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Tree species can influence biogeochemistry through variation in the quantity and chemistry of their litter, and associated impacts on the soil heterotrophic community. However, the role that different plant traits play in these processes is not well understood, nor is it clear whether species effects on soils largely reflect a gymnosperm vs. angiosperm contrast. Using a replicated, long-term monoculture plot experiment, we examined variation in soils among 14 gymnosperm and angiosperm tree species 30 years after plot establishment, and assessed the role of litter chemistry vis-a`-vis such variation. Differences in litter calcium concentrations among tree species resulted in profound changes in soil acidity and fertility that were similar within and among tree groups. Tree species rich in calcium were associated with increased native earthworm abundance and diversity, as well as increased soil pH, exchangeable calcium, per cent base saturation and forest floor turnover rate.

Summary • Here, we tested hypothesized relationships among leaf and fine root traits of grass, forb, legume, and woody plant species of a savannah community. • CO 2 exchange rates, structural traits, chemistry, and longevity were measured in tissues of 39 species grown in long-term monocultures. • Across species, respiration rates of leaves and fine roots exhibited a common regression relationship with tissue nitrogen (N) concentration, although legumes had lower rates at comparable N concentrations. Respiration rates and N concentration declined with increasing longevity of leaves and roots. Species rankings of leaf and fine-root N and longevity were correlated, but not specific leaf area and specific root length. The C 3 and C 4 grasses had lower N concentrations than forbs and legumes, but higher photosynthesis rates across a similar range of leaf N. • Despite contrasting photosynthetic pathways and N 2 -fixing ability among these species, concordance in above- and below-ground traits was evident in comparable rankings in leaf and root longevity, N and respiration rates, which is evidence of a common leaf and root trait syndrome linking traits to effects on plant and ecosystem processes.

The response of respiration to temperature in plants can be considered at both short- and long-term temporal scales. Short-term temperature responses are not well described by a constant Q10 of respiration, and longer-term responses often include acclimation. Despite this, many carbon balance models use a static Q10 of respiration to describe the short-term temperature response and ignore temperature acclimation. We replaced static respiration parameters in the ecosystem model photosynthesis and evapo-transpiration (PnET) with a temperature-driven basal respiration algorithm (Rdacclim) that accounts for temperature acclimation, and a temperature-variable Q10 algorithm (Q10var). We ran PnET with the new algorithms individually and in combination for 5 years across a range of sites and vegetation types in order to examine the new algorithms’ effects on modeled rates of mass- and area-based foliar dark respiration, above ground net primary production (ANPP), and foliar respiration– photosynthesis ratios. The Rdacclim algorithm adjusted dark respiration downwards at temperatures above 181C, and adjusted rates up at temperatures below 51C. The Q10var algorithm adjusted dark respiration down at temperatures below 151C. Using both algorithms simultaneously resulted in decreases in predicted annual foliar respiration that ranged from 31% at a tall-grass prairie site to 41% at a boreal coniferous site. The use of the Rdacclim and Q10varalgorithms resulted in increases in predicted ANPP ranging from 18% at the tallgrass prairie site to 38% at a warm temperate hardwood forest site. The new foliar respiration algorithms resulted in substantial and variable effects on PnETs predicted estimates of C exchange and production in plants and ecosystems. Current models that use static parameters may over-predict respiration and subsequently under-predict and/or inappropriately allocate productivity estimates. Incorporating acclimation of basal respiration and temperature-sensitive Q10 have the potential to enhance the application of ecosystem models across broad spatial scales, or in climate change scenarios, where large temperature ranges may cause static respiration parameters to yield misleading results.

Temperature-mediated changes in plant respiration (R) are now accepted as an important component of the biosphere's response to global climate change. Here we discuss the underlying mechanisms responsible for the dynamic response of plant respiration to short and long-term temperature changes. The Q(10) is often assumed to be 2.0 (i.e. R doubles per 10 degrees C rise in temperature); however, the Q(10) is not constant (e.g. it declines near-linearly with increasing temperature). The temperature dependence of Q(10) is linked to shifts in the control exerted by maximum enzyme activity at low temperature and substrate limitations at high temperature. In the long term, acclimation of R to temperature is common, in effect reducing the temperature sensitivity of R to changes in thermal environment, with the temperature during plant development setting the maximal thermal acclimation of R.

Summary • We tested the hypothesis that biological trait-based plant functional groups provide sufficient differentiation of species to enable generalization about a variety of plant ecophysiological traits or responses to nitrogen (N). • Seedlings of 34 North American grassland and savanna species, representing 5 functional groups, were grown in a glasshouse in an infertile soil with or without N fertilization. • Forbs, C 3 and C 4 grasses, on average, had similar relative growth rates (RGR), followed in declining order by legumes and oaks, but RGR varied greatly among species within functional groups. All measured attributes differed significantly among functional groups, of these, only RGR and photosynthesis differed among functional groups in response to N. All groups, except the legumes, had significantly greater photosynthetic and respiration rates at elevated N supply. Principal components analyses and cluster analyses yielded groupings that corresponded only moderately well to the biologically based a priori functional groupings. • Variation in RGR among species and treatments was positively related to net CO 2 exchange (photosynthesis and respiration) and net assimilation rate, but unrelated to leaf area ratio. Photosynthetic and respiration rates were related to tissue %N among treatments and species. Our data indicate that RGR and related traits differ among the functional groups in significant ways, but in a complex pattern that does not yield simple generalizations about relative performance, controls on RGR, or response to resource supply rate.

With the ability to symbiotically fix atmospheric N2, legumes may lack the N-limitations thought to constrain plant response to elevated concentrations of atmospheric CO2. The growth and photosynthetic responses of two perennial grassland species were compared to test the hypotheses that (1) the CO2 response of wild species is limited at low N availability, (2) legumes respond to a greater extent than non-fixing forbs to elevated CO2 ,a nd (3) elevated CO2 stimulates symbiotic N2 fixation, resulting in an increased amount of N derived from the atmosphere. This study investigated the effects of atmospheric CO2 concentration (365 and 700 µmol mol −1 ) and N addition on whole plant growth and C and N acquisition in an N2-fixing legume (Lupinus perennis) and a non-fixing forb (Achillea millefolium) in controlled-chamber environments. To evaluate the effects of a wide range of N availability on the CO2 response, we incorporated six levels of soil N addition starting with native field soil inherently low in N (field soil + 0, 4, 8, 12, 16, or 20 g N m −2 yr −1 ). Whole plant growth, leaf net photosynthetic rates (A), and the proportion of N derived from N2 fixation were determined in plants grown from seed over one growing season. Both species increased growth with CO2enrichment, but this response was mediated by N supply only for the non-fixer, Achillea. Its response depended on mineral N supply as growth enhancements under elevated CO2 increased from 0% in low N soil to +25% at the higher levels of N addition. In contrast, Lupinus plants had 80% greater biomass under elevated CO2 regardless of N treatment. Although partial photosynthetic acclimation to CO2 enrichment occurred, both species maintained comparably higher A in elevated compared to ambient CO2 (+38%). N addition facilitated increased A in Achillea, however, in neither species did additional N availability affect the acclimation response of A to CO2. Elevated CO2 increased plant total N yield by 57% in Lupinus but had no effect onAchillea. The increased N in Lupinus came from symbiotic N2 fixation, which resulted in a 47% greater proportion of N derived from fixation relative to other sources of N. These results suggest that compared to non-fixing forbs, N2-fixers exhibit positive photosynthetic and growth responses to increased atmospheric CO2 that are independent of soil N supply. The enhanced amount of N derived from N2 fixation under elevated CO2 presumably helps meet the increased N demand in N2-fixing species. This response may lead to modified roles of N2-fixers and N2-fixer/non-fixer species interactions in grassland communities, especially those that are inherently N-poor, under projected rising atmospheric CO2.

