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1.
Biodiversity has been declining in many areas, and there is great interest in determining whether this decline affects ecosystem
functioning. Most biodiversity—ecosystem functioning studies have focused on the effects of species richness on net primary
productivity. However, biodiversity encompasses both species richness and evenness, ecosystem functioning includes other important
processes such as decomposition, and the effects of richness on ecosystem functioning may change at different levels of evenness.
Here, we present two experiments on the effects of litter species evenness and richness on litter decomposition. In the first
experiment, we varied the species evenness (three levels), identity of the dominant species (three species), and micro-topographic
position (low points [gilgais] or high points between gilgais) of litter in three-species mixtures in a prairie in Texas,
USA. In a second experiment, we varied the species evenness (three levels), richness (one, two, or four species per bag),
and composition (random draws) of litter in a prairie in Iowa, USA. Greater species evenness significantly increased decomposition,
but this effect was dependent on the environmental context. Higher evenness increased decomposition rates only under conditions
of higher water availability (in gilgais in the first experiment) or during the earliest stages of decomposition (second experiment).
Species richness had no significant effect on decomposition, nor did it interact with evenness. Micro-topographic position
and species identity and composition had larger effects on decomposition than species evenness. These results suggest that
the effects of litter species diversity on decomposition are more likely to be manifested through the evenness component of
diversity than the richness component, and that diversity effects are likely to be environmentally context dependent. 相似文献
2.
Plant traits, litter quality and decomposition in a Mediterranean old-field succession 总被引:1,自引:0,他引:1
Jacques Cortez Eric Garnier Natalia Pérez-Harguindeguy Max Debussche Dominique Gillon 《Plant and Soil》2007,296(1-2):19-34
Human-induced changes in land use lead to major changes in plant community composition which have strong effects on ecosystem
processes. Here, we tested the hypothesis that changes in traits of living plants induced by such changes resulted in changes
in the quality and decay properties of the litter produced by the different communities. This was done in the context of a
secondary succession following land abandonment in the Mediterranean region of Southern France.
During the course of succession, species with high specific leaf area (the ratio of leaf area to leaf mass), low leaf dry
matter content (the ratio of leaf dry mass to leaf fresh mass) and high leaf nitrogen concentration were progressively replaced
by species with opposite characteristics. Accordingly, the initial litter concentrations of carbon (C) and nitrogen (N) decreased,
while their C:N ratio and their hemicellulose concentration increased with time after abandonment.
Early-successional communities had faster rates of litter decay and N release from litter, but these differences damped out
with decomposition time. Nitrogen release from litter was related to initial litter chemical composition, particularly to
its N concentration. This also held for litter decay rate, but only during the first 18 months of decomposition.
Community functional parameters (i.e. trait values weighed according to the relative abundance of species) were tightly linked
to initial litter N concentration, and thereby to litter decay and N loss rates. The strongest correlations were found with
leaf dry matter content, which therefore appears as a powerful marker of litter properties. This provides further evidence
that characteristics of living leaves persist in litter, and that some ecosystem processes can be inferred from plant functional
traits.
Responsible Editor: Alfonso Escudero 相似文献
3.
Community composition and diversity of riparian forests regulate decomposition of leaf litter in stream ecosystems
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Riparian forest plantings are a well‐established restoration technique commonly used to stabilize banks and intercept nutrient flow from adjacent agricultural fields. Tree species planted for these efforts may not reflect mature forest communities within the same region. Given contemporary research on links between biodiversity and ecosystem functioning, we conducted a leaf‐litter decomposition study to investigate how mixing of detrital resources that reflect forest community composition would regulate in‐stream leaf litter. Leaf litter bags containing material from a mature forest (Liriodendron tulipifera, Acer rubrum, Quercus rubra, full factorial treatments = 7) and a restored riparian forest (Cornus sericea, Fraxinus pennsylvanica, Platanus occidentalis, full factorial treatments = 7) were deployed in a stream reach that experienced riparian reforestation in 2004. Litter from the restored riparian community had less mass remaining (45.28 ± 2.27%) than that from the mature riparian community (54.95 ± 2.19%) after 5 weeks. In addition, mixed litter treatments in the restored riparian community had less mass remaining (40.54 ± 2.37%) than single‐species treatments (51.80 ± 4.05%), a pattern not observed in the mature forest community. Results highlight the importance of planting mixed‐species assemblages as this structure may regulate processes such as decomposition and food‐web structure, processes often not targeted in the restoration plans. 相似文献
4.
