Temporal dynamics of soil spatial heterogeneity in sagebrush-wheatgrass steppe during a growing season

Variability in five soil resources essential for plant growth (NH4+, NO3-, P, K and soil moisture) was quantified using univariate, multivariate and geostatistical techniques in a sagebrush-grass steppe ecosystem at three times (early April, June and August) during the 1994 growing season. Samples were collected every meter in a 10 × 10-m ‘macrogrid’, every 20 cm within nested 1 × 1-m ‘minigrids’, and every 3 cm within additionally nested 15 × 15-cm ‘microgrids’. Strong autocorrelation for all variables in the three sample periods was only found over distances less than 2 m, indicating that patches of high internal uniformity in this soil were smaller than 2 m during the growing season. Differences in semivariograms between sample periods were most pronounced for NO3-, NH4+ and soil moisture, variables that we consider to primarily limit plant growth in this system. The distance over which sample points were autocorrelated for NO3-, NH4+ and soil moisture increased from April to June. In contrast P and K, which are relatively more abundant at the study site, exhibited relatively constant semivariance patterns over the three sample periods.Weak correlation was found between samples collected in the three sample periods for N and soil moisture indicating that the spatial pattern of these limiting resources changed between sample periods. However, P and K had highly significant correlations (p<0.00001) among sample periods, indicating that the distributional patterns of these relatively more abundant resources remained rather constant. There were strong negative correlations between P and K and distance from the base of shrubs for all sample times (p<0.001), indicating an increase in P and K close to shrubs. Similar strong negative correlations were not found between distance from the shrubs and levels of NH4+, NO3-, or soil moisture, nor for any soil variable and distance from perennial tussock grasses. Changes in patterns of nutrient and soil moisture variability within a growing season suggest that not only must plants acquire soil resources that vary in time and space, but that they may also have to adjust to different scales of resource patchiness during the season.

[1]  Richard E. Rossi,et al.  GEOSTATISTICAL ANALYSIS OF RESOURCE ISLANDS UNDER ARTEMISIA TRIDENTATA IN THE SHRUB-STEPPE , 1994 .

[2]  D. DeAngelis,et al.  Competition and Coexistence: The Effects of Resource Transport and Supply Rates , 1994, The American Naturalist.

[3]  D. Tilman.  Plant Strategies and the Dynamics and Structure of Plant Communities. (MPB-26), Volume 26 , 1988 .

[4]  I. Burke,et al.  INTERACTIONS BETWEEN INDIVIDUAL PLANT SPECIES AND SOIL NUTRIENT STATUS IN SHORTGRASS STEPPE , 1995 .

[5]  T. M. Burgess,et al.  Sampling and bulking strategies for estimating soil properties in small regions , 1984 .

[6]  J. P. Riley,et al.  A modified single solution method for the determination of phosphate in natural waters , 1962 .

[7]  David J. Mulla,et al.  Geostatistical Tools for Modeling and Interpreting Ecological Spatial Dependence , 1992 .

[8]  R. Tibshirani,et al.  An introduction to the bootstrap , 1993 .

[9]  R. Webster,et al.  Optimal interpolation and isarithmic mapping of soil properties. II. Block kriging. , 1980 .

[10]  M. Caldwell,et al.  Competition for Phosphorus: Differential Uptake from Dual-Isotope—Labeled Soil Interspaces Between Shrub and Grass , 1985, Science.

[11]  J. R. Sims,et al.  SIMPLIFIED COLORIMETRIC DETERMINATION OF SOIL ORGANIC MATTER , 1971 .

[12]  J. Halvorson,et al.  Evaluating shrub-associated spatial patterns of soil properties in a shrub-steppe ecosystem using multiple-variable geostatistics , 1995 .

[13]  R. B. Jackson,et al.  The Scale of Nutrient Heterogeneity Around Individual Plants and Its Quantification with Geostatistics , 1993 .

[14]  M. Caldwell,et al.  Hydraulic lift: Ecological implications of water efflux from roots , 1991 .

[15]  R. B. Jackson,et al.  Shading and the capture of localized soil nutrients: nutrient contents, carbohydrates, and root uptake kinetics of a perennial tussock grass , 1992, Oecologia.

[16]  M. Caldwell,et al.  Basin Hydrology and Plant Root Systems , 1990 .

[17]  P. B. Tinker,et al.  Solute Movement in the Soil-Root System. , 1978 .

[18]  J. Antonovics,et al.  COMPETITION AND COEXISTENCE IN A NORTH , 1981 .

[19]  K. Gross,et al.  Spatial variation in nitrogen availability in three successional plant communities , 1995 .

[20]  E. Davidson,et al.  Processes Regulating Soil Emissions of NO and N^2O in a Seasonally Dry Tropical Forest , 1993 .

[21]  R. Misra.  Plant strategies and vegetation processes: J.P. Grime, J. Wiley, 1979, xi + 222 pp., 63 figures, 21 tables and 35 plates, £11.50. ISBN 0-471-99695-5 , 1981 .

[22]  N. West,et al.  Plant-Induced Soil Chemical Patterns in Some Shrub-Dominated Semi-Desert Ecosystems of Utah , 1975 .

[23]  I. Burke,et al.  Heterogeneity of soil and plant N and C associated with individual plants and openings in North American shortgrass steppe , 1991, Plant and Soil.

[24]  J. Halvorson,et al.  Spatial relationships of soil microbial biomass and C and N Mineralization in a semi-arid shrub-steppe ecosystem , 1994 .

[25]  Robert B. Jackson,et al.  Geostatistical Patterns of Soil Heterogeneity Around Individual Perennial Plants , 1993 .

[26]  H. Mooney,et al.  Physiological Ecology of North American Plant Communities , 1987, Springer Netherlands.

[27]  Bruce T. Milne,et al.  Spatial Aggregation and Neutral Models in Fractal Landscapes , 1992, The American Naturalist.

[28]  Michael Edward Hohn,et al.  An Introduction to Applied Geostatistics: by Edward H. Isaaks and R. Mohan Srivastava, 1989, Oxford University Press, New York, 561 p., ISBN 0-19-505012-6, ISBN 0-19-505013-4 (paperback), $55.00 cloth, $35.00 paper (US) , 1991 .

[29]  J. P. Grime,et al.  Plant Strategies and Vegetation Processes. , 1980 .

[30]  J F Reynolds,et al.  Biological Feedbacks in Global Desertification , 1990, Science.

[31]  Arthur S. Lieberman,et al.  Landscape Ecology , 1994, Springer New York.

[32]  Jonathan Cohen.  Statistical Methods in Soil and Land Resource Survey , 1992 .

[33]  J. Stark.  Causes of Soil Nutrient Heterogeneity at Different Scales , 1994 .