Radial Growth Analysis Research Articles

Growth and morphological modeling of InP nanowires obtained by Au-catalyzed selective area MOMBE

We present a theoretical analysis of vertical versus radial growth of InP nanowires obtained by selective area metalorganic molecular beam epitaxy at temperatures from 400 to 480°C. It is shown that the nanowire formation is controlled by surface diffusion of indium adatoms whose concentration on the sidewalls determines the local radial growth rate. Two models for the radial growth rate are considered, with linear (step flow) and exponential (two-dimensional nucleation) dependences on the adatom concentration. The linear model reproduces fairly well the vertical elongation rate and the observed shapes of the upper nanowire parts, while the non-linear shapes at the nanowire bottom are described correctly only within the exponential model. We estimate the effective migration lengths of indium, which are of the order of several hundreds of nanometers between 400 and 450°C. The migration length increases up to 2200nm at 480°C so that radial growth is completely suppressed at this high growth temperature.

Disturbance dynamics and history of an old-growth subalpine fir (Abies fargesii) forest in central China

Disturbance history of an old-growth subalpine fir (Abies fargesii) forest in the Shennongjia Mountains of central China was reconstructed using dendroecological methods. Increment cores were extracted from 468 trees within six 100 m × 50 m permanent transects distributed across the old-growth subalpine fir forest of 300 ha. Growth patterns of 299 fir cores were examined for abrupt increases in radial growth to indicate formation of past canopy gaps and for rapid early radial growth to indicate establishment in past canopy gaps. The results showed that 70.8 % of the canopy fir trees experienced an average of 0.78 (ranging from 0 to 2) major release event for an average of 15.8 (ranging from 10 to 24) years, and an average of 1.94 (ranging from 0 to 3) moderate release events for an average of 25.6 (ranging from 10 to 36) years before they reached canopy. Recruitment pulse of trees coincided temporally with the peak of disturbance rate from the 1900s to the 1910s, suggesting occurrence of intense disturbance events during the time period. Radial growth analyses indicated that a history with small-scale disturbance events has resulted in the formation of the old-growth subalpine fir forest, and stand-replacing disturbances might not be necessary for the development of the forest. This study provides strong evidence that there are substantial variations in the disturbance severity and frequency over time. Most disturbance events might rather cause treefall gaps than clear large areas of forest at once. Thus, the old-growth subalpine fir forest experienced frequent gap-scale disturbances and few large-scale disturbances in its development history.

Coastal and interior Douglas-fir provenances differ in growth performance and response to drought episodes at adult age

Since the 2003 drought and heat wave, Douglas-fir dieback has been reported in France in trees older than 30 years. Consequently, it is questioned whether selected Douglas-fir provenances are suited to the frequent and severe drought events which are forecast due to climate change. Our objective was to contribute to the screening of variability in productivity and growth response to soil-water deficit of mature trees from provenances not currently used for plantation in France. We sampled 22 provenances, including coastal and interior Douglas-fir, covering a wide part of its natural distribution, from Oregon to California for coastal provenances and from British Columbia to New Mexico for interior provenances. These provenances were planted at the mid 1970s in two provenance trials located in the south-west area of France. Variability of productivity, of wood density, and of radial growth in response to drought episodes among provenances was quantified and related to soil-water deficit computed by daily water balance calculations. Whatever the provenance, annual radial growth is highly dependent on local soil-water deficit (Felines R 2 = 0.57, Le Treps R2 = 0.49). Radial growth and wood properties exhibit large differences between provenances at 30 years old. Variability between provenances for all wood characteristics studied is mainly structured geographically. Coastal provenances perform best for productivity at 30 years old (619 cm2 ± 59), and exhibit a small growth reduction in 2004, the second successive year of drought (−10.7 % ± 3.8). Surprisingly, the southern interior provenances from the driest environments in the natural range show a large growth reduction in 2004 (−30.5 % ± 5.2). The provenances tested exhibited significant differences in growth performance and growth reduction induced by the soil-water deficit. The approach coupling retrospective analysis of radial growth on mature trees and water balance modelling is relevant for evaluating provenance adaptation to more frequent or severe drought episodes.

