No description available.

The development of graduate students in the sciences preparing for careers in academia has long included elements to advance students as science researchers, but recent emphasis is being placed on developing students as instructors and education researchers as well. As such, objectives of this study included assessments of seedling responses to hydrology typical of floods in urban settings, the role of created microtopography in community development of a bottomland hardwood forest, and the influence of geographic information systems (GIS) on student motivation and conceptual knowledge. Substantial losses of bottomlands in Texas necessitate restoration to regain the ecosystem services that they provide. Restoration of proper hydrology is the most important aspect of wetland restoration, but this can prove difficult in urbanizing environments where hydrology has been irreversibly altered. Microtopography has been shown to be an important component of bottomland hardwood forests, and its restoration may aid in hydrologic restoration as gradients are created that support a diverse community. Tree seedlings were subjected to experimental flooding regimes typical of floodplain forests in rural and urban settings. Growth rates of seedlings varied over time and differed depending on species and treatment. Created microtopography resulted in a spatially heterogeneous system similar to that of natural bottomlands and strongly influenced hydrology, soil properties, survival of planted seedlings, and abundance and distribution of colonizing species. Proper bottomland restoration in urbanizing environments should include species selection based on current and potential future hydrologic conditions. In addition, restoring microtopography may improve survival of a variety of species introduced during restoration, as well as enhance colonization of a diverse plant community under changing hydrologic regimes. Trends indicated a slight improvement in attitude and performance for students that used GIS. More important, the authenticity of the experience appeared to affect student attitude. The effective use of GIS in teaching may be scale-dependent. Smallscale phenomena may be assessed as easily in a field exercise as with GIS. Using GIS to assess large-scale, complex patterns may have a substantial impact on student understanding. Further studies are needed to determine direct benefits of teaching with GIS in undergraduate ecology classrooms.

In this research, the characterization of snow cover is made from data collected in September, February and March of 2002 and 2003, during Cold-land Processes Field Experiments project of the NASA. These data include snow and forests characteristic measurements, meteorological conditions, digital elevation model (DEM) and polarimetric multifrequency SAR data (C, L and P bands) acquired from AIRSAR-POLSAR airborne sensor. These data will be used to analyze multifrequency polarimetric techniques to characterize snow cover over forested areas (open area, sparse coniferous forest, and dense coniferous forest). Different techniques have been developed to detect wet snow over different forested areas. The methodology of wet snow detection developed by Rott and Nagler (1995) is first analyzed. The best result is obtained in HH polarization (13% for the sparse coniferous forest site and 25% for the dense coniferous forest site). C-band data in circular polarizations improves these results, but the errors remain high (22% for the sparse coniferous forest site and 13% for the dense coniferous forest site). The use of [sigma][omicronn] ratio in dB [sigma][omicronn][subscript LHH] /[sigma][omicronn][subscript CHH], [sigma][omicronn][subscript LHV]/[sigma][omicronn] [subscript CHH], [sigma][omicronn][subscript LHV] /[sigma][omicronn][subscript CHV] and [sigma][omicronn][subscript LVV] /[sigma][omicronn][subscript CHH] allows to detect wet snow ([less-than or equal to] 13% errors) for both the open area and the dense coniferous forest sites. However, with this technique, higher errors ([greater-than or equal to] 16%) are obtained for the sparse coniferous forest site. The analysis of polarimetric signatures in the three bands shows that their shapes vary according to snow conditions (wet or dry) and forest densities. The pedestal height of polarimetric signatures in P band allows to apply a thresholding approach to discriminate between snow conditions (wet or dry). The error matrix generated from polarimetric signature techniques applied to snow pit measurements shows error higher than 6%. For the characterization of snow condition, target decomposition theorems show promising results. For the three bands, the Freeman-Durden and Cloude-Pottier decompositions allow to understand scattering mechanisms of snow-covered-forested areas. Also, a thresholding approach applied to volume scattering power of the Freeman-Durden decomposition in C band as well as to entropy parameter together with angle [alpha] value of Cloude-Pottier decomposition shows abilities to detect wet snow over forested areas. The technique using the volume scattered power shows detection errors higher than 16%. No classification error is obtained in the error matrix generated from entropy values over the snow pits. The analysis of backscattering coefficients as a function of forest density (open area, sparse coniferous forest and dense coniferous forest) shows variations in the signal as a function of frequency, polarization, density and forest structures as well as with ground conditions (snow-free, dry snow, wet snow). Three radar vegetation indexes (IVR, IVRD[subscript HH] and IVRD[subscript VV]) are analyzed. The IVR index in C and L bands, as well as the IVRD[subscript VV] index in L band are sensitive to forest density. The volume scattered power of the Freeman-Durden decomposition also allows to characterize forest density in C, L and P bands.In order to partially reduce the effect of forested area on the backscattering of a snow cover, image difference between the C-band backscattering coefficient (HH polarization) and the C-band volume scattered power in wet snow condition is performed. The error matrix generated over the snow pit shows that a threshold of 1.5 dB applied to the image difference leads to errors less than 6%. The obtained results clearly show the utility of multifrequency, multipolarisation and polarimetric SAR data for wet snow detection over different forested areas.

