Formamide deionized accelerates the somatic embryogenesis of Cunninghamia lanceolata

Aim of the study: To improve the efficiency of the somatic embryogenesis (SE) in Cunninghamia lanceolata. Area of the study: The study was conducted at Nanjing Forestry University (Nanjing, China). Material and methods: Immature cones of C. lanceolata, genotype 01A1 which was planted in Yangkou State-owned Forest Farm (Fujian, China), were used to induced callus. These calli were used to induce SE, concentration gradients of 0 g/L, 0.01134 g/L, 0.1134 g/L, 1.1134 g/L and 11.34 g/L of FD was added, to explore the optimal concentration for promoting SE of C. lanceolata. Main results: Low concentration of FD promoted the maturation of somatic embryos, while high concentration of FD lead to browning of embryogenic callus. The seedling rate and rooting number of seedlings induced by different concentrations of FD were significantly different. Research highlights: This study may aid in the rapid maturation of C. lanceolata somatic embryos and is useful for accelerated C. lanceolata breeding.

Growth differential related to wood structure and function of Eucalyptus spp. clones adapted to seasonal drought stress

Aim of the study: To evaluate the growth performance, wood density and anatomical features of four drought-tolerant Eucalyptus spp. clones, at 4 years, and to examine the relationships between these characteristics and some functional parameters. Area of study: The analyzed trees were from a clonal test installed in a region characterized by seasonal drought stress in central-western Brazil. Methods: Trees were felled, followed by obtaining dendrometric parameters and wood disk sampling to determine wood bulk density by x-ray densitometry, and morphometric parameters of fibers and vessels in order to evaluate the xylem hydraulic architecture. Lumen fraction (F), vessel composition (S) and hydraulic conductivity (Ks) were estimated. Results: Clone D (E. urophylla x E grandis) presented the highest growth rates, which was related to anatomical characteristics such as low relative frequency of wide vessels. High theoretical Ks does not necessarily imply higher growth rates and were related to lower wood densities. It is possible to infer that the better xylem adjustability of Eucalyptus trees in response to drought stress conditions is associated with increased vessel composition to the detriment of higher hydraulic conductivity. Research highlights: Vessel composition showed a greater variation among Eucalyptus genotypes and was positively associated with growth performance.

Age-age correlations and prediction of early selection age for diameter growth in a 35-years old Pinus brutia Ten. Genetic experiment

Aim of study: Forest geneticists developed various methods to predict an early selection age for forest tree species in order to shorten the breeding cycles. This study aims to estimate age-age correlations among diameter growth of trees at different ages and predict early selection age for Pinus brutia Ten. Area of study: P. brutia populations in the study were sampled from the most productive distribution range of the species, which is an important forest tree in the eastern Mediterranean Basin. To understand genetic variation and determine early selection age for the species, a common garden experiment was established in two test sites near Antalya city, Turkey, in 1979. Material and methods: Wood increment cores at breast height were collected at age 30 years, and diameters (dbh) were measured for the ages 13, 15, 19, 21, 23, 25, and 27 years on the cores. Diameters at ground level (dgl) and dbh were also measured on live trees at age 35. Variance components, age-age correlations, heritability and selection efficiency were estimated for the diameters. Main results: Age-age genetic correlations for diameters were high (mostly > 0.90). Genetic correlations between dgl (at age 35) and dbh (at all measurement ages) ranged from 0.84 to 0.99. Regressions of genetic correlation on natural log of age ratio (LAR) of juvenile age to older age were significant (P < 0.0001). Selection efficiencies estimated by employing the prediction equation indicated that for rotation age 40, the optimum selection age would be between 3 to 5 years, and for rotation age 100 it would be between 5 to 9 years. Research highlights: The results of this study provide information that can be used to find early selection ages in P. brutia. On relatively poor test sites most trees may not attain enough height growth to have measurable dbh trait. In such cases, dgl and/or tree height traits (both of which are highly correlated with dbh traits of all ages) can be measured and used instead of dbh trait for evaluations.

