Comparing intra- and inter-specific effects on litter decomposition in an old-field ecosystem

Plant species can differ in the quantity and quality of leaf litter they produce, and many studies have examined whether plant species diversity affects leaf-litter decomposition and nutrient release. A growing number of studies have indicated that intra-specific variation within plant species can also affect key ecosystem processes. However, the relative importance of intra- versus inter-specific variation for the functioning of ecosystems remains poorly known. Here, we investigate the effects of intra-specific variation in a dominant old-field plant species, tall goldenrod (Solidago altissima), and inter-specific variation among goldenrod species on litter quality, decomposition, and nitrogen (N) release. We found that the nutrient concentration of leaf litter varied among genotypes, which translated into ～50% difference in decomposition rates. Variation among other goldenrod species in decomposition rate was more than twice that of genetic variation within S. altissima. Furthermore, by manipulating litterbags to contain 1, 3, 6, or 9 genotypes, we found that S. altissima genotype identity had much stronger effects than did genotypic diversity on leaf-litter quality, decomposition, and N release. Taken together, these results suggest that the order of ecological importance for controlling leaf-litter decomposition and N release dynamics is plant species identity?genotype identity>genotypic diversity.     

Detritivore stoichiometric diversity alters litter processing efficiency in a freshwater ecosystem

Many studies have estimated relationships between biodiversity and ecosystem functioning, and observed generally positive effects. Because detritus is a major food resource in stream ecosystems, decomposition of leaf litter is an important ecosystem process and many studies report the full range of positive, negative and no effects of diversity on decomposition. However, the mechanisms underlying decomposition processes in fresh water remain poorly understood. Organism body stoichiometry relates to consumption rates and tendencies, and decomposition processes of litter may therefore be affected by diversity in detritivore body stoichiometry. We predicted that the stoichiometric diversity of detritivores (differences in C: nutrient ratios among species) would increase the litter processing efficiency (litter mass loss per total capita metabolic capacity) in fresh water through complementation regarding different nutrient requirements. To test this prediction, we conducted a microcosm experiment wherein we manipulated the stoichiometric diversity of detritivores and quantified mass loss of leaf litter mixtures. We compared litter processing efficiency among litter species in each microcosm with single species detritivores, and observed detritivores with nutrient‐rich bodies tended to prefer litter with lower C: nutrient ratios over litter with higher C: nutrient ratios. Furthermore, litter processing efficiencies were significantly higher in the microcosms containing species of detritivores with both nutrient‐rich and ‐poor bodies than microcosms containing species of detritivores including only nutrient‐rich or ‐poor bodies. This might mean a higher stoichiometric diversity of detritivores increased litter processing efficiency. Our results suggest that ecological stoichiometry may improve understanding of links between biodiversity and ecosystem function in freshwater ecosystems.     

Genetic mosaics of ecosystem functioning across aspen-dominated landscapes

Genetic diversity is the foundation of all biodiversity, and the genetic variation within species is increasingly recognized as being important to ecosystem level processes. Recent research demonstrates that plant genotype influences above- and belowground communities as well as basic ecosystem functions. However, the extent to which plant genotypes create spatial mosaics of genetically mediated ecosystem processes in natural forests is uncertain. We use Populus tremuloides as a model system to demonstrate the importance of plant genotype on carbon and nitrogen cycling in natural systems. We identified 24 distinct P. tremuloides clones with multiple ramets across 25 km² in southern Wisconsin, United States, using microsatellite makers. We then sampled clone leaf chemistry and belowground nutrient content and microbial extracellular enzyme activity. Aspen-induced variation in belowground carbon and nitrogen content, and microbial activity, varied widely among clones. Variation in green leaf chemistry and belowground microbial activity were correlated with genetic distance among clones, such that more genetically distant clones created more divergent patches of ecosystem processes. These data suggest that aspen genotypes create spatial mosaics of genetically mediated ecosystem functioning across natural landscapes and can therefore have evolutionary consequences for co-occurring species.     

