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Recent warming in the Andes is affecting the region's water resources including glaciers and lakes, which supply water to tens of millions of people downstream. High-elevation wetlands, known locally as 'bofedales', are an understudied Andean ecosystem despite their key role in carbon sequestration, maintenance of biodiversity, and regulation of water flow. Here, we analyze subfossil diatom assemblages and other siliceous bioindicators preserved in a peat core collected from a bofedal in Peru's Cordillera Vilcanota. Basal radiocarbon ages show the bofedal likely formed during a wet period of the Little Ice Age (1520-1680 CE), as inferred from nearby ice core data. The subfossil diatom record is marked by several dynamic assemblage shifts documenting a hydrosere succession from an open-water system to mature peatland. The diatoms appear to be responding largely to changes in hydrology that occur within the natural development of the bofedal, but also to pH and possibly nutrient enrichment from grazing animals. The rapid peat accretion recorded post-1950 at this site is consistent with recent peat growth rates elsewhere in the Andes. Given the many threats to Peruvian bofedales including climate change, overgrazing, peat extraction, and mining, these baseline data will be critical to assessing future change in these important ecosystems. Key words: tropical Andes, cushion bogs, high-elevation peat, Distichia muscoides Nees & Meyen, Cordillera Vilcanota, X-ray fluorescence spectroscopy, climate change. Le rechauffement recent des Andes affecte les ressources en eau de la region, dont les glaciers et les lacs, qui fournissent de l'eau a des dizaines de millions de personnes en aval. Les zones humides de haute elevation, connues localement sous le nom de << bofedal >>, constituent un ecosysteme andin peu etudie malgre leur role cle dans la sequestration du carbone, le maintien de la biodiversite et la regulation du debit d'eau. Les auteurs analysent ici des assemblages de diatomees subfossiles et d'autres bio-indicateurs siliceux pre-serves dans une carotte de tourbe prelevee dans un bofedal de la Cordillere Vilcanota au Perou. L'age des radiocarbones de base montre que le bofedal s'est probablement forme pendant une periode humide du Petit Age glaciaire (1520-1680 CE), comme on peut le deduire des donnees des carottes de glace voisines. La consignation des diatomees subfossiles est marquee par plusieurs changements d'assemblages dynamiques documentant une succession d'hydroseres d'un systeme d'eau libre a une tourbiere mature. Les diatomees semblent repondre en grande partie aux changements hydrologiques qui se produisent dans le cadre du developpement naturel du bofedal, mais aussi au pH et possiblement a l'enrichissement en nutriments par les animaux de paturage. La rapide accretion de tourbe enregistree apres 1950 sur ce site est coherente avec les taux de croissance recents de la tourbe ailleurs dans les Andes. Compte tenu des nombreuses menaces qui pesent sur les bofedal peruviens, notamment les changements climatiques, le surpaturage, l'extraction de tourbe et l'exploitation miniere, ces donnees de reference seront essentielles pour evaluer les changements futurs dans ces ecosystemes importants. [Traduit par la Redaction] Mots-cles : Andes tropicales, tourbieres en coussin, tourbe de haute elevation, Distichia muscoides Nees & Meyen, Cordillera Vilcanota, spectroscopie de fluorescence a rayons X, changements climatiques., Introduction Temperature increases in the tropical Andes are occurring at a rate nearly double the global average (Vuille et al. 2003) and are already resulting in marked environmental changes, including [...]

The Kangerlussuaq area of southwest Greenland encompasses diverse ecological, geomorphic, and climate gradients that function over a range of spatial and temporal scales. Ecosystems range from the microbial communities on the ice sheet and moisture-stressed terrestrial vegetation (and their associated herbivores) to freshwater and oligosaline lakes. These ecosystems are linked by a dynamic glacio-fluvial-aeolian geomorphic system that transports water, geological material, organic carbon and nutrients from the glacier surface to adjacent terrestrial and aquatic systems. This paraglacial system is now subject to substantial change because of rapid regional warming since 2000. Here, we describe changes in the eco- and geomorphic systems at a range of timescales and explore rapid future change in the links that integrate these systems. We highlight the importance of cross-system subsidies at the landscape scale and, importantly, how these might change in the near future as the Arctic is expected to continue to warm.

The organic matter composition of lake sediments influences important in-lake biogeochemical processes and stores information on environmental changes. Extracting this information is notoriously difficult because of the complexity of the organic matter matrix, which routinely imposes trade-offs between high temporal and analytical detail in the selection of methods of analysis. Here, we demonstrate the potential of diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) for achieving both of these objectives using untreated bulk samples from two Holocene lake-sediment cores from central Sweden. We develop quantitative models for sediment total organic carbon (TOC) with the same predictive abilities as models based on samples diluted with KBr and qualitatively characterize the organic matter using a spectra processing-pipeline combined with principal component analysis. In the qualitative analysis we identified four organic matter sub-fractions and the interpretation of these is supported and further advanced with molecular data from pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Within these organic fractions, compound groups such as aromatics, lignin, aliphatics, proteins and polysaccharides were identified by means of DRIFTS and the analyses and processes outlined here enables rapid and detailed quantitative and qualitative analysis of sediment organic matter. The DRIFTS approach can be used as stand-alone method for OM characterization with high temporal resolution in Holocene sediment records. It may also function as a screening process for more specific analyses of sample subsets, such as when coupled with pyrolysis-GC/MS to further tease apart the OM composition, identify sources and determine degradation status. [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2009.03.008 Byline: Ingemar Renberg (a), Christian Bigler (a), Richard Bindler (a), Matilda Norberg (a), Johan Rydberg (a), Ulf Segerstrom (b) Abstract: Establishment of plans for environmental planning and management requires that a number of natural and societal factors must be taken into consideration. Insights into the inherent dynamics of nature as well as the role that past human activities have played for establishing the current condition of the landscape and the natural environment in general are essential. Many natural and man-made changes occur over time scales of decades or centuries, and these are difficult to comprehend without a historical perspective. Such a perspective can be obtained using palaeoecological studies, i.e. by geochemical and biological analyses of lake sediment and peat deposits. To illustrate the long-term dynamics of nature and particularly the role of man, we present here five case studies from Sweden concerning pollution, lake acidification, lake eutrophication, biodiversity, and landscape dynamics and conservation - topics of broad interests - and discuss benefits of including a longer time perspective in environmental management. Author Affiliation: (a) Department of Ecology and Environmental Science, UmeA[yen] University, SE-901 87 UmeA[yen], Sweden (b) Department of Forest Ecology and Management, SLU, SE-901 83 UmeA[yen], Sweden Article History: Received 16 June 2008; Revised 13 March 2009; Accepted 20 March 2009