Search

International audience; Many studies suggest the importance of boundary features on plant community dynamics. Our aim was to investigate the influence of boundary features on edge plant assemblages in semi-natural dry grasslands. For this purpose we selected 16 grassland edges in the central portion of the Natura 2000 site Murgia Alta, in southeastern Italy. These sites were selected according to a combination of boundary features, i.e. the adjoining land use type (road or cereal crop), slope (grassland tilted towards matrix or flat) and stonewall (occurring or not). Within each site, cover value of vascular plant species was sampled along 0.5x2.5m linear plot. A correspondence analysis has been used for the simultaneous ordination of species presence/absence data and the 16 edge plots. Grassland edges with stonewall were characterized either by forest ecotone species in case of sloped edges, or by species typical of sub-mesic calcareous grasslands in case of flat edges. Therefore, stonewall may have a protective role towards the studied communities of conservation concern in case of flat morphology. In case of unbounded edge, no change in species assemblage was clearly explained by adjoining land use type or slope. Assemblages dominated by either ruderal or xerothermic grassland species were observed in all cases of unbounded edges. Furthermore, several species associated with xerothermic conditions were characteristic of highly grazed pastures, suggesting an overlooked role of grazing intensity at the edge. The relevance of boundary features, with regard to their primary role in the definition of multiple and contrasting community dynamics, should be first taken into account when planning land modification, local management actions and for conservation.

At a global level, protected sites have been established for the primary purpose of conserving biodiversity, with survey and monitoring of habitats undertaken largely within their boundaries. However, because of increasing human populations with greater access to resources, there is a need to now consider monitoring anthropic activities in the surrounding landscapes as pressures and disturbances are impacting on the functioning and biodiversity values of many protected sites. Earth Observation (EO) data acquired across a range of spatial and temporal scales offer new opportunities for monitoring biodiversity over varying time-scales, either through direct or indirect mapping of species or habitats. However, Land Cover (LC) and/or Land Use (LU), rather than habitat maps are generated in many national and international programs and, whilst the translation from one classification to the other is desirable, differences in definitions and criteria have so far limited the establishment of a unified approach. Focusing on both natural and non-natural environments associated with Natura 2000 sites in the Mediterranean, this paper considers the extent to which three common LC/LU taxonomies (CORINE, the Food and Agricultural Organisation (FAO) Land Cover Classification System (FAO-LCCS) and the IGBP) can be translated to habitat taxonomies with minimum use of additional environmental attributes and/or in situ data. A qualitative and quantitative analysis based on the Jaccard’s index established the FAOLCCS as being the most useful taxonomy for harmonizing LC/LU maps with different legends and dealing with the complexity of habitat description and as a framework for translating EO-derived LC/LU to habitat categories. As demonstration, a habitat map of a wetland site is obtained through translation of the LCCS taxonomy.

I corsi d’acqua effimeri sono tipici degli ambienti mediterranei. Il loro caratteristico regime di deflusso insieme alla pressione umana sul territorio all’interfaccia tra il corso d’acqua e il piano di campagna ne condizionano la struttura spaziale. Questa a sua volta influenza l’efficienza ecologica di questo complesso sottosistema paesistico lineare relativamete alle sue funzioni ecologiche. Queste comprendono il movimento (sia passivo, sia attivo) dell’energia, dei materiali e degli organismi lungo e attraverso il corridoio. Questo lavoro focalizza l’attenzione sulla verifica della sussistenza della funsione ecologica di habitat nel caso del corridoio ripariale di un corso d’acqua effimero, rapprentativo della tipologia dei bacini carsici della Puglia centrale. La funzione di habitat è rilevante rispetto ai temi cogenti della ricerca ecologica quali quelli della connettività della dispersione di organismi vegetali e delle dinamiche delle metapopolazioni animali. La comprensione di questi processi è cruciale perché su di essa è basata la pianificazione finalizzata alla gestione e conservazione delle risorse naturali e al mantenimento della biodiversità. Inoltre, una delle maggiori minacce alla biodiversità nei paesaggi agricoli mediterranei è rapprentata dalla frammentazione degli habitat, causa del declino delle popolazioni e dell’aumento del rischio di estinzioni locali. Ai fini del lavoro è stata condotta una analisi del paesaggio gerachica e transcalare per il corridoio ripariale. Questo approccio di analisi è stato necessario in relazione alla indubitabile concezione della organizzazione gerarchica dei sistemi ecologici e alla natura gerarchica dei bacini