The mechanical stability of the culms of monocotyledonous bamboos is highly attributed to the proper embedding of the stiff fibre caps of the vascular bundles into the soft parenchymatous matrix. Owing to lack of a vascular cambium, bamboos show no secondary thickening growth that impedes geometrical adaptations to mechanical loads and increases the necessity of structural optimization at the material level. Here, we investigate the fine structure and mechanical properties of fibres within a maturing vascular bundle of moso bamboo, Phyllostachys pubescens, with a high spatial resolution. The fibre cell walls were found to show almost axially oriented cellulose fibrils, and the stiffness and hardness of the central part of the cell wall remained basically consistent for the fibres at different regions across the fibre cap. A stiffness gradient across the fibre cap is developed by differential cell wall thickening which affects tissue density and thereby axial tissue stiffness in the different regions of the cap. The almost axially oriented cellulose fibrils in the fibre walls maximize the longitudinal elastic modulus of the fibres and their lignification increases the transverse rigidity. This is interpreted as a structural and mechanical optimization that contributes to the high buckling resistance of the slender bamboo culms.

Most rivers of the world are supersaturated with carbon dioxide (CO2), resulting in a large gas flux that has only recently been included in global carbon budgeting. However, little is known about CO2 emissions from urban river networks suffering anthropogenic disturbance in the context of global urbanization. We surveyed the partial pressure of carbon dioxide (pCO2) and CO2 flux from 84 locations in the Chongqing metropolitan river network, with an area of 5494 km2. The overall mean pCO2 and CO2 fluxes were 2152 µatm and 163.0 mol C m−2 yr−1, respectively, with 318.9 mol C m−2 yr−1 from rivers in the completely urban area and 49.6 mol C m−2 yr−1 from the least urbanized area. The riverine pCO2 level increased with the proportion of urban land, with 2–4 times higher CO2 flux in the urban areas than the remote rural ones. Sites with low flow velocity, narrow channel, and factitious bottom sediment appeared to be local hot spots of CO2 emission. The pCO2 and CO2 degassing was positively correlated with the nutrients content of surface water (i.e., nitrogen and phosphorus). Carbon was released to the atmosphere as CO2 from Chongqing metropolitan river network at a rate of 12.3 × 109 mol C yr−1. pCO2 exhibited a clear seasonality with lower values in March 2015 and June 2015 but a higher value in September 2014, which was coregulated by temperature, flood dilution, and in situ photosynthesis. The results highlight that rapid urbanization, with increasing nutrients loading and anthropogenic activities, will alter the carbon biogeochemical cycle in the terrestrial‐aqueous‐atmospheric ecosystem and then impact global CO2 budgets.

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This study aims to investigate physical characteristic, mechanical properties, and chemical composition of heat-treated bamboo scrimber. Specimens were heated at 50-230°C in laboratory conditions for 2 h. Test results of heat treatment samples were compared with the controls. Moisture absorption decreased slightly and then increased as temperature increased. It was probably due to changes of crystallinity and chemical structure. Mechanical properties varied greatly according to different temperature levels. Failure types reflected treatment temperature to some extent. Compressive strength reached a maximum when fiber bundles fractured neatly at 170°C, which is a turning point for physical, mechanical, and chemical properties under this heat treatment condition. Increasing mechanical properties of bamboo scrimber after heat treatment was due to solidification of phenolic resin.

The objective of this study was to investigate the compressive strength parallel to the grain of bamboo scrimber during and after exposure to various temperatures, in a range from 20 to 225 °C. These data were used to provide a basis for the evaluation of the fire performance of bamboo structures. A total of 152 specimens, assembled as group “during-fire” and “post-fire”, were tested during and after exposure to high temperatures. The experimental results indicated that there were significant differences in compressive properties between the “during-fire” and “post-fire” groups. At one temperature level, the compressive strength and modulus of elasticity of the “post-fire” group were significantly higher than those properties of the “during fire” group, but the ductility coefficient was reversed. FTIR analysis results showed that 175 °C was a key turning point, at which thermal decomposition occurred in the cellulose of the bamboo and phenolic resin.

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