结构与胸径的关系。结果表明:毛竹林直径结构呈右偏近似正态分布,与乔木同龄林直径结构较接近;Ⅰ、Ⅱ、Ⅲ径级毛竹以及全林分的空间分布格局分别为聚集、随机、随机和随机,毛竹林角尺度随径阶的增加有减小的趋势,且服从幂函数关系,决定系数R2=0.7793,各径阶角尺度无显著性差异(P > 0.05);毛竹林整体处于中庸状态,胸径大小分化不明显,各径级毛竹优势度排序为Ⅲ > Ⅱ > Ⅰ,毛竹林大小比数随径阶的增加而减小,与胸径呈线性关系,决定系数R2=0.9233,各径阶大小比数差异极显著(P < 0.01);毛竹林的平均年龄隔离度为0.8178,属强度至极强度异龄,各径级毛竹年龄隔离程度大小排序为Ⅲ > Ⅱ > Ⅰ,毛竹林年龄隔离度随径阶的增大呈现逐渐递增的趋势,且服从幂函数关系,决定系数R2=0.6774,各径阶年龄隔离度差异极显著(P < 0.01)。 Abstract:Tree diameter structure is an important and basic role in forest structure. For the reason that the diameter at breast height (DBH) can be easily and accurately measured. Because it has a close relationship with variables such as stand density, tree age, tree height, canopy, biodiversity and so on, diameter structure is often used as a direct-response stand structure characteristic. DBH belongs to a set of non-spatial forest structure factors, and is frequently used to analyze the relationship between stand structure and growth, e.g. Recently, studies of forest spatial structure have expanded, partly due to the fact that the DBH is an important factor in explaining the growth of trees, and in many cases because the diameter structure has been used to analyze the relationship between spatial structure and DBH. Similarly, DBH is also an important factor in reflecting the growth of moso bamboo (Phyllpstachys edulis) forests. The DBH of moso bamboo can directly influence leaf area and root area volume, which affects the growth of moso bamboo. Others have performed a number of research studies on the relationship between DBH and other bamboo forest structure factors, such as bamboo height, age composition, canopy structure, and so on. However, these factors are generally measures of non-spatial structure. Recently, research suggests that a distance-dependent spatial index can accurately describe the moso bamboo stand structure, and therefore it is important to analyze and control the relationship between moso bamboo stand structure and function. Previous studies rarely reported the relationship between moso bamboo stand spatial structure and diameter. Therefore, three spatial structure parameters, uniform angle index, neighborhood comparison and age mingling degree were used to analyze the relationship between moso bamboo spatial structure and diameter, and thus provide a theoretical basis for sustainable moso bamboo forest management. The study was established in a close-to nature moso bamboo stand in Tianmu Mountain National Nature Reserve, Zhejiang province. The study design involved a fixed plot of 1hm2 (100 m×100 m), which was divided into 100 units by adjacent grid inventory. Each moso bamboo was located in terms of x-, y-, and z-coordinates using a Total Station. Three spatial structure parameters, including neighborhood comparison, uniform angle index, age mingling degree were evaluated. The DBH was recorded into one of three classes: Ⅰclass (DBH < 7 cm), Ⅱ class (7 cm ≤ DBH < 13 cm), Ⅲ class (DBH ≥ 13 cm). These classes were used to analyzed the relationship between spatial structure and DBH of the close-to-nature moso bamboo stand. The results showed that the frequency distribution of DBH had a right-skewed normal distribution, which is the similar to even-aged arbor stands. The spatial pattern of class Ⅱand class Ⅲ was of random distribution, similar to the distribution of the whole stand, but the pattern of class Ⅰshowed an aggregation distribution pattern. The uniform angle indexes decreased with increasing diameter classes, and results showed that the uniform index had a powerful relationship with DBH, with the determination coefficient between DBH and uniform index being 0.7793. The uniform angle of different diameter classes showed no obvious significant difference (P > 0.05). The neighborhood comparison showed that for stands in an intermediate status, the DBH differentiation was not significant. The neighborhood comparison values showed that the ranking of the dominant degree was: Ⅲ > Ⅱ > Ⅰ. And the neighborhood comparisons decreased with increasing diameter classes, as well as had a significantly linear correlation with DBH (the determination coefficient was 0.9233). The neighborhood comparison of different diameter classes showed significant differences (P < 0.01). The average age mingling of the stand was 0.8178, suggesting the age mingling intensity was intensive. The age mingling values showed the ranking of age segregation was: Ⅲ > Ⅱ > Ⅰ. And age mingling increased with increasing diameter classes, as well as had a strong relationship with DBH, where the determination coefficient was 0.6774. The age mingling of different diameter classes was also significanly different (P < 0.01). 参考文献 相似文献 引证文献

