There is much demand for forest information at the regional, national, and international level, covering aspects as varied as growing stock, carbon pools, and non-wood forest products, as well as ...information on forest biodiversity, risks, and disturbances, or social indicators ...
• Key message
The shrub species richness in Spanish forests is mainly linked to climatic variables and the importance of the groups of variables scarcely differs among forest types. Forest ...surrounding the Mediterranean Basin exhibit the highest levels of shrub richness.
• Context
Shrub species account for a high proportion of the plant diversity in Spanish forests and are a determinant factor in forest dynamics and ecosystem functionality.
• Aims
To investigate the relative importance of climatic, forest stand features, soil and topographic variables in explaining shrub richness in Spanish forests and if the relative importance of these four groups of variables reflects variations among forest types.
• Methods
We used the Spanish National Forest Inventory and a boosted regression trees approach to identify which climatic, soil, stand and topographic variables (
N
= 19 variables) are related to the richness of shrub species in Spanish woodlands.
• Results
The shrub species richness is mainly related to climatic variables followed by soil variables whereas stand and topographic variables play a minor role. The importance of the groups of variables scarcely differs among forest types although forests located around the Mediterranean Sea display the highest levels of shrub richness.
• Conclusion
Shrub richness in Spain is primarily driven by climatic and soil variables, both at country and forest-type scales. Forests surrounding the Mediterranean Basin account for the highest richness of shrub species but are also those most threatened by global change. Therefore, special attention must be paid to the monitoring and assessment of these forest ecosystems.
•Deadwood harmonization efforts by forest type.•We used National Forest Inventory deadwood data encompassing more than 55,000 plots.•We create bridge functions to convert deadwood measurements to 7.5 ...and 10.0 cm.•Bridge equations validation statistics indicate that the models performed adequately.•The standing deadwood trees proportion is not a good indicator of the total deadwood.
National as well as international requirements have led to an increased need to quantify deadwood stocks in forest ecosystems given their important role not only in terms of carbon storage and regulation of the carbon cycle but also as biodiversity refugia. However, differences in definitions and field monitoring as well as gaps in existing data on deadwood mean that comparisons among countries and retrospective analyses are difficult. In this research, we propose two potential approaches to solve the most common gaps in forest deadwood monitoring. First, we develop bridging functions capable of converting deadwood measurements with a specific reference diameter to 7.5 cm (minimum diameter value in Spain) and 10.0 cm (the most common minimum value for international statistics) diameters for the main forest types while also addressing the effect of raising the minimum measurable size on the quantification of deadwood. Furthermore, we aim to calculate the ratios between the amount of standing deadwood, the most common indicator monitored in National Forest Inventories, and the entire deadwood pool as a proxy for estimating complete deadwood stocks when data are not available. For this objective, we use information obtained from the Spanish National Forest Inventory, linear models and 10-fold cross-validation. We estimate the percentage of deadwood omitted when the minimum deadwood size is increased for the main eight forest types in Spain as well as for the entire country, using two different approaches. The ratio between the amount of standing deadwood and the entire deadwood pool ranged between 0.14 and 0.45 depending on the forest type. The lowest values of this ratio were found in Open woodlands and the largest in Mediterranean conifers. The validation statistics (R2 ranging from 0.82 in Evergreen broadleaves to 0.97 in Macaronesian broadleaves) indicate that the bridging functions we propose are robust and accurate. However, the ratios between the amount of standing deadwood and the entire deadwood pool performed poorer (R2 ranging from 0.26 in Macaronesian conifers to 0.65 in Macaronesian broadleaves) and led to an overestimation of the total stocks. Our results are of value not only for the purposes of comparison and harmonization but also for the implementation of new forest monitoring systems.
In 2019, 100 years had elapsed since the first National Forest Inventory (NFI) was established in Norway. Motivated by a fear of over-exploitation of timber resources, NFIs today enable informed ...policy making by providing data vital to decision support at international, national, regional, and local scales. This Collection of articles celebrates the 100th anniversary of NFIs with a description of past, present, and future research aiming at improving the monitoring of forest and other terrestrial ecosystems.
Key message
Every year, about 280,000 ha of forest area burn in the Iberian Peninsula. Both countries national forest inventories were harmonised to provide consistent results of the influence of ...forest stand structure on fire probability. Results show that basal area and vertical structure variables are associated with fire probability; however, that association varies with forest composition. Deciduous oaks and pine forests showed opposite tendencies. Forest management could be oriented considering these results.
Context
Fuel variables, in particular the ones that characterise stand vertical structure, are extremely important to determine the occurrence and severity of fire. However, documentation on fire occurrences and stand characteristics is still scarce in southern Europe.
