Side-effects of plant domestication: ecosystem impacts of changes in litter quality.

Domestication took plants from natural environments to agro-ecosystems, where resources are generally plentiful and plant life is better buffered against environmental risks such as drought or pathogens. We hypothesized that predictions derived from the comparison of low vs high resource ecosystems (faster-growing plants promoting faster nutrient cycling in the latter) extrapolate to the process of domestication. We conducted the first comprehensive assessment of the consequences of domestication on litter quality and key biogeochemical processes by comparing 24 domesticated crops against their closest wild ancestors. Twelve litter chemistry traits, litter decomposability and indicators of soil carbon (C) and nitrogen (N) cycling were assessed in each domesticated vs wild ancestor pair. These assessments were done in microbial-poor and microbial-rich soils to exemplify intensively and extensively managed agricultural soils, respectively. Plant domestication has increased litter quality, encouraging litter decomposability (36% and 44% increase in the microbial-rich and microbial-poor soils, respectively), higher soil NO3 - availability and lower soil C : N ratios. These effects held true for the majority of the crops surveyed and for soils with different microbial communities. Our results support ecological theory predictions derived from the comparison of low- and high-resource ecosystems, suggesting a parallelism between ecosystem-level impacts of natural and artificial selection.