Increased water‐use efficiency does not lead to enhanced tree growth under xeric and mesic conditions

Higher atmospheric CO2 concentrations (c(a)) can under certain conditions increase tree growth by enhancing photosynthesis, resulting in an increase of intrinsic water-use efficiency (i WUE) in trees. However, the magnitude of these effects and their interactions with changing climatic conditions are still poorly understood under xeric and mesic conditions. We combined radial growth analysis with intra- and interannual δ(13)C and δ(18)O measurements to investigate growth and physiological responses of Larix decidua, Picea abies, Pinus sylvestris, Pinus nigra and Pseudotsuga menziesii in relation to rising c(a) and changing climate at a xeric site in the dry inner Alps and at a mesic site in the Swiss lowlands. (i)WUE increased significantly over the last 50 yr by 8-29% and varied depending on species, site water availability, and seasons. Regardless of species and increased (i)WUE, radial growth has significantly declined under xeric conditions, whereas growth has not increased as expected under mesic conditions. Overall, drought-induced stomatal closure has reduced transpiration at the cost of reduced carbon uptake and growth. Our results indicate that, even under mesic conditions, the temperature-induced drought stress has overridden the potential CO2 'fertilization' on tree growth, hence challenging today's predictions of improved forest productivity of temperate forests.

Growth and residual stresses of arterial walls

Growth, residual stresses and mechanical responses of arterial walls under the inner pressure are investigated within the framework of a finite deformation hyper-elasticity theory. A biomechanical model for a two-layer thick-walled circular cylindrical tube is proposed to address the mechanical effects of finite volumetric growth and residual stresses of arterial walls. The active stress due to smooth muscle tone in the media and the dispersion of collagen fiber orientations in the adventitia are also considered. The fields of displacements and stress distributions of arterial walls with growth are solved analytically. Analysis of axial, radial and circumferential growth is considered and residual stress distributions of arterial walls in different cases of growth are compared.

Morphological changes, chitinolytic enzymes and hydrophobin-like proteins as responses of Lecanicillium lecanii during growth with hydrocarbon

Lecanicillium lecanii, Verticillium chlamydosporium, V. fungicola var flavidum and Beauveria bassiana were evaluated on their growth with pure n-hexane, toluene and n-hexane:toluene 17:83 (v:v) mixture. Another set of treatments were conducted with colloidal chitin as additional carbon source. All the strains of Lecanicillium were able to grow using hydrocarbons with or without the addition of chitin, although the presence of hydrocarbons showed significant inhibition evidenced by measured biomass, radial growth and microscopic analyses. Degradation of n-hexane ranged within 43 and 62% and it was higher than that with toluene. The strains L460, L157 and L2149, which presented the highest growth, were further selected for determinations of hydrocarbon consumptions in microcosms. Strain L157 showed the highest consumption of n-hexane (55.6%) and toluene (52.9%) as sole carbon source and it also displayed activities of endochitinases, N-acetylhexosaminidase and production of hydrophobins class I and II.

The Reconstruction of Gypsy Moth Outbreaks on the Zilair Plateau by Oak-Trees Radial Growth Analysis

The Reconstruction of Gypsy Moth Outbreaks on the Zilair Plateau by Oak-Trees Radial Growth Analysis

Assessment of tree response to drought: validation of a methodology to identify and test proxies for monitoring past environmental changes in trees

