The Additive And Non-additive Effects Of The Mixed Litter Decomposition And N, P Release In An Alpine Meadow

Litter decomposition is connected to the aboveground and underground, which is an important process of material circulation and energy flow in the ecosystem. Litter decomposition also affect soil nutrient cycling and soil quality, and further community structure and ecosystem functions. Many species occur in ecosystems, so mixed litter decomposition can really response to the ecosystem functions. There is often non-additive effect in the mixed litter. We selected leaf litter of5component species (Kobresia capillifolia, Elymus nutans, Ligularia virgaurea, Anemone rivularis and Thermopsis lanceolata) in an alpine meadow of the Tibetan Plateau and investigated leaf litter decomposition and nutrient dynamics. The experiments include31species combination treatments. The main results were as follows.1. Litter decomposition: The order of five species decomposition alone: Thermopsis lanceolata>Ligularia virgaurea>Anemone rivularis>Elymus nutans> Kobresia capillifolia; Species richness had no effect on litter decomposition, but species composition affected it significantly. There were additive and non-additive effects in the mixed litter decomposition, which depended on species composition of the mixed litters. Both Kobresia capillifolia and Thermopsis lanceolata could result in non-additive effects, with Kobresia capillifolia inhibiting and Thermopsis lanceolata promoting the mixed litter decomposition, respectively.2. N P dynamics:Litter N showed immobilization-release model; throughout the decomposition time, the litter P has been released. Species richness had no effect on N P dynamics, but species composition affected it significantly. There were additive and non-additive effects in the mixed litter decomposition, which depended on species composition of the mixed litters. Kobresia capillifolia and Ligularia virgaurea inhibited N release, but Thermopsis lanceolata and Elymus nutan had no effect on it. N appeared enrichment-release model in the presence of Thermopsis lanceolata, Kobresia capillifolia inhibited P release, but Elymus nutans and Anemone rivularis promoted P release.Both mixed litter mass loss and N P dynamics appeared significant non-additive effect, suggesting species interactions cannot be ignored in the ecosystem. Species composition not species richness play a role in the mixed litter decomposition, indicating species composition is more important than species richness in understanding ecosystem functions.