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1.
Summary To determine the effects of elevated CO2 and soil moisture status on growth and niche characteristics of birch and maple seedlings, gray birch (Betula populifolia) and red maple (Acer rubrum) were experimentally raised along a soil moisture gradient ranging from extreme drought to flooded conditions at both ambient and elevated atmospheric CO2 levels. The magnitude of growth enhancement due to CO2 was largely contingent on soil moisture conditions, but differently so for maple than for birch seedlings. Red maple showed greatest CO2 enhancements under moderately moist soil conditions, whereas gray birch showed greatest enhancements under moderately dry soil conditions. Additionally, CO2 had a relatively greater ameliorating effect in flooded conditions for red maple than for gray birch, whereas the reverse pattern was true for these species under extreme drought conditions. For both species, elevated CO2 resulted in a reduction in niche breadths on the moisture gradient; 5% for gray birch and 23% for red maple. Species niche overlap (proportional overall) was also lower at elevated CO2 (0.98 to: 0.88: 11%). This study highlights the utility of of experiments crossing CO2 levels with gradients of other resources as effective tools for elucidating the potential consequences of elevated CO2 on species distributions and potential interactions in natural communities. 相似文献
2.
Plant species differ broadly in their responses to an elevated CO2 atmosphere, particularly in the extent of nitrogen dilution of leaf tissue. Insect herbivores are often limited by the availability of nutrients, such as nitrogen, in their host plant tissue and may therefore respond differentially on different plant species grown in CO2-enriched environments. We reared gyspy moth larvae (Lymantria dispar) in situ on seedlings of yellow birch (Betula allegheniensis) and gray birch (B. populifolia) grown in an ambient (350 ppm) or elevated (700 ppm) CO2 atmosphere to test whether larval responses in the elevated CO2 atmosphere were species-dependent. We report that female gypsy moths (Lymantria dispar) reared on gray birch (Betula populifolia) achieved similar pupal masses on plants grown at an ambient or an elevated CO2 concentration. However, on yellow birch (B. allegheniensis), female pupal mass was 38% smaller on plants in the elevated-CO2 atmosphere. Larval mortality was significantly higher on yellow birch than gray birch, but did not differ between the CO2 treatments. Relative growth rate declined more in the elevated CO2 atmosphere for larvae on yellow birch than for those on gray birch. In preference tests, larvae preferred ambient over elevated CO2-grown leaves of yellow birch, but showed no preference between gray birch leaves from the two CO2 atmospheres. This differential response of gypsy moths to their host species corresponded to a greater decline in leaf nutritional quality in the elevated CO2 atmosphere in yellow birch than in gray birch. Leaf nitrogen content of yellow birch dropped from 2.68% to 1.99% while that of gray birch leaves only declined from 3.23% to 2.63%. Meanwhile, leaf condensed tannin concentration increased from 8.92% to 11.45% in yellow birch leaves while gray birch leaves only increased from 10.72% to 12.34%. Thus the declines in larval performance in a future atmosphere may be substantial and host-species-specific. 相似文献
3.
Effects of CO2-mediated changes in paper birch and white pine chemistry on gypsy moth performance 总被引:3,自引:0,他引:3
We examined the effects of CO2-mediated changes in the foliar chemistry of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown under ambient or enriched CO2 conditions, and foliage was subjected to plant chemical assays and insect bioassays. Enriched CO2 atmospheres reduced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations were not markedly altered by CO2 environment. Gypsy moth performance was significantly affected by CO2 level, species, and the CO2 x species interaction. Under elevated CO2 conditions, growth was reduced for larvae fed birch, while development was prolonged for larvae fed pine. Although gypsy moths performed better overall on birch than pine, birch-fed larvae were influenced more by CO2-mediated changes in host quality. 相似文献
4.
