751
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He JS, Wang L, Flynn DFB, Wang X, Ma W, Fang J. Leaf nitrogen:phosphorus stoichiometry across Chinese grassland biomes. Oecologia 2007; 155:301-10. [PMID: 18278518 DOI: 10.1007/s00442-007-0912-y] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2006] [Accepted: 10/22/2007] [Indexed: 11/28/2022]
Abstract
Leaf N and P stoichiometry covaries with many aspects of plant biology, yet the drivers of this trait at biogeographic scales remain uncertain. Recently we reported the patterns of leaf C and N based on systematic census of 213 species over 199 research sites in the grassland biomes of China. With the expanded analysis of leaf P, here we report patterns of leaf P and N:P ratios, and analyze the relative contribution of climatic variables and phylogeny in structuring patterns of leaf N:P stoichiometry. Average values of leaf P and N:P ratio were 1.9 mg g(-1) and 15.3 (mass ratio), respectively, consistent with the previous observation of a higher N:P ratio in China's flora than the global averages (ca. 13.8), resulting from a lower leaf P. Climatic variables had very little direct correlation with leaf P and N:P ratios, with growing season precipitation and temperature together explaining less than 2% of the variation, while inter-site differences and within-site phylogenetic variation explained 55 and 26% of the total variation in leaf P and N:P ratios. Across all sites and species, leaf N and P were highly positively correlated at all levels. However, the within-site, within-species covariations of leaf N and P were weaker than those across sites and across species. Leaf N and P relationships are driven by both variation between sites at the landscape scale (explaining 58% of the variance) and within sites at the local scale (explaining 24%), while the climatic factors exerted limited influence (explaining less than 3%). In addition, leaf N:P ratios in two dominant genera Kobresia and Stipa had different responses to precipitation. This study suggests that geographic variation and between-species variation, rather than climatic variation, are the major determinants of grassland foliar stoichiometry at the biome level.
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Affiliation(s)
- Jin-Sheng He
- Department of Ecology, Peking University, 5 Yiheyuan Road, 100871 Beijing, China.
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752
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Lovelock CE, Feller IC, Ball MC, Ellis J, Sorrell B. Testing the growth rate vs. geochemical hypothesis for latitudinal variation in plant nutrients. Ecol Lett 2007; 10:1154-63. [PMID: 17927772 DOI: 10.1111/j.1461-0248.2007.01112.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two hypotheses have been proposed to explain increases in plant nitrogen (N) and phosphorus (P) concentrations with latitude: (i) geochemical limitation to P availability in the tropics and (ii) temperature driven variation in growth rate, where greater growth rates (requiring greater nutrient levels) are needed to complete growth and reproduction within shorter growing seasons in temperate than tropical climates. These two hypotheses were assessed in one forest type, intertidal mangroves, using fertilized plots at sites between latitudes 36 masculine S and 27 masculine N. The N and P concentrations in mangrove leaf tissue increased with latitude, but there were no trends in N : P ratios. Growth rates of trees, adjusted for average minimum temperature showed a significant increase with latitude supporting the Growth Rate Hypothesis. However, support for the Geochemical Hypothesis was also strong; both photosynthetic P use efficiency and nutrient resorption efficiency decreased with increasing latitude, indicating that P was less limiting to metabolism at the higher latitudes. Our study supports the hypothesis that historically low P availability in the tropics has been an important selective pressure shaping the evolution of plant traits.
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Affiliation(s)
- C E Lovelock
- Centre for Marine Studies and School of Integrative Biology, University of Queensland, St Lucia, Queensland 4072, Australia.
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753
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Anderson TM, Ritchie ME, McNaughton SJ. Rainfall and soils modify plant community response to grazing in Serengeti National Park. Ecology 2007; 88:1191-201. [PMID: 17536405 DOI: 10.1890/06-0399] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Terrestrial plant community responses to herbivory depend on resource availability, but the separate influences of different resources are difficult to study because they often correlate across natural environmental gradients. We studied the effects of excluding ungulate herbivores on plant species richness and composition, as well as available soil nitrogen (N) and phosphorus (P), across eight grassland sites in Serengeti National Park (SNP), Tanzania. These sites varied independently in rainfall and available soil N and P. Excluding herbivores decreased plant species richness at all sites and by an average of 5.4 species across all plots. Although plant species richness was a unimodal function of rainfall in both grazed and ungrazed plots, fences caused a greater decrease in plant species richness at sites of intermediate rainfall compared to sites of high or low rainfall. In terms of the relative or proportional decreases in plant species richness, excluding herbivores caused the strongest relative decreases at lower rainfall and where exclusion of herbivores increased available soil P. Herbivore exclusion increased among-plot heterogeneity in species composition but decreased coexistence of congeneric grasses. Compositional similarity between grazed and ungrazed treatments decreased with increasing rainfall due to greater forb richness in exclosures and greater sedge richness outside exclosures and was not related to effects of excluding herbivores on soil nutrients. Our results show that plant resources, especially water and P, appear to modulate the effects of herbivores on tropical grassland plant diversity and composition. We show that herbivore effects on soil P may be an important and previously unappreciated mechanism by which herbivores influence plant diversity, at least in tropical grasslands.
