The purpose of present study was to find out whether wood ash with a high pH value and neutralizing capacity reduces 137Cs uptake by forest plants many years after the radionuclide fallout. The ...effects of one-time point fertilisation with 137Cs-contaminated and uncontaminated wood ash alone or in combination with KCl on 137Cs transfer from soil to young leaves and green shoots of various dwarf shrubs and tree species were examined in a long-term fertilisation experiment (2012–2021) conducted in Bazar mixed forest, around 70 km from Chernobyl nuclear power plant. The results indicated minor effects of soil fertilisation, although there were differences between 137Cs uptake by species and years. Soil amendment with 137Cs-contaminated wood ash generally did not affect 137Cs uptake by young shoots and leaves of plants over the growing season in the first year and only slightly decreased Tag for 137Cs in the following years. The effect of a single application of 137Cs-uncontaminated wood ash on reducing 137Cs uptake by plants was generally negligible. Application of 137Cs-contaminated wood ash in combination with KCl reduced plant 137Cs uptake by about 45%, however, such reduction was only significant in some years for bilberry berries, young leaves and green shoots of lingonberry and alder buckthorn. Thus application of wood ash to 137Cs-contaminated forest soil many years after radionuclide fallout generally does not reduce 137Cs uptake by forest vegetation in a mixed forest ecosystem and this countermeasure should be applied with caution.
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•Wood ash and KCl fertilisation don't result in consistent decrease of 137Cs uptake.•Effect of non-contaminated wood ash on 137Cs uptake was not detectable.•137Cs-contaminated wood ash caused small or no response on 137Cs uptake.•137Cs-contaminated wood ash + KCl decreases 137Cs uptake only marginally.•Fertilisation of forest soil with wood ash and KCl should be applied with cautions.
Over the past two decades, the burning of fossil fuels in China has been excessive, causing carbon emissions to increase. Surface temperatures and the occurrence of natural disasters have also ...increased. Considering the important role of forests in reducing emissions, China conducted a series of studies on carbon storage by forest vegetation that involved well-developed estimation methods. However, there are still uncertainties in predicting future changes in forest vegetation acting as a carbon sink. This study used data collected from 7801 national forest inventory (NFI) forest plots in 2003, 2008 and 2013 as well as related forest ecosystem biomass data. The dynamic growth, biomass and carbon storage of arbor, economic and shrubbery forests were studied. This study made a breakthrough in predicting forest biomass and carbon storage based on growth-related changes in forest vegetation in China, improved the accuracy of predicting arbor forest carbon storage and filled a gap in research on the carbon storage/sink properties of economic, shrubbery and bamboo forests. In the results of this study, from 2003 to 2050, the carbon storage, density and carbon sink of forest vegetation in China increased rapidly. Mature forests in China played a major role in the increase in carbon storage, and the quality of young, half-mature and mature forests steadily improved. China’s forest carbon storage was mainly concentrated in the southwestern and northeastern regions, between which the southwestern region had the highest carbon density. In addition, carbon storage and density increased faster in the southwestern region than in the northeastern region. The carbon storage and density of forest vegetation were greater in Tibet than in other areas. The carbon storage of forest vegetation in Tibet increased faster than that in other areas, and the carbon density of forest vegetation in Xinjiang increased faster than that in other areas. In addition, the carbon storage and carbon density of forest vegetation in Ningxia increased slower than those in other areas. From 2020 to 2050, China’s forest vegetation will absorb 22.14% of CO2 emissions from fossil fuel combustion, which will play an important role in slowing increases in greenhouse gases in the next 30 years.
•Breakthrough in predicting forest carbon storage from vegetation growth changes.•Filling the carbon sink research gap of economic, shrubbery and bamboo forests.•China’s mature forests will play a major role in the growth of carbon storage.•China’s forest carbon storage is concentrated in southwest and northeast regions.•China’s forest vegetation will absorb 22.14% of CO2 emissions from 2020 to 2050.
