内陆黑河流域植物稳定碳同位素变化及其指示意义

Stable carbon isotope variation in plants and their indicating significances along the inland Heihe River basin of northwestern China

对黑河流域山地、绿洲和荒漠区木本植物叶片或同化枝进行稳定碳同位素分析得出,山地植物稳定碳同位素比率(δ13C)在-23‰^-29‰之间,平均值为-26.3‰;绿洲植物在-26‰^-30‰之间,平均值为-27.2‰;荒漠植物在-23‰^-28‰和-12‰^-15‰两个范围,平均值分别为-26.0‰和-13.8‰,严酷生境植物δ13C值较高。同种植物在不同生境下的δ13C值,也表现为较差生境高于较好生境。荒漠河岸林树种胡杨(Populus euphratica)柳树形叶的δ13C值低于杨树形叶。无论是山区还是荒漠区,随着海拔高度增加,有些植物稳定碳同位素辨别力(Δ)减小,有些变化不明显,青海云杉(Picea crassifolia)的△值随着海拔升高线性递减显著。研究得出,荒漠植被中高水分利用效率(WUE)的C4植物占有一定比例。严酷生境下植物WUE高于较好生境。胡杨长条形叶的WUE最低,圆形叶的最高,由幼苗时期的柳树形叶向杨树形叶的演变中WUE在提高。青海云杉为黑河上游山区环境变化的重要指示植物。同种植物过高的δ13C值指示着植物的衰退和生境的严重胁迫。植物适应干旱环境是沿着有利于提高水分利用效率的方向发展。

The inland Heihe River basin of arid region in northwestern China is composed by three great landscapes： the mountain, the oasis and the desert, The upriver mountain is a sensitive region to the environmental change, which suffers little human interference; in the midriver and downriver regions, the oases and deserts are ecological fragile regions, and their environmental transition is the focus that people pay attention to, Plant is an indicator of environmental change, and compared with the other organs, photosynthetic organ is more sensitive, as its characteristics can imply the influence of the environmental factor change or the adaptation to the environment. Along the Heihe River assimilation shoots of plants carbon isotope ratio （^δ13C） basin, fron, the water source collection area to the water source vanishing area, leaves or were collected to determine the stable carbon isotope ratio. The results showed that stable of the plants on the mountain regions were between - 23‰-- - 29‰, with the mean value of -26.3‰; the ^δ13C of the plants in oases were between -26‰ -- -30‰, with the mean value of -27.2‰; while the ^δ13C of the plants in deserts were among - 23‰ -- - 28‰ and - 12‰ -- - 15‰, with the mean values of - 26.0‰ and -13.8‰, respectively. The ^δ13C was higher in the harsher environments. For the same speeies in different habitats, it showed that the ^δ13C was higher when the habitat was harsher. For Populus euphratica, tree speeies of desert riparian forest, the ^δ13C of its willow leaves were lower than that of its poplar leaves. Either in the mountain region or in the desert, along the inereasing altitude, stable earbon isotope diseriminations （Δ） of some plants redueed, while some were not notable. The Δ of Picea crassifolia signifieantly linearly deereased with the inereasing altitude. It can be concluded that the C4 plants occupy certain proportion in the desert vegetations. Water use efficiency （WUE） of plants in harsh habitat was higher than in suitable habitat. For P. euphratica, WUE of its linear leaves was the lowest, and that of the orbicular leaves was the highest among the different leaf morphologies; WUE rose as the willow leaves in seedling period grew to poplar leaves. P. crassifolia may be used as an important indicator plant to the environmental change of the mountain area of the upriver region of Heihe River. Among the trees in the Qilian Mountain area, the WUE of the evergreen P. crassifolia is the highest, the high WUE may be the reason that P. crassifolia is the dominant species in the Qilian Mountain area. Exorbitant 8~3C of the same species indicates the decline of the plant and the severe stress of the habitat. Plant adapting arid environment is along the direction helping to improve the water use efficiency.