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• Key message: This document provides valuable environmental information about a triplets' essay of Scots pine and Maritime pine in Spain. The dataset characterizes the soil profile (physicochemical parameters of organic and mineral horizons), climate, physiography, understory and overstory. Dataset access is athttps://doi.org/10.5281/zenodo.4384530and associated metadata is available athttps://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/21cca830-daf9-4913-9b5b-a185d77943d5 [ABSTRACT FROM AUTHOR]

Key message: The adoption of new silvicultural methods and approaches requires an understanding of the differences between those and “old” or “conventional” approaches, along with extensive training to break previous knowledge bias. Context: Forestry is in transition towards ecosystem-based management, and new silvicultural approaches are appearing worldwide. However, the adoption of an alternative silvicultural approach is difficult in practice. Aims: We analyzed the effect of forestry background and demographic variables (gender and age) of 24 raters on the application of the systemic approach (SA) and the conventional approach (CA) in the Northern Apennines (Italy) and compared this with tree marking performed by experts. Methods: Data were analyzed as raters’ departures from experts’ selections at the stand and the individual tree level. The probability of tree selection was also calculated. Results: At the stand level, raters with forestry background performed the SA as if they were marking for crown thinning, whereas the CA was less intense than experts’ crown thinning. Non-foresters differentiated poorly between the SA and the CA. At the individual tree level, background and gender affected tree selection. Conclusion: The adoption of the SA as a silvicultural system may be conditioned by previous knowledge. The difference between SA and CA remains unclear when it comes to non-foresters. Gender was a more important variable than age in selecting which trees would be harvested. [ABSTRACT FROM AUTHOR]

Key message: A positive effect of mixed pine forests (Pinus sylvestrisL. andPinus pinasterAit.) on the understory richness and tree regeneration was observed with respect to monospecific stands. Understory species typical of the native Pyrenean oak forests in the Iberian Peninsula contribute to maintaining high understory richness in such mixed pine forests. Context: The influence of stands characteristics on the understory in mixtures that combine coniferous tree species of the same genus deserves more study since they are frequent in Spain. Aims: To assess the effect of mixed versus monospecific stands of Pinus sylvestris L. and Pinus pinaster Ait. on the main tree species regeneration and understory species composition. Methods: Tree regeneration and understory species composition were inventoried in eighteen forest plots (6 triplets) in North-Central Spain. Each triplet consisted of two plots dominated either by Scots pine or Maritime pine and one mixed plot that contained both species. Results: The basal area (%) of both Pinus species was the only characteristic of the stands that significantly influenced the understory composition and tree regeneration. Characteristic species of humid and temperate zones, including P. sylvestris regeneration, dominated in Scots pine stands, and typical species of well-drained Mediterranean areas, including P. pinaster regeneration, dominated in Maritime pine stands. In mixed stands, the highest regeneration of the native Pyrenean oak with respect to monospecific stands was accompanied by understory species typical of native oak forests that share the same regeneration niche. Conclusion: Mixed pine forests allow the development of understory species better than monospecific forests. [ABSTRACT FROM AUTHOR]

Context Silvicultural practices usually include stand density reduction resulting in changes in litterfall and litter decomposition rates. Little is known about the effect on nutrient concentrations in litterfall and nutrient release during decomposition even when this is the main path of nutrient return to soils. Aims The aims of the study are to evaluate the seasonal pattern of nutrient concentration in litterfall, to study how nutrients are released from needle litterfall during decomposition, and to assess whether local basal area of the stand affects nutrient concentration of litterfall and nutrient release during litter decomposition. Methods Eight plots were established on each of four stands covering the widest range in local basal area. A littertrap and 15 litterbags were placed on each plot. Periodically, needle litterfall and litter contained in the litterbags were analyzed for C, N, Ca, K, Mg, P, S, Fe, Cu, Mn, and Zn. Results Local basal area had a positive effect on C, K, and Mg concentration in needle litterfall and a negative effect on the release of all the nutrients studied but Fe and Mn during the first 2 years of litter decomposition. Conclusion Density management of stands has an impact on nutrient cycling, reducing nutrient concentration in needle litterfall, and accelerating nutrient release during decomposition. [ABSTRACT FROM AUTHOR]

