Wind as a Driver of Peat CO2 Dynamics in a Northern Bog.

Excess CO2 accumulated in soils is typically transported to the atmosphere through molecular diffusion along a concentration gradient. Because of the slow and constant nature of this process, a steady state between peat CO2 production and emissions is often established. However, in peatland ecosystems, high peat porosity could foster additional non-diffusive transport processes, whose dynamics may become important to peat CO2 storage, transport and emission. Based on a continuous record of in situ peat pore CO2 concentration within the unsaturated zone of a raised bog in southern Canada, we show that changes in wind speed create large diel fluctuations in peat pore CO2 store. Peat CO2 builds up overnight and is regularly flushed out the following morning. Persistently high wind speed during the day maintains the peat CO2 with concentrations close to that of the ambient air. At night, wind speed decreases and CO2 production overtakes the transport rate leading to the accumulation of CO2 in the peat. Our results indicate that the effective diffusion coefficient fluctuates based on wind speed and generally exceeds the estimated molecular diffusion coefficient. The balance between peat CO2 accumulation and transport is most dynamic within the range of 0-2 m s-1 wind speeds, which occurs over 75% of the growing season and dominates night-time measurements. Wind therefore drives considerable temporal dynamics in peat CO2 transport and storage, particularly over sub-daily timescales, such that peat CO2 emissions can only be directly related to biological production over longer timescales. Supplementary Information: The online version contains supplementary material available at 10.1007/s10021-024-00904-1.

Abortion requests among adolescents in comparison with young adults in a Swiss region (1990-1998).

AIM: To examine the recent evolution of abortion request rates among adolescents and young adults in the Canton of Vaud (Switzerland) and to describe the circumstances of the abortion requests and sociodemographic characteristics by age subgroups and nationality. METHOD: Data for women aged 14 to 24 y living in Vaud were selected from the 12,358 abortion requests from residents aged 14-49 y between 1990 and 1998. RESULTS: Overall, abortion request rates by age were stable over the study period. However, rates for non-Swiss women were two to three times higher than those for Swiss women, at 4.5 [95% confidence interval [CI]: 3.8-5.2] vs 2.4 [95% CI: 2.1-2.7] per 1000 adolescents below the age of 18, 18.1 [95% CI: 17.2-18.9] vs 8.0 [95% CI: 7.1-8.8] per 1000 women aged 18-19 and 30.5 [95% CI: 29.1-32.0] vs 10.2 [95% CI: 9.6-10.8] per 1000 women aged 20-24. The ratio of abortions to live births was greatest for women under 20 y of age. at 1.9, in comparison with the ratio observed among adult women aged 20-24 (at 0.4). The abortion rate per 1000 conceptions >6 wk remained stable; this rate was 590 per 1000 among 14-19-y-olds in 1997. CONCLUSION: The abortion request rate among youths in this Swiss region has not increased between 1990 and 1998. Efforts must be intensified to ensure universal access to family planning services and contraception, especially for young foreign women and adolescents.

Arctic and boreal ecosystems of western North America as components of the climate system.

Synthesis of results from several Arctic and boreal research programmes provides evidence for the strong role of high-latitude ecosystems in the climate system. Average surface air temperature has increased 0.3 °C per decade during the twentieth century in the western North American Arctic and boreal forest zones. Precipitation has also increased, but changes in soil moisture are uncertain. Disturbance rates have increased in the boreal forest; for example, there has been a doubling of the area burned in North America in the past 20 years. The disturbance regime in tundra may not have changed. Tundra has a 3-6-fold higher winter albedo than boreal forest, but summer albedo and energy partitioning differ more strongly among ecosystems within either tundra or boreal forest than between these two biomes. This indicates a need to improve our understanding of vegetation dynamics within, as well as between, biomes. If regional surface warming were to continue, changes in albedo and energy absorption would likely act as a positive feedback to regional warming due to earlier melting of snow and, over the long term, the northward movement of treeline. Surface drying and a change in dominance from mosses to vascular plants would also enhance sensible heat flux and regional warming in tundra. In the boreal forest of western North America, deciduous forests have twice the albedo of conifer forests in both winter and summer, 50-80% higher evapotranspiration, and therefore only 30-50% of the sensible heat flux of conifers in summer. Therefore, a warming-induced increase in fire frequency that increased the proportion of deciduous forests in the landscape, would act as a negative feedback to regional warming. Changes in thermokarst and the aerial extent of wetlands, lakes, and ponds would alter high-latitude methane flux. There is currently a wide discrepancy among estimates of the size and direction of CO2 flux between high-latitude ecosystems and the atmosphere. These discrepancies relate more strongly to the approach and assumptions for extrapolation than to inconsistencies in the underlying data. Inverse modelling from atmospheric CO2 concentrations suggests that high latitudes are neutral or net sinks for atmospheric CO2 , whereas field measurements suggest that high latitudes are neutral or a net CO2 source. Both approaches rely on assumptions that are difficult to verify. The most parsimonious explanation of the available data is that drying in tundra and disturbance in boreal forest enhance CO2 efflux. Nevertheless, many areas of both tundra and boreal forests remain net sinks due to regional variation in climate and local variation in topographically determined soil moisture. Improved understanding of the role of high-latitude ecosystems in the climate system requires a concerted research effort that focuses on geographical variation in the processes controlling land-atmosphere exchange, species composition, and ecosystem structure. Future studies must be conducted over a long enough time-period to detect and quantify ecosystem feedbacks.