Ecosystem carbon in relation to woody plant encroachment and control: Juniper systems in Oregon, USA.
Abdallah, M. A. B., R. Mata-González, J. S. Noller, and C. G. Ochoa. 2020. Ecosystem carbon in relation to woody plant encroachment and control: Juniper systems in Oregon, USA. Agriculture, Ecosystems & Environment 290:106762.
Camp Creek paired watershed, Crook County, central Oregon.
Description of Site
Elevation – 1,370 to 1,524 m (4,495-5,000 ft); Ppt – 358 mm (14 in); Soil series -Westbutte, Madeline, and Simas, range from frigid loamy-skeletal Haploxerolls to clayey lithic Argixerolls; Plant community – western juniper (Juniperus occidentalis), mountain big sagebrush (Artemisia tridentata spp. vaseyana), bitterbrush (Purshia tridentata), green rabbitbrush (Chrysothamnus viscidiflorus), rubber rabbitbrush (Ericameria nauseosa), Idaho fescue (Festuca idahoensis), bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg bluegrass (Poa secunda), and Thurber’s needlegrass (Achnatherum thurberianum).
Treatments and Response Measured
Treatments – 1) untreated and, 2) cut and scattered with chainsaws; Time period – 13-years post treatment; Measurements – aboveground carbon, root carbon, and total below ground carbon.
Researchers quantified above- and belowground carbon stocks (roots and soil) in both watersheds at two soil depths (0−25 cm and 25−50 cm [0-10, 10-20 in]). Aboveground carbon stocks were 5.8 times greater in the untreated than in the treated watershed. However, root carbon stocks were 2.6 times greater in the treated than in the untreated watershed. Soil carbon stocks at both 0−25 cm and 25−50 cm depth were not affected by juniper control. Overall, total ecosystem carbon stocks (average 137.6 Mg C/ha) were not different between watersheds. Most of the total ecosystem carbon resides below ground (84% and 97%) at 0−50 cm soil depth in both untreated and treated watersheds.
These results for changes in aboveground carbon are very similar to Rau and others (2011, 2012) that reported a 6.1-fold difference in aboveground carbon stocks between untreated and treated woodlands, in 13 woodlands across the Great Basin. However, root carbon stocks were 2.6 times greater instead of less in the treated site, as reported by Rau. This may be a result of 1) different site characteristics, 2) varying response of herbaceous vegetation, especially deep-rooted perennial grasses, and/or 3) differences in time since treatment (13 years compared to 1-3 years) allowing more time for carbon input from perennial herbaceous vegetation.
Both reported, little change in total soil carbon between treated and untreated sites. And both estimated over 80% of total carbon stocks were located below ground in both woodland and non-woodland.