ABSTRACT

Fast-growing Eucalyptus plantations evidence high rates of evapotranspiration. The increasing afforestation rates may affect local soil water balances. In this study, we measured transpiration rates in E. grandis at individual and stand level and we modeled it based on climate variables and soil water storage through a climate time series 1981–2010. We also estimated the aboveground net primary productivity and the water use efficiency based on regional empirical models. Transpiration rates were measured by the constant heat measurement method in 6 to 12 trees in three 100 m² plots in an 11-year-old plantation. The model fitted suggested that stand transpiration of E. grandis plantation near harvest age is limited by soil water storage and that the water table does not constitute an additional water source. The transpiration of E. grandis plantation was about 800 mm year⁻¹ which approximates 90% and 40% of the annual precipitation in dry and wet years, respectively. Our estimations compared well to other regional studies and suggest that stand transpiration, aboveground net primary productivity, and water use efficiency can be made based on simple climatic variables. A deeper discussion is needed to evaluate the impact of E. grandis transpiration rates at the regional scale.

摘要

快速生长的桉树种植园证明了高蒸散率。不断增加的造林率可能会影响当地的土壤水平衡。在这项研究中，我们测量了E. grandis在个体和林分水平上的蒸腾速率，并根据 1981-2010 年气候时间序列的气候变量和土壤蓄水量对其进行了建模。我们还基于区域经验模型估算了地上净初级生产力和水资源利用效率。蒸腾速率是通过恒温测量法在一个 11 年历史的人工林中三个 100 m ²地块中的6 到 12 棵树中测量的。拟合的模型表明E. grandis 的站立蒸腾作用接近收获期的种植园受到土壤储水量的限制，并且地下水位不构成额外的水源。E. grandis人工林的蒸腾量约为 800 毫米^-1年，分别接近旱年和雨年年降水量的 90% 和 40%。我们的估计与其他区域研究相比很好，并表明可以基于简单的气候变量来确定林分蒸腾作用、地上净初级生产力和水资源利用效率。需要更深入的讨论来评估E. grandis蒸腾速率在区域范围内的影响。