Scale-dependent relationships between the spatial distribution of a limiting resource and plant species diversity in an African grassland ecosystem
- 433 Downloads
- 51 Citations
Abstract
One cornerstone of ecological theory is that nutrient availability limits the number of species that can inhabit a community. However, the relationship between the spatial distribution of limiting nutrients and species diversity is not well established because there is no single scale appropriate for measuring variation in resource distribution. Instead, the correct scale for analyzing resource variation depends on the range of species sizes within the community. To quantify the relationship between nutrient distribution and plant species diversity, we measured NO3 - distribution and plant species diversity in 16 paired, modified Whittaker grassland plots in Serengeti National Park, Tanzania. Semivariograms were used to quantify the spatial structure of NO3 - from scales of 0.4–26 m. Plant species diversity (Shannon-Weiner diversity index; H ′) was quantified in 1-m2 plots, while plant species richness was measured at multiple spatial scales between 1 and 1,000 m2. Small-scale variation in NO3 - (<0.4 m) was positively correlated with 1-m2 H ′, while 1,000-m2 species richness was a log-normal function of average NO3 - patch size. Nine of the 16 grassland plots had a fractal (self-similar across scales) NO3 - spatial distribution; of the nine fractal plots, five were adjacent to plots that had a non-fractal distribution of NO3 -. This finding offered the unique opportunity to test predictions of Ritchie and Olff (1999): when the spatial distribution of limiting resources is fractal, communities should display a left-skewed log-size distribution and a log-normal relationship between net primary production and species richness. These predictions were supported by comparisons of plant size distributions and biomass-richness relationships in paired plots, one with a fractal and one with a non-fractal distribution of NO3 -. In addition, fractal plots had greater large-scale richness than paired non-fractal plots (1,0–1000 m2), but neither species diversity (H ′) nor richness was significantly different at small scales (1 m2). This result is most likely explained by differences in the scale of resource variation among plots: fractal and non-fractal plots had equivalent NO3 - variation at small scales but differed in NO3 - variation at large scales (as measured by the fractal dimension). We propose that small-scale variation in NO3 - is largely due to the direct effects of plants on soil, while patterns of species richness at large scales is controlled by the patch size and fractal dimension of NO3 - in the landscape. This study provides an important empirical step in understanding the relationship between the spatial distribution of resources and patterns of species diversity across multiple spatial scales.
Keywords
Spatial scale Fractal geometry Nitrogen Serengeti National Park Soil heterogeneityNotes
Acknowledgements
Special thanks to E. M. Peter for help in the field and M. M. McNaughton for help in the laboratory. D. E. O’Connell, L. L. Wolf, and B. Schmedicke improved the manuscripts with editorial comments. Thanks to M. Coughenour for providing a field vehicle and the Serengeti Monitoring Program for providing rainfall data. This research was funded by NSF grant DEB-9903845 to S. J. McNaughton and an NSF doctoral fellowship to T. M. Anderson.
References
- Abrams PA (1983) The theory of limiting similarity. Annu Rev Ecol Syst 14:359–376CrossRefGoogle Scholar
- Adler PB, Raff DA, Lauenroth WK (2001) The effect of grazing on the spatial heterogeneity of vegetation. Oecologia 128:465–479CrossRefGoogle Scholar
- Augustine DJ, Frank DA (2001) Effects of migratory grazers on spatial heterogeneity of soil nitrogen properties in a grassland ecosystem. Ecology 82:3149–3162Google Scholar
- Ball MC, Egerton JJG, Lutze JL, Gutschick VP, Cunningham RB (2002) Mechanisms of competition: thermal inhibition of tree seedling growth by grass. Oecologia 133:120–130CrossRefGoogle Scholar
