共查询到20条相似文献,搜索用时 21 毫秒
1.
Tracing carbon and oxygen isotope signals from newly assimilated sugars in the leaves to the tree-ring archive 总被引:1,自引:0,他引:1
ARTHUR GESSLER ELKE BRANDES NINA BUCHMANN GERHARD HELLE HEINZ RENNENBERG & ROMAIN L. BARNARD 《Plant, cell & environment》2009,32(7):780-795
The analysis of δ 13 C and δ 18 O in tree-ring archives offers retrospective insights into environmental conditions and ecophysiological processes. While photosynthetic carbon isotope discrimination and evaporative oxygen isotope enrichment are well understood, we lack information on how the isotope signal is altered by downstream metabolic processes.
In Pinus sylvestris , we traced the isotopic signals from their origin in the leaf water ( δ18 O) or the newly assimilated carbon ( δ 13 C), via phloem sugars to the tree-ring, over a time-scale that ranges from hours to a growing season.
Seasonally, variable13 C enrichment of sugars related to phloem loading and transport did lead to uncoupling between δ 13 C in the tree-ring, and the c i / c a ratio at the leaf level. In contrast, the oxygen isotope signal was transferred from the leaf water to the tree-ring with an expected enrichment of 27‰, with time-lags of approximately 2 weeks and with a 40% exchange between organic oxygen and xylem water oxygen during cellulose synthesis.
This integrated overview of the fate of carbon and oxygen isotope signals within the model tree species P. sylvestris provides a novel physiological basis for the interpretation of δ13 C and δ 18 O in tree-ring ecology. 相似文献
In Pinus sylvestris , we traced the isotopic signals from their origin in the leaf water ( δ
Seasonally, variable
This integrated overview of the fate of carbon and oxygen isotope signals within the model tree species P. sylvestris provides a novel physiological basis for the interpretation of δ
2.
1. Growth, density and δ13 C of wood and leaf area were measured in two adjacent stands of 6 year-old Eucalyptus globulus growing in the 600–700 mm year–1 rainfall region of south-western Australia. Study sites were identical except for differences in the availability of water owing to physical properties of soil profiles and location of sites within the landscape.
2. Abundance of13 C (expressed as δ13 C) in wood of trees growing on the drought-prone site (– 24·8‰±1·4) was greater than in other trees (– 25·8‰±1·2, P <0·001) throughout the 6 years and, with further development, the δ13 C signatures of wood may become useful indices of drought-susceptibility in plantations within a few years of establishment. The seasonal pattern of δ13 C of wood appeared to reflect seasonal variation in water availability and duration of cambial activity.
3. Basic density of wood of trees growing on the more drought-prone site (496±14·0 kg m–3 ) was reduced compared to other trees (554±5·3 kg m–3 , P <0·001). δ13 C of wood across boundaries of growth-rings suggested that drought stopped cambial activity resulting in less production of late wood and less dense wood.
4. The stand growing on the drought-prone site had reduced growth, wood yield and leaf area but identical specific leaf area. Annual growth was correlated with the previous season's rainfall. Together, these results suggested that within the same evaporative climate, drought reduces growth primarily by reducing leaf area and that there is a lag between onset of drought and reduced productivity. 相似文献
2. Abundance of
3. Basic density of wood of trees growing on the more drought-prone site (496±14·0 kg m
4. The stand growing on the drought-prone site had reduced growth, wood yield and leaf area but identical specific leaf area. Annual growth was correlated with the previous season's rainfall. Together, these results suggested that within the same evaporative climate, drought reduces growth primarily by reducing leaf area and that there is a lag between onset of drought and reduced productivity. 相似文献
3.
