[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conduct...[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conducted using three alpine soils.These soils were collected from the top 10 cm depth in three grassland types：alpine meadow in Haibei,alpine steppe in Naqu and alpine wetland in Dangxiong.[Result] Temperature significantly affected nitrogen mineralization in alpine soils of three grassland types.The mineralization rate in alpine steppe soil rose with the rise of temperature,while the mineralization rate in the alpine meadow soil and alpine wetland soil decreased with the rise of temperature.Nitrogen input had no significant effect on nitrogen mineralization in the alpine meadow soil,but significantly increased nitrogen mineralization in the alpine steppe soil and the alpine wetland soil.Grassland types significantly affected nitrogen mineralization in alpine grasslands.[Conclusion] The effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau were significant.And those different effects depended on different types of grassland.展开更多
The net anthropogenic nitrogen input(NANI) is an important nutrient source that causes eutrophication in water bodies. Understanding the spatio-temporal variation of NANI is important for regional environment assessme...The net anthropogenic nitrogen input(NANI) is an important nutrient source that causes eutrophication in water bodies. Understanding the spatio-temporal variation of NANI is important for regional environment assessment and management.This paper calculated NANI in the upper Yangtze River basin(YRB), upstream of the Three Gorges Dam(TGD), from1990 to 2012, and analyzed its spatio-temporal characteristics. Over the past 23 years of the study, the average annual NANI increased from 3200 kg N km^(-2) to 4931 kg N km^(-2). The major components were fertilizer N application, atmospheric N deposition,and net food and feed N import. In the northwest high mountainous region with a sparse population, the main component was atmospheric N deposition. Fertilizer N application and net food and feed N import were concentrated in the Chengdu Plain because of the high population density and large areas of farmland. This research found that NANI increased with rapid urbanization and increasing population. The Pearson correlation results illustrated that the spatial distributions of NANI and its major components were affected by land cover/use, agricultural GDP and total population. Increasing NANI has been the major cause of the degrading stream water quality over the past 20 years and is becoming a major threat to the water quality of the TGD reservoir.展开更多
In this study the authors determined the nitrogen isotopes of nitrate and the carbon and nitrogen contents of water samples from the Hongfeng Lake and inflowing streams, and, on this basis, discriminated the extraneou...In this study the authors determined the nitrogen isotopes of nitrate and the carbon and nitrogen contents of water samples from the Hongfeng Lake and inflowing streams, and, on this basis, discriminated the extraneous nitrogen input and the interior nitrogen release (organic matter decomposition) in the lake. The results showed that the amount of extraneous nitrogen input into the Hongfeng Lake increases and the interior nitrogen release from the lake is intensified in winter and spring. Nitrogen mixing is relatively obvious at the catchments between the lake inlet and inflowing streams, while organic matter decomposition (nitrification) is most intense in the middle and lower reaches of the lake. In winter and spring the organic matter decomposition takes place mainly at the middle level of the water column in the middle and lower reaches of the lake, which has a bearing on the abundance of degraded organic matter at this water level. This part of degraded organic matter contains a considerable proportion of hydrogenous nitrogen in the lake.展开更多