A thinning experiment stand at Avoca, Ballinvalley, on the east coast of the Republic of Ireland was used to test a developed methodology aimed at monitoring drought stress, based on the analysis of growth rings obtained by coring. The stand incorporated six plots representing three thinning regimes (light, moderate and heavy) and was planted in the spring of 1943 on a brown earth soil. Radial growth (early- and latewood) was measured for the purpose of this study. A multidisciplinary approach was used to assess historic tree response to climate: specifically, the application of statistical tools such as principal component and canonical correlation analysis to dendrochronology, stable isotopes, ring density proxy, blue reflectance and forest biometrics. Results showed that radial growth was a good proxy for monitoring changes to moisture deficit, while maximum density and blue reflectance were appropriate for assessing changes in accumulated temperature for the growing season. Rainfall also influenced radial growth changes but not significantly, and was a major factor in stable carbon and oxygen discrimination, mostly in the latewood formation phase. Stable oxygen isotope analysis was more accurate than radial growth analysis in drought detection, as it helped detect drought signals in both early- and latewood while radial growth analysis only detected the drought signal in earlywood. Many studies have shown that tree rings provide vital information for marking past climatic events. This work provides a methodology to better identify and understand how commonly measured tree proxies relate to environmental parameters, and can best be used to characterize and pinpoint drought events (variously described using parameters such as like moisture deficit, accumulated temperature, rainfall and potential evaporation).

Dominant radial and height growth reveal comparable historical variations for common beech in north-eastern France

While forest productivity is usually inferred from height growth indices, retrospective analyses of tree rings have been intensively used to assess long-term trends in forest productivity. However, radial growth is sensitive to the degree of competition between trees and influenced by management practices or local disturbances. Whether radial growth is accurate for diagnosing and quantifying productivity changes remains a debated question. In a previous study ( Bontemps et al., 2009), we assessed historical variations in dominant height growth of even-aged stands of common beech in north-eastern France as a proxy for their productivity changes. The analysis was based on a sampling design including 14 pairs of young/old (75/150 yr) neighbour stands growing under the same site conditions. Dominant height was reconstructed from stem analyses and was compared between generations using a statistical modelling procedure. In this analysis, we tested whether radial and height growth of dominant trees may provide compatible indications on long-term trends. We therefore measured and analysed the radial growth of dominant trees at breast height for the same sampled trees. The effects of site, developmental stage, and calendar date were separated by applying a similar modelling approach. Consideration of the developmental stage effect led to the formulation of an original growth equation. Analysis of radial growth revealed: (i) a long-term positive increase; (ii) a magnitude of +50% over the last century; and (iii) growth declines in the 1940s and 1990s. These features were remarkably similar to those reported on dominant height, and indicated that radial growth of dominant trees delivered a sound picture of productivity changes. The radial growth chronology also differed by showing a more acute acceleration phase in the early century, and a recent but significant difference between stand generations.

Dendroecological study of a subalpine fir (Abies fargesii) forest in the Qinling Mountains, China

Dendroecological techniques were used to investigate the stand dynamics and the disturbance history of the subalpine fir forest in the Qinling Mountains of Shaanxi Province, China. The results indicated that 68% of the fir trees experienced 1–2 release events for a total of 10–29 (an average of 15.8) years, and 1–2 suppression events for a total of 10–27 (an average of 13.4) years before they reached canopy. Large number of Abies fargesii and Betula albo-sinensis recruitment coincided temporally with larger increases in the ring-width index from the 1830s to 1880s, suggesting occurrence of a major stand-wide disturbance during this time period. Few seedlings and saplings were found in the forest, and there was a dramatic decline in recruitment after 1890, probably because of the intensive cover of understory umbrella bamboo (Fargesia spathacea). Radial growth analyses indicated frequent canopy opening resulting from small-scale disturbances in the forest. Thus, the subalpine fir forest experienced frequent small-scale disturbances and infrequent large-scale disturbances in its developmental history, and these disturbances coupled with the understory umbrella bamboo might have influenced tree growth and species recruitment.

