甘肃北砸山沙冬青种群的空间分布格局

在甘肃省的北砸(音)山区选择不同坡向,在不同坡位上采用样方和样线相结合的方法,调查沙冬青群落和种群的数量特征.结果表明:该区域的沙冬青种群稳定,山地阳坡中部的种群稳定增长,人为干扰较频繁的山坡下部为下降型种群.在山地阳坡和阴坡的上部,中龄个体比例最大,幼龄次之,老龄最少,在未来一段时期内该部位的种群将较稳定.阳坡沙冬青的密度和生长势均大于阴坡,在同一坡向上,山坡中部的种群密度最大,绝对密度约为5 000株/hm~2.在阴坡,沙冬青个体的总平均高度略大于阳坡,但阴坡植株基部的分枝数小于阳坡.不同龄级沙冬青植株的差异主要表现为冠幅.所观测年的沙冬青植株间的生长量差异较小,但同株的生长具有年际差异.不同坡向的沙冬青种群分布格局相似,山坡上部和中部的种群呈均匀分布;在坡体下部,种群则以母株为中心,形成集群分布.北砸山沙冬青种群分布位置特殊,有可能成为沙冬青种群未来存在和扩展的重要源地,应加强保护.

Spatial Distribution Patterns of the Population of Ammopiptanthus Mongolicus in the Beiza Mountain,China

Ammopiptanthus mongolicus is an endangered plant species in desert region of China.To study the dynamic change of Ammopiptanthus mongolicus population in special region will give a theoretic basis for conserving and utilizing the Ammopiptanthus mongolicus resources.At the Beiza Mountain(37°25′28″～37°35′45″N,103°54′48″～103°43′06″E)located in northwest of Hongshui Country of Jintai County of Gansu Province,China,the community and population of Ammopiptanthus mongolicus was observed in sample plots at different slope aspects and positions along a sample line.The results show that Ammopiptanthus mongolicus population is stable in the study area,increases steadily at middle part of tailo,but is decreased at its lower part due to the frequent human disturbance.At the top of the observed slope,the proportion of middle-aged Ammopiptanthus mongolicuz plants is the highest,and then that of the young plants,and that of the old-aged plants is the lowest,these reveal that the population will be stable in the future.The density of Ammopiptanthus mongolicus plants at tailo is higher than that at ubac,and it is the highest at the middle part of slope with an absolute density of 5 000 plants/hm~2.The average height of the plants at ubac is slightly higher than that at tailo,but the branches of plants at ubac are less than that at tailo.The difference between the different-aged plants is mainly in canopy extent.The difference of annual growth among plants is not so obvious,but there is an interannual difference in annual growth.The spatial distribution patterns of Ammopiptanthus mongolicus plants at different slope aspects are similar,that is the plants grow evenly at the top and middle part of slope but in a clumped way around the parent plants in lower part.The population of Ammopiptanthus mongol&us in the Beiza Mountain is destroyed only by human activities,however,the mountain will possibly become as an important field for conserving the population of Ammopiptanthus mongolicus in the future.