Department of Forest Engineering, Resources, and Management, 280 Peavy Hall, 3100 SW Jefferson Way, Oregon State University, Corvallis, OR 97331, USA.
Department of Forest Engineering, Resources, and Management, 280 Peavy Hall, 3100 SW Jefferson Way, Oregon State University, Corvallis, OR 97331, USA; Department of Earth and Atmospheric Sciences, University of Northern Colorado, 501 20th St Box 100, Greeley, CO, 80639, USA.
Sci Total Environ. 2019 Nov 15;691:112-123. doi: 10.1016/j.scitotenv.2019.07.127. Epub 2019 Jul 9.
Natural disturbances help maintain healthy forested and aquatic ecosystems. However, biotic and abiotic disturbance regimes are changing rapidly. For example, the Swiss needle cast (SNC) epidemic in the Coast Range of Oregon in the U.S. Pacific Northwest has increased in area from 53,050 to 238,705ha over the 1996-2015 period. We investigated whether the hydrologic regime (i.e., annual streamflow, runoff ratio, and magnitude and timing of peak flows and low flows) was affected by SNC in 12 catchments in western Oregon. The catchments ranged in size from 183 to 1834km and area affected by SNC from 0 to 90.5%. To maximize the number of catchments included in the study, we analyzed 20years of SNC aerial survey data and 15-26years of stream discharge (Q) and PRISM precipitation (P) and air temperature (T) data to test for trends in hydrologic variables for each catchment. As expected, we found that runoff ratios (Q/P) increased in five catchments, all with an area impacted by SNC >10%. This was likely due to the effects of SNC on the hydraulic architecture (i.e., needle retention, sapwood area, sapwood permeability) of affected trees, leading to decreased canopy interception and transpiration losses. Interestingly, two catchments with the greatest area affected by SNC showed no changes in hydrologic regime. The lack of hydrologic response could either be due to compensatory transpiration by vegetation unaffected by the disease or sub-canopy abiotic evaporation, which counteracted reductions in transpiration. This study is the first to illustrate that chronic canopy disturbance from a foliage pathogen can influence catchment scale hydrology.
自然干扰有助于维持健康的森林和水生生态系统。然而，生物和非生物干扰机制正在迅速变化。例如，在美国太平洋西北地区俄勒冈海岸山脉，瑞士松针凋萎病（SNC）的流行面积从 1996 年至 2015 年期间从 53050 公顷增加到 238705 公顷。我们研究了在俄勒冈西部的 12 个流域中，水文状况（即年径流量、径流量比、以及高峰流量和低流量的幅度和时间）是否受到 SNC 的影响。这些流域的面积从 183 平方公里到 1834 平方公里不等，受 SNC 影响的面积从 0 到 90.5%不等。为了使更多的流域纳入研究，我们分析了 20 年的 SNC 航空调查数据以及 15-26 年的流域径流量（Q）、PRISM 降水（P）和空气温度（T）数据，以检验每个流域的水文变量的趋势。正如预期的那样，我们发现五个流域的径流量比（Q/P）增加，所有这些流域的 SNC 影响面积均>10%。这可能是由于 SNC 对受影响树木水力结构（即针叶保留、边材面积、边材渗透性）的影响，导致树冠截留和蒸腾损失减少。有趣的是，两个受 SNC 影响面积最大的流域的水文状况没有变化。缺乏水文响应可能是由于未受疾病影响的植被的补偿蒸腾作用或树冠下非生物蒸发作用，抵消了蒸腾作用的减少。本研究首次表明，叶病原体的慢性冠层干扰会影响流域尺度的水文状况。
