If controls over primary productivity and plant community composition are mainly environmental, as opposed to biological, then global change may result in large-scale alterations in ecosystem structure and function. This view appears to be favored among investigations of plant biomass and community responses to experimental and observed warming. In far northern and arctic ecosystems, such studies predict increasing dominance of woody shrubs with future warming and emphasize the carbon (C)-sequestration potential and consequent atmospheric feedback potential of such responses. In contrast to previous studies, we incorporated natural herbivory by muskoxen and caribou into a 5-year experimental investigation of arctic plant community response to warming. In accordance with other studies, warming increased total community biomass by promoting growth of deciduous shrubs (dwarf birch and gray willow). However, muskoxen and caribou reduced total community biomass response, and responses of birch and willow, to warming by 19%, 46%, and 11%, respectively. Furthermore, under warming alone, the plant community shifted after 5 years away from graminoid-dominated toward dwarf birch-dominated. In contrast, where herbivores grazed, plant community composition on warmed plots did not differ from that on ambient plots after 5 years. These results highlight the potentially important and overlooked influences of vertebrate herbivores on plant community response to warming and emphasize that conservation and management of large herbivores may be an important component of mitigating ecosystem response to climate change.arctic ͉ climate change ͉ global warming ͉ herbivory ͉ species interactions

The spectral imaging and detection of mid-infrared wavelengths is emerging as an enabling technology of great technical and scientific interest, primarily because important chemical compounds display unique and strong mid-infrared spectral fingerprints that reveal valuable chemical information. Modern quantum cascade lasers have evolved as ideal coherent mid-infrared excitation sources, but simple, low-noise, room-temperature detectors and imaging systems lag behind. We address this need by presenting a novel, field-deployable, upconversion system for sensitive, two-dimensional, midinfrared spectral imaging. A room-temperature dark noise of 0.2 photons/spatial element/second is measured, which is a billion times below the dark noise level of cryogenically cooled InSb cameras. Single-photon imaging and a resolution of up to 200 3 100 spatial elements are obtained with a record-high continuous-wave quantum efficiency of ∼20% for polarized incoherent light at 3 mm. The proposed method is relevant for existing and new mid-infrared applications such as gas analysis and medical diagnostics.O ptical spectroscopy within the ultraviolet, visible and nearinfrared regimes has for decades been an indispensable method for the identification and quantization of chemical analytes. However, emerging mid-infrared applications in environmental gas monitoring or the life sciences call for improved detection systems that challenge today's capabilities in terms of sensitivity and/or imaging functionality. For example, in the face of global warming, mid-infrared detectors capable of measuring minute gas concentrations are required, because important greenhouse gases such as CO 2 , CO, CH 4 and N 2 O have fundamental absorption bands located in the mid-infrared 1 . For example, CO requires a detection sensitivity on the order of 100 ppb (parts per billion) 2 . Monitoring atmospheric trace molecules at these levels provides important inputs for the climate models used for studying global warming and its consequences for life on Earth 3 . In life science, the spectral regime from 0.3 to 2 mm has already been utilized for fundamental studies of breath analysis. However, significant improvements can be expected from using mid-infrared spectroscopy 4,5 . The on-line detection of the numerous different molecules (.1,000) in exhaled human breath may lead to new non-invasive diagnostics tool for doctors. However, such biomarkers are frequently below ppb levels. Indeed, the exhaled concentration of ethane (at 3.3 mm), which is used as a marker for asthma and chronic obstructive pulmonary disease, is found at 100 ppt (parts per trillion) levels, clearly demonstrating the requirement for highly sensitive methods 5 . Similarly, 1-butanol and 3-hydroxy-2-butanone in breath could be useful biomarkers for lung cancer 6 .In the 3-15 mm wavelength regions, two-dimensional mid-infrared spectral imaging demonstrates potential for identifying cancerous tissue, providing a new tool for cancer diagnostics. In this wavelength region, each organic compound an...

