Elements of disturbance that affect epiphyte vitality in a temperate rainforest: an experimental approach

Aims Epiphytes are an abundant and diverse component of many wet temperate forests and have significant roles in ecosystem processes. Little is known about the processes and rates of their death and decomposition when they fall from the canopy, which limits our understanding of their role in forest carbon sequestration and nutrient cycling. In the temperate rainforest of the Quinault River Valley, Washington State, our aim was to test hypotheses regarding four elements of disturbance that might contribute to their decline.     

Can ungulates foraging in a multiple‐use landscape alter forest nitrogen budgets?

Ungulates alter nutrient dynamics within many of Earth's ecosystems. However, whether foraging ungulates transfer nutrients among ecosystems at a magnitude sufficient to alter nutrient budgets and associated ecological processes is unknown. I suggest that within eastern North American landscapes dominated by agriculture and forest, the juxtaposition of high nitrogen crops for foraging and forest used for diurnal concealment promotes a net transfer of nitrogen from cropland to forests by overabundant white-tailed deer ( Odocoileus virginianus ). To estimate the magnitude of this nutrient transfer I apply allometric relationships of deer nitrogen consumption and excretion to populations within a hypothetical landscape in which deer use forest and cropland in equal proportions daily and are not limited in habitat use by landscape spatial pattern. Results indicate a non-linear relationship between deer nitrogen deposition to forest and percent forest cover, with deposition rising toward estimated atmospheric nitrogen deposition when forest covers less than 40% of the landscape. This "spatial subsidy" of nitrogen to the forest-floor represents a previously unrecognized input to the forest nitrogen budget with equally unknown impacts on forest-floor ecosystem processes.     

Small-scale variability in a mosaic tropical rainforest influences habitat use of long-tailed macaques

Pristine habitats have generally been considered to be the most important ecological resource for wildlife conservation, but due to forest degradation caused by human activities, mosaics of secondary forests have become increasingly prominent. We studied three forest types in a mosaic tropical forest consisting of short secondary forest (SS), tall secondary forest (TS) and freshwater swamp forest (SF). These forests differed in stand structure and floristic composition, as well as phenological productivity of fruits, flowers and young leaves. We examined habitat use of long-tailed macaques (Macaca fascicularis) in relation to indices of phenological activity. The macaques used the SS for feeding/foraging more than the TS and the SF. This was because the SS had higher productivity of fruit, which is a preferred food resource for macaques. Stem densities of young leaves in the SS and the TS also influenced habitat use, as they provided more clumped resources. Use of SF was limited, but these forests provided more species-rich resources. Our results showed that M. fascicularis responded to small-scale variability in phenological activity between forest types found in a heterogeneous mosaic forest, with young secondary regrowth forests likely providing the most important food resources. Mosaic landscapes may be important as they can buffer the effects of temporal food resource variability in any given forest type. In our increasingly human-altered landscapes, a better understanding of the role of secondary forest mosaics is crucial to the conservation and management of wildlife habitats and the animals they support.     

Epigaeic Invertebrates as Potential Ecological Indicators of Afromontane Forest Condition in South Africa1

Forest condition and the associated ecological processes vital for forest patch persistence are difficult to judge rapidly and time‐consuming to sample. Here we examine the efficacy of epigaeic invertebrate species as ecological indicators of Afromontane forest condition. Epigaeic invertebrates are potentially good ecological indicators because they play an important role in maintaining ecosystem processes, such as nutrient cycling, rely almost entirely upon the resources provided by the organic leaf litter layer, are known to be sensitive to environmental changes, and are easily surveyed. Epigaeic invertebrate communities were sampled using pitfall traps for 21 days in each of 11 forests that spanned a gradient from large and relatively undisturbed to small and highly disturbed forest patches. Using canonical correspondence analysis, we identified a suite of potential ecological indicator species (eight out of 140 species) and showed that gradients in their population response (abundance) reflect overall forest condition, as judged from the correlated vegetation indicators and position of the forests of varying condition along this gradient. The abundance of all but two of the eight indicator species (a spider and the landhopper, Talitriator africana[Amphipoda]) decreased with increasing disturbance. As a group, the rove beetles (Staphylinidae) show promise as ecological indicators and comprised four of the eight potential indicators species. A strong case is also made for a single‐species ecological indicator in the form of T. africana, which is a robust and sensitive indicator of poor forest condition.     

