Добірка наукової літератури з теми "Biocroûte"

No semiárido brasileiro, a erosão tem comprometido a capacidade produtiva dos solos e desencadeado graves fenômenos socioambientais nas áreas consideradas desertificadas. Faz-se necessário estudos que permitam a compreensão da erosão em nível de detalhe, de forma a contribuir com ações de planejamento, gestão e recuperação ambiental dessas áreas. Nesse trabalho, a erosão foi analisada em uma bacia hidrográfica experimental com área de 2,92 km2, localizada no estado de Pernambuco. A partir de produtos de altíssima resolução, derivados de sensores LiDAR, ARP e trabalhos de campo, foram elaboradas a carta de feições erosivas lineares e a carta de morfoconservação. Foram identificadas 600 incisões erosivas com extensão total de 41,6 km, conectadas em rede e associadas a solos expostos. Em alguns setores, os horizontes superficiais do solo foram completamente removidos. Por outro lado, a erosão foi retardada onde há biocrosta e vegetação arbustiva. Embora as reais causas da desertificação nesta bacia ainda não sejam conhecidas, acredita-se que o avançado estágio de degradação esteja relacionado a fatores complexos, naturais e antropogênicos. Assim, considera-se que a metodologia utilizada pode ser replicada para outros contextos e nortear ações de preservação e recuperação de áreas erodidas.

Les gisements de Terres Rares (REEs) d'argile à adsorption ionique sont l'un des principaux réservoirs de REEs dans le monde. Ils sont principalement distribués dans le Jiangxi, le Guangdong et d'autres provinces du sud de la Chine. Au cours des dernières décennies, leur production a causé de graves dommages environnementaux et laissé une grande superficie de résidus miniers, tels une menace constante sur l'environnement. Les principaux problèmes de ces résidus sont une mauvaise structure physique, une fertilité extrêmement faible, une pollution et une toxicité élevées. Ces facteurs défavorables entravent la colonisation des organismes et la restauration des services écosystémiques. Par conséquent, la restauration de la structure et des fonctions du sol et de l'écosystème sont une question majeure. La succession naturelle et la phytoremédiation sont des stratégies de gestion de ces résidus miniers. Le processus de formation du sol et le mécanisme de succession écologique dans ces différentes stratégies sont différents. Compte tenu du coût et du temps nécessaires, la comparaison de ces approches est essentielle. Le but de cette thèse est d'étudier : 1) la structuration et l'évolution des fonctions du sols et des écosystèmes de stériles miniers en succession naturelle; 2) les effets de différentes stratégies de phytoremédiation et 3) l'évaluation comparative de la qualité des sols et de l'environnement écologique dans le cadre de la succession naturelle et de la phytoremédiation. (1) Dans la succession naturelle, les fonctions pédologiques et écologiques progressent considérablement au fil du temps. En outre, nous avons constaté qu'il y avait trois modèles d'évolution complètement différents au début de la succession (sol nu, croûtes biologiques et végétation vasculaire) et que la relation entre eux est évolutive. La genèse d'agrégats du sol, en particulier les macroagrégats biogéniques, impacte l'accumulation de nutriments, le comportement des REEs et la diversité des micro-organismes. (2) De plus, les macroagrégats associés aux croûtes biologiques (BC) et associés aux racines de plantes vasculaires (RS) échantillonnés sur des résidus de REEs se révèlent être différents. Les modalités BC et RS avaient des concentrations en nutriments significativement plus élevées. La concentration de REEs la plus élevée a été observée pour BC, tandis que la plus faible a été observée pour RS, ce qui suggère que les REEs se redistribueraient entre différents horizons selon la restauration biotique. Fait intéressant, les micro-organismes autotrophes étaient concentrés dans BC, tandis que les bactéries rhizosphériques hétérotrophes favorisant la croissance des plantes étaient concentrées dans RS. Ces résultats montrent que le mécanisme et l'efficacité de la restauration entre les différentes approches sont significativement différents. (3) Différentes stratégies de phytoremédiation ont été testées par des expériences de terrain. Par rapport aux résidus nus, l'ajout d'amendement induit une augmentation significative de la fertilité chimique et favorise la formation de macroagrégats, réduisant ainsi la disponibilité des REEs. De plus, les modifications introduisent de nouvelles bactéries (p. ex. Burkholderia), qui modifient certaines caractéristiques biologiques des résidus et favorisent la circulation des éléments nutritifs. Nos expériences sur le terrain ont prouvé l'efficacité et la durabilité des amendements que nous avons conçus, mais cet effet semble avoir disparu à 16 mois. En conclusion, nos recherches montrent que la nature, en tant qu'« ingénieur », améliore sans interruption la qualité du sol et de l'environnement écologique, tandis que les efforts de phytoremédiation, s'ils améliorent considérablement la fonction du sol et de l'environnement écologique, ont un effet qui s'affaiblit avec le temps, ce qui nécessite une observation à plus long terme
