Authors: Peter Regier1, Kyongho
Son2, Xingyuan Chen2, Yilin
Fang2, Peishi Jiang2, Micah
Taylor2, Wilfred M Wollheim3, James
Stegen2
Affiliations 1Marine and Coastal Research Laboratory, Pacific Northwest National
Laboratory, Sequim, WA, United States2Pacific Northwest National Laboratory, Richland, WA, United States3University of New Hampshire, Durham, NH, United
States
Abstract: Hyporheic zones regulate biogeochemical processes in
streams and rivers, but high spatiotemporal heterogeneity makes it
difficult to predict how these processes scale from individual reaches
to river basins. Recent work applying allometric scaling (i.e.,
power-law relationships between size and function) to river networks
provides a new paradigm to develop a scalable understanding of hyporheic
biogeochemical processes. We used reach-scale hyporheic aerobic
respiration estimates to explore allometric scaling patterns across two
basins, and related these patterns to watershed characteristics. We
found consistent scaling behaviors at lowest and highest exchange flux
(HEF) quantiles, and consistent but HEF-dependent relationships to
watershed elevation, precipitation, and land-cover. Our results also
suggest variability of hyporheic respiration allometry for middle
exchange flux quantiles, and in relation to land-cover. Our findings
provide initial evidence that allometric scaling may be useful for
predicting hyporheic biogeochemical dynamics across watersheds from
reach to basin scales.
Scientific Significance Statement: The hyporheic zone is a
biogeochemical control point in streams and rivers, and processes like
hyporheic respiration are important determinants of how watersheds move
and process carbon and nutrients. However, the hyporheic zone is also
characterized by high spatial heterogeneity, which makes it difficult to
predict how hyporheic functions like respiration change across
watersheds from reach to basin scales. This study applies allometric
scaling theory, which suggests that function scales in a predictable way
with size, to determine if hyporheic respiration scales with watershed
area in two basins with contrasting watershed characteristics. We found
some consistent patterns between basins that suggest allometric scaling
of hyporheic respiration may be a tool for transferable knowledge of
hyporheic function between basins, but also note some site-specific
relationships may constrain the generalizability of this method to other
regions and watersheds.