Abstract:

 Exploring the impacts of precipitation on litter decomposition of plant species will help to deeply understand the biogeochemical cycle of grassland ecosystems under global changes. We carried out a 480-day decomposition experiment based on a field experiment of precipitation change in a desert steppe of Ningxia conducted in 2014. The element release and ecological stoichiometry of four plant species litters were examined, and their relationships with soil element supply level were analyzed. The results showed that the C release from the litters of the four species was slow. Except Artemisia scoparia, the C release rates even did not reach 50% after 360 days of decomposition in most cases. The release of N and P from litters of the four species was faster in the early stage than that in the late stage. The release rates of N and P exceeded 50% after 180 days of decomposition in most cases. The 50% reduction in precipitation significantly decreased the cumulative release of the three elements in the litters of A. scoparia and the cumulative release of P in the litters of Pennisetum centrasiaticum (P<0.05). The increasing precipitation showed opposite effects, but the 50% increase in precipitation significantly reduced the cumulative release of C and N in the litters of A. scoparia (P<0.05). Compared with the 30% reduction in precipitation, the 50% reduction, 30% increase, and 50% increase in precipitation changed litter C∶N∶P ecological stoichiometry of the four species.  However, their impacts were speciesspecific and without clear trends. The cumulative release of P in the litters of A. scoparia and Astragalus melilotoides were significantly positively correlated with soil total P concentration (P<0.05), indicating that the P release from the litters of A. melilotoides and A. scoparia is helpful for soil P accumulation.

Key words: change in precipitation regime, desert steppe, litter decomposition, litter element release, soil element returning.