Inferring the effect of individual trees on slope stability in New Zealand’s pastoral hill country

Abstract

Silvopastoralism in New Zealand’s highly erodible hill country is an important form of erosion and sediment control. Despite a long history in improving sustainable land management and soil conservation since the enactment of the Soil Conservation and Rivers Control Act 1941, there has been little quantitative work to establish the effectiveness of space-planted trees in reducing shallow landslide erosion at farm to landscape scales. This is largely due to the lack of spatially explicit data on individual trees and their influence on slope stability. Therefore, it is difficult to determine the extent to which plantings have targeted slopes susceptible to landslide erosion. Furthermore, root data collection for multiple species and age classes is very time-consuming and costly, which limits the development of root reinforcement models for different species and partly explains the paucity of quantitative data on the effectiveness of space-planted trees.