Asunción Saldaña

What explains variation in the impacts of exotic plant invasions on the nitrogen cycle? A meta‐analysis

Exotic plant invasions can notably alter the nitrogen (N) cycle of ecosystems. However, there is large variation in the magnitude and direction of their impact that remains unexplained. We present a structured meta-analysis of 100 papers, covering 113 invasive plant species with 345 cases of invasion across the globe and reporting impacts on N cycle-related metrics. We aim to explain heterogeneity of impacts by considering methodological aspects, properties of the invaded site and phylogenetic and functional characteristics of the invaders and the natives. Overall, plant invasions increased N pools and accelerated fluxes, even when excluding N-fixing invaders. The impact on N pools depended mainly on functional differences and was greater when the invasive plants and the natives differed in N-fixation ability, plant height and plant/leaf habit. Furthermore, the impact on N fluxes was related mainly to climate, being greater under warm and moist conditions. Our findings show that more functionally distant invaders occurring in mild climates are causing the strongest alterations to the N cycle.

A multi-scale approach to identify invasion drivers and invaders’ future dynamics

Climate, land use and disturbances are well known drivers of invasion. However, their relative influence may change across spatial scales, where climate is expected to be the main filter at broad scales; land use is expected to have more influence at intermediate scales, and disturbance, at fine ones. Understanding the underlying processes that drive invasion patterns at different spatial scales is thus crucial to be able to anticipate the future spread of invaders. Here, we quantified the relative importance of climate, land use, and disturbance on the distribution of the invasive trees Ailanthus altissima and Robinia pseudoacacia, across three nested spatial scales, namely global, country (Spain) and riverbank (three riparian riverbanks). To do so, for each species and scale, we built ensemble species distribution models. We also identified their range filling and inferred the most suitable areas in Spain for them to spread. In general, our study confirms that climate acts as an initial coarse filter of species distribution, whilst both climate and land use were important at the country scale; at the riverbank scale human-mediated disturbances gained importance. However, R. pseudoacacia and A. altissima showed differences in their degree of range filling, where A. altissima has a higher potential for range expansion in the near future. Overall, the integration of different scales into invasion studies shows a great potential to enrich our understanding of species-habitat relationships, and to help anticipate their future dynamics.

Geopedology, a Tool for Soil-Geoform Pattern Analysis

The soilscape is the pedologic portion of the landscape. Soil scientists have examined it mainly within the field of soil landscape analysis, which traditionally regards a quantitative characterization of the spatial pattern and complexity of soil landscapes. Landscape ecology emphasizes the interaction between spatial pattern and ecological process, that is, the causes and consequences of spatial heterogeneity across a range of scales. The spatial component of the environment is crucial in any environmental analysis, and new approaches to soil patterns are necessary for appropriate landscape planning, management, and conservation. Therefore, the integration of landscape ecology fundamentals together with soil science principles can be helpful in this regard. This contribution deals with the principles of soilscape-pattern analysis complemented with the application of landscape ecology metrics. An example of the application of this type of analysis to the Jarama-Henares interfluve, central Spain, is presented.

Biodiversidad y edafodiversidad: cuestión de coincidencia?

El concepto de diversidad es de uso extendido en la literatura ecologica, si bien suele hacer referencia a los componentes biologicos exclusivamente. Lamentablemente, los efectos de las estructuras abioticas (por ejemplo los suelos) sobre las entidades bioticas de los ecosistemas, paisajes y biomas aun son materia de incipientes debates. En el presente articulo se explican las similitudes y diferencias entre los patrones espaciales y temporales de los analisis de biodiversidad y edafodiversidad descritos en la bibliografia. Actualmente, este tipo de analisis comparativos no supone excesivas dificultades debido a la creciente disponibilidad de bases de datos digitalizadas, tanto de suelos como de otros recursos naturales, a diferentes escalas. Las herramientas conceptuales y matematicas utilizadas en los estudios de edafodiversidad son las mismas que las empleadas por los ecologos en el ambito de la biodiversidad. Los resultados obtenidos hasta la fecha demuestran que los patrones espaciales de la edafodiversidad, detectados por los expertos de la ciencia del suelo, son similares a los obtenidos por los ecologos para una amplia gama de ecosistemas y condiciones ambientales.