Carbon stocks in bamboo ecosystems worldwide: estimates and uncertainties.
From a review of 184 studies on bamboo biomass for 70 species (22 genera) we estimate plausible ranges for above-ground carbon (AGC) biomass (16-128 Mg C/ha), below-ground carbon (BGC) biomass (8-64 Mg C/ha), soil organic carbon (SOC; 70-200 Mg C/ha), and total ecosystem carbon (TEC; 94-392 Mg C/ha). The total ecosystem carbon range is below that for most types of forests, on par with that of rubber plantations and tree orchards, but greater than agroforests, oil palm, various types of swidden fallows, grasslands, shrublands, and pastures. High carbon biomass was associated with many Phyllostachys spp., including Moso (P. edulis) in China, Japan, Taiwan, and Korea, as well as other "giant" bamboo species of genera Bambusa, Dendrocalamus, Gigantochloa, and Guadua. The low end of the TEC range for mature bamboo typically included various species of dwarf bamboo, understory species, and stands stressed by climatic factors (temperature, rainfall), soil conditions, and management practices. Limited research and uncertainties associated with determinations prevent a robust assessment of carbon stocks for most species. Moso bamboo was by far the most studied species (>40% of the reported values), as it is commonly grown in plantations for commercial use. Similarly, a review of available allometric equations revealed that more work is needed to develop equations for predicting carbon biomass for most species. Most allometry equations exist for AGC for China, where 33 species have been studied. Allometric equations for BGC are rare, with all work conducted in China (15 species) and India (2). Root:shoot ratio estimate for most groups of species and genera were less than one, with the exception of Phyllostachys spp. (however, some individual species with small sample size were greater than one). Estimated annual carbon accumulation rates were on the order of 8-14 Mg C/ha, relaxing to ≤4 Mg C/ha after selective harvesting of stands commences following maturation-but the timing of this rate change could not be reliably ascertained. The high standing carbon stocks and high annual accumulation rates point to the possibility of successful carbon farming using bamboo, if stands are managed efficiently (sufficient water, adequate nutrients, appropriate thinning/harvesting). Key in long-term carbon sequestration of bamboo is making sure harvested bamboo are turned into durable products (e.g., permanent construction materials, furniture, art). While our review demonstrated the potential of bamboo as an efficient and effective carbon sink, further research is needed to reduce uncertainties in the underlying data, resulting from a lack of standardization of methods, a lack of research for many bamboo species, and limited research of below-ground and soil organic carbon. Another priority is obtaining more carbon estimates for under-represented regions such as Central America, South America and Africa. Finally, we conducted a case study in northern Thailand that demonstrated the difficulty in sampling above- and below-ground components of total ecosystem carbon, as well as the threat of drastic bamboo biomass loss associated with instances of gregarious flowering. Overall, we recommend that instead of being seen as an invasive species with low utility, bamboo should be given greater recognition in policy and management for its value as a carbon sink, critical in mitigating the effects of climate change, and for its ability to provide key ecosystem services for humans, such as stabilizing hillslopes from accelerated soil erosion, improving soil fertility, and providing food and construction materials.