Riparian Forest Conservation

Fences are removed once planted trees are large enough to withstand browsing/Photo Courtesy of Dr. Madeline Kalbach

Since 2001, 26 separate riparian enhancement projects have been completed to benefit Columbian white-tailed Deer (CWTD), birds and more.

 

 


A Glimpse into the Past 

Historically, much of the two diked units were once tidally influenced Sitka Spruce swamps that were flooded twice daily by ocean tides backing up the Columbia River. Once dikes were constructed and most of the old growth trees were cut, the drier sites were transformed into pastures and hayfields. Dikes, tide gates, natural sloughs, and drainage ditches now control flooding during periods of high tides. The native forest of the area is classified as a tideland Sitka spruce community and consists of an over-story of black cottonwood, Sitka spruce, western red cedar, red alder, cascara, and big leaf maple and an under-story of shrubs such as snow berry, creek dogwood, vine maple, red elderberry, willow and salmonberry. Scattered openings in the over-story help maintain the understory and permit growth of other desirable deer forage species such as blackberry, thimbleberry, hawthorn and wild rose. The condition of many of the non-tidal forested sites is declining with little or no understory regeneration.

Getting Back What Has Been Lost 

Restoration of native riparian forest has been of ongoing concern since the establishment of the refuge in 1972. Both forested sites and passively managed fields (most often reed canarygrass fields and brush patches) are being managed to provide escape, resting and fawning cover for the Columbian white-tailed deer (CWTD).

Passive management, in which grass and brush fields that serve as cover for CWTD become reforested through natural plant succession, does not work. The wet, mild climate encourages a lush growth of reed canarygrass and Juncus that continually choke out woody seedlings. Heavy deer, elk, and rodent use also impact tree regeneration. Large scale tree planting began on the Mainland unit in 1999. Newly planted trees are initially protected with a 12-foot tall hog wire fence, individual tree protectors and weed mats to protect them from wildlife until they are larger and can withstand impacts of deer, elk, voles and beavers.

Learn more about the restoration of riparian forests... 

Site Preparation 

Riparian planting sites are initially prepared in the summer when field conditions are capable of supporting the heavy equipment necessary for site preparation. These sites are prepared by disking in summer in anticipation for planting during the following spring. In selective situations, smaller sites may be tilled during March to give native trees additional competitive advantage against invasive reed canary grass. Riparian reforestation corridor sites are generally located along sloughs and other significant waterways. All plantings consist of native bare root stock obtained from local (western Washington/Oregon) growers and nurseries. Trees are planted at a rate of approximately1,000 trees/acre, with a survival  rate of around 60 percent for trees planted in fenced tree lots.

Shelter Me 

Tree protectors are used in the planting sites to protect the base of each plant from meadow vole predation; which can be significant. Tree protectors are a minimum of 18-24 inches in height mainly for the protection of the tree base from meadows voles or other rodents which tend to girdle the base of the plants. The tree protectors gradually break away from the base of the tree over the course of four to five years and eventually fall to the ground and degrade. Fences to protect the trees are usually constructed around the plantings on the mainland unit. Fences are 10 feet in height and capable of keeping large mammals such as deer and elk out of the planting sites. The fences generally remain in place until the plantings are of a sufficient height to be relatively safe from large mammals and beaver. Once the trees are large enough, depending on site conditions between four and six years, the fencing is removed and materials reused when in good condition. Trees are planted in rows throughout each corridor site in random order to permit mowing between the rows during the first year of each planting.