idrografici. Oltrea a ciò, alla gerarchia delle strutture del paesaggio corrisponde una gerachia delle decisioni degli organismi animali. Quindi il concetto di scala non è estraneo a quello di biodiversità. Infine, la pianificazione gerarchica si sta affermando quale approccio alla pianificazione e gestione forestale. È stato identificato un range di scale spaziali che corrisponde alla organizzazione gerarchica del sistema idrografico, così come ai livelli della gerarchia della patchiness del corridoio ripariale, inteso come sottosistema paesistico compelsso e multifunzionale e come risorsa vulnerabile per l’umanità. Per la individuazione del corridoio ripariale e la sua stratificazione in segmenti, alla scala del sistema idrografico, è stata adottata una metodologia basata sulla associazione, a ciascun componente del sistema idrografico, di attributi calssificatori di tipo estrinseco ed intrinseco (ordine gerarchico, litologia, condizioni climatiche, presenza/assenza e tipologia fisionomica delle vegetazioni spontanee). Attraverso questa procedura è stata possibile l'identificazione oggettiva del corridoio ripariale e della porzione di paesaggio maggiormente in grado di influenzarne struttura e funzionamento. Inoltre sono state acquisite informazioni sulle caratteristiche di continuità/discontinuità del corridoio stesso e sull’assetto delle vegetazioni spontanee in termini di isolameto e aggregazione. Alla scala del corridoio ripariale è stata condotta la optimal limit analysis su un transetto lineare che ha permesso il riconoscimento di un modello di configurazione spaziale, riferibile alla microeterogeneità e delle relazioni spaziali tra le differenti tipologie di copertura del suolo. Inoltre le variazioni spaziali della matrice del corridoui sono state studiate per mezzo della moving split-window (MSW) technique applicata ad un treansetto bidimensionale. Sono stati così identificati diversi tipi di paesaggio, caratterizzati in termini di composizione e configurazione delle componenti di naturalità. La configurazione spaziale dei segmenti di corridoio è stata analizzata mediante indici di landscape pattern (LPI) opportunamente selezionati. Al landcape level è stato ottenuto l’ordinamento dei segmenti secondo un gradiente di frammentazione. Al class level le relazioni tra gli indici variano in funzione della tipologia di copertura del suolo considerata, e pertanto forniscono indicazioni circa le statregie da adottare per la riduzione della frammentazione degli habitat. Per la valutazione della funzione di habitat si è fatto riferimento agli uccelli come bioindicatori, secondo quanto risulta dalla letteratura, data la loro sensibilità ai cambiamenti ambientali, connessa alla loro specializzazione e vagilità. Sono state studiate le necessità di habitat delle specie di uccelli, il loro grado di specializzazione ed alcune carattreistiche delle loro popolazioni e comunità, a diffenti livelli interpretativi, che hanno fornito elementi di comprensione circa le intrazioni tra pattern (struttura del paesaggio) e process (distribuzione dei biondicatori). Il corridoio ripariale effettivamente rappresenta un rifugio per molte specie di uccelli forestali. La diversita delle comunità ornitiche è risultata influenzata dal grado di frammentazione degli habitat idonei. È stata anche valutata la qualità ambientale del corridoio ripariale sia rispetto a bioindicatori specifici per l’area studiata (uccelli forestali), sia rispetto a bioindicatori non specifici (i carabidi) di importanza riconosciuta, ma per i quali non si dispone di dati analitici per l’area studiata. Al livello interpretativo del corridoio ripariale, la qualità ambientale della matrice, influenza direttamente quella del corridoio. Nel passaggio di scala dalla matrice del corridoio al corridoio stesso, inoltre, si rileva la non corrispondenza tra gli indici di qualità ambientale riferiti a bioindicatori specifici (uccelli forestali) e non specifici (carabidi) rispetto all’ambiente e al problema di interesse. La qualità ambientale è stata anche posta in relazione con la configurazione del paesaggio e si è potuto confermare che la dominanza relativa e la pervasività delle coperture del suolo a forte determinismo antropico, la frammentazione la diversificazione del paesaggio ne rappresentano i principali detrattori a tutti i livelli interpretativi. Infine una zonizzazione del corridoio ripariale è stata ottenuta in funzione della qualità ambientale che si propone come punto di partenza per la definizione di una strategia di ripristino a questo livello di scala. L’importanza dei corridoi ripariali ai fini della vitalità delle metapopolazioni è stata quindi verificata anche nel caso di corsi d’acqua effimeri, e in condizioni di degrado, ed è stata confermata la loro funzione di habitat, cruciale per la conservazione della biodiversità alla scala di paesaggio. Tuttavia, l’elevato grado di frammentazione, le ridotte dimensioni trasversali del corridoio stesso e la semplificazione delle strutture delle vegetazioni forestali sembrano spiegare la diversificazione delle comunità ornitiche, che portebbe essere interpretato come un segnale che la funzione ecologica di source del corridoio ripariale, in termini di dinamica delle metapopolazioni, si stia modificando in quella di sink. Sono