关键词: 土壤耕作, 秸秆还田, 微生物群体, 酶活性, 产量

Abstract: Based on field observation data from alpine region (3400-4200 m) in the upper reaches of Shule River between 2009 and 2014, the precipitation characteristics in alpine grassland during growing season (May-September) were evaluated by the methods of anomaly percentage, precipitation concentration degree (PCD) and precipitation concentration period (PCP) in this paper. The results showed that precipitation during growing season was between 139.3 and 401.6 mm, with the anomaly percentage generally ranging from -12.9% to 18.8%, and the precipitation gradient up to 21.7 mm·100 m^-1 (2013-2014). The maximum monthly precipitation was mainly concentrated in July or June, and their sum amounted to 55.7%-60.1% of growing season precipitation. The PCD ranged from 0.21 to 0.49 and the PCP occurred in the late June to July. The majority of single precipitation events were characterized by magnitude <10 mm, duration <24 h, intensity <0.5 mm·h^-1. Growing season precipitation in alpine grassland in the upper reaches of Shule River had the characteristics of small interannual variability, obvious vertical variation as well as uneven distribution, and was composed mainly of smallprecipitation events.

Key words: tillage, straw returning, microbial community, enzyme activity, grain yield.