China has large areas of forest vegetation that are critical to biodiversity and carbon storage. It is important to assess vulnerability of forest vegetation to anthropogenic climate change in China ...because it may change the distributions and species compositions of forest vegetation. Based on the equilibrium assumption of forest communities across different spatial and temporal scales, we used species distribution modelling coupled with endemics–area relationship to assess the vulnerability of 204 forest communities across 16 vegetation types under different climate change scenarios in China. By mapping the vulnerability of forest vegetation to climate change, we determined that 78.9% and 61.8% of forest vegetation should be relatively stable in the low and high concentration scenarios, respectively. There were large vulnerable areas of forest vegetation under anthropogenic climate change in northeastern and southwestern China. The vegetation of subtropical mixed broadleaf evergreen and deciduous forest, cold-temperate and temperate mountains needleleaf forest, and temperate mixed needleleaf and broadleaf deciduous forest types were the most vulnerable under climate change. Furthermore, the vulnerability of forest vegetation may increase due to high greenhouse gas concentrations. Given our estimates of forest vegetation vulnerability to anthropogenic climate change, it is critical that we ensure long-term monitoring of forest vegetation responses to future climate change to assess our projections against observations. We need to better integrate projected changes of temperature and precipitation into climate-adaptive conservation strategies for forest vegetation in China.
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•We examined vulnerability of 204 forest communities across 16 vegetation types under climate change.•There were large vulnerable areas of forest vegetation in northeastern and southwestern China.•The vulnerability of forest vegetation may increase due to high greenhouse gas concentrations.•We should integrate projected climate changes into adaptive conservation strategies for forest vegetation in China.
•Region-wide study network examine ecological effects under a changing climate.•Evidence-based restoration treatments maintain effectiveness over a 20-year period.•Restoration treatments improve ...resilience to changing climate and disturbance.•Longer fire intervals are likely to maintain resilience given changing climate.
Broad-scale forest restoration projects are implemented across the western United States to restore seasonally dry, frequent-fire-adapted ecosystems to improve ecological function and enhance resilience by increasing resistance to crown fire and climatic stressors. Despite the widespread use of restoration treatments that center on tree thinning and application of prescribed fire, the longevity of beneficial effects and the robustness of outcomes under future climate change predictions remains unclear. In this study, we remeasured a set of experimental areas established a minimum of 20 years ago that comprise a network of ponderosa pine (Pinus ponderosa) forest restoration study sites in northern Arizona. We analyzed ecological resiliency by evaluating forest conditions in terms of resistance to climatic stressors and potential crown fire in units that were thinned following evidence-based restoration guidelines (ERG), then burned with prescribed fire at multiple intervals, compared against paired untreated controls. Resilience indicators included forest structure, tree mortality, tree growth, regeneration, canopy fuels, and crowning index. We also simulated future forest conditions under a warming climate scenario (RCP 4.5) with a range of prescribed fire return intervals. Results indicated that experimental areas where restoration treatments were implemented remained more resilient to climate stressors compared to controls after 20 years. Treated areas had significantly lower tree mortality and greater average diameter growth compared to controls. Furthermore, forest structure generally remained similar to historical reference conditions in treated units with the exception of increases in ingrowth of sprouting species at the drier sites. Canopy fuel load and crown fire hazard in treated units remained significantly lower than controls, indicating that treatments remained effective in reducing crown fire potential over the 20-year study period without the need for additional tree thinning. Modeling basal area, crowning index, and the proportion of basal area in large trees under a future warming scenario suggested that the treated units underwent less changed than untreated areas. Under climate change, management of fire regimes even at longer-than-historical intervals (historical ≈ 5 yr, tested 5, 10, and 20 yr) would maintain basal area within our historical range of variability and maintain fire resistant forest over the next several decades. However, decline by the end of the century is concerning. Our results suggest that forest restoration treatments, guided by historical reference conditions, promote ecological resilience in the long-term and continued maintenance burning into the future is likely warranted even with continued drought and warming.
