宗宁1,2,石培礼1**,牛犇1,2,蒋婧2,3,宋明华3,张宪洲1,何永涛1
ZONG Ning1,2, SHI Pei-li1, NIU Ben1,2, JIANG Jing2,3, SONG Ming-hua3, ZHANG Xian-zhou1, HE Yong-tao1
摘要: Fertilization is an effective management measure for recovery of degraded grasslands. To better understand the effects of fertilization on community structure and productivity of lightly and severely degraded alpine meadows, we conducted a fertilization experiment in northern Tibet since 2008. The treatments were addition of nitrogen (N) alone (50 kg N·hm-2·a-1, LN; 100 kg N·hm-2·a-1, HN) or addition of both phosphorus (P) and N (50 kg N·hm-2·a-1+50 kg P·hm-2·a-1, LN+P; 100 kg N·hm-2·a-1+50 kg P·hm-2·a -1, HN+P) in each of the two types of degraded alpine meadows. N addition alone significantly affected plant community co-verage or productivity in neither the slightly nor the severely degraded alpine meadow, while addition of both N and P significantly increased plant community coverage, aboveground and belowground biomass of the alpine meadows. This suggested that productivity of this alpine meadow is co-limited by N and P. HN and HN+P significantly decreased species richness and evenness in the lightly degraded grassland, indicating that HN was not beneficial for the lightly degraded grassland to maintain species diversity and community stability. N addition significantly reduced the root to shoot ratio in the severely degraded meadow. In the lightly degraded meadow, N addition alone, especially with a high amount (HN), enhanced the importance values (IV) and biomass of grasses, while fertilization with both N and P increased those of sedges. In the severely degraded meadow, fertilization had little effect on IV of grasses or sedges, but improved biomass of forbs. The results suggested that LN+P could be employed in recovery of lightly degraded alpine meadows, but other management measures such as fencing and reseeding may be needed for recovery of severely degraded alpine meadows.