6种人工针叶幼林下地表苔藓植物层片的物种多样性与结构特征

GROUND BRYOPHYTE COMPOSITION AND SYNUSIA STRUCTURE UNDER SIX TYPES OF YOUNG CONIFEROUS FOREST PLANTATIONS IN THE UPPER MINJIANG RIVER

为了评估人工林苔藓植物发育状况 ,同时为人工林生态功能评价提供依据 ,采用样地取样方法 ,调查分析了岷江上游大沟流域 6种人工幼龄针叶林 (川西云杉 (Piceabalfouriana)林、日本落叶松 (Larixkaempferi)林、油松 (Pi nustabulaeformis)林、华山松 (Pinusarmandii)林、油松_华山松混交林和川西云杉_华山松混交林 )林下地表苔藓植物层片物种组成、多样性以及结构特征及其异同。 6种人工林下共发现了 19种苔藓 ,各林下组成数量在 7～ 13种。除云杉林外 ,纯林下苔藓种数均小于或者等于混交林下 ;6种人工林下地表苔藓植物平均盖度、平均密度、平均厚度分别在 0 .4 1%± 1.4 9%～ 17.79%± 1.6 7%、(2 7.99± 36 7.95 )～ (380 7.11± 4 12 .90 )株·m-2 和 (1.80± 1.5 1)～ (19.89±1.6 9)mm之间。无论是多样性指数 ,还是结构参数 ,均以川西云杉林最高 ,而华山松林最低。总体说来 ,岷江上游人工针叶幼林下地表苔藓组成物种较少、物种多样性指数 (物种丰富度指数、Shannon_Wiener指数 )低、Simpson指数高、结构参数 (密度、盖度、厚度 )较小 ,说明林下地表苔藓植物组成单一、结构相当简单 ,发育不良。综合分析表明 ,具有相对较低林冠郁闭度与林木密度的云杉林是 6类人工林中恢复状况相对最好的类型 。

Bryophytes on the ground under six types of artificial forests, Picea balfouriana forest (P), Pinus tabulaeformis forest (Y), Pinus armandii forest (H), Larix kaempferi forest (L), Picea balfouriana-Pinus tabulaeformis forest (P-Y) and Pinus tabulaeformis-Pinus armandii forest (Y-H), were investigated in the upper Minjiang River in order to understand the bryophyte composition and synusia structure of these different forest types. In the 19 bryophyte species identified, only 13, 10, 7, 11, 9 and 10 species were present in the P, L, H, Y-H, Y and P-H forests, respectively. Four mosses, Brachythecium glaciale, Thuidium cymbifolium, Entodon concinnus and Eurhynchium savatieri, were common in all six plantations. Another three mosses, Entodon macropodus, Mnium spinosum and Polytrichum formosum, occurred only in the Picea balfouriana forest. The highest frequency of bryophyte occurrence was under the P forest (90%) and the lowest frequency under the H forest ( 17.65% ). Thuidium cymbifolium had the highest frequency (60%) of all species under the P forest, and the second was Brachythecium glaciale (50%). The predominant species, based on the importance value, was Thuidium cymbifolium under the P forest and Brachythecium glaciale, occurred under the other five plantations, which indicated that Brachythecium glaciale was the most common moss species in the study area. In all forests, the P forest had the highest bryophyte diversity (Shannon-Wiener index, species richness index) and the H forest had the lowest diversity. The lowest Simpson index was calculated for the H forest and the highest one for the P forest. The highest similarity index (Sorensen similarity) occurred between the H and Y forests (0.89) and the lowest similarity index between the P and H forests (0.40). The greatest percent coverage (17.79%±1.67%), shoot density ((3 807.11±412.90) shoots·m -2 ) and thickness ((19.89±1.69) mm) of bryophytes occurred under the P forest, and the lowest values (0.41% ±1.49%, (27.99±367.95) shoots·m -2 , and (1.80±1.51) mm, respectively) under the H forest. For the Y, L, Y-H and P-H forests, ground bryophyte cover was 5.20%±1.58%, 2.44%±1.58%. 2.73%±1.61%, and 2.71%±1.61%, respectively, shoot density was (623.08±391.71), (566.13±391.71), (253.38±398.41), and (188.69±398.41) shoots·m -2 , respectively, and average bryophyte thickness was (9.60±1.61), (14.93±1.61), (9.59±1.63), and (6.69±1.63) mm, respectively. No statistical differences (p<0.05) were found in any of these measures among the Y, L, Y-H and P-H forests. The low bryophyte diversity and limited structure development (density, coverage, thickness) found under all six plantations indicate that, in general, these are poorly developed bryophyte communities. Our results show that the best bryophyte community have developed under the spruce forest with a relatively open canopy and low tree density. Our results suggest that tree thinning or canopy pruning would be an effective measure for improving bryophyte development under dense forests.