亚高山暗针叶林林缘华西箭竹对岷江冷杉幼苗更新的影响

 大量研究表明在箭竹-冷云杉林下，竹类对冷杉的影响大于其它树种。在卧龙自然保护区岷江冷杉(Abies faxoniana)林下，华西箭竹(Fargesia nitida)为灌木层优势种。为了进一步了解箭竹对岷江冷杉幼苗更新的影响，该文采用样带法在四川省卧龙自然保护区亚高山岷江冷杉林林缘，针对华西箭竹和岷江冷杉幼苗展开调查研究。以竹丛覆盖区域为边界，分别向竹丛外2 m (带1)、1m (带2)，向竹丛内1 m (带3)、2 m (带4)、3 m (带5)做5条长30 m的 相邻样带，每条样带划分为30个连续的1 m×1 m小样方。对岷江冷杉幼苗数量动态、种群结构、生长与生物量的研究表明： 1)离竹丛越远，大年龄岷江冷杉幼苗数量越多；岷江冷杉幼苗转化率（下一径级苗木数量与前一径级苗木数量之比）随年龄增加而减小，随离竹丛距离增大而增大。2)苗木高度与径级结构相似，随深入竹丛，幼苗数量峰值的径级和高度级分布从较大径级(Ⅲ)向小径级(Ⅰ)变化。3)华西箭竹的存在抑制了岷江冷杉小径级幼苗(Ⅰ)的 高生长，基径与高度的回归也表明离竹丛越远，高生长相对更大；但一定密度华西箭竹(带4 )增大了大径级(Ⅲ)岷江冷杉幼苗冠幅的扩展。4)岷江冷杉幼苗总生物量随华西箭竹密度的增高而减小，华西箭竹的大量存在抑制岷江冷杉幼苗对地下生物量的分配。总的看来，一定密度华西箭竹环境下岷江冷杉幼苗的生长和更新较好，华西箭竹大量分布的区域，岷江冷杉幼苗的更新和生长受到抑制，可能会影响岷江冷杉种群的扩散以及群落的发展。

EFFECTS OF FARGESIA NITIDA ON REGENERATION OF ABIES FAXONIANA SEEDLINGS NEAR THE EDGE OF SUBALPINE DARK CONIFEROUS FOREST

Aims Many researches have shown that the interlaced roots of dwarf bamboo (Fargesia nitida) can influence the regeneration of trees and the growth o f seedlings and saplings through competition for light, water and nutrients. We explore the effect of dwarf bamboo on the regeneration of Abies faxoniana on the forest edge and estimate the effect of dwarf bamboo on the dispersal and community development. We asked: 1) how will quantitative characteristics and population structure change under different densities of F. nitida, and 2) how will the density of F. nitida influence the growth and biomass allocation of A. faxoniana seedlings? Methods We sampled five belt transects and analyzed 30 plots within each transect in Wolong Giant Panda Nature Reserve (30°51′41″ N,102°58′21″ E) during August and September 2005. The transects were selected based on different densities ofF. nitida(i.e., distance to the F. nitidacluster): 2 m outside the cluster (Zone 1), 1 m outside the cluster (Zone 2), 1 m inside the cluster (Zone 3), 2 m inside the cluster (Zone 4) and 3 m inside the cluster (Zone 5). We measured the height, basal diameter and crown of each A. faxonianaseedling. We used five BD classes : Ⅰ (0<BD<0.3 cm), Ⅱ (0.3 cm≤BD<0.6 cm), Ⅲ (0.6 cm≤BD<0.9 cm), Ⅳ (0.9 cm≤BD<1.2 cm), Ⅴ (BD≥1.2 cm), and five size classes: Ⅰ (0< H<15 cm), Ⅱ (15 cm≤H<30 cm), Ⅲ (30 cm≤H<45 cm), Ⅳ (45 cm≤H<6 0 cm), and Ⅴ (H≥60 cm). The seedlings were divided into two groups, large (H>0.2 m) and small (H≤0.2 m), to explore the accumulation and allocation of biomass by A. faxoniana seedlings. We obtained data on biomass from regression equations based on a sample of 60 A. faxoniana seedlings. Important findings Regeneration and growth of A. faxoniana seedling s were restrained in the F. nitida-dominated zones, and dispersal of the A. faxoniana population and development of anA. faxoniana-dominated community were affected. Closer toF. nitida clusters, the number of old seedlings and the efficiency of transformation (seedling number ratio of the next BD class to the precedingBD class) were reduced (the older the A. faxoniana seedlings, the smaller the efficiency of transformation); the peak of number of seedlings moved from larger ( Ⅲ) to the smallest size (Ⅰ); The total biomass and allocation of biomass aboveground of A. faxoniana seedlings decreased; and the presence of F. nitida restrained the height growth of small (Ⅰ) A. faxoniana seedlings (confirmed by regression of basal diameter and height). The expansion of crowns of bigger (Ⅲ) seedlings increased in moderate density (Zone 4) of F. nitida.