Soil microbial communities adapt to genetic variation in leaf litter inputs

Plant genotypes can have important community‐ and ecosystem‐level effects. However, whether the extended phenotypes of plants feed back to influence the fitness of causal genotypes through soil processes remains unknown. We investigated whether aspen genotypes create distinct soil microbial communities that could potentially affect plant fitness. Using naturally occurring aspen stands in an old‐field system, we set up reciprocal litter transplants among ten genetically distinct aspen clones and tracked decomposition and changes in belowground nutrients and microbial communities for three years. We found that belowground microbial communities became adapted to process specific genotypes of aspen litter to the extent allowable by environment and litter chemistry. Belowground processes were driven by a combination of little quality and prior exposure to specific genotypes of litter. In general, litter from aspen genotypes native to the soil community decomposed more rapidly than did litter from foreign aspen genotypes (i.e. a home‐field advantage existed). While home‐field advantages have been documented to occur among litters of different species, we show that intraspecific variation can elicit similar, albeit weak, effects within a single species. Because rapid decomposition and nutrient cycling is likely to benefit fast‐growing, early‐successional species such as aspen, genotype‐mediated selection for soil microbial communities may feed back to positively affect plant fitness. In addition, belowground communities exhibited significant shifts in response to leaf litter inputs. When exposed to foreign litter, microbial communities changed to become more similar to the microbial community beneath the foreign litter's origin, indicating that belowground microbial communities are predictable given the genotype of the aboveground aspen clone.     

Imaging spectroscopy links aspen genotype with below-ground processes at landscape scales

Fine-scale biodiversity is increasingly recognized as important to ecosystem-level processes. Remote sensing technologies have great potential to estimate both biodiversity and ecosystem function over large spatial scales. Here, we demonstrate the capacity of imaging spectroscopy to discriminate among genotypes of Populus tremuloides (trembling aspen), one of the most genetically diverse and widespread forest species in North America. We combine imaging spectroscopy (AVIRIS) data with genetic, phytochemical, microbial and biogeochemical data to determine how intraspecific plant genetic variation influences below-ground processes at landscape scales. We demonstrate that both canopy chemistry and below-ground processes vary over large spatial scales (continental) according to aspen genotype. Imaging spectrometer data distinguish aspen genotypes through variation in canopy spectral signature. In addition, foliar spectral variation correlates well with variation in canopy chemistry, especially condensed tannins. Variation in aspen canopy chemistry, in turn, is correlated with variation in below-ground processes. Variation in spectra also correlates well with variation in soil traits. These findings indicate that forest tree species can create spatial mosaics of ecosystem functioning across large spatial scales and that these patterns can be quantified via remote sensing techniques. Moreover, they demonstrate the utility of using optical properties as proxies for fine-scale measurements of biodiversity over large spatial scales.     

Tree species richness affects litter production and decomposition rates in a tropical biodiversity experiment

We report data on leaf litter production and decomposition from a manipulative biodiversity experiment with trees in tropical Panama, which has been designed to explore the relationship between tree diversity and ecosystem functioning. A total of 24 plots (2025 m²) were established in 2001 using six native tree species, with 1‐, 3‐, and 6‐species mixtures. We estimated litter production during the dry season 2005 with litter traps; decomposition was assessed with a litter bag approach during the following wet season. Litter production during the course of the dry season was highly variable among the tree species. Tree diversity significantly affected litter production, and the majority of the intermediate diverse mixtures had higher litter yields than expected based on yields in monoculture. In contrast, high diverse mixtures did not show such overyielding in litter production. Litter decomposition rates were also highly species‐specific, and were related to various measures of litter quality (C/N, lignin/N, fibre content). We found no overall effect of litter diversity if the entire litter mixtures were analyzed, i.e. mixing species resulted in pure additive effects and observed decomposition rates were not different from expected rates. However, the individual species changed their decomposition pattern depending on the diversity of the litter mixture, i.e. there were species‐specific responses to mixing litter. The analysis of temporal C and N dynamics within litter mixtures gave only limited evidence for nutrient transfer among litters of different quality. At this early stage of our tree diversity experiment, there are no coherent and general effects of tree species richness on both litter production and decomposition. Within the scope of the biodiversity‐ecosystem functioning relationship, our results therefore highlight the process‐specific effects diversity may have. Additionally, species‐specific effects on ecosystem processes and their temporal dynamics are important, but such effects may change along the gradient of tree diversity.     

