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Background: Extreme wildfires have increased in recent decades, yet the consequences of extreme fire behaviour are not fully comprehended. The study of prescribed burning provides opportunities to advance understanding of some overlooked processes in fire behaviour, such as the role of the release of volatile organic compounds (VOC). Aims: The aim of this study was to assess VOC (α-pinene, β-pinene, and limonene), NH3, CO and CO2 emissions during prescribed fires in pine barrens vegetation at the Albany Pine Bush Preserve, USA. Methods: Measurements performed by open-path Fourier transform infra-red spectroscopy (OP-FTIR) quantified VOC concentrations and characterised emissions during four independent prescribed burns. Key results: Combustion products (e.g. CO2, CO, CH4) and VOC exhibited similar emission behaviour during thermal degradation, though VOC concentrations appeared to be independent of the type of biomass burned, unlike those of combustion products; Pinus strobus L. emitted two orders of magnitude higher than Pinus rigida Mill.; VOC and CO are statistically correlated (R 2 = 0.84). Conclusions: These results confirmed that OP-FTIR is a feasible approach for gathering qualitative and quantitative information regarding VOC emission during prescribed fires. Implications: Quantification of VOC concentrations during prescribed fires helps characterise its relationships with greenhouse gas emissions (e.g. CO2 and CO) at different burning conditions (e.g. wind, biomass type), which could be incorporated into existing fire behaviour models to enhance their ability to better predict fire propagation. Using Albany Pine Bush Preserve (USA) as a case study, this research reports the potentiality of an open-path Fourier transform methodology to assess the trends of volatile organic compounds emissions during prescribed fires. [ABSTRACT FROM AUTHOR]

Copyright of Revista de Ciências Agrárias is the property of Sociedade de Ciencias Agrarias de Portugal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Revista de Ciências Agrárias is the property of Sociedade de Ciencias Agrarias de Portugal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Forest certification is a voluntary conservation tool that aims to promote sustainable forest management. While research on forest certification has increased recently, there remains a significant gap in understanding how and to what extent certification can promote forest conservation. Mediterranean cork oak open woodlands are ecosystems of high conservation and socio-economic value. However, these ecosystems are threatened by increased adult oak mortality and regeneration failure, often due to inadequate management and the rise of pests and diseases, aggravated by climate change. Forest certification prescribes management practices intended to enhance tree regeneration and maintain stand health conditions. Therefore, it is anticipated that forest certification could mitigate the observed decline of oak trees in Mediterranean regions. Here, we investigate whether forest certification contributes to the ecological sustainability of Mediterranean cork oak open woodlands in Portugal. We compare the stand biometrics of non-certified and certified cork oak stands before and after certification implementation, using both National Forest Inventory data and field sampling from 2005 and 2020. Our findings indicate that the density of adult oak trees decreased by 16 % in certified estates and 28 % in non-certified estates between 2005 and 2020. Similarly, cork oak cover declined by 6 % tree cover in certified plots and 19 % in non-certified plots during the same period. Consequently, by 2020, tree density was 20 % higher in certified stands than in the non-certified ones, and tree cover was 36 % higher in certified stands. Tree diameter and height increased at similar rates in both certified and non-certified stands from 2005 to 2020.The age structure of the stands also remained consistent, showing a bell-shaped distribution of tree diameters in both years. However, results on oak regeneration were inconclusive. Our results suggest that cork oak decline, measured by the changes in density and cover of adult trees from 2005 to 2020, is slower in certified cork oak woodlands. Nonetheless, the increase in tree diameter and the age structure shape indicate potential regeneration issues in both certified and non-certified stands, needing further measures to address the aging of cork oak open woodlands. • Cork oak tree density decreased between 2005 and 2020 throughout the study area. • The decrease in cork oak density was greater in non-certified stands than in certified stands. • In 2020, certified cork oak stands had a higher tree density and cover. • Certification is contributing to mitigating the decline of cork oak woodlands. [ABSTRACT FROM AUTHOR]

