Protected wading bird species threaten relict centenarian cork oaks in a Mediterranean Biosphere Reserve: A conservation management conflict |
| |
| Authors: | Luis V García Cristina Ramo Cristina Aponte Adela Moreno María T Domínguez Lorena Gómez-Aparicio Ramón Redondo Teodoro Marañón |
| |
| Institution: | aInstituto de Recursos Naturales y Agrobiología de Sevilla (CSIC), P.O. Box 1052, 41080 Sevilla, Spain;bEstación Biológica de Doñana (CSIC), Avda, Américo Vespucio s/n, 41092 Sevilla, Spain;cCentre for Ecology and Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, United Kingdom;dStable Isotope Laboratory, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain |
| |
| Abstract: | 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 (δ15N), tree health-related parameters (defoliation, δ13C 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. |
| |
| Keywords: | Quercus suber Stable isotopes δ15N δ13C Indirect effects Colonial waterbirds Heronry Doñ ana |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
