Publication date: 1 August 2017
Source:Geoderma, Volume 299
Author(s): Chunfeng Chen, Wenjie Liu, Xiaojin Jiang, Junen Wu
Rubber-based agroforestry (Hevea brasiliensis) systems are considered the best way to improve soil properties and the overall environmental quality of rubber monoculture, but few reports have examined soil aggregate stability in such systems. The objective of this study was to examine the management and landscape effects on water stable soil aggregates, soil aggregate-associated carbon, nitrogen content and soil carbon, and nitrogen accumulation in Xishuangbanna, southwestern China. Treatments were rubber monoculture (Rm) and four rubber-based agroforestry systems: H. brasiliensis–C. arabica (CAAs), H. brasiliensis–T. cacao (TCAs), H. brasiliensis–F. macrophylla (FMAs) and H. brasiliensis–D. cochinchinensis (DCAs). The results showed that, with the exception of CAAs, the rubber-based agroforestry treatments significantly increased total soil organic carbon (SOC) and N contents and enhanced the formation of macroaggregates compared to the rubber monoculture treatment. SOC and N contents in all water-stable aggregate fractions were significantly higher in rubber-based agroforestry systems (except CAAs) compared to rubber monoculture. The macroaggregate fractions contained more organic carbon and nitrogen than the microaggregate fractions. The proportions of C and N loss from slaking and sieving were shown to have significantly negative correlations with the mean weight diameter and the SOC and N concentrations in bulk soil. The results suggest that soil surface cover with constant leaf litter fall and extensive root systems in the rubber-based agroforestry systems increased soil organic carbon and nitrogen, helped improve soil aggregation, reduced soil erosion, decreased carbon and nitrogen loss, and ultimately improved the carbon and nitrogen accumulation rates. Given that the soil physical-chemical properties improvement and the patterns of the intercropping system played key roles in managing artificial forests, we recommend that local governments and farmers should prefer T. cacao, F. macrophylla and D. cochinchinensis and not C. arabica as the alternative interplanted tree species within rubber plantations.
Publication date: July 2017
Source:Resources, Conservation and Recycling, Volume 122
Author(s): Camila T.D. Numazawa, Sueo Numazawa, Sergio Pacca, Vanderley M. John
Forest management has been repeatedly mentioned as a strategy to reduce damage caused by logging when compared with conventional logging. Much has been learned about logging impacts and prospects for forest management, but there are still too many gaps regarding the CO2 emissions in logging, due to residues and their impact on the carbon balance. Here we compare CO2 emissions between two timber harvesting intensity systems. Logging with an intensity of 30m3 ha−1 (L30) and logging with an intensity of 15m3 ha−1 (L15) were compared over 4 rotation periods (120 year total timeframe). Original logging residues (LR) data was used to determine emissions from residues decomposition. On average, L30 has produced more LR (41.60tha−1), than L15 (20.90tha−1); for each tonne of commercial stem in L30, 2.13 tonnes of logging residues were obtained and 2.05 tonnes of residues were found in L15. Moreover, we have created a scenario representing the carbon balance (emissions from residues versus carbon uptake from biomass re-growth) over a 120 year long period to evaluate the outcomes for both logging intensities. We find that it will need about 38.3 years under L30; whereas 18.2 years were required in the case of L15. The L30 growth period is greater than the cutting cycle, which means that aboveground standing biomass is not able to fully recover until the next cutting cycle. Fully biomass recovery was only achieved when L15 was applied. Furthermore, the diameter of the commercial tree species takes a longer time to recover than the cutting cycle. Finally, ignoring the post harvesting life cycle phases, both CO2 balances were negative, which means that both practices ended up uptaking CO2 from the atmosphere.
By Vincent Gitz, Director, CGIAR Research Program on Forests, Trees and Agroforestry, and Meine van Noordwijk, Landscape Research Leader, CGIAR Research Program on Forests, Trees and Agroforestry. FTA recently organized a two-day virtual symposium entitled Trees, forests and water: cool insights for a hot world to share live online the findings of a recent review paper by David Ellison and …
Agricultural advisory systems aim to improve livelihoods and well-being of the rural community by enhancing information exchange and capacity for collective action. In East Africa, advisory systems are becoming more demand driven and are being provided by an increasingly complex range of actors using participatory approaches. Social network analysis (SNA) provides a tool to examine farmer networks for broad assessment of agricultural advisory systems.