Reviewing the contributions of macrofungi to forest ecosystem processes and services

Macrofungi are vital components of any forest ecosystem, performing different roles crucial to ecosystem functioning. Macrofungi play effective roles in ecosystem processes such as nutrient cycling. Ectomycorrhizal fungi and plant symbionts work together to accumulate, use and transfer essential nutrients, especially in nitrogen/phosphorus-limited environments. Pathogenic and predatory macrofungi exploit other resources such as plants and animals to obtain nutrients needed for growth. These groups of macrofungi also contribute to the species diversity of forest ecosystems. Saprotrophic macrofungi degrade available organic matter from dead plants and soil organic matter. Macrofungi also play an important role in carbon sequestration in the forest underground as well as in soil formation. Macrofungi remediate pollutants in the environment via extracellular enzymes. Mycelial networks that connect macrofungi to their symbiotic hosts and substrates enable most of these functions. Mycelial networks facilitate the absorption and transport of nutrients as well as the secretion of enzymes and other organic substances. Spore-producing bodies of macrofungi serve as a food source for wildlife. Fungal spores can act as aerosols in rain formation. All of these functions of macrofungi are necessary for maintaining biodiversity and healthy forest ecosystems. However, the contributions of macrofungi to ecosystem processes are often taken for granted or not fully recognized, offering key services that are easily overlooked in planning processes and policymaking. The present review summarizes the major roles of macrofungi in ecosystem functioning and services rendered, and the interrelationships between these functions and services in the forest ecosystems.     

基于SOFM网络对黄土高原森林生态系统的养分循环分类研究

对森林生态系统进行分类是认识森林生态过程的根本途径,传统的从结构角度对森林生态系统分类只能反映森林的外在特征,而无法从功能角度区别森林的本质差异.通过对黄土高原3个生物气候区18个不同森林生态系统的养分循环特征测算和分析,选取了能全面反映养分的积累和分布(生物量、枯落物积累量、养分积累量)、循环通量(年吸收量、年存留量、年归还量)以及养分循环效率(循环系数、利用系数、养分生产力)等多方面指标作为分类指标体系,利用自组织映射特征网络(SelfOrganizing Feature Maps,SOFM)聚类方法,从养分循环的角度将黄土高原森林生态系统划分为2个一级类型,6个二级类型.该分类结果与实际较符,从而探索了森林生态系统的功能分类方法,也验证了SOFM网络模型应用于森林养分循环分类的可行性.     

Biological invasions in forest ecosystems: a global problem requiring international and multidisciplinary integration

The world’s forests are crucial biological resources that provide a variety of ecosystem services such as nutrient cycling and provisioning of resources to society. But forests are particularly affected by biological invasions, with regions around the world experiencing invasions by species from virtually every kingdom. Many of these species have severely disrupted forest ecosystem processes, thereby interrupting the provisioning of ecosystem services that societies depend upon. The problem of biological invasion in forests has many facets, and a large diversity of scientific disciplines addresses these issues. To make progress in solving the problems forest invasions pose, developing interdisciplinary collaborations is crucial because the causes of invasions and many of the measures for prevention or management require expertise in biology, economics, and social sciences. The goal of this special issue is to compile a series of articles summarizing various biological, sociological, and policy subject areas associated with forest invasions from a global perspective. These papers were prepared by the task force, “Forests and Biological Invasions,” organized by the International Union of Forest Research Organizations. Publication of this special issue is intended to advance the integration of scientific knowledge and development of solutions to this very serious and growing problem.     