Projections of future climate are highly sensitive to uncertainties regarding carbon (C) uptake and storage by terrestrial ecosystems. The Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment was established to study the effects of elevated atmospheric CO2 concentrations (eCO2 ) on a native mature eucalypt woodland with low fertility soils in southeast Australia. In contrast to other FACE experiments, the concentration of CO2 at EucFACE was increased gradually in steps above ambient (+0, 30, 60, 90, 120, and 150 ppm CO2 above ambient of ~400 ppm), with each step lasting approximately 5 weeks. This provided a unique opportunity to study the short-term (weeks to months) response of C cycle flux components to eCO2 across a range of CO2 concentrations in an intact ecosystem. Soil CO2 efflux (i.e., soil respiration or Rsoil ) increased in response to initial enrichment (e.g., +30 and +60 ppm CO2 ) but did not continue to increase as the CO2 enrichment was stepped up to higher concentrations. Light-saturated photosynthesis of canopy leaves (Asat ) also showed similar stimulation by elevated CO2 at +60 ppm as at +150 ppm CO2 . The lack of significant effects of eCO2 on soil moisture, microbial biomass, or activity suggests that the increase in Rsoil likely reflected increased root and rhizosphere respiration rather than increased microbial decomposition of soil organic matter. This rapid increase in Rsoil suggests that under eCO2, additional photosynthate was produced, transported belowground, and respired. The consequences of this increased belowground activity and whether it is sustained through time in mature ecosystems under eCO2 are a priority for future research.

Summary 1. Our goal was to determine the relationships among ecophysiological, whole-plant and ecosystem traits of a wide variety of grassland species grown under field conditions in the long term. We measured 87 traits for 33 species (32 perennial, one annual) grown in monoculture for 5 years on sandy soils, and determined the relationship among traits and their correspondence with current functional classifications. 2. Among non-legumes, species that produced and maintained large amounts of biomass had tough, low-activity leaves and roots, high root : shoot ratios, and low extractable inorganic nitrogen and N mineralization in their soils. The set of correlations among the functional traits of fine roots for non-legumes parallels the set of correlations for leaf functional traits. Low-N species maintained greater biomass than highN species, more by producing tissues with low N concentrations and greater longevity than by acquiring more N. Greater relative production below ground, and the production of long-lived below-ground structures, were both important in determining the high root : shoot ratio of species. 3. For legumes, N 2 fixation not only led to greater above-ground biomass production, but also was associated with low fine root production; greater relative production of stem biomass; and accelerated ecosystem N cycling compared to non-legumes. 4. The measured traits, as condensed via principal components analysis, differentiated the 32 species into groups that corresponded with a common grassland functional classification scheme (C 3 grasses, C 4 grasses, forbs, legumes, woody species) as well as an alternative, continuous approach. For all traits, species can be arrayed well along two continuous axes. The first axis separates cool-season and warm-season legumes; the second low-N and high-N non-legumes. 5. These continuous classifications show the generality of the two strategies for dealing with low nitrogen availability (N 2 fixation and the low-N suite of traits) and extends the strategies to span organ-level traits to ecosystem processes including roots, whole-plant patterns of productivity, and nutrient cycling. The correlations of traits among species will also be useful in predicting a large number of important parameters associated with plant growth from the measurement of a few, key traits.

Nutrient availability differs across climatic gradients, yet the role of genetic variation in potentially adaptive traits related to nutrient acquisition remains poorly understood. We examined needles of diverse Scots pine provenances grown under common-garden conditions throughout their entire life span. Based on similarities in nutrient concentration patterns, two groups of populations were identified. One comprised northern populations from 60 o to 56 o N, and another included populations from locations between 56 o and 49 o N. Northern populations sustained significantly higher concentrations of N, P, Ca, Mg, Na, Zn, Cu and Pb. Only K concentration was persistently lower in northern plants. We conclude that intraspecific genetic differences exist in foliage nutrient concentration among di- verse populations. Since in northern conditions nutrient availability is often limited as a result of interactions between temperature, litter quality and its mineralization, a tendency toward higher foliage concentrations of macronutrients can be an adaptive feature enhancing plants metabolic activity in their native habitats.

Climate change threatens the ability of agriculture and forestry to meet growing global demands for food, fibre and wood products. Information gathered from genotype-by-environment interactions (G × E), which demonstrate intraspecific variation in phenotypic plasticity (the ability of a genotype to alter its phenotype in response to environmental change), may prove important for bolstering agricultural and forest productivity under climate change. Nonetheless, very few studies have explicitly quantified genotype plasticity-productivity relationships in agriculture or forestry. Here, we conceptualize the importance of intraspecific variation in agricultural and forest species plasticity, and discuss the physiological and genetic factors contributing to intraspecific variation in phenotypic plasticity. Our discussion highlights the need for an integrated understanding of the mechanisms of G × E, more extensive assessments of genotypic responses to climate change under field conditions, and explicit testing of genotype plasticity-productivity relationships. Ultimately, further investigation of intraspecific variation in phenotypic plasticity in agriculture and forestry may prove important for identifying genotypes capable of increasing or sustaining productivity under more extreme climatic conditions.

As rapid climate warming creates a mismatch between forest trees and their home environment, the ability of trees to cope with warming depends on their capacity to physiologically adjust to higher temperatures. In widespread species, individual trees in cooler home climates are hypothesized to more successfully acclimate to warming than their counterparts in warmer climates that may approach thermal limits. We tested this prediction with a climate-shift experiment in widely distributed Eucalyptus tereticornis and E. grandis using provenances originating along a ~2500 km latitudinal transect (15.5–38.0°S) in eastern Australia. We grew 21 provenances in conditions approximating summer temperatures at seed origin and warmed temperatures (+3.5 °C) using a series of climate-controlled glasshouse bays. The effects of +3.5 °C warming strongly depended on home climate. Cool-origin provenances responded to warming through an increase in photosynthetic capacity and total leaf area, leading to enhanced growth of 20– 60%. Warm-origin provenances, however, responded to warming through a reduction in photosynthetic capacity and total leaf area, leading to reduced growth of approximately 10%. These results suggest that there is predictable intraspecific variation in the capacity of trees to respond to warming; cool-origin taxa are likely to benefit from warming, while warm-origin taxa may be negatively affected.

Results are presented of shoot elongation of 10-year-old trees of 19 European Pinus sylvestris populations growing in a provenance experiment in central Poland. Populations exhibited different shoot elongation patterns with montane southern (40–44°N) and lowland northern (58–60°N) populations having lower growth rates and earlier onset of growth cessation than those from the central lowland part (47–55°N) of European species’ range. Average absolute growth rates ranged from 6.6 mm per day for populations of southern origin to 9.2 mm per day for populations from central Europe. Shoot elongation period explained ca. 50–60% and differences in growth rate from 40 to 50% of total differences in annual increment among population groups. There was a linear relationship ( r 2 =0.73, P

Summary • Direct inhibition of dark respiration by elevated atmospheric concentrations of CO2 could alter the carbon balance of plants and ecosystems. The short-term response of leaf dark respiration to elevated CO2 concentrations are reported here in 12 grass and forb species of a North American grassland community. • Specific respiration rates at 25°C and a range of measurement CO2 concentrations were determined for detached leaves of each species field-grown in monoculture. • On average, respiration rates were 1.8% lower at 700 than at 360 µmol mol−1 CO2. Among species, responses ranged from a 6.4% inhibition to a 2.4% stimulation and were generally not statistically significant. Across a range of CO2 concentrations from 360 to 1300 µmol mol−1, respiration rates declined linearly and were 11% lower at 1300 than 360 µmol mol−1 CO2. • Direct inhibition of leaf respiration is small compared with other longer-term, indirect effects of CO2 on carbon exchange. The direct effects of rising atmospheric CO2 concentrations on respiration rates should result in minimal effects on plant carbon exchange in grasslands.

