<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gallardo, A.</style></author><author><style face="normal" font="default" size="100%">Rodriguez-Saucedo, J. J.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil nitrogen heterogeneity in a Dehesa ecosystem</style></title><secondary-title><style face="normal" font="default" size="100%">Plant and Soil</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Dehesa</style></keyword><keyword><style  face="normal" font="default" size="100%">geostatistics</style></keyword><keyword><style  face="normal" font="default" size="100%">grassland</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">soil heterogeneity</style></keyword><keyword><style  face="normal" font="default" size="100%">soil nitrogen</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2000///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/J1335844428H6726.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">222</style></volume><pages><style face="normal" font="default" size="100%">71 - 82</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">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 NHC 4 , NO 3 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 organicmatter and available NHC 4 was strongly influenced by tree canopy size. The semivariograms were adjusted to a spherical model, indicating a maximum NHC 4 variability at a certain distance from the tree crown diameter. The same was not the case for the spatial distribution of the soil NO 3 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.</style></abstract></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gallardo, A</style></author><author><style face="normal" font="default" size="100%">Rodriguez-Saucedo, J J</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil nitrogen heterogeneity in a Dehesa ecosystem</style></title><secondary-title><style face="normal" font="default" size="100%">Plant and Soil</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Dehesa</style></keyword><keyword><style  face="normal" font="default" size="100%">geostatistics</style></keyword><keyword><style  face="normal" font="default" size="100%">grassland</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus ilex</style></keyword><keyword><style  face="normal" font="default" size="100%">soil heterogeneity</style></keyword><keyword><style  face="normal" font="default" size="100%">soil nitrogen</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><volume><style face="normal" font="default" size="100%">222</style></volume><pages><style face="normal" font="default" size="100%">71-82</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">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 NHC 4 , NO 3 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 organicmatter and available NHC 4 was strongly influenced by tree canopy size. The semivariograms were adjusted to a spherical model, indicating a maximum NHC 4 variability at a certain distance from the tree crown diameter. The same was not the case for the spatial distribution of the soil NO 3 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.</style></abstract></record></records></xml>