Tree Growth Patterns Research Articles

Growth patterns in relation to drought-induced mortality at two Scots pine (Pinus sylvestris L.) sites in NE Iberian Peninsula

Drought-related tree mortality has become a widespread phenomenon. Scots pine (Pinus sylvestris L.) is a boreal species with high ecological amplitude that reaches its southwestern limit in the Iberian Peninsula. Thus, Iberian Scots pine populations are particularly good models to study the effects of the increase in aridity predicted by climate change models. A total of 78 living and 39 dead Scots pines trees were sampled at two sites located in the NE of the Iberian Peninsula, where recent mortality events have been recorded. Annual tree rings were used to (1) date dead trees; (2) investigate if there was an association between the occurrence of tree death and severe drought periods characterized by exceptionally low ratios of summer precipitation to potential evapotranspiration (P/PET); and (3) to compare the growth patterns of trees that died with those of surviving ones. Mixed models were used to describe the relationships between tree growth (in terms of basal area increment, BAI, and the percentage of latewood, LW%) and climate variables. Our results showed a direct association between Scots pine mortality and severe drought periods characterized by low summer water availability. At the two sites, the growth patterns of dead trees were clearly distinguishable from those of the trees that survived. In particular, the BAI of dead trees was more sensitive to climate dryness (low P/PETsummer, high temperatures) and started to decline below the values of surviving neighbors 15–40 years before the time of death, implying a slow process of growth decline preceding mortality.

종가시나무(Quercus glauca)의 육종집단 조성과 기후인자

A breeding population of Quercus glauca has been established via simple direct selection. Seedlings from naturally crossed seeds of 35 selected families growing in Jeju Island were placed using stroll repeated planting into two experimental forest located at Hannam and Sanghyo in Jeju. After 3 years of planting, characteristics of growth were examined. Growth pattern of trees in Sanghyo was better than those in Hannam. The average heights of filial were 66.8 cm in Hannam and 92.5 cm in Sanghyo. Root collar diameters of filial in Hannam and Sanghyo were 9.3 mm and 12.2 mm, respectively. A great weather differences especially in precipitation and temperature were shown between two test sites. The result of difference of growth pattern between two sites could be useful in provenance adaptability test. Data within families and individuals obtained from this study was also useful for establishment of seed orchard of Q. glauca.

Effects of thinning intensity on radial growth patterns and temperature sensitivity in Pinus canariensis afforestations on Tenerife Island, Spain

• Context The suitability of thinning to prevent forest growth decline as a result of global warming has not been tested extensively in Macaronesian Canary pine (Pinus canariensis Sweet ex Spreng.). • Aims This study aimed to answer the following questions: (1) are tree growth patterns modified by the aspect and thinning intensity? (2) Is sensitivity to climate modulated by thinning? (3) Do trees of different crown classes respond differentially to thinning intensity and climate? • Methods We used tree-ring series from dominant, codominant, and overtopped trees to study the effects of thinning intensity on basal area increments (BAI) and climate sensitivity on windward (wet) and leeward (dry) slopes on Tenerife, Canary Islands. Three replicated blocks of control, light thinning, and heavy thinning stands were set on each slope in 1988, and cores were extracted in 2007. • Results Heavy thinning induced growth release and increased BAI, mainly on dominant and codominant trees, whereas light thinning effects were negligible; their impacts were more intense on the windward side. Temperature sensitivity was hardly affected by thinning on leeward, where climate control was stronger. On windward, thinning enhanced the influence of summer temperatures. Upper crown classes were more sensitive overall, but overtopped trees responded better in summer. Thinning intensity and aspect greatly influence growth on Canary pine afforestations, but individual responses are highly dependent on crown classes. In addition, thinning may be less effective to modify growth conditions on leeward slopes, at least if not intense. © INRA and Springer Science+Business Media B.V. 2011.