Copyright of Silva Lusitana is the property of Unidade de Investigacao de Silvicultura e Productos Florestais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bulk density for shrubs and tree crowns is an important variable, useful for many purposes, namely estimations for biomass and carbon sequestration and potential fire behavior prediction. In the latter case, bulk density is required to predict the rate of spread and intensity of crown fires. However, bulk density information is scarce. The estimation of bulk density is crucial to help choosing proper pyrosilviculture options to decrease fire susceptibility. Due to the similar environmental conditions and fuel characteristics in Portugal and Spain, we modelled bulk density for the most common woody species in all the Iberian Peninsula. We used 10 different shrub type formations and a set of tree species or groups common to both countries. Equations for bulk density, in both forest canopy and understory layers, were fitted as a function of biometric variables commonly used in forest inventories for the selected species. Standardized estimates of bulk density can be associated with data from the National Forest Inventories from Portugal and Spain, to estimate biomass of the forest ecosystems and to evaluate potential fire behavior involving tree canopies and shrubs. [ABSTRACT FROM AUTHOR]

Copyright of Silva Lusitana is the property of Unidade de Investigacao de Silvicultura e Productos Florestais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Studies about the productivity of forest ecosystems help to quantify sequestered carbon and provide data that are used in forest management. Forests in northern Portugal are an important economic resource, but their productivity in scenarios of future climate change is not yet well understood. The objectives of this study were to evaluate and compare simulated net primary production (NPP) and NPP based on measured data of two tree species located in the Vila Real district forests, pine (Pinus pinaster Aiton) and oak (Quercus pyrenaica Willd.) and assess their simulated NPP in diverse climate conditions, including future climate scenarios and increasing atmospheric CO2 concentrations. An ecosystem process model, Biome-BGC, which simulates carbon, nitrogen and water cycles of forest ecosystems close to equilibrium conditions, was used to examine the importance of site and ecophysiological factors on the productivity of these forests. Climate change scenarios and increased CO2 concentrations were tested to explore potential responses of the studied species. The model provided good estimates of NPP. There was a strong correlation between the simulated and measured NPP values in the pine (15) and oak (15) stands. The NPP of these forests are predicted to increase in the future with a CO2 increase whereas in a climate with higher temperature and lower soil moisture, the NPP will decrease. These results confirm that precipitation is a very important climate variable to growth and productivity in the Mediterranean forest ecosystems. This study also demonstrated the ability of Biome-BGC to accurately simulate forest ecosystems behaviour and encourages the application of model simulations in Portugal. [ABSTRACT FROM AUTHOR]

Forest leaf area index (LAI) is an important structural parameter controlling many biological and physiological processes associated with vegetation. A wide array of methods for its estimation has been proposed, including those based on the sunfleck ceptometer, a ground-based easy-to-use device taking non-destructive LAI measures. However, use of ceptometer in pine stands leads to the underestimation of LAI due to foliage clumping of this species. Previous studies have proposed a correction of biased LAI estimates based on the multiplication by a constant factor. In this study, a new method for obtaining a correction factor is proposed by considering the bias (the difference between the ceptometer measure and the reference LAI) as a function of the stand structural variables, namely the basal area. LAI data were collected from 102 sampling plots (age range: 14-74) established in Pinus pinaster forests all across northern Portugal. Data from 82 sampling plots were used for the adjustment of the LAI ceptometer correction model, while the remaining 20 plots were used for the model validation. The observed LAI ranged from 0.34 to 6.4 as expected from the large heterogeneity of the sampled pine stands. Significant differences were detected between LAI values estimated by ceptometers and LAI reference values. Different correction methods have been compared for their accuracy in predicting LAI reference values. Based on the results of the statistical analysis carried out, the new proposed LAI correction outperformed all the other methods proposed so far. The new approach for bias reduction proposed here has the advantage of being easily applied since the basal area is almost always available from forest inventory or can be inferred from remote sensing surveys. However, the bias correction model obtained is site-specific, being dependent on stand species composition, soil fertility, site aspect, etc. and should therefore be applied only in the study area. Nonetheless, the development of a correction methodology based on an allometric approach has proved to greatly improve LAI ceptometer estimations. [ABSTRACT FROM AUTHOR]

Since the late 1980's the productivity of monocultures vs. mixed-species forests has been the subject of studies by forest managers and ecologists. Mixed plantations have been established in different proportions to determine if mixtures could provide greater yields and more benefits than monocultures of the component species, as well as to understand if they could be an interesting economic option. An experimental design trial was set up in the north of Portugal in a replacement series with pure and mixed Castanea sativa Mill. and Pseudotsuga menziesii (Mirb.) Franco. The objective of this study was to assess growth dynamics and compare the aboveground biomass and net primary production of the two species in pure and mixed treatments in proportions 1:1 and 1:3. The growth was measured at 7, 11, 15, 17, 19, 27 and 28 years after planting and aboveground net primary production was estimated at age 28. As a component of the mixed treatments, P. menziesii exhibited greater height, diameter and aboveground biomass than C. sativa. Relative yield total indicated a higher productivity in the mixtures compared with the pure treatments. Early in the development, pure treatments and mixtures had similar aboveground biomass per hectare, but later the mixtures showed higher yield than pure treatments. The mixture productivity increase through time appears to be the result of both canopy stratification and better use of site resources. The aboveground net primary production was also higher in mixed than in the pure treatments. [ABSTRACT FROM AUTHOR]

