Biogeneous carbon fluxes in the boreal forests of Central Siberia

The assessments of the carbon pool and rate of plant biomass production, phytodetritus destruction, new formations of humic matters, and removal of water-soluble decomposition products for the forest ecosystems of the forest tundra and the northern and southern parts of the Central Siberian taiga were given. The rates of the main processes (organic-matter production and degradation) were demonstrated to be balanced in the ecosystems of the forest tundra. The larch forests of the northern taiga serve as a stock for a C atmosphere, which are equivalent to 32–34% of net primary production (NPP). The secondary birch growth where the understory needle-leaved trees have been formed and the primary old-growth fir forests are characterized by the balance of the main carbon fluxes in the southern taiga. The birch forests where the understory trees are just being formed and the fir forests at the age of 50–90 years serve as a stock for an average of 26% of carbon extracted as dioxide to make NPP.     

Effects of fires in ribbon-like pine forests of southern Siberia

For the Tsasuchei, Balgazyn, Minusinsk, and Shushensk ribbon-like pine forests of southern Siberia, conditions of ignition and development of fires are analyzed and the flammability is evaluated. Fire effects on vegetation, including forest stand condition and reforestation, are evaluated. It is shown that a reduction in the area of ribbon-like pine forests of southern Siberia caused by crown fires leads to steppification of these areas.     

Transformation of soil invertebrate complex after surface fires of different intensity

The effect of surface fires of different intensity on soil invertebrates was evaluated in central taiga Scotch pine forests in the Yenisey Region of Siberia. In the period of 4–5 years, the abundance and ecological and trophic structure of sandy podzol population was almost completely restored after surface fires of medium and low intensity. The recovery process was decelerated after high intensity fires.     

Post-fire restoration of organic substance in the ground cover of the larch forests in permafrost zone of Central Evenkia

The role of ground fires in transformation of organic substance in the ground cover of larch stands in the permafrost zone of Central Siberia was studied as well as the post-fire restoration dynamics of organic substance. Ground fires lead to is a considerable decrease in concentrations and resources of organic carbon and its individual fractions in the ground cover and their restoration takes many decades.     

Climate and socioeconomic drivers of biomass burning and carbon emissions from fires in tropical dry forests: A Pantropical analysis

Global burned area has declined by nearly one quarter between 1998 and 2015. Drylands contain a large proportion of these global fires but there are important differences within the drylands, for example, savannas and tropical dry forests (TDF). Savannas, a biome fire-prone and fire-adapted, have reduced the burned area, while the fire in the TDF is one of the most critical factors impacting biodiversity and carbon emissions. Moreover, under climate change scenarios TDF is expected to increase its current extent and raise the risk of fires. Despite regional and global scale effects, and the influence of this ecosystem on the global carbon cycle, little effort has been dedicated to studying the influence of climate (seasonality and extreme events) and socioeconomic conditions of fire regimen in TDF. Here we use the Global Fire Emissions Database and, climate and socioeconomic metrics to better understand long-term factors explaining the variation in burned area and biomass in TDF at Pantropical scale. On average, fires affected 1.4% of the total TDF' area (60,208 km²) and burned 24.4% (259.6 Tg) of the global burned biomass annually at Pantropical scales. Climate modulators largely influence local and regional fire regimes. Inter-annual variation in fire regime is shaped by El Niño and La Niña. During the El Niño and the forthcoming year of La Niña, there is an increment in extension (35.2% and 10.3%) and carbon emissions (42.9% and 10.6%). Socioeconomic indicators such as land-management and population were modulators of the size of both, burned area and carbon emissions. Moreover, fires may reduce the capability to reach the target of “half protected species” in the globe, that is, high-severity fires are recorded in ecoregions classified as nature could reach half protected. These observations may contribute to improving fire-management.     