Spatial scale is a critical consideration for understanding ecological patterns and controls of ecological processes, yet
very little is known about how rates of fundamental ecosystem processes vary across spatial scales. We assessed litter decomposition
in stream networks whose inherent hierarchical nature makes them a suitable model system to evaluate variation in decay rates
across multiple spatial scales. Our hypotheses were (1) that increasing spatial extent adds significant variability at each
hierarchical level, and (2) that stream size is an important source of variability among streams. To test these hypotheses
we let litter decompose in four riffles in each of twelve 3rd-order streams evenly distributed across four 4th-order watersheds,
and in a second experiment determined variation in decomposition rate along a stream-size gradient ranging from orders 1 to
4. Differences in decay rates between coarse-mesh and fine-mesh litter bags accounted for much of the overall variability
in the data sets, and were remarkably consistent across spatial scales and stream sizes. In particular, variation across watersheds
was minor. Differences among streams and among riffles were statistically significant, though relatively small, leaving most
of the total variance (51%) statistically unexplained. This result suggests that variability was generated mainly within riffles,
decreasing successively with increasing scale. A broad range of physical and chemical attributes measured at the study sites
explained little of the variance in decomposition rate. This, together with the strong mesh-size effect and greater variability
among coarse-mesh bags, suggests that detritivores account, at least partly, for the unexplained variance. These findings
contrast with the widespread perception that variability of ecosystem characteristics, including process rates, invariably
increases (1) with spatial extent and (2), in stream networks, when analyses encompass headwaters of various size. An important
practical implication is that natural variability need not compromise litter decomposition assays as a means of assessing
functional ecosystem integrity.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
1. Leaf litter decomposition is one of the most important ecosystem processes in streams. Recent studies suggest that facilitation, in which litter is processed by a succession of species with differing abilities and requirements, may be important in making the nutrients bound in litter available to the stream assemblage.
2. We predicted that stream invertebrates that feed on terrestrial leaf litter (shredders) and tadpoles would facilitate leaf litter decomposition by changing the quality of leaf material directly via physical contact or indirectly via nutrient release. We experimentally examined the ability of shredders and tadpoles to break down leaves, independently and together, in artificial streams beside a natural forest stream.
3. The decomposition rate was greater when shredders and tadpoles were together than was expected from rates in single-species treatments, indicating that facilitation occurred. This facilitation operated in one direction only: the rate of leaf breakdown by tadpoles was higher when leaves had been partly processed by shredders, but there was no similar effect when leaves previously occupied by tadpoles were processed by shredders. We did not detect facilitation caused by indirect nutrient release.
4. Shredders may have benefited tadpoles by roughening leaf surfaces, making them easier for the tadpoles to consume and enhancing leaf breakdown in the presence of both taxa. This indicates that the loss of a single species can have impacts on ecosystem functioning that go beyond the loss of its direct contribution. 相似文献
2. We predicted that stream invertebrates that feed on terrestrial leaf litter (shredders) and tadpoles would facilitate leaf litter decomposition by changing the quality of leaf material directly via physical contact or indirectly via nutrient release. We experimentally examined the ability of shredders and tadpoles to break down leaves, independently and together, in artificial streams beside a natural forest stream.
3. The decomposition rate was greater when shredders and tadpoles were together than was expected from rates in single-species treatments, indicating that facilitation occurred. This facilitation operated in one direction only: the rate of leaf breakdown by tadpoles was higher when leaves had been partly processed by shredders, but there was no similar effect when leaves previously occupied by tadpoles were processed by shredders. We did not detect facilitation caused by indirect nutrient release.
4. Shredders may have benefited tadpoles by roughening leaf surfaces, making them easier for the tadpoles to consume and enhancing leaf breakdown in the presence of both taxa. This indicates that the loss of a single species can have impacts on ecosystem functioning that go beyond the loss of its direct contribution. 相似文献
6.
7.
Cottonwood hybridization affects tannin and nitrogen content of leaf litter and alters decomposition 总被引:3,自引:0,他引:3
Cottonwoods are dominant riparian trees of the western United States and are known for their propensity to hybridize. We compared
the decomposition of leaf litter from two species (Populus angustifolia and P. fremontii) and their hybrids. Three patterns were found. First, in one terrestrial and two aquatic experiments, decomposition varied
twofold among tree types. Second, backcross hybrid leaves decomposed more slowly than those of either parent. Third, the variation
in decomposition between F1 and backcross hybrids was as great as the variation between species. These results show significant differences in decomposition
in a low-diversity system, where >80% of the leaf litter comes from just two species and their hybrids. Mechanistically, high
concentrations of condensed tannins in leaves appear to inhibit decomposition (r
2=0.63). The initial condensed tannin concentration was high in narrowleaf leaves, low or undetectable in Fremont leaves, and
intermediate in F1 hybrid leaves (additive inheritance). Backcross hybrids were high in condensed tannins and were not different from narrowleaf
(dominant inheritance). Neither nitrogen (N) concentration nor the ratio of ash-free dry weight to N (a surrogate for carbon:nitrogen
ratio) were significantly correlated with decomposition. The N content of leaf material at the end of each year’s experiment
was inversely correlated with rates of litter mass loss and varied 1.6- to 2.1-fold among tree classes. This result suggests
that hybrids and their parental species are used differently by the microbial community.
