The intensive use of soil for pasture establishment has promoted land degradation. However, well-managed pasture systems may contribute to the improvement of the soil biological properties. The aim of this study was to evaluate the soil microbial biomass, enzymes activity, and catabolic diversity under six different pastures: Andropogon gayanus, Brachiaria brizantha, Panicum maximum, Cynodon dactilon, agroforestry system, and native vegetation. Soil microbial biomass was estimated by the fumigation-extraction method, while enzyme activity was determined through substrate use. The catabolic diversity was evaluated by the community-level physiological profiling method. Microbial biomass C was higher in the soils under the agroforestry system and native vegetation, whereas microbial biomass N was higher in the soil under Brachiaria. Acid phosphatase activity and fluorescein diacetate hydrolysis were higher in agroforestry system and native vegetation, respectively. Dehydrogenase activity was higher in the soil under Brachiaria and Cynodon. Richness and diversity of community-level physiological profiling were higher in the soils under the agroforestry system and native vegetation. The highest numbers of C sources metabolized by microorganisms were found in the agroforestry system and native vegetation. This study showed that soil microbial community from pasture systems subjected to different management showed different biomass, activity, and catabolic diversity.

<p><span style="font-family: Times New Roman;"><span style="font-size: medium;">The aim of this study was to assess the carbon pools of a tropical soil where the native forest was replaced with different pasture systems. We studied five pasture production systems, including four monoculture systems with forage grasses such as <em>Andropogon</em>, <em>Brachiaria</em>, <em>Panicum</em>, and <em>Cynodon</em>, and an agroforestry system as well as a native vegetation plot. Greater availability of fulvic acid was detected in the agroforestry system as compared with that in the other systems. Higher lability of C was detected in the <em>Andropogon</em> system during the dry and rainy seasons and during the dry season in <em>Cynodon</em>. During the dry season, all pastures systems showed deficits in the net removal of atmospheric CO₂. The structure and practices of the agroforestry system enables more carbon to be sequestered in the soil as compared with the monoculture pasture, suggesting that it is an important practice to mitigate climatic change and to improve soil quality.</span></span></p>

Arbuscular mycorrhizal communities in different tropical pastures of the brazilian northeast Comunidades micorrízicas arbusculares em diferentes pastagens tropicais do nordeste brasileiro