In order to obtain the optimal input of water and nitrogen(W&N)suitable for the jujube trees in Northern Shaanxi,12 treatments had been set in the demonstration base of micro-irrigation jujube tree of Mizhi County...In order to obtain the optimal input of water and nitrogen(W&N)suitable for the jujube trees in Northern Shaanxi,12 treatments had been set in the demonstration base of micro-irrigation jujube tree of Mizhi County in 2014-2015 through field experiment of jujube trees under surge root irrigation(SRI),in which three soil moisture levels(high moisture level W1:60%-85%θ,middle moisture level W2:50%-75%θ,low moisture level W3:40%-65%θ)and four nitrogen input levels(high nitrogen F75:0.75 kg/plant,middle nitrogen F50:0.50 kg/plant,low nitrogen F25:0.25 kg/plant,no nitrogen F0:0.00 kg/plant)were set.Through analyzing the effects of different W&N inputs on the yield,net income(NI)and W&N utilization efficiency(WUE and NUE)of jujube trees and establishing a weighted grey correlation model,the optimization of W&N input for jujube trees could be achieved under SRI.Results showed that different W&N inputs had significant influences on yield,NI,WUE and NUE.Along with the increase of soil moisture content,the yield and NUE increased,while WUE decreased gradually,and the NI had the tendency to increase first and then decrease.Along with the increase of nitrogen input,the yield,NI and WUE had the tendency to increase first and then decrease while the NUE decreased significantly,and the yield,NI,WUE and NUE could not reach the maximum at the same time.Through the study on the grey correlation model of jujube tree’s comprehensive benefit based on the yield,NI,WUE and NUE,results showed the comprehensive benefit of jujube trees was significantly different when W&N input was different,and the gray correlation degree of W2F25 treatment was the highest in two years,which means that the soil moisture content of 50%-75%θand nitrogen input of 0.25 kg/plant was the optimal W&N input for jujube trees under SRI in Northern Shaanxi area.展开更多
In this study, different welding param eters were selected to investigate the effects of heat-in put on the microstructure and corrosion resistance of the friction stir welded high nitrogen stainless steel joints. The...In this study, different welding param eters were selected to investigate the effects of heat-in put on the microstructure and corrosion resistance of the friction stir welded high nitrogen stainless steel joints. The results show ed that, the welding speed had major influence on the duration at elevated tem perature rather than the peak tem perature. The hardness distribution and tensile properties of the nugget zones (NZs) for various joints were very similar while the pitting corrosion behavior of various NZs showed major differences. Large heat-input resulted in the ferrite bands being the pitting location, while tool wear bands were sensitive to pitting corrosion in the low heat-input joints. Cr diffusion and tool wear were the main reasons for pitting. The mechanisms of pitting corrosion in the NZs were analyzed in detail.展开更多
Cropland nitrate leaching is the major nitrogen(N) loss pathway, and it contributes significantly to water pollution. However, cropland nitrate leaching estimates show great uncertainty due to variations in input data...Cropland nitrate leaching is the major nitrogen(N) loss pathway, and it contributes significantly to water pollution. However, cropland nitrate leaching estimates show great uncertainty due to variations in input datasets and estimation methods. Here, we presented a re-evaluation of Chinese cropland nitrate leaching, and identified and quantified the sources of uncertainty by integrating three cropland area datasets, three N input datasets, and three estimation methods. The results revealed that nitrate leaching from Chinese cropland averaged 6.7±0.6 Tg N yr^(-1)in 2010, ranging from 2.9 to 15.8 Tg N yr^(-1)across 27 different estimates. The primary contributor to the uncertainty was the estimation method, accounting for 45.1%, followed by the interaction of N input dataset and estimation method at 24.4%. The results of this study emphasize the need for adopting a robust estimation method and improving the compatibility between the estimation method and N input dataset to effectively reduce uncertainty. This analysis provides valuable insights for accurately estimating cropland nitrate leaching and contributes to ongoing efforts that address water pollution concerns.展开更多
To analyze the effect of agricultural activity on nitrogen(N) budget at the watershed scale,a comparative study was conducted at two Japanese watersheds,the Shibetsu River watershed(SRW) and Upper-Naka River watershed...To analyze the effect of agricultural activity on nitrogen(N) budget at the watershed scale,a comparative study was conducted at two Japanese watersheds,the Shibetsu River watershed(SRW) and Upper-Naka River watershed(UNRW),and one Chinese watershed,the Jurong Reservoir watershed(JRW).The total area and the proportion of agricultural area(in parentheses) of the watersheds were 685(51%),1 299(21%),and 46 km 2(55%) for SRW,UNRW,and JRW,respectively.The main agricultural land use in SRW was forage grassland,while paddy fields occupied the highest proportion