Stem Diameter Increment Research Articles

Analysis of Individual Tree Competition on Diameter Growth of Silver Birch in Estonia

Aim of study: The present study evaluates a set of competition indices including spatially explicit indices combined with different competitor selection approaches and non-spatially explicit competition indices. The aim was to quantify and describe the neighbouring effects on the tree diameter growth of silver birch trees.Area of study: Region throughout Estonia. Material and methods: Data from the Estonian Network of Forest Research Plots was used. After quantifying the selected indices, the best non-spatial indices and spatial indices (combined with neighbour selection methods) were separately devised into a growth model as a predictor variable to assess the ability of the diameter growth model before and after adding competition measures. To test the species-specific effect on the competition level, the superior indices were recalculated using Ellenberg’s light indicators and incorporated into the diameter growth model. Main results: Statistical analyses showed that the diameter growth is a function of neighbourhood interactions and spatial indices were better growth predictors than non-spatial indices. In addition, the best selections of competitive neighbours were acquired based on the influence zone and the competition elimination angle concepts, and using Ellenberg’s light values had no significant improvement in quantifying the competition effects. Research highlights: Although the best ranking spatial competition measures were superior to the best non-spatial indices, the differences were negligible.Keywords: Competition indices; zone of influence; stem diameter increment; Betula pendula Roth.ERRATUM PDF

Effect of some nutrients in Olive seedlings growth that grown in desert lands

A study was conducted in one of the olive orchard at Al-Forat governorate in Heet city of Al-anbar province during the season 2014 to investigate the effect ofapplying the industrial chicken manure the Orgevit (P) and spraying the Reef PlantCare (V) on some vegetative growth traits of olive seedlings Ashrasi cultivar. Thirty sex identical seedlings as possible were chosen at age of two years with interspace of 6x6 m. The Orgevit was applied in the middle of March, while the Reef PlantCare was at monthly intervals, starting from the 1st of April to October the 1st . A factorial experiment was carried out in R.C.B.D. design (3×4) included 12 treatments repeated three times, using one tree for each experimental unit, The first factor (Orgevit) was used in three levels ( 0 , 0.5 and 1 kg.seedling-1 ), whereas the second factor was spraying with the Reef PlantCare in four levels (0 , 1 , 1.5 and 2 ml.l-1 ) . The results showed the Orgevit manure was significantly affected in growth of olive seedlings Ashrasi cultivar, especially the highest level used (P2) which showed the best values for all the studied traits (average of high increment, average of branches number increment, average of a new branches length, average of leaves number increment and branches dry matter percentage) which reached (11.7 cm, 11.83 branch.seedling-1 , 13.5 cm, 56.4 leaf.seedling-1 and 67.29%) respectively, only the average increment of stem diameter didn't show any significant difference. Treatment of spraying Reef PlantCare at the highest level (V3) was the best by giving the highest significant effect for the two traits (average of branches number increment and branches dry matter percentage) that reached 11.00 branch.seeedling-1 and 65.03%, respectively. Treatment V2 was came after and showed significant effect on traits (average of high increment, average of a new branches length and average of leaves number increment) that reached 11.8 cm, 13.4 cm and 54.7 leaf.seeedling-1, respectively. The interaction combinations gave a significant level for the all studied traits, the highest effects for most traits was for the interaction treatment P2V2

Wood harvest by pollarding exerts long-term effects on Populus euphratica stands in riparian forests at the Tarim River, NW China

