Spatial Distribution of Hemlock Woolly Adelgid Induced Hemlock Mortality in the Southern Appalachians  

作　　者：Tuula Kantola Paivi Lyytikainen-Saarenmaa Robert N.Coulson Sheryl Strauch Maria D.Tchakerian Markus Holopainen Hannu Saarenmaa Douglas A.Streett 

机构地区：[1]Knowledge Engineering Laboratory,Department of Entomology,Texas A&M University,College Station,TX,USA [2]Department of Forest Sciences,University of Helsinki,Helsinki,Finland [3]SIB Labs,School of Computing,University of Eastern Finland,Joensuu,Finland [4]Alexandria Forestry Center,USDA Forest Service,Southern Research Station,Pineville,LA,USA

出　　处：《Open Journal of Forestry》2014年第5期492-506,共15页林学期刊（英文）

基　　金：possible by financial aid from Graduate School in Forest Sciences(GSForest),Finnish Academy project“Centre of Excellence in Laser Scanning Research”(CoE-LaSR,decision number 272195);by the US Forest Service through USDA Forest Service cooperative agreement SRS-12-CA-11330129-077.

摘　　要：Hemlock woolly adelgid (Adelges Tsugae Annand, HWA) outbreaks are posing a major threat to eastern hemlock (Tsuga canadensis L. Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.) forest landscapes in the eastern USA. As foundation species, hemlocks play a variety of functional roles in forest landscapes. These species usually occur as isolated canopies and mixed species in landscapes where variation in topography is extreme. Spatially explicit inventory information on HWA induced hemlock mortality at landscape scale does not exist. High resolution aerial imageries enable landscape scale assessment even at the individual tree level. Accordingly, our goal was to investigate spatial pattern and distribution of HWA induced hemlock mortality using a high resolution aerial image mosaic in the Linville River Gorge, Southern Appalachians, western North Carolina. Our study objectives were: 1) to detect dead trees within the Lower Linville River watershed;2) to estimate the area occupied by dead trees in the forest canopy surface;3) to investigate the relationship of dead hemlocks and topography;and 4) to define the spatial pattern of the dead trees. We found ca. 10,000 dead trees within the study area, occupying over 7 ha of the canopy surface with an average area of 36 m2 per dead tree. The density of the dead trees was higher in proximity to the Linville River, at higher elevations, and on northern and northwestern aspects. Spatial pattern of the dead trees was generally clustered at all spatial scales. We suggest that although the reduction in plant biomass resulting from herbivory within the landscapes is modest, impact of the clustered distribution of hemlock mortality, especially in the riparian zones, is noteworthy. Our analysis of the pattern of hemlock decline provides new means for projecting future impacts of HWA on the range of hemlock distribution in eastern North America.Hemlock woolly adelgid (Adelges Tsugae Annand, HWA) outbreaks are posing a major threat to eastern hemlock (Tsuga canadensis L. Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.) forest landscapes in the eastern USA. As foundation species, hemlocks play a variety of functional roles in forest landscapes. These species usually occur as isolated canopies and mixed species in landscapes where variation in topography is extreme. Spatially explicit inventory information on HWA induced hemlock mortality at landscape scale does not exist. High resolution aerial imageries enable landscape scale assessment even at the individual tree level. Accordingly, our goal was to investigate spatial pattern and distribution of HWA induced hemlock mortality using a high resolution aerial image mosaic in the Linville River Gorge, Southern Appalachians, western North Carolina. Our study objectives were: 1) to detect dead trees within the Lower Linville River watershed;2) to estimate the area occupied by dead trees in the forest canopy surface;3) to investigate the relationship of dead hemlocks and topography;and 4) to define the spatial pattern of the dead trees. We found ca. 10,000 dead trees within the study area, occupying over 7 ha of the canopy surface with an average area of 36 m2 per dead tree. The density of the dead trees was higher in proximity to the Linville River, at higher elevations, and on northern and northwestern aspects. Spatial pattern of the dead trees was generally clustered at all spatial scales. We suggest that although the reduction in plant biomass resulting from herbivory within the landscapes is modest, impact of the clustered distribution of hemlock mortality, especially in the riparian zones, is noteworthy. Our analysis of the pattern of hemlock decline provides new means for projecting future impacts of HWA on the range of hemlock distribution in eastern North America.

关 键 词：Adelges Tsugae Eastern Hemlock Southern Appalachians Spatial pattern TOPOGRAPHY Tree Mortality TSUGA 

分 类 号：R73[医药卫生—肿瘤]