The impacts of fires and clear-cuts on the carbon balance of Russian forests

The system for the regional assessment of a forest carbon budget is expanded with the procedures of uncertainty calculations. The forest carbon balance of the Russian Federation for 1988–2009 is assessed. The impact of fire on the forest carbon budget is estimated using both official statistics and remote sensing data. For the study period, the average carbon sink from the atmosphere to Russian forests was 205 ± 64 × 10⁶ t C yr^?1 on average, varying from 70 ± 81 × 10⁶ t C yr^?1 in 1998 to 287 ± 60 × 10⁶ t C yr^?1 in 2001. The interannual variations of carbon sink are determined by the dynamics of carbon losses due to forest fires. The distribution of the fireinduced carbon losses in Russian regions is examined using remote-sensing data.     

Seedling regeneration and vegetative resprouting after fires in Pinus densiflora forests

Modes of recruitment of each regenerated species after fire were investigated quantitatively in a Pinus densiflora forest in central Japan. There was a continuum of regeneration modes from species with abundant seedling populations (more than one individual m^–2) to sprouters. The former included Erigeron canadensis, Eupatorium chinense var. simplicifolium, Rubus crataegifolius, Lespedeza bicolor forma acutifolia, Mallotus japonicus, Rhus javanica, Eurya japonica, Aralia elata and Weigela decora, whose seedlings accounted for 70% of total recruitment on the forest floor. Sprouts from stem bases which comprised much of the canopy prior to fire (e.g. Quercus serrata, Castanea crenata, Fraxinus sieboldiana and Prunus spp.), were vigorous and grew rapidly. Plants on both ends of the continuum dominated post-fire vegetation in the study sites.     

The carbon balance in natural and disturbed forests of the southern taiga in central Siberia

Abstract. We evaluated the balance of production and decomposition in natural ecosystems of Pinus sylvestris, Larix sibirica and Betula pendula in the southern boreal forests of central Siberia, using the Yenisei transect. We also investigated whether anthropogenic disturbances (logging, fire and recreation pressure) influence the carbon budget. Pinus and Larix stands up to age class VI act as a net sink for atmospheric carbon. Mineralization rates in young Betula forests exceed rates of uptake via photosynthesis assimilation. Old‐growth stands of all three forest types are CO₂ sources to the atmosphere. The prevalence of old‐growth Larix in the southern taiga suggests that Larix stands are a net source of CO₂. The CO₂ flux to the atmosphere exceeds the uptake of atmospheric carbon via photosynthesis by 0.23 t C.ha^‐1.yr^‐1 (47%). Betula and Pinus forests are net sinks, as photosynthesis exceeds respiration by 13% and 16% respectively. The total carbon flux from Pinus, Larix and Betula ecosystems to the atmosphere is 10 387 thousand tons C.yr^‐1. Net Primary Production (0.935 t‐C.ha^‐1) exceeds carbon release from decomposition of labile and mobile soil organic matter (Rh) by 767 thousand tons C (0.064 t‐C.ha^‐1), so that these forests are net C‐sinks. The emissions due to decomposition of slash (101 thousand tons C; 1.0%) and from fires (0.21%) are very small. The carbon balance of human‐disturbed forests is significantly different. A sharp decrease in biomass stored in Pinus and Betula ecosystems leads to decreased production. As a result, the labile organic matter pool decreased by 6–8 times; course plant residues with a low decomposition rate thus dominate this pool. Annual carbon emissions to the atmosphere from these ecosystems are determined primarily by decomposing fresh litterfall. This source comprises 40–79% of the emissions from disturbed forests compared to only 13–28% in undisturbed forests. The ratio of emissions to production (NPP) is 20–30% in disturbed and 52–76% in undisturbed forests.     

Postfire recovery of the ground cover in pine forests of the Lower Angara region

This paper traces the dynamics of the living ground cover at the initial stage of pyrogenic succession (1–9 years) after different-intensity surface fires in the pine forests of the Lower Angara region. Depending on their intensities, fires have reduced the foliage cover and ground-cover biomass. The greatest changes occur in case of medium-intensity and high-intensity fires that change the horizontal structure of plant microgroups and lead to the death of moss-lichen layers.     

The effect of various disturbing factors on the radial increment in pine forests of Central Siberia

The results of study of regeneration periods in pine forests after natural and anthropogenic disturbanses have been presented. It has been found that the rate of recovery depends on the type of disturbing factor. The differentiated effect of climatic factors (air temperature, amount of precipitation) on the growth rate of forests with different types of disturbances has been investigated.     