Drought responsiveness in two Mexican conifer species forming young stands at high elevations

Aim of study: To determine the response of high-altitudinal forests to seasonal drought. Area of study: Monte Tláloc, Estado de México and Rancho Joyas del Durazno, Municipality of Río Verde, San Luis Potosí, México. Materials and methods: In this study, we evaluate the response to drought and hydroclimate in two young Mexican conifers sampled at high elevation, correlating records of tree-ring growth and the Normalized Difference Vegetation Index (NDVI). Main results: The results show that Pinus teocote and Abies religiosa are vulnerable to the precipitation regime and warm conditions of winter-spring. The physiological response mechanisms seem to be differentiated between the species, according to the effects of drought stress. The NDVI demonstrated the different temporal responses of the species according to their inherent physiological mechanisms in response to hydroclimatic limitations. This differentiation can be attributed to the spatial variation present in the particular physical and geographic conditions of each area. The dry and warm seasonal climates reveal P. teocote and A. religiosa to be species that are vulnerable to drought conditions. However, further evaluation of the resistance and resilience of these species is necessary, as well as disentanglement of the effects of associated mechanisms that can influence the predicted processes of extinction or migration. Research highlights: Pinus teocote and Abies religiosa are vulnerable to the seasonal drought conditions. These results are of particular importance given the climatic scenarios predicted for elevated ecotones. Tree-ring widths and NDVI improved the response of radial growth to the climate, enhancing our understanding of forest growth dynamics. The response to climatic variability depends on the particular species.

Biomass equations for rockrose (Cistus laurifolius L.) shrublands in North-central Spain

Aims of the study: To construct biomass weight equations for rockrose (Cistus laurifolius L.) shrublands in North-central Spain comparing different methodologies and evaluating the applicability of the current Spanish open PNOA-LiDAR data. Area of study: The growing extension of Mediterranean shrublands associated with a high wildfire risk in a climate change scenario is considered a relevant source of biomass for energy use and bioproducts. Quantifying the biomass load of the shrublands provides essential information for adequate management, calling for the development of equations to estimate said biomass loads in the most extensive monospecific shrublands. Materials and methods: Biomass dry weight from 290 destructive sampling plots (ø4m) and 426 individual plants along with LiDAR data from PNOA were related to dasometric parameters to fit weight per surface and weight per plant equations. Main results: Three new equations improve rockrose biomass estimations in North-central Spain: a) Weight per unit area (tDM.ha-1) equation (Eq. 1) based on apparent biovolume (product of crown cover in percentage by average height in meters) (Radj2 0.69, MAE 26.1%, RMSE 38.4%); b) Weight per plant (kgDM.plant-1) equation (Eq. 2) from height and crown diameter (Radj2 0.87, MAE 26.5%, RMSE 45.2%) and c) Weight per unit area equation (tDM.ha-1) (Eq. 3) based on LiDAR data contrasted with field data (Radj2 0.89, MAE 15.1%, RMSE 22.9%). Research highlights: Eq. 1 and Eq. 3 combined with high resolution LiDAR information offer rockrose (Cistus laurifolius L.) biomass estimations without added field work costs that are an improvement on certain more general studies carried out in other areas of Spain.

Persistent fire effect on forest dynamics and species composition of an old-growth tropical forest

Aim of the study: To assess structure, recruitment and mortality rates of tree species over almost three decades, 14 years before and 15 years after a forest fire. Material and methods: All trees ≥ 5 cm in DBH were identified and measured in 12 permanent plots (50 m x 50 m), in 1983, 1987, 1989, 1995, 2008, and 2012 of a dense ombrophilous forest in Eastern Amazon, Brazil. The analyses were carried out including all sampled species and their ecological groups: shade-tolerant, light-demanding, and pioneer species. Treatments were compared through a Linear Mixed Effect Model. Main results: The 15-year post-fire period is not enough for the old-growth tropical forest to recover its pre-fire conditions of recruitment and mortality rates. The post-fire recruitment and mortality rates increased, mainly the recruitment of pioneer species (p-value < 0.05). Research highlights: In a period of 15 years after the occurrence of a surface fire, the old-growth tropical forest still has high recruitment rates of shade-tolerant and light-demanding species and high incidence of pioneer species, confirming the persistent fire effects on forest dynamics and species composition in this ecosystem.

