Comparative analysis of the aboveground phytomass assessment of pine forest stands by ground and remote methods

One of the most efficient approaches to provide a current and objective assessment of forest cover over large areas is remote sensing data combining with an empirical models obtained from field ground research. For a detailed study of the phytomass of plantations by GIS technologies, calculations of spectral characteristics and biophysical parameters obtained as a result of decoding satellite images of monitoring objects are usually performed. The object of study – pine stands of the ravine Steppe of Ukraine. The subject of research – bioproductivity of aboveground phytomass components of pine stands. The aim of the study to develop the models for pine stands phytomass assessing at the ravine Steppe of Ukraine by remote sensing. The evaluation of aboveground phytomass pine forests was carried out by combining terrestrial and remote sensing methods. In order to estimate the aboveground biomass in the pine forests of the ravine Steppe based on the Sentinel-2 satellite imagery data for each pixel of images containing temporary sample plots (TSPs), the following indicators were calculated: NDVI, LAI, FAPAR, FCOVER, CAB and CW. In accordance with statistical analysis the distribution of spectral indices in most cases corresponds to normal, given the lower values of asymmetry and excess, compared with the critical values. Correlation analysis revealed that the spectral characteristics obtained from satellite images had a stronger correlation with the aboveground phytomass of trunks and total phytomass, compared with the crown phytomass of pine wood stands. With the help of the obtained geoinformation data, models of aboveground phytomass dependence on vegetation and biophysical parameters were designed with the help of which about 70 % of cases were subject to description. The NDVI, LAI, FARAP, TVI, FCOVER indicators were used as input arguments. The equation of the dependence of the aboveground pine phytomass on the NDVI index is the most significant statistically ftom the designed equations. The lowest approximation accuracy is observed when the LAI index is included in the equation. The comparison of the actual and simulated values of aboveground phytomass of pine stands obtained as a result of ground research revealed insignificant their deviation, which testifies to a rather accurate description of the empirical data model. The most intensive accumulation of pine phytomass at the amount from 150 to 250 tˑha-1 is observed at NDVI values in the range from 0.4 to 0.5. Based on the obtained data, the values of Scots pine aboveground phytomass were transformed into a forest area structure of the Dnieper state forestry of ravine Steppe (on the example of Obukhiv forestry) with the formation of a spatial distribution map of aboveground phytomass forestry. Values of aboveground phytomass pine plantations of Obukhiv forestry was estimated in the range from 75 to 310 tˑha-1. At the same time, most of the Scots pine plantations territory (61 % of the area) has a phytomass in the range from 100 to 200 tˑha-1. It is estimated that the total value of aboveground phytomass of pines in Obukhov forestry, calculated on the basis of spatial data processing, is 195782.40 tons, while the obtained biomass, determined by ground estimation 210861.95 tons, which is 7.2% higher, compared with remote sensing data. The obtained results demonstrate the prospects of the proposed method for the aboveground phytomass of pine plantations assessment at the regional level as an effective method of operational monitoring and management of forest resources in the Steppe zone.