We evaluated diurnal and seasonal patterns of carbon isotope composition of leaf dark-respired CO2 ( δ 13 Cl ) in the C3 perennial shrub velvet mesquite ( Prosopis velutina ) across flood plain and upland savanna ecosystems in the south-western USA. δ 13 Cl of darkened leaves increased to maximum values late during daytime periods and declined gradually over night-time periods to minimum values at pre-dawn. The magnitude of the diurnal shift in δ 13 Cl was strongly influenced by seasonal and habitat-related differences in soil water availability and leaf surface vapour pressure deficit. δ 13 Cl and the cumulative flux-weighted δ 13 C value of photosynthates were positively correlated, suggesting that progressive 13 C enrichment of the CO2 evolved by darkened leaves during the daytime mainly resulted from short-term changes in photosynthetic 13 C discrimination and associated shifts in the δ 13 C signature of primary respiratory substrates. The 13 C enrichment of dark-respired CO2 relative to photosynthates across habitats and seasons was 4 to 6‰ at the end of the daytime period (1800 h), but progressively declined to 0‰ by pre-dawn (0300 h). The origin of night-time and daytime variations in δ 13 Cl is discussed in terms of the carbon source(s) feeding respiration and the drought-induced changes in carbon metabolism. 相似文献
4.
J. R. Ehleringer D. R. Bowling L. B. Flanagan J. Fessenden B. Helliker L. A. Martinelli J. P. Ometto 《Plant biology (Stuttgart, Germany)》2002,4(2):181-189
Abstract: Scaling and partitioning are frequently two difficult challenges facing ecology today. With regard to ecosystem carbon balance studies, ecologists and atmospheric scientists are often interested in asking how fluxes of carbon dioxide scale across the landscape, region and continent. Yet at the same time, physiological ecologists and ecosystem ecologists are interested in dissecting the net ecosystem CO2 exchange between the biosphere and the atmosphere to achieve a better understanding of the balance between photosynthesis and respiration within a forest. In both of these multiple-scale ecological questions, stable isotope analyses of carbon dioxide can play a central role in influencing our understanding of the extent to which terrestrial ecosystems are carbon sinks. In this synthesis, we review the theory and present field evidence to address isotopic scaling of CO2 fluxes. We first show that the 13 C isotopic signal which ecosystems impart to the atmosphere does not remain constant over time at either temporal or spatial scales. The relative balances of different biological activities and plant responses to stress result in dynamic changes in the 13 C isotopic exchange between the biosphere and atmosphere, with both seasonal and stand-age factors playing major roles influencing the 13 C biosphere-atmosphere exchange. We then examine how stable isotopes are used to partition net ecosystem exchange fluxes in order to calculate shifts in the balance of photosynthesis and respiration. Lastly, we explore how fundamental differences in the 18 O isotopic gas exchange of forest and grassland ecosystems can be used to further partition terrestrial fluxes. 相似文献
5.
BEHZAD MORTAZAVI MAUREEN H. CONTE JEFFREY P. CHANTON MATTHEW C. SMITH J. C. WEBER JASMINE CRUMSEY & JALEH GHASHGHAIE 《Plant, cell & environment》2009,32(10):1310-1323
Isotopic labelling experiments were conducted to assess relationships among 13 C of recently assimilated carbon ( δC A ), foliage respiration ( δC F ), soluble carbohydrate ( δC SC ), leaf waxes ( δC LW ) and bulk organic matter ( δC OM ). Slash pine, sweetgum and maize were grown under 13 C depleted CO2 to label biomass and then placed under ambient conditions to monitor the loss of label. In pine and sweetgum, δC F of labelled plants (∼−44 and −35‰, respectively) rapidly approached control values but remained depleted by ∼4–6‰ after 3–4 months. For these tree species, no or minimal label was lost from δC SC , δC LW and δC OM during the observation periods. δC F and δC SC of labelled maize plants rapidly changed and were indistinguishable from controls after 1 month, while δC LW and δC OM more slowly approached control values and remained depleted by 2–6‰. Changes in δC F in slash pine and sweetgum fit a two-pool exponential model, with the fast turnover metabolic pool (∼3–4 d half-life) constituting only 1–2% of the total. In maize, change in δC F fits a single pool model with a half-life of 6.4 d. The 13 C of foliage respiration and biochemical pools reflect temporally integrated values of δC A , with change in isotopic composition dampened by the size of metabolic carbon reserves and turnover rates. 相似文献
6.
1. Changes of δ13 C and its relation to leaf development, biochemical content and water stress were monitored over a 2 year period in two co-occurring Mediterranean oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex .
2. The time course of leaf δ13 C showed different patterns in the two species. Young Q. pubescens leaves had a high δ13 C and a marked decrease occurred during leaf growth. In contrast, leaves at budburst and maturity did not differ significantly in the case of Q. ilex . We suggest that the difference between δ13 C of young leaves was linked to differential use of reserves of carbon compounds in the two species.
3. δ13 C values of mature leaves were negatively correlated with minimum seasonal values of predawn water potential, suggesting that a functional adjustment to water resources occurred.
4. There was a significant correlation between individual δ13 C values for two successive years. This interannual dependence showed that δ13 C rankings between trees were constant through time. 相似文献
2. The time course of leaf δ
3. δ
4. There was a significant correlation between individual δ
7.
Correlations between net primary productivity and foliar carbon isotope ratio across a Tibetan ecosystem transect 总被引:1,自引:0,他引:1
Tianxiang Luo Lin Zhang Huazhong Zhu Christopher Daly Mingcai Li Ji Luo 《Ecography》2009,32(3):526-538
Warming climate could affect leaf-level carbon isotope composition (δ13 C) through variations in photosynthetic gas exchange. However, it is still unclear to what extent variations in foliar δ13 C can be used to detect changes in net primary productivity (NPP) because leaf physiology is only one of many determinants of stand productivity. We aim to examine how well site-mean foliar δ13 C and stand NPP co-vary across large resource gradients using data obtained from the Tibetan Alpine Vegetation Transects (1900–4900 m, TAVT). The TAVT data indicated a robust negative correlation between foliar δ13 C and NPP across ecosystems (NPP=−2.7224δ13 C-67.738, r2 =0.60, p<0.001). The mean foliar δ13 C decreased with increasing annual precipitation and its covariation with mean temperature and soil organic carbon and nitrogen contents. The results were further confirmed by global literature data. Pooled δ13 C data from global literature and this study explained 60% of variations in annual NPP both from TAVT-measures and MODIS-estimates across 67 sites. Our results appear to support a conceptual model relating foliar δ13 C and nitrogen concentration (Nmass ) to NPP, suggesting that: 1) there is a general (negative) relationship between δ13 C and NPP across different water availability conditions; 2) in water-limited conditions, water availability has greater effects on NPP than Nmass ; 3) when water is not limiting, NPP increases with increasing Nmass . 相似文献
8.
Air pollution in the past recorded in width and stable carbon isotope composition of annual growth rings of Douglas-fir 总被引:2,自引:2,他引:2
Abstract. Tree-ring indices (TRIs) of annual growth rings in stems of Douglas-fir ( Pseudotsuga menziesii ) growing near a copper smelter showed reduced growth during two multi-year time periods in the past. These periods coincided with World Wars I and II, which are known to represent periods of particularly high SO2 emissions from the smelter. Reduced growth was correlated with less negative stable carbon isotope composition (δ13 C) in cellulose purified from wood formed in such years. Based on current models for 13 C/12 C in plants, these results indicate that exposure to air pollution resulted in reduced concentration of CO2 in the intercellular air spaces of the needles. This is consistent with the hypothesis that stomatal closure resulted in impaired photosynthesis and reduced growth during past episodes of high air pollution. The pollution-related change in δ13 C was superimposed on a change with time in δ13 C, independent of growth, by - 1.4 per mil from 1902 to 1984. 相似文献
9.
LUCAS A. CERNUSAK KLAUS WINTER & BENJAMIN L. TURNER 《Plant, cell & environment》2009,32(10):1441-1455
Water-use efficiency and stable isotope composition were studied in three tropical tree species. Seedlings of Tectona grandis , Swietenia macrophylla and Platymiscium pinnatum were grown at either high or low water supply, and with or without added fertilizer. These three species previously exhibited low, intermediate and high whole-plant water-use efficiency ( TE ) when grown at high water supply in unfertilized soil. Responses of TE to water and nutrient availability varied among species. The TE was calculated as experiment-long dry matter production divided by cumulative water use. Species-specific offsets were observed in relationships between TE and whole-plant 13 C discrimination (Δ13 Cp ). These offsets could be attributed to a breakdown in the relationship between Δ13 Cp and the ratio of intercellular to ambient CO2 partial pressures ( c i / c a ) in P. pinnatum , and to variation among species in the leaf-to-air vapour pressure difference ( v ). Thus, a plot of v · TE against c i / c a showed a general relationship among species. Relationships between δ 18 O of stem dry matter and stomatal conductance ranged from strongly negative for S. macrophylla to no relationship for T. grandis . Results suggest inter-specific variation among tropical tree species in relationships between stable isotope ratios ( δ 13 C and δ 18 O) and the gas exchange processes thought to affect them. 相似文献
10.