BI-AXIS: AN ALTERNATIVE TO SLENDER SPINDLE FOR APPLE ORCHARDS

The use of the dwarfing M.9 rootstock is widespread in apple orchards due to the high tree efficiency it induces. Today it is possible to purchase a given type of tree congruent with the desired orchard design. Alongside the traditional chip-budded trees produced in a two-year cycle, there are types like two-year knip plants, trees obtained with the June bud (1-year-old) and bench-budded plants in a one-year cycle. These different types of plants are suitable for the spindle training system. The innovative ‘bi-axis’ system requires a pre-formed, split-branch tree produced in the nursery that obviates the need for heading in the orchard and the one-year delay in shoot-system formation. The spindle system is widely employed in apple orchards to boost planting densities up to 4,000 trees per hectare. The bi-axis system utilizes the novel idea of training plants with 2 axes so as to divide the vigour over more branches. Two sets of trials are underway with ‘Fuji’ in different environments, i.e. an upland orchard in Trento Province and a lowland one in the Po valley, to compare the vegetative and cropping traits of bi-axes against the traditional spindle in high density plantings. The comparison of the two systems has so far shown some differences in tree growth patterns and yield. Vigour is distributed over two axes in the Y- tree shape which helps control tree-growth. Shoot length is almost halved in the bi-axis system compared to the spindle. No significant differences in yield and crop quality were found in the first 2-3 years, but the bi-axis trees seem to produce better fruit red overcolour than spindle after four-five years.

Trees for urban environments in northern parts of Central Europe – a dendroecological study in north-east Romania and Republic of Moldavia

A limited number of species and genera currently dominate the tree stock in streets and urban sites. There has been considerable and persistent argumentation for the necessity of using a more varied and stress-tolerant selection of tree species. This paper reports results from a dendroecological study of six steppe forest reserves in north-east Romania and in the adjacent part of the Republic of Moldavia, where water stress regimes during the growing season and winter temperatures are comparable to those of inner city environments in northern parts of Central Europe and adjoining milder parts of Northern Europe (CNE-region). In each forest reserve, tree growth patterns were studied in five 20 m × 20 m plots, resulting in a total of 30 plots with an allocated area of 1.2 hectares. For all trees, height and diameter were measured and related to tree age by coring in order to detect the species growth and performance in these sites. In total 23 tree species were found, 13 of which were represented by 25 or more individuals with documented good growth in the study plots. The majority of these 13 species have very limited use in urban greenery in the CNE-region today and thus have the potential to increase the species diversity of the current urban tree population through further selection work.

아산지역 해안매립지의 복토높이에 따른 토양화학성, 수목 고사율 및 생장 특성

해안매립지에서 식재지반 조성을 위한 복토높이에 따른 토양의 채취, 운반 및 매립에 소요되는 비용이 매우 큰 차이가 있기 때문에 수목의 정상생육이 가능한 적정 복토높이를 구명하는 것은 매우 중요하다. 본 연구는 아산국가산업단지에서 해송, 화백, 느티나무 및 상수리나무에 대하여 복토처리별 (대조구, 0.5 m, 1.0 m, 1.5 m, 2.0 m 복토구) 로 식재 후 2년 6개월 경과한 후 토양화학성, 수목 고사율, 수고 및 근원경 생장의 변화를 조사하였다. 토양화학성은 복토높이가 낮을수록 pH, EC, 염기총량 및 염기포화도가 높아지고 <TEX>$K^+$</TEX>, <TEX>$Na^+$</TEX>, <TEX>$Ca^{2+}$</TEX>, <TEX>$Mg^{2+}$</TEX>, <TEX>$Cl^-$</TEX> 등 염류함량이 증가하였다. 특히 1 m 복토구 이하에서 이들 화학성분의 농도가 높아져, 수목의 고사율 및 생장에 직접적인 영향을 준 것으로 나타났다. 수목 고사율은 복토높이가 높을수록 낮아지는 경향이 있었으며, 1.5 m 복토구 미만에서 고사율이 급격히 증가하였다. 수고와 근원경 생장은 복토처리가 높을수록 양호하게 나타나는 경향이 있었다. 수고생장은 해송의 경우 0.5 m 복토구와 나머지 3개 처리 간에 유의적인 생장차이가 있었으며 화백, 느티나무, 상수리나무는 1.5 m 복토구 미만에서 유의적인 생장차가 있었다. 근원경의 경우 식재수종 모두 복토높이가 높을수록 생장이 양호하였으며 1.5 m 복토구와 2.0 m 복토구 간 생장차이가 없었다. 본 연구결과에 따르면 해안매립지의 복토높이에 따른 고사율 및 생육특성은 식재수종에 따라 차이가 있으며 해송의 경우 1 m 이내의 복토도 가능한 반면에 화백, 느티나무 및 상수리나무는 1.5 m 이상 복토가 필요할 것으로 보인다. It is important to determine optimum soil covering depths for tree survival and growth because soil covering depths for establishing tree planting bases in coastal reclaimed lands are related to the costs for soil collection, transportation and land reclamation. The objectives of this study were carried out to determine optimum soil covering depths for the normal growth of planted trees in a coastal reclaimed land. The study sites were located in Asan National Industrial Complex in Pyeongtaek City, Gyeonggi-do. Four tree species (Pinus thunbergii, Chamaecyparis pisifera, Zelkova serrata, Quercus acutissima) with one hundred eighty trees of each species were planted in various depths of soil covering (no soil covering, 0.5 m, 1.5 m, 2.0 m soil covering treatments) on April 1998, and the tree growth patterns were measured on September 2000. The change of soil properties, tree mortality rate, root collar diameter and height growth were measured from each soil covering depth treatment on September 2000. Soil pH, EC, exchangeable cations (<TEX>$K^+$</TEX>, <TEX>$Na^+$</TEX>, <TEX>$Ca^{2+}$</TEX>, <TEX>$Mg^{2+}$</TEX>), anion <TEX>$Cl^-$</TEX>, and base saturation increased with decreased soil covering depths. The mortality rates of tree species showed decreased with increased soil covering depths. The height growth of tree species increased with increased soil covering depths. Height growth of Pinus thunbergii was significantly different between the soil covering depth below 0.5m and other three covering depths, while the growth of other species (C. pisifera, Z. serrata, Q. acutissima) was significantly higher in soil covering depths below 1.5 m than in other soil covering depth treatments. The root collar diameter growth of all tree species showed increasing trends with increased soil covering depths. It is recommended to cover the soil depths above 1.5 m to decrease mortality and to stimulate the tree growth of C. pisifera, Z. serrata and Q. acutissima, while P. thunbergii which is a salt tolerate species could be planted in the 1.0 m soil covering depth.