Populus euphratica (Euphrates poplar) is the dominant tree species of the riparian (“tugai”) forests of Central Asia, which provide important ecosystem services to a rapidly growing population. However, overuse of the forests by wood harvest (pollarding) contributes markedly to their destabilisation. At the upper reaches of the Tarim River (Xinjiang, NW China), we investigated the effects of past pollarding (in the 1970s and 1980s) on the stand structure, tree morphology, stem diameter increment and intrinsic water use efficiency (iWUE) of poplars with different pollarding intensities in the past (‘No Use’, ‘Moderate’, ‘Intense’) growing on three adjacent plots with the same distance to the groundwater level. Compared to the non-used trees, the pollarded poplars (in particular, the intensely used trees) exhibited smaller figures of the following morphological variables: ratio of tree height to diameter at breast height, vertical crown extension, crown projection area, crown volume, and tree-ring width as well as basal area increment (BAI) during the past 24years; but a higher number of secondary shoots, a higher percentage of hollow stems and a higher degree of hollowness of the stems. The pollarded trees were capable of regenerating to a certain extent, which was obvious from the formation of secondary shoots and, in the intensely pollarded trees, from a lower iWUE (inferred by more negative δ13C isotopic ratios of the tree rings; most probably due to higher rates of gas exchange) as well as from their capability of re-establishing a crown efficiency similar to non-pollarded trees. However, the BAI of the main trunk and the secondary branches of the pollarded trees decreased continuously during the last 24years of investigation. Whilst moderate intensities of pollarding seem to be sustainable for the riparian P. euphratica forests, intense pollarding reduces the growth increment of the trees and, even more importantly, results in a distinct increase in the percentage of hollow stems, which can render the trees less stable and more susceptible to secondary damaging factors. The significant correlations between BAI and morphological variables of crown projection area and crown volume are promising for developing approaches to assess the productivity of P. euphratica stands on a landscape level using methods of remote sensing.

Sustainable management of river oases along the Tarim River (SuMaRiO) in Northwest China under conditions of climate change

Abstract. The Tarim River basin, located in Xinjiang, NW China, is the largest endorheic river basin in China and one of the largest in all of Central Asia. Due to the extremely arid climate, with an annual precipitation of less than 100 mm, the water supply along the Aksu and Tarim rivers solely depends on river water. This is linked to anthropogenic activities (e.g., agriculture) and natural and semi-natural ecosystems as both compete for water. The ongoing increase in water consumption by agriculture and other human activities in this region has been enhancing the competition for water between human needs and nature. Against this background, 11 German and 6 Chinese universities and research institutes have formed the consortium SuMaRiO (Sustainable Management of River Oases along the Tarim River; http://www.sumario.de), which aims to create a holistic picture of the availability of water resources in the Tarim River basin and the impacts on anthropogenic activities and natural ecosystems caused by the water distribution within the Tarim River basin. On the basis of the results from field studies and modeling approaches as well as from suggestions by the relevant regional stakeholders, a decision support tool (DST) will be implemented that will then assist stakeholders in balancing the competition for water, acknowledging the major external effects of water allocation to agriculture and to natural ecosystems. This consortium was formed in 2011 and is funded by the German Federal Ministry of Education and Research. As the data collection phase was finished this year, the paper presented here brings together the results from the fields from the disciplines of climate modeling, cryology, hydrology, agricultural sciences, ecology, geoinformatics, and social sciences in order to present a comprehensive picture of the effects of different water availability schemes on anthropogenic activities and natural ecosystems along the Tarim River. The second objective is to present the project structure of the whole consortium, the current status of work (i.e., major new results and findings), explain the foundation of the decision support tool as a key product of this project, and conclude with application recommendations for the region. The discharge of the Aksu River, which is the major tributary of the Tarim, has been increasing over the past 6 decades. From 1989 to 2011, agricultural area more than doubled: cotton became the major crop and there was a shift from small-scale to large-scale intensive farming. The ongoing increase in irrigated agricultural land leads to the increased threat of salinization and soil degradation caused by increased evapotranspiration. Aside from agricultural land, the major natural and semi-natural ecosystems are riparian (Tugai) forests, shrub vegetation, reed beds, and other grassland, as well as urban and peri-urban vegetation. Within the SuMaRiO cluster, focus has been set on the Tugai forests, with Populus euphratica as the dominant tree species, because these forests belong to the most productive and species-rich natural ecosystems of the Tarim River basin. At sites close to the groundwater, the annual stem diameter increments of Populus euphratica correlated with the river runoffs of the previous year. However, the natural river dynamics cease along the downstream course and thus hamper the recruitment of Populus euphratica. A study on the willingness to pay for the conservation of the natural ecosystems was conducted to estimate the concern of the people in the region and in China's capital. These household surveys revealed that there is a considerable willingness to pay for conservation of the natural ecosystems, with mitigation of dust and sandstorms considered the most important ecosystem service. Stakeholder dialogues contributed to creating a scientific basis for a sustainable management in the future.