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Affiliation(s)
- T Michael Anderson
- Biological Research Laboratories, Syracuse University, Syracuse, New York 13244, USA.
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754
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Abstract
Correlations between foliar nutrient concentrations and soil nutrient availability have been found in multiple ecosystems. These relationships have led to the use of foliar nutrients as an index of nutrient status and to the prediction of broadscale patterns in ecosystem processes. More recently, a growing interest in ecological stoichiometry has fueled multiple analyses of foliar nitrogen:phosphorus (N:P) ratios within and across ecosystems. These studies have observed that N:P values are generally elevated in tropical forests when compared to higher latitude ecosystems, adding weight to a common belief that tropical forests are generally N rich and P poor. However, while these broad generalizations may have merit, their simplicity masks the enormous environmental heterogeneity that exists within the tropics; such variation includes large ranges in soil fertility and climate, as well as the highest plant species diversity of any biome. Here we present original data on foliar N and P concentrations from 150 mature canopy tree species in Costa Rica and Brazil, and combine those data with a comprehensive new literature synthesis to explore the major sources of variation in foliar N:P values within the tropics. We found no relationship between N:P ratios and either latitude or mean annual precipitation within the tropics alone. There is, however, evidence of seasonal controls; in our Costa Rica sites, foliar N:P values differed by 25% between wet and dry seasons. The N:P ratios do vary with soil P availability and/or soil order, but there is substantial overlap across coarse divisions in soil type, and perhaps the most striking feature of the data set is variation at the species level. Taken as a whole, our results imply that the dominant influence on foliar N:P ratios in the tropics is species variability and that, unlike marine systems and perhaps many other terrestrial biomes, the N:P stoichiometry of tropical forests is not well constrained. Thus any use of N:P ratios in the tropics to infer larger-scale ecosystem processes must comprehensively account for the diversity of any given site and recognize the broad range in nutrient requirements, even at the local scale.
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Affiliation(s)
- Alan R Townsend
- INSTAAR and Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, Colorado 80309, USA.
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755
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Crait JR, Ben-David M. EFFECTS OF RIVER OTTER ACTIVITY ON TERRESTRIAL PLANTS IN TROPHICALLY ALTERED YELLOWSTONE LAKE. Ecology 2007; 88:1040-52. [PMID: 17536719 DOI: 10.1890/06-0078] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Animals that deposit aquatically derived nutrients on terrestrial landscapes link food webs and affect a variety of in situ processes. This phenomenon, however, is poorly documented in freshwater habitats, especially where species introductions have drastically changed an ecosystem's trophic structure. In this study, we used stable isotopes to document water-to-land nutrient transport by river otters (Lontra canadensis) around Yellowstone Lake, an ecosystem recently altered by nonnative species invasions. We then investigated the effects of otter fertilization on plant growth and prevalence at latrine (scent-marking) sites and evaluated how the recent changes to the lake's food web could influence these plant responses. Values of delta15N were higher on latrines compared to non-latrine sites in five of seven sample plant taxa. Additionally, latrine grasses had higher percentage N than those from non-latrines. Foliar delta15N positively related to fecal deposition rate for some plants, indicating that increased otter scent-marking led to a rise in these N values. Logistic regression models indicated that otters selected for well-shaded latrines with access to foraging. Atypical latrines, misclassified as non-latrines by the regression models, had values of delta15N similar to correctly classified latrines, suggesting that site effects alone cannot explain elevated N values at otter latrine sites. No difference in plant diversity or percent cover of N-fixing taxa occurred between latrine and nonlatrine sites, though specific genera did differ between site types. Measurements of shoot lengths indicated increased growth of some latrine currants (Ribes sp.). In Yellowstone Lake, a twofold reduction in otter numbers could result in an even greater decline in nutrient deposition at latrines, as otters may become less social in a system with decreased prey availability. Our results highlight the role of animals in linking aquatic and terrestrial habitats in inland freshwater systems and suggest that ongoing changes in the trophic structure of Yellowstone Lake could have unexpected ramifications well beyond the lake itself.
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Affiliation(s)
- Jamie R Crait
- Department of Zoology and Physiology, University of Wyoming, Laramie 82071, USA.
