Stream Temperature Relationships to Forest Harvest in Western Washington 1
Stream Temperature Relationships to Forest Harvest in Western Washington 1
复制标题
华盛顿州西部河流温度与森林采伐的关系 1
DOI：
10.1111/j.1752-1688.2008.00266.x
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
R. Bigley
中科院分区：
文献类型：
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作者：
M. Pollock;T. Beechie;M. Liermann;R. Bigley
翻译后摘要：我们比较了夏季流的温度模式在40个小的森林流域的可可和清水流域在西部奥林匹克半岛，华盛顿，检查以前的河岸和流域范围内的木材采伐活动和流温度之间的相关性。 7个流域未收获，而其余33个流域的总收获量在25%至100%之间，大部分是在过去40年内。 收获和未收获盆地的平均日最高温度显著不同，平均分别为14.5°C和12.1°C。收获和未收获的流域之间的日波动也有显着差异，平均分别为1.7°C和0.9°C。流域总收获量与平均日最高温度（r2 = 0.39），总河岸收获量（r2 = 0.32）。 在我们监测点上游600米范围内，最近被砍伐的河岸森林（<20年）的数量从0%到100%不等，与河流温度升高无关。 我们使用赤池的信息标准（AIC）分析，以评估是否其他物理变量可以解释一些观察到的流温度的变化。我们发现，与海拔，坡度，坡向和地质相关的变量解释了5%至14%的变异性，相对于流域采伐百分比（BasHarv）解释的变异性，并且BasHarv始终是比河岸森林采伐量更好的预测因子。虽然BasHarv在所有表现良好的模型中，但AIC分析表明，有许多模型具有两个变量，表现大致相同，因此很难选择一个作为最佳模型。我们的结论是，增加额外的变量模型不改变的基本发现，有一个相对较强的关系，最高日流温度和总的收获量在一个盆地，强大的，但稍弱的关系，最高日流温度和总的河岸收获在一个盆地。40条溪流中有17条超过了华盛顿州生态部（DOE）定义为“核心鲑鱼和鳟鱼栖息地”（AA级沃茨）的沃茨温度标准。美国能源部对AA类沃茨的温度标准是日最高温度超过16°C的任何七天平均值。超过水质标准的流的概率增加木材采伐活动。所有未收获的地点和收获率为25 - 50%的六个地点中的五个符合DOE水质标准。相比之下，只有18个站点中的9个达到50 - 75%的收获量，9个站点中的2个达到75%以上的收获量符合DOE水质标准。许多溪流与广泛的树冠关闭，估计的河岸树木的年龄，仍然有较高的温度和更大的昼夜波动比未收割的盆地。这表明，过去森林采伐活动对溪流温度的影响无法通过重建河岸缓冲区来完全减轻。
Abstract: We compared summer stream temperature patterns in 40 small forested watersheds in the Hoh and Clearwater basins in the western Olympic Peninsula, Washington, to examine correlations between previous riparian and basin‐wide timber harvest activity and stream temperatures. Seven watersheds were unharvested, while the remaining 33 had between 25% and 100% of the total basin harvested, mostly within the last 40 years. Mean daily maximum temperatures were significantly different between the harvested and unharvested basins, averaging 14.5°C and 12.1°C, respectively. Diurnal fluctuations between harvested and unharvested basins were also significantly different, averaging 1.7°C and 0.9°C, respectively. Total basin harvest was correlated with average daily maximum temperature (r2 = 0.39), as was total riparian harvest (r2 = 0.32). The amount of recently clear‐cut riparian forest (<20 year) within 600 m upstream of our monitoring sites ranged from 0% to 100% and was not correlated to increased stream temperatures. We used Akaike’s Information Criteria (AIC) analysis to assess whether other physical variables could explain some of the observed variation in stream temperature. We found that variables related to elevation, slope, aspect, and geology explain between 5% and 14% more of the variability relative to the variability explained by percent of basin harvested (BasHarv), and that the BasHarv was consistently a better predictor than the amount of riparian forest harvested. While the BasHarv is in all of the models that perform well, the AIC analysis shows that there are many models with two variables that perform about the same and therefore it would be difficult to choose one as the best model. We conclude that adding additional variables to the model does not change the basic findings that there is a relatively strong relationship between maximum daily stream temperatures and the total amount of harvest in a basin, and strong, but slightly weaker relationship between maximum daily stream temperatures and the total riparian harvest in a basin. Seventeen of the 40 streams exceeded the Washington State Department of Ecology’s (DOE) temperature criterion for waters defined as “core salmon and trout habitat” (class AA waters). The DOE temperature criterion for class AA waters is any seven‐day average of daily maximum temperatures in excess of 16°C. The probability of a stream exceeding the water quality standard increased with timber harvest activity. All unharvested sites and five of six sites that had 25‐50% harvest met DOEs water quality standard. In contrast, only nine of eighteen sites with 50‐75% harvest and two of nine sites with >75% harvest met DOEs water quality standard. Many streams with extensive canopy closure, as estimated by the age of riparian trees, still had higher temperatures and greater diurnal fluctuations than the unharvested basins. This suggests that the impact of past forest harvest activities on stream temperatures cannot be entirely mitigated through the reestablishment of riparian buffers.