A quantitative analysis of dendrometric data on Sorbus domestica L. phenotypes for urban greenery

• The crown architecture of Sorbus domestica is less influenced by environmental conditions than diameter increment. • The crown diameter has the highest impact on differentiation of the crown architecture. • The crown volume is significantly correlated with diameter at breast height. • The values of crown volume above 1300 m 3 were recorded for each type of crown. The quantitative parameters characterizing the esthetic and spatial characteristics of the tree species Sorbus domestica L., including the architecture and the crown size, were evaluated in order to assess the qualified sources of planting material for the urban environment. Five types of crown shape (spherical, hemispherical, umbrella-shaped, ovate, and conical) were identified during field assessment of trees growing in the open landscape. Conformity of the classification under specific phenotypes within field studies and classification of trees based on quantitative parameters were evaluated using discriminant analysis. The variables included in the discriminant analysis model (crown diameter, crown length, and stem girth) were obtained from direct measurement in the field. A statistically significant relationship was found between crown volume and diameter at breast height. Under the specific environmental conditions of an open landscape, high values of crown volume were recorded not only for the thickest trees but also for trees with diameters oscillating around the mean values of this parameter. Our results indicate that the environment has a greater effect on the stem diameter increment of trees, than on the crown size and crown architecture of S. domestica .

Differences between competition kernels and traditional size-ratio based competition indices used in forest ecology

Both traditional competition indices and competition kernels are used in many studies to quantify competition between plants for resources. Yet it is not fully clear what the differences between these two concepts really are.For characterising the two approaches we selected two fundamental types of competition indices based on distance weighted size ratios, an additional competition index without distance weighting and developed similar competition kernels. In contrast to the latter approach, competition indices require individual influence zones that for example can be derived from tree crown-radius measurements. We applied these competition measures to two spatio-temporal forest datasets in Europe and one in North America. Stem diameter increment served as observed response variable.The results of both methods indicated similar performance, however, the use of competition kernels produced slightly better results with only one exception out of six computer experiments.Although the performance of both competition measures is not too different, competition kernels are based on more solid mathematical and ecological grounds. Particularly the question of defining the local neighbourhood of a given tree seems to be better handled by competition kernels. Consequently, applications of this method are likely to increase. The trade-off of the use of competition kernels, however, is the need for more sophisticated spatial regression routines that researchers are required to program. Finally, a tabulated summary of differences between competition indices and competition kernels is included.

The effect of elevated air humidity on young silver birch and hybrid aspen biomass allocation and accumulation – Acclimation mechanisms and capacity

Climate change is predicted to bring about a rise in precipitation and atmospheric humidity at northern latitudes, which could have a considerable impact on forest ecology and management. This study investigates the effect of elevated relative air humidity (RH) on tree growth and biomass accumulation and allocation in six-year-old seedling-originated silver birch (Betula pendula Roth) and monoclonal hybrid aspen (Populus tremula L.×P. tremuloides Michx.) stands. The study was conducted in the unique Free Air Humidity Manipulation experimental facility in Estonia. Two understory vegetation types (forest and pasture) were used in the experimental plots. As a short-term response during the first manipulation years, a small rise (6–7%) in RH reduced the growth of both tree species. In the fifth humidification year, suppression of growth continued in aspen, but birch acclimated effectively to elevated RH – differences in biomass and stem diameter increments levelled out in humidified (H) and control (C) plots. The H birches ensured biomass accumulation by changing the biomass and morphology of the physiologically most active tree parts: increasing fine-root biomass, as well as specific areas of fine roots (SRA) and leaves (SLA). The effect of elevated RH on most leaf and fine root characteristics of aspens was in a similar direction as that of birches, but weaker, and the plasticity of the functional traits was also lower compared to birches, probably due to the lack of genetic variation in monoclonal aspens. The biomass of young aspens was 22% lower in H plots. The relative aboveground biomass allocation was not affected by elevated RH. The aboveground biomass of humidified birches was higher in plots with forest understory, where root competition was lower compared to the dense root systems of grasses in pasture understory plots. Aspen biomass was not affected by understory vegetation type. We conclude that young silver birches have sufficient phenotypic plasticity to acclimate to elevated RH and the forests retain biomass accumulation. However, the growth acclimation of planted forests of clonal plant material is more complicated and humidity-tolerance should be considered in the selection of new clones for areas where an increase in RH is anticipated.

