Browsing by Author "Cooper, Hannah V."
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Item Open Access Evaluation of pedotransfer functions to estimate some of soil hydraulic characteristics in North Africa: a case study from Morocco(Frontiers, 2023-02-08) Beniaich, Adnane; Otten, Wilfred; Shin, Ho-Chul; Cooper, Hannah V.; Rickson, R. Jane; Soulaimani, Azia; El Gharous, MohamedSoil hydraulic properties are an important factor to optimize and adapt water management for a given crop. Pedotransfer functions (PTFs) present a solution to predict soil variables such as hydraulic properties, using fundamental soil properties. In this research, we compared two sources of soil information: iSDAsoil data and field data, in four regions in Morocco. We then used this data to evaluate published data and developed new PTFs using soil information to estimate soil gravimetric moisture content at saturation (w0), field capacity (w330) and permanent wilting point (w15000). A total of 331 samples were collected from four regions: Doukkala, Gharb-Loukous, Moulouya and Tadla. The data was divided into calibration and validation datasets. For development of different PTFs, we used simple linear regression, multiple linear regression, regression tree, Cubist algorithm, and random forest approaches. PTFs developed by Dijkerman (Geoderma, 1988, 42, 29–49) presented the best performance, showing lower RMSE, Bias and MAE compared to other PTFs. Using multiple linear regression to develop PTFs, models based on clay, silt and soil organic matter as input variables showed the best performance after calibration (R2 of 0.590, 0.785, 0.786 for w0, w330, and w15000, respectively). Regarding the techniques based on machine learning, random forest showed the best performance after calibration compared with other algorithms (R2 of 0.930, 0.955, 0.954 for w0, w330, and w15000, respectively). PTFs represent a low cost and easy technique to estimate soil hydraulic properties, to improve water management efficiency for the farmers.Item Open Access Long-term zero-tillage enhances the protection of soil carbon in tropical agriculture(Wiley, 2021-03-27) Cooper, Hannah V.; Sjögersten, Sofie; Lark, Richard M.; Girkin, Nicholas T.; Vane, Christopher H.; Calonego, Juliano C.; Rosolem, Ciro; Mooney, Sacha J.Contrasting tillage strategies not only affect the stability and formation of soil aggregates but also modify the concentration and thermostability of soil organic matter associated with soil aggregates. Understanding the thermostability and carbon retention ability of aggregates under different tillage systems is essential to ascertain potential terrestrial carbon storage. We characterised the concentration and thermostability of soil organic carbon (SOC) within various aggregate size classes under both zero and conventional tillage using novel Rock‐Eval pyrolysis. The nature of the pore systems was visualised and quantified by X‐ray Computed Tomography to link soil structure to organic carbon preservation and thermostability. Soil samples were collected from experimental fields in Botucatu, Brazil, which had been under zero‐tillage for 2, 15 and 31 years, along with adjacent fields under conventional tillage. Soils under zero‐tillage significantly increased pore connectivity whilst simultaneously decreasing inter‐aggregate porosity, providing a potential physical mechanism for protection of soil organic carbon in the 0‐20 cm soil layer. Changes in the soil physical characteristics associated with the adoption of zero‐tillage resulted in improved aggregate formation compared to conventionally tilled soils, especially when implemented for at least 15 years. In addition, we identified a chemical change in composition of organic carbon to a more recalcitrant fraction following conversion to zero‐tillage, suggesting aggregates were accumulating rather than mineralising soil organic carbon. These data reveal profound effects of different tillage systems upon soil structural modification, with important implications for the potential of zero‐tillage to increase carbon sequestration compared to conventional tillage.Item Open Access The temperature dependence of greenhouse gas production from Central African savannah soils(Elsevier, 2025-03-01) Girkin, Nicholas T.; Cooper, Hannah V.; Johnston, Alice S.; Ledger, Martha; Niamba, G. R. Mouanda; Vane, Christopher H.; Moss-Hayes, Vicky; Crabtree, Dafydd; Dargie, Greta C.; Vasquez, Saul; Bocko, Yannick; Mampouya Wenina, Emmanuel; Mbemba, Mackline; Boom, Arnoud; Ifo, Suspense Averti; Lewis, Simon L.; Sjögersten, SofieSavannahs cover 20 % of the global land surface, but there have been few studies of greenhouse gas (GHG) dynamics from savannah soils. Here, we assess potential turnover of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from surface (0–10 cm) and subsurface (20–30 cm) soils from two contrasting tropical savannah sites in the Republic of Congo, Central Africa, under dry (40 % water-filled-pore-space, WFPS) and wet (70 % WFPS) conditions. Under baseline conditions (25 °C), we found soils were sources of CO2 and N2O, but a sink for CH4. Assessment of the temperature response of GHG fluxes between 20 and 35 °C revealed variable temperature dependences. That is, CO2 fluxes showed a strong temperature response, whereas the temperature response of N2O fluxes was only significant under dry conditions, and no significant temperature response of CH4 fluxes was observed. The temperature quotient (Q10) of soil respiration increased from 1.58 ± 0.004 to 1.92 ± 0.006 at sites with lower soil organic carbon contents. The relative increase in N2O with CO2 fluxes across temperatures was significantly influenced by moisture conditions at both sites. No temperature or soil moisture response was observed for CH4 fluxes, collectively implying divergent GHG responses to changing climatic conditions. Using Rock-Eval pyrolysis we assessed the organic chemistry of all soil types, which indicated contrasting degrees of stability of carbon sources between sites and with depth which, alongside significant differences in a range of other soil parameters (including organic matter content, total carbon, total nitrogen, electrical conductivity, and pH), may account for site-specific differences in baseline GHG emissions. Taken together, our results are amongst the first measures