Patterns of Fine Root Mass and Distribution along a Disturbance Gradient in a Tropical Montane Forest, Central Sulawesi (Indonesia) |
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Authors: | Christoph Leuschner Maria Wiens Marieke Harteveld Dietrich Hertel S Tjitrosemito |
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Institution: | 1. Plant Ecology, Albrecht-von-Haller-Institute for Plant Sciences, University of G?ttingen, D-37073, G?ttingen, Germany 2. Faculty of Science and Mathematics, Institute Pertanian Bogor, 16144, Bogor, Indonesia
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Abstract: | Large parts of the remaining tropical moist forests of South-east Asia are encroached at their margins by selective logging,
rattan harvesting and the establishment of small agroforest plantations under the rainforest canopy. These slight to heavy
disturbances affect aboveground forest structure by reducing wood biomass and canopy cover; however, they may also have a
profound impact on the belowground compartment. In a lower montane moist forest of Central Sulawesi, we studied the profile
totals of fine root biomass (FRBtot, roots <2 mm until 50 cm of soil depth) and of fine root necromass (FRNtot), the vertical distribution of fine root mass, and the fine root live/dead ratio by root coring in 12 forest stands that
represented a gradient in forest use (or disturbance) intensity (forest use type A: undisturbed natural forest, B and C: slightly
or moderately disturbed forests with selective timber extraction, D: heavily disturbed cacao agroforest systems under a remaining
rainforest cover; each forest types being replicated three times). FRBtot decreased significantly from forest A to the disturbed B, C and D forests, and reached less than 60% of the FRBtot value of A in the agroforest systems D. A similar decrease with increasing disturbance intensity was found for FRNtot. Forest disturbance intensity had no significant influence on the vertical distribution of fine root biomass in the profiles.
According to correlation and principal components analyses, fractional canopy cover was the most important factor influencing
FRBtot and FRNtot, whereas diameter at breast height, stand basal area, stem density, soil pH and base saturation had only a minor or no influence
on root mass. A reduction in canopy cover from 90% (forest type A) to 75% (types C and D) was associated with a reduction
in FRBtot by about 45% which indicates that timber extraction leads not only to canopy gaps but to corresponding ‘root gaps’ in the
soil as well. We conclude that forest encroachment that is widespread in large parts of South-east Asia’s remaining rainforests
significantly reduces tree fine root biomass and associated carbon sequestration, even if it is conducted at moderate intensities
only. |
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Keywords: | agroforestry canopy gaps disturbance intensity fine root biomass selective logging vertical root distribution |
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