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756
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KAZAKOU E, GARNIER E, NAVAS ML, ROUMET C, COLLIN C, LAURENT G. Components of nutrient residence time and the leaf economics spectrum in species from Mediterranean old-fields differing in successional status. Funct Ecol 2007. [DOI: 10.1111/j.1365-2435.2006.01242.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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757
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Nutrient Addition Differentially Affects Ecological Processes of Avicennia germinans in Nitrogen versus Phosphorus Limited Mangrove Ecosystems. Ecosystems 2007. [DOI: 10.1007/s10021-007-9025-z] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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758
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Ghannoum O, Conroy JP. Phosphorus deficiency inhibits growth in parallel with photosynthesis in a C 3 (Panicum laxum) but not two C 4 (P. coloratum and Cenchrus ciliaris) grasses. FUNCTIONAL PLANT BIOLOGY : FPB 2007; 34:72-81. [PMID: 32689333 DOI: 10.1071/fp06253] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/10/2006] [Accepted: 12/14/2006] [Indexed: 06/11/2023]
Abstract
This study compared the growth and photosynthetic responses of one C3 (Panicum laxum L.) and two C4 grasses (Panicum coloratum L. and Cenchrus ciliaris L.) to changes in soil phosphorus (P) nutrition. Plants were grown in potted soil amended with six different concentrations of P. One week before harvest, leaf elongation and photosynthetic rates and the contents of carbohydrate, P and inorganic phosphate (Pi) were measured. Five weeks after germination, plants were harvested to estimate biomass accumulation. At each soil P supply, leaf P contents were lower in the C3 (0.6-2.6 mmol P m-2) than in the two C4 grasses (0.8-4.1 mmol P m-2), and Pi constituted ~40-65% of total leaf P. The P deficiency reduced leaf growth, tillering and plant dry mass to a similar extent in all three grasses. In contrast, P deficiency suppressed photosynthetic rates to a greater extent in the C3 (50%) than the C4 grasses (25%). The foliar contents of non-structural carbohydrates were affected only slightly by soil P supply in all three species. Leaf mass per area decreased at low P in the two C4 grasses only, and biomass partitioning changed little with soil P supply. The percentage changes in assimilation rates and plant dry mass were linearly related in the C3 but not the C4 plants. Thus, P deficiency reduced growth in parallel with reductions of photosynthesis in the C3 grass, and independently of photosynthesis in the two C4 grasses. We propose that this may be related to a greater Pi requirement of C4 relative to C3 photosynthesis. Photosynthetic P use efficiency was greater and increased more with P deficiency in the C4 relative to the C3 species. The opposite was observed for whole-plant P-use efficiency. Hence, the greater P-use efficiency of C4 photosynthesis was not transferred to the whole-plant level, mainly as a result of the larger and constant leaf P fraction in the two C4 grasses.
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Affiliation(s)
- Oula Ghannoum
- Centre for Plant and Food Science, University of Western Sydney, Locked Bag 1797, South Penrith DC, South Penrith, NSW 1797, Australia
| | - Jann P Conroy
- Centre for Plant and Food Science, University of Western Sydney, Locked Bag 1797, South Penrith DC, South Penrith, NSW 1797, Australia
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759
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Gress SE, Nichols TD, Northcraft CC, Peterjohn WT. NUTRIENT LIMITATION IN SOILS EXHIBITING DIFFERING NITROGEN AVAILABILITIES: WHAT LIES BEYOND NITROGEN SATURATION? Ecology 2007; 88:119-30. [PMID: 17489460 DOI: 10.1890/0012-9658(2007)88[119:nlised]2.0.co;2] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The nature of nutrient limitation in large areas of temperate forest may be changing due to human activities. As N availability in these forests increases, other nutrients could increasingly constrain productivity and other ecosystem processes. To determine the nature of nutrient limitation (N, P, and Ca) in forest soils exhibiting differing N availability, we conducted three field studies in the Fernow Experimental Forest, West Virginia, USA. The first used a ubiquitous herbaceous species, Viola rotundifolia, to compare indices of N availability to the activity of root-associated phosphomonoesterase (PME) activity at two spatial scales. The second study used fertilized, root in-growth cores to assess the extent of N, P, and Ca limitation. Finally, we measured the root-associated PME activity of V. rotundifolia growing in experimental plots that have received various combinations of nutrient additions and harvest treatments. For entire watersheds, stream water nitrate concentrations were positively related to PME activities (R2 = 0.986). For small plots, PME activities were positively associated with soil nitrate availability (R2 = 0.425), and to a lesser extent with the leaf N concentrations (R2 = 0.291). Root growth into microsites fertilized with P was greater than growth into microsites fertilized with either N or Ca, especially in watersheds with high N availability. Experimental additions of N increased the root-associated PME activity of V. rotundifolia, supporting the causality of the relationship between N availability and PME activity. Collectively, our results indicate that, as N availability increases, P becomes increasingly limiting at the sites examined. Understanding how nutrient limitations change during N saturation should improve ecosystem models and better inform our attempts to mitigate any undesired effects.
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Affiliation(s)
- Stephen E Gress
- West Virginia University, Department of Biology, Morgantown, West Virginia 26506-6057, USA
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760
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Shannon SP, Chrzanowski TH, Grover JP. Prey food quality affects flagellate ingestion rates. MICROBIAL ECOLOGY 2007; 53:66-73. [PMID: 17186152 DOI: 10.1007/s00248-006-9140-y] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Revised: 06/21/2006] [Accepted: 07/10/2006] [Indexed: 05/13/2023]
Abstract
Flagellate feeding efficiency appears to depend on morphological characteristics of prey such as cell size and motility, as well as on other characteristics such as digestibility and cell surface characteristics. Bacteria of varying morphological characteristics (cell size) and mineral nutrient characteristics or food quality (as determined by the C:N:P ratio) were obtained by growing Pseudomonas fluorescens in chemostats at four dilution rates (0.03, 0.06, 0.10, and 0.13 h-1) and three temperatures (14 degrees C, 20 degrees C, and 28 degrees C). Cells of a given food quality were heat-killed and used to grow the flagellate Ochromonas danica. Ingestion and digestion rates were determined by using fluorescently labeled bacteria of the same food quality as the bacteria supporting growth. Ingestion rates were affected by both food quality and cell size. Cells of high food quality (low carbon:element ratio) were ingested at higher rates than cells of low food quality. Multiple regression analysis indicated that cell size also influenced ingestion rate but to a much lesser extent than did food quality. Digestion rates were not correlated with either food quality or cell size. Results suggest that flagellates may adjust feeding efficiency based on the quality of food items available.
