摘要
为探明高原鼢鼠扰动下亚高山草甸群落的构建机制,在祁连山东段天祝藏族自治县(天祝县)亚高山草甸的禁牧样地中以不同年限(一年、二年、三年、多年、平地对照)的高原鼢鼠鼠丘植被为研究对象,分析高原鼢鼠鼠丘植被演替过程中全部物种、常见种和稀有种的多度变化,选用对数级数模型、几何级数模型、断棍模型、随机分配模型对物种多度数据进行拟合.结果表明:1)在鼠丘植被演替过程中,全部物种、常见种、稀有种的丰富度均为先增加后减少,三年鼠丘物种丰富度分别比一年、两年、多年鼠丘和平地对照高82.4%、16.3%、12.0%和47.6%,多年鼠丘与三年鼠丘相比物种丰富度下降的81.8%来源于大量稀有种的丧失.2)年际间鼠丘群落相似性以三年鼠丘与多年鼠丘间群落相似系数最大(0.622),异质性最小,为中等相似.3)通过模型拟合发现全部物种和常见种物种多度分布均符合生态位模型,而稀有种同时符合生态位模型和中性模型.以上结果表明在天祝县亚高山草甸禁牧管理模式下,第三年为高原鼢鼠鼠丘植物群落结构演变的转折点,常见种在群落构建过程中为确定性过程,而稀有种的丧失受确定性过程和随机性过程的双重影响.
Abstract
To investigate the mechanisms of subalpine meadow community construction disturbed by plateau zokor(Eospalax baileyi),a study was conducted on the vegetation of plateau zokor mounds in the subalpine meadow of Tianzhu County,located in the eastern Qilian Mountains.The study spanned various time periods,including one-year,two-year,three-year,multi-year zokor mounds,and a flat control.The analysis focused on changes in species abundance including all species,common species,and rare species.Species abundance data were fitted using the logarithmic series model,geometric series model,broken stick model,and random assignment model.1)The results showed a temporal pattern of species richness that increased and then decreased during vegetation succession,encompassing all species,common spe-cies,and rare species.Specifically,species richness on three-year zokor mounds was 82.4%,16.3%,12.0%,and 47.6%higher than that on one-year,two-year,and multi-year zokor mounds,respectively.The decline in species richness(81.8%)on multi-year zokor mounds compared to three-year zokor mounds was primarily due to the loss of a substantial number of rare species.2)The similarity coefficient between three-year and multi-year zokor mounds reached its highest value of 0.622,indicating moderate heterogeneity.3)Model fitting revealed that the species abundance distributions of all species and common species conformed to the niche model,while rare species followed both niche and the neutral models.The findings suggested that the third year was a crucial juncture in the evolutionary trajectory of plateau zokor mound community structure under grazing control measures in subalpine meadows of Tianzhu County.Dur-ing this period,the assembly of common species exhibited deterministic processes,while the decline of rare species was influenced by both deterministic and stochastic processes.
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