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The effects of canopy development, solar angle, and weather conditions on temporal variation in photosynthetic photon flux density(PPFD) at three heights within a tropical rain forest canopy in Xishuangbanna, China, were examined. PPFD was measured every second and stored as 10-min averages from 1 December 2002 to 30 November 2003. PPFD variability was examined at three different temporal scales. Specific days in March, September, and December with clear and overcast sky conditions were selected to separate the effects of leaf area index (LAI) and solar angle on diurnal variability. On both clear and overcast days, mean daily average PPFD was significantly different between March and September at all heights, except 10 m on clear days, suggesting that LAI directly influences PPFD. In contrast, the differences in daily average PPFD among three heights between September and December were likely due to variation in solar angle. In addition, daily average PPFD at all locations were significantly lower under overcast than clear sky conditions in March, September and December. Over the year-long study, the mean daily total PPFD at 21 m, 10 m and 4 m was 2.8, 2.7 and 0.7 mol/(m2 · d), which accounted for 9.7%, 9.4% and 2.4% of the daily PPFD above the canopy, respectively. Significant differences in mean daily total PPFD occurred at the same heights among different seasons, and diurnal, day-to-day and seasonal PPFD varied at different heights within the canopy. The possible effects of light variability on physiological and morphological responses of plants are discussed. [ABSTRACT FROM AUTHOR]

The effects of two lignins isolated from black liquor from pulping process on nitrification in soils after addition of urea, (NH[sub4])[sub2] SO[sub4] and (NH[sub4])[sub2] HPO[sub4] were investigated by incubation at 20 or 30°C for 7 or 14 d. The effects of lignin on nitrous oxide emissions from soil were also determined. Results showed that both lignins were more effective for inhibiting nitrification of NH[sub4] [sup+] -N as (NH[sub4])[sub2] SO[sub4] or (NH[sub 4])[sub 2] HPO[sub 4] as compared to urea-N. The effectiveness of lignin on nitrification was markedly affected by different soil type and temperature. Nitrous oxide emissions from soil declined when lignin was used. Urea plus 20 and 50 g/kg lignin reduced N[sub2]O emissions by about 83% and 96%, respectively, while (NH[sub4])[sub2]HPO[sub4] plus 20 and 50 g/kg lignin respectively reduced emissions by 83% and 93%. Because of its low cost and nonhazardous characteristics, lignin has potential value as a fertilizer amendment to improve N fertilizer efficiency. [ABSTRACT FROM AUTHOR]

Abstract: South China has become the third largest region associated with acid deposition following Europe and North America, the area subject to damage by acid deposition increased from 1.75 million km² in 1985 to 2.8 million km² in 1993. Acid deposition has caused serious damage to ecosystem. Combined pollution of acid rain and SO[sub 2] showed the obvious multiple effects on crops. Vegetable was more sensitive to acid deposition than foodstuff crops. Annual economic loss of crops due to acid deposition damage in eleven provinces of south China was 4.26 billion RMB Yuan. Acid deposition caused serious damage to forest. Annual economic loss of wood volume was about 1.8 billion RMB Yuan and forest ecological benefit loss 16.2 billion in eleven provinces of south China. Acid deposition in south China was typical "sulfuric acid type". According to the thoughts of sustainable development, some strategies were brought forward as follows: (1) enhancing environmental management, specifying acid-controlling region, controlling and abating the total emission amount of SO[sub 2]; (2) selecting practical energy technologies of clean coal, for example, cleansing and selecting coal, sulfur-fixed-type industrial briqutting, abating sulfur from waste gas and so on; (3) developing other energy sources to replace coal, including water electricity, atomic energy and the new energy such as solar energy, wind energy and so on; (4) in acid deposition region of south China, selecting acid-resistant type of crop and tree to decrease agricultural losses, planting more green fertilizer crops, using organic fertilizers and liming, in order to improve buffer capacities of soil. [ABSTRACT FROM AUTHOR]

Abstract: The impacts of different O[sub 3] concentration on the biomass and yield of rice were studied by using OTC-1 open-top chambers. Experimental treatments included the activated charcoal-filtered air (CFA), 50 nl/L (CF50), 100 nl/L (CF100) and 200 nl/L (CF200) concentrations of O[sub 3]. The O[sub 3] treatments significantly decreased the total biomass per plant. The elevated O[sub 3] exposure resulted in a more decrease in the root growth than in the shoot growth. Assessments of yield characteristics at the final harvest revealed an O[sub 3]-induced decrease in the number of grains per plant, resulting from fewer ears per plant, fewer grains per ear and more unfilled grains per ear. The 1000 grain dry weight and the harvest index (HI) were not changed significantly under 50 nl/L or 100 nl/L O[sub 3] exposure, but reduced by 17.0% and 4.8% by 200nl/L O[sub 3] treatment, respectively. Compared to the CFA treatment, CF50, CF100 and CF200 treatments caused a 8.2%, 26.1%, 49.1% decrease of the grain yield per plant, and a 14.2%, 31.7%, 51.7% decrease of the total biomass per plant, respectively. Linear regression showed that the 7h - daily mean O[sub 3] concentration exposure for 3 months (July-September) and AOT40 (cumulative exposure accumulation over threshold 40 nl/L) were well correlated with the relative grain yield. A yield loss of 10% was estimated to be at 46.9 nl/L O[sub 3] for 7h-daily mean O[sub 3] concentration exposure or at 12930 nl/(L x h) O[sub 3] for AOT40. [ABSTRACT FROM AUTHOR]

Presents information on a study which calculated the forest volume loss caused by acid deposition in seven provinces of south China. Background on the White Paper on Environment in China; Field investigations and methods; Results and discussion.

Effects of elevated 0[sub 3] on the yields of rice and winter wheat were studied by using open-top chambers(OTCs). Results showed that compared to the control treatment, 200 ppb, 100 ppb, 50 ppb treatments caused a 80.4%, 58.6% and 10.5% decrease in grain yields per winter wheat plant and a 49.1%, 26.1% and 8.2% decrease in grain yield per rice plant, respectively. According to the dose-response relation educed from OTCs experiment and the monitor data of O[sub3] concentrations in spots, it was estimated that the yield losses of rice and winter wheat resulted by O[sub3] pollution in the Yangtze River Delta region in 1999 were 0.599 million ton and 0.669 million ton, economic losses were 0.539 billion RMB Yuan and 0.936 billion RMB Yuan, respectively. [ABSTRACT FROM AUTHOR]