Testing visible ozone injury within a Light Exposed Sampling Site as a proxy for ozone risk assessment for European forests

Biologically meaningful and cost-effective indicators are needed for assessing and monitoring the impacts of tropospheric ozone(O_3) on vegetation and are required in Europe by the National Emission Ceilings Directive(2016).However,a clear understanding on the best suited indicators is missing.The MOTTLES(MOnitoring ozone injury for seTTing new critical LEvelS) project set up a new generation network for O_3 monitoring in forest plots in order to:1) estimate the stomatal O_3 fluxes(Phytotoxic Ozone Dose above a threshold Y of uptake,PODY);and 2) collect visible foliar O_3 injury,both within the forest plot(ITP) and along the Light Exposed Sampling Site(LESS) along the forest edge.Nine forest sites at high O_3 risk were selected across Italy over 2017-2019 and significant correlations(p 0.05) were found between the percentage of symptomatic plant species within the LESS,and POD1(PODY,with Y=1 nmol O_3 m~(-2) s~(-1)) calculated for mixed forest species(r=0.53)and with the occurrence and severity of visible foliar O_3 injury on the dominant species in the plots(r=0.65).A generic flux-based critical level for mixed forest species was derived within the LESS and it was recommended using11 mmol m~(-2) POD1 as the critical level for forest protection against O_3 injury,similar to the critical level obtained in the ITP(12 mmol m~(-2) POD1).It was concluded that the frequency of symptomatic plant species within a LESS is a suitable and effective plant-response indicator of phytotoxic O_3 levels in forest monitoring.LESS is a non-destructive,less complex and less time-consuming approach compared to the ITP for monitoring foliar O_3 injury in the long term.Assessing visible foliar O_3 injury in the ITP might only underestimate the O_3 risk assessment at individual sites.These results are biologically meaningful and useful to monitoring experts and environmental policy makers.     

Modelling drainage fluxes in managed and natural forests in the Dinaric karst: a model comparison study

Two models for calculating the forest water balance were applied to different development stages of managed and non-managed forests in the Dinaric Karst for two hydrologically contrasting growing seasons. A simple model WATBAL, which calculates water balance on a monthly basis, and the BROOK90 model, which calculates water balance on daily basis, were used. Differences between calculated drainage fluxes between the models were less pronounced in the drier growing season and were lower in the forest stands compared to forest gaps. Average calculated drainage fluxes of the two growing seasons were highest in the gaps and lowest in the stand in the virgin forest remnant, followed by the mature stand in the managed forest. According to model fitting, testing the calibration robustness and sensitivity analysis the BROOK90 model was considered best at simulating the water balance of the various research sites. The difference in model behaviour is considered to be mainly the result of the difference in model time step and the inclusion of macropore flow in BROOK90. The greater complexity of the BROOK90 model meant it could be parameterized to describe more fully the complexity of the horizontal and vertical structure of forest stand and soil properties. A disadvantage of the BROOK90 model is the greater need of input data. WATBAL, however, was useful for obtaining rougher estimates of the water balance components and can be applied to areas where there is less data available. Choice of model is therefore determined by data availability.     