Ion-adsorption REE deposits are one of the main reservoirs of REEs worldwide, mainly distributing in southern China. In the past decades, the production of REEs has caused serious environmental damage and left over a large area of tailings which continuously threaten the surrounding environment. The main obstacles for ecological restoration of such tailings are poor physical structure, low nutrients, high pollution of REEs and Al. These unfavourable factors hinder the colonization of organisms and the restoration of ecosystem services. Therefore, how to restore the structure and function of soil and ecosystem has become a major issue. Natural succession and phytoremediation provide an option for restoration of mine tailings. However, so far less is understood in terms of the mechanisms of soil formation and ecological succession of REE tailings under different strategies. Therefore, the objectives of this thesis are to: 1) study the evolution mechanism of structure and function of tailing soils and ecosystem in natural succession; 2) study the restoration effects of various phytoremediation strategies; and 3) assess the soil and ecological environment quality under natural succession and phytoremediation. The main findings are as follows. (1) In natural succession of a 15-year chronosequence, soil and ecological functions are significantly increasing over time. There are three completely different evolution patterns (i.e. visual bare, biocrust and vascular vegetation) in the early stage of succession. The evolution between biocrusts and vascular plants occurs from the initial mutual promotion to the later competition. The formation of large aggregates (> 0.25 mm) is mainly controlled by the electrostatic interaction of minerals and biological activities, which improves the diversity of microorganisms and accumulation of nutrients, and controls the migration of REEs. (2) The macroaggregates associated with biocrusts (BC) and with vascular plant root soils (RS) show different morphologies, that is, longitudinal stratification of biocrust and interlacement within the rhizosphere. Both BC and RS are significantly enriched in nutrients. The highest REE concentration is observed in BC while the lowest is found in RS, suggesting that REEs could be redistributed among different horizons by biotic processes. Interestingly, autotrophic microorganisms are more concentrated in the BC, while heterotrophic rhizosphere growth-promoting bacteria are preferentially distributed in the RS. These results show that, although in the same site, the mechanism of soil formation and recovery of soil function under different evolution patterns are quite different. (3) In consideration of time and efficiency, different phytoremediation strategies (i.e. amendment and plantation of pioneer plant Miscantus sinensis and commercial grasses) were conducted by a plot experiment. Compared with bare tailings, the addition of amendment induces a significant increase in nutrients, promotes the formation of macroaggregates, and reduces the availability of REEs. In addition, phytoremediation introduces nitrogen fixing bacteria (e.g. Burkholderia), which change the biological characteristics of tailings and promote nutrient cycling. Our results have proved the effectiveness and sustainability of the amendment input. Nevertheless, the plant effect is not significantly visible within only a 16 month-experiment in this study. In conclusion, this research shows that nature, as an “engineer”, is uninterruptedly improving the soil and ecological environment quality, while phytoremediation efforts can significantly enhance the soil and ecological environment function but the effect weakens with time, which requires longer-term observation

Le zone aride sono tra le aree più sensibili al cambiamento globale e i modelli prevedono un incremento della loro superficie nei prossimi decenni. La morfologia del terreno ha un ruolo chiave nella distribuzione dell'acqua e delle sostanze nutritive nelle zone aride e nella determinazione della loro composizione. Questi ambienti sono composti da vegetazione e suolo nudo, molte volte colonizzato da biocroste, che si prevede subiranno cambiamenti nella composizione. Il telerilevamento è stato evidenziato come uno strumento importante per il monitoraggio delle zone aride. Si tratta di un approccio molto efficace in termini di costi per identificare gli hotspot di biodiversità, prevedere i cambiamenti nella loro composizione e valutare le relazioni che tali cambiamenti hanno con la morfologia del terreno. Utilizzando specifiche tecniche di analisi delle immagini a seconda del caso di studio, il telerilevamento si è dimostrato utile per il monitoraggio