Defoliation impacts on coppicing browse species in northeast Brazil

Abstract

A study was conducted to determine if manually cutting coppice growth from the stump once or twice in the first growing season, exposing the coppice to 2 periods of intensive goat browsing, or no defoliation of coppice caused mortality or compensatory growth in 4 tree species of the Brazilian caatinga. Sabia' (Mimosa caesalpinia), and catingueira (Caesalpinia pyramidalis) suffered no mortality regardless of treatment, but pau branco (Auxemma oncocalyx), and marmeleiro (Croton hemiargyreus) that were browsed or manually defoliated experienced significant mortality. In the year of treatment undefoliated and browsed trees of all species produced significantly more stem material than manually defoliated plants. Browsed catingueira produced more leaf material than undefoliated or manually defoliated plants. The year after treatment, undefoliated trees produced more leaf and stem than either browsed or manually defoliated trees. Normally pau branco and marmeleio are not browsed and both species suffered significant mortality after manual or browsing defoliation, suggesting they are not adapted to herbivory; whereas intact sabia' and catingueira are palatable and suffered no mortality following browsing or removal of coppice. Undefoliated trees produced more biomass than browsed or manually defoliated trees; thus, removal of coppice growth does not stimulate increased forage production. Browsed trees produced regrowth during the dry season when these species are normally leafless. Manually defoliated trees did not, highlighting the fact that trees respond to browsing differently than to manual defoliation. This study demonstrates that regenerating caatinga stands can be manipulated through browsing or manual defoliation of coppice to achieve specific management objectives.