Spatial and altitudinal bioclimatic zones of the Italian peninsula identified from a beech (Fagus sylvatica L.) tree-ring network

A network of 24 beech (Fagus sylvatica L.) tree-ring chronologies has been developed for the Italian peninsula. Principal component and cluster analyses were used to identify geographical and altitudinal patterns of tree growth. Correlations and response functions were then applied to the main modes of tree-ring variability to uncover climatic signals. In a landscape occupied by humans for millennia, this approach provided a detailed quantitative ecological characterization of forest types. Altitude was significantly correlated with dendrochronological parameters. The Alps and northern Apennines could be distinguished from the central-southern Apennines. In central Italy, we recognized three different vegetation belts occupied by beech forests, from low- to high-elevation sites. Summer drought impacted beech growth with different intensity at different elevations, depending on the onset and duration of the growing season. Moreover, low-elevation beech forests showed a distinct late spring climate signal, which was opposite to that of high-elevation sites. The coherent geographical and ecological patterns of tree-ring variability suggest that dendrochronological networks help define bioclimatic zones and forest types.     

Genetic transformation of cork oak (Quercus suber L.) for herbicide resistance

The bar gene was introduced into the cork oak genome. Cork oak embryogenic masses were transformed using the Agrobacterium strain AGL1 which carried the plasmid pBINUbiBar. This vector harbours the genes, nptII and bar, the latter under control of the maize ubiquitin promoter. The transgenic embryogenic lines were cryopreserved. Varying activities of phosphinothricin acetyl transferase were detected among the lines, which carried 1–4 copies of the insert. Molecular and biochemical assays confirmed the stability and expression of the transgenes 3 months after thawing the cultures. These results demonstrate genetic engineering of herbicide tolerance in Quercus spp. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Rubén álvarez, Ricardo J. Ordás are contributed equally.     

Variability of latewood-widths and -stable isotope ratios in a sessile oak tree (Quercus petraea (Matt.) Liebl.)

Axial variation of latewood-widths and -stable isotopes (δ¹³C and δ¹⁸O) of a single sessile oak tree (Quercus petraea (Matt.) Liebl.) was analyzed. The influence of sampling height was found to be weak for both, latewood-widths and -stable isotopes in the latewood. The observed trends with stem-height show clearly that possible effects due to cambial aging are overrated by annual effects. In addition, relations between samples from different stem-heights are strong for identical calendar years while they are poor for identical cambial age. This indicates that samples from both, living trees and historical wood can be taken from any height position of a trunk or beam as long they are free from anatomical abnormities. Simple correlation and Gleichläufigkeit were used for validation.     

The impact of the 2003–2008 weather variability on intra-annual stem diameter changes of beech trees at a submontane site in central Slovakia

The link between the dynamics of beech (Fagus sylvatica L.) diameter changes, recorded by mechanical dendrometers, and the weather activity was studied at a submontane site in central Slovakia between 2003 and 2008. A new approach was presented by constructing seasonal increment chronologies, dividing them into shorter periods and joining them across several seasons to analyse the main influencing factors. For this purpose, response functions and correlation functions and their intra-seasonal moving variants were calculated. The photoperiod appeared to be synchronising the culmination of the seasonal dynamics of diameter changes; however, the main factors influencing the seasonal dynamics were weather variables. At the beginning of the season, the diameter increase was significantly correlated with temperature and its accumulation over a longer period. In summer, the diameter increase was hampered by long-term heat waves and the positive influence of precipitation became more pronounced. Precipitation towards the end of summer and in autumn significantly positively impacted the variability of the dendrometer signals. In 2003, the unusual seasonal dynamics were caused by a hot May and a hot and dry summer.In view of the expected climate change, including warmer springs and a higher frequency of summer droughts and heat waves, we expect a shift in the culmination of beech seasonal diameter increase towards May. Intensive drought and heat periods during summer will probably stress the beech populations growing close to their lower altitudinal limit.     

