From leaf traits to agroecosystem functioning: effects of changing resource use strategy during silphium domestication on litter quality and decomposition rate

Abstract

Aims: We asked if structural and chemical changes in leaf traits, brought about by early domestication in perennial Silphium integrifolium Michx. (Asteraceae), have influenced litter quantity and quality, and decomposition rates. This process is critical to determine how an ecosystem recycles nutrients, renews soil fertility and sequesters C in the soil. Methods: We compared in a field experiment green and senescent leaves traits of Improved and Wild accessions of Silphium. We performed a laboratory decomposition experiment to determine the decomposition rate, and the change in litter quality over time. Results: Improved accessions of Silphium produced almost two times more litter than the Wild, which should, in turn, contribute to a higher C input to the soil; however, this litter decomposed faster than that of wild types, and thus had shorter C residence time. Slower decay of litter has been recommended for C sequestration in erodible lands and semi-arid zones, also favoring nutrient retention and slower release of nutrients. The key driver of the decomposition process was resin content and not the usual chemical predictors of litter quality (i.e. N content and C/N ratio). Wild-type litter had thicker leaves with higher resin content, and lower C:N ratio. Conclusions: Domestication changed litter quality affecting the rate of decomposition and potentially C cycling in the agroecosystem. Improved accessions contributed with more C input litter but with lower quality. The lower resin content of the Improved accessions reduced the litter residence time of C due to faster rate of decomposition.