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Affiliation(s)
- S Paul Shannon
- Department of Biology, The University of Texas at Arlington, Arlington, TX 76019, USA
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761
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Bucci SJ, Scholz FG, Goldstein G, Meinzer FC, Franco AC, Campanello PI, Villalobos-Vega R, Bustamante M, Miralles-Wilhelm F. Nutrient availability constrains the hydraulic architecture and water relations of savannah trees. PLANT, CELL & ENVIRONMENT 2006; 29:2153-67. [PMID: 17081249 DOI: 10.1111/j.1365-3040.2006.01591.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Leaf and whole plant-level functional traits were studied in five dominant woody savannah species from Central Brazil (Cerrado) to determine whether reduction of nutrient limitations in oligotrophic Cerrado soils affects carbon allocation, water relations and hydraulic architecture. Four treatments were used: control, N additions, P additions and N plus P additions. Fertilizers were applied twice yearly, from October 1998 to March 2004. Sixty-three months after the first nutrient addition, the total leaf area increment was significantly greater across all species in the N- and the N + P-fertilized plots than in the control and in the P-fertilized plots. Nitrogen fertilization significantly altered several components of hydraulic architecture: specific conductivity of terminal stems increased with N additions, whereas leaf-specific conductivity and wood density decreased in most cases. Average daily sap flow per individual was consistently higher with N and N + P additions compared to the control, but its relative increase was not as great as that of leaf area. Long-term additions of N and N + P caused midday PsiL to decline significantly by a mean of 0.6 MPa across all species because N-induced relative reductions in soil-to-leaf hydraulic conductance were greater than those of stomatal conductance and transpiration on a leaf area basis. Phosphorus-fertilized trees did not exhibit significant changes in midday PsiL. Analysis of xylem vulnerability curves indicated that N-fertilized trees were significantly less vulnerable to embolism than trees in control and P-fertilized plots. Thus, N-induced decreases in midday PsiL appeared to be almost entirely compensated by increases in resistance to embolism. Leaf tissue water relations characteristics also changed as a result of N-induced declines in minimum PsiL: osmotic potential at full turgor decreased and symplastic solute content on a dry matter basis increased linearly with declining midday PsiL across species and treatments. Despite being adapted to chronic nutrient limitations, Cerrado woody species apparently have the capacity to exploit increases in nutrient availability by allocating resources to maximize carbon gain and enhance growth. The cost of increased allocation to leaf area relative to water transport capacity involved increased total water loss per plant and a decrease in minimum leaf water potentials. However, the risk of increased embolism and turgor loss was relatively low as xylem vulnerability to embolism and leaf osmotic characteristics changed in parallel with changes in plant water status induced by N fertilization.
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Affiliation(s)
- Sandra J Bucci
- Department of Biology, University of Miami, Coral Gables, FL 33124, USA
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762
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Ellison AM. Nutrient limitation and stoichiometry of carnivorous plants. PLANT BIOLOGY (STUTTGART, GERMANY) 2006; 8:740-7. [PMID: 17203429 DOI: 10.1055/s-2006-923956] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The cost-benefit model for the evolution of carnivorous plants posits a trade-off between photosynthetic costs associated with carnivorous structures and photosynthetic benefits accrued through additional nutrient acquisition. The model predicts that carnivory is expected to evolve if its marginal benefits exceed its marginal costs. Further, the model predicts that when nutrients are scarce but neither light nor water is limiting, carnivorous plants should have an energetic advantage in competition with non-carnivorous plants. Since the publication of the cost-benefit model over 20 years ago, marginal photosynthetic costs of carnivory have been demonstrated but marginal photosynthetic benefits have not. A review of published data and results of ongoing research show that nitrogen, phosphorus, and potassium often (co-)limit growth of carnivorous plants and that photosynthetic nutrient use efficiency is 20 - 50 % of that of non-carnivorous plants. Assessments of stoichiometric relationships among limiting nutrients, scaling of leaf mass with photosynthesis and nutrient content, and photosynthetic nutrient use efficiency all suggest that carnivorous plants are at an energetic disadvantage relative to non-carnivorous plants in similar habitats. Overall, current data support some of the predictions of the cost-benefit model, fail to support others, and still others remain untested and merit future research. Rather than being an optimal solution to an adaptive problem, botanical carnivory may represent a set of limited responses constrained by both phylogenetic history and environmental stress.
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Affiliation(s)
- A M Ellison
- Harvard University, Harvard Forest, 324 North Main Street, Petersham, MA 01366, USA.
