António Albuquerque

Structural and functional responses of riparian vegetation to human disturbance: performance and spatial scale-dependence

Successful protection, enhancement and management of surface inland waters require bioassessment and monitoring of ecological quality, as recognized by the Water Framework Directive (WFD; EU/2000/60). In the present paper, we aimed at assessing the response to disturbance of structural and functional components of the riparian ecosystem in order to develop a plant-based index of biotic integrity (Riparian Vegetation index, RVI). Further, the implications of Mediterranean conditions and the spatial scale dependency in the index performance and its component metrics were investigated and discussed. Aquatic and bankside plant species were sampled at more than 400 sites of Portuguese rivers, in Spring-Summer of 2004 and 2005. Over 300 plant attributes were pre-screened to select 32 candidate metrics. Both single stressors and composite stressor indices were used in this study. Two spatial scale-approaches were evaluated: the Local River Type - LRT - which follows the Portuguese river typology, and the Regional River Type - RRT -, which clusters the LRT into North and South types. Compo- sition (e.g. cover and number of alien and endemic species) and functional metrics associated with life cycle and reproduction (e.g. numbers of perennial species), or with trophic status (e.g. proportion of nitrophyllous species) were the most responsive to disturbance across types. Overall, the RVI displayed a reliable response to disturbance; although the local approach has a higher discriminatory effi ciency, the macro scale approach had a more consistent response to multifaceted human disturbances and a more robust performance, essential for environmental-decision making. Results substantiate the hypothesis that plant-based indices of integrity are scale-dependent, an important consideration in the development of typological-adapted methods either for the WFD implementation or for other assessment and monitoring purposes. Future work is required to calibrate the index for inter-annual variability in plant structure and composition, which is especially relevant in Mediterranean-type rivers.

Invasibility patterns of knotgrass (Paspalum distichum) in Portuguese riparian habitats.

Spatial patterns of the exotic riverine knotgrass (Paspalum distichum L.) were examined in Mediterranean river basins in Southwestern Iberia. The major goals of this study were to assess the degree of invasibility of riparian habitats by this species and to determine the influence of environmental factors and human-induced disturbances that this knotgrass has on both the landscape and the habitat scales. The present study demonstrates the ability of knotgrass to invade riparian habitats in Portuguese freshwater ecosystems. However, most of the spatial variation of the knotgrass cover seemed to be driven by local factors, such as fine sediment enrichment and the fragmentation of riparian woods, and by other anthropogenic interferences in relation to both the fluvial system and the surrounding landscape. Nomenclature: Knotgrass, Paspalum distichum L. #3 PASDS. Additional index words: Exotic species, human disturbances, environmental variables, PASDS, Mediterranean basin.

Relations Between River Plant Richness in the Portuguese Floodplains and the Widespread Water Knotgrass (Paspalum Paspalodes)

The distribution and invasive status of the amphibious plant Paspalum paspalodes (water knotgrass) are observed. The P. paspalodes distribution clearly shows that it is an invasive plant established in Portugal, which has never before been recorded as invasive in Portugal. The purpose of our study is to determine the various stages of invasion of this plant on a large biogeographical scale, in five basins or groups of floodplain river basins belonging to five Portuguese regions covering the principal floodplains of the south and centre of the country. The composition of the river plant community in terms of structure and species richness was obtained from a data set of 401 sites. In some cases, water knotgrass could be a threat for particular river flora and consequently for the integrity of the river system. In other cases, it occurs in highly degraded places, where other taxa considered as invasive plants and/or indicators of degraded ecosystems are present. The pattern of invasion of P. paspalodes is discussed in relation to risk assessment for the other river plants and compared to the North European invasion processes of P. paspalodes. We conclude that the evolution of the distribution of this predominant Portuguese water plant has to be carefully followed in some of the studied floodplains, as well as its North European distribution limits. In-depth survey should be carried out to relate the current biogeographical changes to the hypothesis of indication in climate changes.

Long-term monitoring for conservation management: Lessons from a case study integrating remote sensing and field approaches in floodplain forests

Implementing long-term monitoring programs that effectively inform conservation plans is a top priority in environmental management. In floodplain forests, historical pressures interplay with the complex multiscale dynamics of fluvial systems and require integrative approaches to pinpoint drivers for their deterioration and ecosystem services loss. Combining a conceptual framework such as the Driver-Pressure-State-Impact-Response (DPSIR) with the development of valid biological indicators can contribute to the analysis of the driving forces and their effects on the ecosystem in order to formulate coordinated conservation measures. In the present study, we evaluate the initial results of a decade (2004-2014) of floodplain forest monitoring. We adopted the DPSIR framework to summarize the main drivers in land use and environmental change, analyzed the effects on biological indicators of foundation trees and compared the consistency of the main drivers and their effects at two spatial scales. The monitoring program was conducted in one of the largest and best preserved floodplain forests in SW Europe located within Doñana National Park (Spain) which is dominated by Salix atrocinerea and Fraxinus angustifolia. The program combined field (in situ) surveys on a network of permanent plots with several remote sensing sources. The accuracy obtained in spectral classifications allowed shifts in species cover across the whole forest to be detected and assessed. However, remote sensing did not reflect the ecological status of forest populations. The field survey revealed a general decline in Salix populations, especially in the first five years of sampling -a factor probably associated with a lag effect from past human impact on the hydrology of the catchment and recent extreme climatic episodes (drought). In spite of much reduced seed regeneration, a resprouting strategy allows long-lived Salix individuals to persist in complex spatial dynamics. This suggests the beginning of a recovery resulting from recent coordinated societal responses to control excessive water extraction in the catchment, highlighting the need for continuing long-term monitoring. The DPSIR framework proved useful as a conceptual tool in analyzing the entire environmental system, while both field and remote sensing approaches complemented each other in quantifying indicator trends, improving the monitoring design and informing conservation plans.