怀柔山区荆条灌丛生物量的季节动态

THE SEASONAL DYNAMICS OF THE BIOMASS OF VITEX SHRUBLAND IN MOUNTAINOUS AREA OF HUAIROU COUNTY IN BEIJING

怀柔山区荆条灌丛生物量的80％以上来自其优势种荆条,其根系的生物量占荆条总生物量的55％以上。1986年荆条的第一性净生产量为6363.6kg·ha^(-1)·a^(-1),其中72.4％来自其根系,枝条只占12.4％。荆条根系的最高生长速度出现在5—7月,日均增长量为49.7kg·ha^(-1)·d^(-1),而枝条的最高生长速度在7—10月,日均增长量为8.69kg·ha^(-1)·d^(-1)。在荆条根系中,生物量增长最快和最大的是根球;在枝条中,基部的生物量增长最快。通过和北京地区相似立地条件下的荆条灌丛的生物量比较,阴坡的荆条生物量大于阳坡。与周围地区的人工林生物量的比较表明,样地现有的立地条件可以支持5倍于现有水平的生物量,此类灌丛可以造林。

Vitex shrubland is a typical secondary shrubland in mountainous area of Huairou County and also in the low-mountainous area of north China. Over 80% of the biomass of the shrub- land are contributed by its dominant species-Vitex negundo var. heterophylla. Due to frequent cutting, the aboveground biomass of Vitex shrubland was continually remo- ved, and that of its underground accounts for 55% of the total biomass. In 1986, the primary net production of Vitex was 6363.6 kg. ha^(-1). a^(-1), in which 72.4% came from its roots, only 12.4% was contributed by the stems. The highest growth rate of the roots of Vitex appeared from May to July and the average productivity in this period was 49.7 kg. ha^(-1) d^(-1). The highest growth rate of stems with the average of 8.69 kg. ha^(-1).d^(-1) was found from July to Oc- tober Obviously, the photosynthetic products had firstly transported to the roots and were ac- cumulated, and then transported to the stems. The allocation of photosynthetic products in the different parts of shrub organ showed that photosynthetic products were accumulated in ball root, then transport to other parts of roots. The top of stems was the first part where photosyn- thetic products were accumulated, then other parts of stems. A comparison with the biomass of other Vitex shrublands in the similar enviroment in Bei- jing area shows that biomass of the shrublands in north slope is larger than that in south slo- pe. Comparing the biomass of Vitex shrubland with the biomasses of artificial forests in the same area with similar habitat we found that trees in the site occupied by the shrubs which we studied, can offer 5 times biomass than that of the shrubs.