Thesis (M.S.)--University of Tennessee, Knoxville, 2001. / Vita. Includes bibliographical references (leaves 67-73).

<p class=MsoNormal><span style="mso-spacerun: yes">?????????????????? </span>Stable isotopic analysis of nitrate (¹⁵N/¹⁴N and ¹⁸O/¹⁶O) was used to trace nitrate sources and cycling under undisturbed conditions and following harvest at the Turkey Lakes Watershed (TLW), located near Sault Ste. Marie, Ontario, Canada. <span style="mso-spacerun: yes">?? </span> <p class=MsoNormal><span style="mso-spacerun: yes">?????? </span><span style="mso-spacerun: yes">????????????</span>Bulk precipitation collected biweekly at the TLW from 1995 to 2000 had nitrate isotope values that ranged from +42. 4 to +80. 4&permil; for <span style='font-family:Symbol'>d</span>¹⁸O and -6. 3 to +2. 8&permil; for <span style='font-family:Symbol'>d</span>¹⁵N. <span style="mso-spacerun: yes">?? </span>An incubation experiment indicated that the isotopic composition of atmospheric nitrate was not compromised by collection methods whereby unfiltered bulk precipitation samples remain in the collector for up to two weeks. <span style="mso-spacerun: yes">?? </span> <p class=MsoNormal><span style="mso-spacerun: yes">?????????????????? </span>The first direct measurement of the isotopic composition of microbial nitrate produced <i>in situ</i> was obtained by eliminating precipitation inputs to three forest floor lysimeters and subsequently watering the area with a nitrate-free solution. <span style="mso-spacerun: yes">?? </span>Microbial nitrate had <span style='font-family:Symbol'>d</span>¹⁸O values that ranged from +3. 1 to +10. 1&permil; with a mean value of +5. 2&permil;, only slightly higher than values predicted based on the <span style='font-family:Symbol'>d</span>¹⁸O-H₂O of the watering solution used. <span style="mso-spacerun: yes">?? </span><span style='font-family:Symbol'>d</span>¹⁸O values of soil O₂ (+23. 2 to +24. 1&permil;) down to a depth of 55cm were not significantly different from atmospheric O₂ (+23. 5&permil;) and therefore respiratory enrichment of soil O₂ did not affect the <span style='font-family:Symbol'>d</span>¹⁸O values of microbial nitrate produced at the TLW. <span style="mso-spacerun: yes">?? </span> <p class=MsoNormal><span style="mso-spacerun: yes">?????????????????? </span>Nitrate export from two undisturbed first-order stream basins was dominated by microbial nitrate, with the contribution of atmospheric nitrate peaking at about 30% during snowmelt. <span style="mso-spacerun: yes">?? </span>Clear-cutting of catchment 31 in 1997 resulted in elevated nitrate concentrations, reaching levels that exceeded the drinking water limit of 10 mg N/L. <span style="mso-spacerun: yes">?? </span>Isotopic analysis indicated that the source of this nitrate was predominantly chemolithoautotrophic nitrification. <span style="mso-spacerun: yes">?? </span>The <span style='font-family:Symbol'>d</span>¹⁸O values of microbial nitrate in stream 31 progressively increased during the post-harvest period due to an increase in the proportion of nitrification that occurred in the summer months. <span style="mso-spacerun: yes">?? </span>Despite drastic alteration of nitrogen cycling in the catchment by the harvest, <span style='font-family:Symbol'>d</span>¹⁵N-nitrate values in shallow groundwater did not change from the pre-harvest. <span style="mso-spacerun: yes">???? </span>Denitrification and plant uptake of nitrate in a small forested swamp in catchment 31 attenuated 65 to 100% of surface water nitrate inputs following harvest, reducing catchment-scale nitrate export by 35 to 80%.

No description available.

