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1.
MARTIN SCHÄDLER MAREIKE ROEDER† ROLAND BRANDL DIETHART MATTHIES† 《Global Change Biology》2007,13(5):1005-1015
By affecting plant growth and phytochemistry elevated CO2 may have indirect effects on the performance of herbivores. These effects show considerable variability across studies and may depend on nutrient availability, the carbon/nutrient‐balance in plant tissues and the secondary metabolism of plants. We studied the responses to elevated CO2 and different nutrient availability of 12 herbaceous plant species differing in their investment into secondary compounds. Caterpillars of the generalist herbivore Spodoptera littoralis were reared on the leaves produced and their consumption and growth rates analysed. Elevated CO2 resulted in a similar increase of biomass in all plant species, whereas the positive effect of fertilization varied among plant species. Specific leaf weight was influenced by elevated CO2, but the effect depended on nutrient level and identity of plant species. Elevated CO2 increased the C/N ratio of the leaves of most species. Caterpillars consumed more leaf material when plants were grown under elevated CO2 and low nutrients. This indicates compensatory feeding due to lower tissue quality. However, the effects of elevated CO2, nutrient availability and plant species identity on leaf consumption interacted. Both the effects of CO2 and nutrient availability on the relative growth rate of the herbivore depended on the plant species. The feeding rate of S. littoralis on plant species that do not produce nitrogen‐containing secondary compounds (NCSC) was higher under low nutrient availability. In contrast, in plants producing NCSC nutrient availability had no effect on the feeding rate. This suggests that compensatory feeding in response to low nutrient contents may not be possible if plants produce NCSC. We conclude that elevated CO2 causes species‐specific changes in the quality of plant tissues and consequently in changes in the preferences of herbivores for plant species. This could result in changes in plant community composition. 相似文献
2.
Rising atmospheric [CO2] has the potential to alter soil carbon (C) cycling by increasing the content of recalcitrant constituents in plant litter, thereby decreasing rates of decomposition. Because fine root turnover constitutes a large fraction of annual NPP, changes in fine root decomposition are especially important. These responses will likely be affected by soil resource availability and the life history characteristics of the dominant tree species. We evaluated the effects of elevated atmospheric [CO2] and soil resource availability on the production and chemistry, mycorrhizal colonization, and decomposition of fine roots in an early- and late-successional tree species that are economically and ecologically important in north temperate forests. Open-top chambers were used to expose young trembling aspen (Populus tremuloides) and sugar maple (Acer saccharum) trees to ambient (36 Pa) and elevated (56 Pa) atmospheric CO2. Soil resource availability was composed of two treatments that bracketed the range found in the Upper Lake States, USA. After 2.5 years of growth, sugar maple had greater fine root standing crop due to relatively greater allocation to fine roots (30% of total root biomass) relative to aspen (7% total root biomass). Relative to the low soil resources treatment, aspen fine root biomass increased 76% with increased soil resource availability, but only under elevated [CO2]. Sugar maple fine root biomass increased 26% with increased soil resource availability (relative to the low soil resources treatment), and showed little response to elevated [CO2]. Concentrations of N and soluble phenolics, and C/N ratio in roots were similar for the two species, but aspen had slightly higher lignin and lower condensed tannins contents compared to sugar maple. As predicted by source-sink models of carbon allocation, pooled constituents (C/N ratio, soluble phenolics) increased in response to increased relative carbon availability (elevated [CO2]/low soil resource availability), however, biosynthetically distinct compounds (lignin, starch, condensed tannins) did not always respond as predicted. We found that mycorrhizal colonization of fine roots was not strongly affected by atmospheric [CO2] or soil resource availability, as indicated by root ergosterol contents. Overall, absolute changes in root chemical composition in response to increases in C and soil resource availability were small and had no effect on soil fungal biomass or specific rates of fine root decomposition. We conclude that root contributions to soil carbon cycling will mainly be influenced by fine root production and turnover responses to rising atmospheric [CO2], rather than changes in substrate chemistry. 相似文献
3.
Elevated tropospheric CO2 concentrations may increase plant carbon fixation. In ectomycorrhizal trees, a considerable portion of the synthesized carbohydrates
can be used to support the mutualistic fungal root partner which in turn can benefit the tree by increased nutrient supply.