Summary • To evaluate whether functional groups have a similar response to global change, the responses to CO 2 concentration and N availability of grassland species from several functional groups are reported here. • Sixteen perennial grassland species from four trait-based functional groups (C 3 grasses, C 4 grasses, non-leguminous forbs, legumes) were grown in field mono cultures under ambient or elevated (560 μ mol mol ‐1 ) CO 2 using free-air CO 2 enrichment (FACE), in low N (unamended field soil) or high N (field soil + 4 g N m ‐2 years ‐1 ) treatments. • There were no CO 2 〈 N interactions. Functional groups responded differently to CO 2 and N in terms of biomass, tissue N concentration and soil solution N. Under elevated CO 2 , forbs, legumes and C 3 grasses increased total biomass by 31%, 18%, and 9%, respectively, whereas biomass was reduced in C 4 -grass mono cultures. Two of the four legume species increased biomass and total plant N pools under elevated CO 2 , probably due to stimulated N-fixation. Only one species markedly shifted the proportional distribution of below- vs aboveground biomass in response to CO 2 or N. • Although functional groups varied in responses to CO 2 and N, there was also sub stantial variation in responses among species within groups. These results suggest that current trait-based functional classifications might be useful, but not sufficient, for understanding plant and ecosystem responses to elevated CO 2 and N availability.

Summary • Leaf gas exchange responses to elevated CO 2 and N are presented for 13 perennial species, representing four functional groups: C 3 grasses, C 4 grasses, legumes, and nonleguminous forbs. Understanding how CO 2 and N effects interact is important to predict plant community response to global change. • Plants were field-grown in monoculture under current ambient and elevated (560 μ mol mol - 1 ) CO 2 concentrations (free-air CO 2 enrichment), in combination with soil N treatments, for two growing seasons. • All species, regardless of functional group, showed pronounced photosynthetic acclimation to elevated CO 2 , resulting in minimal stimulation of photosynthesis ( A ) averaging +15% in C 3 grasses, +8% in forbs, + 7% in legumes and - 2% in C 4 grasses. The effects of CO 2 and soil N supply did not interact for any leaf traits measured. Elevated CO 2 consistently decreased stomatal conductance ( g s ) leading to 40% increase in A / g s . • This substantial acclimation of photosynthesis was greater in magnitude than in most field studies, and was associated with the combined effects of decreased g s and decreased leaf N concentrations in response to growth under elevated CO 2 .

Temperature responses of rates of respiratory CO2 efflux from plants, soils, and ecosystems are frequently modelled using exponential functions with a constant Q10 near 2.0 (fractional change in rate with a 10 ∞C increase in temperature). However, we present evidence that Q10 declines with short-term increases in temperature in a predictable manner across diverse plant taxa. Thus, models using a constant Q10 are biased, and use of a temperature-corrected Q10 may improve the accuracy of modelled respiratory CO2 efflux in plants and ecosystems in response to temperature and predicted global climate changes.

On range-wide and regional scales, climate and site factors exert control over tree growth, masking the genetic basis of biomass accumulation and allocation. To determine intrinsic population differences in productivity, aboveground net primary production (ANPP) was measured in 16-year-old Scots pine from 19 geographically distinct populations grown in a common garden experiment in central Poland (52°N). The populations originated from the northern (>55°N), central (54–47°N), and southern (

We tested the hypothesis that acclimation of foliar dark respiration to CO 2 concentration and temperature is associated with adjustments in leaf structure and chemistry. Populus tremuloides Michx., Betula papyrifera Marsh., Larix laricina (Du Roi) K. Koch, Pinus banksiana Lamb., and Picea mariana (Mill.) B.S.P. were grown from seed in combined CO 2 (370 or 580 μmol mol -1 ) and temperature treatments (18/12, 24/18, or 30/24 °C). Temperature and CO 2 effects were predominately independent. Specific respiration rates partially acclimated to warmer thermal environments through downward adjustment in the intercept, but not Q 10 of the temperature-response functions. Temperature acclimation of respiration was larger for conifers than broad-leaved species and was associated with pronounced reductions in leaf nitrogen concentrations in conifers at higher growth temperatures. Short-term increases in CO 2 concentration did not inhibit respiration. Growth in the elevated CO 2 concentration reduced leaf nitrogen and increased non-structural carbohydrate concentrations. However, for a given nitrogen concentration, respiration was higher in leaves grown in the elevated CO 2 concentration, as rates increased with increasing carbohydrates. Across species and treatments, respiration rates were a function of both leaf nitrogen and carbohydrate concentrations (R 2 = 0.71, P < 0.0001). Long-term acclimation of foliar dark respiration to temperature and CO 2 concentration is largely associated with changes in nitrogen and carbohydrate concentrations.

Growth and the distribution of biomass among above- and below-ground components were measured in 12-year-old Scots pine (Pinus sylvestris L.) from 19 populations grown in a provenance experiment in central Poland (52° N). The populations originated from the northern (>55°N in Russia, Sweden and Latvia), central (54–47° N in Poland, Germany, Belgium, France, Slovakia, Hungary), and southern (

In herbaceous dominated patches and ecosystems, tree establishment is influenced partly by the ability of woody seedlings to survive and grow in direct competition with herbaceous vegetation. We studied the importance of season long wet and dry spells on the competitive interactions between herbaceous vegetation and oak seedlings along a light and nitrogen gradient in an infertile secondary successional grassland in central North America. We conducted a field experiment in which seedlings of bur oak (Quercus macrocarpa) and northern pin oak (Q. ellipsoidalis) were exposed to two levels of light (full sun and 80% shade), three levels of nitrogen input (0, 5, 15 g m−1 yr−1), and three levels of water input (low, medium and high). In addition, seedlings were grown with and without the presence of surrounding herbaceous vegetation under both light and all three water levels. Seedling survival, growth, and rate of photosynthesis were significantly affected by competition with herbaceous vegetation and these effects varied along the multiple resource gradient. Overall, seedling survival of both species was significantly greater in wetter and shaded plots and when surrounding herbaceous vegetation was removed and was lower in nitrogen enriched plots. We found that soil water was significantly affected by varying inputs of water, light, and the presence or absence of herbaceous vegetation, and that seedling survival and rate of photosynthesis were highly correlated with available soil water. Our findings show that the impact of season long wet and dry spells on tree seedling success in grasslands can be affected by light and soil nitrogen availability.

Biochemical models of photosynthesis suggest that rising temperatures will increase rates of net carbon dioxide assimilation and enhance plant responses to increasing atmospheric concentrations of CO(2). We tested this hypothesis by evaluating acclimation and ontogenetic drift in net photosynthesis in seedlings of five boreal tree species grown at 370 and 580mgr;mol mol(-1) CO(2) in combination with day/night temperatures of 18/12, 21/15, 24/18, 27/21, and 30/24 degrees C. Leaf-area-based rates of net photosynthesis increased between 13 and 36% among species in plants grown and measured in elevated CO(2) compared to ambient CO(2). These CO(2)-induced increases in net photosynthesis were greater for slower-growing Picea mariana (Mill.) B.S.P., Pinus banksiana Lamb., and Larix laricina (Du Roi) K. Koch than for faster-growing Populus tremuloides Michx. and Betula papyrifera Marsh., paralleling longer-term growth differences between CO(2) treatments. Measures at common CO(2) concentrations revealed that net photosynthesis was down-regulated in plants grown at elevated CO(2). In situ leaf gas exchange rates varied minimally across temperature treatments and, contrary to predictions, increasing growth temperatures did not enhance the response of net photosynthesis to elevated CO(2) in four of the five species. Overall, the species exhibited declines in specific leaf area and leaf nitrogen concentration, and increases in total nonstructural carbohydrates in response to CO(2) enrichment. Consequently, the elevated CO(2) treatment enhanced rates of net photosynthesis much more when expressed on a leaf area basis (25%) than when expressed on a leaf mass basis (10%). In all species, rates of leaf net CO(2) exchange exhibited modest declines with increasing plant size through ontogeny. Among the conifers, enhancements of photosynthetic rates in elevated CO(2) were sustained through time across a wide range of plant sizes. In contrast, for Populus tremuloides and B. papyrifera, mass-based photosynthetic rates did not differ between CO(2) treatments. Overall, net photosynthetic rates were highly correlated with relative growth rate as it varied among species and treatment combinations through time. We conclude that interspecific variation may be a more important determinant of photosynthetic response to CO(2) than temperature.

