The use of stable isotopes of water in characterising the source of water in vegetation

Walker, Colin D.; Richardson, Sue

doi:10.1016/s0009-2541(10)80026-9

Cited by 65 publications

(53 citation statements)

References 18 publications

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“…The lack of fractionation in the uptake of water by roots has been shown in laboratory and glasshouse experiments (Walker & Richardson, 1991;Thorburn et al, 1992) and under field conditions (Brunel et al, 1995). The only exception demonstrated thus far is for halophytes such as mangrove (Lin & Sternberg, 1993).…”

Section: Theorymentioning

confidence: 94%

“…Each stem was divided into pieces 2-3 cm in length and placed in a glass vial containing purified kerosene. Kerosene prevents isotopic exchange and prepares the sample for extraction by an azeotropic distillation (Walker & Richardson, 1991). The rainfall of every rainfall event was collected 2 km from the study sites.…”

Section: Methodsmentioning

confidence: 99%

“…Stable isotopes of water are now widely used in studies of water transport in the soil-vegetation-atmosphere continuum (Brunel et al, 1991;Dawson & Ehleringer, 1991;Flanagan & Ehleringer, 1991;Walker & Richardson, 1991;Ehleringer & Dawson, 1992;Thorburn et al, 1992;Mensforth et al, 1994;Dawson & Pate, 1996). The seasonal distribution of precipitation in the upper San Pedro watershed is bimodal.…”

Section: Introductionmentioning

confidence: 99%

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Sources of water used by natural mesquite vegetation in a semi-arid region of northern Mexico

Brunel¹

2009

Hydrological Sciences Journal

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Vegetation structure in semi-arid regions of northern Mexico and the southwestern USA has changed dramatically over the last century; shrubs such as mesquite (Prosopis sp.) have expanded into, and have become dominant in, ecosystems that once supported semi-arid grassland. The upper San Pedro River watershed, which extends from northern Sonora (Mexico) to southeastern Arizona (USA), highlights these changes. Between 1973 and 1992, grasslands decreased by 18% and the total area dominated by mesquite increased during the same period by 412%. In the areas where the density of mesquite shrub is medium to high, grass has completely disappeared under the shrub canopy and has been replaced by bare soil. Undoubtedly these cover changes have affected surface-atmosphere interactions by introducing a different partitioning of net available energy into sensible and latent heat flux. At the same time, different root system and root density and plant physiology have introduced a change to the surface water balance, reducing inflitration and increasing runoff. Our study addressed the sources of water used by mesquite (Prosopis velutina) along a natural gradient from an area of high mesquite cover with no herbaceous grass cover, to open savanna with high grass cover and widely spaced mesquite. The presented results from the SALSA 1997 monsoon-season campaign (July-October) show that mesquite shrubs that have access to both groundwater and surface water use surface water when available, potentially competing with grass for surface water and out-competing grass during successive periods of drought when only groundwater is available.Key words oxygen-18; mesquite; Prosopis velutina; water use; Sonora, Mexico; Arizona, USA; semi-desert grassland Sources de l'eau utilisée par une végétation naturelle de mesquite dans une région semi-aride du nord du MexiqueRésumé La structure de la végétation dans les régions semi-arides du nord-est du Mexique et du sud-ouest des Etats Unis a changé d'une façon spectaculaire au cours du dernier siècle. Une végétation de buissons de type mesquite (Prosopis sp.) s'est répandue partout pour devenir dominante dans ce qui était autrefois un écosystème de prairies semi-arides. Le haut bassin de la rivière San Pedro qui s'étend du nord-est du Sonora (Mexique) au sud-est de l'Arizona (USA) met bien en relief ces changements. Entre 1973 et 1992, les prairies ont diminué de 18% alors que pendant le même temps la superficie totale dominée par les mesquites s'accroissait de 412%. Dans les zones où la densité de mesquites est moyenne ou forte, l'herbe a complètement disparu sous les arbres et a été remplacée par du sol nu. Il ne fait aucun doute que ces changements de couverture végétale ont affecté les interactions surface-atmosphère en introduisant une répartition différente de l'énergie nette disponible en flux de chaleur sensible et latente. En même temps, l'accroissement du ruissellement, la diminution de l'infiltration mais aussi le développement de systèmes d'enracinement différents, et des densit...

