Yao Huang - Academia.edu (original) (raw)
Papers by Yao Huang
The international journal of lower extremity wounds, Jan 20, 2015
To investigate the information of chronic wounds, especially in the aspect of microbiological pro... more To investigate the information of chronic wounds, especially in the aspect of microbiological profile and to explore the relationship between the wound culture result and chronic wounds infection, we retrospectively reviewed the medical records of 107 patients with chronic wounds from January 2011 to December 2013. The sociodemographic data, wound-related information, therapeutic type, and wound infection status were extracted. Microbial specimens were obtained and processed using standard hospital procedure for wound culture. The predominant pathogen isolated was Staphylococcus aureus (n = 11, 26.2%), followed by Escherichia coli (n = 6, 14.3%), Enterobacter cloacae (n = 3, 7.1%), and Pseudomonas aeruginosa (n = 3, 7.1%). Sixty percent of the infectious chronic wounds had positive culture, and 96.2% of the noninfectious wounds had negative culture. In conclusion, the microbial characteristics were mostly in the site of lower extremity, gram-negative bacteria, and monopathogen, respectively. Furthermore, the relationship between the wound culture result and chronic wound infection was not exactly coincident. It may be useful for guiding the empiric therapy of chronic wounds.
China, the world's most populated country with more than 1.3 billion people, has the world's seco... more China, the world's most populated country with more than 1.3 billion people, has the world's second largest area of rice paddy, which accounts for 19% of the world rice area. Rice cultivation, representing about 28% of the total national grain crops area and contributing 38% of the total grain production, is widely distributed across a vast area spanning wide ranges of temperate, subtropical and tropical climates. In accordance with the general trend of global climate change, surface air temperature in China has increased by 1.1℃ over the last 100 years. More significant increase occurred in the recent 50 years. Model predictions have suggested that the surface air temperature in China will probably increase by 1.5-2.8℃ by 2030, and 2.3-3.3℃ by 2050. The objective of this study is to make a primary assessment of climate change impact on rice production in China from 1961 to 2005, so as to take appropriate adaptation measures for future climate change. Daily temperature in some 300 meteorological stations across rice cultivation area in China was used to estimate the dates of safe sowing and safe heading. The dates of safe sowing and safe heading are defined as the time when the mean daily temperature is consistently above 10℃ with 80% probability and above 20℃ for three successive days in the late season, respectively. The accumulated temperature (>10℃) was computed from safe sowing to heading for each station. Analysis of rice growing season indicated that, on average, the safe sowing time advanced 3-6 days and the safe heading time delayed 2-9 days during 1991-2005 compared with those during 1961-1980. Accordingly, the period from safe sowing to heading increased by 5 days in double rice area at latitudes between 20°N and 30°N, 8 days and 12 days in single rice area in Central China at latitudes between 28°N and 34°N and in Northeast China at latitudes between 39°N and 48°N, respectively. The accumulated temperature (>10℃) from safe sowing to heading increased by 100-300℃·d. Rice productivity in China has been increased over the last 45 years. The amount of grain yield reached 180.6 million tons in 2005. This increase may be partly attributed to the extended length of rice growing season, while it is hard to identify because the application rates of synthetic fertilizer increased during the same period. However, regional assessment may help us to understand the impact of climate change on rice production. Single rice (one harvest per year) is planted in Northeast China (Heilongjiang, Jilin and Liaoning Province). Injury due to low temperature is a major limiting factor in this region. The air temperature increased by approximately 0.5℃/10-yr from 1981 to 2005, which not only increased the accumulated temperature (>10℃) for rice growth, but also reduced the low-temperature injury to rice plants. Analysis of the daily mean temperature indicated that the accumulated temperature (>10℃) from safe sowing to heading increased by 9% and the days of air temperature below 20℃ in rice heading decreased by about 45% during 1986-2005 in contrast with that during 1961-1985. The rice grain yield increased with an annual rate of approximately 70kg/ha during 1986-2005. Moreover, the northward expansion of rice-planting has been occurred since the early 1980s. The rice-planted area was about 0.85Mha in the early 1980s while jumped greatly to 3.07Mha in 2005, accounting for 10.7% of the national rice-planted area. Double rice cropping system (two harvests of rice per year) has been dominant in Jiangxi Province, located at latitudes between 24°29' N and 30°05'N and longitudes between 113°34'E and 118°29'E. The rice grain yield increased with an annual rate of approximately 50kg/ha during 1982-2005. Analysis of datasets from fourteen agrometeorological stations in Jiangxi Province where the application rates of fertilizer were similar from 1982 to 2005 suggested that the early-rice grain yields per unit area increased as the safe sowing time advanced, and that the total grain yields of early-rice plus late-rice were positively correlated with the accumulated temperature (>10℃) from safe sowing to heading. No significant trend in the frequency of high temperature (>35℃) at anthesis was found over the 24 years. The high temperature (>35℃) is recognized to induce spikelet sterility. A further investigation indicated that the variety renewal of rice in this province was practiced to adapt the increasing temperature.
