Humid Subtropical China Research Articles

Influence of elevated UV-B radiation on leaf litter chemistry and subsequent decomposition in humid subtropical China

Exposure to elevated ultraviolet B (UV-B) radiation during plant growth may influence plant tissue chemistry and subsequent decomposition. We conducted a 22-month decomposition experiment to evaluate the effects of UV-B radiation on litter chemistry and subsequent decomposition in humid subtropical forest systems. Leaf litters were derived from five native tree species, including Cunninghamia lanceolata, Cinnamomum camphora, Schima superba, Cyclobalanopsis glauca, and Elaeocarpus sylvestris, which grew under ambient and elevated UV-B radiation treatments for 1 year. UV-B treatment significantly altered the original C, N, P, K, and lignin content and ratios of C/N, lignin/N, and C/P of leaf litter of five species but just slightly accelerated decomposition at variable degree from 2 % to 13 %. Statistical analyses showed litter species, but not UV-B treatment, had significant effect on decomposition. Only initial lignin content was significantly related to the decay rate. Abundant precipitation and warm temperature in subtropical China maybe weaken or even mask the importance of litter chemistry change resulted from UV-B radiation to decomposition especially in early decomposition stage. Exposure to supplemental UV-B level induced significant changes of the initial leaf litter chemistry but did not accelerate significantly subsequent decomposition of each species in humid subtropical areas of China at least in the early phase. The interspecific differences in litter chemistry of the five species showed greater effect on decomposition than elevated UV-B radiation at the early decomposition stage.

Elevated UV-B radiation increased the decomposition of Cinnamomum camphora and Cyclobalanopsis glauca leaf litter in subtropical China

Ultraviolet-B (UV-B) radiation reaching the earth's surface has been increasing due to ozone depletion and can profoundly influence litter decomposition and nutrient cycling in terrestrial ecosystems. The role of UV-B radiation in litter decomposition in humid environments is poorly understood; we thus investigated the effect of UV-B radiation on litter decomposition and nitrogen (N) release in a humid subtropical ecosystem in China. We conducted a field-based experiment using the litterbag method to study litter decomposition and N release under ambient and elevated (31% above ambient) UV-B radiation, using the leaf litter of two common tree species, Cinnamomum camphora and Cyclobalanopsis glauca, native to subtropical China. Elevated UV-B radiation significantly increased the decomposition rate of C. camphora and C. glauca leaf litter by 16.7% and 27.8%, respectively, and increased the N release from the decomposing litter of C. glauca but not C. camphora. Elevated UV-B radiation significantly accelerated the decomposition of litter of two native tree species and the N release from the decomposition litter of C. glauca in humid subtropical China, which has implications for soil carbon flux and forest productivity.

Elevated UV-B radiation did not affect decomposition rates of needles of two coniferous species in subtropical China

The increased level of ultraviolet-B (UV-B) radiation reaching the earth’s surface has profound implications for altering terrestrial ecosystem processes such as litter decomposition and nutrient cycling. Here we report on a field experiment that investigated the direct effect of elevated UV-B radiation on the rate of decomposition, lignin degradation, and N and P release from needle litter of two native coniferous species, Cunninghamia lanceolata and Pinus massoniana, in humid subtropical China. Elevated UV-B irradiation did not significantly accelerate litter mass loss and lignin photodegradation of the two species. Elevated UV-B irradiation accelerated the release of N and P from the litter of C. lanceolata, but not from that of P. massoniana. Our data indicated that elevated UV-B irradiation would accelerate N and P turnover in C. lanceolata forest. Our findings will contribute to the better understanding of the role of UV-B radiation in moist subtropical region.

Air movement preferences observed in naturally ventilated buildings in humid subtropical climate zone in China

Occupants' preferences for air movement in naturally ventilated buildings have been extracted from a database of three thermal comfort surveys conducted in the humid subtropical climate zone in China, during winter, spring, and summer seasons. The distribution of draft sensation shows that only 25.7, 38.5, and 28.7% of the subjects in winter, spring, and summer, respectively, felt that the available air movement was just right, suggesting that indoor air velocity may be a big problem in naturally ventilated buildings in humid subtropical China. Air movement preferences show that 15.8, 61.3, and 80.6% of subjects in winter, spring, and summer, respectively, wanted more air movement. Only a handful of subjects wanted less air movement than they were actually experiencing in any season, suggesting that draft was not much of an issue for thermal comfort. Occupants' preference for air movement is strongly related to thermal sensation, showing that people want to control air movement as a means of improving their comfort. The demand for less air movement under cool sensation is much smaller than the overwhelming demand for more air movement when the sensation was warm. The above results indicate that air movement might have a significant influence over the respondents' comfort sensation and that people required a high level of air movement in order to be comfortable during the summer season. Thus, one efficient way to improve the thermal environment in summer in humid subtropical China could be to provide occupants with effective natural ventilation and allow personal control of the air movement. Our findings are also applicable to other buildings, to encourage designers to provide air movement as a low energy cooling strategy and to ensure that sufficient levels of air movement are available.

05/00981 Viscosity correlations for minor constituent fluids in natural gas: n-octane, n-nonane and n-decane

The increased level of ultraviolet-B (UV-B) radiation reaching the earth’s surface has profound implications for altering terrestrial ecosystem processes such as litter decomposition and nutrient cycling. Here we report on a field experiment that investigated the direct effect of elevated UV-B radiation on the rate of decomposition, lignin degradation, and N and P release from needle litter of two native coniferous species, Cunninghamia lanceolata and Pinus massoniana, in humid subtropical China. Elevated UV-B irradiation did not significantly accelerate litter mass loss and lignin photodegradation of the two species. Elevated UV-B irradiation accelerated the release of N and P from the litter of C. lanceolata, but not from that of P. massoniana. Our data indicated that elevated UV-B irradiation would accelerate N and P turnover in C. lanceolata forest. Our findings will contribute to the better understanding of the role of UV-B radiation in moist subtropical region.