Partitioning the effect of composition and diversity of tree communities on leaf litter decomposition and soil respiration

The decomposition of plant material is an important ecosystem process influencing both carbon cycling and soil nutrient availability. Quantifying how plant diversity affects decomposition is thus crucial for predicting the effect of the global decline in plant diversity on ecosystem functioning. Plant diversity could affect the decomposition process both directly through the diversity of the litter, and/or indirectly through the diversity of the host plant community and its affect on the decomposition environment. Using a biodiversity experiment with trees in which both functional and taxonomic diversity were explicitly manipulated independently, we tested the effects of the functional diversity and identity of the living trees separately and in combination with the functional diversity and identity of the decomposing litter on rates of litter decomposition and soil respiration. Plant traits, predominantly leaf chemical and physical traits, were correlated with both litter decomposition and soil respiration rates. Surface litter decomposition, quantified by mass loss in litterbags, was best explained by abundance‐weighted mean trait values of tree species from which the litter was assembled (functional identity). In contrast, soil respiration, which includes decomposition of dissolved organic carbon and root respiration, was best explained by the variance in trait values of the host trees (functional diversity). This research provides insight into the effect of loss of tree diversity in forests on soil processes. Such understanding is essential to predicting changes in the global carbon budget brought on by biodiversity loss.     

Biodiversity and tallgrass prairie decomposition: the relative importance of species identity, evenness, richness, and micro-topography

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.     

陆地生态系统混合凋落物分解研究进展

凋落物分解在陆地生态系统养分循环与能量流动中具有重要作用,是碳、氮及其他重要矿质养分在生态系统生命组分间循环与平衡的核心生态过程。自然生态系统中,植物群落大多具有较高的物种丰富度和多样性,其混合凋落物在分解过程中也更有可能发生养分传递、化学抑制等种间互作,形成多样化的分解生境,多样性较高的分解者类群以及复杂的级联效应分解,这些因素和过程均对研究混合凋落物分解过程、揭示其内在机制形成了极大的挑战。从构成混合凋落物物种丰富度和多样性对分解生境、分解者多样性及其营养级联效应的影响等方面,综合阐述混合凋落物对陆地生态系统凋落物分解的影响,探讨生物多样性在凋落物分解中的作用。通过综述近些年的研究发现,有超过60%的混合凋落物对其分解速率的影响存在正向或负向的效应。养分含量有差异的凋落物混合分解过程中,分解者优先利用高质量凋落物,使低质量的凋落物反而具有了较高的养分有效性,引起低质量凋落物分解加快并最终使混合凋落物整体分解速率加快;而凋落物物种丰富度对土壤动物群落总多度有轻微的影响或几乎没有影响,但是对线虫和大型土壤动物的群落组成和多样性有显著影响,并随着分解阶段呈现一定动态变化;混合凋落物改变土壤微生物生存的理化环境,为微生物提供更多丰富的分解底物和养分,优化微生物种群数量和群落结构及其分泌酶的活性,并进一步促进了混合凋落物的分解。这些基于植物-土壤-分解者系统的动态分解过程的研究,表明混合凋落物分解作用不只是经由凋落物自身质量的改变,更会通过逐级影响分解者多样性水平而进一步改变分解速率和养分释放动态,说明生物多样性确实在一定程度上调控凋落物分解及其养分释放过程。     

Leaf litter decomposition differs among genotypes in a local <Emphasis Type="Italic">Betula pendula</Emphasis> population

Ecosystem processes, such as plant litter decomposition, are known to be partly genetically determined, but the magnitude of genetic variation within local populations is still poorly known. We used micropropagated field-grown saplings of 19 Betula pendula genotypes, representing genetic variation in a natural birch population, to examine (1) whether genotype can explain variation in leaf litter decomposition within a local plant population, and (2) whether genotypic variation in litter decomposition is associated with genotypic variation in other plant attributes. We found that a local B. pendula population can have substantial genotypic variation in leaf litter mass loss at the early stages of the decomposition process and that this variation can be associated with genotypic variation in herbivore resistance and leaf concentrations of soluble proteins and total nitrogen (N). Our results are among the first to show that fundamental ecosystem processes can be significantly affected by truly intraspecific genetic variation of a plant species.     