We tested the extent to which growth responses to elevated carbon dioxide (CO2) are temperature-dependent and change through early seedling ontogeny among boreal tree species of contrasting relative growth rates (rgr). Populus tremuloides Michx, Betula papyrifera Marsh, Larix laricina (Du Roi) K. Koch, Pinus banksiana Lamb., and Picea mariana (Mill.) B.S.P. were grown from seeds for 3 months in controlled-environment chambers at two CO2 concentrations (370 and 580 μmol mol−1) and five temperature regimes of 18/12, 21/15, 24/18, 27/21 and 30/24°C (light/dark). Growth increases in response to CO2 enrichment were minimal at the lowest temperature and maximal at 21/15°C for the three conifers and at 24/18°C or higher for the two broadleaved species, corresponding with differences in optimal temperatures for growth. In both CO2 treatments, rgr among species and temperatures correlated positively with leaf area ratio (lar) (r0·90, P

SUMMARY Field-grown trees of Alnus incana (L.) Moench, Alnus glutinosa (L.) Geartner and Betula pendula Roth displayed pronounced differences in responses of light-saturated net photosynthesis (Asat) to herbivory by the alder beetle (Agelastica alni L., Galerucinae), a specialized insect which primarily defoliates alders. We found that photosynthetic rates of grazed leaves increased following herbivory in Alnus but not in Betula. Area- and massbased Asat of grazed leaves declined linearly with increasing amount of leaf perforation in B. pendula, by as much as 57 %. By contrast Alnus glutinosa and Alnus incana increased area-based rates of Asat by 10-50 % at all levels of leaf grazing. Given increased Asat in the remaining portion of grazed leaves, a net reduction in photosynthesis per leaf occurred only when the proportion of leaf area grazed exceeded 40 % for Alnus incana and 23 % for Alnus glutinosa. Since vein perforation by Agelastica alni was observed much more frequently in leaves of Betula than in Alnus, we hypothesized that declining Asat in herbivorized Betula was related to this disruption of water transport. A field experiment with artificial leaf perforation demonstrated a greater decline in Asat in veinperforated Betula leaves than perforated leaves with midrib veins intact. However, regardless of leaf perforation regime, birch never showed post-perforation increases in Asat' In all species, rates of transpiration of grazed leaves linearly increased and water-use efficiency decreased with increased amount of leaf perforation. In grazed Alnus incana leaves, increasing leaf area consumption by Agelastica alni resulted in an increase of total phenols, a reduction in starch content and no changes in nitrogen concentration in the remaining portion. The increase in photosynthesis in Alnus incana might be related to declining leaf starch concentration or increasing stomatal conductance, but was unrelated to leaf nitrogen concentration. These gas exchange and leaf chemistry measurements suggest that in contrast to B. pendula, Alnus incana and Alnus glutinosa, which are the major host species for Agelastica alni, possess leaf-level physiological adaptations and defence mechanisms which can attenuate negative effects of herbivory by the alder leaf-beetle.

1. There are conflicting reports concerning the adaptive features of tree populations originating from cold, high-altitude environments. We hypothesize that such trees will possess adaptive features that will be demonstrated in a common environment, such as elevated rates of net CO2 exchange, elevated needle nitrogen concentration and high proportional biomass allocation to roots. To test this hypothesis we measured tree and seed properties of 54 populations of Norway spruce [Picea abies (L.) Karst.] located along eight altitudinal transects (from c.600 to 1500m) in southern Poland. We also measured growth, biomass partitioning, net photosynthetic capacity (Amax), needle dark respiration (RS) and carbohydrate, nitrogen (N) and chlorophyll concentration of seedlings originating from these populations grown for 2 to 7 years in a common garden at 150m elevation. Measured in situ along the elevational transects, there were linear declines in seed mass, average d.b.h. and height growth increment of seed trees with increased altitude or lower mean annual temperature. 2. In the common garden, the Norway spruce populations from colder, high-altitude habitats had higher N concentration in needles than those from low altitudes. Both Amax and needle RS increased with altitude of seed origin and were significantly related to needle N concentration. High-altitude populations also had higher concentrations of chlorophyll and carotene than those from low elevations. Despite higher photosynthetic rates in high-altitude populations, seedling height and dry mass in the common garden declined with altitude of seed origin. Proportional dry mass partitioning to roots nearly doubled with increasing altitude of origin, while the length of the shoot-growth period was reduced. The high respiration rates, high allocation to roots and reduced shoot-growth period are probably responsible for the low growth rate potential of high-altitude populations, more than offsetting their higher photosynthetic rates. 3. The results of this study showed that Norway spruce populations from cold mountain environments are characterized by several potentially adaptive features. Because these were similar to conifer population responses along a latitudinal gradient of origin, they are probably driven by climate. These climate-driven differences were common to all transects: for a given altitude or mean annual temperature, plant traits were independent of mountain range of origin. However, populations originating from cold high-elevation sites often differed per unit change in altitude or mean annual temperature more than did low elevation populations. The scaling of nitrogen, CO2 exchange and biomass and allocation patterns may be useful in modelling Norway spruce response on montane forest ecosystems under changing environments.

1. To test several hypotheses about acclimation and adaptation of photosynthesis and respiration to differing light conditions, we investigated the interspecific relationships between leaf and root metabolism, chemistry and morphology in high and low light conditions for young seedlings of nine boreal tree species that differ in relative growth rate (RGR). 2. Light-saturated net photosynthesis (Asat), whole-plant nitrogen (N) uptake rates, leaf and root respiration and morphology, and RGR all varied in parallel among the nine species when grown in both 5% and 25% of full sunlight. RGR, Asat, leaf and root respiration (Rd), and N uptake rate per unit root mass or length differed significantly among species, ranking (from high to low): Populus, Betula and Larix spp. (all deciduous) and then to five evergreen conifers (Pinus, Picea and Thuja spp.), which were generally comparable in these measures. 3.Asat, leaf and root Rd and N uptake rates were all correlated (r≈ 0·8 to 0·9) with species traits, such as seed mass, leaf life span and shade-tolerance rankings. Mass-based Asat was greater in conifer seedlings raised in low than high light. In contrast, area-based Asat was higher for plants grown in high than low light, especially in the deciduous species. Once adjusted for differences in plant mass, leaf or root respiration rates did not differ for plants grown in low vs high light. 4. Interspecific variation in RGR was positively correlated (r≈ 0·9) with rates of photosynthesis, respiration and N uptake. Leaf photosynthesis and respiration rates were correlated to specific leaf area and leaf N concentrations (r≈ 0·9). Root respiration rates, N uptake rates, specific root length (root length per root dry mass) and root N concentrations were all highly correlated with each other (r≈ 0·8 to 0·9). These data suggest a close coupling of tissue-level metabolism, chemistry and structure with whole-plant performance and species ecophysiological and life-history traits.

