Depth of edge influence of the agricultural-forest landscape boundary, Southwestern China

The landscape boundary is an important component of a landscape and often plays an indispensable role in regulating ecological flows. The primary objective of this study was to estimate how far the edge effects on agricultural-forest landscape boundaries can penetrate into the forest and agricultural field. This will serve as a basis for understanding the interaction between forest and agricultural fields in the mountainous area of southwestern China and provide scientific basis for the practice of the policy of "returning agricultural field to forest." Based on field investigations, three types of boundaries with six sampling transects were selected. We investigated the soil moisture, soil nutrients and vegetation diversity along the transect gradient and explored the depth of edge influence (DEI) with moving split-window techniques for analyzing the data. DEI for soil moisture changed with the seasons, ranging from 6 m in the pepper field to 2 m in the forest during the dry season, and from 12 m in the pepper field to 2 m in the forest after heavy rain. DEI based on soil organic matter ranged from 1.5 to 10 m in the forest field, while it was not detected based on other soil nutrient factors. DEI based on vegetation diversity varied from 4 to 26 m and from 10 to 31 m in the forest and agricultural fields, respectively. These results provide the scientific basis for the policy "returning agricultural field to forest". Based on these field observations, reducing human disturbance and revegetating with natural shrubs and meadows could be more effective for vegetation conservation in terms of soil moisture and soil nutrient content in the arid valley of the Minjiang River.