Outdoor pot experiments with various paddy soils representing five soil types were conducted at N... more Outdoor pot experiments with various paddy soils representing five soil types were conducted at Nanjing Agricultural University during the 2000 and 2001 rice-growing seasons. Eighteen soils and ten out of the eighteen soils were involved in the 2000 and the 2001 experiment, respectively. Two treatments were designed as mineral fertilization (MF) and mineral fertilizer + wheat straw incorporation (MF + WS) for the 2001 experiment. Seasonal average rate of CH 4 emission from different soils ranged from 1.96 to 11.06 mg m À2 h À1 in the 2000 experiment, and from 0.89 to 5.92 mg m À2 h À1 for the MF treatment in the 2001 experiment, respectively. Incorporation of wheat straw enhanced considerably CH 4 emission with an average increment of 7.09 mg m À2 h À1 . CH 4 emissions from the two-year experiment were negatively correlated to soil available and total copper concentration. A further investigation showed that CH 4 emission from the MF treatment was positively related to the dissolved organic carbon (DOC) in the soil (r ¼ 0:904, p < 0:001), and that the DOC was negatively correlated to the concentrations of available copper (r ¼ À0:844, p < 0:01) and total copper (r ¼ À0:833, p < 0:01), respectively. Nevertheless, the incorporation of wheat straw did not enhance the soil DOC, and the relationship between CH 4 emission and soil DOC was not statistically significant (r ¼ 0:470, p < 0:20). It was concluded that higher concentration of copper in the soils resulted in lower soil DOC and thus reduced CH 4 emission when there was no additional organic matter input. Incorporation of wheat straw did not affect soil DOC and available copper concentration but enhanced CH 4 emission.
To identify the key soil parameters influencing methane emission from rice paddies, and to quanti... more To identify the key soil parameters influencing methane emission from rice paddies, and to quantitatively describe the relationship of methane emission with the soil properties, an outdoor pot experiment with a total of 18 paddy soils sampled from different regions in Jiangsu province was conducted in Nanjing Agricultural University during 2000 rice growing season. Seasonal average rate of CH4 emission for all the 18 soils was 6.42 +/- 2.70 mg.(m2.h)-1, ranging from 1.96 to 11.06 mg.(m2.h)-1, approximately a 5.6-fold difference between the maximum and the minimum. Correlation analysis indicated that the seasonal average of CH4 emission was positively dependent on soil sand content (r = 0.528, p = 0.024) and negatively on soil clay content (r = -0.484, p = 0.042). Negative correlation of CH4 emission against soil total nitrogen (r = -0.449, p = 0.062), available nitrogen (r = -0.611, p = 0.007) and NH4(+)-N(r = -0.649, p = 0.004) was also observed. Copper content of soils has a significant negative impact on CH4 emission. The correlation coefficient (r) of CH4 emission against soil available copper and with total copper was -0.594 (p = 0.009) and -0.547 (p = 0.019), respectively. No clear relationship existed between CH4 emission and soil carbon content. A further investigation suggests that the seasonal average rate of CH4 emission can be quantitatively determined by a linear combination of soil available copper, total manganese, and a ratio of available to total iron (R2 = 0.755, p = 0.0001).
To understand the CO2 emission from soil-crop system as influenced by crop growth and tissue N co... more To understand the CO2 emission from soil-crop system as influenced by crop growth and tissue N content, pot and field experiments were carried out during 2001-02 wheat and rice growing seasons. Black chambers were used to take gas samples within a closed soil-crop system. The CO2 emission rate was detected by a gas chromatograph. Seasonal change of the CO2 emission was observed from the soil-crop system. Respiration from the soil-rice system was higher than that from the soil-wheat system. Dark respiration of the crop shoot was positively correlated to the shoot biomass. The respiration coefficient Rd, defined as the amount of CO2-C respired by per unit biomass C within one day under a reference temperature of 25 degrees C, can be well quantitatively expressed by shoot N content for either wheat or rice crop. Relationship between the Rd and the N content can be described as a linear regression of Rd = 0.0124N - 0.0076 (R2=0.9879, p&amp;amp;amp;lt;0.001) for the wheat crop and as a quadratic equation of Rd = 0.0085N2 - 0.0049N (R2=0.9776, p&amp;amp;amp;lt;0.001) for the rice crop, respectively. The crop roots promoted the soil respiration greatly, which increased by 178% for the wheat and 338% for the rice in comparison with the respiration from root-free soil. A further calculation of the root respiration, including root autotrophic respiration and rhizosphere respiration, suggested that the contribution of crop rhizosphere respiration to the total soil respiration was greater in the upland soil than that in the irrigated paddy soil.
