Soil nutrients affect spatial patterns of aboveground biomass and emergent tree density in southwestern Borneo |
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Authors: | Gary D Paoli Lisa M Curran J W F Slik |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of Michigan, 830 N. University Ave, Ann Arbor, MI 48109, USA;(2) Indonesian Resource Institute, Bogor, West Java, Indonesia;(3) Yale School of Forestry and Environmental Studies, 205 Prospect Street, New Haven, CT 06511, USA;(4) Nationaal Herbarium Nederland, Leiden University Branch, PO Box 9514, Einsteinweg 2, 2300 RA Leiden, The Netherlands |
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Abstract: | Studies on the relationship between soil fertility and aboveground biomass in lowland tropical forests have yielded conflicting
results, reporting positive, negative and no effect of soil nutrients on aboveground biomass. Here, we quantify the impact
of soil variation on the stand structure of mature Bornean forest throughout a lowland watershed (8–196 m a.s.l.) with uniform
climate and heterogeneous soils. Categorical and bivariate methods were used to quantify the effects of (1) parent material
differing in nutrient content (alluvium > sedimentary > granite) and (2) 27 soil parameters on tree density, size distribution,
basal area and aboveground biomass. Trees ≥10 cm (diameter at breast height, dbh) were enumerated in 30 (0.16 ha) plots (sample
area = 4.8 ha). Six soil samples (0–20 cm) per plot were analyzed for physiochemical properties. Aboveground biomass was estimated
using allometric equations. Across all plots, stem density averaged 521 ± 13 stems ha−1, basal area 39.6 ± 1.4 m2 ha−1 and aboveground biomass 518 ± 28 Mg ha−1 (mean ± SE). Adjusted forest-wide aboveground biomass to account for apparent overestimation of large tree density (based
on 69 0.3-ha transects; sample area = 20.7 ha) was 430 ± 25 Mg ha−1. Stand structure did not vary significantly among substrates, but it did show a clear trend toward larger stature on nutrient-rich
alluvium, with a higher density and larger maximum size of emergent trees. Across all plots, surface soil phosphorus (P),
potassium, magnesium and percentage sand content were significantly related to stem density and/or aboveground biomass (R
Pearson = 0.368–0.416). In multiple linear regression, extractable P and percentage sand combined explained 31% of the aboveground
biomass variance. Regression analyses on size classes showed that the abundance of emergent trees >120 cm dbh was positively
related to soil P and exchangeable bases, whereas trees 60–90 cm dbh were negatively related to these factors. Soil fertility
thus had a significant effect on both total aboveground biomass and its distribution among size classes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Carbon sequestration Dipterocarpaceae Land use change Nutrient limitation Phosphorus |
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