Abstract
Whilst most hedgerow functions depend upon hedgerow structure and hedgerow network patterns, in many ecological studies information on the fragmentation of hedgerows network and canopy structure is often retrieved in the field in small areas using accurate ground surveys and estimated over landscapes in a semi-quantitative manner. This paper explores the use of radar SAR imagery to (i) detect hedgerow networks; and (ii) describe the hedgerow canopy heterogeneity using TerraSAR-X imagery. The extraction of hedgerow networks was achieved using an object-oriented method using two polarimetric parameters: the Single Bounce and the Shannon Entropy derived from one TerraSAR-X image. The hedgerow canopy heterogeneity estimated from field measurements was compared with two backscattering coefficients and three polarimetric parameters derived from the same image. The results show that the hedgerow network and its fragmentation can be identified with a very good accuracy (Kappa index: 0.92). This study also reveals the high correlation between one polarimetric parameter, the Shannon entropy, and the canopy fragmentation measured in the field. Therefore, VHSR radar images can both precisely detect the presence of wooded hedgerow networks and characterize their structure, which cannot be achieved with optical images.
Highlights
Hedgerows are important features in many landscapes of the world [1]
The extraction of hedgerow networks was achieved with an object-oriented method using two polarimetric parameters: the single bounce parameter and the Shannon entropy index derived from one TerraSAR-X image
This paper explores the use of radar SAR imagery to (i) detect hedgerow networks; and (ii) describe hedgerow canopy heterogeneity using TerraSAR-X imagery
Summary
Hedgerows are important features in many landscapes of the world [1]. They are linear features composed of trees and/or shrubs of various species, managed by people as fences or for the provision of wood. They have very different structures at tree and hedgerow scales in different landscapes [2]. They fulfill ecological, as well as cultural functions, such as control of soil erosion, microclimatic effects, landscape beautification, wood production, and water quality [3]. The linear fragmentation of hedgerow networks and canopy fragmentation (Figure 1)
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