Nutrient transport within and between habitats through seed dispersal processes by woolly monkeys in north‐western Amazonia

The contribution of vertebrate animals to nutrient cycling has proven to be important in various ecosystems. However, the role of large bodied primates in nutrient transport in neotropical forests is not well documented. Here, we assess the role of a population of woolly monkeys (Lagothrix lagothricha lugens) as vectors of nutrient movement through seed dispersal. We estimated total seed biomass transported by the population within and between two habitats (terra firme and flooded forests) at Tinigua Park, Colombia, and quantified potassium (K), phosphorus (P) and nitrogen (N) content in seeds of 20 plant species from both forests. Overall, the population transported an estimated minimum of 11.5 (±1.2 SD) g of potassium, 13.2 (±0.7) g of phosphorus and 34.3 (±0.1) g nitrogen, within 22.4 (±2.0) kg of seeds ha^?1 y^?1. Approximately 84% of all nutrients were deposited in the terra firme forest mostly through recycling processes, and also through translocation from the flooded forest. This type of translocation represents an important and high‐quality route of transport since abiotic mechanisms do not usually move nutrients upwards, and since chemical tests show that seeds from flooded forests have comparatively higher nutrient contents. The overall contribution to nutrient movement by the population of woolly monkeys is significant because of the large amount of biomass transported, and the high phosphorus content of seeds. As a result, the phosphorus input generated by these monkeys is of the same order of magnitude as other abiotic mechanisms of nutrient transport such as atmospheric deposition and some weathering processes. Our results suggest that via seed dispersal processes, woolly monkey populations can contribute to nutrient movement in tropical forests, and may act as important nutrient input vectors in terra firme forests. Am. J. Primatol. 72:992–1003, 2010. © 2010 Wiley‐Liss, Inc.     

Cascading effects of moose (<Emphasis Type="Italic">Alces alces</Emphasis>) management on birds

Large herbivores often have key functions in their ecosystems, and may affect ecosystem processes with cascading effects on other animals. The mechanisms often involve relocations of resources of various kinds, including reduction in resource availability following foraging and increase in resources from animal excreta. As large herbivore populations in Europe generally are intensely managed, management activities may interact with the activities of the herbivores themselves in the effect on other ecosystem components. We investigated the effects of moose (Alces alces) winter browsing, together with the effect of net nutrient input via supplementary winter feeding of moose on functional composition and species richness of birds in a boreal forest. Supplementary feeding stations for moose had a net zero effect on bird species richness and abundance, because negative effects of moose browsing were balanced by positive effects of nutrient input. Sites with a similar browsing intensity as at feeding stations but without nutrient input had lower abundance and species richness than feeding stations. Functional groups of bird species showed differing responses: birds nesting at or below browsing height were negatively affected by moose browsing, whereas species nesting above the browsing zone were positively affected by moose browsing. Insect-eating species responded negatively to moose browsing on birch but positively to nutrient input at feeding stations, whereas seed-eating species responded positively to birch browsing and negatively to feeding stations. This study showed that both high levels of cervid activity and human management interventions influence bird communities.     

Canopy soil greenhouse gas dynamics in response to indirect fertilization across an elevation gradient of tropical montane forests

Canopy soils can significantly contribute to aboveground labile biomass, especially in tropical montane forests. Whether they also contribute to the exchange of greenhouse gases is unknown. To examine the importance of canopy soils to tropical forest‐soil greenhouse gas exchange, we quantified gas fluxes from canopy soil cores along an elevation gradient with 4 yr of nutrient addition to the forest floor. Canopy soil contributed 5–12 percent of combined (canopy + forest floor) soil CO₂ emissions but CH₄ and N₂O fluxes were low. At 2000 m, phosphorus decreased CO₂ emissions (>40%) and nitrogen slightly increased CH₄ uptake and N₂O emissions. Our results show that canopy soils may contribute significantly to combined soil greenhouse gas fluxes in montane regions with high accumulations of canopy soil. We also show that changes in fluxes could occur with chronic nutrient deposition.     