Component and whole-system respiration fluxes in northern deciduous forests

We measured component and whole-system respiration fluxes in northern hardwood (Acer saccharum Marsh., Tilia americana L., Fraxinus pennsylvanica Marsh.) and aspen (Populus tremuloides Michx.) forest stands in Price County, northern Wisconsin from 1999 through 2002. Measurements of soil, leaf and stem respiration, stem biomass, leaf area and biomass, and vertical profiles of leaf area were combined with biometric measurements to create site-specific respiration models and to estimate component and whole-system respiration fluxes. Hourly estimates of component respiration were based on site measurements of air, soil and stem temperature, leaf mass, sapwood volume and species composition. We also measured whole-system respiration from an above-canopy eddy flux tower. Measured soil respiration rates varied significantly among sites, but not consistently among dominant species (P < 0.05 and P > 0.1). Annual soil respiration ranged from 8.09 to 11.94 Mg C ha(-1) year(-1). Soil respiration varied linearly with temperature (P < 0.05), but not with soil water content (P > 0.1). Stem respiration rates per unit volume and per unit area differed significantly among species (P < 0.05). Stem respiration per unit volume of sapwood was highest in F. pennsylvanica (up to 300 micro mol m(3) s(-1)) and lowest in T. americana (22 micro mol m(3) s(-1)) when measured at peak summer temperatures (27 to 29 degrees C). In northern hardwood stands, south-side stem temperatures were higher and more variable than north-side temperatures during leaf-off periods, but were not different statistically during leaf-on periods. Cumulative annual stem respiration varied by year and species (P < 0.05) and averaged 1.59 Mg C ha(-1) year(-1). Leaf respiration rates varied significantly among species (P < 0.05). Respiration rates per unit leaf mass measured at 30 degrees C were highest for P. tremuloides (38.8 nmol g(-1) s(-1)), lowest for Ulmus rubra Muhlenb. (13.1 nmol g(-1) s(-1)) and intermediate and similar (30.2 nmol g(-1) s(-1)) for T. americana, F. pennsylvanica and Q. rubra. During the growing season, component respiration estimates were dominated by soil respiration, followed by leaf and then stem respiration. Summed component respiration averaged 11.86 Mg C ha(-1) year(-1). We found strong covariance between whole-ecosystem and summed component respiration measurements, but absolute rates and annual sums differed greatly.     

Deciphering the ozone-induced changes in cellular processes: a prerequisite for ozone risk assessment at the tree and forest levels

Key message

Ozone, one of the major atmospheric pollutants, alters tree growth, mainly by decreasing carbon assimilation and allocation to stems and roots. To date, the mechanisms of O₃ impact at the cellular level have been investigated mainly on young trees grown in controlled or semi-controlled conditions. In the context of climate change, it is necessary to introduce a valuable defence parameter in the models that currently predict O₃ impact on mature trees and the carbon sequestration capacity of forest ecosystems.

Context

Air pollution is an important factor that affects negatively forest ecosystems. Among oxidative air pollutants, ozone is considered as the most toxic in terms of impact on vegetation.

Aims

This paper focuses on the negative impacts of ozone on trees in controlled conditions or in their natural environment. The current knowledge of the responses at cell level is presented and ways to improve their use for ozone risk assessment of forest stands are discussed.

Methods

Information was collected from original papers or reviews, providing an overview of the research conducted over the last 60 years.

Results

The negative effects of ozone on carbon assimilation and tree biomass production were reviewed and discussed, with a focus on effects on cell processes implied in cell defence, including stomatal regulation, detoxification, signalling, and biosynthesis of wood compound.

Conclusion

In the context of increasing significance of O₃ flux approach, this review intends to shed light into the black box of defence processes, which are playing a crucial part within the effective O₃ dose modelling. Today, it is recognized that tropospheric ozone inhibits tree growth and its role on the future carbon sink of the forest ecosystem is discussed along with the combination of other environmental factors like elevated temperature, water, and nitrogen supply, likely to be modified in the context of climate change.

     

Mixed forests to mitigate risk of insect outbreaks

The majority of agricultural and forest production systems are typically simplified systems and therefore thought to be sensitive to disturbance. Ecosystems might be less sensitive to disturbance if complexity increases. The resource concentration hypothesis predicts that complexity makes it more difficult for herbivores to find and exploit their food. The natural enemy hypothesis predicts less damage in diverse environments because enemy abundance and diversity remain higher and more stable in environments providing more alternative food sources. We explore the effect of tree diversity in two types of pine stands differing in tree diversity. We ask whether European pine sawfly (Neodiprion sertifer) larval group distribution and larval mortality, imposed by specialist natural enemies, is affected by tree diversity. We find fewer larval groups on pine trees surrounded by non-host trees, indicating that fewer egg-batches were laid. Mortality rates by specialist enemies are not affected by tree diversity but parasitism rates are likely to be higher in larger trees. Herbivores are inhibited by increased tree diversity and density, whereas natural enemies seem to be unaffected, partly increasing the resistance of more diverse forest stands against insect damage. Thus, managing for more mixed forests could mitigate risk of herbivore damage.     

