Transformation of forest litter properties under controlled burning of fir forests defoliated by Siberian moths in the Lower Angara River basin

The results of studying the dynamics of forest litter properties in the loci of a Siberian moth (Dendrolimus sibiricus) mass outbreak are considered. As a fir forest defoliated by this pest burns, the reserves and fractional composition of the forest litter, its actual acidity, and its chemical composition drastically change. Upon the burning out of such forests, the litter complex of invertebrates is fully destroyed and begins restoring only two years after the fire.     

Microbiological diagnostics of the status of pyrogenically changed pine forests in the Lower Angara River basin

The structure and functions of the microbial complexes in the soils after surface fires of different intensity were studied. The fires of high and medium intensity were found to lead to a significant decrease in the number and functional activity of microorganisms participating in the nitrogen-carbon cycle. The degree of changes in the postfire status of the soil microbocenoses was revealed to be related to the joint action of pyrogenesis and the hydrothermal conditions at the moment of the fire rather than to the fire intensity. The favorable combination of the elevated soil moisture and soil heating stimulates the microbiological processes of organic matter mineralization, thus, improving the forest-growing conditions for the pine forests. The microbial biomass, basal respiration, and the microbial metabolic coefficient are shown to adequately reflect the postfire status of the microbial complexes.     

Post-fire transformation of the microbial complexes in soils of larch forests in the lower Angara River region

The postfire transformation of the functional activity of the microbial cenoses and the main soil properties under mixed larch forests were studied in the lower reaches of the Angara River. It was shown that the intensity of the postfire changes in the population density, biomass, and activity of the microorganisms in the dark podzolized brown forest soil depended on the degree of burning of the ground cover and the surface litter during the fire. The maximum effects of the fire on the microbial cenoses were observed in the litter and the upper 5-cm-thick layer of the dark-humus horizon in the areas of intense burning. The postfire restoration of the structural-functional activity of the microbial cenoses was determined by the degree of transformation of soil properties and by the postpyrogenic succession in the ground cover. The microbial complexes of the dark podzolized brown forest soils under mixed larch forests in the studied region restored their functional activity after the fires of different intensities quicker than the microbial cenoses of the sandy podzols in the pyrogenic lichen-green-moss pine forests of the same zone.     

Transformation of old-plowed gray forest soils under the influence of differently aged pine forests in the middle Angara River region

The long-term (55–85 years) influence of pine forests on old-plowed gray forest soils (in the middle Angara River basin) has been reflected in the character of the biological cycle and intensity of the biological processes. The population of actinomycetes decreased, and that of fungi increased, within the whole profiles of these soils. The soil profiles became more differentiated according to eluvial-illuvial types. The thickness of the humus (former plowed) horizons decreased. The thicker differently decomposed litter with the abundant fungal mycelium was formed. The most conservative were relic morphological characteristics: plow sole, humus tongues, and the illuvial-metamorphic horizon.     

The influence of pine forests of different ages on the biological activity of layland soils in the middle Angara River basin

The influence of pine forests of different ages (from 25 to 85 years) restoring on old plow land soils is reflected in the biological processes proceeding in them. The drastic decrease in the absolute and relative number of actinomycetes, along with an increase of the fungal population in the microbial complexes of the soils (within the whole profiles), indicates that the microbocenoses acquire “forest” properties. In the soils under the younger pine forests, the processes of microbiological mineralization and specific respiration activity are more active than in the soils under the older pine forests. With the age of the pine forests, the soil profiles become more differentiated according to the eluvial-illuvial type.     

Pyrogenic disturbances of the hydrothermic regime of cryogenic soils under light coniferous forests in southeastern Siberia

Pyrogenic transformations of the physical state of cryogenic soils in the southern and middle taiga were investigated. The long-term dynamics of the microclimate on burns and the soil temperature and moisture to the depth of 120 cm were studied. Data on the postfire restoration of the ground cover are presented. Experiments on artificial sprinkling of burned areas differing in the degree of the burning out of the forest litter, the slope gradient, etc., have been performed. An experimental model demonstrating the relationships between the surface runoff and five environmental factors has been proposed. The pyrogenic destruction of the ground cover and the lower phytocenosis layers was accompanied by significant disturbances of the microclimate and anomalous thawing of the permafrost on the burns. In the pine stand on the colluvial fan after the intense fire, the soil temperature at the depth of 10 cm (in the summer) exceeded the control value by 3–5°C; in the larch forest on the southern slope of the Stanovoi Ridge, it increased by 1.5–2.0 times after the fire of medium intensity. On the mountain slopes, the surface runoff was significantly intensified, which resulted in drastic environmental and silvicultural consequences.     

