昆仑山北坡不同海拔塔里木沙拐枣的光合生理生态特性

在2008年7月25日-8月6日的连续晴天中,选择昆仑山北坡塔里木沙拐枣自然分布区3个海拔高度(2100,2300,2500m),利用便携式光合测定仪LI-6400测定塔里木沙拐枣的光合生理生态特性。结果表明:2100m处塔里木沙拐枣的光补偿点(LCP)和光饱和点(LSP)与2300m,2500m处差异分别达到显著,而3者间的最大净光合速率(P_max)差异均达显著。表观量子效率(AQY)在3个海拔之间差异均不显著,但在2100m处的羧化效率(CE)分别与2300m和2500m处的差异显著。相同海拔下塔里木沙拐枣的暗呼吸速率值(R_day)要高于光呼吸速率值(R_p),且2500m处的暗呼吸速率分别与2100m和2300m处的有显著的差异,2100m处的光呼吸速率分别与2300m和2500m差异显著。3个海拔塔里木沙拐枣的净光合速率(P_n)、蒸腾速率(T_r)和气孔导度(G_s)的日变化均为单峰曲线。随着海拔的升高,塔里木沙拐枣P_n,T_r,G_s和L_s的日均值降低,但光能利用率(LUE)和水分利用效率(WUE)却显著增加。塔里木沙拐枣的P_n与叶温(T_l)、大气温度(T_a)和光照强度(PPFD)具有极显著的正相关关系,与海拔呈显著负相关,与空气相对湿度(RH)和大气CO₂浓度(C_a)之间均不具有显著相关性。T_r与T_a,T_l和PPFD具有极显著的正相关性,与RH之间存在显著的负相关。G_s只与C_a之间呈极显著的负相关。P_n与T_r,L_s,G_s,WUE和V_pdl分别具有极显著的正相关性,与C_i呈极显著的负相关。通过对不同海拔高度塔里木沙拐枣光合生理参数与光、温等生态因子关系的对比分析表明:塔里木沙拐枣对山地荒漠草地自然环境变化的温度和光照有很好的生态适应性。

Photosynthetically and ecophysiological characteristics of Calligonum roborowasikii in different altitudes on the northern slope of Kunlun Mountain

The northern slope of the Kunlun Mountains is next to the Taklamakan Desert, which is the most arid center of the Asian continent belonging to the Xinjiang-Uighur Autonomous Region, NW China. The desert grassland at an altitude between 2100 and 2600 m consists mainly of Calligonum roborovskii, Ceratoides latens, Sympegma regelii, and Seriphidium korovinii Poljak. It is the main source of livestock food in winter, and it conserves water, prevents wind erosion, and maintains ecological stability. But currently, desertification becomes a serious problem. Sandstorms cause erosion as well as sand deposition. Therefore, research on protection and recovery of the vegetation on the northern slope of the Kunlun Mountains is necessary. C. roborowasikii, an important vegatation component, does not only effectively prevent wind erosion but is also a good food for camels and sheep. However, researches on eco-physiological adaptation of C. roborowasikii to natural habitat had not been reported by far. A better knowledge of the adaptation mechanisms of this characteristic species to the unique site conditions can contribute to the scientific basis for protection and recovery of the vegetation on the northern slope of the Kunlun Mountains. In order to know the photosynthetic and ecophysiological characteristics of C. roborowasikii better, we selected C. roborowasikii in three elevation (2100, 2300, 2500m) zones of its natural distribution for measure the photosynthetically and relevant ecophysiological characteristics by a Portable LI-6400 Photosynthesis System from 25 July to 6 August, 2008. The results showed that there was significant difference in light compensation point (LCP) and light saturation point (LSP) of C. roborowasikii between 2100m and 2300m or 2500m respectively, while the maximum net photosynthetic rate (P_max) was significantly different among the three elevations. There was no significant difference in apparent quantum requirement (AQY) among the three, while significant difference existed in carboxylation efficiency (CE) among 2100m and 2300m, 2500m respectively. In the same elevation, dark respiration (R_day) was higher than photorespiration (R_p). From 08:00 to 20:00, the diurnal changes of net photosynthetic rate(P_n) , transpiration rate(T_r) and stomatal conductance (G_s) showed a single peak in three elevations. The mean values of P_n , T_r , G_s and stomatal limiting value(L_s )decreased with increasing elevation, while light use efficiency(LUE) and water use efficiency(WUE) increased significantly. P_n of Calligonum roborowasikii was significantly and positively correlated with leaf temperature(T_l), air temperature(T_a), photosynthetic photon flux density(PPFD), T_r, L_s, G_s, WUE and vapor pressure deficit (V_pdl), but negatively correlated with elevation and intercellular CO₂ concentration(C_i), and had no significant correlation with relative humidity(RH) and air CO₂ concentration(C_a). T_r significantly and positively correlated with T_l, T_a and PPFD, negatively correlated with RH. G_s negatively correlated with C_a only. P_n significantly and positively correlated with T_r, L_s, G_s, WUE and V_pdl, negatively correlated with C_i. Through comparison analysis of the relationships between photosynthetic characteristics of C. roborowasikii and light, temperature in different elevations, the results showed that C. roborowasikii had a good ecological adaptation to the changes of light and temperature in desert grassland.