Modelowanie charakterystyk spektralnych heterogenicznych zbiorowisk trawiastych przy użyciu modelu transferu promieniowania

Meadows are important ecosystems and should be protected. Also, in Poland organic agriculture and farming, where crops from meadows are used, is getting more popular. That is why meadows monitoring and predicting crops is important issue. Much information can be calculated from spectrum of plants and that is why remote sensing data are very useful tool. Two approaches are used to calculate biophysical variables: statistical and modelling. In statistical, values from field measurements have to be compared with images. In modelling, radiative transfer models are used. RTM are physical models based on the fundamental equation of radiative transfer. After all necessary adjustments, models can give the description of the canopy with fewer field measurements. In this paper model on leaf level was chosen. PROSPECT uses only five input variables: chlorophyll and carotenoid content, water content, dry matter and leaf structure parameter. Model is normally used to homogeneous canopy, like corn. In this paper, PROSPECT was used to simulate spectrum for heterogenic meadows using field measurements. Biophysical variables were collected during field measurements in the Bystrzanka catchment in the Low Beskid Mountains. In the same time more than 10 samples of spectrum were collected using ASD FieldSpec 3 FR and then averaged. The minimum size of polygon was 100m2. All input parameters for every polygon were included into the model and spectrum was modelled. Then spectrum was compared with measured samples of each polygon. In the end the vegetation indices were calculated using two kinds of spectrum and compared. All used vegetation indices are describing plant condition or crop monitoring: Normalized Difference Vegetation Index, Red Edge Normalized Difference Vegetation Index, Photochemical Reflectance Index, Normalized Difference Nitrogen Index, Normalized Difference Lignin Index, Cellulose Absorption Index, Carotenoid Reflectance Index, Water Band Index and Moisture Stress Index. Researches shows, that it is possible to simulate spectra for heterogeneous meadows using PROSPECT. The average RMSE value for all polygons was 0,0346, which mean the spectra are well modelled. The biggest mistake was for near infrared range, where is the strongest influence of dry matter content. The differences between measured and modelled spectrum were also noticed on the part of visible light – 400-500nm. For most calculated vegetation indices values were similar for both kinds of spectra. Values of NDVI,WBI and NDLI were very close. The biggest differences were noticed form PRI and CRI.