The importance of competition for light depends on productivity and disturbance.
Ontology highlight
ABSTRACT:
SUBMITTER: Hautier Y
PROVIDER: S-EPMC6262729 | biostudies-literature | 2018 Nov
REPOSITORIES: biostudies-literature
Publications
The importance of competition for light depends on productivity and disturbance.
Hautier Yann Y Vojtech Eva E Hector Andy A
Ecology and evolution 20181026 22
Eutrophication is a major cause of biodiversity loss. In grasslands, this appears to occur due to asymmetric competition for light following the increases in aboveground biomass production. Here, we report the results of an experiment with five grass species that tests how well-competitive outcomes can be predicted under a factorial combination of fertilized and disturbed (frequent cutting) conditions. Under fertile conditions, our results confirm earlier success in predicting short-term competi ...[more]
Similar Datasets
Project description:Ecologists have long recognized the roles of competition and disturbance in shaping ecological communities, and the combinatorial effects of these two factors have been the subject of substantial ecological research. Nevertheless, it is still unclear whether competition remains as an important structuring force in habitats strongly influenced by disturbance. The conventional belief remains that the importance of competition decreases with increasing disturbance, but limited theory suggests otherwise. Using protist communities established in laboratory microcosms, we demonstrate that disturbance does not diminish the importance of competition. Interspecific competition significantly increased rates of species extinction over a broad disturbance gradient, and increasing disturbance intensities increased, rather than decreased, the tempo of competitive exclusion. This community-level pattern is linked to the species-level pattern that interspecific competition led to most frequent extinctions of each species at the highest level of disturbance that the species can tolerate. Consequently, despite a strong tradeoff between competitive ability and disturbance tolerance across the competing species, species diversity generally declined with disturbance. The consistent structuring role of competition throughout the disturbance gradient underscores the need to understand competitive interactions and their consequences even in highly disturbed habitats.
| S-EPMC2919955 | biostudies-literature
Project description:Chance events such as seed dispersal determine the potential composition of plant communities, but the eventual assemblage is determined in large part by subsequent interactions among species. Postcolonization sorting also affects the ultimate composition of communities assembled by people for restoration, horticulture, or conservation. Thus, knowledge of the mechanisms controlling interspecific interactions in plant communities is important for explaining patterns observed in nature and predicting success or failure of utilitarian combinations. Relationships among species, especially those from studies of biological diversity and ecosystem functioning, are largely based on studies of short-lived, temperate-zone plants. Extrapolation to perennial plants in the humid tropics is risky because functional relationships among large-stature species change with time. Shifts in competitive relationships among 3 life forms--trees, palms, and perennial herbs--occurred during 13 yr in experimental tropical ecosystems. In 2 cases the novel competitive mechanism responsible for the shift was reduction in crown volume, and therefore light-capturing capability, of overtopping deciduous trees by intrusive growth from below a palm. In a third case, complementary resource use developed between 2 evergreen life forms (overstory tree and palm), probably because of differential nutrient acquisition. Species-level traits and adequate time for shifts in interspecific relationships to emerge are crucial for predicting community trajectories.
| S-EPMC2596203 | biostudies-literature
Project description:Plant structural diversity is usually considered as beneficial for ecosystem functioning. For instance, numerous studies have reported positive species diversity-productivity relationships in plant communities. However, other aspects of structural diversity such as individual size inequality have been far less investigated. In forests, tree size inequality impacts directly tree growth and asymmetric competition, but consequences on forest productivity are still indeterminate. In addition, the effect of tree size inequality on productivity is likely to vary with species shade-tolerance, a key ecological characteristic controlling asymmetric competition and light resource acquisition. Using plot data from the French National Geographic Agency, we studied the response of stand productivity to size inequality for ten forest species differing in shade tolerance. We fitted a basal area stand production model that included abiotic factors, stand density, stand development stage and a tree size inequality index. Then, using a forest dynamics model we explored whether mechanisms of light interception and light use efficiency could explain the tree size inequality effect observed for three of the ten species studied. Size inequality negatively affected basal area increment for seven out of the ten species investigated. However, this effect was not related to the shade tolerance of these species. According to the model simulations, the negative tree size inequality effect could result both from reduced total stand light interception and reduced light use efficiency. Our results demonstrate that negative relationships between size inequality and productivity may be the rule in tree populations. The lack of effect of shade tolerance indicates compensatory mechanisms between effect on light availability and response to light availability. Such a pattern deserves further investigations for mixed forests where complementarity effects between species are involved. When studying the effect of structural diversity on ecosystem productivity, tree size inequality is a major facet that should be taken into account.