Scaling ozone responses of forest trees to the ecosystem level in a changing climate 总被引:13,自引:0,他引:13
D. F. KARNOSKY K. S. PREGITZER D. R. ZAK M. E. KUBISKE G. R. HENDREY D. WEINSTEIN M. NOSAL & K. E. PERCY 《Plant, cell & environment》2005,28(8):965-981
Many uncertainties remain regarding how climate change will alter the structure and function of forest ecosystems. At the Aspen FACE experiment in northern Wisconsin, we are attempting to understand how an aspen/birch/maple forest ecosystem responds to long-term exposure to elevated carbon dioxide (CO2) and ozone (O3), alone and in combination, from establishment onward. We examine how O3 affects the flow of carbon through the ecosystem from the leaf level through to the roots and into the soil micro-organisms in present and future atmospheric CO2 conditions. We provide evidence of adverse effects of O3, with or without co-occurring elevated CO2, that cascade through the entire ecosystem impacting complex trophic interactions and food webs on all three species in the study: trembling aspen (Populus tremuloides Michx.), paper birch (Betula papyrifera Marsh), and sugar maple (Acer saccharum Marsh). Interestingly, the negative effect of O3 on the growth of sugar maple did not become evident until 3 years into the study. The negative effect of O3 effect was most noticeable on paper birch trees growing under elevated CO2. Our results demonstrate the importance of long-term studies to detect subtle effects of atmospheric change and of the need for studies of interacting stresses whose responses could not be predicted by studies of single factors. In biologically complex forest ecosystems, effects at one scale can be very different from those at another scale. For scaling purposes, then, linking process with canopy level models is essential if O3 impacts are to be accurately predicted. Finally, we describe how outputs from our long-term multispecies Aspen FACE experiment are being used to develop simple, coupled models to estimate productivity gain/loss from changing O3. 相似文献
5.
We studied seedling growth responses to ambient and elevated CO2 (350 and 700 μL L?1) of three maternal families of yellow birch (Betula alleghaniensis), raised both individually and in high-density stands. Seedlings in competitive, dense stands exhibited markedly lower average CO2-induced growth enhancements than individually grown plants (16% vs. 49%). Maternal families differed in their growth responses to elevated CO2. However, differences among families were contingent upon density; families which exhibited the greatest CO2-induced growth at low density exhibited the least CO2-responsiveness at high density. These data are discussed in two separate contexts; the reliability of estimates of the CO2 fertilization potential of forest species based solely on individually grown plants, and the potential evolutionary consequences of rising CO2 on regenerating forest tree populations. 相似文献
6.
TEMPORAL AND SPATIAL PATTERNS OF SPECIFIC LEAF WEIGHT IN SUCCESSIONAL NORTHERN HARDWOOD TREE SPECIES
Thomas W. Jurik 《American journal of botany》1986,73(8):1083-1092
Temporal and spatial patterns of specific leaf weight (SLW, g/m2) were determined for deciduous hardwood tree species in natural habitats in northern lower Michigan to evaluate the utility of SLW as an index of leaf photosynthetic capacity. No significant diurnal changes in SLW were found. Specific leaf weight decreased and then increased during leaf expansion in the spring. Most species, especially those located in the understory, then had relatively constant SLW for most of the growing season, followed by a decline in SLW during autumn. Specific leaf weight decreased exponentially down through the canopy with increasing cumulative leaf area index. Red oak (Quercus rubra), paper birch (Betula papyrifera), bigtooth aspen (Populus grandidentata), red maple (Acer rubrum), sugar maple (A. saccharum), and beech (Fagus grandifolia) generally had successively lower SLW, for leaves at any one level in the canopy. On a given site, comparisons between years and comparisons of leaves growing within 35 cm of each other showed that differences in SLW among species were not due solely to microenvironmental effects on SLW. Bigtooth aspen, red oak, and red maple on lower-fertility sites had lower SLW than the same species on higher-fertility sites. Maximum CO2 exchange rate, measured at light-saturation in ambient CO2 and leaf temperatures of 20 to 25 C, increased with SLW. Photosynthetic capacities of species ranked by SLW in a shaded habitat suggest that red oak, red maple, sugar maple, and beech are successively better adapted to shady conditions. 相似文献
7.
