Abstract
The Dehesa are savannah-like ecosystems that occupy extensive areas in the mediterranean regions of Southern Spain and Portugal. The changes in the soil nitrogen (N) potential mineralisation rate, microbial biomass-N and available mineral N in soils were studied over 1 year in a Dehesa ecosystem, in the SW of Spain. The temporal variability of soil samples was compared by using the coefficient of variation of samples taken on a monthly basis. Spatial variability of the soil samples was measured by comparing the variograms generated with geostatistical techniques. The potential N mineralisation reached a maximum in the spring and summer samples, and a minimum in the autumn. However, the soil NH4 +, NO3 - and microbial biomass-N showed maximum levels in winter, compared with minimum levels in the spring and summer. The potential mineralisation rate showed a higher temporal variability in the samples taken under tree canopies, due to highest maximum and similar minimum levels reached during the sampling period. The potential mineralisation rate, microbial biomass-N and soil mineral N were higher under the tree canopies than in the open grassland. The spatial distribution of the soil organic matter and available NH4 + was strongly influenced by tree canopy size. The semivariograms were adjusted to a spherical model, indicating a maximum NH4 + variability at a certain distance from the tree crown diameter. The same was not the case for the spatial distribution of the soil NO3 - from the tree crown. Our results indicate that the tree component of a Dehesa ecosystem is a major influence in the spatial and temporal heterogeneity of soils.
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Belsky A J, Amundson R G, Duxbury J M, Riha S J and Mwonga S W1989 The effects of trees on their physical, chemical, and biological environments in a semiarid savannah in Kenya. J. Appl. Ecol. 26, 1005–1024.
Belsky A J, Mwonga S M, Amundson R G, Duxbury J M and Ali A R 1993 Comparative effects of isolated trees on their undercanopy environments in high-low-rainfall savannahs. J. Appl. Ecol. 30, 143–155.
Belsky A J 1994 Influences of trees of savannah productivity: test of shade, nutrients and tree-grass competition. Ecology 75, 922–932.
Boettcher S E and Kalisz P J 1990 Single-free influence on soil properties in the mountains of eastern Kentucky. Ecology 71, 1365–1372.
Bottner P 1985 Response of microbial biomass to alternate moist and dry conditions with 14C and 15N-labelled plant material. Soil Biol. Biochem. 17, 329–337.
Breman H and Kessler J J 1995 Woody plants in agro-ecosystems of semiarid regions. Springer-Verlag, Berlin. 340 pp.
Brookes P C, Landman A, Pruden G and Jenkinson D S 1985 Chloroform fumigation and the release of soil nitrogen: a rapid direct extraction method to measure microbial biomass nitrogen in soil. Soil Biol. Biochem. 17, 837–842.
Cabrera M L and Beare M H 1993 Alkaline persulphate oxidation for determining total nitrogen in microbial biomass extracts. Soil Sci. Soc. Am. J. 57, 1007–1012.
Chapin F S III 1980 The mineral nutrition of wild plants. Annu. Rev. Ecol. Syst. 11, 233–260.
Daget 1977 Le bioclimat méditerranéen: analyse des formes climatiques par le système d'Emberger. Vegetatio 34, 87–103.
Davidson E A, Stark JM and Firestone MK 1990 Microbial production and consumption of nitrate in an annual grassland. Ecology 71, 1968–1975.
D'Elia C F, Steudler P A and Corwin N 1977 Determination of total nitrogen in aqueous samples using persulphate digestion. Limmnol. Oceanogr. 22, 760–764.
Escudero A 1985 Efecto de arboles aislados sobre las propiedadesquímicas del suelo. Revue d'Ecologie et de Biologie du Sol 22, 149–159.
Fernández-Alés R, Ortega F and Laffarga J 1993 Strategies in mediterranean grassland annuals in relation with stress and disturbance. J. Veg. Sci. 4, 313–322.
Flowers T H and Bremner J M 1991 A rapid dichromate procedure for routine estimation of total nitrogen in soils. Commu. Soil Sci. Plant Anal. 22, 1409–1416.