discusse questioni metodologiche relative al filone della ricerca ecologica finalizzata allo studio delle implicazioni ecologiche e pianificatorie della natura gerarchica dei sistemi ecologici complessi, alla legittimità del ricorso agli indici di landscape pattern per la comprensione dei processi che sottendono all’ecologia dei paesaggi, alla dipendenza dalla scala della eterogeneità spaziale. Ephemeral streams are typical of Mediterranean environments. Their characteristic flow regime as well as the strong human pressure on the land at the stream/upland interface condition the spatial configuration of the stream corridor. This in turn affects the ecological efficiency of such complex linear landscape element with regard to its major functions. These involve movement (either passive or active) of materials, energy and organisms along or across the corridor. This work focuses on the assessment of the subsistence of the habitat function in the case of the stream corridor of an ephemeral stream, representative for karstic torrents in the Puglia region (southern Italy). The habitat function is relevant to key issues of ecological research, such as connectivity, plant dispersal and animal metapopulation dynamics. Insights on these issues are crucial as on them relies planning for management and conservation of natural resources and biodiversity maintenance. Moreover, one of the major threats to biodiversity in agricultural Mediterranean landscapes is habitat fragmentation, which causes populations decline and enhances local extinction risk. To the ends of the work, a multiple scale analysis of landscape configuration for the stream corridor was performed. Such a need descends from the, by now unquestionable, notion of the hierarchical organisation of ecological systems and from the hierarchical nature or watershed systems. In addition, to the hierarchy of landscape pattern corresponds a hierarchy of decisions of animal organisms. Hence, the concept of scale is not alien from the notion of biodiversity. Finally, hierarchical planning is steadily gaining momentum as an approach to forest planning. A range of spatial scales was identified that corresponds to the hierarchical organisation of the stream system, as well as to the levels of the hierarchy of the patchiness for the stream corridor understood as a complex and multifunctional landscape subsystem as well as a vulnerable resource for mankind. For the detection of the stream corridor and its stratification into segments, at the scale of the hydrological system, a methodology was adopted that is based on the association of both extrinsic and intrinsic classificatory attributes (e.g. hierarchy within the hydrological system, lithology, climatic conditions as well as the presence/absence and the physiognomy of natural vegetation) to each component of the hydrological system. This procedure yielded the objective identification of both the stream corridor and the limits of the portion of the landscape more likely to affects its structural and functional features. In addition it brougth forward information on characteristics of the corridor, such as continuity/discontinuity, heterogeneity/homogeneity of sub-natural vegetation and their degree of isolation and distribution. At the scale of stream corridor the optimal limit analysis of a line transect was performed that has allowed for the recognition of a micro-heterogeneous landscape pattern, as well as the spatial relations among land cover types. Also the spatial variations of the landscape matrix were analysed based on the moving split-window (MSW) technique applied to a plane transect. Different landscape types were thus identified and their characteristic structure described both in terms of composition and of spatial arrangement of sub-natural vegetation. Segments’ spatial configuration was analised by means of selected landscape pattern indices (LPI). At the landscape scale segments were ordered according to a fragmentation gradient. At the class level the relations among the LPI depend on land cover type, thus providing information on the kind of restoration strategy needed to reduce habitat fragmentation. For the assessment of the habitat function, birds were used as bioindicators, consistently with the most significant literature on this topic, given their sensitivity to environmental change in connection with their specialisation and vagility at the landscape scale. Bird species habitat needs, degree of specialisation, population and community traits were investigated at the different hierarchical levels and insights on the interaction between pattern (landscape structure) and process (bird distribution) were gained. The stream corridor performs as a refuge for many specialised species which prefer forest type vegetation as well as less intensively managed agricultural land cover types. Bird communities diversity is affected by the degree of fragmentation of suitable habitat types. The environmental quality of the stream corridor was also assessed with respect of specialised bird species and a comparison was made with respect to carabid beetles, whose importance as bioindicators is also recognised, but for which analytical data are not available for the study area. At higher levels both taxonomic groups yield comparable