臺灣南部多納崩塌地演替初期不同耐陰性樹種組成及優勢度的變化

Variations in the Composition and Dominance of Tree Species with Different Shade Tolerances During the Early Phase of Succession at the Duona Landslide Site, Southern Taiwan

鍾安晴(An-Ching Chung) ； 郭耀綸(Yau-Lun Kuo) ； 周富三(Fu-Shan Chou) ； 林文智(Wen-Chih Lin) ； 陳永修(Yung-Hsiu Chen)

《台灣林業科學》 37卷1期 (2022/03) Pp. 41-60

https://doi.org/10.7075/TJFS.202203_37(1).0003

摘要

臺灣南部多納崩塌地於2009年莫拉克颱風時形成，經歷約11年自然演替，已有局部區域形成次生林。本研究之目的為瞭解該崩塌地次級演替8至11年期間，不同耐陰性樹種之成樹及幼齡木的組成及優勢度的變化，並藉林分耐陰性指標值（SSI）量化此林分的演替階段狀況。2017年於該崩塌地設立1 ha樣區，並將林分依垂直高度區分為4個層次。結果顯示該崩塌地樣區於演替11年時（2020年），共有68種成樹，密度為3677 stems ha^(-1)，陽性樹種重要值指數（IVI）76.8%最為優勢；中等耐陰及耐陰樹種之IVI值分別為17.6及5.5%。山黃麻為樣區內最優勢樹種，卻缺乏天然更新苗而使族群明顯衰退，未來可能被幼齡木充足的白匏子取代。研究期間發現陽性樹種越往樹冠上層越具優勢，但各垂直分層的IVI值逐年降低。中等耐陰及耐陰樹種越往地被層越具優勢，且在各垂直分層的IVI值逐年增加。2020年樹冠層、次冠層、灌木層及地被層的SSI值分別為1.1、16.0、28.3及44.2%，顯示越往森林下層，SSI值會越高。全林分之SSI值由2017年的10.6%提高為2020年的16.8%，各垂直分層的SSI值亦逐年增加，顯示該崩塌地之林分逐漸往演替中期推進，但與成熟林相比，仍只處於演替早期階段。本研究結果可作為臺灣南部崩塌地種植耐陰樹種以加速演替之依據。SSI可用來當做判斷森林次級演替階段的實用量化工具。

關鍵字

重要值指數 ； 崩塌地 ； 耐陰樹種 ； 林分耐陰性指標值 ； 演替階段

並列摘要

The Duona landslide site in southern Taiwan was formed during Typhoon Morakot in 2009. It has undergone natural succession for about 10 yr, and secondary forests have been formed in some areas. The purposes of this study were to investigate the dynamics of the composition and dominance of trees and juveniles with different shade-tolerance levels during the 8~11 yr of secondary succession at the Duona landslide site, and we used the stand shade-tolerance index (SSI) to quantify the successional status of the stands. In the beginning of 2017, 1-ha plot was set up at the Duona landslide site. According to the canopy profiles, the stands were divided into 4 vertical layers. Results showed that at the 11^(th) year (2020) of secondary succession, there were 68 tree species with a stand density of 3677 stems ha^(-1). Shade-intolerant species dominated the composition, and the importance value index (IVI) value was 76.8%. IVI values of mid-tolerant and shadetolerant species were 17.6 and 5.5%, respectively. The population abundance of Trema orientalis, the most dominant shade-intolerant species at this landslide site, significantly declined due to a lack of natural recruits and was replaced by Mallotus paniculatus var. paniculatus, which had abundant recruits. In the vertical layers of stands toward the canopy, shade-intolerant species were more dominant, and IVI values of shade-intolerant species in each vertical layer decreased over the years. On the other hand, in the vertical layers toward the understory, mid-tolerant and shadetolerant species were more dominant, and their IVI values in each vertical layer increased over the years. SSI values of the canopy, sub-canopy, shrub, and understory layers were 1.1, 16.0, 28.3, and 44.2% respectively, in 2020, indicating that SSI values of the vertical layers toward the understory increased. The SSI value of the entire stand increased from 10.6% in 2017 to 16.8% in 2020, and the SSI value of each vertical layer also increased over the years, indicating that the stand at the Duona landslide site had a tendency to gradually advance towards a mid-successional stage. However, compared to mature forests, it was still in the early phase of succession. Results of this study can be used as a basis for planting shade-tolerant species at landslide sites in southern Taiwan to accelerate succession. The SSI value can be used as a practical tool to quantify the succession phases of secondary forests.

並列關鍵字

importance value index ； landslide site ； shade-tolerant species ； stand shade-tolerance index ； successional status