Tree/wood quality in slash pine following long-term cattle grazing

Tree height, diameter, and grade were measured on 14 cattle grazing trial plots located on the Palustris Experimental Forest in Louisiana's Kisatchie National Forest. These plots had been established in the early 1960s. Mensurational data was gathered on 28 trees from grazed sites and another 28 from ungrazed plots. Increment cores were also taken from these trees. Statistical analyses showed no effect attributable to grazing on any of the variables measured: tree height, tree diameter at breast height, tree grade, growth rate, amount of latewood, unextracted specific gravity, or tracheid length. This revised version was published online in June 2006 with corrections to the Cover Date.     

Studies on the Health of Beech Trees in Surrey, England: Relationship between Winter Canopy Assessment by Roloff's Method and Twig Analysis

Trees and saplings of all sizes (total 229) were studied atthree amenity sites in Surrey representing mixed woodland, beechhigh forest and open parkland. Roloff's winter assessment ofthe twig pattern of growth demonstrated an underlying differencebetween the sites, which was consistent with an associationbetween greater deterioration and more exposure to climate extremesand pollutants. Trees showed deterioration with age but prematureageing was seen in 35–50-year-old parkland trees. Withinthe woodland the more exposed trees had worse scores. Quantitative twig analysis was carried out on twigs from theupper canopy of 19 trees and saplings. In the most severelysuppressed trees yearly growth declined from the 1976 drought.Subsidiary shoot development was markedly reduced in such treesand there were high numbers of distorted and acute angled shoots.The latter two characteristics increased with age with younghealthy trees having very few of these types of shoots, buttwo 35-year-old trees in open parkland showed premature ageingwith larger numbers of such shoots. Twig analysis defined categories of twig pattern according toage and deterioration levels. There was generally good correlationbetween these categories and the Roloff twig canopy score beforeanalysis or with canopy scores of similar sized neighbours.Objective criteria suggested for future studies were: (1) measurementof annual primary shoot growth; (2) total secondary shoot lengthrelative to a standard primary shoot length; (3) mean numberof subsidiary shoots per year; and (4) proportion of shootsgrowing at 40° or less.     

Corresponding patterns of site quality,decline and tree growth in a sessile oak stand

This study focuses on two rarely studied aspects of oak decline: relations with site characteristics and effects on tree growth. The study was carried out in a 5.5 ha stand in Hungary which is strongly affected by oak decline. The nearly pure sessile oak (Quercus petraea) stand of mostly coppice origin was 90 years old at the beginning of the study. Within-stand site heterogeneity was described by the herbaceous vegetation. Four ecological site types were distinguished by the species composition of herbs, and characterized by the ecological indicator values of the species. Tree growth between 1987 and 1993 was measured, and tree vigour was estimated from visual characteristics five times between 1987 and 1993. Potential volume increment of declining trees was estimated with the growth rates of healthy trees of the same size. Volume increment loss caused by oak decline was also assessed. Significant positive relationships were found between tree vigour and tree size and between tree vigour and tree growth. The growth of seriously declining trees dropped to almost one-half of that of healthy ones. Growth reduction of living trees at the stand level amounted to 5.4%, whereas growth reduction of all trees, including those that died during the observation period, amounted to 19.9% of the potential growth. Tree size and growth were greater on better sites. A strong relationship was also found between tree vigour and site type, but sessile oak was more susceptible to decline at better sites.     

Some Consequences of the 1975-1976 Drought for Dutch Elm Disease in Southern England

During the exceptionally hot, dry summer of 1976 the large elmbark beetle, Scolytus scolytus, was able to invade and successfullybreed in apparently healthy, undiseased elms. A conspicuousfeature was the clustering of wasps, bees and ladybirds on thestems, attracted by sap exudation. The trees were probably sufferingfrom drought, although many showed no symptoms. The phenomenonoccurred mainly on shallow soils over limestone; trees on chalkwere not generally affected. In 1976, and to some extent in 1975, the downward developmentof Ceratocystis ulmi through the tree was less than in previousyears, and only a low proportion of the numerous maturationfeeding wounds became infected. However the drought does notappear to have significantly influenced the course of the epidemic. The attacks by S. scolytus on undiseased trees are discussedin respect of 19th Century reports of attacks on elms, and itis concluded that the ability of S. scolytus to assume a moreprimary role may have been underestimated.     