Summary 1. To test hypotheses concerning adaptation and acclimation of tree species to shaded habitats we determined the growth, biomass partitioning and morphology of seedlings of nine near-boreal tree species in high- and low-light greenhouse environment (25 and 5% of full sunlight, respectively), comparable to sunlit gap and shaded microsites in boreal forests. The species differ widely in shade tolerance, seed size and leaf life span. 2. In low light, all species allocated proportionally more biomass to stems and less to roots, but the same to foliage, compared with the high-light environment. At a common size, all species had finer leaf morphology (higher specific leaf area, SLA) but coarser root morphology (lower specific root length, SRL) in low than high light. From a whole plant perspective, all species enhanced leaf area per unit plant mass (leaf area ratio, LAR) in low light and root length per unit plant mass (root length ratio, RLR) in high light. 3. Shade-intolerant deciduous species had higher RGR, SLA and SRL than larger seeded evergreens: ranking from Populus, Betula and Larix spp., then to five evergreen Pinus, Picea and Thuja spp., which were generally comparable in these traits. There were no changes in growth rankings of species between high- and low-light environments, nor consistent differences among species in biomass partitioning. Hence, species differences in leaf and root morphology (SLA, SRL) drove whole plant patterns, such as Populus, Betula and Larix had greater total leaf area and root length per unit plant mass (LAR and RLR, respectively) than the evergreens. Interspecific variation in RGR in both high and low light was positively correlated ( r  0·9) with SLA, SRL, LAR and RLR, and negatively correlated (r ‐0·9) to seed mass and leaf life span. 4. These data suggest that SLA, SRL, NAR and RGR are closely associated with variation in life-history traits and that variation in leaf and root structure more strongly influences patterns of RGR among species and light environments than does biomass partitioning.

Pinus heldreichii Christ is a long-lived, slow-growing Tertiary relict from the Balkans. In this study we evaluated the physiological characteristics of eight needle-age classes of P. heldreichii grown at the Arboretum of the Institute of Dendrology in Kornik, Poland. At the end of the growing season, current-year foliage had the highest rates of mass-based light-saturated net photosynthesis (Asat) of 33.5 nmol CO2· g–1· s–1. Asat decreased with needle age, but older needle classes retained from approximately 62 to 26% of the current needles’ rate. The relationship between leaf N and chlorophyll a concentration among all needle-age classes was highly significant (r = 0.96, P = 0.0006). The variation in Asat of 1- to 7-year-old needles was linearly related to needle N concentration (r = 0.98, P = 0.0001). Needle dark respiration rates among these needle age classes ranged from 0.8 to 2.2 nmol · g–1· s–1 and decreased with needle age and nitrogen concentration. Total phenols and glucose concentrations increased linearly with needle age. A similar pattern was observed in acid buffering capacity and the pH of tissue homogenates. The water content ranged from 62% for the current needles to 51% for the 6-year-old needles. Greater investment in leaf structural tissue and increased chemical defense is associated with higher structural cost of older needles and may reduce their photosynthetic activity. Significant declines in water and nitrogen content with needle age and an increase in content of phenolics is most likely a defense adaptation of P. heldreichii related to the species’ long-lived leaves.

One-year-old Scots pine (Pinus sylvestris L.) seedlings were grown for 9 weeks in nutrient solutions containing 0, 0.5, 1, 2 and 4 mM aluminum nitrate (Al(NO3)3) at pH 4.2. Nine weeks exposure to Al significantly reduced total plant, shoot and root mass and caused a linear decline in proportional allocation of biomass to roots. Relative growth rate of roots declined to as low as zero. Aluminum treatment decreased calcium and magnesium uptake and increased Al content in roots and needles. After 3 weeks of exposure a 10–60% increase in total phenols in roots and a 20–40% increase in o-diphenols in roots and needles were noted. Roots affected by Al showed degeneration of meristematic cells, fewer cell divisions, deformation in cell walls and higher lignification and suberization. The majority of root apices were structurally similar to dormant roots, and a premature senescence of the entire root system was observed. Net photosynthetic rate after 6 weeks of treatment was negatively correlated with needle Al content and Al/Ca ratio (r < -0.9, P < 0.1). The results suggest that Scots pine may be more susceptible to Al than was expected based on previous experiments.

The effects of elevated CO2 on the short-term temperature response of leaf dark respiration (R) remain uncertain for many forest tree species. Likewise, variation in leaf R among populations within tree species and potential interactive effects of elevated CO2 are poorly understood. We addressed these uncertainties by measuring the short-term temperature response of leaf R in 15 provenances of Eucalyptus grandis W. Hill ex Maiden from contrasting thermal environments grown under ambient [CO2] (aCO2; 400 µmol mol–1) and elevated [CO2] (640 µmol mol–1; eCO2). Leaf R per unit area (Rarea) measured across a range of temperatures was higher in trees grown in eCO2 and varied up to 104% among provenances. However, eCO2 increased leaf dry mass per unit area (LMA) by 21%, and when R was expressed on a mass basis (i.e. Rmass), it did not differ between CO2 treatments. Likewise, accounting for differences in LMA among provenances, Rmass did not differ among provenances. The temperature sensitivity of R (i.e. Q10) did not differ between CO2 treatments or among provenances. We conclude that eCO2 had no direct effect on the temperature response of R in E. grandis, and respiratory physiology was similar among provenances of E. grandis regardless of home-climate temperature conditions.

Ozone pollution may reduce net carbon gain in forests, yet data from mature trees are rare and the effects of irradiance on the response of photosynthesis to ozone remain untested. We used an open-air system to expose 10 branches within the upper canopy of an 18-m-tall stand of sugar maple (Acer saccharum Marsh.) to twice-ambient concentrations of ozone (95 nmol mol -1 , 0900 to 1700, 1h mean) relative to 10 paired, untreated controls (45nmol mol -1 ) over 3 months. The branch pairs were selected along a gradient from relatively high irradiance (PPFD 14.5 mol m -2 d -1 ) to deep shade (0.7 mol m -2 d -1 ). Ozone reduced light-saturated rates of net photosynthesis (A sat ) and increased dark respiration by as much as 56 and 40%, respectively. Compared to sun leaves, shade leaves exhibited greater proportional reductions in A sat and had lower chlorophyll concentrations, quantum efficiencies, and leaf absorptances when treated with ozone relative to controls. With increasing ozone dose over time, A sat became uncoupled from stomatal conductance as ratios of internal to external concentrations of carbon dioxide increased, reducing water-use efficiency. Ozone reduced net photosynthesis and impaired stomatal function, with these effects depending on the irradiance environment of the canopy leaves. Increased ozone sensitivity of shade leaves compared to sun leaves has consequences for net carbon gain in canopies.

We present two comprehensive data sets that describe xylem vessel diameters and related sapwood traits for species of Eucalyptus from arid and semi-arid woodlands and forests in Australia. Between 2009 and 2014, sapwood of mature trees was sampled in south-western, south-eastern and eastern Australia. One additional species was sampled from tropical north-western Australia. The first data set describes samples collected from the basal stem section (130 cm above ground) of three individuals of 31 species of which eight species were replicated at sites that differed in climatic conditions. The second data set describes vessel characteristics of three trees from each of 10 species that were sampled at 8 m below the tree apex. The sampled trees of these 10 species are also part of the first data set. In total, we report diameters (D) for over 25 100 vessels, from 494 digital images taken from 117 trees. We also report vessel frequencies, void-to-wood ratios, sapwood densities and hydraulically weighted vessel diameters (Dh). Supporting data of the first data set include tree diameter at breast height (130 cm above ground), tree height, sample locations, and summary climate data. In this data set, diameter of individual vessels ranges from 10 to over 300 μm, and vessel frequency from 360 to 9070 vessels cm−2. Wood density ranges from 0.47 to 0.96 g cm−3. Void-to-wood ratio ranges from 6% to 27% and Dh ranges from 46 to 236 μm. Mean annual rainfall (P) at sample sites ranges from 246 to 2274 mm and FAO56 reference evaporation (E) from 777 to 2110 mm. The aridity index (E/P) ranges from 0.15 to 2.93 (dimensionless). Tree diameters range from 9 to 90 cm and tree heights range from 6 to 70 m. D and Dh in the second data set range from 11 to 271 and 68 to 205 μm, respectively. These datasets will make a valuable contribution to future continental-scale and global-scale studies of the relationship between xylem hydraulic architecture and climate. The data sets are unique in the sense that they are phylogenetically constrained, allowing in-depth assessment of plasticity of hydraulic attributes within a single tree genus.