灌木层及主要灌木树种在蒙古栎林养分循环中的地位和作用

本文对次生蒙古栎林中的灌木层及主要灌木树种（毛榛子,溲疏和刺五加）在林分分生物循环中的地位与作用进行了研究。研究结果表明,虽然灌木层在生物量,养分量,存留量,归还量等方面在林分中次于乔木层,但循环速率为０．６８,高于乔木层（０．６０）,又高于林分（０．６４）,在林分养分步入良性循环中起着重要的不可缺少的作用,毛棒子和溲疏是灌木中的优势或亚优势树种,是在养分良性循环中具有突出贡献的树种,是重点保护的     

A review of the role of fire in nutrient cycling in Australian native forests,and of methodology for studying the fire-nutrient interaction*

Previous studies relating to the effects of fire on nutrient cycling in Australian native forests are reviewed. It is apparent that: (a) the action of fire on soil fertility is likely to be important in affecting the functioning of Australian plant communities, (b) work to date only gives a guide as to the nature and magnitude of the effects of fire on some nutrient pools and nutrient cycling processes, but has not established the significance of such effects to the nutrient budget of entire forest systems, or established the links between fire, soil fertility and the functioning of forest communities. The difficulties associated with studying and predicting the long-term effects of fire on the fertility of forest soils are discussed. A new methodology applicable to study of the interaction between fire and plant nutrition is advocated, and is based on examination of the effects of fire on nutrient stores and flux rates in the soil-litter compartment of the forest. This approach emphasizes the use of changes in rates of nutrient cycling processes as an index of the-effects of disturbances such as fire on a forest ecosystem. The application of the methodology in a study of the effects of repeated low-intensity prescribed burning on soil fertility is discussed briefly.     

Habitat edge context and the distribution of phyllostomid bats in the Andean forest and anthropogenic matrix in the Central Andes of Colombia

Bats play an important role in the ecosystem as seed dispersers, pollinators and pest controllers. In particular, frugivorous bats are important for regeneration processes in open and degraded areas, because they disperse the seeds of pioneer plant species, which are essential for succession. Depending on the type of habitat that is established at the fragment edge, resources and bat movement patterns toward open areas can be affected. The structure and composition of bats was compared between two ‘interior-edge-pasture’ gradients, in an Andean forest fragment located at the Reserva Natural la Montaña del Ocaso (Quindío, Colombia). The two edge-types considered were forest-edge and bamboo-edge (Guadua angustifolia, Poaceae), both located in the same fragment. Bat abundance was significantly different in the two edge habitats. The forest-edge is a soft edge, in that it allows bat species to move from the interior of the forest to the pasture in front of it. In contrast, the bamboo-edge can be defined as semi-permeable, because it allows less movement of species and individuals from the interior to the pasture. Here we evaluate the possible effects of habitat edge type on bat movement in degraded areas in the main coffee producing region of Colombia.     

The role of plant resources in forest succession: changes in radiation, water and nutrient fluxes, and plant productivity over a 300-yr-long chronosequence in NW-Germany

In the past insufficient attention has been paid to quantitative measurements of resource fluxes in ecosystems that undergo successional change. In this study, simultaneous changes in seven plant resources (photosynthetically active radiation (PAR), water, nitrogen, phosphorus, calcium, magnesium and potassium) are quantified by a chronosequence approach for a 300-yr-long secondary succession on poor soil from Calluna vulgaris heathland to Fagus sylvatica-Quercus petraea late-successional forest (heathland-to-forest succession).Above-ground net primary production increases sevenfold, and total above-ground phytomass about fortyfold during heathland-to-forest succession. Plant organs that capture resources increase much more slowly (leaf area index: threefold; fine root biomass: 1.3-fold). The increase in productivity is based both on higher absorptivity and conversion efficiency of PAR by the canopies of the successional plants.Accumulation of organic material on the forest floor significantly improves soil water availability. Evapotranspiration losses increase early in succession as the growing vegetation increases in both height and leaf area but tend to decrease again in the late-successional community. Drainage losses are at their minimum at the conifer-dominated pioneer forest stage.Accumulation of available nutrients in the soil is a key process in heathland-to-forest succession that significantly improves plant nutrient availability but leads to only minor changes in carbon/nutrient ratios and humus quality. Litter decomposition rates increase and result in a more rapid nutrient turnover in late successional stages. External nutrient inputs (from the atmosphere and soil weathering) significantly contribute to plant nutrient supply early in succession, whereas the internal cycling of nutrients through litter fall and nutrient mineralisation by far exceeds external inputs at the late stages.Vitousek & Reiners' (1975) ecosystem nutrient loss hypothesis is supported by the heathland-to-forest succession data. Odum's (1969) hypotheses on how nutrient cycles change during the course of succession is, in one part, rejected, in part supported. Tilman's (1988) hypothesis on nutrient limitation early, and light limitation late in primary succession is rejected.     

