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The role of young generations including students was crucial in orang utan conservation. They are not only agent of change, but they are also capable of distinguishing attitudes which are able to influence policy in the future. The purpose of this study was to examine high school students’ perceptions of establishment of the orang utan sanctuary in Balikpapan Bay. We used quantitative and qualitative approaches for data collection with students on the grade of XII as respondent. Data was analyzed descriptively and quantitatively. The findings showed that students had good perceptions towards unreleased orang utan conservation. They agreed that the orang utan sanctuary should be established. Students also had positive perceptions relating to the positive impacts of orang utan sanctuary on the village and environment. However, students had neutral perceptions towards negative impacts of orang utan sanctuary. There were no differences between male and female students’ perceptions towards the establishment of orang utan sanctuary. Conversely, male and female students’ perceptions in regards with the impacts of orang utan sanctuary on the village and environment were differed.

Some small islands in Balikpapan Bay consist of dry land which may have different vegetation structure and composition. Our study was the first to uncover vegetation conditions and soil proper-ties of dry land on small islands in Balikpapan Bay, which has never been conducted before. The research was carried out on Kalawasan and Karantina islands. Information on vegetation was obtained by applying a line transect method. Data on soil properties were col-lected by setting up 3 sampling plots in each transect of vegetation. Parameters used for analysing vegetation including relative densi-ty, relative frequency, relative dominance, Shannon-Wiener diversi-ty index, evenness index, and similarity index. Meanwhile, data on soils were analysed descriptively. Trees on Kalawasan island were comprised of 241 individuals belonging to 21 species. There were 61 individuals (22 species) of trees on Karantina island. The diver-sity index of trees on Kalawasan and Karantina island was 2.55 and 2.72, respectively. The tree evenness index was 0.84 on Kalawasan island and 0.88 on Karantina island. The index of similarity for trees between the two islands was 0.21. Furthermore, the soil character-istics on Kalawasan and Karantina islands showed similarities. In general, soil in Kalawasan and Karantina islands could be catego-rised as marginal soil which was common in East Kalimantan. Con-sidering the rapid loss of tropical forests in the mainland of Kali-mantan indicates that the small islands of Balikpapan Bay play an important role in future biodiversity conservation in East Kalimantan.

Post-coal mining areas need rehabilitation to restore its functionality. Not all plants could grow well on bare ex-coal mining area because of the excessive light intensity and extreme temperature fluctuations. This study is aimed to determine suitable local tree species for rehabilitating mined areas. Planting was carried out in November 2012, and observations were made in November 2015. The study site was in the district of Samboja, Kutai Kartanegara, East Kalimantan Province, Indonesia. Research results revealed that seven tree species survived well in the ex-coal mining land, i.e., Vitex pinnata L., Syzygium scortechinii (Merr.) Merr. & Perry, Syzygium polyanthum (Wight) Walp., Shorea balangeran (Korth.) Burck, Macaranga motleyana (Mull.Arg.) Mull.Arg., Cleistanthus myrianthus (Hassk.) Kurz and Syzygium lineatum (DC.) Merr. & L.M. Perry. From the seven species V. pinnata, Sy. scortechinii and Sy. polyanthum performed best in both survival and growth rates. This study suggests those three species are excellent local tree species for ex-coal mining rehabilitation, not only because of their high survival rate (≥80%) and fast-growing but also they produce favourable fruits and flowers for wildlife.

Land degradation in Borneo, one of the world's richest biodiversity hotspots, is extensive. In East Kalimantan, 5,000,000 ha of land are zoned for surface‐mined coal. Deforestation from this mining threatens biodiversity and results in soil degradation, erosion, and polluted runoff, all directly impacting human populations. Revegetation methods developed for temperate forests are commonly used globally for mine rehabilitation. However, few empirical studies of native forest restoration as part of mine rehabilitation exist from wet tropical regions. Here, a chronosequence was established to observe forest succession under leguminous plantations at the PT Singlurus Pratama coal mine in East Kalimantan, Indonesia. Soil and natural regeneration data were recorded from samples of ten 20 × 60‐m plots randomly located in plantings aged 2, 7, and, 9 years postmining. Linear models (LMEMs) did not reveal greater soil pH, woody plant diversity, or soil phosphorus and nitrogen in older plantings. Rather, they showed higher soil carbon in older plantings, whereas nitrogen and pH were positively correlated with woody species diversity and abundance. Graminoids were less abundant, but ferns were more abundant in older sites in an ordination analysis. The implications are exotic tree plantations shade‐out competitive understory herbaceous species (such as graminoids), opening growing space for other vegetation. However, the establishment of woody species is spatially limited possibly by differences in soil degradation among sites. Our results suggest that planting leguminous trees alone may not be sufficient to restore native forests, and future management should conserve and facilitate the establishment of tropical forest topsoil.

