Tíscar Espigares

Trends and fluctuations in species abundance and richness in Mediterranean annual pastures

Floristic data collected from permanent plots dur- ing 14 consecutive years are used to model the frequency of the 62 most abundant species in relation to post-ploughing succession, topography and rainfall in annual Mediterranean grasslands located in a Quercus rotundifolia dehesa. The interannual dynamics of species richness are also analysed. From 1980 to 1993, presence/absence data of grassland spe- cies were noted in five 20 cm × 20 cm permanent quadrats placed at random in 1980 in 14 permanent plots on a south- facing slope along the topographic gradient. Weekly autumn rainfall data over the 14 years were analysed using a profile attributes index and Hybrid Multidimensional Scaling to ar- range the years according to their autumn rainfall pattern. Generalized Linear Models were used to fit the species rich- ness and species frequency according to topographic position, age since the last ploughing episode, total rainfall in the growing season and autumn rainfall pattern using a forward stepwise procedure. The richness model includes all of these variables, and reveals a relatively high goodness-of-fit (71 %). The fact that the meteorological factors play a key role in modelling richness forces us to include them if we wish to use richness as an indicator of the degree of disturbance in these highly fluctuating annual pastures. Models of species dynam- ics show that although roughly 33 % of the species have a successional behaviour, the majority are more dependent on temporal heterogeneity associated with rainfall or spatial het- erogeneity linked to the topographic gradient.

Spatial segregation of plant species caused by Retama sphaerocarpa influence in a Mediterranean pasture: a perspective from the soil seed bank

Retama sphaerocarpa is a leguminous shrub whose important role in the semi-arid regions of south-eastern Spain has already been assessed: shrub canopies reduce light intensity, and thus evapotranspiration; also their extensive radical system take water and nutrients from great volumes of soil, concentrating them in the understorey. Consequently, subcanopy vegetation benefits from these facilitation processes, increasing its productivity. However, these shrublands have been rarely studied at a broader scale, i.e. as a savannah-like system composed of a variable number of shrubs scattered in a herbaceous matrix. As the microenvironmental conditions associated to the understorey are rather different from those of the open spaces among shrubs, species composition of the herbaceous matrix is expected to change accordingly. Thus, R. sphaerocarpa would be an important and still unknown source of spatial heterogeneity to the system. Our main purpose was to evaluate, through the soil seed bank, the heterogeneity in the herbaceous community induced by this shrub species. Soil samples were collected around adult shrubs from three positions relative to the canopy: near the centre of the shrubs, at the edge of the understorey, and completely outside the canopy. Floristic composition was evaluated by germination under greenhouse conditions. The results show that each position has a different floristic composition, characterised by a group of different species. The herbaceous species associated with the external position have functional traits which enable them to resist water stress and herbivore pressure, such as hairs, CAM metabolism, early flowering, horizontal growth or tiny stature. The species associated with the central position lack those traits, and are more competitive in more mesic environments, rich in nitrogen. The lowest number of seedlings and species was found in the internal position, suggesting that in our study the facilitation process may have less importance for community dynamics due to less stressful environmental conditions.

Seed predation in a Mediterranean pasture: can ants modify the floristic composition of soil seed banks?

La mirmecofauna juega un papel fundamental sobre la dinamica de la vegetacion, especialmente en zonas de caracter arido o semiarido, donde puede llegar a consumir una elevada proporcion de las semillas producidas, condicionando la composicion floristica de la vegetacion. Aunque algunos trabajos han analizado la influencia de la depredacion de semillas por hormigas sobre la densidad de la vegetacion en ecosistemas de pastizal del centro peninsular, hasta el momento no hay estudios sobre como afecta este factor a la composicion floristica de los bancos de semillas. Se ha estudiado el efecto de la exclusion de hormigas sobre la composicion floristica del banco de semillas de un pastizal mediterraneo de la provincia de Madrid. En las parcelas sometidas a exclusion de hormigas, la densidad de semillas de Cerastium semidecandrum fue casi cuatro veces mayor que en las parcelas con actividad de la mirmecofauna. Dada la elevada heterogeneidad espacial, las diferencias en composicion floristica encontradas en el banco se han corregido utilizando la composicion de la comunidad de primavera, fuente directa del banco de semillas recogido en otono. Los resultados ponen de manifiesto un efecto significativo de la exclusion de hormigas sobre la composicion floristica del banco de semillas del pastizal

Aridity Induces Nonlinear Effects of Human Disturbance on Precipitation-Use Efficiency of Iberian Woodlands

The effects of ecosystem degradation are pervasive worldwide and increasingly concerning under the present context of global changes in climate and land use. Theoretical studies and empirical evidence increasingly suggest that drylands are particularly prone to develop nonlinear functional changes in response to climate variations and human disturbance. Precipitation-use efficiency (PUE) represents the ratio of vegetation production to precipitation and provides a tool for evaluating human and climate impacts on landscape functionality. Holm oak (Quercus ilex) woodlands are one of the most conspicuous dry forest ecosystems in the western Mediterranean basin and present a variety of degraded states, due to their long history of human use. We studied the response of Iberian holm oak woodlands to human disturbance along an aridity gradient (that is, semi-arid, dry-transition and sub-humid conditions) using PUE estimations from enhanced vegetation index (EVI) observations of the Moderate-Resolution Imaging Spectroradiometer (MODIS). Our results indicated that PUE decreased linearly with disturbance intensity in sub-humid holm oak woodlands, but showed accelerated, nonlinear reductions with increased disturbance intensity in semi-arid and dry-transition holm oak sites. The impact of disturbance on PUE was larger for dry years than for wet years, and these differences increased with aridity from sub-humid to dry-transition and semi-arid holm oak woodlands. Therefore, aridity may also interact with ecosystem degradation in holm oak woodlands by reducing the landscape ability to buffer large changes in vegetation production caused by climate variability.

Estudio, gestión, conservación y restauración de ecosistemas ante el cambio global: 1º Jornadas FORECO en la Universidad de Alcalá

Bonache, J., de Mingo-Sancho, G., Serrada, J., Amengual, P., Perales, J., Martinez, R., Rodado, S., Albornos, E. 2016. Long-term monitoring and evaluation in Spanish National Parks Network. Ecosistemas 25(1): 31-48. Doi.: 10.7818/ECOS.2016.25-1.05 The Spanish National Parks Network, consisting of a selection of natural spaces containing a representative sample of the main existing natural systems in Spain, is a very appropriate setting for research and long-term monitoring, in which the rules protects and promotes the improvement of knowledge and its application to management. In this regard, the National Parks Agency develops, in collaboration with the Autonomous Communities and with specific Scientific advise, a Research Program and a Monitoring and Evaluation Plan of the National Parks Network, latter having programs of ecological, sociological monitoring and functional. The article briefly explains the various monitoring initiatives underway, with examples of outcomes in each: mapping of natural systems, productivity monitoring through remote sensing, monitoring plant health, common bird monitoring, studies of social perception etc. Future prospects and areas for improvement of long-term monitoring in the National Parks Network are explained taking into account the synergies with the LTER Network, which is useful for monitoring in National Parks, especially concerning the application of comparable protocols and information management.