<p class=MsoNormal><span style="mso-spacerun: yes">          </span>Stable isotopic analysis of nitrate (¹⁵N/¹⁴N and ¹⁸O/¹⁶O) was used to trace nitrate sources and cycling under undisturbed conditions and following harvest at the Turkey Lakes Watershed (TLW), located near Sault Ste. Marie, Ontario, Canada. <span style="mso-spacerun: yes">  </span> <p class=MsoNormal><span style="mso-spacerun: yes">    </span><span style="mso-spacerun: yes">      </span>Bulk precipitation collected biweekly at the TLW from 1995 to 2000 had nitrate isotope values that ranged from +42. 4 to +80. 4&permil; for <span style='font-family:Symbol'>d</span>¹⁸O and -6. 3 to +2. 8&permil; for <span style='font-family:Symbol'>d</span>¹⁵N. <span style="mso-spacerun: yes">  </span>An incubation experiment indicated that the isotopic composition of atmospheric nitrate was not compromised by collection methods whereby unfiltered bulk precipitation samples remain in the collector for up to two weeks. <span style="mso-spacerun: yes">  </span> <p class=MsoNormal><span style="mso-spacerun: yes">          </span>The first direct measurement of the isotopic composition of microbial nitrate produced <i>in situ</i> was obtained by eliminating precipitation inputs to three forest floor lysimeters and subsequently watering the area with a nitrate-free solution. <span style="mso-spacerun: yes">  </span>Microbial nitrate had <span style='font-family:Symbol'>d</span>¹⁸O values that ranged from +3. 1 to +10. 1&permil; with a mean value of +5. 2&permil;, only slightly higher than values predicted based on the <span style='font-family:Symbol'>d</span>¹⁸O-H₂O of the watering solution used. <span style="mso-spacerun: yes">  </span><span style='font-family:Symbol'>d</span>¹⁸O values of soil O₂ (+23. 2 to +24. 1&permil;) down to a depth of 55cm were not significantly different from atmospheric O₂ (+23. 5&permil;) and therefore respiratory enrichment of soil O₂ did not affect the <span style='font-family:Symbol'>d</span>¹⁸O values of microbial nitrate produced at the TLW. <span style="mso-spacerun: yes">  </span> <p class=MsoNormal><span style="mso-spacerun: yes">          </span>Nitrate export from two undisturbed first-order stream basins was dominated by microbial nitrate, with the contribution of atmospheric nitrate peaking at about 30% during snowmelt. <span style="mso-spacerun: yes">  </span>Clear-cutting of catchment 31 in 1997 resulted in elevated nitrate concentrations, reaching levels that exceeded the drinking water limit of 10 mg N/L. <span style="mso-spacerun: yes">  </span>Isotopic analysis indicated that the source of this nitrate was predominantly chemolithoautotrophic nitrification. <span style="mso-spacerun: yes">  </span>The <span style='font-family:Symbol'>d</span>¹⁸O values of microbial nitrate in stream 31 progressively increased during the post-harvest period due to an increase in the proportion of nitrification that occurred in the summer months. <span style="mso-spacerun: yes">  </span>Despite drastic alteration of nitrogen cycling in the catchment by the harvest, <span style='font-family:Symbol'>d</span>¹⁵N-nitrate values in shallow groundwater did not change from the pre-harvest. <span style="mso-spacerun: yes">   </span>Denitrification and plant uptake of nitrate in a small forested swamp in catchment 31 attenuated 65 to 100% of surface water nitrate inputs following harvest, reducing catchment-scale nitrate export by 35 to 80%.

A study was undertaken to characterize two dynamic fuel types not included in the Canadian Forest Fire Behaviour Prediction System: forested bogs and blowdown. Fuel load and structure were measured at ten forested bog sites in central Alberta along a 108 year post-fire chronosequence. Canopy bulk density increased following a sigmoidal curve between 0.00 and 0.54 kg•m-3. Crown fire potential was modeled using a general crown fire behaviour model and found to follow a similar sigmoidal pattern increasing with time-since-fire. Blowdown fuel loads were measured at six sites in northwestern Ontario and ranged from 13.4 to 18.9 kg•m-2. Elevated fine blowdown fuels were found to have faster reaction times and dry more rapidly than predicted by the Fine Fuel Moisture Code. Detailed observations were also made of fire behaviour in blowdown fuels

A study was undertaken to characterize two dynamic fuel types not included in the Canadian Forest Fire Behaviour Prediction System: forested bogs and blowdown. Fuel load and structure were measured at ten forested bog sites in central Alberta along a 108 year post-fire chronosequence. Canopy bulk density increased following a sigmoidal curve between 0.00 and 0.54 kg•m-3. Crown fire potential was modeled using a general crown fire behaviour model and found to follow a similar sigmoidal pattern increasing with time-since-fire. Blowdown fuel loads were measured at six sites in northwestern Ontario and ranged from 13.4 to 18.9 kg•m-2. Elevated fine blowdown fuels were found to have faster reaction times and dry more rapidly than predicted by the Fine Fuel Moisture Code. Detailed observations were also made of fire behaviour in blowdown fuels

The Mississippi Alluvial Valley (MAV) contained vast bottomland hardwood forests into the 20th century. Humans cleared forests, and altered hydrology, yet the MAV remains important for North American waterfowl and other wildlife. To estimate standing crops of aquatic invertebrates as food in hardwood bottomlands for wintering waterfowl, I quantified dry mass of invertebrates in naturally flooded forests (NFFs) and greentree reservoirs (GTRs) during winters 2008–2010. The MAV had greater invertebrate mass in NFFs (x̄ = 18.39 kg/ha; SE = 2.815 [CV = 15.3%]) than GTRs (x̄ = 5.16; SE = 0.492 [CV = 9.5%]), compared with lesser masses in Mississippi Interior Flatwoods’ GTR (x̄ = 2.26; SE = 0.320) and NFF (x̄= 1.45; SE = 1.305). Invertebrate diversity was greatest in NFFs and in depths from 10–40 cm. Flooding GTRs ≤ 40 cm and managing naturally dynamic hydrology may benefit invertebrates, ducks, and associated bottomland hardwood communities