Epidemiological derivation of flux-based critical levels for visible ozone injury in European forests

The European MOTTLES project set-up a newgeneration network for ozone(O_3) monitoring in 17 plots in France, Italy and Romania. These monitoring stations allowed:(1) estimating the accumulated exposure AOT40 and stomatal O_3 fluxes(PODY) with an hourly threshold of uptake(Y) to represent the detoxifi cation capacity of trees(POD1, with Y = 1 nmol O_3 m~(-2) s~(-1) per leaf area); and(2) collecting data of forest-response indicators, i.e. crown defoliation and visible foliar O_3-like injury over the time period 2017–2019. The soil water content was the most important parameter aff ecting crown defoliation and was a key factor aff ecting the severity of visible foliar O_3-like injury on the dominant tree species in a plot. The soil water content is thus an essential parameter in the PODY estimation, particularly for water-limited environments. An assessment based on stomatal flux-based standard and on real plant symptoms is more appropriated than the exposure-based method for protecting vegetation. From flux-eff ect relationships, we derived flux-based critical levels(CLef) for forest protection against visible foliar O_3-like injury. We recommend CLef of 5 and 12 mmol m~(-2) POD1 for broadleaved species and conifers, respectively. Before using PODY as legislative standard in Europe, we recommend using the CLec for ≥ 25% of crown defoliation in a plot: 17,000 and 19,000 nmol mol~(-1) h AOT40 for conifers and broadleaved species, respectively.     

Sap flux in pure aspen and mixed aspen-birch forests exposed to elevated concentrations of carbon dioxide and ozone

Elevated concentrations of atmospheric carbon dioxide ([CO2]) and tropospheric ozone ([O3]) have the potential to affect tree physiology and structure and hence forest water use, which has implications for climate feedbacks. We investigated how a 40% increase above ambient values in [CO2] and [O3], alone and in combination, affect tree water use of pure aspen and mixed aspen-birch forests in the free air CO2-O3 enrichment experiment near Rhinelander, Wisconsin (Aspen FACE). Measurements of sap flux and canopy leaf area index (L) were made during two growing seasons, when steady-state L had been reached after more than 6 years of exposure to elevated [CO2] and [O3]. Maximum stand-level sap flux was not significantly affected by elevated [O3], but was increased by 18% by elevated [CO2] averaged across years, communities and O(3) regimes. Treatment effects were similar in pure aspen and mixed aspen-birch communities. Increased tree water use in response to elevated [CO2] was related to positive CO2 treatment effects on tree size and L (+40%). Tree water use was not reduced by elevated [O3] despite strong negative O3 treatment effects on tree size and L (-22%). Elevated [O3] predisposed pure aspen stands to drought-induced sap flux reductions, whereas increased tree water use in response to elevated [CO2] did not result in lower soil water content in the upper soil or decreasing sap flux relative to control values during dry periods. Maintenance of soil water content in the upper soil in the elevated [CO2] treatment was at least partly a function of enhanced soil water-holding capacity, probably a result of increased organic matter content from increased litter inputs. Our findings that larger trees growing in elevated [CO2] used more water and that tree size, but not maximal water use, was negatively affected by elevated [O3] suggest that the long-term cumulative effects on stand structure may be more important than the expected primary stomatal closure responses to elevated [CO2] and [O3] in determining stand-level water use under possible future atmospheric conditions.     

