Realm: Terrestrial
Climate: Temperate
Biome: Temperate broadleaf and mixed forests
Central latitude: 47.400000
Central longitude: -95.120000
Duration: 3 years, from 1984 to 1996

1406 records

25 distinct species

Across the time series Acer saccharum is the most frequently occurring species

Citation(s):

Webb, S. L. & Scanga, S. E. (2001) Windstorm Disturbance without Patch Dynamics: Twelve Years of Change in a Minnesota Forest. Ecology, 82, 893 –897.

Methods

Itasca State Park. Minnesota. is a 13 000-ha forestpreserve at 478N latitude. with a cold continental climate(mean annual temperature 3.78C. mean annualprecipitation 640 mm; Kuehnast 1972) and with diversesoils on glacial and meltwater deposits within a terminalmoraine. Forest cover in the 16-ha study area(T143N. R36W. Sec. 36. N?. NE?; pine?maple/BuddLake area of Webb [1988. 1989]) is heterogeneous withelements of northern hardwoods. white pine. red pine.and aspen?sugar maple cover types (Eyre 1980). Clustersof Pinus resinosa and scattered individual Pinusstrobus amidst hardwoods date back over 250 yr basedon our tree ring counts and originated after fire (Frissell1973; Clark 1989). The understory is also heterogenous.with thickets of Corylus cornuta shrubs. clumpsof the shrub Acer spicatum. carpets of seedlings of Acersaccharum and Acer rubrum. and patches of saplingsof Ostrya virginiana and Acer saccharum. The herbaceousflora is sparse and thus omitted from this analysis.Nomenclature follows Gleason and Cronquist 1991.METHODSPlots were sampled in mid-summer 1984. 1992. and1996. Each treefall had four 2 3 2 m plots: one plotnear the base (0.5 m north of the stump?s north edge).one plot in the fallen crown area (north of the bole justbeyond the first branch of the fallen crown). and twocontrol plots in parallel configuration at undamagedconspecific trees. Two base plots and three crown plotswere omitted due to interference from trails or treelesswet meadows. Note that plot locations were not permanentlymarked in the original survey. Thus. althoughthe treefall plots were likely to coincide in repeatedsampling. the control plots were less likely to be placedin exactly the same location in subsequent surveys. Ineach plot. all trees and shrubs were identified. counted.and recorded by height class (small. .50 cm in height;medium. 50-200 cm; tall. .200 cm in height. but dbh. 2.5 cm). Of 30 treefalls sampled originally in 1984.17 were still distinguishable in 1992. and 11 were distinguishablein 1996. In some cases. we are certain thatwe found the location of the old treefall. but the primarywindthrown tree had been obliterated by subsequenttreefalls. or (particularly for Betula papyrifera)entirely decomposed. Windthrown pines were still visibleand were all relocated. In contrast. fallen Populustremuloides. P. grandidentata. and other hardwoodswere less persistent. Any resulting bias in plot retrievalshould exaggerate the effects of windstorms. since largertreefalls were most likely to be included in the latersurveys. To accommodate decreasing sample size overtime. comparisons are based on densities per unit area.The data set contained a total of 58 individual plots in1984 and 1992. and 40 plots in 1996. Sample size wassufficient to reveal significant changes over time in thestatistical analysis; thus differences between treefalland control areas should also be detectable.We used repeated-measures ANOVA to identify differencesin vegetation that might be related to windstormdisturbance. The dependent variables. run one ata time. were species richness overall. for shrubs. andfor trees; and stem density by height class for all woodystems combined. for all shrubs. for all trees. and byspecies. The three independent variables. modeled together.were (1) treefall vs. control plot. (2) base vs.crown plot. and (3) year (1984. 1992. 1996). The base/crown factor was not significant and is not discussedhere. For those species for which ??year?? was significant.we checked for carry-over effects using a test forsphericity. In cases where the sphericity assumption ofthe univariate model was violated (the case of P .0.05). we tested again using a multivariate test that wasless powerful but more conservative (von Ende 1993;Norusis 1993). Unit of abundance = Count, Unit of biomass = NA