Shredder–tadpole facilitation of leaf litter decomposition in a tropical stream

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.     

Species richness and trophic diversity increase decomposition in a co-evolved food web

Ecological communities show great variation in species richness, composition and food web structure across similar and diverse ecosystems. Knowledge of how this biodiversity relates to ecosystem functioning is important for understanding the maintenance of diversity and the potential effects of species losses and gains on ecosystems. While research often focuses on how variation in species richness influences ecosystem processes, assessing species richness in a food web context can provide further insight into the relationship between diversity and ecosystem functioning and elucidate potential mechanisms underpinning this relationship. Here, we assessed how species richness and trophic diversity affect decomposition rates in a complete aquatic food web: the five trophic level web that occurs within water-filled leaves of the northern pitcher plant, Sarracenia purpurea. We identified a trophic cascade in which top-predators--larvae of the pitcher-plant mosquito--indirectly increased bacterial decomposition by preying on bactivorous protozoa. Our data also revealed a facultative relationship in which larvae of the pitcher-plant midge increased bacterial decomposition by shredding detritus. These important interactions occur only in food webs with high trophic diversity, which in turn only occur in food webs with high species richness. We show that species richness and trophic diversity underlie strong linkages between food web structure and dynamics that influence ecosystem functioning. The importance of trophic diversity and species interactions in determining how biodiversity relates to ecosystem functioning suggests that simply focusing on species richness does not give a complete picture as to how ecosystems may change with the loss or gain of species.     

Phenotypic diversity and litter chemistry affect nutrient dynamics during litter decomposition in a two species mix

We have previously demonstrated that the intraspecific diversity of leaf litter can influence ecosystem functioning during litter decomposition in the field. It is unknown whether the effects of phenotypic diversity persist when litter from an additional species is present. We used laboratory microcosms to determine whether the intraspecific diversity effects of turkey oak leaf litter on nutrient dynamics are confounded by the presence of naturally co-occurring longleaf pine litter. We varied the phenotypic diversity of oak litter (1, 3, and 6 phenotype combinations) in the presence and absence of pine litter and measured fluxes of carbon and nitrogen over a 42-week period. The average soil C:N ratio peaked at intermediate levels of oak phenotypic diversity and the total amount of dissolved organic carbon leached from microcosms decreased (marginally) with increasing oak phenotypic diversity. The soil carbon content, and the total amount of ammonium, nitrate, and dissolved organic carbon leached from microcosms were all influenced by initial litter chemistry. Our results suggest that the effects of phenotypic diversity can persist in the presence of another species, however specific litter chemistries (condensed and hydrolysable tannins, simple phenolics, C:N ratios) are more important than phenotypic litter diversity to most nutrient fluxes during litter decomposition.     

Genetic variation in a tropical tree species influences the associated epiphytic plant and invertebrate communities in a complex forest ecosystem

Genetic differences among tree species, their hybrids and within tree species are known to influence associated ecological communities and ecosystem processes in areas of limited species diversity. The extent to which this same phenomenon occurs based on genetic variation within a single tree species, in a diverse complex ecosystem such as a tropical forest, is unknown. The level of biodiversity and complexity of the ecosystem may reduce the impact of a single tree species on associated communities. We assessed the influence of within-species genetic variation in the tree Brosimum alicastrum (Moraceae) on associated epiphytic and invertebrate communities in a neotropical rainforest. We found a significant positive association between genetic distance of trees and community difference of the epiphytic plants growing on the tree, the invertebrates living among the leaf litter around the base of the tree, and the invertebrates found on the tree trunk. This means that the more genetically similar trees are host to more similar epiphyte and invertebrate communities. Our work has implications for whole ecosystem conservation management, since maintaining sufficient genetic diversity at the primary producer level will enhance species diversity of other plants and animals.     