In this study, Norway spruce seedlings were inoculated with either Piloderma croceum (medium distance “fringe” exploration type) or Tomentellopsis submollis (medium distance “smooth” exploration type). We studied the impact of either species regarding fungal biomass production,
seedling biomass, nutrient status and nutrient use efficiency in rhizotrons under ambient and twice-ambient CO2 concentrations. A subset was amended with ammonium nitrate to prevent nitrogen imbalances expected under growth promotion
by elevated CO2. The two fungal species exhibited considerably different influences on growth, biomass allocation as well as nutrient uptake
of spruce seedlings. P. croceum increased nutrient supply and promoted plant growth more strongly than T. submollis despite considerably higher carbon costs. In contrast, seedlings with T. submollis showed higher nutrient use efficiency, i.e. produced plant biomass per received unit of nutrient, particularly for P, K and
Mg, thereby promoting shoot growth and reducing the root/shoot ratio. Under the given low soil nutrient availability, P. croceum proved to be a more favourable fungal partner for seedling development than T. submollis. Additionally, plant internal allocation of nutrients was differently influenced by the two ECM fungal species, particularly
evident for P in shoots and for Ca in roots. Despite slightly increased ECM length and biomass production, neither of the
two species had increased its capacity of nutrient uptake in proportion to the rise of CO2. This lead to imbalances in nutritional status with reduced nutrient concentrations, particularly in seedlings with P. croceum. The beneficial effect of P. croceum thus diminished, although the nutrient status of its host plants was still above that of plants with T. submollis. We conclude that the imbalances of nutrient status in response to elevated CO2 at early stages of plant development are likely to prove particularly severe at nutrient-poor soils as the increased growth
of ECM cannot cover the enhanced nutrient demand. Hyphal length and biomass per unit of ectomycorrhizal length as determined
for the first time for P. croceum amounted to 6.9 m cm−1 and 6.0 μg cm−1, respectively, across all treatments. 相似文献
4.
Species-specific responses of plant communities to altered carbon and nutrient availability 总被引:7,自引:0,他引:7
Geeske Joel † F. Stuart Chapin III ‡ Nona R. Chiariello † Susan S. Thayer† Christopher B. Field 《Global Change Biology》2001,7(4):435-450
In a field microcosm experiment, species‐specific responses of aboveground biomass of two California annual grassland communities to elevated CO2 and nutrient availability were investigated. One community grows on shallow, nutrient‐poor serpentine‐derived soil whereas the other occurs on deeper, modestly fertile sandstone/greenstone‐derived substrate. In most species, CO2 effects did not appear until late in the growing season, probably because the elevated CO2 increased water‐use‐efficiency easing, the onset of the summer drought. Responses of aboveground biomass to elevated CO2 differed depending on nutrient availability. Similarly, biomass responses to nutrient treatments differed depending on the CO2 status. For the majority of the species, production increased most under elevated CO2 with added nutrients (N,P,K, and micro nutrients). Some species were losers under conditions that increased overall community production, including Bromus hordeaceus in the serpentine community (negative biomass response under elevated CO2) and Lotus wrangelianus in both communities (negative biomass response with added nitrogen). Treatment and competitive effects on species‐specific biomass varied in both magnitude and direction, especially in the serpentine community, significantly affecting community structure. Individual resource environments are likely to be affected by neighbouring plants, and these competitive interactions complicate predictions of species' responses to elevated CO2. 相似文献
5.
The hypothesis that plants grown under elevated CO2 allocate more carbon to the production of latex and C‐rich secondary compounds whereas nutrient addition counteracts this effect was tested. Two similar experiments were conducted in two different experimental facilities. In both facilities seedlings of Euphorbia lathyris were exposed to factorial combinations of two CO2 concentrations and two levels of nutrient availability for 2 months. The CO2 treatments and growth conditions differed substantially between these two experiments but treatment responses to elevated CO2 and fertilizer addition were remarkably similar, underlining the robustness of our findings. Elevated CO2 increased biomass to a greater extent in fertilized than in unfertilized plants and reduced the leaf biomass fraction by accelerating leaf senescence. Concentrations of non‐structural carbohydrates (NSC) increased in elevated CO2. However, this apparent carbon surplus did not feed into the whole plant latex pool. The latex harvest per leaf (?25%) and the concentration of latex‐related hydrocarbons (?20%) even decreased under elevated CO2 (both experiments P < 0.05). Fertilization reduced NSC concentrations (?25%) but neither affected latex yield per leaf nor the concentration of latex‐related hydrocarbons. It is concluded that latex and related hydrocarbons in CO2‐enriched plants are a negligible sink for excess carbon irrespective of nutrient status and thus, vigour of growth. 相似文献
6.