We tested whether snow gum (Eucalyptus pauciflora) trees growing in thermally contrasting environments exhibit generalizable temperature (T) response functions of leaf respiration (R) and fluorescence (Fo). Measurements were made on pot-grown saplings and field-grown trees (growing between 1380 and 2110 m a.s.l.). Using a continuous, high-resolution protocol, we quantified T response curves of R and Fo--these data were used to identify an algorithm for modelling R-T curves at subcritical T's and establish variations in heat tolerance. For the latter, we quantified Tmax [T where R is maximal] and Tcrit [T where Fo rises rapidly]. Tmax ranged from 51 to 57 °C, varying with season (e.g. winter summer). Tcrit ranged from 41 to 49 °C in summer and from 58 to 63 °C in winter. Thus, surprisingly, leaf energy metabolism was more heat-tolerant in trees experiencing ice-encasement in winter than warmer conditions in summer. A polynomial model fitted to log-transformed R data provided the best description of the T-sensitivity of R (between 10 and 45 °C); using these model fits, we found that the negative slope of the Q10 -T relationship was greater in winter than in summer. Collectively, our results (1) highlight high-T limits of energy metabolism in E. pauciflora and (2) provide a framework for improving representation of T-responses of leaf R in predictive models.

Savanna tree–grass interactions may be particularly sensitive to climate change. Establishment of two tree canopy dominants, post oak (Quercus stellata) and eastern redcedar (Juniperus virginiana), grown with the dominant C4 perennial grass (Schizachyrium scoparium) in southern oak savanna of the United States were evaluated under four climatic scenarios for 6 years. Tree–grass interactions were examined with and without warming (+1.5 °C) in combination with a long-term mean rainfall treatment and a modified rainfall regime that redistributed 40% of summer rainfall to spring and fall, intensifying summer drought. The aim was to determine: (1) the relative growth response of these species, (2) potential shifts in the balance of tree–grass interactions, and (3) the trajectory of juniper encroachment into savannas, under these anticipated climatic conditions. Precipitation redistribution reduced relative growth rate (RGR) of trees grown with grass. Warming increased growth of J. virginiana and strongly reduced Q. stellata survival. Tiller numbers of S. scoparium plants were unaffected by warming, but the number of reproductive tillers was increasingly suppressed by intensified drought each year. Growth rates of J. virginiana and Q. stellata were suppressed by grass presence early, but in subsequent years were higher when grown with grass. Quercus stellata had overall reduced RGR, but enhanced survival when grown with grass, while survival of J. virginiana remained near 100% in all treatments. Once trees surpassed a threshold height of 1.1 m, both tiller number and survival of S. scoparium plants were drastically reduced by the presence of J. virginiana, but not Q. stellata. Juniperus virginiana was the only savanna dominant in which neither survival nor final aboveground mass were adversely affected by the climate scenario of warming and intensified summer drought. These responses indicate that climate warming and altered precipitation patterns will further accelerate juniper encroachment and woody thickening in a warm-temperate oak savanna.

We developed a chamberless system to expose branches to elevated concentrations of ozone with little alteration of micro-meteorological conditions. In a 35-year-old stand of sugar maple (Acer saccharum Marsh.), scaffolding and a platform (14 m in height) provided access to 10 branches and ten paired controls within the canopy. Ozone was delivered to the canopy through a manifold and an array of loops (38 cm in diameter) of teflon tubing individually fitted to each branch. Ozone-enriched air was discharged through numerous small holes in each loop positioned beneath the exposed foliage. A sampling system controlled by a microcomputer monitored ozone concentrations for each loop by means of composite air samples from 12 leaves, drawn through small teflon tubes (1.65 mm diameter) attached to the petioles. On average, coefficients of variation for ozone concentrations for the sample points within each branch loop were less than 50%. Between 0900 and 1700 h for 68 d of exposure, the mean hourly ozone concentrations among the branches averaged 95nmol mol−1 (±13SD), about twice the ambient mean. Frequency distributions of mean hourly concentrations during exposure were unimodal and approximately log-normal, comparable to ambient ozone concentrations. The open-air loop system enables exposure of branches to gaseous pollutants under relatively natural conditions.

Seedlings of 24 European Scots pine (Pinussylvestris L.) populations were grown in controlled environment chambers under simulated photoperiodic conditions of 50 and 60°N latitude to evaluate the effect of seed mass on germination and seedling growth characteristics. Seeds of each population were classified into 1-mg mass classes, and the four classes per population with the highest frequencies were used. Photoperiod had minimal influence on seed mass effects. Overall, seed mass was positively related to the number of cotyledons and hypocotyl height. Populations differed significantly in seed mass effect on biomass. In northern populations (55–61°N), dry mass at the end of the first growing season was little affected by seed mass. However, dry mass in 9 of 15 central populations (54–48°N) and all southern (2 > 0.6) with seed mass in 15 populations. To check the duration of seed mass effects, height growth of 1- to 7-year-old field experiments established with the same seed lots were compared. Seed mass effects on height were strongest for 1-year-old seedlings and declined or disappeared by the age of 5–7 years among central and southern populations, but remained stable over that time in northern populations.

Light-saturated net photosynthesis (Asat), dark respiration (RD), and foliar nutrient content of eight European Scots pine (Pinus sylvestris L.) provenances were measured at experimental sites in western Poland. Two-year-old seedlings were planted in 1984 at two sites with similar soils in areas of contrasting air pollution. One site was near a point source of SO2 and other pollutants, and another 12 km to the southeast in an area free of acute air pollution was treated as a control. The eight provenances were from a large north-tosouth latitudinal range (60 to 43° N). At the heavily polluted site Scots pine trees exhibited lower growth rates and crown dieback and deformation. Soil pH, Ca and Mg were at least 10 times lower, and Al 10 times higher at the polluted than the control site. In 1991, concentrations of Al, P, Ca, S, Mn, Fe, and Zn in oneyear old Scots pine foliage were higher and Mg lower at the polluted than control site. At both sites foliar Mg levels were within the range considered deficient (≤0.6 mg g-1), and at the polluted site, Al concentrations were very high (670 to 880 μg g-1). In all provenances, RD of one-year-old needles was higher (by 22% on average) and Asat was lower (by 37% on average) at the polluted than the control site. The ratio of Asat: RD was half as great in all provenances at the polluted (4 to 6) than control site (8 to 11). Provenances of southern origin had greater increases in RD and water-use efficiency at the polluted site than other provenances. Within the polluted site alone, or across both sites, Asat in Scots pine was negatively correlated to the Al: Ca ratio (p

Hybrid poplar (Populus tristis Fisch. ×P. balsamifera L., cv. Tristis) and sugar maple (Acer saccharum Marsh.) seedlings were grown under contrasting light and ozone treatments to investigate the role of the light environment in their response to chronic ozone stress. In consecutive growth chamber experiments, cuttings of shade-intolerant poplar and 3-yr-old seedlings of shade-tolerant sugar maple were grown in pots for 6 and 10 wk, respectively, under shaded, low light irradiance (c. 2.5 mol m-2 d-1 PPFD or 7% of full sunlight) and six-fold greater irradiance (c. 16.6 mol m-2 d-1 PPFD or 45% of full sunlight) in combination with low (< 10 nl 1-1 ) and elevated levels of ozone (c. 99-115 nl 1-1 ). In unshaded poplar plants, ozone exposure reduced root dry mass by 33% at final harvest, while shaded plants had no such response. By comparison, sugar maple root dry mass was reduced by ozone in shaded plants by 10%, but was unaffected by ozone in unshaded plants. In poplar, leaf area: plant dry mass ratios were unaffected by ozone, whereas in sugar maple ozone-exposed plants had a 24% lower leaf area: plant dry mass ratio in the shaded treatment. In shade-grown sugar maple, ozone doubled dark respiration rates of leaves, but in unshaded seedlings ozone had no effect on respiration. In comparison, in poplar plants ozone exposure resulted in greater increases in dark respiration under unshaded than shaded conditions. In unshaded plants, ozone treatment resulted in lower in situ net photosynthesis in poplar, but not in sugar maple. Overall, shade-grown sugar maple appeared more sensitive to ozone stress than unshaded plants in terms of lower leaf area: plant dry mass ratio and root growth and higher leaf respiration. In poplar on the other hand, root growth, leaf respiration and photosynthesis were more affected by ozone in unshaded than in shaded plants. These findings suggest that shade-grown sugar maple and unshaded poplar may experience greater reductions in carbon gain and growth under elevated levels of ozone than plants under the opposite light conditions.

