Soil Nutrient Enrichment Research Articles

Nutrient Trapping by Sediment Deposition in a Seasonally Flooded Lakeside Wetland

AbstractSediment and nutrient retention was studied in a seasonally flooded lakeside wetland as a natural mechanism for preventing water quality deterioration. Both wetland and upland soils in the watershed had comparable concentrations of inorganic P on a per‐volume basis, while NH4+‐N and organic forms of N and P were much higher in the wetland soils. Nitrate concentrations expressed in a per‐volume basis were lower in the wetland soils than in the upland soils.The distribution of sediment and nutrients in the wetland was correlated with distance from a small stream flowing through the wetland. Deposition patterns were affected by recent stream channel migrations.The accumulation of nutrients and sediment delivered from the upland to wetland soils was estimated in two ways: (i) by calculating the volume of alluvium deposited in low natural levees adjacent to the stream; and (ii) by estimating nutrient and ash enrichment of histic surface soils farther away from the stream. Although the levees constituted only about 20% of the wetland surface area, they accounted for 81% of the sediment, 84% of the N, and 67% of the P retained by the wetland.The depth of Cs‐137 in the soil was used to estimate net sedimentation rates. Average annual accumulations over the wetland as a whole were: 2.0 kg sediment m−2 yr−1, 2.6 g P m−2 yr−1, and 12.8 N g m−2 yr−1. Since these values exceed those published for average annual storage by wetland plants, soil mechanisms are more important than vegetative uptake for long‐term nutrient and sediment retention in the White Clay Lake wetland.

The Role of the Western Harvester Ant (Pogonomyrmex occidentalis) in Soil Formation

AbstractThe effects of harvester ants (Pogonomyrmex occidentalis) on the physical and chemical properties of soils were determined for 20 ant mounds in the semiarid subalpine region of south‐central Colorado. Comparisons of soil materials in mounds of active colonies with surrounding unaffected soils showed significant differences in particlesize distribution and concentrations of CaCO3, exchangeable K, Na, Mg, and total N. The activity of ants in the study area appears to affect less ground surface area than in more humid regions (1 to 10% of respective land areas by regional comparison). The ants also tend to rearrange particles preferentially in the sand fraction instead of in the finer fractions as recorded for more humid regions. However, their role in nutrient enrichment of mound soils is similar to that of different ant species in other regions. The soil alterations induced by P. occidentialis are favorable for plant growth, and the ant mounds may aid revegetation in disturbed areas.

Vehicle Perturbation Effects upon a Tundra Soil‐Plant System: II. Effects on the Chemical Regime

AbstractChemical regime alterations of a soil‐plant system resulting from tracked‐vehicle perturbation were determined in Tundra soils near Barrow, Alaska. The study was a contribution to the USIBP Tundra Biome Program.Six years following the perturbation, soils within track scars had lower redox potentials (negative) and lower amounts of exchangeable acidity than undisturbed soils. Furthermore, exchangeable bases (Ca, Mg, K and Na) were higher in the track influenced soils. Consequently, soil pH and base saturation were also higher.Soluble nutrient (Ca, Mg, K, Na, and NH4‐N) levels in soil solutions were considerably higher in track‐influenced soils than in undisturbed soils. Correspondingly, soil solution pH was also higher.Plants growing in the altered environment of the track scars were enriched in nutrients and were larger in size. Increased productivity and quality of track‐influenced vegetation was apparently stimulated by an increase in available nutrients in less acid, warmer, nutrient enriched soils. The track perturbation also resulted in changes in floristic composition of the vegetation at different locations within track‐affected soils.The intensity of soil alteration and resulting changes in the soil‐plant chemical regime were related to the degree of scarring of the landscape which, in turn, was related to differences in the natural drainage of soils along the tracks; scarring being greater, the poorer the natural drainage.Results show that a slight amount of disturbance to the tundra surface may be beneficial in terms of increased productivity and nutrient content of vegetation.