Jake Alexander


Last Name

Alexander

First Name

Jake

ORCID

0000-0003-2226-7913

Organisational unit

09716 - Hille Ris Lambers, Janneke / Hille Ris Lambers, Janneke

Search Results

Publications1 - 10 of 100
  • The invasion of plant communities following extreme weather events under ambient and elevated temperature
    Item type: Journal Article
    Sheppard, Christine S.; Alexander, Jake; Billeter, Regula (2012)
    Plant Ecology
  • Limits to the niche and range margins of alien species
    Item type: Journal Article
    Alexander, Jake; Edwards, Peter J. (2010)
    Oikos
  • Genetic and plastic responses of nonnative plants along altitudinal gradients
    Item type: Other Conference Item
    Alexander, Jake; Kueffer, Christoph; Seipel, Tim; et al. (2010)
  • Ecological lags govern the pace and outcome of plant community responses to 21st-century climate change
    Item type: Journal Article
    Block, Sebastián; Maechler, Marc-Jacques; Levine, Jacob I.; et al. (2022)
    Ecology Letters
    Forecasting the trajectories of species assemblages in response to ongoing climate change requires quantifying the time lags in the demographic and ecological processes through which climate impacts species' abundances. Since experimental climate manipulations are typically abrupt, the observed species responses may not match their responses to gradual climate change. We addressed this problem by transplanting alpine grassland turfs to lower elevations, recording species' demographic responses to climate and competition, and using these data to parameterise community dynamics models forced by scenarios of gradual climate change. We found that shifts in community structure following an abrupt climate manipulation were not simply accelerated versions of shifts expected under gradual warming, as the former missed the transient rise of species benefiting from moderate warming. Time lags in demography and species interactions controlled the pace and trajectory of changing species' abundances under simulated 21st-century climate change, and thereby prevented immediate diversity loss.
  • Widespread phenotypic and genetic divergence along altitudinal gradients in animals
    Item type: Journal Article
    Keller, Irene; Alexander, Jake; Holderegger, Rolf; et al. (2013)
    Journal of Evolutionary Biology
  • Lowland plant migrations into alpine ecosystems amplify soil carbon loss under climate warming
    Item type: Working Paper
    Walker, Tom W.N.; Gavazov, Konstantin; Guillaume, Thomas; et al. (2021)
    bioRxiv
    Climate warming is releasing carbon from soils around the world, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown. Here we used alpine grasslands as a model system to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences short-term soil carbon storage under warming. We found that warming (<1 year) led to negligible alpine soil carbon loss, but its effects became significant and 52% ± 31% (mean 95% CIs) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that soil carbon loss likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration and CO2 release. Our findings suggest that warming-induced range expansions of herbaceous plants may yield a rapid positive climate feedback in this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics.
  • Positive species interactions shape species' range limits
    Item type: Journal Article
    Stephan, Pauline; Bramon Mora, Bernat; Alexander, Jake (2021)
    Oikos
    The relationship between niche and distribution, and especially the role of biotic interactions in shaping species' geographic distributions, has gained increasing interest in the last two decades. Most ecological research has focused on negative species interactions, especially competition, predation and parasitism. Yet the relevance of positive interactions - mutualisms and commensalisms - have been brought to the fore in recent years by an increasing number of empirical studies exploring their impact on range limits. Based on a review of 73 studies from a Web of Science search, we found strong evidence that positive interactions can influence the extent of species' geographic or ecological ranges through a diversity of mechanisms. More specifically, we found that while obligate interactions, and especially obligate mutualisms, tend to constrain the ranges of one or both partners, facultative positive interactions tend to widen ranges. Nonetheless, there was more variation in effects of facultative interactions on range limits, pointing to important context-dependencies. Therefore, we propose that conceptual development in this field will come from studying ecological interactions in the context of networks of many species across environmental gradients, since pairwise interactions alone might overlook the indirect and environmentally-contingent effects that species have on each other in communities of many interacting species. Finally, our study also revealed key data gaps that limit our current understanding of the pervasiveness of effects that positive interactions have on species' ranges, highlighting potential avenues for future theoretical and experimental work.
  • Lowland plant arrival in alpine ecosystems facilitates a decrease in soil carbon content under experimental climate warming
    Item type: Journal Article
    Walker, Thomas; Gavazov, Konstantin; Guillaume, Thomas; et al. (2022)
    eLife
    Climate warming is releasing carbon from soils around the world, constituting a positive climate feedback. Warming is also causing species to expand their ranges into new ecosystems. Yet, in most ecosystems, whether range expanding species will amplify or buffer expected soil carbon loss is unknown. Here, we used two whole-community transplant experiments and a follow-up glasshouse experiment to determine whether the establishment of herbaceous lowland plants in alpine ecosystems influences soil carbon content under warming. We found that warming (transplantation to low elevation) led to a negligible decrease in alpine soil carbon content, but its effects became significant and 52% ± 31% (mean ± 95% confidence intervals) larger after lowland plants were introduced at low density into the ecosystem. We present evidence that decreases in soil carbon content likely occurred via lowland plants increasing rates of root exudation, soil microbial respiration, and CO2 release under warming. Our findings suggest that warming-induced range expansions of herbaceous plants have the potential to alter climate feedbacks from this system, and that plant range expansions among herbaceous communities may be an overlooked mediator of warming effects on carbon dynamics.
  • Alien flora of mountains
    Item type: Journal Article
    McDougall, Keith; Alexander, Jake; Haider, Sylvia; et al. (2011)
    Diversity and Distributions
  • Snow Height Sensors Reveal Phenological Advance in Alpine Grasslands
    Item type: Journal Article
    Zehnder, Michael; Pfund, Beat; Svoboda, Jan; et al. (2025)
    Global Change Biology
    Long-term phenological data in alpine regions are often limited to a few locations and thus, little is known about climate-change-induced plant phenological shifts above the treeline. Because plant growth initiation in seasonally snow-covered regions is largely driven by snowmelt timing and local temperature, it is essential to simultaneously track phenological shifts, snowmelt, and near-ground temperatures. In this study, we make use of ultrasonic snow height sensors installed at climate stations in the Swiss Alps to reveal the phenological advance of grassland ecosystems and relate them to climatic changes over 25 years (1998–2023). When snow is absent, these snow height sensors additionally provide information on plant growth at a uniquely fine temporal scale. We applied a two-step machine learning algorithm to separate snow- from plant-height measurements, allowing us to determine melt-out for 122 stations between 1560 and 2950 m a.s.l., and to extract seasonal plant growth signals for a subset of 40 stations used for phenological analyses. We identified the start of growth and calculated temperature trends, focusing particularly on thermal conditions between melt-out and growth initiation. We observed an advance of green-up by −2.4 days/decade coinciding with strong warming of up to +0.8°C/decade. Although the timing of snowmelt has not changed significantly over the study period in this focal region, phenological responses to early melt-out years varied due to differing influences of photoperiodic and thermal constraints, which were not equally important across elevations and communities. Phenological shifts of alpine grasslands are thus likely to become even more pronounced if snowmelt timing advances in the future as predicted. As climate change continues to reshape mountain ecosystems, understanding the interplay between phenological changes and species turnover will be essential for predicting future biodiversity patterns and informing conservation strategies in alpine regions.
Publications1 - 10 of 100