Acacia mangium is one of the most important hardwood plantation species in the tropics. The question of how to grow Acacia productively and sustainably remains a major issue for the forestry sector in many tropical countries. We analyzed the productivity of A. mangium plantations across five contrasting ecological zones in Vietnam. These covered gradients in rainfall from 1750 mm to 3060 mm and a mean annual temperature range of 22 - 27 degrees C. Plantation productivity across these zones varied from an MAI of 6 m(3) ha(-1) to 31 m(3) ha y(-1). A comprehensive suite of statistical methods was utilized for variable and model selection to minimize confounding and multicollinearity issues among predictors and identify determinants of plantation productivity using 27 biophysical variables. These variables encompass plantation age, climate parameters, as well as site and soil properties. Results showed that, apart from plantation age, the factors influencing plantation productivity and explaining a majority of variation in mean annual timber increment are soil organic carbon content and the number of foggy days. Soil carbon is probably an index of overall soil fertility and its significance reflects the fact that the plantations have often been established on relatively degraded sites. The lower productivity at sites having a higher frequency of foggy days (up to 57 days per year in some regions) may arise from lower solar radiation and temperature during fog. The results of this study can inform site selection and plantation management tools aimed at maximizing Acacia mangium productivity in Vietnam and other countries with similar ecological conditions. Planting A. mangium in high-intensity fog areas is not recommended. Further studies on the ecophysiological mechanisms of how fog influences the growth of tropical A. mangium plantations are also needed.

Climate change is causing glaciers to retreat across much of the Himalaya, leading to a rapid shift of the vegetation cover to higher altitudes. However, the rate of vegetation shift with respect to glacier retreat, climate change, and topographic parameters is not empirically quantified. Using remote sensing measurements, we estimate (a) the rate of glacier-ice mass loss, (b) the upward vegetation line shift rate, (c) regional greening trends, and (d) a relationship between the factors influencing the greenness of the landscape and vegetation change in the Himalaya. We find that the glacier mass loss rate is 10.9 +/- 1.2 Gt/yr and the mean vegetation line shifts upward in altitude by 7-28 +/- 1.5 m/yr. Considering the land use/land cover change pattern, the grassland area is found to be expanding the most, particularly in the de-glaciated regions. The vegetation change is found to be controlled by soil moisture and slope of the area.