放牧对短花针茅草原地下部分生产力及氮素周转率的影响

Effect of Grazing to Underground Productivity and Nitrogen Turnover of Stipa breviflora Steppe.

放牧作为一种干扰因子，通过对群落地上部分和土壤的影响，导致地下部分的生产力和物质周转率的变化。在短花针茅草原上，中度强度轮牧下，群落地下部分生物量现存量增加，但年生产力降低，轮牧区比封育区低１２．８ｇ／ｍ２·Ｙ；同时，使地下部分氮贮量增大，氮的流通速率加快，轮牧区群落地下部分氮贮量比封育区高２．０５ｇ／ｍ２，氮素周转率轮牧区比封育区高０．０９，是封育区的２倍。

Grazing not only directly affects above ground part of grass communities and grassland soil, also indirectly influences underground productivity and material turnover. Under rotational grazing at medium grazing pressure, biomass of underground part in the Stipa breviflora steppe increased, however, annual productivity decreased. Biomuss of rotational grazing plots decreased by 12.8g/m 2. Y as compared with enclosure plots. Grazing enhanced nitrogen reserve in underground part and nitrogen turnover speed up. The amout of nitrogen reserve of underground part in rotational grazing plots incresed by 2.05g/m 2 over the enclosure plots. The nitrogen turnover rate in rotational grazing plots increased 0.09 over the enclosure plots and was twice of the enclosure plots.