Nutrient fluxes via litterfall and leaf litter decomposition vary across a gradient of soil nutrient supply in a lowland tropical rain forest

The extent to which plant communities are determined by resource availability is a central theme in ecosystem science, but patterns of small-scale variation in resource availability are poorly known. Studies of carbon (C) and nutrient cycling provide insights into factors limiting tree growth and forest productivity. To investigate rates of tropical forest litter production and decomposition in relation to nutrient availability and topography in the absence of confounding large-scale variation in climate and altitude we quantified nutrient fluxes via litterfall and leaf litter decomposition within three distinct floristic associations of tropical rain forest growing along a soil fertility gradient at the Sepilok Forest Reserve (SFR), Sabah, Malaysia. The quantity and nutrient content of small litter decreased along a gradient of soil nutrient availability from alluvial forest (most fertile) through sandstone forest to heath forest (least fertile). Temporal variation in litterfall was greatest in the sandstone forest, where the amount of litter was correlated negatively with rainfall in the previous month. Mass loss and N and P release were fastest from alluvial forest litter, and slowest from heath forest litter. All litter types decomposed most rapidly in the alluvial forest. Stand-level N and P use efficiencies (ratios of litter dry mass to nutrient content) were greatest for the heath forest followed by the sandstone ridge, sandstone valley and alluvial forests, respectively. We conclude that nutrient supply limits productivity most in the heath forest and least in the alluvial forest. Nutrient supply limited productivity in sandstone forest, especially on ridge and hill top sites where nutrient limitation may be exacerbated by reduced rates of litter decomposition during dry periods. The fluxes of N and P varied significantly between the different floristic communities at SFR and these differences may contribute to small-scale variation in species composition.     

Divergent responses of flagship,keystone and resource-limited bio-indicators to forest structure

Bio-indicators are often proposed to set conservation priorities in forest habitat owing to the difficulties of determining forest intrinsic ecological value. Here, we tested the efficacy of a number of potential bird indicator groups in monitoring beech Fagus sylvatica forest status by analyzing their associations with the spatial and structural variables of forest vegetation that indicate key ecological patterns and processes. The density of cavity nesting birds, indicating the presence of limited forest resources (resource-limited indicators), was influenced by tree species diversity, vertical species mingling and diameter, parameters reflecting maturity, gap-dynamic processes, as well as resource and shelter availability. Heterogeneity in shrub species composition, another parameter depending on forest dynamics, was positively associated with the occurrence of Capercaillie, a “flagship” species for forest conservation. The presence of woodpeckers, a “keystone” group that provides shelter and foraging substrate to other organisms, was positively affected by the basal area of standing dead trees that is indirectly associated with natural nutrient availability. These findings suggest that single indicators fail to provide a complete assessment of forest status, and their use in monitoring or managing forest ecosystem need to be contextualized to specific ecological patterns. The combined use of several indicators, representing various taxa, functions and life histories, appears to be preferable, and is logistically feasible if these can be surveyed together. Several indicators would likely display a wider range of sensitivities to the modification of natural processes and permit more comprehensive tracking of forest dynamics than single flagship, keystone or resource-limited indicators.     

