摘要
对分布于毛乌素沙地南缘的禾草杂类草草地的根系生物量动态及光能转化率进行了研究。由于人为过度利用，草地植被出现退化。４～１１月期间，根系生物量的动态变化呈双峰形，最大值出现在５月中旬，为７０７．５３ｇ·ｍ－２（为干物质，以下同），第二峰值出现在７月中旬，为６７７．２９ｇ·ｍ－２。根系净第一性生产力为２３２．６５ｇ·ｍ－２·ａ－１，以能量计算，则为４７３．９９ｋＪ·ｍ－２·ａ－１。根系生物量的垂直分异明显，呈Ｔ形分布，７０％以上分布在０～２０ｃｍ土层，４０～５０ｃｍ深处的根量只占８％。根系生物量的生长率在营养生长期要高于生殖生长期，生长率的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。根系对太阳总辐射的转化率为０．００８％；对光合有效辐射的转化率为０．０１６％；对生长期生理辐射转化率为０．０２８％。根系对太阳总辐射的正向表观转化率在最高期可达０．２４％。
The biomass dynamics and conversion efficiency to the total solar radiation of rhizotaxy of grass+forbs steppe in southern fringe of Mu Us sandland were stu died in the paper. The variation of rhizotaxy biomass, in the measuring period, expressed a two peak curve. The maximum value, occurred on May 15, was 707 53 g\5m -2 (Dry material) and the second maximum value, appeared on July 15, w as 677 29 g\5 m -2 . The maximum value of biomass of living roots, came out in the middle ten days of July, was 99 56 g\5m -2 ; while that of dead roots, appeared in the middle of May, was 610 69 g\5m -2 . The biomass of dead roots in the measuring period averagely made up 88% of the rhizotaxy biomass, which constitut ed the majority of total rhizotaxy biomass. The NPP (Net Primary Productivity) of rhizotaxy of grass+forbs steppe in southern fringe of Mu Us sandland was 232 65 g\5m -2 \5a -1 , but from the energy point of view, the NPP of that was 473 99 kJ\5m -2 \5a -1 . The discrepancy of vertical distribut ion of rhizotaxy biomass in different soil layers was obvious and showed a T' style distribution in the soil. More than 70% of the rhizotaxy, including 63 6% of the living roots and 71 4% of the dead roots distributed in the 0￣20 cm soi l layer, while only 8% of the total roots existed in the 40￣50 cm soil layer. Th is phenomenon showed the general characteristics of rhizotaxy distribution of gr amineous plants and the therophyte. The relationship between the rizotaxy biomas s and the depth of soil layer could be simulated by the power equation which we re Y L=10 4532x -0.7537 ,Y D=110 480x -0.8678 ,Y T=120 712x - 0.8540 , representing the relationships btween the biomass of living roots, d ead roots, the total roots and the depth of soil layer respectively. The grow th rate of rhizotaxy biomass in vegetative period of the community was higher th an that in reproductive period. And the variation regularity of RGR (Rate of Growth) of the rhizotaxy biomass was related to the partitioning of photosynthe tic material. Between the aboveground and underground parts of the community in different growth period of the plants, the maximum RGR of living roots of th e community appeared before the green turning period so as to storage nutrients for the community turning green. The conversion efficiency to total solar radi ation for rhizotaxy biomass was 0.008%. The efficiency to physiological radi ation for it was 0.016% and that of growing period was 0.028%. The maxim um efficien cy of rhizotaxy to total radiation could reached 0.24% and occurred in the end of growing peri od of the community.
出处
《中国沙漠》
CSCD
北大核心
1999年第2期151-155,共5页
Journal of Desert Research
关键词
禾草杂类草
根系生物量
毛乌素沙地
能量效率
Grass+forbs steppe\ Rhizotaxy biomass\ Conversion efficiency to solar radiation Mu Us sandland