DENDROCHRONOLOGICAL RESEARCH OF SCOTS PINE (PINUS SYLVESTRIS L.) GROWING IN VILNIUS AND KAUNAS FOREST PARKS/PAPRASTOSIOS PUŠIES (PINUS SYLVESTRIS L.), AUGANČIOS VILNIAUS IR KAUNO MIESTŲ MIŠKO PARKUOSE, DENDROCHRONOLOGINIAI TYRIMAI/ ДЕНДРОХРОНОЛОГИЧЕСКИЕ ИССЛЕДОВАНИЯ СОСНЫ ОБЫКНОВЕННОЙ (PINUS SYLVESTRIS L.), ПРОИЗРАСТАЮЩЕЙ В ЛЕСНЫХ ПАРКАХ ГОРОДОВ ВИЛЬНЮСА И КАУНАСА

This study is aimed at dendrochronological indication of unfavourable environmental conditions in Vilnius and Kaunas cities on Scots pine's (Pinus sylvestris L.) radial increment and comparison of city trees growth with the tree growth in relatively unpolluted areas (control forest stands). 330 sample trees in Kaunas and 456 sample pines in Vilnius city and forest parks, 72 sample pines in 3 control forest stands at the distance of 30 km west from Kaunas city were chosen for the radial growth analysis. It was determined that tree radial increment (in per cent) of transformed pine dendro‐scales is lower in cities than in control stands. These alterations were caused by environmental disturbances: exceptionally cold winter in 1979/1980 and air pollution level which was considerably higher in cities than in controlled stands. Though transport emission has constantly been growing since 2000, no clear difference between pine radial growth dynamics in controll stands in Kaunas and Vilnius sample plots was detected. Santrauka Dendrochronologiniai tyrimai, atlikti Vilniaus ir Kauno miestų miško parkuose augančiuose paprastosios pušies (Pinus sylvestris L.) medynuose ir kontroliniuose medynuose, sąlygiškai neužterštoje aplinkoje (Lekėčių girininkijoje; 30 km į vakarus nuo Kauno), indikuoja blogesnes medžių augimo sąlygas miesto aplinkoje nei vietovėje, kurioje nėra vietinės taršos, tuo laikotarpiu, kai miestų tarša buvo gerokai didesnė ir jos poveikį sustiprino ekstremaliai šalta žiema. Tyrimo tikslas – palyginti paprastosios pušies medžių metinio radialiojo prieaugio dinamiką nepalankiomis miestų taršos sąlygomis su gerokai švaresnėje aplinkoje augančių medžių radialiojo prieaugio rodikliais. Analizei buvo parinkta 330 apskaitos medžių Kauno, 456 apskaitos medžiai Vilniaus miestų parkuose bei miško parkuose ir 72 apskaitos medžiai kontroliniuose medynuose teritorijoje, kurioje nėra vietinės taršos. Nustatyta, kad metinis radialusis prieaugis patikimai skyrėsi tik 1981– 1995 m., kai buvo išskirtinai šalta 1979–1980 m. žiema ir oro tarša miestuose buvo daug didesnė nei vietovėje, kurioje nėra vietinės taršos. Nors automobilių transporto emisija nuolat didėja nuo 2000 m., tačiau aiškių skirtumų tarp paprastosios pušies radialiojo augimo kaitos kontroliniuose medynuose bei Kauno ir Vilniaus miestų tyrimo objektuose nenustatyta. Резюме Дендрохронологические исследования сосны обыкновенной (Pinus sylvestris L.) были проведены в лесных парках городов Вильнюса, Каунаса и контрольных древостоях в относительно чистой окружающей среде (в лесничестве Лекечай в 30 км от г. Каунаса). Целью исследования был сравнительный анализ годичного радиального прироста сосны, произрастающей в неблагоприятной для роста городской среде, по сравнению с произрастающей на территории без локального загрязнения. Для анализа годичного радиального прироста в городских парках г. Каунаса были подобраны 330 учетных деревьев, г. Вильнюса – 456 учетных деревьев и на контрольных участках в лесничестве Лекечай – 72 учетных дерева. Значительное различиe в радиальном приросте сосны обыкновенной, произрастающей в городских парках, по сравнению с произрастающей в контрольных древостоях установлено лишь в 1981–1995 гг. (при неблагоприятных для роста климатических условиях экстремально холодной зимы 1979–1980 гг.), когда загрязнение городского воздуха было значительно выше, чем в лесах. Несмотря на увеличение автотранспортной эмиссии с 2000 г., существенных различий в радиальном приросте сосны обыкновенной (Pinus sylvestris L.), произрастающей в городских условиях и на территории без локального загрязнения, не установлено.

