Many eukaryotic communities exhibit predictable seasonality in species composition, but such phenological patterns are not well-documented in bacterial communities. This study quantified seasonal variation in the community composition of bacterioplankton in a high-elevation lake in the Sierra Nevada of California over a 3-year period of 2004-2006. Bacterioplankton exhibited consistent phenological patterns, with distinct, interannually recurring community types characteristic of the spring snowmelt, ice-off and fall-overturn periods in the lake. Thermal stratification was associated with the emergence of specific communities each summer and increased community heterogeneity throughout the water column. Two key environmental variables modulated by regional meteorologic variation, lake residence time and thermal stability, predicted the timing of occurrence of community types each year with 75% accuracy, and each corresponded with different aspects of variation in community composition (orthogonal ordination axes). Seasonal variation in dissolved organic matter source was characterized fluorometrically in 2005 and was highly correlated with overall variation in bacterial community structure (r(Mantel)=0.75, P<0.001) and with the relative contributions of specific phylotypes within the Cyanobacteria, Actinobacteria and beta-Proteobacteria. The seasonal dynamics of bacterial clades (tracked through coupling of randomized clone sequence libraries to restriction fragment length polymorphism fingerprints) matched previous results from alpine lakes and were variously related to solute inputs, thermal stability and temperature. Taken together, these results describe a phenology of high-elevation bacterioplankton communities linked to climate-driven physical and chemical lake characteristics already known to regulate eukaryotic plankton community structure.

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Phenology of high-elevation pelagic bacteria: the roles of meteorologic variability, catchment inputs and thermal stratification in structuring communities.

The development of hydroelectricity in the French central Pyrenees at the beginning of the 20 century gave rise to some strong resistance, all in the name of landscape preservation and protection of the tourist resource that it represented. Space had to be shared, and some reserves of picturesque features were obtained from the industrialists, in exchange for a free hand in tourist development. The chapter analyses how the interplay of actors brings about this spatial partition. It shows the ambivalence of the discourse constructed to legitimise it. By looking in depth at the case of the protected site of Gavarnie, it sheds light on the nature of the social issues that were emerging as a background to this resistance to hydroelectricity in the landscape and shows how, through it, the power of an elite as an aesthetic authority, was imposed on communities in the mountain areas. The arrival around 1900 of the energy paradigm of hydroelectric power marked a decisive historical threshold for a great number of mountain massifs in Europe. The development of hydroelectricity first transformed the mountains into an area that welcomed industrial modernity, then, especially after the end of the First World War, into a production area for an energy that could now be transported, and which mainly benefited the low-lying plains. Today this separation of energy production and consumption is almost complete, with the majority of electrometallurgical and electrochemical factories in the high mountain valleys having been dismantled and reconverted. This gives the mountains the status of "energy reserve" (according to the terms used in the 1992 Rio Declaration) which can only be exploited and developed through national and trans-national networks (Blanc and Bonin 2008). The flow of energy between the mountains and the plains which started at the beginning of the 20 century was an extremely powerful vector for assimilating the populations and economies of the mountain areas. This was especially so since at this very time when the mountains were required to satisfy the energy needs of the lowlands and the towns, a new stage was reached in developing the tourist potential of the high massifs, with hydroelectricity creating the conditions for improving the accessibility and attractiveness of the high mountain areas (Bouneau 1997, 2003, Métailié and Rodriguez 2011, Rodriguez 2012). 1 . Traduit du français par Hilary Koziol. 2 This observation and all the analyses that follow are based on the initial results of research entitled "Landscape resources and energy resources in mountains in Southern Europe. History, comparison, experimentation", in the context of the programme Ignis mutat res. Considering architecture, cities and landscapes through the prism of energy, and financed by the Atelier International du Grand Paris. This research covers four mountain regions in Europe: the Sierra Nevada, the Dolomites, the Valais and the Pyrenees.

Ressources paysagères et ressources énergétiques dans les montagnes sud-européennes. Histoire, comparaison, expérimentation

Late Quaternary glacial phases in the Iberian Peninsula

We characterized spatial and temporal variability in net ecosystem production (NEP), community respiration (CR), and gross primary production (GPP) over an ice-free season in an oligotrophic high-elevation lake using high-frequency measurements of dissolved oxygen. We combined the use of free-water and incubation chamber measurements to compare pelagic and benthic habitats and estimate their relative contributions to whole-lake metabolism. Despite a brief period of predominant heterotrophy after snowmelt, both free-water and incubation chamber measurements confirmed autotrophy of the epilimnion in all habitats throughout the ice-free season. In contrast, benthic incubation chambers showed the benthos to be consistently heterotrophic. Although temperature was the strongest seasonal driver of benthic metabolism, bacterioplankton density and indexes of organic matter quality explained the most variability in pelagic metabolism. Driven largely by benthic metabolism, free-water measurements of GPP and CR were twice as high in littoral than pelagic habitats. However, rates of water column primary production overlying the littoral benthos were high enough to overcome net benthic heterotrophy, and seasonal mean NEP in littoral habitats remained positive and not significantly different from pelagic habitats. Benthic rates averaged about 25% of whole-lake metabolism. Pelagic metabolism measurements were affected by littoral rates about half the time, with the degree of isolation between the two a function of advection and water column stability. These results emphasize the importance of characterizing spatial and temporal variability in metabolism within the context of physical dynamics and challenge the notion that benthic metabolism will necessarily be larger than pelagic metabolism in oligotrophic lakes.

Spatial and Temporal Variability in the Ecosystem Metabolism of a High-elevation Lake: Integrating Benthic and Pelagic Habitats

Linking pesticides and human health: a geographic information system (GIS) and Landsat remote sensing method to estimate agricultural pesticide exposure.

When we reflect that the mountain valleys were thickly populated as far east as Yosemite (in summer, still further up), and consider the great extent and fertility of the San Joaquin plains … . then add to this the long and fish-full streams, the Mokelumne, the Stanislaus, the Tuolumne, the Merced, the Chowchilla, and the San Joaquin encircling all, along whose banks the Indians anciently dwelt in multitudes, we shall see what a capacity there was to support a dense population.

The Sierra Nevada

The banks of the Sacramento and San Joaquin, and the numerous tributaries of these rivers, and the Tule Lake (i.e., Tulare Lake), were at this time studded with Indian villages of from one to twelve hundred inhabitants each. The population of this extensive valley was so great that it caused surprise, and required a close investigation into the nature of a country that without cultivation, could afford the means of subsistence to so great a community, and who were such indifferent hunters.

The Central Valley Region

This is certainly a fine harbour: It presents on sight a beautiful fitness, and it has no lack of good drinking water and plenty of firewood and ballast. Its climate, though cold, is altogether healthful and it is free from such troublesome daily fogs as there are at Monterey, since these scarcely come to its mouth and inside there are very clear days. To these many good things is added the best of all: The heathens all around this harbour are always so friendly and so docile that I had Indians aboard several times with great pleasure, and the crew as often visited them on land.

San Francisco Bay and Central Coast Regions

This brief note calls attention to the previously unreported discovery of a prehistoric rubber ball, apparently of Mesoamerican origin, at a high-elevation site in the central Sierra Nevada, California.

Michael J. Moratto

Papers

The Sierra Nevada

The Central Valley Region

San Francisco Bay and Central Coast Regions

A Pre-Columbian Rubber Ball from the Central Sierra Nevada, Alta California