Vol 11, No 7 (2018)

Average carbon-deposit values in soils of pine and spruce forests have been assessed on the basis of long-term studies of Karelian soils (122.3 and 117.9 t ha^–1 respectively). The higher average carbon content in soils of pine forests is caused by a high share of waterlogged forest types in the total area occupied by pine forests. It is found that average carbon deposits in the forest litter increase with a growth in soil moisture content from 7.6 to 24.3 t ha^–1 in pine forests and from 11.1 to 61.3 t ha^–1 in spruce forests. The carbon deposits are assessed in layers of 0–25 cm (9.1^–170.4 t ha^–1 in pine forests and 31.2–228.6 t ha^–1 in spruce forests), 0–50 cm (18.8–329.9 t ha^–1 in pine forests and 36.4–345.1 t ha^–1 in spruce forests), and 0^–100 cm (23.9–434.3 t ha^–1 in pine forests and 38.9–402.4 t ha^–1 in spruce forests). The total carbon deposits in soils of the pine forests of Karelia are estimated at 614.6 million t and, in soils of the spruce forests of Karelia, at 276.2 million t. Such a difference is determined by different areas occupied by the above forest types in the region: the pine forests occupy over 5 million ha and the spruce forests cover 2.3 million ha. These data differ from carbon-deposit estimations calculated for Russian soils in general.

Reforestation on nonforest lands (including abandoned agricultural lands) in Smolenskoe Poozerye National Park has been assessed from summer Landsat image series taken in 1984 to 2016. The boundaries of nonforest lands have been delimited using cartographic materials from the 1970s–1980s. The continuous time series of reflectance for each pixel of spectral bands have been obtained by the simple moving average method. Thematic processing is performed using the Random Forest supervised classification algorithm. An analysis of the obtained cartographic products for different stages of recovery successions shows a monotonous decrease in open soil areas from 3651 ha (9.7%) in 1990 to 1489 ha (4%) in 2016. Almost 38% of nonforest lands had been covered by woody vegetation by 1990. The area of forest lands increased by about 18% over the next 25 years (generally due to deciduous species); half of this forest growth was observed during the 1990s. In 2015, 46.0% of the initial nonforest lands were naturally reforested by young birch forests and 9.6% were occupied by young pine forests. Ground survey data showed that the type of succession is primarily determined by the lithological conditions and species composition of the nearby forests and influences the pattern of preceding land use during the natural reforestation of nonforest lands.

This paper presents the results of studying a promising area related to the remote assessment of canopy spaces in forests by thresholding methods of image segmentation. The study is conducted based on the example of mixed forests in the Losiny Ostrov National Park. The proposed methodological approach to assessing the pattern of forest canopy on super-high (detailed) resolution satellite images is based on an analysis of light and shaded plots of canopy spaces using image-thresholding algorithms.

The pixel count for different brightness thresholds give enough information to estimate a range of biometric indexes, including volume density and average age and height of stands from statistical relationships. The accuracy of estimates is assessed for prescribed deviations and verified against the norms of estimation of corresponding taxation data.

We have found a statistical relationship of forest-canopy morphology indicators with brightness thresholds for shaded plots of canopy spaces and stemwood phytomass in forest ecosystems. Thus, super-high-resolution images may be considered an information basis for estimating the biometric parameters of stands, morphological indicators of forest canopy, and the productivity of forest ecosystems.

An equation of the balance of chemicals is proposed which makes it possible to estimate the changes in their quantity in the soil under a growing stand. When determining the sources of chemicals for forest soils, the measured data of their contents in atmospheric precipitation and estimated inputs of dieback are used. Sinks of elements are calculated from lysimetric data and their accumulation is determined for phytomass increase. Due to the insufficient study of element migration during transpiration, the influence of this process on the balance is evaluated for two options: with and without taking possible losses of chemicals as a result of biogenic evaporation into account. Growth increment and dieback phytomass are estimated differentially for the soil cover and the stand. We have documented the species-averaged contents of certain chemicals accumulating by growing phytomass and returning with dieback in pine and spruce stands and their soil covers. The accumulation of elements in soil cover rises due to precipitation falling through the forest canopy. The greatest increase is obtained in the input of potassium and calcium. Their contribution is the highest in the precipitation flux of all studied chemicals in the soil cover. However, the precipitation of potassium is comparable to its uptake by phytomass. Dieback is the dominant source of silicon, nitrogen, and total phosphorus for the forest soils. The balance model shows that the mature and old-growth stands support the accumulation of nutritional elements in the soils. Losses of silicon might be compensated by its soil storage.

