荒漠绿洲边缘降水和地下水对白刺群落消长的影响

通过在甘肃民勤荒漠绿洲外围设固定样方连年观测，结合小区域地下水位动态监测和气象观测数据，定量研究了降水和地下水位变化对白刺群落消长的影响。结果表明，以地下水位逐年下降为主要驱动因素的绿洲外围的环境旱化，促使优势种白刺群落的发育适应环境，更具旱生性。在民勤绿洲外围，地下水位下降在近期内不是白刺生长的限制因素，在该区白刺将能较长时间生存，并发挥其优良的固沙、阻沙作用。民勤绿洲外围地区约１１０ｍｍ年降水

Impact of precipitation and underground water level in the edge of oases on growth and decline of Nitraria tangugtorum community

Based on the data from underground water monitoring,meteorological measuring and fixed sample square investigating in successive years at the edge of the oasis in Minqin,Gansu,the impact of precipitation and underground water on the growth and decline of Nitraria tangutorum community was studied.The result showed that the desiccated environment in oases driven by the decline of underground water level was favorable for the growth and develoment of N.tangutorum community,and made this species more xerophilous.This declining underground water level was not a limiting factor for N.tangutorum growth in late years.These N.tangutorum dominated communities were predicted to survive comparatively longer,and to function as sand fixer and wind breaker at oasis edge in Minqin.When average annual precipitation was about 110mm, N.tangutorum would maintain its normal growth,but the community couldn't spread freely.Only when the annual precipitation was up 140mm in two years running,could its growth be improved.