TY - JOUR

T1 - Evaluating grazing response strategies in winter annuals

T2 - A multi-trait approach

AU - Kurze, Susanne

AU - Bilton, Mark C.

AU - Álvarez-Cansino, Leonor

AU - Bangerter, Sara

AU - Prasse, Rüdiger

AU - Tielbörger, Katja

AU - Engelbrecht, Bettina M.J.

N1 - Funding Information: We thank Pierre Liancourt for support in the coordination and conductance of the grazing exclosure experiment and for valuable comments on the manuscript, Fabian Nützel for assistance in raising the plants, Burkhard Stumpf for assistance in setting up the greenhouse experiments and in several trait measurements, Rafael Piper for measurements of reproductive traits in the grazing simulation experiment, many students whose help was invaluable in the greenhouse experiments, and Eun‐Young Jung for stimulating discussions. The BayCEER Laboratory of Isotope Biogeochemistry in Bayreuth carried out the carbon and nitrogen analyses. This study was funded by the German Research Foundation (DFG, AL 1952/1‐1 and TI 338/12‐1). The grazing exclosure experiment was part of the GLOWA Jordan River project funded by the BMBF (granted to K.T. and R.P.). Open access funding enabled and organized by Projekt DEAL.

PY - 2021/8

Y1 - 2021/8

N2 - Plants minimize fitness losses through grazing by three fundamental strategies: tolerance, avoidance and escape. Annual species have been traditionally assumed to escape grazing through their short life cycle and seed dormancy; however, their grazing response strategies remain almost unexplored. How traits and their coordination affect species' grazing responses, and whether the generalized grazing model, which posits convergent filtering by grazing and drought, is applicable to this ecologically and economically important species group thus remain unclear. We used a trait-based approach to evaluate grazing response strategies of winter annuals from the Middle East. Across 23 species, we examined the coordination of 16 traits hypothesized to be relevant for grazing responses, and linked them to species' fecundity responses, as proxy for fitness responses, to simulated grazing in controlled conditions, to species' abundance responses to grazing in the field and to species' distribution along a large-scale rainfall gradient. Winter annuals exhibited both grazing escape and to a lesser extent tolerance indicated by (a) independent coordination of escape and tolerance traits, and (b) maintenance of higher fecundity in species with more pronounced escape or tolerance traits under simulated grazing. In the natural habitat, species with a more pronounced escape but not tolerance strategy maintained higher abundance under grazing in dry habitats, indicating convergent favouring of escape by both grazing and drought. However, this finding at the local scale was not mirrored by a strategy shift along a large-scale rainfall gradient. Synthesis. The convergent favouring of escape traits by grazing and drought in annuals is consistent with the generalized grazing model. This model, which has been developed for perennials based on the avoidance strategy, can thus be extended to annuals based on escape, a finding that should facilitate projecting consequences of global change in drylands dominated by annuals.

AB - Plants minimize fitness losses through grazing by three fundamental strategies: tolerance, avoidance and escape. Annual species have been traditionally assumed to escape grazing through their short life cycle and seed dormancy; however, their grazing response strategies remain almost unexplored. How traits and their coordination affect species' grazing responses, and whether the generalized grazing model, which posits convergent filtering by grazing and drought, is applicable to this ecologically and economically important species group thus remain unclear. We used a trait-based approach to evaluate grazing response strategies of winter annuals from the Middle East. Across 23 species, we examined the coordination of 16 traits hypothesized to be relevant for grazing responses, and linked them to species' fecundity responses, as proxy for fitness responses, to simulated grazing in controlled conditions, to species' abundance responses to grazing in the field and to species' distribution along a large-scale rainfall gradient. Winter annuals exhibited both grazing escape and to a lesser extent tolerance indicated by (a) independent coordination of escape and tolerance traits, and (b) maintenance of higher fecundity in species with more pronounced escape or tolerance traits under simulated grazing. In the natural habitat, species with a more pronounced escape but not tolerance strategy maintained higher abundance under grazing in dry habitats, indicating convergent favouring of escape by both grazing and drought. However, this finding at the local scale was not mirrored by a strategy shift along a large-scale rainfall gradient. Synthesis. The convergent favouring of escape traits by grazing and drought in annuals is consistent with the generalized grazing model. This model, which has been developed for perennials based on the avoidance strategy, can thus be extended to annuals based on escape, a finding that should facilitate projecting consequences of global change in drylands dominated by annuals.

KW - annual species

KW - ecological filtering

KW - escape

KW - plant–herbivore interaction

KW - rainfall gradient

KW - semi-arid rangelands

KW - tolerance

KW - trait coordination

UR - http://www.scopus.com/inward/record.url?scp=85108851892&partnerID=8YFLogxK

U2 - 10.1111/1365-2745.13721

DO - 10.1111/1365-2745.13721

M3 - Article

AN - SCOPUS:85108851892

VL - 109

SP - 3074

EP - 3086

JO - Journal of Ecology

JF - Journal of Ecology

SN - 0022-0477

IS - 8

ER -