Carbon dioxide,methane, and nitrous oxide exchanges in an age‐sequence of temperate pine forests

We investigated soil carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) exchanges in an age‐sequence (4, 17, 32, 67 years old) of eastern white pine (Pinus strobus L.) forests in southern Ontario, Canada, for the period of mid‐April to mid‐December in 2006 and 2007. For both CH₄ and N₂O, we observed uptake and emission ranging from ?160 to 245 μg CH₄ m^?2 h^?1 and ?52 to 21 μg N₂O m^?2 h^?1, respectively (negative values indicate uptake). Mean fluxes from mid‐April to mid‐December across the 4, 17, 32, 67 years old stands were similar for CO₂ fluxes (259, 246, 220, and 250 mg CO₂ m^?2 h^?1, respectively), without pattern for N₂O fluxes (?3.7, 1.5, ?2.2, and ?7.6 μg N₂O m^?2 h^?1, respectively), whereas the uptake rates of CH₄ increased with stand age (6.4, ?7.9, ?10.8, and ?23.3 μg CH₄ m^?2 h^?1, respectively). For the same period, the combined contribution of CH₄ and N₂O exchanges to the global warming potential (GWP) calculated from net ecosystem exchange of CO₂ and aggregated soil exchanges of CH₄ and N₂O was on average 4%, <1%, <1%, and 2% for the 4, 17, 32, 67 years old stand, respectively. Soil CO₂ fluxes correlated positively with soil temperature but had no relationship with soil moisture. We found no control of soil temperature or soil moisture on CH₄ and N₂O fluxes, but CH₄ emission was observed following summer rainfall events. LFH layer removal reduced CO₂ emissions by 43%, increased CH₄ uptake during dry and warm soil conditions by more than twofold, but did not affect N₂O flux. We suggest that significant alternating sink and source potentials for both CH₄ and N₂O may occur in N‐ and soil water‐limited forest ecosystems, which constitute a large portion of forest cover in temperate areas.     

Influence of temperature on the spatial distribution of first spawning dates of the common frog (Rana temporaria) in the UK

Between 1998 and 2007, the UK Phenology Network collected nearly 70 000 records of the first spawn dates of the common frog Rana temporaria . Annual national mean dates varied by more than 2 weeks and were closely related to January–March temperatures. A 1 °C increase in Central England Temperature advanced national mean spawning by 5.1 days. The temporal pattern of spawning records varied between years; sometimes unimodal in form, sometimes multimodal, seemingly associated with steady or erratic rises in spring temperatures, respectively. Spatial patterns of frogspawn were similar in different years, the earliest records occurring in the southwest with records progressively later in the north and east. On average, 100 km of eastwards progression took 7.4 days and 100 km of northwards progression took 4.7 days. A composite map for the 1998–2007 period is constructed and compared with an earlier published map based on data 60 years previously. The similarity and dissimilarity of these two maps is discussed; the general progression pattern of frogspawn phenology is similar but an advance of a 10-day contour category is apparent. We anticipate further advances of frog spawning dates in the future and an increase in the numbers of pre-January 1 records of frog breeding.     

Are local weather,NDVI and NAO consistent determinants of red deer weight across three contrasting European countries?

There are multiple paths via which environmental variation can impact herbivore ecology and this makes the identification of drivers challenging. Researchers have used diverse approaches to describe the association between environmental variation and ecology, including local weather, large-scale patterns of climate, and satellite imagery reflecting plant productivity and phenology. However, it is unclear to what extent it is possible to find a single measure that captures climatic effects over broad spatial scales. There may, in fact, be no a priori reason to expect populations of the same species living in different areas to respond in the same way to climate as their population may experience limiting factors at different times of the year, and the forms of regulation may differ among populations. Here, we examine whether the same environmental indices [seasonal Real Bioclimatic Index (RBI), seasonal Normalized Difference Vegetation Index (NDVI) and winter North Atlantic Oscillation (NAO)] influence body size in different populations of a large ungulate living in Mediterranean Spain, Western Scotland and Norway. We found substantial differences in the pattern of weight change over time in adult female red deer among study areas as well as different environmental drivers associated with variation in weight. The lack of general patterns for a given species at a continental scale suggest that detailed knowledge regarding the way climate affects local populations is often necessary to successfully predict climate impact. We caution against extrapolation of results from localized climate–population studies to broad spatial scales.     

