Ecosystems are comprised of organisms living as a community within their abiotic environment and interacting as a system. No ecosystem on Earth is unaffected by people.
In the presence of energy, inorganic chemicals are assimilated into producer organisms, commonly plants, and then travel through and between ecosystems within their bodies as they move and are fed on by other organisms. Earth’s physical and chemical conditions vary greatly from tropics to poles, from mountains to ocean trenches, giving rise to diverse ecosystems. Their inhabitants are well adapted to these conditions but they themselves are engineers changing the abiotic environment, creating a multitude of habitats. Human are the ecosystem engineers of the modern epoch, creating the ecosystems that we inhabitat.
Research into ecosystems occurs across Cambridge, including the Cambridge Conservation Initiative, and departments of Geography, Land Economy, Plant Sciences and Zoology. Earth observation techniques enable ground-based measurements to be expanded to the ecosystem scale.
I am interested in how we adapt landscapes to our needs, and how we can make those landscapes work for us and the wider environment long-term. Increasing forest cover is widely known to affect carbon storage…
Carbon flux and forest dynamics: Increased deadwood decomposition in tropical rainforest tree‐fall canopy gaps
Tree mortality rates are increasing within tropical rainforests as a result of global environmental change. Little is known however about the effect of tree‐fall canopy gaps on the activity of decomposer communities and the rate of deadwood decay in forests. Therefore, to determine the effect of canopy openings on wood decay rates and regional carbon flux, we carried out the first assessment of deadwood mass loss within canopy gaps in old‐growth rainforest. Our results provide the first insights into how small‐scale disturbances in rainforests can generate hotspots for decomposer activity and carbon fluxes. In doing so, we show that including canopy gap dynamics and their impacts on wood decomposition in forest ecosystems can help improve the predictive accuracy of the carbon cycle in land surface models. Griffiths (2021) Global Change Biology
Monitoring ash dieback (Hymenoscyphus fraxineus) in British forests using hyperspectral remote sensing
Fungal ash dieback (Hymenoscyphus fraxineus) is posing an imminent threat to forest health in Europe. Using airborne hyperspectral imagery trained against 422 tree crowns of known species and ash dieback severity, we built PLS-DA and RF models that classified individual tree crowns (ITCs) into five species (>90% OA) and ash crowns into three disease severity classes (77% OA) respectively. Dark pixel filtering was found to improve the accuracy of species (+6%) but not disease classification. By incorporating automatic ITC segmentation and the classification models, we further demonstrated how species and fungal ash dieback can be mapped at a region scale for forest management and epidemiological research. Chan (2020) Remote Sensing in Ecology and Conservation
Resilience of Spanish forests to recent droughts and climate change
Time-series of canopy greenness derived from satellite imagery can be analysed alongside environmental factors, species composition and management regimes, to better understand forest resilience to drought. In Spain, forests are on average greening despite drying trends. This resilience manifests in the short-term with native species activating drought tolerance and avoidance mechanisms observable from space (i.e. losing and gaining little greenness like chestnuts to losing and gaining a lot of greenness like maritime pines). The non-native eucalypt dominated forests reveal a low short-term resilience (i.e. do not recover enough after droughts) and hence have a higher percentage of declining pixels. Factors such as water balance, elevation, and protection status greatly influence these drought response patterns. Khoury (2020) Global Change Biology
Dynamics of a human‐modified tropical peat swamp forest revealed by repeat lidar surveys
In this study, two lidar surveys are compared to map forest biomass dynamics of PSF in Kalimantan, Indonesia. We found that historically logged forests were recovering biomass near old canals and railways used by the concessions. Lidar detected substantial illegal logging activity of logging canals were located beneath the canopy. Unexpectedly, rapid growth was also observed in intact forest that had not been logged. Carbon sequestration in above‐ground biomass may have offset roughly half the carbon efflux from peat oxidation. This study demonstrates the power of repeat lidar survey to map fine‐scale forest dynamics in remote areas, revealing previously unrecognized impacts of anthropogenic global change. Wedeux (2020) Global Change Biology
Imaging spectroscopy reveals the effects of topography and logging on the leaf chemistry of tropical forest canopy trees
In this study we show that logged tropical forests have reduced leaf nutrient concentrations compared with old-growth forests and this becomes more pronounced as forests recover in stature. Our findings suggest rock-derived nutrients, such as phosphorus, in short supply in tropical forests on old soils, are depleted by as much as 30% by logging. This changes the concentration of these nutrients in leaves and may lead to shifts in species composition, and possibly reduced ecosystem function. To achieve landscape-scale maps of canopy nutrients, hyperspectral imagery was used to predict ground-based measurements taken directly from trees… Swinfield (2019) Global Change Biology
Mapping individual trees in tropical forests
Laser scanning has revolutionised forest ecology by providing high-resolution maps of forest structure over large spatial scales, but extracting information on individual trees remains a challenge. We describe a graph-based approach for delineating trees in dense forests which paves for remote sensing of the impacts of anthropogenic change on dense tropical forests. Williams (2019) IEEE
Beta-diversity of tropical forests using imaging spectroscopy
Why are tropical forests so biodiverse? Doesn’t survival of the fittest tell us that all but the most competitive species should be wiped out? We used remote sensing to map turnover of tree species across a tropical landscape. Composition varied with soil type and topography, indicating that species occupy different niches. Close-together patches were more alike in their species than those further apart, consistent with local dispersal of seeds. The study indicates that a combination of niches and “neutral” dispersal process help support the great diversity of species found in tropical forests. Bongalov (2019) Ecology Letters