Browsing by Subject "Species"

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Biological indicators of climate change: trends in fish communities and the timing of walleye spawning runs in Minnesota.
    (2010-06) Schneider, Kristal N.
    I conducted research on two projects to examine effects of climate change on Minnesota’s aquatic communities. I used walleye egg-take records from the Minnesota Department of Natural Resources for 12 spawning locations and historical ice-out data to determine if the timing of these events is changing. I used ice-out data instead of temperature for our analyses because historical temperature data is not available and ice-out has been previously related to climate change. Because ice-out has been previously related to climate change, I regressed the dates of first egg-take against ice-out dates to determine if the timing of walleye spawning runs could be a useful biological indicator of climate change. For the second project to determine if fish species abundances are changing in response to climate change, I used historical lake survey records for 34 lakes, each with 15 to 43 years of data, and regressed catch-per-unit-effort (CPUE) against year. I examined species distributions by regressing mean latitude against year. I regressed slopes of CPUE over time against 5 local air temperature variables to determine if changes in abundance were associated with air temperature. I also used stepwise regressions (forward and backward selection) and one-way analysis of variance (ANOVA) to determine if variability in trends could be explained by lake physical and chemical characteristics. Results were reported for 7 species with the strongest trends: Centrarchids (Micropterus salmoides, Micropterus dolomieu, and Lepomis macrochirus); Ictalurids (Ameiurus melas and Ameiurus natalis); Whitefish (Coregonus artedi and Coregonus clupaeformis).For the walleye spawning analyses I found that spawning runs and ice-out are occurring earlier in some lakes but not all. However, there was a strong relationship between first eggtake and ice-out dates, and walleye egg-take appears to provide a good biological indicator of climate change. For the lake survey analysis, centrarchid abundance in lakes was increasing over time, black bullhead abundance was decreasing, and other species were increasing in some lakes and decreasing in others. Slopes of CPUE versus year increased more quickly over time in smaller lakes and more quickly moving east across the state than in larger lakes toward the west. All species’ ranges were significantly advancing northward except smallmouth bass and whitefish. Regressions of CPUE versus air temperature showed that centrarchids are increasing in lakes as summer air temperatures increase, and whitefish are decreasing in lakes as air temperatures increase. In summary, the abundances and distributions of these 7 species over time may be responsive to climate change, and trends for species abundances may be influenced by lake characteristics. Centrarchids and bullhead may be good indicators, and thus, further research is warranted. Also, because there is a strong relationship between dates of first egg-take and ice-out, and because ice-out has previously been related to climate change, the timing of walleye spawning runs may be a useful biological indicator of climate change.
  • Thumbnail Image
    Item
    Effects of site and climate characteristics on forest invasibility by non-native plants in the Midwest.
    (2010-07) Kurtz, Cassandra Marie
    Non-native invasive plant (NNIP) species can have significant effects on forest regeneration, structure, biodiversity, and wildlife habitat, costing billions of dollars annually. Understanding how NNIPs in the Midwest may spread in the future requires understanding their response to site and climate characteristics. Current research suggests climate change may influence invasive plant presence and spread. In this study, I modeled the relationship between invasive species presence, site characteristics (e.g. disturbance, live tree volume, city distance, edge distance, physiography, and type of water [e.g. streams] present on plot), and climate (annual average number of days the temperature is ≥ 90˚F and annual average number of days the temperature is ≤ 32˚F) for five non-native invasive plants (multiflora rose [Rosa multiflora], common buckthorn [Rhamnus cathartica], non-native bush honeysuckles [Lonicera spp.], garlic mustard [Alliaria petiolata], and reed canary grass [Phalaris arundinacea]) sampled by the USDA Forest Service’s Forest Inventory and Analysis program in seven Midwestern states for 2005-2006 Species’ response to site and temperature predictors varied due to trait differences such as shade tolerance and moisture affinity. For most species, presence was positively related to biotic disturbance (disease(s) and/or animal(s)) and mesic physiography and negatively related to distance from a city or a nonforest edge. The best predictor for the presence of NNIPs was annual average number of days the temperature is ≤ 32˚F, with all five species presence correlated with the annual average number of days the temperature is ≤ 32˚F. Understanding the effect of site characteristics and climate on NNIP distribution provides insights into important drivers of species presence at a regional scale and allows land managers, scientists, and concerned citizens to predict invasion risk and future ecosystem response.
  • Thumbnail Image
    Item
    The influence of natural disturbance-based silviculture treatments on northern hardwood forests in Northeastern Minnesota, USA.
