Evaluating the sustainability of tree fodder harvesting: A modelling approach

摘要

Tree fodder is harvested by means of periodic primings. The cutting interval of fodder trees is ually quite short, because the proportion of nitrogen-rich foliage out of total harvest is high in the young resprouts (Catchpoole and Blair, 1990), and the nutritive value of the young leaves is high (Mochiutti, 1995). Short cutting interval also reduces forage loss in litterfall. The tree regrowth following the pruning depends on the reserves of non-structural carbohydrates (Erdmann et al., 1993; Tschaplinski and Blake, 1994), and the pruning interval must be long enough to allow for the regeneration of these reserves. Pruning of dinitrogen fixing legume trees, which are common in tree fodder production, causes turnover of nodules and subsequent cessation of Nj fixation (Nygren and Ramirez, 1995). The dieback and renodulation rate seem to depend on pruning intensity (Nygren and Cruz, 1998). In this paper, we used a process-based tree growth model, which takes into account the reserve carbohydrate and N2 fixation dynamics (Berninger et al., 2000), for evaluating the effects of four pruning intensities on 10-year productivity and N yield of Gliricidia sepium (Jacq.) Kunth ex Walp., a legume tree common in silvopastoral systems throughout the tropics (Simons and Stewart, 1994).