氮、磷添加对高寒草原群落多样性和生物量的影响

为探讨环青海湖区域轻度退化高寒草原适宜的氮（N）、磷（P）添加量，筛选区域N，P合施的优化方案，本试验选用尿素与磷酸二铵，采用随机区组设计，设置3个氮元素水平（35，70，140 kg·hm^-2）和3个磷元素水平（26，52，65 kg·hm^-2），氮元素和磷元素水平组合为：N1P1（35，26 kg·hm^-2），N1P2（35，52 kg·hm^-2），N1P3（35，65 kg·hm^-2），N2P1（70，26 kg·hm^-2），N2P2（70，52 kg·hm^-2），N2P3（70，65 kg·hm^-2），N3P1（140，26 kg·hm^-2），N3P2（140，52 kg·hm^-2），N3P3（140，65 kg·hm^-2）9个施肥梯度，以不施肥为对照，研究N、P合施当年和次年对该草原群落特征的影响。结果表明：N、P合施显著（P<0.05）增加禾本科、豆科植物的盖度、高度和重要值。施肥不同程度降低了高寒草原植物群落多样性，但差异性不显著（P>0.05）。施肥当年与次年地上生物量分别增产59.22%~205.57%，73.41%~180.10%，次年比当年增产2.72%~17.34%。该区域最适宜植物生长的N、P添加量分别为70~140 kg·hm^-2，26~52 kg·hm^-2。综上所述，人工施肥是天然高寒草原轻度退化草地改良一种快速有效的措施，能够有效的提高草地生物量，同时也有利于草地植被的恢复。

Effects of Nitrogen and Phosphorus Addition on Community Diversity and Biomass of Alpine Steppe

In order to explore the suitable amount of nitrogen(N) and phosphorus (P) in the light degraded alpine grassland in the surrounding area of Qinghai lake,screen the optimized combination of N and P,urea and diammonium phosphate were used for this study and conducted with a randomized block design. Three levels of N (35,70,140 kg·hm^-2) and three levels of P (26,52,65 kg·hm^-2) were set with the combinations of N and P levels:N1P1 (35,26 kg·hm^-2),N1P2 (35,52 kg·hm^-2),N1P3 (35,65 kg·hm^-2),N2P1 (70,26 kg·hm^-2),N2P2 (70,52 kg·hm^-2),N2P3 (70,65 kg·hm^-2),N3P1 (140,26 kg·hm^-2),N3P2 (140,52 kg·hm^-2),N3P3 (140,65 kg·hm^-2) as 9 fertilization gradients,with no fertilization as a control. The effects of N and P combined application on the community characteristics of grassland community were studied for the year and the following year of fertilization. The results showed that,the combined application of N and P significantly (P<0.05) increased the coverage,height and important values of Gramineae and Leguminosae. The diversity of plant communities in alpine grassland were reduced,but not significant(P>0.05). The aboveground biomass of plant communities increased by 59.22%~205.67% and 73.41%~180.10% in the year and the following year of fertilization;Compared with the current year,the aboveground biomass increased by 2.72%~17.34% in the following year. The optimal N and P additions for plant growth in this area were 70~140 kg·hm^-2 and 26~52 kg·hm^-2. In summary,artificial fertilization is a rapid and effective measure for the improvement of light degraded grassland in natural alpine grassland,which can effectively improve grassland biomass and facilitate grassland vegetation restoration.