Effect of Plant Roots on Chemical and Biochemical Properties of Surrounding Discrete Soil Zones

Dormaar, J. F.

doi:10.4141/cjss88-023

Cited by 45 publications

(23 citation statements)

References 25 publications

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“…In the rhizosphere of the irrigation treatment, all P fractions were lower than the control with significant reductions of Pi in the E and Bh horizons and Po in the Bh horizon (Table 2). Therefore, we suggest a close coupling between rapid increase in aboveground growth and relative depletion of P. This hypothesis is also supported by a number of investigations in both the laboratory and field (Tarafdar and Junk 1987;Dormaar 1988;Häussling and Marschner 1989). In a previous study of roots and P in the humus at Skogaby, demand for P by roots was assayed by short-term uptake of 32 P and acid phosphatase activity (Clegg et al 1993).…”

Section: Treatment Effectssupporting

confidence: 78%

Rhizosphere chemistry in an ammonium sulfate and water manipulated Norway spruce [Picea abies(L.) Karst.] forest

Clegg¹,

Gobran²,

Guan³

1997

Can. J. Soil. Sci.

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K in forest soil manipulated with ammonium sulfate and water. Can. J. Soil Sci. 77: 525-533. This study shows how the stress manipulations, ammonium sulfate, drought and irrigation changed the P and K status of three soil fractions (bulk soil, rhizosphere and soil-root interface) from E, Bh and Bs horizons of a Norway spruce stand in southwestern Sweden. The results indicate that dynamic linkages exist between the three soil fractions and tree growth. Accumulation rather than depletion of P and K were observed in the vicinity of the roots which we attribute primarily to accumulated organic matter and high rates of mineralization. Relative depletion of P and K around roots resulted from treatments that stimulated tree growth and P and K uptake. The ratio of organic P, the largest extractable P fraction, to inorganic P indicated that organic P is an important P resource when inorganic P is heavily utilized in treatments where growth has increased. There are indications that K supply was reduced by stimulating growth with ammonium sulfate and irrigation, suggesting that K rather than P can become the second limiting factor to growth at this site after N. A partir de nos observations, on peut conclure à l'existence de liens entre les trois fractions de sol et la croissance des arbres. C'est l'accumulation, plutôt que l'épuisement du P et du K disponibles que nous avons observée dans le voisinage immédiat des racines, phénomène que nous expliquons en grande partie par l'accumulation de la matière organique et par les taux élevés de minéralisation. L'appauvrissement relatif en P et en K autour des racines était dû aux traitements qui stimulaient la croissance des arbres et l'absorption de P et de K. Le rapport du P organique, la fraction de P extractible la plus grande, au P minéral révèle que le P organique peut devenir un important fournisseur de P en situation de forte utilisation du P minéral dans les traitements stimulant la croissance des arbres. Par ailleurs, il semble que les disponibilités de K étaient réduites à la suite de stimulation de croissance causée par le sulfate d'ammonium et par l'irrigation, indication que K pourrait supplanter P comme second facteur limitant la croissance après N à cet emplacement.

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Section: Treatment Effectssupporting

confidence: 78%

Rhizosphere chemistry in an ammonium sulfate and water manipulated Norway spruce [Picea abies(L.) Karst.] forest

Clegg¹,

Gobran²,

Guan³

1997

Can. J. Soil. Sci.

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“…It will then be of interest to determine the total mass of P in a soil profile to the depth of the various root masses. It may also confirm on a field scale the conclusion reached in growth chambers that rhizospere changes in P and phosphatase activity levels are a function of plant species and soil type (Dormaar 1988, McKenzie et al 1995. Within the 6 cultivated treatments it is clear that the presence of vegetation, even via partially intact root mass, is already indicative of a plant-soil interaction.…”

Section: Discussionsupporting

confidence: 63%

Journal of Range Management, Volume 53, Number 4 (July 2000)

2000

REM

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“…Comparing between sites does not seem realistic, since it is difficult to have each site at the same climatic conditions at the time of sampling. Comparing within sites supports the conclusions on a field scale that were obtained under growth chamber conditions by Dormaar (1988) and McKenzie et al (1995). Biological activity parameters can be used as soil quality indicators on a routine basis to follow within-site temporal and botanical changes.…”