Highlights: [•] Estimation of aboveground biomass and net primary production of pine, oak and pine–oak mixed stands. [•] Mixed stands had significantly higher ANPP than the pure stands. [•] Aboveground biomass was not significantly different among the 3 stands types. [•] Stem NPP in mixed stands lower for each species than in pure stands. [•] Production efficiency was significantly greater for mixed stands. [Copyright &y& Elsevier]

Copyright of Silva Lusitana is the property of Unidade de Investigacao de Silvicultura e Productos Florestais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Silva Lusitana is the property of Unidade de Investigacao de Silvicultura e Productos Florestais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Silva Lusitana is the property of Unidade de Investigacao de Silvicultura e Productos Florestais and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

National Forest Inventories (NFIs) collect and provide a large amount of information regarding the forest volume, carbon stocks, vitality, biodiversity, non-wood forest products and their changes. Forest stands variables data are paramount to understanding their composition, especially on those related with understory characteristics and the coverage of species according to canopy layers; they are essential to assess biodiversity and to support forest management. At the same time, these inventories allow the development of harmonized forest descriptions beyond the national scale. This study aims to develop a homogeneous characterization of the Iberian Peninsula's forests, in order to classify and identify the forest types. For this purpose, harmonized data from NFIs of Portugal and Spain were used to assess the composition of species, dominance and the percentage of cover for each species in a vertical space defined by seven canopy layers. Using the "K-means" clustering algorithm, a set of clusters was identified and georeferenced using forest polygons from land use and cover maps of both countries. The interpretation and description of the clusters lead to the establishment of 28 forest types that characterize all of the Iberian Peninsula forests. Each forest area has been described through one of the forest types and their relation with other ecological characteristics of the stands was analyzed. Shrubs formations are generally widely distributed in the forest area of the Iberian Peninsula, however their abundance in terms of cover is lower in comparison with tree species. Around 71% of the forest types are dominated by trees, mainly species from the genera Pinus and Quercus, and 21% are dominated by shrub formations with species of Ulex spp., Cytisus spp., and Cistus spp. The Quercus ilex s.l. L. and Pinus pinaster Aiton are the common species of importance for both NFIs. The results represent a powerful and homogenous multi-use tool describing the Iberian Peninsula's forestlands with applications on landscape analysis, forest management and conservation. This information can be used for comparisons at larger scales, allowing cross-border analysis in relation to various aspects, such as hazards and wildfires, as well as management and conservation of forest biodiversity. The developed method is adaptable to an updated dataset from more recent NFIs and to other study areas. [ABSTRACT FROM AUTHOR]

Key message: There is a need to improve the consistency of international information concerning the conservation status assessment of the species and habitat types in the Natura 2000 reports. National Forest Inventories could contribute towards a more objective and harmonised assessment although their use shows some challenges as low precision for rare or small area habitats. Recommendations for a set of 12 structural and functional indicators are provided. Context: There are differences among Member States as regards applying conservation status assessment and priorities according to the Directive on the conservation of natural habitats (Habitats Directive). Aims: This paper aims to analyse the consistency as regards forest habitat types reporting and the use and suitability of National Forest Inventories (NFIs) to assess their conservation status, as well as to provide recommendations for harmonised assessments through NFIs. Methods: A survey was carried out concerning the use of NFI data to report within the commitments of the Habitat Directive. The survey covered 13 European countries, accounting for 62% of forest habitat area. Additionally, case studies were carried out in four countries. Results: The identification of forest habitat types and the set of quantitative and/or qualitative indicators differ between countries. The use of NFI data is being considered in seven countries and it is expected to increase for the 2013–2018 reporting period. The main challenges reported of use of NFI data are related to the habitat identification and their mapping, and the monitoring frequency, design and costs (i.e. rare or small area habitats). Conclusion: It is necessary to improve the comparability of the conservation status assessments between countries. [ABSTRACT FROM AUTHOR]