Toekomstbeeld broeikasgasbalans van het Nederlandse landschap

De mondiale emissies van CO2 zijn de afgelopen jaren substantieel gestegen. Een afbuiging van deze trend lijkt noodzakelijk, wil de concentratie in de atmosfeer niet te hoog oplopen. De internationale gemeenschap probeert die te realiseren door stevige reductiedoelstellingen vast te stellen voor de komende tien tot dertig jaar. De inspanningen zijn gericht op terugdringen van emissies, compensatie van de uitstoot door afvang en opslag van CO2 en de omschakeling naar een duurzame energievoorziening

The carbon budget of a tundra in the north-eastern Russian Arctic during the snow free season and its stability in the 2003-2016 period

Large quantities of carbon are stored in the terrestrial permafrost of the Arctic region where the rate of climate warming is two to three times more than the global mean and the largest temperature anomalies observed in autumn and winter. The quantification of the impact of climate warming on the degradation of permafrost and the associated potential release to the atmosphere of carbon stocked in the soil in the form of greenhouse gases, thus further increasing the radiative forcing of the atmosphere, is a research priority in the field of biogeosciences. Land-atmosphere turbulent fluxes of CO2 and CH4 have been monitored at the tundra site of Kytalyk in north-eastern Siberia (70,82 N; 147.48 E) by means of eddy covariance since 2003 and 2008, respectively; regular measurement campaigns have been carried out since then. Here we present results of the seasonal CO2 budget of the tundra ecosystem for the 2003-2016 period based on observations encompassing the permafrost thawing season and analyze the inter-annual differences in the seasonal patterns of CO2 fluxes considering the separate the contribution of climatic drivers and ecosystem functional parameters relative to the processes of respiration and photosynthesis. The variability of the CO2 budget is also discussed in view of the impact of the timing and length of the snow free period. The Kytalyk tundra acted as an atmospheric carbon dioxide sink with relatively small inter-annual variability (-96.1±11.9 gC m-2) during the snow free season and the seasonal CO2 budget did not show any trend over time. The pronounced meteorological variability characterizing Arctic summers was a key factor in shaping the length of the carbon uptake period, which did not progressively increased despite its tendency to start earlier, and in determining the magnitude of CO2 fluxes. No clear evidence of inter-annual changes in the eco-physiological response parameters of CO2 fluxes to climatic drivers (global radiation and air temperature) was found along the course of the analysed period. Methane fluxes had a minor contribution to the carbon budget of the snow-free season representing on average an emission of 3.2 gC m-2 (2008-2016) with apparently small inter-annual variability. Similarly, the size of the carbon exported laterally from the ecosystem in the form of dissolved organic carbon flux amounted to 3.1 gC m-2 as determined experimentally. After including these last terms in the budget, the magnitude of the carbon sink associated with the net ecosystem productivity is reduced by 6%, while the GHG budget still denotes a sink of -60.4 ± 11.9 gC-CO2eq (methane GWP over 100-year time horizon). The monitored tundra was to date exerting a steady climate warming mitigation effect as far as the snow free season is concerned, however the figure of its carbon sink could be potentially sensibly lower due to overlooked emissions in the autumn freeze-up and early winter periods. Also, nonlinear accelerations in the permafrost degradation could happen once tipping points in the Arctic climate are exceeded. Both aspects underline the relevance of long term and continuous biogeochemical monitoring in permafrost tundra environments

Effects of habitat and livestock on nest productivity of the Asian houbara Chlamydotis macqueenii in Bukhara Province, Uzbekistan

