藏东南高山松天然林土壤种子库及天然更新特征

高山松是藏东南针叶林的主要建群种之一,高山松林是雅鲁藏布江中下游、尼洋河、帕隆藏布等流域的重要水源涵养林.采用样地样方调查、野外定位监测、室内试验分析等方法对藏东南高山松天然林的高山松种子雨、土壤种子库、高山松种子萌发及天然更新特征进行了研究.结果表明,高山松种子雨强度平均为249.30±78.42粒/m2,其中饱满种子为168.09±56.36粒/m2、虫蛀种子为41.11±20.25粒/m2、空种子为40.10±21.04粒/m2,种子雨强度随时问表现出先增加后减少的单峰型趋势.整个落种过程和不同落种时间的种子空问分布格局均表现为聚集分布,在一定范围内随着与母树距离的增加,种子雨扩散强度减弱,表现为近似正态分布高山松土壤种子库高山松种子平均密度为231粒/m2,其中62.77％的种子分布在枯落物层中、37.23％的种子分布在土壤层中,种子雨到土壤种子库过程中有近8％的种子损失.野外实地播种观测发现,高山种子累积萌发率与萌发天数的关系符合Logistics力程v=91.404/(1+e6.619-0.4491).高山松幼苗和幼树的高度结构、基径结构和年龄结构均呈反”J”型,表明高山松天然更新良好,保护好现有的环境状况,种群将呈稳定增长型.研究结果为高山松资源的有效保护和可持续利用提供了科学依据,同时进一步丰富了西藏高原同家生态安全屏障评价内容.

Characteristics of Soil Seed Bank and Natural Regenerations in Pinus densata Natural Forest of Southeast Tibet

Pinusdensata is one of the main constructive species for coniferous forests in southeast Tibet.P.densata forests are important water conservation forests in the drainage basins of the middle and lower reaches of Yalu Tsangpo River,Nyang River and Parlung Zangbo River.In this study,with P.densata forest distributed in southeast Tibet as research object,the seed rain,soil seed bank,seed germination and natural regeneration of P.densata were monitored and analyzed by field investigation,located monitoring and indoor experimental analysis.The results showed that the average intensity of the seed rain of P.densata was 249.30±78.42 seeds/m2,in which the intensity of full seeds was 168.09±56.36 seeds/m2,the intensity of seeds damaged by worms was 41.11±20.25 seeds/m2,and the intensity of empty seeds was 40.10±21.04 seeds/m2.The intensity of the seed rain exhibited a single-peak trend of increasing at first and decreasing then over time.The spatial distribution patterns in the whole seed falling process and at different seed falling time all exhibited clumping distribution,and within in certain range,with the distance from the seed tree increasing,the diffusion intensity of the seed rain was weakened,exhibiting approximately normal distribution.In average density of P.densata seeds in the soil seed bank of P.densata was 231 seeds/m2,in which 62.77％ of seeds were distributed in the litter layer,and 37.23％ of seeds were distributed in the soil layer,and about 8％ of seeds were lost during the process from seed rain to soil seed bank.Field sowing observation showed that the accumulated germination rate curve of P.densata fitted with Logistics equation y=91.404/(1+e6.619-0.4491）.The height structure,basal diameter structure and age structure of seedlings and young trees of P.densata were all of reverse "J" type,indicating good natural regeneration of P.densata.This study would provide a science basis for protection and resource management of P.densata,and further enrich the evaluation content of national ecological safety curtain of the Tibet plateau.