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Section: Theorymentioning

confidence: 94%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sources of water used by natural mesquite vegetation in a semi-arid region of northern Mexico

Brunel¹

2009

Hydrological Sciences Journal

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“…Analogamente, gli isotopi stabili dell'idrogeno nell'acqua possono essere impiegati per tracciare le risorse idriche utilizzate dalle piante e per completare le informazioni sui modelli spaziali di sviluppo radicale (Dawson & Ehleringer 1991, Walker & Richardson 1991, Sternberg & Swart 1987, Flanagan et al 1992, Valentini et al 1992, Dawson 1996, Dawson et al 2002, poiché durante l'assorbimento di acqua dalle piante non intervengono fenomeni di frazionamento isotopico dell'idrogeno. Durante il trasporto dell'acqua all'interno della pianta, la composizione isotopica dell'idrogeno (δD) mantiene lo stesso valore di quella dell'acqua nel suolo, fino alla superficie fogliare, dove si innescano i processi evapotraspirativi.…”

Section: Introduzioneunclassified

“…Nelle foreste sottoposte a trattamenti selvicolturali questa risposta può essere mediata o anche "sopraffatta" da un simultaneo incremento dei nutrienti o della disponibilità di radiazione luminosa associato alla perturbazione (Warren et al 2001). Per contro, in termini assoluti il rapporto A/E potrebbe rimanere invariato in seguito al diradamento (Leavitt & Long 1986, McDowell et al 2003, sebbene i due parametri possano variare in funzione dell'incremento della disponibilità di luce o di azoto, che può determinare un aumento di A, e per effetto dell'incremento di disponibilità idrica del suolo, che può determinare un aumento di E.Analogamente, gli isotopi stabili dell'idrogeno nell'acqua possono essere impiegati per tracciare le risorse idriche utilizzate dalle piante e per completare le informazioni sui modelli spaziali di sviluppo radicale (Dawson & Ehleringer 1991, Walker & Richardson 1991, Sternberg & Swart 1987, Flanagan et al 1992, Valentini et al 1992, Dawson 1996, Dawson et al 2002, poiché durante l'assorbimento di acqua dalle piante non intervengono fenomeni di frazionamento isotopico dell'idrogeno. Durante il trasporto dell'acqua all'interno della pianta, la composizione isotopica dell'idrogeno (δD) mantiene lo stesso valore di quella dell'acqua nel suolo, fino alla superficie fogliare, dove si innescano i processi evapotraspirativi.…”

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Application of isotope discrimination techniques to evaluate the functional response of Mediterranean coppices to high-forest conversion cut

Matteo¹,

Angelis²,

Mugnozza³

2005

Forest@

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Application of isotope discrimination techniques to evaluate the functional response of Mediterranean coppices to high-forest conversion cut.Discrimination of stable isotopes of carbon and hydrogen provides an effective tool for interpreting time-integrated responses of plants to environmental conditions and delineate sources of plant water uptake. In this work, isotopic analyses were carried out in two Mediterranean oak forests in which a thinning experiment on replicated plots has been performed. Changes in carbon isotope discrimination suggests an increase of water use efficiency soon after thinning. Together with changes in the hydrogen isotopic composition in xylem sap, this may suggest that trees are able of a rather prompt physiological acclimation to cope effectively to new environmental conditions and changes in resource availability. Keywords IntroduzioneLa gestione dei boschi cedui nell'area mediterranea, dopo la crisi degli anni '50, si è andata caratterizzando per successivi adattamenti ai mutamenti economici e sociali, sia con adeguamenti del trattamento, sia con la scelta di opzioni colturali diversificate. Queste ultime si sono tradotte nella sospensione delle utilizzazioni, che hanno determinato il cosiddetto "invecchiamento" dei cedui, e nell'avviamento all'alto fusto, che ha interessato sopratutto le zone di proprietà pubblica (Amorini et al. 1996a).L'attuale presenza sul territorio di queste realtà colturali non è ancora consistente, ma la tendenza in atto a valorizzare anche le funzioni non produttive del bosco fa presumere un loro incremento nel prossimo futuro, unitamente ad una revisione complessiva del trattamento selvicolturale delle formazioni di origine agamica. Numerosi studi sono stati focalizzati sugli aspetti tecnici di questa opzione selvicolturale, con importanti applicazioni pratiche sulla gestione forestale pubblica. Per contro, le conoscenze scientifiche dell'impatto dei trattamenti di conversione sulla funzionalità e l'efficienza d'uso delle risorse di questi ecosistemi (efficienza d'uso dell'acqua, efficienza fotosintetica ed efficienza d'uso dell'azoto) sono limitate. Quando, invece, l'opportunità di applicare opzioni gestionali diversificate impone la definizione di tecniche di trattamento fondate sulla valutazione di parametri non solo produttivi ma anche di ordine funzionale.Oggigiorno sono disponibili nuovi strumenti di indagine per studiare la risposta degli alberi e dei popolamenti forestali alla variazione dei fattori ambientali. Tra questi, di particolare rilevanza è l'uso degli isotopi stabili del carbonio e dell'idrogeno, per la loro capacità di integrare nel tempo le risposte a livello di processi fisiologici e per l'idoneità ad essere utilizzati anche in schemi di indagine che prevedano campionamenti intensivi.I valori di discriminazione dell'isotopo stabile del carbonio 13 rispetto al carbonio 12, più abbondante in natura, e del deuterio rispetto all'idrogeno, possono fornire importanti indicazioni, rispettivamente sul rapporto tra assimilazione fot...

