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Water-use advantage for lianas over trees in tropical seasonal forests
Chen, Y.J. ; Cao, K.F. ; Schnitzer, S.A. ; Fan, Z.X. ; Zhang, J.L. ; Bongers, F. - \ 2015
New Phytologist 205 (2015)1. - ISSN 0028-646X - p. 128 - 136.
rain-forest - canopy trees - soil-water - sw china - aboveground biomass - secondary forest - eastern amazonia - stomatal control - stable-isotopes - woody-plants
•Lianas exhibit peak abundance in tropical forests with strong seasonal droughts, the eco-physiological mechanisms associated with lianas coping with water deficits are poorly understood. •We examined soil water partitioning, sap flow, and canopy eco-physiological properties for 99 individuals of 15 liana and 34 co-occurring tree species in three tropical forests that differed in soil water availability. •In the dry season, lianas used a higher proportion of deep soil water in the karst forest (KF; an area with severe seasonal soil water deficit (SSWD)) and in the tropical seasonal forest (TSF, moderate SSWD), permitting them to maintain a comparable leaf water status than trees in the TSF or a better status than trees in the KF. Lianas exhibited strong stomatal control to maximize carbon fixation while minimizing dry season water loss. During the dry period, lianas significantly decreased water consumption in the TSF and the KF. Additionally, lianas had a much higher maximum photosynthetic rates and sap flux density in the wet season and a lower proportional decline in photosynthesis in the dry season compared with those of trees. •Our results indicated that access to deep soil water and strong physiological adjustments in the dry season together with active wet-season photosynthesis may explain the high abundance of lianas in seasonally dry forests.
Consequences of mixing assumptions for time-variable travel time distributions
Velde, Y. van der; Heidbüchel, I. ; Lyon, S.W. ; Nyberg, L. ; Rodhe, A. ; Bishop, K. ; Troch, P.A. - \ 2015
Hydrological Processes 29 (2015)16. - ISSN 0885-6087 - p. 3460 - 3474.
solute transport - stream chemistry - stable-isotopes - residence time - transit times - water storage - catchment - model - age - dispersion
The current generation of catchment travel time distribution (TTD) research, integrating nearly three decades of work since publication of Water's Journey from Rain to Stream, seeks to represent the full distribution in catchment travel times and its temporal variability. Here, we compare conceptualizations of increasing complexity with regards to mixing of water storages and evaluate how these assumptions influence time-variable TTD estimates for two catchments with contrasting climates: the Gårdsjön catchment in Sweden and the Marshall Gulch catchment in Arizona, USA. Our results highlight that, as long as catchment TTDs cannot be measured directly but need to be inferred from input-output signals of catchments, the inferred catchment TTDs depend strongly on the underlying assumptions of mixing within a catchment. Furthermore, we found that the conceptualization of the evapotranspiration flux strongly influences the inferred travel times of stream discharge. For the wet and forested Gårdsjön catchment in Sweden, we inferred that evapotranspiration most likely resembles a completely mixed sample of the water stored in the catchment; however, for the drier Marshall Gulch catchment in Arizona, evapotranspiration predominantly contained the younger water stored in the catchment. For the Marshall Gulch catchment, this higher probability for young water in evapotranspiration resulted in older water in the stream compared to travel times inferred with assumptions of complete mixing. New observations that focus on the TTD of the evapotranspiration flux and the actual travel time of water through a catchment are necessary to improve identification of mixing and consequently travel times of stream water. Copyright © 2014 John Wiley & Sons, Ltd.
Monitoring Least Weasels after a Winter Peak of Lemmings in Taimyr: Body Condition, Diet and Habitat Use
Feige, N. ; Enrich, D. ; Popov, I.Y. ; Broekhuizen, S. - \ 2012
Arctic 65 (2012)3. - ISSN 0004-0843 - p. 273 - 282.
stable-isotopes - dicrostonyx-groenlandicus - dynamics - nitrogen - residuals - greenland - abundance - selection - ecology - indexes
Least weasels are highly specialized small-rodent predators. Despite the fact that they are hypothesized to play an important role in generating the lemming cycles, a key process for the functioning of the terrestrial tundra ecosystem,. very little is known about the biology of these miniature carnivores in the Arctic. At Mys Vostochny in western Taimyr, Russia, least weasels were observed for the first time during a lemming peak in 2005, but not in two subsequent years with low lemming densities. Here we report observations about weasel signs in lemming winter nests, body condition, habitat use, and diet in summer 2008, a year when lemmings had been numerous under the snow but populations crashed before the summer, and least weasels were abundant. Stable isotope analyses revealed that weasel diet was dominated by Siberian lemmings during spring. As expected, given lower resource availability when the lemming population crashed, weight (taking into account body length) was somewhat lower in 2008 than in 2005. Tracking tunnels and trapping showed that in summer least weasels mostly used sheltered habitats such as rocky outcrops and driftwood. Together with surveys of lemming winter nests, tracking tunnels appeared to be a promising method for monitoring least weasels in the Arctic tundra.