Abstract. Climatic warming is associated with organisms breeding earlier in the season than is typical for their species. In some species, however, response to warming is more complex than a simple advance in the timing of all life history events preceding reproduction. Disparities in the extent to which different components of the reproductive phenology of organisms vary with climatic warming indicate that not all life history events are equally responsive to environmental variation. Here, we propose that our understanding of phenological response to climate change can be improved by considering entire sequences of events comprising the aggregate life histories of organisms preceding reproduction. We present results of a two-year warming experiment conducted on 33 individuals of three plant species inhabiting a low-arctic site. Analysis of phenological sequences of three key events for each species revealed how the aggregate life histories preceding reproduction responded to warming, and which individual events exerted the greatest influence on aggregate life history variation. For alpine chickweed (Cerastium alpinum), warming elicited a shortening of the duration of the emergence stage by 2.5 days on average, but the aggregate life history did not differ between warmed and ambient plots. For gray willow (Salix glauca), however, all phenological events monitored occurred earlier on warmed than on ambient plots, and warming reduced the aggregate life history of this species by 22 days on average. Similarly, in dwarf birch (Betula nana), warming advanced flower bud set, blooming, and fruit set and reduced the aggregate life history by 27 days on average. Our approach provides important insight into life history responses of many organisms to climate change and other forms of environmental variation. Such insight may be compromised by considering changes in individual phenological events in isolation.

Temporal advancement of resource availability by warming in seasonal environments can reduce reproductive success of vertebrates if their own reproductive phenology does not also advance with warming. Indirect evidence from large-scale analyses suggests, however, that migratory vertebrates might compensate for this by tracking phenological variation across landscapes. Results from our two-year warming experiment combined with seven years of observations of plant phenology and offspring production by caribou (Rangifer tarandus) in Greenland, however, contradict evidence from large-scale analyses. At spatial scales relevant to the foraging horizon of individual herbivores, spatial variability in plant phenology was reduced-not increased-by both experimental and observed warming. Concurrently, offspring production by female caribou declined with reductions in spatial variability in plant phenology. By highlighting the spatial dimension of trophic mismatch, these results reveal heretofore unexpected adverse consequences of climatic warming for herbivore population ecology.

Two main hypotheses have been proposed to explain reproductive synchrony exhibited by many species of large herbivores: the predation hypothesis and the seasonality hypothesis. Although examples supporting both hypotheses have been presented, no study has compared the intraseasonal progression of parturition and plant phenology in depredated and non-depredated populations of large herbivores. We monitored, on a daily or near-daily basis, the progression of the caribou (Rangifer tarandus) calving seasons in two populations: the Caribou River population in Alaska, U.S.A., where predators of caribou are present and the Kangerlussuaq-Sisimiut population in West Greenland where such predators have been absent for approximately 4000 years. Simultaneously, we quantified directly the phenological progression of caribou forage plants on spatially replicated plots in both study sites. Parturition was significantly more synchronous in the West Greenland (predator-free) population than in the Alaskan (depredated) population. Progression of the calving seasons in both populations was highly synchronized to the progression of forage plant phenology, and the slopes of these relationships were statistically indistinguishable, with 50% of births having occurred when approximately 60%–70% of forage plant species were emergent. These results document clear synchronization of the timing of parturition by caribou to plant phenology, regardless of predation pressure.

The potential for improving the penetration depth of optical coherence tomography systems by using light sources with longer wavelengths has been known since the inception of the technique in the early 1990s. Nevertheless, the development of mid-infrared optical coherence tomography has long been challenged by the maturity and fidelity of optical components in this spectral region, resulting in slow acquisition, low sensitivity, and poor axial resolution. In this work, a mid-infrared spectral-domain optical coherence tomography system operating at a central wavelength of 4 µm and an axial resolution of 8.6 µm is demonstrated. The system produces two-dimensional cross-sectional images in real time enabled by a high-brightness 0.9- to 4.7-µm mid-infrared supercontinuum source with a pulse repetition rate of 1 MHz for illumination and broadband upconversion of more than 1-µm bandwidth from 3.58–4.63 µm to 820–865 nm, where a standard 800-nm spectrometer can be used for fast detection. The images produced by the mid-infrared system are compared with those delivered by a state-of-the-art ultra-high-resolution near-infrared optical coherence tomography system operating at 1.3 μm, and the potential applications and samples suited for this technology are discussed. In doing so, the first practical mid-infrared optical coherence tomography system is demonstrated, with immediate applications in real-time non-destructive testing for the inspection of defects and thickness measurements in samples that exhibit strong scattering at shorter wavelengths.

