trees that establish in open meadows can exert strong effects on
local vegetation. In a companion study to the chronosequence
analysis, we posed the following questions:
does tree age (i.e., duration of influence) affect the cover and
richness of meadow and forest understory species?
effects of individual trees more pronounced on meadow or forest
Do lodgepole pine and grand fir differ in their effects on meadow
or forest species?
areas of open meadow, we selected 39 lodgepole pine and 46 grand
fir (>1.4 m tall) of a range of sizes and ages (20-70 yr).
the base of each tree, ground vegetation was sampled with a transect
extending to the SW and NE. Each
transect was sampled in two equal lengths —under the canopy
and in open meadow— (photo, above
right), using a series of 20 x 50 cm quadrats (photo,
below right). Within
each quadrat, we estimated cover of each plant species.
Plant species were classified into two groups, based on habitat
affinity (meadow and forest understory; see Plant
each quadrat we tallied the number, and summed the cover of forest
and meadow species. Effects of individual trees were expressed as
the mean difference between under-canopy and open-meadow quadrats.
General linear models were then used to test effects of tree age
and tree species on each measure of response.
R. D., and C. B. Halpern. 2010.
Tree age and tree species shape positive and negative interactions
in a montane meadow. Botany 88:488-499.
transect extending from the base of a young grand
fir into open meadow.
plant cover in a sampling quadrat under a young