Mini-Review: Stemflow as a Resource Limitation to Near-Stem Soils

Area of Science:

• Ecohydrology
• Forest Ecology
• Soil Science

Background:

• Stemflow is precipitation and solute delivery to soils near tree stems, influencing ecosystem functions.
• Research has focused on high-volume stemflow, assuming it's primarily a resource subsidy.
• This overlooks stemflow's potential role in resource limitation when volumes are low.

Purpose of the Study:

• Evaluate the prevalence of stemflow as a potential resource limitation in near-stem soils.
• Characterize the solute flux from low stemflow generators.
• Re-evaluate the ecohydrological significance of stemflow in diverse forest ecosystems.

Main Methods:

• Literature review across numerous global forests.
• Analysis of stemflow volume distribution (skewness and kurtosis).
• Assessment of solute concentration and flux in low-volume stemflow.

Main Results:

• Global stemflow observations are highly skewed and leptokurtic, with 69% of cases yielding ≤2% of rainfall.
• Low-volume stemflow (≤2% of rainfall) is chemically enriched but delivers negligible solute flux (<1 g m^-2 y^-1).
• Reduced stemflow is likely the global norm, leading to dry near-stem soils with infrequent, concentrated precipitation.

Conclusions:

• Low stemflow can create significant resource limitations in near-stem soils, contrary to the subsidy assumption.
• Understanding stemflow scarcity is crucial for accurately assessing ecosystem functioning.
• Future research should consider stemflow's role in resource limitation to fully grasp soil nutrient dynamics, energy flow, and biogeochemical processes.