Background— To assess cardiovascular actions of APJ agonism during prolonged (Pyr 1 )apelin-13 infusion and renin–angiotensin system activation. Methods and Results— Forty-eight volunteers and 12 patients with chronic stable heart failure attended a series of randomized placebo–controlled studies. Forearm blood flow, cardiac index, left ventricular dimensions, and mean arterial pressure were measured using bilateral venous occlusion plethysmography, bioimpedance cardiography, transthoracic echocardiography, and sphygmomanometry, respectively, during brief local (0.3–3.0 nmol/min) and systemic (30–300 nmol/min) or prolonged systemic (30 nmol/min) (Pyr 1 )apelin-13 infusions in the presence or absence of renin–angiotensin system activation with sodium depletion or angiotensin II coinfusion. During sodium depletion and angiotensin II coinfusion, (Pyr 1 )apelin-13–induced vasodilatation was preserved ( P <0.02 for both). Systemic intravenous (Pyr 1 )apelin-13 infusion increased cardiac index, whereas reducing mean arterial pressure and peripheral vascular resistance index ( P <0.001 for all) irrespective of sodium depletion or angiotensin II (0.5 ng/kg per minute) coinfusion ( P >0.05 for all). Prolonged 6-hour (Pyr 1 )apelin-13 infusion caused a sustained increase in cardiac index with increased left ventricular ejection fraction in patients with chronic heart failure (ANOVA; P <0.001 for all). Conclusions— APJ agonism has sustained cardiovascular effects that are preserved in the presence of renin–angiotensin system activation or heart failure. APJ agonism may hold major promise to complement current optimal medical therapy in patients with chronic heart failure. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifiers: NCT00901719, NCT00901888, NCT01049646, NCT01179061.

Aim Species–area relationships (SARs) are fundamental scaling laws in ecology although their shape is still disputed. At larger areas, power laws best represent SARs. Yet, it remains unclear whether SARs follow other shapes at finer spatial grains in continuous vegetation. We asked which function describes SARs best at small grains and explored how sampling methodology or the environment influence SAR shape. Location Palaearctic grasslands and other non‐forested habitats. Taxa Vascular plants, bryophytes and lichens. Methods We used the GrassPlot database, containing standardized vegetation‐plot data from vascular plants, bryophytes and lichens spanning a wide range of grassland types throughout the Palaearctic and including 2,057 nested‐plot series with at least seven grain sizes ranging from 1 cm2 to 1,024 m2. Using nonlinear regression, we assessed the appropriateness of different SAR functions (power, power quadratic, power breakpoint, logarithmic, Michaelis–Menten). Based on AICc, we tested whether the ranking of functions differed among taxonomic groups, methodological settings, biomes or vegetation types. Results The power function was the most suitable function across the studied taxonomic groups. The superiority of this function increased from lichens to bryophytes to vascular plants to all three taxonomic groups together. The sampling method was highly influential as rooted presence sampling decreased the performance of the power function. By contrast, biome and vegetation type had practically no influence on the superiority of the power law. Main conclusions We conclude that SARs of sessile organisms at smaller spatial grains are best approximated by a power function. This coincides with several other comprehensive studies of SARs at different grain sizes and for different taxa, thus supporting the general appropriateness of the power function for modelling species diversity over a wide range of grain sizes. The poor performance of the Michaelis–Menten function demonstrates that richness within plant communities generally does not approach any saturation, thus calling into question the concept of minimal area.