冬季火烧与收割对互花米草地上部分生长与繁殖的影响

Effects of winter burning and cutting on aboveground growth and reproduction of Spartina alterniflora: a field experiment at Chongming Dongtan, Shanghai

自1995年首次在崇明东滩发现互花米草(Spartinaalterniflora)以来,该外来种已在东滩扩张成为最具优势的植物之一。作为东滩常见的两种人为干扰,冬季火烧和收割可能会对互花米草的生长和繁殖有一定的促进作用,并可能进一步促进互花米草的入侵。因此,作者选择崇明东滩为实验地点,探讨冬季一次性火烧和收割以及相对高程对互花米草生长与繁殖的影响。结果表明:冬季火烧与收割能显著提高互花米草的植株密度和结穗率,显著降低其植株基部直径,即对其生长与繁殖有一定的促进作用,原因可能在于这两种干扰使其生境改变,光照条件得到改善;从Wilks’值的大小可看出,与相对高程相比,这两种干扰对互花米草生长繁殖的影响相对较小,而且这两种干扰对互花米草的影响差异不显著。上述结果表明,冬季火烧与收割将可能促进互花米草在东滩的入侵,有必要采取措施加以管理。

Winter burning and cutting facilitate growth and reproduction of certain plant species. These two human disturbances occurred in winter as a result of economic activities at Chongming Dongtan, where saltmarsh cordgrass （Spartina alterniflora）, an American native, has been naturalized. To test the hypothesis that these two disturbances can also facilitate the growth and reproduction of S. alterniflora, a simulated field experiment was carried out at Dongtan. At the same time, the effect of elevation was also considered in the experiment. We found that both winter burning and cutting, to a certain extent, promoted regeneration of S. alterniflora, as they significantly increased ramet density and heading ratio, and reduced culm diameter. This effect was probably caused by the changes of habitat and the improvement of light conditions due to the disturbances. The effects of the two disturbances on S. alterniflora were unexpectedly weaker than those of elevational variation based on Wilks＇ ~ from multivariate ANOVA. Little difference occurred in the effects between the two disturbances. We can conclude that disturbances should be managed appropriately because they might facilitate invasion of S. alterniflora.