Background： Information on forest structure, growth, and disturbance history is essential for effective forest management in a dynamic landscape. Because most of our research concerning the ecology and growth of Thuj...Background： Information on forest structure, growth, and disturbance history is essential for effective forest management in a dynamic landscape. Because most of our research concerning the ecology and growth of Thujo ocddenralis comes from sites in northern portions of its range, highly contextual biotic and abiotic factors that affect the species in more southern locales may not be fully accounted for. This research characterized the structural attributes and growth dynamics of Thuja occidentolis in disjunct forest stands south of its contiguous range margin. Methods： The Thujo occidentalis forests examined in this research were located in the central Appalachian Mountains, USA, approximately 440 km south of the contiguous range margin of the species. Forest structural attributes were characterized in two Thujo occidentalis forest stands, which are rare in the region. Tree-ring chronologies were used to examine the influences of disturbance and climate on the growth of Thuja occidentolis. Results： The forests contained a total of 13 tree species with Thuja occidentalis contributing substantially to the basal area of the sites. Thujo occidentalis stems were absent in the smallest size class, while hardwood species were abundant in the smallest classes. Thuja occidentalis stems also were absent from the 〈 70 years age class. By contrast, Thuja occidentalis snags were abundant within stands. Growth-release events were distributed across the disturbance chronology and generally affected a small number of trees. The Thujo occidentolis tree-ring chronology possessed an interseries correlation of 0.62 and mean sensitivity of 0.25. The correlation between mean temperature and Thuja occidentalis growth was weak and variable. Growth and moisture variables were more strongly correlated, and this relationship was predominantly positive. Conclusions： Structural attributes indicate the forests are in the understory reinitiation stage of forest development. Silvicultural manipulations may be necessary to promote Thu展开更多
The problem of radar target recognition using range profiles is investigated in this paper, based on a Radial Basis Function Network(RBFN). A preprocessing method is proposed, which performs amplitude average of the r...The problem of radar target recognition using range profiles is investigated in this paper, based on a Radial Basis Function Network(RBFN). A preprocessing method is proposed, which performs amplitude average of the range profiles to obtain more stable patterns. After pointing out the limitedness of traditional empirical formula, this paper also gives a method of estimating the shape parameter a of a Gaussian kernel function according-to spatial distribution of the training samples. It is shown that the method proposed in this paper offers promise for target recognition, from both the theoretical analysis and the experimental results of rotating platform imaging based on data acquired in a microwave anechoic chamber.展开更多
文摘Background： Information on forest structure, growth, and disturbance history is essential for effective forest management in a dynamic landscape. Because most of our research concerning the ecology and growth of Thujo ocddenralis comes from sites in northern portions of its range, highly contextual biotic and abiotic factors that affect the species in more southern locales may not be fully accounted for. This research characterized the structural attributes and growth dynamics of Thuja occidentolis in disjunct forest stands south of its contiguous range margin. Methods： The Thujo occidentalis forests examined in this research were located in the central Appalachian Mountains, USA, approximately 440 km south of the contiguous range margin of the species. Forest structural attributes were characterized in two Thujo occidentalis forest stands, which are rare in the region. Tree-ring chronologies were used to examine the influences of disturbance and climate on the growth of Thuja occidentolis. Results： The forests contained a total of 13 tree species with Thuja occidentalis contributing substantially to the basal area of the sites. Thujo occidentalis stems were absent in the smallest size class, while hardwood species were abundant in the smallest classes. Thuja occidentalis stems also were absent from the 〈 70 years age class. By contrast, Thuja occidentalis snags were abundant within stands. Growth-release events were distributed across the disturbance chronology and generally affected a small number of trees. The Thujo occidentolis tree-ring chronology possessed an interseries correlation of 0.62 and mean sensitivity of 0.25. The correlation between mean temperature and Thuja occidentalis growth was weak and variable. Growth and moisture variables were more strongly correlated, and this relationship was predominantly positive. Conclusions： Structural attributes indicate the forests are in the understory reinitiation stage of forest development. Silvicultural manipulations may be necessary to promote Thu
基金Supported by Foundation of Electronic Science Institute,Ministry of Electronic Industry
文摘The problem of radar target recognition using range profiles is investigated in this paper, based on a Radial Basis Function Network(RBFN). A preprocessing method is proposed, which performs amplitude average of the range profiles to obtain more stable patterns. After pointing out the limitedness of traditional empirical formula, this paper also gives a method of estimating the shape parameter a of a Gaussian kernel function according-to spatial distribution of the training samples. It is shown that the method proposed in this paper offers promise for target recognition, from both the theoretical analysis and the experimental results of rotating platform imaging based on data acquired in a microwave anechoic chamber.
