2种嵩草属植物形态特征对生境干旱化的响应

该研究于西藏自治区东南部的东达山高山草甸沿生境干旱化梯度设置10个样地,采用线性回归方法分析优势种高山嵩草(Kobresia pygmaea)和矮生嵩草(K.humilis)叶片数量与其它构件数值(分株数量、茎基直径、根系数量和根系长度)之间的关系,并采用线性回归斜率测度分株功效、叶片萌生能力、根系分生功效和根系伸长功效,以探讨嵩草的分株能力、茎基生长和根系生长对生境干旱化过程的响应机制。结果显示:(1)2种嵩草植物的叶片数量与4种构件数值均为显著线性正相关关系。(2)随着生境干旱化程度增加,高山嵩草分株数量增加,矮生嵩草分株受干旱抑制程度高,分株数量呈下降趋势;2种嵩草分株功效下降,即单株叶片数量因干旱化程度增加而减少。(3)2种嵩草的茎基直径、叶片萌生能力随着生境干旱化程度增加而下降;高山嵩草叶片萌生能力的变化与生境干旱化梯度一致,具有连续性;矮生嵩草叶片萌生能力对生境干旱化的适应性弱,干旱到一定程度发生骤降。(4)随着生境干旱化,高山嵩草的根系数量和长度均增加,矮生嵩草根系长度增加,但数量却无规律变化;2种嵩草的根系分生功效和根系伸长功效均下降。研究表明:嵩草属植物分布的最适宜生境为表面稍有积水的沼生生境。为适应生境干旱化,高山嵩草降低叶片萌生率以减少蒸腾作用,增加分株数量以增强对空间的占有能力,并增加根系数量和长度来提高对土壤水分的吸收能力,因此对干旱有较强适应性且分布范围广;矮生嵩草只通过降低叶片萌生率,增加根系长度响应干旱化生境,其分布范围较窄。

Response of Morphological Character to Aridification of Habitat for Two Plants of Genus Kobresia

10 sample plots were set along a gradient of aridity in the alpine meadow, the Dongda Mountain in Southeastern Tibet. Species Kobresia pygmaea and K. humilis were selected as the study materials, and liner regression analysis was used to analyze the correlation between the amount of leaf and numerical value of other components of plants, such as amount of ramet, diameter of base stem, amount of root and length of root. The slopes of liner regressions were used to measure the effect of tillering, germination ability of leaf, effect of root branching and root elongating. The results showed: (1) leaf amount and numerical value of other components of the two Kobresia plants were significantly positive liner correlated (P< 0.01). (2) With aggravation of aridification, ramet amount of K. pygmaea increased, while that of K. humilis decreased. For two plants, the tillering effect decreased, which indicated that leaf amount of per ramet reduced due to the aridification. (3) Diameter of base stem and germination ability of two plants decreased with aggravation of aridification. Germination ability of K. pygmaea was in correspondence with drought gradient; there was no regular variation of germination ability of K. humilis along the gradient of aridification, but it decreased to an extreme value when habitats presented to be very dry. (4) For plant K. pygmaea, its amount and length of root both increased; for plant K. humilis, its root length increased, but root amount showed irregular variation; the effect of root branching and root elongating both decreased along the gradient of aridification. In summary, this study showed that the most suitable habitat for Kobresia plants was marsh land with shallow water. K. pygmaea can better adapt to aridification and distributes at a wide range by lowering germination rate of leaf for decreasing transpiration, increasing ramet amount for increasing the spatial occupation ability, and increasing root amount and length to enhance the ability to absorb soil water, while K. humilis responses to aridification only by lowering germination rate of leaf and increasing root length, which shows a weak adaptation to arid habitat and distributes at a narrower range.