Received: 7 April 1999 / Accepted: 2 November 1999 相似文献
8.
Climate change leads to summer low flow conditions and premature litter input in lowland streams in Central Europe. This may
cause a sudden reduction of flow and fragmentation into isolated pools of permanently flowing streams, with a simultaneous
increase in the food supply for detrivores during summer months. We performed a mesocosm study to investigate shredder and
microbial mediated litter decomposition under these conditions. Leaf litter was placed in a lowland stream with a natural
flow regime (reference) and in a stream mesocosm with significant flow reduction (FR) and a representative density of macroinvertebrates
and detritus. Physicochemical parameters, leaf mass loss, macroinvertebrate abundance and biomass, leaf-associated respiration,
fungal sporulation, and biomass were measured at regular intervals for 6 weeks. Coarse and fine-mesh bags were used to include
or exclude macroinvertebrate shredders. In the coarse-mesh bags, leaf mass loss was significantly lower in the FR system than
in the reference regime. In the fine-mesh bags, leaf respiration, fungal sporulation, and biomass but not leaf mass losses
were substantially lower with flow reduction. Chironomid larvae (Micropsectra spp.) appeared to effectively fragment leaf litter in fine-mesh bags. In the FR system, leaf respiration was higher in the
coarse-than in the fine-mesh bags. Our results suggest that, in temperate lowland streams, premature litter input during or
after a sudden fragmentation into isolated pools and a reduction of stream flow reduces direct shredder-mediated litter decomposition,
but shredders may indirectly influence the decomposition process.
Handling editor: B. Oertli 相似文献
9.
Riparian vegetation is closely connected to stream food webs through input of leaf detritus as a primary energy supply, and therefore, any alteration of plant diversity may influence aquatic ecosystem functioning. We measured leaf litter breakdown rate and associated biological parameters in mesh bags in eight headwater streams bordered either with mixed deciduous forest or with beech forest. The variety of leaf litter types in mixed forest results in higher food quality for large-particle invertebrate detritivores (‘shredders’) than in beech forest, which is dominated by a single leaf species of low quality. Breakdown rate of low quality (oak) leaf litter in coarse mesh bags was lower in beech forest streams than in mixed forest streams, a consequence of lower shredder biomass. In contrast, high quality (alder) leaf litter broke down at similar rates in both stream categories as a result of similar shredder biomass in coarse mesh bags. Microbial breakdown rate of oak and alder leaves, determined in fine mesh bags, did not differ between the stream categories. We found however aquatic hyphomycete species richness on leaf litter to positively co-vary with riparian plant species richness. Fungal species richness may enhance leaf litter breakdown rate through positive effects on resource quality for shredders. A feeding experiment established a positive relationship between fungal species richness per se and leaf litter consumption rate by an amphipod shredder (Gammarus fossarum). Our results show therefore that plant species richness may indirectly govern ecosystem functioning through complex trophic interactions. Integrating microbial diversity and trophic dynamics would considerably improve the prediction of the consequences of species loss. 相似文献
10.
11.
Fallopia japonica succeeds in invading different ecosystems likely because of its huge biomass production. This biomass is characterized by low nutritional quality and low decomposition rates but knowledge on whether these features are correlated to microbial decomposers is still lacking. The aims of this work were: i) to determine litter decomposition rates of native grassland vegetation and F. japonica under different conditions in a year-round experiment; ii) to evaluate litter quality and/or site effect on the decomposition of the invader and native vegetation and iii) to characterize mycoflora isolated from F. japonica and native vegetation litter. The results showed that F. japonica litter decomposes 3–4 times slower than that of native grassland, mainly due to its low N content and consequently high C/N ratio both in leaves and stems. As decomposition proceeds C/N in F. japonica litter decreases to values approaching those of the grassland litter. Site had no effect on the decomposition rates of F. japonica and grassland litter. Total fungal load and composition differed between F. japonica and native litter, and also varied across sites. These results indicate that the successful invasive plant F. japonica affects the structure and functions of the invaded ecosystem through a huge production of low quality, slow-decomposing litter that selects saprotrophic fungi. 相似文献
12.