Clonal Propagation of Two Clones Eucalyptus Pellita F. Muell By Mini-Cutting

Normal 0 false false false IN X-NONE X-NONE Eucalypt is known as the fastest growing tree species in the world. Some advantages such as fast growing, hight yielding, short rotation, less desease, lots of purposes and good economic benefit have made Eucalypt as the most important forest tree product for industrial raw material in Indonesia. However, those advantages of Eucalypt including fast growing, high yielding, short rotation and less desease can only be achieved through selecting a good clone. Cutting propagation is considered as one of the main methode to produce good seedling. Sprouts of two clones of Eucalyptus pellita F. Muell (E. 13 and E. 77) were collected from mini hedge. Total of 1080 of each clone was planted in greenhouse . The result showned that Clone E. 77 was better than E. 13 in term of growth of rooting, the increment of height, stem diameter and number of leaves at 60 and 75 days after planting /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Biomass productivity and water use relation in short rotation poplar coppice (Populus nigra x P. maximowiczii) in the conditions of Czech Moravian Highlands

The plantations of short rotation coppice (SRC) usually based on poplar or willow species are promising source of biomass for energy use. To contribute to decision-making process where to establish the plantations we evaluated the water consumption and its relation to biomass yields of poplar hybrid clone J-105 (Populus nigra x P. maximowiczii) in representative conditions for Czech-Moravian Highlands. Water availability is usually considered as one of the main constraints of profitable SRC culture and therefore we focused on analyzing of the linkage between the aboveground biomass increments and the total stand actual evapotranspiration (ETa) and on water use efficiency of production (WUEP). During the seasons 2008 and 2009 the total stand ETa measured by Bowen ratio energy balance system constructed above poplar canopy and the stem diameter increments of randomly chosen sample trees were examined. The stem diameters were subsequently converted to total aboveground biomass (AB) by allometric equation obtained by destructive analysis at the beginning of 2010. The biomass volume and its increment of particular trees were subsequently converted to the whole canopy growth and correlated with the ETa values. Our results revealed that there was a statistically significant relation between water lost and biomass growth with coefficients of determination r2 0.96 and 0.51 in 2008 and 2009 respectively. By using multiple linear regression analysis additionally accounting for effect of precipitation events and thermal time (sums of effective temperatures above +5 °C) the AB growth was explained from 98 and 87% in 2008 and 2009, respectively. Therefore for further analysis the multiple linear regression model was applied. The dynamic of seasonal WUEP (expressed as gram of AB dry matter per thousand grams of water) reached up to 6.2 and 6.8 g kg−1 with means 3.13 and 3.54 g kg−1 in both executed years respectively. These values are situated in higher range comparing to the other broadleaved tree species of temperate climate zone and suggest that economically profitable plantation (defined by yield at least in the range of 10–12 Mg ha−1 year−1 of dry matter content) will consume more than 450–500 mm per growing season and thus will demand a locality with higher and adequately temporally distributed amount of precipitation especially in rain fed areas such as the discussed Czech-Moravian Highlands.

Deriva simulada de triclopyr e fluroxypyr + triclopyr no desenvolvimento de mudas de clones de Eucalyptus

O Estado do Tocantins tem-se destacado nos últimos anos como promissor em reflorestamentos com eucalyptus . Um dos problemas com grande destaque na silvicultura tocantinense é o amplo número de espécies infestantes (conhecidas comumente como rebrotas de Cerrado), resultantes de áreas recém-desmatadas. Objetivou-se com este trabalho avaliar o efeito da deriva simulada do herbicida triclopir e da mistura formulada triclopir + fluroxipir em mudas de clones de eucalipto, ambos em duas doses, correspondentes a 50 e 25% da dose de 7 L ha-1 p.c, recomendados tradicionalmente em pastagem. Foram avaliadas as variações em altura de plantas, variações de diâmetro do caule, relação altura/diâmetro, acúmulo de massa de matéria seca: de folhas, de caules, de ramos, de raízes e total. Os herbicidas afetaram negativamente o crescimento dos clones de eucalipto até os 28 dias após a aplicação. Com base nos resultados, pode-se concluir que o efeito da deriva é menor quando os herbicidas triclopir e fluroxipir + triclopir são aplicados, ambos na dose de 25%, diminuindo, assim, o risco de perdas.

