Litter decomposition under drought related with litter and decomposer diversity

<p>Litter decomposition is a crucial ecosystem process that driven carbon and nutrient cycling, which can be determined by the diversity of biota that involved in decomposition process. Forest ecosystems at globally have been or being expected to experience drought stress and cause dieback, consequently may lead losses of tree species and soil biota. However, how projected drought affect litter decomposition and its relationship with biodiversity is less understood. We hypothesize that 1) drought depressed the activity of soil biota and retard litter decomposition, while biodiversity loss at both plant and soil organism levels exacerbated the drought induced retarding of litter decomposition; 2) soil biota interaction or the top down control of ecosystem process can be relieved under drought stress. In our study, throughfall reduction experiments were conducted in five locations representing different forest types (i.e., temperate broadleaf-Korean pine mixed forest, warm-temperate oak forest, subtropical bamboo forest, south subtropical evergreen forest, tropical rainforest) along a climate gradient in China. In each location, leaf litter from 4 common native plants and 11 mixtures of these litter types were enclosed in three types of nylon mesh screens litterbags, and were placed in the field of throughfall reduction and control treatments replicated five times. Different combination of litter types represent diversity of litters, and mesh size of litterbags represent diversity of functional group of soil biota (i.e., microorganism, medium-sized fauna, large-bodied fauna) participate into decomposition. The litterbags were incubated in situ for a period of time and were collected, all litter samples were separated into the constituent species immediately after litter retrieval, mass loss, C and N loss of each sample was determined. Thereby the hypothesizes can be testified.</p>

Arbuscular mycorrhiza has little influence on N2O potential emissions compared to plant diversity in experimental plant communities

ABSTRACT Denitrification is an ecosystem process linked to ongoing climate change, because it releases nitrous oxide (N2O) into the atmosphere. To date, the literature covers mostly how aboveground (i.e. plant community structure) and belowground (i.e. plant-associated soil microbes) biota separately influence denitrification in isolation of each other. We here present a mesocosm experiment where we combine a manipulation of belowground biota (i.e. addition of Rhizophagus irregularis propagules to the indigenous mycorrhizal community) with a realized gradient in plant diversity. We used a seed mix containing plant species representative of mesophytic European grasslands and by stochastic differences in species establishment across the sixteen replicates per treatment level a spontaneously established gradient in plant diversity. We address mycorrhizal-induced and plant-diversity mediated changes on denitrification potential parameters and how these differ from the existing literature that studies them independently of each other. We show that unlike denitrification potential, N2O potential emissions do not change with mycorrhiza and depend instead on realized plant diversity. By linking mycorrhizal ecology to an N-cycling process, we present a comprehensive assessment of terrestrial denitrification dynamics when diverse plants co-occur.

Distinguishing disturbance from perturbations in fire-prone ecosystems

Fire is a necessary ecosystem process in many biomes and is best viewed as a natural disturbance that is beneficial to ecosystem functioning. However, increasingly, we are seeing human interference in fire regimes that alters the historical range of variability for most fire parameters and results in vegetation shifts. Such perturbations can affect all fire regime parameters. Here, we provide a brief overview of examples where anthropogenically driven changes in fire frequency, fire pattern, fuels consumed and fire intensity constitute perturbations that greatly disrupt natural disturbance cycles and put ecosystems on a different trajectory resulting in type conversion. These changes are not due to fire per se but rather anthropogenic perturbations in the natural disturbance regime.