Species diversity and genetic diversity, the most basic elements of biodiversity, have long been treated as separate topics, although populations evolve within a community context. Recent studies on community genetics and ecology have suggested that genetic diversity is not completely independent of species diversity. The Mexican Picea chihuahuana Martínez is an endemic species listed as “Endangered” on the Red List. Forty populations of Chihuahua spruce have been identified. This species is often associated with tree species of eight genera in gallery forests. This rare Picea chihuahuana tree community covers an area no more than 300 ha and has been subject of several studies involving different topics such as ecology, genetic structure and climate change. The overall aim of these studies was to obtain a dataset for developing management tools to help decision makers implement preservation and conservation strategies. However, this unique forest tree community may also represent an excellent subject for helping us to understand the interplay between ecological and evolutionary processes in determining community structure and dynamics. The AFLP technique and species composition data were used together to test the hypothesis that species diversity is related to the adaptive genetic structure of some dominant tree species (Picea chihuahuana, Pinus strobiformis, Pseudotsuga menziesii and Populus tremuloides) of the Picea chihuahuana tree community at fourteen locations. The Hill numbers were used as a diversity measure. The results revealed a significant correlation between tree species diversity and genetic structure in Populus tremuloides. Because the relationship between the two levels of diversity was found to be positive for the putative adaptive AFLP detected, genetic and species structures of the tree community were possibly simultaneously adapted to a combination of ecological or environmental factors. The present findings indicate that interactions between genetic variants and species diversity may be crucial in shaping tree communities.

Abstract• Key message To implement adaptive management in post-fire-regenerated Aleppo pine forests, we developed specific biomass equations in two early-thinned climatically contrasting stands. We found thinning enlarged biomass components, although climate primarily constrained biomass accumulation and biomass allocation.• Context The increase in burnt surface by wildfires in the Mediterranean Basin has triggered the proliferation of large unmanaged forested areas, particularly Aleppo pine stands in drier and lower altitudinal areas. These young naturally regenerated stands require specific biomass models for accurate carbon stock quantification.• Aims The aim of this study is to analyse the effects of climate (dry vs. semiarid), age and forest management (early thinning) on biomass accumulation and biomass allocation of young Pinus halepensis components: stem, crown (crown wood, needles and cones) and roots.• Methods We sampled 251 individual Aleppo pine trees across an age sequence of 5-16 years old to develop component biomass equations.• Results We observed that biomass allocation differed with climate, age and tree density. The crown was the largest biomass fraction, followed by root fraction and stem fraction. At the most limiting site (semiarid climate), we found major reproductive efforts, which may be shaped by adaptive traits to recurrent fires or recurrent drought episodes.• Conclusion Climate was the first limiting factor to constrain biomass accumulation and biomass allocation. Thinning played a key role in promoting positive effects on biomass components at both sites, which were enlarged under less stressful site conditions (dry climate). These results may help managers understand how altering stand density promotes more resilient forests.

International audienceKey messageReforestation programmes have been widely used in many forest areas worldwide but scarcely compared to nearby natural woodlands. As an example, we selected aPinusspecies devoted to the Mediterranean basin in order to validate the naturalness of the plantations. We found that natural Aleppo pine stands are more structurally complex with more developed and diverse understory compared to planted stands.ContextMaintaining a large biodiversity is a major concern for reforestation programmes in the Mediterranean basin, which displays a large area of planted forests.AimsWe compared mature planted forests (over 50 years old) to nearby natural forests in relation to the structure, composition and diversity of the understory vegetation. An efficient comparison method should provide guidelines to improve the effectiveness of reforestation management programmes.MethodsWe selected three pairs of nearby planted and natural Pinus halepensis Mill. stands in southeastern Spain along a precipitation gradient and compared stand overstory structure (density, basal area and canopy cover), and understory vegetation (plant cover, species richness and evenness index).ResultsPine tree density was lower but basal area was higher in natural stands than in the nearby planted stands. Natural stands displayed also higher understory plant cover and species richness, but no difference was found regarding evenness. These differences were larger in the most mesic sites and were due to the density and arrangement of the pine tree cover.ConclusionThese results provide (i) valuable information for evaluating the success of reforestation programmes to recreate natural forest ecosystems and (ii) guidelines for silviculture and management

