Karyati, Ipor IB, Jusoh I, Wasli ME. 2018. Tree stand floristic dynamics in secondary forests of different ages in Sarawak, Malaysia. Biodiversitas 19: 717-723. Succession is a series sequential processes of the development of floristic community which involves changes in community structure, species composition and diversity over time. The information on tree stand floristic dynamics of various stages of succession in secondary forests in Malaysia is currently lacking. This study was conducted to determine tree stand structure, floristic composition, and species diversity in various stages of secondary forest development in the study areas. A total of 997, 1,842, and 834 tree stems with diameter at breast height (DBH) of > 5 cm were recorded in one-hectare-plots of 5, 10, and 20 year old secondary forests, respectively. The ten most common species in 5 and 10 year old of secondary forests consisted mostly of light demanding species. In the 20 year old secondary forest, these species did not exist. Macaranga gigantea was the most dominant tree species in the 5 and 10 year old secondary forests in terms of basal area and volume per hectare. The most common species, based on density, basal area, volume, and Importance Value Index (IVi), in the 20 year old secondary forest was Adinandra dumosa. The diversity and richness indices of the 10 year old secondary forest were the highest among all study sites.

Upaya revegetasi pada lahan pasca tambang diharapkan dapat memperbaiki sifat-sifat tanah, memulihkan kesuburan tanah, dan memperbaiki iklim mikro tanah. Tujuan penelitian ini adalah menganalisis karakteristik suhu dan kelembaban tanah pada lahan revegetasi berbeda umur. Suhu dan kelembaban tanah diukur pada kedalaman 10 cm dan 20 cm pada revegetasi pasca tambang umur 3, 4, 5, 6, dan 7 tahun. Hasil menunjukkan bahwa suhu tanah tertinggi pada kedalaman 10 cm dan 20 cm masing-masing sebesar 27,7ºC dan 26,6ºC pada revegetasi umur 3 tahun. Sedangkan suhu tanah terendah pada revegetasi umur 7 tahun pada kedalaman 10 cm dan 20 cm berturut-turut sebesar 26,1ºC dan 24,9ºC. Kelembaban tanah tertinggi adalah 87,8% (pada kedalaman 10 cm) dan 88,0% (pada kedalaman 20 cm) pada lahan revegetasi umur 7 tahun. Ditambahkan, kelembaban tanah terendah pada kedalaman 10 cm (81,3%) dan 20 cm (81,5%) adalah pada kawasan revegetasi umur 3 tahun. Perbedaan umur tanam berpengaruh terhadap fluktuasi iklim mikro, termasuk suhu dan kelembaban tanah pada kedalaman tanah berbeda.

Sarminah S, Karyati, Karmini, Simbolon J, Tambunan E. 2018. Rehabilitation and soil conservation of degraded land using sengon (Falcataria moluccana) and peanut (Arachis hypogaea) agroforestry system. Biodiversitas 19: 222-228. Rehabilitation and soil conservation effort on degraded lands is not always a success. Multiple factors, such as the field’ biogeophysical conditions and the choice of suitable plant species determine the effectivity of the rehabilitation program. Our research aimed to implement agroforestry system of sengon (Falcataria moluccana) and peanut (Arachis hypogaea) on degraded land at different soil slopes (a steep and a slightly steep slope gradient) and to analyze the effect of the system on silvicultural and hydro-orological aspects of the degraded land. The silvicultural parameters examined in this study were the ground coverage of peanut growth and the stem diameter and height of sengon trees. Meanwhile, the hydro-orological parameters included potential erosion rate, erosion hazard index, and erosion hazard level. Our study revealed that on the land with the slightly steep slope (15-25%), the survival rate of sengon reached 90%, the ground coverage of the peanuts was 70-80%, the diameter and height increment of sengon trees reached 2.47 cm/year and 17.58 cm/year, respectively. Meanwhile, the potential erosion rate was 20.05 ton/ha/year, with an erosion hazard index of 0.80 (low) and a low hazard level. In the steeper ground (25-40%), the survival rate of sengon reached 90%, the peanut coverage was 50-60% and the diameter and height increment of the sengon were 2.37 cm/year and 16.41 cm/year, respectively. In the steep ground, potential erosion rate was 45.50 ton/ha/year, with an erosion hazard index of 3.25 (moderate) and a low hazard level. We concluded that the rehabilitation and soil conservation using sengon-peanut agroforestry system effectively suppressed erosion rate to a low erosion hazard.

There is a large area of abandoned land that is not taken manage of after plantation activities in the tropic. These abandoned gardens which have been neglected for a long time have important ecological and economic values. This study aims to assess the existence of abandoned land in the tropic from an ecological and economic perspective. The ecological aspects assessed were stand structure, floristic composition, and species diversity. Meanwhile, the economic aspects analyzed were log price, harvesting cost, profit margin, and stumpage value. The vegetation survey was carried out on all woody trees with a diameter at bresst height (DBH) > 5 cm in 10 subplots each sized 20 m × 20 m. A total of.192 trees were recorded of 29 species belonging to 19 genera and 17 families. The most dominant species were Macaranga triloba (Importance Value, IV of 46.16), Macaranga tanarius (IV of 22.97), and Nephelium lappaceum (IV of 20.94). The indexes of diversity, dominance, evenness, and richness in the studied plots were 1.33, 0.06, 0.40, and 5.33, respectively. The means of wood price, logging cost, profit margin, and stumpage value at abandoned land were USD199.55 m-3, USD69.01 m-3, USD25.45 m-3, and USD51.56 ha-1, respectively. The abandoned lands with high ecological and economic value indicate the important role of abandoned lands in the secondary succession process in the tropics.

Abstract. Karyati, Ipor IB, Jusoh I, Wasli ME. 2019. Allometric equations to estimate the above-ground biomass of trees in the tropical secondary forests of different ages. Biodiversitas 20: 2427-2436. The allometric equations for trees of secondary forests of different ages in abandoned lands after shifting cultivation are still rarely available. The objective of this study was to develop allometric equations to estimate the above-ground biomass (AGB) of trees (DBH of > 5 cm) in the tropical secondary forest of different ages, namely 5, 10, and 20 years after abandonment. The selected trees in this study represented the dominant and rare species and DBH classes in each study site. The trunk dry biomass and AGB showed strong correlations (adjusted R2= 0.59-0.95) with diameter at breast height (DBH) and height. The leaf and branch dry biomass had weak correlations with height (adjusted R2=0.36-0.50). The developed allometric equations were suitable for trees of secondary forests of different ages, because the selected samples used in the destructive method were based on a field inventory data of forest structure and floristic composition.