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763
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Kerkhoff AJ, Fagan WF, Elser JJ, Enquist BJ. Phylogenetic and Growth Form Variation in the Scaling of Nitrogen and Phosphorus in the Seed Plants. Am Nat 2006; 168:E103-22. [PMID: 17004214 DOI: 10.1086/507879] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2005] [Accepted: 04/26/2006] [Indexed: 11/03/2022]
Abstract
Plant biomass and nutrient allocation explicitly links the evolved strategies of plant species to the material and energy cycles of ecosystems. Allocation of nitrogen (N) and phosphorus (P) is of particular interest because N and P play pivotal roles in many aspects of plant biology, and their availability frequently limits plant growth. Here we present a comparative scaling analysis of a global data compilation detailing the N and P contents of leaves, stems, roots, and reproductive structures of 1,287 species in 152 seed plant families. We find that P and N contents (as well as N : P) are generally highly correlated both within and across organs and that differences exist between woody and herbaceous taxa. Between plant organs, the quantitative form of the scaling relationship changes systematically, depending on whether the organs considered are primarily structural (i.e., stems, roots) or metabolically active (i.e., leaves, reproductive structures). While we find significant phylogenetic signals in the data, similar scaling relationships occur in independently evolving plant lineages, which implies that both the contingencies of evolutionary history and some degree of environmental convergence have led to a common set of rules that constrain the partitioning of nutrients among plant organs.
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Affiliation(s)
- Andrew J Kerkhoff
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA.
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764
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Karpinets TV, Greenwood DJ, Sams CE, Ammons JT. RNA:protein ratio of the unicellular organism as a characteristic of phosphorous and nitrogen stoichiometry and of the cellular requirement of ribosomes for protein synthesis. BMC Biol 2006; 4:30. [PMID: 16953894 PMCID: PMC1574349 DOI: 10.1186/1741-7007-4-30] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2006] [Accepted: 09/05/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mean phosphorous:nitrogen (P:N) ratios and relationships of P:N ratios with the growth rate of organisms indicate a surprising similarity among and within microbial species, plants, and insect herbivores. To reveal the cellular mechanisms underling this similarity, the macromolecular composition of seven microorganisms and the effect of specific growth rate (SGR) on RNA:protein ratio, the number of ribosomes, and peptide elongation rate (PER) were analyzed under different conditions of exponential growth. RESULTS It was found that P:N ratios calculated from RNA and protein contents in these particular organisms were in the same range as the mean ratios reported for diverse organisms and had similar positive relationships with growth rate, consistent with the growth-rate hypothesis. The efficiency of protein synthesis in microorganisms is estimated as the number of active ribosomes required for the incorporation of one amino acid into the synthesized protein. This parameter is calculated as the SGR:PER ratio. Experimental and theoretical evidence indicated that the requirement of ribosomes for protein synthesis is proportional to the RNA:protein ratio. The constant of proportionality had the same values for all organisms, and was derived mechanistically from the characteristics of the protein-synthesis machinery of the cell (the number of nucleotides per ribosome, the average masses of nucleotides and amino acids, the fraction of ribosomal RNA in the total RNA, and the fraction of active ribosomes). Impairment of the growth conditions decreased the RNA:protein ratio and increased the overall efficiency of protein synthesis in the microorganisms. CONCLUSION Our results suggest that the decrease in RNA:protein and estimated P:N ratios with decrease in the growth rate of the microorganism is a consequence of an increased overall efficiency of protein synthesis in the cell resulting from activation of the general stress response and increased transcription of cellular maintenance genes at the expense of growth related genes. The strong link between P:N stoichiometry, RNA:protein ratio, ribosomal requirement for protein synthesis, and growth rate of microorganisms indicated by the study could be used to characterize the N and P economy of complex ecosystems such as soils and the oceans.
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Affiliation(s)
- Tatiana V Karpinets
- Department of Plant Sciences, University of Tennessee, 2431 Joe Johnson Drive. Knoxville, TN 37996-4561, USA
- Computer Science and Mathematics Division, Oak Ridge National Laboratory, P.O. Box 2008, MS6164, Oak Ridge, TN 37831, USA
| | | | - Carl E Sams
- Department of Plant Sciences, University of Tennessee, 2431 Joe Johnson Drive. Knoxville, TN 37996-4561, USA
| | - John T Ammons
- Biosystems Engineering & Environmental Science Department, University of Tennessee, 2506 E. J. Chapman Drive, Knoxville, TN 37996-4531, USA
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765
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Bennett JP, Jepsen EA, Roth JA. Field responses of Prunus serotina and Asclepias syriaca to ozone around southern Lake Michigan. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2006; 142:354-66. [PMID: 16343714 DOI: 10.1016/j.envpol.2005.09.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2005] [Revised: 08/23/2005] [Accepted: 09/27/2005] [Indexed: 05/05/2023]
Abstract
Higher ozone concentrations east of southern Lake Michigan compared to west of the lake were used to test hypotheses about injury and growth effects on two plant species. We measured approximately 1000 black cherry trees and over 3000 milkweed stems from 1999 to 2001 for this purpose. Black cherry branch elongation and milkweed growth and pod formation were significantly higher west of Lake Michigan while ozone injury was greater east of Lake Michigan. Using classification and regression tree (CART) analyses we determined that departures from normal precipitation, soil nitrogen and ozone exposure/peak hourly concentrations were the most important variables affecting cherry branch elongation, and milkweed stem height and pod formation. The effects of ozone were not consistently comparable with the effects of soil nutrients, weather, insect or disease injury, and depended on species. Ozone SUM06 exposures greater than 13 ppm-h decreased cherry branch elongation 18%; peak 1-h exposures greater than 93 ppb reduced milkweed stem height 13%; and peak 1-h concentrations greater than 98 ppb reduced pod formation 11% in milkweed.
