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Doctoral thesis, 2011

Aspects of regeneration in tropical secondary forests of Northeast Borneo affected by selective logging, El Niño-induced drought and fire

Romell, Eva

Abstract

A large proportion of the world´s tropical rainforests are today secondary forests, a term encompassing forests in various degrees of degeneration. For the main traits of old-growth forests´ structures, species composition and ecosystem functions to recover, regeneration of non-pioneer tree species is essential. In the studies this thesis is based upon I addressed various aspects of regeneration, both natural and artificial, mainly in secondary forests of northeast Borneo subjected to selective logging in the early 1980´s followed by prolonged El Niño-induced drought and forest fires in 1982-83. The field studies underlying this thesis included one survey of natural regeneration in transects and two experiments with artificial regeneration; gap creation with under-planting nursery raised tree seedlings and direct seeding. Forest floor light conditions in created gaps were measured as photosynthetic photon flux density and proportion canopy openness. Methods applied to analyze data were ordinations (NMS and MRPP), ANCOVA and general linear model ANOVA. Based upon these results some general conclusions and implications for forest management are addressed for secondary forests with this type of disturbance history: Forest patches with remnant potential seed trees and a more intact canopy structure had more diversified tree species recruits and are therefore less demanding of artificial regeneration. In artificial gap creation a sub-canopy reduction would be the preferable method compared to girdling or felling pioneer canopy trees since the positive effect of sub-canopy treatments is longer lasting. Under-planted dipterocarp seedlings increase height growth in high-light environments while their survival appeared unaffected by light conditions, therefore a medium shade reduction would be preferable as this leads to only moderate release of competing vegetation. Direct seeding must be evaluated further before large scale application, especially the timing and species choice merits special attention.

Keywords

regeneration; tropical rain forests; secondary forests; selective felling; logging; borneo

Published in

Acta Universitatis Agriculturae Sueciae
2011, number: 2011:57
ISBN: 978-91-576-7601-6
Publisher: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences

Authors' information

Romell, Eva
Swedish University of Agricultural Sciences, Department of Forest Ecology and Management

UKÄ Subject classification

Ecology
Forest Science

URI (permanent link to this page)

https://res.slu.se/id/publ/33842