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Aim of study: The native species of warm humid climates Ceiba pentandra, Tabebuia rosea, Gliricidia sepium, Enterolobium cyclocar-pum and Brosimum alicastrum are often included in Mexican reforestation programs. We evaluated the growth response in sandy soils of these species that could serve as pioneers in the restoration of coastal areas.Area of study: Alluvial plain in Frontera, Tabasco, Mexico.Material and methods: A total of 1080 plants were planted in 2014 and evaluated for 23 months in 30 plots under a randomized block design with six replications. The sample plots each occupied 36 m2 (each with 16 plants). Survival percentage, stem height (SH), basal diameter (BD) and basal area (BA) were quantified. Survival and growth variables were analyzed using logistic regression and ANOVA for repeated measures, respectively.Main results: At the end of the experiment (2016), high survival was demonstrated in G. sepium (88 %) and in C. pentandra (86 %), while B. alicastrum presented total mortality at six months. The highest values of SH and BD were presented in C. pentandra (2.9 m and 7.8 cm, respectively) and in G. sepium (2.6 m and 4.2 cm, respectively). Gliricidia sepium differed significantly from C. pentandra in terms of BA (5.9 vs. 23 m2 ha-1, respectively).Research highlights: The native species C. pentandra and G. sepium presented high survival and growth in the sandy soils; G. sepiumshowed strong adaptation to the environment and C. pentandra offered suitable coverage, characteristics that are necessary for the success of reforestation and restoration programs.

Pathogen life history traits influence epidemic development and pathogen adaptive ability to interact with their hosts in different environments. Reduced traits variation may compromise pathogen evolutionary potential, which is particularly important for introduced pathogens. Fusarium circinatum (cause of pine pitch canker) is an invasive fungal pathogen in Europe, with current distribution restricted to forest stands of Pinus radiata and Pinus pinaster in northern Spain and Portugal. This study aimed to quantify pathogenic traits of Spanish isolates of F. circinatum, with two of the strains representing the two dominant haplotypes in the Spanish population. Disease severity was measured on P. radiata, analyzing the influence of temperature and moisture duration on infection as well as the influence of temperature on spore germination, sporulation, and mycelial growth. Results indicated that the isolate representing the most common haplotype caused more severe disease on P. radiata at 25 and 30°C compared with the second most common haplotype but caused less severe disease at 15°C. Spore germination was higher for the most common haplotype, which produced more spores at 20 and 25°C. The isolate showed hyphal melanization at 5°C, which has been associated with survival and may be important because no resting structures have been described for F. circinatum. Our study determined that longer moisture periods during infection result in more severe disease from 7 to 24 h, regardless of the isolate virulence. This is the first study on virulence of the most abundant haplotypes of F. circinatum in Spain as affected by temperatures and moisture.

Litterfall production and composition, fall pattern and nutrient content were studied in a mixed stand of Pinus nigra and Pinus pinaster (El Pozuelo), as well as in a pure stand of Pinus nigra (Beteta) in the Cuenca Mountains in order to determine the effect of two-season prescribed burning treatments. Needles were the most abundant fraction. Pinecone fraction decreased after burning in the mixed stand and the opposite occurred in the pure stand. The inflorescence fraction showed a decrease in the spring-burned plots at El Pozuelo and Beteta. Bark, branch and miscellaneous fractions were affected mainly by meteorological events. Low-intensity prescribed burning was not found to cause significant perturbations. The perturbation was mitigated over the years. An immediate effect of prescribed burning in spring was seen at El Pozuelo and Beteta, although it was more significant for the pure stand. The effect of prescribed burning in autumn at Beteta had a delayed response. As regards nutrient contents, no differences in carbon concentrations were detected. Overall, an increasing trend in N, P, K concentrations in needles after the burning treatment was found. Calcium was not a limiting factor. Magnesium content exhibited no clear trend.

Management of forest genetic resources requires experimental data related to the genetic variation of the species and populations under different climatic conditions. Foresters also demand to know how the main selective drivers will influence the adaptability of the genetic resources. To assess the inter- and intraspecific variation and plasticity in seedling drought tolerance at a relevant genetic resource management scale, we tested the changes in growth and biomass allocation of seedlings of Pinus oocarpa, P. patula and P. pseudostrobus under two contrasting watering regimes. We found general significant intraspecific variation and intraspecific differences in plasticity, since both population and watering by population interaction were significant for all three species. All the species and populations share a common general avoidance mechanism (allometric adjustment of shoot/root biomass). However, the intraspecific variation and differences in phenotypic plasticity among populations modify the adaptation strategies of the species to drought. Some of the differences are related to the climatic conditions of the location of origin. We confirmed that even at reduced geographical scales, Mexican pines present differences in the response to water stress. The differences among species and populations are relevant in afforestation programs as well as in genetic conservation activities.

