Anthropogenic disturbance expands the climatic limits of annual plant dominance
Authors:
Niv DeMalach,
Roberto Salguero-Gomez,
Oded Hollander,
Jane Lucas,
Alexander T. Strauss,
Tilak Chaudhary,
Y. Anny Chung,
James K. McCarthy,
Bruno Moreira,
Laís Petri,
Rachael Thornley,
Ingrid J. Slette,
Elizabeth T. Borer,
Eric W. Seabloom,
Joe Atkinson,
Karen H. Beard,
Lars A. Brudvig,
Christopher P. Catano,
Jane A. Catford,
Aimee Classen,
Adam Thomas Clark,
Ciara Dwyer,
Charles Fenster,
Oscar Godoy,
Or Gross
, et al. (32 additional authors not shown)
Abstract:
Disturbance regimes and nutrient inputs are changing worldwide, with consequences for the structure and functioning of plant communities. Classical life-history theory predicts that disturbance should shift communities from long-lived perennials toward short-lived annuals, and that nutrient enrichment may amplify this shift. However, these predictions have not been tested experimentally across bro…
▽ More
Disturbance regimes and nutrient inputs are changing worldwide, with consequences for the structure and functioning of plant communities. Classical life-history theory predicts that disturbance should shift communities from long-lived perennials toward short-lived annuals, and that nutrient enrichment may amplify this shift. However, these predictions have not been tested experimentally across broad environmental gradients. Here, using a global coordinated grassland experiment spanning 37 sites, we tested how physical disturbance, vegetation removal and shallow soil tillage, and fertilisation reshape annual-perennial balance, and whether disturbance relaxes the climatic limits of annual dominance. Disturbance nearly doubled the proportion of annual species and more than doubled the relative cover of annuals, whereas fertilisation had little influence and did not interact with disturbance. The disturbance-driven shift arose through contrasting pathways: in graminoids and legumes, it reflected the loss of perennial cover, while in forbs, the expansion of annual cover. In the absence of disturbance, annual dominance was restricted to systems with extremely hot and dry summers, but disturbance nearly tripled the extent of climate space in which annuals dominated. By rapidly reassembling after disturbance, annuals may help maintain vegetation cover, but their expansion also signals loss of perennial cover and the long-term ecosystem functions associated with it.
△ Less
Submitted 9 July, 2026;
originally announced July 2026.
Mediation Analysis in the Presence of Sample Selection Bias with an Application to Disparities in Liver Transplantation Listing
Authors:
Zain Khan,
Lynnette Sequeira,
Alexandra T. Strauss,
Vedant Jain,
Juliette Dixon,
Eric Moughames,
Tyrus Vong,
Daniel Malinsky
Abstract:
The study of disparities in the liver transplantation process may focus on quantifying causal effects, particularly the average, direct, or indirect effects of various social determinants of health on being listed as a candidate for transplant. Selection bias arises when the data sample does not represent the target population, defined here as all individuals referred to the transplant clinic. Lis…
▽ More
The study of disparities in the liver transplantation process may focus on quantifying causal effects, particularly the average, direct, or indirect effects of various social determinants of health on being listed as a candidate for transplant. Selection bias arises when the data sample does not represent the target population, defined here as all individuals referred to the transplant clinic. Listing decisions are made for the subset of patients who complete the evaluation process, who may differ systematically from the referred population. There is evidence that selection is associated with patient characteristics that also impact outcomes. Using data only from the selected population may yield biased causal effect estimates. However, incorporating data from the referred population allows for analytic correction. This correction leverages hypothesized causal relationships among selection, the outcome (getting listed), exposures, and mediators. Using directed acyclic graphs (DAGs), we establish graphical conditions under which a reweighted mediation formula identifies effect of interest - direct, indirect, and path-specific effects - in the presence of sample selection. In a clinical case study, we investigate mediated and direct effects of a patient's socioeconomic position on being listed for transplant, allowing selection to depend on race, gender, age, and other social determinants.
△ Less
Submitted 2 September, 2025;
originally announced September 2025.