We developed a quantitative chironomid-July air temperature inference model based on surface sediments from 81 Swiss lakes and applied it to the Holocene subfossil chironomid record of Hinterburgsee, a small subalpine lake in the northern Swiss Alps (present-day mean July air temperature of 11.3°C). After smoothing to reduce the high between-sample variability of inferred temperatures, the reconstruction indicates July air temperatures of 10.4– 10.9°C at the end of the Younger Dryas, of 11.9–12.8°C during the early and mid-Holocene (11500–4000 cal. BP), and slightly lower temperatures of 11.5–12.0°C during the late Holocene (3500–1000 cal. BP). A warming trend inferred for the past millennium is most likely an artifact of human impact on Hinterburgsee's chironomid fauna, rather than a genuine temperature signal. The most prominent climatological events during the Holocene were two periods of lower temperatures at c. 10700–10500 cal. BP and 8200–7700 cal. BP and an abrupt shift to a cooler late-Holocene climate around 4000–3700 cal. BP. Although the chironomid-inferred climate signals were within the prediction error of the model (1.51°C), major inferred temperature changes agree well with other northern and central European climate reconstructions and underline the potential of subfossil chironomid analysis to reconstruct even the moderate climatic changes within the Holocene.

The eutrophication of lowland lakes in Europe by excess nitrogen (N) and phosphorus (P) is severe because of the long history of land‐cover change and agricultural intensification. The ecological and socio‐economic effects of eutrophication are well understood but its effect on organic carbon (OC) sequestration by lakes and its change overtime has not been determined. Here, we compile data from ~90 culturally impacted European lakes [~60% are eutrophic, Total P (TP) >30 μg P l⁻¹] and determine the extent to which OC burial rates have increased over the past 100–150 years. The average focussing corrected, OC accumulation rate (C AR_FC) for the period 1950–1990 was ~60 g C m⁻² yr⁻¹, and for lakes with >100 μg TP l⁻¹ the average was ~100 g C m⁻² yr⁻¹. The ratio of post‐1950 to 1900–1950 C AR is low (~1.5) indicating that C accumulation rates have been high throughout the 20th century. Compared to background estimates of OC burial (~5–10 g C m⁻² yr⁻¹), contemporary rates have increased by at least four to fivefold. The statistical relationship between C AR_FC and TP derived from this study (r² = 0.5) can be used to estimate OC burial at sites lacking estimates of sediment C‐burial. The implications of eutrophication, diagenesis, lake morphometry and sediment focussing as controls of OC burial rates are considered. A conservative interpretation of the results of the this study suggests that lowland European meso‐ to eutrophic lakes with >30 μg TP l⁻¹ had OC burial rates in excess of 50 g C m⁻² yr⁻¹ over the past century, indicating that previous estimates of regional lake OC burial have seriously underestimated their contribution to European carbon sequestration. Enhanced OC burial by lakes is one positive side‐effect of the otherwise negative impact of the anthropogenic disruption of nutrient cycles.

A principle response of C3 plants to increasing concentrations of atmospheric CO ₂ ( CO ₂ ) is to reduce transpirational water loss by decreasing stomatal conductance ( g _s ) and simultaneously increase assimilation rates. Via this adaptation, vegetation has the ability to alter hydrology and climate. Therefore, it is important to determine the adaptation of vegetation to the expected anthropogenic rise in CO ₂ . Short-term stomatal opening–closing responses of vegetation to increasing CO ₂ are described by free-air carbon enrichments growth experiments, and evolutionary adaptations are known from the geological record. However, to date the effects of decadal to centennial CO ₂ perturbations on stomatal conductance are still largely unknown. Here we reconstruct a 34% (±12%) reduction in maximum stomatal conductance ( g _smax ) per 100 ppm CO ₂ increase as a result of the adaptation in stomatal density ( D ) and pore size at maximal stomatal opening ( a _max ) of nine common species from Florida over the past 150 y. The species-specific g _smax values are determined by different evolutionary development, whereby the angiosperms sampled generally have numerous small stomata and high g _smax , and the conifers and fern have few large stomata and lower g _smax . Although angiosperms and conifers use different D and a _max adaptation strategies, our data show a coherent response in g _smax to CO ₂ rise of the past century. Understanding these adaptations of C3 plants to rising CO ₂ after decadal to centennial environmental changes is essential for quantification of plant physiological forcing at timescales relevant for global warming, and they are likely to continue until the limits of their phenotypic plasticity are reached.