Research Paper

The vegetation status of regrowth forests in abandoned farmlands in the subtropical forest of Eastern Bhutan Himalaya

Kelzang Gayley, Kitichate Sridith

Published on: 29 June 2020

DOI: 10.6165/tai.2020.65.336

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2020 vol.65 no.3 pp.336-347

Abstract

Many regrowth forests have occurred in abandoned farmlands all over the world. The regrowth forests of 20‒60 years old on abandoned farmlands and old-growth forests in a subtropical forest of Eastern Bhutan Himalaya are studied and their floristic and structural compositions are compared. A total of 64 and 43 plots were sampled in regrowth forests and old-growth forests respectively based on stratified random sampling method. Species richness of woody plants and predominant ground covers in regrowth forests is lower than old-growth forests though few of them show higher species richness in woody stems. Species composition of trees (≥5cm DBH) in younger regrowth forests (<30 yrs.) and older regrowth forests (>30 yrs.) show 10% and 42‒51% of Bray Curtis similarity to their adjacent old-growth forests respectively. A total of 53% of trees and 63% of large saplings/shrubs (≤4cm DBH and ≥1m height) are shared species between two forest types. The top dominant species such as Betula alnoides Buch.-Ham. ex D.Don, Lithocarpus fenestratus (Roxb.) Rehder, Schima wallichi Choisy, and Itoa oreintalis Hemsl. in regrowth forests make distinct patches different from old-growth forests. Species composition of trees in regrowth forests retains the variation along the elevation gradient like old-growth forests. Land-use history of the regrowth forests has also affected the regeneration of forest. Basal area and density of trees in regrowth forests are close or even higher than old-growth forests. The regrowth forests reveal robust recovery of old-growth species and growth of unique species.

Keyword: Abandoned farmlands, Bhutan Himalaya, old-growth forests, regrowth forests, subtropical forest

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