氮素及水分添加对科尔沁沙地4种优势植物地上生物量分配的影响

Response of Aboveground Biomass Allocation in Four Dominant Species to Water and Nitrogen Addition in the Horqin Sandy Land

氮素和水分是半干旱沙地生态系统植物生长主要的影响因素,氮沉降和降水量与降水格局的变化可能会对植物生长产生深刻影响,进而影响沙地生态系统功能。本文通过科尔沁沙地草地连续2年增加水分(夏季增雨,冬季增雪)、添加氮素和同时添加氮素和水分的田间试验,分析了不同处理对4种优势草本植物种(尖头叶藜Chenopodium acuminatum、白草Pennisetum centrasiaticum、糙隐子草Cleistogenes squarrosa和狗尾草Setaria viridi)地上生物量积累和分配的影响。结果表明:单纯添加氮素或水分对当地4种优势植物平均地上总生物量、各构件平均生物量及繁殖体和茎平均生物量分配无显著影响。夏季增雨×氮素添加使4种植物平均地上总生物量及各构件平均生物量在2010年显著增加,冬季增雪×氮素添加使叶生物量分配在2010年显著增加;但是在2012年各处理对生物量的分配影响不显著。这说明夏季增雨×氮素添加能够解除氮素对水分的限制作用,使植物将所获得的有限资源供于叶片生物量的积累和分配。但是添加氮素与水分影响的生物量分配变化程度因物种而异,对尖头叶藜、白草、糙隐子草的影响不明显,对狗尾草的影响显著。

Nitrogen and water are the main constraints in semi-arid sandy land,nitrogen deposition and variations in precipitation probably affect plant growth and thereby affect ecosystem function in sandy land.A field study was conducted to detect the effects of nitrogen and water addition on the aboveground biomass accumulation and allocation of the four dominant herbaceous species(Pennisetum centrasiaticum,Setaria viridi, Cleistogenes squarrosa and Chenopodium acuminatum)by adding water(precipitation in summer and snow in winter),nitrogen and nitrogen-water interaction for two consecutive years in the Horqin Sandy Land.The results showed that adding nitrogen or water lonely would have no noticeable effects on the average total biomass,the average biomass of its components and its allocation of the propagules and stems in4 dominant species.Adding nitrogen with water in summer,however,leaded to a significant increase in the average of aboveground total biomass and the average biomass of it components in 2010.Meanwhile,adding nitrogen with snow in winter increased the allocation of leaf biomass remarkably in 2010 and but showed no significant effect on biomass allocation in every treatment in 2012.This implies that adding nitrogen with water could alleviate the interactive constraining between nitrogen and water,subsequently enhance allocation of the limiting resources to leaf.The influences of nitrogen and water addition on aboveground biomass allocation were somewhat related to plant species.The results showed that adding nitrogen and water significantly affected aboveground biomass and its allocation in S.viridis.However,no significant effects were detected in P.centrasiaticum,C.acuminatumand C.squarrosa.