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•Line-intercept tree canopy cover was measured on 1706 inventory plots across Oregon.•Predictors included crown width equations, crown overlap functions, and stand metrics.•The most ...accurate crown width approach adjusted for social position and capped sums.•Random crown overlap only performed well in low cover, drier forest types.•Statistical models were more precise, but crown width sums are simpler and flexible.
Quantifying tree canopy cover is fundamental to applications in forestry and ecology, but estimates vary substantially depending on type of field measurement, imagery, or active sensing used. Our objective was to improve estimates of stand-level canopy cover from standard tree inventory measurements, using representative data collected across diverse forest plant association groups across Oregon, USA. Canopy cover was measured with line intercept sampling on 1706 inventory plots and compared to calculations from individually tallied trees. We investigated adjustments of tree crown area equations, adjustments of crown overlap factors, and modeling from climatic variables and standard forest measurements to estimate line intercept cover. Estimates based on simple crown width equations adjusted for tree social position and caps on maximum cover, had the lowest error (RMSE = 14% cover) of crown width approaches across all vegetation types. Random crown overlap applied to unadjusted crown area only performed well in drier forest types and was unable to match high line intercept cover levels (>90%) often found in productive forest types. Although statistical models had somewhat greater precision than the simpler crown-width summation approaches (RMSE of 12%), accuracy was comparable. The greater flexibility of crown width summation approaches could make them more useful in forestry applications and beyond our study area.
•Mechanical thinning can moderate fire behavior in the absence of prescribed fire.•Fuel loading in a dry ponderosa pine forest increased for a year or two after thinning and then declined.•Woody fuel ...particles increased somewhat following thinning but litter and duff fuel loading declined dramatically as a result of thinning.•Prescribed fire treatments are useful for extending the longevity of fuel treatments after significant conifer regeneration.
Reducing fuels to better manage risk of high severity wildfire in seasonally dry, fire-prone forests of the western U.S. is an important goal of forest managers, including private landowners, non-governmental organizations, tribal, state, and local governments, and federal agencies. Managing fire risk is a critical objective of the U.S. Forest Service, which emphasizes the use of thinning to reduce tree density and ladder fuels followed by prescribed fire to reduce surface fuel. But the area of Forest Service land treated with thinning and prescribed fire is lagging far behind the area treated only with mechanical thinning due to regulatory and logistical challenges in prescribed fire implementation. Determining if mechanical thinning alone (without prescribed fire) can achieve adequate fire risk reduction has important implications for addressing the fire and fuel management goals set by Congress and the Administration, as well as the management objectives set by non-federal actors. In this study, we report on the effects of mechanical thinning and standard post-thinning fuels management but without prescribed fire on modeled fire behavior and changes in fuel loading over time in a ponderosa pine forest in Eastern Oregon. Thinning without prescribed fire significantly reduced potential crown fire immediately following thinning and also moderated surface modeled fire behavior beginning 2–3 years following thinning. Although small (<7.6 cm diameter) woody surface fuel loading increased following thinning, other ground and surface fuels (i.e., litter and duff) declined substantially, which we attribute to surface disturbance from ground-based logging, decreased deposition of litter, and increased decomposition. These results suggest that fuel reduction and fire risk management objectives can be met with mechanical thinning alone for a number of years. Prescribed fire is likely necessary to extend the effectiveness of mechanical thinning after significant tree or shrub regeneration. Continued monitoring will allow managers to use prescribed fire most efficiently to achieve fire and fuel management objectives.
•Recent forest changes in relation to climate change were investigated for the first time in Romania.•Countrywide NDVI and climate data were processed within forest boundaries between 1987 and ...2018.•General greening (increasing NDVI in 65% of all ecological changes) of forests were detected nationally.•Browning (35% decreasing NDVI) trends were found regionally, mainly in the lowland areas of Romania.•National/regional greening/browning trends are mainly explained by climate warming/evapotranspiration increases.
