Herbaceous Restoration of Juniper Dominated Grasslands With Chaining and Fire

Abstract

Juniper (Juniperus spp.) encroachment in grasslands usually progresses toward a stable woody state of mature trees that requires a significant disturbance to shift succession in another direction. Fire alone is often inadequate to shift succession in dense stands of mature juniper and must be preceded by a mechanical treatment such as chaining to reduce juniper competition and increase herbaceous growth that fuels a subsequent fire. However, little long-term data are available that measure combined effects of mechanical and fire treatments on restoration of juniper-dominated grasslands. Here, on a degraded (40% bare ground) north Texas site dominated by redberry juniper (Juniperus pinchotii Sudw), we quantify long-term herbaceous responses to mechanical chaining followed by fire. Two types of chaining, ground-level and elevated, were evaluated and all chained plots were burned 4 years after chaining. Herbaceous and woody responses were measured for several years after both chaining and fire treatments and compared to untreated controls. At study termination, both of the chaining + fire treatments reduced juniper cover from 32% to < 6%, but mortality was < 10%, because most plants basal-sprouted. Total grass production did not increase in chained treatments over the untreated until 3 growing seasons after chaining. Grass production declined the first growing season following the fire treatment, but increased in treated plots to 3 times the untreated the second and third year postfire. Total grass cover in treated plots did not increase over the untreated until the second year after the fire treatment. There was no difference in juniper or herbaceous responses between the 2 chain types. Results suggest increases in herbaceous production from chaining alone were due to increased growth of existing vegetation patches whereas the fire treatment appeared to stimulate herbaceous recruitment into bare soil areas.