Form factors and volume models are often be used in the estimation of tree volumes. However, a few studies have developed and evaluated the accuracy of form factors and volume models for estimating tree volumes of community forests. This study aimed to formulate form factors and volume models and assess their prediction accuracy for estimating tree bole volumes of mahogany at community forests in Central Java. This study used 120 sample trees with diameters of 6–38 cm to formulate artificial and absolute form factors and to develop tree bole volume models. These form factors coupled with bole height and total height were used in simple volume equations. Regression analyses were used to develop volume models using the diameter and total height as predictors. The simple volume equations and volume models' prediction accuracy was evaluated using a cross-validation dataset and independent dataset (30 sample trees). The artificial form factor (0.68 ± 0.11) of mahogany, which was higher than the absolute form factor (0.46 ± 0.09), provided accurate estimates of tree bole volumes when it was used with the bole height instead of the total height. The volume model that uses diameter and total height produced the most accurate estimates, while the volume model that uses diameter alone provided the most practical yet reliable tool for estimating tree bole volumes of mahogany. The results of this study are useful for improving community forest management.

The Subur farmer group is located in Sugihwaras Village, Maospati District, Magetan Regency, East Java which develops sugarcane (Saccharum officinarum) and teak (Tectona grandis) with a monoculture pattern. Monoculture cultivations produce a single income for farmers, hence other adaptive intolerant commodities and sites that generate alternative income are needed. One of them is Porang (Amorphophallus muelleri Blume). The farmer group’s knowledge and skills related to porang cultivation are very limited. The aims of this activity were: 1) To train farmer groups related to porang cultivation planted with agroforestry patterns; 2) To analyze knowledge changes of farmer groups regarding porang cultivation; and 3) To evaluate the implementation of the training program. The results showed that training on porang cultivation and making agroforestry demonstration plots were able to increase the knowledge of the Subur farmer group. The pre-test score was 65,1 (55%) while the post-test was 88,6 (75%). Based on the evaluation of the assessment of training activities by farmers, as many as 74,3% of farmers stated that they strongly agreed that the porang cultivation training was very useful and suitable for their needs. In addition, the activity feasibility analysis showed that this training is categorized as very feasible to be implemented with a score of 94%. Porang cultivation training for the Subur farmer group was able to increase knowledge and the potential to earn additional income for the people of Sugihwaras Village, Magetan Regency, East Java.