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Affiliation(s)
- J P Bennett
- U.S. Geological Survey and Institute for Environmental Studies, University of Wisconsin, Madison, WI 53706, USA.
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766
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HÄRDTLE WERNER, NIEMEYER MARION, NIEMEYER THOMAS, ASSMANN THORSTEN, FOTTNER SILKE. Can management compensate for atmospheric nutrient deposition in heathland ecosystems? J Appl Ecol 2006. [DOI: 10.1111/j.1365-2664.2006.01195.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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767
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Kerkhoff AJ, Enquist BJ. Ecosystem allometry: the scaling of nutrient stocks and primary productivity across plant communities. Ecol Lett 2006; 9:419-27. [PMID: 16623727 DOI: 10.1111/j.1461-0248.2006.00888.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
A principal challenge in ecology is to integrate physiological function (e.g. photosynthesis) across a collection of individuals (e.g. plants of different species) to understand the functioning of the entire ensemble (e.g. primary productivity). The control that organism size exerts over physiological and ecological function suggests that allometry could be a powerful tool for scaling ecological processes across levels of organization. Here we use individual plant allometries to predict how nutrient content and productivity scale with total plant biomass (phytomass) in whole plant communities. As predicted by our model, net primary productivity as well as whole community nitrogen and phosphorus content all scale allometrically with phytomass across diverse plant communities, from tropical forest to arctic tundra. Importantly, productivity data deviate quantitatively from the theoretically derived prediction, and nutrient productivity (production per unit nutrient) of terrestrial plant communities decreases systematically with increasing total phytomass. These results are consistent with the existence of pronounced competitive size hierarchies. The previously undocumented generality of these 'ecosystem allometries' and their basis in the structure and function of individual plants will likely provide a useful quantitative framework for research linking plant traits to ecosystem processes.
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768
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Vegetation responses to environmental conditions in floodplain grasslands: Prerequisites for preserving plant species diversity. Basic Appl Ecol 2006. [DOI: 10.1016/j.baae.2005.09.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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769
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He JS, Fang J, Wang Z, Guo D, Flynn DFB, Geng Z. Stoichiometry and large-scale patterns of leaf carbon and nitrogen in the grassland biomes of China. Oecologia 2006; 149:115-22. [PMID: 16639565 DOI: 10.1007/s00442-006-0425-0] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2005] [Accepted: 03/23/2006] [Indexed: 11/25/2022]
Abstract
Nitrogen (N) and carbon-nitrogen (C:N) ratio are key foliar traits with great ecological importance, but their patterns across biomes have only recently been explored. We conducted a systematic census of foliar C, N and C:N ratio for 213 species, from 41 families over 199 research sites across the grassland biomes of China following the same protocol, to explore how different environmental conditions and species composition affect leaf N and C:N stoichiometry. Leaf C:N stoichiometry is stable in three distinct climatic regions in Inner Mongolia, the Tibetan Plateau, and Xinjiang Autonomous Region, despite considerable variations among co-existing species and among different vegetation types. Our results also show that life form and genus identity explain more than 70% of total variations of foliar N and C:N ratio, while mean growing season temperature and growing season precipitation explained only less than 3%. This suggests that, at the biome scale, temperature affects leaf N mainly through a change in plant species composition rather than via temperature itself. When our data were pooled with a global dataset, the previously observed positive correlation between leaf N and mean annual temperature (MAT) at very low MATs, disappeared. Thus, our data do not support the previously proposed biogeochemical hypothesis that low temperature limitations on mineralization of organic matter and N availability in soils lead to low leaf N in cold environments.
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Affiliation(s)
- Jin-Sheng He
- Department of Ecology, College of Environmental Sciences and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, 5 Yiheyuan Rd., 100871 Beijing, China.