Risk assessment for biodiversity conservation planning in Pacific Northwest forests

Risk assessment can provide a robust strategy for landscape-scale planning challenges associated with species conservation and habitat protection in Pacific Northwest forests. We provide an overview of quantitative and probabilistic ecological risk assessment with focus on the application of approaches and influences from the actuarial, financial, and technical engineering fields. Within this context, risk refers to exposure to the chance of loss and typically involves likelihood estimates associated with outcomes. Risk assessment can be used to evaluate threats and uncertainty by providing: (1) an estimation of the likelihood and severity of species, population, or habitat loss or gain, (2) a better understanding of the potential tradeoffs associated with management activities, and (3) tangible socioeconomic integration. Our discussion is focused on threats identified as important influences on forest biodiversity in the region: natural, altered, and new disturbance regimes, and alien and invasive species. We identify and discuss three key challenges and opportunities specific to these threats and quantitative and probabilistic approaches to risk assessment: (1) endpoint selection and calculation of net value change, (2) probability calculations and stochastic spatial processes, and (3) evaluation of multiple interacting threats. Quantitative and probabilistic risk assessment can help bridge the current gap between information provided by general assessment and planning procedures and the more detailed information needs of decision and policy makers. However, management decisions may still fail to win public approval because important risks and issues can be missed or perceived differently by stakeholders. Stakeholder involvement at the inception of a risk assessment can help attenuate these problems. Stakeholder involvement also provides opportunities to communicate information that can influence public risk perceptions and attitudes.     

“3S”技术及其在林业的应用现状与展望

本文介绍了"3S"技术的的内涵及特点,从森林资源调查、森林资源动态监测、林业专题图的绘制等方面分析了"3S"技术在林业中的应用现状,并对"3S"技术的发展趋势作了展望。     

Long-term adaptation potential of Central European mountain forests to climate change: a GIS-assisted sensitivity assessment

An ecological risk assessment is described for determining the adaptation potential of the approximately 11 000 Swiss Forest Inventory points (FIP) to a hypothetically changing climate. The core of the study is a spatially explicit forest community model that generates estimates of the potential natural vegetation for the entire potential forest area of Switzerland under today's as well as under altered climate regimes. The model is based on the Bayes formula. The probabilities of the communities occurring along ecological gradients are derived from empirical data featuring the relationships between quasi-natural vegetation types and measured site variables. Bioclimatological input variables are the quotient between July temperature and annual precipitation (model version A) or mean annual temperature (model version B). Other site variables include aspect, acidity of top soil and, to account for continentality, geographical region. Climate change scenarios are defined as follows: ‘Moderate climate change’ implies an increase of the mean annual temperature of 4°C to 1.4°C depending on the region (model version B) or an increase of the July temperature of 1.5°C (model version A). ‘Strong climate change’ implies an increase of the mean annual temperature of 2°C to 2.8°C (model version B) or an increase of the July temperature of 3.0°C (model version A).

The simulation experiment showed that the geographical distribution of 15 potential natural forest types (distinguished on the basis of floristic affinities) varies considerably with changing temperature. Under moderate warming 30–55% of the FIP change their potential natural vegetation type, whereas under strong climate change the values increase to 55–89% depending on the model version used. In the ecological risk assessment the existing tree species composition on any FIP was compared with the expected tree species composition under today's as well as under altered climate regimes. A major finding indicated that, under the current climate conditions, approximately 25–30% (depending on the model version used) of all FIP must be considered as poorly adapted, i.e. less than 20% of the actual basal area consists of tree species that are expected as dominating taxa. This definition applies for trees with a diameter at breast height (DBH) ≥ 12 cm. Moderate warming increases the percentage of poorly adapted FIP by 5–10% (relative to all FIP considered), strong warming leads to a 10–30% increase of poorly adapted FIP (relative to all FIP considered). If trees with a DBH < 12cm are considered, the percentage of FIP that have to be classified as poorly adapted is reduced significantly. There are strong regional differences as exhibited in risk maps of 10 km × 10 km resolution.     

