<?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%">Casals, Pere</style></author><author><style face="normal" font="default" size="100%">Lopez-Sangil, Luis</style></author><author><style face="normal" font="default" size="100%">Carrara, Arnaud</style></author><author><style face="normal" font="default" size="100%">Gimeno, Cristina</style></author><author><style face="normal" font="default" size="100%">Nogués, Salvador</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Autotrophic and heterotrophic contributions to short-term soil CO 2 efflux following simulated summer precipitation pulses in a Mediterranean dehesa</style></title><secondary-title><style face="normal" font="default" size="100%">Global Biogeochemical Cycles</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">d13C</style></keyword><keyword><style  face="normal" font="default" size="100%">Drought</style></keyword><keyword><style  face="normal" font="default" size="100%">precipitation manipulation (voyant)</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil CO2 efflux</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2011</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2011///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.agu.org/pubs/crossref/2011/2010GB003973.shtml</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">25</style></volume><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Autotrophic and heterotrophic components of soil CO2 efflux may have differential responses to environmental factors, so estimating the relative contribution of each component during summer precipitation pulses is essential to predict C balance in soils experiencing regular drought conditions. As even small summer rains induced high instantaneous soil respiration rates in Mediterranean wooded grasslands, we hypothesized that standing dead mass, surface litter, and topsoil layer could play a dominant role in the initial flush of CO2 produced immediately after soil rewetting; in contrast, soil CO2 effluxes during drought periods should be mostly derived from tree root activity. In a grazed dehesa, we simulated four summer rain events and measured soil CO2 efflux discontinuously, estimating its d 13 C through a Keeling plot nonsteady state static chamber approach. In addition, we estimated litter contribution to soil CO2 efflux and extracted soil available C fractions (K2SO4‐extracted C and chloroform‐fumigated extracted C). The d 13 C‐CO2 from in‐tube incubated excised tree roots and rewetted root‐free soil was −25.0‰ (±0.2) and −28.4‰ (±0.2), respectively. Assuming those values as end‐members’ sources, the autotrophic component of soil CO2 efflux was dominant during the severe drought, whereas the heterotrophic contribution dominated from the very beginning of precipitation pulses. As standing dead mass and fresh litter contribution was low (&lt;25%) in the first day and negligible after, we concluded that CO2 efflux after rewetting was mostly derived from microbial mineralization of available soil organic C fractions.</style></abstract><issue><style face="normal" font="default" size="100%">3</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%">García, Luis V.</style></author><author><style face="normal" font="default" size="100%">Ramo, Cristina</style></author><author><style face="normal" font="default" size="100%">Aponte, Cristina</style></author><author><style face="normal" font="default" size="100%">Moreno, Adela</style></author><author><style face="normal" font="default" size="100%">Domínguez, María T.</style></author><author><style face="normal" font="default" size="100%">Gómez-Aparicio, LORENA</style></author><author><style face="normal" font="default" size="100%">Redondo, Ramón</style></author><author><style face="normal" font="default" size="100%">Marañón, Teodoro</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Protected wading bird species threaten relict centenarian cork oaks in a Mediterranean Biosphere Reserve: A conservation management conflict</style></title><secondary-title><style face="normal" font="default" size="100%">Biological Conservation</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Colonial waterbirds</style></keyword><keyword><style  face="normal" font="default" size="100%">d13C</style></keyword><keyword><style  face="normal" font="default" size="100%">d15N</style></keyword><keyword><style  face="normal" font="default" size="100%">Doñana</style></keyword><keyword><style  face="normal" font="default" size="100%">Heronry</style></keyword><keyword><style  face="normal" font="default" size="100%">Indirect effects</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus suber</style></keyword><keyword><style  face="normal" font="default" size="100%">Stable isotopes</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2011</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2011///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://linkinghub.elsevier.com/retrieve/pii/S000632071000474X</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">144</style></volume><pages><style face="normal" font="default" size="100%">764 - 771</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Conservation management conﬂicts frequently arise when an overpopulation of