PJB-2021-486
REVIEW: THE EFFECTS OF WATER ADDITION ON GRASSLAND PRODUCTIVITY
Iqnaa Naseer
Abstract
Changes in precipitation (PPT) regimes (size, amount, seasonality and frequency) have substantial impacts on grassland productivity (GP). To understand summarized effects of altering PPT on GP, in terms of above ground net productivity (ANPP), below ground net productivity (BNPP), gross primary productivity (GPP) and net primary productivity (NPP) under different climatic conditions, we synthesized results from global case studies of water addition experiments in grasslands. We found that, experimentally increased PPT enhanced GP by enhancing soil water, nitrogen contents (SWC, SIN) and activities of soil microbial communities (SMC). Both ANPP and BNPP are sensitive to changes in amount and frequency of PPT, BNPP shows almost similar trends under different water addition treatments, but ANPP shows more sensitive tends to water additions in dry and wet climatic conditions. In drier grassland ecosystems (GE), a significant increase in productivity was evidenced, but a decline in GP was documented in wet climates. Additionally, in water limited regions small PPT events are ecologically significant resource for productivity in GE but, in wet and extreme wet regions, productivity didn’t had a significant relationship with PPT changes. Likewise, large and few PPT events tends to significantly increase productivity by increasing SWC, SIN and SMC. Correspondingly in wet region large PPT events tends to result in N loss. The summary of global water addition studies, highlights the importance of PPT gradients (ranging from small to extreme increases) projected in future climate change. Currently, under shifting PPT scenario, we can predict productivity responses of GE (in terms of ANPP, BNPP, NPP and GPP).
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