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Fraterrigo, Jennifer M. Block, Corinne 2012-02-01T00:47:29Z 2014-02-01T11:00:28Z 2011-12 2012-02-01T00:47:29Z 2011-12 The impacts of exotic insects and pathogens on forest ecosystems are increasingly recognized, yet the factors influencing the magnitude of effects remain poorly understood. Eastern hemlock (Tsuga canadensis) exerts strong control on nitrogen (N) dynamics, and its loss due to infestation by the hemlock woolly adelgid (Adelges tsugae) is expected to affect nutrient dynamics in impacted stands. I evaluated the potential for variation in N availability to influence the magnitude of effects of hemlock decline on N and P dynamics in mixed hardwood stands. I measured N and P pools and fluxes at three elevations (low, mid, high) subjected to increasing atmospheric N deposition where hemlock was declining or absent (as reference), in western North Carolina. Nutrient pools varied substantially with elevation and increasing N availability; total forest floor and mineral soil N increased (p<0.0001, p=0.0017, resp.) and forest floor and soil carbon (C) to N ratio decreased with elevation (p<0.0001, p=0.0123, resp.), suggesting that these high elevation pools are accumulating available N. Total extractable soil P was similar across the study area, however, P fractionation revealed distinct changes in the distribution of soil P fractions as N increased. Soils from high elevation, high N-available sites had 310% higher concentration of organic P and 55% smaller residual and refractory P pools than soils from low elevation, low N-available stands, suggesting that increased N availability has driven the depletion of recalcitrant P pools by stimulating biotic demand. Contrary to expectations, subsurface leaching of inorganic N was minimal overall (<1 kg ha-1 9 mo-1), and was not higher in stands with hemlock mortality. Across all elevation classes, hardwood foliar N:P ratios were lower in stands with declining hemlocks, suggesting trees are incorporating available P into biomass. Higher foliar N and P concentrations as well as observed increases in the growth of hardwood species in high elevation stands post-HWA infestation suggest that hemlock decline has stimulated nutrient uptake by healthy vegetation within this mixed forest, and may thereby contribute to decoupling the relationship between N deposition and ecosystem nutrient loss. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2011-11-18T22:40:49Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 7 6. Appendix A.docx: 20703 bytes, checksum: 5cb40622c3a52bf4a22850ac8cc9a39f (MD5) 5. Conclusion.docx: 16246 bytes, checksum: e6f33a7556a9f9f7f97e528bc26ea6d0 (MD5) 4. Chapter 2.docx: 206768 bytes, checksum: 7a3420a65d8d0b058f449028bb993f82 (MD5) 3. Chapter 1.docx: 306217 bytes, checksum: c17a308b66985674ce814053f6f18e4c (MD5) 2. Introduction.docx: 59936 bytes, checksum: c0f916d12d676b448159cb2f8bfa4f1e (MD5) 1. Preface.docx: 28788 bytes, checksum: 489b506e6a2edda8a2dadeebca9386d7 (MD5) Block_Corinne.pdf: 505223 bytes, checksum: 66c414eb8949de67498586e205562e4c (MD5) Made available in DSpace on 2012-02-01T00:47:29Z (GMT). No. of bitstreams: 8 Block_Corinne.pdf: 505023 bytes, checksum: 7cd0b7e9ff6a890afe30c41a5814050a (MD5) license.txt: 4062 bytes, checksum: 5548ecc30ddd840640a1d225f784a7ef (MD5) 1. Preface.docx: 28752 bytes, checksum: d83d8e2db6f54be02c97ad0852e05910 (MD5) 2. Introduction.docx: 59936 bytes, checksum: c0f916d12d676b448159cb2f8bfa4f1e (MD5) 3. Chapter 1.docx: 306207 bytes, checksum: ca91c4456af50f82fce8adbecd55b611 (MD5) 4. Chapter 2.docx: 206946 bytes, checksum: f40137770328f742f6de6b52f20e4aaa (MD5) 5. Conclusion.docx: 16381 bytes, checksum: 5ed82c38e617a847bf6df6e5e99e04e9 (MD5) 6. Appendix A.docx: 20718 bytes, checksum: 1dcce6571feae70f1970150f8dd891bc (MD5) Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by William Ingram (wingram2@illinois.edu) on 2012-02-01T00:50:37Z Item is restricted until 2014-02-01T00:50:07Z Item reinstated by Sarah Shreeves (sshreeve@illinois.edu) on 2014-02-01T11:00:28Z Item was in collections: Graduate Theses and Dissertations at Illinois (ID: 204) Dissertations and Theses - Natural Resources and Environmental Sciences (ID: 671) No. of bitstreams: 8 Block_Corinne.pdf: 505023 bytes, checksum: 7cd0b7e9ff6a890afe30c41a5814050a (MD5) license.txt: 4062 bytes, checksum: 5548ecc30ddd840640a1d225f784a7ef (MD5) 1. Preface.docx: 28752 bytes, checksum: d83d8e2db6f54be02c97ad0852e05910 (MD5) 2. Introduction.docx: 59936 bytes, checksum: c0f916d12d676b448159cb2f8bfa4f1e (MD5) 3. Chapter 1.docx: 306207 bytes, checksum: ca91c4456af50f82fce8adbecd55b611 (MD5) 4. Chapter 2.docx: 206946 bytes, checksum: f40137770328f742f6de6b52f20e4aaa (MD5) 5. Conclusion.docx: 16381 bytes, checksum: 5ed82c38e617a847bf6df6e5e99e04e9 (MD5) 6. Appendix A.docx: 20718 bytes, checksum: 1dcce6571feae70f1970150f8dd891bc (MD5) Item released from any restrictions by Sarah Shreeves (sshreeve@illinois.edu) on 2014-02-01T11:00:28Z http://hdl.handle.net/2142/29466 en Copyright 2011 Corinne Block exotic insects hemlock phosphorus fractionation N and P co-limitation atmospheric nitrogen deposition hemlock woolly adelgid nitrogen flux pest outbreaks phosphorus (P) nitrogen (N) Interactive effects of hemlock mortality and nitrogen availability on nutrient pools and fluxes in the southern Appalachian Mountains Dissertation / Thesis text Natural Res & Env Sci 1875 Natural Res & Env Sciences 0190 University of Illinois at Urbana-Champaign Thesis M.S. MS:Nat Res & Envrn Sci -UIUC 10KS0190MS