di zone aride ben differenziate, ma non in caso di composizione mista. Pertanto, l’obiettivo principale di questa tesi di dottorato è stato quello di studiare come la composizione eterogenea e il funzionamento delle zone aride sono influenzati dalla morfologia del terreno integrando l’utilizzo di diversi sensori di telerilevamento e piattaforme. Sono stati utilizzati dati provenienti da immagini RGB, termiche ad infrarosso (TIR), multi- e iperspettrali ad altissima risoluzione spaziale acquisite in laboratorio e in campo utilizzando piattaforme aeree, UAV e stazionarie. Sono stati definiti i seguenti obiettivi specifici: - Valutare se le tecniche Structure from Motion (SfM) possono essere utilizzate in zone aride dalla superficie complessa per ricavare la morfologia del terreno da immagini UAV; - Sviluppare una tecnica riproducibile per mettere in relazione le azioni antropiche con i cambiamenti nello stato di salute delle comunità vegetali in ecosistemi aridi utilizzando tecniche di analisi object-based; - Valutare se l'eterogeneità spettrale dei licheni può essere utilizzata per stimare la loro α-diversità utilizzando immagini iperspettrali; - Sviluppare una metodologia per valutare l’influenza della morfologia del terreno sulla distribuzione delle biocroste in zone aride utilizzando informazioni acquisite esclusivamente mediante UAV; - Valutare se le immagini TIR possono essere usate per stimare l'umidità del suolo in zone aride eterogenee. Questa tesi di dottorato comprende una valutazione delle tecniche SfM a diverse scale e della loro applicabilità a diversi livelli. Affronta lo sviluppo di una nuova metodologia per monitorare la vegetazione in un ecosistema dipendente dalle acque sotterranee, dove la loro salute è fondamentale per il funzionamento dell'ecosistema. Inoltre, l'utilizzo di immagini iperspettrali acquisite a distanza ravvicinata ha permesso di stimare la α-diversità dei licheni che formano le biocroste utilizzando la loro diversità spettrale. Questo ha portato ad una migliore comprensione del comportamento spettrale delle biocroste a seconda della loro composizione, permettendo di sviluppare una metodologia per produrre mappe accurate della copertura del suolo in un ecosistema eterogeneo e di relazionare l'effetto della morfologia del terreno sulla composizione degli ambienti aridi.
Drylands are among the most sensitive areas to actual global change and their cover will increase in the next decades. Terrain has a key role in the distribution of water and nutrients in drylands and shaping their composition. These environments are composed by vegetation and bare soil, many times colonized by biocrusts, which are expected to suffer compositional changes. Remote sensing has been highlighted as an important tool for dryland monitoring. It is a very cost-effective approach to identify biodiversity hotspots, predict changes in their composition, and to evaluate the relationships these changes have with the terrain. Using the proper image analysis according to the study case, remote sensing has proved to be useful for monitoring well differentiated drylands, but not when dryland components are mixed. Thus, the main aim of this dissertation was to study how heterogeneous dryland composition and functioning is affected by the terrain using different multiple remote sensing sensors and platforms. Data from very high spatial resolution RGB, thermal infrared, multi- and hyperspectral imagery, retrieved in the laboratory and in the field using airborne, UAV and stationary platforms were used. The next specific objectives were set: - Evaluating whether SfM techniques can be used in drylands with complex surfaces to derive their terrain from UAV imagery; - Developing a reproducible technique to relate human actions to changes in the health of dryland scarce vegetation communities by using object-based image analysis; - Testing whether the spectral heterogeneity of lichens can be used to estimate their α-diversity using hyperspectral imagery; - Developing a methodology to evaluate the control that terrain has on dryland biocrusts’ distribution using information solely retrieved from UAV; - Testing if TIR imagery can estimate soil moisture in heterogeneous drylands. This PhD thesis comprises an evaluation of SfM techniques at different scales and their applicability at different levels. It also comprises a novel methodology to monitor vegetation in a ground-water dependent ecosystem, where their health is key for the ecosystem’s functioning. Moreover, the application of close-range hyperspectral imagery allowed to estimate the α-diversity of biocrust-forming lichens using their spectral diversity. This led to a better understanding of the spectral behaviour of biocrusts depending on their composition and allowed to develop a methodology to produce accurate maps of land cover in a dryland ecosystem of heterogeneous composition and to relate the effect of terrain atrributes on dryland composition.