Age-dependent responses of tree-ring growth and intra-annual density fluctuations of Pinus pinaster to Mediterranean climate

Dendrochronology generally assumes that climate–growth relationships are age independent once the biological growth trend has been removed. However, tree physiology, namely, photosynthetic capacity and hydraulic conductivity changes with age. We tested whether the radial-growth response to climate and the intra-annual density fluctuations (IADFs) of Pinus pinaster Ait. varied with age. Trees were sampled in Pinhal de Leiria (Portugal), and were divided in two age classes: young (<65 years old) and old (>115 years old). Earlywood and tree-ring width of young P. pinaster trees were more sensitive to climate influence while the response of latewood width to climate was stronger in old trees. Young trees start the growing season earlier, thus a time window delay occurs between young and old trees during which wood cells of young trees integrate environmental signals. Young trees usually have a longer growing season and respond faster to climate conditions, thus young P. pinaster trees presented a higher frequency of IADFs compared with old trees. Most of the IADFs were located in latewood and were positively correlated to autumn precipitation. The radial-growth response of P. pinaster to climate and the IADFs frequency were age dependent. The use of trees with different age to create a tree-ring chronology for climate studies can increase the resolution of climatic signals. Age-dependent responses to climate can also give important clues to predict how young and old trees react to climate change.     

Climatic impacts and drought control of radial growth and seasonal wood formation in Pinus halepensis

Short- and long-term growth responses to drought and climatic influences still remain poorly understood. In this study, we investigated the impact of climatic drivers (temperature, precipitation) and drought, using the Standardized Precipitation Index (SPI) calculated at different time scales (1–48?months), on earlywood (EW) and latewood (LW) widths in Pinus halepensis. Nine forests subjected to dry summer conditions were sampled in Mediterranean semi-arid areas from north-eastern Spain. In addition, we explored the seasonal dynamics of cambial activity and wood formation in relation to short-term climate variability. We found two peaks of tracheid cell production corresponding to EW (May–June) and LW (mid-July–August) growth phases, associated with a sharp decrease in enlarging cells in early July in response to low water availability. In the period of analysis (1970–2005), EW growth was positively correlated with precipitation in previous December and current January, April, May and June, while it was negatively correlated with temperature in June and July. LW was correlated positively with minimum temperatures in January. Probably this was an indirect relationship as a consequence of increased EW width at higher January temperatures. Drought affected more negatively EW than LW formation as evidenced the higher SPI-EW correlation (r?=?0.72) than the SPI-LW one (r?=?0.54). The strongest EW response to drought was observed in July, whereas the highest LW response to drought occurred in September; and this seasonal pattern matched the phases of lowest EW and LW tracheid production. Under a future reduction of winter and spring precipitation, the studied forests may show a decrease in tracheid cell production, causing a decline of radial growth, a reduction in hydraulic conductivity and, indirectly, a hampered carbon uptake in such semi-arid woodlands.     

Climate impact on growth dynamic and intra-annual density fluctuations in Aleppo pine (Pinus halepensis) trees of different crown classes

Mediterranean environments are of special interest for the study of the relationships between climate, growth and anatomic features. Dendrochronological techniques were applied at eight sampling sites that were selected throughout the natural distribution area of Pinus halepensis in the Iberian Peninsula. The objectives of this paper were: (i) to identify relationships between radial growth and climate for different crown classes of Aleppo pine (P. halepensis Mill.); (ii) to quantify the presence of intra-annual density fluctuations (IADFs) according to crown class and cambial age; (iii) to establish the relationships between IADFs and climate. In the more mesic sites, dominant trees showed higher climatic sensitivity than suppressed trees, while in the more xeric sites suppressed trees showed higher sensitivity than dominant trees. Tree-ring growth of both crown classes correlated positively with precipitation during and prior to the growing season. IADFs were more frequent in young than in old stands without differences between crown classes. Precipitation in April and December was positively correlated to the occurrence of IADFs, while precipitation in July correlated negatively. A higher frequency in IADFs occurred in the last 50 years, which coincides with the increase in drought events in the Iberian Peninsula.     

