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Person

Nathan R DeJager

Ecologist

Upper Midwest Environmental Sciences Center

Email: ndejager@usgs.gov
Office Phone: 608-781-6232
Fax: 608-783-6066
ORCID: 0000-0002-6649-4125

Location
UMESC - Laboratory/Office - #1
2630 Fanta Reed Road
La Crosse , WI 54603
USA

Supervisor: Jennifer S Sauer
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This data set consists of monthly averages of soil and litter properties. Rows are grouped in the following order: year, month, vegetation type, plot ID. Within a single month five plots were sampled within each of the 2 vegetation types (10 plots total). Columns F+ represent individual measurements.
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Premise of the study: Consistent with the self-thinning law of plant population ecology, Niklas et al. in 2003 proposed that stem size-density distributions (SDDs) of multispecies forest communities should change in very predictable ways as a function of the effects of past disturbances on average tree size. To date, empirical tests of this hypothesis have not been pursued in floodplain settings. Methods: SDDs were constructed using tree stem-size and density data from forest plots positioned along a flood frequency and duration gradient in the Upper Mississippi River floodplain. Key Results: As flooding (both frequency and duration) increased, several small tree species were eliminated from forest plots and...
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Geographic patterns can change through time and/or across space, and these changes can lead to differences in the movement pattern and body condition of organisms, their interactions with each other and their environment, and ultimately lead to population and community-level changes. When quantifying landscape patterns using remotely sensed data, it is important to recognize that each pixel (i.e. picture element) has a temporal and spatial context. A pixel’s temporal context refers to its past and present classification. The spatial context of a pixel depends on the classification of neighbouring pixels, and the size of the area considered as the neighbourhood. Despite the fact that pixels are the basic unit of...
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Floodplain forests have historically been resilient to the effects of flooding because the tree species that inhabit these ecosystems regenerate and grow quickly following disturbances. However, the intensity and selectivity of ungulate herbivory in floodplains has the potential to modify the community-level effects of flooding by delaying forest recruitment and leaving sites vulnerable to invasive species. We established a series of exclosures along an elevation gradient in an actively recruiting floodplain forest along the Upper Mississippi River prior to three large-magnitude flood events. Pre-flood browsing by Odocoileus virginianus (white-tailed deer) ranged from 20% to 85% of all available stems, and reduced...
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c) We examined effects of flooding on supply rates of 14 nutrients in floodplain areas invaded by Phalaris arundinacea (reed canarygrass), areas restored to young successional forests (browsed by white-tailed deer and unbrowsed), and remnant mature forests in the Upper Mississippi River floodplain. Plant Root Simulator ion-exchange probes were deployed for four separate 28-day periods. The first deployment occurred during flooded conditions, while the three subsequent deployments were conducted during progressively drier periods. Time after flooding corresponded with increases in NO3--N, K+ and Zn+2, decreases in H2PO4--P, Fe+3, Mn+2, and B(OH)4-B, a decrease followed by an increase in NH4+-N, Ca+2, Mg+2 and Al+3,...
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