Radial growth patterns of dominant trees in two old-growth forests in eastern Fennoscandia

We investigated the characteristics and variability of radial growth patterns and the occurrence of growth releases in dominant trees in two old-growth forests in eastern Finland, one dominated by Picea abies and the other by Pinus sylvestris. The dominant trees exhibited high variation in radial growth patterns suggesting that the trees had experienced very different growing conditions and competitive situations during their lifespans. Based on visual evaluation, five types of radial growth patterns were distinguished: descending, even, unimodal (one peak in the growth rate), bimodal (two peaks in the growth rate with an intermediate depression) and fuzzy (no clear pattern). One or more growth releases were detected in 18% of the sampled Picea and in 21% of the Pinus trees. In both the Picea- and the Pinus-dominated sites, the temporal distribution of growth releases was relatively even, except for a moderate peak in 1855–1860. This suggests that small-scale disturbances have been the predominant disturbance mode in both sites during the last 150 years. We conclude that the detected variability in radial growth patterns likely reflects the overall small-scale heterogeneity of structure and developmental processes that are typical of old-growth forests.

Buffered climate change effects in a Mediterranean pine species: range limit implications from a tree-ring study

Within-range effects of climatic change on tree growth at the sub-regional scale remain poorly understood. The aim of this research was to use climate and radial-growth data to explain how long-term climatic trends affect tree growth patterns along the southern limit of the range of Pinus nigra ssp. salzmannii (Eastern Baetic Range, southern Spain). We used regional temperature and precipitation data and measured sub-regional radial growth variation in P. nigra forests over the past two centuries. A dynamic factor analysis was applied to test the hypothesis that trees subjected to different climates have experienced contrasting long-term growth variability. We defined four representative stand types based on average temperature and precipitation to evaluate climate-growth relationships using linear mixed-effect models and multi-model selection criteria. All four stand types experienced warming and declining precipitation throughout the twentieth century. From the onset of the twentieth century, synchronised basal-area increment decline was accounted for by dynamic factor analysis and was related to drought by climate-growth models; declining basal-area increment trends proved stronger at lower elevations, whereas temperature was positively related to growth in areas with high rainfall inputs. Given the contrasting sub-regional tree-growth responses to climate change, the role of drought becomes even more complex in shaping communities and affecting selection pressure in the Mediterranean mountain forests. Potential vegetation shifts will likely occur over the dry edge of species distributions, with major impacts on ecosystem structure and function.