Forest decline: modeling the effect of climate in tree rings

Tree rings provide an historical record of forest growth that reflects changes with time in site factors including, competition, tree and stand age, fire and other disturbances, and climate. Statistical methods can be used to factor out climatic influences on radial growth to yield a climate response model that can indicate whether declines in forest productivity are related to the modeled climatic variables or to other influences such as atmospheric pollutants. A general method, based on ordinary least squares, is presented for creating climatic response models for forest decline studies. The crux of the method is model verification, whereby the time-stability of the model is tested before it is used to forecast tree-ring variations during a period of decline. Three studies are described that employ monthly mean temperatures to predict tree-ring indices in declining red spruce (Picea rubens Sarg.) stands in the Appalachian Mountains of North America. The results indicate that, since 1960, red spruce trees at most of the sites sampled have undergone a period of growth decline that is unrelated to changes in mean monthly temperature. However, an association between annual ring width and unusual departures from the mean summer and winter temperatures during both present and past periods of decline suggests that climatic effects are implicated to some degree in the current decline.     

Effect of Late-season Top-dressings of N (and K) applied to Conifer Transplants in the Nursery on their Survival and Growth on British Forest Sites

At two English forest nurseries, transplants of five coniferspecies—Picea sitchensis, Picea abies, Tsuga heterophylla,Abies grandis, and Pinus contorta—were grown with fertilizersupplying N, P, K, and Mg in amounts intended to be adequatefor producing healthy green trees with nutrient concentrationsin the ‘sufficiency range’ as determined by earlierexperiments. ‘Luxury uptake’ of nitrogen was obtainedwith top-dressings of ‘Nitro-Chalk’ applied in thenursery during early September, when top growth had nearly ceased.Tests of the effect of this extra N on forest establishmentwere repeated in four successive years under a wide range ofsoil and climatic conditions, keeping the trees in a cold storeduring each winter and planting them on forest sites in England,Scotland, or Wales during the following spring. Except for Grandfir, nitrogen advanced bud-break of all species during the firstsummer after planting and had no deleterious influence on survival.It tended to increase growth of Sitka spruce during the seasonafter planting, but in later years the differences became smallin relation to tree size. The effects on other species weresmall, except for one considerable decrease in the growth responseof Grand fir at a single site. Frost damage of Sitka spruce of Washington origin was severeon a Welsh and a Scottish site where this frost-sensitive provenancewould not normally be grown. At the Welsh, but not the Scottishsite, the nitrogen treatment increased the damage. In the few experiments (confined to Picea sitchensis) whichtested late-season potassium in the nursery, K concentrationswere increased from deficiency to barely sufficiency level;growth in the forest was increased in two of the four experiments.The extra K had no effect on frost damage.     

Growth responses of three coexisting conifer species to climate across wide geographic and climate ranges in Yukon and British Columbia

This work aimed to compare radial growth–climate relationships among three coexisting coniferous tree species across a wide geographic and climate range from southern British Columbia (BC) to central Yukon, Canada. Tree-ring data were collected from 20 mature stands of white spruce (Picea glauca), lodgepole pine (Pinus contorta var. latifolia), and subalpine fir (Abies lasiocarpa). Linear relationships between annual growth variation and monthly and seasonal climate were quantified with correlation and regression analyses, and variation in climate–growth responses over a climatic gradient were quantified by regressing growth responses against local mean climatic conditions. Temperatures had more consistent and stronger correlations with growth for all three species than precipitation, but growth–climate responses varied among species and among sites. In particular, pine and fir populations showed different responses between BC and Yukon, whereas spruce showed a more consistent response across the study domain. Results indicate that (1) the response and sensitivity of trees to seasonal climate variables vary among species and sites and (2) winter temperatures prior to growth may have significant impacts on pine and fir growth at some sites. The capacity to adapt to climate change will likely vary among the study species and across climatic gradients, which will have implications for the future management of mixed-species forests in Yukon and BC.     