Importance of root system in total biomass for Eucalyptus globulus in northern Spain

Biomass equations have become a vital estimation tool and a prerequisite for studies on forest productivity, nutrient cycling and carbon sequestration.In this paper a new set of biomass equations were fitted for Eucalyptus globulus in Northern Spain. These equations allow us to estimate the total biomass and above- and below-ground fractions from the basal area and the height of the tree. A dummy variable was included in the model to calculate the root fraction of planted versus coppice stands.A descriptive study of the root system was also carried out to complete the information about this component. Root fraction plays an important role in forest structure, but is often omitted in carbon sequestration estimates due to the difficulties and cost associated with measurement. Our results indicated that root biomass accounted for 15% and 35% of total biomass in planted and coppice stands, respectively, at a shoot age equal to 9 years. We also found that the stand type and plantation age influenced the number of roots per root system, the volume of the root system and root length.This paper brings to light how coppice stands accumulate significant amounts of carbon in their root systems from the time a plantation is established. Such information makes it possible to orient ecosystem management towards potential for C fixation.

Dominant Drivers of Seedling Establishment in a Fire-Dependent Obligate Seeder: Climate or Fire Regimes?

Climate change is causing fire regime shifts in ecosystems worldwide. Plant species with regeneration strategies strongly linked to a fire regime, such as obligate seeders, may be particularly threatened by these changes. It is unclear whether changes in fire regimes or the direct effects of climate change will be the dominant threats to obligate seeders in future. We investigated the relative importance of fire-related variables (fire return interval and fire severity) and environmental factors (climate and topography) on seedling establishment in the world’s tallest angiosperm, an obligate seeder, Eucalyptus regnans. Throughout its range, this species dominates the wet montane forests of south-eastern Australia and plays a keystone role in forest structure. Following major wildfires, we investigated seedling establishment in E. regnans within 1 year of fire as this is a critical stage in the regeneration niche of obligate seeders. Seedling presence and abundance were strongly related to the occurrence of fire but not to variation in fire severity (moderate vs. high severity). Seedling abundance increased with increasing fire return interval (range 26–300 years). First-year seedling establishment was also strongly associated with low temperatures and with high elevations, high precipitation and persistent soil water availability. Our results show that both climate and fire regimes are strong drivers of E. regnans seedling establishment. The predicted warming and drying of the climate might reduce the regeneration potential for some obligate seeders in future and these threats are likely to be compounded by changes in fire regimes, particularly increases in fire frequency.

Bird functional diversity and wildfires in the Amazon: the role of forest structure

AbstractFire is becoming a common phenomenon in Amazonian forest, modifying the structure and composition of natural assemblages. In particular, fire is known to affect patterns of bird diversity in tropical forests, but we have little understanding of the consequences of this for the functional diversity of bird assemblages. For example, frequent fires could act as an environmental filter selecting species with similar traits and, thus, producing a functional clustering pattern. Here, we used body mass, and dietary and foraging traits to calculate the functional structure of understorey bird assemblages in Amazonian forests analysed 3 years after they had passed under three disturbance levels within the 1997–1998 El‐Niño period: unburned, burned once and burned twice. First, we tested whether observed levels of functional diversity were different among these forests and also from what one would expect by chance. Then, we investigated if habitat structure was able to predict changes in the functional structure of the studied bird assemblages. In general, there was no evidence of fire reducing functional diversity nor selecting species functionally more similar than expected by chance. Therefore, bird functional diversity was not different from random in unburned and burned forests. This provides some evidence in favour of high functional redundancy of bird species in the tropics, but also indicates that neutral theories of biodiversity, where processes such as dispersal and survival are more important than biological traits to community assembly, may apply to the assemblages studied. Also, we showed that bird assemblages from forests disturbed by wildfires have the tendency to be functionally overdispersed whereas assemblages from pristine forests tend to be functionally clustered. Thus, environmental structure, in part driven by forest responses to fire, is more important than simple categorical definitions of burn frequency for explaining trait‐based assembly rules of understorey birds in the Amazon forest.

Variation in liana abundance and biomass along an elevational gradient in the tropical Atlantic Forest (Brazil)

AbstractLianas play a key role in forest structure, species diversity, as well as functional aspects of tropical forests. Although the study of lianas in the tropics has increased dramatically in recent years, basic information on liana communities for the Brazilian Atlantic Forest is still scarce. To understand general patterns of liana abundance and biomass along an elevational gradient (0–1,100 m asl) of coastal Atlantic Forest, we carried out a standard census for lianas ≥1 cm in five 1‐ha plots distributed across different forest sites. On average, we found a twofold variation in liana abundance and biomass between lowland and other forest types. Large lianas (≥10 cm) accounted for 26–35% of total liana biomass at lower elevations, but they were not recorded in montane forests. Although the abundance of lianas displayed strong spatial structure at short distances, the present local forest structure played a minor role structuring liana communities at the scale of 0.01 ha. Compared to similar moist and wet Neotropical forests, lianas are slightly less abundant in the Atlantic Forest, but the total biomass is similar. Our study highlights two important points: (1) despite some studies have shown the importance of small‐scale canopy disturbance and support availability, the spatial scale of the relationships between lianas and forest structure can vary greatly among tropical forests; (2) our results add to the evidence that past canopy disturbance levels and minimum temperature variation exert influence on the structure of liana communities in tropical moist forests, particularly along short and steep elevational gradients.

