Comparing different densities of pigeon pea (Cajanus cajan (L.) Millsp.) for restoration of forest reserves in Pontal do Paranapanema, SP

Increasing reductions of tropical forests, especially in the Mata Atlantica bioma, have led to serious environmental consequences. However, there is a great need for new restoration models in tropical forestry. The aim of this work was to evaluate alternatives to accelerate restoration and decrease costs for such restoration. Pigeon pea may help ecological restoration. The main hypothesis was that different densities of Cajanus cajan can promote ecological restoration. Cajanus cajan was interplanted with native trees in a 2 x 4 m spacing. After 22 and 34 months of planting, four different treatments were evaluated. The treatments were: no guandu between tree lines; two seeds between tree lines; elimination of the one guandu plant after six months of planting and complete elimination of the two guandu plants after six months of planting. For data collection 100 trees were chosen by chance in each treatment. The results showed an increase in height where Cajanus cajan was present. 34 months after planting the total basal area of native trees planted close to two pigeon pea plants were significantly smaller when compared to those planted close to one pigeon pea per tree. The mortality of pioneer species without pigeon pea was significantly superior to the mortality of non-pioneer species in the same condition. The soil structure around Cajanus cajan showed a larger content of organic matter and less phosphorus, when compared to the testimony treatment. This study suggests negative and positive effects for the intercropping of Cajanus cajan and the native trees; therefore the first hypothesis is refuted and the second hypothesis is not.