Intra-annual stem diameter growth of Tamarix ramosissima and association with hydroclimatic factors in the lower reaches of China’s Heihe River

High-resolution observations of cambial phenology and intra-annual growth dynamics are useful approaches for understanding the response of tree growth to climate and environmental change. During the past two decades, rapid socioeconomic development has increased the demand for water resources in the oases of the middle reaches of the Heihe River in northwestern China, and the lower reaches of the Heihe River have changed from a perennial river to an ephemeral stream with a decreased and degraded riparian zone. Tamarisk (Tamarix ramosissima) is the dominant shrub species of the desert riparian forest. In this study, the daily and seasonal patterns of tamarisk stem diameter growth, including the main period of tree ring formation, were examined. Observations concerning the driving forces of growth changes, along with implications for the ecology of the dendrohydrological area and management of desert riparian forests in similar arid regions, are also presented. The diurnal-seasonal activity of stem diameter and the dynamics of growth ring formation were studied using a point dendrometer and micro-coring methods during the 2012 growing season in shrub tamarisk in a desert riparian forest stand in the lower reaches of the Heihe River in Ejin Banner, Inner Mongolia of northwestern China. Generally, the variation in diurnal diameter of tamarisk was characterized by an unstable multi-peak pattern, with the cumulative stem diameter growth over the growing season following an S-shaped curve. The period from late May to early August was the main period of stem diameter growth and growth-ring formation. Among all of the hydroclimatic factors considered in this study, only groundwater depth was significantly correlated with stem diameter increment during this period. Therefore, for the dendrochronological study, the annual rings of the tamarisk can be used to reconstruct processes that determine the regional water regime, such as river runoff and fluctuations in groundwater depth. For the management of desert riparian forests, suitable groundwater depths must be maintained in the spring and summer to sustain tree health and a suitable stand structure.

Cork oak physiological responses to manipulated water availability in a Mediterranean woodland

This study details the physiological responses of cork oak (Quercus suber L.) to manipulated water inputs. Treatments named as dry, ambient and wet, which received 80, 100 and 120% of the annual precipitation, respectively, were applied to a Mediterranean woodland in southern Portugal. Tree ecophysiology and growth were monitored from 2003 to 2005.The impacts of the water manipulation were primarily observed in tree transpiration, especially during summer drought. Rainfall exclusion reduced the annual stand canopy transpiration by 10% over the 2-year study period, while irrigation increased it by 11%. The accumulated tree transpiration matched precipitation in spring 2004 and 2005 at the stand level, suggesting that cork oak trees rely on precipitation water sources during the peak of the growing season. However, during the summer droughts, groundwater was the main water source for trees.Despite the significant differences in soil water content and tree transpiration, no treatment effects could be detected in leaf water potential and leaf gas exchange, except for a single event after spring irrigations in the very dry year 2005. These irrigations were intentionally delayed to reduce dry spell duration during the peak of tree growing season. They resulted in an acute positive physiological response of trees from the wet treatment one week after the last irrigation event leading to a 32% raise of stem diameter increment the following months. Our results suggest that in a semi-arid environment precipitation changes in spring (amount and timing) have a stronger impact on cork oak physiology and growth than an overall change in the total annual precipitation.The extreme drought of 2005 had a negative impact on tree growth. The annual increment of tree trunk diameter in the ambient and dry treatments was reduced, while it increased for trees from the wet treatment. Water shortage also significantly reduced leaf area. The latter dropped by 10.4% in response to the extreme drought of 2005 in trees from the ambient treatment. The reduction was less pronounced in trees of the wet treatment (−7.6%), and more pronounced in trees of the dry treatment (−14.7%).Cork oak showed high resiliency to inter-annual precipitation variability. The annual accumulated tree transpiration, the minimum midday leaf water potential and the absolute amount of groundwater used by trees appeared unaffected by the extreme drought of 2005. Our study shows that cork oak rapidly and completely recovered from the extreme dry year of 2005 or from rainfall exclusion. Our results support the eco-hydrological equilibrium theory by which plant acquire complementary protective mechanisms to buffer the large variability in water availability experienced in semi-arid ecosystems. In optimizing their structural biomass increase in response to increasing drought stress, cork oak trees succeeded in restricting water losses to maintain the minimum leaf water potential above the critical threshold of xylem embolism, though with narrower hydraulic safety margins in 2005.Our findings highlight cork oak's sensitivity to the amount and timing of late spring precipitation. This could be critical as future climate scenarios predict a reduction of spring precipitation as well as enhanced severity of droughts in the Iberian Peninsula by the end of the 21st century. In inducing water stress before the onset of summer droughts, the predicted spring precipitation decline could drive the species closer to the threshold of catastrophic xylem embolism at the peak of the drought period.

