内蒙古鄂尔多斯高原典型草原百里香-本氏针茅草地地上生物量对气候响应动态回归分析

Relation between climate variables and the aboveground biomass of Thymus mongolicus-Stipa bungeana community in steppe of Ordos Plateau, Inner Mongolia

在对鄂尔多斯高原典型草原百里香 -本氏针茅 (Thymusmongolicus-Stipa bungeana)群落地上生物量进行 7a逐月定位观测基础上 ,利用多元回归方法 ,逐月建立生物量与气候因子之间的定量关系模型。研究表明 :(1 )不同气候因子在植物不同生长阶段产生不同影响 ,光照时数只在 5月份 ,平均气温只在 6月份对植物产生显著影响 ,在其他月份都不是重要影响因子 ,而降水量则在植物生长过程中各个阶段都是重要因子 ;(2 )同一气候因子在植物生长不同阶段上的影响作用也可不同 ,降水量在生长季各月都是重要影响因子 ,但重要性存在差异 ,重要程度依次是 5 >6>7月份 ;(3 )植物进入枯凋期后 ,9和 1 0月份的生物量只与 8月份生物量峰值有关 ,各气候因子不对其产生影响 ;(4 )在生长季中各月地上生物量都与上月生物量密切相关 ,说明生长的连续性对地上生物量的积累是重要的。应用逐月回归模型对降水量充裕、平均和偏少 3种水分条件 ,各月地上生物量的波动范围进行了估计。采用的逐月回归建模方法是对传统的累积因子建模方法的改进 ,为了比较这两种方法的差异 ,用 8月份生物量作为植物生物量峰值 ,对生长季节 5～ 8份月气候因子的累积量进行回归 ,建立了生物量对累积气候因子的回归模型 ,并将结果与逐月回归结果进行对比 。

Ranging from 106°27′ to 111°28′ east longitude, and from 37°38′ to 40°52′ northern latitude, the Ordos Plateau in Inner Mongolia, northern China, is located at a transitional ecotone from the sub-humid area in the southeast to the arid and semi-arid area in the northwest.Clmiatic conditions in this area are typicaly semi-arid.The sushine and warmthh condition is quite suitable for plant growth.Annual sunshine hour ranges from 2700～3200 h, about 62%～74% for all time. Amount of light radiation is one of the most abundant areas in China, ranging from 5520 to 5937 MJm -2 a -1 . Annual temperature varies between 5.0～8.7℃, with mean -13.1～-8.4℃ in January and 20.9～24.1℃ in July. The light warmth potential production of this area is quite high, however, hindered by severe hydrological limitation. Annual precipitation at Ordos Plateau ranges from 401.6 mm in the southeast to 162.4 mm in the northwest, with more than 60% concentrated in the two months during summer. Measured annual pan evaporation varies from 2047 to 3085 mm, about 8～10 times the precipitation. The problem of insufficient water supply is further amplified by sandy soils, which have poor water retention capacity, and the hilly topography of the area. Climate conditions are sharply changed from year to year and this is one of the most prominent characteristics in Ordos Plateau, especially for the precipitation. The variable ratio of the precipitation rages from 20% to 50% from year to year. This kind of sharp variation of climate conditions always lead the severe shaking of the forage and stocking raising production. A good understanding for the relation of climatic variables and plant aboveground biomass is essential for animal grazing management and ecological research in Ordos Plateau. In the present paper, the relation between the climatic variables and the Thymus mongolicus Stipa bungeana community in steppe of Ordos plateau was studied by monthly models presented in this research. From 1985 to 1991, the aboveground biomass of Thymus mongolicus Stipa bungeana community was investigated monthly from the fenced field in stepppe of Ordos Plateau. Using data of aboveground biomass, and climatic varibales of the same time, monthly regression models were presented. Following conclusions on the relation between the climatic variables and the aboveground biomass were drawn: (1) different climate variable impacts plant biomass at different periods. Hour of sunshine and averaged temperature only make influence on the aboveground biomass remarkably in May and June, respectively, and does not work at any other period. The precipitation is sensitive variable to biomass at any period during the whole growing process. (2) The same climate variable makes different influence on biomass at different month. The climatic variable of precipitation is an important factor to plant biomass at the whole process, however, the importance is quite different for different months. Partial correlation indexex were calculated to classify the priority order of precipitation and the result is May>June>July. (3) At the dormancy month September and October, the aboveground biomass is not impacted cy any climatic variables, but by the biggest biomass in August. (4) The aboveground biomass at any month during the growing process is closely connected with that of previous month. This shows that the continuity of growth is important for plant biomass. The variation range of aboveground biomass under three different water condition was predicted by applying the monthly regress models presented in this paper. The mean of building the monthly models for the relation between climate and biomass of Thymus mongolicus Stipa bungeana community is developed from the traditional way. To compare the difference of the monthly models in the present paper with the traditionally accumulative models, we also made the traditional regression model using the biomass in August as the dependent variable for the independent variables of accumulated climatic variables from May to Augus