of cropland in UNRW(11% of total area) and JRW(31% of total area).The farmland surplus N was 61,48,and 205 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The total input and output for the whole watershed were 89 and 76,83 and 61,and 353 and 176 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The proportion of discharged N to net anthropogenic N input was 31%,37%,and 1.7% for SRW,UNRW,and JRW,respectively.The two watersheds in Japan showed similar proportions of discharged N to those of previous reports,while the watershed in China(JRW) showed a totally different characteristic compared to previous studies.The high N input in JRW did not increase the amount of discharged N at the outlet of the watershed due to high proportions of paddy fields and water bodies,which was an underestimated N sink at the landscape scale.展开更多
Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an intensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposit...Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an intensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposition was determined at three agricultural sites using a manual integrated total nitrogen input (ITNI) system during growth of winter wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) from September 2005 to May 2006. Total estimated N deposition averaged 54.9 and 43.2 kg N/hm2 across the three sites when wheat was grown to flowering and maturing, respectively. The average value was 50.2 kg N/hm2 when ryegrass was the indicator plant. Both indicator species gave similar total airborne N input results. The intermediate level of N supplied resulted in the highest N deposition, and the ratio of N acquired from deposition to total N content of the whole system decreased with increasing N supply to the roots. The contribution of atmospheric N to the total N content of the wheat and ryegrass sand culture systems ranged from 10% to 24%.展开更多
气候变化和人类活动的加剧引起高寒生态系统外源氮输入上升,导致其碳排放增加。本研究采用Meta分析方法,基于30篇青藏高原相关文献建立数据库,评价了高寒生态系统土壤呼吸对氮添加的响应。结果表明:氮添加对高寒生态系统土壤呼吸具有显...气候变化和人类活动的加剧引起高寒生态系统外源氮输入上升,导致其碳排放增加。本研究采用Meta分析方法,基于30篇青藏高原相关文献建立数据库,评价了高寒生态系统土壤呼吸对氮添加的响应。结果表明:氮添加对高寒生态系统土壤呼吸具有显著的正效应(P<0.05),氮添加量是控制土壤呼吸的决定因素;即≤200 kg N·hm^(-2)·a^(-1)显著促进土壤呼吸,>200 kg N·hm^(-2)·a^(-1)对土壤呼吸的促进作用显著降低;氮添加年限对土壤呼吸的正效应存在2年临界值(P<0.05),即>2年对土壤呼吸的正效应显著降低;氮添加对不同类型高寒生态系统土壤呼吸正效应差异显著(P<0.05),即亚高山森林>高寒草甸>高寒沼泽湿地。氮添加对年均温>2℃,或年均降水>800 mm,或海拔≤3000 m高寒生态系统土壤呼吸增强效应最显著。本研究对我国高寒脆弱区生态保护提供理论和实践数据。展开更多
长江三角洲地区是我国重要的粮食生产基地,定量该地区主要稻作类型水稻生产的资源投入和碳氮足迹可为水稻种植结构调整和绿色低碳生产提供数据支撑。利用2016-2020年统计数据,运用生命周期评价方法,研究了长江三角洲地区的苏、浙、皖3...长江三角洲地区是我国重要的粮食生产基地,定量该地区主要稻作类型水稻生产的资源投入和碳氮足迹可为水稻种植结构调整和绿色低碳生产提供数据支撑。利用2016-2020年统计数据,运用生命周期评价方法,研究了长江三角洲地区的苏、浙、皖3省主要稻作类型水稻生产的资源投入和碳氮足迹。结果表明,粳稻氮肥用量最高,为279 kg/hm^(2),碳、氮足迹最高,分别为1.11 kg CO_(2)-eq/kg和13.7 kg N/t,产量较高。早籼稻氮肥用量最低,产量最低,分别为199 kg/hm^(2)和6371 kg/hm^(2),碳、氮足迹处于中间水平。中籼稻产量最高,为8687 kg/hm^(2),碳、氮足迹最低,分别为0.82 kg CO_(2)-eq/kg和10.3 kg N/t,氮肥用量处于中间水平。晚籼稻氮肥用量、产量及碳、氮足迹均处于中间水平。不同地区中江苏水稻氮肥用量最高,为309 kg/hm^(2),产量最高,为9319 kg/hm^(2),碳、氮足迹分别为0.948 kg CO_(2)-eq/kg和13.5 kg N/t。浙江水稻氮肥用量为216 kg/hm^(2),产量7364 kg/hm^(2),碳、氮足迹分别为0.989 kg CO_(2)-eq/kg和11.9 kg N/t。安徽水稻氮肥用量为204 kg/hm^(2),产量为7414 kg/hm^(2),碳、氮足迹分别为0.946 kg CO_(2)-eq/kg和11.1 kg N/t。由此可知,粳稻投入产出较高,碳氮足迹最高,存在较大的减排空间。中籼稻的投入较低,产量最高,碳氮足迹最低,是可推广的稻作类型。江苏水稻产量最高,投入最高,氮足迹最高,浙江和安徽水稻投入产出差异较小,碳氮足迹差异较小。展开更多
基金Supported by Young Talents Project of Chinese Academy of Sciences (KZCX2-YW-QN302)the National Natural Science Found ofChina (41071209,30870424)~~
文摘[Objective] The study aimed to investigate the effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau.[Method]An incubation experiment in the laboratory was conducted using three alpine soils.These soils were collected from the top 10 cm depth in three grassland types：alpine meadow in Haibei,alpine steppe in Naqu and alpine wetland in Dangxiong.[Result] Temperature significantly affected nitrogen mineralization in alpine soils of three grassland types.The mineralization rate in alpine steppe soil rose with the rise of temperature,while the mineralization rate in the alpine meadow soil and alpine wetland soil decreased with the rise of temperature.Nitrogen input had no significant effect on nitrogen mineralization in the alpine meadow soil,but significantly increased nitrogen mineralization in the alpine steppe soil and the alpine wetland soil.Grassland types significantly affected nitrogen mineralization in alpine grasslands.[Conclusion] The effects of temperature and nitrogen input on nitrogen mineralization in alpine soils on the Tibetan Plateau were significant.And those different effects depended on different types of grassland.