Context Soil enzymes play a key role in nutrient turnover in forest ecosystems, as they are responsible for the transformation of organic matter into available nutrients for plants. Enzyme activities are commonly influenced by temperature, humidity, nutrient availability, pH, and organic matter content. Aims To assess the differences between enzyme activities in calcareous soils below Pinus halepensis and acidic soils below Pinus sylvestris plantations in Spain and to trace those differences back to edapho-climatic parameters to answer the questions: Which environmental factors drive enzyme activities in these soils? How can forest management improve them? Methods The differences in climatic, soil physical, chemical, and biochemical parameters and the correlations between these parameters and enzyme activities in soils were assessed. Results Low pH and high level of phenols in acidic soils under Pinus sylvestris and water deficit in calcareous soils under Pinus halepensis plantations appeared to be the most limiting factors for enzyme activities. Conclusion Options such as the promotion of native broadleaf species in the Pinus sylvestris stands and the modulation of Pinus halepensis stand density or the implementation of soil preparation techniques may improve enzyme activities and, therefore, nutrient availability. [ABSTRACT FROM AUTHOR]

Key message : This work presents a discriminant model to predict Pinus halepensis forest productivity using parameters related to water availability (Annual Hydric Index, soil porosity and slope) and information about the N immobilization by soil microorganisms (microbial biomass N). Context : Pinus halepensis is a circum-Mediterranean species that has been widely used for afforestation of poor and degraded soils in water-limited regions. Determining forest and stand productivity is very useful for forest managers as it supports decision making. Aims : The aim of this study was to develop a model to predict Pinus halepensis productivity using environmental parameters. Methods : A set of 57 soil, climatic and physiographic parameters were determined in 32 Pinus halepensis plots, which were categorized into three site index classes. Principal component analysis (PCA) was used to select the 14 environmental variables that accounted for the highest data variability. Discriminant models with three, four and five environmental variables as predictors were studied. Results : The selected discriminant model included three parameters related to water availability (Annual Hydric Index, soil porosity and slope), which is the main driver of forest productivity in Mediterranean ecosystems, and one nutrient-related parameter known as microbial biomass N, by which microorganisms inform about N immobilization. The model correctly classified 62.5% of the plots. Conclusion : This model may be a very useful tool for supporting decision making in forestry practices aimed at sustainable stand management. [ABSTRACT FROM AUTHOR]

Key message : Biomass equations are presented for five tree species growing in a natural forest in Ethiopia. Fitted models showed more accurate estimations than published generalized models for this dry tropical forest. Context : Biomass equations are needed to correctly quantify harvestable stock and biomass for sustainability efforts in forest management, but this kind of information is scarce in Ethiopia. Aims : This study sought to develop biomass models for five of the most common native tree species in the Chilimo dry afro-montane mixed forest in the central highlands of Ethiopia: Allophyllus abyssinicus, Olea europaea ssp . cuspidata, Olinia rochetiana, Rhus glutinosa, and Scolopia theifolia. Comparison with generalized models was intended to show the greater accuracy of the specific models. Methods : A total of 90 trees from different diameter classes were selected, felled, and divided into different biomass compartments. Biomass equation models were fitted using joint-generalized least squares regression to ensure the additivity property between the biomass compartments and total biomass. Results : These were the first models developed for these species in African tropical forests. Models were including diameter at breast height and total height as independent variables, obtaining more accurate biomass estimations using these models than from generalized models. Conclusion : Fitted models are reliable for estimating aboveground biomass in the Chilimo forest and for more general application in similar forest types. Model applicability for biomass or carbon estimation is high within forest inventory data contexts. [ABSTRACT FROM AUTHOR]

• Context: Modification of stand density by thinning may buffer the response of tree growth and vigor to changes in climate by enhancing soil water availability. • Aims: We tested the impact of thinning intensity on cambial growth of Aleppo pine ( Pinus halepensis L.) under semi-arid, Mediterranean conditions. • Methods: A multiple thinning experiment was established on an Aleppo pine plantation in Spain. We analysed the stem growth dynamics of two different crown classes under four different thinning intensities (15 %, 30 %, and 45 % removal of the basal area) for 2 years, based on biweekly band dendrometer recordings. Local relative extractable soil water was derived from the use of a water balance model Biljou© (available at https://appgeodb.nancy.inra.fr/biljou/) and used as an explanatory variable. • Results: Radial growth was mainly controlled by soil water availability during the growing season, and differed by crown class. The growth rates of dominant trees were significantly higher than the growth rates of suppressed trees. Removal of 30 % and 45 % of the initial basal area produced a growth release in both dominant and suppressed trees that did not occur under less intense thinning treatments. • Conclusions: Soil water availability was the main driver of radial growth during the growing season. Forest management confirmed its value for ameliorating the effects of water limitations on individual tree growth. These results may help managers understand how altering stand density will differentially affect diameter growth responses of Aleppo pine to short-term climatic fluctuations, promoting forests that are resilient to future climatic conditions. [ABSTRACT FROM AUTHOR]

