Tatyana P. Kolchugina

Carbon sources and sinks in forest biomes of the former Soviet Union

The carbon budget of the forest biomes of the former Soviet Union (FSU) and their sequestration potential were assessed by considering (1) net ecosystem productivity (NEP) of different age forest stands and actual forest coverage, (2) carbon flux related to forest fires, (3) the rate of peat accumulation, and (4) anthropogenic influences. The area of forest biomes in the FSU was estimated at 1426.1 million hectares (Mha); forest ecosystems comprised 799.9 Mha, nonforest ecosystems and arable land comprised 506.3 and 119.9 Mha, respectively. The vegetation pool (phytomass and coarse woody debris) was 68.7 Gt C (carbon). The litter and soil carbon pools were 12.2 and 319.1 Gt C, respectively. The net primary productivity (NPP) of forest biomes ecosystems was 5.6 Gt C/yr, the rate of foliage formation was 2.3 Gt C/yr, the rate of humus formation was 161 Mt C/yr with 73 Mt C/yr in the stable form. The NEP of the forest biomes was assessed from the data on NEP of young, middle-age, and premature forest stands. The NEP of the forest biomes was 825 Mt C/yr. Peat was accumulating at an average rate of 23 Mt C/yr. Carbon effluxes from mortmass, litter, and soil organic matter decomposition were calculated from the NPP, NEP, foliage, and humus formation rates. The efflux from mortmass decomposition was 2.6 Gt C/yr, from litter decomposition 2.1 Gt C/yr, and from soil organic matter decomposition 61 Mt C/yr. Peat combustion represented a carbon efflux of 30 Mt C/yr. The carbon efflux from forest fires and agricultural activities was 199 and 10 Mt C/yr, respectively. Carbon efflux from wood harvesting (carbon sequestration in regrowing vegetation was excluded) was 152 Mt C/yr. Considering all components of the natural carbon cycle and the anthropogenic influences, FSU forest biomes were a net sink of 485 Mt C/yr of atmospheric carbon. The Siberian and Far East forests represent approximately 82% of the net sink. The total carbon sink in FSU forests was equivalent to one half of the annual CO2 fossil fuel emissions in the FSU or one half the carbon released from deforestation in subtropical regions.

Comparison of two methods to assess the carbon budget of forest biomes in the Former Soviet Union

The sink of CO2 and the C budget of forest biomes of the Former Soviet Union (FSU) were assessed with two distinct methods: (1) ecosystem/ecoregional, and (2) forest statistical data. The ecosystem/ecoregional method was based on the integration of ecoregions (defined with a GIS analysis of several maps) with soil/vegetation C data bases. The forest statistical approach was based on data on growing stock, annual increment of timber, and FSU yield tables.Applying the ecosystem/ecoregional method, the area of forest biomes in the FSU was estimated at 1426.1 Mha (106 ha); forest ecosystems comprised 799.9 Mha, non-forest ecosystems and arable land comprised 506.1 and 119.9 Mha, respectively. The FSU forested area was 28% of the global area of closed forests. Forest phytomass (i.e., live plant mass), mortmass (i.e., coarse woody debris), total forest plant mass, and net increment in vegetation (NIV) were estimated at 57.9 t C ha−1, 15.5 t C ha−1, 73.4 t C ha−1, and 1.0 t C ha−1 yr−1, respectively. The 799.9 Mha area of forest ecosystems calculated in the ecosystem/ecoregional method was close to the 814.2 Mha reported in the FSU forest statistical data. Based on forest statistical data forest phytomass was estimated at 62.7 t C ha−1, mortmass at 37.6 t C ha−1; thus the total forest plant mass C pool was 100.3 t C ha−1. The NIV was estimated at 1.1 t C ha−1 yr−1. These estimates compared well with the estimates for phytomass, total forest plant mass, and NIV obtained from the ecosystem/ecoregional method. Mortmass estimated from the forest statistical data method exceeded the estimate based on the ecosystem/ecoregional method by a factor of 2.4. The ecosystem/ecoregional method allowed the estimation of litter, soil organic matter, NPP (net primary productivity), foliage formation, total and stable soil organic matter accumulation, and peat accumulation (13.9 t C ha−1, 125.0 t C ha−1, 3.1 t C ha−1 yr−1, 1.4 t C ha−1 yr−1, 0.11, and 0.056 t C ha−1 yr−1, respectively). Based on an average value of NEP (net ecosystem productivity) from the two methods, and following a consideration of anthropogenic influences, FSU forests were estimated to be a net sink of approximately 0.5 Gt C yr−1 of atmospheric C.