Tree growth in Swiss forests between 1995 and 2010 in relation to climate and stand conditions: Recent disturbances matter

Forest growth is affected by various concurrent and counteracting climate change related factors and the overall impact of environmental changes on forest growth is still uncertain. In order to evaluate the variability of tree and forest growth and the possible impact of climate change, we analysed 15years (1995–2010) of tree growth data from 18 Level II plots in Switzerland, spanning a wide range of altitude, temperature and precipitation conditions.Stem diameter of all trees within the Level II plots was measured every 5years. Other above- and belowground parts of the trees were modelled by allometric relationships and validated with measurements if available. We analysed individual tree growth (basal area increment, bai) and the whole forest net primary productivity (NPP), here the sum of carbon gain by tree growth within the plot during three inventory periods. Additionally, annual stem diameter increment, assessed on single trees at each plot since 2001, was used to approximate annual NPP of the forest.Temporal patterns of NPP could not easily be related to climate conditions, since forest management and disturbance events (e.g. storms, diseases) overshadowed the climate impact on NPP. However, when looking at the individual trees, a clear decrease of bai by 2–30% (mean 19.3%) was observed for most of the sites during the second inventory period (2000–2005), which could not solely be explained by increasing stand density over time. Tree growth was most likely reduced due to the dry conditions during this period that included the extreme year 2003. An increased tree growth during the third inventory period (2006–2010) at a few sites could be clearly related to growth enhancement after stand density reducing events, such as storms or thinning. Thus, understanding climate impact on forest growth requires detailed site history knowledge and available long-term data sets.The variability of mean NPP levels could be described with a function of the sites’ climate conditions and nutrient deposition (adj. r2=0.86), with N deposition enhancing forest productivity up to a threshold of 20–25kgha−1yr−1 of N and with no further growth increase beyond that threshold.

Effect of ethephon on hardening of Pachystroma longifolium seedlings

Immediately after planting, tree seedlings face adverse environmental and biotic stresses that must be overcome to ensure survival and to yield a desirable growth. Hardening practices in the nursery may help improve seedling stress resistance through reduction of aboveground plant tissues and increased root volume and biomass. We conducted an assay to quantify changes in the morphogenesis following application of ethephon on seedlings of Pachystroma longifolium (Ness) I. M. Johnst.during hardening. The results showed no effect of the ethephon treatments on the number of leaves but a reduction of up to 50% in seedling height increment, and an increase in stem diameter increment of up to 44% with the 600 mg L-1 ethephon treatment, which consequently altered seedling Dickson Quality Index. Our results indicate that ethephon may help to promote desired morphological changes that occur during seedling hardening in nurseries.