Litter and soil biodiversity jointly drive ecosystem functions

The decomposition of litter and the supply of nutrients into and from the soil are two fundamental processes through which the above- and belowground world interact. Microbial biodiversity, and especially that of decomposers, plays a key role in these processes by helping litter decomposition. Yet the relative contribution of litter diversity and soil biodiversity in supporting multiple ecosystem services remains virtually unknown. Here we conducted a mesocosm experiment where leaf litter and soil biodiversity were manipulated to investigate their influence on plant productivity, litter decomposition, soil respiration, and enzymatic activity in the littersphere. We showed that both leaf litter diversity and soil microbial diversity (richness and community composition) independently contributed to explain multiple ecosystem functions. Fungal saprobes community composition was especially important for supporting ecosystem multifunctionality (EMF), plant production, litter decomposition, and activity of soil phosphatase when compared with bacteria or other fungal functional groups and litter species richness. Moreover, leaf litter diversity and soil microbial diversity exerted previously undescribed and significantly interactive effects on EMF and multiple individual ecosystem functions, such as litter decomposition and plant production. Together, our work provides experimental evidence supporting the independent and interactive roles of litter and belowground soil biodiversity to maintain ecosystem functions and multiple services.     

Genotypic trait variation modifies effects of climate warming and nitrogen deposition on litter mass loss and microbial respiration

Intraspecific variation in genotypically determined traits can influence ecosystem processes. Therefore, the impact of climate change on ecosystems may depend, in part, on the distribution of plant genotypes. Here we experimentally assess effects of climate warming and excess nitrogen supply on litter decomposition using 12 genotypes of a cosmopolitan foundation species collected across a 2100 km latitudinal gradient and grown in a common garden. Genotypically determined litter‐chemistry traits varied substantially within and among geographic regions, which strongly affected decomposition and the magnitude of warming effects, as warming accelerated litter mass loss of high‐nutrient, but not low‐nutrient, genotypes. Although increased nitrogen supply alone had no effect on decomposition, it strongly accelerated litter mass loss of all genotypes when combined with warming. Rates of microbial respiration associated with the leaf litter showed nearly identical responses as litter mass loss. These results highlight the importance of interactive effects of environmental factors and suggest that loss or gain of genetic variation associated with key phenotypic traits can buffer, or exacerbate, the impact of global change on ecosystem process rates in the future.     

Consumer and resource diversity effects on marine macroalgal decomposition

Few manipulative experiments that explicitly test the relationship between biodiversity and ecosystem function have focussed on regenerative processes such as decomposition and nutrient cycling. Of the studies that have taken place, most have concentrated on the effects of leaf litter diversity rather than the effects of consumer diversity on decomposition. In the present study, we established an in‐situ mesocosm experiment on an intertidal mudflat in the Ythan Estuary, Scotland, to investigate the interactive effects of consumer diversity, resource diversity and microbial activity on algal consumption and decomposition. We assembled communities of three commonly occurring macrofaunal species (Hediste diversicolor, Hydrobia ulvae and Littorina littorea) in monoculture and all possible combinations of two and three species mixtures and supplied them with single vs two‐species mixtures of the algae Fucus spiralis and Ulva intestinalis. Further, we also investigated whether algal decomposition changes nutrient remineralisation within the sediment by determining the C:N ratio of the surficial sediment. Data were analysed using extended linear regression with generalized least squares estimation to characterise the variance structure. We found that consumer species diversity effects are best explained by compositional effects and that species richness per se may not be the single most important determinant of resource use and decomposition in this community. Algal identity and invertebrate identity effects underpin the observed response and reflect species‐specific traits associated with algal consumption and processing. The role of the microbial community is comparatively weak, but strongly linked to faunal activities and behaviour. The C:N ratio of the sediment increased with consumer species richness, indicating increased mineralisation in more diverse communities. Overall, our results suggest that although consumer species richness effects per se are weak, decomposition and subsequent incorporation of resources is nevertheless dependent on the composition of the decomposer community, which, in turn, has important implications for biogeochemical nutrient cycling in marine coastal habitats.     

