The influence of island area on ecosystem properties

Science

Volumn 277, Issue 5330, 1997, Pages 1296-1299

  Wardle, David A ^a,c   Zackrisson, Olle ^a   Hörnberg, Greger ^a   Gallet, Christiane ^b  

^a SWEDISH UNIVERSITY OF AGRICULTURAL SCIENCES   (Sweden)

^b UNIVERSITÉ DE SAVOIE   (France)

^c LANDCARE RESEARCH   (New Zealand)

Author keywords

[No Author keywords available]

Indexed keywords

COMMUNITY COMPOSITION; FIRE; ISLAND AREA; WILDFIRE;

ARTICLE; DECOMPOSITION; ECOSYSTEM; FIRE; FOREST; GEOGRAPHY; LIGHTNING; NITROGEN FIXATION; PLANT; PRIORITY JOURNAL; SPECIES; SWEDEN;

SWEDEN;

EID: 0030800859     PISSN: 00368075     EISSN: None     Source Type: Journal    
DOI: 10.1126/science.277.5330.1296     Document Type: Article

References (52)

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13. For evaluation of tree species composition, two circular plots (each 10 m in radius) were established on each island, except for the smallest islands for which only one plot was usually used. In each plot, the diameter of each tree was measured at a height of 1.3 m. Established relationships for converting diameter into biomass for each species [L. G. Marklund, Biomassafunktioner för Tall, Gran och Björk i Sverige (Sveriges Lantbruksuniversiteit, Umeå, Sweden, 1988)] were used for determining total tree biomass on an areal basis. In the area used for these plots, four plots of 0.5 m by 0.5 m were also established, and all dwarf shrub and moss species were trimmed at ground level and sorted into component species. All trimmed material was dried at 80°C for 24 hours for biomass determinations, and leaf subsamples of the dwarf shrubs E. hermaphroditum, V. myrtillus, and V. vitis-idaea and shoot samples of the bryophyte P. schreberi were measured with micro-Kjeldahl analysis for N concentration. All plots were centered 5 to 15 m from the island edge and were always similar distances from the shore, regardless of island area, to prevent edge and climate effects from confounding the results.
14. 14C analyses of these particles at the Tandemlaboratory, Uppsala, Sweden [I. U. Olsson, in Handbook of Palaeoecology and Palaeo-Hydrology, B. E. Berglund, Ed. (Wiley, London, 1986), pp. 272-310; S. Bouwman, Radiocarbon Dating (British Museum Publications, London, 1990)]. We emphasize that the age of the charcoal we measured is not necessarily the same as the time of the most recent fire, because charcoal from fires with low intensity is sometimes undetectable in humus profiles; fire-scar data on the largest islands indicated occurrence of fires that were obviously more recent than the uppermost charcoal we found.
15. 14C analyses of these particles at the Tandemlaboratory, Uppsala, Sweden [I. U. Olsson, in Handbook of Palaeoecology and Palaeo-Hydrology, B. E. Berglund, Ed. (Wiley, London, 1986), pp. 272-310; S. Bouwman, Radiocarbon Dating (British Museum Publications, London, 1990)]. We emphasize that the age of the charcoal we measured is not necessarily the same as the time of the most recent fire, because charcoal from fires with low intensity is sometimes undetectable in humus profiles; fire-scar data on the largest islands indicated occurrence of fires that were obviously more recent than the uppermost charcoal we found.
16. 14C analyses of these particles at the Tandemlaboratory, Uppsala, Sweden [I. U. Olsson, in Handbook of Palaeoecology and Palaeo-Hydrology, B. E. Berglund, Ed. (Wiley, London, 1986), pp. 272-310; S. Bouwman, Radiocarbon Dating (British Museum Publications, London, 1990)]. We emphasize that the age of the charcoal we measured is not necessarily the same as the time of the most recent fire, because charcoal from fires with low intensity is sometimes undetectable in humus profiles; fire-scar data on the largest islands indicated occurrence of fires that were obviously more recent than the uppermost charcoal we found.
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23. Humus samples were collected to the entire humus depth from each of the four plots used for ground-layer vegetation determination (7) and were combined for each island. Total water-soluble phenolics were measured for aqueous extracts by use of Folin-Ciocalteu reagent [G. Marigo, Analytica 2, 106 (1973)]; nitrogen was determined by micro-Kjeldahl analysis. Microbial basal respiration and substrate-induced respiration (a relative measure of active microbial biomass) [J. P. E. Anderson and K. H. Domsch, Soil Biol. Biochem. 10, 215 (1978)] were determined through the use of a modified form of infrared gas analysis [D. A. Wardle, Funct. Ecol. 7, 346 (1993)]. The fumigation-extraction approach was used for determining total microbial biomass C [E. D. Vance, P. C. Brookes, D. S. Jenkinson, Soil Biol. Biochem. 19, 703 (1987)] and N [P. C. Brookes, A. Landman, G. Pruden, D. S. Jenkinson, ibid. 17, 837 (1985)].
