Plant Organic Matter in Palsa and Khasyrei Type Mires: Direct Observations in West Siberian Sub-Arctic

This article presents the first results of long-term direct measurements of a few major components of carbon cycle in permafrost mire landforms in the sub-Arctic region of Western Siberia, Russia. It reveals the main features of geographical distribution of plant organic matter, including both the above-ground and below-ground fractions of live biomass, the biomass of dead roots (mortmass), and net primary production (NPP) in peat-accumulating flat palsa mires and in “khasyrei”—ecosystems of drained lakes in thermokarst depression on epigenetic permafrost. The study based on original methods of direct field measurements elaborated by authors for northern peatlands. In northern taiga, the NPP of palsa mires was found in the range of 300–580 g m−2 yr−1 and an average biomass of 1800 g m−2; in khasyrei, it accounts for 1100 g m−2 yr−1 and 2000 g m−2 of NPP and live biomass, respectively. In forest tundra, the live biomass of palsa mires was found in the range of 1000–1800 g m−2, and in khasyrei it was 2300 g m−2. The NPP of palsa mires were in the range of 400–560 g m−2 yr−1, and in khasyrei it was 800 g m−2 yr−1. Overall, we conclude that the south–north climatic gradient in Western Siberia is the main driver of plant organic matter accumulation. It was found different across mire ecosystems of the same types but located in different bioclimatic regions.

Organic carbon in vegetal biomass of forests in Kyiv region

Carbon sequestrative capacity of forest plant communities is one of the main criteria for the potential for low-carbon development of the country and the fulfillment of international obligations in the context of the Paris climate agreement. The information basis of the research is formed by information from the database of IA "Ukrderzhlisproekt", which contains the detailed biometric characteristics of forest stands located in the research region. Another component is represented by a system of mathematical models for quantitative assessment of live biomass and forest dead organic matter. As a result, in this research we have determined the quantitative values of organic carbon content in live biomass and dead organic matter of forests of Kyiv region. In total, the amount of carbon accumulated in vegetal biomass of the region's forests equals 61.8 million tons, of which 60 % is accounted for by pine stands. The share of carbon accumulated in dead organic matter is 10.5 %. The highest density of sequestered carbon per unit area is typical for ash and oak stands with indicators of 10.08 and 9.921 kg∙(m2)-1, respectively. More than 40 % of organic carbon is accumulated in vegetal biomass of stands of I site index class, which mainly grow in relatively poor forest conditions. Recreational, health-improving and protective forests of the region are characterized by the highest indicators of organic carbon density per unit area – 10.53 and 10.49 kg∙(m2)-1, respectively. Among the objects of the nature reserve fund, the dominant positions in the volume of the studied indicator belong to nature reserves – 82.7 %, national nature parks account for another 8 %. In the total structure of carbon capacity of dead organic matter (6.5 million tons) more than 60% belongs to forest litter. At the same time, carbon content in dead organic matter of coniferous stands equals 4.1 million tons, or 62.9 %. The results of the research will serve as an information basis for the formation of a strategy for regional low-carbon development.

Effects of Fencing on Vegetation and Soil Nutrients of the Temperate Steppe Grasslands in Inner Mongolia

Grazing exclusion has been widely implemented in degraded grassland. However, the changes of plant communities and soil nutrients in response to fencing are still controversial. Thus, the effects of free grazing, 17 and 36 years of fencing on the plant biomass and litter biomass, carbon (C), nitrogen (N) and phosphorus (P) concentrations and stocks of plant, litter and soil were investigated in the temperate steppe grasslands of northern China. The results indicated that fencing increased the aboveground live biomass and litter biomass. In addition, fencing increased C, N and P stocks of aboveground live biomass, litter biomass and soil. Although root biomass and its nutrient stocks were also significantly increased by 17 years of fencing, they were decreased with fencing extending from 17 to 36 years. Moreover, there were no significant differences in aboveground live biomass and soil N and P stocks between 17 and 36 years of fencing. Litter biomass and its C, N and P stocks were positively correlated with soil C, N and P stocks. Our results demonstrated that 17 years of fencing is an effective way to restore vegetation and soil nutrients in the temperate steppe of Inner Mongolia, but a longer fencing duration has no further positive effects on biomass production and soil nutrients accumulation.

Farm Rejuvenation-Induced Changes in Tree Spatial Pattern and Live Biomass Species of Cocoa Agroforests in Central Cameroon: Insights for Tree Conservation Incentives in Cocoa Landscapes

