The turnover of humic compounds and biomass components in the soil was investigated. The majority of nitrogen introduced to the soil was found to pass through soil biomass. Microbial cell debris provides the substratum for the renewal of humic compounds.

The biodegradation, incorporation into biomass, and stabilization in humus of specific carbons of ferulic, p-hydroxycinnamic, anisic, and benzoic acids and catechol were followed in Steinbeck loam (pH 5.0) and Greenfield sandy loam (pH 7.0). Biomass was estimated by the fumigation procedure. The least incorporation into biomass was noted for the three-side chain carbon of ferulic acid (1.0 to 1.4%) and the greatest for the two-side chain carbons of either ferulic or p-hydroxycinnamic acids (10.9 to 17.6%). Greater amounts of carbon were evolved as carbon dioxide (CO₂) and incorporated into the biomass in the acid soil than in the neutral soil. Approximately 74% of the ring carbons of catechol were stabilized in the neutral soil after 12 weeks but only 2% of that was in biomass. The amount of residual carbon found in the biomass decreased with time. The amount of residual ring-carbons of anisic and benzoic acids incorporated into the biomass were 19 and 15%, respectively. As the substrate concentration increased from 1 to 10,000 ppm, the carbon released as CO₂ from ferulic acid and glucose ranged from 47 to 85% and from 63 to 85%, respectively. The residual ferulic acid and glucose carbons in biomass ranged from 2.2 to 11% and 19 to 39%, respectively. The study indicated that relatively higher amounts of the phenolic carbons were stabilized in the soil humus while greater amounts of the glucose carbons were incorporated into the soil biomass, and that compared to glucose, greater amounts of the residual carbons of the phenolic compounds were not solubilized by 6N HCl hydrolysis.

Sulfur (S) constituents, microbial biomass, and sulfohydrolase activity were determined for each soil horizon at both hardwood and conifer sites in a Becket soil (Adirondack Mountains, New York). Drying of soil before analysis altered the S constituents. There was a threefold increase (p < 0.05) in sulfate in the organic horizons. Total S was greatest in the O horizons with 2,010 and 1,690 µg S/g in conifer and hardwood solums, respectively. Mineral soil had a maximum S concentration in the B21h horizon. Sulfate concentrations were a small proportion (<15%) of total S in B horizons. Organic S was dominant (93% of total S) in all horizons. Carbon-bonded S and ester sulfate were 74 and 18% of total S, respectively. Microbial biomass was greatest in the 01 horizon of both hardwood and conifer solums (59 and 70 mg biomass C · 100 g⁻¹ dry mass, respectively). The B21h horizon contained the greatest biomass in the mineral soil. Sulfohydrolase activity exhibited the same distribution. Total S, carbon-bonded S, and ester sulfate were all positively correlated (p < 0.05) to percent organic matter in the soil horizons. Correlations between microbial biomass and sulfohydrolase activity with organic S indicate the potential for microbial S transformations. Sulfate formation by mineralization may be more important than exogenous inputs. This has major implications for assessing the impact of atmospheric S deposition on soils.

This study was designed to investigate the changes in soil properties under the natural forest, the tranformation type of different land use as well as distribution of biomass and the total nutrients within plant and soil sub-systems at Sakaerat Environmental Research Station. Some physical properties of soil under the cultivating fields and abandoned fields differ markedly from primary forest. Bulk density and particle density of surface soils under MF, OC1 and OC2 sites increased 7-9% and 5-10% respectively as compared to the forest sites but those at lower depth decreased. Both bulk and particle densities of CF increased 5-9% in all layers. Soil porosity in the cultivating fields and abandoned fields at the depth of 20 cm. and in the deeper layers show an increasing trend about 3-15% as compared to the forest areas. Chemical properties of soils also show the same patterns as the physical properties. Chemical properties that suggest some increasing trends in the cultivating fields and abandoned fields are pH, K, Ca, Mg and C.E.C. but they are demonstrated in different soil layers. The amount and distribution of biomass and total nutrient are high in natural forest areas. Biomass of Dry Evergreen Forest and Dry Diptrocarp Forest are accounted for 242.32 and 94.82 ton/ha. respectively. The amount of plant nutrient contained in living and litter layers are about 20% while the other 80% is in the soil. In the abandoned fields which possess the biomass content between 21.12-31.49 ton/ha. contain 5.7% of plant nutrient within plant sub-system while 94.3% of nutrient is in the soil. In the maize and cassava fields, living plant is between 3.47-4.00 ton/ha. but the nutrient is only 1-2%. The remaining 98-99% of nutrients is in the soil

This study was designed to investigate the changes in soil properties under the natural forest, the tranformation type of different land use as well as distribution of biomass and the total nutrients within plant and soil sub-systems at Sakaerat Environmental Research Station. Some physical properties of soil under the cultivating fields and abandoned fields differ markedly from primary forest. Bulk density and particle density of surface soils under MF, OC1 and OC2 sites increased 7-9% and 5-10% respectively as compared to the forest sites but those at lower depth decreased. Both bulk and particle densities of CF increased 5-9% in all layers. Soil porosity in the cultivating fields and abandoned fields at the depth of 20 cm. and in the deeper layers show an increasing trend about 3-15% as compared to the forest areas. Chemical properties of soils also show the same patterns as the physical properties. Chemical properties that suggest some increasing trends in the cultivating fields and abandoned fields are pH, K, Ca, Mg and C.E.C. but they are demonstrated in different soil layers. The amount and distribution of biomass and total nutrient are high in natural forest areas. Biomass of Dry Evergreen Forest and Dry Diptrocarp Forest are accounted for 242.32 and 94.82 ton/ha. respectively. The amount of plant nutrient contained in living and litter layers are about 20% while the other 80% is in the soil. In the abandoned fields which possess the biomass content between 21.12-31.49 ton/ha. contain 5.7% of plant nutrient within plant sub-system while 94.3% of nutrient is in the soil. In the maize and cassava fields, living plant is between 3.47-4.00 ton/ha. but the nutrient is only 1-2%. The remaining 98-99% of nutrients is in the soil.