| S-EPMC4801349 | biostudies-literature
Project description:Recent advances in climate research have discovered that permafrost is particularly vulnerable to the changes occurring in the atmosphere and climate, especially in Alaska where 85% of the land is underlain by mostly discontinuous permafrost. As permafrost thaws, research has shown that natural and anthropogenic soil disturbance causes microbial communities to undergo shifts in membership composition and biomass, as well as in functional diversity. Boreal forests are home to many plants that are integral to the subsistence diets of many Alaska Native communities. Yet, it is unclear how the observed shifts in soil microbes can affect above ground plant communities that are relied on as a major source of food. In this study, we tested the hypothesis that microbial communities associated with permafrost thaw affect plant productivity by growing five plant species found in Boreal forests and Tundra ecosystems, including low-bush cranberry and bog blueberry, with microbial communities from the active layer soils of a permafrost thaw gradient. We found that plant productivity was significantly affected by the microbial soil inoculants. Plants inoculated with communities from above thawing permafrost showed decreased productivity compared to plants inoculated with microbes from undisturbed soils. We used metagenomic sequencing to determine that microbial communities from disturbed soils above thawing permafrost differ in taxonomy from microbial communities in undisturbed soils above intact permafrost. The combination of these results indicates that a decrease in plant productivity can be linked to soil disturbance driven changes in microbial community membership and abundance. These data contribute to an understanding of how microbial communities can be affected by soil disturbance and climate change, and how those community shifts can further influence plant productivity in Boreal forests and more broadly, ecosystem health.
| S-EPMC7882522 | biostudies-literature
Project description:Climatic change will affect elevational vegetation distribution because vegetation distribution is related to thermal conditions. However, how elevational species distributions are determined by biotic and abiotic factors is not clear. The long-term plot census along an elevational gradient is indispensable to clarify mechanisms of elevational distribution of tree species. Two congeneric conifers, the less shade-tolerant Abies veitchii and shade-tolerant A. mariesii, dominate at low and high elevations, respectively, in the subalpine zone in Japan. This study investigated the population dynamics of the two species at three elevations (low, middle, high) for 13 years to examine why the two species dominated the different elevations from the viewpoints of competition and disturbance. This study showed that growth and survival rates were not highest at the most dominant elevations for each species. At the high elevation where A. mariesii dominated and small disturbances frequently occurred, the recruitment rate of A. mariesii was highest among the three elevations and that of A. veitchii was largely decreased by tree competition. However, A. veitchii was dominant earlier than A. mariesii at the low elevation after large disturbances by the high growth rate of individual trees. Therefore, A. mariesii was superior to A. veitchii at the high elevation because of its high recruitment rate and large reduction of recruitment of A. veitchii due to competition, while A. veitchii was superior to A. mariesii at the low elevation after large disturbances because of higher growth rate than A. mariesii. It is suggested that the elevational distributions of the two species were determined by elevational changes in population dynamics in relation to competition and disturbance. Long-term observational studies of forest dynamics among various elevations are indispensable to predict the effects of climatic change on vegetation distribution.
| S-EPMC8858215 | biostudies-literature
Project description:Although the impacts of the loss of biodiversity on ecosystem functioning are well established, the importance of the loss of biodiversity relative to other human-caused drivers of environmental change remains uncertain. Results of 11 experiments show that ecologically relevant decreases in grassland plant diversity influenced productivity at least as much as ecologically relevant changes in nitrogen, water, CO(2), herbivores, drought, or fire. Moreover, biodiversity became an increasingly dominant driver of ecosystem productivity through time, whereas effects of other factors either declined (nitrogen addition) or remained unchanged (all others). In particular, a change in plant diversity from four to 16 species caused as large an increase in productivity as addition of 54 kg · ha(-1) · y(-1) of fertilizer N, and was as influential as removing a dominant herbivore, a major natural drought, water addition, and fire suppression. A change in diversity from one to 16 species caused a greater biomass increase than 95 kg · ha(-1) · y(-1) of N or any other treatment. Our conclusions are based on >7,000 productivity measurements from 11 long-term experiments (mean length, ~ 13 y) conducted at a single site with species from a single regional species pool, thus controlling for many potentially confounding factors. Our results suggest that the loss of biodiversity may have at least as great an impact on ecosystem functioning as other anthropogenic drivers of environmental change, and that use of diverse mixtures of species may be as effective in increasing productivity of some biomass crops as fertilization and may better provide ecosystem services.
