Organic matter stoichiometry influences nitrogen and phosphorus uptake in a headwater stream

Gibson, Catherine A.; O’Reilly, Catherine M.

doi:10.1899/11-033.1

Cited by 22 publications

(33 citation statements)

References 48 publications

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“…Striegl et al (2005) found decreased export of dissolved organic carbon to Subarctic rivers from 1978Subarctic rivers from -1980Subarctic rivers from to 2001Subarctic rivers from -2003, suggesting that increased flow path, residence time, and microbial mineralization rates within the soil active layer allowed much of the carbon to be respired before reaching rivers. This is because recalcitrant organic matter contains both nitrogen and phosphorus and, by resisting mineralization, moves the two nutrients through ecosystems in a coupled manner (Gibson & O'Reilly, 2012). Results are restricted to well-supported models (ΔAIC ≤ 2) and the null intercept-only model, and we also report number of parameters (k) and model weights (w i ).…”

Section: Discussionmentioning

confidence: 99%

Pronounced chemical response of Subarctic lakes to climate‐driven losses in surface area

Lewis

Lindberg

Schmutz

et al. 2014

Global Change Biology

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Losses in lake area have been observed for several Arctic and Subarctic regions in recent decades, with unknown consequences for lake ecosystems. These reductions are primarily attributed to two climate-sensitive mechanisms, both of which may also cause changes in water chemistry: (i) increased imbalance of evaporation relative to inflow, whereby increased evaporation and decreased inflow act to concentrate solutes into smaller volumes; and (ii) accelerated permafrost degradation, which enhances sublacustrine drainage while simultaneously leaching previously frozen solutes into lakes. We documented changes in nutrients [total nitrogen (TN), total phosphorus (TP)] and ions (calcium, chloride, magnesium, sodium) over a 25 year interval in shrinking, stable, and expanding Subarctic lakes of the Yukon Flats, Alaska. Concentrations of all six solutes increased in shrinking lakes from 1985-1989 to 2010-2012, while simultaneously undergoing little change in stable or expanding lakes. This created a present-day pattern, much weaker or absent in the 1980s, in which shrinking lakes had higher solute concentrations than their stable or expanding counterparts. An imbalanced evaporation-to-inflow ratio (E/I) was the most likely mechanism behind such changes; all four ions, which behave semiconservatively and are prone to evapoconcentration, increased in shrinking lakes and, along with TN and TP, were positively related to isotopically derived E/I estimates. Moreover, the most conservative ion, chloride, increased >500% in shrinking lakes. Conversely, only TP concentration was related to probability of permafrost presence, being highest at intermediate probabilities. Overall, the substantial increases of nutrients (TN >200%, TP >100%) and ions (>100%) may shift shrinking lakes towards overly eutrophic or saline states, with potentially severe consequences for ecosystems of northern lakes.

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Section: Discussionmentioning

confidence: 99%

Pronounced chemical response of Subarctic lakes to climate‐driven losses in surface area

Lewis

Lindberg

Schmutz

et al. 2014

Global Change Biology

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“…Likewise, empirical nutrient‐productivity models are widely used because many nutrient‐productivity variables are correlated with one another (Ostrofsky and Rigler ; Phillips et al ). The correlation among nutrient‐productivity variables is partly due to coupled biogeochemical cycles (Schlesinger et al ; Gibson and O'Reilly ). For example, nutrients and other elements do not cycle independently, as illustrated by co‐limitation of growth of primary producers (Sterner ; Harpole et al ).…”

mentioning

confidence: 99%

Combining nutrient, productivity, and landscape‐based regressions improves predictions of lake nutrients and provides insight into nutrient coupling at macroscales

