COS 283-2 - Eastern Red Cedar Encroachment Increases Soil Carbon and Infiltration

Abstract: Background/Question/Methods

Woody plant encroachment (WPE) is a global challenge causing the expansion of woody plants into grasslands resulting in loss and degradation of grasslands and their important ecosystem services. With the increased risk of climate extremes and drought brought on by climate change, WPE and increased tree cover on grasslands have been suggested as a potential mitigating factor for combatting climate change through increasing carbon sequestration capacity in grasslands. Further, given that WPE has also been shown to disrupt the water cycle, the impact of WPE on ecosystem functions and services in grasslands could be significant. For this study, we aimed to better understand the role WPE plays in the amount of soil carbon and rate of infiltration in grasslands.

Specifically, we studied the effects of WPE on soil carbon and infiltration in grasslands across three sites currently experiencing eastern red cedar (Juniperus virginiana) encroachment in central Oklahoma. In 2022, we collected field saturated hydraulic conductivity (used as a proxy for soil infiltration), bulk density, soil texture, organic matter, and total nitrogen data (10 cm soil core) equally within cedar canopies and grass areas at each site. We analyzed the data using linear mixed models or generalized linear models.

Results/Conclusions

We found that eastern red cedar encroachment increased soil carbon and infiltration. Average organic matter under cedar canopies was 6.30% compared to 4.57% in areas with grass. Field saturated hydraulic conductivity was almost 3 times greater under cedar canopies (mean = 770.4 mm/h) than areas with grass (mean = 254.3 mm/h). Further, soils under cedar canopies had higher amounts of total nitrogen and clay content, but lower bulk densities than areas with grass.

Our study determined that WPE has the potential to positively influence both the carbon and water cycles. Our study shows that woody plant encroachment can have a positive effect on ecosystem function in some regions, which is contrary to literature that states WPE negatively impacts ecosystem services suggesting that WPE may create tradeoffs for management. Given that the restoration of encroached grasslands is difficult and the effects of climate change will continue, conservationists, land managers, and policy makers should consider the tradeoffs that WPE creates to maintain ecosystem functions and services in the future.