Gallardo A and Merino J 1992 Nitrogen immobilization in leaf litter at two Mediterranean ecosystems of SW Spain. Biogeochemistry 15, 213–228.
Garwood E A and Tyson K C 1973 Losses of nitrogen and other plant nutrients to drainage from soil under grass. J. Agr. Sci. 80, 303–312.
Gonçalves J L M and Carlyle J C 1994 Modelling the influence of moisture and temperature on net nitrogen mineralisation in a forested sandy soil. Soil Biol. Biochem. 26, 1557–1564.
Harrison A F, Taylor K, Hatton J C and Howard D M 1994 Role of nitrogen in herbage production by Agrostis-Festuca hill grassland. J. Appl. Ecol. 31, 351–360.
Haynes R J 1986 The decomposition process: mineralisation, immobilisation, humus formation and degradation. In Mineral Nitrogen in the Plant-Soil System. Ed. RJ Haynes. pp 52–126. Academic Press, London.
Hook P B, Burke I C and Lauenroth WK 1991 Heterogeneity of soil and plant N and C associated with individual plants and openings in North American shortgrass steppe. Plant Soil 138, 247–256.
Hossain A K M A, Khanna P K and Field J B 1993 Acid-peroxide digestion procedure for determining total nitrogen in chloroformfumigated and non-fumigated soil extracts. Soil Biol. Biochem. 25, 967–969.
Isechei A O and Muoghalu J I 1992 The effects of tree canopy covers on soil fertility in a Nigerian savannah. J. Trop. Ecol. 8, 329–338.
Jackson R B and Caldwell M M 1993 The scale of nutrient heterogeneity around individual plants and its quantification with geostatistics. Ecology 74, 612–614.
Jackson L E, Strauss R B, Firestone M K and Bartolome J W 1988 Plant and soil nitrogen dynamics in California annual grassland. Plant Soil 110, 9–17.
Jackson L E, Strauss R B, Firestone M K and Bartolome J W 1990 Influence of tree canopies on grassland productivity and nitrogen dynamics in deciduous oak savannah. Agr. Ecosyst. Environ. 32, 89–105.
Joffre R 1990 Plant and soil nitrogen dynamics in Mediterranean grasslands: a comparison of annual and perennial grasses. Oecologia 85, 142–149.
Joffre R and Rambal S 1988 Soil water improvement by trees in the rangelands of southern Spain. Oecologia Plantarum 9, 405–422.
Joffre R and Rambal S 1993 How tree cover influences the water balance of Mediterranean Rangelands. Ecology 74, 570–582.
Joffre R, Vacher J, De los LLanos C and Long G 1988 The dehesa: an agrosilvopastoral system of the Mediterranean region with special reference to the Sierra Morena area of Spain. Agroforest Syst. 6, 71–96.
Kandeler E and Bohm K E 1996 Temporal dynamics of microbial biomass, xylanase activity, N mineralisation and potential nitrification in different tillage systems. Appl. Soil Ecol. 4, 181–191.
Kieft T L, Soroker E and Firestone M K 1987 Microbial biomass response to a rapid increase in water potential when dry soil is wetted. Soil Biol. Biochem. 19, 119–126.
Kitanidis P K 1997 Introduction to geostatistics: applications to hydrogeology. Cambridge University Press, Cambridge, UK. 249 p.
Krige D F 1981 Lognormal-de Wijsian geostatistics for ore evaluation. South African Institute of Mining and Metallurgical Monograph Series. Geostatistics I. South African Institute of Mining and Metallurgical. Johannesburg, South Africa.
Kuo S 1996 Phosphorus. In Methods of Soil Analysis. Part 3. Chemical methods. SSSA Book Series no. 5.
Mazzarino M J, Oliva J, Nuñez A N G and Buffa E 1991 Nitrogen mineralisation and soil fertility in the dry Chaco ecosystem (Argentina). Soil Sci. Soc. Am. J. 55, 515–522.
