Location: Forage and Livestock Production Research2012 Annual Report
1a. Objectives (from AD-416):
Eastern redcedar (ERC) (Juniperus virginiana L.) is an invasive species on tallgrass prairie and adjacent landscapes in the southern Great Plains region of the U.S. with an estimated 8 million acres impacted in the state of Oklahoma alone. Historically, Oklahoma’s western native prairie burned periodically and these fires destroyed seedling redcedars and eliminated their establishment over most of the region. Average annual rate of acreage increasingly infested is reportedly 4% per year and at this rate the expectation is a doubling of infested acres every 18 years. Redcedar impact on rangeland is fairly direct and forage growth outside of the canopy area is not impacted significantly. However, beneath the canopy forage growth is virtually non-existent. Therefore, canopy cover is a fairly direct indication of the extent of reduction in grassland productivity. It is also a popular belief that the increasing number of ERC may be affecting local water resources and potentially robbing downstream water supplies. There is some evidence that ERC invasion, and the resulting changes in plant community leaf area, is negatively impacting rangeland water balance through increased transpiration and interception of precipitation. Similarly, the deep rooting habit of redcedar may be exploiting soil moisture not normally depleted by native grassland species. Control measures can be targeted at the landscape, watershed, and field scales. However, determination of effectiveness of control measures necessitates development of spatial scale techniques that will provide an understanding of scale and complexity of ERC invasion. Similarly, plans to utilize ERC as an economic resource for rural communities, particularly as a biofuels resource, will also necessitate documentation of extent of ERC invasion and an estimate of the available resource and its total energy potential. The objectives of this project are to develop prediction equations for estimation of total available ERC dry biomass feedstock, identify fragmentation patterns of grassland landscapes over time as a result of ERC invasion, and assess hydrologic response in grassland watersheds in response to ERC removal.
1b. Approach (from AD-416):
Initial research will identify relationships between redcedar biomass and tree number, tree age, bole diameter and canopy cover. Replicated study areas will be identified and trees will be counted and harvested to determine age, height, bole diameter, weight, and canopy cover. Satellite imagery of the study areas will be used to correlate metrics obtained from these studies with spectral reflectance and estimates of redcedar coverage. Equations relating redcedar cover to biomass feedstock will be developed and verified in conjunction with USDA Forestry Service. Wells will be installed in appropriate transects of three wells (replicates) each, to determine the impact of redcedar on ground water, a network of shallow ground water. One transect will be situated in un-cleared pasture where cedars were not removed and represents land with heavy cedar infestation. A second transect will be situated on cleared pasture where red cedars were removed and represents a re-mediated landscape. A third transect will be located next to a riparian area and will be used to monitor the stream flow influence on ground water levels. Ground water wells will be installed with pressure transducers equipped with data loggers to measure and record readings twice daily. Aerial photographs of a target watershed over a series of years will be identified. Over this historical time line the impacts of redcedar infestation and spread will be determined. At each selected time point, forms of land management (ie cropland, pastureland, rangeland, riparian corridors), and their location and boundaries will also be identified. These landforms will be ground truthed to ascertain exactly how croplands, etc, appear on aerial photos. Ground observations will also be required to define the presence of redcedar, and develop some estimate of density or other useful parameters. Allometric measures obtained may be converted to estimate landscape biofuel capacity by using some of the equations developed from previously mentioned aspects of this project.
3. Progress Report:
Sap flux sensors have been installed on selected trees and tree branches to estimate redcedar transpiration, and four redcedars have been instrumented to estimate throughfall, canopy interception, and stemflow as a function of precipitation amount. Data collection has been completed, data analysis is completed on the canopy interception study, and data analysis of sapflux (transpiration) is 90% complete. A manuscript describing research results is nearing completion and will be ready for submission to a journal by the end of the fiscal year.