Soil processes drive seasonal variation in retention of 15N tracers in a deciduous forest catchment

TitleSoil processes drive seasonal variation in retention of 15N tracers in a deciduous forest catchment
Publication TypeJournal Article
Year of Publication2015
AuthorsGoodale, CL, Fredriksen, G, Weiss, MS, McCalley, CK, Sparks, JP, Thomas, SA
Pagination2653 - 2668
Date Published2015/05/11/
ISBN Number0012-9658
Keywords15N tracer, Arnot Forest, New York, USA, deciduous forest, N retention, seasonality, soil fractions, soil nitrogen, stream nitrate

Seasonal patterns of stream nitrate concentration have long been interpreted as demonstrating the central role of plant uptake in regulating stream nitrogen loss from forested catchments. Soil processes are rarely considered as important drivers of these patterns. We examined seasonal variation in N retention in a deciduous forest using three whole-ecosystem 15N tracer additions: in late April (post-snowmelt, pre-leaf-out), late July (mid-growing-season), and late October (end of leaf-fall). We expected that plant 15N uptake would peak in late spring and midsummer, that immobilization in surface litter and soil would peak the following autumn leaf-fall, and that leaching losses would vary inversely with 15N retention. Similar to most other 15N tracer studies, we found that litter and soils dominated ecosystem retention of added 15N. However, 15N recovery in detrital pools varied tremendously by season, with >90% retention in spring and autumn and sharply reduced 15N retention in late summer. During spring, over half of the 15N retained in soil occurred within one day in the heavy (mineral-associated) soil fraction. During summer, a large decrease in 15N retention one week after addition coincided with increased losses of 15NO3− to soil leachate and seasonal increases in soil and stream NO3− concentrations, although leaching accounted for only a small fraction of the lost 15N (

Short TitleEcology