Growth reactions of Pinus sylvestris L. and Quercus pubescens Willd. to drought years at a xeric site in Valais, Switzerland

In Valais, an inner-Alpine dry valley in Switzerland, low-elevation Scots pine (Pinus sylvestris L.) forests are changing. While pine shows high mortality rates, deciduous species, in particular pubescent oak (Quercus pubescens Willd.), are becoming more abundant. We hypothesise that increasing drought and the species-specific drought tolerance are key factors in these processes. In this study, the growth reaction to drought years of pine and oak growing at a xeric site in Valais was analysed using dendrochronological and wood anatomical methods. Congruent with theoretical expectations, the tree-ring widths of both species, the mean lumen area of earlywood vessels in oak and the number of tracheids in a radial row in pine decreased in response to dry conditions. However, both species also showed reactions deviating from those known from mesic sites: In oak, the mean lumen area of latewood vessels increased in drought years. In pine, in the driest year of the period (1976), the mean radial diameter increased in latewood and decreased only slightly in earlywood. These results emphasises that the process of wood formation and cell functionality at xeric sites is not completely understood yet. Both species seem to have difficulties to adapt the size of their water-conducting cells to strongly reduced water availability in drought years. Additionally, the cell number is strongly reduced. Thus it remains unclear if both species can maintain sufficient water transport under increasingly dry conditions.     

Rhizospheric NO interacts with the acquisition of reduced N sources by the roots of European beech (Fagus sylvatica L.)

The gas phase of the soil plays an important role in plant growth and development. We investigated the effect of rhizospheric NO as a signalling compound for N uptake of beech roots. Following exposure to NO, ammonium and glutamine uptake into roots were determined using ¹⁵N-labelling, and gene expression of selected transporters was analysed by quantitative real-time PCR. Uptake of both N sources increased significantly with elevated NO concentration. However, with one exception, this increase was not reflected in up-regulation of expression of the respective transporters.     

Wood growth response of Calluna vulgaris (L.) Hull to elevated N deposition and drought

Ring diameters and ring number counts were recorded from Calluna stem cross-sections harvested during an N manipulation experiment. The application of dendrochronological methods permitted accurate ageing of shrubs growing in a heathland of known age. Linear regression analyses demonstrated a highly significant association between increasing levels of N input and stem diameter in both watered and droughted plots (droughted in 1997 only). N inputs were identified as the most significant environmental stressor, appearing to speed ageing vis the Calluna growth cycle. Drought sensitivity was noted in the high N treatment plots (120 kg N ha⁻¹ yr⁻¹) with decreased stem diameters. This may have implications in the response of Calluna growth under current climate change scenarios.     

Effect of PEG and olive cake feed blocks supply on feed intake, digestion, and health of goats given kermes oak (Quercus coccifera L.) foliage

Four groups of four Alpine × local male goats (20-month-old), each on kermes oak (Quercus coccifera L.) foliage were used to investigate nutrient intake and utilisation, blood metabolites and clinical parameters when supplemented with polyethylene-containing and polyethylene-free feed blocks and with polyethylene glycol (PEG, molecular weight 4000). PEG was used to neutralise tannins. The composition (g/kg DM) of feed blocks (B and B_PEG, respectively) was: olive cake (367 and 331), cactus fruit (90 and 80), wheat bran (243 and 218), quicklime (154 and 139), urea (73 and 66), salt (73 and 66) and PEG (0 and 100). Group 1 was not supplemented (control) and group 2 was supplemented with feed blocks (B). PEG-containing feed blocks were fed to goats in group 3 (B_PEG). The fourth group received feed blocks and PEG separately, i.e. mixed with 5 g processed barley (B+PEG). The amount of PEG distributed to the latter group was calculated so that goats supplemented with B_PEG or B+PEG consume the same amount of PEG. Animals were adapted on experimental diets for 21 days before starting a 6-day-faecal collection period. The nutritive value of kermes oak foliage was low due mainly to high levels of phenolic compounds particularly lignin (236 g/kg DM) and tannins (34.8 g equivalent tannic acid/kg DM) and low concentration of crude protein (62 g/kg DM). Accordingly, dry matter intake (34.8 g/kg W^0.75) and apparent digestibility of DM (0.527), CP (0.332) and neutral detergent fibre (NDF, 0.429) were low in goats fed on this shrub species as a sole diet. Although DM intake of feed blocks was low (113 g per day), supplementation of PEG-free blocks almost doubled consumption of kermes oak (61.2 g/kg W^0.75) and intakes of digestible organic matter and CP increased from 17.4 and 1.0 g/W^0.75, respectively, to 46.6 and 33.0 g/W^0.75. Further improvement of these parameters was not observed by incorporation of PEG in block or by PEG supply along with the block (B_PEG and B+PEG versus B, P>0.05). Irrespective of dietary treatments, blood metabolites, i.e. glucose, urea, total proteins, albumin, creatinine, gamma-glutamyltranspeptidase, calcium, phosphorus and magnesium were within the normal range for local goats. Feed blocks increased serum urea (P<0.05), probably as consequence of improved N value of the diet. Biochemical parameters and clinical signs suggested a partial intoxication of goats solely on kermes oak. Supplementation with feed blocks with or without PEG improved cardiac, respiratory and rumen contraction frequencies and raised body temperature to the normal value (37 °C). Olive cake-based feed block enriched with squeezed cactus fruits was found to be a cost effective supplement to substantially improve the nutritive value of kermes oak-based diet and to maintain healthy goats.     