Aims
In this study, we analyse the stand and structure variables from National Forest Inventories (NFIs) in order to identify the important ones that are associated with the presence/absence of wildfires in the Iberian Peninsula.
Methods
A harmonised database including a characterization of the vertical structure of the stand and its species composition was obtained by combining data from NFIs from Spain and Portugal and data from burned areas that occurred between 2005 and 2015.
Results
Stand characteristics results show that the plots that were later burned have lower average stand basal area. For deciduous oaks, more canopy cover has less probability to burn, and for all the other oaks, in different degrees, more understory cover has higher probability to burn. Regarding pine species, more canopy cover has lower probability to burn.
Conclusion
The results indicate important associations between stand variables and the presence/absence of wildfires that could support the forest management with the objective of reducing the probability of forest fires.
To understand the state and trends in biodiversity beyond the scope of monitoring programs, biodiversity indicators must be comparable across inventories. Species richness (SR) is one of the most ...widely used biodiversity indicators. However, as SR increases with the size of the area sampled, inventories using different plot sizes are hardly comparable. This study aims at producing a methodological framework that enables SR comparisons across plot‐based inventories with differing plot sizes. We used National Forest Inventory (NFI) data from Norway, Slovakia, Spain, and Switzerland to build sample‐based rarefaction curves by randomly incrementally aggregating plots, representing the relationship between SR and sampled area. As aggregated plots can be far apart and subject to different environmental conditions, we estimated the amount of environmental heterogeneity (EH) introduced in the aggregation process. By correcting for this EH, we produced adjusted rarefaction curves mimicking the sampling of environmentally homogeneous forest stands, thus reducing the effect of plot size and enabling reliable SR comparisons between inventories. Models were built using the Conway–Maxell–Poisson distribution to account for the underdispersed SR data. Our method successfully corrected for the EH introduced during the aggregation process in all countries, with better performances in Norway and Switzerland. We further found that SR comparisons across countries based on the country‐specific NFI plot sizes are misleading, and that our approach offers an opportunity to harmonize pan‐European SR monitoring. Our method provides reliable and comparable SR estimates for inventories that use different plot sizes. Our approach can be applied to any plot‐based inventory and count data other than SR, thus allowing a more comprehensive assessment of biodiversity across various scales and ecosystems.
Species richness is a commonly used biodiversity indicator. Because it strongly depends on the area sampled, comparability of species richness estimates across inventories using different plot sizes is not directly possible. We provide a methodological framework based on rarefaction curves to tackle this challenge.
Abstract
Key message
This paper proposes a methodology that could be considered as a base for a harmonized protocol for stem-quality reporting in Europe while conducting National Forest Inventories, ...in order to cost-efficiently obtain a visual wood quality proxy. The importance of the variables selected, the limitations identified, and some improvements to the methodology are suggested. Forest areas with better wood quality, which in turn it would be useful for breeding programs, can be easily detected.
Context
The establishment of harmonized standards or indicators that allow us to determine the quality of the wood present in a forest prior to its exploitation has long been demanded by the European forestry sector, although agreed methodologies for the evaluation of wood quality in standing trees, which is one of the sector’s most urgent requirements, have not, as yet, been implemented.
Aims
To develop a protocol that visually characterizes wood quality on standing trees in a cost-effective way for the National Forest Inventory (NFI). After some improvements, it can be considered as a base for a European harmonized protocol.
Methods
In this article, we analyze the implementation, in the NFI, of a visual wood-quality assessment methodology in forests of Central Spain based on the different European standards as well as on research papers addressing this issue.
Results
The silvicultural practices employed are of the utmost importance to obtain the best wood quality, regardless of the species. Several areas with higher wood quality were identified as well as areas most affected by specific pests in the studied region. The impact of the variables measured (e.g., branchiness, crookedness, maximum branch diameter) is discussed.
Conclusion
It is feasible to estimate a proxy for wood quality on standing trees in the NFI. Furthermore, after studying the inventory data provided, several enhancements are proposed, not only to improve wood-quality estimates but also to optimize fieldwork costs. Harmonizing NFIs to assess and map European standing wood quality can be achieved.
