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Expansion of rubber plantations into sub-optimal environments has been a dominating land conversion in continental South-East Asia in the last decade. Regional evaluation of the carbon sequestration potential of rubber trees depends largely on the selection of suitable allometric equations and the biomass-to-carbon conversion factor. Most equations are age-, elevation-, or clone-specific, and their application therefore gives uncertain results at the landscape level with varying age groups, elevation ranges, and clone types. Currently, for rubber-based systems, none of the allometric equations takes environmental factors (e.g. climate, topographic condition, soil properties, and management scheme) into consideration to allow pan-tropical usage. Against this background, 30 rubber trees with a root profile of up to 2 m were destructively harvested and 882 rubber trees were measured non-destructively in 27 plots, covering rotation lengths of 4–35 years, elevation gradients of 621–1127 m, and locally used clone types (GT1, PRIM600, Yunyan77-4) in mountainous South Western China. Allometric equations for aboveground biomass ( AGB ) estimations considering diameter at breast height ( DBH ), tree height ( H ), and wood density were superior to other equations. A simpler model with similar performance ( AGB = 0.0419 DBH 2.316 H 0.478 ) can be used if tree-specific wood density is not available. For belowground biomass ( BGB ) a model using only DBH can provide a robust prediction ( BGB = 0.207 DBH 1.668 ). We also tested goodness of fit for the recently proposed pan-tropical forest model, which includes a bioclimatic factor E , combining indices of temperature and precipitation variability and drought intensity. Prediction of AGB by the model calibrated with the harvested rubber tree biomass and wood density was more accurate than the results produced by the pan-tropical forest model adjusted to local conditions. The relationships between DBH and height and between DBH and biomass were influenced by tapping, therefore biomass and C stock calculations for rubber have to be done using species-specific allometric equations. Based on the analysis of environmental factors acting at the landscape level, we found that above- and belowground carbon stocks were mostly affected by stand age, soil clay content, aspect, and planting density. Increasing planting density to >570 trees per ha according to the regional plantation management strategy had a negative impact on aboveground carbon stock of old rubber plantations. The integration of bioclimatic and regional management factors is a further approach to build widely applicable biomass models for pan-tropical rubber-based systems. The results of this study provide reference for reliable carbon accounting in other rubber-cultivated regions. [ABSTRACT FROM AUTHOR]

Determining the age of rubber tree plantations (Hevea brasiliensis) is of great interest to plantation managers and land-use decision makers as it enables, among others, reliable forecasts of resource availability. The acquisition of age information with field campaigns, however, is time consuming, laborious and expensive. We present an approach that facilitates rapid assessment of rubber plantation age at regional scales applying very dense Landsat times series (LTS) satellite data over China's second largest rubber planting area – Xishuangbanna. We aggregated 270 Landsat TM and ETM + surface reflectance images into annual best-available-pixel composites of minimum Normalized Difference Moisture Index ( NDMI ). The annual composites were classified into vegetated and non-vegetated pixels applying a global NDMI threshold of 0. As it is common practice in Xishuangbanna to clear the land before a new plantation is established, the last year in which a pixel located in a rubber plantation, was classified as non-vegetated, was recorded as the year of plantation establishment. The resultant plantation age map was validated using a stratified random sample of 184 data points, collected by visual interpretation of historical Landsat data. A Root Mean Square Error (RMSE) of 2.5 years was achieved. We estimate that in 2015 50% of Xishuangbanna's rubber plantations had an age suitable for latex tapping (8–25 years), 27% were too young to be tapped (< 8 years) and 24% had already reached an age of reduced latex productivity (> 25 years) and will be presumably harvested for wood in the near future. The proposed technique enables acquisitions of accurate rubber plantation age information from Landsat time series and NDMI over large areas with the potential of providing insights into land cover dynamics and allowing for the development of improved management strategies and local decision support activities. [ABSTRACT FROM AUTHOR]

Tropical lowland rainforests are increasingly threatened by the expansion of agriculture and the extraction of natural resources. In Jambi Province, Indonesia, the interdisciplinary EFForTS project focuses on the ecological and socio-economic dimensions of rainforest conversion to jungle rubber agroforests and monoculture plantations of rubber and oil palm. Our data confirm that rainforest transformation and land use intensification lead to substantial losses in biodiversity and related ecosystem functions, such as decreased above- and below-ground carbon stocks. Owing to rapid step-wise transformation from forests to agroforests to monoculture plantations and renewal of each plantation type every few decades, the converted land use systems are continuously dynamic, thus hampering the adaptation of animal and plant communities. On the other hand, agricultural rainforest transformation systems provide increased income and access to education, especially for migrant smallholders. Jungle rubber and rubber monocultures are associated with higher financial land productivity but lower financial labour productivity compared to oil palm, which influences crop choice: smallholders that are labour-scarce would prefer oil palm while land-scarce smallholders would prefer rubber. Collecting long-term data in an interdisciplinary context enables us to provide decision-makers and stakeholders with scientific insights to facilitate the reconciliation between economic interests and ecological sustainability in tropical agricultural landscapes. [ABSTRACT FROM AUTHOR]

The rapidly growing car industry in China has led to an equally rapid expansion of monoculture rubber in many regions of South East Asia. Xishuangbanna, the second largest rubber planting area in China, located in the Indo-Burma biodiversity hotspot, supplies about 37% of the domestic natural rubber production. There, high income possibilities from rubber drive a dramatic expansion of monoculture plantations which poses a threat to natural forests. For the first time we mapped rubber plantations in and outside protected areas and their net present value for the years 1988, 2002 (Landsat, 30 m resolution) and 2010 (RapidEye, 5 m resolution). The purpose of our study was to better understand the pattern and dynamics of the expansion of rubber plantations in Xishuangbanna, as well as its economic prospects and conservation impacts. We found that 1) the area of rubber plantations was 4.5% of the total area of Xishuangbanna in 1988, 9.9% in 2002, and 22.2% in 2010; 2) rubber monoculture expanded to higher elevations and onto steeper slopes between 1988 and 2010; 3) the proportion of rubber plantations with medium economic potential dropped from 57% between 1988 and 2002 to 47% in 2010, while the proportion of plantations with lower economic potential had increased from 30% to 40%; and 4) nearly 10% of the total area of nature reserves within Xishuangbanna has been converted to rubber monoculture by 2010. On the basis of our findings, we conclude that the rapid expansion of rubber plantations into higher elevations, steeper terrain, and into nature reserves (where most of the remaining forests of Xishuangbanna are located) poses a serious threat to biodiversity and environmental services while not producing the expected economic returns. Therefore, it is essential that local governments develop long-term land use strategies for balancing economic benefits with environmental sustainability, as well as for assisting farmers with the selection of land suitable for rubber production. [ABSTRACT FROM AUTHOR]