To inform population support measures for the unsustainably hunted Asian houbara Chlamydotis macqueenii (IUCN Vulnerable) we examined potential habitat and land-use effects on nest productivity in the Kyzylkum Desert, Uzbekistan. We monitored 177 nests across different semi-arid shrub assemblages (clay-sand and salinity gradients) and a range of livestock densities (0–80 km-2). Nest success (mean 51.4%, 95% CI 42.4–60.4%) was similar across four years; predation caused 85% of those failures for which the cause was known, and only three nests were trampled by livestock. Nesting begins within a few weeks of arrival when food appears scarce, but later nests were more likely to fail owing to the emergence of a key predator, suggesting foraging conditions on wintering and passage sites may be important for nest productivity. Nest success was similar across three shrub assemblages and was unrelated to landscape rugosity, shrub frequency or livestock density, but was greater with taller mean shrub height (range 13–67 cm) within 50 m. Clutch size (mean = 3.2 eggs) and per-egg hatchability in successful nests (87.5%) did not differ with laying date, shrub assemblage or livestock density. We therefore found no evidence that livestock density reduced nest productivity across the range examined, while differing shrub assemblages appeared to offer similar habitat quality. Asian houbara appear well-adapted to a range of semi-desert habitats and tolerate moderate disturbance by pastoralism. No obvious in situ mitigation measures arise from these findings, leaving regulation and control as the key requirement to render hunting sustainable

Cumulative energetic costs of military aircraft, recreational and natural disturbance in roosting shorebirds

Knowing the consequences of disturbance for multiple species and all disturbance sources is crucial to mitigate disturbance impacts in densely populated areas. However, studies that observe the complete disturbance landscape to estimate cumulative costs of disturbance are scarce. Therefore, we quantified responses, frequencies and energetic costs of disturbance of four shorebird species on five high tide roosts in the Wadden Sea. Roosts were located either in a military air force training area or were predominantly affected by recreational disturbance. In the military training area, infrequent transport airplanes and bombing jets elicited the strongest responses, whereas regular, predictable activities of jet fighters and small civil airplanes elicited far smaller responses. Disturbance occurred more frequently at roosts near recreational than near military activities, as recreation was prohibited in the military area during operation days. On average, birds took flight due to military, recreational or natural disturbance (e.g. raptors) 0.20–1.27 times per hour. High tide disturbance increased daily energy expenditure by 0.1%–1.4%, of which 51% was due to anthropogenic disturbance in contrast to natural disturbance. Costs were low for curlews Numenius arquata, oystercatchers Haematopus ostralegus and gulls Larus spp, but higher – and potentially critical – for bar-tailed godwits Limosa lapponica as they were most susceptible to aircraft and raptors. Given that bar-tailed godwits have previously been found to be least susceptible to walker disturbances, our results suggest that interspecific differences in susceptibility depend on disturbance source type. In our study area, aircraft disturbance impacts can be reduced by avoiding jet fighter activities during periods when high water levels force birds closer to military targets and by limiting bombing and transport airplane exercises

Fracture toughness testing using photogrammetry and digital image correlation

Digital image correlation (DIC) is an optical technique commonly used for measuring displacement fields by tracking artificially applied random speckle patterns, which can sometimes be a problem for tracking small-scale displacements. DIC is particularly useful for tracking the crack mouth opening displacement (CMOD) of a notched metallic specimen subjected to three-point bending for fracture toughness determination because the edges of the notch provide the required textural features for DIC without the need for speckle patterns. This simplifies the set-up process as the specimen and stage geometries do not need to account for the placement of a strain gauge. To enhance the accuracy of DIC, this study then successfully downscaled a photogrammetry technique commonly used to track crack propagation in large scale concrete tests so that the pixel coordinates of the captured images can be automatically related to their real-world coordinates, allowing for small scale displacements to be accurately tracked.ARC Linkage Project LP130100111, ARC DECRA DE15010170

NAADP mobilizes Ca2+ from a thapsigargin-sensitive store in the nuclear envelope by activating ryanodine receptors