Disentangling the relative importance of climate, size and competition on tree growth in Iberian forests: implications for forest management under global change

Most large-scale multispecies studies of tree growth have been conducted in tropical and cool temperate forests, whereas Mediterranean water-limited ecosystems have received much less attention. This limits our understanding of how growth of coexisting tree species varies along environmental gradients in these forests, and the implications for species interactions and community assembly under current and future climatic conditions. Here, we quantify the absolute effect and relative importance of climate, tree size and competition as determinants of tree growth patterns in Iberian forests, and explore interspecific differences in the two components of competitive ability (competitive response and effect) along climatic and size gradients. Spatially explicit neighborhood models were developed to predict tree growth for the 15 most abundant Iberian tree species using permanent-plot data from the Spanish Second and Third National Forest Inventory (IFN). Our neighborhood analyses showed a climatic and size effect on tree growth, but also revealed that competition from neighbors has a comparatively much larger impact on growth in Iberian forests. Moreover, the sensitivity to competition (i.e. competitive response) of target trees varied markedly along climatic gradients causing significant rank reversals in species performance, particularly under xeric conditions. We also found compelling evidence for strong species-specific competitive effects in these forests. Altogether, these results constitute critical new information which not only furthers our understanding of important theoretical questions about the assembly of Mediterranean forests, but will also be of help in developing new guidelines for adapting forests in this climatic boundary to global change. If we consider the climatic gradients of this study as a surrogate for future climatic conditions, then we should expect absolute growth rates to decrease and sensitivity to competition to increase in most forests of the Iberian Peninsula (in all but the northern Atlantic forests), making these management considerations even more important in the future.

Ecotone characteristics of a southern Appalachian Mountain wetland

article i nfo Article history: Southern Appalachian Mountain wetlands support important habitat and serve several hydrologic functions. However, they may be threatened by human activities and global climate change. These wetlands are often located in remote, biogeographically isolated locations at high elevations. One of the largest of these wetlands — the peatlands within the Cranberry Glades Botanical Area — was assessed for meadow-forest ecotone characteristics. The Cranberry Glades have been reported to be infilling with trees from the surrounding forest, but little research has been conducted on the patterns of tree growth within the moss-dominated communities. Tree establishment patterns were analyzed in regard to location within the ecotone, hummock/hollow topography, and soil conditions by recording the growing conditions of 1389 trees located within nine, 10×100 m belt transects. The results indicated that tree growth within the ecotone occurred in decreasing density fromthe forest tothe meadow interior, and much of the tree establishment occurred intreeislands (80% of trees were found in tree islands). Significantly more trees (92%) were also found on hummocks than hollows (8%), likely in response to the greater distance from the water table that the hummocks provide. Most soil properties did not vary significantly across the ecotone or in association with topography. The results add to the minimal literature on southern peatlands and may assist in peatland restoration and conservation efforts.

Editorial note for the special issue on ‘Tropical Dendroecology’

