Precipitation is the key determinant of topsoil δ15N values in southern Patagonia's semiarid rangelands

Nitrogen (N) cycling in rangeland soils could potentially be controlled by water supply, stocking rates, or a range of other variables, such as ecosystem N stocks. To gauge the relative importance and elucidate possible interactions among these factors, we measured many abiotic variables to identify...

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Bibliographic Details
Published in:Vadose zone journal 2022-03, Vol.21 (2), p.n/a
Main Authors: Peri, Pablo L., Duarte‐Guardia, Sandra, Amelung, Wulf, Ladd, Brenton
Format: Article
Language:English
Subjects:
Additives
Aridity
Availability
Biodiversity
Cycles
Ecosystems
Efficiency
Fertilizers
Grazing
Grazing intensity
Isotopes
Land use
Nitrogen
Precipitation
Pressure effects
Productivity
Rangelands
Sheep
Soil
Soils
Stocking rates
Stocks
Topsoil
Vadose water
Variables
Variation
Water availability
Water supply
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Summary:Nitrogen (N) cycling in rangeland soils could potentially be controlled by water supply, stocking rates, or a range of other variables, such as ecosystem N stocks. To gauge the relative importance and elucidate possible interactions among these factors, we measured many abiotic variables to identify first‐order controls of δ15N for Patagonia's rangeland soils under contrasting historical grazing intensities. The results showed that δ15N values declined as water availability increased. The effects of precipitation and stocking rate on soil δ15N values were additive, and the effect of precipitation far outweighed the effects of grazing pressure. The soil N stock was a weak predictive variable for modeling variation in δ15N of the soil. Earlier assumptions about an inflection point for N cycling and δ15N values related to aridity were not confirmed. We conclude that variation in water availability drives variation in δ15N values irrespective of grazing intensity. We also conclude that meaningful interpretation of δ15N in soil will require a better mechanistic understanding of the interactions between water and N in the vadose zone than we currently possess. Core Ideas  Interpretation of δ15N values in soils remains a significant and unresolved challenge.  Precipitation is the main driver of variation in δ15N values in Patagonian soils.  Vadose zone research is needed to better understand the interactive effects of water and N on δ15N in soil.
ISSN:1539-1663
1539-1663
DOI:10.1002/vzj2.20183