Modelling long-term impacts of environmental change on mid- and high-latitude European forests and options for adaptive forest management

The process based model SMART–SUMO–WATBAL was applied to 166 intensive monitoring forest plots of mid- and high-latitude Europe to evaluate the effects of expected future changes in carbon dioxide concentration, temperature, precipitation and nitrogen deposition on forest growth (net annual increment). These results were used in the large-scale forest scenario model EFISCEN (European Forest Information SCENario model) to upscale impacts of environmental change and to combine these results with adapted forest management. Because of the few plots available, Mediterranean countries were excluded from analyses. Results are presented for 109 million ha in 23 European countries.     

The impact of tropospheric ozone on landscape-level merchantable biomass and ecosystem carbon in Canadian forests

Studies have shown that tropospheric ozone (O₃) impacts trees in various ways, including growth reductions. To date, the landscape-level response of Canadian forests carbon (C) to O₃ exposure has not been quantified. We used a modified version of the Carbon Budget Model of the Canadian Forest Sector and data from Aspen FACE to quantify the landscape-level impacts of different O₃ exposure modelling experiments. The main strengths of our approach consisted of using the most complete empirical data available to estimate the amount and location of forest C across Canada, as well as explicitly simulating the consequences of fire, insect, and harvest disturbances on forest C dynamics. These disturbances lead to younger forests and, considering trees sensitivity to O₃ exposure to decrease with age, thus result in higher landscape-level modelled impacts for the same O₃ levels. Despite various sources of uncertainty, our results indicate that even under a modelling experiment where O₃ increases continuously over four decades, the landscape-level impacts on the merchantable biomass and ecosystem C remain limited. Our results also suggest that the current direct impacts of O₃ on Canadian forests are likely below detection at the landscape level.     

Wildland fires and moist deciduous forests of Chhattisgarh,India: divergent component assessment

We studied moist deciduous forests of Chhattisgarh, India （1） to assess the effect of four levels of historic wildland fire frequency （high, medium, low, and no-fire） on regeneration of seedlings in fire affected areas during pre and post-fire seasons, （2） to evaluate vegetation struc- ture and diversity by layer in the four fire frequency zones, （3） to evalu- ate the impact of fire frequency on the structure of economically impor- tant tree species of the region, and （4） to quantify fuel loads by fire fre- quency level. We classified fire-affected areas into high, medium, low, and no-fire frequency classes based on government records. Tree species were unevenly distributed across fire frequency categories. Shrub density was maximum in zones of high fire frequency and minimum in low- frequency and no-fire zones. Lower tree density after fires indicated that regeneration of seedlings was reduced by fire. The population structure in the high-frequency zone was comprised of seedlings of size class （A） and saplings of size class （B）, represented by Diospyros melanoxylon, Dalbergia sissoo, Shorea robusta and Tectona grandis. Younger and older trees were more abundant for Tectona grandis and Dalbargia sis- soo after fire, whereas intermediate-aged trees were more abundant pre- fire, indicating that the latter age-class was thinned by the catastrophic effect of fire. The major contributing components of fuel load included duff litter and small woody branches and twigs on the forest floor. Total fuel load on the forest floor ranged from 2.2 to 3.38 Mg/ha. The netchange in fuel load was positive in high- and medium-frequency fire zones and negative under low- and no-fire zones. Repeated fires, how- ever, slowly reduced stand stability. An ecological approach is needed for fire management to restore the no-fire spatial and temporal structure of moist deciduous forests, their species composition and fuel loads. The management approach should incorporate participatory forest manage- ment. Use of c     

Influence of plant communities and soil properties on trace gas fluxes in riparian northern hardwood forests

