Abstracts, Reviews, and Meetings

Grasslands

Pyric Herbivory: Rewilding Landscapes through the Recoupling of Fire and Grazing. 2009. Fuhlendorf, S.D. (Natural Resource Ecology & Management, Oklahoma State University, 008C AGH, Stillwater, OK 74078, sam.fuhlendorf@okstate.edu), D.M. Engle, J. Kerby and R. Hamilton. Conservation Biology 23(3):588–598.

Most studies of fire and grazing are controlled small-scale experiments that fail to consider spatial and temporal interactions on complex landscapes. This essay proposes a new focus, which recognizes that fire and grazing interact through positive and negative feedbacks rendering disturbance patterns a shifting mosaic ("pyric herbivory"). Data from the Nature Conservancy's Tallgrass Prairie Preserve in Oklahoma demonstrate that the interaction between random fires and free-ranging bison (Bison bison) promotes heterogeneity, and likely could provide the foundation for biodiversity and ecosystem function in grasslands everywhere. The authors suggest that management by pyric herbivory based on any grazing herbivore, including domestic livestock, may be more effective than reintroduction of large grazers without coupling grazing to fire.

Do Seed and Microsite Limitation Interact with Seed Size in Determining Invasion Patterns in Flooding Pampa Grasslands? 2009. Herrera, L.P. (Facultad de Ciencias Agrarias, Universidad Nacional de Mar del Plata. Instituto Nacional de Tecnología Agropecuaria, Estación Experimental Agropecuaria Balcarce, CC 276, Ruta 226, Km 73.5 (7620), Balcarce, Argentina, lherrera@mdp.edu.ar) and P. Laterra. Plant Ecology 201(2):457–469.

The authors studied the emergence of seedlings of common grassland colonizer species in the Argentine Pampas, considering 1) large or small seed size; 2) patch seeded or not seeded; 3) species-poor patch dominated by a tall tussock grass, or species-rich and dominated by short grasses; and 4) canopy cut or uncut. "Invasion" depended on interactions among these factors. Seeding promoted emergence to varying degrees in seven of the ten species sown, especially in tall-grass patches, and large seeds had an advantage over small seeds. However, after seed limitations were accounted for, the relative invasiveness of study species depended on both the species composition of the plant community being colonized and its disturbance treatment (cut or uncut).

Receptiveness of Foraging Wild Bees to Exotic Landscape Elements. 2009. Hinners, S.J. (Dept of Ecology & Evolutionary Biology and Cooperative Institute for Research in Environmental Sciences, Campus Box 216, University of Colorado, Boulder, CO 80309, hinners@colorado.edu) and M.K. Hjelmroos-Koski. American Midland Naturalist 162(2):253–265.

Analysis of the species composition of pollen from bees collected in native grassland fragments in the greater Denver–Boulder metropolitan area found that at least 45% of the pollen load came from non-native plants. During peak flowering in early summer, bees obtained more pollen from the grassland fragments than from nearby suburban residential yards, although 58.5% was from species found in both grasslands and yards. By midsummer, nearly 60% of the pollen came from plants found only in grasslands, and the fraction of pollen from species restricted to yards was very small. The authors concluded that the foraging behavior of wild bees changes throughout the season, but in general, bees accept non-native plant species more readily than they accept anthropogenically altered habitats.

Woodlands

Invasion of Tallow Tree into Southern US Forests: Influencing Factors and Implications for Mitigation. 2009. Gan, J. (Dept of Ecosystem Science & Management, 2138 TAMU, Texas A&M University, College Station, TX 77843-2138, j-gan@tamu.edu), J.H. Miller, H. Wang and J.W. Taylor Jr. Canadian Journal of Forest Research 39(7):1346–1356.

The authors found the best predictors of Chinese tallow (Triadica sebifera) invasions in Texas, Louisiana, Mississippi, and Alabama forests to be elevations lower than 50 m and slope less than two percent. Contributing factors were adjacent water or roads, disturbance or recent timber harvesting, natural regeneration, young forests, private ownership, and mean extreme minimum temperature above –12°C. The authors warn that as climate warms, the range and severity of tallow invasions will increase, and greater frequency and intensity of disturbance could exacerbate the situation. Intensive management to enhance the vigor of planted species and control competition can lessen the risk of invasion. Studies across different ecosystems would increase understanding of tallow invasion...