Intensity and timing of warming and drought differentially affect growth patterns of co-occurring Mediterranean tree species

Climate change involves warmer temperatures, altered precipitation patterns, increased climatic variability and, in Mediterranean regions, increased frequency and severity of droughts. Tree species may show different growth responses to these components of climatic change, which may trigger changes in forest composition and dominance. We assessed the influence of recent climatic changes on secondary growth of mature trees from four species co-occurring in a Mediterranean continental forest: Quercus ilex, Quercus faginea, Pinus nigra and Juniperus thurifera. We used dendrochronology to relate radial-growth variables [earlywood and latewood widths, basal area increment (BAI)] to annual and seasonal climatic variables for the period 1977–2007. Our results showed that Q. faginea BAI has declined, whereas J. thurifera BAI has increased over time while Q. ilex and P. nigra have maintained their growth rates. Growth was mainly favored by higher precipitations and tree size for all species. Reduced growth during extremely dry years was observed for all study species, but all of them except Q. faginea recovered their growth levels 2 years after drought. Our findings illustrate how the effects of climatic changes on growth should include analyses of seasonal climatic trends and extreme events such as severe droughts. We conclude that the seasonal timing of warming and precipitation alterations leading to drought events caused contrasting effects on growth of co-occurring Mediterranean tree species, compromising their future coexistence.     

Growth and chemical composition of silver birch: Comparative study between Lithuania and Romania

The effects of different climatic conditions on growth and chemical composition of Betula pendula in geographically different European regions,Lithuania and Romania,were compared.Birch species in the entire area have a wide natural distribution,but B.pendula is commercially more important in Lithuania than in Romania.Here we evaluated tree ring width,wood density and foliar chemical composition of mature birch trees in two European regions.Trees at the Lithuanian sites had greater radial growth and wood density with no clear changes in foliar chemistry than those at the Romanian sites.Mean wood density was 600-700 kg m~(-3) at Lithuanian and 350-450 kg m~(-3) at Romanian sites.Mean width of wood ring,earlywood and latewood for Lithuanian birch trees were several times higher than the means for Romanian birch trees.We hypothesized that the main differences in birch radial growth and wood density were due to the different climatic conditions in the studied regions.Ca,K and Mg concentrations were significantly higher and Fe and Mn were lower in the birch foliage at the Lithuanian sites compared those at the Romanian sites.Overall assessment of growth showed that silver birch cultivation is more appropriate for colder climate regions and that birch growth may change in the context of a warming climate.     

Effects of spacing and genetic entry on radial growth and ring density development in Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.)

• Introduction  

The objective of this work was to study how spacing and genetic entry and/or origin group affect radial growth (ring width and cumulative diameter development) and ring density from pith to bark in Scots pine (Pinus sylvestris L.) and in what sense their annual variability could be explained by the climatic variables. The spacing trial was located in central Finland, with current stand density range of 2,000–4,000 trees per hectare. All the six genetic entries had Kanerva pine (plus tree S1101) as a father tree, whereas the mother tree represented Finnish plus trees from southern, central and northern Finland.     

银盏林场海南榄仁试验林活立木生长调查与分析

海南榄仁（Terminalia nigrovenulosa Pierre ex Lanessen）是原产于海南岛热带林区的一类商品用材树种,银盏林场于1976年从海南引进进行试种,现保存46株,通过活立木物候观察和树干解析结果发现,海南榄仁在银盏林场表现较强的适应性;能完成开花和结实的完整生殖生长过程;林下自然更新良好,表明该树种能适应当地的立地和气候条件。在清远银盏的引种成功,表明该物种可作为珍贵用材树种在清远市南部地区及以南的广东南部区域种植和发展。     

Divergent growth responses and increasing temperature limitation of Qinghai spruce growth along an elevation gradient at the northeast Tibet Plateau