Understanding local community perceptions towards ecotourism is important since community has a crucial role in determining sustainable ecotourism. This research aimed to identify community perceptions towards impacts of ecotourism as well as to analyse the relationships between perception and ecotourism responsible behaviour. Other goal of this study was to analyse the relationship between ecotourism responsible behaviour and social factors. Data was collected in 4 villages adjacent to the Balikpapan bay, namely Maridan, Telemow, Binuang, and Mentawir. We used the quota technique to sample respondents. For each village, we took 40 respondents randomly. Data was then analysed using descriptive statistics, Spearman correlation, and Kruskal Wallis test. We found that community around the Balikpapan Bay thought that ecoto u rism was able to bring positive impacts for village and community. A Kruskal Wallis test revealed that there was no significant difference regarding perceptions among 4 villages. We found that there was a correlation between ecotourism responsible behaviour and gender. Implications of community’s perceptions to ecotourism development around the Balikpapan bay were then discussed. Keywords: ecotourism, perception, benefits, behaviour towards ecotourism, Balikpapan Bay

Simple Summary Like humans, great apes have extended childhoods during which they depend on maternal pedagogy. To help rescued orphans recover from maternal loss our rehabilitation programme is modelled on the natural infant development of orangutans. Orphaned apes cannot be released back into freedom before they have learned the skills necessary to survive alone. To prevent suffering after release we documented the development of survival skills during the rehabilitation process. Seven orangutan orphans aged 1.5–9 years were observed over 18 months in their forest school, immersed in a natural forest environment with human surrogate mothers and other orphans. Social interactions deviated from wild mother-reared immatures: Infant orphans spent more time playing with peers, rested less, and were far from their human surrogate mothers earlier and often than wild immatures are from their biological mothers. Around weaning age, 4- to 7-year-old orphans took up a typical orangutan life-style: they interacted less with human surrogate mothers and peers, stayed high in the trees and slept in nests in the forest. Their time budgets resembled those of wild adults. We conclude that it is not only ethical but also possible to assess survival competences of rehabilitant orphans before release and choose release candidates accordingly. Abstract Orangutans depend on social learning for the acquisition of survival skills. The development of skills is not usually assessed in rescued orphans’ pre-release. We collected data of seven orphans over an 18-months-period to monitor the progress of ontogenetic changes. The orphans, 1.5–9 years old, were immersed in a natural forest environment with human surrogate mothers and other orphans. Social interactions deviated significantly from those of wild mother-reared immatures. Infants spent more time playing socially with peers, at the expense of resting and solitary play. Infants were also more often and at an earlier age distant from their human surrogate mothers than wild immatures are from their biological mothers. We found important changes towards an orangutan-typical lifestyle in 4- to 7-year-old orphans, corresponding to the weaning age in maternally reared immatures. The older orphans spent less time interacting with human surrogate mothers or peers, started to use the canopy more than lower forest strata and began to sleep in nests in the forest. Their time budgets resembled those of wild adults. In conclusion, juvenile orphans can develop capacities that qualify them as candidates for release back into natural habitat when protected from humanising influences and immersed in a species-typical environment.

Indonesian government has enacted regulations requiring reclamation and rehabilitation activities on post coal mining areas. However, the evaluation related to the ecological restoration concepts is yet unavailable. This study aims to evaluate the regulations on rehabilitation and reclamation of post coal mining areas in Indonesia conforming on ecological restoration concepts. Employing desk study and content anaysis, this research focussed on three technical regulations concerning reclamation guidance and post-mining evaluation guidance, namely ESDM Decree No 7 Year 2014, MoF Decree No P.60/Menhut-II/2009, and MoF Decree No P.4/Menhut-II/2011. Each regulation was comprehensively evaluated whether the regulation already regulates matters relating to ecological restoration criterias, such as biodiversity recovery, soil remediation, planting of local plants, bans on invasive plant species and monitoring and evaluation. The result showed that there was no regulation complying with all ecological restoration criterias. Meanwhile, all the regulations have mandated monitoring and evaluation after rehabilitation and reclamation activities. However, there was no regulation mandating prohibition on planting invasive plant species. In conclusion, regulations related to post coal mining rehabilitation and reclamation have not fully complied with the ecological restoration concepts, therefore improvement to that regulations are necessary.

