季节性积雪对高山草甸生态因子的影响

Effects of Seasonal Snow Cover on Ecological Factors in a Natural Alpine Meadow in the Eastern Tibetan Plateau

在青藏高原东部的一个天然高山草甸上,设置早融、中融及晚融3个融雪部位,每个部位随机设置30个1m×1m的小样方,采用野外测量及实验室测量相结合的方法,研究了不同融雪部位之间生态因子的差异。结果表明:从早融部位到晚融部位,融雪时间逐渐推迟,和早融部位相比,晚融部位的融雪时间延迟了20多天。土壤水份含量在各部位间有明显的不同,从早融部位到晚融部位,水分含量增加了35.9%。土壤营养成分中,总氮、总磷、总钾以及可溶性的氮在各部位间无明显的差异;可溶性的磷盐在3个梯度上的浓度都极低;可溶性的钾盐、钙盐和有机质含量从早融到晚融都呈显著减少的趋势。土壤pH在各部位间无显著的差异。从早融部位到晚融部位,地表温度的日较差有明显的变化,在3月、4月、5月份,日温差的平均值从样地早融部位到晚融部位分别降低5°C、14°C和8.2°C。显然,早融部位的温度日较差较大,冻融交替明显,容易导致草地植物的冻害。

In a natural alpine meadow in the eastern Tibetan Plateau,three portions（early-melting,medium-melting and late-melting） were established along the snowmelt gradient.At each portion,30 quadrats of 1m×1m were randomly set up.Field and laboratory methods were employed to study the differences among three poritons.The results showed that at late-melting portion,snow melting time was delayed for more than 20 days compared with that at early-melting portion.Soil water content was significantly different anong portions,increasing by 35.9% from early-to late-melting portion.As to soil nutritive matter,total N,total P,total K and soluble N were not different among portions;concentration of soluble P was quite low at all portions;soluble K,soluble Ca and organic matter were significantly decreased from early-to late-melting portion.In addition,soil pH was almost constant at all portions.From early-to late-melting portion,diurmal range of soil surface temperature differed greatly,decreasing by 5°C,14°C and 8.2°C in March,April and May,respectly.Obviously,wide diurmal range of temperature at early-melting portion leads to intense alternation of freezing and thawing,which easily results in plants’ freezing injury.Differences of ecological factors at different portions may be one of the reasons why vegetations distribute heterogeneously in eastern Tibetan Plateau.