Wetlands contribute significant amounts of greenhouse gases to the atmosphere, yet little is known about what variables control gas emissions from these ecosystems. There is particular uncertainty about forested riparian wetlands, which have high variation in plant and soil properties due to their location at the interface between land and water. We investigated the fluxes of carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) and associated understory vegetation and soil parameters at five northern hardwood riparian sites in the Adirondack Park, NY, USA. Gas fluxes were measured in field chambers 4 times throughout the summer of 2008. CO₂ flux rates ranged from 0.01 to 0.10 g C m⁻² h⁻¹, N₂O fluxes ranged from −0.27 to 0.65 ng N cm⁻² h⁻¹ and CH₄ flux rates ranged from −1.44 to 3.64 mg CH₄ m⁻² d⁻¹. Because we observed both production and consumption of N₂O and CH₄, it was difficult to discern relationships between flux and environmental parameters such as soil moisture and pH. However, there were strong relationships between ecosystem-scale variables and flux. For example, CO₂ and N₂O flux rates were most strongly related to percent plant cover, i.e., the site with the lowest vegetation cover had the lowest CO₂ and highest N₂O emissions. These ecosystem-scale predictive relationships suggest that there may be prospects for scaling information on trace gas fluxes up to landscape and regional scales using information on the distribution of ecosystem or soil types from remote sensing or geographic information system data.     

A journey towards shared governance: status and prospects for collaborative management in the protected areas of Bangladesh

Establishment of Protected Areas (PAs), in the face of rapid deforestation, forest degradation and climate change has been one of the key efforts in conservation of biodiversity worldwide in recent times. While Bangladesh has gained a degree of prominence in the world for its successful social forestry programs, the concept of collaborative protected area management is rather new in the country, initiated in 2004 by the Bangladesh Forest Department in five PAs with financial assistance from USAID. Based on empirical evidence from three of the pilot PAs, we examined the achievements and associated challenges and prospects for co-management. Our fieldwork revealed a number of challenges faced by co-management institutions: (1) institutions were dominated by the elite group, overshadowing the voice of the community people; (2) mutual trust and collective performance are key to good governance but had not taken root in the PAs; (3) encroachment onto forest land and subsequent conversion to agriculture remained a serious problem that discouraged forest-dependent people from participating actively in co-management initiatives; (4) legal provisions (including acts, rules and policies) were not clearly and adequately disseminated and understood at the community level; (5) there remained a degree of ambiguity regarding the roles and responsibilities of forest department (FD) and co-management committees (CMC) in field operations, and this was not enhancing transparency and accountability of the overall initiative; (6) the long-term sustainability of co-management institutions was another major concern, as the local intuitional structure was still in a nascent stage, and provisioning of resources (either internally or externally) remained somewhat uncertain. We offer recommendations for improvement.     

Heterobasidion annosum root rot in Picea abies: Modelling economic outcomes of stump treatment in Scandinavian coniferous forests

Abstract

The economic outcomes of stump treatment against spore infections of the root rot pathogen Heterobasiodion annosum s. l. were analysed based on simulations in four stands typical of Swedish forestry and forest management: (A) Norway spruce [Picea abies (L.) Karst.] stand on former agricultural soil (SI?=?32), (B) Norway spruce stand (SI?=?26) on forest land; (C) Mixed stand of Norway spruce and Scots pine (Pinus sylvestris L.) (SI?=?24) with only H. parviporum present, i.e. no infection of Scots pine and no possibility of interspecies spread of disease between hosts; and (D) same as C, but H. annosum s. str. (Fr.) Bref and H. parviporum Niemelä & Korhonen present, i.e. interspecies spread of disease possible. Models for disease development, growth and yield and cross-cutting were used in the simulations. The simulated decay frequency in Norway spruce trees ranged between 2 and 90%. Stump treatment at the previous final felling and in all thinning operations was profitable at interest rates 1 and 3% in stands A, B and D, but not in stand C. In stand C, no stump treatment at all or treatment in thinnings only gave the highest net future value. Implications for stump treatment in practical forestry are discussed.     

浅谈光泽县油茶产业发展的现状与对策

通过对光泽油茶产业的现状分析,得出光泽油茶产业发展存在不成规模、产量和效益不高、缺乏油茶产品生产加工企业、科技含量不高、缺乏优良种苗的问题;提出了油茶产业发展的具体措施是要加强种苗的管理与监督、加大扶持力度、优化产业布局、强化科技支撑、建设优质高产示范基地、培育产业主体、加强行业指导。