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491.
Michelle M. Steen-Adams David J. Mladenoff Nancy E. Langston Feng Liu Jun Zhu 《Landscape Ecology》2011,26(8):1165-1178
Landscape ecology studies have demonstrated that past modifications of the landscape frequently influence its structure, highlighting
the utility of integrating historical perspectives from the fields of historical ecology and environmental history. Yet questions
remain for historically-informed landscape ecology, especially the relative influence of social factors, compared to biophysical
factors, on long-term land-cover change. Moreover, methods are needed to more effectively link history to ecology, specifically
to illuminate the underlying political, economic, and cultural forces that influence heterogeneous human drivers of land-cover
change. In northern Wisconsin, USA, we assess the magnitude of human historical forces, relative to biophysical factors, on
land-cover change of a landscape dominated by eastern white pine (Pinus strobus L.) forest before Euro-American settlement. First, we characterize land-cover transitions of pine-dominant sites over three
intervals (1860–1931; 1931–1951; 1951–1987). Transition analysis shows that white pine was replaced by secondary successional
forest communities and agricultural land-covers. Second, we assess the relative influence of a socio-historical variable (“on-/off-Indian
reservation”), soil texture (clay and sand), and elevation on land-cover transition. On the Lake Superior clay plain, models
that combine socio-historical and biophysical variables best explain long-term land-cover change. The socio-historical variable
dominates: the magnitude and rate of land-cover change differs among regions exposed to contrasting human histories. Third,
we developed an integrative environmental history-landscape ecology approach, thereby facilitating linkage of observed land-cover
transitions to broader political, economic, and cultural forces. These results are relevant to other landscape investigations
that integrate history and ecology. 相似文献
492.
COMPARISON OF RADIOGRAPHY, MYELOGRAPHY AND COMPUTED TOMOGRAPHY FOR THE EVALUATION OF CANINE VERTEBRAL AND SPINAL CORD TUMORS IN SIXTEEN DOGS 总被引:1,自引:1,他引:1
Wm. Tod Drost DVM Nancy E. Love DVM Clifford R. Berry DVM 《Veterinary radiology & ultrasound》1996,37(1):28-33
Radiographic, myelographic and computed tomographic (CT) studies from sixteen dogs with histologically diagnosed vertebral or spinal cord neoplasia (seventeen lesions) were retrospectively evaluated. Radiographs were compared with CT images to evaluate vertebral bony changes (bone production, lysis or both). Myelographic and CT images were evaluated to separate lesions into one of three categories, extradural, intradural/extramedullary, or intramedullary. These findings were compared to histologic tumor type from surgical or necropsy samples. Histologically, seven lesions were vertebral tumors and were classified as extradural lesions; ten lesions were spinal cord tumors of which eight were classified as intradural/extramedullary and two as intramedullary. Using CT, the amount of bony change associated with extradural lesions was greater than or equal to the amount of bony change visualized using radiographs. Myelography more correctly differentiated between intradural/ extramedullary and intramedullary lesions than did CT, although three open diagnoses detracted from the CT results. This study suggests that when evaluating extradural lesions, the amount of bony change was better visualized using CT than survey radiographs. Myelography was better when compared to CT for classifying spinal cord lesions, however, standardization of the CT imaging protocol may help determine the specific clinical indications for using CT in dogs with suspected vertebral or spinal cord tumors. 相似文献
493.