Genetic and Silvicultural Foundations for Management Team


	Land and Watershed Management Program

	Pacific Northwest Research Station

	Olympia Forestry Sciences Laboratory
	3625 93rd Ave. SW Olympia, WA 98512 (360) 753-7747

	Corvallis Forestry Sciences Laboratory
	3200 SW Jefferson Way Corvallis, OR 97331 (541) 750-7250


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Genetic and Silvicultural Foundations for Management

Selected Studies

Response of Tree Seedlings Planted Under a Range of Overstory Densities

View of overstory stand with planted seedlngs.

Land managers today are looking for alternative silvicultural systems to enhance non-timber values and reduce the visual impact of clearcutting. How Douglas-fir, western redcedar and western hemlock will regenerate and develop under these alternative systems remains a question. To understand some of the physiological and genetic aspects involved in the response to different growing environments, a new study has been established in conjunction with the Washington State Department of Natural Resources in the Capitol State Forest near Olympia, Washington.

The study will look at how six levels of overstory retention (0, 8, 16, 24, 32, and 40 percent of "full stocking") impact the growth of three trees species (Douglas-fir, western hemlock and western redcedar) planted in the understory. In addition, we will also be examining the genetic component of the Douglas-fir seedlings by following the development of 24 full-sib crosses and a 'woods-run' standard. Past breeding programs have focused on the selection of parents based on the assumption that the seedlings will be planted in an open light environment. This partnership with the Washington State DNR will allow for operational testing of shade experiments previously done in seedbeds. How the different families perform in alternative environments will help us answer the questions: 'how much choice do we have in species selection?' and 'are we selecting the right trees for our breeding programs?'

Table 1. Overstory retention levels
Unit	% Normal	Residual BA/acre/ft2	Residual TPA
1	0	0	0
	8	22	10
	16	44	21
	24	66	33
	32	88	44
	10	110	59
2	0	0	0
	8	25	9
	16	50	13
	24	72	22
	32	96	24
	40	122	34
3	0	0	0
	8	25	8
	16	49	14
	24	73	24
	32	94	26
	40	123	35

Low level aerial photography and electronic monitoring of understory environmental conditions (such as soil temperature and moisture and light) will help to interpret seedling response to the different conditions created by the range in overstory tree densities.

A supplemental study is being conducted in the buffer areas of the 0, 16, and 40% overstory densities. Understory vegetation has been removed from 0, 50, or 100% of the growing space of selected conifer seedlilngs. This additional treatment seeks to identify whether associated shrub and herbaceous vegetation moderates or compounds the competitive effects resulting from the overstory trees.

Example of aerial photography used to monitor treatment stands.

Various levels of 'full basal area stocking' will provide different environments in which to monitor seedling growth and development.

For more information on this study, please contact Leslie C. Brodie at lbrodie@fs.fed.us or (360)753-7681.

Land and Watershed Management