模拟降水量变化对毛乌素油蒿幼苗生物生态过程中的影响研究

毛乌素是中国干旱、半干旱沙区典型沙地，其中水分是最大限制因子，随着未来全球变化，尤其是降水变化进一步激烈，将给这里的陆地生态系统分布格局和生产力带来巨大影响，本文选择毛乌素沙地优势灌木油蒿为研究对象，人控４种降水量梯度来探讨油蒿幼苗的生理生态对降水量的响应。结果表明，不同施水量的油蒿幼苗净水合速率、蒸腾速率、气孔导度、胞间ＣＯ２浓度、叶片温度、光能利用率、水分利用率日变化动态存在明显差异，当少量施水时，幼苗受到明显水分胁迫，故而关闭气孔，降低气孔度和蒸腾速度，以免过多的蒸腾失水。当充分施水时，幼苗叶片气孔开放，提高气孔导率、胞间ＣＯ２浓度和蒸腾速率，降低叶片温度、以此提高光合作用。不同施水的油蒿幼苗表现出不同的生理生态适应策略，幼苗荧光效率随着施水量增大，从机理上解释了幼苗光合作用随着施水量的增加而增长；向后剔除变量分析表明，随着施水量的增加，限制幼苗净光合速度的主要因子逐渐减少。当充人地水时，幼苗主要受到光合有效辐射和叶片温度的限制。当中度施水时，幼苗主要受到蒸腾速率、胞间／大气ＣＯ２浓度差值的限制，不少量施水量时，幼苗主要受到蒸腾速率、气孔导度、胞间／大气ＣＯ２浓度差值、叶片／大气温度差值及其大气温度的限制。

STUDY ON THE EFFECT OF SIMULATED PREGIPITATION CHANGE ON THE PHYSIOLOGICAL ECOLOGY PROCESS FOR ARTEMISIA ORDOSICA SEEDLINGS IN MAOWUSU SANDLAND

Maowusu sandland is classical one of arid and semi|arid sandland in China.Water is the most limited factor there.The distribution pattern and productivity of terrestrial ecosystem are greatly affected with the future global severer change,especially global precipitation change.It is investigated for the response of physiological ecology of A.ordosica seedlings,a dominant shrub in Maowusu sandland,to the global precipitation change by artificially controlling four water supply gradients.The results show that the diurnal changes of photosynthetic rate,transpiration rate,stomatal conductance,intercellular CO 2 concentration,leaf temperature,solar energy utilization efficiency,and water utilization efficiency of A.ordosica seedlings show significantly different under different water supply treatments.The seedlings have low stomatal conductance and transpiration rate by shutting stomata so as to lower losing water by transpiration,mainly due to severe water stress in the deficit water supply,but high stomatal conductance,intercellular CO 2 concentration,transpiration rate and low leaf temperature by opening stomata so as to increase photosynthesis in full water supply.So the seedlings show different physiological ecological adaptation strategies under different water supply.The fluorescence efficienc increases with the increase of water supply,which explains on mechanism why photosynthesis increases with the increase of water supply treatments.The analyses of backward eliminated variable indicate that the number of main factors which restrict photosynthetic rate of seedlings decrease with the increase of water supply.PAR and leaf temperature are most restricted factor in full water supply,and transpiration rate,intercellular/air CO 2 concentration margin and PAR in middle water supply,but transpiration rate,stomatal conductance,intercellular/air CO 2 concentration margin,leaf/air temperature and air temperature in deficient water supply.