results, yet the lower levels the need of operating with specific bioindicators emerges. Environmental quality was also compared to landscape configuration and it was confirmed that the relative dominance and pervasiveness of land cover types with a high anthropogenic determinism, landscape fragmentation and diversity negatively affect environmental quality at all levels of the hierarchy. Finally a zoning of the stream corridor was proposed with respect to both environmental quality and landscape configuration that represents the base to built a restoration strategy at this level. Thus the importance of even ephemeral, depleted, stream corridors for metapopulation viability and their effectiveness in the performance of the habitat function is confirmed, which are crucial for biodiversity maintainance at the landscape scale. However the high fragmentation degree, the narrowness of the stream corridor and possibly the simple structure of such phytocoenoses, seem to explain the diversification within bird communities. This could be a signal that the turning point from source to sink for this subsystem may have been reached. Methodological issues are discussed, such as those relevant to the wide stream of landscape ecological research aimed at exploring both ecological and planning/management implications of the space-time hierarchical nature of complex ecological systems, to the legitimacy of the use of landscape indices to draw inferences on processes underlying the ecology of landscapes, and to the scale dependence of landscape heterogeneity. Dottorato di ricerca in Ecologia forestale

Projections of landscape dynamics are uncertain, partly due to uncertainties in model formulations. However, quantitative comparative analyses of forest landscape models are lacking. We conducted a systematic comparison of all forest landscape models currently applied in temperate European forests (LandClim, TreeMig, LANDIS-II, iLand). We examined the uncertainty of model projections under several future climate, disturbance, and dispersal scenarios, and quantified uncertainties by variance partitioning. While projections under past climate conditions were in good agreement with observations, uncertainty under future climate conditions was high, with between-model biomass differences of up to 200 t ha−1. Disturbances strongly influenced landscape dynamics and contributed substantially to uncertainty in model projections (~25–40% of observed variance). Overall, model differences were the main source of uncertainty, explaining at least 50% of observed variance. We advocate a more rigorous and systematic model evaluation and calibration, and a broader use of ensemble projections to quantify uncertainties in future landscape dynamics., Environmental Modelling & Software, 134, ISSN:1364-8152, ISSN:1873-6726

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich., This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively., Understanding the causes and effects of species invasions is a priority in ecology and conservation biology. One of the crucial steps in evaluating the impact of invasive species is to map changes in their actual and potential distribution and relative abundance across a wide region over an appropriate time span. While direct and indirect remote sensing approaches have long been used to assess the invasion of plant species, the distribution of invasive animals is mainly based on indirect methods that rely on environmental proxies of conditions suitable for colonization by a particular species. The aim of this article is to review recent efforts in the predictive modelling of the spread of both plant and animal invasive species using remote sensing, and to stimulate debate on the potential use of remote sensing in biological invasion monitoring and forecasting. Specifically, the challenges and drawbacks of remote sensing techniques are discussed in relation to: i) developing species distribution models, and ii) studying life cycle changes and phenological variations. Finally, the paper addresses the open challenges and pitfalls of remote sensing for biological invasion studies including sensor characteristics, upscaling and downscaling in species distribution models, and uncertainty of results.

Forest disturbances are sensitive to climate. However, our understanding of disturbance dynamics in response to climatic changes remains incomplete, particularly regarding large-scale patterns, interaction effects and dampening feedbacks. Here we provide a global synthesis of climate change effects on important abiotic (fire, drought, wind, snow and ice) and biotic (insects and pathogens) disturbance agents. Warmer and drier conditions particularly facilitate fire, drought and insect disturbances, while warmer and wetter conditions increase disturbances from wind and pathogens. Widespread interactions between agents are likely to amplify disturbances, while indirect climate effects such as vegetation changes can dampen long-term disturbance sensitivities to climate. Future changes in disturbance are likely to be most pronounced in coniferous forests and the boreal biome. We conclude that both ecosystems and society should be prepared for an increasingly disturbed future of forests. © 2017 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.