<?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%">Puerto, A</style></author><author><style face="normal" font="default" size="100%">Rico, M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Trees as a homogenizing factor of the herbaceous community structure and nutrient content in Mediterranean grasslands</style></title><secondary-title><style face="normal" font="default" size="100%">AGROCHIMICA</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><publisher><style face="normal" font="default" size="100%">IST CHIMICA AGRARIA</style></publisher><pub-location><style face="normal" font="default" size="100%">UNIV PISA VIA S MICHELE DEGLI SCALZI, 2 PISA 56100, ITALY</style></pub-location><volume><style face="normal" font="default" size="100%">40</style></volume><pages><style face="normal" font="default" size="100%">197-208</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The dehesa system consists of two subsystems, situated under the tree&lt;br/&gt;crowns and in the open spaces. They differ clearly in structure and&lt;br/&gt;function. The locations under trees are less variable, tending to&lt;br/&gt;greater similarity in species diversity, homogeneity, plant biomass,&lt;br/&gt;percentage of biomass of constituent families, and plant tissue nutrient&lt;br/&gt;content (N, P, K, Na, Ca and Mg), thus showing a certain independence in&lt;br/&gt;relation to the topographic situation. By contrast, the open spaces are&lt;br/&gt;very much influenced by the position they occupy in the slope gradients.&lt;br/&gt;It seems that homogenizing factors interact with others which tend to&lt;br/&gt;intensify heterogeneity. The less variable structures (under trees)&lt;br/&gt;could be interpreted as agents pumping fertility from the subsoil and&lt;br/&gt;presenting it for the use of herbaceous species. The most influenced&lt;br/&gt;structures are undoubtedly those situated under the tree crowns, but the&lt;br/&gt;whole system is influenced in this way. Consequently, topography and&lt;br/&gt;trees create a large number of habitats for herbaceous species,&lt;br/&gt;especially due to the overlapping of both factors. The harmony of the&lt;br/&gt;combination of the two factors gives stability to the system and has&lt;br/&gt;permitted its survival, without degradation, for many centuries.</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%">Puerto, A</style></author><author><style face="normal" font="default" size="100%">Rico, M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Differences between oligotrophic communities resulting from old-field succession in relation to bedrock</style></title><secondary-title><style face="normal" font="default" size="100%">Plant Ecology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">biomass</style></keyword><keyword><style  face="normal" font="default" size="100%">diversity</style></keyword><keyword><style  face="normal" font="default" size="100%">granite</style></keyword><keyword><style  face="normal" font="default" size="100%">mediterranean grasslands</style></keyword><keyword><style  face="normal" font="default" size="100%">slate</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1994</style></year></dates><volume><style face="normal" font="default" size="100%">113</style></volume><pages><style face="normal" font="default" size="100%">83-92</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Dehesa ecosystems on granite and on slate clearly differ in soil characteristics. Our aim was to find out whether floristic composition differed too. We selected an equal number of plots, on both granite and slate, in different successional stages of development and at various ages after field abandonment (the youngest 15-20 years). Plots with rock-outcrops, which had never been cultivated, were also included in the study. The results showed that floristic differences between granite and slate communities were not detectable in the younger successional stages. However, they showed up with time and on stabilized grasslands became significant. But on plots with rock-outcrops the differences were not observable. This was undoubtedly influenced by the peculiar features of these plots, characterised by poor arid soils and surface parent material. In fact they did not show significant differences in the analysed soil parameters either. Species diversity and biomass showed a similar pattern of differences to floristic composition. The highest species diversity was found on plots with lower biomass (the youngest ones). The lowest biomass in conjunction with quite low species diversity was found on plots with rock-outcrops, which again is consistent with their peculiar features.</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%">Puerto, A</style></author><author><style face="normal" font="default" size="100%">Rico, M</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">TREE CANOPY EFFECTS ON COMMUNITY STRUCTURE IN SLOPES OF MEDITERRANEAN RANGELANDS</style></title><secondary-title><style face="normal" font="default" size="100%">EKOLOGIA-BRATISLAVA</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">1994</style></year></dates><publisher><style face="normal" font="default" size="100%">SLOVAK ACADEMIC PRESS LTD</style></publisher><pub-location><style face="normal" font="default" size="100%">PO BOX 57, NAM SLOBODY 6, 810 05 BRATISLAVA, SLOVAKIA</style></pub-location><volume><style face="normal" font="default" size="100%">13</style></volume><pages><style face="normal" font="default" size="100%">161-171</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the dehesa systems there are considerable differences in community&lt;br/&gt;structure between grassland situated under trees and in the open spaces&lt;br/&gt;between them. This difference is superimposed by another one based on a&lt;br/&gt;trophic gradient in the form of sectors which develop along slopes.