Biomass allocation in old-field annual species grown in elevated CO2 environments: no evidence for optimal partitioning 总被引:1,自引:0,他引:1
C. J. Bernacchi J. S. Coleman † F. A. Bazzaz‡ K. D. M. McConnaughay 《Global Change Biology》2000,6(7):855-863
Increased atmospheric carbon dioxide supply is predicted to alter plant growth and biomass allocation patterns. It is not clear whether changes in biomass allocation reflect optimal partitioning or whether they are a direct effect of increased growth rates. Plasticity in growth and biomass allocation patterns was investigated at two concentrations of CO2 ([CO2]) and at limiting and nonlimiting nutrient levels for four fast‐ growing old‐field annual species. Abutilon theophrasti, Amaranthus retroflexus, Chenopodium album, and Polygonum pensylvanicum were grown from seed in controlled growth chamber conditions at current (350 μmol mol?1, ambient) and future‐ predicted (700 μmol mol?1, elevated) CO2 levels. Frequent harvests were used to determine growth and biomass allocation responses of these plants throughout vegetative development. Under nonlimiting nutrient conditions, whole plant growth was increased greatly under elevated [CO2] for three C3 species and moderately increased for a C4 species (Amaranthus). No significant increases in whole plant growth were observed under limiting nutrient conditions. Plants grown in elevated [CO2] had lower or unchanged root:shoot ratios, contrary to what would be expected by optimal partitioning theory. These differences disappeared when allometric plots of the same data were analysed, indicating that CO2‐induced differences in root:shoot allocation were a consequence of accelerated growth and development rates. Allocation to leaf area was unaffected by atmospheric [CO2] for these species. The general lack of biomass allocation responses to [CO2] availability is in stark contrast with known responses of these species to light and nutrient gradients. We conclude that biomass allocation responses to elevated atmospheric [CO2] are not consistent with optimal partitioning predictions. 相似文献
7.
Carbon-based secondary and structural compounds in Mediterranean shrubs growing near a natural CO2 spring 总被引:1,自引:0,他引:1
We studied carbon‐based secondary and structural compounds (CBSSCs) in Myrtus communis, Erica arborea, and Juniperus communis co‐occurring in a natural CO2 spring site and in a nearby control site in a Mediterranean environment. Leaf concentrations of phenolics and CBSSCs, such as lignin, cellulose, and hemicellulose, total nonstructural carbohydrates (TNCs), and lipids were measured monthly (phenolics) and every two months (the other compounds) throughout a year. There was a slight seasonal trend towards maximum concentrations of most of these CBSSCs during autumn–winter and minimum values during the spring season, particularly in Myrtus communis. For most of the CBSSCs and species, there were no consistent or significant patterns in response to the elevated [CO2] (c. 700 μmol mol?1) of the spring site. These results were not due to a dilution effect by increased structural or nonstructural carbon. Therefore, in contrast to many experimental studies of CO2 enrichment, mainly conducted for short periods, there were no greater concentrations of phenolics, and, as in many of these studies, there were neither greater concentrations of the other CBSSCs. These results do not agree with the predictions of the carbon source‐sink hypotheses. Possible causes of this disagreement are discussed. These causes include the complex heterogeneous environmental conditions and the variability of resource availabilities in the field, photosynthetic down‐regulation, and/or the homeostatic and evolutionary nature of organisms. These results suggest evolutionary adaptive responses to changes in CO2. They also suggest caution in attributing increased CBSSC concentrations to elevated [CO2] at long‐term scale in natural conditions, and therefore in their implications for plant–herbivore interactions and for decomposition. 相似文献
8.
