Abstract.We present results from a study of canopyatmosphere fluxes of carbon dioxide from 2007 to 2009 above a site in Wytham Woods, an ancient temperate broadleaved deciduous forest in southern England. Gapfilled net ecosystem exchange (NEE) data were partitioned into gross primary productivity (GPP) and ecosystem respiration (R e ) and analysed on daily, monthly and annual timescales. Over the continuous 24 month study period annual GPP was estimated to be 21.1 Mg C ha −1 yr −1 and R e to be 19.8 Mg C ha −1 yr −1 ; net ecosystem productivity (NEP) was 1.2 Mg C ha −1 yr −1 . These estimates were compared with independent bottom-up estimates derived from net primary productivity (NPP) and flux chamber measurements recorded at a plot within the flux footprint in 2008 (GPP = 26.5 ± 6.8 Mg C ha −1 yr −1 , R e = 24.8 ± 6.8 Mg C ha −1 yr −1 , biomass increment = ∼1.7 Mg C ha −1 yr −1 ). Over the two years the difference in seasonal NEP was predominantly caused by changes in ecosystem respiration, whereas GPP remained similar for equivalent months in different years. Although solar radiation was the largest influence on daily values of CO 2 fluxes (R 2 = 0.53 for the summer months for a linear regression), variation in R e appeared to be driven by temperature. Our findings suggest that this ancient woodland site is currently a substantial sink for carbon, resulting from continued growth that is probably a legacy of past management practices abandoned over 40 years ago. Our GPP and R e values are generally higher than other broadleaved temperate deciduous woodlands and may represent the influence of the UK's maritime climate, or the particular species composition of this site. The carbon sink value of Wytham Woods Correspondence to: Y. Malhi (yadvinder.malhi@ouce.ox.ac.uk) supports the protection and management of temperate deciduous woodlands (including those managed for conservation rather than silvicultural objectives) as a strategy to mitigate atmospheric carbon dioxide increases.

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The Chinese Loess Plateau, the world’s largest and oldest loess record, preserves evidence of Asia’s long-term dust source dynamics, but there is uncertainty over the source of the deposits. Recent single-grain detrital zircon U-Pb age analysis has progressed this issue, but debates remain about source changes, and the generation and interpretation of zircon data. To address this, we analyze different groupings of new and existing datasets from the Loess Plateau and potential sources. We also present the results of a first high resolution sampling, multi-proxy provenance analysis of Beiguoyuan loess using U-Pb dating of detrital zircons and detrital garnet geochemistry. The data shows that some small source differences seem to exist between different areas on the Loess Plateau. However, sediment source appears to be unchanging between loess and palaeosols, supporting a recent material recycling hypothesis. Our zircon and garnet data demonstrates, however, that Beiguoyuan experienced a temporary, abrupt source shift during the last glacial maximum, implying that local dust sources became periodically active during the Quaternary. Our results highlight that grouping data to achieve bigger datasets could cause identification of misleading trends. Additionally, we suggest that multi-proxy single-grain approaches are required to gain further insight into Chinese Loess Plateau dust sources.

While there are numerous thick loess-palaeosol sequences preserved across the Carpathian Basin, well dated sites that provide terrestrial palaeoenvironmental records extending beyond last glacial-interglacial cycle are scarce. Robust chronologies are essential for correlations of loess with other long-term Quaternary records and to further understanding of the palaeoenvironment and climate of this important region beyond the last 125 ka. Here a new geochronology based on 13 post-infrared infrared stimulated luminescence ages focused on the lower part of the loess-palaeosol sequence at Erdut is presented. The results show that the lower part of the Erdut profile spans the penultimate glacial cycle (MIS 7 to MIS 5). The considerable sediments overlaying the investigated part of the profile suggest that this section spans two glacial cycles, rather than the previously suggested one. The most likely source of the discrepancy is the use of uncorrected infrared stimulated luminescence signal, which can cause age underestimation if not accounted for. This study demonstrates the need to revisit sites such as Erdut, re-date them using updated measurement protocols, and update existing palaeoenvironmental interpretations.

There exist very few comprehensive descriptions of the productivity and carbon cycling of forest ecosystems. Here we present a description of the components of annual Net Primary Productivity (NPP), Gross Primary Productivity (GPP), autotrophic and heterotrophic respiration, and ecosystem respiration (<i>R</i>_ECO) for a temperate mixed deciduous woodland at Wytham Woods in southern Britain, calculated using "bottom-up" biometric and chamber measurements (leaf and wood production and soil and stem respiration). These are compared with estimates of these parameters from eddy-covariance measurements made at the same site. NPP was estimated as 7.0&plusmn;0.8 Mg C ha⁻¹ yr⁻¹, and GPP as 20.3+1.0 Mg C ha⁻¹ yr⁻¹, a value which closely matched to eddy covariance-derived GPP value of 21.1 Mg C ha⁻¹ yr⁻¹. Annual <i>R</i>_ECO was calculated as 18.9&plusmn;1.7 Mg C ha⁻¹ yr⁻¹, close to the eddy covariance value of 19.8 Mg C ha⁻¹ yr⁻¹; the seasonal cycle of biometric and eddy covariance <i>R</i>_ECO estimates also closely matched. The consistency between eddy covariance and biometric measurements substantially strengthens the confidence we attach to each as alternative indicators of site carbon dynamics, and permits an integrated perspective of the ecosystem carbon cycle. 37% of NPP was allocated below ground, and the ecosystem carbon use efficiency (CUE, = NPP/GPP) calculated to be 0.35&plusmn;0.05, lower than reported for many temperate broadleaved sites

We present results from a study of canopy-atmosphere fluxes of carbon dioxide from 2007 to 2009 above a site in Wytham Woods, an ancient temperate broadleaved deciduous forest in southern England. Gap-filled Net Ecosystem Exchange (NEE) data were partitioned into Gross Primary Productivity (GPP) and ecosystem respiration (<i>R</i>_e) and analysed on daily, monthly and annual timescales. Over the continuous 24 month study period annual GPP was estimated at 21.1 Mg C ha⁻¹ yr⁻¹ and <i>R</i>_e at 19.8 Mg C ha⁻¹ yr⁻¹; Net Ecosystem Productivity (NEP) was 1.2 Mg C ha⁻¹ yr⁻¹. These estimates are very consistent with independent bottom-up estimates derived from Net Primary Productivity (NPP) and flux chamber measurements in 2008 (GPP=20.3&plusmn;1.0 Mg C ha⁻¹ yr⁻¹, <i>R</i>_e=18.9&plusmn;1.7 Mg C ha⁻¹ yr⁻¹, biomass increment =~1.4 Mg C ha⁻¹ yr⁻¹). Interannual variability of seasonal NEP was predominantly driven by changes in ecosystem respiration, whereas GPP remained similar for equivalent months in different years. Although solar radiation was the largest influence on daytime CO₂ fluxes (<i>R</i>²=0.53 for the summer months), interannual variation in <i>R</i>_e appeared to be driven by temperature. Our findings suggest that this ancient woodland site is currently a substantial sink for carbon, resulting from continued growth that is probably a legacy of past management practices abandoned over 40 years ago. Our GPP and <i>R</i>_e values are generally higher than other broadleaved temperate deciduous woodlands and may represent the influence of the UK's maritime climate, or the particular species composition of this site. The carbon sink value of Wytham Woods supports the protection and management of temperate deciduous woodlands (including those managed for conservation rather than silvicultural objectives) as a strategy to mitigate atmospheric carbon dioxide increases