1. The δ13 C and δ15 N signatures of zooplankton vary with dissolved organic carbon (DOC), but inconsistent and limited taxonomic resolution of previous studies have masked differences that may exist among orders, genera or species and are attributable to dietary and/or habitat differences. Here we investigate differences among the isotopic signatures of five zooplankton taxa ( Daphnia , Holopedium , large Calanoida, small Calanoida and Cyclopoida) in Precambrian shield lakes with a sixfold range of DOC concentration.
2. δ13 C signatures of Daphnia , small calanoids and large calanoids became more depleted with increasing lake DOC, whereas Holopedium and cyclopoid δ13 C became enriched with increasing DOC concentration.
3. The variability of δ13 C and δ15 N isotopic signatures among zooplankton groups was reduced in high-DOC, compared to low-DOC lakes, especially for δ13 C. Differences in δ13 C and POM-corrected δ15 N accounted for up to 33.7% and 19.5% of the variance, respectively, among lakes of varying DOC concentration.
4. The narrow range of signatures found in higher DOC lakes suggests that different taxa have similar food sources and/or habitats. In contrast, the wide range of signatures in low-DOC lakes suggests that different taxa are exploiting different food sources and/or habitats. Together with the variable trends in zooplankton isotopic signatures along our DOC gradient, these results suggest that food web dynamics within the zooplankton community of temperate lakes will change as climate and lake DOC concentrations change. 相似文献
2. δ
3. The variability of δ
4. The narrow range of signatures found in higher DOC lakes suggests that different taxa have similar food sources and/or habitats. In contrast, the wide range of signatures in low-DOC lakes suggests that different taxa are exploiting different food sources and/or habitats. Together with the variable trends in zooplankton isotopic signatures along our DOC gradient, these results suggest that food web dynamics within the zooplankton community of temperate lakes will change as climate and lake DOC concentrations change. 相似文献
11.
Correlations Between Foliar Stable Carbon Isotope Composition and Environmental Factors in Desert Plant Reaumuria soongorica (Pall.) Maxim. 总被引:2,自引:0,他引:2
Jian-Ying MA Tuo CHEN Wei-Ya QIANG Gang WANG 《植物学报(英文版)》2005,47(9):1065-1073
Leaves of 407 individuals of Reaumuria soongorica (Pall.) Maxim. collected from the major distribution areas were measured to investigate the distribution characteristics of the stable carbon isotope in this desert plant, as well as correlations between δ^13C values and environmental factors. Results showed that δ^13C values in R. soongorica ranged from -22.77‰ to -29.85‰ and that the mean δ^13C value (-26.52‰) was higher than a previously reported δ^13C value for a different desert ecosystem. This indicates that R. soongorica belongs to the C3 photosynthetic pathway and has higher water use efficiency than other species. The correlations between δ^13C values and environmental factors demonstrated that the foliar δ^13C values in R. soongorica increased significantly with decreasing mean annual precipitation and mean relative humidity, and decreased with decreasing duration of sunshine and evaporation. The spatial distribution trend of δ^13C values in R. soongorica was not obvious and there was no significant correlation between the δ^13C values and mean annual temperature. We conclude that different distribution trends in δ^13C values for R. soongorica were likely caused by stomatal limitation rather than by nutrient-related changes in photosynthetic efficiency and that precipitation played an important role in the wide distribution range of R. soongorica. This pattern of δ^13C values for R. soongorica reinforced that it is a super-xerophil in terms of its adaptive strategies to a desert environment. 相似文献
12.
