The impact of drought in 2015 on the health forest condition determined using Landsat-8 OLI images

Abstract

The main aim of this research was to determine the impact of drought (in 2015) on forests stand condition using remote sensing and statistical techniques. The study was based on the analysis of vegetation indices calculated from a series of Landsat-8 OLI satellite images covering the 2014 and 2015 growing seasons. Various tree biophysical and physical parameters as well as forest habitat characteristics were tested in order to find the most significant factors affecting drought resistance. Three approaches were used: (i) index differences, (ii) PCA analysis, and (iii) ANOVA statistical analysis. All three approaches used in this study indicate that forest biodiversity is the most important factor determining habitat response to stress conditions. Coniferous and mixed tree habitats were less sensitive than deciduous ones. Statistical analysis revealed the relationship between stress and soil types, as those more permeable were less dependent on rainwater. The highest stress was found for precipitation-dependent gley soils. Undergrowth density and height were also indicated as important factors inducing habitat response to a changing weather situation. All the results confirmed the usefulness of mid-infrared based indices for water shortage monitoring in forests. They confirmed that habitat biodiversity has a positive effect on its resistance to stressful conditions. Also forest type (conifer/deciduous) determines it’s sensitivity. Precipitation and groundwater shortages have different effects on the forest condition depending on soil type.

Satellite data reveal differential responses of Swiss forests to unprecedented 2018 drought

“…For conifers, however, this effect might be diluted by the presence of older, less vulnerable needles. Additionally, while European beech is the most prominent deciduous species in Switzerland, the study site of Nasiłowska et al (2019) is dominated by pedunculated oak ( Quercus robur ), a more drought resistant species than European beech (Scharnweber et al, 2011), additionally indicating the importance of timing in drought events (D’Orangeville et al, 2018).…”

Species Diversity of Oak Stands and Its Significance for Drought Resistance

“…The method was found to be efficient for land-cover changes [45] or the mapping of crop plantations [46]. A technique based on differential images was successfully used and recommended for operational application in forests, using the vegetation indices calculated from surface reflectance level products [47] in a habitat suffering from oak dieback [48,49]. The use of the multiplicity of the standard deviation as a change/no change (±σ) (standard deviation) threshold is also a popular approach [5,50].…”

“…In our research, the following four steps were carried out [49] for images located on path 190, row 24, of the Landsat system.…”

“…Imaging was performed in six optical channels within the visible light and near-infrared ranges. An algorithm for an iterative application of a factor analysis of multispectral images was used in post-processing [49,75,77]. Six-dimensional color space was reduced using Principal Component Analysis (PCA) to a two-dimensional Principal Component Plane (PCP) covering over 99.5% color variability.…”

“…At the same time, division MD50 showed the highest species diversity index (88.24%), while SO27 had the largest share of Scotch pine. It should be noted that Nasiłowska et al (2017) [49] indicated both species diversity and the share of Scotch pine within a division as factors enhancing the response to drought. In turn, the values of indices decreasing within the ranges (−0.79 to −0.99), (−0.67 to −0.81), and (−0.68 to −0.87) could be seen for divisions DBB 126, DBB 129, and DBB 96, evidencing a negative trend in the development of the local vegetation.…”