24. Humus samples were collected to the entire humus depth from each of the four plots used for ground-layer vegetation determination (7) and were combined for each island. Total water-soluble phenolics were measured for aqueous extracts by use of Folin-Ciocalteu reagent [G. Marigo, Analytica 2, 106 (1973)]; nitrogen was determined by micro-Kjeldahl analysis. Microbial basal respiration and substrate-induced respiration (a relative measure of active microbial biomass) [J. P. E. Anderson and K. H. Domsch, Soil Biol. Biochem. 10, 215 (1978)] were determined through the use of a modified form of infrared gas analysis [D. A. Wardle, Funct. Ecol. 7, 346 (1993)]. The fumigation-extraction approach was used for determining total microbial biomass C [E. D. Vance, P. C. Brookes, D. S. Jenkinson, Soil Biol. Biochem. 19, 703 (1987)] and N [P. C. Brookes, A. Landman, G. Pruden, D. S. Jenkinson, ibid. 17, 837 (1985)].
25. Humus samples were collected to the entire humus depth from each of the four plots used for ground-layer vegetation determination (7) and were combined for each island. Total water-soluble phenolics were measured for aqueous extracts by use of Folin-Ciocalteu reagent [G. Marigo, Analytica 2, 106 (1973)]; nitrogen was determined by micro-Kjeldahl analysis. Microbial basal respiration and substrate-induced respiration (a relative measure of active microbial biomass) [J. P. E. Anderson and K. H. Domsch, Soil Biol. Biochem. 10, 215 (1978)] were determined through the use of a modified form of infrared gas analysis [D. A. Wardle, Funct. Ecol. 7, 346 (1993)]. The fumigation-extraction approach was used for determining total microbial biomass C [E. D. Vance, P. C. Brookes, D. S. Jenkinson, Soil Biol. Biochem. 19, 703 (1987)] and N [P. C. Brookes, A. Landman, G. Pruden, D. S. Jenkinson, ibid. 17, 837 (1985)].
26. Humus samples were collected to the entire humus depth from each of the four plots used for ground-layer vegetation determination (7) and were combined for each island. Total water-soluble phenolics were measured for aqueous extracts by use of Folin-Ciocalteu reagent [G. Marigo, Analytica 2, 106 (1973)]; nitrogen was determined by micro-Kjeldahl analysis. Microbial basal respiration and substrate-induced respiration (a relative measure of active microbial biomass) [J. P. E. Anderson and K. H. Domsch, Soil Biol. Biochem. 10, 215 (1978)] were determined through the use of a modified form of infrared gas analysis [D. A. Wardle, Funct. Ecol. 7, 346 (1993)]. The fumigation-extraction approach was used for determining total microbial biomass C [E. D. Vance, P. C. Brookes, D. S. Jenkinson, Soil Biol. Biochem. 19, 703 (1987)] and N [P. C. Brookes, A. Landman, G. Pruden, D. S. Jenkinson, ibid. 17, 837 (1985)].
27. Humus samples were collected to the entire humus depth from each of the four plots used for ground-layer vegetation determination (7) and were combined for each island. Total water-soluble phenolics were measured for aqueous extracts by use of Folin-Ciocalteu reagent [G. Marigo, Analytica 2, 106 (1973)]; nitrogen was determined by micro-Kjeldahl analysis. Microbial basal respiration and substrate-induced respiration (a relative measure of active microbial biomass) [J. P. E. Anderson and K. H. Domsch, Soil Biol. Biochem. 10, 215 (1978)] were determined through the use of a modified form of infrared gas analysis [D. A. Wardle, Funct. Ecol. 7, 346 (1993)]. The fumigation-extraction approach was used for determining total microbial biomass C [E. D. Vance, P. C. Brookes, D. S. Jenkinson, Soil Biol. Biochem. 19, 703 (1987)] and N [P. C. Brookes, A. Landman, G. Pruden, D. S. Jenkinson, ibid. 17, 837 (1985)].
28. Litter decomposition was determined by use of litter bags. We placed 10 litter bags on each island (approximately 10 m from the shore) on 22 to 27 June 1995; each contained 0.5 g air-dried litter of V. myrtillus. Five of these bags were placed on the humus surface, while the other five were buried at a depth of 8 cm. These were retrieved on 18 to 25 June 1996, and the litter weight remaining and litter N concentration were determined, the latter through micro-Kjeldahl analysis.