Muslim T, Sari UK, Yassir I. 2017. The dominant species of herpetofauna in the coal mining area at East Kalimantan, Indonesia. Biodiversitas 18: 773-779. Changing of habitat condition influences the variety of species including Herpetofauna. Herpetofauna is one of the components in the ecosystem that plays an important role, both from the ecological and economical aspect. From the ecological aspect, it has a specific role in the food chain, and it can also be used as a bio-indicator of the environment’s condition. Furthermore, herpetofauna found in reclamation area of coal mining not only stabilizes the ecosystem in the food chain, but also it can be used as a bioindicator of environment changes and the success rate of reclamation. The aim of this research was to find out the community of herpetofauna comprising and dominating the coal mining reclamation area, especially the wet and dry areas. The research location was located at PT. Singlurus Pratama Kalimantan Timur. The methods used in this research were visual encounter survey and patch sampling. This research found 10 species from 5 families of reptiles and 11 species from 6 families of amphibians. The highest dominant index score for reptile was 0.71, found in the fragmented forests. Meanwhile, the dominant reptile species were Eutropis multifasciata (20 individuals), Enhydris enhydris (4 individuals), and Dendrelaphis pictus (4 individuals). The highest dominant index score for amphibian was 1, found in the settling pond. Moreover, the dominant amphibian species were Polypedates leucomystax (42 individuals) and Fejervarya cancrivora (41 individuals). These two species were the ones able to survive in the degraded areas and they were easily found in the areas with disrupted habitats.

Wana Patra Lestari (WPL) is a remaining forest in the center of Balikpapan City. It is located in the working area of PT Pertamina Refinery Unit (RU) V Balikpapan. Besides having cultural and historical value, the existence of the WPL area also has environmental service value as a habitat for birds and mammals. This study aims to analyze the diversity of bird and mammal species in the WPL area. We collected all related bird record by using a combination of point count and mist-netting methods. Furthermore, mammal was sampled by using a combination of line transect, live-trapping, camera-trapping, and also mist-netting survey. The results showed that in the WPL area 17 species of birds and 6 species of mammals were identified. There are 14 species of birds and 2 species of mammals added from previous studies. Of all the identified species, there is only one protected species in Indonesia, namely Elang Bondol (Haliastur indus). Periodic monitoring is needed to find out more about population dynamics and diversity of wildlife in the WPL.

Regeneration of Imperata grassland areas is becoming increasingly important, both to create new secondary forest and to recover the original biodiversity. The diversity of plant communities in secondary succession of Imperata grasslands was studied using 45 subplots of 9 linear transects (10 m x 100 m). Data was collected and all stems over 10 cm dbh were identified, the Importance Values Index (IVI) for all trees were calculated, saplings and seedlings were counted and analysed, and soil samples were taken and analysed. Results showed that after more than 10 years of regeneration, 65 families were encountered consisting of 164 species, which were dominated by Vernonia arborea Buch.-Ham, Vitex pinnata L., Macaranga gigantea (Reichb.f. & Zoll.) Muell.Arg., Symplocos crassipes C.B. Clarke, Artocarpus odoratissimus Miq., and Bridelia glauca Blume. The effects of regeneration, from Imperata grassland to secondary forest, on soil were the strongest in the A-horizon where an increase in carbon, N content, and pH were observed. Our result shows that Imperata grasslands appear to be permanent because of frequent fires and human interferences and so far few efforts have been made to promote sustainable rehabilitation. If protected from fire and other disturbances, such as shifting cultivation, Imperata grassland will grow and develop into secondary forest.

Less than half of anthropogenic carbon dioxide emissions remain in the atmosphere. While carbon balance models imply large carbon uptake in tropical forests, direct on-the-ground observations are still lacking in Southeast Asia. Here, using long-term plot monitoring records of up to half a century, we find that intact forests in Borneo gained 0.43 Mg C ha−1 per year (95% CI 0.14–0.72, mean period 1988–2010) in above-ground live biomass carbon. These results closely match those from African and Amazonian plot networks, suggesting that the world’s remaining intact tropical forests are now en masse out-of-equilibrium. Although both pan-tropical and long-term, the sink in remaining intact forests appears vulnerable to climate and land use changes. Across Borneo the 1997–1998 El Niño drought temporarily halted the carbon sink by increasing tree mortality, while fragmentation persistently offset the sink and turned many edge-affected forests into a carbon source to the atmosphere., The existence of a pan-tropical forest carbon sink remains uncertain due to the lack of data from Asia. Here, using direct on-the-ground observations, the authors confirm remaining intact forests in Borneo have provided a long-term carbon sink, but carbon net gains are vulnerable to drought and edge effects.