The ectomycorrhizal (ECM) symbiosis can cause both positive and negative feedback with trees under elevated CO2. Positive feedback arises if the additional carbon (C) increases both nutrient uptake by the fungus and nutrient transfer to the plant, whereas negative feedback results from increased nutrient uptake and immobilization by the fungus and reduced transfer to the plant. Because species of ECM fungi differ in their C and nitrogen (N) demand, understanding fungal species‐specific responses to variation in C and N supply is essential to predict impacts of global change. We investigated fungal species‐specific responses of ECM Scots pine (Pinus sylvestris) seedlings under ambient and elevated CO2 (350 or 700 μL L−1 CO2) and under low and high mineral N availability. Each seedling was associated with one of the following ECM species: Hebeloma cylindrosporum, Laccaria bicolor and Suillus bovinus. The experiment lasted 103 days. During the final 27 days, seedlings were labeled with 14CO2 and 15N. Most plant and fungal parameters were significantly affected by fungal species, CO2 level and N supply. Interactions between fungal species and CO2 were also regularly significant. At low N availability, elevated CO2 had the smallest impact on the photosynthetic performance of seedlings inoculated with H. cylindrosporum and the largest impact on seedlings with S. bovinus. At ambient CO2, increasing N supply had the smallest impact on seedlings inoculated with S. bovinus and the largest on seedlings inoculated with H. cylindrosporum. At low N availability, extraradical hyphal length increased after doubling CO2 level, but this was significant only for L. bicolor. At ambient CO2, increasing N levels reduced hyphal length for both H. cylindrosporum and S. bovinus, but not for L. bicolor. We discuss the potential interplay of two major elements of global change, elevated CO2 and increased N availability, and their effects on plant growth. We conclude that increased N supply potentially relieves mycorrhiza‐induced progressive N limitation under elevated CO2. 相似文献
9.
Environmental changes are likely to alter the chemical composition of plant tissues, including content and concentrations
of secondary compounds, and thereby affect the food sources of herbivores. After 10 years of experimental increase of temperature,
nutrient levels and light attenuation in a sub-arctic, alpine ecosystem, we investigated the effects on carbon based secondary
compounds (CBSC) and nitrogen in one dominant deciduous dwarf shrub, Salix herbacea × polaris and two dominant evergreen dwarf shrubs, Cassiope tetragona and Vaccinium vitis-idaea throughout one growing season. The main aims were to compare the seasonal course and treatment effects on CBSC among the
species, life forms and leaf cohorts and to examine whether the responses in different CBSC were consistent across compounds.
The changes in leaf chemistry both during the season and in response to the treatments were higher in S. herbacea × polaris than in the corresponding current year’s leaf cohort of the evergreen C. tetragona. The changes were also much higher than in the 1-year-old leaves of the two evergreens probably due to differences in dilution
and turnover of CBSC in growing and mature leaves paired with different rates of allocation. Most low molecular weight phenolics
in the current year’s leaves decreased in all treatments. Condensed tannins and the tannin-to-N ratio, however, either increased
or decreased, and the strength and even direction of the responses varied among the species and leaf cohorts, supporting views
of influential factors additional to resource-based or developmental controls, as e.g. species specific or genetic controls
of CBSC. The results indicate that there is no common response to environmental changes across species and substances. However,
the pronounced treatment responses imply that the quality of the herbivore forage is likely to be strongly affected in a changing
arctic environment, although both the direction and strength of the responses will be different among plant species, tissue
types and substances. 相似文献
10.
We investigated the effects of elevated CO2 (600 μl l−1 vs 350 μl l−1) and phosphorus supply (1 g P m−2 year−1 vs unfertilized) on intact monoliths from species-rich calcareous grassland in a greenhouse. Aboveground community dry mass
remained almost unaffected by elevated CO2 in the first year (+6%, n.s.), but was significantly stimulated by CO2 enrichment in year two (+26%, P<0.01). Among functional groups, only graminoids contributed significantly to this increase. The effect of phosphorus alone
on community biomass was small in both years and marginally significant only when analyzed with MANOVA (+6% in year one, +9%
in year two, 0.1 ≥P > 0.05). Belowground biomass and stubble after two seasons were not different in elevated CO2 and when P was added. The small initial increase in aboveground community biomass under elevated CO2 is explained by the fact that some species, in particular Carex flacca, responded very positively right from the beginning, while others, especially the dominant Bromus erectus, responded negatively to CO2 enrichment. Shifts in community composition towards more responsive species explain the much larger CO2 response in the second year. These shifts, i.e., a decline in xerophytic elements (B. erectus) and an increase in mesophytic grasses and legumes occurred independently of treatments in all monoliths but were accelerated
significantly by elevated CO2. The difference in average biomass production at elevated compared to ambient CO2 was higher when P was supplied (at the community level the CO2 response was enhanced from 20% to 33% when P was added, in graminoids from 17% to 27%, in legumes from 4% to 60%, and in
C. flacca from 120% to 298% by year two). Based on observations in this and similar studies, we suggest that interactions between CO2 concentration, species presence, and nutrient availability will govern community responses to elevated CO2.