Climatic influences on intra-annual stem radial increment of Pinus sylvestris (L.) exposed to drought

Within a dry inner Alpine valley in the Eastern Central Alps (750 m a.s.l., Tyrol, Austria), the influence of climate variables (precipitation, air humidity, temperature) and soil water content on intra-annual dynamics of tree-ring development was determined in Scots pine (Pinus sylvestris L.) at two sites differing in soil water availability (xeric and dry-mesic site). Radial stem development was continuously followed during 2007 and 2008 by band dendrometers and repeated micro-sampling of the developing tree rings of mature trees. Daily and seasonal fluctuations of the stem radius, which reached almost half of total annual increment, primarily reflected changes in tree water status and masked radial stem growth especially during drought periods in spring. However, temporal dynamics of intra-annual radial growth determined by both methods were found to be quite similar, when onset of radial growth in dendrometer traces was defined by the occurrence of first enlarging xylem cells. Radial increments during the growing period, which lasted from early April through early August, showed statistically significant relationships with precipitation (Kendall τ = 0.234, p < 0.01, and τ = 0.184, p < 0.05, at the xeric and dry-mesic site, respectively) and relative air humidity (Pearson r = 0.290, p < 0.05, and r = 0.306, p < 0.05 at the xeric and dry-mesic site, respectively). Soil water content and air temperature had no influence on radial stem increment. Culmination of radial stem growth was detected at both study plots around mid-May, prior to occurrence of more favourable climatic conditions, i.e., an increase in precipitation during summer. We suggest that the early decrease in radial growth rate is due to a high belowground demand for carbohydrates to ensure adequate resource acquisition on the drought-prone substrate.     

Ectomycorrhizal fungi of Pinus pinaster

A study was undertaken to determine the ability to form ectomycorrhizae with Pinus pinaster Ait. in pure culture syntheses of 98 isolates of putative mycorrhizal fungi, mainly collected in northern Spain. A total of 35 species in 16 genera — Amanita, Cenococcum, Collybia, Cortinarius, Hebeloma, Laccaria, Lactarius, Lyophyllum, Melanogaster, Paxillus, Pisolithus, Rhizopogon, Scleroderma, Suillus, Thelephora and Xerocomus — formed ectomycorrhizae. Many of these fungal species were not previously reported as symbiotic with Pinus pinaster. Results obtained increase the range of potential fungal candidates for inoculation of nursery seedlings.     

Climate control on ring width and intra-annual density fluctuations in <Emphasis Type="Italic">Pinus kesiya</Emphasis> growing in a sub-tropical forest of Manipur,Northeast India

Key message

Growth ring study of Pinus kesiya (khasi pine) growing in sub-tropical forest in Manipur, northeast India was performed to understand climate signatures in ring widths and intra-annual density fluctuations.

Abstract

The growth rings in khasi pine (Pinus kesiya Royle ex Gordon) growing in sub-tropical Reserve Forest in Imphal, Manipur, northeast India were analysed to understand environmental signals present in ring-width series and intra-annual density fluctuations (IADFs). For this the growth ring sequences in increment core samples collected from 28 trees were precisely dated and a ring-width chronology spanning AD 1958–2014 developed. The correlation analyses between ring-width chronology and weather data of Imphal revealed that a cool April–May–June favour tree growth. The wood anatomical features of growth rings revealed the occurrence of IADFs in early- and latewoods. The IADFs in earlywood were found to be associated with reduced precipitation in months from April to July. However, the wetter conditions in late growing season, especially August/September triggered the formation of IADFs in latewood. Our findings endorse that the IADF chronologies of khasi pine could emerge as an important proxy of summer monsoon rainfall in long-term perspective in data scarce region of northeast India.

     

Climatic signals in tree-ring widths and wood structure of Pinus halepensis in contrasted environmental conditions

Tree-ring widths (RW), earlywood (EW) and latewood (LW) widths, the transition from early to latewood (T) and the occurrence of intra-annual density fluctuations in EW (E-ring) and in LW (L-ring), as well as the presence of resin canals in EW and LW, were analyzed in Aleppo pine (Pinus halepensis Mill.) from three sites in Spain and one in Slovenia to find out if the anatomical characteristics can provide additional seasonal climate–growth information from contrasted environmental conditions. Principal component analysis was applied to elucidate the relationship between the measured parameters and climate. Principal component factor PC1 proved to be related to parameters of EW and the climatic variables of winter-spring; PC2 to parameters of LW and climatic variables of summer–autumn; PC3 to conditions during transitions from humid to dry periods. The three PCs vary between sites and are determined by the climatic conditions during their formation. The study demonstrates that wood anatomical features may provide complementary information to that contained in tree-ring widths. Since such results are obtained on contrasting sites, it is likely that it may be generalized over the wide range of P. halepensis distribution representing a useful proxy for studies on a regional scale.     