Forests are the most biodiverse terrestrial ecosystems. National forest inventories (NFIs) are the main source of information on the status and trends of forests, but they have traditionally been ...designed to assess land coverage and the production value of forests rather than forest biodiversity. The primary international processes dealing with biodiversity and sustainable forest management, the Convention on Biological Diversity (CBD), Forest Europe, Streamlining European Biodiversity Indicators 2010 of the European Environmental Agency, and the Montréal Process, all include indicators related to forest biodiversity. The scope of this article is to review and present possibilities offered by NFIs to harmonize estimation of indicators useful for international forest biodiversity monitoring and reporting. We summarize key findings from Working Group 3 of Action E43 (“Harmonisation of National Forest Inventories in Europe: Techniques for Common Reporting“) of the European program Cooperation in Science and Technology (COST). We discuss definitions and techniques for harmonizing estimates of possible biodiversity indicators based on data from NFIs in Europe and the United States. We compare these possible indicators with indicators selected by international processes. The results demonstrate that NFIs can report comparable or harmonized estimates of indicators for multiple biodiversity features (forest categories, deadwood, forest age, forest structure, and forest naturalness), but for others (ground vegetation and regeneration) NFIs should invest more in harmonization efforts. On the basis of these key findings, we recommend that NFIs should represent a main component of a future global biodiversity monitoring network as urgently requested by the CBD.
Key message
An in-depth characterization of the forests of 10 dominant species by stand variables at national scale showed, that overall, stands growing in the southernmost regions of Spain display ...low regeneration. Otherwise, the relationships between stand variables and geographic location are species dependent. Similarly, the degree of inter and interregional variability varies strongly among species.
Context
The regions of provenance can potentially be used as units with uniform ecological, phenotypic, and genetic traits to characterize forests.
Aims
Our objective was to characterize forests through stand variables at national scale for the 10 most widespread dominant tree species in Spain (five
Pinaceae
and five
Fagaceae
species) using the regions of provenance as ecologically homogeneous areas.
Methods
We used the National Forest Inventory as the dataset and multivariate analyses of variance with a bootstrapping and principal coordinates analysis for the statistical evaluation.
Results
Overall, the mean diameter of adult trees was negatively related to recruitment variables, and the mean height of adult trees was negatively related to shrub coverage and number of shrub species. The statistical analyses revealed significant differences between regions of provenance for all variables. The regions of provenance where
Pinus sylvestris
,
P. nigra
,
P. pinea
,
Quercus suber
, and
Q. ilex
are dominant, displayed a large variability among regions. In contrast, the regions of provenance for
P. halepensis
,
Q. pyrenaica
, and
Q. faginea
displayed a small low inter-regional variability.
Conclusion
Forest management as well as climate conditions shaped deeply forests, which lead to differences on stand variables among provenances by species. Stands growing on the southernmost locations, overall, are more prone to the forecasted climate change due to the low rates of regeneration.
Accurate carbon-balance accounting in forest soils is necessary for the development of climate change policy. However, changes in soil organic carbon (SOC) occur slowly and these changes may not be ...captured through repeated soil inventories. Simulation models may be used as alternatives to SOC measurement. The Yasso07 model presents a suitable alternative because most of the data required for the application are readily available in countries with common forest surveys. In this study, we test the suitability of Yasso07 for simulating SOC stocks and stock changes in a variety of European forests affected by different climatic, land use and forest management conditions and we address country-specific cases with differing resources and data availability. The simulated SOC stocks differed only slightly from measured data, providing realistic, reasonable mean SOC estimations per region or forest type. The change in the soil carbon pool over time, which is the target parameter for SOC reporting, was generally found to be plausible although not in the case of Mediterranean forest soils. As expected under stable forest management conditions, both land cover and climate play major roles in determining the SOC stock in forest soils. Greater mean SOC stocks were observed in northern latitudes (or at higher altitude) than in southern latitudes (or plains) and conifer forests were found to store a notably higher amount of SOC than broadleaf forests. Furthermore, as regards change in SOC, an inter-annual sink effect was identified for most of the European forest types studied. Our findings corroborate the suitability of Yasso07 to assess the impact of forest management and land use change on the SOC balance of forests soils, as well as to accurately simulate SOC in dead organic matter (DOM) and mineral soil pools separately. The obstacles encountered when applying the Yasso07 model reflect a lack of available input data. Future research should focus on improving our knowledge of C inputs from compartments such as shrubs, herbs, coarse woody debris and fine roots. This should include turnover rates and quality of the litter in all forest compartments from a wider variety of tree species and sites. Despite the limitations identified, the SOC balance estimations provided by the Yasso07 model are sufficiently complete, accurate and transparent to make it suitable for reporting purposes such as those required under the UNFCCC (United Nations Framework Convention on Climate Change) and KP (Kyoto Protocol) for a wide range of forest conditions in Europe.
Display omitted
•The applicability of Yasso07 for European forests and international requirements is tested.•Yasso07 provides realistic and plausible mean SOC estimations by region or forest type.•SOC balance simulation, the target parameter for reporting, is reasonable but in Mediterranean forest soils.•The complete, comparable, accurate and transparent SOC estimations sustain its use for reporting.•Research should focus on turnover-rates and quality of the litter from more forests and all its compartments.
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