Mordelet P, Abbadie L and Menaut J C 1993 Effects of tree clumps on soil characteristics in a humid savannah of West Africa (Lamto, Cote d'Ivoire). Plant Soil 153, 103–111.
Nelson D W and Sommers L E 1996 Total carbon, organic carbon and organic matter. In Methods of Soil Analysis. Part 3. Chemical methods. SSSA Book Series no. 5.
Pannatier Y 1996 Variowin. Software for spatial data analysis in 2D. Springer-Verlag, New York.
Paul E A and Clark F E 1989 Soil Microbiology and Biochemistry. Academic Press, San Diego.
Pimm S L 1991 The Balance of Nature. University of Chicago Press, Chicago.
Reynolds H L, Hungate B A, Chapin III F S and D'Antonio C M 1997 Soil heterogeneity and plant competition in an annual grassland. Ecology 78, 2076–2090.
Rhoades C C 1997 Single-tree influences on soil properties in agroforestry: lessons from natural forest and savannah ecosystems. Agroforest. Syst. 35, 71–94.
Robertson G P 1987 Geostatistics in ecology: interpolating with known variance. Ecology 68, 744–748.
Robertson G P, Klingensmith K M, Klug M J, Paul E A, Crum J R and Ellis B G 1997 Soil resources, microbial activity and primary production across an agricultural ecosystem. Ecol. Appl. 7, 158–170.
Rossi R E, Mulla D J, Journel A G and Franz E H 1992 Geostatistical tools for modelling and interpreting ecological spatial dependence. Ecol. Monogr. 62, 277–314.
Santruckova H 1992 Microbial biomass, activity and soil respiration in relation to secondary succession. Pedobiología 36, 341–350.
Schlesinger W H and Pilmanis A M 1998 Plant-soil interactions in deserts. Biogeochemistry 42, 169–187.
Schlesinger W H, Raikes J A, Hartley A E, Cross A F 1996 On the spatial pattern of soil nutrients in desert ecosystems. Ecology 77, 364–374.
Scholes R J and Archer S R 1997 Tree-grass interactions in savannahs. Annu. Rev. Ecol. Syst. 28, 517–544.
Singh J S, Raghubanshi A S, Singh R S and Srivastava S C 1989 Microbial biomass acts as a source of plant nutrients in dry tropical forest and savannah. Nature 338, 499–500.
Srivastava S C and Singh J S 1989 Effects of cultivation onmicrobial carbon and nitrogen in a dry tropical forest soil. Biol. Fert. Soils 8, 343–348.
Tilman D 1996 Biodiversity: Population vs. ecosystem stability. Ecology 77, 97–107.
Trangmar B B, Yost R S and Uehara G 1985 Application of geostatistics to spatial studies of soil properties. Adv. Agron. 38, 45–95.
Vaughn C E, Center D M and Jones M B 1986 Seasonal fluctuations in nutrient availability in some northern California annual range soils. Soil Sci. 141, 43–51.
Wardle D A 1998 Controls of temporal variability of the soil microbial biomass: a global-scale synthesis. Soil Biol. Biochem. 30, 1627–1637.
Wardle D A 1992 A comparative assessment of factors which influence microbial biomass carbon and nitrogen levels in soils. Biol. Rev. 67, 321–358.
Whitehead D C 1995 Grassland nitrogen. CAB International, Wallingford, UK. 397 p.
Yeomans J C and Bremner JM 1988 A rapid and precise method for routine determination of organic carbon in soil. Commun. Soil Sci. Plant Anal. 19, 1467–1476.
Zinke P J 1962 The patterns of influence of individual forest trees on soil properties. Ecology 43, 130–133.
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Gallardo, A., Rodríguez-Saucedo, J., Covelo, F. et al. Soil nitrogen heterogeneity in a Dehesa ecosystem. Plant and Soil 222, 71–82 (2000). https://doi.org/10.1023/A:1004725927358
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DOI: https://doi.org/10.1023/A:1004725927358