Over the past decade an increasing amount of research has sought to understand how the diversity of species in an ecosystem
can influence fluxes of biologically important materials, such as the decomposition of organic matter and recycling of nutrients.
Generalities among studies have remained elusive, perhaps because experimental manipulations have been performed at relatively
small spatial scales where site-specific variation generates patterns that appear idiosyncratic. One approach for seeking
generality is to perform parallel experiments at different sites using an identical species pool. Here we report results from
a study where we manipulated the diversity of leaf litter from the same six dominant tree species in the litter layer of three
forested ecosystems. These ecosystems spanned a 300 km latitudinal transect in Wisconsin, USA, and were characterized by a
large gradient in temperature and moisture, and thus, rates of decomposition. After allowing combinations of one, two, four,
and six species of leaf litter to decompose for 1 year, we found that increasing leaf litter richness led to slower rates
of decomposition and higher fractions of nitrogen lost from litter. Across all sites, climate and initial litter chemistry
explained more of the variation in decomposition rates than did litter richness. Effects of leaf litter diversity were non-additive,
meaning they were greater than expected from the impacts of individual species, and appeared to be strongly influenced by
the presence/absence of just 1–2 species (Tilia americana and Acer saccharum). The rate of decomposition of these two species was highly site-specific, which led to strong negative effects of litter
richness only being observed at the southernmost sites where T. americana and A. saccharum decomposed more quickly. In contrast, litter diversity increased nitrogen loss at the northernmost sites where decomposition
of T. americana was notably slowed. Our study shows that species diversity affected at least one of the two litter processes at each site
along this 300-km gradient, but the exact nature of these effects were spatially variable because the performance of individual
species changed across the heterogeneous landscape. 相似文献
13.
M. Scherer-Lorenzen 《Functional ecology》2008,22(3):547-555
14.
探究功能性状沿着环境梯度如何变化一直以来是基于性状的群落生态学的核心问题之一。尽管功能性状存在种内和种间变异, 但种内变异沿环境梯度如何变化仍有待探究。本文以鼎湖山南亚热带常绿阔叶林1.44 ha塔吊样地内16个树种的2,820个个体为研究对象, 探究4种叶功能性状(比叶面积、叶干物质含量、叶厚度和叶面积)沿群落垂直层次的种内变异。首先, 利用随机效应线性模型量化塔吊样地内的种内变异和种间变异; 其次, 利用Kmeans函数将森林的垂直层次划分为灌木层、亚冠层和林冠层, 并通过构建回归模型探究叶功能性状在群落垂直层次中的种内变异格局。最后, 应用混合线性模型和单因素方差分析的方法探究叶功能性状沿垂直层次的种内变异是否具有物种依赖性。结果表明: 在局域群落中, 并非所有叶功能性状的种内变异都低于种间变异; 叶功能性状在不同垂直层次的种内变异格局存在显著差异, 且种内变异与垂直范围呈正相关; 叶功能性状的种内变异具有较强的物种依赖性, 因此树种差异相对于小环境解释了更多的性状变异; 此外, 不同叶功能性状的种内变异沿垂直层次的变化趋势并不一致。本研究发现种内变异对于物种共存具有重要作用。 相似文献
15.
16.
Despite growing recognition of the importance of a natural flow regime in river-floodplain systems, researchers struggle to quantify ecosystem responses to altered hydrological regimes. How do frequency, timing, and duration of inundation affect fundamental ecosystem processes such as leaf litter decomposition? Along the semi-natural Tagliamento River corridor, located in northeastern Italy, we employed in situ experiments to separate effects of different inundation components on breakdown rates of black poplar (Populus nigra). We used a litter-bag method with two different mesh sizes to investigate how fungi and macroinvertebrates influence leaf breakdown rates. Ten treatments, each representing a specific combination of duration and frequency of inundation, were deployed in two seasons (summer, winter) to mimic complex inundation patterns. After 30 days of exposure, mean percentage of remaining leaf litter (ash free dry mass) ranged between 51% (permanent wet) and 88% (permanent dry). Leaf breakdown was significantly faster in winter than in summer. Duration of inundation was the main inundation component that controlled leaf breakdown rates. Leaf-shredding macroinvertebrates played only a role in the permanent wet treatment. Fungal parameters explained the faster leaf breakdown in winter. Our study suggests that modifications of the inundation regime will directly modify established decomposition processes. Factors reducing duration of inundation will decelerate leaf breakdown rates, whereas a decrease in flow variation will reduce leaf breakdown heterogeneity. 相似文献
17.
