Conversion of pastures into Tectona grandis plantations in western Panamá: effects on soil properties and the mechanisms underlying these changes.

Abstract

Abstract This study was conducted to understand how soil C and fine roots change in response to pasture conversion and teak plantation establishment in western Panama. The potential positive or negative effects of teak plantations on physical (bulk density) and chemical soil properties (pH, cation exchange capacity and base saturation), were evaluated. A chronosequence of teak stands spanning 10 years of development on former pastures was used. It was hypothesized that pastures and teak plantations differ in their soil properties and expected that effects, including increased soil C storage and soil fertility, are achieved to a greater extent in older teak plantations. Further, it was assumed that land-use history, site management, and species effects are the mechanisms driving these changes. Results showed that conversion of pastures into teak plantations in Panama altered soil properties and fine root biomass. Differences were strongest in the surface layer. In contrast to the expected results, soil C stocks under young teak plantations did not exceed the soil C stock under pastures. Still, soil C is an important C stock as more C was stored in the topsoil (0-30 cm) than in the aboveground teak biomass. Despite the pressure to plant fast-growing tree species such as teak for timber and C sequestration, the potential negative effects on ecosystem health have to be evaluated before establishing plantations. Based on the findings of the study, landowners and decision makers should consider the following aspects when establishing and managing teak plantations in order to maintain SOC concentrations at pre-plantation levels and enhance other ecosystem services: planting teak in mixture, minimizing soil disturbance during site preparation and planting, promoting the development of an understorey and limiting activities that restrict or undermine its development.