Dynamics of dipterocarp seedlings in forest fragments in Sabah, Malaysia

Yeong, Kok Loong (2015) Dynamics of dipterocarp seedlings in forest fragments in Sabah, Malaysia. Masters thesis, Universiti Malaysia Sabah.

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Abstract

Primary rainforest once dominated the landscape of the Malaysian state of Sabah. Since the 1950s, extensive areas of these forests have been exploited in the pursuit of socio-economic gains. Some have been degraded through logging while others converted to non-forestry uses. For the latter, only remnants of forest patches existed in the agricultural landscape. Forest fragments are known to support high levels of biodiversity and potentially could promote landscape connectivity within the agricultural landscape. The aim of this study was to investigate the dynamics of dipterocarp seedlings in forest fragments in relation to their size and quality. A total of 12 transects were established in 10 sites; one transect each for eight forest fragment ranging from 3 to 3,290 ha, two in continuous logged forests (LF: 33,969 ha), and two in undisturbed primary forests (PF: 44,800 ha). At each transects, one to three S0xS0 m main plot(s) were established at 500 m intervals along a line transect. Natural dipterocarp seedlings were measured in twenty lm2 quadrats established in a stratified random manner within each main plot. Vegetation structure (tree density, tree species, canopy cover, ground cover, and litter layers) and environmental conditions (light, soil moisture and pH, soil nitrogen, phosphorus and carbon, and C:N ratio) were quantified within the main plot. Dipterocarp seedlings of three ecological contrasting species i.e. Parashorea malaanonan (PM, light demander), Dryobalanops /anceolata (DL, intermediate), Hopea nervosa (HN, shade tolerant) were planted randomly in 30x36m in the center of each main plot to examine survival, growth and herbivory rates. The purpose of using planted seedlings was to standardize their age and species composition across study sites. Leaf litter decomposition rates of the same species (PM, DL and HN) were quantified from 5 litterbags in a lOxSm plot within each main plot for 120 days (total of 15 bags per plot and 480 litter bags in all sites). The abundance of natural dipterocarp seedlings in PF ( x density= S.27 seedlings m-2±0. 73(SE); x richness=0.29 species m-2±0.03(SE)) was 6 to 25 times higher than in LF (xdensity=0.38 seedlings m-2±0.05; X richness= 0.16 species m-2±0.03) and FF ( i density= 0.04 seedlings m- 2±0.02; x richness= 0.03 species m-2±0.01), and increased with increasing forest fragment size. Forest quality characterized by abundance of dipterocarp trees, canopy structure, soil moisture content and low soil pH was highest in PF and increased with increasing forest fragment size. In relation to forest quality, dipterocarp seedlings abundance increased with increasing forest quality. Survival rates of the planted seedlings in FF (range: 30% to 70%) were ca. 10% lower than PF (range: 60% to 80%) and LF (range: 50% to 80%) and increased with increasing forest fragment size and forest quality. Seedlings growth and herbivory, however, was highest in FF due to higher light environment and decreased with increasing forest fragment size and quality. Leaf litter decomposition rates of three dipterocarp species were highest in PF (range: 47-58%); followed by LF (range: 32-47%) and FF (range: 28-40%), and increased with increasing forest fragment size and quality. The result from this study suggested that forest fragments larger than 12 ha had responded to artificial regeneration, thus suggested such forest fragments be retained and should not be replaced for other uses.

Item Type:	Thesis (Masters)
Keyword:	Dipterocarp seedlings, Forest fragments, Forest quality, Leaf litter decomposition
Subjects:	S Agriculture > SD Forestry > SD1-669.5 Forestry > SD391-410.9 Sylviculture
Department:	FACULTY > Faculty of Science and Natural Resources
Depositing User:	DG MASNIAH AHMAD -
Date Deposited:	29 Sep 2025 11:40
Last Modified:	29 Sep 2025 11:40
URI:	https://eprints.ums.edu.my/id/eprint/45262

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