1] Soil organic carbon (SOC) in cropland is of great importance to the global carbon (C) balance ... more 1] Soil organic carbon (SOC) in cropland is of great importance to the global carbon (C) balance and to agricultural productivity, but it is highly sensitive to human activities such as irrigation and crop rotation. It has been observed that under certain improved management practices, cropland soils can sequestrate additional C beyond their existing SOC level before reaching the C saturation state. Here we use data from worldwide, long-term agricultural experiments to develop two statistical models to determine the saturated SOC level (SOC S ) in upland and paddy agroecosystems, respectively. We then use the models to estimate SOC sequestration potential (SOC P ) in Chinese croplands. SOC P is the difference between SOC S and existing SOC level (SOC E ). We find that the models for both the upland and paddy agroecosystems can reproduce the observed SOC S data from long-term experiments. The SOC E and SOC S stock in Chinese upland and paddy croplands (0-30 cm soil) are estimated to be 5.2 and 7.9 Pg C with national average densities of 37.4 and 56.8 Mg C ha À1 , respectively. As a result, the total SOC sequestration potential is estimated to be 2.7 Pg C or 19.4 Mg C ha À1 in Chinese cropland. Paddy has a relatively higher SOC E (45.4 Mg C ha À1 ) than upland (34.7 Mg C ha À1 ) and also a greater SOC P at 26.1 Mg C ha À1 compared with 17.2 Mg C ha À1 in the upland. The SOC varies dramatically among different regions. Northeast China has the highest SOC E and SOC S density, while the Loess Plateau has the greatest SOC P density. The time required to reach SOC saturation in Chinese cropland is highly dependent on management practices applied. Chinese cropland has relatively low SOC density in comparison to the global average but could have great potentials for C sequestration under improved agricultural management strategies.
ABSTRACT Based on the databases of soil , climate , crop production and agricultural management ,... more ABSTRACT Based on the databases of soil , climate , crop production and agricultural management , changes of soil organic carbon of agroecosystems in Jiangsu province were simulated , using a soil organic carbon model with a linkage of GIS. Four data sets of soil organic carbon measured from various field experiments in Jiangsu province were used to vali2 date the model . It was demonstrated that the model simulation in general agreement with the field measurements. Model simulation indicated that the soil organic carbon content in approximately 77 % of the agricultural soils in Jiangsu province has increased since the 2nd national soil survey completed in the early 1980s. Compared with the values in 1985 , the soil organic carbon content in 2000 was estimated to increase by 1. 0~3. 0 g· kg - 1 for the north and the coastal areas of the province , and by 3. 5~5. 0 g· kg - 1 for the region of Taihu lake in the south. A slight decrease (about 0. 5~1. 5 g· kg - 1) was estimated for the central region of Jiangsu and the Nanjing2Zhenjiang hilly area. Model prediction for the 2010 , assuming under two scenarios , i . e. , with 30 % and 50 % of the harvested crop straw incorporation , suggested that the soil organic carbon in Jiangsu province would increase , and thus that the agricultural soils would have potential as or2 ganic carbon storage. The incorporation of crop straw into soils is of great benefit to increase soil carbon storage , conse2 quently to benefit the control of the rise of atmospheric CO2 concentration and to maintain the sustainable development of agriculture.
This REgional Carbon Cycle Assessment and Processes regional study provides a synthesis of the ca... more This REgional Carbon Cycle Assessment and Processes regional study provides a synthesis of the carbon balance of terrestrial ecosystems in East Asia, a region comprised of China, Japan, North-and South-Korea, and Mongolia. We estimate the current terrestrial carbon balance of East Asia and its driving mechanisms during 1990-5 2009 using three different approaches: inventories combined with satellite greenness measurements, terrestrial ecosystem carbon cycle models and atmospheric inversion models. The magnitudes of East Asia's natural carbon sink from these three approaches are comparable: −0.264 ± 0.033 Pg C yr −1 from inventory-remote sensing model-data fusion approach, −0.393 ± 0.141 Pg C yr −1 (not considering biofuel emis-10 sions) or −0.204 ± 0.141 Pg C yr −1 (considering biofuel emissions) for carbon cycle models, and −0.270 ± 0.507 Pg C yr −1 for atmospheric inverse models. The ensemble of ecosystem modeling based analyses further suggests that at the regional scale, climate change and rising atmospheric CO 2 together resulted in a carbon sink of −0.289 ± 0.135 Pg C yr −1 , while land use change and nitrogen deposition had a con-15 tribution of −0.013 ± 0.029 Pg C yr −1 and −0.107 ± 0.025 Pg C yr −1 , respectively. Although the magnitude of climate change effects on the carbon balance varies among different models, all models agree that in response to climate change alone, southern China experienced an increase in carbon storage from 1990 to 2009, while northern East Asia including Mongolia and north China showed a decrease in carbon storage.
