Forested mineral soils

The effects of five phenolic compounds, catechol, protocatechuic, p-coumaric, p-hydroxybenzoic, ferulic acids and their mixture were studied on pH, organic matter, organic-nitrogen, total phenolic content and certain inorganic ions of forest mineral soils (Ae and B horizons). The A- and B-horizon soils, were amended with 104 M concentration of each phenolic compound and their mixture. In general, soil properties were affected by phenolics amendement. However, soils amended with catechol did not influence any of the soil characteristics. Contents of organic matter, nitrogen and phosphate were lower in soils amended with different phenolic compounds compared to the unamended control soil (Inderjit and Mallik, 1997). 

In soils of non-agricultural ecosystems, above ground biomass (foliar uptake) and metal cycling is considered important (see Figure 8), due to large impact on the metal distribution in the humus layer and mineral soil profile. Especially in soils of Forest ecosystems, it may affect the accumulation in the humus layer, which is considered a very relevant compartment regarding the calculation of a critical load. In these soils, however, a steady-state element cycle is assumed, which implies that mineralization, Minj, equals litterfall, Mjf. 

The regulation of biogeochemical cycles by microbial populations is of most direct importance in the cycling of N, S, P, and C. Most of the ecosystem pool of these elements resides as organic forms in forest floor and mineral soil compartments. These organic complexes are subjected to microbial transformations, which regulate nitrate, sulfate and phosphate ions dynamics and availability. In turn, this influences indirectly... 

Figure 8. Relative distribution ofN, P and K in the Boreal Forest ecosystem. Total amounts for the different fractions are given, expect for in the mineral soils down to 30 cm depth, where exchangeable amounts are given for P and K (Nihlgard et al., 1994).

The atmospheric deposition of lead was 190 g/ha/yr and this value was connected with declining of leaded petrol use in USA from 1975. The mineral soil and forest floor were the major pools of Pb in the ecosystem. Mineral soil pools (<2 mm size fraction) are generally the largest element pools for the HBEF, however this includes relatively unreactive soil minerals. Deposition and accumulation of Pb in the forest floor have been the focus of a number of investigations. It has been shown that at... 

Figure 2. The distribution of between forest litter and mineral thickness of forest soil (to the depth of mineral soil 30 cm) in different types of forest habitats.

Ktlsel K, Wagner C, Drake HL. 1999a. Enumeration and metabolic product profiles of the anaerobic microflora in the mineral soil and litter of a beech forest. FEMS Microb Ecol 29 91-103. 

In those climatic regions where humus is developed, it is normally found in undisturbed forested areas above the normal mineral soil. Decomposed black coloured organic material (humus) should be sampled. 

Depending on factors such as watershed slope, depth of water table, antecedent soil moisture, and barriers to precipitation and throughfall infiltration, DOM from the forest floor and organic soil horizon can contribute a large flux of allochthonous DOM to surface waters. Soil solution for DOM analysis is typically collected with zero-tension lysimeters placed at the boundary between organic soil and mineral soil. 

FIGURE 5 Mean concentrations of DOC and DON in throughfall, forest floor and organic soil horizons, and mineral soil B horizons in cool conifer and cool deciduous biomes. Error bars indicate 1 standard deviation of the mean. 

FIGURE 7 Flux of dissolved organic carbon in precipitation, throughfall, organic soil horizons, and mineral soil horizons in a cool temperate and wet tropical forest (kg ha). Source of data McDowell and Likens (1988) and McDowell (1998). Illustration by L. Isaacson, University of New Hampshire. 

Fauna also influence soil carbon cycling. Bioturbation mixes and aerates soil, physically breaks down litter, creates flow paths for water in soil, and can reduce surface litter stocks and enhance erosion (Bohlen et al., 2004). For example, along a gradient of European earthworm (Lumbricus terrestris) colonization in a deciduous forest of northern Michigan, earthworms are associated with a decrease in litter-layer thickness, apparently mixing some forest floor organic matter into the mineral soil. Thus, fauna can create spatial patterns in SOM stocks. 

For a number of German chernozems, up to 45% of SOM was identified as charcoal, which mostly occurred in the light fraction (Schmidt et al., 1999). In Japanese andosols the contribution of charred plant fragments in the light fractions ranged from 3.4% to 33% (Shindo et al., 2004). In coastal temperate forest sites of southern Vancouver Island, Canada, BC characteristics were detected in the water-floatable fraction separated from mineral soils (Preston et al., 2002). 

Entry, J.A., P.K. Donnelly, and W.H. Emmingham (1995a). Atrazine and 2,4-D mineralization in relation to microbial biomass in soils of young-, second-, and old-growth riparian forests. Appl. Soil Ecol., 2 77-84. 

In addition to the effect of pH on mobility, the type of acid entering environmental systems may also be important. Nitric acid was found to leach more aluminum from soil columns representative of high-elevation forest floor soils than did sulfuric acid (James and Riha 1989). This is most likely due to the higher solubility of aluminum nitrate than aluminum sulfate. However, in mineral horizons below the forest floor, the study found that concentrations of aluminum leached by these acids did not differ from concentrations of aluminum leached by distilled, deionized water at a pH of 5.7. The authors concluded... 

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