BIODIVERSITAS ISSN: 1412-033X Volume 22, Number 4, April 2021 E-ISSN: 2085-4722 Pages: 1750-1756 DOI: 10.13057/biodiv/d220419 Application of selected teak clone and organic fertilizer to accelerate rehabilitation of lowland forest in Java, Indonesia SURYO HARDIWINOTO, FIQRI ARDIANSYAH, WIDIYATNO ♥ Department of Silviculture, Faculty of Forestry, Universitas Gadjah Mada. Jl. Agro, Bulaksumur, Sleman 55281, Yogyakarta, Indonesia. Tel.: +62-274-550541, ♥ email: widiyatno@ugm.ac.id Manuscript received: 16 December 2020. Revision accepted: 11 March 2021. Abstract. Hardiwinoto S, Ardiansyah F, Widiyatno. 2021. Application of selected teak clone and organic fertilizer to accelerate rehabilitation of lowland forest of Java, Indonesia. Biodiversitas 22: 1750-1756. Lowland forest in Java Island Indonesia is dominated by teak forest. However, for some decades, the forest has degraded and decreased teak wood production. Rehabilitation of the degraded forest is needed to accelerate the forest land cover. Vegetative propagation of selected clones is one of the techniques used in the asexual reproduction of plants to maintain superior genetics from ancestors to their offspring. In addition, adding organic fertilizer can improve the chemical and physical properties of degraded sites. In this study, vegetative propagation techniques of selected teak clones and addition of organic fertilizer were used to rehabilitate the degraded forest. The objectives of the research were to determine the best propagation technique and appropriate dosage of organic fertilizer toward the early growth of clonal teak plantations. The results showed that the height and diameter parameters did not significantly differ for vegetative propagation and interaction with organic fertilizer dosage (P > 0.05). However, the dosage of organic fertilizer significantly increased the DBH of the teak (P < 0.05), although the height parameter did not significantly differ among dosages of organic fertilizer (P > 0.05). The best dosage of organic fertilizer was 5 kg/individual, under which the average growth in height and diameter of teak at 14 months was 3.79 and 5.60 cm, respectively. This suggests that vegetative propagation of selected teak clones and addition of 5 kg/individual organic fertilizer could be implemented to support the successful rehabilitation of degraded forests. Keywords: Degraded forest, rehabilitation, selected teak clone, vegetative propagation, organic fertilizer INTRODUCTION Teak is one of the most valuable species developed in the lowland forests (Bailey et al. 2005; Pandey and Brown 2000), and the total area of natural and planted teak forest worldwide is 29 million ha and 4.35-6.89 million ha, respectively (Koller and Kleine 2017a)..Teak is known to have good wood quality in terms of color and texture as well as ease of wood processing and resistance to termites, mold, and weather (Kaosa-ard 1998). Worldwide demand for teak is high, with about 2.0-2.5 million cubic meters of teak roundwood harvested annually from natural and planted forests (Koller and Kleine 2017b). In Indonesia, the demand for teak is increasing because it supports the teak wood processing industry, which produces wood products such as flooring, furniture, and so on. Unfortunately, teak wood production has recently declined, especially in natural forests, due to overcutting, agricultural expansion, grazing, etc. (Koller and Kleine 2017b). In Indonesia, forest degradation in Java Island dominated by teak forest was more than 14,000 ha.year -1 and dominated by young age classes of tree (MOEF 2019). Thus, the deficit of teak wood was more than 2,000,000 m 3 per year (Iskak 2005), resulting in the instability of the teak wood processing industry. Forest rehabilitation aims to restore the capacity of degraded land to produce the forest products and services of a forest (ITTO 2002). One benefit of forest rehabilitation improves the economic value of degraded forests that use the species suitable for existing or potential markets (ITTO 2001; Lamb and Gilmour 2003). To address the rehabilitation of degraded lowland forests in Java island, selected clonal teak material should be used to support the success of rehabilitation program to increase forest productivity and forest land cover (Evans 2009; Evans and Turnbull 2004). On the other hand, the soil characteristic of Java lowland forest is suitable for teak plantation (Tanaka et al. 1998). Clonal forestry of teak begins with plant breeding. The teak breeding program in Indonesia was initiated by establishing cooperation between the Faculty of Forestry UGM and Perum Perhutani in the 1980s. This program has successfully collected 600 plus trees from all teak distributed in Indonesia, both inside and outside Java. Thus, the plus trees of teak were established as the clonal bank, progeny test, and ex-situ teak conservation model. The results of progeny and clonal test showed that the selected teak clones could grow well at various sites (Na'iem 2012) and grow well in degraded areas, with annual diameter increase of >3 cm (Budiadi et al. 2017). This technique is expected to improve rehabilitation success using selected teak clones in Java, which currently has 3 m³ ha -1 year -1 (Pandey and Brown 2000). Studies on clonal forestry of teak have mainly focused on selection techniques for superior teak cloning (Palanisamy et al. 2009), seed propagation techniques for teak clones in nurseries (Goh et al. 2007; Adinugraha and Mahfudz 2014), and the effects of IBA dosage on clone