Forests have become increasingly stressed by climate change, including in Romania over recent decades, but their response to climate dynamics has not yet been analysed in this country. This study aims to investigate, for the first time, recent ecological changes in forests across Romania, in relation to climate dynamics that affected the country from 1987 to 2018. To this end, countrywide remote sensing (Landsat) data were processed for forest boundaries over the 32 years, in order to compute annual (summer season data) Normalized Difference Vegetation Index (NDVI) datasets, which were subsequently investigated as trends using the Mann-Kendall test and Sen's slope estimator. Simultaneously, various climatic data (temperature, precipitation and reference evapotranspiration) were processed through interpolation techniques and via the same two statistical tools, and were subsequently used for exploring the impact of climate change on Romanian forestlands after 1987. The results highlighted general greening (increasing NDVI) trends of forests nationally (65% of all NDVI changes, which total over 30.000 km2 across Romania), which were dominated by widespread positive NDVI trends detected in the Carpathians region of Romania. This general ecological dynamic suggests a possible enhancement in vegetation productivity in the country’s high-altitude areas. Contrasting browning (decreasing NDVI) trends were found for 35% of Romanian forestlands marked by NDVI changes, especially apparent in the Extra-Carpathians (lowland) region, which indicates that in these cases forests were degraded or devitalized. However, the statistical significance of both greening and browning trends is limited across the country. The analysis of climatic trends and of correlations between annual NDVI and climate data indicated that recent warming throughout Carpathians may be an important driving force of forest greening in temperature-limited mountain regions. This finding is supported by an at least moderate intensity of air temperature – NDVI relationships (r correlation coefficient values of ∼50%, the highest of all eco-climatic relationships analysed), generally detected throughout mountain environments. At the same time, it seems that evapotranspiration increase accounted at least in part for forest browning in lowland areas, while the impact of precipitation in forest ecological dynamics remains unclear. All these findings can be useful for a better forest management under the future climate change conditions in Romania.
Biogenic volatile organic compounds (BVOCs) have significant effects on atmospheric chemistry, ozone formation and secondary organic aerosol formation. Considering few investigations about BOVCs ...emissions in north China where is facing serious air pollution in recent years, emissions of various BVOCs from 24 dominant forest species in Beijing were measured from June to September in 2018, using a dynamic headspace sampling method. More than one hundred BVOCs in the collected samples were identified by using an automatic thermal desorption-gas chromatography/mass spectrometry, and their emission rates based on leaf biomass were calculated. Isoprene and monoterpenes were verified to be the dominant BVOCs emitted from the tree species, accounting for more than 50% of the total BVOCs. Generally, broad-leaved species displayed high isoprene emission rates, especially the Platanus occidentalis (21.36 µg/(g⋅hr)), Robinia pseudoacacia (11.55 µg/(g⋅hr)), and Lonicera maackii (9.17 µg/(g⋅hr)), while coniferous species emitted high rates of monoterpenes, such as Platycladus orientalis (27.18 µg/(g⋅hr)), Pinus griffithii (23.11 µg/(g⋅hr)), and Pinus armandii (7.42 µg/(g⋅hr)). High emission rates of monoterpenes from the broad-leaved species of Buxus megistophylla (13.07 µg/(g⋅hr)) and Ligustrum vicaryi (5.74 µg/(g⋅hr)), and high isoprene emission rate from the coniferous tree of Taxus cuspidata (5.86 µg/(g⋅hr)) were also observed. The emission rates of sesquiterpenes from each tree were usually 10–100 times smaller than those of isoprene and monoterpenes. Additionally, relatively high emission rates of oxygenated volatile organic compounds and other alkenes than isoprene and monoterpenes were also found for several tree species.