Stable carbon and nitrogen ratios in the sand smelt from a Mediterranean coastal area: feeding habits and effect of season and size 总被引:1,自引:0,他引:1
Enriched δ13 C values (annual average – 11.2‰) suggest that in the study site (Stagnone di Marsala, Italy) the sand smelt Atherina boyeri exploited benthic prey throughout the year. In particular, Mysidacea and Isopoda seemed to dominate the diet. Stomach content data from the literature was in partial agreement with the present isotopic analysis suggesting that, while Mysidacea and Isopoda are exploited by A. boyeri , Copepoda Harpacticoida and Amphipoda are the dominant food items of the sand smelt diet. Several hypotheses are proposed to explain such partially different results from the two techniques. Both season and size influenced the δ13 C and δ15 N values of A. boyeri . Although throughout the sampling year, A. boyeri showed very enriched δ13 C and δ15 N values consistent with a diet based on benthic resources, it showed significant seasonal differences in both nitrogen and carbon isotope ratios. Such a finding suggests that the food preferences of A. boyeri undergo small seasonal differences, probably as a consequence of prey availability. Size also affected the isotopic composition of the sand-smelt indicating that this species shows ontogenetic diet shifts in the study site. Compared with other Mediterranean trophic data of the sand smelt these results substantiate the great adaptability of A. boyeri to the local environmental resources and its trophic plasticity. 相似文献
13.
M. DURANCEAU J. GHASHGHAIE F. BADECK E. DELEENS & G. CORNIC 《Plant, cell & environment》1999,22(5):515-523
The variations in δ 13 C in both leaf carbohydrates (starch and sucrose) and CO2 respired in the dark from the cotyledonary leaves of Phaseolus vulgaris L. were investigated during a progressive drought. As expected, sucrose and starch became heavier (enriched in 13 C) with decreasing stomatal conductance and decreasing p i / p a during the first half (15 d) of the dehydration cycle. Thereafter, when stomata remained closed and leaf net photosynthesis was near zero, the tendency was reversed: the carbohydrates became lighter (depleted in 13 C). This may be explained by increased p i / p a but other possible explanations are also discussed. Interestingly, the variations in δ 13 C of CO2 respired in the dark were correlated with those of sucrose for both well-watered and dehydrated plants. A linear relationship was obtained between δ 13 C of CO2 respired in the dark and sucrose, respired CO2 always being enriched in 13 C compared with sucrose by ≈ 6‰. The whole leaf organic matter was depleted in 13 C compared with leaf carbohydrates by at least 1‰. These results suggest that: (i) a discrimination by ≈ 6‰ occurs during dark respiration processes releasing 13 C-enriched CO2 ; and that (ii) this leads to 13 C depletion in the remaining leaf material. 相似文献
14.
The sloughed skin from three captive manatees at Lowry Park Zoological Garden (Tampa, Florida) was examined over a period of one year to determine its stable carbon isotopic composition (δ13 C). The food consumed by these manatees in a controlled diet was also sampled and its δ13 C values determined. The sloughed skin δ13 C values from the captive manatees were enriched by an average of +4.1%0 relative to lettuce (generally >98% of the diet) the animals consumed. δ13 C values of the skin were shown to be related to changes in δ13 C values of the lettuce.
The stable carbon isotopic composition of internal tissues (liver, kidney, and blubber) and skin from dead, stranded manatees was also determined. These values were compared to values of vegetation that manatees are known to eat in the wild. The δ13 C values of the internal tissues and skin of wild manatees were consistent with the range of δ13 C values of their expected diet. 相似文献
The stable carbon isotopic composition of internal tissues (liver, kidney, and blubber) and skin from dead, stranded manatees was also determined. These values were compared to values of vegetation that manatees are known to eat in the wild. The δ
15.
