Response of caatinga vegetation to decreasing levels of canopy cover

Abstract

Although clearing of the caatinga forest is conducted primarily to open areas for crop production and to harvest wood, vegetation manipulation is being promoted as a means of increasing forage availability to livestock. Response of caatinga vegetation to various levels of canopy cover removal is being studied in two experiments at the CNPC, Sobral, CE, Brazil. Complete removal of the tree canopy resulted in a six to eightfold increase in first year production of herbaceous vegetation. This magnitude of increase was also true for canopy covers of 20% - 30% and 50% - 60%. Caatinga species coppice readily following cutting and, therefore, canopy cover for the cleared treatment (complete removal) was equal to that of the control (approximately 95%) by the end of the fourth year post treatment. As a result, herbaceous vegetation and leaf litter yields for the two treatments were similar, too. Sabiá (Mimosa caesalpiniaefolia), a tree species which produces palatable browse and valuable wood, responded very favorably to clearing. Not only did many new plants establish, but by the fourth year post treatment sabiá coppice on the cleared areas produced as much as ten times more foliar biomass than did the intact trees on the control area. The high herbaceous vegetation yields under a thinned canopy and the favorable responses to cutting of tree species such as sabiá indicate that a multiple use approach involving selectively thinned caatinga could be developed whereby production of the naturally renewable wood and forage resources would be optimized