Using Airborne Laser Scanning to Characterize Land-Use Systems in a Tropical Landscape Based on Vegetation Structural Metrics

Many Indonesian forests have been cleared and replaced by fast-growing cash crops (e.g., oil palm and rubber plantations), altering the vegetation structure of entire regions. Complex vegetation structure provides habitat niches to a large number of native species. Airborne laser scanning (ALS) can provide detailed three-dimensional information on vegetation structure. Here, we investigate the potential of ALS metrics to highlight differences across a gradient of land-use management intensities in Sumatra, Indonesia. We focused on tropical rainforests, jungle rubber, rubber plantations, oil palm plantations and transitional lands. Twenty-two ALS metrics were extracted from 183 plots. Analysis included a principal component analysis (PCA), analysis of variance (ANOVAs) and random forest (RF) characterization of the land use/land cover (LULC). Results from the PCA indicated that a greater number of canopy gaps are associated with oil palm plantations, while a taller stand height and higher vegetation structural metrics were linked with rainforest and jungle rubber. A clear separation in metrics performance between forest (including rainforest and jungle rubber) and oil palm was evident from the metrics pairwise comparison, with rubber plantations and transitional land behaving similar to forests (rainforest and jungle rubber) and oil palm plantations, according to different metrics. Lastly, two RF models were carried out: one using all five land uses (5LU), and one using four, merging jungle rubber with rainforest (4LU). The 5LU model resulted in a lower overall accuracy (51.1%) due to mismatches between jungle rubber and forest, while the 4LU model resulted in a higher accuracy (72.2%). Our results show the potential of ALS metrics to characterize different LULCs, which can be used to track changes in land use and their effect on ecosystem functioning, biodiversity and climate.

Soil macroporosity, physical properties and nutrient leaching after forest conversion to rubber and oil palm plantation in an Acrisol of Jambi, Indonesia

Soil degradation is expected to continue as forest conversion into other land uses increases significantly. In Indonesia, Jambi is one of the main areas for the development of oil palm and rubber, whichare mainly converted from the forest. As a base for better management, we attempted to study macro-porosity in rubber and oil palm plantation, in comparison to secondary forests. Four landuse systems (secondary forest, jungle rubber, rubber plantation and oil palm plantations) in Bukit Duabelas, Sarolangun District, Jambi Province, Sumatera, were selected for this study. The number of macropores in vertical or horizontal planes and their related factors (root mass, litter thickness, % organic C, bulk density, water content at pF 0 and pF 2.54, aggregate stability) were measured within the soil profiles. Forest conversion to jungle rubber, rubber and oil palm plantation led to a decrease of macro-porosity in the soil profile, especially in the upper 50 cm. Macropores, both at vertical and horizontal planes in the secondary forest was significantly higher than other landuses. Horizontal macropores in jungle rubber were higher than rubber and oil palm plantation, but not the vertical macropores. Among the soil properties measured, litter thickness, coarse root dry mass (Ø >2 mm), mesopores and aggregate stability were closely associated with soil macro-porosity. However, macro-porosity in the soil profile was insignificantly correlated to soil bulk density and % organic C. Increasing the number of horizontal macropores resulted in higher nutrient leaching, especially K and Na.

Using a Bottom-Up Approach to Scale Leaf Photosynthetic Traits of Oil Palm, Rubber, and Two Coexisting Tropical Woody Species

Rainforest conversion to woody croplands impacts the carbon cycle via ecophysiological processes such as photosynthesis and autotrophic respiration. Changes in the carbon cycle associated with land-use change can be estimated through Land Surface Models (LSMs). The accuracy of carbon flux estimation in carbon fluxes associated with land-use change has been attributed to uncertainties in the model parameters affecting photosynthetic activity, which is a function of both carboxylation capacity (Vcmax) and electron transport capacity (Jmax). In order to reduce such uncertainties for common tropical woody crops and trees, in this study we measured Vcmax25 (Vcmax standardized to 25 °C), Jmax25 (Jmax standardized to 25 °C) and light-saturated photosynthetic capacity (Amax) of Elaeis guineensis Jacq. (oil palm), Hevea brasiliensis (rubber tree), and two native tree species, Eusideroxylon zwageri and Alstonia scholaris, in a converted landscape in Jambi province (Sumatra, Indonesia) at smallholder plantations. We considered three plantations; a monoculture rubber, a monoculture oil palm, and an agroforestry system (jungle rubber plantation), where rubber trees coexist with some native trees. We performed measurements on leaves at the lower part of the canopy, and used a scaling method based on exponential function to scale up photosynthetic capacity related traits to the top of the canopy. At the lower part of the canopy, we found (i) high Vcmax25 values for H. brasiliensis from monoculture rubber plantation and jungle rubber plantation that was linked to a high area-based leaf nitrogen content, and (ii) low value of Amax for E. guineensis from oil palm plantation that was due to a low value of Vcmax25 and a high value of dark respiration. At the top of the canopy, Amax varied much more than Vcmax25 among different land-use types. We found that photosynthetic capacity declined fastest from the top to the lower part of the canopy in oil palm plantations. We demonstrate that photosynthetic capacity related traits measured at the lower part of the canopy can be successfully scaled up to the top of the canopy. We thus provide helpful new data that can be used to constrain LSMs that simulate land-use change related to rubber and oil palm expansion.

