Bayesian Hierarchical Modeling of Nitrate Concentration in a Forest Stream Affected by Large‐Scale Forest Dieback. Issue 2 (23rd February 2021)

• Record Type: Journal Article
• Authors: Jung, Hoseung; Senf, Cornelius; Beudert, Burkhard; Krueger, Tobias
• Is Part Of: Water resources research. Volume 57:Issue 2(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-02-23
• Subjects: Bark beetle -- Bayesian hierarchical modeling -- forest dieback -- nitrate; Hydrology -- Periodicals; 333.91
• DOI: 10.1029/2020WR027264
• Languages: English
• ISSNs: 0043-1397

Abstract

Abstract: The ecosystem function of vegetation to attenuate export of nutrients is of substantial importance for securing water quality. This ecosystem function is at risk of deterioration due to an increasing risk of large‐scale forest dieback under climate change. The present study explores the response of the nitrogen (N) cycle of a forest catchment in the Bavarian Forest National Park, Germany, in the face of a severe bark beetle ( Ips typographus Linnaeus) outbreak and resulting large‐scale forest dieback using top‐down statistical‐mechanistic modeling. Outbreaks of bark beetle killed the dominant tree species Norway spruce ( Picea abies (L.) H.Karst.) in stands accounting for 55% of the catchment area. A Bayesian hierarchical model that predicts daily stream NO3 concentration (C) over three decades with discharge (Q) and temperature (T) (C‐Q‐T relationship) outperformed alternative statistical models. A catchment model was subsequently developed to explain the C‐Q‐T relationship in top‐down fashion. Annually varying parameter estimates provide mechanistic interpretations of the catchment processes. Release of NO3 from decaying litter after the dieback was tracked by an increase of the nutrient input parameter cs0 . The slope of C‐T relation was near zero during this period, suggesting that the nutrient release was beyond the regulating capacity of the vegetation and soils. Within a decade after the dieback, the released N was flushed out and nutrient retention capacity was restored with the regrowth of the vegetation. Key Points: Pulse of nitrate export from a forest catchment in response to bark beetle infestation followed by recovery of nutrient retention capacity Top‐down, data‐driven Bayesian hierarchical model assists mechanistic interpretation of hydrochemical processes Concentration‐discharge‐temperature relationship is shaped by spatial heterogeneity of nutrient and seasonality of biogeochemical reactions