Diagnostic parameters of soil formation in gray forest soils of abandoned fields overgrowing with pine forests in the middle reaches of the Angara River

The content, differentiation in the profile, and dynamics of the mobile iron compounds can serve as adequate diagnostic parameters of the direction of the pedogenesis upon the overgrowing of abandoned fields with pine forests in the middle reaches of the Angara River Region in the area affected by the Bratsk water reservoir. The bulk chemical composition of the soil remains relatively stable in the entire profile against the background of the eluvial-illuvial redistribution of the finest particle-size fractions and mobile iron compounds under the impact of the long-term seasonal freezing, the percolative soil water regime, and the alternating redox conditions. The development of accumulative processes in the soil is accompanied by the weak manifestation of eluvial and pulsating gley processes as the initial stages of podzolization under the influence of the growing pine forests.     

Response of protozoan and microbial communities in various coniferous forest soils after transfer to forests with different levels of atmospheric pollution

During recent decades, forest ecosystems have been exposed to high levels of atmospheric pollution, and it has been argued that this affects the composition and activity of decomposer communities and, subsequently, ecosystem functioning. To investigate the effects of atmospheric pollution on protozoa and microflora, a new experimental design was used. Undisturbed soil columns, originating from six coniferous forests across Europe and representing different stages of soil acidification, were transferred to two Scots pine forests (Fontainebleau and Wekerom) with different levels of N and S deposition (NH₄ ⁺-N=4.90 and 42.50?kg ha^–1 year^–1; SO₄ ^–S=10.90 and 30.40?kg ha^–1 year^–1, respectively). The number of protozoa, microbial biomass C and microbial activity were estimated in the organic layer (Of) of the transferred soils at the two host sites after 21 months of incubation. The experiment aimed at answering two questions: (1) Do changes in environmental conditions, studied by transferring soils from one site to another, affect protozoa and microbial communities and, if so, (2) how important are changes in both N and S deposition in explaining the effects of soil transfer on protozoa and microbial communities? The interaction between protozoa and microbial communities was addressed with regard to these changes in environmental conditions. No effect of enhanced N or S deposition on protozoan numbers and microbial biomass C, basal respiration and caloric quotient was revealed. Reciprocal transfer of various soil columns resulted in lower abundance and activity of protozoa and microbes. This reduction could not be explained by differences in N and S deposition, but by differences in microclimate and adaptation. In some cases, protozoa correlated with pH, C/N ratio, P and S content and leached mineral N.     

The influence of fires on the properties of forest soils in the Amur River basin (the Norskii Reserve)

The influence of forest fires on the properties of taiga brown, gley taiga brown, and alluvial bog soils widespread in the area of the Norskii Reserve (the Amur River basin) was studied. During several years after the fire, the humus content increased, especially in the soils subjected to fires of high intensity. In the soils of steep slopes, the humus content decreased due to damage to the forest vegetation and activation of lateral runoff after the fire. As a rule, in the soils subjected to fire, the C ha-to-C fa ratio increased and correlated with the fire intensity. Some relationships between the forest fires and the acid-base properties of the soils were revealed. After the fires, the pH values often became higher. The stronger the fire, the higher the pH values. The stony soils differed from the other ones, since the reaction of their upper horizons turned out to be more acid after the fires. The analysis of the authors’ and literature data showed that the pyrogenic changes of some soil properties have been poorly studied and need further investigation, including their geographical aspects.     

Timber harvesting alters soil carbon mineralization and microbial community structure in coniferous forests

Timber harvesting influences both above and belowground ecosystem nutrient dynamics. Impact of timber harvesting on soil organic matter (SOM) mineralization and microbial community structure was evaluated in two coniferous forest species, ponderosa pine (Pinus ponderosa) and lodgepole pine (Pinus contorta). Management of ponderosa pine forests, particularly even-aged stand practices, increased the loss of CO₂-C and hence reduced SOM storage potential. Changes in soil microbial community structure were more pronounced in ponderosa pine uneven-aged and heavy harvest stands and in lodgepole pine even-aged stand as compared to their respective unmanaged stands. Harvesting of trees had a negative impact on SOM mineralization and soil microbial community structure in both coniferous forests, potentially reducing coniferous forest C storage potential.     