Divergent responses between tree growth and climate factors have been widely reported at high latitudes in the northern hemisphere. Here we show variable climate-growth relationships and divergent growth responses of Qinghai spruce (Picea crassfolia) along an elevation gradient at a mid-latitude site at the northeastern Tibetan Plateau, China. Trees from higher elevations, limited mainly by temperature, show divergent growth trends over time and two responses to climate. Some trees show increasing positive and some increasing negative responses to growing season temperature during the last decades. Trees from lower treeline show a strengthening drought stress signal over time and no divergent growth trends within sites. Our results indicate that single tree analysis might be a worthwhile tool to (1) uncover spatial–temporal changes in climate-growth relationships of trees, (2) better understand future growth performance and (3) help overcome current limitations of tree ring based climatic reconstructions.     

Growth–climate responses of high-elevation conifers in the central Hengduan Mountains,southwestern China

Improved understanding of tree-growth responses to climate is needed to model and predict forest ecosystem responses to current and future climatic variability. We applied dendroclimatological techniques to assess the effects of inter-annual climate variations on radial growth of high-elevation conifers in the central Hengduan Mountains, southwestern China. Eight tree-ring width chronologies of the major tree genera Abies and Picea that are aligned along an elevation gradient from 3200 to 4200 m a.s.l. were developed. Correlation and principal component analyses for the eight chronologies identified three groups of sites, representing different patterns of growth–climate relationships. Correlation and redundancy analyses with regional climate data revealed that radial growth of fir growing at high-elevation sites is enhanced by normal or warm summer temperatures (June and July) during the current growing season. In addition, radial growth of trees growing from high to middle elevations is sensitive to low temperatures during winter season. At low-elevation sites, trees display low sensitivity to temperature variation. However spring moisture availability becomes crucial for radial growth regardless of tree species. High- to middle-elevation conifers in the central Hengduan Mountains may benefit from the current climate warming, especially from rising winter temperatures.     

Quantifying stem growth loss at the tree-level in a Pinus radiata plantation to repeated attack by the aphid, Essigella californica

Since its detection in 1998, the exotic aphid pest, Essigella californica Essig (Hemiptera: Aphididae) has caused extensive defoliation in commercial Pinus radiata plantations throughout Australia. A total of one hundred and twenty plots encompassing thirty tree ages, and three thinning treatments were established in September 2006 in southern New South Wales, Australia to assess crown health and tree growth. Assessments were carried out annually during 2006-2009 to quantify the relationship between natural aphid-induced defoliation and growth loss at the individual tree level. Over the course of the four years, particularly in 2006, trees were subjected to moisture stress, as indicated by average annual rainfalls that were below the long-term average. In general, the diameter growth of individual trees appeared unaffected by crown damage severity across most tree ages, indicating that the productivity in Green Hills was limited by the interactive effects of climatic and biotic stressors (both cause premature loss of foliage). Furthermore, the results from this four-year experiment demonstrated that both moisture stress and aphid-induced defoliation constrained the growth response to thinning. However, thinning may have assisted damaged trees to maintain growth rates similar to trees with little or no damage. Understanding the impact of disturbances such as insect pest outbreaks on growth yield models is critical for optimal modelling of long-term plantation growth and management. Our results highlight the difficulty in quantifying the effect of aphid-induced defoliation when combined with chronic moisture stress.     

Effects of growth rates, tree morphology and site conditions on longevity of Norway spruce in the northern Swiss Alps

Longevity of trees is known to be associated with growth rates, but also with tree morphology and spatial influences. However, very little quantitative information is available on the effects of these biotic and abiotic influences on maximum ages of trees. The objectives of this study were to investigate the trade-off between longevity and growth rates of Norway spruce (Picea abies) and to quantify the effects of tree morphology and abiotic site conditions on longevity of this species. Data were collected along different topographical and climatic gradients in a 20?×?25?km study area in the northern part of the Swiss Alps (Glarus). The ages of the more than 100 sampled dead Norway spruces ranged between 50 and 367?years. Longevity of these trees was negatively related to tree growth, i.e. slow-growing trees tended to grow older than fast-growing trees. Tree height was positively associated with longevity for both upper and lower storey trees. Longevity of lower storey trees was increased with large crown diameter, but decreased with long crown length. Upper storey trees growing at higher altitude tended to get older than at lower altitude. We conclude that the combined effects of growth rates, variability in site conditions and different traits of tree morphology determine tree longevity of Norway spruce in the Swiss Alps. Because longevity is tightly linked to mortality rates of tree populations, our study may improve our understanding of long-term processes of forest dynamics under current and future climate.     

