Uncertainties surrounding tree carbon allocation to growth are a major limitation to projections of forest carbon sequestration and response to climate change. The prevalence and extent to which carbon assimilation (source) or cambial activity (sink) mediate wood production are fundamentally important and remain elusive. We quantified source-sink relations across biomes by combining eddy-covariance gross primary production with extensive on-site and regional tree ring observations. We found widespread temporal decoupling between carbon assimilation and tree growth, underpinned by contrasting climatic sensitivities of these two processes. Substantial differences in assimilation-growth decoupling between angiosperms and gymnosperms were determined, as well as stronger decoupling with canopy closure, aridity, and decreasing temperatures. Our results reveal pervasive sink control over tree growth that is likely to be increasingly prominent under global climate change.

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Ventilated windows have shown great po tential in conserving energy in buildings and provide fresh air to i mprove indoor air qua lity. This paper reports our effort to use EnergyPlus to simulate the energy performance of a dual airflow window under different climate. Our investigation first develope d a network m odel to accoun t for th e twodimensional heat transfer in the window sy stem and i mplemented it in EnergyPlus. The two-dimensional assumption and the modified EnergyPlus program were validated by the measured temperatures of the window and th e energy dem and of a test cell with the window under actual weather conditions. Then EnergyPlus was applied to analyze energy performance of a s mall apartm ent installe d with the dual airflow windows in fi ve different climate zones in China. The energy used by the ap artment with blinds wind ows and low-e windows was also calculated for com parison. The dual airflow window can reduce heating energy of the apartment, especi ally in cold clim ate. The cooling energy reduction by the window was less im portant th an that by shading solar radiation. The dual airflow window is recomm ended for colder clim ate. If im proving air quality is a major consideration for a building, the window can be used in any climate.

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