Genetic control of stem form in Pinus pinaster Ait. seedlings exposed to lateral light

 In order to compare family differences in stem form determination, seedlings of eight half-sib progenies of Pinus pinaster were exposed to three different light treatments: fixed lateral light (T1), alternate lateral light (T2), and direct sunlight (T3). From spatial coordinates of several points along the stem we computed four variables: global leaning (GL), apical leaning (APL), flexuosity index (FL) and length of the stem (LEN). Based on comparisons of the four variables, the phototropic stimulus caused different responses in stem form at the familial level. Treatment had an important effect on stem form, although the familial response to treatments was quite variable. Heritability values (h²) of the four analyzed variables showed a different pattern of variation for the three treatments, being very stable for LEN and FL, whereas h² of APL was much greater based on T1 and T2 compared to T3, and h² of GL based on T2 was much greater compared to T3 and T1. Differences in stem form were due not only to photomorphogenetic response to different light stimuli, but also to the straightening processes such as compression wood formation. The results suggest that lateral light treatments may be useful in revealing differences in efficiency of the mechanisms involved in stem form determination. Received: 1 June 1995 / Accepted: 1 April 1997     

In vitro rooting of cloned shoots in Pinus pinaster

In vitro plantlet regeneration will be a sueful tool in reforestation only when rooting problems are overcome. Our study was therefore focused on Pinus pinaster rooting conditions.
Methods were used which permit multiple axillary (instead of adventitious) bud production in order to obtain genetically identical explants and hence to procure more homogeneous resutls. The hormonal treatment efficiency was then tested on several clones for rooting. Different substrates were compared. A mixture of peat and perlite (1/3, v/v) permitted rooting and the further development of the root system if humidity was properly controlled. The use of an agar medium avoided this difficulty; it supported root induction but resulted in limited growth.
For hormonal treatment, explants, submitted to a 12-day-period with NAA (10⁻⁶ M ) and then subcultured in an auxin-free medium, gave rooting percentages ranging from 80 to 100%. In terms of rooting quality (intensity, growth rate and branching ability), a 15-to 19-day-period of auxin treatment was more effective.
Application of this optimal treatment to several clones revealed slight differences within clones and between clones (80 to 100% of rooting according to the clone). Regenerated plantlets were able to undergo an autotrophic growth after transplantation under greenhouse conditions.     

Root architecture and wind-firmness of mature Pinus pinaster

This study aims to link three-dimensional coarse root architecture to tree stability in mature timber trees with an average of 1-m rooting depth. Undamaged and uprooted trees were sampled in a stand damaged by a storm. Root architecture was measured by three-dimensional (3-D) digitizing. The distribution of root volume by root type and in wind-oriented sectors was analysed. Mature Pinus pinaster root systems were organized in a rigid 'cage' composed of a taproot, the zone of rapid taper of horizontal surface roots and numerous sinkers and deep roots, imprisoning a large mass of soil and guyed by long horizontal surface roots. Key compartments for stability exhibited strong selective leeward or windward reinforcement. Uprooted trees showed a lower cage volume, a larger proportion of oblique and intermediate depth horizontal roots and less wind-oriented root reinforcement. Pinus pinaster stability on moderately deep soils is optimized through a typical rooting pattern and a considerable structural adaptation to the prevailing wind and soil profile.     

Climatic changes in western Spain

Possible interactions between climatic changes and vegetation during the present century in western Spain have been examined using a phytoclimatic model. Statistical analysis of meteorological data for the period 1901–1989 suggests a tendency towards a reduction in temperature differences with a negative tendency for maximums and variability and a positive tendency for minimum temperatures. Rainfall, number of rainy days and number of rainy sequences have shown positive tendencies since the beginning of the century. Phytoclimatic determination for the same period showed dominant mediterranean conditions until 1950. Around 1951, a point of inflection was detected, the more humid conditions thereafter becoming dominant, and more favorable to deciduous broad-leaf forests in transition towards mediterranean forests. In accordance with the results of other studies these data would indicate the changing tendencies detected could be affecting a large part of the northeastern Iberian Peninsula.     

Short-term growth responses and associated wood density fluctuations in variously irrigated Eucalyptus globulus

Cambial growth and wood properties respond to fluctuating environmental conditions. Understanding the nature of these responses is crucial to understanding their cumulative effect on the wood quality characteristics of a forest stand. This paper reports on a study conducted over a period of 3? years in continuously irrigated, alternately irrigated and non-irrigated Eucalyptus globulus, in which changes in wood density occurring in response to short-term growth responses were examined. The study showed that continuous irrigation led to the production of wood with significantly more homogenous density than was the case in situations, where trees experienced large fluctuations in temporal water availability. Although the trees which were not irrigated had the highest wood density overall, trees in which growth was relatively continuous tended to produce the largest volumes of wood with relatively high density, compared to trees in which periodic growth responses were caused by intermittent irrigation, in which wood density was actually reduced. This was largely due to more growth days in summer under the conditions of higher radiation, and a reduction in the number of growth events leading to the production of disproportionately large amounts of low density wood. Soil water deficits contributed to density variation in all treatments, but the effect of energy limitations became more important in continuously irrigated trees.     

Climatic fluctuations and forestry in Lapland

Climatic fluctuation is a serious problem for forestry in Lapland. Some indications about the nature and causal relationships of such fluctuation have been discussed. Cyclic variation can be explained by a memory in the atmosphere, variation in the Moons's gravitation, and solar activity.
The index of atmospheric circulation over the northern hemisphere was the most effective climatic parameter in explaining the growth variation of Scots pine.     