Canopy recruitment in the beech (Fagus engleriana) forest of Mt. Shennongjia, Central China

A dendrochronological technique was used to investigate canopy recruitment of beech (Fagus engleriana Seem.) trees in western Hubei Province of Central China by identifying growth releases through gap formation. The results indicated that 83% and 17% of the canopy trees regenerate in gaps and the understory, respectively. Radial growth analyses demonstrated that there are three modes for beech regeneration and canopy recruitment: (1) gap origin without suppression; (2) gap origin with period(s) of suppression; and (3) understory origin. Multiple periods of release and suppression imply that beech regeneration and canopy recruitment are very sensitive to gap formation.

Long-term dynamics in growth of Scots pine and Siberian spruce in Komi Republic (European part of Russia)

The main objective was to investigate the long-term growth dynamics of Scots pine (Pinus sylvestris L.) and Siberian spruce (Picea obovata Lebed.) trees in the Komi Republic, in the currently changing environment. Positive long-term growth trends of Scots pine and Siberian spruce were identified in the Komi Republic using empirical data from radial growth and height growth analysis in the forest-tundra transition zone, the northern taiga zone, the middle taiga zone, and the southern taiga zone. The statistically significant increase in height increment of 40% for Siberian spruce and 30% for Scots pine was identified for the whole Komi Republic. Within this region statistically significant increases were found in the middle taiga zone for Siberian spruce by 240%, Scots pine 140%, and in the northern taiga for Siberian spruce by 164%. Increases in the radial growth of Siberian spruce in the forest-tundra was 134% while in the northern taiga zone it was 35% over successive 50 year periods from 1901 to 1950 and from 1951 to 2000. In the middle taiga zone a 76% increase in radial growth of spruce was found (over 100 years), whilst in the southern taiga zone the changes were not statistically significant. The increase in radial growth of Scots pine in the northern taiga zone was 32%. In the middle taiga zone the radial growth increase in Scots pine was 55% and in the southern taiga zone the changes were not statistically significant. During the last 20 years, a temperature increase was recorded by all the meteorological stations in Komi Republic; whilst levels of precipitation have been increasing for the last 40 years ago. This is reflected in the radial increment of Siberian spruce and Scots pine. Thus, climate change could partly explain the increased site productivity. The total variance explained by temperature varied from 22% to 41% and precipitation from 19% to 38%. A statistically significant correlation between Normalized Difference Vegetation Index (NDVI) data and tree-ring width has been identified for the territory of the Komi Republic. The increased site productivity caused the increase in integrated NDVI values from June to August. This indicates that NDVI can be used as a proxy for estimating the forest growth trends of recent decades for generalization on a large scale. The increased site productivity in the southern and middle sub zones of taiga in the Komi Republic has been shown using NDVI data for 20 years. In the region under discussion, the distribution of the trends in NDVI data changes on a south-west to north-east gradient. NDVI data could be used to increase the spatial resolution of tree-ring width series. The decrease in precipitations was reflected in increase in NDVI. An increase in productivity reflected in NDVI data is maximal on the sites with increased temperature and decreased precipitations. Taking into account the relatively small influence of humans in the Komi Republic compared to Europe, the site productivity during recent decades has also increased in relatively untouched forests.

Radial growth and climate responses of white oak (Quercus alba) and northern red oak (Quercus rubra) at the northern distribution limit of white oak in Quebec, Canada

