Cellular structure and chemical composition of cork from the Chinese cork oak (Quercus variabilis)

Quercus variabilis Blume, the Chinese cork oak, is an oak species with a thick cork outer bark. The cork is exploited at a limited scale in China and considered of lower quality than the commercial cork from Quercus suber. We studied an industrial cork granulate feedstock of Q. variabilis in relation to cellular structure and chemical composition and compared it to Q. suber cork under a material’s perspective. The cork of Q.variabilis has 1.1 % ash, 9.6 % extractives, 34.8 % suberin and 19.1 % lignin. The monosaccharide composition with shows a predominance of hemicelluloses: glucose 42.8 % of total neutral sugars, xylose 27.5 %, arabinose 15.4 %, galactose 9.0 %, mannose 4.0 %, rhamnose 1.2 %. The FT-IR spectrum shows the indicative peaks of suberin. The composition is overall similar to that of Q. suber cork. Q. variabilis cork has the typical cellular characteristics of bark cork tissues with a regular and radially aligned structure of cells without intercellular voids. Solid volume fraction was estimated at approximately 16 %. Compared with Q. suber, the Q. variabilis cork cells are smaller, the cell wall undulation and the overall row alignment less homogeneous, the cell surface is irregular and the solid volume proportion higher. The characteristics of Q. variabilis cork support its use as a cellular material for sealing, insulation and energy absorption, but the overall quality is lower than that of Q. suber cork. The negative impact of the higher density and structural lower uniformity at tissue and cell level should be evaluated for processing and product performance.     

Assessing foraging strategies of herbivores in Mediterranean oak woodlands: a review of key issues and selected methodologies

Montados are agro-silvo-pastoral ecosystems, typical of the Southwest Iberian Peninsula, of high socio-economic and conservation importance, where grazing is a dominant activity. Montados are characterized by an open tree canopy of Quercus sp. and a diverse undercover of shrubs and grasslands that constitute the plant food resources for grazing animals. Plant food resources of Montados are highly variable, both spatially and seasonally, in quantity and quality. Reliable and easy to use methods to monitor grazing are necessary to allow proper understanding of foraging strategies of grazing animals and to set sustainable grazing management. We describe the main characteristics of the plant food resources available for grazing animals, striking its variability, and revise the potential of using N-alkanes and saliva proteome methods to assess foraging strategies in Montados. In a scenario of dynamic multiple choices, we discuss the use of n-alkane methodology for the simultaneous estimation of diet composition and voluntary intake and saliva proteome as a mean of increasing the knowledge on diet adjustments.     

Clues to wood quality and production from analyzing ring width and density variabilities of fertilized Pinus taeda trees

Tree growth and wood density are influenced by forest management. Nevertheless, few studies have evaluated their variability responses to fertilizer treatments at inter-annual, inter-tree and stand-production levels. Therefore, the annual ring width (RW) and density (RD) of sixty 17-year-old-Pinus taeda trees fertilized with six doses of composted pulp-mill sludge (CPMS) were analyzed. Ten trees for each treatment were felled and from which wood discs were taken at different trunk heights. The annual RW and RD were provided by X-ray microdensitometry, synchronized and the trunk basic specific gravity (SG_B) and biomass calculated. The effects of CPMS treatments were explored using interaction of variables RW and RD with cambial age, diameter, trunk SG_B and biomass production. Trees treated with CPMS grow faster, increasing their biomass (up to 108%), presenting lower wood density values (significant up to the 6th year) and reaching the mature wood later than untreated trees. Furthermore, the potential use of RW and RD in allometric equations showed good accuracy to predict trunk SG_B and biomass. Altogether, our results indicated that ring width and density revealed the impacts of fertilization treatment on wood quality and production. Our study also provides useful information for forest managers on the fertilization monitoring process.

     

Response of saproxylic insect communities to logging history,tree species,stage of decay,and wood posture in the central Nearctic boreal forest

Saproxylic insect assemblages are essential functional components of forest ecosystems that can be affected by forest management.We used a split-plot ANOVA design to analyze differences in selected saproxylic insects(all arthropod orders and dipteran and parasitic hymenopteran families) emerging from dead wood of sites with different logging histories(horse-logged,mechanically-logged and unlogged),tree species(Populus and Picea),stage of decay(early-and late-decay stages) and posture(standing and downed logs) in the boreal forest of central Canada.No clear effects of logging history were seen for the studied taxa; however,interaction between logging history and other dead wood features was apparent.Cecidomyiidae consistently emerged more from Populus than from Picea dead wood.Most of the studied saproxylic families were more abundant in late-decay than in early-decay wood.Dipterans of the Cecidomyiidae,Ceratopogonidae,Empididae,Mycetophilidae and Sciaridae families,and hymenopterans of the Diapriidae and Ichneumonidae families were significantly more abundant in downed than in standing dead wood.In contrast,Mymaridae was most abundant in standing dead wood.Our study provides evidence that some insects at high taxonomic levels respond differently to dead wood quality,and this could inform future management strategies in the boreal forest for the conservation of saproxylic fauna and their ecological functions.     