Chemical nitrogen (N) fertilizer has long been used to help meet the increasing food demands in C... more Chemical nitrogen (N) fertilizer has long been used to help meet the increasing food demands in China, the top N fertilizer consumer in the world. Growing concerns have been raised on the impacts of N fertilizer uses on food security and climate change, which is lack of quantification. Here we use a carbon-nitrogen (C-N) coupled ecosystem model, to quantify the food benefit and climate consequence of agronomic N addition in China over the six decades from 1949 to 2008. Results show that N fertilizer-induced crop yield and soil C sequestration had reached their peaks, while nitrous oxide (N 2 O) emission continued rising as N was added. Since the early 2000s, stimulation of excessive N fertilizer uses to global climate warming through N 2 O emission was estimated to outweigh their climate benefit in increasing CO 2 uptake. The net warming effect of N fertilizer uses, mainly centered in the North China Plain and the middle and lower reaches of Yangtze River Basin, with N 2 O emission completely counteracting or even exceeding, by more than a factor of 2, the CO 2 sink. If we reduced the current N fertilizer level by 60% in 'over-fertilized' areas, N 2 O emission would substantially decrease without significantly influencing crop yield and soil C sequestration.
An extensive dataset on rice phenology in China, including 202 series broadly covering the past t... more An extensive dataset on rice phenology in China, including 202 series broadly covering the past three decades (1980s-2000s), was compiled. From these data, we estimated the responses of growth duration length to temperature using a regression model based on the data with and without detrending. Regression coefficients derived from the detrended data reflect only the temperature effect, whereas those derived from data without detrending represent a combined effect of temperature and confounding cultivar shifts. Results indicate that the regression coefficients calculated from the data with and without detrending show an average shortening of the growth duration of 4.1-4.4 days for each additional increase in temperature over the full growth cycle. Using the detrended data, 95.0% of the data series exhibited a negative correlation between the growth duration length and temperature; this correlation was significant in 61.9% of all of the data series. We then compared the difference between the two regression coefficients calculated from data with and without detrending and found a significantly greater temperature sensitivity using the data without detrending (-2.9 days °C(-1) ) than that derived from the detrended data (-2.0 days °C(-1) ) in the period of emergence to heading for the late rice, producing a negative difference in temperature sensitivity (-0.9 days °C(-1) ). This implies that short-duration cultivars were planted with increase in temperature and exacerbated the undesired phenological change. In contrast, positive differences were detected for the single (0.6 days °C(-1) ) and early rice (0.5 days °C(-1) ) over the full growth cycle, which might indicate that long-duration cultivars were favoured with climate warming, but these differences were insignificant. In summary, our results suggest that a major, temperature induced change in the rice growth duration is underway in China and that using a short-duration cultivar has been accelerating the process for late rice.
n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) ... more n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) Croplands 72 0.52 (0.18-1.58) 51 72 12.1 (5.5-19.3) 24 72 0.76 (0.37-2.16) 53 72 3.18 (1.06-10.72) 56 57 0.31 (0.07-0.57) 37 54 7.5 (5.0-8.7) 14 Grasslands 113 0.84 (0.05-2.75) 66 113 11.7 (À1.0 to 26.5) 52 113 0.79 (0.16-2.93) 63 78 5.30 (0.32-12.54) 56 62 0.48 (0.01-1.02) 48 85 6.8 (5.3-8.5) 11 Forests 465 0.99 (0.16-2.45) 45 465 12.8 (À4.8 to 27.6) 54 462 1.24 (0.28-4.82) 63 321 6.52 (0.60-22.06) 61 266 0.46 (0.04-1.46) 73 187 5.2 (3.5-8.6) 20 All 657 0.91 (0.05-2.75) 52 657 12.4 (À4.8 to 27.6) 53 654 1.10 (0.08-4.82) 67 474 5.83 (0.32-22.06) 65 388 0.43 (0.01-1.46) 68 329 6.0 (3.5-8.7)
Large areas in the Upper Tana river catchment, Kenya, have been over-exploited, resulting in soil... more Large areas in the Upper Tana river catchment, Kenya, have been over-exploited, resulting in soil erosion, nutrient depletion and loss of soil organic matter (SOM). This study focuses on sections of the catchment earmarked as being most promising for implementing Green Water Credits, an incentive mechanism to help farmers invest in land and soil management activities that affect all fresh water resources at source. Such management practices can also help restore SOM levels towards their natural level. Opportunities to increase soil organic carbon (SOC) stocks, for two broadly defined land use types (croplands and plantation crops, with moderate input levels), are calculated using a simple empirical model, using three scenarios for the proportion of suitable land that may be treated with these practices (low = 40 per cent, medium = 60 per cent, high = 80 per cent). For the medium scenario, corresponding to implementation on~348 000 ha in the basin, the eco-technologically possible SOC gains are estimated at 4Á8 to 9Á3 Â 10 6 tonnes (Mg) CO 2 over the next 20 years. Assuming a conservative price of US$10 per tonne CO 2 -equivalent on the carbon offset market, this would correspond to~US$48-93 million over a 20-year period of sustained green water management. This would imply a projected (potential) payment of some US$7-13 ha À1 to farmers annually; this sum would be in addition to incentives that are being put in place for implementing green water management practices and also in addition to the benefits that farmers would realize from the impact on production of these practices themselves.
