Assessing land rehabilitation in Indonesia : a case study in Karanganyar District, Central Java Province : a thesis presented in partial fulfilment of the requirements for the degree of Master of Environmental Management at Massey University, Manawatu, New Zealand
The Ministry of Forestry (MoF) has established hundreds rehabilitation projects to improve productivity of degraded land under the National Movement of Forest and Land Rehabilitation (GN-RHL/Gerhan) scheme. In Karanganyar Regency, Java, MoF?s two-year assessments of these projects have shown high seedling survival rates and detailed the extent of the rehabilitated area but there is no subsequent information on tree growth and the maintenance of rehabilitated areas.
This research assessed the longer term success of the Gerhan projects. Stand density, stem diameter and height of timber species: teak (Tectona grandis), mahogany (Swietenia macrophylla), red cedar/suryan (Toona sureni) were measured. The productivity of Multi Purposes Tree Species (MPTS) in three sub-districts (10 villages) and area planted-maintained were also observed and estimated. At each village four 0.04 ha circular plots were established. Species, stem diameter and height of all trees in each plot were recorded. Mean height and diameter for the main timber species in each sub-district were compared with growth model (Harbagung, 2010; Orwa et al., 2009) predictions, while MPTS productivity was compared to Ministry of Agriculture (MoA)?s guidelines. The extent of the area maintained was also compared to the MoF standard of 55%. All projects below this standard were considered unsuccessful.
Stand density ranged from 575-2,488 stems/ha in different districts, higher than the MoF minimum (400 stems/ha), a result of supplementary planting by farmers. Albizia (Paraserianthes falcataria) was the most commonly planted supplementary species. Comparison of mean stem diameter and height for each district revealed that stem diameter for teak and mahogany, 11.5–12.7 cm and 9.8-11.3 cm respectively, generally exceeded the diameters predicted by the growth models, 10.4 cm and 10.0 cm respectively. In contrast, heights, 7.8-11.8 m and 6.7-7.8 m for teak and mahogany respectively, were lower than those predicted by the models, 13.4 m and 11.4 m respectively while diameter (10.0-11.3 cm) and height (6.9–8.9 m) for suryan were similar to those predicted by the growth model (11.2 cm and 7.2 m respectively). The area maintained varied; 3 villages in Tawangmangu ranged from 61-91%, while those in Jumantono and Matesih ranged from 21% to 34%.
In terms of tree growth, the projects can be categorised as successful, especially for teak and mahogany suggesting that species selection was appropriate. For MPTS productivity, all No villages achieved success with MPTS projects mostly because of poor management. Using the criteria of planted area maintained, the Gerhan was unsuccessful in Jumantono and Matesih but that in Tawangmangu was categorised as successful.
Keywords: GN-RHL/Gerhan, Karanganyar District, stand density, diameter, height, teak, mahogany, suryan, Multi Purposes Tree Species