毛乌素沙地南缘禾草杂类草草地地上部生物量动态及光能转化率研究

Study on dynamics of aboveground biomass and conversion efficiency to the total solar radiation of grass+forbs steppe in southern fringe of Mu Us sandland

对分布于毛乌素沙地南缘的禾草杂类草草地地上部生物量动态、净第一性生产力和光能转化率进行了研究。由于过度利用，该草地群落出现退化，一、二年生植物及对家畜有害植物的盖度占草地群落总盖度的５０％ ～６０％ 。４～１１ 月期间，其地上部生物量（ＤＭ）的变化呈单峰曲线，最大值出现在９ 月１３ 日，为９４．００ ｇ／ｍ ２。草地群落地上部净第一性生产力（ＤＭ）为８４．９４ ｇ／（ｍ ２·年），以能量计算，则为１ ２２５．６３ ｋＪ／（ｍ ２·年）。地上部生物量的生长率在营养生长期要高于生殖生长期，其变化规律与草层的营养生长和生殖生长对光合产物的分配有关。草层地上部对太阳总辐射的转化率为０．０２１％ ；生理辐射转化率为０．０４２％ ；生长期（日均温≥０℃～≤０℃）的生理辐射转化率为０．０７２％ 。

The dynamics of above ground biomass, the net primary productivity(NPP) and the conversion efficiency to the total solar radiation of grass+forbs steppe in southern fringe of Mu Us sandland were studied in the paper. Owing to overgrazing, the community of steppe appeared degenerated. The number of the annual and biennial plants increased gradually, the cover of which constituted over 50%～60% of that of the community. In the study period, the variation of aboveground biomass expressed a monopeak curve and the maximum value, occurred at Sept.13, was 94.00 g/(m 2·a) . The aboveground NPP of community was 84.94 g/(m 2·a) , from the energy point of view, was 1 225.63 kJ/(m 2·a) . The RGR of aboveground biomass in vegetative period was higher than that in reproductive period. The variation regularity of RGR of biomass was related to the partitioning of photosynthetic materiel between the aboveground and underground parts of the community in different growth period of plants. The conversion efficiency of total solar radiation for aboveground biomass was 0.021% . The efficiency of physiological radiation for it was 0.042% and that of during ≥0 ℃～≤0 ℃ growing period was 0.072% . The maximum efficiency of aboveground of community for total radiation only reached 0.08%,occurred in the second month of growing period.