Assessing the impact of ozone on photosynthesis of European beech (Fergus sylvatica L.) in environmental chambers

An exposure — response study with proportionalto-ambient ozone levels was conducted in closed chambers on 3-year-old European beech (Fagus sylvatica L.) of montane origin. The fumigation started in April 1990 and lasted for a single growing season. Climate data and ozone concentrations monitored at an experimental station of the Institute for Applied Plant Biology, Schönenbuch, Switzerland were simulated in the exposure chambers 12 days later (1*O₃). To test exposure-response relations three additional treatments were applied, subambient (0.2*O₃) and two proportionally increased ozone treatments (1.5*O₃ and 2*O₃). The photosynthetic behaviour of the trees in August revealed the light reactions to be less affected than parameters which are related to the dark reactions of photosynthesis. Assimilation (A₃₅₀), apparent carboxylation efficiency (CE), and maximum photosynthetic capacity (A₂₅₀₀) were reduced with increasing ozone concentration. For the ozone response of CE and A₂₅₀₀ Critical Levels were calculated.     

Coexistence of Abies alba (Mill.) - Fagus sylvatica (L.) and climate change impact in the Iberian Peninsula: A climatic-niche perspective approach

Abies alba Mill. (European silver fir) and Fagus sylvatica L. (beech) are Eurosiberian species dispersed over the Iberian Peninsula. Climate change predictions indicate a rise in temperature and a decrease in precipitation in this region, threatening the future existence of these species. In the present study we analyzed the future topo-climatic suitability of Abies alba and Fagus sylvatica and the mixed forests of these two species, using the General Linear Models technique and data from the third National Forest Inventory (Ministerio de Agricultura PyA, 2007). We considered two modeling approaches based on niche theory: modeling community (Abieti-Fagetum) and overlapping individual species models. General trends showed an overall decrease in both species’ topo-climatic suitability and indicated that the Pyrenees will play a crucial role as a climatic refuge. The modeling approaches markedly differed, however, in their current and future spatial agreement. Despite good accuracy results, community modeling through co-occurrence does not encompass the environmental space of individual species prejudicing future assessments in new environmental situations, suggesting a need for future studies in community modeling.     

Probing the responses of barley cultivars (Hordeum vulgare L.) by chlorophyll a fluorescence OLKJIP under drought stress and re-watering

