降水量对荒漠草原骆驼蓬( Peganum harmala )地上生物量的影响

Effects of precipitation on above-ground biomass of Peganum harmala in desert steppe in Inner Mongolia,China

了解降水变化对荒漠草原植物生长发育的影响对于预测荒漠草原植物对气候变化的响应和适应具有重要意义。本文研究了3年的降水量增减(±50%)对乌拉特荒漠草原优势植物骆驼蓬(Peganum harmala)的数量特征(分枝数、果实数和植株密度)、地上生物量(AGB)和功能性状的影响。利用相关分析研究各指标与AGB的相关性,并建立结构方程模型(SEM)来探究降水变化、骆驼蓬的数量特征及功能性状对AGB的影响机制。结果表明:(1)增加50%降水量处理下,骆驼蓬的分枝数、果实数和株高显著提高(P<0.05);减少50%降水量下,AGB、比叶面积(SLA)和株高显著降低(P<0.05),但叶干物质含量(LDMC)显著增加(P<0.05)。(2)生长季前期降水量(EGSP)增多有利于对骆驼蓬分枝和果实的发育,也缓解了年降水量减半对其SLA、LDMC和株高的胁迫。(3)骆驼蓬AGB与分枝数、果实数、植株密度和株高显著正相关(P<0.05),与LDMC和叶片碳含量显著负相关(P<0.05)。(4)SEM表明,增加的年降水量通过增加株高、果实数和植株密度来间接增加AGB,EGSP则通过改变果实数间接影响AGB。研究干旱草原植物生产力对降水变化的响应时,EGSP和年降水量的变化都值得关注。植物数量特征和功能性状在驱动植物生产力对降水变化的响应方面具有重要作用。

Understanding the effects of precipitation change on plant growth and development in desert steppe is crucial for predicting the response and adaptation of desert steppe plants to climate change.Here,we conducted a 3-years experiment to examine the effects of precipitation changes(background and±50%precipitation)on quantitative characteristics(branch number,fruit number and plant density),aboveground biomass(AGB)and functional traits of the dominant plant Peganum harmala in Urat desert steppe.Correlation analysis was conducted to study the correlation between each factor and AGB.And structural equation model(SEM)was established to explore the influence mechanisms of precipitation change,quantitative characteristics and functional traits on AGB of P.harmala.The results showed that:(1)Under the treatment of increased 50%precipitation,the number of branches,the number of fruits and the plant height were significantly increased(P<0.05).Under decreased 50%precipitation,AGB,specific leaf area(SLA)and plant height were significantly decreased(P<0.05),but leaf dry matter content(LDMC)was significantly increased(P<0.05).(2)The increase of precipitation in the early growing season(EGSP)was beneficial to the growth of branch and fruit.It also alleviated the stress of decreased precipitation on SLA,LDMC and plant height.(3)AGB was significantly positively correlated with branch number,fruit number,plant density and plant height(P<0.05),but negatively correlated with LDMC and leaf carbon content(P<0.05).(4)The SEM showed that increasing annual precipitation indirectly increased AGB by inducing the increase of plant height,fruit number and plant density;EGSP indirectly affected AGB by inducing the change of fruit number.Both the changes of EGSP and annual precipitation deserve more attention in studying the effect of precipitation change on plant productivity in arid steppe.Our results highlight the importance of plant quantitative characteristics and functional traits in driving the responses of plant productivity to precipitation change in desert steppe ecosystems.