边缘效应对原始花旗松林冬季温度的影响(英文)

Winter temperature changes across an old-growth Douglas-fir forest edge

由林缘到林内 ,夏季温度有明显的梯度变化。但还未有人对其它季节的温度变化 ,进行研究。自 1 991年 1 0至 1 992年 5月 ,对林缘至原始花旗松林林内的温度 ,进行了连续的实地测量 ,并与相应的夏季温度变化加以比较。主要研究目的 ,是测定沿林缘两侧 ,是否存在有一个最小的温度阈值 ,当温度低于这个阈值时 ,林缘及林内的温度差异会消失。研究中 ,由林缘到 2 4 0 m的林内 ,设立了一条样带 ,并在样带 0 ,3 0 ,60 ,1 2 0 ,1 80 ,和 2 4 0 m,6处装设气象站 ,每 3 0 min连续记录气温、土壤温度和其他微气象指标。通过计算每点的相对温度并同实际温度加以对比 ,夏季和冬季的林缘效应显著性指数 (Significance of edge influences,SEI)进行了分析。此外 ,计算了不同气象条件下的林缘效应深度 (DEI)。结果表明 ,非夏季最小的气温阈值在 0℃左右。土温的变化则因土壤很少结冻 ,而存在明显不同的最小的温度阈值格局。林缘效应对土壤温度的影响 ,比对气温的影响更显著 ,但冬季和夏季之间没有太大的差异。但以 DEI而论 ,林缘效应对气温的影响比较大。对非生长季节气候因子沿林缘梯度的分析。

Microclimatic variables collected in summer have been shown to vary greatly across forest edge interior gradients, and therefore affect ecological patterns and processes. However, winter (October～May) microclimatic data has not been studied in relation to these gradients. We examined winter temperature gradients across old growth Douglas fir forest edges and compared these to corresponding summer gradients. We sought to determine whether there is a minimum temperature threshold, below which variation across edge is insignificant. Air and soil temperature were collected along transects extending from clearcut edges to 240 m into the forest. Minimum temperature thresholds were evaluated by plotting relative temperature against actual temperature for the same observation. The significance of winter temperature variation across edge gradients vs. summer temperature variation was evaluated by comparing the Significance of Edge Influence ( SEI ) index to previously calculated summer SEI data. Depth of Edge Influence ( DEI ) was also compared between seasons. The minimum threshold point for winter air temperature was found to lie near 0℃. Soil temperature variation exhibited different minimum threshold patterns because actual soil temperature rarely dropped below 0° C. Edge effects were more significant to soil temperature than air temperature, and not greatly different between summer and winter. However, edge influences extended farther into the forest for air temperature than soil. These findings on non growing season climatic conditions across a forest edge gradient should provide insight to several related seasonal biotic and abiotic processes.