Effects of aggregated classifications of forest composition on estimates of evapotranspiration in a northern Wisconsin forest
Effects of aggregated classifications of forest composition on estimates of evapotranspiration in a northern Wisconsin forest
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DOI：
10.1046/j.1365-2486.2002.00554.x
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发表时间：
2002-12
影响因子：
11.6
通讯作者：
D. Mackay;D. Ahl;B. Ewers;S. Gower;S. N. Burrows;S. Samanta;K. Davis
中科院分区：
文献类型：
--
作者：
D. Mackay;D. Ahl;B. Ewers;S. Gower;S. N. Burrows;S. Samanta;K. Davis
由于森林经营改变了森林的结构和组成，对准确预测地表与大气之间的水碳交换提出了挑战。我们研究了北方威斯康星州的森林物种类型如何影响遥感森林分类模型预测的景观尺度水通量。为研究中心制定了特定于研究中心的分类。利用这些信息和数字土壤数据库的网站，我们确定了四个关键的林分类型：红松，北方硬木，白杨，和森林湿地。在这些林分类型中，代表7个物种的64棵树连续监测液流传感器。将从树干液流得到的林分水平蒸腾量与双源土壤蒸发模型相结合，然后应用于WLEF AmeriFlux塔（福尔斯公园，威斯康星州）周围2.5 km × 3.0 km的区域，以估算蒸散量。在塔的水通量数据被用来检查这些估计。在此基础上，研究了不同植被类型对国际地圈-生物圈计划（IGBP）水通量预测的影响。分类聚集导致物种水平信息的损失显着改变景观水通量的预测。然而，每日的水通量没有显着影响的空间聚集时，森林湿地蒸发。结果表明，白杨的重要性，它具有较高的单位叶面积的蒸腾速率比其他森林物种。然而，更显着的不确定性的结果不包括森林湿地的高蒸发率在潮湿的夏天。
Forest management presents challenges to accurate prediction of water and carbon exchange between the land surface and atmosphere, due to its alteration of forest structure and composition. We examined how forest species types in northern Wisconsin affect landscape scale water fluxes predicted from models driven by remotely sensed forest classification. A site-specific classification was developed for the study site. Using this information and a digital soils database produced for the site we identified four key forest stand types: red pine, northern hardwoods, aspen, and forested wetland. Within these stand types, 64 trees representing 7 species were continuously monitored with sap flux sensors. Scaled stand-level transpiration from sap flux was combined with a two-source soil evaporation model and then applied over a 2.5 km × 3.0 km area around the WLEF AmeriFlux tower (Park Falls, Wisconsin) to estimate evapotranspiration. Water flux data at the tower was used as a check against these estimates. Then, experiments were conducted to determine the effects of aggregating vegetation types to International Geosphere– Biosphere Program (IGBP) level on water flux predictions. Taxonomic aggregation resulting in loss of species level information significantly altered landscape water flux predictions. However, daily water fluxes were not significantly affected by spatial aggregation when forested wetland evaporation was included. The results demonstrate the importance of aspen, which has a higher transpiration rate per unit leaf area than other forest species. However, more significant uncertainty results from not including forested wetland with its high rates of evaporation during wet summers.