of GHG temperature sensitivity of tropical savannah soils, and demonstrate that soil CO2 emissions are more sensitive to warming and changes in moisture than the emissions of other GHGs, although relatively low compared to responses reported for soils from other tropical ecosystems. This implies that GHG fluxes form savannah soils in the region may be at least partially resilient to climate-induced soil warming compared to other ecosystems.Item Open Access The three-peat challenge: business as usual, responsible agriculture, and conservation and restoration as management trajectories in global peatlands(Taylor and Francis, 2023-11-01) Girkin, Nicholas T.; Burgess, Paul J.; Cole, Lydia; Cooper, Hannah V.; Coronado, Euridice Honorio; Davidson, Scott J.; Hannam, Jacqueline A.; Harris, Jim A.; Holman, Ian P.; McCloskey, Christopher S.; McKeown, Michelle M.; Milner, Alice M.; Page, Susan; Smith, Jo; Young, DylanPeatlands are a globally important carbon store, but peatland ecosystems from high latitudes to the tropics are highly degraded due to increasingly intensive anthropogenic activity, making them significant greenhouse gas (GHG) sources. Peatland restoration and conservation have been proposed as a nature-based solution to climate change, by restoring the function of peatlands as a net carbon sink, but this may have implications for many local communities who rely on income from activities associated with transformed peatlands, particularly those drained for agriculture. However, without changing the way that humans interact with and exploit peatlands in most regions, peatlands will continue to degrade and be lost. We propose that there are ultimately three potential trajectories for peatland management: business as usual, whereby peatland carbon sink capacity continues to be eroded, responsible agricultural management (with the potential to mitigate emissions, but unlikely to restore peatlands as a net carbon sink), and restoration and conservation. We term this the three-peat challenge, and propose it as a means to view the benefits of restoring peatlands for the environment, as well as the implications of such transitions for communities who rely on ecosystem services (particularly provisioning) from degraded peatlands, and the consequences arising from a lack of action. Ultimately, decisions regarding which trajectories peatlands in given localities will follow torequire principles of equitable decision-making, and support to ensure just transitions, particularly for communities who rely on peatland ecosystems to support their livelihoods.Item Open Access Tropical peatlands in the anthropocene: lessons from the past(Elsevier, 2022-01-25) Cole, Lynda E. S.; Åkesson, Christine M.; Hapsari, K. Anggi; Hawthorne, Donna; Roucoux, Katherine H.; Girkin, Nicholas T.; Cooper, Hannah V.; Ledger, Martha J.; O’Reilly, Patrick; Thornton, Sara A.The status of tropical peatlands, one of Earth’s most efficient natural carbon stores, is of increasing international concern as they experience rising threat from deforestation and drainage. Peatlands form over thousands of years, where waterlogged conditions result in accumulation of organic matter. Vast areas of Southeast Asian peatlands have been impacted by land use change and fires, whilst lowland tropical peatlands of Central Africa and South America remain largely hydrologically intact. To predict accurately how these peatlands may respond to potential future disturbances, an understanding of their long-term history is necessary. This paper reviews the palaeoecological literature on tropical peatlands of Southeast Asia, Central Africa and South America. It addresses the following questions: (i) what were the past ecological dynamics of peatlands before human activity?; (ii) how did they respond to anthropogenic and natural disturbances through the palaeoanthropocene, the period from whence evidence for human presence first appeared?; and, (iii) given their past ecological resilience and current exposure to accelerating human impacts, how might the peatlands respond to drivers of change prevalent in the anthropocene? Throughy synthesising palaeoecological records, this review demonstrates how tropical peatland ecosystems have responded dynamically, persisting through fire (both natural and anthropogenic), climatic and human-induced disturbances in the palaeoanthropocene. Ecosystem resilience does, however, appear to be compromised in the past c. 200 years in Southeast Asian peatlands, faced with transformative anthropogenic impacts. In combination, this review’s findings present a pantropical perspective on peatland ecosystem dynamics, providing useful insights for informing conservation and more responsible management.Item Open Access Tropical peatlands in the Anthropocene: the present and the future(Elsevier, 2022-11-28) Girkin, Nicholas T.; Cooper, Hannah V.; Ledger, Martha J.; O’Reilly, Patrick; Thornton, Sara A.; Åkesson, Christine M.; Cole, Lydia E. S.; Hapsari, K. Anggi; Hawthorne, Donna; Roucoux, Katherine H.Tropical peatlands are a globally important carbon store. They host significant biodiversity and provide a range of other important ecosystem services, including food and medicines for local communities. Tropical peatlands are increasingly modified by humans in the rapid and transformative way typical of the “Anthropocene,” with the most significant human—driven changes to date occurring in Southeast Asia. This review synthesizes the dominant changes observed in human interactions with tropical peatlands in the last 200 years, focusing on the tropical lowland peatlands of Southeast Asia. We identify the beginning of transformative anthropogenic processes in these carbon-rich ecosystems, chart the intensification of these processes in the 20th and early 21st centuries, and assess their impacts on key ecosystem services in the present. Where data exist, we compare the tropical peatlands of Central Africa and Amazonia, which have experienced very different scales of disturbance in the recent past. We explore their global importance and how environmental pressures may affect them in the future. Finally, looking to the future, we identify ongoing efforts in peatland conservation, management, restoration, and socio-economic development, as well as areas of fruitful research toward sustainability of tropical peatlands.