Guandu bean (Cajanus cajan (L.) Millsp.) on tropical forest restoration

Abstract

This work aims to evaluate alternative models in forest restorations by means of agroforestry systems, where a leguminous species is incorporated to the system. The hypothesis is that guandu bean Cajanus cajan (L.) Millsp., in combination and intercropped with native species, can promote restoration by decreasing mortality and increasing tree basal area and height. Cajanus cajan was planted in line with the forest seedlings in 2 x 4 m spacing. Four different treatments were analyzed; 1) control, with no Cajanus cajan ; 2) one seedling of Cajanus cajan between the forest seedlings in the plantation line; 3) two seedlings of Cajanus cajan between the forest seedlings in the plantation line; and 4) full harvest Cajanus cajan six months after plot implementation. In each treatment, 100 native trees (Fifty pioneer, and fifty non pioneer trees) were measured and evaluated in mortality rates, height, and basal diameter. Guandu planting reduced pioneer mortality, increased basal area, and tree height of all species. In spite of the mortality was not affected by guandu density, the density of one plant of guandu was associated with larger basal area and tree average height. The mortality reduction of non pioneers on the absence of guandu trees was interpreted as a response of antropic pioneers to the increased solar radiation. This result points to the differences in tree behavior between fertile gaps (on which the classification on sucessional stages was based) and degraded areas. The positive effects of guandu planting recommend its use for the ecological restoration cost reduction.