内蒙古典型草原克氏针茅与冰草的生存策略

Survival strategy of Stipa krylovii and Agropyron cristatum in typical steppe of Inner Mongolia

在内蒙古自治区多伦县中国科学院植物所生态恢复试验站,选择优势种克氏针茅(Stipa krylovii)和冰草(Agropyroncristatum),使用Li-6400便携式光合测定系统测定二者光合生理生态特征的生长季变化,微气象观测系统测定环境因子变化(DOY155-265)。结果表明:(1)光合有效辐射(PAR)与冰草的水分利用率(WUE)显著相关(P<0.01),与克氏针茅的水分利用效率相关度不显著(P<0.05);(2)光合有效辐射与冰草的光合利用率(LUE)显著相关(P<0.05),与克氏针茅的光合利用效率相关度不显著(P<0.05);(3)相对湿度(RH)与冰草和克氏针茅的气孔导度(Gs)均显著相关(P<0.01),与冰草的光能利用率在0.01水平下显著相关;(4)饱和水汽压差(VPD)与冰草的气孔导度显著相关(P<0.05)。(5)冰草与克氏针茅的气孔导度受5cm和20cm深度土壤含水率(SWC)的影响较大,且随着土壤深度的增加这种影响呈下降趋势。表层5cm土层深度的土壤含水量与冰草、克氏针茅的拟合度分别为0.4192和0.3057,20cm土层深度拟合度分别为0.3763和0.2546。(6)植物水分利用率和光合利用率可作为评价植物的环境适应能力优良指标,冰草在土壤含水率很低的情况下,仍然能保持良好的水分利用率,为胁迫忍耐性对策者;而克氏针茅在整个生长季的光能利用率低于冰草,反而在降水充沛、土壤含水量较高的生境下光能利用率高于冰草,为竞争性对策者。

How plants in arid and semiarid ecosystems respond to variations in environment variables is crucial for understanding survival strategy of the plants and assessing the impacts of climate change on terrestrial ecosystems.The objective of this paper is to explore physiological and ecological characteristics of photosynthesis,water use efficiency and light use efficiency of Stipa krylovii and Agropyron cristatum,two dominant species in typical steppe in Inner Mongolia,with focus on their relations to environmental factors.We used Component Analysis to identify major environmental factors and reveal the responses and strategic adaptation of S.krylovii and A.cristatum to climate change.The field experiment was conducted at typical semi-arid steppe in Duolun County,Inner Mongolia,China.We chose the dominant species S.krylovii and A.cristatum,and measured their photosynthetic characteristics in the growing season（DOY 155-265） by a portable photosynthesis system（Li-6400）,furthermore,we monitored the change of environmental factors by a micro-meteorological observation system.The results shows that：（1） there was a significant correlation between photosynthetically active radiation（PAR） and water use efficiency（WUE） of A.cristatum（P 0.01）,but there was no significant correlation between PAR and water use efficiency（WUE） of S.krylovii（P 0.05）;（2） light use efficiency（LUE） significantly correlated with PAR for Agropyron cristatum（P 0.05）,but not for S.krylovii（P 0.05）;（3） stomatal conductance（Gs） significantly correlated with relative humidity（RH） for both A.cristatum and S.krylovii,and there was a significant relationship between LUE and RH for A.cristatum（P 0.01）;（4） stomatal conductance of A.cristatum was significantly correlated with vapor pressure deficit（VPD）（P 0.05）;（5） there is obvious effect of soil water content（SWC） at 5 cm and 20 cm depths on the stomatal conductance of A.cristatum and S.krylovii.SWC at 5 cm depth and the stomatal conductance of A.cristatum and S.krylovii whose goodness of fit was 0.4192 and 0.3057 respectively,SWC at 20cm depth and the stomatal conductance of A.cristatum and S.krylovii whose goodness of fit was 0.3763 and 0.2546 respectively;and（6） WUE and LUE of plants can be used as good indicators of their environmental adaptability,A.cristatum was still able to maintain high WUE while SWC is very low,which might be identified as stress tolerance strategy.The LUE of S.krylovii was lower than A.cristatum throughout the growing season,but under abundant rainfall and higher SWC conditions,the LUE of S.krylovii was higher than that of A.cristatum,which might be identified as a competitive strategy.