Seedlings of yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh.) were grown for 2 years in mono-culture and mixed-culture and at three fertility levels. Following the second growing season, senescent leaves were analysed for N concentration, acid hydrolysable substances (AHS), and nonhydrolysable remains (NHR). A litter sub-sample was then inoculated with indigenous soil microflora, incubated 14 weeks, and mass loss was measured. Litter-N was significantly higher at medium than at poor fertility, as well as in yellow birch than in sugar maple litter. The species effect on litter-N increased with increasing fertility. At medium fertility, litter-N of sugar maple litter was lower in mixed-culture than in mono-culture. AHS, NHR as well the NHR/N ratio were significantly higher in yellow birch than in sugar maple litter. At medium fertility, the NHR/N ratio of sugar maple litter was significantly lower in mono-culture than in mixed-culture. Mass loss was significantly greater at medium and rich fertility than at poor fertility, and in yellow birch than in sugar maple litter. At poor fertility, mixed-litter decomposed at a rate comparable to yellow birch, whereas at medium and rich fertility, mixed-litter decomposed at a rate comparable to sugar maple. There was a significant positive relationship between litter-N and mass loss. A similar positive relationship between NHR and mass loss was presumed to be a species effect on decomposition. Results support the hypothesis that species × fertility and species × mixture interactions can be important determinants of litter quality and, by implication, of site nutrient cycling. 相似文献
8.
Nitrogen cycling in a northern hardwood forest: Do species matter? 总被引:23,自引:7,他引:16
Gary M. Lovett Kathleen C. Weathers Mary A. Arthur Jack C. Schultz 《Biogeochemistry》2004,67(3):289-308
To investigate the influence of individual tree species on nitrogen (N) cycling in forests, we measured key characteristics of the N cycle in small single-species plots of five dominant tree species in the Catskill Mountains of New York State. The species studied were sugar maple (Acer saccharum), American beech (Fagus grandifolia), yellow birch (Betula alleghaniensis), eastern hemlock (Tsuga canadensis), and red oak (Quercus rubra). The five species varied markedly in N cycling characteristics. For example, hemlock plots consistently showed characteristics associated with "slow" N cycling, including low foliar and litter N, high soil C:N, low extractable N pools, low rates of potential net N mineralization and nitrification and low NO
3
–
amounts trapped in ion-exchange resin bags buried in the mineral soil. Sugar maple plots had the lowest soil C:N, and the highest levels of soil characteristics associated with NO
3
–
production and loss (nitrification, extractable NO
3
–
, and resin bag NO
3
–
). In contrast, red oak plots had near-average net mineralization rates and soil C:N ratios, but very low values of the variables associated with NO
3
–
production and loss. Correlations between soil N transformations and litter concentrations of N, lignin, lignin:N ratio, or phenolic constituents were generally weak. The inverse correlation between net nitrification rate and soil C:N that has been reported in the literature was present in this data set only if red oak plots were excluded from the analysis. This study indicates that tree species can exert a strong control on N cycling in forest ecosystems that appears to be mediated through the quality of soil organic matter, but that standard measures of litter quality cannot explain the mechanism of control. 相似文献
9.
Norikazu Eguchi Kazuki Karatsu Tatsushiro Ueda Ryo Funada Kentaro Takagi Tsutom Hiura Kaichiro Sasa Takayoshi Koike 《Trees - Structure and Function》2008,22(4):437-447
Though birch and alder are the common pioneer tree species which dominate in northeast Asia, little is known about the effects
of the predicted increase in atmospheric CO2 concentrations ([CO2]) upon their photosynthesis in field conditions. To investigate this, we grew 2-year-old saplings of three Betulaceae species
(Betula platyphylla var. japonica Hara, Betula maximowicziana Regel, and Alnus hirsuta Turcz) for 2 years in a free air CO2 enrichment system in northern Japan. Since the effect of high [CO2] is known to depend on soil conditions, we evaluated the responses in two soils which are widely distributed in northern
Japan: infertile and immature volcanic ash (VA) soil, and fertile brown forest (BF) soil. For B. platyphylla, photosynthetic down-regulation occurred in both soils, but for B. maximowicziana, down-regulation occurred only in VA soil. The explanation is reduced nitrogen and Rubisco content in the leaf. For A. hirsuta, down-regulation occurred only in BF soil because of the accumulation of starch in foliage, which restricts CO2 diffusion inside the chloroplast. The higher photosynthetic rate of A. hirsuta in infertile VA soil could be due to the sink for photosynthates in the N2-fixing symbiont. These three species are all able to down-regulate at high [CO2]. However, it is possible that A. hirsuta would dominate in VA soil and B. maximowicziana in BF soil in the early stages of forest succession in a CO2-enhanced world. 相似文献
10.
