The Combined Influence of Grazing, Fire, and Herbaceous Productivity on Tree–Grass Interactions

摘要: Although Juniperus communities are native to most regions of North America, they have proliferated in many areas the Great Basin and Plains that historically supported grasslands, shrublands, savannas. Explanations for observed increases dominance, as well other woody plant communities, subject ongoing debate. The balance between herbaceous vegetation is regulated by complex interactions climate (e.g., amount seasonality rainfall), soils soil texture depth), disturbance regimes fire, gazing, browsing) (Walker 1987; Scholes Archer 1997; Higgins et al. 2000). Changes one or more these factors can potentially elicit a change ratio plants. Accordingly, change, intensification grazing, elimination fire browsing (Hastings Turner 1965; Grover Musick 1990; 1994; Fuhlendorf 1996), atmospheric CO 2 enrichment (Idso 1992; Johnson 1993), nitrogen deposition (Kochy Wilson 2001) all been invoked potential reasons proliferation over past century (see reviews Van Auken However, because correlative interact across multiple spatiotemporal scales, it neither feasible nor realistic assess their relative importance using traditional, short-term factorial experiments. Field studies based on space-for-time substitutions comparisons landscapes with differing management histories used long-term changes, but results from such difficult replicate, interpolate, extrapolate do not explicitly test causality. As result, there still considerable debate climate, influences community dynamics drylands (O’Connor 1995; Fernandez-Gimenez Allen-Diaz 1999; Illius O’Connor 2001). Dynamic simulation modeling an underutilized tool be evaluate how climate–disturbance affect tree– grass ratios competing hypotheses attempting account century. Grazing, strongly influence abundance via effects production composition. High rainfall promote