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Owing to human activity, global nitrogen (N) cycles have been altered. In the past 100 years, global N deposition has increased. Currently, the monitoring and estimating of N deposition and the evaluation of its effects on global carbon budgets are the focus of many researchers. NO2columns retrieved by space-borne sensors provide us with a new way of exploring global N cycles and these have the ability to estimate N deposition. However, the time range limitation of NO2columns makes the estimation of long timescale N deposition difficult. In this study we used ground-based NOxemission data to expand the density of NO2columns, and 40 years of N deposition (1970–2009) was inverted using the multivariate linear model with expanded NO2columns. The dynamic of N deposition was examined in both global and biome scales. The results show that the average N deposition was 0.34 g N m–2year–1in the 2000s, which was an increase of 38.4% compared with the 1970s’. The total N deposition in different biomes is unbalanced. N deposition is only 38.0% of the global total in forest biomes; this is made up of 25.9%, 11.3, and 0.7% in tropical, temperate, and boreal forests, respectively. As N-limited biomes, there was little increase of N deposition in boreal forests. However, N deposition has increased by a total of 59.6% in tropical forests and croplands, which are N-rich biomes. Such characteristics may influence the effects on global carbon budgets. [ABSTRACT FROM PUBLISHER]

Observations of carbon monoxide (CO) retrieved from Scanning Imaging Absorption SpectroMeter for Atmospheric Chartography (SCIAMACHY), Measurement of Pollution in the Troposphere (MOPITT), and Atmospheric Infrared Sounder (AIRS) are compared in this article. To better validate the retrieved data from SCIAMCHY, AIRS, and MOPITT, six surface stations at different locations and with various elevations were chosen. The results show these three instruments can all reflect CO spatial distribution well and show same temporal variations of CO concentration as well as six surface station measurements. MOPITT and AIRS have similar retrieval results with correlation coefficients being mostly over 0.70, except for a sixth field station on Crozet Island. The three satellites all have the ability to monitor CO concentration change on land, but SCIAMCHY results show a relatively larger bias than MOPITT and AIRS in low CO concentration areas because of systematic error. [ABSTRACT FROM PUBLISHER]

Climate change has significantly influenced the productivity of terrestrial ecosystems through water cycles. Water use efficiency (WUE) is an important indicator for understanding how water couples with the carbon cycle. Abiotic factors such as climatic factors and CO 2 concentration have been investigated to understand the mechanisms involved in the coupled carbon-water cycle of terrestrial ecosystems in response to climate change. However, the effects of biotic factors on WUE are less clear. By analyzing 66 site-years of flux and meteorological data obtained from 8 temperate deciduous broadleaf forest sites across North America and Europe, we found that ecosystem-scale WUE (defined here as the ratio of gross primary production (GPP) to evapotranspiration (ET)) in the spring significantly increased with the advance of the flux-based photosynthetic onset (FPO), mainly because an earlier FPO could lead to a steeper increase in GPP than in ET. However, the advance of FPO probably reduced summer WUE as a result of the enhancement of water stress by ET in the spring in temperate deciduous broadleaf forest. Our results also implied that spring warming had an indirectly positive effect on WUE through advancing spring phenology, but such a positive effect will likely weaken once the sensitivity of spring phenology to warming decreases as reported. Here, we argue that phenology, which exerts critical biotic control over most ecological processes, plays a larger role than expected in the regulation of the seasonal WUE and cannot be ignored in earth system models. [ABSTRACT FROM AUTHOR]