The international journal of lower extremity wounds, Jan 20, 2015
To investigate the information of chronic wounds, especially in the aspect of microbiological pro... more To investigate the information of chronic wounds, especially in the aspect of microbiological profile and to explore the relationship between the wound culture result and chronic wounds infection, we retrospectively reviewed the medical records of 107 patients with chronic wounds from January 2011 to December 2013. The sociodemographic data, wound-related information, therapeutic type, and wound infection status were extracted. Microbial specimens were obtained and processed using standard hospital procedure for wound culture. The predominant pathogen isolated was Staphylococcus aureus (n = 11, 26.2%), followed by Escherichia coli (n = 6, 14.3%), Enterobacter cloacae (n = 3, 7.1%), and Pseudomonas aeruginosa (n = 3, 7.1%). Sixty percent of the infectious chronic wounds had positive culture, and 96.2% of the noninfectious wounds had negative culture. In conclusion, the microbial characteristics were mostly in the site of lower extremity, gram-negative bacteria, and monopathogen, respectively. Furthermore, the relationship between the wound culture result and chronic wound infection was not exactly coincident. It may be useful for guiding the empiric therapy of chronic wounds.
China, the world's most populated country with more than 1.3 billion people, has the world's seco... more China, the world's most populated country with more than 1.3 billion people, has the world's second largest area of rice paddy, which accounts for 19% of the world rice area. Rice cultivation, representing about 28% of the total national grain crops area and contributing 38% of the total grain production, is widely distributed across a vast area spanning wide ranges of temperate, subtropical and tropical climates. In accordance with the general trend of global climate change, surface air temperature in China has increased by 1.1℃ over the last 100 years. More significant increase occurred in the recent 50 years. Model predictions have suggested that the surface air temperature in China will probably increase by 1.5-2.8℃ by 2030, and 2.3-3.3℃ by 2050. The objective of this study is to make a primary assessment of climate change impact on rice production in China from 1961 to 2005, so as to take appropriate adaptation measures for future climate change. Daily temperature in some 300 meteorological stations across rice cultivation area in China was used to estimate the dates of safe sowing and safe heading. The dates of safe sowing and safe heading are defined as the time when the mean daily temperature is consistently above 10℃ with 80% probability and above 20℃ for three successive days in the late season, respectively. The accumulated temperature (>10℃) was computed from safe sowing to heading for each station. Analysis of rice growing season indicated that, on average, the safe sowing time advanced 3-6 days and the safe heading time delayed 2-9 days during 1991-2005 compared with those during 1961-1980. Accordingly, the period from safe sowing to heading increased by 5 days in double rice area at latitudes between 20°N and 30°N, 8 days and 12 days in single rice area in Central China at latitudes between 28°N and 34°N and in Northeast China at latitudes between 39°N and 48°N, respectively. The accumulated temperature (>10℃) from safe sowing to heading increased by 100-300℃·d. Rice productivity in China has been increased over the last 45 years. The amount of grain yield reached 180.6 million tons in 2005. This increase may be partly attributed to the extended length of rice growing season, while it is hard to identify because the application rates of synthetic fertilizer increased during the same period. However, regional assessment may help us to understand the impact of climate change on rice production. Single rice (one harvest per year) is planted in Northeast China (Heilongjiang, Jilin and Liaoning Province). Injury due to low temperature is a major limiting factor in this region. The air temperature increased by approximately 0.5℃/10-yr from 1981 to 2005, which not only increased the accumulated temperature (>10℃) for rice growth, but also reduced the low-temperature injury to rice plants. Analysis of the daily mean temperature indicated that the accumulated temperature (>10℃) from safe sowing to heading increased by 9% and the days of air temperature below 20℃ in rice heading decreased by about 45% during 1986-2005 in contrast with that during 1961-1985. The rice grain yield increased with an annual rate of approximately 70kg/ha during 1986-2005. Moreover, the northward expansion of rice-planting has been occurred since the early 1980s. The rice-planted area was about 0.85Mha in the early 1980s while jumped greatly to 3.07Mha in 2005, accounting for 10.7% of the national rice-planted area. Double rice cropping system (two harvests of rice per year) has been dominant in Jiangxi Province, located at latitudes between 24°29' N and 30°05'N and longitudes between 113°34'E and 118°29'E. The rice grain yield increased with an annual rate of approximately 50kg/ha during 1982-2005. Analysis of datasets from fourteen agrometeorological stations in Jiangxi Province where the application rates of fertilizer were similar from 1982 to 2005 suggested that the early-rice grain yields per unit area increased as the safe sowing time advanced, and that the total grain yields of early-rice plus late-rice were positively correlated with the accumulated temperature (>10℃) from safe sowing to heading. No significant trend in the frequency of high temperature (>35℃) at anthesis was found over the 24 years. The high temperature (>35℃) is recognized to induce spikelet sterility. A further investigation indicated that the variety renewal of rice in this province was practiced to adapt the increasing temperature.
