{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/33196"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/33196","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"In-Stream Hemlock Twig Breakdown and Effects of Reach-Scale Twig Additions on Appalachian Headwater Streams","abstract":"Eastern hemlock (Tsuga canadensis) is a prominent tree in the forests of eastern North America, where it commonly grows along headwater streams. It is experiencing widespread mortality due to infestations of an introduced insect, the hemlock woolly adelgid (Adelges tsugae). Eliminations of tree species are known to have ecosystem-level effects, and one consequence of hemlock death is a change in allochthonous inputs to headwater streams. I predicted that hemlock twigs' dendritic structure, abundance, and resistance to decay currently make them highly effective retainers of leaves in headwater streams, with consequences for nutrient uptake. To understand the role of hemlock twigs in streams and to compare their functions to those of a potential replacement species, I (1) quantified the decomposition and microbial colonization of twigs and (2) manipulated twig standing crops to quantify effects on leaf retention and nutrient uptake. Hemlock twigs provide a poor-quality substrate for microbial colonization and growth relative to birch (Betula lenta) twigs and are more resistant to breakdown than birch. Although hemlock twigs appear to be effective in retaining leaves, they do not substantially affect reach-scale uptake of ammonium, which is much more strongly influenced by the timing of leaf inputs. Although hemlock death may subtly change patterns of organic matter accumulation and breakdown, the potentially important effects of hemlock death include changes in large wood inputs, changes in hydrologic regime, and increases in rhododendron cover.","abstract_html":"Eastern hemlock (Tsuga canadensis) is a prominent tree in the forests of eastern North America, where it commonly grows along headwater streams. It is experiencing widespread mortality due to infestations of an introduced insect, the hemlock woolly adelgid (Adelges tsugae). Eliminations of tree species are known to have ecosystem-level effects, and one consequence of hemlock death is a change in allochthonous inputs to headwater streams. I predicted that hemlock twigs' dendritic structure, abundance, and resistance to decay currently make them highly effective retainers of leaves in headwater streams, with consequences for nutrient uptake. To understand the role of hemlock twigs in streams and to compare their functions to those of a potential replacement species, I (1) quantified the decomposition and microbial colonization of twigs and (2) manipulated twig standing crops to quantify effects on leaf retention and nutrient uptake. Hemlock twigs provide a poor-quality substrate for microbial colonization and growth relative to birch (Betula lenta) twigs and are more resistant to breakdown than birch. Although hemlock twigs appear to be effective in retaining leaves, they do not substantially affect reach-scale uptake of ammonium, which is much more strongly influenced by the timing of leaf inputs. Although hemlock death may subtly change patterns of organic matter accumulation and breakdown, the potentially important effects of hemlock death include changes in large wood inputs, changes in hydrologic regime, and increases in rhododendron cover.","abstract_has_math":false,"creators":["Morkeski, Kate"],"institution":"Virginia Tech","degree_name":"Master of Science","degree_level":"masters","degree_discipline":"Biology","degree_department":"Biology","school":null,"contributors":[],"advisors":[],"committee_chairs":["Webster, Jackson R."],"committee_members":["Valett, H. Maurice","Dolloff, C. Andrew","Benfield, Ernest F."],"year":2007,"date_issued":"2007-05-10","date_published":"2007-05-10","updated_at":"2026-07-22T22:19:54Z","subjects":["fungi","ammonium","breakdown","respiration","stream","Coweeta","hemlock","birch","Wood"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-05242007-161155"],"render_values":[{"text":"etd-05242007-161155","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/33196","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Webster, Jackson R."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Valett, H. Maurice","Dolloff, C. Andrew","Benfield, Ernest F."]