REMOTE SENSING FOR DESCRIBING VEGETATION DYNAMICS UNDER AGRICULTURAL LAND CONDITIONS

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Mihai HERBEI
Florin SALA

Abstract

The study was based on remote sensing to obtain satellite images, spectral information and on calculating specific indices in order to describe the dynamics of crop vegetation in the case of an agricultural area. The research was carried out within the Didactic and Experimental Station of BUASVM Timisoara, Timis County, Romania. The agricultural perimeter under study is located within the Western Plain, Romania, with the general characteristics of a chernozem type soil and the climatic specificity of the area. The study interval was January - November 2021, in which 8 sets of satellite images were taken: 2.01.2021 (D1); 25.02.2021 (D2); 13.03.2021 (D3); 15.05.2021 (D4); 26.06.2021 (5); 14.08.2021 (D6); 6.09.2021 (D7) and 10.11.2021 (D8). The images were analyzed and based on spectral information the indices NDWI, NDVI, MSAVI and MTVI2 were calculated. The ANOVA test, single factor, confirmed the presence of the variance and the statistical security of the data. The NDVI index (CVNDVI=32.1113) showed high variability, followed by the MSAVI index (CVMSAVI=20.4953) and the MTVI2 index (CVMTVI2=5.5512). Very strong correlations were recorded between NDVI and NDWI  (-0.971***), between NDVI and MSAVI (0.994***), and between MSAVI and NDWI (-0.957***). The NDVI variation was described by a linear equation in relation to NDWI under conditions of R2=0.943, p<0.001, F=98.734 and by a polynomial equation of 2nd degree in relation to MSAVI(R2=0.998, p<0.001, F=1384). A spline model was found to describe the NDVI variation over time (T, days) over the study period, under conditions of statistical accuracy ( ). Within PCA, PC1 explained 76,693% of variance, while PC2 explained 23,174% of variance. The cluster analysis grouped the variables (D1 to D8) on the basis of similarity, in relation to the studied indices, in statistical accuracy conditions (Coph.corr=0.912).

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