Search results for "NK"
showing 10 items of 14343 documents
Experimental δ13C evidence for a contribution of methane to pelagic food webs in lakes
2006
We tested the hypothesis that low stable carbon isotope (δ13C) values commonly observed for zooplankton in humic lakes are due to their feeding on isotopically light methane-oxidizing microbes, and thus that methane-derived carbon is important in the food webs of these lakes. In replicate laboratory cultures, Daphnia longispina, a common crustacean zooplankter in humic lakes, were fed microbial suspensions with or without enrichment by biogenic methane. The δ13C values of Daphnia indicated consumption of 13C-depleted methanotrophic bacteria, while growth rates, survival, and reproduction of Daphnia in cultures enriched with methane were equal to or greater than those in nonenriched cultures…
Phytoplankton distribution in Mar Menor coastal lagoon (SE Spain) during 2017.
2020
The Mar Menor is a Spanish coastal lagoon of great ecological and economic interest. The agricultural and tourist activities developed in the surroundings of the lagoon, together with the modifications in its channels of connection with the Mediterranean Sea, have notably affected the quality of its waters, which is altering the natural balance of the ecosystem. In this work, an analysis of the density of phytoplankton present in the lagoon between the months of May to December 2017 was carried out. The results indicate a significant increase in phytoplankton density between 2500 and 67,300 cells/mL compared to previous data of 1981 (between 10 and 500 cells/mL). Concentration of Chlorophyl…
Ecosystem responses to increased organic carbon concentration: comparing results based on long-term monitoring and whole-lake experimentation
2019
Recent increases in terrestrial dissolved organic carbon (DOC) concentrations in northern inland waters have many ecological consequences. We examined available data on carbon cycles and food webs of 2 boreal headwater lakes in southern Finland. Basic limnology and catchment characteristics of a pristine lake, Valkea-Kotinen (VK), were monitored over the past 25 years while the lake has undergone browning and DOC increased from similar to 11 to 13 mg L-1. Pronounced changes in the early 2000s represent a regime shift in DOC concentration and color. Lake Alinen Mustajarvi (AM) was manipulated for 2 years by additions of labile DOC (cane sugar), raising the DOC concentration from similar to 1…
Forest multifunctionality is not resilient to intensive forestry
2021
AbstractThere is ample evidence that intensive management of ecosystems causes declines in biodiversity as well as in multiple ecosystem services, i.e., in multifunctionality. However, less is known about the permanence and reversibility of these responses. To gain insight into whether multifunctionality can be sustained under intensive management, we developed a framework building on the concept of resilience: a system’s ability to avoid displacement and to return or transform to a desired state. We applied it to test the ability of forest multifunctionality to persist during and recover from intensive management for timber production in a boreal forest. Using forest growth simulations and…
Managing boreal forests for the simultaneous production of collectable goods and timber revenues
2016
Timber Production is an economically important provisioning ecosystem service in forests, but is often in conflict with the provision of other ecosystem services. In multifunctional forestry, the production of timber and non-timber ecosystem services should coexist in the same landscape. To this end, we explored the capacity of a boreal landscape to simultaneously produce collectable goods − bilberry (Vaccimium myrtillus L.), cowberry (Vaccinium vitis-idaea L.) and cep (Boletus edulis Bull.) − alongside timber revenues. We also identified optimal forest management plans to achieve this. Furthermore, we analyzed trade-offs between collectable good yields and timber production, as well as bet…
Changes in evapotranspiration and phenology as consequences of shrub removal in dry forests of central Argentina
2014
More than half of the dry woodlands (forests and shrublands) of the world are in South America, mainly in Brazil and Argentina, where in the last years intense land use changes have occurred. This study evaluated how the transition from woody-dominated to grass-dominated system affected key ecohydrological variables and biophysical processes over 20 000 ha of dry forest in central Argentina. We used a simplified surface energy balance model together with moderate-resolution imaging spectroradiometer–normalized difference vegetation index data to analyse changes in above primary productivity, phenology, actual evapotranspiration, albedo and land surface temperature for four complete growing …
Toros-Menalla (Chad, 7 Ma), the earliest hominin-bearing area: how many mammal paleocommunities?
2014
12 pages; International audience; The fossiliferous area of Toros-Menalla (TM) (Djurab Desert, northern Chad) has yielded one of the richest African mammal faunas of the late Miocene. It is also the place where the earliest known hominin, Sahelanthropus tchadensis, was found. Although more than 300 localities are recorded in that area, previous paleoecological studies focused only on the largest and richest one. The integration of the material from other TM localities, and thus of a significant number of mammal taxa, is crucial to improve the corresponding paleoenvironmental reconstructions. Before such inferences can be drawn, it is necessary to test for the ecological integrity of these m…
Evolutionary trends of Triassic ammonoids.
2015
The Triassic represents a key interval in the evolutionary history of ammonoids. Characterized by the dominance of the Ceratitida with their typical suture line indented on the lobes only, the Triassic quasi-monophyletic clade shows a remarkable biostratigraphic and geographic record. However, very few studies have thoroughly investigated their evolutionary trends, except for taxonomic richness. Although Triassic ammonoids show a very large range of morphologies, suture complexity and adult size, little is currently known about their trends, except for peculiar time intervals or taxonomic groups. Nevertheless, it seems that taxonomic diversity and morphological disparity of Triassic ammonoi…
Does quality of winter food affect spring condition and breeding in female bank voles (Clethrionomys glareolus)?
2004
We studied the effects of food supplementation on 16 bank vole populations in spring. We manipulated food quantity and quality in eight populations that were enclosed and eight other populations th...
Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well
2017
Following general life history theory, immediate reproductive investment (egg mass × fecundity/body mass) in oviparous teleosts is a consequence of both present and past environmental influences. This clarification questions the frequent use of season-independent (general) fecundity formulas in marine fish recruitment studies based on body metrics only. Here we test the underlying assumption of no lag effect on gametogenesis in the planktivorous, determinate-fecundity Atlantic herring (Clupea harengus) displaying large plasticity in egg mass and fecundity, examining Norwegian summer–autumn spawning herring (NASH), North Sea autumn-spawning herring (NSAH), and Norwegian spring-spawning herri…