岳桦和暗针叶林两种植被类型下土壤碳氮元素的转化过程

Soil samples were taken from an Ermans birch (Betula ermanii)-dark coniferous forest (Picea jezoensis and Abies nephrolepis) ecotone growing on volcanic ejecta in the northern slope of Changbai Mountains of Northeast China, to compare soil carbon (C) and nitrogen (N) transformations in the two forests. The soil type is Umbri-Gelic Cambosols in Chinese Soil Taxonomy. Soil samples were incubated aerobically at 20℃ and field capacity of 700 g kg^-1 over a period of 27 weeks. The amount of soil microbial biomass and net N mineralization were higher in the Ermans birch than the dark coniferous forest (P < 0.05), whereas the cumulative C mineralization (as CO₂ emission)in the dark coniferous forest exceeded that in the Ermans birch (P < 0.05). Release of the cumulative dissolved organic C and dissolved organic N were greater in the Ermans birch than the dark coniferous forest (P < 0.05). The results suggested that differences of forest types could result in considerable change in soil C and N transformations.     

Transformation of ecofunctional parameters of soil microbial cenoses in clearings for power transmission lines in Central Siberia

Changes in soil microbial processes and phytocenotic parameters were studied in clearings made for power transmission lines in the subtaiga and southern taiga of Central Siberia. In these clearings, secondary meadow communities play the main environmental role. The substitution of meadow vegetation for forest vegetation, the increase in the phytomass by 40–120%, and the transformation of the hydrothermic regime in the clearings led to the intensification of the humus-accumulative process, growth of the humus content, reduction in acidity and oligotrophy of the upper horizons in the gray soils of the meadow communities, and more active microbial mineralization of organic matter. In the humus horizon of the soils under meadows, the microbial biomass (C_micr) increased by 20–90%, and the intensity of basal respiration became higher by 60–90%. The values of the microbial metabolic quotient were also higher in these soils than in the soils under the native forests. In the 0- to 50-cm layer of the gray soils under the meadows, the total C_micr reserves were 35–45% greater and amounted to 230–320 g/m³; the total microbial production of CO₂ was 1.5–2 times higher than that in the soil of the adjacent forest and reached 770–840 mg CO₂-C/m³ h. The predominance of mineralization processes in the soils under meadows in the clearings reflected changes in edaphic and trophic conditions of the soils and testified to an active inclusion of the herb falloff into the biological cycle.     

淹水后可变电荷土壤铁锰形态的转化

Ectomycorrhizal fungus Laccaria bicolor S238N,isolated from a forest soil in central France in 1990s,has demonstrated unequivocally and ability to promote pine growth.In the present nursery bed experiment,the ability of this ectomycorrhizal fungus to increase growth and P and K uptake of Douglas Fir seedlings (Zone 22) was examined.Growth of inoculated seedlings was over twice(plant height) and three times (biomass)that of non-inoculated ones.Similarly,both the concentrations and the amounts of P and K uptake by seedlings were significantly increased by fungal inoculation,indicating the improvement of P and K nutrition in mycorrhizal seedlings.In contrast,Al-P in the soils was decreased obviously by plants,especially by mycorrhizas,suggesting utilization of this soil P pool by plants and more efficient Al-P mobilization by mycorrhizas than by nomycorrhizas.Moreover,K extracted by 1mol/L HCl following consecutive extraction of H2O and CH3COONH4,which may not be plant available,could be utilized by fungus colonied roots.This could be explained by the release of protons and oxalate by hypae which leads to replacement of interlayer K in nonexpanded 2:1 clay minerals and bio-weathering of phyllosilicates.     

Soil microbial abundance and community structure vary with altitude and season in the coniferous forests,China

Purpose

Soil microbes control the bioelement cycles and energy transformation in forest ecosystems, and are sensitive to environmental change. As yet, the effects of altitude and season on soil microbes remain unknown. A 560 m vertical transitional zone was selected along an altitude gradient from 3023, 3298 and 3582 m, to determine the potential effects of seasonal freeze-thaw on soil microbial community.

Materials and methods

Soil samples were collected from the three elevations in the growing season (GS), onset of freezing period (FP), deeply frozen period (FPD), thawing period (TP), and later thawing period (TPL), respectively. Real-time qPCR and polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) were used to measure the abundance and structure of soil microbial community.

Results and discussion

The bacterial, archaeal, and fungal ribosomal DNA (rDNA) copy numbers decreased from GS to freezing stage (FP and FPD) and then increased in thawing stage (TP and TPL). Similarly, the diversity of microbial community varied with seasonal freeze-thaw processes. The diversity index (H) of the bacterial and archaeal communities decreased from GS to FP and then increased to TPL. The fungal community H index increased in the freezing process.