Biomarkers from individual carbonate phases of an Oligocene cold‐seep deposit,Washington State,USA

An Oligocene cold‐seep limestone (Lincoln Creek Formation, Washington State, USA) was studied for its lipid biomarker inventory. Biomarker analysis on minute amounts of sample (tens of mg) and complementary ¹³C_carbonate analyses allowed us to link biogeochemical processes with individual, closely intertwined carbonate phases. The ancient seep deposit exhibits four major carbonate phases, according to the paragenetic sequence of (I) micrite, (II) yellow aragonite, (III) clear aragonite and (IV) equant calcite spar. For the micrite, varying but significant amounts of archaea‐derived isoprenoids clearly indicate that the precipitation of this phase was induced by the microbial anaerobic oxidation of methane (AOM). However, water column‐derived lipids present in this carbonate phase reflect the incorporation of organic matter from background sediment cemented by authigenic micrite. Yellow aragonite made up only a minor rock component (<10% vol.), but contained a major portion of lipid biomarkers indicative of AOM. Along with low δ¹³C_carbonate values (less than ?30‰ Pee Dee Belemnite), this points to an intimate spatial association of AOM consortia with the precipitation of yellow aragonite. Clear aragonite showed similar δ¹³C_carbonate values but much lower, if any, contents of AOM biomarkers. This suggests that AOM‐derived carbonate ions diffused over a greater distance to the site of precipitation compared with yellow aragonite. The latest phase, equant calcite spar, did not yield appreciable biomarkers, but showed a notable ¹³C_carbonate‐enrichment that is most likely caused by methanogenesis that prevailed in the sediments after AOM activity had ceased. A comparison of the ancient seep carbonates with modern counterparts from Hydrate Ridge (offshore Oregon, USA) revealed a remarkable coincidence of the respective mineral phases and their biomarker patterns. This suggests that the mechanisms of carbonate formation and the associated biogeochemical processes remained unchanged over geological times. □Biomarkers, carbonates, cold seeps, Hydrate Ridge, isotopes, Oligocene, Washington.     

A method for the rapid measurement of thermal tolerance traits in studies of small insects

Abstract A technique for rapidly measuring non‐lethal thermal tolerance traits in small insects and terrestrial arthropods of similar size is described. Single or multiple individuals are heated or cooled in an arena milled into a temperature‐controlled aluminium block and their behaviour recorded continuously using a digital video camera. Data are collected retrospectively by playback of the stored images. To illustrate this technique measurement of six thermal tolerance traits using this method is described using first instar nymphs (body length = 0.66 mm) of the aphid Myzus persicae. These traits are high and low temperatures at which individual aphids cease walking, high and low temperatures at which aphids move for the final time, the temperature at which aphids begin to recover from chill coma, and the temperature at which they begin to walk again. The method is validated by comparing the results of multiple low temperature assays. No significant differences are detected between assays. Potential applications, limitations and technical problems are discussed.     

Diurnal fluctuations of dissolved nitrous oxide (N2O) concentrations and estimates of N2O emissions from a spring-fed river: implications for IPCC methodology

