Abstract
Differences between growth forms in root responses to experimentally created heterogeneity have been documented in many greenhouse and plot studies, but not in natural vegetation. Here we examined the response of roots to experimental nutrient patches in undisturbed grassland and forest at the northern edge of the North American Great Plains. Forest vegetation increases the spatial heterogeneity of soil resources, and we tested for differences between forest and grassland roots in response to patches. Ten minirhizotrons (clear tubes, 5 cm diameter, 180 cm long) were installed in both grassland and forest 3 years before the experiment. Minirhizotrons ran horizontally 10 cm beneath the soil surface. Patches of available nitrogen (N) were created over the tubes, using three concentrations (0, 3, 15 g N m−2 yr−1) and two patch sizes (1␣and 10 cm2). Root images were collected beneath patches over the course of a growing season. Root length was significantly greater in grassland than forest at the start and end of the growing season, but did not respond to N patches. Root production was also significantly greater in grassland than forest, and was significantly greater (about 20%) in high-N patches than in unfertilized patches. This increase, however, did not differ between vegetation types. Turnover did not vary with any treatment, and patch size had no effect on any response variable. Overall, differences caused by experimental patches were much smaller than differences between habitats, and did not vary between habitats. Realistic levels of experimentally imposed hetereogeneity in established vegetation may not be much greater than background levels, and field vegetation has extant root systems which respond to patches via uptake instead of growth. Both mechanisms should contribute to less root proliferation in field experiments than in greenhouse experiments.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Anonymous 1992. Soil Landscapes of Canada: Saskatchewan. Centre for Land and Biological Resources Research, Research Branch, Agriculture Canada, Contribution 87–45, Publication 5243/B, Ottawa
Bardgett R.D., Streeter T.C., and Bol R. (2003). Soil microbes compete effectively with plants for organic-nitrogen inputs to temperate grasslands. Ecology 84: 1277–1287
Bilbrough C.J. and Caldwell M.M. (1995). The effects of shading and N status on root proliferation in nutrient patches by the perennial grass Agropyron desertorum in the field. Oecologia 103: 10–16
Bilbrough C.J. and Caldwell M.M. (1997). Exploitation of springtime ephemeral N pulses by six Great Basin plant species. Ecology 78: 231–243
Cui M.Y. and Caldwell M.M. (1997). A large ephemeral release of nitrogen upon wetting of dry soil and corresponding root responses in the field. Plant and Soil 19: 291–217
Day K.J., Hutchings M.J., and John E.A. (2003). The effects of spatial pattern on nutrient supply on yield structure and mortality in plant populations. Journal of Ecology 91: 541–553
Espeleta J.F. and Donovan L.A. (2002). Fine root demography and morphology in response to soil resources availability among xeric and mesic sandhill tree species. Functional Ecology 16: 113–121
Farley R.A. and Fitter A.H. (1999). Temporal and spatial variation in soil resources in a deciduous woodland. Journal of Ecology 87: 688–696
Fitter A.H., Hodge, A. and Robinson D. (2000). Plant response to patchy soils. In: Hutchings M.J., John E.A., and Stewart A.J.A. (eds) The ecological consequences of environmental heterogeneity. Blackwell Science, Oxford, pp. 71–90
Grime J.P. (1994). The role of plasticity in exploiting environmental heterogeneity. In: Caldwell M.M. and Pearcy R.W. (eds), Exploitation of environmental heterogeneity by plants. Academic Press, San Diego, pp. 1–19
Hodge A. (2004). The plastic plant: root responses to heterogeneous supplies of nutrients. New Phytologist 162: 9–24
