Premise of the Study
Changing climates are expected to affect the abundance and distribution of global vegetation, especially plants and lichens with an epiphytic lifestyle and direct exposure to ...atmospheric variation. The study of epiphytes could improve understanding of biological responses to climatic changes, but only if the conditions that elicit physiological performance changes are clearly defined.
Methods
We evaluated individual growth performance of the epiphytic lichen Evernia mesomorpha, an iconic boreal forest indicator species, in the first year of a decade‐long experiment featuring whole‐ecosystem warming and drying. Field experimental enclosures were located near the southern edge of the species’ range.
Key Results
Mean annual biomass growth of Evernia significantly declined 6 percentage points for every +1°C of experimental warming after accounting for interactions with atmospheric drying. Mean annual biomass growth was 14% in ambient treatments, 2% in unheated control treatments, and −9% to −19% (decreases) in energy‐added treatments ranging from +2.25 to +9.00°C above ambient temperatures. Warming‐induced biomass losses among persistent individuals were suggestive evidence of an extinction debt that could precede further local mortality events.
Conclusions
Changing patterns of warming and drying would decrease or reverse Evernia growth at its southern range margins, with potential consequences for the maintenance of local and regional populations. Negative carbon balances among persisting individuals could physiologically commit these epiphytes to local extinction. Our findings illuminate the processes underlying local extinctions of epiphytes and suggest broader consequences for range shrinkage if dispersal and recruitment rates cannot keep pace.
Ontogenetic niche theory predicts that individuals may undergo one or more changes in habitat or diet throughout their lifetime to maintain optimal growth rates, or to optimize trade-offs between ...mortality risk and growth. We combine skeletochronological and stable nitrogen isotope (δ¹⁵N) analyses of sea turtle humeri (n = 61) to characterize the growth dynamics of juvenile loggerhead sea turtles (Caretta caretta) during an oceanic-to-neritic ontogenetic shift. The primary objective of this study was to determine how ontogenetic niche theory extends to sea turtles, and to individuals with different patterns of resource use (discrete shifters, n = 23; facultative shifters n = 14; non-shifters, n = 24). Mean growth rates peaked at the start of the ontogenetic shift (based on change in δ¹⁵N values), but returned to pre-shift levels within 2 years. Turtles generally only experienced 1 year of relatively high growth, but the timing of peak growth relative to the start of an ontogenetic shift varied among individuals (before, n = 14; during, n = 12; after, n = 8). Furthermore, no reduction in growth preceded the transition, as is predicted by ontogenetic niche theory. Annual growth rates were similar between non-transitioning turtles resident in oceanic and neritic habitats and turtles displaying alternative patterns of resource use. These results suggest that factors other than maximization of size-specific growth may more strongly influence the timing of ontogenetic shifts in logger-head sea turtles, and that alternative patterns of resource use may have limited influence on somatic growth and age at maturation in this species.
Background Ecologists fiercely debate the role of soil conditions and fire regimes in controlling forest – savanna boundaries. A prominent component of this debate centres on the plausibility and ...existence of fire-mediated alternative stable state dynamics (FMASS), a model first proposed by the Tasmanian ecologist WD Jackson in 1968. The FMASS model asserts that increased or decreased landscape fire activity, often due to human intervention, can overwhelm physical environmental (e.g. topography and edaphic factors) controls of forest and savanna mosaics, thereby creating landscape dynamism. Many FMASS models include fire-vegetation-soil interactions (FVS), in which changes in fire frequency can change soil fertility and hence tree growth. This interaction, in turn, affects the capacity offorests to recover from disturbance and long unburnt savanna to convert to forest. Scope We evaluate support for the FMASS-FVS model in the context of the dynamics of the Tasmanian forests that have recently been drawn into wider, global debates surrounding the co-occurrence of tree and treeless vegetation states. We develop a simple spatial simulation model to illuminate the difficulties in analysing landscape pattern to draw inferences about the existence of FMASS-FVS. Conclusions Our review of the Tasmanian evidence shows that FMASS-FVS cannot unambiguously explain all tracts of sedgelands in Tasmanian wet forests, and hence Tasmania should not be used as an exemplar of these theories globally. Our simulations highlight that soil sampling that targets forest boundaries risks erroneously concluding that the distribution of forest and savanna boundaries is decoupled from edaphic factors. We describe a structured methodological pathway that can identify the role of FMASS-FVS in Tasmanian forest dynamics, and elsewhere in the world. This approach use cross-scale temporal and spatial analyses, and targeted experimental teste, to illuminate the interplay of fire, vegetation and edaphic factors in controlling tree establishment and growth and forest boundary dynamics.