Age effects and climate response in trees: a multi-proxy tree-ring test in old-growth life stages

Aging in trees implies a progressive reduction in the growth rate, related to a shortening of the growing period and changes in the photosynthetic capability and efficiency. These changes may continue during the old-growth life stages following the juvenile phase and are reflected in tree-ring properties such as growth increment, density or stable isotopes. We studied possible climate age effects in time series of several tree-ring parameters (ring width, wood density and stable carbon and oxygen isotopes) of mature individuals from two age groups of Pinus uncinata and P. nigra at two locations in Spain. The aim was to test whether age differences in trees in the old-growth life stages could lead to diverging climate responses. The results show some differences in response to climate between age groups at a monthly level, but most of these divergences are not significant for seasonal climate variables. Regardless of the age group, the main limiting climate factors constrained tree growth equally. Although our findings do not support the idea of an age-dependent response to climate that may lead to inaccurate climate reconstructions, further studies using tree-ring density and stable isotope series are urgently needed to verify the current results.     

First report on Meloidogyne chitwoodi hatching inhibition activity of essential oils and essential oils fractions

The Columbia root-knot nematode (CRKN), Meloidogyne chitwoodi, is an EPPO A2 type quarantine pest since 1998. This nematode causes severe damage in economically important crops such as potato and tomato, making agricultural products unacceptable for the fresh market and food processing. Commonly used nematicidal synthetic chemicals are often environmentally unsafe. Essential oils (EOs) may constitute safer alternatives against RKN. EOs, isolated from 56 plant samples, were tested against CRKN hatching, in direct contact bioassays. Some of the most successful EOs were fractionated and the hydrocarbon molecules (HM) and oxygen-containing molecules (OCM) fractions tested separately. 24 EOs displayed very strong hatching inhibitions (≥90 %) at 2 µL mL^?1 and were further tested at lower concentrations. Dysphaniaambrosioides, Filipendula ulmaria, Ruta graveolens, Satureja montana and Thymbra capitata EOs revealed the lowest EC₅₀ values (<0.15 µL mL^?1). The main compounds of these EOs, namely 2-undecanone, ascaridol, carvacrol, isoascaridol, methyl salicylate, p-cymene and/or γ-terpinene, were putatively considered responsible for CRKN hatching inhibition. S. montana and T. capitata OCM fractions showed hatching inhibitions higher than HM fractions. The comparison of EO and corresponding fractions EC₅₀ values suggests interactions between OCM and HM fractions against CRKN hatching. These species EOs showed to be potential environmentally friendly CRKN hatching inhibitors; nonetheless, bioactivity should be considered globally, since its HM and OCM fractions may contribute, diversely, to the full anti-hatching activity.     

Circumferential variation of heartwood and stem quality in maritime pine stems

Maritime pine (Pinus pinaster Ait.) is an important timber and pulpwood species covering about 4 million ha in Portugal, Spain and France. This work studied the cross-sectional distribution of heartwood and sapwood along the stem using 3D modelling on 20 trees. The target was to assess the potential of this species for the industrial production of heartwood sawn products. The maritime pine stems were characterized by wide sapwood of 10 cm, in average, and the presence of heartwood at all height levels with constant diameter up to 35 % tree height, decreasing afterwards. In the radial section, the heartwood follows a circumferential-like shape which changes along the stem. Pith eccentricity index values were low and homogeneous regarding to stem and higher for heartwood. Heartwood cross-sectional shape was constant up to 45 % of total height of the tree and more elongated upwards. The constant heartwood diameter, low taper and pith eccentricity index, and an approximate circular shape up to 10 m height indicated these species’ potential to produce solid wood products made out of heartwood.     

Determinants of income-earning strategies and adoption of conservation practices in hillside communities in rural Honduras

Based on the results of participatory diagnostic surveys conducted in 95 rural communities in the hillsides of Honduras, we determine income earning strategies at the community level; identify their main determinants; and analyze the adoption of of conservation practices. Eight income-earning strategies were distinguished that reflect differences in comparative advantage between communities. We explain the choice of income earning strategy using a multinomial logit model that includes biophysical, economic, social and institutional variables. We use a probit model to show that adoption of conservation practices is determined by the type of income earning strategy, population density, market access, and organizational variables.