Effects of density, species interactions, and environmental stochasticity on the dynamics of British bird communities

Our knowledge of the factors affecting species abundances is mainly based on time-series analyses of a few well-studied species at single or few localities, but we know little about whether results from such analyses can be extrapolated to the community level. We apply a joint species distribution model to long-term time-series data on British bird communities to examine the relative contribution of intra- and interspecific density dependence at different spatial scales, as well as the influence of environmental stochasticity, to spatiotemporal interspecific variation in abundance. Intraspecific density dependence has the major structuring effect on these bird communities. In addition, environmental fluctuations affect spatiotemporal differences in abundance. In contrast, species interactions had a minor impact on variation in abundance. Thus, important drivers of single-species dynamics are also strongly affecting dynamics of communities in time and space.Peer reviewe

Growth rings show limited evidence for ungulates' potential to suppress shrubs across the Arctic

Global warming has pronounced effects on tundra vegetation, and rising mean temperatures increase plant growth potential across the Arctic biome. Herbivores may counteract the warming impacts by reducing plant growth, but the strength of this effect may depend on prevailing regional climatic conditions. To study how ungulates interact with temperature to influence growth of tundra shrubs across the Arctic tundra biome, we assembled dendroecological data from 20 sites, comprising 1153 individual shrubs and 223 63 annual growth rings. Evidence for ungulates suppressing shrub radial growth was only observed at intermediate summer temperatures (6.5 degrees C-9 degrees C), and even at these temperatures the effect was not strong. Multiple factors, including forage preferences and landscape use by the ungulates, and favourable climatic conditions enabling effective compensatory growth of shrubs, may weaken the effects of ungulates on shrubs, possibly explaining the weakness of observed ungulate effects. Earlier local studies have shown that ungulates may counteract the impacts of warming on tundra shrub growth, but we demonstrate that ungulates' potential to suppress shrub radial growth is not always evident, and may be limited to certain climatic conditions

Growth rings show limited evidence for ungulates’ potential to suppress shrubs across the Arctic

Global warming has pronounced effects on tundra vegetation, and rising mean temperatures increase plant growth potential across the Arctic biome. Herbivores may counteract the warming impacts by reducing plant growth, but the strength of this effect may depend on prevailing regional climatic conditions. To study how ungulates interact with temperature to influence growth of tundra shrubs across the Arctic tundra biome, we assembled dendroecological data from 20 sites, comprising 1153 individual shrubs and 223 63 annual growth rings. Evidence for ungulates suppressing shrub radial growth was only observed at intermediate summer temperatures (6.5 ◦C–9 ◦C), and even at these temperatures the effect was not strong. Multiple factors, including forage preferences and landscape use by the ungulates, and favourable climatic conditions enabling effective compensatory growth of shrubs, may weaken the effects of ungulates on shrubs, possibly explaining the weakness of observed ungulate effects. Earlier local studies have shown that ungulates may counteract the impacts of warming on tundra shrub growth, but we demonstrate that ungulates’ potential to suppress shrub radial growth is not always evident, and may be limited to certain climatic conditions.Research Council of Norwayhttp://iopscience.iop.org/1748-9326dm2022Mammal Research InstituteZoology and Entomolog

Spatiotemporal patterns of plant growth in a warming high Arctic: insights from dendrochronology of Salix polaris

Climate change is most pronounced at high latitudes, where plant and animal populations are often strongly regulated by environmental drivers. Theory suggests that if these environmental drivers are synchronized over large distances, this spatial synchrony should also be reflected in the population synchrony of wildlife. Here, I used dendrochronological tools to analyse for climate drivers and their role in the synchronization of fluctuations in Salix polaris ring-width growth across large distances in high-Arctic Svalbard. I found that while summer temperature had an overall strong positive effect on S. polaris tree-ring growth across Svalbard, growth responded strongly negatively to rain-on-snow events at some wet coastal sites. Shrub growth across Svalbard was correlated over large distances, and summer temperature contributed significantly to the observed synchrony. There was a marked decline in the spatial synchrony in plant growth since the late 1990s, which was partly explained by the reduced spatial synchrony in summer temperatures occurring in parallel with the overall warming trend. These findings have fundamental implications for understanding ecosystems in space and time

