Inceptisol

Abstract: Mediterranean climates are characterized by winter rains — with some months of excess rainfall over evatranspiration, warm and dry summer months with moisutre deficits — drying out soils and their annual vegetation (xeric moisture regime). They are found on western parts of all continents, between the cooler temperature zone and the hot dry desert zone. The largest Mediterranean region, surrounding the Mediterranean Sea extends over 4,300,000 km2 and exhibits a wide variety of soils and geo-ecosystems. Characteristics landscape attributes are the high proportion of mountains with sleep slopes, significant additions of Saharan desert dust to practically all soils of the region, and a large proportion of limestone and other calcareous rocks as soil parent materials. Characteristics soil behavior features are moderate weathering with pervection (leaching, lessivage) of mostly 2:1 clays into B horizons (Xeralfs:Luvisols), hematite-induced reddening of the clays due to summer dehydration of free iron oxyhydroxides, carbonate dissolution and reprecipitation with prevalence of calcic horizons (Xerolls; Calcisols) in semiarid regions, and development of Vertisols, mostly in lowlands, where deep layers of swelling/cracking clays have sedimented. Shallows soils on nearly bare slopes, mostly a result of erosion subsequent to deforestation, are frequent (Leptosols, Cambiosols; Inceptisols, Entisols). Red (or Brown) Mediterranean soils are no longer used as a separate classification group in modern, well defined, soil property-controlled taxonomies (Soil Taxonomy; FAO system), but were partially replaced by Duchaufour's term Fersiallitic soils in some classification systems. Terra Rossa continues to be used in some classification for hard limestone derived red soils, mostly shallow. The effects of man's past and current interference with the lanscape are pervasive in most regions, and predictions for possible future effects on the soils and ecosystems, due to greenhouse gas induced warming and rainfall change, are partly negative, partly still too uncertain.

Abstract: Soil carbon turnover models generally divide soil carbon into pools with varying intrinsic decomposition rates. Although these decomposition rates are modified by factors such as temperature, texture, and moisture, they are rationalized by assuming chemical structure is a primary controller of decomposition. In the current work, we use near edge X-ray absorption fine structure (NEXAFS) spectroscopy in combination with differential scanning calorimetry (DSC) and alkaline cupric oxide (CuO) oxidation to explore this assumption. Specifically, we examined material from the 2.3–2.6 kg L � 1 density fraction of three soils of different type (Oxisol, Alfisol, Inceptisol). The density fraction with the youngest 14 C age (Oxisol, 107 years) showed the highest relative abundance of aromatic groups and the lowest O-alkyl C/aromatic C ratio as determined by NEXAFS. Conversely, the fraction with the oldest C (Inceptisol, 680 years) had the lowest relative abundance of aromatic groups and highest O-alkyl C/aromatic C ratio. This sample also had the highest proportion of thermally labile materials as measured by DSC, and the highest ratio of substituted fatty acids to lignin phenols as indicated by CuO oxidation. Therefore, the organic matter of the Inceptisol sample, with a 14 C age associated with ‘passive’ pools of carbon (680 years), had the largest proportion of easily metabolizable organic molecules with low thermodynamic stability, whereas the organic matter of the much younger Oxisol sample (107 years) had the highest proportion of supposedly stable organic structures considered more difficult to metabolize. Our results demonstrate that C age is not necessarily related to molecular structure or thermodynamic stability, and we suggest that soil carbon models would benefit from viewing turnover rate as codetermined by the interaction between substrates, microbial actors, and abiotic driving variables. Furthermore, assuming that old carbon is composed of complex or ‘recalcitrant’ compounds will erroneously attribute a greater temperature sensitivity to those materials than they may actually possess.

Abstract: A long-term field experiment was established to determine the influence of mineral fertilizer (NPK) or organic manure (composed of wheat straw, oil cake and cottonseed cake) on soil fertility. A tract of calcareous fluvo-aquic soil (aquic inceptisol) in the Fengqiu State Key Experimental Station for Ecological Agriculture (Fengqiu county, Henan province, China) was fertilized beginning in September 1989 and N 2 O emissions were examined during the maize and wheat growth seasons of 2002–2003. The study involved seven treatments: organic manure (OM), half-organic manure plus half-fertilizer N (1/2 OMN), fertilizer NPK (NPK), fertilizer NP (NP), fertilizer NK (NK), fertilizer PK (PK) and control (CK). Manured soils had higher organic C and N contents, but lower pH and bulk densities than soils receiving the various mineralized fertilizers especially those lacking P, indicating that long-term application of manures could efficiently prevent the leaching of applied N from and increase N content in the plowed layer. The application of manures and fertilizers at a rate of 300 kg N ha −1 year −1 significantly increased N 2 O emissions from 150 g N 2 O-N ha −1 year −1 in the CK treatment soil to 856 g N 2 O-N ha −1 year −1 in the OM treatment soil; however, there was no significant difference between the effect of fertilizer and manure on N 2 O emission. More N 2 O was released during the 102-day maize growth season than during the 236-day wheat growth season in the N-fertilized soils but not in N-unfertilized soils. N 2 O emission was significantly affected by soil moisture during the maize growth season and by soil temperature during the wheat growth season. In sum, this study showed that manure added to a soil tested did not result in greater N 2 O emission than treatment with a N-containing fertilizer, but did confer greater benefits for soil fertility and the environment.