Tag: Carbon cycle
The effect of water table levels and short-term ditch restoration on mountain peatland carbon cycling in the Cordillera Blanca, Peru
Many tropical mountain peatlands in the Andes are formed by cushion plants. These unique cushion plant peatlands are intensively utilized for grazing and are also influenced by climate change, both of which alter hydrologic conditions. Little is known about the natural hydroperiods and greenhouse gas fluxes of these peatlands or the consequences of hydrologic alteration for these fluxes. Therefore, our objectives were to assess how carbon dioxide (CO2) and methane (CH4) fluxes varied across a hydrological gradient caused by ditching and evaluate how short-term carbon cycling responds after rewetting from ditch blocking in a tropical mountain peatland. The study was carried out in Huascarán National Park, Peru using static chamber methods. Comparing reference to highly drained conditions, mid-day net ecosystem exchange (NEE) was higher (1.07 ± 0.06 vs. 0.76 ± 0.11 g CO2 m−2 h−1), and the light compensation point for CO2 uptake was lower. Gas fluxes were relatively stable in the rewetted and reference treatments, with small positive responses of NEE to rising water tables. CH4 emissions averaged 2.76 ± 1.06 mg CH4 m−2 day−1, with negative fluxes at water tables >10 cm below the soil surface, and positive fluxes at higher water levels. Our results indicate that undrained peatlands appear to be carbon sinks, highly drained peatlands were likely carbon sources, and rewetting of moderately drained peatlands increased NEE and the ability to store carbon to undrained reference conditions. Ditching of peatlands will likely increase their susceptibility to negative climate change impacts, and hydrologic restoration could moderate these impacts.
A Role for Drylands in a Carbon Neutral World?
Drylands are a critical part of the earth system in terms of total area, socioeconomic and ecological importance. However, while drylands are known for their contribution to inter-annual atmospheric CO2 variability, they are sometimes overlooked in discussions of global carbon stocks. Here, in preparation for the November 2021 UN Climate Change Conference (COP26), we review dryland systems with emphasis on their role in current and future carbon storage, response to climate change and potential to contribute to a carbon neutral future. Current estimates of carbon in dryland soils and vegetation suggest they are significant at global scale, containing approximately 30% of global carbon in above and below-ground biomass, and surface-layer soil carbon (top 30 cm). As ecosystems that are limited by water, the drylands are vulnerable to climate change. Climate change impacts are, however, dependent on future trends in rainfall that include both drying and wetting trends at regional scales. Regional rainfall trends will initiate trends in dryland productivity, vegetation structure and soil carbon storage. However, while management of fire and herbivory can contribute to increased carbon sequestration, impacts are dependent on locally unique ecosystem responses and climate-soil-plant interactions. Similarly, while community based agroforestry initiatives have been successful in some areas, large-scale afforestation programs are logistically infeasible and sometimes ecologically inappropriate at larger scales. As climate changes, top-down prescriptive measures designed to increase carbon storage should be avoided in favour of locally-adapted approaches that balance carbon management priorities with local livelihoods, ecosystem function, biodiversity and cultural, social and economic priorities.