Chemical weathering and cation loss in a base-poor watershed

Hyman, Marita E.; Johnson, Chris; Bailey, Scott W.; Hornbeck, James W.; April, Richard

doi:10.1130/0016-7606(1998)110<0085:cwacli>2.3.co;2

Cited by 43 publications

(37 citation statements)

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“…Concentrations of all elements (except P) and Ca/Sr and Sr/Ba ratios of digestible fractions generally increase with depth. Ca/(Ca+Na) molar ratios range from 0.19 to 0.24, close to the average value for plagioclase (0.26) observed by Hyman et al (1998) during an earlier study of soils at the Cone Pond watershed. There are no consistent trends of 87 Sr/ 86 Sr with depth, but as shown in Figure 3a the data define a robust 'isochron' when plotted against 87 Rb/ 86 Sr ratios of the digestible fractions.…”

Section: Soilssupporting

confidence: 72%

“…The chemical and Sr isotope variations resulting from leaching temperature differences are thus consistent with dissolution of apatite and variable leaching of a soil mineral having high Mg, K, Rb and Ba concentrations and K/Sr and 87 Sr/ 86 Sr ratios, such as biotite. We note that Mg/ K ratios of the 20 and 30°C leachates range from $1 to 3, similar to the value for biotite ($2) and considerably less than that for hornblende ($25) separated from Cone Pond soils (Hyman et al 1998). The substantial Al (and Fe) in the leachates at all temperatures may be due to dissolution of oxyhydroxide coatings on mineral surfaces.…”

Section: Soilsmentioning

confidence: 63%

“…Primary minerals in the soils, in order of decreasing modal abundance, are quartz, plagioclase feldspar (average composition, An 26 ), K-feldspar, muscovite, biotite, chlorite and hornblende. Pyroxene, garnet, epidote and apatite are present in minor to trace amounts (Bailey et al 1996;Hyman et al 1998). Unlike many neighboring watersheds such as Hubbard Brook, the Cone Pond watershed was not logged during the 19th and early 20th centuries.…”

Section: Study Area and Methodsmentioning

confidence: 97%

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Identifying calcium sources at an acid deposition-impacted spruce forest: a strontium isotope, alkaline earth element multi-tracer approach

Bullen

Bailey

2005

Biogeochemistry

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Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid depositionimpacted watershed. We measured 87 Sr/ 86 Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. 87 Sr/ 86 Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, 87 Sr/ 86 Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible alternative explanations of aspects of the observed trends, the chemical buffering capacity of the forest floor-biomass pool limits their effectiveness as causal mechanisms.

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Section: Soilssupporting

confidence: 72%

Section: Soilsmentioning

confidence: 63%

Section: Study Area and Methodsmentioning

confidence: 97%

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Identifying calcium sources at an acid deposition-impacted spruce forest: a strontium isotope, alkaline earth element multi-tracer approach

Bullen

Bailey

2005

Biogeochemistry

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“…Typical Cl À concentrations reported are 5300 mg kg À1 in hornblende, 2400 mg kg À1 in biotite, and 5000 mg kg À1 in apatite. At the nearby Cone Pond Research Watershed, Hyman et al (1998) estimated hornblende and biotite weathering flux at 3.4 and 11 mol ha À1 year À1 respectively. Using these flux estimates with the typical Cl À concentrations reported by Deer et al (1963) yields 0.45 mol Cl ha À1 year À1 released by hornblende and 0.33 mol Cl ha À1 year À1 released by biotite.…”

Section: Weathering Inputsmentioning

confidence: 99%

The biogeochemistry of chlorine at Hubbard Brook, New Hampshire, USA

et al. 2005

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Chlorine is a minor constituent of most rocks and a minor (although essential) element in plants, but it cycles rapidly through the hydrosphere and atmosphere. In forest ecosystem studies, chloride ion (Cl À ) is often thought to be conservative in the sense that the sources and sinks within the ecosystem are assumed negligible compared to inputs and outputs. As such, Cl À is often used as a conservative tracer to assess sources and transformations of other ions. In this paper we summarize research on chloride over the course of 36 years at the Hubbard Brook Experimental Forest (HBEF) in central New Hampshire, USA. Evidence presented here suggests that in the 1960s and 1970s the dominant source of atmospheric Cl À deposition was from pollutant sources, probably coal burning. In the 1970s the Cl À inputs in bulk deposition declined, and the lower Cl À deposition in the last two decades is dominated by marine sources. Between 1964 and 2000 there was no significant trend in Cl À export in stream flow, thus the net hydrologic flux (NHF = bulk deposition inputs À streamflow outputs) has changed over this period. Early in the record the NHF was on average positive, indicating net retention of Cl À within the system, but since about 1980 the NHF has been consistently negative, indicating an unmeasured input or source within the ecosystem. Dry deposition can account for at least part of that unmeasured source, and it appears that release of Cl À from mineralization of soil organic matter (SOM) may also play an important role. We believe that accumulation of Cl À in vegetation during the 1960s and 1970s offset the unmeasured source and resulted in net ecosystem retention. Accumulation of vegetative biomass has ceased since about 1982, leading to the apparent net export (negative NHF) since that time. Although we have no direct measurements of Cl À accumulation in vegetation, our estimates suggest that an aggrading forest could sequester about 32 mol Cl ha À1 year À1 , or about a third of the annual average bulk deposition flux to this ecosystem. Experimental additions of Cl À to the forest floor cause increases in Cl À concentration in foliage, throughfall, and soil solution. Manipulations of vegetation also affect the Cl À cycle. Harvesting or devegetation of watersheds causes an increase in the Cl À concentration and flux in stream water for several years after the disturbance. This period of release is followed by a period of reaccumulation of Cl À that may last more than 15 years. In this respect, the behavior of Cl À after disturbance parallels that of NO 3 À , for which export increases after disturbance due to reduced plant nitrogen uptake and mineralization of nitrogen from detritus, rather than SO 4 2À , for which export decreases after disturbance due to pH-dependent adsorption onto mineral soils. The interannual pattern of Cl À export from the system primarily reflects the atmospheric inputs, but the net retention and cycling of Cl À within the system appears to be largely under biological, rather than geochem...

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“…At the HBEF W3 and the Bowl, 11 soil pits were sampled. At CPW, samples were collected near twelve previously-established, randomly located soil pits (Hyman et al, 1998). Oie and Oa horizons were separated in the field; mineral horizons were separated in the laboratory.…”

Section: Soil Sample Collectionmentioning

confidence: 99%