Outdoor pot experiments with various paddy soils representing five soil types were conducted at N... more Outdoor pot experiments with various paddy soils representing five soil types were conducted at Nanjing Agricultural University during the 2000 and 2001 rice-growing seasons. Eighteen soils and ten out of the eighteen soils were involved in the 2000 and the 2001 experiment, respectively. Two treatments were designed as mineral fertilization (MF) and mineral fertilizer + wheat straw incorporation (MF + WS) for the 2001 experiment. Seasonal average rate of CH 4 emission from different soils ranged from 1.96 to 11.06 mg m À2 h À1 in the 2000 experiment, and from 0.89 to 5.92 mg m À2 h À1 for the MF treatment in the 2001 experiment, respectively. Incorporation of wheat straw enhanced considerably CH 4 emission with an average increment of 7.09 mg m À2 h À1 . CH 4 emissions from the two-year experiment were negatively correlated to soil available and total copper concentration. A further investigation showed that CH 4 emission from the MF treatment was positively related to the dissolved organic carbon (DOC) in the soil (r ¼ 0:904, p < 0:001), and that the DOC was negatively correlated to the concentrations of available copper (r ¼ À0:844, p < 0:01) and total copper (r ¼ À0:833, p < 0:01), respectively. Nevertheless, the incorporation of wheat straw did not enhance the soil DOC, and the relationship between CH 4 emission and soil DOC was not statistically significant (r ¼ 0:470, p < 0:20). It was concluded that higher concentration of copper in the soils resulted in lower soil DOC and thus reduced CH 4 emission when there was no additional organic matter input. Incorporation of wheat straw did not affect soil DOC and available copper concentration but enhanced CH 4 emission.
To identify the key soil parameters influencing methane emission from rice paddies, and to quanti... more To identify the key soil parameters influencing methane emission from rice paddies, and to quantitatively describe the relationship of methane emission with the soil properties, an outdoor pot experiment with a total of 18 paddy soils sampled from different regions in Jiangsu province was conducted in Nanjing Agricultural University during 2000 rice growing season. Seasonal average rate of CH4 emission for all the 18 soils was 6.42 +/- 2.70 mg.(m2.h)-1, ranging from 1.96 to 11.06 mg.(m2.h)-1, approximately a 5.6-fold difference between the maximum and the minimum. Correlation analysis indicated that the seasonal average of CH4 emission was positively dependent on soil sand content (r = 0.528, p = 0.024) and negatively on soil clay content (r = -0.484, p = 0.042). Negative correlation of CH4 emission against soil total nitrogen (r = -0.449, p = 0.062), available nitrogen (r = -0.611, p = 0.007) and NH4(+)-N(r = -0.649, p = 0.004) was also observed. Copper content of soils has a significant negative impact on CH4 emission. The correlation coefficient (r) of CH4 emission against soil available copper and with total copper was -0.594 (p = 0.009) and -0.547 (p = 0.019), respectively. No clear relationship existed between CH4 emission and soil carbon content. A further investigation suggests that the seasonal average rate of CH4 emission can be quantitatively determined by a linear combination of soil available copper, total manganese, and a ratio of available to total iron (R2 = 0.755, p = 0.0001).
To understand the CO2 emission from soil-crop system as influenced by crop growth and tissue N co... more To understand the CO2 emission from soil-crop system as influenced by crop growth and tissue N content, pot and field experiments were carried out during 2001-02 wheat and rice growing seasons. Black chambers were used to take gas samples within a closed soil-crop system. The CO2 emission rate was detected by a gas chromatograph. Seasonal change of the CO2 emission was observed from the soil-crop system. Respiration from the soil-rice system was higher than that from the soil-wheat system. Dark respiration of the crop shoot was positively correlated to the shoot biomass. The respiration coefficient Rd, defined as the amount of CO2-C respired by per unit biomass C within one day under a reference temperature of 25 degrees C, can be well quantitatively expressed by shoot N content for either wheat or rice crop. Relationship between the Rd and the N content can be described as a linear regression of Rd = 0.0124N - 0.0076 (R2=0.9879, p&amp;amp;amp;lt;0.001) for the wheat crop and as a quadratic equation of Rd = 0.0085N2 - 0.0049N (R2=0.9776, p&amp;amp;amp;lt;0.001) for the rice crop, respectively. The crop roots promoted the soil respiration greatly, which increased by 178% for the wheat and 338% for the rice in comparison with the respiration from root-free soil. A further calculation of the root respiration, including root autotrophic respiration and rhizosphere respiration, suggested that the contribution of crop rhizosphere respiration to the total soil respiration was greater in the upland soil than that in the irrigated paddy soil.