Fires and pyrogenic successions in the forests of the south Baikal region

The southern coast of Baikal is characterized by the most humid climate in the Baikal region. Precipitation falls mainly on summer, thus reducing the actual of fire occurrence in mountain forests of the region. However, since 1989 the fire occurrence has been increased and disastrous crown fires have become more frequent, especially in the west. It is shown that fire occurrence is a function of the number, duration of rainless periods and monthly sums of rain precipitation, which have large amplitude of changes from year to year. Progressive pyrogenic successions in dark coniferous forests take place mostly without usual replacement by small-leaved tree species at the expense of successful regeneration of Pinus sibirica (in the western Khamar-Daban mountains) and Abies sibirica (in the central part) on the burnt areas during 15–25 years.     

Effects of species composition, land surface cover, CO2 concentration and climate on isoprene emissions from European forests.

Emissions of isoprene from terrestrial vegetation are known to affect atmospheric chemical properties, like its oxidation capacity or the concentration of tropospheric ozone. The latter is of concern, since besides being a potent greenhouse gas, O(3) is toxic for humans, animals, and plants even at relatively low concentrations. Isoprene-emitting forests in the vicinity of NO(x) pollution sources (like cities) can contribute considerably to O(3) formation, and to the peak concentrations observed during hot summer weather. The biogenic contribution to O(3) concentrations is generally thought to increase in a future, warmer climate--pushing values beyond health thresholds possibly even more frequently and over larger areas--given that emissions of isoprene are highly temperature-dependent but also because of the CO(2) fertilisation of forest productivity and leaf growth. Most projections of future emissions, however, do not include the possible CO(2)-inhibition of leaf isoprene metabolism. We explore the regional distribution of emissions from European woody vegetation, using a mechanistic isoprene-dynamic vegetation model framework. We investigate the interactive effects of climate and CO(2) concentration on forest productivity, species composition, and isoprene emissions for the periods 1981-2000 and 2081-2100. Our projection of future emissions includes a direct CO(2)-isoprene inhibition. Across the model domain, we show that this direct effect has the potential to offset the stimulation of emissions that could be expected from warmer temperatures and from the increased productivity and leaf area of emitting vegetation. Changes in forest species composition that may result from climate change can play a substantial additional role in a region's future emissions. Changes in forest area or area planted in woody biofuels in general are not noticeable in the overall European forest isoprene budget, but--as was the case for changes in species composition--may substantially affect future projections in some regions of the continent.     

上海城市森林植被固碳功能及其抵消能源碳排放效果评估

植被固碳功能是城市森林的重要生态服务之一,但是定量揭示城市森林植被固碳功能空间格局及其抵消碳排放的研究较少。基于光合速率法和生物量法测算了上海城市森林植被的固定CO₂功能,并结合其空间分布格局与区域CO₂排放状况对比分析了抵消能源CO₂排放的成效。结果表明,2017年上海城市森林植被可固定CO₂ 135.57万t,约合单位面积固碳17.02 t/hm²。上海城市森林植被的固定CO₂功能呈现出"中间低、四周高"的空间格局,崇明区和浦东新区的城市森林植被提供了近52.8%的固定CO₂效益。2017年上海市能源消费的CO₂排放量高达2.73亿t,且呈现出"中间高、四周低"空间分布特征,中心城区能源CO₂排放约占11.49%。整体来看,上海城市森林植被可抵消0.50%的能源CO₂排放,但植被固定CO₂功能与能源CO₂排放的空间匹配较差,中心城区城市森林植被的CO₂抵消率仅为0.08%。因此,重点提升中心城区森林植被的固碳功能并加强海洋碳吸收功能的监测与利用尤其重要。     