Cocoa agroforests sustain ecosystem services (ESs) to varying degrees. These services are otherwise mostly provided by other non-cocoa shade or companion trees. However, the density of shade trees is associated with services and/or disservices that drive farm-specific tree management successions. Considering the growing impacts of climate crisis on farm productivity and the need for adaptation strategies, the ESs are increasingly provisional and contingent on the prevailing vegetation, land tenure, and management successions, amongst others social and ecological factors. To assess the temporal changes in shade management, we surveyed an age gradient of “family farms” in cocoa agroforests created from forest (fCAFS) and savannah (sCAFS) land cover. We evaluated the temporal changes in farm structure, relative tree abundance, and live aboveground biomass of the major canopy strata. We used a spatial point process and linear mixed effect analysis to assess the contributions of associated perennial trees (AsT) on farm rejuvenation patterns. The density of cocoa trees was inconsistent with farm age; this was significantly high on farms in sCAFS (1544 trees ha−1) with spatially random configuration across farm age. On farms in fCAFS, we observed a transition of the cocoa tree configuration in the order regular, random, and clustering from young (with highest density of 1114 trees ha−1) to old farms. On a temporal scale, there is no clear distinction of farm structure and biomass between fCAFS and sCAFS. However, the cycle of tree species and structural composition of the canopy strata are dissimilar; the live biomass allocation for the considered use groups of tree species was different with farm age. The observed dynamics in canopy tree structure and live biomass provide insights into farmers’ temporal allocation of uses and prioritization of different tree species with farm age. We recommend the consideration of such landscape-specific, tree management dynamics in proposing on-farm tree conservation incentives. Our results are also conducive to reliable estimates of the ecosystem services from CAFS in the national implementation of conservation mechanisms such as REDD+.

Changes in global terrestrial live biomass over the 21st century

Live woody vegetation is the largest reservoir of biomass carbon, with its restoration considered one of the most effective natural climate solutions. However, terrestrial carbon fluxes remain the largest uncertainty in the global carbon cycle. Here, we develop spatially explicit estimates of carbon stock changes of live woody biomass from 2000 to 2019 using measurements from ground, air, and space. We show that live biomass has removed 4.9 to 5.5 PgC year−1 from the atmosphere, offsetting 4.6 ± 0.1 PgC year−1 of gross emissions from disturbances and adding substantially (0.23 to 0.88 PgC year−1) to the global carbon stocks. Gross emissions and removals in the tropics were four times larger than temperate and boreal ecosystems combined. Although live biomass is responsible for more than 80% of gross terrestrial fluxes, soil, dead organic matter, and lateral transport may play important roles in terrestrial carbon sink.

Energy content in woody biomass of Zhytomyr Polissia’s forests

Development of renewable energy production is one of the main directions of decarbonizing the Ukraine’s energy sector as well as the forestry sector. Increase in woody biomass utilization efficiency at producing energy, alongside with securing the proper level of technological processes and technical equipment, also requires a reliable information support toolbox that would facilitate managerial decisions. An important constituent of this toolbox is represented by the regional assessments of energy function of forest plant communities. The information basis of the research is formed by the information from the industrial database of IA “Ukrderzhlisproekt”, which contains the detailed biometric characteristics of the stands in the studied region, as well as by a system of mathematical models for quantitative assessment of foersts’ live biomass and dead organic matter. As a result, the quantitative values of the total energy content in live biomass and daed organic matter of Zhytomyr Polissia’s forests were determined. The total amount of energy accumulated in vegetal biomass of the region's forests is 3035.7 PJ, which corresponds to 100.2 million tons of conventional fuel. At the same time, the share of the total energy content in dead organic matter is 11.1 %. The structure of energy content in vegetal biomass in the region is dominated by pine stands, which accumulate more than 60 % of the energy of forests of Zhytomyr region, including 70.8 % - in live biomass of tree trunks. More than 40 % of energy is accumulated in vegetal biomass of stands of I site index class, which mainly grow in fairly infertile forest growth conditions. In the general structure of energy content in dead organic matter (336.2 PJ) more than 60 % belongs to forest litter (212.8 PJ which is not considered a source of renewable energy), standing dead trees 12.3 % (41.3 PJ), dry branches – 17.8 % (close to 60 PJ). The results obtained in the course of the research will serve as an information background for the formation of a strategy for development of forest bioenergy in Zhytomyr region.

Nutrients cause grassland biomass to outpace herbivory

Human activities are transforming grassland biomass via changing climate, elemental nutrients, and herbivory. Theory predicts that food-limited herbivores will consume any additional biomass stimulated by nutrient inputs (‘consumer-controlled’). Alternatively, nutrient supply is predicted to increase biomass where herbivores alter community composition or are limited by factors other than food (‘resource-controlled’). Using an experiment replicated in 58 grasslands spanning six continents, we show that nutrient addition and vertebrate herbivore exclusion each caused sustained increases in aboveground live biomass over a decade, but consumer control was weak. However, at sites with high vertebrate grazing intensity or domestic livestock, herbivores consumed the additional fertilization-induced biomass, supporting the consumer-controlled prediction. Herbivores most effectively reduced the additional live biomass at sites with low precipitation or high ambient soil nitrogen. Overall, these experimental results suggest that grassland biomass will outstrip wild herbivore control as human activities increase elemental nutrient supply, with widespread consequences for grazing and fire risk.

Universal patterns of matter and energy fluxes in land and ocean ecosystems

In work [1], the fundamental relationships for the fluxes of matter and energy in terrestrial ecosystems were obtained. Taking into account the universal characteristics of biota, these relationships permitted an estimate to be made of the vertical thickness of the live biomass layer for autotrophs and heterotrophs. The distribution of consumption of biota production as dependent on the body size of heterotrophs was also investigated. For large animals (vertebrates), the energy consumption in sustainable ecosystems was estimated to be of the order of one percent of primary production. In this comment, it is shown that the results of work [1] also hold true for ocean ecosystems and thus are universal for life as a whole. This is of paramount importance for human life on Earth.