Effects of diversity loss on ecosystem function across trophic levels and ecosystems: A test in a detritus‐based tropical food web

Abstract We investigated the effects of biodiversity loss across trophic levels and across ecosystems (terrestrial to aquatic) on ecosystem function, in a detritus‐based tropical food web. Diversities of consumers (stream shredders) and resources (leaf litter) were experimentally manipulated by varying the number of species from 3 to 1, using different species combinations, and the effects on leaf breakdown rates were examined. In single‐species shredder treatments, leaf diversity loss affected breakdown rates, but the effect depended on the identity of the leaves remaining in the system: they increased when the most preferred leaf species remained, but decreased when this species was lost (leaf preferences were the same for all shredders). In multi‐species shredder assemblages, breakdown rates were lower than expected from single‐species treatments, suggesting an important role of interspecific competition. This pattern was also evident when oneleaf species was available but not with higher leaf diversity, suggesting that lowered leaf diversity promotes competitive interactions among shredders. The influence of diversity and identity of species across trophic levels and ecosystems on stream functioning points to complex interactions that may well be reflected in other types of ecosystem.     

Decomposition and nutrient dynamics in mixed litter of Mediterranean species

In the last decade a great research effort addressed the effects of litter diversity on ecosystem functions, reporting both synergistic and antagonistic effects for decomposition dynamics. Four coexisting Mediterranean species, representing a range of litter quality, were used to arrange litter mixtures at three diversity levels for a litterbag decomposition experiment. Species identity appeared as the major determinant for litter mass loss (Coronilla emerus～Hedera helix>Festuca drymeia>Quercus ilex) and nutrient release, with rates for all leaf litter types following the sequence K>N>Mg≥Ca>>Fe. Additive diversity effects were prevalent pooling together all data but also for nutrients separately. Antagonistic interactions were more common than synergistic in the cases of mass loss, N and Ca contents, but not for K, Mg and Fe dynamics. The number of species in the litterbag significantly affected the outcome of non-additive interactions, which were mostly antagonistic for two-species mixtures, and synergistic for the combined 4 species. Litter quality appears to be the most important factor affecting mass loss and nutrient dynamics, while litter diversity, influencing the rates of these processes, plays an important role in reducing their variability, thus suggesting a greater stability of ecosystems properties in presence of mixed litter.     

Genotype × Herbivore Effect on Leaf Litter Decomposition in Betula Pendula Saplings: Ecological and Evolutionary Consequences and the Role of Secondary Metabolites

Plant genetic variation and herbivores can both influence ecosystem functioning by affecting the quantity and quality of leaf litter. Few studies have, however, investigated the effects of herbivore load on litter decomposition at plant genotype level. We reduced insect herbivory using an insecticide on one half of field-grown Betula Pendula saplings of 17 genotypes, representing random intrapopulation genetic variation, and allowed insects to naturally colonize the other half. We hypothesized that due to induced herbivore defence, saplings under natural herbivory produce litter of higher concentrations of secondary metabolites (terpenes and soluble phenolics) and have slower litter decomposition rate than saplings under reduced herbivory. We found that leaf damage was 89 and 53% lower in the insecticide treated saplings in the summer and autumn surveys, respectively, which led to 73% higher litter production. Litter decomposition rate was also affected by herbivore load, but the effect varied from positive to negative among genotypes and added up to an insignificant net effect at the population level. In contrast to our hypothesis, concentrations of terpenes and soluble phenolics were higher under reduced than natural herbivory. Those genotypes, whose leaves were most injured by herbivores, produced litter of lowest mass loss, but unlike we expected, the concentrations of terpenes and soluble phenolics were not linked to either leaf damage or litter decomposition. Our results show that (1) the genetic and herbivore effects on B. pendula litter decomposition are not mediated through variation in terpene or soluble phenolic concentrations and suggest that (2) the presumably higher insect herbivore pressure in the future warmer climate will not, at the ecological time scale, affect the mean decomposition rate in genetically diverse B. pendula populations. However, (3) due to the significant genetic variation in the response of decomposition to herbivory, evolutionary changes in mean decomposition rate are possible.