Mangrove Forest and Soil Development on a Rapidly Accreting Shore in New Zealand

Mangrove forests are rapidly expanding their distribution in New Zealand, which is at the southern limit of their range. We investigated how these expanding mangrove forests develop through time. We assessed patterns in forest structure and function at the Firth of Thames, which is a rapidly accreting mangrove site in New Zealand where 1 km of mangrove of Avicennia marina has established seaward since the 1950s. Across the intertidal region, mangrove forest structure was highly variable. We used bomb-pulse radiocarbon dating to age the forest. Two major forest establishment events were identified; one in 1978–1981 and another in 1991–1995. These events coincided with sustained El Niño activity and are likely the result of reduced wind and wave energy at the site during these periods. We used the two forests of different ages to assess whether mangroves in New Zealand mature at similar rates as other mangroves and whether they conform to classic models of succession. The timing of forest maturation is similar in New Zealand as in more tropical locations with trees exhibiting features of mature forests as they age from about 10 to about 30 years. In older forest (~30 years old) trees become larger and stands more homogenous than in the younger forest (~10 years old). Carbon and nutrient concentrations in soils increased and soils become more aerobic in older forest compared to younger forest. Additionally, using fertilization experiments, we established that despite reduced growth rates in older forests, nitrogen remained limiting to growth in both older and young forests. However, in contrast to classic successional models leaf tissue nutrient concentrations and nutrient conservation (nutrient resorption from senescence leaf tissue) were similar in forests of differing ages and did not vary with fertilization. We conclude that mangrove forest expansion in New Zealand is influenced by climatic factors. Mangrove forests mature rapidly, even at the limits of their range and they satisfy many of the successional patterns predicted by Odum (1969) for the early stages of forest succession.     

大气CO_2浓度升高与森林群落结构的可能性变化

大气 CO2 浓度升高所引起的森林生态系统生态稳定性的变化会导致森林在结构和功能上的变动 ,概述了大气 CO2浓度升高和陆地森林生态系统可能性变化之间的相互关系的研究情况。由于大气 CO2 浓度升高出现了额外多的 C,供应 ,讨论了以这些额外多的 C经大气 -植物 -土壤途径的流动走向 ,来研究大气 CO2 浓度的升高 ,与森林结构的相互作用 ,探讨了大气 CO2 浓度升高对森林植物生长、冠层结构、引发的生物量增量的分配、凋落物质量和根质量的变化造成的土壤生态过程的变化、微生物共生体、有机质周转率、营养循环的潜在效应以及气温上升对森林植物产生的可能性影响 ,这些受影响的生物要素和生态过程 ,会引起群落内植物间对资源原有的竞争关系发生变化 ,对资源竞争的格局发生变化最终将会导致森林结构的改变。     

巨桉人工林土壤动物群落结构特征

为深入了解巨桉人工林生物养分循环及土壤肥力变迁,客观全面地评价巨桉人工林的生态效益,对比研究了四川省洪雅县巨桉人工林和青冈次生林土壤动物群落结构特征。研究方法,大型土壤动物采用野外分层手捡计数,中小型土壤动物用取土器分层取土,带回室内分别用干湿漏斗分离并镜检。结果表明：（1）洪雅巨桉人工林共获1312头土壤动物,分属6门10纲21目,其优势类群分别为蜱螨目、弹尾目、线虫纲、膜翅目;（2）巨桉人工林土壤动物群落的类群数和个体数均低于青冈次生林．其Shannon—Wiener指数和密度一类群指数分别为1．818和4．002,低于青冈次生林的1．963和8．091;（3）巨桉人工林土壤动物群落中腐食性同功能种团比例为81．78％高于青冈次生林的64．18％;（4）巨桉人工林与青冈次生林土壤动物密度剖面分布具明显表聚性,二者经F-检验无显著差异;（5）巨桉人工林与青冈次生林土壤动物群落有比较高的Jaccard相似性系数和Gower,系数,表明两类林分在土壤动物类群和个体数量分布上有比较大的相似度。     

Importance of short-lived components of a dry tropical forest for biomass production and nutrient cycling

Abstract. Short-lived components in a dry tropical forest ecosystem in India - tree foliage, fine roots and herbaceous plants - are shown to be important for biomass production and nutrient cycling. With 62 % they contribute much more to the dry matter production than the long-lived components- tree boles, branches and coarse roots - which make up only 38 %. The contribution of short-lived components to the total uptake of different nutrients was also high: 18 - 30 % for tree foliage, 26 - 34 % for fine roots and 6–19 % for herbs; their share in the total nutrient storage is less: 6–19 % for tree foliage, 4–8 % for fine roots and 0.6–1.3 % for herbs. The transfer of nutrients by the short-lived components was also substantial: 31 - 46 % for foliage, 7–24% for herbs and 33–45% for fine roots. The results indicate that the short-lived components play a significant role in the functioning of a dry tropical forest.