Expansion and population structure of transplanted Aristida beyrichiana (wiregrass) tussocks: results of a 37‐year study

Abstract

Aristida beyrichiana (wiregrass) is a foundation bunchgrass species in many southeastern U.S. native pine communities, but it has been dramatically reduced in extent. The potential for reintroduced wiregrass to reproduce and spread is not well studied because of its slow growth and limited conditions for successful reproduction. We present a case study where tussocks of wiregrass were transplanted and recensused 18 and 37 years later to study their population dynamics. We remeasured a subset of tussocks to estimate diameter growth over 2 years. With frequent prescribed fires (1-3 year intervals, about half in April-July when flowering is induced), the initial population of 160 tussocks increased to 1,199 through seed dispersal and clonal fragmentation, and the total basal area approximately tripled. Relationships among tussock density, diameter, and basal area per m 2 and their changes over time suggest density-dependent regulation of population structure, possibly from intraspecific competition and competitive exclusion. Tussock diameter growth averaged 0.9 cm per year over a 2-year period and was independent of initial diameter. This study, the longest of a wiregrass population to date, suggests that a low-density population established in native soil types has a slow but robust tendency to reproduce by seed and expand if provided frequent fire, including April-July burns, in a high light environment without soil disturbance. Wiregrass can be characterized as a competitive, late-successional, dominant species in stable, climax-like native savannas, promising long-term success under appropriate conditions as part of restoration efforts.

Mechanical soil disturbance in a pine savanna has multiyear effects on plant species composition

“…Also, we have observed that most of these are masting species, producing abundant fruit and seeds only in certain years, thus limiting opportunities for establishment. The lack of A. beyrichiana , the dominant perennial grass in the undisturbed sites, is consistent with many soil disturbance studies documenting its limited dispersal capacity, low seed viability, and requirement for late spring or summer fires to flower (Laucevicius et al, 2021; Mulligan et al, 2002; Perez, 2014). Other species that were absent or greatly underrepresented in the repeated‐disturbance plots compared with undisturbed plots included Ceanothus americanus L., Eupatorium album L., Malus angustifolia (Aiton) Michx., Mimosa quadrivalvis L., Pteridium pseudocaudatum (Clute) Christenhusz., Sericocarpus tortifolius (Michx.)…”