Dinâmica de deposição e decomposição de serapilheira em sistema silvipastoril com eucalipto

Abstract

Silvopastoral systems (SSP) are associations of forest species with herbaceous or creeping forage plants and herbivorous animals. The interaction of the components within the system generates mutual benefits, among them, the nutrient cycling, provided by the greater deposition and later decomposition of the litter. Therefore, understanding the dynamics of deposition and decomposition of litter and its consequences in other components is fundamental to study the functioning of silvopastoral systems. The objective of this study was to quantify and qualify the deforested litter and to study the dynamics of decomposition in a silvopastoral system with eucalyptus, comparing the studied variables with a semideciduous and monoculture secondary forest of Urochloa decumbens during the four seasons of the year a property in Barbacena, MG, from February to December 2018. A completely randomized design was used in the arrangement of subdivide plots in time, where the plots were: Silvopastoral System (SSP), Semidecidual Secondary Forest (FL) and Urochloa monoculture decumbens (PS). The subplots were: Summer, Autumn, Winter and Spring. Litter deposition, decomposition constant (k), half-life time for decomposition (t0.5), forage mass production, canopy height (ALT) dry matter (DM), mineral matter (MM) , crude protein content (CP) and neutral detergent fiber (NDF) in forage. Regarding deposition, there was significant interaction (P <0.05) between the factors. The SSP presented higher deposition in all seasons, with annual average yield of 12.09 Mg MS ha-1, followed by FL with 8.13 Mg MS ha-1 and PS with 1.93 Mg MS ha-1. Among the seasons, there was no significant difference (P> 0.05) in SSP and PS, but FL had higher deposition (P <0.05) during the winter season. The SSP presented 65% leaf, 18% of branch, 15% of seed and 2% of bark of trees in their deposited litter during the year. The FL presented 83% of leaf, 15% of branch and 2% of seed. The constant k was 0.0021 and 0.0025 g g-1 for SSP and FL, respectively, showing a T2 of 322 days in SSP and 272 days in FL. As for the mass production of forage, the PS showed higher value in the summer season, while in the other seasons were statistically the same. ALT did not present statistical difference (P> 0.05). PB content was significantly different between treatments (P <0.05), where SSP was higher in all seasons, with a mean of 12.60% CP, whereas PS presented a mean of 9.76% and PB . The NDF values were higher (P <0.05) for PS in the summer and spring seasons. Among the treatments, the SSP obtained higher value (P <0.05) in the fall, while the PS obtained in autumn and summer. Based on the data, it is concluded that the studied SSP was able to produce more litter, while the FL litter is decomposed in a shorter time. The reduced luminosity of the SSP influenced the production of forage mass only in the summer, but favored its nutritional quality, increasing the CP content and decreasing the NDF when compared to the PS. Therefore, SSP is a viable alternative to conventional production systems.