Predicting the spatial distribution of major species composition in secondary hardwood forests on Mt. Gozu,central Japan,based on environmental factors

Our goal was to predict the spatial distribution of canopy species composition in secondary deciduous hardwood forests at a fine spatial resolution, based on climatic and topographical factors using a geographic information system. We studied secondary forests on Mt. Gozu, Niigata Prefecture, central Japan. Canopy species composition was investigated in 100 sample plots within the study area. A digital elevation model (DEM) was created, and topographical, hydrological, and light factors were calculated using the DEM. Climatic factors were interpolated by kriging. The five major species used as response variables were Fagus crenata, Quercus serrata, Quercus crispula, Magnolia obovata, and Castanea crenata. We prepared three possible explanatory variable sets: climatic variables only, both climatic and topographic variables, and topographic variables only. Multivariate regression trees were derived, and the accuracy of predicting the major species composition was tested. The multivariate regression trees derived from the climatic variable set and from the climatic and topographic variable set had better accuracy than the regression tree derived from the topographic variable set. In the regression tree generated by the climatic and topographic variable set, the warmth index was the principal explanatory variable in classifying forest types, followed by topographic factors. This regression tree would be preferable to the other two regression trees for the prediction of canopy species composition.     

Crown Index: a canopy balance indicator to assess growth and regeneration in uneven-aged forest stands of the Coastal Range of Chile

A balanced diameter structure, i.e. similar crown area allocatedto the different cohorts in uneven-aged forest stands, has beentraditionally regarded as a requirement for achieving bettergrowth rates and regeneration. Long-term experiments have demonstratedthe sustainability of these structures, but quantitative datainforming on how growth and regeneration behave under a balanceddiameter structure compared with other structures have beenscarce. Similarly, vertical structure has not been properlyaccounted for as a variable that can affect growth and regenerationin uneven-aged stands. In this study a Crown Index (CI) wasused as a surrogate of a balanced diameter structure and anindicator of vertical structure. This new index is obtainedby dividing the canopy area of trees in the main and upper canopypositions in a stand by the canopy area in lower strata. A CIof 1.0 indicates, on average, an even allocation of canopy areato each of four strata, namely, a balanced structure; values>1.0 or <1.0 reflect unbalanced structures, with excesscanopy cover of large trees or medium and small trees, respectively.From data obtained from stands at relatively poorer and bettersites in uncut and partially cut old-growth stands in the CoastalCordillera of southern Chile, the effects of CI, proportionof large and small trees, canopy area, and basal area on diametergrowth of Laurelia philippiana Looser (Monimiaceae) –the most important species in these forests – and regenerationof all canopy tree species were tested. Results indicated thefollowing: the CI was most strongly correlated to the proportionof large and of small trees (i.e. structural indicator), andto a lesser extent to basal area (a density indicator); theCI was by far the best explanatory variable of growth at bettersites and of regeneration at poor sites; and, in general, greatergrowth and more seedlings occurred as CI values decreased towards1, which reflects a balanced diameter structure. Results supportthe value of balanced diameter structures in managed uneven-agedstands, but also suggest that alternative structures could besought.     