- Barnes GR, Bransby DI, Tainton NM (1987) Fertilization of southern tall grassveld of Natal: effects on botanical composition and utilization under grazing. J Grassl Soc S Afr 4:63–67Google Scholar
- Binkley D (1984) Ion exchange resin bags: factors affecting estimates of nitrogen availability. Soil Sci Soc Am J 48:1181–1184Google Scholar
- Brown JH (1995) Macroecology. The University of Chicago Press, Chicago, Ill.Google Scholar
- Burke IC (1989) Control of nitrogen mineralization in a sagebrush steppe landscape. Ecology 70:1115–1126Google Scholar
- Burke IC, Lauenroth WK, Riggle R, Brannen P, Madigan B, Beard S (1999) Spatial variability of soil properties in the shortgrass steppe: the relative importance of topography, grazing, microsite, and plant species in controlling spatial patterns. Ecosystems 2:422–438CrossRefGoogle Scholar
- Burnett MR, August PV, Brown JH Jr, Killingbeck KT (1998) The influence of geomorphological heterogeneity on biodiversity. I. A patch-scale perspective. Biol Conserv 12:363–370CrossRefGoogle Scholar
- Casper BB, Jackson RB (1997) Plant competition underground. Annu Rev Ecol Syst 28:545–570Google Scholar
- Chesson P (1994) Multispecies competition in variable environments. Theor Popul Biol 45:227–276CrossRefGoogle Scholar
- Chesson P (2000) Mechanisms of maintenance of species diversity. Annu Rev Ecol Syst 31:343–366Google Scholar
- Connolly SR, Roughgarden J (1999) Theory of marine communities: competition, predation, and recruitment-dependent interaction strength. Ecol Monogr 69:277–296Google Scholar
- Crawley MJ, Harral JE (2001) Scale dependence in plant biodiversity. Science 291:864–868CrossRefPubMedGoogle Scholar
- Currie DJ (1991) Energy and large-scale patterns of animal and plant species richness. Am Nat 137:27–49CrossRefGoogle Scholar
- Dixon MD, Turner MG, Jin C (2002) Riparian tree seedling distribution on Wisconsin river sandbars: controls at different scales. Ecol Monogr 72:465–485Google Scholar
- Fisk MC, Schmidt SK, Seastedt TR (1998) Topographic patterns of above- and belowground production and nitrogen cycling in alpine tundra. Ecology 79:2253–2266Google Scholar
- Frank DA, McNaughton SJ, Tracy BF (1998) The ecology of the earth’s grazing ecosystems. Bioscience 48:513–521Google Scholar
- Fransen B, Blijjenberg J, de Kroon H (1999) Root morphological and physiological plasticity of perennial grass species and the exploitation of spatial and temporal heterogeneous nutrient patches. Plant Soil 211:179–189CrossRefGoogle Scholar
- Gibson DJ (1986) Spatial and temporal heterogeneity in soil nutrient supply measured using in situ ion-exchange resin bags. Plant Soil 96:445–450Google Scholar
- Gough L, Osenberg CW, Gross KL, Collins SL (2000) Fertilization effects on species density and primary productivity in herbaceous plant communities. Oikos 89:428–439Google Scholar
- Groffman PM, Eagan P, Sullivan WM, and Lemunyon JL (1996) Grass species and soil type effects on microbial biomass and activity. Plant Soil 183:61–67Google Scholar
- Gross KL, Peters A, Pregitzer KS (1993) Fine root growth and demographic responses to nutrient patches in four old-field species. Oecologia 95:61–64Google Scholar
- Gross KL, Pregitzer KS, Burton AJ (1995) Spatial variation in nitrogen availability in three successional plant communities. J Ecol 83:357–367Google Scholar
- Halverson JJ, Smith JL, Bolton Jr H, Rossie RE (1995) Evaluating shrub-associated spatial patterns of soil properties in a shrub-steppe ecosystem using multiple-variable geostatistics. Soil Sci Soc Am J 59:1476–1487Google Scholar
- Hamilton EW III, Frank DA (2001) Can plants stimulate soil microbes and their own nutrient supply? Evidence from a grazing tolerant grass. Ecology 82:2397–2402Google Scholar
- Harner RF, Harper KT (1976) The role of area, heterogeneity, and favorability in plant species diversity of pinyon-juniper ecosystems. Ecology 57:1254–1263Google Scholar
- Hobbie SE (1992) Effects of plant species on nutrient cycling. Trends Ecol Evol 7:336–339CrossRefGoogle Scholar
- Hooper DU, Vitousek PM (1997) The effect of plant composition and diversity on ecosystem processes. Science 277:1302–1305Google Scholar