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770
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Niklas KJ. Plant allometry, leaf nitrogen and phosphorus stoichiometry, and interspecific trends in annual growth rates. ANNALS OF BOTANY 2006; 97:155-63. [PMID: 16287903 PMCID: PMC2803372 DOI: 10.1093/aob/mcj021] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2005] [Revised: 10/14/2005] [Accepted: 10/17/2005] [Indexed: 05/05/2023]
Abstract
BACKGROUND Life forms as diverse as unicellular algae, zooplankton, vascular plants, and mammals appear to obey quarter-power scaling rules. Among the most famous of these rules is Kleiber's (i.e. basal metabolic rates scale as the three-quarters power of body mass), which has a botanical analogue (i.e. annual plant growth rates scale as the three-quarters power of total body mass). Numerous theories have tried to explain why these rules exist, but each has been heavily criticized either on conceptual or empirical grounds. N,P-STOICHIOMETRY: Recent models predicting growth rates on the basis of how total cell, tissue, or organism nitrogen and phosphorus are allocated, respectively, to protein and rRNA contents may provide the answer, particularly in light of the observation that annual plant growth rates scale linearly with respect to standing leaf mass and that total leaf mass scales isometrically with respect to nitrogen but as the three-quarters power of leaf phosphorus. For example, when these relationships are juxtaposed with other allometric trends, a simple N,P-stoichiometric model successfully predicts the relative growth rates of 131 diverse C3 and C4 species. CONCLUSIONS The melding of allometric and N,P-stoichiometric theoretical insights provides a robust modelling approach that conceptually links the subcellular 'machinery' of protein/ribosomal metabolism to observed growth rates of uni- and multicellular organisms. Because the operation of this 'machinery' is basic to the biology of all life forms, its allometry may provide a mechanistic explanation for the apparent ubiquity of quarter-power scaling rules.
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Affiliation(s)
- Karl J Niklas
- Department of Plant Biology, Cornell University, Ithaca, NY 14853, USA.
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771
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HOFFMANN WA, FRANCO AC, MOREIRA MZ, HARIDASAN M. Specific leaf area explains differences in leaf traits between congeneric savanna and forest trees. Funct Ecol 2005. [DOI: 10.1111/j.1365-2435.2005.01045.x] [Citation(s) in RCA: 135] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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772
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Han W, Fang J, Guo D, Zhang Y. Leaf nitrogen and phosphorus stoichiometry across 753 terrestrial plant species in China. THE NEW PHYTOLOGIST 2005; 168:377-85. [PMID: 16219077 DOI: 10.1111/j.1469-8137.2005.01530.x] [Citation(s) in RCA: 339] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Leaf nitrogen and phosphorus stoichiometry of Chinese terrestrial plants was studied based on a national data set including 753 species across the country. Geometric means were calculated for functional groups based on life form, phylogeny and photosynthetic pathway, as well as for all 753 species. The relationships between leaf N and P stoichiometric traits and latitude (and temperature) were analysed. The geometric means of leaf N, P, and N : P ratio for the 753 species were 18.6 and 1.21 mg g(-1) and 14.4, respectively. With increasing latitude (decreasing mean annual temperature, MAT), leaf N and P increased, but the N : P ratio did not show significant changes. Although patterns of leaf N, P and N : P ratios across the functional groups were generally consistent with those reported previously, the overall N : P ratio of China's flora was considerably higher than the global averages, probably caused by a greater shortage of soil P in China than elsewhere. The relationships between leaf N, P and N : P ratio and latitude (and MAT) also suggested the existence of broad biogeographical patterns of these leaf traits in Chinese flora.
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Affiliation(s)
- Wenxuan Han
- Department of Ecology, College of Environmental Sciences and Key Laboratory for Earth Surface Processes of the Ministry of Education, Peking University, Beijing, China
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773
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Milla R, Castro-Díez P, Maestro-Martínez M, Montserrat-Martí G. Relationships between phenology and the remobilization of nitrogen, phosphorus and potassium in branches of eight Mediterranean evergreens. THE NEW PHYTOLOGIST 2005; 168:167-78. [PMID: 16159331 DOI: 10.1111/j.1469-8137.2005.01477.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Few studies have examined the effects of plant growth on nutrient remobilization in phenologically contrasting species. Here we evaluated the consequences of above-ground seasonality of growth and leaf shedding on the remobilization of nutrients from branches in eight evergreen Mediterranean phanaerophytes that differ widely in phenology. Vegetative growth, flower bud formation, flowering, fruiting, leaf shedding, and the variations in nitrogen (N), phosphorus (P) and potassium (K) pools in branches throughout the year were monitored in each species. Nitrogen and P remobilization occurred in summer, after vegetative growth and synchronously with leaf shedding. Despite the time-lag between growth and remobilization, the branches that invested more nutrients in vegetative growth also remobilized more nutrients from their old organs. Potassium remobilization peaked in the climatically harshest periods, and appears to be related to osmotic requirements. We conclude that N and P remobilization occurs mainly associated with leaf senescence, which might be triggered by factors such as the replenishment of nutrient reserves in woody organs, the hormonal relations between new and old leaves, or the constraints that summer drought poses on the amount of leaf area per branch in summer.
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Affiliation(s)
- R Milla
- Instituto Pirenaico de Ecología (CSIC), PO Box 202, E-50080 Zaragoza, Spain.