It is not very long ago that tree-ring studies on tropical trees were in their pioneering stage, being regarded as exceptional studies. Since dendroecology evolved in the temperate climate zones, the majority of dendroecologists trusted in the paradigm that trees growing in tropical climates do not exhibit annual growth rings and hence are not suitable for dendroecology, a discipline based on the principle of exactly datable annual growth structures formed in the wood of trees. The vast majority of the present tree-ring studies is still carried out in extra-tropical environments, whereas ‘the Tropics’ are still regarded as a region where analyzing annual growth structures in trees is a challenging task. However, ‘the Tropics’ are by far less homogeneous. The high phanerophyte biodiversity of tropical forests and woodlands, the vast variety of wood anatomical structures and the occasionally faint growth boundaries and tangential growth inhomogeneity of tropical trees are some of the obstacles dendroecologists are facing in studying tropical trees. While temperature is rarely a growth-limiting factor in tropical environments except at high-altitude tree line ecotones, moisture availability and the seasonality of precipitation causes a large number of hydroclimates within the Tropics (located within the Tropic of Capricorn and the Tropic of Cancer) and the subtropics, e.g., in summer-hot regions with a winter-rainfall regime. The number and length of dry seasons, when evapotranspiration exceeds precipitation, and edaphically controlled soil water capacity determine the individual water resources available for trees and hence their physiological activity. Topographic and hydrological factors may strongly alter the general climatic conditions, leading to drought-prone climatic conditions in mountain basins or in the leeward side of high mountain systems, or to seasonal water input or even anoxic conditions in riverine inundation forests. Thus, growth conditions may alter from everhumid to almost completely arid within areas outlined under the same climatic regime. This makes tropical environments more complex and leads to a high spatial and temporal variability of growth patterns of trees. It is exactly this high spatio-temporal variability of moisture regimes that make trees in tropical regions such interesting recorders of the environmental history. The past years witnessed a rapid increase of dendroecological case studies in the Tropics around the world, questioning the aforementioned paradigm or at least leading to much less generalized conclusions about tree growth in the Tropics. With the development of more sophisticated techniques, especially in wood anatomy studies, in the documentation of cambial dynamics, and in high-resolution stable isotope techniques with intra-annual resolution, more and more insight of the growth patterns and controlling environmental factors of tree growth in tropical regions has been gained. Thus, while in many regions dendroecology is still in its infancy, basically detecting the annual nature of tree growth boundaries, it is in the state of becoming an applied science in other areas. This special issue provides an outline of applications of new techniques and state-of-the art approaches in tree-ring research in different tropical environments. The majority of the contributions were presented in a session on ‘Tropical Dendroecology’ held at the first joint conference of the Germany-based GTOE (Society for Tropical Ecology) and the ATBC (Association for Tropical Biology and Conservation) held in Marburg (Germany) during 27–30 July A. Brauning (&) Institute of Geography, Friedrich-Alexander-University Erlangen-Nuremberg, Kochstr. 4/4, 91054 Erlangen, Germany e-mail: abraeuning@geographie.uni-erlangen.de

The effect of anthropogenic activities on the reduction of urban tree sensitivity to climatic change: dendrochronological evidence from Chinese pine in Shenyang city

To understand how urban tree growth has responded to the accelerating expansion in population and urbanization, an understanding of the tree-climate–urban ecosystem relationship is necessary. To this end, a metropolitan, suburban, and rural forest stand in and near Shenyang; and a rural forest stand in Weichang, were sampled in southern Northeast China. Radial growth variability of 109 Chinese pines (Pinus tabulaeformis Carr.), established before 1900 within and around the city, was measured. The contents of trace elements in tree rings were also examined to detect the possible relationship to urban environmental contamination. All sampled trees crossdated well, indicating a homogeneous common influence of regional climate. For the common period of 1901–2000, the radial growth of all trees was significantly affected by local and regional climate, especially temperature and precipitation in winter and spring, respectively. From the rural to the metropolitan areas, a significant decreasing relationship in the response of trees to climatic factors was detected. These decreases occurred over time and in tree stands within the same location or between different sites, and also corresponded with the increasing influence of local urbanization and industrialization on the urban environment during the last century. Particularly strong influences are the increase of population, urban built-up area, and urban agricultural and industrial activities. Decreases in mean sensitivity of Chinese pines were also found and are most likely related to the intensification of anthropogenic activities and environmental change. Based on tree-ring width growth in rural areas, a growth pattern of urban trees without anthropogenic disturbances was established. After removing the climate-related signals from actual urban tree growth, the impact of anthropogenic disturbances was chronologically developed. The results indicate that the periods of heaviest disturbances occurred from 1914 to 1922, 1932 to 1935, 1943 to 1946, 1955 to 1969, and 1973 to 2000.

Forest Policy Impact Assessment in the Ouachita National Forest and the Valuation of Conserving Red-Cockaded Woodpeckers