Anne Kasurinen Johanna Riikonen Elina Oksanen Elina Vapaavuori Toini Holopainen 《Plant and Soil》2006,282(1-2):261-280
Two field-growing silver birch (Betula pendula Roth) clones (clone 4 and 80) were exposed to elevated CO2 and O3 over three growing seasons (1999–2001). In each year, the nutrients and cell wall chemistry of naturally abscised leaf litter
were analyzed in order to determine the possible CO2- and O3-induced changes in the litter quality. Also CO2 and O3 effects on the early leaf litter decomposition dynamics (i.e. decomposition before the lignin decay has started) were studied
with litter-bag experiments (Incubation 1 with 1999 leaf litter, Incubation 2 with 2000 leaf litter, and Incubation 3 with
2001 leaf litter) in a nearby silver birch forest. Elevated CO2 decreased N, S, C:P and α-cellulose concentrations, but increased P, hemicellulose and lignin+polyphenolic concentrations,
C:N and lignin+polyphenolic:N in both clones. CO2 enrichment decreased the subsequent decomposition of leaves of clone 4 transiently (in Incubations 1 and 2), whereas elevated
CO2 effects on the subsequent leaf decomposition of clone 80 were inconsistent. In contrast to CO2, O3 decreased P concentrations and increased C:P, but both of these trends were visible in elevated O3 treatment only. O3-induced decreases in Mn, Zn and B concentrations were observed also, but O3 effects on the cell wall chemistry of leaf litter were minor. Some O3-induced changes either became more consistent in leaf litter collected during 2001 (decrease in B concentrations) or appeared
only in this litter lot (decrease in N concentrations, decrease in decomposition at the end of Incubation 3). In conclusion,
in northern birch forests elevated CO2 and O3 levels have the potential to affect leaf litter quality, but consistent CO2 and O3 effects on the decomposition process remain to be validated. 相似文献
11.
The future capacity of forest ecosystems to sequester atmospheric carbon is likely to be influenced by CO2-mediated shifts in nutrient cycling through changes in litter chemistry, and by interactions with pollutants like O3. We evaluated the independent and interactive effects of elevated CO2 (560 μl l−1) and O3 (55 nl l l−1) on leaf litter decomposition in trembling aspen (Populus tremuloides) and paper birch (Betula papyrifera) at the Aspen free air CO2 enrichment (FACE) site (Wisconsin, USA). Fumigation treatments consisted of replicated ambient, +CO2, +O3, and +CO2 + O3 FACE rings. We followed mass loss and litter chemistry over 23 months, using reciprocally transplanted litterbags to separate
substrate quality from environment effects. Aspen decayed more slowly than birch across all treatment conditions, and changes
in decomposition dynamics of both species were driven by shifts in substrate quality rather than by fumigation environment.
Aspen litter produced under elevated CO2 decayed more slowly than litter produced under ambient CO2, and this effect was exacerbated by elevated O3. Similarly, birch litter produced under elevated CO2 also decayed more slowly than litter produced under ambient CO2. In contrast to results for aspen, however, elevated O3 accelerated birch decay under ambient CO2, but decelerated decay under enriched CO2. Changes in decomposition rates (k-values) were due to CO2- and O3-mediated shifts in litter quality, particularly levels of carbohydrates, nitrogen, and tannins. These results suggest that
in early-successional forests of the future, elevated concentrations of CO2 will likely reduce leaf litter decomposition, although the magnitude of effect will vary among species and in response to
interactions with tropospheric O3. 相似文献
12.
