Forest Canopy Properties and Variation in Aboveground Net Primary Production over Upper Great Lakes Landscapes |
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Authors: | Iryna Dronova Kathleen M Bergen David S Ellsworth |
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Institution: | (1) School of Natural Resources and Environment, University of Michigan, 440 Church Street, Ann Arbor, Michigan 48109-1041, USA;(2) Present address: Department of Environmental Science, Policy and Management, University of California at Berkeley, 137 Mulford Hall #3114, Berkeley, California 94720, USA;(3) Hawkesbury Institute for the Environment, University of Western Sydney, Locked Bag 1797, Penrith, New South Wales, 2751, Australia |
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Abstract: | Relationships among aboveground net primary production (ANPP) and forest canopy properties were investigated in secondary
successional forests of similar age and disturbance history in northern Lower Michigan, USA. Aboveground biomass, ANPP, canopy
leaf area index (LAI), and several canopy nitrogen (N) measures were estimated from 12 stands representing major landform-level
ecosystems and vegetation associations. Stand single-date and growing season average normalized difference vegetation indices
(NDVI) were derived from Landsat TM. ANPP correlated most strongly with total canopy N content (r
2 = 0.81, P < 0.001), followed by LAI (r
2 = 0.73, P < 0.001) and area-based canopy-average leaf N concentration (r
2 = 0.37, P < 0.05). No significant relationship was detected between ANPP and mass-based canopy-average leaf N concentration. Stand
ANPP correlated positively with both total canopy N content (r
2 = 0.62, P < 0.05) and mass-based leaf N concentration (r
2 = 0.53, P < 0.05) of commonly dominant Populus spp. Relatively higher ANPP, total canopy N content and LAI corresponded to simultaneous presence of shade-intolerant P. grandidentata with shade-tolerant species. Both forms of NDVI were significantly related to ANPP, and more strongly to total canopy N content
and LAI; relationships were stronger for seasonally averaged (r
2 ≥ 0.75, P < 0.001) than for single-date NDVI (r
2 ≥ 0.52, P < 0.01). Results indicate that on the transitioning study landscapes, ANPP was more closely related to canopy N content than
to LAI, seasonally averaged NDVI was a more reliable predictor of ANPP and canopy properties than the single-date index, whereas
measured canopy characteristics varied significantly between major landform-level ecosystems. The ongoing decline of P. grandidentata is likely to alter aboveground carbon and pools and fluxes in the course of succession. |
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