Biology subjects

Layton-Matthews, K.

Publications and source records attributed to Layton-Matthews, K..

4 recordsLinked to original sources

bioRxiv2026

Time-lagged causal inference corroborates presumed drivers of North Atlantic seabird ecology

Disentangling causation from correlation is the foundation of the scientific method. Yet, growing evidence suggests that much observational ecology research has not correctly made this distinction due to inappropriate statistical modelling and unappreciated time-delays. Here, we apply time-lagged causal inference techniques to assess the drivers of seabird declines, using multi-decadal North Atlantic seabird data across the behaviour, mass, survival, reproduction and population size of two species ecology (Atlantic puffin, Fratercula arctica, and black-legged kittiwake, Rissa tridactyla). We demonstrate that both climate and anthropogenic activity can suppress breeding success and cause population declines. Moreover, population size is specifically impacted by delayed recruitment effects where both species decline after a lag corresponding to their estimated age of first reproduction. These North Atlantic seabirds are therefore at risk from future environmental and anthropogenic changes, as time-delays may result in populations already on an extinction trajectory prior to changes being detectable in their abundance.

ecology↗

bioRxiv2023

Path analysis reveals combined winter climate and pollution effects on the survival of a marine top predator

Marine ecosystems are experiencing growing pressure from multiple threats caused by human activities, with far-reaching consequences for marine food webs. Determining the effects of multiple stressors is complex, in part, as they can affect different levels of biological organisation (behaviour, individual traits, demographic rates). Knowledge of the cumulative effects of stressors is key to predict the consequences for threatened populations viability under global change. Due to their position in the food chain, top predators such as seabirds are considered more sensitive to environmental changes. Climate change is affecting the prey resources available for seabirds, through bottom-up effects, while organic pollutants can bioaccumulate in food chains with the greatest impacts on top predators. However, knowledge of their combined effects on seabird population dynamics is lacking. Using a path analysis, we quantify the effects of both climate change and pollution, via an effect on body mass, on the survival of adult great black-backed gulls. Warmer ocean temperatures in gulls winter foraging areas in the North Sea were correlated with higher survival, potentially explained by shifts in prey availability associated with global climate change. We also found support for indirect negative effects of organochlorines, highly toxic pollutants to seabirds, on survival acting through a negative effect on body mass. The results from this path analysis highlight how, even for such long-lived species where variance in survival tends to be limited, two stressors still have had a marked influence on adult survival and illustrate the potential of such models to improve predictions of population variability under multiple stressors.

ecology↗

bioRxiv2023

Long-term herbivore removal experiments reveal different impacts of geese and reindeer on vegetation and ecosystem CO2-fluxes in high-Arctic tundra

O_LIGiven the current and anticipated rates of global change, with associated shifts in herbivore population densities, understanding the role of different herbivores in shaping ecosystem structure and processes is critical for predicting ecosystem responses. Here, we examined the controls exerted by migratory geese and resident, non-migratory ungulates, two dominating yet functionally contrasting herbivores, on the rapidly warming Arctic tundra. C_LIO_LIWe collected vegetation and ecosystem carbon flux data at peak plant growing season in the two longest running herbivore removal experiments in high-Arctic Svalbard. Herbivore exclosures had been set up independently in a wet habitat utilised by barnacle geese (Branta leucopsis) in summer and in mesic-to-dry habitats utilised by wild reindeer (Rangifer tarandus platyrhynchus) year-round. C_LIO_LIExcluding geese produced vegetation state transitions from heavily grazed, moss-dominated (4 g m-2 dry weight of live aboveground vascular plants) to ungrazed, graminoid-dominated (60 g m-2; after 4-yr exclusion) and then horsetail-dominated (150 g m-2; after 15-yr exclusion) tundra. This caused large increases in vegetation carbon and nitrogen pools, dead biomass and moss-layer depth. Modifications in nitrogen concentrations and carbon-to-nitrogen ratios of vegetation and soil suggested overall slower nutrient cycling rates in the short-term absence of geese. Long-term goose removal quadrupled the net ecosystem carbon sequestration by increasing gross ecosystem photosynthesis more than ecosystem respiration. C_LIO_LIExcluding reindeer for 21 years also produced detectable, but weaker, increases in live and dead biomass, vegetation carbon and nitrogen pools, moss-layer depth and ecosystem respiration. Yet, reindeer removal did not alter the chemistry of either vegetation or soil, nor net ecosystem carbon sequestration. C_LIO_LIOur findings suggest that, though both herbivores were key drivers of ecosystem structure and processes, localised effects of geese, highly concentrated in space and time, are larger than those exerted by more widely dispersed reindeer. We illustrate that the impacts of herbivory across the tundra landscape are contingent on the habitat utilised for foraging, its sensitivity, the exerted grazing pressure, and herbivore characteristics. Our results underscore the conspicuous heterogeneity in how Arctic herbivores control ecosystem functioning, with important implications under current and future global change. C_LI

ecology↗

bioRxiv2021

Towards rainy Arctic winters: experimental icing impacts tundra plant productivity and reproduction

The Arctic is warming rapidly, with winters warming up to seven times as fast as summers in some regions. Warm spells in winter lead to more frequent extreme rain-on-snow events that alter snowpack conditions and can encapsulate tundra vegetation in basal ice ( icing) for several months. However, tundra climate change studies have mainly focused on summer warming. Here, we investigate icing effects on vascular plant phenology, productivity, and reproduction in a pioneer field experiment in high Arctic Svalbard, simulating rain-on-snow and resultant icing in five consecutive winters, assessing vascular plant responses throughout each subsequent growing season. We also tested whether icing responses were modified by experimentally increased summer temperatures. Icing alone delayed early phenology of the dominant shrub, Salix polaris, but with evidence for a catch-up (through shortened developmental phases and increased community-level primary production) later in the growing season. This compensatory response occurred at the expense of delayed seed maturation and reduced community-level inflorescence production. Both the phenological delay and allocation trade-offs were associated with icing-induced lags in spring thawing and warming of the soil, crucial to regulating plant nutrient availability and acquisition. Experimental summer warming modified icing effects by advancing and accelerating plant phenology (leaf and seed development), thus increasing primary productivity already early in the growing season, and partially offsetting negative icing effects on reproduction. Thus, winter and summer warming must be considered simultaneously to predict tundra plant climate change responses. Our findings demonstrate that winter warm spells can shape high Arctic plant communities to a similar level as summer warming. However, the absence of accumulated effects over the years reveals an overall resistant community which contrasts with earlier studies documenting major die-off. As rain-on-snow events will be rule rather than exception in most Arctic regions, we call for similar experiments in coordinated circumpolar monitoring programmes across tundra plant communities.

plant biology↗