Section: Initial Effect Of Cultivationsupporting

confidence: 54%

“…For the 4 comparisons of the first 2 years, the phosphatase activities were consistently lower for the Dark Brown than for the Brown Chernozemic soil. Conversely, under growth chamber conditions phosphatase activity was Brown<Dark Brown<Black Chernozemic soils (Dormaar 1988). Although the rea- Table 3.…”

Section: Initial Effect Of Cultivationmentioning

confidence: 99%

“…Attempts have also been made to determine the impact of the interaction of root systems of 4 different plant species on the quantities and composition of root exudates. Dormaar (1988) and McKenzie et al (1995) concluded that the properties of rhizosphere soil are system specific, that is, rhizosphere changes are a function of plant species, soil type, and time. Dick (1994) noted that the primary value of measuring soil enzyme activities may not be to estimate biological activity per se, but rather as an integrative indicator of a change in the biology and biochemistry of soil.…”

Section: Initial Effect Of Cultivationmentioning

confidence: 99%

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Journal of Range Management, Volume 53, Number 2 (March 2000)

2000

REM

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POSTMASTER: Return entire journal with address change -R E T U R N P O S TA G EG U A R A N- T h e Journal of Range Management is a publication of the Society for RangeManagement. It serves as a forum for the presentation and discussion of facts, ideas, and philosophies pertaining to the study, management, and use of rangelands and their several resources. Accordingly, all material published herein is signed and reflects the individual views of the authors and is not necessarily an official position of the Society. Manuscripts from anyone-nonmembers as well as members-are welcome and will be given every consideration by the editors. Editorial comments by an individual are also welcome and, subject to acceptance by the editor, will be published as a "Viewpoint." In AbstractWe compared the herbage standing crop on 31 farms along a rainfall gradient in Namibia (southwestern Africa) in 1997 with the results attained for the same gradient by Walter (1939). We found that the slope for the regression of herbage yield on mean annual rainfall in 1997 was 5.93, i.e. 5.93 kg herbage was produced per hectare for every 1 mm increase in rainfall along the gradient. This regression slope is considerably lower than that in Walter's (1939) study (slope = 10.34). Thus, current grassland productivity per unit of rainfall in Namibia is about half that of 50 years ago. There is no evidence of a change in annual rainfall over this period, nor is there any evidence that either short-term (current) or longer-term (11 years) stocking densities affect current herbage yield. We conclude that, while desertification has taken place, grazing over the last decade has not been the cause of this reduced productivity.Key Words: Africa, rangelands, historical records, grazing, rainfall There is widespread concern over desertification (i.e. a longterm decline in productivity) of the semi-arid grasslands of the world (Schlesinger et al. 1990, 1996, Hall and Scurlock 1991, Strohbach 1992, Parton et al. 1995. However, it is often difficult to unequivocally determine whether desertification has occurred, because different types of information (e.g. on soil quality, carbon isotopes, vegetation quality and quantity) may give conflicting results (Hoffman et al. 1995, Parton et al. 1995, Parsons et al. 1997. Also, logistical problems such as variability in annual rainfall cause great natural fluctuations in herbage growth, making it difficult to differentiate pattern in declining productivity from noise caused by random or event-driven fluctuations (Hoffman and Cowling 1990, Sullivan 1996, Hoffman 1997, Ward et al. 1998, Ward et al. 1999. Long-term cycles in rainfall can further exacerbate this problem. For example, Hoffman and Cowling (1990) and Hoffman (1997) have shown that Acocks ' (1953) claim that desertification was rampant in the semi-arid Karoo region of South Africa was probably caused by the long dry period in the 1950's. When one compares photographs of the vegetation taken in 1925 by I.B. Pole Evans with photographs taken at the same ...

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Effect of Plant Roots on Chemical and Biochemical Properties of Surrounding Discrete Soil Zones

Cited by 45 publications

References 25 publications

Rhizosphere chemistry in an ammonium sulfate and water manipulated Norway spruce [Picea abies(L.) Karst.] forest

Rhizosphere chemistry in an ammonium sulfate and water manipulated Norway spruce [Picea abies(L.) Karst.] forest

Journal of Range Management, Volume 53, Number 4 (July 2000)

Journal of Range Management, Volume 53, Number 2 (March 2000)

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