Optical Properties of the Extractable Organic Matter Fractions in Typical Chernozems of Long-Term Field Experiments

Eurasian Soil Science - The extractable fractions of organic matter (OM) differing in their mobility—water-extractable organic matter, labile humic substances, and humic substances—have...     

Effects of fragmentation on functional diversity associated with aboveground biomass in a high Andean forest in Colombia

Context

Forest fragmentation alters the composition, structure and function of ecosystems and affects ecological processes that are fundamental for the provision of ecosystem services where functional diversity is sensitive to its effects. Analyzing the functional responses of the plant community to fragmentation can provide new approaches to its conservation and management.

Objectives

We analyzed whether the functional diversity of woody individuals associated with aboveground biomass (AGB) in a high Andean forest in Colombia is affected by fragmentation.

Methods

Based on three fragmentation categories identified using landscape metrics, we selected ten forest fragments. Multitrait and monotrait functional diversity indexes (foliar and wood) weighted by aboveground biomass were calculated in plots of 0.1 ha in each fragment. Analysis of variance was performed, and simple linear regressions were quantified to identify the relationships between functional diversity and fragmentation.

Results

The category of large fragments had a higher average AGB than did the medium and small fragments. Fragmentation had effects on the variance of some foliar and stem traits but not on functional dominance. For the multitraits indexes, the edge contrast was negatively related with functional dispersion.

Conclusions

The categories analyzed have similar responses in terms of functionality associated with AGB. We highlight the importance of small fragments in the maintenance of plant functional diversity and as reservoirs of AGB. We underline that small fragments are important to consider in the development of conservation and connectivity strategies.

     

Quality of Russian soils for agricultural exploitation

Based on a specially developed model and Russia’s national soil geographical database, the quality of soils for agricultural exploitation is evaluated. All the country’s soils are ranked according to their properties and response to economic activities. Quality categories of soil for use in the agricultural industry are proposed. According to this assessment, approximately 76% of soils in Russia (without considering their current use) are not favorable for agricultural exploitation.     

Radiocarbon pollution and self-purification of humus in chernozems of the East-European plain in 1900–2008

The dynamics of the ¹⁴C content in the humus of chernozems in 1900?C2008 are considered. The elevated ¹⁴C content in the atmosphere because of nuclear weapons tests has led to the contamination of humus with bomb radiocarbon. In 1966?C1968, the ¹⁴C reserves in the profiles of chernozems exceeded the background ones by 15%; in 1978, by 12%; and, in 1998, by 2%. By the year of 2008, its reserves became equal to the background ones. The ¹⁴C distribution along the soil profiles changed. By 1978, the 0- to 30-cm-thick soil layer became free from radiocarbon due to its self-purification; however, at depths of 40?C70 and 100?C115 cm, its weak accumulation was registered. By 2008, the whole soil profile was free from ¹⁴C. The main mechanism of the soil self-purification from radiocarbon is suggested to be the constant substitution of fragments of humus compound structures for those of fresh organic matter entering the soils with the ¹⁴C content being in equilibrium with the atmospheric one, i.e., due to the renewal of the carbon in the humus. The rate of the carbon renewal and its migration in the soils are assed based on the ¹⁴C concentrations in the humus.     

Soils and the soil cover of the arkaim reserve (Steppe Zone of the Trans-Ural Region)

Soils of the Arkaim Reserve in the area around a unique settlement-fortress of the Bronze Age in Chelyabinsk oblast have been studied. These soils are generally typical of the entire Trans-Ural Plateau. The soil properties are characterized in detail on the basis of factual data on 170 soil pits and four soil catenas. The soil cover of the reserve is specified into six geomorphic groups: (a) denudational surfaces of the low mountains, (b) accumulative-denudational surfaces of the low mountains, (c) denudational-accumulative plain surfaces, (d) lacustrine-alluvial plain surfaces, (e) floodplain surfaces, and (f) slopes and bottoms of the local ravines and hollows. Chernozems occupy about 50% of the reserve; solonetzes and saline soils, 32%; meadow chernozems, 7%; and forest soils, 1%. The soils of the reserve are relatively thin; they have a distinct tonguing of the humus horizon and are often saline and solonetzic. The latter properties are inherited from the parent materials and are preserved in the soils for a long time under the conditions of a dry continental climate. The genetic features of the soils differ in dependence on the composition and age of the parent materials. With respect to the thickness of the soil profiles and the reserves of soil humus, the soils can be arranged into the following lithogenic sequence: the soils developed from the eluvium of igneous rocks-redeposited kaolin clay-montmorillonite-hydromica nonsaline and saline loams and clays. The content of C_org in the upper 20 cm varies from 2.5 to 5.6%, and the reserves of C_org in the layers of 0?C0.5 and 0?C1.0 m reach 57?C265 and 234?C375 t/ha, respectively. The soils of pastures subjected to overgrazing occupy two-thirds of the reserve. Their humus content is 10?C16% higher in comparison with that in the analogous plowed soils. Another characteristic feature of the humus in the soils of the pastures is its enrichment in the labile fraction (28?C40% of C_org).