Management of burnt forests is a topic that should include monitoring of burnt areas immediately after burning, in order to implement emergency actions that ensure conditions for ecosystem recovery. However, if excessive regeneration is observed, early silvicultural treatments have to be implemented to assist the natural recovery of the ecosystem. This paper discusses the effects of silvicultural management in two burnt areas naturally regenerated. One of the study areas was located in southern Albaceteprovince, covered of Aleppopine (Pinus halepensis Mill.) stands that were burnt in summer 1994. The other area was located in eastern Cuenca province, showing Holm oak (Quercus ilex L. ssp. ballota (Desf.) Samp) stands burnt twice in summer 1993 and 2001. The objective of the current study was to monitor the biomass recovery and carbon stock in two different ways: direct field sampling and calculation of stocks by using available published datasets. Direct sampling showed that in 2010 (nine years after fire), lower amounts of carbon were stored in the young Holm oak standards which were not totally recovered from previous thinning, carried out two years ago. In 2010, sixteen years after the fire and nine after thinning, high intensity thinning contributed to improve the total amount of carbon stock in tree biomass in theAleppo pine stands. In addition, values for unthinned areas were similar to those obtained from the Third Spanish National Forest Inventory. In this study we highlight the interest of implementing a classical tool of silvicultural management in the adaptive forest management of regenerating areas. We propose to consider the inclusion of young regenerated stands in carbon stocks, at least at province and regional level.

Abbreviations S = Species richness index; H' = Shannon diversity index; J' = Jaccard index; NMDS = Non-metric multidimensional scaling; GLM = Generalized linear models Nomenclature Flora Ib erica (Castroviejo 1986(Castroviejo -2012; Flora Europaea (Tutin et al. AbstractQuestion: Adaptive forest management requires scientific knowledge about post-fire vegetation dynamics, mainly on initial and transitional stages. We hypothesized that management practices are as important as the timing of the operations themselves, with respect to diversity and species composition of the understorey post-fire regenerated Pinus halepensis forests.Location: Two post-fire regenerated P. halepensis stands burned in 1994 under contrasting climatic conditions (Dry -595 mmÁyr À1 -and Semi-arid -340 mmÁyr À1 -sites) in southeast Spain.Methods: At both sites, we set experimental plots to test early treatments, including removal of the understorey vegetation (scrubbing, at post-fire year 5), thinning (at post-fire years 5 and 10) and control plots. Alpha diversity indices, including species richness, Shannon diversity index and plant cover, as a measure of vegetation abundance, and beta diversity indices, such as Jaccard index and non-metric multidimensional scaling were diachronically analysed at postfire years 5 (before the treatments) and 16.Results: At both sites, the most abundant species were obligate seeders or grass resprouters. Low overlap in the occurrence of species was also found between sites on both dates, but the number of shared species increased by the end of the study period. Significant differences in the diversity indices were detected between sites. Despite the silvicultural treatments, the species richness and Shannon diversity index values at the Dry site were similar in the treated and control plots at 16 yr. Conversely, at the Semi-arid site, the species richness and Shannon diversity index values were enhanced by the thinning treatments carried out 10 yr after the fire. Plant cover increased despite the treatments (scrubbing and thinning) on both the pine and understorey layers in every treated plot.Conclusion: Our forest management trials enhanced the diversity indices when applied to very high tree density post-fire regenerated stands, even applied to areas with very limited resources (nutrients, water, etc.) such as semi-arid ecosystems. Thus, scrubbing at post-fire year 5 plus thinning carried out at post-fire year 10 proved to be a suitable option to reduce fire hazards in the short term at both sites and to enhance plant diversity at the Semi-arid site.