摘要
家榆是典型的风播植物,在科尔沁沙地可以形成单一优势种林地。通过对林缘和孤立树不同方向从树基部向外的有序取样与林下和林窗的随机取样调查,分析了家榆林下和林窗不同生境的种子沉降和幼苗分布特征、林缘和孤立树种子散布方向的差异性与规律性。结果表明,家榆种子密度在林下生境阴坡和阳坡明显大于丘顶和丘底,在林窗生境丘顶明显大于丘底。家榆向周围不同方向种子散布的距离和累积数量均有较大差异,其中林缘和孤立树均以当地多逆风频率的西南方向最近,累积数量也最少;孤立树以多顺风频率的东北方向最远,累积数量也最多。林缘和孤立树共6个方向断面从树基部向外单位面积种子数量频度均适合于韦伯分布和对数-正态分布(X2(α)<0.500)密度函数,具有相同的种子散布格局。家榆幼苗密度在林下阴坡明显大于阳坡,林下和林窗均为丘顶明显大于丘底。林缘19 m内家榆幼苗呈连续分布。在科尔沁沙地,如果不加限制或人为扰动,家榆林不仅可以很好地进行自然更新,而且可以在适宜的沙地生境逐渐扩大其分布空间。
Ulums pumila,a typical anemochorous plant,is the single dominant species of many woodlands in the Keerqin Sandy Land,China.To understand habitat differences in the characteristics of seed deposition and seedling distribution in U.pumila,we randomly surveyed the numbers of seed and seedlings in the habitats of both understory and the wooland gaps.We also measured the abundance of seed and/or seedlings along transects of different directions starting from the woodland edges and the bases of isolated trees to illustrate differences and regulation of seed dispersal directions on the woodland edges and isolated trees.For the understory habitats,U.pumila seed densities on either shady or sunny slopes were significantly higher than both at the top of sand dunes or on the bottom of sand dunes.For the canopy gaps,seed densities on the bottom of sand dunes were greater than at the top of sand dunes.The number and distance of seed dispersal differed apparently among directions with the least amount of cumulative number of seed dispersal and the nearest dispersal distance were observed in the southwest direction（southwesterly winds are prevailing winds for the studied area）;whereas the greatest amout of cumulative number of seed dispersal and the farthest dispersal distance were observed in the northeast direction for both woodland edges and isolated U.pumila trees.In the six sampled directions,seed dispersal patterns of both woodland edges and istolated trees can be discribed by density functions of the Weibull distribution and the Log-normal distribution（X2（α）0.500）.For the understory habitats,the seedling densities on the shady slope were higher than on the sunny slope.We also observed that the seedling densities at the top of sand dunes were greater than on the bottom of sand dunes for both the understory habitats and gaps.The seedlings were continuously distributed within a range of 19 m starting from thewoodland edges.In the Keerqin Sandy Land,without restrictions and human disturbance,U.pumila woodlands c
出处
《生态学报》
CAS
CSCD
北大核心
2013年第2期374-381,共8页
Acta Ecologica Sinica
基金
国家自然科学基金项目(31170504
30770397)
高等学校博士学科点专项科研基金(20110043110005)
关键词
家榆
林下
林缘
孤立树
种子散布
幼苗更新
风播植物
Ulums pumila
understory
woodland edge
isolated tree
seed dispersal
seedling recruitment
anemochorous plant