- Hutchinson TF, Boerner RE, Iverson LR, Sutherland S, Kennedy Sutherland E (1999) Landscape patterns of understory composition and richness across a moisture and nitrogen mineralization gradient in Ohio (U.S.A.) Quercus forests. Plant Ecol 144:177–189CrossRefGoogle Scholar
- Jackson RB, Caldwell MM (1993a) Geostatistical patterns of soil heterogeneity around individual perennial plants. J Ecol 81:682–692Google Scholar
- Jackson RB, Caldwell MM (1993b) The scale of nutrient heterogeneity around individual plants and its quantification with geostatistics. Ecology 74:612–614Google Scholar
- Jackson RB, Manwaring JH, Caldwell CC (1990) Rapid physiological adjustment of roots to localized soil enrichment. Nature 344:58–60Google Scholar
- Jager Tj (1982) Soils of the Serengeti woodlands, Tanzania. Agricultural research reports no. 912. Pudoc, Wageningen, pp 1–239Google Scholar
- Jumpponen A, Hoegberg P, Huss-Danell K, Mulder CP (2002) Interspecific and spatial differences in nitrogen uptake in monocultures and two-species mixtures in north European grasslands. Funct Ecol 16:454–461CrossRefGoogle Scholar
- Kleb HR, Wilson SD (1997) Vegetation effects on soil resource heterogeneity in prairie and forest soils. Am Nat 150:283–298CrossRefGoogle Scholar
- Lawton JH, Brown VK (1993) Redundancy in ecosysytems. In: Schulze E-D, Mooney HA (eds) Biodiversity and ecosystem function. Springer, Berlin Heidelberg New York, pp 255–270Google Scholar
- McKane RB, Johnson LC, Shaver GR, Nadelhoffer KJ, Rastetter EB, Fry B, Giblin AE, Kielland K, Kwiatkowski BL, Laundre JA, Murray G (2002) Resource-based niches provide a basis for plant species diversity and dominance in arctic tundra. Nature 412:68–71CrossRefGoogle Scholar
- McNaughton SJ (1983) Serengeti grassland ecology: the role of composite environmental factors and contingency in community organization. Ecol Monogr 53:291–320Google Scholar
- McNaughton SJ (1985) Ecology of a grazing ecosystem: the Serengeti. Ecol Monogr 55:259–294Google Scholar
- McNaughton SJ (1990) Mineral nutrition and seasonal movements of African migratory ungulates. Nature 345:613–615Google Scholar
- McNaughton SJ (1994) Conservation goals and the configuration of biodiversity. In: Forey PL, Humphries CJ, Vane-Wright RI (eds) Systematics and conservation evaluation, volume no. 50. Clarendon Press, Oxford, pp 41–62Google Scholar
- McNaughton SJ, Banyikwa FF, McNaughton MM (1998) Root biomass and productivity in a grazing ecosystem: the Serengeti. Ecology 79:587–592Google Scholar
- Mittelbach GG, Steiner CF, Scheiner SM, Gross KL, Reynolds HL, Waide RB, Willig MR, Dodson SI, Gough L (2001) What is the observed relationship between species richness and productivity? Ecology 82:2381–2396Google Scholar
- Morse DR, Lawton JH, Dodson MM, Williamson MH (1985) Fractal dimension of vegetation and the distribution of arthropod body lengths. Nature 314:731–732Google Scholar
- Nichols WF, Killingbeck KT, August PV (1998) The influence of geomorphological heterogeneity on biodiversity. II. A landscape perspective. Conserv Biol 12:371–379CrossRefGoogle Scholar
- Norton-Griffiths M, Herlocker D, Pennycuick L (1975) The patterns of rainfall in the Serengeti ecosystem, Tanzania. East Afr Wildl J 13:347–374Google Scholar
- Pacala SW, Tilman D (1994) Limiting similarity in mechanistic and spatial models of plant competition in heterogeneous environments. Am Nat 143:222–257CrossRefGoogle Scholar
- Pake CE, Venable DL (1996) Seed banks in desert annuals: implications for persistence and coexistence in variable environments. Ecology 77:1427–1435Google Scholar
- Palmer MW (1992) The coexistence of species in fractal landscapes. Am Nat 139:375–397CrossRefGoogle Scholar
- Ricklefs RE, Schluter D (1993) Species diversity in ecological communities: historical and geographical perspectives. University of Chicago Press, Chicago, Ill.Google Scholar
- Ritchie ME, Olff H (1999) Spatial scaling laws yield a synthetic theory of biodiversity. Nature 400:557–560CrossRefPubMedGoogle Scholar
