According to the Intergovernmental Panel on Climate Change report released in September 2014, unprecedented changes in temperature and precipitation patterns have been recorded globally in recent decades and further change is predicted to occur in the near future, mainly as the result of human activity. In particular, projections show that the Mediterranean climate zone will be markedly affected with significant implications for lake water levels and salinity. This may be exacerbated by increased demands for irrigation water. Based on long-term data from seven lakes and reservoirs covering a geographical gradient of 52°of latitudes and a literature review, we discuss how changes in water level and salinity related to climate change and water abstraction affect the ecosystem structure, function, biodiversity and ecological state of lakes and reservoirs. We discuss mitigation measures to counteract the negative effects on ecological status that are likely to result from changes in climate and water abstraction practices. Finally, we highlight research required to improve knowledge of the impacts of anthropogenically induced changes on lake water level and consequent changes in salinity.

No abstract

Willows are dominant woody plants of many high-elevation riparian areas of the western USA, and constitute an important food resource for various ungulates, which tend to concentrate in riparian areas. The response of willow to browsing was analyzed in the elk winter range of Rocky Mountain National Park, by considering the effect of elk browsing on Salix monticola Bebb, one of the most common willow species in this area. Unbrowsed and browsed treatments were established during the 1997 growing season (May to October), using eight long-term exclosures built in the fall of 1994. Plants in the browsed treatment were in the areas open to browsing, but they were protected from browsing by small exclosures during the experimental period. Winter browsing by elk induced the following measured responses in plant morphology and development: (1) higher shoot biomass production but similar leaf biomass and leaf area per plant, (2) a lower number of and bigger shoots, (3) a lower number of and bigger leaves, and (4) flower inhibition. In addition, we infer that browsing induces (5) lower belowground allocation and (6) a more negative N balance but a higher soil N uptake. We conclude that elk browsing negatively affects willow even though willow compensate for aboveground biomass removal. Continuous browsing produces long-term changes in willow morphology which constrain plant growth and development. High browsing utilization, as occurred in this experiment, could therefore reduce the competitive ability and survivorship of willow, in particular under drier environmental conditions.

We used 35‐year and 4‐year ungulate exclosures to determine the effects of elk (Cervus elaphus) herbivory on above‐ground and below‐ground production and soil fertility on the elk winter range in Rocky Mountain National Park (RMNP), Colorado, USA. We used paired grazed and ungrazed plots to evaluate ungulate herbivory effects in short and tall willow (Salix spp.), aspen (Populus spp.), and upland grass/shrub vegetation associations. We measured nitrogen (N) fluxes (litter deposition, fecal and urinary deposition from elk, movements of N by elk, N mineralization, soil N availability, elk consumption rates) within the elk winter, above‐ground and below‐ground N pools (herbaceous, shrub and root biomass, %N in plants, roots, and soil), and N fluxes on and off the elk winter range (seasonal movement of N by elk). Nitrogen mineralization and soil nitrate (NO3) pools were reduced in the short willow community (P = 0.07 and 0.10, respectively; n = 4 sites) in grazed plots, but not in the upland grass/shrub community or tall willow sites (P > 0.10). Annual growth of willows was reduced by 98% in grazed plots, relative to 35‐year exclosures, and 66% relative to 4‐year exclosures. Thus, height, canopy size, and litter biomass of willows were reduced, and N yield of willows was 64% less in grazed plots. We evaluated movement of N by elk among 6 major vegetation associations and found that elk grazed more and bedded less in willow vegetation association compared to mixed conifer, mesic meadow, and grassland/shrub associations (P = 0.014, 0.001, and 0.026, respectively), suggesting that elk herbivory and movement led to a net loss of N in the willow vegetation association. Elk spent less total time in willows than mesic meadow association, yet they consumed large amounts of willow plant biomass. We recommend management of elk numbers and elk herbivory that takes into consideration impacts to N process function, as negative effects from current levels of herbivory were observed in ≥1 of 3 vegetation associations studied.