AbstractAim The objectives of this study were: (1) to compare radial growth patterns between white oak (Quercus alba L.) and northern red oak (Quercus rubra L.) growing at the northern distribution limit of white oak; and (2) to assess if the radial growth of white oak at its northern distribution limit is controlled by cold temperature.Location The study was conducted in three regions of the Ottawa valley in southern Québec. All stands selected were located at the northern limit of distribution of Q. alba.Methods Twelve mixed red and white oak stands were sampled and increment cores were extracted for radial growth analyses. For each oak species, 12 chronologies were derived from tree‐ring measurement (residual chronologies). Principal components analysis and redundancy analysis were used to highlight the difference between radial growth in both species and to determine their radial growth–climate association.Results There was little difference between the radial growth of each species; Q. alba, however, exhibits more year‐to‐year variation in growth than Q. rubra. More than 65% of the variance in radial growth was shared among sites and species. Both species showed a similar response to climate, which suggested that the limit of distribution of Q. alba might not be determined by effects on growth. Both species had a classic response to climate and drought in the early growing season.Main conclusions The northern distribution limit of Q. alba does not appear to be directly controlled by effects on growth processes as indicated by the similarities in radial growth and response to climate between the two species. The location of the stands on southern aspects suggested that cold temperature could have been a major factor controlling the distribution limit of Q. alba. However, it is speculated that stands growing on southern aspects may be more prone to forest fires or to drought, which would favour the maintenance and establishment of oaks, and of Q. alba in particular. Models relating the northern distribution limits of species to broad climate parameters like annual mean temperature will need to be reviewed to incorporate more biologically relevant information. Such assessments will in turn provide better estimates of the effect of climate changes on species distribution.

DBH growth model for Pinus densiflora and Quercus variabilis mixed forests in central Korea

This study presents an individual tree diameter at breast height (dbh) growth model for mixed Pinus densiflora (Red pine) and Quercus variabilis (Oak) uneven-aged stands in central region of Korean peninsula. The different model components, including the effects of tree age, tree size, competition and growing site are evaluated for both Red pine and Oak. The aim is to understand and model the individual growth patterns of the two species. Based on sensitivity analysis of radial growth using a variety of combinations of independent variables, the conclusion could be reached that the size and aspect components have a positive effect on radial growth, while the other variables such as age, competition index, elevation, and slope have a negative influence. All model component effects, except the effect of elevation, are greater in pine than in Oak, indicating that Red pine is relatively less suppressed than Oak in the study area. Among the topographic variables, slope appears to be an important critical factor for Red pine. For Oak, elevation is the primary critical factor and other variables have no great effect. These interrelationships between radial growth and the age, size, competition, and site variables correspond quite well with ecological expectations and silvicultural experience of the two species in Korea.

Succession from bog pine (Pinus uncinata var. rotundata) to Norway spruce (Picea abies) stands in relation to anthropic factors in Les Saignolis bog, Jura Mountains, Switzerland

In Jura bogs, on deep and nutrient-poor peat, the ecotone between bog pine forest and Norway spruce forest is sharp and, in a few disturbed situations, no succession pine forest-spruce forest occurs. The bog Les Saignolis lies at the top of an anticline, on thin and oligotrophic peat. Several documents attest some anthropic disturbances (clear cut and drainage). Beside these historical data and with the aim of reconstructing vegetation dynamics and tree growth, we realised synusial phytosociological releves and, in a mixed pine-spruce stand, we studied tree radial growth. Following the clear cut, the bog pine, the pubescent birch, and the Norway spruce settled simultaneously. The birch disappeared rapidly. The present cohort of pine settled and grew rapidly, and then declined because of the competition by spruce. Spruce settled progressively and increased its growth regularly except when pine settled and grew. Interspecific competition between pines and spruces and intraspecific competition between dominant and sub-dominant spruces were put into evidence by radial growth analysis.

Spatio-temporal growth dynamics of a subAlpine Pinus uncinata stand in the French Alps

Natural forests are characterised by a high level of both spatial and temporal heterogeneity. The major processes involved in the creation and maintenance of forest heterogeneity in temperate climates are small-sized canopy disturbances. The resulting openings also modify the growth conditions for the remaining trees. The analysis of tree growth responses using dendrochronological techniques allows the reconstruction of the time sequence of the disturbances. The radial growth analysis is coupled here with both a spatial analysis and a demographic analysis of the forest structure. The age classes are temporally organised in cohorts and spatially distributed in spatial aggregates. The analysis of the most documented disturbance event allowed us to determine the size of the disturbance response patch (between 0.036 and 0.073 ha) and the duration of the disturbance (six years). We considered that this small-scale disturbance event may have been caused by the fall of a single tree and has freed the surrounding trees of its competition. To cite this article: C. Rathgeber, P. Roche, C. R. Biologies 326 (2003).