A global study of relationships between leaf traits, climate and soil measures of nutrient fertility 总被引:7,自引:0,他引:7
Jenny C. Ordoñez Peter M. van Bodegom Jan-Philip M. Witte Ian J. Wright Peter B. Reich Rien Aerts 《Global Ecology and Biogeography》2009,18(2):137-149
Aim This first global quantification of the relationship between leaf traits and soil nutrient fertility reflects the trade‐off between growth and nutrient conservation. The power of soils versus climate in predicting leaf trait values is assessed in bivariate and multivariate analyses and is compared with the distribution of growth forms (as a discrete classification of vegetation) across gradients of soil fertility and climate. Location All continents except for Antarctica. Methods Data on specific leaf area (SLA), leaf N concentration (LNC), leaf P concentration (LPC) and leaf N:P were collected for 474 species distributed across 99 sites (809 records), together with abiotic information from each study site. Individual and combined effects of soils and climate on leaf traits were quantified using maximum likelihood methods. Differences in occurrence of growth form across soil fertility and climate were determined by one‐way ANOVA. Results There was a consistent increase in SLA, LNC and LPC with increasing soil fertility. SLA was related to proxies of N supply, LNC to both soil total N and P and LPC was only related to proxies of P supply. Soil nutrient measures explained more variance in leaf traits among sites than climate in bivariate analysis. Multivariate analysis showed that climate interacted with soil nutrients for SLA and area‐based LNC. Mass‐based LNC and LPC were determined mostly by soil fertility, but soil P was highly correlated to precipitation. Relationships of leaf traits to soil nutrients were stronger than those of growth form versus soil nutrients. In contrast, climate determined distribution of growth form more strongly than it did leaf traits. Main conclusions We provide the first global quantification of the trade‐off between traits associated with growth and resource conservation ‘strategies’ in relation to soil fertility. Precipitation but not temperature affected this trade‐off. Continuous leaf traits might be better predictors of plant responses to nutrient supply than growth form, but growth forms reflect important aspects of plant species distribution with climate. 相似文献
18.
19.
1. To assess whether the reported slow breakdown of litter in tropical Cerrado streams is due to local environmental conditions or to the intrinsic leaf characteristics of local plant species, we compared the breakdown of leaves from Protium brasiliense, a riparian species of Cerrado (Brazilian savannah), in a local and a temperate stream. The experiment was carried out at the time of the highest litter fall in the two locations. An additional summer experiment was conducted in the temperate stream to provide for similar temperature conditions. 2. The breakdown rates (k) of P. brasiliense leaves in the tropical Cerrado stream ranged from 0.0001 to 0.0008 day−1 and are among the slowest reported. They were significantly (F = 20.12, P < 0.05) lower than in the temperate stream (0.0046–0.0055). The maximum ergosterol content in decomposing leaves in the tropical Cerrado stream was 106 μg g−1, (1.9% of leaf mass) measured by day 75, which was lower than in the temperate stream where maximum ergosterol content of 522 μg g−1 (9.5% of leaf mass) was achieved by day 30. The ATP content, as an indicator of total microbial biomass, was up to four times higher in the tropical Cerrado than in the temperate stream (194.0 versus 49.4 nmoles g−1). 3. Unlike in the temperate stream, leaves in the tropical Cerrado were not colonised by shredder invertebrates. However, in none of the experiments did leaves exposed (coarse mesh bags) and unexposed (fine mesh bags) to invertebrates differ in breakdown rates (F = 1.15, P > 0.05), indicating that invertebrates were unable to feed on decomposing P. brasiliense leaves. 4. We conclude that the slow breakdown of P. brasiliense leaves in the tropical Cerrado stream was because of the low nutrient content in the water, particularly nitrate (0.05 mgN L−1), which slows down fungal activity and to the low density of invertebrates capable of using these hard leaves as an energy source. 相似文献
20.
Aims
Plants play an important role in ecosystem processes. Functional meaning of trait variation in wide environmental gradients is well known but is scarcely known across narrow gradients. We analyze the variation of morphological, physical and chemical traits of dominant plant species and the potential rates of dry mass loss and N release/immobilization during senesced leaf decomposition of these species across a narrow aridity gradient, and to identify indicative traits useful to set species functional groups sharing decomposition patterns. 相似文献