Abstract
Savanna ecosystems and their woody vegetation provide valuable resources and ecosystem services. Locally calibrated and cost effective estimates of these resources are required in order to satisfy commitments to monitor and manage change within them. Baseline maps of woody resources are important for analyzing change over time. Freely available, and highly repetitive, C-band data has the potential to be a viable alternative to high-resolution commercial SAR imagery (e.g., RADARSAT-2, ALOS2) in generating large-scale woody resources maps. Using airborne LiDAR as calibration, we investigated the relationships between hyper-temporal C-band ASAR data and woody structural parameters, namely total canopy cover (TCC) and total canopy volume (TCV), in a deciduous savanna environment. Results showed that: the temporal filter reduced image variance; the random forest model out-performed the linear model; while the TCV metric consistently showed marginally higher accuracies than the TCC metric. Combinations of between 6 and 10 images could produce results comparable to high resolution commercial (C- & L-band) SAR imagery. The approach showed promise for producing a regional scale, locally calibrated, baseline maps for the management of deciduous savanna resources, and lay a foundation for monitoring using time series of data from newer C-band SAR sensors (e.g., Sentinel1).
Highlights
Savanna ecosystems are ecologically and economically significant systems that are defined by a continuous herbaceous layer interspersed with trees [1,2]
The results of the first scenario are presented in Figure 4a–f), were we found a similar pattern of improvement in the RF model root mean squared error (rRMSE) results for each cycle, and for both metrics
The analysis presented above has explored the relationship between a time series of C-band synthetic aperture radar (SAR)
Summary
Savanna ecosystems are ecologically and economically significant systems that are defined by a continuous herbaceous layer interspersed with trees [1,2]. They cover more than 30% of the worlds’. The (potential) impacts of these combined pressures on woody resources in (African) savannas need to be monitored in order to avoid significant losses, both in terms of ecosystem services, as well as Remote Sens. This requires being able to accurately measure, report, and verify available woody resources in order that they are sustainably managed. There are no regularly updated national spatial products or datasets, regarding the status or trends in South(ern) Africa’s woodland and forest resources
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