29. D. A. Wardle and P. Lavelle, in Driven by Nature - Plant Litter Quality and Decomposition, G. Cadisch and K. E. Giller, Eds. (CAB International, Wallingford, UK, 1997), pp. 107-124; M. J. Swift, O. W. Heal, J. M. Anderson, Decomposition in Terrestrial Ecosystems (Univ. of California Press, Berkeley, CA, 1979).
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32. R. W. Wein, in The Role of Fire in Northern Circumpolar Ecosystems, R. W. Wein and D. A. MacLean, Eds. (Wiley, Chichester, UK, 1983), pp. 81-95; C. O. Tamm, Nitrogen in Terrestrial Ecosystems (Springer, Berlin, 1991); K. Van Cleve, F. S. Chapin III, C. T. Dyrness, L. A. Viereck, Bioscience 41, 78 (1991); O. Zackrisson, M.-C. Nilsson, D. A. Wardle, Oikos 77, 10 (1996).
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41. J. P. Grime, Plant Strategies and Vegetation Processes (Wiley, Chichester, UK, 1979); M. A. Huston, Biological Diversity. The Coexistence of Species in Changing Landscapes (Cambridge Univ. Press, Cambridge, 1994).
42. J. P. Grime, Plant Strategies and Vegetation Processes (Wiley, Chichester, UK, 1979); M. A. Huston, Biological Diversity. The Coexistence of Species in Changing Landscapes (Cambridge Univ. Press, Cambridge, 1994).
43. Nearly all studies that have claimed to identify positive effects of species diversity on ecosystem function involve relatively short-term experiments in which species richness of live plants has been manipulated. However, most plant productivity eventually enters the decomposer subsystem as litter, where it has important long-term "afterlife effects" [S. Findlay, M. Carreiro, V. Krischic, C. J. Jones, Ecol. Appl. 6, 269 (1996)]. Those studies that have explicitly investigated effects of species diversity of litter, or of organisms associated with litter breakdown, on ecosystem processes have failed to find simple cause-effect relationships [O. Andrén, M. Clarholm, J. Bengtsson, in The Significance and Regulation of Soil Biodiversity, H. P. Collins, G. P. Robertson, M. J. Klug, Eds. (Kluwer, Dordrecht, Netherlands, 1995), pp. 141-151; D. A. Wardle, K. I. Bonner, K. S Nicholson, Oikos 79, 247 (1997)]. Our study represents a situation in which ecosystem properties are largely regulated by the decomposer subsystem in the long-term perspective.
44. Nearly all studies that have claimed to identify positive effects of species diversity on ecosystem function involve relatively short-term experiments in which species richness of live plants has been manipulated. However, most plant productivity eventually enters the decomposer subsystem as litter, where it has important long-term "afterlife effects" [S. Findlay, M. Carreiro, V. Krischic, C. J. Jones, Ecol. Appl. 6, 269 (1996)]. Those studies that have explicitly investigated effects of species diversity of litter, or of organisms associated with litter breakdown, on ecosystem processes have failed to find simple cause-effect relationships [O. Andrén, M. Clarholm, J. Bengtsson, in The Significance and Regulation of Soil Biodiversity, H. P. Collins, G. P. Robertson, M. J. Klug, Eds. (Kluwer, Dordrecht, Netherlands, 1995), pp. 141-151; D. A. Wardle, K. I. Bonner, K. S Nicholson, Oikos 79, 247 (1997)]. Our study represents a situation in which ecosystem properties are largely regulated by the decomposer subsystem in the long-term perspective.
45. Nearly all studies that have claimed to identify positive effects of species diversity on ecosystem function involve relatively short-term experiments in which species richness of live plants has been manipulated. However, most plant productivity eventually enters the decomposer subsystem as litter, where it has important long-term "afterlife effects" [S. Findlay, M. Carreiro, V. Krischic, C. J. Jones, Ecol. Appl. 6, 269 (1996)]. Those studies that have explicitly investigated effects of species diversity of litter, or of organisms associated with litter breakdown, on ecosystem processes have failed to find simple cause-effect relationships [O. Andrén, M. Clarholm, J. Bengtsson, in The Significance and Regulation of Soil Biodiversity, H. P. Collins, G. P. Robertson, M. J. Klug, Eds. (Kluwer, Dordrecht, Netherlands, 1995), pp. 141-151; D. A. Wardle, K. I. Bonner, K. S Nicholson, Oikos 79, 247 (1997)]. Our study represents a situation in which ecosystem properties are largely regulated by the decomposer subsystem in the long-term perspective.