a protected organism has negative effects on other valuable elements in the same ecosystem. We studied the interactions between a colony of protected tree-nesting wading birds and a remnant population of centenarian cork oaks that was part of the formerly dominant forests in the Doñana Biological Reserve (SW Spain). A signiﬁcant increase in the tree mortality rates has been recorded in areas that are yearly inﬂuenced by the bird colony. We analysed a cohort of surviving trees using a gradient of nesting bird inﬂuence. Tree-nesting history, bird isotopic signature (d 15 N), tree health-related parameters (defoliation, d 13 C and leaf surface coverage by faeces) and several soil variables were evaluated. Bird inﬂuence was related to increased soil salinity. This increase correlated to increased water-use efﬁciency for the leaves and to crown defoliation, suggesting that the heavily occupied trees are under higher stress and in poorer health condition than the unoccupied ones. We tested structural equations models (SEM) that were based on hypothesised bird effects on the health of the trees. Soil-mediated effects of the nesting birds best explained the symptoms of the declining health of the trees, whereas the percent of leaves’ surface that was covered by faeces did not improve the ﬁtted SEM model. For the reserve’s managers, a challenging trade-off exists between preserving the relict trees, which have a high genetic diversity and a key ecological role in these savannah-like ecosystems, and maintaining the current nesting area for these protected, but expanding, wading birds.</style></abstract><issue><style face="normal" font="default" size="100%">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%">Unger, Stephan</style></author><author><style face="normal" font="default" size="100%">Máguas, Cristina</style></author><author><style face="normal" font="default" size="100%">Pereira, João S.</style></author><author><style face="normal" font="default" size="100%">David, Teresa S.</style></author><author><style face="normal" font="default" size="100%">Werner, Christiane</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The influence of precipitation pulses on soil respiration – Assessing the “Birch effect” by stable carbon isotopes</style></title><secondary-title><style face="normal" font="default" size="100%">Soil Biology and Biochemistry</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Birch effect</style></keyword><keyword><style  face="normal" font="default" size="100%">d13C</style></keyword><keyword><style  face="normal" font="default" size="100%">Irrigation experiment</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean woodland</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil respiration</style></keyword><keyword><style  face="normal" font="default" size="100%">Stable isotopes</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2010</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2010///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://linkinghub.elsevier.com/retrieve/pii/S0038071710002282</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">42</style></volume><pages><style face="normal" font="default" size="100%">1800 - 1810</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Sudden pulse-like events of rapidly increasing CO2-efﬂux occur in soils under seasonally dry climates in response to rewetting after drought. These occurrences, termed “Birch effect”, can have a marked inﬂuence on the ecosystem carbon balance. Current hypotheses indicate that the “Birch” pulse is caused by rapidly increased respiration and mineralization rates in response to changing moisture conditions but the underlying mechanisms are still unclear. Here, we present data from an experimental ﬁeld study using straight-forward stable isotope methodology to gather new insights into the processes induced by rewetting of dried soils and evaluate current hypotheses for the “Birch“-CO2-pulse. Two irrigation experiments were conducted on bare soil, root-free soil and intact vegetation during May and August 2005 in a semi-arid Mediterranean holm oak forest in southern Portugal. We continuously monitored CO2-ﬂuxes along with their isotopic compositions before, during and after the irrigation. d 13 C signatures of the ﬁrst CO2-efﬂux burst, occurring immediately after rewetting, ﬁt the hypothesis that the “Birch” pulse is caused by the rapid mineralization of either dead microbial biomass or osmoregulatory substances released by soil microorganisms in response to hypo-osmotic stress in order to avoid cell lyses. The response of soil CO2-efﬂux to rewetting was smaller under mild (May) than under severe drought (August) and isotopic compositions indicated a larger contribution of anaplerotic carbon uptake with increasing soil desiccation. Both length and severity of drought periods probably play a key role for the microbial response to the rewetting of soils and thus for ecosystem carbon sequestration.</style></abstract><issue><style face="normal" font="default" size="100%">10</style></issue><notes><style face="normal" font="default" size="100%">The following values have no corresponding Zotero field:&lt;br/&gt;publisher: Elsevier Ltd</style></notes></record></records></xml>