Regeneration of Imperata grassland areas is becoming increasingly important, both to create new secondary forest and to recover the original biodiversity. We studied the diversity of plant communities in secondary succession of Imperata grasslands using 45 subplots of 9 linear transects (10 m x 100 m). Data was collected and all stems over 10 cm dbh were identified , the Importance Values Index (IVI) for all trees were calculated, saplings and seedlings were counted and analysed, and soil samples were taken and analysed. Results showed that after more than 10 years of regeneration, 65 families were encountered consisting of 164 species, which were dominated by Vernonia arborea Buch.-Ham, Vitex pinnata L., Macaranga gigantea (Reichb.f. & Zoll.) Muell.Arg., Symplocos crassipes C.B. Clarke, Artocarpus odoratissimus Miq., and Bridelia glauca Blume. The effects of regeneration, from Imperata grassland to secondary forest, on soil were the strongest in the A-horizon where an increase in carbon, N content, and pH were observed. Our result shows that Imperata grasslands appear to be permanent because of frequent fires and human interferences and so far few efforts have been made to promote sustainable rehabilitation. If protected from fire and other disturbances, such as shifting cultivation, Imperata grassland will grow and develop into secondary forest.

Knowledge of the spatial distribution of total carbon is important for understanding the impact of regional land use change on the global carbon cycle. We studied spatial total carbon variability using transect sampling in an Imperata grassland area. Spatial variability was modeled following an isotropic stationary process with spherical and exponential variogram functions. Range and sill were estimated at 100 m and 82.29 ton2 ha-2, respectively. For nugget, sill ratio was estimated at 24%, implying a rather strong spatial dependence. In a subsequent total carbon stock inventory based on the sampling design mentioned above, we applied three types of estimators, namely, “naive average procedure,” “spatial average procedure,” and “spatial optimal procedure.” Estimation of total carbon stock (in ton ha-1) following naive average procedure (which erroneously ignores the spatial dependence) resulted in a considerably too narrow 95% confidence interval of 37.52 to 39.75, whereas the outcomes using spatial average procedure and spatial optimal procedure were 36.54 to 40.73 and 37.14 to 40.78), respectively, using the spherical model, and 36.63 to 40.64 and 37.07 to 40.64, respectively, using the exponential model. Our research indicated that, when total carbon stock estimation is the main goal, random sampling is optimal, whereas wide design sampling (i.e., shortest distance between sampling locations not less than the range) can be preferred in some cases

Penelitian pengaruh penyiapan lahan terhadap pertumbuhan tanaman Shorea leprosula Miq. dan Shorea balangeran (Korth.) Burck telah dilakukan di areal rehabilitasi lahan Samboja Lestari. Tujuan dari penelitian ini adalah untuk mendapatkan informasi pengaruh teknik penyiapan lahan terhadap pertumbuhan S. leprosula Miq. dan S. balangeran (Korth.) Burck yang ditanam pada lahan kritis yang ditumbuhi alang-alang. Empat perlakuan penyiapan lahan yang dicoba dalam penelitian ini adalah sistem cemplongan, jalur, jalur herbisida dan herbisida total. Rancangan percobaan yang digunakan adalah rancangan acak kelompok lengkap. Setiap perlakuan penyiapan lahan pada masing-masing jenis ditanam sebanyak 25 tanaman dengan jarak tanam 5 m x 5 m, jumlah kelompok 3 buah, sehingga total jumlah tanaman yang diamati sebanyak 600 tanaman. Hasil penelitian menunjukkan bahwa perlakuan penyiapan lahan tidak memberikan perbedaan yang nyata baik terhadap persen hidup, pertumbuhan tinggi dan pertumbuhan diameter. Hasil penelitian ini memberikan input bahwa pemilihan teknik penyiapan lahan termurah berupa cemplongan dan jalur merupakan alternatif terbaik, sedangkan pengaturan cahaya atau kebutuhan naungan pada tahap awal pertumbuhan S. leprosula Miq., diperlukan, lain halnya dengan Shorea balangeran (Korth.) Burck yang dapat tumbuh dengan baik pada lahan alang-alang tanpa diberi naungan.

