Budi Leksono

Reliable data on CO₂ quantification is increasingly important to quantify the climate benefits of forest landscape restoration and international commitments, such as the Warsaw REDD+ Framework and Nationally Determined Contributions under the Paris Agreement. Calophyllum inophyllum L. (nyamplung as a local name or tamanu tree for the commercial name) is an increasingly popular tree species in forest landscape restoration and bioenergy production for a variety of reasons. In this paper, we present allometric equations for aboveground biomass (AGB), belowground biomass (BGB), and total above- and belowground biomass (TABGB) predictions of C. inophyllum L. Data collection was carried out twice (2017 and 2021) from 40 trees in Java, Indonesia. Allometric equations using the natural logarithm of diameter at breast height (lnDBH) and ln height (lnH) for biomass prediction qualified the model’s fit with statistical significance at 95% of the confidence interval for AGB, BGB, and TABGB predictions. The results showed that the linear models using both lnDBH and lnH were well fit and accurate. However, the model with lnDBH is more precise than the model using lnH. Using lnDBH as a predictor, the R² values were 0.923, 0.945, and 0.932, and MAPE were 24.7, 37.0, and 25.8 for AGB, BGB, and TABGB, respectively. Using lnH as a predictor, the R² values were 0.887, 0.918, and 0.898 and MAPE were 37.4, 49.0, and 39.8 for AGB, BGB, and TABGB, respectively. Consequently, the driven allometric equations can help accurate biomass quantification for carbon-trading schemes of C. inophyllum L.

Indonesia has 14 million ha of degraded and marginal land, which provides very few benefits for human wellbeing or biodiversity. This degraded land may require restoration. The leguminous tree Pongamia pinnata syn. Milettia pinnata (pongamia) has potential for producing biofuel while simultaneously restoring degraded land. However, there is limited information on this potential for consideration. This paper aims to address the scientific knowledge gap on pongamia by exploring its potential as a biofuel and for restoring degraded land in Indonesia. We applied a literature review to collect relevant information of pongamia, which we analyzed through narrative qualitative and narrative comparative methods with careful compilation and scientific interpretation of retrieved information. The review revealed that pongamia occurs naturally across Indonesia, in Sumatra, Java, Bali, Nusa Tenggara and Maluku. It can grow to a height of 15–20 m and thrive in a range of harsh environmental conditions. Its seeds can generate up to 40% crude pongamia oil by weight. It is a nitrogen-fixing tree that can help restore degraded land and improve soil properties. Pongamia also provides wood, fodder, medicine, fertilizer and biogas. As a multipurpose species, pongamia holds great potential for combating Indonesia’s energy demand and restoring much of the degraded land. However, the potential competition for land and for raw material with other biomass uses must be carefully managed.

This study spatially estimated degraded lands in Indonesia that have limited functions for food production, carbon storage, and conservation of biodiversity and native vegetation and examined their suitability to grow biodiesel species (Calophyllum inophyllum, Pongamia pinnata, and Reutealis trisperma) and biomass species (Calliandra calothyrsus and Gliricidia sepium). Results showed ~3.5 million ha of degraded lands potentially suitable for these species in Indonesia. With the all-five-species scenario, these lands had the potential to produce 1105 PJ year⁻¹ of biomass and 3 PJ year⁻¹ of biodiesel. With the biodiesel-only-species scenario, these lands showed the potential to produce 10 PJ year⁻¹ of biodiesel. Despite this energy potential, however, the land sizes were too small to support economies of scale for biofuel production. The study findings contribute to identifying lands with limited functions, modeling the growth of biofuel species on regional lands, and estimating carbon stocks of restored degraded lands in Indonesia.