Changes in diversity and community assembly of jumping spiders (Araneae: Salticidae) after rainforest conversion to rubber and oil palm plantations

Rainforest conversion into monoculture plantations results in species loss and community shifts across animal taxa. The effect of such conversion on the role of ecophysiological properties influencing communities, and conversion effects on phylogenetic diversity and community assembly mechanisms, however, are rarely studied in the same context. Here, we compare salticid spider (Araneae: Salticidae) communities between canopies of lowland rainforest, rubber agroforest (“jungle rubber”) and monoculture plantations of rubber or oil palm, sampled in a replicated plot design in Jambi Province, Sumatra, Indonesia. Overall, we collected 912 salticid spider individuals and sorted them to 70 morphospecies from 21 genera. Salticid richness was highest in jungle rubber, followed by rainforest, oil palm and rubber, but abundance of salticids did not differ between land-use systems. Community composition was similar in jungle rubber and rainforest but different from oil palm and rubber, which in turn were different from each other. The four investigated land-use systems differed in aboveground plant biomass, canopy openness and land use intensity, which explained 12% of the observed variation in canopy salticid communities. Phylogenetic diversity based on ~850 bp 28S rDNA fragments showed similar patterns as richness, that is, highest in jungle rubber, intermediate in rainforest, and lowest in the two monoculture plantations. Additionally, we found evidence for phylogenetic clustering of salticids in oil palm, suggesting that habitat filtering is an important factor shaping salticid spider communities in monoculture plantations. Overall, our study offers a comprehensive insight into the mechanisms shaping communities of arthropod top predators in canopies of tropical forest ecosystems and plantations, combining community ecology, environmental variables and phylogenetics across a land-use gradient in tropical Asia.

Rubber Agroforestry Systems (RAS) in West Kalimantan, Indonesia: An historical perspective

In 1994 in the Sanggau/Sintang area in West Kalimantan province, most farmers relied mainly on jungle rubber, an old agroforestry system based on rubber seedling with low productivity, low establishment cost and low maintenance but high biomass and biodiversity. Most farmers at that period wanted to have access to clonal rubber planting material in order to improve their productivity (rubber clones do produce 3 times more than seedlings). The CIRAD/ICRAF/IRRI project called SRAP (Smallholder Rubber Agroforestry project) has set-up in 1994 on farm trials with 60 farmers in order to optimize clonal based new RAS according to local conditions and constraints. When SRAP started (1994/2007), the original objectives were multiple: i) to provide clone and high rubber productivity, ii) to maintain agroforestry practices to profit from positive externalities, and iii) to diversify income through timber, fruits, resins (Gaharu, Damar…) and other forest products (rattan, medicinal plants, forest vegetables etc). In 1997, came in the landscape oil palm estates though the very high and rapid development of private concessions. Oil palm became in the 2000’s the main priority for most smallholders. Today, all forest and most local jungle rubber have disappeared to the profit of roughly 2/3 of the area planted with oil palm (estates and smallholder) and 1/3 with clonal rubber for smallholder, either in monoculture or agroforestry. In 2019, CIFOR/FTA program funded a mission to CIRAD to obtain information about the evolution of RAS trials plots evolution in the province of West Kalimantan. The survey provide an idea of the historical and current trend in terms of local farming strategies concerning agroforestry. It raised also the question of clonal planting material availability for replanting and the poor tapping quality that lead to a reduction of the clonal rubber lifespan. Evolution of trials status over the period1994/2019 display the following results: i) Conversion to oil palm (20 %) or to clonal rubber monoculture (20 % mainly in Trimulia in Transdmigration area), ii) with agroforestry systems maintained in RAS 1 or 2 (50 %) and iii) evolution to tembawang at the end of rubber lifespan (10 %). We are back to the same problems faced in 1994: poor access to clonal planting material, no training on tapping frequency and practices but with some knowledge on clones and AF practices. The lessons learned are the following: i) Rubber agroforestry trials came right in time in 1994, with a strong demand from farmers, ii) but oil palm came in 1997 with a very strong pressure from concession companies providing a lucrative alternative to rubber cultivation with full credit (but loss of land) and better return to labor, iii) Interest in agroforestry practices remains high for old men but no interest is witnessed from younger generation, iv) It is now time for rubber replanting but the same old story remains: poor access to planting material), v) no good tapping practices, poor technical information available). These are essential to be able to maximize tree lifespan up to 35 years long.