A. KOHZU T. YOSHIOKA T. ANDO M. TAKAHASHI K. KOBA & E. WADA 《The New phytologist》1999,144(2):323-330
The natural abundance of 13 C and 15 N was measured in basidiocarps of at least 115 species in 88 genera of ectomycorrhizal, wood-decomposing and litter-decomposing fungi from Japan and Malaysia. The natural abundance of 13 C and 15 N was also measured in leaves, litter, soil and wood from three different sites. 15 N and 13 C were enriched in ectomycorrhizal and wood-decomposing fungi, respectively, relative to their substrates. Ectomycorrhizal and wood-decomposing fungi could be distinguished on the basis of their δ13 C and δ15 N signatures. Although there was high variability in the isotopic composition of fungi, the following isotope- enrichment factors (ε, mean±SD) of the fungi relative to substrates were observed:
εectomycorrhizal fungi/litter = 6.1±0.4‰15 N
εectomycorrhizal fungi/wood = 1.4±0.8‰13 C
εwood-decomposing fungi/wood = −0.6±0.7‰15 N
εwood-decomposing fungi/wood = 3.5±0.9‰13 C
The basis of isotope fractionation in C metabolism from wood to wood-decomposing fungus is discussed. 相似文献
ε
ε
ε
ε
The basis of isotope fractionation in C metabolism from wood to wood-decomposing fungus is discussed. 相似文献
16.
AKIRA KAGAWA ATSUKO SUGIMOTO KANA YAMASHITA & HISASHI ABE 《Plant, cell & environment》2005,28(7):906-915
Using a combined method of pulse-labelling trees and analysing detailed distribution of 13 C tracer within tree rings, we studied how photo-assimilates incorporated on a given day are then distributed in a tree ring. A branch of a 4-year-old Cryptomeria japonica D.Don tree growing in Tsukuba, Japan was pulse-labelled with non-radioactive 13 CO2 on two occasions: 29 May 2001 and 18 September 2001. Two discs were cut from the stem on 4 March 2002, one immediately under and the other 0.5 m below the branch and put through high-resolution δ 13 C analysis. δ 13 C peaks were observed in both the earlywood and latewood of the concerned tree ring, corresponding to each pulse-labelling date. The earlywood peaks was broader than the latewood peaks, possibly reflecting seasonal variation of the width of wood developing zone. Half-widths of the peaks were measured and used as indicators for the potential time resolution of tree-ring isotope analysis. The half-widths of the peaks indicated a time resolution no finer than 8.7–28 and 33–42 d in the early and latewood, respectively. Holocellulose extraction yielded only a slight change to the shape of the δ 13 C peaks. 13 C tracer pulse-labelled in May and September reached tangentially different locations in the lower disc, suggesting a seasonal change in the pathway of carbohydrates. Local consumption of spring assimilates and long-distance downward transport of autumn assimilates were also suggested. 相似文献
17.
We examined the environmental variables that influence the δ 13 C value of needle and phloem sugars in trees in a subalpine forest. We collected sugars from Pinus contorta , Picea engelmannii and Abies lasiocarpa from 2006 to 2008. Phloem and needle sugars were enriched in 13 C during the autumn, winter and early spring, but depleted during the growing season. We hypothesized that the late-winter and early-spring 13 C enrichment was due to the mobilization of carbon assimilated the previous autumn; however, needle starch concentrations were completely exhausted by autumn, and we observed evidence of new starch production during episodic warm weather events during the winter and early-spring. Instead, we found that 13 C enrichment was best explained by the occurrence of cold night-time temperatures. We also observed seasonal decoupling in the 13 C/12 C ratios of needle and phloem sugars. We hypothesized that this was due to seasonally-changing source-sink patterns, which drove carbon translocation from the needles towards the roots early in the season, before bud break, but from the roots towards the needles later in the season, after bud break. Overall, our results demonstrate that the 13 C/12 C ratio of recently-assimilated sugars can provide a sensitive record of the short-term coupling between climate and tree physiology. 相似文献
18.
1. The influence of leaf thickness on internal conductance for CO2 transfer from substomatal cavity to chloroplast stroma ( g i ) and carbon isotope ratio (δ13 C) of leaf dry matter was investigated for some evergreen tree species from Japanese temperate forests. g i was estimated based on the combined measurements of gas exchange and concurrent carbon isotope discrimination.
2. Leaves with thicker mesophyll tended to have larger leaf dry mass per area (LMA), larger surface area of mesophyll cells exposed to intercellular air spaces per unit leaf area ( Smes ) and smaller volume ratio of intercellular spaces to the whole mesophyll (mesophyll porosity).