The main objective of this study was to evaluate the effects of drought and re-watering on 10 varieties of barley (Hordeum vulgare L.) originating from Morocco. Five varieties obtained from the National Institute of Agricultural Research (INRA) of Morocco and five landraces (local varieties defined by high stress tolerance, high yield stability, an intermediate yield and low-input demand) collected at five localities in the south of Morocco were used in the present study. After 2 weeks of growth, drought stress was initiated by withholding water for 2 weeks followed by 1 week of re-watering. The polyphasic OJIP fluorescence transient was used to evaluate photosystem II (PSII) criteria at the end of the first week of drought stress (moderate drought), at the end of the second week (severe drought) and the end of the recovery phase. Drought and re-watering had little effect on the maximum quantum yield of primary photochemistry φ_Po(=F_V/F_M). The photosynthetic performance index (PI) is the product of an antenna, reaction center and electron transport dependent parameter. It revealed differences between varieties as a function of drought and re-watering. For the screening for drought stress tolerance, changes in the PI during a 2-week drought stress treatment were analysed and a new parameter was defined: the drought factor index (DFI) = log(PI_week 1/PI_control) + 2 log(PI_week 2/PI_control). The DFI of the tested varieties correlated with their drought tolerance. Another parameter that was analysed was the relative water content. It decreased during the drought stress treatment varying between 61% and 78.2% at the end of the drought period. During the subsequent recovery period, it increased in a species-dependent manner (65.1–94.1%). A third parameter studied were changes in the initial fluorescence rise. The fluorescence rise during the first 300 μs (L-band) can give information on the energetic connectivity between PSII units whereas changes in the rise during the first 2 ms (K-band) offer information on developing limitations on the donor side of PSII. Changes in respectively the L and K-bands of the fluorescence transients OJIP were shown to have predictive value with respect to the vitality of leaves and the tolerance of the varieties to drought stress.     

In vivo and in vitro effects of copper and cadmium on the plasma membrane H+-ATPase from cucumber (Cucumis sativus L.) and maize (Zea mays L.) roots

The plasmalemma vesicles isolated from cucumber and maize roots were used to study the effect of Cu²⁺ and Cd²⁺ on the hydrolytic and proton pumping activities of ATPase. In vivo application of metal ions to the plant growth solutions resulted in stimulation of the proton transport in maize. In cucumber roots the action of metals was not the same: cadmium stimulated the H⁺ transport through plasmalemma whereas Cu²⁺ almost completely inhibited it. Copper ions decreased the hydrolytic activity of H⁺-ATPase in cucumber, without any effect on this activity in membranes isolated from maize roots. The effect of cadmium on the hydrolytic activities was opposite: ATP-hydrolysis activity in plasmalemma was not altered in cucumber, whereas in maize its stimulation was observed. The amount of accumulated metals was not the main reason of different influence of metals on H⁺-ATPase activity in tested plants. In in vitro experiments Cu²⁺ inhibited H⁺ transport in the cucumber, to a higher degree than Cd²⁺ and both metals did not change this H⁺-ATPase activity of plasmalemma isolated from corn roots. Cu²⁺ added into the incubation medium reduced the hydrolytic activity of ATPase in the plasma membrane isolated from cucumber as well as from corn roots. Cd²⁺ diminished the hydrolytic activity of ATPase in cucumber, and no effect of Cd²⁺ in the plasmalemma isolated from corn roots was found. Our results indicated different in vitro and in vivo action of both metals on H⁺-ATPase and different response of this enzyme to Cu²⁺ and Cd²⁺ in maize and cucumber.     

Topochemical investigation of early stages of lignin modification within individual cell wall layers of Scots pine (Pinus sylvestris L.) sapwood infected by the brown-rot fungus Antrodia vaillantii (DC.: Fr.) Ryv.

The initiation and progress of wood degradation of Pinus sylvestris sapwood exposed to the brown-rot fungus Antrodia vaillantii was studied on a cellular level by scanning UV microspectrophotometry (UMSP 80, Zeiss, MSP 800 Spectralytics). This improved analytical technique enables direct imaging of lignin modification within individual cell wall layers. The topochemical analyses were supplemented by light and transmission electron microscopy (TEM) studies in order to characterize morphological changes during the first days of degradation. Small wood blocks (1.5 × 1.5 × 5 mm) of Scots pine (P. sylvestris) were exposed to fungal decay by A. vaillantii for 3, 7, 11, 16, and 22 days. No significant weight loss was determined in the initial decay periods within three up to 7 days. After three days of decay the topochemical investigation revealed that the lignin modification starts at the outermost part of the secondary wall layer, especially in the region of the latewood tracheids. During advanced degradation after exposure of 22 days, lignin modification occurs non-homogeneously throughout the tissue. Even among the significantly damaged cells, some apparently unmodified cells still exist. Knowledge about lignin modification at initial stages of wood degradation is of fundamental importance to provide more information on the progress of brown-rot decay.     