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774
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Gillooly JF, Allen AP, Brown JH, Elser JJ, Martinez del Rio C, Savage VM, West GB, Woodruff WH, Woods HA. The metabolic basis of whole-organism RNA and phosphorus content. Proc Natl Acad Sci U S A 2005; 102:11923-7. [PMID: 16091465 PMCID: PMC1187991 DOI: 10.1073/pnas.0504756102] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2004] [Indexed: 11/18/2022] Open
Abstract
Understanding the storage, flux, and turnover of nutrients in organisms is important for quantifying contributions of biota to biogeochemical cycles. Here we present a model that predicts the storage of phosphorus-rich RNA and whole-body phosphorus content in eukaryotes based on the mass- and temperature-dependence of ATP production in mitochondria. Data from a broad assortment of eukaryotes support the model's two main predictions. First, whole-body RNA concentration is proportional to mitochondrial density and consequently scales with body mass to the -1/4 power. Second, whole-body phosphorus content declines with increasing body mass in eukaryotic unicells but approaches a relatively constant value in large multicellular animals because the fraction of phosphorus in RNA decreases relative to the fraction in other pools. Extension of the model shows that differences in the flux of RNA-associated phosphorus are due to the size dependencies of metabolic rate and RNA concentration. Thus, the model explicitly links two biological currencies at the individual level: energy in the form of ATP and materials in the form of phosphorus, both of which are critical to the functioning of ecosystems. The model provides a framework for linking attributes of individuals to the storage and flux of phosphorus in ecosystems.
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Affiliation(s)
- James F Gillooly
- Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
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775
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GUSEWELL S, FREEMAN C. Nutrient limitation and enzyme activities during litter decomposition of nine wetland species in relation to litter N : P ratios. Funct Ecol 2005. [DOI: 10.1111/j.1365-2435.2005.01002.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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776
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Wakefield AE, Gotelli NJ, Wittman SE, Ellison AM. PREY ADDITION ALTERS NUTRIENT STOICHIOMETRY OF THE CARNIVOROUS PLANT SARRACENIA PURPUREA. Ecology 2005. [DOI: 10.1890/04-1673] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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777
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Blanke V, Renker C, Wagner M, Füllner K, Held M, Kuhn AJ, Buscot F. Nitrogen supply affects arbuscular mycorrhizal colonization of Artemisia vulgaris in a phosphate-polluted field site. THE NEW PHYTOLOGIST 2005; 166:981-92. [PMID: 15869657 DOI: 10.1111/j.1469-8137.2005.01374.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Root colonization by arbuscular mycorrhizal fungi (AMF) was investigated in industrially polluted grassland characterized by exceptionally high phosphorus levels (up to 120 g kg(-1) soil). Along a pollution-induced nitrogen gradient, soil and tissue element concentrations of Artemisia vulgaris plants and their mycorrhizal status were determined. Additionally, we compared mycorrhization rates and above-ground biomass of A. vulgaris at N-fertilized and control plots in the N-poor area. Despite high soil and tissue P concentrations, plants from N-deficient plots, which were characterized by low tissue N concentrations and N : P ratios, were strongly colonized by AMF, whereas at a plot with comparable P levels, but higher soil and plant N concentrations and N : P ratios, mycorrhization rates were significantly lower. Correlation analyses revealed a negative relationship between percentage root colonization of A. vulgaris by AMF and both tissue N concentration and N : P ratio. Accordingly, in the fertilization experiment, control plants had higher mycorrhization rates than N-fertilized plants, whereas the species attained higher biomass at N-fertilized plots. The results suggest that N deficiency stimulates root colonization by AMF in this extraordinarily P-rich field site.
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Affiliation(s)
- Verena Blanke
- Friedrich-Schiller-University of Jena, Institute of Ecology, Jena, Germany.
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778
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Wright IJ, Reich PB, Cornelissen JHC, Falster DS, Garnier E, Hikosaka K, Lamont BB, Lee W, Oleksyn J, Osada N, Poorter H, Villar R, Warton DI, Westoby M. Assessing the generality of global leaf trait relationships. THE NEW PHYTOLOGIST 2005; 166:485-96. [PMID: 15819912 DOI: 10.1111/j.1469-8137.2005.01349.x] [Citation(s) in RCA: 1086] [Impact Index Per Article: 57.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Global-scale quantification of relationships between plant traits gives insight into the evolution of the world's vegetation, and is crucial for parameterizing vegetation-climate models. A database was compiled, comprising data for hundreds to thousands of species for the core 'leaf economics' traits leaf lifespan, leaf mass per area, photosynthetic capacity, dark respiration, and leaf nitrogen and phosphorus concentrations, as well as leaf potassium, photosynthetic N-use efficiency (PNUE), and leaf N : P ratio. While mean trait values differed between plant functional types, the range found within groups was often larger than differences among them. Future vegetation-climate models could incorporate this knowledge. The core leaf traits were intercorrelated, both globally and within plant functional types, forming a 'leaf economics spectrum'. While these relationships are very general, they are not universal, as significant heterogeneity exists between relationships fitted to individual sites. Much, but not all, heterogeneity can be explained by variation in sample size alone. PNUE can also be considered as part of this trait spectrum, whereas leaf K and N : P ratios are only loosely related.
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Affiliation(s)
- Ian J Wright
- Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
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779
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Niklas KJ, Owens T, Reich PB, Cobb ED. Nitrogen/phosphorus leaf stoichiometry and the scaling of plant growth. Ecol Lett 2005. [DOI: 10.1111/j.1461-0248.2005.00759.x] [Citation(s) in RCA: 183] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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780
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Güsewell S, Bailey KM, Roem WJ, Bedford BL. Nutrient limitation and botanical diversity in wetlands: can fertilisation raise species richness? OIKOS 2005. [DOI: 10.1111/j.0030-1299.2005.13587.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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