Growth of indigenous mountainous Indonesian Hibiscus macrophyllus in agroforestry system from various age, seed sources and slopes

Abstract

In East Java, forest degradation on the slopes resulted landslides during rainy seasons, because of a farming change toward mountainous terrain. Government encouraged community to build agroforestry systems using Hibiscus macrophyllus, therefore this study examined the H. macrophyllus growth on slopes from 15° to 75° in two trials from 6 months to three years, using a variety of eight seed sources. The objectives of this study were to determine the growth responses of H. macrophyllus of various ages on various land slopes in two locations (Mount Kawi and Mount Willis). The trials in two locations were established by Incomplete Block Design (IBD) comprising of 4-6 replications with 50 open pollinated families from 8 seed sources. In both trials, this plant was grown alongside agricultural crops. The General Linear Model (GLM) was used to analyse the growth data from two trials to identify variations in plant age, location, slopes and seed sources. The results showed that growth was significantly different between locations, slopes, seed source and ages. It was found that there was an interaction between site and slope. Height varies, with three times more in Willis (72.6 cm) than in Kawi (26.05 cm). Dramatic changes in slopes, induce more than doubled the height between 75° and 30° slope, which influence considerable wood biomass volume at the end. Increasing growth occurred from 6 months to 3 years i.e.: >7.5 times for height and >6.5 times for diameter. This fast growth at 3 years immediately benefits in ameliorating the mountainside ecosystem. Seed sources perform differently, and considerable variances also occur between families. Comparison between the lowest and greatest seed sources were 40% greater in height and 9% in diameter, indicating that seed sources, as well as family selection, should be considered. The best growth response of H. macrophyllus was found at Willis after 3 years at 30° slope.

Keywords

• Hibiscus macrophyllus
• Slope
• Growth
• Seed Source
• Agroforestry