Abstract
North America’s midcontinent forest–prairie ecotone is currently exhibiting extensive eastern redcedar (ERC) (Juniperus virginiana L.) encroachment. Rapid expansion of ERC has major impacts on the species composition and forest structure within this region and suppresses previously dominant oak (Quercus) species. In Kansas, the growing-stock volume of ERC increased by 15,000% during 1965–2010. The overarching goal of this study was to evaluate the spatio-temporal dynamics of ERC in the forest–prairie ecotone of Kansas and understand its effects on deciduous forests. This was achieved through two specific objectives: (i) characterize an effective image classification approach to map ERC expansion, and (ii) assess ERC expansion between 1986 and 2017 in three study areas within the forest–prairie ecotone of Kansas, and especially expansion into deciduous forests. The analysis was based on satellite imagery acquired by Landsat TM and OLI sensors during 1986–2017. The use of multi-seasonal layer-stacks with a Support Vector Machine (SVM)-supervised classification was found to be the most effective approach to classify ERC distribution with high accuracy. The overall accuracies for the change maps generated for the three study areas ranged between 0.95 (95 CI: ±0.02) and 0.96 (±0.03). The total ERC cover increased in excess of 6000 acres in each study area during the 30-year period. The estimated percent increase of ERC cover was 139%, 539%, and 283% for the Tuttle Creek reservoir, Perry reservoir, and Bourbon County north study areas, respectively. This astounding rate of expansion had significant impacts on the deciduous forests where the conversion of deciduous woodlands to ERC, as a percentage of the total encroachment, were 48%, 56%, and 71%, for the Tuttle Creek reservoir, Perry reservoir, and Bourbon County north study areas, respectively. These results strongly affirm that control measures should be implemented immediately to restore the threatened deciduous woodlands of the region.
Highlights
The estimated percent increase of eastern redcedar (ERC) cover was 139%, 539%, and 283% for the Tuttle
Vegetation communities in ecotones are vulnerable to alterations in species composition due to the combined effects of climate change and land management practices since they are close to the limits of their natural ranges [1]
In Kansas, the Forest Inventory and Analysis (FIA) data suggest that the growing-stock volume of ERC increased by 15,000% between 1965 and 2010 [7]
Summary
Vegetation communities in ecotones are vulnerable to alterations in species composition due to the combined effects of climate change and land management practices since they are close to the limits of their natural ranges [1]. Within the schema of ecoregion classification for the United States [2], the transitional region between the heavily forested eastern US and the prairie grasslands of the Midwest is identified as the forest–prairie transitional region [3] This midcontinent forest–prairie transitional region/ecotone of North America is currently experiencing extensive eastern redcedar. Eastern redcedar (ERC) continues to expand in area and density, in Missouri, Nebraska, Kansas, and Oklahoma. It drives major alterations in species composition and forest structure in this region, suppressing the dominant oak (Quercus) species [1,6]. Conversion of oak forests to ERC will intensify ERC expansion into the neighboring grasslands [6]
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