Carbon exchange rates (CER) and whole-plant carbon balances of beech (Fagus grandifolia) and sugar maple (Acer saccharum) were compared for seedlings grown under low irradiance to determine the effects of atmospheric CO2 enrichment on shade-tolerant seedlings of co-dominant species. Under contemporary atmospheric CO2, photosynthetic rate per unit mass of beech was lower than for sugar maple, and atmospheric CO2 enrich ment enhanced photosynthesis for beech only. Aboveground respiration per unit mass decreased with CO2 enrichment for both species while root respiration per unitmass decreased for sugar maple only. Under contemporary atmoapheric CO2, beech had lower C uptake per plant than sugar maple, while C losses per plant to nocturnal aboveground and root respiration were similar for both species. Under elevated CO2, C uptake per plant was similar for both species, indicating a significant relative increase in whole-seedling CER with CO2 enrich ment for beech but not for sugar maple. Total C loss per plant to aboveground respiration was decreased for beech only because increase in sugar maple leaf mass counterbalanced a reduction in respiration rates. Carbon loss to root respiration per plant was not changed by CO2 enrichment for either species. However, changes in maintenance respiration cost and nitrogen level suggest changes in tissue composition with elevated CO2. Beech had a greater net daily C gain with CO2 enrichment than did sugar maple in contrast to a lower one under contemporary CO2. Elevated CO2 preferentially enhances the net C balance of beech by increasing photosynthesis and reducing respiration cost. In all cases, the greatest C lost was by roots, indicating the importance of belowground biomass in net C gain. Relative growth rate estimated from biomass accumulation was not affected by CO2 enrichment for either species possibly because of slow growth under low light. This study indicates the importance of direct effects of CO2 enrichment when predicting potential change in species distribution with global climate change. 相似文献
13.
Population dynamics and growth patterns for a cohort of northern red oak (Quercus rubra) seedlings 总被引:3,自引:0,他引:3
T. R. Crow 《Oecologia》1992,91(2):192-200
Summary I studied the survival and development of a 1986 cohort of northern red oak (Quercus rubra L.) seedlings growing under a variety of overstory and microsite conditions in a northern hardwood forest dominated by northern red oak, red maple (Acer rubrum L.) paper birch (Betula papyrifera Marsh.), and scattered white pine (Pinus strobus L.). Fifty naturally regenerating seedlings of oak were randomly selected in each of three canopy classes: no overstory, partial overstory, and complete overstory. Growth and mortality were measured for six years. Seedling height growth decreased with overstory density, with less growth evident with even a partial overstory. Seedling survival also declined with overstory density and depended on microtopography to a lesser extent. After six years, 92% of the seedlings survived in the open, compared to 54% under the partial overstory, and 36% under the complete overstory. The open environment, in which woody and herbaceous regrowth formed a low canopy reducing light intensities to about 50% of full sunlight, provided a favorable site for the growth and survival of northern red oak. 相似文献
14.
Recently, it has been suggested that small pots may reduce or eliminate plant responses to enriched CO2 atmospheres due to root restriction. While smaller pot volumes provide less physical space available for root growth, they
also provide less nutrients. Reduced nutrient availability alone may reduce growth enhancement under elevated CO2. To investigate the relative importance of limited physical rooting space separate from and in conjunction with soil nutrients,
we grew plants at ambient and double-ambient CO2 levels in growth containers of varied volume, shape, nutrient concentration, and total nutrient content. Two species (Abutilon theophrasti, a C3 dicot with a deep tap root andSetaria faberii, a C4 monocot with a shallow diffuse root system) were selected for their contrasting physiology and root architecture. Shoot demography
was determined weekly and biomass was determined after eight and ten weeks of growth. Increasing total nutrients, either by
increasing nutrient concentration or by increasing pot size, increased plant growth. Further, increasing pot size while maintaining
equal total nutrients per pot resulted in increased total biomass for both species. CO2-induced growth and reproductive yield enhancements were greatest in pots with high nutrient concentrations, regardless of
total nutrient content or pot size, and were also mediated by the shape of the pot. CO2-induced growth and reproductive yield enhancements were unaffected by pot size (growth) or were greater in small pots (reproductive
yield), regardless of total nutrient content, contrary to predictions based on earlier studies. These results suggest that
several aspects of growth conditions within pots may influence the CO2 responses of plants; pot size, pot shape, the concentration and total amount of nutrient additions to pots may lead to over-or
underestimates of the CO2 responses of real-world plants. 相似文献
15.
The effect of elevated atmospheric CO2 and nutrient supply on elemental composition and decomposition rates of tree leaf litter was studied using litters derived from birch (Betula pendula Roth.) plants grown under two levels of atmospheric CO2 (ambient and ambient +250 ppm) and two nutrient regimes in solar domes. CO2 and nutrient treatments affected the chemical composition of leaves, both independently and interactively. The elevated CO2 and unfertilized soil regime significantly enhanced lignin/N and C/N ratios of birch leaves. Decomposition was studied using field litter-bags, and marked differences were observed in the decomposition rates of litters derived from the two treatments, with the highest weight remaining being associated with litter derived from the enhanced CO2 and unfertilized regime. Highly significant correlations were shown between birch litter decomposition rates and lignin/N and C/N ratios. It can be concluded, from this study, that at levels of atmospheric CO2 predicted for the middle of the next century a deterioration of litter quality will result in decreased decomposition rates, leading to reduction of nutrient mineralization and increased C storage in forest ecosystems. However, such conclusions are difficult to generalize, since tree responses to elevated CO2 depend on soil nutritional status. 相似文献
16.