城市森林碳汇及其抵消能源碳排放效果——以广州为例

城市森林及其管理相关政策作为减少CO₂排放的有效策略得到了较为广泛的关注。采用材积源生物量方程与净初级生产力方法来定量分析了广州市城市森林碳储量和碳固定量,根据化石能源使用量及其碳排放因子核算了广州城市能源碳排放,最后评估了城市森林碳抵消效果。结果显示广州市城市森林碳储量为654.42×10⁴t,平均碳密度为28.81 t/hm²,而森林碳固定量为658732 t/a,平均固碳率为2.90 t·hm^-2·a^-1。2005-2010年广州市年均能源碳排放则达到2907.41×10⁴t。广州城市森林碳储量约为城市年均能源碳排放的22.51%,其通过碳固定年均能够抵消年均碳排放的2.27%,不过从城市森林综合效益来看其仍是城市低碳发展重要举措之一。分析了林型组成和林龄结构对于广州森林碳储量和碳固定量的影响,并从森林管理角度为城市森林碳汇提升提出建议。这些结果和讨论有助于评估城市森林碳汇在抵消碳排放中所起的效果。     

Tree allometry and improved estimation of carbon stocks and balance in tropical forests

Tropical forests hold large stores of carbon, yet uncertainty remains regarding their quantitative contribution to the global carbon cycle. One approach to quantifying carbon biomass stores consists in inferring changes from long-term forest inventory plots. Regression models are used to convert inventory data into an estimate of aboveground biomass (AGB). We provide a critical reassessment of the quality and the robustness of these models across tropical forest types, using a large dataset of 2,410 trees ≥ 5 cm diameter, directly harvested in 27 study sites across the tropics. Proportional relationships between aboveground biomass and the product of wood density, trunk cross-sectional area, and total height are constructed. We also develop a regression model involving wood density and stem diameter only. Our models were tested for secondary and old-growth forests, for dry, moist and wet forests, for lowland and montane forests, and for mangrove forests. The most important predictors of AGB of a tree were, in decreasing order of importance, its trunk diameter, wood specific gravity, total height, and forest type (dry, moist, or wet). Overestimates prevailed, giving a bias of 0.5–6.5% when errors were averaged across all stands. Our regression models can be used reliably to predict aboveground tree biomass across a broad range of tropical forests. Because they are based on an unprecedented dataset, these models should improve the quality of tropical biomass estimates, and bring consensus about the contribution of the tropical forest biome and tropical deforestation to the global carbon cycle. Electronic Supplementary Material Supplementary material is available for this article at     

中度强度森林火灾对马尾松次生林土壤有机碳密度的影响

森林火灾作为森林非连续的干扰因子, 是生物地球化学循环的驱动因子, 显著改变生态系统的结构和功能及养分循环与能量传递, 引起森林碳库与碳分配格局的变化, 进而影响森林演替进程及固碳能力。该研究以广东省马尾松(Pinus massoniana)次生林为研究对象, 采用相邻样地比较法和空间代替时间法, 以野外调查采样与室内试验分析为主要手段, 定量研究突发性森林火灾对土壤有机碳密度的影响, 探讨森林火灾对土壤有机碳固持的影响机制。结果表明: 与对照相比, 森林火灾后的幼龄林、中龄林和成熟林的土壤有机碳密度分别为35.12、40.80和52.34 t·hm^-2, 依次降低了10.93%、8.52%和7.56%。相比对照, 幼龄林、中龄林和成熟林土壤剖面(0-60 cm)的土壤有机碳密度变化范围分别为5.04-7.76、5.26-10.27和6.33-13.58 t·hm^-2, 依次降低了2.51%-16.83%、1.31%-11.85%和1.09%-12.50%; 森林火灾显著降低了幼龄林和中龄林0-30 cm的土壤有机碳密度, 显著降低了成熟林0-20 cm的土壤有机碳密度。马尾松次生林土壤有机碳密度与土壤理化性质具有显著相关关系。通径分析表明, 对照样地和过火样地中, 土壤全氮含量均对土壤有机碳密度的直接作用最大, 土壤细根生物量对土壤有机碳密度的直接作用较小, 但其通过土壤全氮含量对土壤有机碳密度的影响均表现在间接作用上。嵌套方差分析表明, 土壤深度解释了土壤有机碳密度变异的70.60%, 林龄解释了其变异的25.35%, 森林火灾解释了其变异的2.34%。研究发现: 森林火灾减少了马尾松次生林各林龄的土壤有机碳密度。在水平方向上, 随着林龄增长, 土壤有机碳密度的减少幅度降低; 在垂直方向上, 土壤有机碳密度随着土壤土层深度加深而降低, 且随林龄增长减少幅度下降。研究森林火灾对森林生态系统土壤有机碳的影响, 有助于理解森林生态系统土壤碳固持和碳循环过程, 对制定旨在减缓全球变化的科学合理的林火管理策略具有重要意义。     

