黄河上游高寒草甸矮嵩草生理特征对流域不同生境的响应

Physiological responses of Kobresia humilis to different habitats in the alpine meadow of the Yellow River

以黄河上游青海河南县南旗村黄河二级支流小流域高寒草甸中的优势种矮嵩草为研究对象,研究其生理特征对小流域生境(山顶、坡地、滩地、1级阶地、2级阶地地形因子下的相应生境)变化的响应,同时探讨其与土壤温湿度理化性质因子间的关系。结果表明:1)生境特征,流域不同生境土壤理化性质中的湿度、全氮、全磷、碱解氮、速效磷、有机质含量在1级阶地、2级阶地、滩地、山顶中较高,在坡地的含量较低,滩地中的pH最低,全钾、速效钾含量最高。由于流域生境的差异,总生物量在1级阶地、2级阶地、滩地中较高,山顶、坡地较低。矮嵩草植物除在1级阶地的河漫滩湿地无分布外,其他生境均有分布,且在滩地为优势种,其盖度、重要值、生物量及生物量比重均最高,坡地次之。2)生理特征,山顶、坡地、1级阶地矮嵩草体内丙二醛含量、可溶性蛋白质含量、可溶性糖含量、脯氨酸含量、类胡萝卜素含量、过氧化氢酶活性增加,叶绿素a、b含量减小,而在滩地中以上指标呈现相反趋势。3)生境和生理特性相关分析,矮嵩草生理特性变化与立地生境的土壤湿度、pH、全钾含量相关性较高。综合分析,矮嵩草植物生态幅较广,喜适于pH较低、水热养分条件适宜的滩地高寒草甸植被生境;在胁迫生境下,通过增加体内抗逆物质活性和竞争来适应立地生境。

Kobresia humilis is one of the dominant species in the alpine meadow.We analyzed the physiological and ecological characteristics of K.humilis growing in several different habitats in a small catch-pit with secondary tributaries draining into the Yellow River,near Nanqi village,Henan County,Qinghai Province.The habitats were hill top,hill slope,beach land,terrace 1,and terrace 2.We explored the interaction between K.humilis and soil factors in these habitats.Soil analyses showed that soil moisture,total nitrogen,total P2 O5,available phosphorus,and organic matter were higher in the terrace 1,terrace 2,beach land,and hill top habitats,and lower on the hill slope.Beach land showed the lowest soil pH and total K2 O,and highest available potassium content.Therefore,soil fertility was higher in the terrace 1,terrace 2,and beach land habitats.Because of the different catch-pits in the various habitats,total biomass was higher in the terrace 1,terrace 2,and beach land habitats,and lower in the hill top and hill slope habitats.K.humilis was distributed in every habitat except on the floodplain wetland in terrace 1,and it was the dominant species in the beach land habitat.Its coverage,importance value,biomass,and proportion of total biomass were higher in the beach land habitat than in the hill slope habitat.Catalase activity and the contents of malondialdehyde,soluble protein,soluble sugars,proline,and carotenoids were higher in K.humilis from the hill top,hill slope,and terrace 2 habitats than in K.humilis from other habitats,but the chlorophyll a and b contents were lower.These indexes showed the opposite trends in the beach land habitat.Correlation analyses between soil factors and the physiological characteristics of K.humilis showed that some physiological characteristics were strongly correlated with soil moisture,pH,and total K2 O.According to these comprehensive analyses of K.humilis across a range of ecological habitats,we conclude that K.humilis is suited to growth on soil with low pH,and moderate moisture and nutrition status.It can adapt to its habitat by increasing its resistance and competitive abilities under the conditions of low soil moisture and low nutrient content.