<?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, Antonio</style></author><author><style face="normal" font="default" size="100%">Paramá, Rocio</style></author><author><style face="normal" font="default" size="100%">Covelo, Felisa</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Differences between Soil Ammonium and Nitrate Spatial Pattern in Six Plant Communities. Simulated Effect on Plant Populations</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%">geostatistics</style></keyword><keyword><style  face="normal" font="default" size="100%">plant populations</style></keyword><keyword><style  face="normal" font="default" size="100%">root system size</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil</style></keyword><keyword><style  face="normal" font="default" size="100%">soil ammonium</style></keyword><keyword><style  face="normal" font="default" size="100%">soil heterogeneity</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil nitrate</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2005///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/10.1007/s11104-005-7013-7http://www.springerlink.com/index/10.1007/s11104-005-8552-7</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">279</style></volume><pages><style face="normal" font="default" size="100%">333 - 346</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Geostatistical descriptions of soil heterogeneity patterns for plant communities are abundant in literature, however there is no information on the consequences of diﬀerent soil spatial patterns on resource availability for plant populations. Conditional simulations on the spatial distribution of soil NH4–N and NO3–N were carried out in order to study the eﬀect of contrasted patch sizes on nitrogen availability for individuals with increasing root system size. The semivariogram range (an indication of patch size) for soil NH4–N and NO3–N in six plant communities was found to be very variable, and was higher for soil NH4– N than for soil NO3–N in each community. A positive correlation was observed between organic matter and NH4–N spatial ranges in the six plant communities, but not between NO3–N and NH4–N. Probabilities of ﬁnding a high soil N concentration within simulated plant populations depended on N patch size and root system size. Thus, a population taking up NH4 –N (higher spatial range values) would be more heterogeneous (i.e. Individuals will have diﬀering probabilities of ﬁnding a high soil N concentration) than the same population taking up NO3–N. Likewise, a seedling population taking up NH4–N or NO3–N would be more heterogeneous than a large tree population in the same area, where individuals would have similar probability of ﬁnding a high soil N concentration. These results showed that the spatial patch size of limiting resources has important consequences at the population level, since it determines the probability of ﬁnding a favourable site and therefore diﬀering performances of individuals within a population.</style></abstract><issue><style face="normal" font="default" size="100%">1-2</style></issue></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><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></records></xml>