Problem statement: The Ouachita National Forest received approval in 1996 for an amendment to its Forest Plan that would allocate 10 % of the Forest to long-rotation silviculture. The purpose of the new management area is to restore pr e-European settlement forest conditions and recreate habitat for the endangered red-cockaded wo odpecker. Approach: This study explored the effects of restoring an ecosystem, from changes in the growth patterns of individual trees to ecosyste m valuation of the endangered red-cockaded woodpecker. It developed procedures for estimating the magnitude of economic impacts resulting from changes in timber production in the pine-bluestem management to project the value of conserving red-c ockaded woodpeckers. Results: Over the entire simulation period, pine-bluestem management returns 75% of the undiscounted revenue generated by traditional management (660 versus 875 million doll ars). For all 40,245 ha of the new management area managed for pine-bluestem, this cost amounts t o $2.9 million per year. When combined with the $137 million decline in the present value of projec ted timber sale revenue from the area, the total co st rises to $4.2 million per year. Conclusion: The implied value for each pair of woodpeckers is either $10,550 per year for the desired 400 total pairs or $16,880 per year for the 250 reproducing pairs. Judging from the changes resulting from the transit ion to pine-bluestem management, adopting the new scenario will not cause significant adverse reg ional economic consequences. The success of the pine-bluestem restoration requires the maintenance of a burning regime that prevents competing vegetation from occupying the middle canopy layer.

Dendroecology in the tropics: a review

Over the last decade the field of tropical dendroecology has developed rapidly and major achievements have been made. We reviewed the advances in three main themes within the field. First, long chronologies for tropical tree species were constructed which allowed climate reconstructions, revealed sources of climatic variation and clarified climate–growth relations. Other studies combined tree-ring data and stable isotope (13C and 18O) measurements to evaluate the response of tropical trees to climatic variation and changes. A second set of studies assessed long-term growth patterns of individual trees throughout their life. These studies enhanced the understanding of growth trajectories to the canopy, quantified autocorrelated tree growth and yielded new estimates of tree ages. Such studies were also used to reconstruct the disturbance history of tropical forests. The last set of studies applied tree-ring data to growth models. Tree-ring data can replace diameter measurements from research plots, provide additional information to construct population models, improve timber yield models and validate model output. Based on our review, we propose two main directions for future research. (1) An evaluation of the causes and consequences of growth variation within and among trees and their relation to environmental variation. Studies evaluating this directly contribute to improved understanding of tropical tree ecology. (2) The simultaneous measurement of widths and stable isotope fractions in tree rings offers the potential to study responses of trees to climatic change. Given the major role of tropical forests in the global carbon cycle, knowing these responses is of high priority.

Gender-Related Climate Response of Radial Growth in Dioecious Fraxinus mandshurica Trees

Abstract This paper presents an analysis of tree-ring growth patterns of male and female Fraxinus mandshurica trees from 1931 to 2007. The specific object was to study the response of radial growth to climate variables separately for male and female trees. The results show that the growth patterns in the two genders were similar during the mid-1950s to 1970s but different in the periods 1931–1940s and 1980–2007. In the period 1980–2007, the mean sensitivity and mean widths of the tree rings were significantly different between the genders (p < 0.05). The climate-growth response in female and male trees was also different. Female trees are sensitive to precipitation in November of the previous year, whereas male trees respond to mean temperature in November of the previous year. The results confirm that climatic sensitivity in male and female trees of dioecious species is different, yet this difference is not stable through time.

Contemporary Concepts of Root System Architecture of Urban Trees

Knowledge of the extent and distribution of tree root systems is essential for managing trees in the built environment. Despite recent advances in root detection tools, published research on tree root architecture in urban settings has been limited and only partially synthesized. Root growth patterns of urban trees may differ considerably from similar species in forested or agricultural environments. This paper reviews literature documenting tree root growth in urban settings as well as literature addressing root architecture in nonurban settings that may contribute to present understanding of tree roots in built environments. Although tree species may have the genetic potential for generating deep root systems (&gt;2 m), rooting depth in urban situations is frequently restricted by impenetrable or inhospitable soil layers or by underground infrastructure. Lateral root extent is likewise subject to restriction by dense soils under hardscape or by absence of irrigation in dry areas. By combining results of numerous studies, the authors of this paper estimated the radius of an unrestricted root system initially increases at a rate of approximately 38 to 1, compared to trunk diameter; however, this ratio likely considerably declines as trees mature. Roots are often irregularly distributed around the tree and may be influenced by cardinal direction, terrain, tree lean, or obstacles in the built environment. Buttress roots, tap roots, and other root types are also discussed.