Context: Excessive recruitment in post-fire regeneration of Pinus halepensis can require pre-commercial thinning. The 1994 Moratalla fire (Spain) and the thinning applied there since 2004 provided good conditions for testing pre-commercial thinning effectiveness. Aims: To analyse pre-commercial thinning effects on tree size, reproductive potential, stem biomass and annual growth in 15-year-old saplings. Methods: Twenty nine circular plots (5 m radius) were established based on (1) years since thinning and (2) aspect. Non-thinned plots were included as controls. Sapling variables were measured and pine cones were counted and classified according to maturity. Three saplings per plot were felled, five sample disks were extracted from each and tree rings were analysed with Windendro® software. Results: Sapling size, annual growth and stem biomass were higher in thinned plots than in control plots 2-4 years after thinning. Annual growth declined five years after thinning. Cone counts were higher 2-5 years after thinning, depending on the cone type. Aspect influenced some variables. Conclusion: Thinning accelerated stand maturity but positive effects were indiscernible until 2-5 years later. Serotinous cones, which are fundamental to regeneration after fire, increased in number after 5 years. The effects of aspect were inconclusive due to interactions with years since thinning. [ABSTRACT FROM AUTHOR]

Context: Information about variations in basic density (BD) and carbon content (%C) along tree stems is key to assessing forest carbon sinks. Aims: The aim of the study was to determine any differences in %C and BD between different woody tissues (bark, sapwood and heartwood) in two widespread European oak species ( Quercus pyrenaica and Quercus petraea). Methods: Twenty trees were felled in northern Spain, and 317 discs cut from the trees were dried and analysed to determine %C and BD. Results: There were significant differences in %C between bark, heartwood and sapwood, and between species. There were also significant differences in BD between the tissues (heartwood > sapwood > bark), and the BD was higher in Q. petraea than in Q. pyrenaica. Both %C and BD varied along the stem. Conclusion: More accurate estimates of carbon contents were obtained by using specific values for different heights and anatomical parts, than by using single values. [ABSTRACT FROM AUTHOR]

• Context: Understanding biological processes in forests is necessary to orientate ecosystem management towards potential C sequestration. To achieve this, information is required about changes in forest biomass C pools, including the stem components (bark, sapwood and heartwood). • Aims: This study aimed to determine whether there are differences in C concentration in axial and radial directions within stem biomass in Pinus nigra, Pinus pinaster and Pinus sylvestris. • Methods: Wood samples from a permanent plantation in northern Spain were examined for C concentration and wood bulk density. • Results: The results showed that C concentration was higher in heartwood than in sapwood in the three species. Pinus spp. sapwood C concentration increased along the stem, while the C concentration in heartwood tissue showed the opposite behavior. In bark, Pinus pinaster showed a decreasing trend, in contrast to Pinus nigra and Pinus sylvestris, where higher values were found at the base and top of the stem. Finally, wood bulk density decreased in heartwood, sapwood and bark areas when stem height increased. Estimating C content taking into account different anatomical parts and heights is important in considering the specificity of the different parts because of their potential commercial or ecological use in forest ecosystems. [ABSTRACT FROM AUTHOR]