基金supported by the Basic Research Fund Program of the State key Laboratory of Hydroscience and Engineering (Grant Nos. 2014-KY-04 & 2013-KY-03)
文摘The net anthropogenic nitrogen input(NANI) is an important nutrient source that causes eutrophication in water bodies. Understanding the spatio-temporal variation of NANI is important for regional environment assessment and management.This paper calculated NANI in the upper Yangtze River basin(YRB), upstream of the Three Gorges Dam(TGD), from1990 to 2012, and analyzed its spatio-temporal characteristics. Over the past 23 years of the study, the average annual NANI increased from 3200 kg N km^(-2) to 4931 kg N km^(-2). The major components were fertilizer N application, atmospheric N deposition,and net food and feed N import. In the northwest high mountainous region with a sparse population, the main component was atmospheric N deposition. Fertilizer N application and net food and feed N import were concentrated in the Chengdu Plain because of the high population density and large areas of farmland. This research found that NANI increased with rapid urbanization and increasing population. The Pearson correlation results illustrated that the spatial distributions of NANI and its major components were affected by land cover/use, agricultural GDP and total population. Increasing NANI has been the major cause of the degrading stream water quality over the past 20 years and is becoming a major threat to the water quality of the TGD reservoir.
基金The work was supported by the National Natural Science Foundation of China (Grant No. 40173012)the Key and Innovation Project Foundation of the Chinese Academy of Sciences (Grant No. KZCX2-105).
文摘In this study the authors determined the nitrogen isotopes of nitrate and the carbon and nitrogen contents of water samples from the Hongfeng Lake and inflowing streams, and, on this basis, discriminated the extraneous nitrogen input and the interior nitrogen release (organic matter decomposition) in the lake. The results showed that the amount of extraneous nitrogen input into the Hongfeng Lake increases and the interior nitrogen release from the lake is intensified in winter and spring. Nitrogen mixing is relatively obvious at the catchments between the lake inlet and inflowing streams, while organic matter decomposition (nitrification) is most intense in the middle and lower reaches of the lake. In winter and spring the organic matter decomposition takes place mainly at the middle level of the water column in the middle and lower reaches of the lake, which has a bearing on the abundance of degraded organic matter at this water level. This part of degraded organic matter contains a considerable proportion of hydrogenous nitrogen in the lake.
基金This study was financially supported by the National Key R&D Program(No.2016YFC0400204)by the National Natural Science Foundation of China(No.51279157).
文摘In order to obtain the optimal input of water and nitrogen(W&N)suitable for the jujube trees in Northern Shaanxi,12 treatments had been set in the demonstration base of micro-irrigation jujube tree of Mizhi County in 2014-2015 through field experiment of jujube trees under surge root irrigation(SRI),in which three soil moisture levels(high moisture level W1:60%-85%θ,middle moisture level W2:50%-75%θ,low moisture level W3:40%-65%θ)and four nitrogen input levels(high nitrogen F75:0.75 kg/plant,middle nitrogen F50:0.50 kg/plant,low nitrogen F25:0.25 kg/plant,no nitrogen F0:0.00 kg/plant)were set.Through analyzing the effects of different W&N inputs on the yield,net income(NI)and W&N utilization efficiency(WUE and NUE)of jujube trees and establishing a weighted grey correlation model,the optimization of W&N input for jujube trees could be achieved under SRI.Results showed that different W&N inputs had significant influences on yield,NI,WUE and NUE.Along with the increase of soil moisture content,the yield and NUE increased,while WUE decreased gradually,and the NI had the tendency to increase first and then decrease.Along with the increase of nitrogen input,the yield,NI and WUE had the tendency to increase first and then decrease while the NUE decreased significantly,and the yield,NI,WUE and NUE could not reach the maximum at the same time.Through the study on the grey correlation model of jujube tree’s comprehensive benefit based on the yield,NI,WUE and NUE,results showed the comprehensive benefit of jujube trees was significantly different when W&N input was different,and the gray correlation degree of W2F25 treatment was the highest in two years,which means that the soil moisture content of 50%-75%θand nitrogen input of 0.25 kg/plant was the optimal W&N input for jujube trees under SRI in Northern Shaanxi area.
