Meteorological Institute, Albert-Ludwigs-University of Freiburg, Werthmannstr. 10, 79085, Freiburg, Germany.
Int J Biometeorol. 2010 Jan;54(1):23-36. doi: 10.1007/s00484-009-0248-x. Epub 2009 Jul 21.
We investigated the water balances of two beech stands (Fagus sylvatica L.) on opposite slopes (NE, SW) of a narrow valley near Tuttlingen in the southern Swabian Jura, a low mountain range in Southwest Germany. Our analysis combines results from continuous measurements of forest meteorological variables significant to the forest water balance, stand transpiration (ST) estimates from sap flow measurements, and model simulations of microclimate and water fluxes. Two different forest hydrological models (DNDC and BROOK90) were tested for their suitability to represent the particular sites. The investigation covers the years 2001-2007. Central aims were (1) to evaluate meteorological simulations of variables below the forest canopy, (2) to evaluate ST, (3) to quantify annual water fluxes for both beech stands using the evaluated hydrological models, and (4) to analyse the model simulations with regard to assumptions inherent in the respective model. Overall, both models were very well able to reproduce the observed dynamics of the soil water content in the uppermost 30 cm. However, the degree of fit depended on the year and season. The comparison of experimentally determined ST within the beech stand on the NE-slope during the growing season of 2007 with simulated transpiration did not yield a reliable statistical relationship. The simulation of water fluxes for the beech stand on the NE- and SW-slopes showed similar results for vegetation-related fluxes with both models, but different with respect to runoff and percolation flows. Overall, the higher evaporation demand on the warmer SW-slope did not lead to a significantly increased drought stress for the vegetation but was reflected mainly in decreased water loss from the system. This finding is discussed with regard to potential climate change and its impact on beech growth.
我们研究了位于德国西南部低山侏罗山南部图特林根附近一条狭窄山谷两侧（东北、西南）的两个山毛榉林的水分平衡。我们的分析结合了对森林水分平衡有重要意义的连续森林气象变量测量结果、树木液流测量得出的林分蒸腾（ST）估算值以及微气候和水通量的模型模拟结果。我们测试了两种不同的森林水文模型（DNDC 和 BROOK90），以确定它们在代表特定地点方面的适用性。研究涵盖了 2001-2007 年。主要目的是：（1）评估林冠以下变量的气象模拟，（2）评估 ST，（3）使用评估后的水文模型量化两个山毛榉林分的年水量通量，（4）分析模型模拟结果，以评估各自模型中固有的假设。总体而言，两种模型都非常好地再现了最上层 30 厘米土壤含水量的观测动态。然而，拟合程度取决于年份和季节。2007 年生长季，在东北坡山毛榉林中，实验测定的 ST 与模拟蒸腾量的比较并没有产生可靠的统计关系。东北坡和西南坡山毛榉林分的水量通量模拟结果表明，两种模型的植被相关通量相似，但径流量和渗透流量不同。总体而言，温暖的西南坡蒸发需求较高，并未导致植被明显干旱胁迫，而是主要反映在系统水分损失减少。这一发现与潜在气候变化及其对山毛榉生长的影响有关。