Penelitian pengaruh pemberian pupuk organik terhadap pertumbuhan tanaman mahoni ( S wietenia macrophylla King) telah dilakukan di Kawasan Rehabilitasi Hutan Samboja Lestari. Tujuan penelitian ini adalah untuk mendapatkan informasi dosis pupuk organik optimal terhadap pertumbuhan mahoni pada lahan kritis yang ditumbuhi alang-alang. Empat dosis pupuk organik (1 kg, 2 kg, 3 kg, dan 4 kg) yang dicoba dalam percobaan ini. Rancangan percobaan yang digunakan adalah acak lengkap berblok yang diulang sebanyak lima kali. Setiap perlakuan ditanam sebanyak lima tanaman. Jumlah tanaman yang diamati sebanyak 125 tanaman. Hasil penelitian menunjukkan bahwa perlakuan dosis pupuk organik tidak berbeda nyata terhadap persen hidup dan pertumbuhan tinggi. Tetapi, pemberian dosis lebih dari satu kg pupuk organik menyebabkan banyak tanaman yang mati hingga sebesar 35 % dibandingkan dengan kontrol. Namun, untuk pertumbuhan tinggi perlakuan dosis sebanyak dua kg telah memberikan pertumbuhan yang optimal.

Soil organic matter (SOM) dynamics upon secondary succession in Imperata grassland was studied by stable carbon isotope analysis. The data of litter and soil samples of twenty plots in four different stages of succession were compared. These different stages were represented by plots that were; (1) last burned 3 years before sampling (Imperata grassland), (2) last burned 9 years before, (3) a secondary forest (≥15 years) and (4) a primary forest. Result showed that isotopic signatures of all soil horizons of the regeneration stages were statistically different from those of the primary forest. The A-horizon under the 3-years Imperata plot still contained 23% forest (C3) carbon, and this fraction increased to 51% in the-B-horizon. In the 9-years plot and in the secondary forest, the C3 carbon on the A-horizon increased to 51% and 96%, respectively. In the topsoil, the loss of C4-C between the 3-years and the 9-years plot was significant, while it appeared negligible in the AB-horizon. The strong decay in the topsoil under Imperata grassland may be due to the rather high carbohydrate content of the SOM, which is considered easily decomposable. Further research is needed especially to explore the relation between carbon stocks and chemical of SOM composition. Such insight may help to better understand and predict soil carbon changes in relation to climate and vegetation change.

Penelitian tentang hubungan antara Cendawan Mikoriza Arbuskula (CMA) dengan sifat-sifat fisik dan kimia tanah pada lahan kritis telah dilakukan di areal rehabilitasi Samboja Lestari km 35, Kalimatan Timur. Tujuan penelitian ini adalah untuk mengetahui hubungan antara sifat-sifat fisik dan kimia tanah terhadap potensi CMA pada lahan kritis. Percobaan ini dilakukan dengan menggunakan metoda petak tunggal berdasarkan letak topografi dan komposisi tumbuhan. Pada setiap kondisi topografi (puncak, lereng dan lembah) dibuat petak yang berukuran 10 m x 10 m masing-masing sebanyak 5 buah petak. Di dalam petak berukuran 10 m x 10 m dibuat petak berukuran 1 m x 1 m yang ditempatkan secara acak dan diulang sebanyak 3 kali. Jumlah petak yang diamati seluruhnya sebanyak 3 x 5 x 3 = 45 buah petak. Hasil penelitian menunjukkan bahwa kondisi tanah di lokasi penelitian secara umum tidak subur, yang ditunjukkan dengan pH tanah yang masam (4, 32), bahan organik yang rendah sampai dengan sedang, yaitu C-organik (2, 15%), kandungan N total (0, 13%) P tersedia (498 ppm), K tersedia (0, 44 me/g) dan KTK (8, 99 me/100g). Kepadatan spora CMA cukup baik, dengan jumlah 1288-2321 spora/50 g pada bulan kering dan pada bulan basah 1274-2163 spora/50 g tanah, dari genus Glomus , Acaulospora dan Gigaspora . Untuk hubungan antara potensi CMA dengan sifat-sifat tanahnya sangat ditentukan oleh kandungan P tersedia, dan terjadi korelasi negatif antara jumlah spora dengan kandungan P tersedia, yang ditunjukkan oleh jumlah spora CMA yang menurun selaras dengan meningkatnya kandungan P tersedia di dalam tanah.

