林分密度对云顶山柏木人工林林下物种多样性和土壤理化性质的影响

以成都云顶山柏木(Cupressus funebris)人工林为对象,采用典型样地法研究不同林分密度(1100、950、800、650、500株/hm~2)对林下物种多样性和土壤理化性质及林下物种多样性与土壤理化性质相关性的影响。结果表明:共发现维管植物168种,隶属75科140属。随林分密度的降低,灌木层多样性指数呈先增后减的单峰变化,在密度650株/hm~2出现峰值,草本层多样性指数呈先增后减再增再减的双峰变化,在密度950株/hm~2和650株/hm~2出现峰值。同时发现光照为影响林下植物多样性的重要因素。林分密度对土壤全氮、全钾、速效钾、有机质影响显著,有机质、全氮、全钾、速效钾随林分密度降低呈先增后减的变化趋势。钾、氮、有机质与林下植被物种多样性关系最密切。结论:林分密度650株/hm~2为云顶山柏木人工林最适密度,该密度能较好的提高林下物种多样性和土壤肥力。

Effects of stand density on understory species diversity and soil physicochemical properties of a Cupressus funebris plantation in Yunding Mountain

We investigated the understory species diversity, soil physicochemical properties, and their relationships with a Cupressus funebris plantation using typical plot methods under five different stand densities (1,100, 950, 800, 650, 500 tree/hm²) in the Yunding Mountain, Chengdu, to find a density that could maintain a stable community structure. The results identified a total of 168 vascular plant species belonging to 75 families and 140 genera. With a decrease of stand density, the shrub layer diversity indexes initially increased and then decreased. The highest species diversity appeared at a density of 650 tree/hm². The herb layer diversity indexes showed a double-peak distribution:initially increased, then decreased, and increased again, then finally decreased. The turning point appeared at densities of both 950 and 650 tree/hm². Meanwhile, we found that the sunlight played an important role affecting the species richness index variation. Our results also suggested that different stand densities had significant effects on the contents of total nitrogen, total potassium, available potassium, and organic matter in the soil. The responses of organic matter, total nitrogen, total potassium, and available potassium were similar to the shrub layer diversity index variation. Moreover, there was a significant correlation among potassium, nitrogen, organic matter, and understory species diversity. The results indicated that a stand density of 650 tree/hm² would optimally enhance the understory species diversity and soil fertility.