Western Juniper Woodland Management
Management of western juniper woodlands is an important concern in the northern Great Basin. Woodland expansion during the past 100 years (See Miller for more on Juniper Woodland Expansion) into adjacent plant communities (sagebrush grassland, riparian, aspen) is typically accompanied by (1) reductions in shrub/understory productivity, cover, and diversity, (2) increased site aridity, (3) reduced wildlife habitat, and (4) accelerated soil erosion. Juniper dominates sites by out competing other vegetation for soil water and nutrients.
The most cost effective means of preventing juniper dominance in these plant communities is with the use of natural or prescribed fire. Burning is an viable option in situations were the shrub/understory components are intact, and thus able to carry a fire through the community and effectively kill a high percentage of invading juniper. Burning is most successful when juniper encroachment is in early to mid-successional stages. Burning becomes less of an option in late successional woodlands and is effectively eliminated as a management tool when juniper fully dominates a site (See Miller for more on Fire Effects on Juniper Woodlands).
When burning is no longer an option restoration of a site can only be accomplished by mechanical treatment. The most common mechanical treatment in western juniper woodlands is cutting trees down with chain saws. Costs typically range from $.50 to $1.00 per tree.
Our research has primarily focused on sagebrush/steppe restoration in areas which are fully dominated by juniper and require cutting with chainsaws. These sites have entirely lost the shrub component, have extremely low understory cover, and accelerated erosion clearly evident.
The first picture shows a typical juniper dominated system.
The next picture shows the same area two years after tree cutting.
The picture demonstrates that tree cutting can result in restoration of understory productivity and cover relatively quickly. On this site no seeding was done, thus it was remnant understory grass and forb populations that responded to increased soil water and nutrients made available by juniper cutting. Response on this site showed a 400% increase in understory ground cover, a 1000% increase in understory productivity, and a doubling of plant diversity. Long-term monitoring of plant succession of this site and other juniper control projects are still underway.
We are also investigating the management of juniper debris after cutting. On drier, low elevation sites (below 5000 ft) we have noticed large increases of exotic annual grasses under juniper debris. By removing this microsite we may reduce annual grass establishment in these areas. We investigated the effects of winter burning of juniper debris within the first and second year after cutting on understory vegetation. Burning was conducted during the winter when soils and surface litter were saturated and frozen to reduce loss of preferred native plants. This project is still ongoing but thus far results are encouraging. Survival of established perennial grasses does not appear to be detrimentally affected by burning of juniper debris and the preferred microsites for annual grass establishment are virtually eliminated.