An influential body of scholarship in political science has investigated the impact of economic crisis on various political outcomes. The vast majority of these studies rely on annual growth rates ...(AGR) to specify economic crisis. I argue that this canonical approach comes with several logical shortcomings. It leads to misguided impressions of crisis severity; it makes no distinction between rapid expansion years and rapid recovery years; and it disregards the financial dimension of economic crises. I present and discuss three alternative approaches of measuring economic crisis, imported from economics: economic shocks, economic slumps, and measures of financial crises. Examples from the regime instability literature demonstrate that these alternative crisis measurements provide results that are theoretically more nuanced and empirically more robust. On this basis, the article encourages researchers to pay more attention to the way they measure economic crisis in general and to supplement the AGR approach with alternative crisis measures in particular.
Previous research has shown that red light conditions may improve growth and decrease aggressive behaviors in chickens and turkeys; however, more recent studies suggest that blue–green light may ...improve production of broilers over red light. To date, no research has been conducted to examine whether different wavelengths of light have an impact on production in the Pekin duck. To determine this, we raised Pekin ducks under aviary conditions that were similar to standard commercial barns. The ducks were kept in 3 different pens: red light (approximately 625 nm), blue light (approximately 425 nm), and white light. Light sources in each pen were standardized to produce a peak energy at 1.6 × 103 μM photons/m2/s at the level of the ducks’ heads. Ducks were given ad libitum access to water and commercial duck diet, and were housed on pine shavings at a density of 0.43 m2/duck. Ducks were evaluated weekly for BW and condition and a subjective measure of the duck's anxiety levels was determined. We found that ducks housed under blue light had significantly (P < 0.01) reduced BW at every age until the end of the study (processing age; 35 d). Unlike ducks housed under red or white light, ducks housed in the blue pen showed a higher level of anxiety; while evaluators were in the pen a majority of them began panting, they were much less inquisitive than other ducks, they took longer to exhibit normal social behavior once evaluation was completed, and they frequently “swarmed” when no people were present. There were no differences in any measurements between the red and white-lighted pens. These data suggest that unlike the chicken, blue lights may be inappropriate for raising Pekin ducks in a commercial setting.
Species of the genus
Wolffia
(duckweed) are harvested from natural water bodies in many countries for human consumption. Relative growth rates (RGR) of 25 clones (ecotypes) representing all 11 ...species of the genus
Wolffia
were investigated under standardized laboratory conditions in search for potential candidates for production of
Wolffia
biomass at a biotechnological scale. This is the first report of large-scale screening of physiological properties of
Wolffia
species. Large differences in RGR of different clones were detected, e.g., in
Wolffia globosa
. Interestingly, intraspecific differences, i.e., at the level of clones are much higher than differences between species. Rate of photosynthesis (oxygen production in light) and respiration (oxygen consumption in dark) in clones of
W. globosa
, measured under standardized conditions, are in positive correlation with their respective RGR. Higher rate of photosynthesis seems to be a determining factor for higher RGR. The RGR of the first available axenic clone of the re-discovered species,
Wolffia microscopica
(clone 2005), depends strongly on the nutrient medium used, in contrast to other investigated species. This clone of
W. microscopica
has a doubling time of 29.3 h and represents the fastest growing flowering plant known till date.
Ocean acidification is a direct consequence of carbon dioxide (CO₂) dissolution in seawater and has the potential to impact marine phytoplankton. Although community composition and species ...interactions may be affected, few studies have taken the latter into account. Here, we assessed how species interactions and competition shape physiological responses by testing monospecific and mixed cultures of (1) the haptophyte Phaeocystis globosa and the chain-forming diatoms Chaetoceros sp. and Asterionellopsis glacialis under present CO₂ levels, and (2) Chaetoceros sp. and P. globosa under increasing CO₂. The interactions established between the 3 phytoplankton cultures were species- and abundance-dependent. The 2 diatoms did not interact; however, in the presence of P. globosa the growth rates of A. glacialis decreased and those of Chaetoceros sp. increased (depending on a Chaetoceros sp. abundance threshold). Conversely, when Chaetoceros sp. was reasonably abundant, P. globosa was also positively affected (alternating between an abundance/biomass-dependent commensalistic and/or mutualistic interaction). Under enhanced CO₂ concentrations, the responses of Chaetoceros sp. and P. globosa mixed cultures were altered, mainly due to Chaetoceros sp. showing a physiological optimum at higher CO₂ concentrations than P. globosa. While P. globosa was hindered by increased CO₂, Chaetoceros sp. registered augmentation of growth rates, chain length and cellular elemental quotas up to ~750 μatm. Our work emphasizes the role of species interactions when addressing effects of enhanced CO₂ on marine phytoplankton. Species-specific response trends to increasing CO₂ concentrations revealed significant alterations to species interaction and biomass build-up, which may consequently affect future phytoplankton communities’ composition and dynamics.
