甘肃民勤绿洲-流沙过渡带植物群落光合和呼吸特征的比较研究

在甘肃省民勤绿洲选择典型的绿洲农田。流沙过渡带，研究了2种主要群落类型红柳群落和白刺群落的建群物种红柳(Tamarix ledeb)和白刺(Nitraia tongutorum)的净光合速率、暗呼吸速率和水分利用特征，并比较了不同部位的土壤呼吸速率。虽然2种植物单位叶片干重的净光合速率相似，但是红柳植株和以它为建群种的红柳群落比白刺植株和白刺群落具有更高的净光合速率和土壤呼吸速率，因而也具有更大的碳素地球化学循环强度。在红柳群落到白刺群落直至流沙的荒漠化演替过程中，群落及整个区域的碳素循环和养分周转发生了较大的变化，循环强度和时空变异程度呈下降趋势。

COMPARISON OF PHOTOSYNTHESIS AND RESPIRATION OF PLANT COMMUNITIES IN ECOTONE BETWEEN DESERT AND OASIS IN MINQIN, GANSU

Ecological processes occurred in the ecotone from shifting sand desert to oasis cropland are by far important for desertification development and oasis sustainability. Carbon fixation and emission, the principal ecosystem process along a desertification gradient in the ecotone in Minqin Oasis, Gansu Province was studied. Net photosynthetic rate, leaf dark respiration rate and water use efficiency of Tamarix ledeb and Nitraria tongutorum, the dominant species in the sucessional plant communities were examined. Leaf and soil respiration were also measured in the gradient. Although the two species had similar leaf dry weight based photosynthetic rate, T. ledeb plant and its dominated plant community had higher rate of photosynthesis and soil respiration, therefore, its intensity of carbon biogeochemical cycling was higher than that of N. tongutorum community. During the desertification process from T.ledeb community to N. tongutorum community and further to mobile sand, local and regional carbon cycling and nutrient turnover changed dramatically. The strength of cycling as well as temporal and spatial variation decreased.