African tropical forests are thought to play an important role in global carbon sequestration. However, the increasing rate of deforestation and the impact of changes in land use require a critical and updated look at what is happening. This work emphasizes the role of bulk density as a main driver in carbon (C) and nitrogen (N) stock in four land-use categories natural forest, tree plantations, crop land and degraded soil. The study was conducted in the Central Highlands of Ethiopia, where deforestation and human pressure on native forests are exacerbated and erosion has caused extensive soil loss. The methodological approach consisted of evaluating the confounding effect of bulk density and then estimating C and N stocks based on a fixed-mass method rather than the usual fixed-depth method, in order to compare differences across land use categories. We hypothesized that elevation gradient would play a determining role in C and N concentrations and stocks in native forest, whereas tree species would be the main factor in plantations. C and N concentrations and bulk densities in mineral soil were analyzed as repeated measures in an irregular vertical space ranging from 0-10. cm, 10-30. cm, 30-50. cm and 50-100. cm, using a linear mixed model approach. Single observations from the forest floor were analyzed by a general linear model. Results indicated that soil depth is a more important factor than elevation gradient in native forests, though C and N concentrations and stocks diminished near human settlements. Native forest stored on average 84.4%, 26.4% and 33.7% more carbon and 82.4%, 51.8% and 27.1% more nitrogen than bare soil, crop land and plantations, respectively. Conversion of crop and degraded land to plantations ameliorated soil degradation conditions, but species selection did not affect carbon and nitrogen stocks. © 2015 Elsevier B.V.

Key message AcaciasenegalandAcacia seyalpresent different drought stress coping mechanisms that are independent of substrate fertility. Higher substrate fertility increased aboveground plant growth, even with low watering. The potential of native African tree species for agriculture and forestry have not yet been thoroughly investigated. In this experiment, we studied the early growth of Acacia senegal and Acacia seyal plants in an experiment with two substrates of contrasting fertility (low/high) and two watering frequency regimes (low = 24.40 l/m2 per month, high = 48.80 l/m2 per month). Our objectives were (1) to study whether the mechanisms by which nutrients affect plant growth at the seedling stage operate differently when water availability varies, and (2) to look for differences in the growth strategies of the two species in early stages. Higher substrate fertility increased aboveground plant growth at the expense of roots in both water regimes. Though water stress significantly limited growth under both soil conditions, substrate fertility effects were relatively higher in plants with low water supply than in those with high water supply. However, even with low resources the root-to-shoot ratio was between 0.7 and 0.9, plants presented adequate nutrition and no mortality was observed. This indicates opportunistic mechanisms for water and nutrient use. A. seyal showed the lowest negative pre-dawn stem water potential value (−0.15 MPa) and shed nearly all leaves in the hottest month of the assay, which suggests a different drought avoidance strategy and adaptation to water stress than A. senegal. Both species can be produced successfully in local nursery conditions and can survive and thrive with low watering. The study also demonstrated that fast growing genotypes can be effectively isolated in nursery conditions. © 2014, Springer-Verlag Berlin Heidelberg.

Gremmeniella abietina (Lagerberg) Morelet is a pathogenic fungus that causes severe damage in coniferous forests, causing the death of the trees, in Central and Northern Europe, North America and Japan. Biological control (i.e. the use of biologically antagonistic organisms) is being considered as an alternative and an eco-friendly method to deal with plant diseases. Among such organisms several fungal endophytes have been successfully used to reduce or inhibit the growth of pathogens. Thus, the aim of this study was to evaluate the ability of several fungal endophytes to reduce the G. abietina spreading on pine seedlings, with the goal of exploring the mechanisms involved in that reduction. The experiment was carried out on two-year old Pinus halepensis seedlings under greenhouse conditions. Five fungal endophytes ( Trichoderma spp., Aureobasidium pullulans, Aureobasidium spp., endophyte 20.1 and Leotiomycete spp.) obtained from healthy P. halepensis trees were used to evaluate their effect on six G. abietina isolates. The pathogen and the endophyte were both inoculated in every seedling. At the end of the experiment seedlings were cut and brought to the laboratory where the necrosis length and total phenol content of the plant were measured. The pathogen presence was determined by a nested PCR with specific primers of G. abietina. The presence of all endophytes significantly reduced the necrosis length caused by G. abietina in most of the cases. However, the phenolic content of the plant, which is an indicator of the activation of the plant's defence mechanisms, had not increased with the endophyte inoculation. Therefore, the reduction in the necrosis observed could be attributed to a direct effect of the endophyte on the Gremmeniella spreading. These results suggest that the use of fungal endophytes could be an effective way to protect against G. abietina infections.