Pengujian vigor benih menjadi komponen penting dari analisis benih karena vigor benih mempengaruhi kemampuan benih untuk tumbuh dan berproduksi normal pada kondisi sub optimal. Penelitian ini bertujuan untuk mengetahui vigor kekuatan tumbuh relatif dan vigor daya simpan relatif pada benih Acacia crassicarpa A.Cunn.Ex Benth dari 5 sumber benih. Rancangan percobaan yang digunakan adalah rancangan acak lengkap pola faktorial dengan ulangan 4 kali, setiap ulangan terdiri dari 100 benih. Hasil penelitian menunjukkan bahwa benih A. crassicarpa yang berasal dari sumber benih kebun benih semai (KBS) memiliki vigor yang lebih baik dibandingkan dengan benih dari areal produksi benih (APB). Vigor kekuatan tumbuh benih KBS memiliki peningkatan daya berkecambah sebesar 11% dan t kecepatan berkecambah sebesar 0,8% per etmal. Vigor daya simpan benih dari KBS memiliki peningkatan daya berkecambah sebesar 12% dan kecepatan berkecambah sebesar 0,84% per etmal.

Vigor benih dapat dibagi dua yaitu vigor kekuatan tumbuh yang mencerminkan vigor benih bila ditanam di lapangan dan vigor daya simpan yang mencerminkan kemampuan benih untuk berapa lama benih dapat disimpan. Benih yang berasal dari kebun benih semai (KBS) memiliki keragaman yang tinggi secara genetik dan bila penanganannya dilakukan secara benar maka akan memiliki viabilitas dan vigor yang baik. Penelitian ini bertujuan untuk mengetahui vigor kekuatan tumbuh relatif dan vigor daya simpan relatif pada benih A. crassicarpa dari beberapa sumber benih. Rancangan percobaan yang digunakan adalah rancangan acak lengkap pola faktorial dengan ulangan sebanyak 4 kali, setiap ulangan terdiri dari 100 benih. Hasil penelitian menunjukkan bahwa benih A.crassicarpa yang berasal dari sumber benih KBS (kebun benih semai) memiliki vigor yang lebih baik dibandingkan dengan benih dari APB (areal produksi benih) yaitu vigor kekuatan tumbuh relatif dapat meningkatkan daya berkecambah sebesar 11% dan mempercepat kecepatan berkecambah sebesar 0,8%/etmal dan vigor daya simpan relatif dapat meningkatkan daya berkecambah sebesar 12% dan mempercepat kecepatan berkecambah sebesar 0,84%/etmal.

TEKNIK PERLAKUAN PENDAHULUAN DAN METODE PERKECAMBAHAN UNTUK MEMPERTAHANKAN VIABILITAS BENIH Acacia crassicarpa HASIL PEMULIAAN

The first generation genetic gains in four second-generation seedling seed orchards of Eucalyptus pellita established at two locations in Indonesia (Kalimantan and Sumatra) were examined by analyzing data on the height, diameter and stem form of the trees during years 1 to 3. The seed orchards each consisted of 60 open-pollinated families: 48–49 families from first-generation plus trees (improved population) and 11–12 families from natural forest (unimproved population). The realized gains for height and diameter were ca. 16 and 19%, respectively. These gains were highly significant and consistent, irrespective of age and location. However, the gains in stem form were much lower (4%) in Kalimantan than in Sumatra (21%) and only significant in the latter, possibly because of the more intensive silvicultural management regimes at the Sumatran sites. The results confirmed that the first-generation tree improvement program for E. pellita has been effective in Indonesia, and that it should provide improved seeds for operational plantation, thus raising their productivity.

The time trend of genetic parameters related to diameter growth was investigated using data at ages from 1 to 6 years to determine the optimum age for selection in four seedling seed orchards of Eucalyptus pellita in South Kalimantan and Riau (Sumatra), Indonesia. The seed orchards at each location were from three geographically distinct provenances from Papua New Guinea. The pooled sum of squares and sum of cross products derived from an analysis of variance of growth of the three provenance populations were used to estimate genetic parameters at each location. Because the genetic parameters at rotation age, 8 years in this study, were not available, they were estimated using functions derived from their time trends. Phenotypic variances and genetic variances calculated at each age were converted to the corresponding square roots, and then analyzed by the linear regression using means as independent variables. The trend of juvenile–mature correlation was fitted by a modified Richards function with the ratio of the older diameter mean to the juvenile diameter as an independent variable. Early selection always resulted in more genetic gain per year than selection at rotation age, and the optimum age for selection, where genetic gain per year was maximized, was found to be 4 and 5 years in the two locations.