Received: 12 July 1997 / Accepted: 28 March 1998 相似文献
11.
We examined the extent to which carbon investment into secondary compounds in loblolly pine (Pinus taeda L.) is changed by the interactive effect of elevated CO2 and N availability and whether differences among treatments are the result of size-dependent changes. Seedlings were grown
for 138 days at two CO2 partial pressures (35 and 70 Pa CO2) and four N solution concentrations (0.5, 1.5, 3.5, and 6.5 mmol l−1 NO3NH4) and concentrations of total phenolics and condensed tannins were determined four times during plant development in primary
and fascicular needles, stems and lateral and tap roots. Concentrations of total phenolics in lateral roots and condensed
tannins in tap roots were relatively high regardless of treatment. In the smallest seedlings secondary compound concentrations
were relatively high and decreased in the initial growth phase. Thereafter condensed tannins accumulated strongly during plant
maturation in all plant parts except in lateral roots, where concentrations did not change. Concentrations of total phenolics
continued to decrease in lateral roots while they remained constant in all other plant parts. At the final harvest plants
grown at elevated CO2 or low N availability showed increased concentrations of condensed tannins in aboveground parts. The CO2 effect, however, disappeared when size differences were adjusted for, indicating that CO2 only indirectly affected concentrations of condensed tannins through accelerating growth. Concentrations of total phenolics
increased directly in response to low N availability and elevated CO2 in primary and fascicular needles and in lateral roots, which is consistent with predictions of the carbon-nutrient balance
(CNB) hypothesis. The CNB hypothesis is also supported by the strong positive correlations between soluble sugar and total
phenolics and between starch and condensed tannins. The results suggest that predictions of the CNB hypothesis could be improved
if developmentally induced changes of secondary compounds were included.
Received: 27 March 1997 / Accepted: 25 July 1997 相似文献
12.
HISAE NAGASHIMA TAKASHI YAMANO KOUKI HIKOSAKA TADAKI HIROSE 《Global Change Biology》2003,9(4):619-629
To investigate the effect of elevated CO2 on the size inequality and size structure, even‐aged monospecific stands of an annual, Chenopodium album, were established at ambient and doubled CO2 with high and low nutrient availabilities in open top chambers. The growth of individual plants was monitored non‐destructively every week until flowering. Elevated CO2 significantly enhanced plant growth at high nutrients, but did not at low nutrients. The size inequality expressed as the coefficient of variation tended to increase at elevated CO2. Size structure of the stands was analyzed by the cumulative frequency distribution of plant size. At early stages of plant growth, CO2 elevation benefited all individuals and shifted the whole size distribution of the stand to large size classes. At later stages, dominant individuals were still larger at elevated than at ambient CO2, but the difference in small subordinate individuals between two CO2 levels became smaller. Although these tendencies were found at both nutrient availabilities, difference in size distribution between CO2 levels was larger at high nutrients. The CO2 elevation did not significantly enhance the growth rate as a function of plant size except for the high nutrient stand at the earliest stage, indicating that the higher biomass at elevated CO2 at later stages in the high nutrient stand was caused by the larger size of individuals at the earliest stage. Thus the effect of elevated CO2 on stand structure and size inequality strongly depended on the growth stage and nutrient availabilities. 相似文献
13.
The effects of CO2 enrichment and soil nutrient status on tissue quality were investigated and related to the potential effect on growth and decomposition. Two California annuals, Avena fatua and Plantago erecta, were grown at ambient and ambient plus 35 Pa atmospheric CO2 in nutrient unamended and amended serpentine soil. Elevated CO2 led to significantly increased Avena shoot nitrogen concentrations in the nutrient amended treatment. It also led to decreased lignin concentrations in Avena roots in both nutrient treatments, and in Plantago shoots and roots with nutrient addition. Concentrations of total nonstructural carbohydrate (TNC) and carbon did not change with elevated CO2 in either species. As a consequence of increased biomass accumulation, increased CO2 led to larger total pools of TNC, lignin, total carbon, and total nitrogen in Avena with nutrient additions. Doubling CO2 had no significant effect on Plantago. Given the limited changes in the compounds related to decomposibility and plant growth, effects of increased atmospheric CO2 mediated through tissue composition on Avena and Plantago are likely to be minor and depend on site fertility. This study suggests that other factors such as litter moisture, whether or not litter is on the ground, and biomass allocation among roots and shoots, are likely to be more important in this California grassland ecosystem. CO2 could influence those directly as well as indirectly. 相似文献
14.
