Adelaide Clemente

Ammonium as a driving force of plant diversity and ecosystem functioning: Observations based on 5 years' manipulation of n dose and form in a mediterranean ecosystem

Enhanced nitrogen (N) availability is one of the main drivers of biodiversity loss and degradation of ecosystem functions. However, in very nutrient-poor ecosystems, enhanced N input can, in the short-term, promote diversity. Mediterranean Basin ecosystems are nutrient-limited biodiversity hotspots, but no information is available on their medium- or long-term responses to enhanced N input. Since 2007, we have been manipulating the form and dose of available N in a Mediterranean Basin maquis in south-western Europe that has low ambient N deposition (<4 kg N ha−1 yr−1) and low soil N content (0.1%). N availability was modified by the addition of 40 kg N ha−1 yr−1 as a 1∶1 NH4Cl to (NH4)2SO4 mixture, and 40 and 80 kg N ha−1 yr−1 as NH4NO3. Over the following 5 years, the impacts on plant composition and diversity (richness and evenness) and some ecosystem characteristics (soil extractable N and organic matter, aboveground biomass and % of bare soil) were assessed. Plant species richness increased with enhanced N input and was more related to ammonium than to nitrate. Exposure to 40 kg NH4 +-N ha−1 yr−1 (alone and with nitrate) enhanced plant richness, but did not increase aboveground biomass; soil extractable N even increased under 80 kg NH4NO3-N ha−1 yr−1 and the % of bare soil increased under 40 kg NH4 +-N ha−1 yr−1. The treatment containing less ammonium, 40 kg NH4NO3-N ha−1 yr−1, did not enhance plant diversity but promoted aboveground biomass and reduced the % of bare soil. Data suggest that enhanced NHy availability affects the structure of the maquis, which may promote soil erosion and N leakage, whereas enhanced NOx availability leads to biomass accumulation which may increase the fire risk. These observations are relevant for land use management in biodiverse and fragmented ecosystems such as the maquis, especially in conservation areas.

Human-Nature Relationship in Mediterranean Streams: Integrating Different Types of Knowledge to Improve Water Management

The social and ecological systems of Mediterranean streams are intrinsically linked as a result of long human occupation. In this region, these links vary greatly across small distances due to geomorphology, resulting in great diversity across space, which poses particular challenges for understanding and managing these systems. This demands (i) interdisciplinary integration of knowledge that focuses on the social-ecological interactions, while according due consideration to the whole; and also (ii) transdisciplinary integration, integrating lay and expert knowledge to understand local specificities. To address these needs—a focus on interactions and local knowledge—the research presented here studies the human-nature relationship in Mediterranean streams. Its main objective is to improve understanding of Mediterranean streams, but it also provides practical inputs to enhance local-level management. The study adopts an applied approach from the perspective of natural resources management. A case study was developed conducting field work on streams within the Natura 2000 site of Monfurado, Portugal—a mainly privately owned area with conflicting land uses between conservation and farming. Rivers and streams in Portugal are considered to be in very bad condition, particularly with regard to water quality. The experimental design was based, from a critical realism perspective of inter- and trans-disciplinarity, on the complementarities between methodologies from (i) the social sciences: value survey and analysis of discourse; and (ii) the natural sciences: biomonitoring and integrity biotic indexes. Results characterized the connected systems from both ecological and social points of view. They also characterized the relationship between both dimensions. We concluded that well-established riparian vegetation cover of streams is a key structural element of the human-nature relationship in the Mediterranean streams of Monfurado at several levels. The central role this structure might have in the dialog between the conflicting land uses with regard to water management is discussed, and priority targets for management are identified. The tree stratum in streams may work as a conciliation factor in the conflict between farming and conservation, as it is in the interest of both sectors to maintain it; however, the shrub stratum is effectively a source of conflict between the two perspectives and needs further work at the social-change level.