The role of forest structure, fragment size and corridors in maintaining small mammal abundance and diversity in an Atlantic forest landscape

Using the abundance and distribution of small mammals at 26 sites in an Atlantic forest landscape, we investigated how species abundance and alpha and beta diversity are affected by fragment size and the presence of corridors. To account for the variability in forest structure among fragments, we described and minimized the influence of foliage density and stratification on small mammal data. Sites were distributed among three categories of fragment size and in continuous forest. For small and medium-sized categories, we considered isolated fragments and fragments connected by corridors to larger remnants. Small mammal abundance and alpha and beta diversity were regressed against site scores from the first axis of a Principal Component Analysis on forest structure variables. Residuals were used in analyses of variance to compare fragment size and connectivity categories. Forest structure influenced total abundance and abundance of some species individually, but not the diversity of small mammal communities. Total abundance and alpha diversity were lower in small and medium-sized fragments than in large fragments and continuous forest, and in isolated compared to connected fragments. Three species were less common, but none was more abundant in smaller fragments. At least one species was more abundant in connected compared to isolated fragments. Beta diversity showed an opposite relationship to fragment size and corridors, increasing in small and isolated fragments. Results highlight the importance of secondary forest for the conservation of tropical fauna, the hyper-dynamism of small isolated fragments and the potential of corridors to buffer habitat fragmentation effects in tropical landscapes.

Tropical forest structure: a missing dimension to Pleistocene landscapes

AbstractBy focusing on the horizontal distribution of Pleistocene vegetation types within tropical landscapes, we may be overlooking an equally important feature of palaeovegetation, namely their vertical structure. Tropical forest structure is a critical factor contributing to canopy microclimatology and thus plays a role in defining canopy habitats and species population dynamics. Because of this tight relationship between forest structure and canopy microclimate, flora and fauna with narrow canopy niches may have responded to glacial reductions in forest canopy density in the same manner as if the tropical forest were completely replaced by grassland. This alternative interpretation of palaeo‐forest response to past climate change holds significance for the application of the Pleistocene refugia hypothesis in explaining various biogeographical trends. The role of forest structure in influencing hydrological cycling and the exchange of carbon between the biosphere and atmosphere are highlighted to illustrate how palaeoprecipitation and palaeoproductivity proxy data may be misinterpreted when forest structure is not explicitly considered. This is accomplished through theoretical scenarios using hydrological mass balance equations and simulations using a soil–plant–atmosphere landscape model. Available methodologies to reconstruct tropical palaeovegetation structure are identified, including the use of fully coupled earth system models. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Between‐forest variation in vertical stratification of drosophilid populations

Abstract1. The spatial distribution pattern of forest‐dwelling drosophilid flies was compared among species and among four forests with markedly different vertical foliage structures, including secondary and primary forests, with special reference to vertical stratification.2. All 20 drosophilid species analysed showed vertically stratified distribution patterns, which were detected statistically in at least one forest site during the 2‐year study period. As a whole, the vertical distribution patterns were stable, with or without stratification, over the 2 years.3. The ratio of species with stratified distribution to the total number of species changed in a similar trend with the vertical foliage complexity of forests, both showing a large gap between secondary and primary forests, even for species common to all four forests.4. Many species, most of which were tree‐sap feeders, showed highly predictable patterns of vertical stratification across forests and years. This was associated strongly with regular preference for microhabitat, mostly for the canopy, suggesting that the unvarying nature of canopy environments in any forest is very important in producing, maintaining, and promoting the vertical stratification in organism abundance, and contributes to the ubiquity of the pattern.5. Some species with a wider range of food resources than other species, most of which showed no clear preference for the canopy, were characterised by large between‐forest differences in vertical distribution patterns and tended to show non‐stratified patterns in secondary forests, contributing to the lower ratio of species with stratified distribution in the two secondary forests than in the primary forests.6. The role of forest structure in organising the environment is discussed; it is suggested that vertical complexity of foliage structure affects the prevalence of vertical stratification in animal communities indirectly through the vertical heterogeneity of environmental conditions.