John Kanowski 《Austral ecology》2001,26(2):165-172
The present study examined the effects of elevated levels of atmospheric CO2 on foliar concentrations of nitrogen, mineral nutrients and phenolics, and leaf toughness, in seedlings of two common rainforest trees from north‐east Queensland, Australia. The trees were the pioneer species Alphitonia petriei Braid and C. White and the mid‐successional species Flindersia brayleyana F. Muell. Both species are important in the diets of folivorous marsupials endemic to the region. Seedlings were grown in native rainforest soils (nutrient‐rich basalt and nutrient‐poor rhyolite) and exposed to unreplicated treatments of ambient (350 p.p.m.) and elevated (790 p.p.m.) CO2 for 60 days in a glasshouse. The foliage of seedlings exposed to elevated CO2 had lower concentrations of nitrogen and sodium than did seedlings exposed to ambient conditions. Nitrogen levels declined by 4.5 mg g‐1 in Alphitonia and 5.9 mg/g in Flindersia, or 25 and 29% of ambient levels, respectively. Sodium levels declined by 44% in both species. In Flindersia, concentrations of phosphorus, potassium and calcium were also reduced in elevated CO2 by 19–28% of ambient levels, but these minerals did not vary with CO2 treatment in Alphitonia. In elevated CO2, levels of condensed tannins were higher in Flindersia, but not Alphitonia. Levels of total phenolics did not vary significantly with CO2 in Flindersia; whereas in Alphitonia, total phenolics were lower in elevated CO2, but only on basalt soils. Leaves were thicker in both species in elevated CO2. Leaves were tougher in both species in elevated CO2, but only on rhyolite soils. If the results of the present study can be extrapolated to mature trees exposed to elevated CO2 over the long‐term, folivores would be expected to become less abundant under elevated CO2 conditions, as foliar chemistry is a good predictor of folivore abundance in the higher elevation rainforests of north‐east Queensland. 相似文献
15.
JOHN E. ERICKSON J. PATRICK MEGONIGAL GARY PERESTA BERT G. DRAKE 《Global Change Biology》2007,13(1):202-215
Elevated atmospheric carbon dioxide concentrations ([CO2]) generally increase plant photosynthesis in C3 species, but not in C4 species, and reduce stomatal conductance in both C3 and C4 plants. In addition, tissue nitrogen concentration ([N]) often fails to keep pace with enhanced carbon gain under elevated CO2, particularly in C3 species. While these responses are well documented in many species, implications for plant growth and nutrient cycling in native ecosystems are not clear. Here we present data on 18 years of measurement of above and belowground biomass, tissue [N] and total standing crop of N for a Scirpus olneyi‐dominated (C3 sedge) community, a Spartina patens‐dominated (C4 grass) community and a C3–C4‐mixed species community exposed to ambient and elevated (ambient +340 ppm) atmospheric [CO2] in natural salinity and sea level conditions of a Chesapeake Bay wetland. Increased biomass production (shoots plus roots) under elevated [CO2] in the S. olneyi‐dominated community was sustained throughout the study, averaging approximately 35%, while no significant effect of elevated [CO2] was found for total biomass in the C4‐dominated community. We found a significant decline in C4 biomass (correlated with rising sea level) and a concomitant increase in C3 biomass in the mixed community. This shift from C4 to C3 was accelerated by the elevated [CO2] treatment. The elevated [CO2] stimulation of total biomass accumulation was greatest during rainy, low salinity years: the average increase above the ambient treatment during the three wettest years (1994, 1996, 2003) was 2.9 t ha−1 but in the three driest years (1995, 1999, 2002), it was 1.2 t ha−1. Elevated [CO2] depressed tissue [N] in both species, but especially in the S. olneyi where the relative depression was positively correlated with salinity and negatively related with the relative enhancement of total biomass production. Thus, the greatest amount of carbon was added to the S. olneyi‐dominated community during years when shoot [N] was reduced the most, suggesting that the availability of N was not the most or even the main limitation to elevated [CO2] stimulation of carbon accumulation in this ecosystem. 相似文献
16.
