黄土高原现代C4和C3植物生物量及其对环境的响应

文章从表土总有机碳同位素和现代植被间的关系入手, 研究C4/C3植物与气候要素的关系, 以期能更好 的理解影响C4、C3植物生物量的主要因素。研究区域位于黄土高原塬面, 我们计算了共67个采样点的C4植物的生物量, 估算出草本植物中C4植物的比例。结果表明, 黄土高原塬面上最主要的C4植物是白羊草(Bothriochloa ischaemum), C3植物主要由草类植物和灌木组成, 如长芒草(Stipa bungeana)、胡枝子(Lespedeza davurica)和禾叶嵩草(Kobresia graminifolia)等, 它们主要分布在研究区域的阴坡和山谷。表土的总有机碳同位素组成是反映C3和C4相对生物量贡献的可靠指标。在黄土高原地区, 夏季降水量的增加会引起C4植物比例上升, 同时C4植物生物量的变化也反映了降水的变化。本文的研究有助于理解亚洲季风气候下黄土高原地区C4/C3植物的变化机制。

ABUNDANCE OF C4/C3 PLANTS IN THE CHINESE LOESS PLATEAU AND THEIR RESPONSE TO PLANT GROWING ENVIRONMENT

Stable carbon isotope of soil organic matters is used as indicator of changing vegetation and environment. This paper analyzed the relationship between C4/C3 biomass and their growing environment in the Chinese Loess Plateau Table, the mean geographic unit on the Chinese Loess Plateau, in order that we could get a better understanding on factors influencing C4/C3 biomass. We calculated C4 biomass of 67 sampling sites, mainly in Shaanxi, Shanxi and Gansu provinces along the rainfall gradient from 700mm to 300mm. We estimated the ratio of C4 plants in each investigated site by choosing 1~2 quadrats covering 4~8m2. Our investigations show that the Bothriochloa ischaemum, which is favorable in warm season and more rainfall, takes up the most abundance of C4 plant on the loess table. Other C4 plant, Salsola collina and Corispermum hyssopifolium, etc, are less abundant. Natural C3 plants are composed of grasses and shrubs such as Stipa bungeana(Gramineae), Lespedeza davurica(Leguminosae)and Kobresia graminifolia(Labiatae), etc., and they are widely distributed in the shady slope and valley in the research area. The mean stable carbon isotope values of C3 and C4 plants are -27.04 ‰ and -12.99 ‰, respectively. Our results confirmed that stable carbon isotope of surface soil organic matters is reliable in reconstructing palaeovegetation. Our results also show that growing season precipitation(from May to October)results in C4 biomass increase and C4 biomass is responding to changes of seasonal precipitation of the Chinese Loess Plateau today. This paper helps us understand how C4/C3 biomass changes under the control of Asian monsoon climate.