Diversity of butterflies (Lepidoptera) across rainforest transformation systems in Jambi, Sumatra, Indonesia

Panjaitan R, Drescher J, Buchori D, Peggie D, Harahap IS, Scheu S, Hidayat P. 2020. Diversity of butterflies (Lepidoptera) across rainforest transformation systems in Jambi, Sumatra, Indonesia. Biodiversitas 21: 5119-5127. The high rate of land conversion has put pressure on biodiversity, especially in the tropics. The lowlands of Sumatra, for example, are dominated by increasingly extensive areas of oil palm and rubber monoculture plantations, while rainforests are continuously vanishing. The status of many rainforest animal populations, including iconic insect groups such as butterflies, is largely unclear. With a rapid assessment approach, we studied butterflies along land-use gradients from lowland rainforest, via jungle rubber plantations (rubber agroforest system), to monocultures of rubber and oil palm in Jambi Province, Sumatra. Butterflies were caught in a nested replication design at eight research plots at each of the forest, jungle rubber, and rubber and oil palm locations. Butterfly abundance was the highest in the rainforest (204.3±82.1), slightly lower in the jungle rubber and oil palm areas (164.9±61 and 169.3±94.9, respectively), and the lowest in the rubber plantation (108.8±38.5). Similarly, butterfly species richness was the highest in the forest and jungle rubber areas (47.1±7.7 and 38.8±7.6, respectively), followed by the oil palm area (33.3±9.8), and the lowest in the rubber plantation (26.1±9.1). Likewise, Shannon-Wiener diversity was the highest in the rainforest, at an intermediate level in the jungle rubber, and lowest in the oil palm and rubber plantations. Butterfly community composition in the rainforest was very different from that in the other three land-use systems, in which it was similar. Overall, the study demonstrates that rainforest butterfly communities cannot be sustained in agricultural systems, highlighting the importance of rainforests for conserving the diversity of arthropods.

Peranan Semut di Ekosistem Transformasi Hutan Hujan Tropis Dataran Rendah

Deforestasi atau perubahan fungsi dari hutan menjadi non-hutan berperan dalam perubahan ekosistem dan spesies di dalamnya. Serangga sebagai salah satu fauna di dalamnya merupakan aspek yang menarik untuk dikaji khususnya semut. Tujuan penelitian ini adalah mengidentifikasi peranan-peranan dari genus semut yang ditemukan di ekosistem transformasi. Penelitian dilaksanakan di Desa Bungku, Kecamatan Bajubang, Kabupaten Batanghari, Provinsi Jambi. Metode yang digunakan dalam penelitian ini adalah membuat plot pengamatan secara purposive sampling. Plot pengamatan dipasang di empat eksosistem hutan dengan jumlah masing - masing ekosistem sebanyak empat plot. Setiap plot memiliki lima sub plot yang tersebar di empat eksosistem hutan untuk pemasangan pitfall trap. Teknik pengambilan sampel semut menggunakan pitfall trap di empat ekosistem. Empat ekosistem tersebut yaitu hutan sekunder, perkebunan kelapa sawit, kebun karet, dan hutan karet. Hasil penelitian ditemukan sebanyak 33 genus dari 6 subfamili. Selanjutnya dari 33 genus dikelompokkan berdasarkan peranannya. Berdasarkan peranannya terdapat 46% pencari makan , 36% predator, 3% semut tentara, 3% pemakan bangkai, dan 3% lainnya (semut pemanen/pemetik, omnivora, predator, dan pemakan bangkai). Camponotus sebagai genus dominan memiliki peranan pencari makan, dan Pheidole mempunyai peranan sebagai penghancur biji dan sebagian lainnya adalah omnivora. The Role of Ants in Lowland Tropical Rainforest TransformationAbstractDeforestation or changes functions from forest to non-forest play a role in changing ecosystems and the species within them. Insect as one of the fauna is an interesting aspect to study, especially ants. Aims of this study is to identify the roles of the genus of ants that found in the transformation ecosystem. This study was conducted in Bungku Village, Bajubang District, Batanghari Regency, Jambi. Method used in this study is to make a plot of observation by purposive sampling. Ant sampling techniques use pitfall traps in four ecosystems i.e.. secondary forest, oil palm plantation,rubber plantation, and jungle rubber. This study found 33 genera from 6 subfamilies. Furthermore, 33 genera are grouped based on their roles, i.e. (1) 46% foragers, (2) 36% for predators, (3) 3% for army ants, (4) 3% for scavengers, and (5) 3% for others (harvesting ants, omnivores, predators and scavengers too). Camponotus as the dominant genus has a role for foragers, and Pheidole has a role as a seed destroyer and the other part is omnivorous.