Shrub_Semmeldalen_info

Description of the individual cross-sections with a description of the column names in the second sheet of this document

Data from: Annual ring growth of a widespread high-arctic shrub reflects past fluctuations in community-level plant biomass

1. Long time-series of primary production are rarely available, restricting our mechanistic understanding of vegetation and ecosystem dynamics under climate change. Dendrochronological tools are increasingly used instead, particularly in the Arctic – the world’s most rapidly warming biome. Yet, high-latitude plant species are subject to strong energy allocation trade-offs, and whether annual allocations to secondary growth (e.g. ‘tree-rings’) actually reflects primary production above-ground remains unknown. Taking advantage of a unique ground-based monitoring time-series of annual vascular plant biomass in high Arctic Svalbard (78N), we evaluated how well retrospective ring growth of the widespread dwarf shrub Salix polaris represents above-ground biomass production of vascular plants. 2. Using a balanced design in permanent plots for plant biomass monitoring, we collected 30 S. polaris shrubs across five sites in each of two habitats. We established annual ring growth time-series using linear mixed-effects models and related them to local weather records and 13 years of above-ground biomass production in six habitats. 3. Annual ring growth was positively correlated with above-ground biomass production of both S. polaris (r = 0.56) and the vascular plant community as a whole (r = 0.70). As for above-ground biomass, summer temperature was the main driver of ring growth, with this ecological signal becoming particularly clear when accounting for plant, site and habitat heterogeneity. The results suggest that ring growth measurements performed on this dominating shrub can be used to track fluctuations in past vascular plant production of high-arctic tundra. 4. Synthesis. Dendrochronological tools are increasingly used on arctic shrubs to enhance our understanding of vegetation dynamics in the world’s most rapidly warming biome. Fundamental to such applications is the assumption that annual ring growth reflects between-year variation in above-ground biomass production. Here we showed that ring growth indeed was a robust proxy for the annual above-ground productivity of both the focal shrub and the vascular plant community as a whole. Despite the challenges of constructing ring growth chronologies from irregularly growing arctic shrubs, our findings confirm that shrub dendrochronology can open new opportunities for community-dynamic studies under climate change, including in remote places where annual field sampling is difficult to achieve

Semmeldalen LME output

Ring growth and above-ground biomass time-series obtained from linear mixed-effects models. See the description of the column names in the second sheet of this document

rwl_Semmeldalen

Cross-section raw ring-widths (micrometers) in format "Tucson". See the associated file "Shrub_Semmeldalen_info"

Growth rings show limited evidence for ungulates’ potential to suppress shrubs across the Arctic

Global warming has pronounced effects on tundra vegetation, and rising mean temperatures increase plant growth potential across the Arctic biome. Herbivores may counteract the warming impacts by reducing plant growth, but the strength of this effect may depend on prevailing regional climatic conditions. To study how ungulates interact with temperature to influence growth of tundra shrubs across the Arctic tundra biome, we assembled dendroecological data from 20 sites, comprising 1153 individual shrubs and 223 63 annual growth rings. Evidence for ungulates suppressing shrub radial growth was only observed at intermediate summer temperatures (6.5 ◦C–9 ◦C), and even at these temperatures the effect was not strong. Multiple factors, including forage preferences and landscape use by the ungulates, and favourable climatic conditions enabling effective compensatory growth of shrubs, may weaken the effects of ungulates on shrubs, possibly explaining the weakness of observed ungulate effects. Earlier local studies have shown that ungulates may counteract the impacts of warming on tundra shrub growth, but we demonstrate that ungulates’ potential to suppress shrub radial growth is not always evident, and may be limited to certain climatic conditions