Conclusions

Our results suggested that abundance and structure of soil microbial community in the Tibetan coniferous forests varied by season and bacterial and archaeal communities respond more promptly to seasonal freeze-thaw processes relative to fungal community. This may have important implications for carbon and nutrient cycles in alpine forest ecosystems. Accordingly, future warming-induced changes in seasonal freeze-thaw patterns would affect soil nutrient cycles via altering soil microbial properties.

     

Microbial cenoses of alas soils on the Lena-Amga interfluve in Central Yakutia

The specific features of the microbial population in the soils of alases (thermokarst depressions) of Central Yakutia were revealed: a high number of microorganisms of all the groups (1.1 × 10³–3.9 × 10⁸ cell/g), which is compatible with the microbial density in the steppe soils of Transbaikalia; a particular distribution of the microorganisms along their profiles without decreasing of their number with the depth; and insignificant fluctuations of their population density in some soil horizons. The enrichment of these soils with microorganisms depends on the hydrothermal conditions. The microbial number gradually increases from the elevated peripheral parts of the alases to their centers and drastically decreases towards the lower lakeside areas of the alases. At the same time, the composition of the microorganisms changes, and nitrogen-fixing bacteria appear.     

The state of microbial complexes in soils of forest ecosystems after fires and defoliation of stands by gypsy moths

The state of microbial cenoses in the soils of forest ecosystems damaged by fires of different strengths and gypsy moth outbreaks (Central Siberia) was assessed by the intensity of the basal respiration, the content of carbon of the microbial biomass, and the microbial metabolic quotient. The degree of the disturbance of the microbial cenoses in the soils under pine forests after fires was higher than that in the soils under the forests defoliated by gypsy moths. The greatest changes of the microbial complexes were recorded after the fires of high and medium intensity. In the litters, the content of the microbial biomass, the intensity of basal respiration, and the microbial metabolic quotient value were restored on the fifth year after the fires, whereas in the upper (0–10 cm) soil layer, these parameters still differed from those in the control variant, especially after the highly intense fires. After the weak fires, the ecophysiological state of the microbial complexes was restored within two-three years.     

Regularities of the distribution and heavy metal forms in technogenically transformed chernozems of the southern Angara River basin and northeastern China

Specific features of heavy metals and As migration in the system soil-plant are considered on the basis of the results obtained in the analysis of different forms of toxic elements in technogenically transformed chernozems of the southern Baikal Lake basin. These results are compared to the data of analogous studies conducted in northeastern China. The regularities in the bioaccumulation of heavy metals and As were related to their forms, their concentration in the soils, and the plant species. Cadmium was found to be the most mobile element, which accumulated in the chernozems to the greatest degree; lead was the least mobile element.     

Postpyrogenic transformation of soils under Pinus sibirica forests in the southern Lake Baikal basin

The results of experimental investigations of the postpyrogenic dynamics of the widespread rawhumus podzols under Pinus sibirica forests in the southern Lake Baikal basin are discussed. Ground fires transform the diagnostic surface organic soil horizons into organic pyrogenic horizons (Opir, OL/Opir, and AOpir). The adverse effect of ground fires of different intensities on the changes in the reserves, the fractional composition of the litters, and the chemical composition of the organic horizons is shown. The soils of dark coniferous forests are inclined to long-lasting restoration. The Pinus sibirica regrowth under the canopy of deciduous species serves as the basis for the restoration of native stands and the formation of the soils characteristic of the southern part of the Lake Baikal basin.     

Modeling of the thermal influence of fires on the physicochemical properties and microbial activity of litter in cryogenic soils

Periodic surface fires in the cryolithozone (the northern taiga subzone) are the main factor determining the qualitative and quantitative characteristics of the soil organic matter. The specific features of the changes in the physicochemical parameters and microbial activity of the organic horizons in the cryogenic soils under larch forests of the northern taiga after the impact of high temperatures were revealed. The temperatures of fires of different intensity were simulated in laboratory conditions. The thermal impact on the litter organic matter during the surface fires may increase the CO₂ emission from the surface of the soil in the postfire communities due to the destruction of organic compounds only for a short time. After fires of high intensity with strong mineralization of the litters, during a period of more than 1 month, the pyrogenic effect on the organic horizons of the soils under the larch forests of the cryolithozone determined the reduction of the CO₂ emissions in the freshly burned areas as compared to the intact stands.     

Acidification of soils by trees and forests

Abstract. The impact of isolated trees and natural forest vegetation on soil acidity is discussed. There is a considerable variation in impact between species on similar soils and between sites for any given species. The effect of coniferous plantations on soil acidity is reviewed and the causes of any increased acidity discussed. Crop species, initial soil conditions, silvicultural practices and the proportion of the tree removed at felling are all important factors influencing the long-term impact of plantations on soil acidity.