昆仑山北坡4种优势灌木的气体交换特征

The gas exchange characteristics of four shrubs on the northern slope of Kunlun Mountain

在自然条件下对昆仑山北坡4种灌木塔里木沙拐枣(Calligonum roborowasikii)、驼绒藜(Ceratoides latens)、合头草(Sympegma regelii)和昆仑绢蒿(Seriphidium korovinii)的气体交换、水势的季节变化特征及生长季末δ13C值进行了比较研究。结果表明:驼绒藜、塔里木沙拐枣和合头草气体交换日变化为单峰曲线,昆仑绢蒿为双峰曲线;其中塔里木沙拐枣属高光合、高蒸腾型,水分利用效率最高;合头草属低光合、低蒸腾型;驼绒藜属高光合、低蒸腾型;昆仑绢蒿属低光合、高蒸腾,水分利用效率最低。驼绒藜光合速率8月日变化,10:00-12:00,16:00—20:00两个时段,Pn下降,主要决定因素均为非气孔因素。沙拐枣6月光合速率日变化,12:00-14:00时,Pn下降,主要受气孔导度因素影响;16:00-20:00时,Pn下降,可能是同时受气孔和非气孔因素的影响。从耐旱机理可以将4种灌木归类:塔里木沙拐枣和昆仑绢蒿属于高水势延迟脱水耐旱机理;驼绒藜和合头草属于低水势忍耐脱水机理。用1δ3C表征植物水分利用效率时,只有部分物种有很好的一致性。

The northern slope of the Kunlun Mountains is next to the Taklamakan Desert, which the Asian continent belonging to the Xinjiang-Uighur Autonomous Region, NW China. The main is the most arid center of plant types in the desert grassland at an altitude between 2100 and 2600 m are Calligonum roborovskii, Ceratoides latens, Sympegma regelii, and Seriphidium korovinii Poljak which are the very important source of livestock food in winter. The plant over conserves water, prevents wind erosion, and maintains ecological stability. Desertification in this area became a serious problem recently and caused sandstorms, erosion as well as sand deposition. Researches on protection and recovery of the vegetation on the northern slope of the Kunlun Mountains are of great importance. C. roborowasikii, C. latens, S. regelii and S. korovinii, are very important four species on the northern slope of Kunlun Mountain. The gas exchange of these plants is closely related to the ecological conditions. It is an effective way to reveal the mechanism of plant adaptation to environmental conditions. Water potential is the most sensitive degree of water condition in plant. Low water potential indicates good water condition of the plant. Accordingly, high water potential reflects that the plant lies in drought stress. Water use efficiency is an important index to distinguish the ability of the plants adapt to drought environment, h can be divided into instantaneous water use efficiency and long-term water use efficiency. Long-term water use efficiency is difficult to be acquired. Many studies suggested that stable carbon isotopic content and long-term water use efficiency are closely related. The content of carbon isotopes in plant leaves is used as an indicator for long-term water use efficiency. The technology has been widely used in plant physiology ecological research. In this study, gas exchange, water potential characteristics in seasonal courses and δ^13C values of these plants were studied. The results showed that the gas exehange diurnal courses of C. latens, C. roborowasikii and S. regelii displayed a single peak pattern with double peak pattern of S. korovinii. Within the four species, C. roborowasikii displayed a high Pn Tr and the highest WUE ; While those of S. regelii were low Pn and Tr ; C. latens was high Pn and low Tr ; S. korovinii displayed a low Pn, high T and the lowest WUE. The two decline of C. latens in Pn was due to the low carboxylation eapaeity of the leaf mesophyll; the effect of Gs contributed to the first deline of C. roborowasikii in 12：00- 14：00, while the second decline might be due to the two factors. Different species had different mechanisms to adapt to drought stress. C. roborowasikii and S. korovinii maintained higher water potential to delay dehydration. Comparatively, C. latens and S. regelii maintained lower water potential to endure dehydration. When trying to establish the relationships of WUE and δ^13C, only some species were found to have a good consistency.