We have tested management practices at monitoring plots of the Institute of Forest, Russian Academy of Sciences, in Ermakovo station (Western Sayan) to develop Siberian pine forests (Pinus sibirica Du Tour) from young coniferous–deciduous forests that were formed in the place of clearcuttings in tall-grass–fern fir and Siberian pine forests in the low-mountain dark Chern zone. The dynamics of all layers and structural elements of the communities were studied from 1966 to 2014 at two experimental monitoring plots (each with an area of 2500 m²) and compared to the control. The article considers the case of admitting the complete lighting of Siberian pine undergrowth at first thinning. This practice proved to be optimal for further forest-management recommendations. Siberian pine gained competitive advantages over aspen or fir after the first thinning for a short period until the dominant species (aspen, birch, or fir) started to actively regenerate. Repeated thinning made Siberian pine steadily dominant in stands. Our experiment has shown that highly productive Siberian pine forests can be formed for 50 years under the unique natural and climate conditions of the low-mountain Chern zone of the Western Sayan, while the natural course of succession could not yield this result even after 200 or more years. These forests are comparable to indigenous dark Siberian pine forests with respect to their density (0.4–0.6) and wood stock (182 m³/ha at the age of 70–80 years and 270 m³/ha at the age of 80–90 years); however, the managed stands yield many more nuts (about 300 kg/ha) at the age of 70–90 years. Thinning induced the growth of a stand dominated by Siberian pine, as well as the formation of a phytocenotic structure similar to indigenous dark Siberian pine forests, i.e., a structure with a high diversity.

We have studied the features of annual ring development in stands of Bryansk oblast polluted by radionuclides from the Chernobyl accident. The evidence of relationships between average annual radial increment and the average width of spring and summer layers of timber within an annual ring and stand density is observed in 80-year-old blueberry pine forests. We find direct links between annual increment and its spring and summer components with average distance between trees. The stand density has the most pronounced effect on the spring growth of timber, with an increment gradient from 0.204 to 0.244 mm m^–1. In summer it varies from 0.038 to 0.066 mm m^–1. The contribution of the late timber in a tree ring increases from 50.4–54.8% in the least dense to 72.5–75.8% in the densest stands. However, chronic irradiation does not differ across the stand density gradient. The stimulation of the annual growth increment by irradiance is estimated from 50.4 to 51.9%. It contributes from 39.1 to 46.1% of the spring increment to 43.2–58.6% of the summer increment with 95% confidence.

Experimental studies in forest steppes show that the oak yields its position to associate species: the ash, Norway maple, field maple, lime, and elm. We conclude that the long-term exploitation of the same areas of oak forests hoping for coppice reforestation of clearcuts decreases its share in a stand canopy and productivity class. In the meanwhile, oak could go extinct from leaf stands of the forest steppe. We provide the taxation features of the stands, including the mass-based formula of stand composition in 2012 and the number-based formula of stand composition across stories, based on sample plots assessments made during 2012–2015. The number- based formula more vividly describes relations between species in a stand. This was significant in understanding the process of forest-canopy formation. We suggest that the only way to preserve the oak gene resources as edificatory species with regional protective functions and which are important for economic activity is the afforestation of oak at clearcuts. We suggest an improved way of oak reproduction, focusing on intensive monitoring of the stand until the canopy closes at around 15 years. This is the age when oak occupies the root and light space and makes associate species unable to compete. Two kinds of thinnings, cutting-backs and accretion cuttings, are excluded to significantly decrease the expenses for growth of an oak stand.