| S-EPMC3387045 | biostudies-literature
Project description:While various relationships between productivity and biodiversity are found in forests, the processes underlying these relationships remain unclear and theory struggles to coherently explain them. In this work, we analyse diversity-productivity relationships through an examination of forest structure (described by basal area and tree height heterogeneity). We use a new modelling approach, called 'forest factory', which generates various forest stands and calculates their annual productivity (above-ground wood increment). Analysing approximately 300 000 forest stands, we find that mean forest productivity does not increase with species diversity. Instead forest structure emerges as the key variable. Similar patterns can be observed by analysing 5054 forest plots of the German National Forest Inventory. Furthermore, we group the forest stands into nine forest structure classes, in which we find increasing, decreasing, invariant and even bell-shaped relationships between productivity and diversity. In addition, we introduce a new index, called optimal species distribution, which describes the ratio of realized to the maximal possible productivity (by shuffling species identities). The optimal species distribution and forest structure indices explain the obtained productivity values quite well (R2 between 0.7 and 0.95), whereby the influence of these attributes varies within the nine forest structure classes.
| S-EPMC5319316 | biostudies-literature
Project description:A variety of factors can affect the biodiversity of tropical mammal communities, but their relative importance and directionality remain uncertain. Previous global investigations of mammal functional diversity have relied on range maps instead of observational data to determine community composition. We test the effects of species pools, habitat heterogeneity, primary productivity and human disturbance on the functional diversity (dispersion and richness) of mammal communities using the largest standardized tropical forest camera trap monitoring system, the Tropical Ecology Assessment and Monitoring (TEAM) Network. We use occupancy values derived from the camera trap data to calculate occupancy-weighted functional diversity and use Bayesian generalized linear regression to determine the effects of multiple predictors. Mammal community functional dispersion increased with primary productivity, while functional richness decreased with human-induced local extinctions and was significantly lower in Madagascar than other tropical regions. The significant positive relationship between functional dispersion and productivity was evident only when functional dispersion was weighted by species' occupancies. Thus, observational data from standardized monitoring can reveal the drivers of mammal communities in ways that are not readily apparent from range map-based studies. The positive association between occupancy-weighted functional dispersion of tropical forest mammal communities and primary productivity suggests that unique functional traits may be more beneficial in more productive ecosystems and may allow species to persist at higher abundances.
| S-EPMC7934904 | biostudies-literature
Project description:Ideas about how plant competition varies with productivity are rooted in classic theories that predict either increasing (Grime) or invariant (Tilman) competition with increasing productivity. Both predictions have received experimental support, although a decade-old meta-analysis supports neither. Attempts to reconcile the conflicting predictions and evidence include: expanding the theory to include other conditions (e.g. stress gradient hypothesis), development of indices to differentiate either the 'intensity' or 'importance' of competition, a focus on resource supply and demand, and explicit recognition that both growth and survival may exhibit different relationships with productivity. To determine which of these theories accurately predict how competition varies with productivity within a native grassland site, we estimated competitive intensity and relative competitive importance using 22 species across the range of productivity naturally occurring within that site. Plant performance was measured as survival and size with and without neighbours and the local environment was quantified according to variability in standing crop, gross water supply, and net water supply. On average, neighbours weakly facilitated seedling survival, but strongly reduced seedling growth. For both seedling survival and growth, relative competitive importance and competitive intensity declined with some measure of productivity; neighbour effects on survival declined with standing crop, while effects on growth declined with gross water supply. These results add to the growing evidence that plant-plant interactions vary among life history components with different life history components contingent upon separate environmental factors. Although the range of productivity measured in this study was not large, our results do not support the theories of Grime or Tilman. However, our results are consistent with the meta-analysis and parts of other theories, although no single theory is capable of explaining the entirety of these results. This suggests that, at least in moderately productive grasslands, new theory needs to be developed.
| S-EPMC3424220 | biostudies-other
Project description:Memory encoding and retrieval problems are inherent to aging. To date, however, the effect of aging upon the neural correlates of forming memory traces remains poorly understood. Resting-state fMRI connectivity can be used to investigate initial consolidation. We compared within and between network connectivity differences between healthy young and older participants before encoding, after encoding and before retrieval by means of resting-state fMRI. Alterations over time in the between-network connectivity analyses correlated with retrieval performance, whereas within-network connectivity did not: a higher level of negative coupling or competition between the default mode and the executive networks during the after encoding condition was associated with increased retrieval performance in the older adults, but not in the young group. Data suggest that the effective formation of memory traces depends on an age-dependent, dynamic reorganization of the interaction between multiple, large-scale functional networks. Our findings demonstrate that a cross-network based approach can further the understanding of the neural underpinnings of aging-associated memory decline.
| S-EPMC4288239 | biostudies-literature