Both light conditions and ozone fumigation alter the chemical composition of tree foliage and are thus likely to influence tree-insect interactions. We investigated the direct and interactive effects of light environment and ozone exposure on the performance of gypsy moth (Lymantria dispar L.) larvae reared on hybrid poplar (Populus tristis Fisch. ×P. balsamifera L. cv. Tristis) and sugar maple (Acer saccharum Marsh). We used a split-plot experimental design (light nested within ozone) and fourth-instar bioassays to calculate standard indices of insect growth and feeding performance. For insects fed poplar, consumption, growth and processing efficiencies were affected more by light environment than by ozone. Larvae ate and grew less on high-light foliage, responses attributable to higher levels of phenolic glycosides in those leaves. For insects fed maple, no significant effects of light, ozone, or light x ozone were observed. These results demonstrate that light environment and ozone pollution can alter the dynamics of interactions between trees and associated insects and that responses are species-specific.

Two-year-old red spruce (Picearubens Sarg.) seedlings were grown in a poorly buffered soil from a high-elevation site in the Great Smoky Mountains and exposed for 16 weeks to acid mist and rain chemically similar to that occurring at high-elevation sites in the southern Appalachian Mountains. Measurements of seedling growth, root distribution, saturated net photosynthesis, dark respiration, and nutrient content were made to test the hypothesis that acid deposition had caused reductions in the carbon economy noted at high-elevation sites in previous field studies. The role of base cation depletion in these changes was examined by evaluating soil amendments of Ca, Mg, or Ca plus Mg. Acidified rain and mist reduced (i) the apparent carbon economy of foliage, (ii) seedling growth, and (iii) rooting depth in these controlled greenhouse studies. Changes in gas exchange physiology paralleled responses observed for sapling trees in the field with increasing elevation and included both reduced net photosynthesis and increased dark respiration. Calcium deficiency induced by acid deposition is apparently an important mechanism underlying physiological responses of red spruce previously observed in the field. Calcium addition to soil partially reduced the effects of acid deposition, but observed responses suggest that both foliar- and soil-driven reactions are involved. Changes in carbon metabolism associated with reduced Ca availability, when high levels of acid deposition are superimposed on poorly buffered soils, support the inferential association of acid deposition with growth decline of mature red spruce in high-elevation forests of the Appalachian Mountains.

summary Seedlings of 24 European populations of Scots pine (Pinus sylvestris L.) were grown from seed for 4 months in controlled environments under photoperiod conditions of 50° or 60° N, but with similar temperatures and total daily quantum flux in both photoperiods. During the experiment the photoperiod was continually changed to simulate the photoperiod from 1 May to 1 September at each latitude. Secondary needle length, plant height and dry mass at harvest were greater at 60° than the 50° N photoperiod. All populations allocated significantly greater proportions of their biomass to roots at 50° than 60° N photoperiod, yet central populations allocated less to roots than northern ones in both photoperiods. Northern populations (origin > 55° N latitude) stopped height growth up to 50 d earlier than the other populations when grown under 50° N photoperiod conditions. Under the 60° N photoperiod, all populations, except the most southern one, developed terminal leader buds and ceased growth in height between 87 and 105 d after sowing. Using cluster analysis, populations with similar growth and photoperiod responses were assigned to two major groups: northern (61–56° N from Sweden and USSR), and central (55–40° N from the USSR, Poland, Germany, Belgium, France, Czechoslovakia, Yugoslavia, and Turkey). The most southern population, from Turkey, was classified independent from the central group based on growth characteristics alone. No single mechanism of height growth cessation can explain the response of all populations of 1-yr-old seedlings of Scots pine. Our findings support the hypothesis that northern plants respond to a combination of increasing night length and accumulated degree-days. However, the evidence suggests that central and southern populations do not respond to increased night length as they all ceased growth earlier in the 60° than the 50° photoperiod. As hypotheses for further testing, we propose that central and southern populations are either photoperiodically insensitive or respond to short nights or to accumulated degree-days at their native latitudes.

Flowering and height growth of 20 Scots pine (Pinus sylvestris L.) populations from 10 countries were analyzed at two replicated provenance sites established in 1984 in western Poland. One site was 2 km from a phosphate fertilizer factory that emits SO2 and fluorides, and the other 12 km to the southeast in an area free of acute air pollution levels was treated as a control. Slow-growing populations from the southern (40 to 45°N) and northern (58 to 61°N) part of the species range exhibited relatively smaller air pollutioninduced growth reductions than those from the central part of the range (45 to 58°N). Trees growing in the control area started flowering 4 yrs earlier than those at the polluted site. The percent of trees flowering at the control site differed significantly among provenances in both 1988 and 1990. The mean percent of trees with flowers was three times lower at the polluted site. The least sensitive southern and northern provenances in terms of pollutioninduced reductions in growth exhibited the largest pollution-induced decreases in flowering. These findings indicate that the sensitivity of vegetative organs to air pollution stress is not always paralleled by the sensitivity of reproductive organs.

To assess seasonal and site variation in foliar nitrate reductase activity and its utility as a biochemical marker for the uptake of nitrogen oxide pollutants in high-elevation forests, we measured nitrate reductase activity in current-year needles of red spruce (Picearubens Sarg.) saplings at two high-elevation stands (1935 and 1720 m) in the Great Smoky Mountains, North Carolina. Measurements spanned two growing seasons between September 1987 and September 1988. Nitrate reductase activity peaked near 60 nmol•g−1•h−1 at both sites in September and October 1987 and August 1988 and declined 80% in November 1987 and 65% in September 1988. Although nitrate reductase activity was 30% greater in saplings at the higher site relative to the lower site in September and October 1987, activity dropped to approximately 10 nmol•g−1•h−1 at both sites in November 1987. No differences among sites were evident the following year. Comparing deposition of nitric acid vapor at a nearby site to nitrate reductase activity suggests that needle nitrate reductase activity is not an unequivocal marker for foliar uptake of nitrogen oxides during air pollutant episodes. The changes in soil nitrate levels in this system provide preliminary evidence that foliar nitrate assimilation may, in part, include nitrate taken up from the soil, as the highest activity occurred during periods of higher A-horizon nitrate concentrations in 1988. These measurements of nitrate reductase activity suggest that red spruce are capable of assimilating nitrate in foliage in the field and that the nitrate assimilation capacity varies throughout the year.

Rates of net photosynthesis and dark respiration of red spruce (Picearubens Sarg.) foliage were examined in relationship to soil and foliar nutrient status at three elevations across each of three mountains in the southern Appalachians. These studies tested our previously stated hypothesis that increased dark respiration and reduced growth were associated with natural or induced nutrient deficiency at higher elevation sites. A consistent and highly significant reduction in the ratio of net photosynthesis to dark respiration was found at the highest sites on each mountain compared with lower sites, as had been previously reported for the initial two test sites. This response was produced by significant increases in dark respiration that were associated with low foliar calcium levels and high foliar aluminum levels found at the higher elevation sites in this region. Net photosynthesis was generally comparable between sites. A consistently inverse relationship between dark respiration and foliar calcium was found across highest and lowest elevation sites, while the midelevation sites, where calcium:aluminum ratios were highest, showed less evidence of respiratory response to calcium. Calcium in shoots was significantly reduced in association with increasing levels of soil aluminum in the rooting zone across all sites. Collectively, these studies suggest that reduced calcium supply, occurring in association with competitive inhibition of calcium uptake by high concentrations of aluminum found in soil, may have reduced the availability of carbon for red spruce growth at higher elevation sites. Inferential evidence examined, including atmospheric deposition levels, soil solution chemistry, and historical tree-ring chemistry, suggests that acidic deposition would have been a contributing factor in inducing or amplifying calcium deficiency.

