Hybrid poplars in dryland riparian agricultural buffers in eastern Washington: Performance and phosphorus removal

This study assessed how well hybrid poplars grew under non-commercial dryland conditions in eastern Washington. Initially the study site consisted of 360 trees, which were planted in rows along a small stream. Surrounding the site were agricultural fields. Growth measurements (heights and diameters) of the trees were taken for a number of years, concluding when the trees were six years old. Nine different hybrid poplar clones were included. Detailed measurements were made of the amount of biomass present in leaf tissue, bark and wood for some of the trees.; Because phosphorus is frequently the limiting nutrient in aquatic ecosystems and because hybrid poplars grow rapidly, it is thought that the use of hybrid poplar plantings in riparian strips would be beneficial. The physical removal of commercially useful amounts of hybrid poplar biomass would be removing phosphorus from the site, thus potentially benefiting aquatic ecosystems.; The quantity of phosphorus present in various plant tissues (leaves, bark, and wood) was assessed in this study. It was found that overall, by dry weight, 0.11% of a tree is phosphorus. This value is similar to that of many deciduous trees. By calculation, the amount of biomass based on tree height and diameter as well as the phosphorus content were used to quantify the amount of phosphorus at the study site. Biomasses obtained during the study ranged from 22.0 kg to 33.0 kg for a 6-year-old tree.; Similar calculations may be utilized to determine the necessary numbers of trees to be planted to result in certain levels of phosphorus reduction to stream systems. Different clone choices would result in differing biomasses accordingly. This site included some of the earliest clones selected for this dryland region. Subsequent selections indicate improved growth and probably will be of increased benefit to aquatic ecosystems in the future.