Seasonal trends in five traits of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula allegheniensis Britt.) leaves thought to influence feeding by herbivores were measured from 17 May through 19 September, 1979. Total nitrogen and water contents declined and toughness increased through the growth season. These seasonal changes were more pronounced in sugar maple than in yellow birch. Total polyphenol contents and tanning coefficients of leaf extracts from both species reached a season high by the end of May and changed very little after that date; these patterns differ from those reported by several other investigators. Sugar maple leaf extracts exhibited much higher tanning coefficients than did those of yellow birch, a finding which is consistent with current plant defense theory. Significant differences in total polyphenol content and tanning coefficients were found between individual trees in yellow birch, but not sugar maple. The relationship between successional status, leaf quality traits, and variability in these traits in forest trees is discussed. 相似文献
17.
Despite its importance in the terrestrial C cycle rhizosphere carbon flux (RCF) has rarely been measured for intact root–soil systems. We measured RCF for 8‐year‐old saplings of sugar maple (Acer saccharum) and yellow birch (Betula allegheniensis) collected from the Hubbard Brook Experimental Forest (HBEF), NH and transplanted into pots with native soil horizons intact. Five saplings of each species were pulse labeled with 13CO2 at ambient CO2 concentrations for 4–6 h, and the 13C label was chased through rhizosphere and bulk soil pools in organic and mineral horizons for 7 days. We hypothesized yellow birch roots would supply more labile C to the rhizosphere than sugar maple roots based on the presumed greater C requirements of ectomycorrhizal roots. We observed appearance of the label in rhizosphere soil of both species within the first 24 h, and a striking difference between species in the timing of 13C release to soil. In sugar maple, peak concentration of the label appeared 1 day after labeling and declined over time whereas in birch the label increased in concentration over the 7‐day chase period. The sum of root and rhizomicrobial respiration in the pots was 19% and 26% of total soil respiration in sugar maple and yellow birch, respectively. Our estimate of the total amount of RCF released by roots was 6.9–7.1% of assimilated C in sugar maple and 11.2–13.0% of assimilated C in yellow birch. These fluxes extrapolate to 55–57 and 90–104 g C m?2 yr?1 from sugar maple and yellow birch roots, respectively. These results suggest RCF from both arbuscular mycorrhizal and ectomycorrhizal roots represents a substantial flux of C to soil in northern hardwood forests with important implications for soil microbial activity, nutrient availability and C storage. 相似文献
18.
Direct and interactive effects of CO2 and light on tree phytochemistry and insect fitness parameters were examined through experimental manipulations of plant growth conditions and performance of insect bioassays. Three species of deciduous trees (quaking aspen, Populus tremuloides; paper birch, Betula papyrifera; sugar maple, Acer saccharum) were grown under ambient (387±8 μL/L) and elevated (696±2 μL/L) levels of atmospheric CO2, with low and high light availability (375 and 855 μmol×m?2×s?1 at solar noon). Effects on the population and individual performance of a generalist phytophagous insect, the white‐marked tussock moth (Orgyia leucostigma) were evaluated. Caterpillars were reared on experimental trees for the duration of the larval stage, and complementary short‐term (fourth instar) feeding trials were conducted with insects fed detached leaves. Phytochemical analyses demonstrated strong effects of both CO2 and light on all foliar nutritional variables (water, starch and nitrogen). For all species, enriched CO2 decreased water content and increased starch content, especially under high light conditions. High CO2 availability reduced levels of foliar nitrogen, but effects were species specific and most pronounced for high light aspen and birch. Analyses of secondary plant compounds revealed that levels of phenolic glycosides (salicortin and tremulacin) in aspen and condensed tannins in birch and maple were positively influenced by levels of both CO2 and light. In contrast, levels of condensed tannins in aspen were primarily affected by light, whereas levels of ellagitannins and gallotannins in maple responded to light and CO2, respectively. The long‐term bioassays showed strong treatment effects on survival, development time, and pupal mass. In general, CO2 effects were pronounced in high light and decreased along the gradient aspen birch maple. For larvae reared on high light aspen, enriched CO2 resulted in 62% fewer survivors, with increased development time, and reduced pupal mass. For maple‐fed insects, elevated CO2 levels had negative effects on survival and pupal mass in low light. For birch, the only negative CO2 effects were observed in high light, where female larvae showed prolonged development. Fourth instar feeding trials demonstrated that low food conversion efficiency reduced insect performance. Elevated levels of CO2 significantly reduced total consumption, especially by insects on high light aspen and low light maple. This research demonstrates that effects of CO2 on phytochemistry and insect performance can be strongly light‐dependent, and that plant responses to these two environmental variables differ among species. Overall, increased CO2 availability appeared to increase the defensive capacity of early‐successional species primarily under high light conditions, and of late‐successional species under low light conditions. Due to the interactive effects of tree species, light, CO2, and herbivory, community composition of forests may change in the future. 相似文献
19.
