Aggregate-Size Stability Distribution and Soil Stability

Aggregate-Size Stability Distribution and Soil Stability,10.2136/sssaj2004.0725,Soil Science Society of America Journal,C. O. Márquez,V. J. Garcia,C.

Aggregate-Size Stability Distribution and Soil Stability   (Citations: 22)
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These indices account for the total weighted average of stable aggre- gates and the total weighted average of stable macroaggregates, re- release of this large buildup of internal air pressure spectively. Both the SAI and the SMaI indices were shown to be (Cambardella and Elliott, 1993a; Gale et al., 2000). sensitive to the effects of vegetation on soil stability under different The combined use of the capillary-wetted and the riparian buffer communities. The SAI and the SMaI indices were slaked pretreatments has been used for contrasting dif- higher in surface soils under cool-season grass than any of the other ferences in aggregate-size distributions for soils with treatments. These soils samples are well aggregated with SAI 74% different management histories and also for understand- and SMaI 56% followed by SAI 55% and SMaI 37% under ing the factors that influence aggregate stability (Elliott, existing riparian forest, SAI 40% and SMaI 21% under 7-yr 1986; Cambardella and Elliott, 1993a; Six et al., 1998). switchgrass and SAI 36% and SMaI 18% under cropped system. More recently, Gale et al. (2000) used the comparison of slaked versus capillary-wetted pretreatments as a means to differentiate stable macroaggregates from un- S oil aggregate stability is the result of complex in- stable macroaggregates based on their resistance to slak- teractions among biological, chemical, and physical ing. Although the conceptualization of Gale's idea rep- processes in the soil (Tisdall and Oades, 1982). Factors resents an important contribution, more work is needed affecting aggregate stability can be grouped as abiotic to clearly separate the stable macroaggregates from the (clay minerals, sesquioxides, exchangeable cations), biotic unstable macroaggregates and accurately specify aggre- (soil organic matter, activities of plant roots, soil fauna, gate-size stability distributions. The aggregate-size sta- and microorganisms), and environmental (soil tempera- bility distribution is the quantity of stable and unstable ture and moisture) (Chen et al., 1998). The concept of soil aggregates categorized by their size and stability aggregate stability depends on both the forces that bind to disruption. particles together and the nature and magnitude of the Existing approaches for studying soil aggregates do disruptive stress (Beare and Bruce, 1993). not fully distinguish between stable and unstable aggre- Several methods have been proposed to determine soil gates based on their resistance to slaking. In turn, this aggregate-size distribution and stability (Kemper and causes significant errors in assessing soil stability by the Rosenau, 1986). The suitability of these methods de- wet-sieve method and the dynamics of soil aggregates pends on the purpose of the study. The most widely used and the C associated with aggregates. The disruption of approaches are based on the wet-sieving method (Kemper, unstable macroaggregates during the slaking treatment 1966; Kemper and Rosenau, 1986). In this method, cycli- produces smaller constituent aggregates that are ac- cally submerging and sieving soil in water emulates the counted for in smaller aggregate-size fractions biasing natural stresses involved in the entry of water into soil the aggregate-size distribution. In contrast, the capil- aggregates. The moisture content of the soil aggregates lary-wetted pretreatment does not account for differ- before wet sieving controls the severity of the disruption ences in stable and unstable macroaggregates because
Journal: Soil Science Society of America Journal - SSSAJ , vol. 68, no. 3, 2004
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