Wagner

Schliep

2018

Limnology & Oceanography

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Empirical nutrient models that describe lake nutrient, productivity, and water clarity relationships among lakes play a prominent role in limnology. Landscape‐based regressions are also used to understand macroscale variability of lake nutrients, clarity, and productivity (hereafter referred to as nutrient‐productivity). Predictions from both models are used to inform eutrophication management globally. To date, these two classes of models are generally conducted separately, which ignores the known dependencies among nutrient‐productivity variables. We present a statistical model that integrates nutrient‐productivity and landscape‐based regressions—where lake nutrients, productivity, and clarity variables are modeled jointly. We fitted a joint nutrient‐productivity model to over 7000 lakes with three nutrients (total phosphorus, total nitrogen, nitrate concentrations), chlorophyll a concentrations, and Secchi disk depth as response variables and landscape features as predictor variables. Because lakes in different regions respond to landscape features differently, we focused our analysis on two subregions with different dominant land uses, the agricultural Midwest and the forested Northeast U.S. Predictive performance was enhanced by modeling nutrient‐productivity variables jointly. We also found strong evidence that nutrient‐productivity variables were coupled, and that only nitrate may be decoupled from other nutrient‐productivity variables in the forested region. We speculate that these regional differences may be related to differences in the strength of biogeochemical cycles and stoichiometric controls between these regions. Jointly modeling nutrient‐productivity variables in lakes effectively integrates the two dominant approaches for studying lakes nutrient‐productivity relationships and provides novel insight into macroscale patterns of the coupling of nutrients, chlorophyll, and water clarity in lakes.

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“…Litter quality and quantity could have a critical temporal interaction on nutrient dynamics in stream ecosystems (Gibson & O'Reilly, 2012). We showed that litter species quality, as a function of species identity, can mediate stream ecosystem nutrient dynamics, possibly through reduction of litter quantity.…”

Section: Discussionmentioning

confidence: 79%

“…This strong retention, even with substantial N mineralisation in cottonwood and other litters, is not unexpected. Differences in N and P dynamics do, however, suggest that the coupling of N and P demand in detritus-dominated streams could depend on riparian detritus composition and inputs (Gibson & O'Reilly, 2012). N) will probably not occur at the same time as others (e.g.…”

Section: Discussionmentioning

confidence: 99%

Leaf litter identity alters the timing of lotic nutrient dynamics

et al. 2019

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The effects of resource quality on ecosystems can shift through time based on preferential use and elemental needs of biotic consumers. For example, leaf litter decomposition rates are strongly controlled by initial litter quality, where labile litter is processed and depleted more quickly than recalcitrant litters. We examined the effect of this processing continuum on stream nutrient dynamics. We added one of four different litter compositions differing in litter quality (cottonwood [Populus deltoides], labile; sycamore [Platanus occidentalis], recalcitrant; bur oak [Quercus macrocarpa], recalcitrant; and mixed [equivalent mixture of previous three species]) to 12 large (c. 20 m long, with riffle, glide and pool sections) outdoor stream mesocosms to assess the effect of litter species composition on whole‐stream nutrient uptake. Nutrients were dosed once weekly for 8 weeks to measure uptake of NH4–N, NO3–N, and PO4–P. We also measured changes in litter C, N, and P content on days 28 and 56 of the study. Nutrient uptake rates were highly variable, but occasionally very different among litter treatments (c. 5× between highest and lowest uptake rates by species). Uptake rates were generally greatest in cottonwood (labile) streams early in the study. However, during the last 4 weeks of the study, bur oak streams (recalcitrant) took up more nutrients than cottonwood streams, resulting in more cumulative NO3–N uptake in bur oak than in cottonwood streams. Cumulative NO3–N uptake was greater in mixed streams than expected (non‐additive) on two dates of measurement, but was generally additive. Changes in litter nutrient content largely corroborated nutrient uptake patterns, suggesting strong N immobilisation early in the study and some N mineralisation later in the study. P was strongly retained by most litters, but especially bur oak. Nutrient content of litter also largely changed additively, suggesting minimal evidence for non‐additive diversity effects on nutrient source/sink status. Our results demonstrate that litter species identity can have whole‐ecosystem effects on stream nutrient dynamics, with important implications for the form and fate of nutrients exported downstream. Further, diverse litter assemblages may serve as temporal stabilisers of ecosystem processes, such as nutrient sequestration, due to microbial nutrient requirements and differential decomposition rates, or the classic litter processing continuum.

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Organic matter stoichiometry influences nitrogen and phosphorus uptake in a headwater stream

Cited by 22 publications

References 48 publications

Pronounced chemical response of Subarctic lakes to climate‐driven losses in surface area

Pronounced chemical response of Subarctic lakes to climate‐driven losses in surface area

Combining nutrient, productivity, and landscape‐based regressions improves predictions of lake nutrients and provides insight into nutrient coupling at macroscales

Leaf litter identity alters the timing of lotic nutrient dynamics

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