Contribution to the knowledge of the oribatid mite genus Kalloia (Acari, Oribatida, Carabodidae), with description of a new species from Indonesia

The genus Kalloia (Oribatida, Carabodidae) is recorded in the Oriental region for the first time. A new species — Kalloia gerdweigmanni n. sp. — is described from litter of oil palm plantations and jungle rubber agroforests from Sumatra, Indonesia. It differs from Kalloia simpliseta Mahunka, 1985 by the presence of a transverse ridge in the mediodistal part of the lamellae, translamella and two thick, diagonal, convergent ridges forming a triangular structure in the medioanterior part of the notogaster, and by the localization of notogastral setae da, dm, la, lm, lp and h1. The generic status of Kalloia is discussed and supported. Kalloia mahunkai Pérez-Íñigo and Baggio, 1989 and Machadocepheus foveolatus Mahunka, 1978, which were considered representatives of Kalloia, are removed from this genus and combined preliminarily in Gibbicepheus. Revised generic diagnosis and data on ecology and distribution of known species of Kalloia are presented.

Conversion of tropical forests to smallholder rubber and oil palm plantations impacts nutrient leaching losses and nutrient retention efficiency in highly weathered soils

Conversion of forest to rubber and oil palm plantations is widespread in Sumatra, Indonesia, and it is largely unknown how such land-use conversion affects nutrient leaching losses. Our study aimed to quantify nutrient leaching and nutrient retention efficiency in the soil after land-use conversion to smallholder rubber and oil palm plantations. In Jambi province, Indonesia, we selected two landscapes on highly weathered Acrisol soils that mainly differed in texture: loam and clay. Within each soil type, we compared two reference land uses, lowland forest and jungle rubber (defined as rubber trees interspersed in secondary forest), with two converted land uses: smallholder rubber and oil palm plantations. Within each soil type, the first three land uses were represented by 4 replicate sites and the oil palm by three sites, totaling 30 sites. We measured leaching losses using suction cup lysimeters sampled biweekly to monthly from February to December 2013. Forests and jungle rubber had low solute concentrations in drainage water, suggesting low internal inputs of rock-derived nutrients and efficient internal cycling of nutrients. These reference land uses on the clay Acrisol soils had lower leaching of dissolved N and base cations (P= 0.01–0.06) and higher N and base cation retention efficiency (P < 0.01–0.07) than those on the loam Acrisols. In the converted land uses, particularly on the loam Acrisol, the fertilized area of oil palm plantations showed higher leaching of dissolved N, organic C, and base cations (P < 0.01–0.08) and lower N and base cation retention efficiency compared to all the other land uses (P < 0.01–0.06). The unfertilized rubber plantations, particularly on the loam Acrisol, showed lower leaching of dissolved P (P=0.08) and organic C (P < 0.01) compared to forest or jungle rubber, reflecting decreases in soil P stocks and C inputs to the soil. Our results suggest that land-use conversion to rubber and oil palm causes disruption of initially efficient nutrient cycling, which decreases nutrient availability. Over time, smallholders will likely be increasingly reliant on fertilization, with the risk of diminishing water quality due to increased nutrient leaching. Thus, there is a need to develop management practices to minimize leaching while sustaining productivity.

Conversion of tropical forests to smallholder rubber and oil palm plantations impacts nutrient leaching losses and nutrient retention efficiency in highly weathered soils

Conversion of forest to rubber and oil palm plantations is widespread in Sumatra, Indonesia, and it is largely unknown how such land-use conversion affects nutrient leaching losses. Our study aimed to quantify nutrient leaching and nutrient retention efficiency in the soil after land-use conversion to smallholder rubber and oil palm plantations. In Jambi province, Indonesia, we selected two landscapes on highly weathered Acrisol soils that mainly differed in texture: loam and clay. Within each landscape, we compared two reference land uses: lowland forest and jungle rubber (defined as rubber trees interspersed in secondary forest) with two converted land uses, smallholder rubber and oil palm plantations. Within each landscape, the first three land uses were represented by four replicate sites and the oil palm by three sites, totaling to 30 sites. We measured leaching losses using suction cup lysimeters, sampled biweekly to monthly from February to December 2013. Forests and jungle rubber had low solute concentrations in drainage water, suggesting low internal inputs of rock-derived nutrients and efficient internal cycling of nutrients. These reference land uses on the clay Acrisol soils had lower leaching of dissolved N and base cations (P = 0.01–0.06) and higher N and base cation retention efficiency (P