|Miller, Richard - OREGON STATE UNIVERSITY|
Submitted to: Journal of Arid Environments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2006
Publication Date: July 1, 2007
Citation: Bates, J.D., Svejcar, A.J., Miller, R.F. 2007. Litter decomposition in cut and uncut western juniper woodlands. Journal of Arid Environments. Journal of Arid Environments 70(2):222-236. Interpretive Summary: This study evaluated litter decomposition and litter nitrogen dynamics in cut and uncut western juniper woodlands for a two year period in eastern Oregon. This information is important for evaluating the impacts of juniper control treatments to nutrient and carbon cycling in semi-arid woodlands which have expanded exponentially the past 150 years. Results showed that litter decay is increased after cutting but that litter N is retained on site either in litter or in the soil. The retention of juniper debris on site permits storage and release of nutrients through decay processes and may be important in maintaining long-term site productivity.
Technical Abstract: The expansion of western juniper (Juniperus occidentalis ssp. occidentalis Hook.) woodlands into northern Great Basin rangelands has resulted in large scale efforts to reduce juniper by prescribed fire or tree cutting, with the objective of restoring shrub-grassland plant communities. This study evaluated the effects of cutting trees on litter decomposition and nitrogen (N) release for a two year period in eastern Oregon, USA. Litter bags were used to estimate juniper leaf litter decomposition and follow litter carbon and N fluxes in cut and uncut juniper woodland treatments. Litter mass loss was 37% greater in the cut woodland compared to the uncut woodland after 2 years. Greater litter inputs and higher litter quality from juniper debris were suggested to have caused a priming effect, resulting in the higher litter decay rates in cut woodlands. In both treatments, litter N was released by the second year of decay, which was earlier than was anticipated, and suggested that N may not be the limiting factor for litter decomposition in juniper woodlands. The results also indicated that there is no fixed carbon/N ratio determining the timing of N release from juniper litter. Leaving juniper debris in place as a source of nutrients may be important in continued vegetative recovery in cut woodlands.