Throughfall Chemistry and Canopy Processing Mechanisms

Schaefer, Douglas; Reiners, William A.

doi:10.1007/978-1-4612-4454-7_7

Cited by 52 publications

(31 citation statements)

References 155 publications

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“…The limited data available (54 -56) suggest that leaching of P is minimal because leaf P is mostly in organic, immobile forms (58). We also find that mature forest throughfall [P] declines with increasing storm depth, whereas bulk deposition [P] (open-field collection) is not affected by storm size.…”

Section: Methodsmentioning

confidence: 48%

“…This pattern is characteristic of dry deposition input, where material is washed out of the canopy relatively quickly and concentrations decrease with time. Conversely, leaching losses would result in a relatively constant throughfall concentration and increasing inputs with increased storm size (57,58). In this study, we treat throughfall P data as an indication of deposited, rather than leached, P.…”

Section: Methodsmentioning

confidence: 99%

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Ecological feedbacks following deforestation create the potential for a catastrophic ecosystem shift in tropical dry forest

Lawrence

D’Odorico

Diekmann

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

132

117

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The long-term ecological response to recurrent deforestation associated with shifting cultivation remains poorly investigated, especially in the dry tropics. We present a study of phosphorus (P) dynamics in the southern Yucatán, highlighting the possibility of abrupt shifts in biogeochemical cycling resulting from positive feedbacks between vegetation and its limiting resources. After three cultivation–fallow cycles, available soil P declines by 44%, and one-time P inputs from biomass burning decline by 76% from mature forest levels. Interception of dust-borne P (“canopy trapping”) declines with lower plant biomass and leaf area, limiting deposition in secondary forest. Potential leaching losses are greater in secondary than in mature forest, but the difference is very small compared with the difference in P inputs. The decline in new P from atmospheric deposition creates a long-term negative ecosystem balance for phosphorus. The reduction in soil P availability will feed back to further limit biomass recovery and may induce a shift to sparser vegetation. Degradation induced by hydrological and biogeochemical feedbacks on P cycling under shifting cultivation will affect farmers in the near future. Without financial support to encourage the use of fertilizer, farmers could increase the fallow period, clear new land, or abandon agriculture for off-farm employment. Their response will determine the regional balance between forest loss and forest regrowth, as well as the frequency of use and rate of recovery at a local scale, further feeding back on ecological processes at multiple scales.

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Section: Methodsmentioning

confidence: 48%

Section: Methodsmentioning

confidence: 99%

Ecological feedbacks following deforestation create the potential for a catastrophic ecosystem shift in tropical dry forest

Lawrence

D’Odorico

Diekmann

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

132

117

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“…The rate coefficients, b\ and b 2 , represent canopy exchange and dry deposition rates, respectively. Field studies (Schaefer & Reiners 1990) empirically support the assumption that dry deposition wash-off is proportional to ADP and canopy exchange is proportional to EA. Model results are most reliable for water-soluble aerosol components deposited to leaf surfaces.…”

Section: Spatial Variability In Net Throughfall Fluxesmentioning

confidence: 94%

Atmospheric Deposition and Foliar Leaching in a Regenerating Southern Appalachian Forest Canopy

Potter¹,

Ragsdale²,

Swank³

1991

The Journal of Ecology

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SUMMARY(1) Incident precipitation, throughfall and stemflow were collected to examine the importance of factors potentially determining net canopy element fluxes, and to quantify canopy exchange and dry deposition rates in a regenerating southern Appalachian forest.(2) Net throughfall fluxes (throughfall minus precipitation transfers) showed consistent canopy effects on rainfall chemistry, with SO 4 2~, PO 4 3~, Cl~, K + , Ca 2+ and Mg 2+ added to rainfall by foliage, whereas NO 3~-N, NH 4 + -N and H + ions were absorbed from precipitation. Storm characteristics (event amount and duration) accounted for the largest portion of the variability in growing season net throughfall fluxes, suggesting that canopy exchange was the major mechanism of throughfall transfer.(3) Stemflow fluxes increased canopy exchange rates of SO 4 2~, PO 4 ?~, Cl~, K + , and Mg 2+ by greater than 20% in a regression model of total below-canopy element fluxes.(4) Cation leaching fluxes were highly variable (C.V.>50%) over spatial scales of several m 2 , but could be explained largely by heterogeneity in canopy cover. (5) Foliar cation leaching losses in the early successional forest accounted for 4-13% of leaf nutrient reserves. As cation throughfall transfers were highest during storms with the greatest hydrogen ion uptake from rainwater, it is hypothesized that acid precipitation is causing accelerated foliar nutrient leaching in south-eastern hardwood forests.

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“…Although some N is retained by vegetation, and only reaches the soil when the plant dies or sheds its leaves, most passes through the canopy fairly quickly and enters the soil as throughfall (TF = canopy drip) or stem flow (SF = water running down tree stems). Canopy uptake or retention of inorganic N (ammonium or nitrate) and organic N has long been recognised as an important fate for N in forests, where it is relatively simple to measure TF and SF for comparison with wet deposition, although its dependence on dry deposition is less easily established (Parker, 1983, Schaefer and Reiners, 1990, Tukey, 1970. It is not clear, however, what happens to the N that is retained in the canopy.…”

Section: Introductionmentioning

confidence: 99%

Experimental field estimation of organic nitrogen formation in tree canopies

Cape

Sheppard

Crossley

et al. 2010

Environmental Pollution

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The content of organic N has been shown in many studies to increase during the passage of rain water through forest canopies. The source of this organic N is unknown, but generally assumed to come from canopy processing of wet or dry deposited inorganic N. There have been very few experimental studies in the field to address the canopy formation or loss of organic N. We report two studies: a Scots pine canopy exposed to ammonia gas, and a Sitka spruce canopy exposed to ammonium and nitrate as wet deposition. In both cases, organic N deposition in throughfall was increased, but only represented a small fraction (<10%) of the additional inorganic N supplied, suggesting a limited capacity for net organic N production, similar in both conifer canopies under Scottish summertime conditions, of less than 1.6 mmol N m -2 mth -1 (equivalent to 3 kg N ha -1 y -1 ).

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Throughfall Chemistry and Canopy Processing Mechanisms

Cited by 52 publications

References 155 publications

Ecological feedbacks following deforestation create the potential for a catastrophic ecosystem shift in tropical dry forest

Ecological feedbacks following deforestation create the potential for a catastrophic ecosystem shift in tropical dry forest

Atmospheric Deposition and Foliar Leaching in a Regenerating Southern Appalachian Forest Canopy

Experimental field estimation of organic nitrogen formation in tree canopies

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