Hutchings M.J., John E.A., and Stewart A.J.A. (2000). The ecological consequences of environmental heterogeneity. Blackwell Science, Oxford
Hutchings M.J., John E.A. and Wijesinghe D.K. (2003). Toward understanding the consequences of soil heterogeneity for plant populations and communities. Ecology 84: 2322–2334
Hutchings M.J., Wijesinghe D.K. and John E.A. (2000). The effects of heterogeneous nutrient supply on plant peformance: a survey of responses with special reference to clonal herbs. In: Hutchings M.J., John E.A., and Stewart A.J.A. (eds), The ecological consequences of environmental heterogeneity. Blackwell Science, Oxford, pp. 91–110
Ivans C.Y., Leffler A.J., Spaulding U., Stark J.M., Ryel R.J. and Caldwell M.M. (2003). Root responses and nitrogen acquisition by Artemisia tridentata and Agropyron desertorum following small summer rainfall events. Oecologia 134: 317–324
Jackson L.E., Schimel J.P. and Firestone M.K. (1989). Short-term partitioning of ammonium and nitrate between plants and microbes in an annual grassland. Soil Biology and Biogeochemistry 21: 409–415
Jackson R.B., Mooney H.A. and Schulze E.-D. (1997). A global budget for fine root biomass, surface area, and nutrient contents. Proceedings of the National Academy of Sciences USA 94: 7362–7366
Kleb H.R. and Wilson S.D. (1997). Vegetation effects on soil resource heterogeneity in prairie and forest. American Naturalist 150: 283–298
Köchy M. and Wilson S.D. (2001). Nitrogen deposition and forest expansion in the northern Great Plains. Journal of Ecology 89: 807–817
Pärtel M. and Wilson S.D. (2001). Root and leaf production mortality and longevity in response to soil heterogeneity. Functional Ecology 15: 748–753
Pärtel M. and Wilson S.D. (2002). Root dynamics and spatial pattern in prairie and forest. Ecology 83: 1199–1203
Peltzer D.A., Wilson S.D. and Gerry A.K. (1998). Competition intensity along a productivity gradient in a low-diversity grassland. American Naturalist 151: 465–476
Pregitzer K.S., Hendrick R.L. and Fogel R. 1993. The demography of fine roots in response to patches of water and nitrogen. New Phytologist. 125: 575–580
Schlesinger W.H., Raikes J.A., Hartley A.E. and Cross A.F. (1996). On the spatial pattern of soil nutrients in desert ecosystems. Ecology 77: 364–374
Schlesinger W.H., Reynolds J.F., Cunningham G.L., Huenneke L.F., Jarrell W.M., Virginia R.A. and Whitford W.G. (1990). Biological feedbacks in global desertification. Science 247: 1043–1048
Smilauerova M. (2001). Plant root response to heterogeneity of soil resources: Effects of nutrient patches, AM symbiosis, and species composition. Folia Geobotanica 36: 337–351
Tilman D. (1987). Secondary succession and the pattern of plant dominance along experimental nitrogen gradients. Ecological Monographs 57: 189–214
Wilson S.D. (1993). Belowground competition in forest and prairie. Oikos 68: 146–150
Wilson S.D. (2000). Heterogeneity, diversity, and scale in plant communities. In: Hutchings M.J., John E.A., and Stewart A.J.A. (eds), Ecological consequences of habitat heterogeneity. Blackwell Science, Oxford, pp. 53–69
Wilson S. D. and Kleb H. (1996). The influence of prairie and forest vegetation on soil moisture and available nitrogen. American Midland Naturalist 136: 222–231
Wilson S.D. and Tilman D. (2002). Quadratic variation in old-field species richness along gradients of disturbance and nitrogen. Ecology 83: 492–504
Acknowledgements
We thank M. Pärtel for tube installation, F. Gendron, J. Roy and D. Steinaker for field assistance, Saskatchewan Environment for permission to work at White Butte, D. Kolybaba for making the injection guide, M. Oesterheld, D. Steinaker and reviewers for comments on the manuscript, and NSERC for funding.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Moar, S.E.L., Wilson, S.D. Root responses to nutrient patches in grassland and forest. Plant Ecol 184, 157–162 (2006). https://doi.org/10.1007/s11258-005-9059-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11258-005-9059-2