Pasture trees: regeneration, farmer management or original flora remnant?

Abstract

Despite of the growing consensus that scattered trees decline in agricultural landscapes deserves urgent attention, such countryside elements have received little consideration in conservation programs. In part this is due to lack of knowledge about the factors affecting these trees. There are few studies addressing the relationship between farmer management and pasture trees, and the effects of distance from forest fragments on species composition of these trees are poorly understood yet. Our aims were (i) describe the vegetation structure of pasture trees, and (ii) investigate whether the distance from forest fragments and the farmer management affect such vegetation structure. Our research was carried out in nine pastures from a semideciduous forest region in southern Minas Gerais state, Brazil. All pasture trees with the diameter at breast height (d.b.h.) ≥ 5 cm were measured and identified in 1.96 ha of each pasture (totaling 17.64 ha). We found 700 trees belonging to 30 families and 90 species. Tree abundance and species richness decreased with increasing distance from the forest fragments, while we found no relationship between tree size and this explanatory variable. The most important species found are characteristics from early successional stages or are exotics. The natural regeneration is the acting factor on tree abundance and species richness in six studied pastures, while the farmer management acts on species composition and tree size in other pastures. Our study is an important step to better understanding about the factors that affect the tree coverage in pastures, and may guide conservation programs. Since the knowledge that in some pastures natural regeneration is responsible for tree component whilst in others farmer management is decisive in species composition provides a basis to help with planning actions to maintain and/or improve tree species richness in these pastures.