基金supported financially by the National Natural Science Foundation of China (Nos. 51671190 and 51471171)
文摘In this study, different welding param eters were selected to investigate the effects of heat-in put on the microstructure and corrosion resistance of the friction stir welded high nitrogen stainless steel joints. The results show ed that, the welding speed had major influence on the duration at elevated tem perature rather than the peak tem perature. The hardness distribution and tensile properties of the nugget zones (NZs) for various joints were very similar while the pitting corrosion behavior of various NZs showed major differences. Large heat-input resulted in the ferrite bands being the pitting location, while tool wear bands were sensitive to pitting corrosion in the low heat-input joints. Cr diffusion and tool wear were the main reasons for pitting. The mechanisms of pitting corrosion in the NZs were analyzed in detail.
基金supported by the National Key Research and Development Program of China (2023YFD1902703)the National Natural Science Foundation of China (Key Program) (U23A20158)。
文摘Cropland nitrate leaching is the major nitrogen(N) loss pathway, and it contributes significantly to water pollution. However, cropland nitrate leaching estimates show great uncertainty due to variations in input datasets and estimation methods. Here, we presented a re-evaluation of Chinese cropland nitrate leaching, and identified and quantified the sources of uncertainty by integrating three cropland area datasets, three N input datasets, and three estimation methods. The results revealed that nitrate leaching from Chinese cropland averaged 6.7±0.6 Tg N yr^(-1)in 2010, ranging from 2.9 to 15.8 Tg N yr^(-1)across 27 different estimates. The primary contributor to the uncertainty was the estimation method, accounting for 45.1%, followed by the interaction of N input dataset and estimation method at 24.4%. The results of this study emphasize the need for adopting a robust estimation method and improving the compatibility between the estimation method and N input dataset to effectively reduce uncertainty. This analysis provides valuable insights for accurately estimating cropland nitrate leaching and contributes to ongoing efforts that address water pollution concerns.
基金Supported by the Strategic International Cooperative Program "Comparative Study of Nitrogen Cycling and Its Impact on Water Quality in Agricultural Watersheds in Japan and China" by the Japan Science and Technology Agency and the National Natural Science Foundation of China(No.41071196)
文摘To analyze the effect of agricultural activity on nitrogen(N) budget at the watershed scale,a comparative study was conducted at two Japanese watersheds,the Shibetsu River watershed(SRW) and Upper-Naka River watershed(UNRW),and one Chinese watershed,the Jurong Reservoir watershed(JRW).The total area and the proportion of agricultural area(in parentheses) of the watersheds were 685(51%),1 299(21%),and 46 km 2(55%) for SRW,UNRW,and JRW,respectively.The main agricultural land use in SRW was forage grassland,while paddy fields occupied the highest proportion of cropland in UNRW(11% of total area) and JRW(31% of total area).The farmland surplus N was 61,48,and 205 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The total input and output for the whole watershed were 89 and 76,83 and 61,and 353 and 176 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The proportion of discharged N to net anthropogenic N input was 31%,37%,and 1.7% for SRW,UNRW,and JRW,respectively.The two watersheds in Japan showed similar proportions of discharged N to those of previous reports,while the watershed in China(JRW) showed a totally different characteristic compared to previous studies.The high N input in JRW did not increase the amount of discharged N at the outlet of the watershed due to high proportions of paddy fields and water bodies,which was an underestimated N sink at the landscape scale.
基金the One-hundred Talents Program of CAS,the Special Fund for Agricultural Profession (200803030)the Sino-German project (DFG Training Group,GK1070)
文摘Atmospheric nitrogen (N) deposition has been poorly documented in northern China, an intensive agricultural and industrial region with large emissions of NHx and NOy. To quantify N deposition, total airborne N deposition was determined at three agricultural sites using a manual integrated total nitrogen input (ITNI) system during growth of winter wheat (Triticum aestivum L.) and Italian ryegrass (Lolium multiflorum Lam.) from September 2005 to May 2006. Total estimated N deposition averaged 54.9 and 43.2 kg N/hm2 across the three sites when wheat was grown to flowering and maturing, respectively. The average value was 50.2 kg N/hm2 when ryegrass was the indicator plant. Both indicator species gave similar total airborne N input results. The intermediate level of N supplied resulted in the highest N deposition, and the ratio of N acquired from deposition to total N content of the whole system decreased with increasing N supply to the roots. The contribution of atmospheric N to the total N content of the wheat and ryegrass sand culture systems ranged from 10% to 24%.
