岩溶石漠化地区几种生态恢复植物的生理生态学特征

The ecophysiological traits of three karst rockey desert restoration species

选择石漠化地区树种任豆树、金银花和苦丁茶的植株为对象,测定其光响应曲线和光合、蒸腾、气孔导度的日变化,研究其光合、蒸腾、气孔导度与环境因子间的关系。在岩石裸露率高、地表水缺乏、白天温度极高的石漠化地区,对任豆和苦丁茶进行光响应模拟表明,两者的最大净光合速率分别为15.88μmol.m-2.s-1、4.58μmol.m-2.s-1。从气体交换特征日变化看出,这三种植物均有光合午休现象,任豆午休程度最弱而苦丁茶最强,光合与气孔导度均呈显著的正相关关系;通过对胞间CO2浓度Ci与气孔限制Ls关系分析,任豆和金银花的光合作用上午以气孔限制为主,下午有非气孔因素影响,而苦丁茶则以非气孔限制为主。任豆树具有较高的水分利用效率,金银花次之,而苦丁茶最小。通过综合分析,认为地表缺水并不是石漠化地区简单唯一的限制因子,高温胁迫也造成该区植物同化CO2减少的原因。根系的下扎能力也应是石漠化地区植物长期存活的关键。因此通过人工诱导构建石漠化地区植物群落时一定要考虑植物本身的根系遗传性状。

The light curve and diurnal patterns of gas exchange were measured for 3 plant species（Zenia insignis, Lonicera japonica and Cratoxylum prunifolium）grown under dryland karst rocky desert conditions in Guangxi. Our objective was to characterize some of the physiological traits of these species to gain more insight into its ecophysiological characteristics, which may in turn contribute to the improvement of management practices in ecological restoration. Maximum photosynthetic rates,obtained by light curve in the morning, peaked at 15.88μmol·m^-2·s^-1 of Z. insignis and 4. 58 μmol·m^-2·s^-1 of C. prunifolium,suggesting that Z. insignis is better adaptation to rocky desert condition than C. prunifolium does. A marked decrease in photosynthesis was observed during midday together with a reduction in stomatal conductance and transpiration rate. It is significant correlated between Pn and gs of three speties; the relationship between Ls and Ci showed that the decline in photosynthesis of Z. insignis and L. japonica were mainly the result of stomatal limitations before 14 ： 00 but nonstomatal limitation in the afternoon,while that of C. prunifolium was mainly the result of nonstomatal limitation. These limitations on photosynthetic activity are likely induced by intensive solar radiation and high temperature, and enhanced by the increasing vapor pressure deficit. Stomata of Z. insignis and L. japonica were open with a decreasing rate toward midday. However,the openness of stomata of C. prunifolium remained very small and slightly decrease toward 14 ： 20 and throughout the brief adverse conditions of midday. Z. insigni processed highest water use efficiency （WUE）, followed by L. japonica and C. prunifolium. With the result, we suggest that in karst rocky desert area, drought and high temperature are two main stress factors to affect plant photosynthesis, transpiration and WUE. Plant with a deep and developed root system, e. g. Z. insignis and L. japonica, was probably to uptake water from deep karst volume to allow transpiration so as to protect the photosynthetic apparatus and meanwhile to maintain high photosynthesis during midday, thereby to enhance the WUE. But plant like young C. prunifolium with a shallow root distribution,is easily suffered by drought that unsufficient water for transpiration may increase the leaf temperature therefore damage the photosynthetic apparatus. The result suggests that a root trait of capacity of plunge into rock gap would be a key feature for plant to survive in rocky desert terrain while plants are introduced for vegetation restoration.