Ca2+ release from the envelope of isolated pancreatic acinar nuclei could be activated by nicotinic acid adenine dinucleotide phosphate (NAADP) as well as by inositol 1,4,5-trisphosphate (IP3) and cyclic ADP-ribose (cADPR). Each of these agents reduced the Ca2+ concentration inside the nuclear envelope, and this was associated with a transient rise in the nucleoplasmic Ca2+ concentration. NAADP released Ca2+ from the same thapsigargin-sensitive pool as IP3. The NAADP action was specific because, for example, nicotineamide adenine dinucleotide phosphate was ineffective. The Ca2+ release was unaffected by procedures interfering with acidic organelles (bafilomycin, brefeldin, and nigericin). Ryanodine blocked the Ca2+-releasing effects of NAADP, cADPR, and caffeine, but not IP3. Ruthenium red also blocked the NAADP-elicited Ca2+ release. IP3 receptor blockade did not inhibit the Ca2+ release elicited by NAADP or cADPR. The nuclear envelope contains ryanodine and IP3 receptors that can be activated separately and independently; the ryanodine receptors by either NAADP or cADPR, and the IP3 receptors by IP3

Land Surface Temperature from Ka-band (37 GHZ) Passive Microwave Observations

An alternative to thermal infrared satellite sensors for measuring land surface temperature (T<inf>s</inf>) is presented. The 37 GHz vertical polarized brightness temperature is used to derive T<inf>s</inf> because it is considered the most appropriate microwave frequency for temperature retrieval. This channel balances a reduced sensitivity to soil surface characteristics with a relatively high atmospheric transmissivity. It is shown that with a simple linear relationship, accurate values for T<inf>s</inf> can be obtained from this frequency, with a theoretical bias of within 1 K for 70% of vegetated land areas of the globe. Barren, sparsely vegetated, and open shrublands cannot be accurately described with this single channel approach because variable surface conditions become important. The precision of the retrieved land surface temperature is expected to be better than 2.5 K for forests and 3.5 K for low vegetation. This method can be used to complement existing infrared derived temperature products, especially during clouded conditions. With several microwave radiometers currently in orbit, this method can be used to observe the diurnal temperature cycles with surprising accuracy. © 2009 by the American Geophysical Union

Effects of experimental land management on habitat use by Eurasian Stone‐curlews

Funder: Royal Society for the Protection of BirdsFunder: Natural England; Id: http://dx.doi.org/10.13039/501100001293Funder: Defence Infrastructure OrganisationFunder: Heritage Lottery Fund; Id: http://dx.doi.org/10.13039/501100016135Abstract: Effective conservation is often informed by focal species studies to identify beneficial land management interventions. For nocturnal or cryptic species, quantifying habitat use across individually marked animals can allow unbiased assessment of intervention efficacy and identify other important habitats. Here, using a landscape‐scale experiment, we examine whether interventions intended to create nesting habitat for the largely nocturnal Eurasian Stone‐curlew Burhinus oedicnemus within semi‐natural grassland also provide foraging habitat. GPS loggers were fitted to five adult Stone‐curlews during the breeding season within an extensive area of semi‐natural grassland (3850 ha, hereafter ‘grassland’), surrounded by a mosaic of arable cropland (total study area 118 600 ha). The largely closed‐sward grassland was diversified by experimental ground‐disturbance plots (the intervention) prior to this study. We used the GPS fixes to identify 1881 foraging locations (510 during nesting and 1371 post‐breeding) across the grassland and surrounding landscape. Most foraging locations were close to the nest‐site during the nesting period (90% within 1 km) or day‐roost during post‐breeding (90% within 5 km), but birds travelled up to 4.1 km from these sites during nesting and 13 km post‐breeding. Stone‐curlews were two‐ (by night) or three‐times (by day) more likely to select disturbed‐grassland over unmodified grassland for foraging during nesting, and c. 15 times more likely to do so post‐breeding. Spring‐sown crops and pig fields or manure heaps were also selected over grassland for nocturnal foraging. Given that central place foraging occurs in this species, conservation efforts that promote breeding attempts through ground‐disturbance should ensure suitable foraging habitat is near the nest (<1 km). Creating multiple areas of disturbed‐ground close to the edge of large grassland blocks can provide a network of nesting and foraging habitats, while allowing access to foraging habitats on the surrounding arable farmland. Similar interventions may benefit other disturbance associated grassland waders