Long-term effects of CO&lt;sub&gt;2&lt;/sub&gt; enrichment on bud phenology and shoot growth patterns of Norway spruce juvenile trees

Bud phenology and shoot elongation growth were monitored on Norway spruce (Picea abies [L.] Karst.) trees grown inside glass domes with adjustable windows for six years under ambient (355 &amp;micro;mol CO&lt;sub&gt;2&lt;/sub&gt;∙mol&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) and elevated (700 &amp;micro;mol CO&lt;sub&gt;2&lt;/sub&gt;∙mol&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) atmospheric CO&lt;sub&gt;2&lt;/sub&gt; concentrations CO&lt;sub&gt;2&lt;/sub&gt;. Each treatment consisted of two stand densities &amp;ndash; sparse (5,000 trees∙ha&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;) and dense (10,000 trees∙ha&lt;sup&gt;&amp;ndash;1&lt;/sup&gt;). The age of spruce trees was 10 years at the beginning of the experiment.Elevated CO&lt;sub&gt;2&lt;/sub&gt; slightly accelerated the consequential bud germinating phases and it significantly induced shoot elongation growth, especially of sun-exposed shoots in a stand with sparse density. This accelerated growth lasted one to three weeks after full bud development in E compared to A. At the end of the growing season the total shoot length did not show any differences between the treatments. We supposed that limiting nitrogen supply to needles slowed down subsequent shoot elongation growth in E treatment. Nevertheless, faster shoot growth in elevated CO&lt;sub&gt;2&lt;/sub&gt; conditions can enhance the carbon sink in spruce due to prolongation of the growing season.

A new method for evaluating forest thinning: growth dominance in managed Pinus resinosa stands

Growth dominance is a relatively new, simple, quantitative metric of within-stand individual tree growth patterns, and is defined as positive when larger trees in the stand display proportionally greater growth than smaller trees, and negative when smaller trees display proportionally greater growth than larger trees. We examined long-term silvicultural experiments in red pine ( Pinus resinosa Ait.) to characterize how stand age, thinning treatments (thinned from above, below, or both), and stocking levels (residual basal area) influence stand-level growth dominance through time. In stands thinned from below or from both above and below, growth dominance was not significantly different from zero at any age or stocking level. Growth dominance in stands thinned from above trended from negative at low stocking levels to positive at high stocking levels and was positive in young stands. Growth dominance in unthinned stands was positive and increased with age. These results suggest that growth dominance provides a useful tool for assessing the efficacy of thinning treatments designed to reduce competition between trees and promote high levels of productivity across a population, particularly among crop trees.

Evidence for a recent increase in forest growth.

Forests and their soils contain the majority of the earth's terrestrial carbon stocks. Changes in patterns of tree growth can have a huge impact on atmospheric cycles, biogeochemical cycles, climate change, and biodiversity. Recent studies have shown increases in biomass across many forest types. This increase has been attributed to climate change. However, without knowing the disturbance history of a forest, growth could also be caused by normal recovery from unknown disturbances. Using a unique dataset of tree biomass collected over the past 22 years from 55 temperate forest plots with known land-use histories and stand ages ranging from 5 to 250 years, we found that recent biomass accumulation greatly exceeded the expected growth caused by natural recovery. We have also collected over 100 years of local weather measurements and 17 years of on-site atmospheric CO(2) measurements that show consistent increases in line with globally observed climate-change patterns. Combined, these observations show that changes in temperature and CO(2) that have been observed worldwide can fundamentally alter the rate of critical natural processes, which is predicted by biogeochemical models. Identifying this rate change is important to research on the current state of carbon stocks and the fluxes that influence how carbon moves between storage and the atmosphere. These results signal a pressing need to better understand the changes in growth rates in forest systems, which influence current and future states of the atmosphere and biosphere.

Climate–growth relationships of Qilian juniper Sabina przewalskii in the Anyemaqen Mountains, Tibet

Climate-growth relationships were investigated for 5 mountain slopes of the Anye- maqen Mountains on the northeastern Tibetan Plateau, using a tree-ring width network indicating the chronologies of 20 Qilian junipers Sabina przewalskii. Tree growth is mainly controlled by regional climate conditions, which are modulated by altitudinal factors. The tree growth patterns in this region were classified asccording to a west-east orientation. Temperature and precipitation from August to October of the previous year and May of the current year are the major limiting factors for most chronologies, as indicated by simple correlation analysis. In general, precipitation plays a more important role in governing tree growth than temperature, and tree rings in the east are more sensi- tive to precipitation than those in the west. Differences in the climate-growth relationship may be caused by varying climate conditions between the western and eastern Anyemaqen Mountains.