Cascading influences of grassland degradation on nutrient limitation in a high mountain lake and its inflow streams.

摘要: Nitrogen (N) and phosphorus (P) are key growth-limiting nutrients for organisms their absolute relative supplies regulate the structure function of ecosystems. Landcover changes lead to modifications terrestrial biogeochemistry, consequently influencing aquatic nutrient conditions. This study sought evaluate potential impacts grassland degradation on availability limitation in Qinghai Lake (China) its inflow streams. We sampled concentrations tested stream by conducting diffusing substrata (NDS) bioassays streams flowing through subbasins with different status. To test responses lake phytoplankton inflows, were conducted adding (N, P, joint NP) as well water from phytoplankton, respectively. In general, N N:P ratios decreased while P increased normalized difference vegetation index (NDVI, an status), especially September, suggesting that (low NDVI) has differentially decrease increase Consistent this, (RR) periphyton combined NP enrichments NDS ratios. responded strongly addition indicating strong P-limitation phytoplankton. RR nitrate concentration ammonium, total phosphorus, soluble reactive higher but lower degraded subcatchments is associated impact P-limited Overall, this suggests influence delivered substantial increases decreases N:P, alleviating and, ultimately, stimulating growth lake.