Change in phytomass and net primary productivity for Siberia from the Mid-Holocene to the Present

Phytomass (live plant mass) and net primary productivity are major components of the terrestrial carbon balance. A major location for phytomass storage is the subcontinent of Siberia, which is dominated by extensive reaches of taiga (boreal forest). The responsiveness of the phytomass component of the carbon pool is examined by comparing vegetation in the mid-Holocene (4600–6000 years before present) to modern potential vegetation. The mid-Holocene was warmer and moister in middle and northern Siberia than today, producing conditions ideal for boreal forest growth. As a result, both northern and middle taiga were dominated by shade-tolerant dark-needled species that thrive in moist climates. Today, shade-tolerant dark-needled taiga is restricted to western Siberia and the highlands of central Siberia, with its central and eastern components in the mid-Holocene replaced today by light-demanding light-needled species with lower productivity and phytomass. Total phytomass in Siberia in the mid-Holocene was 105.0 ± 3.1 Pg, compared to 85.9 ± 3.2 Pg in modern times, a loss of 19.1 ± 3.1 Pg of phytomass. The reduction in dark-needled northern and middle taiga classes results in a loss of 28.8 Pg, while the expansion of the corresponding light-needled taiga results in a gain of 13.5 Pg, a net loss of 15.3 Pg. The loss is actually greater, because the modern figures are for potential vegetation and not adjusted for agriculture and other anthropogenic disturbances. Given long periods for vegetation to approach equilibrium with climate, the phytomass component of the carbon pool is responsive to climate change. Changes in net primary productivity (NPP) for Siberia between the mid-Holocene and the present were not as large as changes in phytomass. A minor decrease in NPP (0.6 Pg yr−1, 10%) has occurred under our cooler modern climate, primarily due to the shift from dark-needled taiga in the mid-Holocene to light-needled taiga today.

Pools and Fluxes of Biogenic Carbon in the Former Soviet Union

The Former Soviet Union (FSU) was the largest country in the world. It occupied one-sixth of the land surface of the Earth. An understanding of the pools and fluxes of biogenic C in the FSU is essential to the development of international strategies aimed at mitigation of the negative impacts of global climate change. The territory of the FSU is represented by a variety of climate conditions. The major part of the FSU territory is in the boreal and temperate climatic zones. The climate in the FSU changes from arctic and subarctic in the North to subtropical and desert in the South. From west to east, the climate makes a transition from maritime to continental to monsoon. The vegetation of the FSU includes the following principal types: forest, woodland, shrubland, grassland, tundra, desert, peatlands and cultivated land. Arctic deserts and tundra formations are found in the northern part of the FSU; deserts and semi-deserts are found in the southern part.

Potential effect of no-till management on carbon in the agricultural soils of the former Soviet Union

Abstract Agricultural soils act as both a source and a sink for atmospheric carbon. Since the onset of cultivation, the 211.5 million ha of agricultural soils in the former Soviet Union (FSU) have lost 10.2 Gt of carbon. No-till management represents a promising option to increase the amount of carbon sequestered in the agricultural soil of the FSU. No-till management reduces erosion and sequesters additional carbon in the soil by lowering the soil temperature and raising soil moisture. To determine the carbon sequestered under no-till management, a data base containing precultivation estimates of soil carbon for the seven major classes of soil found in the agricultural areas of the FSU was used to establish an equilibrium carbon content for each soil. Other published data provided a method to quantify the change in soil carbon brought about by converting to no-till management. Soils suitable for no-till management were analyzed and estimates of changes in carbon storage were made. No-till management is not suitable in areas where crop production is limited by cold, wet soils. Based on the results of a geographic information system analysis using maps of climatic factors and soil characteristics, 181 million ha in the FSU were identified as climatically suitable for no-till management (almost 86% of all agricultural land). Complete conversion of all climatically suitable land to no-till management would sequester 3.3 Gt of carbon. This represents a 10% increase in carbon in the agricultural soils of the FSU. This estimated accumulation of carbon is associated with a new soil carbon equilibrium condition. Accumulation of carbon in the soil produced by a conversion from conventional to no-till management is expected to take at least 10 years. The carbon accumulation produced by conversion to no-till management is not a continuing process; once a new no-till equilibrium condition has been reached, additional quantities of atmospheric carbon will not be sequestered in agricultural soils through continued no-till management.

Carbon cycle of terrestrial ecosystems of the former Soviet Union

Abstract Two to three percent of the organic matter accumulating annually in the terrestrial ecosystems of the FSU (8.2 Pg C/yr) was sequestered in relatively long-term storage pools. The total C store of the FSU, estimated at 601.1 Pg C (with 84% allocated in SOM, 10% in phytomass and approximately 3% each in CWD and litter), was increasing by 0.03%/yr. The remaining C was returned to the atmosphere through natural processes (over 90%) and disturbances (5%). Terrestrial ecosystems of the FSU represented a sink for 0.181 Pg C/yr. This C sink was provided by forest ecosystems (0.375 Pg C/yr), while agro–ecosystems and peatlands represented a net source of C to the atmosphere (0.194 Pg C/yr). Implementation of a number of forest management practices to a full extent would result in an increase in the forest C pools by 0.5%/yr. Management options in the agricultural sector may increase the total SOM C pool by 0.1%/yr. With climate warming, FSU terrestrial ecosystems within the permafrost area may make a transition to become a source of 0.2–0.5 Pg C/yr, which may concurrently be balanced by forest migration to the north and an increase in plant productivity. In the future, FSU terrestrial ecosystems may still represent a sink for atmospheric C if there would be a substantial amount of young to maturing forest ecosystems and forest logging would not increase dramatically.