Temperature acclimation of respiration may contribute to climatic adaptation and thus differ among populations from contrasting climates. Short-term temperature responses of foliar dark respiration were measured in 33-yr-old trees of jack pine (Pinus banksiana) in eight populations of wide-ranging origin (44-55 degrees N) grown in a common garden at 46.7 degrees N. It was tested whether seasonal adjustments in respiration and population differences in this regard resulted from changes in base respiration rate at 5 degrees C (R(5)) or Q(10) (temperature sensitivity) and covaried with nitrogen and soluble sugars. In all populations, acclimation was manifest primarily through shifts in R(5) rather than altered Q(10). R(5) was higher in cooler periods in late autumn and winter and lower in spring and summer, inversely tracking variation in ambient air temperature. Overall, R(5) covaried with sugars and not with nitrogen. Although acclimation was comparable among all populations, the observed seasonal ranges in R(5) and Q(10) were greater in populations originating from warmer than from colder sites. Population differences in respiratory traits appeared associated with autumnal cold hardening. Common patterns of respiratory temperature acclimation among biogeographically diverse populations provide a basis for predicting respiratory carbon fluxes in a wide-ranging species.

Coupled surface–atmosphere models are being used with increased frequency to make predictions of tropospheric chemistry on a ‘future’ earth characterized by a warmer climate and elevated atmospheric CO 2 concentration. One of the key inputs to these models is the emission of isoprene from forest ecosystems. Most models in current use rely on a scheme by which global change is coupled to changes in terrestrial net primary productivity (NPP) which, in turn, is coupled to changes in the magnitude of isoprene emissions. In this study, we conducted measurements of isoprene emissions at three prominent global change experiments in the United States. Our results showed that growth in an atmosphere of elevated CO 2 inhibited the emission of isoprene at levels that completely compensate for possible increases in emission due to increases in aboveground NPP. Exposure to a prolonged drought caused leaves to increase their isoprene emissions despite reductions in photosynthesis, and presumably NPP. Thus, the current generation of models intended to predict the response of isoprene emission to future global change probably contain large errors. A framework is offered as a foundation for constructing new isoprene emission models based on the responses of leaf biochemistry to future climate change and elevated atmospheric CO 2 concentrations.

1. Paleorecord of Norway spruce A. Srodon, K. Tobolski.- 2. Morphology T. Przybylski.- 3. Taxonomy W. Bugala.- 4. Geographic distribution K. Boratynska.- 5. The Central European disjunctions in the range of Norway Spruce A. Boratynski.- 6. Anatomy, embryology, and karyology. Bud structure and shoot development A. Hejnowicz.- 7. Growth and nutrition. 7.1. Hormonal regulation of growth andd evelopment S. Pukacka. 7.2. Mineral nutrition H. Fober.- 8. Reproduction. 8.1. Reproductive development W. Chalupka. 8.2. Vegetative propagation W. Barzdajn.- 9. Genetics. 9.1. Provenance variation andinheritance M. Giertych. 9.2. Biochemical genetics L. Mejnartowicz, A. Lewandowski.- 10. Mycorrhiza. 10.1. The mycorrhizal status of Norway spruce M.L. Rudawska. 10.2. Ectomycorrhizal symbiosis and environmental stresses B. Kieliszewska-Rokicka.- 11. Outline of ecology. 11.1. Ecology J. Modrzynski. 11.2. Community dynamics of Norway spruce W. Danielewicz, P. Pawlaczyk.- 12. Tree health. 12.1. Major infectious diseases M. Manka. 12.2. Bark beetles J. Michalski.- 13. Silviculture of Norway Spruce S. Szymanski.- 14. Norway spruce function in polluted environments. 14.1. Sensitivity to environmental pollution P. Karolewski. 14.2. Effects of pollutants on needle and wood anatomy A. Werner.- 15.Wood properties and uses J. Surminski.- References.- Authors' Index.- Index of Names of Organisms.- Subject Index.

The effects of short- and long-term changes in temperature on plant respiration (R) are reviewed. We discuss the methods available for quantifying the short- and long-term temperature-dependence of R. The extent to which the Q10 (the proportional change in R with a 10 °C increase in temperature) and the degree of thermal acclimation (change in the temperature-response curve of R following a long-term change in growth temperature) vary within and amongst plant species are assessed. We show that Q10 values are highly variable (e.g., being affected by measuring and growth temperature, irradiance and drought), but most plant species exhibit similar Q10 values (in darkness) when grown and measured under identical conditions (i.e. little evidence of inherent differences in the Q10 of plant R). The possible mechanisms responsible for variability in the Q10 are discussed; high Q10 values occur in tissues where respiratory flux is substrate saturated (i.e. capacity limited). This is illustrated using plots of reduced ubiquinone versus O2 uptake in isolated mitochondria. The degree of acclimation is also highly variable amongst plant species. This variability is due, in part, to some studies exposing pre-existing roots/leaves to a new growth temperature, whereas others compare roots/leaves that develop at different temperature. In most cases, maximal acclimation requires that new leaves and/or roots be developed following a change in growth temperature. In addition to its link with development, acclimation is also often associated with changes in the Q10, particularly in pre-existing leaves/roots transferred from one environment to another. The importance of acclimation in determining annual rates of R as a component of net primary productivity and net ecosystem CO2 exchange is discussed. The importance of acclimation for future atmospheric CO2 concentrations is highlighted, including a positive feedback effect of climate warming on the carbon cycle. This review shows that the assumptions of coupled global circulation models (that Q10 values are constant and that R does not acclimate to long-term changes in temperature) are incorrect, and this may lead to overestimation of the effects of climate warming on respiratory CO2 flux.

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

When predicting the effects of climate change, global carbon circulation models that include a positive feedback effect of climate warming on the carbon cycle often assume that (1) plant respiration increases exponentially with temperature (with a constant Q10) and (2) that there is no acclimation of respiration to long-term changes in temperature. In this review, we show that these two assumptions are incorrect. While Q10 does not respond systematically to elevated atmospheric CO2 concentrations, other factors such as temperature, light, and water availability all have the potential to influence the temperature sensitivity of respiratory CO2 efflux. Roots and leaves can also differ in their Q10 values, as can upper and lower canopy leaves. The consequences of such variable Q10 values need to be fully explored in carbon modelling. Here, we consider the extent of variability in the degree of thermal acclimation of respiration, and discuss in detail the biochemical mechanisms underpinning this variability; the response of respiration to long-term changes in temperature is highly dependent on the effect of temperature on plant development, and on interactive effects of temperature and other abiotic factors (e.g. irradiance, drought and nutrient availability). Rather than acclimating to the daily mean temperature, recent studies suggest that other components of the daily temperature regime can be important (e.g. daily minimum and / or night temperature). In some cases, acclimation may simply reflect a passive response to changes in respiratory substrate availability, whereas in others acclimation may be critical in helping plants grow and survive at contrasting temperatures. We also consider the impact of acclimation on the balance between respiration and photosynthesis; although environmental factors such as water availability can alter the balance between these two processes, the available data suggests that temperature-mediated differences in dark leaf respiration are closely linked to concomitant differences in leaf photosynthesis. We conclude by highlighting the need for a greater process-based understanding of thermal acclimation of respiration if we are to successfully predict future ecosystem CO2 fluxes and potential feedbacks on atmospheric CO2 concentrations.