There is uncertainty in the estimates of indirect nitrous oxide (N₂O) emissions as defined by the Intergovernmental Panel on Climate Change (IPCC). The uncertainty is due to the challenge and dearth of in situ measurements. Recent work in a subtropical stream system has shown the potential for diurnal variability to influence the downstream N transfer, N form, and estimates of in‐stream N₂O production. Studies in temperate stream systems have also shown diurnal changes in stream chemistry. The objectives of this study were to measure N₂O fluxes and dissolved N₂O concentrations from a spring‐fed temperate river to determine if diurnal cycles were occurring. The study was performed during a 72 h period, over a 180 m reach, using headspace chamber methodology. Significant diurnal cycles were observed in radiation, river temperature and chemistry including dissolved N₂O‐N concentrations. These data were used to further assess the IPCC methodology and experimental methodology used. River NO₃‐N and N₂O‐N concentrations averaged 3.0 mg L⁻¹ and 1.6 μg L⁻¹, respectively, with N₂O saturation reaching a maximum of 664%. The N₂O‐N fluxes, measured using chamber methodology, ranged from 52 to 140 μg m⁻² h⁻¹ while fluxes predicted using the dissolved N₂O concentration ranged from 13 to 25 μg m⁻² h⁻¹. The headspace chamber methodology may have enhanced the measured N₂O flux and this is discussed. Diurnal cycles in N₂O% saturation were not large enough to influence downstream N transfer or N form with variability in measured N₂O fluxes greater and more significant than diurnal variability in N₂O% saturation. The measured N₂O fluxes, extrapolated over the study reach area, represented only 6 × 10⁻⁴% of the NO₃‐N that passed through the study reach over a 72 h period. This is only 0.1% of the IPCC calculated flux.     

Brood guarding in a bethylid wasp

Abstract.

• 1 Atypical of the parasitoid Hymenoptera, female Goniozus nephantidis Muesebeck remain with offspring until they pupate. This behaviour will only have evolved if the consequent reduction in fecundity is outweighed by fitness returns.
• 2 G.nephantidis competes for hosts with conspecific and non-conspecific parasitoids. The effectiveness of G.nephantidis at deterring superparasitism and multiparasitism is tested. Brood survivorships were compared when G.nephantidis and Bracon hebetor Say intrude on hosts with the mother present and absent and with offspring at different developmental stages.
• 3 Laying by the intruder reduced brood survivorship. Guarding reduced oviposition on unparasitized hosts by intruding females, and prevented superparasitism of hosts with egg broods. Hosts with larval broods were rarely superparasitized. Multiparasitism was common except on hosts with guarded larval broods, but even here survivorship was reduced.
• 4 Competitive asymmetries determined the outcome of contests for possession of host resources.
• 5 The costs of remaining seem at least partially offset by the prevention of oviposition by competing parasitoids.

     

Foraging and courtship behaviour in males of the solitary bee Anthophora plumipes (Hymenoptera: Anthophoridae): thermal physiology and the roles of body size

Abstract.

• 1 The effects of climate and body size on male behaviour were examined in the solitary bee Anthophora plumipes (Hymenoptera: Anthophoridae), which shows resource-based polygyny at floral food sources in Britain in spring.
• 2 Larger males are able to fly at lower temperatures than smaller males, and can therefore court females under conditions in which smaller males cannot fly. This is predicted from patterns of endothermic ability at low temperatures already demonstrated within this species.
• 3 Video analysis of male competition for opportunities to initiate courtship with tethered females showed that larger males are also competitively superior, and can displace smaller males from favoured flight positions immediately behind females.
• 4 The mating system shown by male A plumipes is strongly dependent on male density. At low densities, males show exclusive territoriality at floral sources. As male density increases, this strategy is abandoned in favour of patrolling with considerable spatial overlap between males, and opportunistic Polygyny.
• 5 Despite high endothermic abilities, male behaviour is highly dependent on weather, and particularly ambient temperature. Males bask in the early morning and maintain high thoracic temperatures. Temperature data from freshly killed bees show that thoracic warming from solar sources effectively doubles the thermogenic power generated by the bee alone at low ambient temperatures.
• 6 Male strategies in A.plumipes are compared to female responses to climate. Having controlled for differences in body size there is no difference in endothermic abilities between the sexes. Males do not, however, fly under conditions in which females of the same size would remain active. These results are discussed in the light of differential dependence of reproductive success on flight activity for the two sexes.