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ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #314394
Title: Scale-dependent feedbacks between patch size and plant reproduction in desert grassland

Author
item SVEJCAR, LAUREN - New Mexico State University
item Bestelmeyer, Brandon
item DUNIWAY, MICHAEL - Us Geological Survey (USGS)
item James, Darren

Submitted to: Ecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2014
Publication Date: 1/15/2015
Publication URL: http://handle.nal.usda.gov/10113/60355
Citation: Svejcar, L.N., Bestelmeyer, B.T., Duniway, M., James, D.K. 2015. scale-dependent feedbacks between patch size and plant reproduction in desert grassland. Ecosystems. 18:146-153.

Interpretive Summary: We tested whether black grama plants occurring in different sized patches, ranging from the smallest (usually one isolated plant) to the interior of large patches (about a meter or more across) differed with respect to reproductive rates (producing stolons and especially ramets/baby plants). We show that plants in medium sized patches, from 20-60 cm across, had the highest rates of ramet production. Plants in the middle of big patches are probably water limited due to competition, but plants in small patches are suffering either from the lack of enough neighbors to keep the soil around them moist or perhaps to resist erosion or herbivory effects. But, in at least some time periods, its better to be a plant in a small rather than large patch (maybe during dry summers with small rainfall events).

Technical Abstract: Theoretical models suggest that scale-dependent feedbacks between plant reproductive success and plant patch size govern transitions from highly to sparsely vegetated states in drylands, yet there is scant empirical evidence for these mechanisms. Scale-dependent feedback models suggest that an optimal patch size exists for growth and reproduction of plants and that a threshold patch organization exists below which positive feedbacks between vegetation and resources can break down, leading to critical transitions. We examined the relationship between patch size and plant reproduction using an experiment in a Chihuahuan Desert grassland. We tested the hypothesis that reproductive effort and success of a dominant grass (Bouteloua eriopoda) would vary predictably with patch size. We found that focal plants in medium-sized patches featured higher rates of grass reproductive success than when plants occupied either large patch interiors or small patches. These patterns support the existence of scale-dependent feedbacks in Chihuahuan Desert grasslands and indicate an optimal patch size for reproductive effort and success in B. eriopoda. We discuss the implications of these results for detecting ecological thresholds in desert grasslands.