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Spatial scaling of ecosystem C and N in a subtropical savanna landscape

Summary: Spatial scaling of ecosystem C and N in a subtropical
savanna landscape
F E N G L I U *, X . B E N W U *, E . B A I *, T H O M A S W. B O U T T O N * and S T E V E N R . A R C H E R w
*Department of Ecosystem Science and Management, Texas A&M University, College Station, TX 77843-2138, USA, wSchool of
Natural Resources, University of Arizona, Tucson, AZ 85721-0043, USA
Widely occurred woody encroachment in grass-dominated ecosystems has the potential to
influence soil organic carbon (SOC) and total nitrogen (TN) pools at local, regional, and global
scales. Evaluation of this potential requires assessment of both pool sizes and their spatial
patterns. We quantified SOC and TN, their relationships with soil and vegetation attributes,
and their spatial scaling along a catena (hill-slope) gradient in the southern Great Plains, USA
where woody cover has increased substantially over the past 100 years. Quadrat variance
analysis revealed spatial variation in SOC and TN at two scales. The larger scale variation (40
45 m) was approximately the distance between centers of woody plant communities and their
adjoining herbaceous patches. The smaller scale variation (10 m) appeared to reflect the local
influence of shrubs on SOC and TN. Litter, root biomass, shrub, and tree basal area (a proxy
for plant age) exhibited not only similar spatial scales, but also strong correlations with SOC
and TN, suggesting invasive woody plants alter both the storage and spatial scaling of SOC
and TN through ecological processes related primarily to root turnover and, to a lesser extent
litter production, as mediated by time of occupancy. Forb and grass biomass were not


Source: Archer, Steven R. - Savanna/Woodland Ecology Lab., School of Natural Resources and the Environment, University of Arizona
Boutton, Thomas W. - Department of Ecosystem Science and Management, Texas A&M University


Collections: Environmental Sciences and Ecology