Model Prediction of the Soil Moisture Regime and Soil Nutrient Regime Based on DEM-Derived Topo-Hydrologic Variables for Mapping Ecosites

Abstract

Ecosites are required for stand-level forest management and can be determined within a two-dimensional edatopic grid with soil nutrient regimes (SNRs) and soil moisture regimes (SMRs) as coordinates. A new modeling method is introduced in this study to map high-resolution SNR and SMR and then to design ecosites in Nova Scotia, Canada. Using coarse-resolution soil maps and nine topo-hydrologic variables derived from high-resolution digital elevation model (DEM) data as model inputs, 511 artificial neural network (ANN) models were developed by a 10-fold cross-validation with 1507 field samples to estimate 10 m resolution SNR and SMR maps. The results showed that the optimal models for mapping SNR and SMR engaged eight and seven topo-hydrologic variables, together with three coarse-resolution soil maps, as model inputs, respectively; 82% of model-estimated SNRs were identical to field assessments, while this value was 61% for SMRs, and the produced ecosite maps had 67–68% correctness. According to the error matrix, the predicted SNR and SMR maps greatly alleviated poor prediction in the areas of extreme nutrient or moisture conditions (e.g., very poor or very rich, wet, or very dry). Thus, the new method for modeling high-resolution SNR and SMR could be used to produce ecosite maps in sites where accessibility is hard.

Potential of Remote Sensing Images for Soil Moisture Retrieving Using Ensemble Learning Methods in Vegetation-Covered Area

“…The MⅣ mode was slightly worse than the MⅤ mode, with a higher RMSE value but a slightly higher R value In densely vegetated areas, the radar signal may not reach the soil through the plant canopies, resulting in less accurate estimation of SM. Some studies have shown that， the C-band radar signal is insensitive to SM when NDVI > 0.7 [48][49][50].…”

“…Therefore, in this section, we reanalyze the different sensitivity of C-band to soil when NDVI is in different range. First, we divided the range of measured SM (2 to 40 vol.%), which we divided into two parts: dry to slightly moist (0 ~ 25 vol.%), based on experience; and very wet (25 ~ 40 vol.%) [48]. Second, we perform inversion analysis in different NDVI ranges using four methods.…”