Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon （OC） and nitrogen （N） in response to the fertilization of grasslands are not well understood. Understan...Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon （OC） and nitrogen （N） in response to the fertilization of grasslands are not well understood. Understanding these changes is essential to the sustainable development of artificial grasslands. For understanding these changes, we collected soil samples at 0-20 and 20-40 cm depths from a semi-arid artificial alfalfa grassland after 27 years of applications of phosphorus （P） and nitrogen＋phosphorus＋manure （NPM） fertilizers on the Loess Pla- teau of China. The distribution of aggregate sizes and the concentrations and stocks of OC and N in total soils were determined. The results showed that NPM treatment significantly increased the proportions of 〉2.0 mm and 2.0-0.25 mm size fractions, the mean geometric diameter （MGD） and the mean weight diameter （MWD） in the 0-20 cm layer. Phosphorous fertilizer significantly increased the proportion of 〉2.0 mm size fractions, the MGD and the MWD in the 0-20 cm layer. Long-term application of fertilization （P and NPM） resulted in the accumulation of OC and N in soil aggregates. The largest changes in aggregate-associated OC and N in the 0-20 cm layer were found at the NPM treatment, whereas the largest changes in the 20-40 cm layer were found at the P treatment. The results suggest that long-term fertilization in the grassland leads to the accumulation of OC and N in the coarse size fractions and the redistribution of OC and N from fine size fractions to coarse size fractions.展开更多
Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studi...Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L.(alfalfa) grassland biomass carbon and soil organic carbon density(SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period(viz. 0–10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0–10 year. During 0–30 year, the SOCD from 0–100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.展开更多
近年来,我国人工草地建设进入了快速发展阶段,及时、准确地获取大区域范围内人工草地空间分布信息,有助于提升草业宏观管理的数字化水平。以内蒙古阿鲁科尔沁旗的苜蓿人工草地为例,基于Sentinel-2多时相遥感图像,结合苜蓿光谱反射率随...近年来,我国人工草地建设进入了快速发展阶段,及时、准确地获取大区域范围内人工草地空间分布信息,有助于提升草业宏观管理的数字化水平。以内蒙古阿鲁科尔沁旗的苜蓿人工草地为例,基于Sentinel-2多时相遥感图像,结合苜蓿光谱反射率随刈割期变化的规律,利用ENVI NET 5深度学习模型提取苜蓿人工草地空间分布信息,并与面向对象的随机森林模型提取结果进行了比较。结果表明:(1)深度学习方法提取的2020年和2021年苜蓿草地的用户者精度分别为100.00%和98.80%,制图精度分别为98.42%和100.00%,总体精度分别为99.17%和99.33%,Kappa系数分别为0.98和0.99。随机森林模型的用户者精度分别为98.90%和96.61%,制图精度分别为97.82%和94.48%,总体精度分别为98.28%和94.68%,Kappa系数分别为0.94和0.90。深度学习模型提取的苜蓿人工草地空间分布信息各项精度指标均优于随机森林模型。(2)深度学习方法提取结果中的噪声像元较少,简化了复杂的分类后处理流程。此外,深度学习模型无需逐年建模,普适性强。综上所述,深度学习模型可以精确、便利地提取研究区域苜蓿人工草地信息,具有在类似地区大面积推广应用的潜力。展开更多
基金funded by the Program for New Century Excellent Talents in University (NCET-13-0487)the Program from Northwest A&F University (2014YQ007)+4 种基金the National Basic Research Program of China (2009CB118604)the National Science and Technology Support for Major Projects of China (2011BAD31B01)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-JC408)Science and Technology Generalized Program for the Overall Development of Agriculture in Ningxia (NTKJ-2014-01)the Scientific Research Program from Education Department of Shaanxi Province (11JK0650).
文摘Changes in the distribution of soil aggregate sizes and concentrations of aggregate-associated organic carbon （OC） and nitrogen （N） in response to the fertilization of grasslands are not well understood. Understanding these changes is essential to the sustainable development of artificial grasslands. For understanding these changes, we collected soil samples at 0-20 and 20-40 cm depths from a semi-arid artificial alfalfa grassland after 27 years of applications of phosphorus （P） and nitrogen＋phosphorus＋manure （NPM） fertilizers on the Loess Pla- teau of China. The distribution of aggregate sizes and the concentrations and stocks of OC and N in total soils were determined. The results showed that NPM treatment significantly increased the proportions of 〉2.0 mm and 2.0-0.25 mm size fractions, the mean geometric diameter （MGD） and the mean weight diameter （MWD） in the 0-20 cm layer. Phosphorous fertilizer significantly increased the proportion of 〉2.0 mm size fractions, the MGD and the MWD in the 0-20 cm layer. Long-term application of fertilization （P and NPM） resulted in the accumulation of OC and N in soil aggregates. The largest changes in aggregate-associated OC and N in the 0-20 cm layer were found at the NPM treatment, whereas the largest changes in the 20-40 cm layer were found at the P treatment. The results suggest that long-term fertilization in the grassland leads to the accumulation of OC and N in the coarse size fractions and the redistribution of OC and N from fine size fractions to coarse size fractions.
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05000000)National Natural Science Foundation of China(No.41271518)Sci-technology Project of Shaanxi Province(No.2013kw19-01)
文摘Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L.(alfalfa) grassland biomass carbon and soil organic carbon density(SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period(viz. 0–10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0–10 year. During 0–30 year, the SOCD from 0–100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.
文摘近年来,我国人工草地建设进入了快速发展阶段,及时、准确地获取大区域范围内人工草地空间分布信息,有助于提升草业宏观管理的数字化水平。以内蒙古阿鲁科尔沁旗的苜蓿人工草地为例,基于Sentinel-2多时相遥感图像,结合苜蓿光谱反射率随刈割期变化的规律,利用ENVI NET 5深度学习模型提取苜蓿人工草地空间分布信息,并与面向对象的随机森林模型提取结果进行了比较。结果表明:(1)深度学习方法提取的2020年和2021年苜蓿草地的用户者精度分别为100.00%和98.80%,制图精度分别为98.42%和100.00%,总体精度分别为99.17%和99.33%,Kappa系数分别为0.98和0.99。随机森林模型的用户者精度分别为98.90%和96.61%,制图精度分别为97.82%和94.48%,总体精度分别为98.28%和94.68%,Kappa系数分别为0.94和0.90。深度学习模型提取的苜蓿人工草地空间分布信息各项精度指标均优于随机森林模型。(2)深度学习方法提取结果中的噪声像元较少,简化了复杂的分类后处理流程。此外,深度学习模型无需逐年建模,普适性强。综上所述,深度学习模型可以精确、便利地提取研究区域苜蓿人工草地信息,具有在类似地区大面积推广应用的潜力。