Edge fires drive the shape and stability of tropical forests

In tropical regions, fires propagate readily in grasslands but typically consume only edges of forest patches. Thus, forest patches grow due to tree propagation and shrink by fires in surrounding grasslands. The interplay between these competing edge effects is unknown, but critical in determining the shape and stability of individual forest patches, as well the landscape‐level spatial distribution and stability of forests. We analyze high‐resolution remote‐sensing data from protected Brazilian Cerrado areas and find that forest shapes obey a robust perimeter–area scaling relation across climatic zones. We explain this scaling by introducing a heterogeneous fire propagation model of tropical forest‐grassland ecotones. Deviations from this perimeter–area relation determine the stability of individual forest patches. At a larger scale, our model predicts that the relative rates of tree growth due to propagative expansion and long‐distance seed dispersal determine whether collapse of regional‐scale tree cover is continuous or discontinuous as fire frequency changes.     

Assessment of vegetation cover by lichen-indication methods (by the example of the north of Central Siberia)

The vegetation cover in the north of Central Siberia has been assessed from lichenological data. The approaches and methods of lichen-based indication of the state of vegetation cover have been developed with the application of the data on diversity of lichens and lichen synusias, their projective cover and morphological deviations. The species of lichens and synusias that can be used for indication purposes have been defined. The changes in the characteristics of the lichen component in vegetation cover under the increasing chemical air pollution caused by industrial plants have been examined. The early deviations are indicated by morphological changes of lichen thalli, species depletion, and diversity of lichen synusias. Practical recommendations on lichen indication of the vegetation cover in the north of Siberia have been given.     

Linking forest fires to lake metabolism and carbon dioxide emissions in the boreal region of Northern Québec

Natural fires annually decimate up to 1% of the forested area in the boreal region of Québec, and represent a major structuring force in the region, creating a mosaic of watersheds characterized by large variations in vegetation structure and composition. Here, we investigate the possible connections between this fire‐induced watershed heterogeneity and lake metabolism and CO₂ dynamics. Plankton respiration, and water–air CO₂ fluxes were measured in the epilimnia of 50 lakes, selected to lie within distinct watershed types in terms of postfire terrestrial succession in the boreal region of Northern Québec. Plankton respiration varied widely among lakes (from 21 to 211 μg C L^?1 day^?1), was negatively related to lake area, and positively related to dissolved organic carbon (DOC). All lakes were supersaturated in CO₂ and the resulting carbon (C) flux to the atmosphere (150 to over 3000 mg C m² day^?1) was negatively related to lake area and positively to DOC concentration. CO₂ fluxes were positively related to integrated water column respiration, suggesting a biological component in this flux. Both respiration and CO₂ fluxes were strongly negatively related to years after the last fire in the basin, such that lakes in recently burnt basins had significantly higher C emissions, even after the influence of lake size was removed. No significant differences were found in nutrients, chlorophyll, and DOC between lakes in different basin types, suggesting that the fire‐induced watershed features influence other, more subtle aspects, such as the quality of the organic C reaching lakes. The fire‐induced enhancement of lake organic C mineralization and C emissions represents a long‐term impact that increases the overall C loss from the landscape as the result of fire, but which has never been included in current regional C budgets and future projections. The need to account for this additional fire‐induced C loss becomes critical in the face of predictions of increasing incidence of fire in the circumboreal landscape.     

Contrasting patterns of carbon sequestration between Gilbertiodendron dewevrei monodominant forests and Scorodophloeus zenkeri mixed forests in the Central Congo basin

Plant and Soil - Plant growth promoting rhizobacteria (PGPR) have been shown to reduce abiotic stress on plants, but these effects have not been quantitatively synthesized. We evaluated the degree...