新疆伊犁河谷镰叶锦鸡儿(Caragana aurantiaca)幼株种群年龄结构

Age structure of Caragana aurantiaca young populations in the Yili valley,Xinjiang

镰叶锦鸡儿(Caragana auruntiaca)为豆科矮小灌木,我国仅分布于伊犁河谷特克斯河河岸带,目前对镰叶锦鸡儿幼株种群年龄结构的研究尚无报道。本研究在特克斯河沿岸镰叶锦鸡儿的集中分布地段,选择围封禁牧的解放桥和放牧干扰的76团作为样地,每个样地选择河岸、河漫滩和阶地3种生境,每种生境设置3个20 m×20 m的样方,采用芽鳞痕辨别年龄的方法,对比研究了两种管理方式下镰叶锦鸡儿幼株种群的年龄结构,并分析了土壤因子对幼株年龄结构的影响。结果表明,围封样地无1~3 a实生幼株,幼株株数集中在5~10 a,3种生境种群及总体均属于衰退型年龄结构。而在放牧样地,阶地和河岸实生幼株种群为衰退型年龄结构,河漫滩和总体为增长型年龄结构。低龄级实生幼株(1~5 a)与土壤速效氮含量密切相关,高龄级实生幼株(6~11 a)与土壤速效磷含量密切相关。灌丛分株种群总体以1~5 a最多,占69.9%,为增长型年龄结构。在未来镰叶锦鸡儿灌丛生态系统管理中,可进行适度的放牧利用,增加土壤速效氮含量,降低灌丛间杂草盖度,有利于镰叶锦鸡儿种群的种子萌发和实生幼株生长,促进种群的补充更新。镰叶锦鸡儿通过营养繁殖方式弥补了实生幼株种群衰退所引起的负面影响,维持种群数量的优势与建群地位。

Caragana auruntiaca,a dwarf legume shrub,only distributes in the Tekes riparian zone of Yili Valley in China. There is limited information on the age structure of C. auruntiaca young populations. In this study,two plots,an enclosure plot( Jiefang Bridge) and a grazed plot( 76 Tuan),were set up in the concentrated distribution area of C. auruntiaca along the Tekes River. Three types of habitats,i.e. riverbank,floodplain and terrace,were selected in each plot,and three quadrats( 20 m×20 m) were set up within each habitat. The age of young populations were identified by bud scale scar. The age structure of C. auruntiaca young population under two management regimes was examined,and the effects of soil factors on the age structure of juvenile plants was analyzed. In the enclosure plot,there were no 1-3 year-old seedlings,and the number of juvenile plants was concentrated in 5-10 year-old,suggesting the population belonged to the declining age structure in all the three habitats. In grazed plot,young populations in terraces and riparian habitat had declining age structure,while those in floodplain and in general had increasing age structure. Seedlings( 1-5 year-old) were closely related to soil available nitrogen con-tent,while trees( 6-11 year-old) were closely related to soil available phosphorus content. The shrub ramet population was the most in 1-5 year-old,accounting for 69.9%,which belonged to increasing age structure. In the future management of C. auruntiaca shrub ecosystem,it is feasible to use moderate grazing to increase soil available nitrogen content,reduce forb coverage between shrubs,facilitate seed germination and seedling growth of C. auruntiaca,and promote population regeneration. C. auruntiaca can compensate for the negative effects from the decline of seedling population through vegetative reproduction,and thus could maintain the dominance of population number and its status as a constructive species.