Mulching to regenerate a harsh site: effect on Douglas-fir seedlings, forbs, grasses, and ferns

Abstract

Douglas-fir seedlings on the Arcata District, Bureau of Land Management, U.S. Department of the Interior, in central coastal California, were planted in an effort to restore the natural forest to what was then pastureland. Douglas-fir seedlings were released from a complex forb-grass-fern plant community by applying very large (10-ft square) and very small (2-foot square) durable mulches one month after planting. The large mulches were installed directly over the existing plant community, and the small mulches were applied over a similar-sized scalp. Two-foot-square scalps and an untreated control provided additional comparisons. After five growing seasons, stem diameter (measured at 12 inches above mean groundline) of Douglas-fir seedlings with large mulches was 1.61 inches, and of seedlings with small mulches was 1.36 inches. Only seedlings with large mulches were significantly larger than counterparts with small scalps (1.22 inches) or in the control (1.26 inches) after 5 years. In spite of high cost, the promising role of large mulches for establishing fast-growing Douglas-fir seedlings on a harsh site and the increased stability and sustainability that the future trees will bring to the more natural plant community give large mulches a place in the toolkit of ecosystem managers. Retrieval Terms: central California, Douglas-fir seedlings, herbaceous species, mulches, plant community dynamicsAs the 21st century approaches, sustainable ecosystems are receiving increasing attention. Such ecosystems in general are those that contain the species composition, structure, and functions that were present before severe perturbation by humans. Past logging, deliberate burning to promote pasture, and many years of grazing, first by sheep and then by cattle, certainly count as a severe disturbance. Chronic disturbance also leads to an unnatural and unstable ecosystem, and one that cannot provide the full range of commodities and amenities of which it is capable. Foresters in the Arcata District, Bureau of Land Management, U.S. Department of the Interior, recognized this and wished to begin restoring the land and its plant and animal components to a more desirable and sustainable future condition.This was a formidable job. The plant community consisted of a complex arrangement of forbs, grasses, and bracken fern. Rabbits and deer were animal components of this community as well. These plants and animals, plus steep slopes, summer drought, and incessant wind, caused this to be a harsh site for conifer regeneration. Planting Douglas-fir seedlings was the first of four steps in the restoration process, getting the seedlings to survive and grow well the second, treating the existing plant community to be less competitive the third, and mitigating animal damage was the fourth.Five years after treatment, Douglas-fir seedling survival ranged from 70 to 98 percent and did not differ signifi cantly among treatments. Also after 5 years, mean stem diameter, measured at 12 inches above groundline, of Douglas-fir seedlings with large ...

Assessment of Microenvironmental Conditions Related to the Use of Synthetic Sheet Mulches for Protecting Newly Planted Trees in Semi-Arid Environments

“…Within-treatment variation was high probably because of heavy deer damage in some plots located near a fence row. Increased deer browse has been reported on trees mulched with synthetic sheet mulches compared to unmulched controls (Yawney and Carl, 1970;Stange and Shea, 1998;McDonald et al, 1994), but a similar preference for mulched trees was not observed in our study.…”

“…The woven construction is meant to allow water infiltration and gas exchange but still slow evaporation and weed penetration. Although published studies have found little improvement in seedling survival or growth using woven polypropylene (McDonald et al, 1994;McDonald and Everest, 1996;Windell and Haywood, 1996), many general field observations in the central Great Plains indicate seedling performance is improved (Wright, 1991). Tests conducted in Wyoming (Perko and Arnold, unpublished data) found higher soil moisture in the summer and fall under woven polypropylene.…”