Climate Influence on the Expansion and Tree-Ring Growth of Pinus nigra L. at High Altitude in the Central Apennines

Scattered expansion of European black pine (Pinus nigra Arnold) has been observed above the current timberline in the central Apennines. We aimed to detect possible common pattern of structure and growth dynamics of pine regeneration in treeline sites. Over 700 black pine samples growing above the timberline were sampled at four sites in the limestone Apennines of Marche and Abruzzo regions. For each tree we measured basal stem diameter, total height and annual height increments; a wooden core was extracted from the stem near the ground for cambial age determination and detection of intra-annual density fluctuations (IADF). We used multivariate analysis to assess patterns of the main tree structural attributes and dendrochronological analysis for age structure and growth dynamics. Expansion of European black pine started about 35 years ago featuring similar germination peaks, tree structure and growth patterns in all the sites. IADF have similar frequencies and peaks and occur in mid-late summer. These similar patterns occur at all sites besides the local differences and grazing histories suggesting the presence of an overall climate driver.

Climate change at northern latitudes: rising atmospheric humidity decreases transpiration, N-uptake and growth rate of hybrid aspen.

At northern latitudes a rise in atmospheric humidity and precipitation is predicted as a consequence of global climate change. We studied several growth and functional traits of hybrid aspen (Populus tremula L.×P. tremuloides Michx.) in response to elevated atmospheric humidity (on average 7% over the ambient level) in a free air experimental facility during three growing seasons (2008–2010) in Estonia, which represents northern temperate climate (boreo-nemoral zone). Data were collected from three humidified (H) and three control (C) plots, and analysed using nested linear models. Elevated air humidity significantly reduced height, stem diameter and stem volume increments and transpiration of the trees whereas these effects remained highly significant also after considering the side effects from soil-related confounders within the 2.7 ha study area. Tree leaves were smaller, lighter and had lower leaf mass per area (LMA) in H plots. The magnitude and significance of the humidity treatment effect – inhibition of above-ground growth rate – was more pronounced in larger trees. The lower growth rate in the humidified plots can be partly explained by a decrease in transpiration-driven mass flow of NO3 − in soil, resulting in a significant reduction in the measured uptake of N to foliage in the H plots. The results suggest that the potential growth improvement of fast-growing trees like aspens, due to increasing temperature and atmospheric CO2 concentration, might be smaller than expected at high latitudes if a rise in atmospheric humidity simultaneously takes place.

Influence of climate on seasonal patterns of stem increment of balsam fir in a boreal forest of Québec, Canada

It is important to develop a better understanding of the climatic factors controlling the growth of boreal forests. Dendrometer measurements were used to characterize inter-annual variation in seasonal patterns of stem diameter increment of balsam fir trees (n=3) over seven growing seasons (2004–2010) in a boreal forest of Québec, Canada. For the period studied, cumulative seasonal growth ranged from 1.1mm to 2.9mm. Cumulative seasonal growth was a function of the timing of tree growth initiation and cessation along with the maximum growth rate observed throughout the growing season. The start and finish of diameter growth showed variations of 21 and 53 days, respectively, and duration of the growing season ranged from 38 to 107 days while maximum growth rates observed throughout a season ranged from 36.0μmd−1 to 57.6μmd−1. Interestingly, similar cumulative annual growth can be achieved through very different seasonal growth patterns, depending on the inter-annual variation of the three factors mentioned above. Air temperature and photosynthetically active radiation appeared to regulate the initiation of tree growth with high photosynthetically active radiation and cool spring conditions delaying the start of growth. The maximum growth rate within a given season was related to snowpack depth and the timing of snowmelt. Deeper snowpack that melt earlier in spring was associated to higher maximum growth rates during the following season. Apart from exceptional climatic conditions that led to a very early growth cessation in 2006, the timing of growth cessation cannot be explained by climatic variables, suggesting that this phenological event is internally controlled by a physiological mechanism. Overall, the results indicate that the onset of growth as well as the maximum growth rate were regulated by climatic triggers. Consequently, changes in climate seasonality may have considerable effects on both seasonal pattern of growth and tree growth itself.