3. gi of these leaves was correlated positively to S mes but negatively to mesophyll porosity. The variation in g i among these species would be therefore primarily determined by variation of the conductance in liquid phase rather than that in gas phase.
4. δ13 C was positively correlated to mesophyll thickness and leaf nitrogen content on an area basis. However, g i values did not correlate to δ13 C. These results suggest that difference in δ13 C among the species was not caused by the variation in g i , but mainly by the difference in long-term photosynthetic capacity.
5. Comparison of our results with those of previous studies showed that the correlation between leaf thickness and gi differed depending on leaf functional types (evergreen, deciduous or annual). Differences in leaf properties among these functional types were discussed. 相似文献
2. Leaves with thicker mesophyll tended to have larger leaf dry mass per area (LMA), larger surface area of mesophyll cells exposed to intercellular air spaces per unit leaf area ( S
3. g
4. δ
5. Comparison of our results with those of previous studies showed that the correlation between leaf thickness and g
19.
LUCAS C. R. SILVA MADHUR ANAND JULIANO M. OLIVEIRA† VALÉRIO D. PILLAR† 《Global Change Biology》2009,15(10):2387-2396
Araucaria angustifolia (Bertol.) Kuntze is an indigenous conifer tree restricted to the southern region of South America that plays a key role in the dynamics of regional ecosystems where forest expansion over grasslands has been observed. Here, we evaluate the changes in intrinsic water use efficiency (iWUE) and basal area increment (BAI) of this species in response to atmospheric CO2 , temperature and precipitation over the last century. Our investigation is based on tree-rings taken from trees located in forest and grassland sites in southern Brazil. Differences in carbon isotopic composition ( δ 13 C), 13 CO2 discrimination (Δ13 C) and intracellular carbon concentration ( C i ) are also reported. Our results indicate an age effect on Δ13 C in forest trees during the first decades of growth. This age effect is not linked to an initial BAI suppression, suggesting the previous existence of nonforested vegetation in the forest sites. After maturity all trees show similar temporal trends in carbon isotope-derived variables and increasing iWUE, however, absolute values are significantly different between forest and grassland sites. The iWUE is higher in forest trees, indicating greater water competition or nutritional availability, relative to grassland, or both. BAI is also higher in forest trees, but it is not linked with iWUE or atmospheric CO2 . Nevertheless, in both forest and grassland sites A. angustifolia has had growth limitations corresponding to low precipitation and high temperatures observed in the 1940s. 相似文献
20.
Isotopic analysis of the sources of organic carbon for zooplankton in shallow subarctic and arctic waters 总被引:1,自引:0,他引:1
Shallow high-latitude lakes and ponds are usually characterized by an oligotrophic water column overlying a biomass-rich, highly productive benthos. Their pelagic food webs often contain abundant zooplankton but the importance of benthic organic carbon versus seston as their food sources has been little explored. Our objectives were to measure the δ13 C and δ15 N isotopic signatures of pelagic and benthic particulate organic matter (POM) in shallow water bodies in northern Canada and to determine the relative transfer of this material to zooplankton and other aquatic invertebrates. Fluorescence analysis of colored dissolved organic matter (CDOM) indicated a relatively strong terrestrial carbon influence in five subarctic waterbodies whereas the CDOM in five arctic water columns contained mostly organic carbon of autochthonous origin. The isotopic signatures of planktonic POM and cohesive benthic microbial mats were distinctly different at all study sites, while non-cohesive microbial mats often overlapped in their δ13 C signals with the planktonic POM. Zooplankton isotopic signatures indicated a potential trophic link with different fractions of planktonic POM and the non-cohesive mats whereas the cohesive mats did not appear to be used as a major carbon source. The zooplankton signals differed among species, indicating selective use of resources and niche partitioning. Most zooplankton had δ13 C values that were intermediate between the values of putative food sources and that likely reflected selective feeding on components of the pelagic or benthic POM. The results emphasize the likely importance of benthic-pelagic coupling in tundra ecosystems, including for species that are traditionally considered pelagic and previously thought to be dependent only on phytoplankton as their food source. 相似文献