Tree ring growth by core sampling at the CONECOFOR Permanent Monitoring Plots. The deciduous oak (Quercus cerris L.) type

Radial growth analysis evaluates the ability of trees to grow under different site and environmental conditions, thus contributing to bio-ecological studies aimed at increasing understanding of forest stand evolution. Tree ring growth is analysed in five Permanent Monitoring Plots (PMPs) dominated by Turkey oak (Quercus cerris L.). Common structural features of these PMPs are their origin (coppice forest) and their current physiognomy as stored coppice and transitory crop. A dendroecological approach was used to analyse past radial stem growth, the influence of silvicultural background and stand age, as well as to compare the growth rhythm of stands in different site-indexes and environmental conditions. Tree coring was carried out at the time of the first inventory (winter 1996/97) by sampling 8 to 11 dominant and co-dominant trees representative of the upper storey in the buffer area of each PMP. The basic stem and crown growth variables were measured for each tree sampled and two cores collected at 1.30 m. Annual ring width was determined by the Tree Ring Measurement System SMIL3 and the data were elaborated by the ANAFUS software. Site mean curves and growth trend per social class in each stand were defined both by visual comparison and statistical analysis among individual tree series. The main results were as follows: i) social differentiation becomes established earlier with better site indexes and higher tree densities; ii) sensitivity to external disturbances is higher and more defined in the dominant class than in the co-dominant tree layer; iii) competition cycles are clearly discernible and related to both stand density and site-index in young stands under natural evolution (stored coppices); iv) when silvicultural interventions were performed in the past is quite visible readable in the stands under conversion into high forest (transitory crops); v) the mean series per site are statistically related and common periods characterized by a similar growth trend have been recognized.

High-resolution analysis of radial growth and wood density in Eucalyptus nitens, grown under different irrigation regimes

Wood density is the most important determinant of wood quality and a critical factor in short rotation forestry. Daily radial growth of six-year-old Eucalyptus nitens trees were monitored on a two hectare plantation in south-eastern Tasmania using point dendrometers, under dif- ferent irrigation regimes. At the end of the second growing season 12-mm cores were extracted from the trees and processed for high-resolution wood density using SilviScan-2. The dendrometer measurements were utilized to rescale wood density on a time axis. In general, lower density was formed early in the growing season, and higher wood density later. The irrigated-droughted trees showed an obvious relationship between wood density and soil water deficits with the density decreasing in response to water stress releases. The density decrease was accompanied by acceleration in daily increment. With the presented approach the annual level is no longer the basis of analysis. This opens new opportunities for genotype × environmental interaction studies of trees, which is of particular importance in clonal forestry.

THE ROLE OF VEGETATION DYNAMICS IN CHOCTAWHATCHEE SAND PINE INVASION OF LONGLEAF PINE FORESTS

The expansion of Choctawhatchee sand pine (Pinus clausa) into longleaf pine forests (Pinus palustris) has been widespread on the Florida Panhandle since the early 1900s. This study examines the population-level processes of this sand pine invasion. Expansion of sand pine started by 1920, but rapidly increased in the 1940s. Population establishment and growth in invasive stands has been rapid, with establishment of many sand pine pioneer individuals followed by rapid infilling as these individuals reached reproductive maturity. Both noninvasive and invasive stands had numerous sand pine seedlings and saplings. Sand pine will likely persist in these communities in the near future. Analyses of hemispherical canopy photographs and regeneration patterns illustrate the ability of sand pine to establish under a variety of light conditions. Radial growth analysis of incremental tree cores highlights the importance of episodic wind disturbances in maintaining these sand pine populations. [Key words: sand pine, longleaf pine, Pinus clausa, Florida, pine invasion, Pinus palustris.]