William J. Mattson Kari Kuokkanen† Pekka Niemelä† Riitta Julkunen-Tiitto‡ Seppo Kellomäki† Jorma Tahvanainen‡ 《Global Change Biology》2004,10(8):1402-1413
We studied the three‐way interaction of elevated CO2, nitrogen (N), and temperature (T), and the two‐way interaction of elevated CO2 and early‐season defoliation on the secondary chemistry and resistance of Eurasian silver birch (Betula pendula) and North American paper birch (B. papyrifera) against the Eurasian hare (Lepus timidus) and the North American eastern cottontail rabbit (Sylvilagus floridanus), respectively. Elevated CO2 decreased the palatability of winter‐dormant silver and paper birch stems to both hares and rabbits, respectively. But the effect on hares was only apparent at intermediate levels of N fertilization. Elevated T had no effect on palatability. The effects of elevated CO2, N, and T on levels of silver birch bark phenolics and terpenoids were dominated by two‐way interactions between N and CO2, and N and T. Generally, however, N amendments elicited a parabolic response in carbon partitioning to most biosynthetic classes of silver birch phenolics (i.e. highest concentrations occurring at intermediate N). CO2 elevation was most enhancing at highest levels of N. On the other hand, T increases, more often than not, elicited reductions in phenolics, but especially so at the highest N level. In the case of B. papyrifera, elevated CO2 increased carbon partitioning to Folin‐Denis stem and branch phenolics and condensed tannins. Early‐season defoliation, on the other hand, had no effect on phenolics and tannins but lowered both N and energy levels of branches. Elevated CO2 substantially ameliorated the negative effects of severe defoliation on tree growth. These results support the hypothesis that continuing anthropogenic alterations of the atmosphere may trigger significant changes in plant phenotypic resistance to mammalian herbivores owing to an increasing net carbon balance between the highly vagile supply and demand capacities of plant carbon sources and sinks. 相似文献
17.
Leaf quality and insect herbivory in model tropical plant communities after long-term exposure to elevated atmospheric CO2 总被引:1,自引:0,他引:1
Results from laboratory feeding experiments have shown that elevated atmospheric carbon dioxide can affect interactions between plants and insect herbivores, primarily through changes in leaf nutritional quality occurring at elevated CO2. Very few data are available on insect herbivory in plant communities where insects can choose among species and positions in the canopy in which to feed. Our objectives were to determine the extent to which CO2-induced changes in plant communities and leaf nutritional quality may affect herbivory at the level of the entire canopy. We introduced equivalent populations of fourth instar Spodoptera eridania, a lepidopteran generalist, to complex model ecosystems containing seven species of moist tropical plants maintained under low mineral nutrient supply. Larvae were allowed to feed freely for 14 days, by which time they had reached the seventh instar. Prior to larval introductions, plant communities had been continuously exposed to either 340 l CO2 l–1 or to 610 l CO2 l–1 for 1.5 years. No major shifts in leaf nutritional quality [concentrations of N, total non-structural carbohydrates (TNC), sugar, and starch; ratios of: C/N, TNC/N, sugar/N, starch/N; leaf toughness] were observed between CO2 treatments for any of the species. Furthermore, no correlations were observed between these measures of leaf quality and leaf biomass consumption. Total leaf area and biomass of all plant communities were similar when caterpillars were introduced. However, leaf biomass of some species was slightly greater-and for other species slightly less (e.g. Cecropia peltata)-in communities exposed to elevated CO2. Larvae showed the strongest preference for C. peltata leaves, the plant species that was least abundant in all communites, and fed relatively little on plants species which were more abundant. Thus, our results indicate that leaf tissue quality, as described by these parameters, is not necessarily affected by elevated CO2 under relatively low nutrient conditions. Hence, the potential importance of CO2-induced shifts in leaf nutritional quality, as determinants of herbivory, may be overestimated for many plant communities growing on nutrient-poor sites if estimates are based on traditional laboratory feeding studies. Finally, slight shifts in the abundance of leaf tissue of various species occurring under elevated CO2 will probably not significantly affect herbivory by generalist insects. However, generalist insect herbivores appear to become more dependent on less-preferred plant species in cases where elevated CO2 results in reduced availability of leaves of a favoured plant species, and this greater dependency may eventually affect insect populations adversely. 相似文献
18.
