Restauración ecológica de taludes de carretera en ambiente mediterráneo: comunidades de suelo y efectos del manejo
- Autores: Sandra Magro Ruiz
- Directores de la Tesis: Miguel Ángel Casado González (dir. tes.)
- Lectura: En la Universidad de Alcalá ( España ) en 2014
- Idioma: español
- Tribunal Calificador de la Tesis: Fernando Valladares Ros (presid.), Antonio Gómez Sal (secret.), Berta Martínez Jáuregui (voc.), Stefano Mocali (voc.), Adrián Escudero Alcántara (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TESEO
- Resumen
- español
Esta Tesis Doctoral estudia el desarrollo de las comunidades biológicas de taludes en diferentes carreteras de la comunidad de Madrid, así como los efectos de distintas técnicas de manejo sobre la composición, la diversidad y los procesos ecológicos responsables de la funcionalidad ecosistémica.
Tras el Capítulo I, de introducción, el Capítulo II analiza las comunidades de microartrópodos edáficos en terraplenes de carretera y los factores que determinan la variación en la composición. Además se evalúa la funcionalidad de suelo utilizando estas comunidades de invertebrados como indicador. Los resultados mostraron la comunidad de artrópodos varió en el espacio y en el tiempo desde comunidades caracterizadas por grupos primocolonizadores hacia otras dominadas por grupos sensibles a las perturbaciones y ligados a condiciones edáficas estables. Los cambios en la composición de debieron a variaciones en el contenido de material orgánica, arcillas y la humedad del suelo. Además estos suelos presentaron una funcionalidad, en algunos casos, comparable a la observada en sistemas Mediterráneos naturales.
El Capítulo III estudia las comunidades bacterianas de terraplenes de carretera así como los factores que determinan el desarrollo de estas comunidades y su organización espacial. Los resultados mostraron que estas comunidades de bacterianas poseen niveles de diversidad similares a los observados en otros suelos de origen antrópico. Estas comunidades están dominadas por grupos relacionados con la dinámica de la materia orgánica del suelo e indicadores de condiciones edáficas estables. La composición de las comunidades varió en relación al pH y la textura del suelo (contenido en arcillas y arenas).
El Capítulo IV evalúa el efecto de las siegas, la aplicación de fertilizantes y la adición experimental de biomasa sobre la composición y la diversidad de las bacterias del suelo, así como sobre la descomposición de la hojarasca y la disponibilidad de fases minerales de nitrógeno en el suelo. Los resultados mostraron que los ecosistemas de taludes de carretera son sensibles a las perturbaciones, lo que se traduce en una alternación rápida y significativa tanto de la estructura de las comunidades bacterianas como de los procesos ecológicos del suelo. La adición de biomasa y la aplicación de fertilizantes afectaron la diversidad y la composición de las comunidades de bacterias, mientras las siegas modificaron las condiciones físico-químicas de suelo y la tasa de descomposición de hojarasca.
Por último, en el Capítulo V, se analizan los procesos de primocolonización y ensamblaje de comunidades en un desmonte de carretea bajo el efecto de dos tratamientos diferentes: extendido de tierra vegetal y escarificación de la superficie del talud.
Los resultados mostraron que la tierra vegetal facilitó el ensamblaje temprano de la comunidad de plantas en desmontes mediante la mejora del contenido de nutrientes, el pH, la textura del suelo y la estabilidad de sustrato. Además, este tratamiento favoreció la emergencia de un mayor número de especies y la supervivencia de plántulas lo que se tradujo en mayores niveles de riqueza y cobertura en la comunidad durante los dos años siguientes a la construcción de la carretera.
- English
This Doctoral Thesis studies the development of biological communities in roadslopes from different highways in Madrid, as well as the effects of varying management techniques on the composition, diversity and ecological processes that are in turn responsible for ecosystem functionality. The goal is to provide new insight and knowhow to improve the effectiveness of efforts to assist the recovery and reassembly of soilborne biota, pedological processes, and resilient plant communities in these highly perturbed settings.
Following an introductory chapter, chapters II and III of the thesis analyze microarthropod and bacterial communities in heavily disturbed, anthropogenic soils, or Anthrosols in roadside embankments. These topics were given priority in the thesis in view of the importance of these soilborne communities in basic soil processes that underlie long term development and resilience of terrestrial ecosystems.
The next two chapters of the thesis describe the effects of different commonly used techniques employed to restore and maintain roadside ecosystems. Chapter IV evaluates the effect of mowing, fertilizing, and also experimental biomass addition, on the composition and diversity of soil bacterial communities, and on ecological processes such as rate of litter decomposition and soil nutrient availability, especially nitrates and ammonium. This experiment was carried out in the same four road embankments studied in Chapter III, in each of which experimental plots were set up. Results revealed that roadside ecosystems are sensitive in their response to treatments with both bacterial community structure and processes being rapidly and significantly affected. In particular, biomass addition and fertilization affected diversity and community composition, while mowing affected soil properties and litter decomposition. The fact that neither structure nor function was affected under the effect of a given treatment may be related to bacterial community attributes such as functional plasticity or redundancy.
Finally, Chapter V analyzes primary colonization and early community assembly in a south-oriented roadcut constructed in 2008 with slope greater than 40%, and where no management techniques were applied prior to our investigations. Abiotic filters such as water and nutrient availability, as well as the abundance of safe-sites for incoming seeds and propagules are the main constraints for plant community development in this kind of relatively harsh environment. Thus, in this chapter we describe an experiment in which we manipulated abiotic filters through the application of two different treatments, namely topsoil spreading and shallow tillage. We also set up control plots. Specifically, we analyzed the effect of treatments on seed availability (both soil seed bank and seed rain), seedling emergence, and seedling survival, as well as their effects on plant community attributes such as species richness and plant cover from 2010 to 2011.
Results showed that topsoil spreading facilitated early community assembly by improving soil properties in term of nutrients, pH, soil stability, and texture. Additionally, it favored the emergence of higher species and improved seedling survival, with further consequences on plant community richness and cover. This treatment also increased species recruitment over two years after road construction. Although there was no effect of tillage on seed availability, emergence, and survival, by the end of the experiment in 2011, it appeared that this treatment had increased plant species richness on the upper-slope zone.
In conclusion, our results showed that local soil conditions mainly related with organic carbon, pH, soil texture, and structure, were in large part responsible for the organization of soil communities and secondary succession processes on roadside sites undergoing restoration in our study area. Moreover, the application of conventional techniques oriented to overcome abiotic filters through the improvement of soil conditions did facilitate plant community reassembly. However, other management techniques that have been traditionally used in roadslope engineering and restoration, such as fertilization and mowing, significantly changed soil community structure, by increasing evenness and the abundance of certain groups related to low resource availability; they also affected functionality, by accelerating biodegradation of leaf litter. Given that changes in belowground communities may also induce changes in aboveground communities and vice versa, our results should be taken into account when selecting management techniques in order to ensure the maintenance of the ecosystem services that these ‘young’ or emerging ecosystems are expected to provide. Based on our results, conventional management techniques applied in roadside systems should be oriented to improve soil conditions after roadslope building, and aim to preserve and promote soil stability in the subsequent stages in order to ensure secondary succession processes and ecosystem development.
- español
