羊草与大针茅根系构型对水分梯度响应的比较研究

羊草(Leymus chinensis)与大针茅(Stipa grandis)是内蒙古锡林郭勒典型草原的两大建群种,也是内蒙古草原的重要优良牧草。选取锡林郭勒草原以大针茅和羊草为优势种的围封草场为研究样地,通过原状土柱移栽,进行了两年的水分梯度控制实验(150、300、450、600 mm),分别模拟当地年降雨量由干旱年到是湿润年的变化情况,分析比较羊草种群和大针茅种群地上高度和根系构型对水分梯度的响应情况。结果表明:相比大针茅种群,羊草种群对水分梯度的响应更敏感,随着水分梯度的增加,羊草地上高度和根系直径显著增加,根系长度和根系深度显著减少;而大针茅的地上高度和根系特征各项指标均没有显出与水分梯度的相关性,显然大针茅比羊草更能适应干旱生境。在干旱条件(模拟年降雨量150 mm处理)下,大针茅种群地上高度达到峰值,生长状况良好;羊草种群则采用地上个体小型化,地下主根变细,分叉,向土壤深层扩展的生长策略。因此,在气候变化背景下,干旱化的气候将导致大针茅种群在群落中的优势地位逐渐增加,反之羊草种群则会随着气候湿润化而占据更大的优势。

A comparative study of the response of Leymus chinensis and Stipa grandis root characteristics to moisture gradients

Leymus chinensis and Stipa grandis are two of the main species of typical grasslands of Xilingol, Inner Mongolia, and are important forage grasses. An enclosed grassland, with L. chinensis and S. grandis as the dominant species, in Xilingol was selected as the research area, and moisture gradient control experiments (150, 300, 450, 600 mm) were carried out over two years by transplanting the original soil column, to simulate changes of local annual rainfall from drought to wet years, and the response of plant height and root architecture of L. chinensis and S. grandis populations were analyzed and compared under the different moisture gradients. The results showed that the response of L. chinensis populations was more sensitive to moisture gradients than that of S. grandis. With increasing moisture gradients, the plant height and root diameter of L. chinensis increased, whereas the root length and depth decreased significantly((P < 0.05). However, for S. grandis, the indicators of root architecture and plant height showed no correlation with the moisture gradient. Therefore, S. grandis could adapt to arid habitats more effectively than L. chinensis, and under drought conditions (simulated rainfall of 150 mm) the plant height of S. grandis populations reached a peak value and grew efficiently, whereas L. chinensis populations adopted a growth strategy of individual miniaturization, with thinner taproots and bifurcation to extend to the deep soil. Therefore, with climate change, a drying climate will result in increased S. grandis populations as the dominant species in the community, and L. chinensis populations will have a greater advantage in wetter climates.