Competition for nitrogen between Pinus sylvestris and ectomycorrhizal fungi generates potential for negative feedback under elevated CO2 总被引:1,自引:0,他引:1
We investigated fungal species-specific responses of ectomycorrhizal (ECM) Scots pine (Pinus sylvestris) seedlings on growth and nutrient acquisition together with mycelial development under ambient and elevated CO2. Each seedling was associated with one of the following ECM species: Hebeloma cylindrosporum, Laccaria bicolor, Suillus bovinus, S. luteus, Piloderma croceum, Paxillus involutus, Boletus badius, or non-mycorrhizal, under ambient, and elevated CO2 (350 or 700 μl l−1 CO2); each treatment contained six replicates. The trial lasted 156 days. During the final 28 days, the seedlings were labeled
with 14CO2. We measured hyphal length, plant biomass, 14C allocation, and plant nitrogen and phosphorus concentration. Almost all parameters were significantly affected by fungal
species and/or CO2. There were very few significant interactions. Elevated CO2 decreased shoot-to-root ratio, most strongly so in species with the largest extraradical mycelium. Under elevated CO2, ECM root growth increased significantly more than hyphal growth. Extraradical hyphal length was significantly negatively
correlated with shoot biomass, shoot N content, and total plant N uptake. Root dry weight was significantly negatively correlated
with root N and P concentration. Fungal sink strength for N strongly affected plant growth through N immobilization. Mycorrhizal
fungal-induced progressive nitrogen limitation (PNL) has the potential to generate negative feedback with plant growth under
elevated CO2.
Responsible Editor: Herbert Johannes Kronzucker 相似文献
19.
Although desert ecosystems are predicted to be the most responsive to elevated CO2, low nutrient availability may limit increases in productivity and cause plants in deserts to allocate more resources to root biomass or activity for increased nutrient acquisition. We measured root respiration of two Mojave Desert shrubs, Ambrosia dumosa and Larrea tridentata, grown under ambient (~375 ppm) and elevated (~517 ppm) CO2 concentrations at the Nevada Desert FACE Facility (NDFF) over five growing seasons. In addition, we grew L. tridentata seedlings in a greenhouse with similar CO2 treatments to determine responses of primary and lateral roots to an increase in CO2. In both field and greenhouse studies, root respiration was not significantly affected by elevated CO2. However, respiration of A. dumosa roots <1 month old was significantly greater than respiration of A. dumosa roots between 1 and 4 months old. For both shrub species, respiration rates of very fine (<1.0 mm diameter) roots were significantly greater than those of fine (1–2 mm diameter) roots, and root respiration decreased as soil water decreased. Because specific root length was not significantly affected by CO2 and because field minirhizotron measurements of root production were not significantly different, we infer that root growth at the NDFF has not increased with elevated CO2. Furthermore, other studies at the NDFF have shown increased nutrient availability under elevated CO2, which reduces the need for roots to increase scavenging for nutrients. Thus, we conclude that A. dumosa and L. tridentata root systems have not increased in size or activity, and increased shoot production observed under elevated CO2 for these species does not appear to be constrained by the plant's root growth or activity. 相似文献
20.
Changes in the atmospheric concentration of carbon dioxide ([CO2]), nutrient availability and biotic diversity are three major drivers of the ongoing global change impacting terrestrial ecosystems worldwide. While it is well established that soil nutrient heterogeneity exerts a strong influence on the development of plant individuals and communities, it is virtually unknown how nutrient heterogeneity and global change drivers interact to affect plant performance and ecosystem functioning. We conducted a microcosm experiment to evaluate the effect of simultaneous changes in [CO2], nutrient heterogeneity (NH), nutrient availability (NA) and species evenness on the biomass and nutrient uptake patterns of assemblages formed by Lolium perenne, Plantago lanceolata and Holcus lanatus. When the nutrients were heterogeneously supplied, assemblages exhibited precise root foraging patterns, and had higher above‐ and belowground biomass (average increases of 32% and 29% for above‐ and belowground biomass, respectively). Nutrient heterogeneity also modulated the effects of NA on biomass production, complementarity in nitrogen uptake and below: aboveground ratio, as well as those of [CO2] on the nutrient use efficiency at the assemblage level. Our results show that nutrient heterogeneity has the potential to influence the response of plant assemblages to simultaneous changes in [CO2], nutrient availability and biotic diversity, and suggest that it is an important environmental factor to interpret and assess plant assemblage responses to global change. 相似文献