Ring width and element concentrations in beech (Fagus sylvatica L.) from a periurban forest in central Belgium

The Forêt de Soignes is a beech high forest located near Brussels (Belgium), established on a strongly acidic soil and subjected to atmospheric pollution and recreational pressure. We investigated variations in ring width and mineral element concentrations (N, P, K, Ca, Mg, Mn, Al) over the last 95 years in five 135-year-old trees, variations in ring width in four 40-year-old trees and tested associations with climatic parameters. Growth curves showed a striking increase in mean sensitivity in the last 20 years in the old trees but not in the young ones, starting with the 1976 summer drought. Mean sensitivity is a statistical measure of the mean relative variability between adjacent ring widths within a tree, which is correlated to susceptibility to climatic stress (Fritts, H.C., 1976. Tree Rings and Climate, Academic Press, London, 567pp). May rainfall and, to a lesser extent, soil water recharge (i.e. pooled rainfall from October to May) correlated significantly with ring width. However, two of the five growth depressions in the last 20 years could not readily be accounted for by adverse climatic conditions. Element concentration profiles were suggestive of a decrease in the availability of Mn, Mg and Ca, but no trend of increasing N was obvious. The possible causes of the recent increase in sensitivity of old beech trees are discussed in terms of interactions between ageing and extreme climatic events, aggravated by soil compaction due to logging traffic.     

Factors driving growth responses to drought in Mediterranean forests

We lack information regarding the main factors driving growth responses to drought in tree species with different vulnerability against this stressor and considering sites with contrasting climatic conditions. In this paper, we identify the main drivers controlling growth response to a multi-scalar drought index (Standardized Precipitation Index, SPI) in eight tree species (Abies alba, Pinus halepensis, Quercus faginea, Pinus sylvestris, Quercus ilex, Pinus pinea, Pinus nigra, Juniperus thurifera). We sampled forests growing across a pronounced climatic gradient under Mediterranean conditions in north-eastern Spain. To summarize the patterns of growth responses to drought, we used principal component analysis (PCA). To determine the main factors affecting growth responses to drought, correlation and regression analyses were carried out using a set of abiotic (climate, topography, soil type) and biotic (Normalized Difference Vegetation Index, Enhanced Vegetation Index, tree-ring width, diameter at breast height) predictors and the PCs loadings as response variables. The PCA analysis detected two patterns of growth responses to drought corresponding to xeric and mesic sites, respectively. The regression analyses indicated that growth responses to drought in xeric forests were mainly driven by the annual precipitation, while in mesic sites the annual water balance was the most important driver. The management of Mediterranean forests under the forecasted warmer and drier conditions should focus on the main local factors modulating the negative impacts of drought on tree growth in xeric and mesic sites.     

Drought matters - Declining precipitation influences growth of Fagus sylvatica L. and Quercus robur L. in north-eastern Germany

For north-eastern Germany regional climate models project rising temperatures in combination with decreasing summer and increasing winter precipitation. The resulting overall drier conditions during the growing season will considerably impact forest growth there. We evaluate the consequences of increasing drought on the growth of the two locally most important broadleaf tree species common beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.). Three mixed forests of beech and oak were sampled along a west-east gradient of declining precipitation. In total we used 257 ring-width samples from 133 trees to build six species and site specific chronologies. Additionally, we modelled the soil water budget for each site. We performed continuous and discontinuous (pointer year) analysis of climate-tree-growth relationships with particular emphasis on inter-annual-variations and their dependence upon climatic factors (temperature, precipitation, soil moisture) and on the stability of the obtained relationships. Results of climate-growth correlations together with pointer year analysis indicate a strong dependency of growth of both species from water availability, especially during early summer (June and July). General correlation pattern between growth and climate are similar for both species, but climate sensitivity of beech is generally higher. We identified drought as the main driver of negative growth depressions in both species. Increasing drought stress along the gradient is expressed in higher correlations to climatic variables, higher sensitivity (variance) of growth, and a higher number of negative pointer years for both species. For beech we also found a significant trend of decreasing average growth rates along the gradient. Growth superiority of beech compared to oak declines with decreasing precipitation. The relationships were generally stable throughout the 20th century. A rise of sensitivity together with a higher frequency of negative pointer years during the last decades suggests that increasing climatic variability together with rising temperatures might be influencing growth of Fagus at the more humid sites. If we substitute space by time it seems that already small changes in precipitation regime can have considerable impact, especially on the growth of beech. Other, more drought tolerant species like oak might gain competitive advantages under the projected climatic changes.