Background: How environmental factors affect forest regeneration is relevant for systems that depend partially or fully on natural regeneration. Methods: P. pinaster post-disturbance regeneration and its relationship to environmental factors was studied in five P. pinaster forest populations of central Spain. We expected that: 1) different harvesting methods or wildfire would promote natural regeneration in all populations, but with local and regional variations,or 2) alternatively, different site-dependent stand factors would affect natural regeneration, although generalized climate effects would be seen. Analysis of variance and multivariate analysis were used to test differences, to classify ecological variations, and to search for the most important factors affecting regeneration. Results: The results suggest that the recovery of P. pinaster forest in burnt stands, and stand replacement in harvested stands, can be achieved soon after disturbance if climatic conditions and other local-site factors (e.g., soil and overstory structure in harvested stands, cone bank in burnt stands) make the stand suitable for natural regeneration. Heterogeneous regeneration can be expected in all cases. The time of precipitation strongly influenced seedling density and successive regeneration development stages. Conclusion: Edaphic properties, combined with water availability from precipitation, can seriously limit the natural establishment of P. pinaster in xeric systems or during years of intense drought. Although many factors contribute to high variability, natural regeneration has been very effective (successful) in P. pinaster forests, which contributes to the generalization that natural regeneration is a viable forestry option in many forest types. [ABSTRACT FROM AUTHOR]

• Introduction: Understanding diameter growth of the Mediterranean pine species is fundamental for evaluating and making appropriate strategic decisions in forest management. A matrix diameter growth model for two Mediterranean pine forest ecosystems in Spain has been developed. • Methods: Multinomial logistic (MNL) regression was employed to estimate the transition probabilities of a matrix growth model. The model combines individual tree and stand attributes and explores the effects of independent variables and their relationships with tree size and the probabilities of stand diameter growth. The aim was to predict growth of individual trees by diameter class for a 5-year period. • Results: MNL model results for diameter growth gave better predictions for Maritime pine ( Pinus pinaster Aiton) than for Scots pine ( Pinus sylvestris L.). Stand simulations showed that diameter growth probabilities depended on productivity and stand density. Stand simulations under fixed conditions showed that the probabilities of diameter growth increased as site productivity increased and decreased with increased stand density index. • Conclusions: This study demonstrates the usefulness of matrix growth models as tools to predict growth in Mediterranean pine forests. Stand density and site productivity are key factors in explaining Scots pine and Maritime pine forest growth in the study area. [ABSTRACT FROM AUTHOR]

Key message: Pinus sylvestrisL. productivity in Spanish plantations is driven by P availability, which, in turn, is determined by the activity of soil microorganisms, responsible for inorganic P solubilization; Fe and Al contents, responsible for P retention; and organic matter, which is source of organic P, inhibits its precipitation as insoluble compounds, and reduces P retention. Context: Phosphorus is often a limiting nutrient in forest ecosystems mainly due to the low solubility of P compounds and the sorption processes occurring in soils. Aims: The main aims of this work were to evaluate soil P availability, to assess which soil properties are driving P availability, and to study whether soil P availability is determining forest productivity in Pinus sylvestris L. plantations in Northern Spain. Methods: Soil properties and forest productivity were studied in 34 plots located in monospecific P. sylvestris plantations. Tiessen and Moir (Canadian Society of Soil Science 75–86, 1993) sequential fractionation method was carried out to determine different forms of soil P and to provide a comprehensive assessment of available P in soils. To explore the relationships between these variables, canonical correlation analyses and Pearson's correlations were studied. Results: Significant correlations were found between P fractions and soil properties related to Fe and Al contents, organic matter, and microbial biomass. Besides, significant correlations were found between site index and the studied P fractions except for P extracted with anion exchange membrane (PAEM) and the recalcitrant P fraction. Conclusion: In the studied soils, P availability is low and the predominant fractions of P are the recalcitrant forms. Aluminum and iron contents in the soils studied play an important role in sorption processes related to the highly and moderately labile P fractions and the organic phosphorus. P availability seems to be regulated by both processes: biochemical mineralization, where phosphatase activity is relevant, and biological mineralization of the soil organic matter. Phosphorus availability affects forest productivity in the Pinus sylvestris plantations studied. [ABSTRACT FROM AUTHOR]

Key message: This data set provides valuable environmental information aboutPinus halepensisandPinus sylvestrisplantations in Spain. An array of 74 physical, chemical and biochemical soil (organic horizon and 10 cm topsoil), climatic, physiographic and stand variables from 32P. halepensisand 77 variables from 35P. sylvestrisplantations are provided. Dataset access is at 10.5281/zenodo.1294607. Associated metadata is available athttps://agroenvgeo.data.inra.fr/geonetwork/srv/eng/catalog.search#/metadata/b769554a-2e62-414a-9392-ebd307f0c76f. [ABSTRACT FROM AUTHOR]