Abstract
Although studies on edge effects on species richness and abundance are numerous, the responses of ecosystem processes to these effects have received considerably less attention. How ecosystem processes respond to edge effects is particularly important in temperate forests, where small fragments and edge habitats form a considerable proportion of the total forest area. Soil fauna are key contributors to decomposition and soil biogeochemical cycling processes. Using the bait lamina technique, we quantified soil fauna feeding activity, and its dependence on soil moisture and distance to the edge in a broad-leaved forest in Southern England. Feeding activity was 40% lower at the forest edge than in the interior, and the depth of edge influence was approximately 75 m. A watering treatment showed that moisture limitation was the main driver of the reduced feeding activity at the edge. In England, only 33% of the forest area is greater than 75 m from the edge. Therefore, assuming that the results from this single-site study are representative for the landscape, it implies that only one- third of the forest area in England supports activity levels typical for the forest core, and that edge effects reduce the mean feeding activity across the landscape by 17% (with lower and upper 90% confidence intervals of 1.3 and 23%, respectively). Changing climatic conditions, such as summer droughts may exacerbate such effects as edges lose water faster than the forest interior. The results highlight the importance of taking edge effects into account in ecological studies and forest management planning in highly fragmented landscapes.
Highlights
Edge effects influence species’ distributions and ecosystem processes
Recent studies on the edge effect have indicated that increased evapotranspiration and reduced soil moisture levels near the forest edge are among the main drivers behind the differences in the ecosystem processes between the forest edge and core (Herbst and others 2007; Riutta and others 2012)
The watered plots had higher soil moisture levels than the control plots (F1,51 = 6.91, p = 0.0113), and the watering treatment effect decreased towards the forest edge
Summary
Edge effects influence species’ distributions and ecosystem processes. Forest edges are typically characterised by higher and more variable temperatures, higher vapour pressure deficits, and increased light and wind speeds compared with the forest core (Chen and others 1993; Young and Mitchell 1994; Chen and others 1995; Davies-Colley and others 2000). The impacts of these changes are species and process specific as well as scale dependent, and there have been recent attempts to quantify the depth of edge influence (DEI) along a continuous gradient for individual processes (Ewers and Didham 2006a; Crockatt and Bebber 2014; Riutta and others 2014) Such studies suggest that fragments of less than nine hectares will be dominated by edge patterns and that fragments of less than one hectare will not support forest core conditions or vegetation associations (Young and Mitchell 1994; Riutta and others 2014)
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