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Zhuj U.,Xinjiang Institute of Ecology and Geography | Zhuj U.,Research for Desert grass Land Ecosystemn Xinjiang | Zhuj U.,University of Chinese Academy of Sciences | Li X.,Xinjiang Institute of Ecology and Geography | And 8 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2011

The northern slope of the Kunlun Mountains is next to the Taklamakan Desert, which s 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 n winter, and t 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 (Pmax) 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 (Rday) was higher than photorespiration (Rp). From 08:00 to 20:00, the diurnal changes of net photosynthetic rate (Pn), transpiration rate (Tr.) and stomatal conductance (Gs) showed a single peak in three elevations. The mean values of Pn, Tr, GB and stomatal limiting value (Ls) decreased with increasing elevation, while light use efficiency (LUE) and water use efficiency (WUE) increased significantly. Pn of Calligonum roborowasikii was significantly and positively correlated with leaf temperature (Tl), air temperature (Ta), photosynthetic photon flux density (PPFD), Tr, Ls, Gs, WUE and vapor pressure deficit (Vpdl), but negatively correlated with elevation and intercellular C02 concentration (C;), and had no significant correlation with relative humidity (RH) and air C02 concentration (Ca). Tr significantly and positively correlated with negatively correlated with RH. Gs, negatively correlated with Ca only. Pn significantly and positively correlated with Tr, Ls, Gs, WUE and Vpdl, negatively correlated with Ci. Through comparison analysis of the relationships between photosynthetic characteristics of C. roborowasikii and light, temperature n different elevations, the results showed that C. roborowasikii had a good ecological adaptation to the changes of light and temperature in desert grassland.

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