New particle formation (NPF) was investigated at a coastal background site in Southwest Spain over a four-year period using a Scanning Particle Mobility Sizer (SMPS). The goals of the study were to ...characterise the NPF and to investigate their relationship to meteorology, gas phase (O3, SO2, CO and NO2) and solar radiation (UVA, UVB and global). A methodology for identifying and classifying the NPF was implemented using the wind direction and modal concentrations as inputs. NPF events showed a frequency of 24% of the total days analysed. The mean duration was 9.2±4.2h. Contrary to previous studies conducted in other locations, the NPF frequency reached its maximum during cold seasons for approximately 30% of the days. The lowest frequency took place in July with 10%, and the seasonal wind pattern was found to be the most important parameter influencing the NPF frequency. The mean formation rate was 2.2±1.7cm−3s−1, with a maximum in the spring and early autumn and a minimum during the summer and winter. The mean growth rate was 3.8±2.4nmh−1 with higher values occurring from spring to autumn. The mean and seasonal formation and growth rates are in agreement with previous observations from continental sites in the Northern Hemisphere. NPF classification of different classes was conducted to explore the effect of synoptic and regional-scale patterns on NPF and growth. The results show that under a breeze regime, the temperature indirectly affects NPF events. Higher temperatures increase the strength of the breeze recirculation, favouring gas accumulation and subsequent NPF appearance. Additionally, the role of high relative humidity in inhibiting the NPF was evinced during synoptic scenarios. The remaining meteorological variables (RH), trace gases (CO and NO), solar radiation, PM10 and condensation sink, showed a moderate or high connection with both formation and growth rates.
•New particle formation (NPF) was observed over 4-years in the South-western Spain.•New particle formation events showed a frequency of 24% of the total days analysed.•NPF was more frequent in cold seasons and less frequent in summer time.•NPF parameters were different under synoptic or regional-scale atmospheric patterns.•Formation and growth rates were dependent on the solar radiation and gas levels.
In this article, global stabilization for a class of nonlinear uncertain time-delay systems with saturated input is considered. The saturated input is handled by a new auxiliary system with dynamic ...gain and the linear growth condition with unknown growth rates is removed. A novel adaptive observer-controller coupling design framework is put forward, under which the closed-loop system is globally bounded. Finally, a simulation shows that the proposed technique is effective.
Stem analysis allows us to obtain an abundant amount of information on tree growth. A couple of algorithms exist to utilize section height and growth ring data for reconstructing height and age ...time‐series information.
I evaluated two alternatives, a well‐known and a newly proposed algorithm using stem analysis data of four species, including deciduous and evergreen broadleaves and a conifer. I reconstructed height–age pairs by both algorithms. I fit height growth equations in a mixed‐effects model framework for each species, using the generated data with the respective algorithm. Comparisons considered confidence intervals of the estimated parameters, as well as regression‐based equivalence tests.
Results showed that the fitted growth models obtained from both stem analysis algorithms were statistically equivalent. However, the proposed algorithm is simpler and thus provides a useful alternative to current methods.
Based on the findings, I recommend using this new stem analysis algorithm to reconstruct tree height growth with stem analysis data.
Resumen
El análisis fustal permite obtener abundante información del crecimiento de los árboles. Existen una cantidad importante de algoritmos que utilizando los datos de los anillos de crecimiento en cada sección permiten reconstruir las series de tiempo altura‐edad.
Evalué dos alternativas, un algoritmo muy conocido y otro nuevo propuesto usando datos de análisis fustal provenientes de cuatro especies, incluyendo latifoliadas deciduas y siempreverdes y una conífera. Reconstruí los pares de datos altura‐edad con ambos algoritmos. Luego, a partir de los datos generados por cada algoritmo, ajuste una ecuación de crecimiento en altura mediante modelos de efectos mixtos para cada especie. Finalmente, compare los intervalos confidenciales de los parámetros estimados de los modelos de crecimiento, así como también mediante pruebas de equivalencia.
Los resultados indicaron que los modelos de crecimiento obtenidos a partir de los datos generados por ambos algoritmos son estadísticamente equivalentes. Sin embargo, el algoritmo propuesto es más simple y por lo tanto ofrece una alternativa muy útil a los métodos actuales.
Basado en esta investigación, recomiendo usar este nuevo algoritmo para reconstruir el crecimiento en altura a partir de datos de análisis fustal.
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