不同水分条件下苔藓结皮光合能力对氮素添加量的响应

Responses of Bryophytes' Photosynthesis to Nitrogen Addition Under Different Water Content

[目的]探究苔藓结皮失水过程中光合能力对不同梯度氮添加的响应,为进一步研究苔藓结皮对氮沉降的响应过程以及为干旱、半干旱区荒漠生态系统的管理提供理论依据。[方法]选取毛乌素沙地的优势藓种拟双色真藓(Bryum pachytheca)为研究对象,在控制条件下采用氮添加的模拟试验手段。[结果]苔藓结皮净光合速率在低于0.2g/(m2·a)的氮添加量时受到促进,在高于0.2g/(m2·a)的氮素添加量下,低水分含量时被抑制,高水分含量时会受促进;同时,0.2g/(m2·a)是苔藓结皮能承受的最优氮添加量,此时苔藓结皮的光合固碳能力达到最大,年光合固碳量为对照条件的2倍。[结论]氮沉降引起的氮素增加对于干旱、半干旱区苔藓结皮的光合能力以及固碳潜力具有显著的影响。

[Objective]The responses of bryophytes＇ photosynthesis to nitrogen addition in the process of its dehydration were studied in order to demonstrate how it will respond to nitrogen deposition and to provide relevant theoretical knowledge for management of desert ecosystems in arid or semi-arid region.[Methods]The dominant bryophytes,Bryum pachythecain Mu Us desert was selected to examine the responses of bryophytes＇ photosynthesis to nitrogen addition with eight levels.[Results]The net photosynthetic rates of bryophytes（Pn）increased when nitrogen addition was less than 0.2g/（m^2·a）.When nitrogen addition was over 0.2g/（m^2·a）,the responses of Pnvaried under different water condition.It was enhanced under high levels of water content,and was suppressed under low levels.In terms of bryophytes＇ photosynthetic carbon sequestration capacity in tested site,the optimal adding amount of nitrogen was 0.2g/（m^2·a）.At this addition amount,carbon fixed by bryophytes＇ photosynthesis was doubled as compared with that without adding nitrogen.[Conclusion]Nitrogen increment from deposition can strongly influence photosynthesis and carbon sequestration capacity of bryophytes in arid and semi-arid regions.