BVOCs emission rates from 24 dominant tree species in Beijing. Display omitted
To explore the carbon sequestration potential of hardwood forests in the eastern United States, the forest vegetation simulator (FVS) and life cycle assessment (LCA) were integrated to analyze the ...forest carbon dynamics for the four subregions of the eastern United States: northeast (NE), mid-Atlantic (MA), southeast (SE), and north central (NC). This study quantitatively assessed current forest management practices for timber production and their associated life-cycle environmental impacts. The system boundary was selected to be consistent with the A1 module (extraction and upstream production) required by an Environmental Product Declaration (EPD) for wood products. The results indicate that uneven-aged (UA) forest management yields higher carbon stocks and growth than even-aged (EA) management across all subregions. In contrast, clearcutting under EA management results in higher carbon removal. It was found that fuel consumption-related greenhouse gas (GHG) emissions for manual and mechanized harvesting systems for both management types ranged between 9.13 and 12.15 kg of CO2 equivalent per cubic meter (kg CO2e/m3), with an average of 11 kg CO2e/m3 of hardwood timber harvested across all subregions. It is estimated that 63–187 megajoules (MJ) of energy is needed to produce 1 m3 of hardwood sawlogs. The extraction and loading processes contributed more to the total GHG emissions than the felling and processing within the system boundary. The study concludes that UA management led to higher forest carbon and net carbon balance (excluding carbon stock) compared to EA management in the eastern U.S. hardwood forests. Forest management strategies should be determined based on the ecological goal of increasing forest carbon stock and the economic goal of maximizing revenue from the timber market. The findings of this study have implications for policymakers and forest managers in mitigating climate change and carbon sequestration through sustainable forest management for timber production.
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•LCA was integrated with FVS to analyze the carbon sequestration potential of hardwood forests in the eastern United States.•GHG emissions from manual and mechanized harvesting systems ranged from 9.13 to 12.15 kg CO2e/m3.•Uneven-aged management resulted in a forest carbon balance of 7.72 kg/m2 and a net carbon balance of 1.69 kg/m2 for the 9.99 × 1011 m2 hardwood forests in the eastern United States annually.•Even-aged management yielded a carbon balance of 6.20 kg/m2 and a net carbon balance of 0.91 kg/m2 for the 9.99 × 1011 m2 hardwood forests in the eastern United States annually.•The Fire and Fuels Extension of FVS did not account for soil carbon, encompassing both dead tree roots and live tree fine roots.
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•We built a new forest landscape management model that leveraged existing US Forest Service models.•The model was used to simulate wildfires and landscape restoration over 50 ...yrs.•High levels of management eliminated the restoration backlog in 20 years.•Wildfire activity was highly stochastic among replicate scenarios.•Management was more effective at reducing fire intensity compared to burned area.
We integrated a widely used forest growth and management model, the Forest Vegetation Simulator, with the FSim large wildfire simulator to study how management policies affected future wildfire over 50 years on a 1.3 million ha study area comprised of a US national forest and adjacent lands. The model leverages decades of research and development on the respective forest growth and wildfire simulation models, and their integration creates a strategic forest landscape model that has a high degree of transparency in the existing user communities. The study area has been targeted for forest restoration investments in response to wildland fires that are increasingly impacting ecological conditions, conservation areas, amenity values, and surrounding communities. We simulated three alternative spatial investment priorities and three levels of management intensity (area treated) over a 50-year timespan and measured the response in terms of area burned, fire severity, wildland-urban interface exposure and timber production. We found that the backlog of areas in need of restoration on the national forest could be eliminated in 20 years when the treatment rate was elevated to a maximum of 3× the current level. However, higher rates of treatments early in the simulation created a future need to address the rapid buildup of fuels associated with understory shrub and tree regeneration. Restoration treatments over time had a large effect on fire severity, on average reducing potential flame length by up to 26% for the study area within the first 20 years, whereas reductions in area burned were relatively small. Although wildfire contributed to reducing flame length over time, area burned was only 16% of the total disturbed area (managed and burned with prescribed fire) under the 3× management intensity. Interactions among spatial treatment scenarios and treatment intensities were minimal, although inter-annual variability was extreme, with the coefficient of variation in burned area exceeding 200%. We also observed simulated fires that exceeded four times the historically recorded fire size. Fire regime variability has manifold significance since very large fires can homogenize fuels and eliminate clumpy stand structure that historically reduced fire size and maintained landscape resiliency. We discuss specific research needs to better understand future wildfire activity and the relative influence of climate, fuels, fire feedbacks, and management to achieve fire resiliency goals on western US fire frequent forests.
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