Effects of light on terpene hydrocarbon synthesis in Pinus pinaster

The biosynthesis of terpene hydrocarbons has been investigated in maritime pine (Pinus pinaster Ait.) seedling primary leaves under light and darkness and with different precursors. Impossible in darkness, the synthesis of monoterpenes (mainly α- and β-pinene) is strongly activated by light. Only ¹⁴C-carbonate and ¹⁴C-acetate can be incorporated into monoterpenes. Activation by light is comparatively much more effective for seedling leaves previously cultivated under short days than in leaves from seedlings given long days. The spectral bands which are efficient for the synthesis of monoterpenes are located around 480 and 685 nm with ¹⁴C-carbonate and 480 and 630 nm with l-¹⁴C-acetate. Furthermore, this light activation does not occur if leaf pieces instead of whole leaves are used for the incorporation experiments. When 2-¹⁴C-mevalonic acid and 1-¹⁴C-isopentenyl pyrosphosphate are applied as precursors, no radioactivity is recorded in monoterpene hydrocarbons even after light exposures. In contrast, sesquiterpene hydrocarbons (caryophyllene and humulene) are easily synthesized under light or darkness in intact or fragmented leaves from the different precursors of photosynthetic or exogenous origin. From these results the compartmentalization in the synthesis of C₁₀ and C₁₅ hydrocarbons appears clear. There is a metabolic cooperation between the photosynthetic tissues and the specific site of elaboration of C₁₀ hydrocarbons, which site is located in the parts where the epithelial cells of resin ducts are functional. The synthesis of sesquiterpene hydrocarbons takes place in the whole leaf without activation by light.     

Purification and properties of peroxidase from Pinus pinaster needles

Peroxidase (Ec 1.11.1.7) was purified from needles of Pinus pinaster to apparent homogeneity by DE-52 cellulose chromatography with a final recovery of enzyme activity of about 85%. The purified enzyme (A402/A275 = 1.05) had a specific activity of about 948 U/mg of protein and ran as a single protein band both on SDS-PAGE and native PAGE with Mr of 37,000 and 151,000, respectively. Both native PAGE and isoelectric focusing gels of the purified enzyme were stained for activity which coincided with the protein band. The pI of the purified enzyme was found to be 3.2 by isoelectric focusing on an ultrathin polyacrylamide gel. The enzyme has an optimum pH of activity of 5.0 and temperature optimum of 30 degrees C. Stability studies of the enzyme as a function of pH and temperature suggest that it is most stable at pH 5.0 and 0-40 degrees C, respectively.     

Establishment and characterization of Pinus pinaster suspension cell cultures

We report the establishment of a Pinus pinaster (Ait.) cell suspension culture in a modified MS medium supplemented with 2 mg ml⁻¹ 2,4-D and 1 mg ml⁻¹ BA. Calli were obtained from seedling root segments and established a friable isodiametric cell suspension, suitable for in vitro studies of maritime pine at the cellular level. Growth (dry weight), cell viability, pH, and nutrient consumption: carbon source (sucrose, fructose and glucose), nitrogen source (ammonia and nitrate) and phosphate were monitored over 24 h. Suspension cells exhibited a 15-day exponential growth stage, during which a biphasic consumption profile was observed for all nutrients. Phosphate was the first limiting nutrient and preferable consumption was observed for glucose over fructose and nitrate over ammonium.     

Mycorrhizal symbiosis affected by different genotypes of Pinus pinaster

Background and aims

Higher growth rate and morphological traits have been the major criteria for selecting trees in breeding programs. The symbiotic associations between P. pinaster and ectomycorrhizal fungi can be an effective approach to enhance plant development. The aim of this work was to assess whether the establishment of mycorrhizal symbiosis at nursery stage was affected by tree breeding.

Methods

Seeds of P. pinaster from a clonal population, designed to select for various traits, and from neighboring wild plants were inoculated with compatible ectomycorrhizal fungi: Suillus bovinus, Pisolithus tinctorius or Rhizopogon roseolus, and grown in individual cells containing forest soil, in a commercial forest nursery. Growth and nutritional traits, colonisation parameters and the fungal community established were assessed.

Results

R. roseolus and P. tinctorius were the most efficient isolates in promoting plant development. Inoculated selected saplings had an overall superior development than their wild counterparts, with up to a 4.9-fold in root dry weight and a 13.6-fold increase in the total number of ectomycorrhizal root tips. Differences in fungal community were revealed through the denaturing gradient gel electrophoresis profile of each treatment.

Conclusions

The results from our study suggest that the selected genotype benefits more from the mycorrhizal association and therefore this could be a valuable biotechnological tool for the nursery production of P. pinaster.