Silvicultural Treatments Influence Seasonal Patterns of Soil Water and Annual Growth of Douglas-fir. (6231)
Authors:
W.D. Devine* - USDA-FS, Olympia, WA C.A. Harrington - USDA-FS, Olympia, WA T.A. Terry - Weyerhaeuser Co., Centralia, WA
Abstract:
The Fall River Long-Term Site Productivity Study examines how treatments at final harvest and planting affect future site resources in an intensively managed Douglas-fir plantation. In this part of the study we evaluate: i) the effects of two organic matter retention treatments and chemical vegetation control on volumetric soil water content (VSWC), and ii) relationships between microsite VSWC and seedling growth. The study is on a highly productive western WA site, and soil is of the Boistfort series (silt loam over silty clay loam; high available water capacity). Treatments were bole-only harvest of the previous stand (± vegetation control) and total-tree harvest with removal of all woody debris (+
vegetation control). VSWC was measured at depths from 10-100 cm during the third and fourth growing seasons after planting. In both years, vegetation control provided greater VSWC from 20-60 cm from July through September. With vegetation control, VSWC was not affected by organic matter retention. Annual height growth of trees was positively correlated with VSWC from 20-60 cm; highest correlations were for 30- and 40-cm depths in July and August. Annual diameter growth was correlated with VSWC from late July through early September; correlations were highest for the 30-cm depth.
Increases in tree growth with vegetation control emphasize the importance of controlling vegetation to increase availability of soil water in a young plantation on a highly productive site.
Speaker Information: Warren Devine, USDA-FS, Olympia, WA, 3625 93rd Ave SW, Olympia, WA 98512-9193; Phone: 360-753-7675; E-mail: [email protected]
Session Information: Wednesday, November 3, 2004, 3:00 PM-5:00 PM Presentation Start: 3:00 PM (Poster Board Number: 1733)
Keywords: Douglas-fir; soil water; plantation; silviculture
