Том 10, № 7 (2017)

The microbial contribution to the respiration of sod-podzolic soils has been estimated during two seasons (2012–2013) in boreal forest (Valdai district in Novgorod oblast, Russia) by a combination of methods of substrate induced respiration (SIR) and integration of components (IC). Despite the higher accuracy of SIR in estimating soil microbial respiration (R_mic), it is found that the combined application of these two methods results in a better correspondence of field experiments to the published data based on laboratory experiments. The contribution of microbial respiration differs between wooded and degraded sites. Hence, these sites should be investigated separately in upscaling studies of microbial respiration in soils of a boreal forest. The underestimation of microbial respiration should also be noted when using the IC method in field experiments. Among the main controls of R_mic are abiotic ones (soil temperature at a depth of 10 cm; month of the vegetation season), as well as the type of the mesohabitat. The seasonal dynamics of microbial respiration was related to the Selyaninov hydrothermal factor. Despite seasonal and cross-habitat differences in R_mic, it was specific for the particular type of soil and ecosystem.

The proposed approach to the study of regularities of spatial variability of plant cover and to mapping forest vegetation is illustrated by the example of European Russia. It is shown that remote sensing and GIS technologies require particular standards of plant cover classification and reflection in maps. The given principles of classification and compilation of explications for maps of forest cover enable an assessment of its status and dynamics and a comparison of materials of different scales. We use the ecological–phytocoenotic approach to classifying forest vegetation. The specified units correspond to the categories of the main classifications of plant cover used in Russian geobotanics. In our classification, we have verified some parameters and the semantics of the mapped units, using satellite images, for their definite identification and interpretation. The elaborated approach to the classification and mapping of forest cover is applied for the study of the diversity of spruce forests under different climatic conditions in two regions, where they occupy about 20% of the total area. The first example characterizes the northern taiga subzone of forests of eastern Fennoscandia in the center of Murmansk oblast, and the second one represents the subzone of broad-leaved–coniferous forest in the southwest of Moscow oblast.

We have studied the morphometric indices of needles in Scots pine populations that grow in Bryansk oblast in sites with radioactive contamination long after the Chernobyl accident. The variability in needle weight and length, as well as the fluctuating asymmetry indices and occurrence of necroses and morphoses, were studied in four contaminated and two reference populations of Scots pine in 2011, 2013, and 2014. The exposure of needles in radioactively contaminated sites varied from 7 to 130 mGy/yr. We found brachyblasts with three needles in contaminated Scots pine populations; this morphosis was absent in the reference populations. A dependence of the occurrence of needles damaged by necrosis on the levels of radiation exposure in 2011 was found. However, it was statistically insignificant in other years. The length and weight of needles in contaminated populations differed from the control values; however, the dependence of these indices on the level of radiation exposure was not revealed in the studied range of doses. In 2011 and 2013, the index of fluctuating asymmetry in needle length exceeded the control levels in sites where the absorbed doses were 90 and 130 mGy; this index also tended to grow (statistically significantly in 2011) with an increase in the characteristics of radioactive contamination of the studied plots: the exposure dose rate and the specific activity of ⁹⁰Sr and ¹³⁷Cs in cones and of ¹³⁷Cs in the soil. Therefore, one can observe the consequences of chronic radiation exposure at the organismic level in populations of Scots pine (one of the most radiosensitive plant species) even 25 years after the accident. The data that we obtained in natural habitats confirm the international estimates, according to which the annual chronic radiation exposure of 100 mGy can be considered the limit of safe radiation exposure of natural populations according to morphological and ontogenetic parameters.

We study the dynamics of radial increment in Scots pine in the forests of Bryansk oblast contaminated with radionuclides after the Chernobyl disaster. We have developed regression models of the relationship between specific soil activity and the radial increment of trees for the transition stage of the disaster in 1987–1989 and four 5-year-long periods from 1990 to 2009, characterizing 20 years of the recovery period. We have found a strong positive correlation between the radial increment and specific soil activity. The correlation coefficients vary from 0.695 ± 0.198 to 0.895 ± 0.124 for early increment, and from 0.549 ± 0.231 to 0.937 ± 0.097 for late increment in different time periods. It is found that the cubic parabolic equation is the optimal statistical description of the relationship between the radial increment and concentration of radiocesium in soil. The minimal effective specific soil activity for the stimulation of radioactivity decreased from 25–26 kBq kg^–1 in 1987–1989 to 9–10 kBq kg^–1 in 2004–2009. The same value for the late increment varied from 20–21 to 16–17 kBq kg^–1 in the same periods. The maximal effective specific soil activity indicative of the highest effect of radiation decreased consequently from 110–120 kBq kg^–1 in 1987–1989 to 60–70 kBq kg^–1 in 2004–2009 for early increment. The same value for late increment varied in the same range with no tendencies in the same periods. Based on the model of radial increment dynamics, we assessed the role of radiation in the elevation of standing volume in a typical pine forest in the study area 25 years after the Chernobyl disaster.

We review the specificity of early and late phenological types of pedunculate oak differing in the spring flushing of leaves, namely, its occurrence in topographical elements, soil conditions and hydrology, responses to weather, and vulnerability to unfavorable factors. We show that phenological forms differ in a set of morphological and physiological indicators, growth energy, and peculiarities of the wood. We focus on the importance of the phenological specificity of planting materials when organizing oak plantations with regard to ongoing climatic changes and the ubiquitous decline of oak forests. The late form of oak is more preferable in most cases, because it is more resistant to spring frosts and insect damage, as well as the fact that it has higher quality wood in solid-volume trunks.