1] Soil organic carbon (SOC) in cropland is of great importance to the global carbon (C) balance ... more 1] Soil organic carbon (SOC) in cropland is of great importance to the global carbon (C) balance and to agricultural productivity, but it is highly sensitive to human activities such as irrigation and crop rotation. It has been observed that under certain improved management practices, cropland soils can sequestrate additional C beyond their existing SOC level before reaching the C saturation state. Here we use data from worldwide, long-term agricultural experiments to develop two statistical models to determine the saturated SOC level (SOC S ) in upland and paddy agroecosystems, respectively. We then use the models to estimate SOC sequestration potential (SOC P ) in Chinese croplands. SOC P is the difference between SOC S and existing SOC level (SOC E ). We find that the models for both the upland and paddy agroecosystems can reproduce the observed SOC S data from long-term experiments. The SOC E and SOC S stock in Chinese upland and paddy croplands (0-30 cm soil) are estimated to be 5.2 and 7.9 Pg C with national average densities of 37.4 and 56.8 Mg C ha À1 , respectively. As a result, the total SOC sequestration potential is estimated to be 2.7 Pg C or 19.4 Mg C ha À1 in Chinese cropland. Paddy has a relatively higher SOC E (45.4 Mg C ha À1 ) than upland (34.7 Mg C ha À1 ) and also a greater SOC P at 26.1 Mg C ha À1 compared with 17.2 Mg C ha À1 in the upland. The SOC varies dramatically among different regions. Northeast China has the highest SOC E and SOC S density, while the Loess Plateau has the greatest SOC P density. The time required to reach SOC saturation in Chinese cropland is highly dependent on management practices applied. Chinese cropland has relatively low SOC density in comparison to the global average but could have great potentials for C sequestration under improved agricultural management strategies.
ABSTRACT Based on the databases of soil , climate , crop production and agricultural management ,... more ABSTRACT Based on the databases of soil , climate , crop production and agricultural management , changes of soil organic carbon of agroecosystems in Jiangsu province were simulated , using a soil organic carbon model with a linkage of GIS. Four data sets of soil organic carbon measured from various field experiments in Jiangsu province were used to vali2 date the model . It was demonstrated that the model simulation in general agreement with the field measurements. Model simulation indicated that the soil organic carbon content in approximately 77 % of the agricultural soils in Jiangsu province has increased since the 2nd national soil survey completed in the early 1980s. Compared with the values in 1985 , the soil organic carbon content in 2000 was estimated to increase by 1. 0~3. 0 g· kg - 1 for the north and the coastal areas of the province , and by 3. 5~5. 0 g· kg - 1 for the region of Taihu lake in the south. A slight decrease (about 0. 5~1. 5 g· kg - 1) was estimated for the central region of Jiangsu and the Nanjing2Zhenjiang hilly area. Model prediction for the 2010 , assuming under two scenarios , i . e. , with 30 % and 50 % of the harvested crop straw incorporation , suggested that the soil organic carbon in Jiangsu province would increase , and thus that the agricultural soils would have potential as or2 ganic carbon storage. The incorporation of crop straw into soils is of great benefit to increase soil carbon storage , conse2 quently to benefit the control of the rise of atmospheric CO2 concentration and to maintain the sustainable development of agriculture.
This REgional Carbon Cycle Assessment and Processes regional study provides a synthesis of the ca... more This REgional Carbon Cycle Assessment and Processes regional study provides a synthesis of the carbon balance of terrestrial ecosystems in East Asia, a region comprised of China, Japan, North-and South-Korea, and Mongolia. We estimate the current terrestrial carbon balance of East Asia and its driving mechanisms during 1990-5 2009 using three different approaches: inventories combined with satellite greenness measurements, terrestrial ecosystem carbon cycle models and atmospheric inversion models. The magnitudes of East Asia's natural carbon sink from these three approaches are comparable: −0.264 ± 0.033 Pg C yr −1 from inventory-remote sensing model-data fusion approach, −0.393 ± 0.141 Pg C yr −1 (not considering biofuel emis-10 sions) or −0.204 ± 0.141 Pg C yr −1 (considering biofuel emissions) for carbon cycle models, and −0.270 ± 0.507 Pg C yr −1 for atmospheric inverse models. The ensemble of ecosystem modeling based analyses further suggests that at the regional scale, climate change and rising atmospheric CO 2 together resulted in a carbon sink of −0.289 ± 0.135 Pg C yr −1 , while land use change and nitrogen deposition had a con-15 tribution of −0.013 ± 0.029 Pg C yr −1 and −0.107 ± 0.025 Pg C yr −1 , respectively. Although the magnitude of climate change effects on the carbon balance varies among different models, all models agree that in response to climate change alone, southern China experienced an increase in carbon storage from 1990 to 2009, while northern East Asia including Mongolia and north China showed a decrease in carbon storage.
