Tropical forest wood production: A cross-continental comparison

1. Tropical forest above-ground wood production (AGWP) varies substantially along environmental gradi-ents. Some evidence suggests that AGWP may vary between regions and speci fically that Asian forests haveparticularly high AGWP. However, comparisons across biogeog raphic regions using standard ized methodsare lacking, limiting our assessment of pan-tropical variation in AGWP and potential causes.

2. We sampled AGWP in NW Amazon (17 long-term forest plots) and N Borneo (11 plots), bothwith abundant year-r ound precipitation. Within each region, forests growing on a broad range ofedaphic conditions were sampled using standardiz ed soil and forest measurement techniques.

3. Plot-level AGWP was 49% greater in Borneo than in Amazonia (9.73  0.56 vs. 6.53  0.34 Mg drymass ha1a1, respective ly; regi onal me an  1 SE). AGWP was positively associated with soil fertility(PCA axes, sum of bases and total P). After controlling for the edaphic environment, AGWP remained signifi-cantly higher in Bornean plots. Differences in AGWP were largely attributable to differing height –diameterallometry in the two regions and the abundance of large trees in Borneo. This may be explained, in part, bythe greater solar radiation in Borneo compared with NW Amazonia.

4. Trees belonging to the dominant SE Asian family, Dipterocarpacea e, gained woody biomass faster thanotherwise equivalent, neighbouring non-dipterocarps, implying that the exceptional production of Borneanforests may be driven by floristic elements. This dominant SE Asian family may partition biomass differentlyor be more efficient at harvesting resources and in converting them to woody biomass.

5. Synthesis. N Bornean forests have much greater AGWP rates than those in NW Amazon when soil condi-tions and rainfall are controlled for. Greater resource availability and the highly productive dipterocarps may, incombination, explain why Asian forests produce wood half as fast again as comparable forests in the Amazon.Our results also suggest that taxonomic groups differ in their fundamental ability to capture carbon and that dif-ferent tropical regions may therefore have different carbon uptake capacities due to biogeographic history.