Influence of in vitro growth conditions on in vitro and ex vitro photosynthetic rates of easy- and difficult-to-acclimatize sea oats (Uniola paniculata L.) genotypes

Net photosynthetic rates (P _n) of easy (EK 16-3) and difficult-to-acclimatize (EK 11-1) sea oats genotypes were examined under the following culture conditions: (1) photoautotrophic [sugar-free medium, high photosynthetic photon flux (PPF), high vessel ventilation rates and CO₂ enrichment, (PA)]; (2) modified photomixotrophic [sugar-containing medium diluted with sugar-free medium over time, high PPF, and high vessel ventilation rates (PM)]; (3) modified photomixotrophic enriched [same as PM with CO₂ enrichment, (PME)]; or (4) conventional photomixotrophic [sugar-containing medium, low PPF, and low vessel ventilation rates (control)]. Regardless of genotype, plantlets cultured under PA conditions died within 2 wk, whereas under PM and PME conditions, plantlets increased their P _n. After 6 wk, P _n per gram dry weight was 1.7 times greater in EK 16-3 than EK 11-1 plantlets cultured under PME conditions. In vitro-produced leaves of EK 16-3 plantlets were elongated with expanded blades, whereas EK 11-1 produced short leaves without expanded blades, especially under control conditions. After in vitro culture, EK 16-3 PME plantlets exhibited the highest dry weights among treatments. EK 16-3 PME and EK 16-3 PM had similarly high survivability, shoot and root dry weights and leaf lengths ex vitro compared to EK 16-3 control and EK 11-1 PM and PME plantlets. Ex vitro growth, survivability and P _n per leaf area of either genotype were not affected by CO₂ enrichment under modified photomixotrophic conditions. These results suggest that growth and survivability of sea oats genotypes with different acclimatization capacities can be enhanced by optimizing culture conditions.     

Influences of fallow age and season on the foraging behavior and diet selection pattern of goats (Capra hircus L.)

A study was undertaken to determine the foraging behavior and diet selection pattern of goats maintained on communal exclosures in relation to the influence of fallow age (years since effective protection initiated; <8 years vs. >12 years) and season (long rainy, dry, and short rainy seasons). The frequency of browsing was higher (P < 0.05) in the exclosures fallowed for >12 years compared to those fallowed for <8 years and this frequency was also highest during the short rainy season. More (P < 0.05) herbaceous bites were recorded in the <8 years fallow exclosures, compared to the >12 years fallow exclosures. Herbaceous species bites were maximized during the long rainy season whereas woody species bites were maximized during the dry season. The goats foraged upon 48 plant species of which 69% were woody species, 19% grasses, and the rest comprised of various forb species. The top species that significantly (P < 0.05) contributed to the diet of goats were Acacia etbaica, Balanites aegyptica, Cadaba farinosa, Capparis tomentosa, Dichrostachys cinerea, and Ocimum forskolei. The goats targeted taller woody species than the average of the exclosures. Maurea angolensis, Jasminium abyssinicum, C. farinosa, and Ormocarpum pubescence were among the preferred species that appeared to be on the verge of disappearance in most of the exclosures investigated in this study and require immediate attention. Using goats to reduce the threat of potential bush infestation appears to be a viable option for managing and sustaining production from exclosures since the goats showed preference for D. cinerea, the species considered a prolific invader plant. There is, however, a need to conduct further research on the impacts of direct browsing by the goats and this should also entail the determination of optimum number of goats/unit area.     

The effect of water soluble Scots pine (Pinus sylvestris L.) and Sitka spruce [Picea sitchensis (Bong.) carr.] heartwood and sapwood extracts on the growth of selected Trichoderma species

Extractable materials from some timber species have been identified which prevent wood decay; however, little has been reported on the effect(s) of such materials against mould species that colonize timber. With increasing interest in the use of Trichoderma species, both as agents of permeability enhancement and biological control, more information is required on how chemical components within fresh and processed timber influence growth of Trichoderma. Fresh and dried samples of Scots pine and Sitka spruce sapwood and heartwood were leached in a Soxhlet apparatus and the resulting extract was combined with malt extract agar and inoculated with Trichoderma. Trichoderma isolates were inhibited to varying degrees by extractives removed from fresh and dried heartwood of the two timbers. Growth on sapwood extractives, however, showed a lesser degree of inhibition. The implications of the results for applications of Trichoderma in timber are discussed.