46. A recent critique [M. A. Huston, Oecologia, 110, 449 (1997)] of those experimental studies claiming evidence for cause-effect relationships between species diversity and ecosystem properties (18) proposes that the observed trends can be explained in terms of "hidden treatments" affecting plant productivity independent of species diversity, and which are manifested through problems with experimental design, inappropriate interpretation of data, and incorrect application of statistical techniques. If this is the case, then presumably cause-effect relationships between diversity and ecosystem properties could have been detected in those studies even if they did not exist.
47. Plant communities are not random assemblages of species [J. B. Wilson and S. H. Roxburgh, Oikos 69, 267 (1994)], and plant species that dominate in low-diversity situations probably have very different ecophysiological traits from those that dominate in high-diversity situations. These traits regulate the ecological performance of plant species, including their participation in biotic interactions [P. D. Coley, J. P. Bryant, F. S. Chapin III, Science 230, 895 (1985); J. P. Grime et al., Oikos 79, 259 (1997)] and responses to disturbances [C. W. MacGillivray et al., Funct. Ecol. 9, 640 (1995)]; this is, in turn, likely to have important effects at the ecosystem level of resolution [P. B. Raich, M. B. Walters, D. S. Ellsworth, Ecol. Monogr. 62, 365 (1992)], including ecosystem function.
48. Plant communities are not random assemblages of species [J. B. Wilson and S. H. Roxburgh, Oikos 69, 267 (1994)], and plant species that dominate in low-diversity situations probably have very different ecophysiological traits from those that dominate in high-diversity situations. These traits regulate the ecological performance of plant species, including their participation in biotic interactions [P. D. Coley, J. P. Bryant, F. S. Chapin III, Science 230, 895 (1985); J. P. Grime et al., Oikos 79, 259 (1997)] and responses to disturbances [C. W. MacGillivray et al., Funct. Ecol. 9, 640 (1995)]; this is, in turn, likely to have important effects at the ecosystem level of resolution [P. B. Raich, M. B. Walters, D. S. Ellsworth, Ecol. Monogr. 62, 365 (1992)], including ecosystem function.
49. Plant communities are not random assemblages of species [J. B. Wilson and S. H. Roxburgh, Oikos 69, 267 (1994)], and plant species that dominate in low-diversity situations probably have very different ecophysiological traits from those that dominate in high-diversity situations. These traits regulate the ecological performance of plant species, including their participation in biotic interactions [P. D. Coley, J. P. Bryant, F. S. Chapin III, Science 230, 895 (1985); J. P. Grime et al., Oikos 79, 259 (1997)] and responses to disturbances [C. W. MacGillivray et al., Funct. Ecol. 9, 640 (1995)]; this is, in turn, likely to have important effects at the ecosystem level of resolution [P. B. Raich, M. B. Walters, D. S. Ellsworth, Ecol. Monogr. 62, 365 (1992)], including ecosystem function.
50. Plant communities are not random assemblages of species [J. B. Wilson and S. H. Roxburgh, Oikos 69, 267 (1994)], and plant species that dominate in low-diversity situations probably have very different ecophysiological traits from those that dominate in high-diversity situations. These traits regulate the ecological performance of plant species, including their participation in biotic interactions [P. D. Coley, J. P. Bryant, F. S. Chapin III, Science 230, 895 (1985); J. P. Grime et al., Oikos 79, 259 (1997)] and responses to disturbances [C. W. MacGillivray et al., Funct. Ecol. 9, 640 (1995)]; this is, in turn, likely to have important effects at the ecosystem level of resolution [P. B. Raich, M. B. Walters, D. S. Ellsworth, Ecol. Monogr. 62, 365 (1992)], including ecosystem function.
51. Plant communities are not random assemblages of species [J. B. Wilson and S. H. Roxburgh, Oikos 69, 267 (1994)], and plant species that dominate in low-diversity situations probably have very different ecophysiological traits from those that dominate in high-diversity situations. These traits regulate the ecological performance of plant species, including their participation in biotic interactions [P. D. Coley, J. P. Bryant, F. S. Chapin III, Science 230, 895 (1985); J. P. Grime et al., Oikos 79, 259 (1997)] and responses to disturbances [C. W. MacGillivray et al., Funct. Ecol. 9, 640 (1995)]; this is, in turn, likely to have important effects at the ecosystem level of resolution [P. B. Raich, M. B. Walters, D. S. Ellsworth, Ecol. Monogr. 62, 365 (1992)], including ecosystem function.
52. 14C datings, and A. Sundberg for field assistance.