The chemical composition of soil organic matter (SOM) following secondary succession in Imperata grassland was investigated by Pyrolysis-Gas Chromatography/Mass Spectrometry (GC/MS). We studied 46 samples from different stages of succession using plots that last burned 3 and 9 years previously, secondary forest (≥ 15 years), primary forest and Acacia mangium plantation (9 years). During regeneration of Imperata grasslands the chemical composition of SOM changes considerably. Differences between litters and SOM were larger than within SOM, which is mainly due to a rapid degradation of lignin in the soil. Both litter and SOM under Imperata contain larger amounts of carbohydrates and fewer lignin moieties, aliphatics and N-compounds than those under secondary and primary forest. Nevertheless, SOM degradation under grassland is less efficient because of scarcity of N-compounds. SOM decomposition is most advanced under forest, as indicated by lower amounts of plant derived compounds and higher contribution of microbial matter. Decomposition efficiency appears to be related to SOM chemistry, but more to abundance of N-compounds than to that of potentially recalcitrant compounds. C stocks were linked to decomposition efficiency and litter production.

Regeneration of grassland areas is becoming increasingly important, not only to create new secondary forest and recover the original biodiversity, but also recover for agriculture. We studied an early succession in Imperata grasslands in East Kalimantan, Indonesia, using plots that last burned 3 years, 4 years and 9 years previously on, secondary and primary forest. The species coverage data were analyzed using CANOCO. While Imperata decreases, the average percentage of shrubs and young trees clearly increases with time. In the burned plots, Melastoma malabathricum, Eupatorium inulaefolium, Ficus sp., and Vitex pinnata L. strongly increase with the age of regeneration, but these species were rare in the secondary forest. Texture strongly influenced regeneration: soils with more than 50% sand had a slower development towards secondary forest. The number of species was lower in the more sandy soils. The latter showed a stronger increase with time of Pteridium aquilinum L., which appears to slow down the subsequent vegetation development. Canonical correspondence analysis (CCA) of the environmental gradient and vegetation showed that pH, bulk density, sand and clay are the factors influencing the distribution of species. CCA showed also that soil properties had a strong influence on vegetation composition. M. malabathricum, V. pinnata L., Lycopodium cernum, Vernonia arborea Buch.-Ham., Dicranopteris linearis are all species associated with high levels of exchangeable Al and low pH. Imperata grasslands are not a final and stable stage of land degradation, but, when not maintained by frequent fires and human disturbances, regenerate spontaneously and rapidly to secondary forest. The introduction of native shrubs and trees will speed up this process. Recovery for agriculture has not been studied but should not pose major problems under management system without fire.

Soil carbon changes upon secondary succession in Imperata grasslands are important both for their effect on potential production and for possible implications of forest degradation and regeneration on global climate change. We studied the effect of forest regeneration after fire in Imperata (speargrass) grasslands of East Kalimantan on soil properties, using 47 plots that last burned in 2004, 94 plots that last burned in 2003, 126 plots last burned before 2003, 43 plots of secondary forest, and 28 plots of primary forest. Although soil carbon stocks increase upon natural regeneration from grassland to secondary forest, highest carbon stocks are found in the later regeneration phases and lowest under primary forest. This is contrary to the situation in other forest systems. Low C stocks under primary forests may be due to extremely low fertility, combined with shallow soils and low root mass in the topsoil. Root density—as observed in the field—is much higher under the grass vegetation. The effects of regeneration on soil are strongest in the A-horizon, where soil carbon content increases with 14%, from 14.5 g kg− 1 in Imperata grassland to 16.5 g kg− 1 in secondary forest, while carbon stocks in the A-horizon increase from 16.51 ton C ha− 1 to 18.70 ton C ha− 1. This is accompanied by a decrease in pH and an increase in bulk density. The total soil carbon stocks in Kalimantan (fixed mass, approximate depth section 40 cm) are 36.19 ton ha− 1 in Imperata grassland, 38.98 ton ha− 1 in secondary forest and 33.19 ton ha− 1 in primary forest, which is considerably lower than in Sumatra. Above-ground C/below-ground C ratios are higher in Kalimantan primary forest but lower in Kalimantan secondary forest than in Sumatra. Soil carbon stocks in Imperata grassland could be lower than previously thought. This has important consequences for carbon sequestration projects in East Kalimantan, because carbon storage potentials could be higher.