Fine root litter derived from birch (Betula pendula Roth.) and Sitka spruce (Picea sitchensis (Bong.) Carr.) plants grown under two CO2 atmospheric concentrations (350 ppm and 600 ppm) and two nutrient regimes was used for decomposition studies in laboratory
microcosms. Although there were interactions between litter type, CO2/fertiliser treatments and decomposition rates, in general, an increase in the C/N ratio of the root tissue was observed for
roots of both species grown under elevated CO2 in unfertilized soil. Both weight loss and respiration of decomposing birch roots were significantly reduced in materials
derived from enriched CO2, whilst the decomposition of spruce roots showed no such effect.
A parallel experiment was performed using Betula pendula root litter grown under different N regimes, in order to test the relationship between C/N ratio of litter and root decomposition
rate. A highly significant (p<0.001) negative correlation between C/N ratio and root litter respiration was found, with an r2=0.97. The results suggest that the increased C/N ratio of plant tissues induced by elevated CO2 can result in a reduction of decomposition rate, with a resulting increase in forest soil C stores. 相似文献
20.
Anne Kasurinen Petri A. Peltonen Riitta Julkunen-Tiitto Elina Vapaavuori Visa Nuutinen Toini Holopainen Jarmo K. Holopainen 《Plant and Soil》2007,292(1-2):25-43
Two field-growing silver birch (Betula pendula Roth) clones (clone 4 and 80) were exposed to elevated CO2 and O3 for three growing seasons (1999–2001). The phenolic compounds of naturally abscised leaf litter were analyzed in order to
determine the possible CO2- and O3-induced changes in the litter quality. The potential litter-mediated CO2 and O3 effects on litter-feeding soil macrofauna (detritivore) performance were assessed in microcosm experiments, i.e., the relative
growth rates (RGR) of Lumbricus terrestris and Porcellio scaber, the relative consumption rates (RCR) of P. scaber, and mortality of the test animals were measured. The leaf litter grown under elevated CO2 had increased concentrations (weight per mass unit) and contents (weight per leaf) of phenolic acids, flavonol glycosides,
condensed tannins and total measured phenolics. Elevated O3 increased the concentrations of 3,4’-dihydroxypropiophenone 3-β-d-glucoside (DHPPG) and flavonoid aglycones but only under ambient CO2. However, elevated O3 effects on the content of some low-molecular-weight phenolic (LMWP) compounds (i.e. phenolic acids, DHPPG, flavonoid aglycones)
and total LMWP changed over time emphasizing the importance of conducting long-term (>3 years) exposure studies. In general,
RGR of young L. terrestris was affected by the litter quality changes induced by elevated CO2 and O3, as the animal growth rates were reduced when they were fed with CO2- and O3-exposed leaf litter of clone 80 in Experiment 1. P. scaber RCR or RGR responses to CO2- and O3-induced changes in litter quality were more variable and inconsistent, and neither were there any litter-mediated CO2 and O3 effects on animal mortality in these microcosm experiments. In conclusion, elevated CO2 has the potential to alter silver birch leaf litter quality, but the possible O3 effects on phenolic compounds and litter-mediated CO2 and O3 effects on detritivores are more difficult to validate. 相似文献