在放牧干扰下冷蒿种群脯氨酸含量的变化

对放牧干扰下土壤含水量、冷蒿体内含水量、脯氨酸含量变化进行的研究结果表明随着放牧强度的增加土壤含水量降低,冷蒿叶片、根中含水量呈下降趋势。在生长初期,随着放牧强度的增加冷蒿叶片内脯氨酸含量迅速积累;生长盛期脯氨酸含量虽随牧压有所增加,但增加的幅度较小;生长末期脯氨酸含量较高,而且随着牧压的增加略有下降。地下部分,脯氨酸含量在牧压梯度间变化较小。相关分析表明,在生长初期和盛期,冷蒿叶片、根的含水量与土壤含水量呈正相关,生长末期不相关。冷蒿脯氨酸含量与植物的含水量呈负相关,在生长初期和末期呈显著负相关,而生长盛期相关不显著;与此不同,在生长初期冷蒿体内脯氨酸含量与土壤含水量呈负相关,在生长末期二者负相关性不显著,这说明随着放牧干扰强度的增加土壤含水量降低,导致冷蒿体内水分胁迫增加,致使脯氨酸开始逐渐积累。而生长末期的降温和群落中植物种间竞争减少,使脯氨酸的积累速度也相应放慢。在放牧干扰下,脯氨酸大量积累,对冷蒿的生存和生长起到了重要的作用,是冷蒿种群耐啃食、耐践踏、逐渐取代禾本科植物而成为退化草原的优势植物的生理基础之一。

Change of Contents of Proline of Atemisia Frigida Population under the Disturbance of Grazing

The soil moisture and contents of proline and moisture of Atemisia frigida populations under different grazing intensities were studied. The results showed: With grazing intensity increased, soil moisture, leaves and roots moisture decreased. With grazing intensity increased, contents of proline of leaves rapidly accumulated, especially in early growth period; that increased a little in middle growth period and decreased in late growth period. Contents of proline in roots had few changes. Correlations analysis showed: there was significant positive correlation between plant moisture and soil moisture in early and middle growth period, there was not positive correlation between them in late growth period. There was significant negative correlation between contents of proline and plant moisture in early and late growth period, but there was not correlation in middle growth period. There was significant negative correlation between contents of proline and soil moisture in early growth period, but there was not correlation between them in late growth period. All these indicated that with the grazing intensities increased, soil moisture decreased ,which made plant moisture decreased, then contents of proline accumulated gradually. But lower temperature and decrease of interspecific competition made proline accumulate slowly in late growth period. It was very important to Atemisia frigida population to survive and grow that proline accumulated under grazing disturbance. This was one of important reason that Atemisia frigida population endured grazing and trampling strongly, and with the grazing intensities increase, Atemisia frigida population replaced gramineus plants, and become the dominant species.