The aim of this research was to determine how changes in soil moisture and temperature influence ecosystem C fluxes in the context of changing grazing regimes in subalpine grasslands in the Pyrenees. We (i) measured CO2 fluxes in the field in cattle- and sheep-grazed areas, and (ii) compared responses of CO2 and CH4 fluxes from soil turf samples from cattle- and sheep-grazed areas to changes in soil temperature and moisture. The cattle-grazed area showed greater ecosystem respiration and gross ecosystem photosynthesis than the sheep-grazed areas. With respect to the temperature and moisture treatments, the two areas responded in a similar way: Soil moisture was the strongest driver of soil respiration rates; although temperature also increased CO2 effluxes from the soils, the effects were transient. The greatest effluxes of CO2 were found in soils incubated at elevated temperature and 80% soil moisture content. Methane fluxes were only influenced by the moisture treatment, with the greatest methane oxidation rates found at 40% soil moisture content. We conclude that regional changes in moisture availability resulting from climate change are likely to be the most important driver of soil respiration and methane fluxes in these grazed subalpine ecosystems.
Tropical peatlands are globally important ecosystems for carbon storage, biodiversity conservation, water storage and regulation, and several other valuable ecosystem services. Despite their importance, peatlands in Southeast Asia have been heavily degraded by anthropogenic disturbances such as drainage, agricultural conversion, and fire. In this spatially extensive study we characterised peat properties, nutrient concentrations, surface subsidence rates and greenhouse gas emissions from peatlands of Selangor, Peninsular Malaysia under different land-uses: Secondary Forest, Fire affected and replanted forest (Burnt), Pineapple Plantation, Mixed Agriculture, Smallholder Oil Palm Monoculture, and Industrial Oil Palm Monoculture. All the measured peat physico-chemical properties and nutrient concentrations were significantly different between land-uses. Principal component analyses indicated that peat under the Mixed Agriculture and Burnt land-uses showed the greatest degree of modification relative to peat under the Secondary Forest land-use. Burnt land-use also showed a significantly higher subsidence rate (4.4 ± 1.2 cm yr−1) than all the other land-uses (ranging between 1.8 ± 0.47 and 3.2 ± 0.5 cm yr−1). Water table was significantly higher at the Burnt land-use (-26 cm) than all other land-uses, likely reflecting fire-prevention drain blocking measures as well as lower land surface heights post fire. Smallholder oil palm land-use had the lowest water table (−68 cm), while water table level in all other land-uses did not significantly differ from that of Secondary Forest (−43 cm). Peat surface level changes were positively related to increase in drainage, showing the importance of maintaining a high water table level in reducing peat degradation and carbon loss from peatlands. Total CO2 (mean range 492 to 1019 mg m−2 hr-1) and CH4 emissions (mean range 637 to 1422 µg m−2 hr-1) did not significantly differ between land-uses or seasons. CH4 emissions were negligible under all land-uses and higher emissions were correlated with a higher water table level. Taken together, the results show that anthropogenic land-use change impacts the physico-chemical properties and nutrient content of peat, and that increased drainage alongside changes in other peat properties leads to increased peat subsidence and carbon loss.
The Arctic is warming four times faster than the global average, and plant communities are responding through shifts in species abundance, composition and distribution. However, the direction and magnitude of local plant diversity changes have not been explored thus far at a pan-Arctic scale. Using a compilation of 42,234 records of 490 vascular plant species from 2,174 plots at 45 study areas across the Arctic, we quantified how species richness and composition have changed over time during a period of up to four decades (1981 – 2022), and identified the geographic, climatic and biotic drivers behind these changes. Despite plant species richness being greater at lower latitudes and warmer plots, pan-Arctic species richness did not change directionally over time at the plot level. However, 99% of the plots experienced changes in species abundance, with 66% of plots either gaining or losing species. Species richness increased most where temperatures had warmed most over time, and shrub expansion led to greater species losses and decreasing richness. Yet, Arctic plant communities did not become more similar to each other over time, suggesting that no biotic homogenisation has occurred thus far. Overall, we found that Arctic plots changed in richness and composition in all possible directions, yet climate and biotic interactions still emerged as the main drivers of directional change. Our results show a variety of diversity trends, which could be precursors of future changes for Arctic plant biodiversity, ecosystem function, wildlife habitats and livelihoods for Arctic Communities.
The central Congo Basin contains the largest known peatland complex in the tropics. Here we present a detailed multi-proxy record from a peat core, CEN-17.4, from the centre of a 45 km wide interfluvial peatland (Ekolongouma), the first record of its kind from the central Congo peatlands. We use pollen, charcoal, sedimentological and geochemical data to reconstruct the site's history from the late Pleistocene to the present day. Peat began accumulating at the centre of the peatland ∼19,600 cal BP (∼17,500–20,400 cal BP, 95% confidence interval), and between ∼9500 (9430–9535 cal BP) and 10,500 (10,310–10,660 cal BP) cal BP towards the margins. Pollen data from the peatland centre show that an initial grass- and sedge-dominated vegetation, which burned frequently, was replaced by a Manilkara-type dominated flooded forest at ∼12,640 cal BP, replaced in turn by a more mixed swamp forest at ∼9670 cal BP. Mixed swamp forest vegetation has persisted to the present day, with variations in composition and canopy openness likely caused at least in part by changes in palaeo-precipitation. Stable isotope data (δDn-C29-v&icecorr) indicate a large reduction in precipitation beginning ∼5000 and peaking ∼2000 cal BP, associated with the near-complete mineralization of several metres of previously accumulated peat and with a transition to a drier, more heliophilic swamp forest assemblage, likely with a more open canopy. Although the peatland and associated vegetation recovered from this perturbation, the strong response to this climatic event underlines the ecosystem's sensitivity to changes in precipitation. We find no conclusive evidence for anthropogenic activity in our record; charcoal is abundant only in the Pleistocene part of the record and may reflect natural rather than anthropogenic fires. We conclude that autogenic succession and variation in the amount and seasonality of precipitation have been the most important drivers of ecological change in this peatland since the late Pleistocene.
Tropical peatland across Southeast Asia is drained extensively for production of pulpwood, palm oil and other food crops. Associated increases in peat decomposition have led to widespread subsidence, deterioration of peat condition and CO 2 emissions. However, quantification of subsidence and peat condition from these processes is challenging due to the scale and inaccessibility of dense tropical peat swamp forests. The development of satellite interferometric synthetic aperture radar (InSAR) has the potential to solve this problem. The Advanced Pixel System using Intermittent Baseline Subset (APSIS, formerly ISBAS) modelling technique provides improved coverage across almost all land surfaces irrespective of ground cover, enabling derivation of a time series of tropical peatland surface oscillations across whole catchments. This study aimed to establish the extent to which APSIS-InSAR can monitor seasonal patterns of tropical peat surface oscillations at North Selangor Peat Swamp Forest, Peninsular Malaysia. Results showed that C-band SAR could penetrate the forest canopy over tropical peat swamp forests intermittently and was applicable to a range of land covers. Therefore the APSIS technique has the potential for monitoring peat surface oscillations under tropical forest canopy using regularly acquired C-band Sentinel-1 InSAR data, enabling continuous monitoring of tropical peatland surface motion at a spatial resolution of 20 m.
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