&lt;br/&gt;We studied these differences and our results show that:&lt;br/&gt;1. Community diversity decreased and spatial heterogeneity increased&lt;br/&gt;from the higher to the lower sectors of the slope gradient.&lt;br/&gt;2. These trends were significantly smaller under trees.&lt;br/&gt;3. In the open spaces there was a contrast in community structure; fine&lt;br/&gt;grain in high sectors and coarse grain in the lower ones.&lt;br/&gt;4. Community heterogeneity in pares of consecutive sectors of the slope&lt;br/&gt;gradient was lower under trees than in the open spaces.&lt;br/&gt;That means that trees act as a homogenizing factor on slopes,&lt;br/&gt;maintaining a basic herbaceous structure which tends to be similar in&lt;br/&gt;various sectors. Steady conditions are thus created, which influence&lt;br/&gt;both the same sector of different slopes as well as various sectors of&lt;br/&gt;each of the slopes. The alternation of one relatively uniform structure&lt;br/&gt;(under trees) with another much more variable one (open spaces) is&lt;br/&gt;considered as essential for the functioning of the system; just as it&lt;br/&gt;has developed following the traditional land-use practices in the area.</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%">Puerto Martín, A</style></author><author><style face="normal" font="default" size="100%">Puerto, A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">FITOMASA SUBTERRÁNEA Y AÉREA EN PASTOS DE DEHESA</style></title><secondary-title><style face="normal" font="default" size="100%">Pastos</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">España</style></keyword><keyword><style  face="normal" font="default" size="100%">fitomasa</style></keyword><keyword><style  face="normal" font="default" size="100%">Grasslands</style></keyword><keyword><style  face="normal" font="default" size="100%">influencia del arbolado</style></keyword><keyword><style  face="normal" font="default" size="100%">ladera</style></keyword><keyword><style  face="normal" font="default" size="100%">pastos</style></keyword><keyword><style  face="normal" font="default" size="100%">phytomass</style></keyword><keyword><style  face="normal" font="default" size="100%">Salamanca</style></keyword><keyword><style  face="normal" font="default" size="100%">Salamanca (Spain)</style></keyword><keyword><style  face="normal" font="default" size="100%">slope</style></keyword><keyword><style  face="normal" font="default" size="100%">tree canopy ¡nfluence</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1992</style></year></dates><volume><style face="normal" font="default" size="100%">22</style></volume><pages><style face="normal" font="default" size="100%">3-19</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A study has been conducted on the spatial variations undergone by root biomass, aerial phytomass and the root/shoot ratio in grassland communities (dehesa systems). These variations are governed by the prevailing gradients: topographic and the effect of the tree canopy. The greatest biomass, both underground and aerial, and the lowest root/shoot ratio are usually found in the more fertile sites (deposition sector of slope) and shaded áreas (under the crowns of the trees), in contrast to the results of some researchs performed in cultures or at the laboratory. In the case of natural or semi-natural groupings of herba- ceous species in severe environments, the adaptive responses of each species appear to predomínate over any generalized type of response. Key</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%">Rico, M</style></author><author><style face="normal" font="default" size="100%">Puerto, A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Estructura básica generada por el arbolado en pastos semiáridos (ecosistemas de dehesa)</style></title><secondary-title><style face="normal" font="default" size="100%">Pastos</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Canopy effect</style></keyword><keyword><style  face="normal" font="default" size="100%">Dominance</style></keyword><keyword><style  face="normal" font="default" size="100%">exclusivity</style></keyword><keyword><style  face="normal" font="default" size="100%">floristic richness</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">19</style></volume><pages><style face="normal" font="default" size="100%">13-28</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A study was made of the effect on spatial distribution of species from semiarid grasslands. The basic structural aspects considered were: num- ber of species, exclusive species, and dominant species. Comparisons were made among the sites: under crown, canopy edge, and open grassland; in all three cases the N-S orientation was taken into account. The reduced number of species below the crown contrasts with the much higher number found at the canopy edge. However, in the latter case there were almost no exclusive or dominant species present since, owing to its intermedíate position, the most contrasted ecological charac- teristics correspond to the location receiving the most direct influence of the tree canopy and to the open spaces. Additionally, the similarity between the locations under the crown and the N exposure of the edge, and between the open spaces and S exposure of the edge leads to different results, according to whether orientation is considered or not</style></abstract></record></records></xml>