文摘气候变化和人类活动的加剧引起高寒生态系统外源氮输入上升,导致其碳排放增加。本研究采用Meta分析方法,基于30篇青藏高原相关文献建立数据库,评价了高寒生态系统土壤呼吸对氮添加的响应。结果表明:氮添加对高寒生态系统土壤呼吸具有显著的正效应(P<0.05),氮添加量是控制土壤呼吸的决定因素;即≤200 kg N·hm^(-2)·a^(-1)显著促进土壤呼吸,>200 kg N·hm^(-2)·a^(-1)对土壤呼吸的促进作用显著降低;氮添加年限对土壤呼吸的正效应存在2年临界值(P<0.05),即>2年对土壤呼吸的正效应显著降低;氮添加对不同类型高寒生态系统土壤呼吸正效应差异显著(P<0.05),即亚高山森林>高寒草甸>高寒沼泽湿地。氮添加对年均温>2℃,或年均降水>800 mm,或海拔≤3000 m高寒生态系统土壤呼吸增强效应最显著。本研究对我国高寒脆弱区生态保护提供理论和实践数据。
文摘长江三角洲地区是我国重要的粮食生产基地,定量该地区主要稻作类型水稻生产的资源投入和碳氮足迹可为水稻种植结构调整和绿色低碳生产提供数据支撑。利用2016-2020年统计数据,运用生命周期评价方法,研究了长江三角洲地区的苏、浙、皖3省主要稻作类型水稻生产的资源投入和碳氮足迹。结果表明,粳稻氮肥用量最高,为279 kg/hm^(2),碳、氮足迹最高,分别为1.11 kg CO_(2)-eq/kg和13.7 kg N/t,产量较高。早籼稻氮肥用量最低,产量最低,分别为199 kg/hm^(2)和6371 kg/hm^(2),碳、氮足迹处于中间水平。中籼稻产量最高,为8687 kg/hm^(2),碳、氮足迹最低,分别为0.82 kg CO_(2)-eq/kg和10.3 kg N/t,氮肥用量处于中间水平。晚籼稻氮肥用量、产量及碳、氮足迹均处于中间水平。不同地区中江苏水稻氮肥用量最高,为309 kg/hm^(2),产量最高,为9319 kg/hm^(2),碳、氮足迹分别为0.948 kg CO_(2)-eq/kg和13.5 kg N/t。浙江水稻氮肥用量为216 kg/hm^(2),产量7364 kg/hm^(2),碳、氮足迹分别为0.989 kg CO_(2)-eq/kg和11.9 kg N/t。安徽水稻氮肥用量为204 kg/hm^(2),产量为7414 kg/hm^(2),碳、氮足迹分别为0.946 kg CO_(2)-eq/kg和11.1 kg N/t。由此可知,粳稻投入产出较高,碳氮足迹最高,存在较大的减排空间。中籼稻的投入较低,产量最高,碳氮足迹最低,是可推广的稻作类型。江苏水稻产量最高,投入最高,氮足迹最高,浙江和安徽水稻投入产出差异较小,碳氮足迹差异较小。
文摘氮磷输入对咸盐湖泊中陆源有机质降解的影响目前仍不清晰。文章采用微宇宙培养和地质微生物学分析方法,探究无机氮和/或磷输入对不同盐度湖泊(即柴窝堡湖:2.15 g/L,巴里坤湖:74.56 g/L,幻彩湖:103.41 g/L)沉积物中陆源有机质(羊茅草)矿化的影响。结果表明,添加草源有机质实验组的CO_(2)产生速率(1.01~127.52μg C g^(-1)d^(-1))显著(P<0.05)高于不添加任何有机质和氮磷的对照组(0.58~5.05μg C g^(-1)d^(-1))。添加10倍氮和/或磷实验组的CO_(2)产生速率显著低于添加1倍氮和/或磷的实验组。实验样品中CO_(2)产生速率与Bacteroidia、Desulfobulbia及Desulfobacteria的相对丰度呈显著正相关,而与Alphaproteobacteria相对丰度及盐度呈显著负相关。综上,该研究结果为评估陆源有机质和氮磷输入增加对咸盐湖泊碳循环的影响提供了数据基础和理论支撑。