- Robertson GP, Gross KL (1994) Assessing the heterogeneity of belowground resources: quantifying pattern and scale. In: Caldwell MM, Pearcy RW (eds) Exploitation of environmental heterogeneity by plants. Academic Press, San Diego, Calif., pp 237–253Google Scholar
- Robertson GP, Huston MA, Evans FC, Tiedje JM (1988) Spatial variability in a successional plant community: patterns of nitrogen availability. Ecology 69:1517–1524Google Scholar
- Robertson GP, Crum JR, Ellis BG (1993) The spatial variability of soil resources following long-term disturbance. Oecologia 96:451–456Google Scholar
- Robertson GP, Klingensmith KM, Klug MJ, Paul EA, Crum JR, Ellis BG (1997) Soil resources, microbial activity, and primary production across an agricultural ecosystem. Ecol Appl 7:158–170Google Scholar
- Rosales J, Petts G, Knabb-Vispo C (2001) Ecological gradients within riparian forests of the lower Caura River, Venezuela. Plant Ecol 152:101–118CrossRefGoogle Scholar
- Schimel D, Stillwell MA, Woodmansee RG (1985) Biogeochemistry of C, N, and P in a soil catena of the shortgrass steppe. Ecology 66:276–282Google Scholar
- Schlesinger WH, Raikes JA, Hartley AE, Cross AF (1996) On the spatial pattern of soil nutrients in desert ecosystems. Ecology 77:364–374Google Scholar
- Schneider DC (2001) The rise of scale in ecology. Bioscience 51:545–553Google Scholar
- Seastedt TR, Vaccaro L (2001) Plant species richness, productivity, and nitrogen and phosphorus limitations across a snowpack gradient in alpine tundra, Colorado, USA. Arct Antarct Alp Res 33:100–106Google Scholar
- Shmida A, Wilson MV (1985) Biological determinants of species diversity. J Biogeogr 12:1–20Google Scholar
- Stohlgren TJ, Falkner MB, Schell LD (1995) A modified-Whittaker nested vegetation sampling method. Vegetatio 117:113–121Google Scholar
- Sugihara G, May RM (1990) Applications of fractals in ecology. Trends Ecol Evol 5:79–86CrossRefGoogle Scholar
- Tilman D (1982) Resource competition and community structure. (Monographs in population biology, vol 17) Princeton University Press, Princeton, N.J., pp 1–296Google Scholar
- Tilman D (1984) Plant dominance along an experimental nutrient gradient. Ecology 65:1445–1453Google Scholar
- Tilman D (1988) Plant strategies and the dynamics and structure of plant communities. (Monographs in population biology, vol 26) Princeton University Press, Princeton, N.J., pp 1–359Google Scholar
- Tilman D (1994) Competition and biodiversity in spatially structured habitats. Ecology 75:2–16Google Scholar
- Tilman D, Pacala S (1993) The maintenance of species richness in plant communities. In: Ricklefs RE, Schluter D (eds) Species diversity in ecological communities: historical and geographical perspectives. University of Chicago Press, Chicago, Ill., pp 13–25Google Scholar
- Towne EG (2000) Prairie vegetation and soil nutrient responses to ungulate carcasses. Oecologia 122:232–239Google Scholar
- Van Der Krift TAJ, Berendse F (2001) The effect of plant species on soil nitrogen mineralization. J Ecol 89:555–561CrossRefGoogle Scholar
- Vincent TLS, Scheel D, Brown JS, Vincent TL (1996) Trade-offs and coexistence in consumer resource models: Its all depends on what and where you eat. Am Nat 148:1039–1058CrossRefGoogle Scholar
- Vitousek PM, Howarth RW (1991) Nitrogen limitation on land and sea: how can it occur? Biogeochemistry 13:87–115Google Scholar
- Walker BH (1992) Biodiversity and ecological redundancy. Conserv Biol 6:18–23CrossRefGoogle Scholar
- Wedin DA, Tilman D (1990) Species effects on nitrogen cycling: a test with perennial grasses. Oecologia 84:433–441Google Scholar
- Whittaker RH, Niering WA (1975) Vegetation of the Santa Catalina Mountains, Arizona. V. Biomass, production and diversity along an elevational gradient. Ecology 56:771–790Google Scholar
- Wiens JA (1989) Spatial scaling in ecology. Funct Ecol 3:385–397Google Scholar
- Wit HA de (1978) Soils and grassland types of the Serengeti plain (Tanzania). Dissertation. University of Wageningen, WageningenGoogle Scholar
- Yavitt JB, Wright SJ (1996) Temporal patterns of soil nutrients in a Panamanian moist forest revealed by ion-exchange resin and experimental irrigation. Plant Soil 183:117–129Google Scholar