Carbon conversion and metabolic rate in two marine sponges
Koopmans, M. ; Rijswijk, P. van; Martens, D.E. ; Egorova-Zachernyuk, T.A. ; Middelburg, J.J. ; Wijffels, R.H. - \ 2011
Marine Biology 158 (2011)1. - ISSN 0025-3162 - p. 9 - 20.
fatty-acids - stable-isotopes - organic-carbon - demospongiae - growth - lipids - invertebrates - regeneration - biomarkers - porifera
The carbon metabolism of two marine sponges, Haliclona oculata and Dysidea avara, has been studied using a 13C isotope pulse-chase approach. The sponges were fed 13C-labeled diatoms (Skeletonema costatum) for 8 h and they took up between 75 and 85%. At different times, sponges were sampled for total 13C enrichment, and fatty acid (FA) composition and 13C enrichment. Algal biomarkers present in the sponges were highly labeled after feeding but their labeling levels decreased until none was left 10 days after enrichment. The sponge-specific FAs incorporated 13C label already during the first day and the amount of 13C label inside these FAs kept increasing until 3 weeks after labeling. The algal-derived carbon captured by the sponges during the 8-h feeding period was thus partly respired and partly metabolized during the weeks following. Apparently, sponges are able to capture enough food during short periods to sustain longer-term metabolism. The change of carbon metabolic rate of fatty acid synthesis due to mechanical damage of sponge tissue was studied by feeding sponges with 13C isotope–labeled diatom (Pheaodactylum tricornutum) either after or before damaging and tracing back the 13C content in the damaged and healthy tissue. The filtration and respiration in both sponges responded quickly to damage. The rate of respiration in H. oculata reduced immediately after damage, but returned to its initial level after 6 h. The 13C data revealed that H. oculata has a higher metabolic rate in the tips where growth occurs compared to the rest of the tissue and that the metabolic rate is increased after damage of the tissue. For D. avara, no differences were found between damaged and non-damaged tissue. However, the filtration rate decreased directly after damage.
Seabird seasonal trophodynamics: isotopic patterns in a community of Pacific alcids
Davies, W.E. ; Hipfner, J.M. ; Hobson, K.A. ; Ydenberg, R.C. - \ 2009
Marine Ecology Progress Series 382 (2009). - ISSN 0171-8630 - p. 211 - 219.
auklets ptychoramphus-aleuticus - stable-isotopes - trophic relationships - rhinoceros auklets - british-columbia - triangle island - ocean climate - piscivorous seabird - breeding success - foraging areas
We measured delta N-15 and delta C-13 values in the blood of breeding adults and nestlings of 5 species of alcids at Triangle Island, British Columbia, to estimate the extent to which these seabirds alter their foraging ecology across successive breeding stages. Considerable intraspecific (stage-to-stage) and interspecific variation was found. Two species-common murre Uria aalge and pigeon guillemot Cepphus columba-fed consistently at high trophic levels (i.e. diets of fish) in inshore or benthically linked habitats. The foraging ecology of 3 others-Cassin's auklet Ptychoramphus aleuticus, rhinoceros auklet Cerorhinca monocerata and tufted puffin Fratercula cirrhata-was more variable. Tufted puffins exhibited especially dramatic trophic and habitat shifts between early and late-season diets. With the exception of tufted puffin, the diet of provisioning adults differed from that. fed to their nestlings. Trophic level of the community as a whole increased as the season progressed due to the combination of trophic shifting by rhinoceros auklets and tufted Puffins, and earlier breeding by zooplanktivorous Cassin's auklets than by piscivorous murres and guillemots. Our results contribute to a growing body of evidence that marine bird species exhibit considerable flexibility in their foraging behaviour and also shed new light on seasonal patterns in the trophic relations within marine bird communities.
Trace element profiles as unique identifiers of western sandpiper (Calidris mauri) populations
Norris, D.R. ; Lank, D.B. ; Pither, J. ; Chipley, D. ; Ydenberg, R.C. ; Kyser, T.K. - \ 2007
Canadian Journal of Zoology 85 (2007)4. - ISSN 0008-4301 - p. 579 - 583.
spruce grouse feathers - mineral profiles - stable-isotopes - birds - markers
Understanding the ecology and evolution of migratory animals requires information on how populations are geographically linked between periods of the annual cycle. To examine whether trace elements could be used to track migratory birds, we analyzed concentrations of 42 trace elements in feathers of western sandpipers (Calidris mauri (Cabanis, 1857)) that were grown at five different wintering sites ranging from San Francisco Bay (USA) to the Bay of Panama. Linear discriminant analysis of 15 elements correctly classified all 26 individuals to their wintering sites, including two sites that were separated by less than 3 km. A randomization procedure confirmed the robustness of these findings. Our analysis suggests that trace elements can be used to assign individuals to specific sites of origin. Although we did not sample feathers from all wintering areas, the regions our sites represented comprised a significant percentage of the global population. However, since trace element profiles appear to be highly specific to geographic sites, we suggest that this technique is best suited for cases where samples can be obtained from the majority of populations throughout a species range. Thus, under certain circumstances, trace element profiles may provide the potential to identify populations with a high degree of spatial accuracy.