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Stable isotopes in ecosystem science: structure, function and dynamics of a subtropical savanna

Boutton

Archer

Midwood³

1999

Rapid Commun. Mass Spectrom.

140

104

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Stable isotopes are often utilized as intrinsic tracers to study the effects of human land uses on the structural and functional characteristics of ecosystems. Here, we illustrate how stable isotopes of H, C, and O have been utilized to document changes in ecosystem structure and function using a case study from a subtropical savanna ecosystem. Specifically, we demonstrate that: (1) delta 13C values of soil organic carbon record a vegetation change in this ecosystem from C4 grassland to C3 woodland during the past 40-120 years, and (2) delta 2H and delta 18O of plant and soil water reveal changes in ecosystem hydrology that accompanied this grassland-to-woodland transition. In the Rio Grande Plains of North America, delta 13C values of plants and soils indicate that areas now dominated by C3 subtropical thorn woodland were once C4 grasslands. delta 13C values of current organic matter inputs from wooded landscape elements in this region are characteristic of C3 plants (-28 to -25/1000), while those of the associated soil organic carbon are higher and range from -20 to -15/1000. Approximately 50-90% of soil carbon beneath the present C3 woodlands is derived from C4 grasses. A strong memory of the C4 grasslands that once dominated this region is retained by delta 13C values of organic carbon associated with fine and coarse clay fractions. When delta 13C values are evaluated in conjunction with 14C measurements of that same soil carbon, it appears that grassland-to-woodland conversion occurred largely within the past 40-120 years, coincident with the intensification of livestock grazing and reductions in fire frequency. These conclusions substantiate those based on demographic characteristics of the dominant tree species, historical aerial photography, and accounts of early settlers and explores. Concurrent changes in soil delta 13C values and organic carbon content over the past 90 years also indicate that wooded landscape elements are behaving as sinks for atmospheric CO2 by sequestering carbon derived from both the previous C4 grassland and the present C3 woody vegetation. Present day woodlands have hydrologic characteristics fundamentally different from those of the original grasslands. Compared to plants in remnant grasslands, tree and shrub species in the woodlands are rooted more deeply and have significantly greater root biomass and density than grasslands. delta 18O and delta 2H values of plant and soil water confirm that grassland species acquire soil water primarily from the upper 0.5 m of the soil profile. In contrast, trees and shrubs utilize soil water from throughout the upper 4 m of the profile. Thus, soil water that formerly may have infiltrated beyond the reach of the grassland roots and contributed to local groundwater recharge or other hydrologic fluxes may now be captured and transpired by the recently formed woodland plant communities. The natural abundances of stable isotopes revealed fundamental information regarding the impacts of human land use activities on the structure and function of th...

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The use of stable isotopes of water in characterising the source of water in vegetation

Cited by 65 publications

References 18 publications

Sources of water used by natural mesquite vegetation in a semi-arid region of northern Mexico

Sources of water used by natural mesquite vegetation in a semi-arid region of northern Mexico

Application of isotope discrimination techniques to evaluate the functional response of Mediterranean coppices to high-forest conversion cut

Stable isotopes in ecosystem science: structure, function and dynamics of a subtropical savanna

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