In nature litter is usually heterogeneous and may not decompose the way homogeneous litter does. For example, heterogeneous litter decomposition is frequently non-additive. This makes the fluxes associated with decomposition impossible to predict. We have investigated factors that contribute to non-additive decomposition of heterogeneous litter (oat straw/clover) by testing several common hypotheses used to explain non-additive decomposition. These include increased microarthropod abundance, increased water content, and the transfer of carbon and/or nitrogen compounds from clover to oat straw. We also tested a new hypothesis, which is that C, N and other nutrients are simultaneously supplied by clover to stimulate the decomposition of oat straw.
Results/Conclusions
The decomposition rate of oat straw is consistently and significantly increased by the presence of clover. However, clover did not increase microarthropod abundance, the addition of water to oat straw did not increase oat straw decomposition, and adding glucose and ammonium chloride to oat straw had no significant effect on oat straw decomposition. When soil was in contact with oat straw and glucose and ammonium chloride were added, oat straw decomposition was stimulated as if clover were present. These results suggest that microarthropods, water and C or N transfer were not responsible for non-additive decomposition, but that soil supplied some nutrient(s) other than C or N and that the combination of C, N and these nutrients were responsible for non-additive decomposition of oat straw. We are currently evaluating which specific nutrient(s) can take the place of soil. Our research provides insight into the dynamics of heterogeneous litter decomposition and will allow us to better model nutrient cycling.