    (2010-12) Bolton, Nicholas William
    Natural disturbance-based silviculture (NDBS) has been suggested as an approach for promoting late-successional forest characteristics and maintaining native biodiversity in managed forests. Harvest gaps based on the natural disturbance patterns found in the upper Great Lakes (46 study gaps) were created throughout northern hardwood forests in northeastern Minnesota, USA, during the winters of 2002 and 2003. Gaps were measured 6- and 7-years post-treatment and subsequent analysis of these measurements was used to evaluate the success of these treatments at meeting structural and compositional objectives. Results indicated that these gaps have done little to increase tree diversity, including the recruitment of shade mid-tolerant species; however, the richness of herbaceous understory vegetation has responded positively to larger gap sizes. Herbaceous species increasing in harvest gaps included Actaea spp. L. (baneberry), Botrychium virginianum L. (rattlesnake fern), Mertensia paniculata Aiton (Northern bluebell), Rubus idaeus L. (red raspberry), Sanguinaria canadensis L. (bloodroot) and Cirsium arvense L. (Canada thistle). Results also indicated that subtle patterns were found among species spatial establishment within gaps (e.g., gap edge and gap center) and species that expressed no preference between the intact forest and harvest gaps. Levels of downed coarse woody debris (CWD) differed among gap size and all gaps had lower levels of CWD compared to the surrounding intact forest. Due to the historical importance of Betula alleghaniensis in these systems, the factors affecting the recruitment of this species were also investigated. Based on these investigations, it was found that B. alleghaniensis establishment was strongly related to highly decayed, large coniferous pieces of CWD with little recruitment occurring on the undisturbed forest floor. As such, providing appropriate seedbed conditions for shade mid-tolerant species and utilizing natural canopy gap sizes would improve the success of maintaining this species on the landscape.
  • Thumbnail Image
    Item
    Post-stratified estimation of Coarse Woody debris Volume using the down woody materials sample of forest inventory and analysis.
    (2010-05) Hatfield, Mark A.
    The Forest Inventory and Analysis (FIA) program of the USDA Forest Service conducts a nation wide survey of America’s forests. FIA field crews collect data on tree size, condition, and species, as well as data on the conditions in which they grow from a network of permanent ground plots known as Phase two plots (P2). FIA crews also collect more detailed forest health indicators, including data on Coarse Woody Materials (CWD), on a 1 16 subset of the P2 sample. This subset is known as the Phase 3 (P3) sample. FIA regularly publishes reports on the quantity and quality of America’s forests using data from the P2 sample. A post-stratified estimation technique is used increase the precision of the estimates without increasing the sample size. Currently, research on how to best apply the post-stratified estimator to produce estimates of the P3 forest health indicators has been lacking. This thesis will address this gap by testing 18 candidate geospatial layers (both categorical and continuous) as stratification layers to produce estimates of CWD volume in the Lake-states region of Minnesota, Wisconsin, and Michigan. Continuous geospatial layers will be broken into two to five strata using an optimization algorithm. A simulation experiment is used estimate the long term effectiveness of successful geospatial layers. The simulation experiment is performed to compare the conditional and unconditional variance estimators of the post-stratified estimators. Successful geospatial layers are then applied to sub-populations of varying sizes to determine the effect of spatial extent on the post-stratification method. Stratification layers derived from remote sensing products provided the best results. Using two or three strata is recommended because further partition of the population simply produces ineffective sliver strata. No difference was detected between the two competing variance estimators. The effect of spatial extent of the stratification was volatile. The use of large spatial extents is recommended. The conclusion of this thesis summarizes the lessons learned throughout as well as ideas for future research on the topic.
  • Thumbnail Image
    Item
    Predicting breeding habitat of the Connecticut Warbler (Oporornis agilis)
    (2010-05) Lapin, Carly
    The Connecticut warbler (Oporornis agilis) is an uncommon Neotropical migrant that breeds in the north-central United States and south-central Canada. Breeding populations of this species are reported to be declining. I analyzed habitat and landscape at three spatial scales (buffer radii of 100 m, 500 m, and 1,000 m) for 86 sites within 28 forest stands in northern Minnesota for Connecticut Warblers sampled over an 18-year period. I regressed combinations of habitat variables with two response variables, Connecticut Warbler abundance (the total number ever recorded at a site or stand) and Connecticut Warbler frequency (the number of years recorded out of 18 years) using a zero-inflated negative binomial distribution and logistic regression, respectively. A subset of models with #1;AICc ≤ 4.0 was retained and model-averaged predictions were calculated for each combination of buffer size and response variable. When comparing model-averaged predictions to observed data, the best models were those using Connecticut Warbler frequency at the 1,000 m buffer (r2 = 0.52). These models were used to create a map of predicted Connecticut Warbler breeding habitat in the two national forests sampled. At the 1,000 m scale, Connecticut Warblers were positively associated with large, simple patches of upland coniferous and lowland black spruce forest, and were negatively associated with upland deciduous forest.