干旱气候对白羊草群落地下部生长影响的初步观察

对大旱之后白羊草（Bothrichloa ischaemum）群落地下部的生长状况与1991平水年该群落地下部的生长关况进行比较，以反映干旱气候对白羊草群落地下部生长的影响，结果表明，极旱年下生物量的峰值达到1249g.m^-2，比平水年峰值586g.m^-2高1倍多，在极旱年或旱季根系主要集中分布的层次下移，而在平水年或雨季则上移，极旱年群落地下生物量的周转值为52．64％，显著高于平水年时的周转值18．36％，极旱年群落的地下生物量与地上生物量在生长中互为消长关系，而平水年两者在生长季同时增另，基本呈直线关系，极旱年群落的地下生物量与地上生物量比为11．19，显著高于水平年时的比值2．03，极旱年群落的地下净初级生产量为390．7g.m^-2.年^-1，比平水年时的生产量107．6g.m^-2.年^-1高2．63倍。

Effect of arid climate on underground growth of Bothrichloa ischaemum community

The underground growth of Bothrichloa ischaemum community in extremely arid year were compared with that of the community in 1991 with normal precipitation, and hence, could reflect the effect of drought on underground growth of Bothrichloa ischaemum community. The results indicated that the peak value of underground biomass reached 1249 g.m-2 in extremely arid year, higher than that in normal year (586 g.m-2). Most roots distributed downwards in extremely arid year or arid seasons, and distributed upwards in normal year or rain seasons. The turnover rate of underground biomass in extremely arid year was 52.64%, significantly higher than that in normal year (18.36%). In extremely arid year, underground part and aboveground part competed with each other at the middle and later stage of growth, however, in normal year, they increased simultaneously presenting beeline correlativity on the whole. The biomass ratio of underground to aboveground in extremely arid year was 11.19 and significantly higher than that in normal year (2.03). Net underground primary production in extremely arid year was 390.7 g.m-2.yr.-1 and 2.63 times higher than that in normal year.