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Biogeochemistry is the study of how chemical elements flow through living systems and their physical environments. It investigates the factors that influence cycles of key elements such as carbon, nitrogen and phosphorous.
Reliable estimates of the total forest carbon (C) pool are lacking due to insufficient information on dead organic matter (DOM). Here, the authors estimate that the current DOM C stock in China is 925 ± 54 Tg and that it grew by 6.7 ± 2.2 Tg C/yr over the past two decades primarily due to increasing forest area
Estimates of stomatal conductance are important for models of crop and ecosystem water and carbon flux. Here, data from temperate tree species show interspecific variation in stomatal function that can be accounted for to make models more accurate.
Trace elements are enriched in plants by natural processes, human activities or both. An analysis of mercury in Arctic tundra vegetation offers fresh insight into the uptake of trace metals from the atmosphere by plants. See Letter p.201
Warm conditions in the Arctic Ocean have been linked to cold mid-latitude winters. Observations and simulations suggest that warm Arctic anomalies lead to a dip in CO2 uptake capacity in North American ecosystems and to low crop productivity.
Ambitious greenhouse–gas emissions cuts are needed to limit the global mean annual temperature increase to 1.5 °C above preindustrial levels. A study now finds that the land sink for CO2 appears much smaller than is currently factored into climate models, suggesting that emissions cuts may need to be even more ambitious than currently estimated.
Permafrost soils represent a massive pool of organic carbon that could be released to the atmosphere due to future climate change. A study now shows that previously frozen soil carbon contained in peatlands may make a relatively modest contribution to future methane emissions following permafrost thaw.
Phosphorus loading can cause eutrophication of lakes. Analyses of lake chemistry in China reveal that policies have led to lower phosphorus levels overall, but increasing trends in some lakes suggest that expanded policies may be needed.