Quarry rehabilitation: a case study

Quarrying activities such as limestone extraction entail significant visual impacts and degradation problems as a result of soil depletion and deep alteration to the original topography. These areas are at high risk of erosion due to removal of vegetation and the lack of available soil on steep slopes. In addition, the common method of quarry exploitation in platforms increases drainage and the physical and chemical erosion of the substrate, hindering natural germination and establishment of young plants, and thus delaying recolonisation. In the past, quarries were simply abandoned after extraction. However, natural colonisation of disused limestone quarries is slow. The time scales involved in the creation of new communities are not considered acceptable for reclamation or restoration. A reclamation project was conducted in a limestone quarry within the Serra da Arribida Natural Park (Portugal), one example of well-preserved Mediterranean vegetation in Europe. We compared the revegetation of 5 abandoned platforms sequentially revegetated over the last 15 years, at 3 year intervals. The successive revegetation of each platform resulted in distinct plant communities, differing in age and cover. This allowed the evaluation of establishment and growth of introduced species as well as the succession of spontaneous species and stabilisation of natural vegetation. The evolution of soil characteristics was also evaluated as well as the contribution of different species to soil formation on the platforms. The results obtained allowed us to recommend strategies and to establish criteria for evaluation of the success of the revegetation in these degraded areas.

Restoration of Disturbed Areas in the Mediterranean — a Case Study in a Limestone Quarry

Limestone quarrying activities have extremely strong environmental impact, since they imply vegetation clearing and loss of soil. A reclamation project was conducted in a limestone quarry of the Serra da Arrabida (southwest Portugal), a natural park with a dense evergreen sclerophyllous shrub community. The successive revegetation of quarry terraces results in distinct plant communities of different age and cover. In this work we examined five different terraces, which were revegetated at 3-year intervals, to evaluate the establishment and growth of introduced species as well as colonization and succession of natural vegetation.

Too Many Is Too Bad: Long-Term Net Negative Effects of High Density Ungulate Populations on a Dominant Mediterranean Shrub.

Plant–animal interactions imply costs and benefits with net balance depending on interacting species and ecological context. Ungulates, in particular, confer costs (e.g., plant leaf consumption, flower bud predation) and benefits (e.g., plant overcompensation, seed dispersal) to plants. Magnitude of costs and benefits may be altered by habitat management or ecological conditions favoring high density ungulate populations. Little is known however on whether plant costs or benefits predominate over the years, or the long-term outcomes of plant-animal interactions in habitat types sustaining high density ungulate populations. We investigated how high density ungulate populations alter plant costs and benefits by quantifying ungulate long-term effects on the shrub Cistus ladanifer (Cistaceae) individual size, seed weight and number, seed bank, and population density, through a 12-year ungulate exclusion experiment in a Mediterranean scrubland. We monitored plant size and flower buds in plants exposed or protected from ungulates and number of developed capsules and seeds consumed (potential seed dispersal) by ungulates during three reproductive seasons. We found that ungulates negatively affected shrub size and led to a dramatically decline of shrub reproductive structures and seed production, affecting the plant reproductive cycle. Number of buds was 27 times higher and number of developed seed 5 times higher in ungulate-excluded as compared to ungulate-exposed plots. After 9 years of ungulate exclusion, the C. ladanifer seed bank was 2.6 times higher in ungulate-excluded plots. The population density of C. ladanifer was 4 times higher in ungulate-excluded plots. Our long-term experiment showed that high density ungulate populations can alter plant-animal interactions by reducing plant benefits and increasing plant costs.

The Impact of the Rural Land-Use on the Ecological Integrity of the Intermittent Streams of the Mediterranean 2000 Natura Network

The main objective was to understand the impact of the neighbouring land-use and of water pollution on the integrity of the riparian vegetation in intermittent Mediterranean streams of the 2000 Natura network in a rural area. The ecological integrity of the riparian vegetation of intermittent streams in the Mediterranean was negatively associated with the aquatic NH4 + concentration, which might a consequence of direct and indirect effects. There was a significant increase in frequency of exotic shrub species with increasing PO4 3− concentration in stream waters and high NO3 − concentrations in stream waters did not affected the QBR index or its components. Despite occupying a large area, pastures were not a source of eutrophication elements to the stream waters. Agricultural practices close to streams i.e. < 200 m, should be avoided. When the latter is not possible a well established native vegetation buffers should surround such areas.