Frequent, low-amplitude disturbances drive high tree turnover rates on a remote, cyclone-prone Polynesian island

Aim How important are frequent, low-intensity disturbances to tree community dynamics of a cyclone-prone forest? We tested the following hypotheses concerning the ‘inter-cataclysm’ period on a remote Polynesian island: (1) tree turnover would be high and recruitment rates would be significantly higher than mortality; (2) low-intensity disturbance would result in a marginal increase in tree mortality in the short term; (3) turnover would vary among species and would be associated with plant traits linked to differences in life history; and (4) mortality and recruitment events would be spatially non-random. Location Tutuila, a volcanic island in the Samoan Archipelago, Polynesia. Methods We censused the tree (stem diameter ≥ 10 cm) community in 3.9 ha of tropical forest three times over a 10-year period, 1998–2008. We calculated annual mortality, recruitment and turnover rates for 36 tree species. We tested for non-random spatial patterns and predictors of mortality, and non-random spatial patterns of tree recruitment. A 2004 cyclone passing within 400 km allowed us to measure the effects of a non-cataclysmic disturbance on vital rates. Results Annual turnover was 2.8% and annual recruitment was 3.6%; these are some of the highest rates in the tropics, and likely to be a response to a cyclone that passed < 50 km from Tutuila in 1991. Species turnover rates over 10 years were negatively correlated with wood specific gravity, and positively correlated with annual stem diameter increment. Mortality was spatially aggregated, and a function of site, species and an individual’s growth rate. Recruitment was highest on ground with low slope. The low-magnitude cyclone disturbance in 2004 defoliated 29% of all trees, but killed only 1.8% of trees immediately and increased annual mortality over 5 years by 0.7%. Main conclusions The inter-cataclysm period on Tutuila is characterized by frequent, low-amplitude disturbances that promote high rates of tree recruitment and create a dynamic, non-equilibrium or disturbed island disequilibrium tree community. Species with low wood density and fast growth rates have enhanced opportunities for recruitment between cataclysms, but also higher probabilities of dying. Our results suggest that increases in the frequency of cyclone activity could shift relative abundances towards disturbance-specialist species and new forest turnover rates.

Desempenho de mudas de gravioleira inoculadas com fungos micorrízicos arbusculares em solo não-esterilizado, com diferentes doses de fósforo

Performance of soursop seedlings inoculated with arbuscular mycorrhizal fungi in non-sterilized soil, with different phosphorus doses. The objective of this work was to evaluate the development of soursop (Annona muricata L.) seedlings inoculated with arbuscular mycorrhizal fungi (AMFs) cultivated with different doses of phosphorus (P). The experiment was carried out in a greenhouse with a completely randomized factorial design (4 x 4), with non inoculated plants (controls), three species of arbuscular mycorrhizal fungi, Glomus clarum, Gigaspora margarita and native AMFs (Glomus macrocarpum, G. etunicatum and Entrosphopora colombiana) and four doses of P (0, 25, 50, 100 mg kg -1 ) with three replications. The seedlings were cultivated in plastic bags of 2 dm 3 in a mix composed of non- sterilized soil and sand (2:1 v v -1 ). After 90 days, it was observed that AMFs inoculation promoted an increment in height and stem diameter, increased biomass and P content of shoot and roots, and K content in the roots of the seedlings in comparison with controls. The non inoculated plants did not respond to phosphorus fertilization, concluding that the inoculation with AMFs with phosphate fertilization increased growth and nutritional state of soursup seedlings even when cultivated in non-sterilized soil.

Effects of selective tree harvests on aboveground biomass and net primary productivity of a second-growth northern hardwood forest

Restoring structural features of old-growth forests, such as increased canopy gap sizes and coarse woody debris, is a common management goal for second-growth, even-aged stands. We experimentally manipulated forest structure by creating variable-size canopy gaps in a second-growth northern hardwood forest in north-central Wisconsin following two growing seasons of pre-treatment monitoring. The objectives of this study were to quantify the influence of canopy gaps of different sizes (50–380 m2) on aboveground biomass and productivity of each vegetation stratum two growing seasons following treatment. Two years after treatment, ground layer biomass in canopy openings increased significantly relative to surrounding undisturbed transition zones. The response of ground layer biomass was greatest in the large versus the medium and small gaps. Sapling aboveground net primary productivity was significantly greater in undisturbed transition zones than within gaps across gap sizes following the second post-treatment growing season. Annual stem diameter increment was greatest for trees along gap borders and was correlated with crown class, percentage of crown perimeter exposed, gap area, and shade tolerance. Total aboveground net primary productivity was significantly lower in the gap addition plots the first year but by the second post-treatment growing season no longer differed from that in the control plots.