Chemical nitrogen (N) fertilizer has long been used to help meet the increasing food demands in C... more Chemical nitrogen (N) fertilizer has long been used to help meet the increasing food demands in China, the top N fertilizer consumer in the world. Growing concerns have been raised on the impacts of N fertilizer uses on food security and climate change, which is lack of quantification. Here we use a carbon-nitrogen (C-N) coupled ecosystem model, to quantify the food benefit and climate consequence of agronomic N addition in China over the six decades from 1949 to 2008. Results show that N fertilizer-induced crop yield and soil C sequestration had reached their peaks, while nitrous oxide (N 2 O) emission continued rising as N was added. Since the early 2000s, stimulation of excessive N fertilizer uses to global climate warming through N 2 O emission was estimated to outweigh their climate benefit in increasing CO 2 uptake. The net warming effect of N fertilizer uses, mainly centered in the North China Plain and the middle and lower reaches of Yangtze River Basin, with N 2 O emission completely counteracting or even exceeding, by more than a factor of 2, the CO 2 sink. If we reduced the current N fertilizer level by 60% in 'over-fertilized' areas, N 2 O emission would substantially decrease without significantly influencing crop yield and soil C sequestration.
An extensive dataset on rice phenology in China, including 202 series broadly covering the past t... more An extensive dataset on rice phenology in China, including 202 series broadly covering the past three decades (1980s-2000s), was compiled. From these data, we estimated the responses of growth duration length to temperature using a regression model based on the data with and without detrending. Regression coefficients derived from the detrended data reflect only the temperature effect, whereas those derived from data without detrending represent a combined effect of temperature and confounding cultivar shifts. Results indicate that the regression coefficients calculated from the data with and without detrending show an average shortening of the growth duration of 4.1-4.4 days for each additional increase in temperature over the full growth cycle. Using the detrended data, 95.0% of the data series exhibited a negative correlation between the growth duration length and temperature; this correlation was significant in 61.9% of all of the data series. We then compared the difference between the two regression coefficients calculated from data with and without detrending and found a significantly greater temperature sensitivity using the data without detrending (-2.9 days °C(-1) ) than that derived from the detrended data (-2.0 days °C(-1) ) in the period of emergence to heading for the late rice, producing a negative difference in temperature sensitivity (-0.9 days °C(-1) ). This implies that short-duration cultivars were planted with increase in temperature and exacerbated the undesired phenological change. In contrast, positive differences were detected for the single (0.6 days °C(-1) ) and early rice (0.5 days °C(-1) ) over the full growth cycle, which might indicate that long-duration cultivars were favoured with climate warming, but these differences were insignificant. In summary, our results suggest that a major, temperature induced change in the rice growth duration is underway in China and that using a short-duration cultivar has been accelerating the process for late rice.
n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) ... more n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) n Mean (min.-max.) CV (%) Croplands 72 0.52 (0.18-1.58) 51 72 12.1 (5.5-19.3) 24 72 0.76 (0.37-2.16) 53 72 3.18 (1.06-10.72) 56 57 0.31 (0.07-0.57) 37 54 7.5 (5.0-8.7) 14 Grasslands 113 0.84 (0.05-2.75) 66 113 11.7 (À1.0 to 26.5) 52 113 0.79 (0.16-2.93) 63 78 5.30 (0.32-12.54) 56 62 0.48 (0.01-1.02) 48 85 6.8 (5.3-8.5) 11 Forests 465 0.99 (0.16-2.45) 45 465 12.8 (À4.8 to 27.6) 54 462 1.24 (0.28-4.82) 63 321 6.52 (0.60-22.06) 61 266 0.46 (0.04-1.46) 73 187 5.2 (3.5-8.6) 20 All 657 0.91 (0.05-2.75) 52 657 12.4 (À4.8 to 27.6) 53 654 1.10 (0.08-4.82) 67 474 5.83 (0.32-22.06) 65 388 0.43 (0.01-1.46) 68 329 6.0 (3.5-8.7)
Large areas in the Upper Tana river catchment, Kenya, have been over-exploited, resulting in soil... more Large areas in the Upper Tana river catchment, Kenya, have been over-exploited, resulting in soil erosion, nutrient depletion and loss of soil organic matter (SOM). This study focuses on sections of the catchment earmarked as being most promising for implementing Green Water Credits, an incentive mechanism to help farmers invest in land and soil management activities that affect all fresh water resources at source. Such management practices can also help restore SOM levels towards their natural level. Opportunities to increase soil organic carbon (SOC) stocks, for two broadly defined land use types (croplands and plantation crops, with moderate input levels), are calculated using a simple empirical model, using three scenarios for the proportion of suitable land that may be treated with these practices (low = 40 per cent, medium = 60 per cent, high = 80 per cent). For the medium scenario, corresponding to implementation on~348 000 ha in the basin, the eco-technologically possible SOC gains are estimated at 4Á8 to 9Á3 Â 10 6 tonnes (Mg) CO 2 over the next 20 years. Assuming a conservative price of US$10 per tonne CO 2 -equivalent on the carbon offset market, this would correspond to~US$48-93 million over a 20-year period of sustained green water management. This would imply a projected (potential) payment of some US$7-13 ha À1 to farmers annually; this sum would be in addition to incentives that are being put in place for implementing green water management practices and also in addition to the benefits that farmers would realize from the impact on production of these practices themselves.