Análise das propriedades nutricionais do solo e da estrutura florestal no bioma Caatinga

Abstract

Soil nutrients and forest structure play a fundamental role in terrestrial ecosystems and are essential for understanding the effects of global changes. In the Caatinga, there are still few studies that seek to evaluate the controllers of the spatial variability of C, N, P in the soil, and even less those that explore the use of modeling to estimate structural parameters of vegetation in space. This work aims to analyze C, N, C:N and P contents in soils and structural parameters of vegetation height and density in the caatinga biome. First, a descriptive analysis of the data was carried out. After that, environmental variables were used as entries in the Random Forest model. Validation was performed with metrics and cross-validation of 10 repetitions (divided into training data (75%) and test (25%)) for nutrients and for GEDI data (rh98, cover and father) divided the samples into training and test sets for 353 grids (0.5° × 0.5°) created in the study area. The descriptive result shows the following mean values: 5.68±8.76 g/kg of carbon content, 0.62±0.47 g/kg for nitrogen content, 7.51 pm3.19 of C:N ratio and 13.79±46.95 mg/kg for phosphorus. The Tall Shrub and Intermediate Tree strata had the best values for C, N, C:N and P. These strata are representative assets of the preserved caatinga condition. It was not possible to identify a pattern in relation to soil nutrients and canopy cover. Overall, validation metrics demonstrated moderate to low accuracy of predictive soil models. The height of the modeled canopy ranges from 2.8 to 17.7 m and an average value of 5.6±1.7 m. Modeled total canopy cover ranged from 0% (no canopy cover present) to 87% (dense to closed canopy cover) and averaged 13±0.08%, which highlights the rather sparse levels canopy cover conditions in the Caatinga. As for the total plant area index, it presents an average value of 0.36±0.33 m2/m2. Therefore, these results are essential for the creation of environmental policies and the development of new studies and, mainly, contribute to the understanding of one of the most threatened and least studied biomes in Brazil.