},{"key":"dc:contributor.department","label":"Department","values":["Biology"]},{"key":"dc:creator","label":"Author","values":["Morkeski, Kate"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T20:38:29Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T20:38:29Z","2007-06-17"]},{"key":"dc:date.issued","label":"Date","values":["2007-05-10"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Biology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["fungi","ammonium","breakdown","respiration","stream","Coweeta","hemlock","birch","Wood"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-05242007-161155"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/10919/33196"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Eastern hemlock (Tsuga canadensis) is a prominent tree in the forests of eastern North America, where it commonly grows along headwater streams. It is experiencing widespread mortality due to infestations of an introduced insect, the hemlock woolly adelgid (Adelges tsugae). Eliminations of tree species are known to have ecosystem-level effects, and one consequence of hemlock death is a change in allochthonous inputs to headwater streams. I predicted that hemlock twigs' dendritic structure, abundance, and resistance to decay currently make them highly effective retainers of leaves in headwater streams, with consequences for nutrient uptake. To understand the role of hemlock twigs in streams and to compare their functions to those of a potential replacement species, I (1) quantified the decomposition and microbial colonization of twigs and (2) manipulated twig standing crops to quantify effects on leaf retention and nutrient uptake. Hemlock twigs provide a poor-quality substrate for microbial colonization and growth relative to birch (Betula lenta) twigs and are more resistant to breakdown than birch. Although hemlock twigs appear to be effective in retaining leaves, they do not substantially affect reach-scale uptake of ammonium, which is much more strongly influenced by the timing of leaf inputs. Although hemlock death may subtly change patterns of organic matter accumulation and breakdown, the potentially important effects of hemlock death include changes in large wood inputs, changes in hydrologic regime, and increases in rhododendron cover."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science"]},{"key":"dc:title","label":"Title","values":["In-Stream Hemlock Twig Breakdown and Effects of Reach-Scale Twig Additions on Appalachian Headwater Streams"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Webster, Jackson R."],"dc:contributor.committeemember":["Valett, H. Maurice","Dolloff, C. Andrew","Benfield, Ernest F."],"dc:contributor.department":["Biology"],"dc:creator":["Morkeski, Kate"],"dc:date.accessioned":["2014-03-14T20:38:29Z"],"dc:date.available":["2014-03-14T20:38:29Z","2007-06-17"],"dc:date.issued":["2007-05-10"],"dc:description.abstract":["Eastern hemlock (Tsuga canadensis) is a prominent tree in the forests of eastern North America, where it commonly grows along headwater streams. It is experiencing widespread mortality due to infestations of an introduced insect, the hemlock woolly adelgid (Adelges tsugae). Eliminations of tree species are known to have ecosystem-level effects, and one consequence of hemlock death is a change in allochthonous inputs to headwater streams. I predicted that hemlock twigs' dendritic structure, abundance, and resistance to decay currently make them highly effective retainers of leaves in headwater streams, with consequences for nutrient uptake. To understand the role of hemlock twigs in streams and to compare their functions to those of a potential replacement species, I (1) quantified the decomposition and microbial colonization of twigs and (2) manipulated twig standing crops to quantify effects on leaf retention and nutrient uptake. Hemlock twigs provide a poor-quality substrate for microbial colonization and growth relative to birch (Betula lenta) twigs and are more resistant to breakdown than birch. Although hemlock twigs appear to be effective in retaining leaves, they do not substantially affect reach-scale uptake of ammonium, which is much more strongly influenced by the timing of leaf inputs. Although hemlock death may subtly change patterns of organic matter accumulation and breakdown, the potentially important effects of hemlock death include changes in large wood inputs, changes in hydrologic regime, and increases in rhododendron cover."],"dc:description.degree":["Master of Science"],"dc:identifier.other":["etd-05242007-161155"],"dc:identifier.uri":["http://hdl.handle.net/10919/33196"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["fungi","ammonium","breakdown","respiration","stream","Coweeta","hemlock","birch","Wood"],"dc:title":["In-Stream Hemlock Twig Breakdown and Effects of Reach-Scale Twig Additions on Appalachian Headwater Streams"],"dc:type":["Thesis"],"thesis:degree_discipline":["Biology"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:54Z"}