Management Options to Conserve and Sequester Carbon in the Agricultural Sector of the Former Soviet Union

Several management practices are available to conserve and sequester C in the agricultural sector of the former Soviet Union (FSU). The highest rate of C accumulation would result from the implementation of a no-till management option which will only continue during the first ten years until new C equilibrium is reached. Agroforestry management options provide a longer period for C accumulation, but at a lower rate. It is possible that the longest period of C conservation may be achieved by increasing the area under perennial grasses in the crop rotation. During the first decade of implementation of the management practices, the amount of C conserved or sequestered would be approximately equal to the current rate of net C sequestration in FSU forest sector. At present, agricultural soils and vegetation of the FSU store approximately 120 Pg C; the accumulation of soil organic matter is 0.032 Pg C yr−1. The annual C loss in the FSU agricultural sector was estimated at 0.21 Pg C yr−.

Terrestrial Carbon Dynamics: Case Studies in the Former Soviet Union, the Conterminous United States, Mexico and Brazil

This research assessed land-use impacts on C flux at a national level in four countries: former Soviet Union, United States, Mexico and Brazil, including biotic processes in terrestrial ecosystems (closed forests, woodlands, and croplands), harvest of trees for wood and paper products, and direct C emission from fires. The terrestrial ecosystems of the four countries contain approximately 40% of the worlds terrestrial biosphere C pool, with the FSU alone having 27% of the global total. Average phytomass C densities decreased from south to north while average soil C densities in all three vegetation types generally increased from south to north. The C flux from land cover conversion was divided into a biotic component and a land-use component. We estimate that the total net biotic flux (Tg/yr) was positive (= uptake) in the FSU (631) and the U.S. (332), but negative in Mexico (−37) and Brazil (−16). In contrast, total flux from land use was negative (= emissions) in all four countries (TgC/yr): FSU −343; U.S. −243; Mexico −35; and Brazil −235. The total net effect of the biotic and land-use factors was a C sink in the FSU and the U.S. and a C source in both Brazil and Mexico.

Greenhouse gas mitigation options in the Forest sector of Russia: National and project level assessments

Greenhouse gas (GHG) mitigation options in the Russian forest sector include: afforestation and reforestation of unforested/degraded land area; enhanced forest productivity; incorporation of nondestructive methods of wood harvesting in the forest industry; establishment of land protective forest stands; increase in stand age of final harvest in the European part of Russia; increased fire control; increased disease and pest control; and preservation of old growth forests in the Russian Far-East, which are presently threatened. Considering the implementation of all of the options presented, the GHG mitigation potential within the forest and agroforestry sectors of Russia is approximately 0.6–0.7 Pg C/yr or one half of the industrial carbon emissions of the United States. The difference between the GHG mitigation potential and the actual level of GHGs mitigated in the Russian forest sector will depend to a great degree on external financing that may be available. One possibility for external financing is through joint implementation (JI). However, under the JI process, each project will be evaluated by considering a number of criteria including also the difference between the carbon emissions or sequestration for the baseline (or reference) and the project case, the permanence of the project, and leakage. Consequently, a project level assessment must appreciate the near-term constraints that will face practitioners who attempt to realize the GHG mitigation potential in the forest and agroforestry sectors of their countries.

Simulating Carbon Storage in Forests of Eastern Russia

In a pilot study investigating a method for estimating carbon (C) in forested ecosystems of Russia, a forest growth model was selected and applied to a test area. BORFOR, a forest gap model which simulates growth of trees, mosses and forest floor decay was used to model a mountainous area in the Russian Far East. Vegetation and landcover were identified using an unsupervised classification of Global Vegetation Index (GVI). The continental scale image class descriptions required a supplemental description of the species-specific to the area before they could be used as input data. Site level data was provided for soils and disturbances using published literature and thematic maps. Carbon values for forest ecosystems estimated with BORFOR were compared to other estimates. Good comparisons were noted for living tree C in all forest types, except mountain deciduous forests. Forest floor C was both overestimated or underestimated depending on forest type. Spatial resolution of ecosystem identification data was found to be very important to the estimation of C in mountainous regions. The BORFOR model could be improved to provide better C estimates with species-specific biomass calculations and improved simulation of decay of dead trees.