TV025
Ecosystem responses to the creation of tree-fall gaps in the western Cascades of Oregon and Washington (Experimental Gap Study), 1990 to 2006

CREATOR(S): Jerry F. Franklin, Thomas A. Spies, Kristiina A. Vogt

PRINCIPAL INVESTIGATOR(S): Thomas A. Spies

ORIGINATOR(S): Thomas A. Spies, Jerry F. Franklin, Kristiina A. Vogt

OTHER RESEARCHER(S): Robert P. Griffiths, Andrew N. Gray, Robert J. Pabst

DATA SET CONTACT PERSON: Andrew N. Gray

METADATA CONTACT: Andrew N. Gray

FORMER INVESTIGATOR: Robert Van Pelt, Mark J. Easter

DATA SET CREDIT:

Primary work on the database was by Mark Easter, Rob Pabst, and Andrew Gray. Funding for data collection, and database creation, was provided in part by NSF BSR-8909038 NSF DEB-9527701, USDA NRICGP ORER-9600884, and the USDA Forest Service Pacific Northwest Research Station.

METADATA CREATION DATE:

1 Aug 2002

MOST RECENT METADATA REVIEW DATE:

23 Jan 2014

KEYWORDS:

Disturbance, Disturbance, Primary production, microclimate, species diversity, primary production, regeneration, disturbance

PURPOSE:

Small canopy disturbances are important to the structure and function of forest ecosystems. Fine-scale disturbances (the death of one to many trees) largely control the population dynamics in our forests between larger catastrophic events. An experimental study of ecosystem responses to the creation of tree-fall gaps of varying size was conducted in northwestern coniferous forests. Gaps were created in the fall of 1990 in mature (80 to 150 years) and old-growth (400-500 years old) ecosystems dominated by Douglas-fir (Pseudotsuga menziesii) and western hemlock (Tsuga heterophylla). Five gap sizes ranging from 0 to 2000 m² were created in four stands, with gap diameters scaled in fixed proportion to the average canopy height in each stand. Roots were severed in trench plots placed in open- and closed-canopy areas to compare with gap responses. Both above-ground and below-ground processes were studied. Establishment, survival, and growth of trees and understory vegetation were measured within and surrounding gaps. Solar radiation, air and soil temperature, and soil moisture were measured. Litter input, decomposition, root density, N-mineralization and N-leaching, soil microbial response and myccorrhyzal mats have been studied. Population biology of selected understory herbs, and composition and abundance of small mammal communities, have also been examined.

METHODS:

Experimental Design - TV025:

Description: 40 gaps in 4 stands stratified by successional stage (2: mature and old-growth) and gap size (5: defined as gap diameter/canopy height = 0, 0.2, 0.4, 0.6, and 1.0), with two of each size in each stand. Gap diameter defined as distance from crown edge to crown edge. Microplots were sampled in a grid that covers the gap outline and immediate area in the surrounding canopy. Information on cover by species was collected at intervals before and after the gap creation. Densities of regeneration of tree species was also collected as well as information about diameters and growth of the canopy trees surrounding the gaps. Data on soil moisture, temperature and radiation within the gaps was also collected for a period before and after gap creation.

Field Methods - TV025:

Description: See publication

Citation: Gray, A.N., and T.A. Spies. 1996. Gap size, within-gap position, and canopy structure effects on seedling establishment of conifer species in forest canopy gaps. Journal of Ecology 84(5): 635-645.

SITE DESCRIPTION:

http://andrewsforest.oregonstate.edu/data/studies/tv025/tv025_sitedescription.pdf

TAXONOMIC SYSTEM:

Garrison et al., 1976

GEOGRAPHIC EXTENT:

west-slope forests of the Oregon and Washington Cascades

ELEVATION_MINIMUM (meters):

550

ELEVATION_MAXIMUM (meters):

900

MEASUREMENT FREQUENCY:

varies with type of data

PROGRESS DESCRIPTION:

Complete

UPDATE FREQUENCY DESCRIPTION:

irregular

CURRENTNESS REFERENCE:

Ground condition

RELATED MATERIAL:

Easter, M.J., and T.A. Spies. 1994. Using hemispherical photography for estimating photosynthetic flux density under canopies and in gaps in Douglas-fir forests of the Pacific Northwest. Canadian Journal of Forest Research 24: 2050-2058

Gray, A.N., and T.A. Spies. 1995. Water content measurement in decayed wood and forest soils using time domain reflectometry. Canadian Journal of Forest Research 25: 376-385.

Gray, A.N., and T.A. Spies. 1996. Gap size, within-gap position, and canopy structure effects on seedling establishment of conifer species in forest canopy gaps. Journal of Ecology 84(5): 635-645.

Gray, A.N., and T.A. Spies. 1997. Microsite controls on tree seedling establishment in conifer forest canopy gaps. Ecology 78(8):2458-2473. Gray, Andrew N., Thomas A. Spies, and Mark J. Easter. 2002. Microclimatic and soil moisture responses to gap formation in coniferous forests.

Canadian Journal of Forest Research 32: 332-343. McCune, B. 1993. Gradients in epiphyte biomass in three Pseudotsuga-Tsuga forests of different ages in western Oregon and Washington. Bryologist 96: 405-411.

McCune, B. 1994. Using epiphyte litter to estimate epiphyte biomass. Bryologist 97: 396-401.

Van Pelt, R., and M.P. North. 1996. Analyzing canopy structure in Pacific Northwest old-growth forests with a stand-scale crown model. Northwest Science 70(special issue): 15-30.

Van Pelt, Robert, and Jerry F. Franklin. 1999. Response of understory trees to experimental gaps in old-growth Douglas-fir forests. Ecological Applications 9(2): 504-512.

Van Pelt, Robert, and Jerry F. Franklin. 2000. Influence of canopy structure on the understory environment in tall, old-growth conifer forests. Canadian Journal of Forest Research 30(8): 1231-1245.

Vogt, K.A., D.A. Publicover, J. Bloomfield, J.M. Perez, D.J. Vogt and W.L. Silver. 1993. Belowground responses as indicators of environmental change. Environmental and Experimental Botany 33:189-205.

Vogt, K.A., D.J. Vogt, H. Asbjornsen, and R.A. Dahlgren. 1995. Roots, nutrients and their relationship to spatial patterns. Plant and Soil 168-169: 113-123.

Gitzen, R.A. 1999. The Effects of Experimental Canopy Gaps on Small Mammal Communities in the Southern Washington Cascades. M.S. Thesis. University of Washington, Seattle, WA.

Gray, A. N. 1995. Tree seedling establishment on heterogenous microsites in Douglas-fir forest canopy gaps. Dissertation. Oregon State University, Corvallis, OR .<br> London, S.G. 1999. Spatial Distribution of Understory Vegetation in Tree Canopy Gaps of the Pacific Northwest. M.S. Thesis. Oregon State University, Corvallis, OR.

Monteleone, S.E. 1997. Light spectra distributions in temperate conifer_forest canopy gaps, Oregon and in tropical cloud_forest canopy, Venezuela. Dissertation. University of North Texas, Denton, TX.

St. Pierre, E.A. 2000. Effects of canopy gaps in Douglas-fir forests and resource gradients on fecundity and growth of understory herbs. Dissertation. Oregon State University, Corvallis, OR.

Van Pelt, R. 1995. Understory Tree Response to Canopy Gaps in Old-growth Douglas-fir Forests of the Pacific Northwest. Dissertation. University of Washington, Seattle, WA.