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While soils can act either as a source or as a sink for atmospheric carbon dioxide and nitrogen, depending
on land cover change and management, there is a great need to improve our understanding of the dynamics of soil structure and chemistry following land conversion in tropical regions. In this study, we investigated various soil structural and chemical variables (bulk density, pH, cation exchange capacity,
phosphorus, magnesium, potassium), soil carbon (C), soil nitrogen (N), 0
13C, and o
,sN in relation to conversion of rain forest to tea cultivation and subsequent changes due to agricultural abandonment and
reforestation with Caribbean pine. Although Caribbean pine has shown potential for reforestation
throughout Asia and Latin America, effects on soil properties in comparison with other land uses have
not been quantified. Our study compared: (1) the original rnixed-dipterocarp rain forest, (2) tea plantations, (3) Kekilla fernlands and (4) Caribbean pine plantations. Tea plantations show higher bulk density
(BD) as an evidence of compaction. Although soil C concentration in tea plantations were lower than
other land uses at 0-10 em, when bulk density was used with C as a composite measure, tea plantation
showed the highest value for both soil C and N stocks. Disregarding tea plantations, Caribbean pine plantations had the highest C but showed the lowest N stocks at both soil depths. Soil 013Cand o15Nvalues of
all land uses increase with increasing soil depth; but Caribbean pine plantations showed the greatest
increase in 013Cat both soil depths (e.g. -27.82 ± 0.38%0 at 0-10 em to -26.50 ± 0.37%0 at 10-20 em).
For both Kekilla fernlands and Caribbean pine plantations the relationship between 013Cand o15N was
strongly linear. By comparing the physical and chemical soil properties of these land uses with undisturbed rain forest, we established baseline data to determine influence of land conversion on soil properties. Based on soil pH, CECand other major nutrients (P, K, Mg), there are strong legacy effects of land
use potentially from both fertilization and fire. Our results also showed strong evidence that 013C and
o15Nwas both increased with depth under pine reforestation and fernlands, suggesting soils can recuperate with a consistent input of litter and slower decomposition processes. There is some evidence that
recruitment of natural regeneration beneath pine can help facilitate faster litter decomposition that
can revert soil structure and fertility to a status similar to that of the original forest.
