氮添加对青藏高原高寒草甸土壤磷组分的影响

磷是一种影响草地植物生产力和生态系统功能的重要养分。本文研究了3个氮添加水平下(5，10和15 g ·m^-2)青藏高原海北高寒草甸(海拔3 100 m)土壤磷组分的变化特征及其主要影响因素。研究表明：N5处理下土壤磷的生物有效性增加。N5处理显著提高了活性磷库的含量，其中NaHCO₃-Pi的含量和比例均显著增加。N15处理下植物生物量和地上部含磷量增加，土壤活性磷含量无显著变化，N15处理下仅土壤残余态磷(Residual-P)显著下降。氮添加下影响土壤磷组分变化的关键因素包括土壤pH值、微生物生物量碳(Microbial biomass carbon,MBC)和微生物生物量氮(Microbial biomass nitrogen,MBN)。在高寒草甸氮添加能够通过降低土壤pH值和增加微生物生物量来提高土壤磷的有效性。

Effects of Nitrogen Addition on Soil Phosphorus Fractions in an Alpine Meadow of Qinghai-Tibet Plateau

Phosphorus (P) is an essential nutrient that affects plant productivity and ecosystem function in grasslands. In this study,we investigated the responses of soil P fractions to different levels of nitrogen (N) addition (5,10 and 15 g·m^-2 for N5,N10,and N15 respectively) and the mechanisms in an alpine meadow of Haibei,Qinghai-Tibet Plateau (3 100 m). We found that low N addition could improve the availability of soil P,as N5 treatment significantly increased the content of the labile P pool,as well as the content of NaHCO₃-Pi. In contrast,high N addition increased the aboveground biomass and P content in plant shoots,but no significant changes of labile P pool in the soil. Actually,only soil residual-P was significantly decreased under N15 treatment. The further analysis revealed key factors which might affect soil P fractions under N addition,including soil pH,microbial biomass carbon (MBC),and microbial biomass nitrogen (MBN). In conclusion,N additions increased the soil P availability,due to decreased soil pH and increased microbial biomass content in alpine meadows.