Lake-effect snow as the dominant control of mesic-forest distribution in Michigan, USA

1Recent studies demonstrated the sensitivity of northern forest ecosystems to changes in the amount and duration of snow cover at annual to decadal time scales. However, the consequences of snowfall variability remain uncertain for ecological variables operating at longer time scales, especially the distributions of forest communities. 2The Great Lakes region of North America offers a unique setting to examine the long-term effects of variable snowfall on forest communities. Lake-effect snow produces a three-fold gradient in annual snowfall over tens of kilometres, and dramatic edaphic variations occur among landform types resulting from Quaternary glaciations. We tested the hypothesis that these factors interact to control the distributions of mesic (dominated by Acer saccharum, Tsuga canadensis and Fagus grandifolia) and xeric forests (dominated by Pinus and Quercus spp.) in northern Lower Michigan. 3We compiled pre-European-settlement vegetation data and overlaid these data with records of climate, water balance and soil, onto Landtype Association polygons in a geographical information system. We then used multivariate adaptive regression splines to model the abundance of mesic vegetation in relation to environmental controls. 4Snowfall is the most predictive among five variables retained by our model, and it affects model performance 29% more than soil texture, the second most important variable. The abundance of mesic trees is high on fine-textured soils regardless of snowfall, but it increases with snowfall on coarse-textured substrates. Lake-effect snowfall also determines the species composition within mesic forests. The weighted importance of A. saccharum is significantly greater than of T. canadensis or F. grandifolia within the lake-effect snowbelt, whereas T. canadensis is more plentiful outside the snowbelt. These patterns are probably driven by the influence of snowfall on soil moisture, nutrient availability and fire return intervals. 5Our results imply that a key factor dictating the spatio-temporal patterns of forest communities in the vast region around the Great Lakes is how the lake-effect snowfall regime responds to global change. Snowfall reductions will probably cause a major decrease in the abundance of ecologically and economically important species, such as A. saccharum.

Meteorological data, stem radius measurements (SR) and derivates of SR of the three Swiss forest sites Visp, Davos and Lägeren

. Separating continuously measured stem radius (SR) fluctuations into growth-induced irreversible stem expansion (GRO) and tree water deficit-induced reversible stem shrinkage (TWD) requires a concept to decide on potential growth processes during periods of shrinking and expanding SR below a precedent maximum. Here we investigated two physiological concepts: the linear growth (LG) concept assuming linear growth vs. the zero growth (ZG) concept assuming no growth during periods of shrunken stems. . We evaluated the physiological mechanisms underlying these two concepts and assessed the respective plausibility with SR data obtained from 15 deciduous and evergreen trees. . The LG concept showed steady growth rates, whereas the ZG concept showed strongly varying growth rates over time, more in accordance with mechanistic expectations. Further, growth increased for maximally 120 min after periods of shrunken stems, indicating limited growth activity during that period. However, the fraction of this extra growth was found to be small. Furthermore, TWD of the ZG concept was better explained by a hydraulic plant model than TWD of the LG concept. . We conclude that periods of shrunken stems allow for very little growth in the four tree species investigated. However, further studies should focus on obtaining independent growth data to ultimately validate these findings.

Forest Hills Gardens : the suburban land development of the Russell Sage Foundation.

Mode of access: Internet.

Notes on the flora, especially the forest flora, of the Bitter Root mountains.

Proceedings of the Iowa academy of sciences. v.12, p.87-100, pl.22-27, 1905.

Fair Em, the miller's daughter of Manchester : with the love of William the Conqueror /

Imprint fictitious. Printed by the editor for private circulation. Cf. Jaggard, William. Shakespeare bibliography, 1911, page 552.

Conflicting laws and regulations : gridlock on the national forests : oversight hearing before the Subcommittee on Forests and Forest Health of the Committee on Resources, U.S. House of Representatives, One Hundred Seventh Congress, first session, December 4, 2001.

"Serial no. 107-76."

Management of old growth forests [microform] : oversight hearing before the Subcommittee on General Oversight, Northwest Power, and Forest Management of the Committee on Interior and Insular Affairs, House of Representatives, Ninety-ninth Congress, second session ... hearing held in Salem, OR, April 28, 1986.

"Serial no. 99-47."

Management of the Tongass National Forest [microform] : hearings before the Subcommittee on Forests, Family Farms, and Energy of the Committee on Agriculture, House of Representatives, One Hundredth Congress, second session, on H.R. 1516, May 25 and 26, 1988.

"Serial no. 100-86."

Forest service wilderness management [microform] : oversight hearing before the Subcommittee on National Parks and Public Lands of the Committee on Interior and Insular Affairs, House of Representatives, One Hundredth Congress, second session ... hearing held in Washington, DC, July 26, 1988.

"Serial no. 100-63."

Exchange certain national forest system lands in the Targhee National Forest [microform] : hearing before the Subcommittee on Forests, Family Farms, and Energy of the Committee on Agriculture, House of Representatives, One Hundredth Congress, second session, on H.R. 4028, April 16, 1988; Driggs, ID and April 27, 1988.

"Serial no. 100-88."

Middle Atlantic Interstate Forest Fire Protection Compact to include the state of Ohio; land conveyance in Henderson, TN; and release a revisionary interest of the United States in certain land located in Oktibbeha County, MS [microform] : hearings before the Subcommittee on Forests, Family Farms, and Energy of the Committee on Agriculture, House of Representatives, One Hundredth Congress, second session, on H.R. 2756, H.R. 2835, and H.R. 4724, May 4, 1988 ... September 22, 1988 ....

"Serial no. 100-89."

Review the effects of the 1987 forest fires and the recovery efforts in the national forests in California [microform] : hearing before the Subcommittee on Forests, Family Farms, and Energy of the Committee on Agriculture, House of Representatives, One Hundredth Congress, second session, May 20, 1988, Redding, CA.

"Serial no. 100-90."

Flowers of the field and forest. From original water-color drawings. after nature,

Mode of access: Internet.

The forest resources of the Far Eastern Republic.

Mode of access: Internet.