Tree-ring reconstruction of March-June precipitation from the Atlas cedar forest of Mount Takoucht, Béjaïa (northern Algeria)

Aim of study: A March-June precipitation has been reconstructed for the period 1830-2015 using Atlas cedar (Cedrus atlantica Manetti) tree-ring records. Area of study: Atlas cedar forest of Mount Takoucht (Béjaïa, northern Algeria). Material and methods: Seasonal correlations were computed in order to identify the best period of the year for the climate reconstruction. The temporal stability of the tree-ring signal for precipitation was checked using the split-sample calibration-verification procedure. The reconstruction was performed using the transfer function method. Main results: The reconstructed data revealed high interannual to decadal variation in late winter to early summer precipitation. Wet conditions dominated during the 1830s and 1840s and were followed by sustained dry conditions during the mid-19th century, which registered two of the most severe droughts (1858 and 1869) over the period of reconstruction. Relatively moderate climate conditions marked the late 19th and early 20th centuries. A gradual return towards drier conditions was observed from the 1920s and reached high frequencies of drought around mid-20th century. After an exceptional prolonged wet period of 24 years (1966-1989), the reconstruction registered its highest frequency in extreme dry/wet events: the decade 1993-2002 recorded the highest drought frequency of the reconstruction, with the third most severe dry event (1999), while the last years were marked by a clear shift toward wet conditions. Research highlights: These findings provide relevant records on past climate variability in one of the rainiest areas in Algeria and constitute valuable knowledge for specific drought and wet periods monitoring in the region.

Timing of resin-tapping operations in maritime pine forests in Northern Spain

Aim of study: To optimize the timing of resin-tapping activities for maximizing the economic efficiency of resin tapping in Atlantic maritime pine forests. Area of study: Northern Spain. Material and methods: We conducted three small experiments in a mature maritime pine forest aimed to test: i) the impact of groove frequency on resin production, ii) the effect of previous grooves as a driver of temporal patterns of resin production along the seasons and iii) the impact of previous tapping on resin production in the following campaign. Main results: The resin produced decreased as groove frequency decreased, but the reduction was low. Considering that the number of trees that a worker can tap increases with more spaced grooves, higher tapping efficiency can be achieved with monthly grooves. Previous tapping increased resin yield during the following campaign but resin production was not affected by the previous grooves during the current tapping campaign. Research highlights: Responses to wounding seem to require time to be effective and temporal patterns of resin production appear to be driven by weather conditions alone.

Sources of phenotypic variation of wood density and relationships with mean growth in two Eucalyptus species in Argentina

Aims of the study: To describe the radial patterns of wood density, and to identify their main sources of variation, and the potential tradeoffs with mean tree growth, in two Eucalyptus species. Area of study: Mesopotamian (Corrientes and Entre Ríos provinces) and Pampean region (Buenos Aires province) of Argentina. Materials and methods: Eucalyptus grandis and Eucalyptus viminalis, growing in genetic trials installed in two sites per species were studied. X-ray wood microdensity profiles were developed from core samples. Each profile was proportionally divided in 10 sections. Mean, maximum, minimum and the standard deviation of wood density, for each section were computed. Mean annual growth was used to study the relationships with wood microdensity variables. A linear mixed-effects model computed the significance of different sources of phenotypic variation. Pearson´s correlation computed the relationships between variables. Main results: The pattern of radial variation in E. grandis showed a decrease in wood density from pith to bark, mainly due to the decrease in minimum wood density, while in E. viminalis, wood density increased towards the outer wood. In both species, the standard deviation of the wood density increased along the radial profile from pith to bark. Significant variation in wood density was explained by site, provenance and clone/family effects. In E. grandis mean, maximum and minimum wood density were negatively correlated with mean growth, whereas in E. viminalis correlations were positive but close to zero. Research highlights: Both the pattern of radial variation of wood density and the relationship between wood density and mean growth were different in the studied Eucalyptus species, and they varied within species depending on the site they were growing and genetic provenance.

Characterization of wood popularly known as “Louros” in the Brazilian amazon by visible spectroscopy and CIELAB parameters

Aim of study: The objective of this work was to evaluate the potential of colorimetry to discriminate wood from the “louros” group, in particular to contribute to a database of Brazilian native species for future application in logging control actions. Area of study: The wooden discs were collected in a Sustainable Forest Management Area (AMFS) belonging to two extractivist communities, Paraiso and Arimum, both in the “Green Forever” Extractivist Reserve, in the municipality of Porto de Moz, Pará state, Brazil. Material and methods: Colorimetric evaluation was carried out based on data from the CIEL*a*b* system, analyzed using PCA and ANOVA in a completely randomized design in a two-factor scheme. Main results: PCA produced some evidence of color patterns and some parameters may be more useful in caracterization. Longitudinal surfaces were more indicated for this group caracterization. The data from CIEL*a*b* system produce helpful information for distinction of wood from “louros” group, and so, the colorimetric technique can be an auxiliary tool for separation of this group, complementary to other techniques as wood anatomy. Research highlights: Correct discrimination of wood from “louros” group in commerce control; Brazilian native species.