Aporte de serrapilheira, fenologia da catingueira e dinâmica do CO2 do solo em áreas da Caatinga no Cariri paraibano

Abstract

The Caatinga biome has mostly deciduous vegetation, as a mechanism of leaf loss to minimize water loss, due to the edaphoclimatic conditions of the semiarid region in which it is inserted. The study of aspects related to litter deposition and the interactions of processes with climatic and soil parameters are necessary to improve the understanding of vegetation behavior and its variations mainly in semiarid regions, as this contributes to the use of appropriate management practices and coexistence. The objective of this work was to estimate the contribution of the litter deposition of the catingueira, to evaluate the phenology of the species and to verify the soil CO2 concentrations in caatinga areas in Paraíba Cariri. Experiment was carried out in a Caatinga area located in the São João do Cariri Experimental Station - PB, and the experimental area consisted of 2 pickets, where Area I was managed with the presence of 10 animals and area II without animals. To quantify the litter input, 3 catingueira plants were selected in each area and 4 collectors with dimensions of 1.2 × 0.5 m were installed under the crown of each individual. Collected material was fractionated (leaves, branches, reproductive material and miscellaneous) to estimate the percentage contribution of each fraction. Phenology was performed by selecting 20 individuals, recording the percentage of leaves in the crown of individuals and associating the phenophases budding, flowering, fruiting and senescence. CO2 dynamics was performed following three parallel transects 200 m, where 10 reading points were marked in each transect. Reading was performed at 6, 11 and 16 hours, using the model C-02 Carbon Dioxide Analyzer (Instrutherm®). Rainfall of 504.7 mm was recorded during the evaluation period and total estimated litter yield of 376.03 kg ha-1 in area I and 497.55 kg ha-1 in Area II. Regarding phenology, individuals from Area I presented a higher phenological response than individuals from Area II, concentrating the highest percentage of total leaves throughout the experimental period. In the dynamics of soil CO2 there was a statistical difference between the hours, between months and between the evaluated areas, with higher concentrations in Area II in the months of february, march and september at 11 hours. Catingueira is a species that contributes to litter input in Caatinga areas, where precipitation influences leaf abscission, and the leaves fraction contributes predominantly to dry matter of the input. Its phenology responds to the precipitation pulses, where the intensity and duration of the phenophases are according to the amplitude and frequency of the rains. Highest concentrations of soil CO2 occur in the area without goat management at 11 o'clock, having influences of temperature and relative humidity in the concentrations.