Downloads & Free Reading Options - Results

The Mediterranean region of central Chile is experiencing extensive “mega-droughts” with detrimental effects for the environment and economy of the region. In the northern hemisphere, nitrogen (N) limitation of Mediterranean ecosystems has been explained by the decoupling between N inputs and plant uptake during the dormant season. In central Chile, soils have often been considered N-rich in comparison to other Mediterranean ecosystems of the world, yet the impacts of expected intensification of seasonal drought remain unknown. In this work, we seek to disentangle patterns of microbial N transformations and their seasonal coupling with climate in the Chilean sclerophyll forest-type. We aim to assess how water limitation affects microbial N transformations, thus addressing the impact of ongoing regional climate trends on soil N status. We studied four stands of the sclerophyll forest-type in Chile. Field measurements in surface soils showed a 67% decline of free-living diazotrophic activity (DA) and 59% decrease of net N mineralization rates during the summer rainless and dormant season, accompanied by a stimulation of in-situ denitrification rates to values 70% higher than in wetter winter. Higher rates of both free-living DA and net N mineralization found during spring, provided evidence for strong coupling of these two processes during the growing season. Overall, the experimental addition of water in the field to litter samples almost doubled DA but had no effect on denitrification rates. We conclude that coupling of microbial mediated soil N transformations during the wetter growing season explains the N enrichment of sclerophyll forest soils. Expected increases in the length and intensity of the dry period, according to climate change models, reflected in the current mega-droughts may drastically reduce biological N fixation and net N mineralization, increasing at the same time denitrification rates, thereby potentially reducing long-term soil N capital.

Cover title

Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils 作者： LANG Man 1,2 LI Ping 1,2 WEI Wei 1,2 作者单位： 1. Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China 2. Department of Agricultural Resources and Environment, Nanjing University of Information Science & Technology, Nanjing 210044, China 通讯作者： LI Ping Email:[email protected] 提交时间： 2021-06-04 摘要: The soil type is a key factor influencing N (nitrogen) cycling in soil; however, gross N transformations and N2O emission sources are still poorly understood. In this study, a laboratory 15N tracing experiment was carried out at 60% WHC (water holding capacity) and 25ºC to evaluate the gross N transformation rates and N2O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province, China. The results showed that the gross rates of N mineralization, immobilization, and nitrification were 3.60, 1.90, and 5.63 mg N/(kg•d) in silt loam soil, respectively, which were 3.62, 4.26, and 3.13 times those in sandy loam soil, respectively. The ratios of the gross nitrification rate to the ammonium immobilization rate (n/ia) in sandy loam soil and silt loam soil were all higher than 1.00, whereas the n/ia in sandy loam soil (4.36) was significantly higher than that in silt loam soil (3.08). This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil, and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO3– leaching. Under aerobic conditions, both nitrification and denitrification made contributions to N2O emissions. Nitrification was the dominant pathway leading to N2O production in soils and was responsible for 82.0% of the total emitted N2O in sandy loam soil, which was significantly higher than that in silt loam soil (71.7%). However, the average contribution of denitrification to total N2O production in sandy loam soil was 17.9%, which was significantly lower than that in silt loam soil (28.3%). These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions. gross N transformation rates 15N tracing N2O emission sources sandy loam silt loam semi-arid region 期刊： Journal of Arid Land 分类： 地球科学 >> 地理学 引用： ChinaXiv:202106.00012 (或此版本 ChinaXiv:202106.00012V1 ) DOI:10.1007/s40333-021-0098-x CSTR:32003.36.ChinaXiv.202106.00012.V1 推荐引用方式： LANG Man,LI Ping,WEI Wei.(2021).Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils.Journal of Arid Land.doi:10.1007/s40333-021-0098-x 版本历史 [V1] 2021-06-04 18:51:53 ChinaXiv:202106.00012V1 下载全文

Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils 作者： LANG Man 1,2 LI Ping 1,2 WEI Wei 1,2 作者单位： 1. Jiangsu Key Laboratory of Agricultural Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China 2. Department of Agricultural Resources and Environment, Nanjing University of Information Science & Technology, Nanjing 210044, China 通讯作者： LI Ping Email:[email protected] 提交时间： 2021-06-04 摘要: The soil type is a key factor influencing N (nitrogen) cycling in soil; however, gross N transformations and N2O emission sources are still poorly understood. In this study, a laboratory 15N tracing experiment was carried out at 60% WHC (water holding capacity) and 25ºC to evaluate the gross N transformation rates and N2O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province, China. The results showed that the gross rates of N mineralization, immobilization, and nitrification were 3.60, 1.90, and 5.63 mg N/(kg•d) in silt loam soil, respectively, which were 3.62, 4.26, and 3.13 times those in sandy loam soil, respectively. The ratios of the gross nitrification rate to the ammonium immobilization rate (n/ia) in sandy loam soil and silt loam soil were all higher than 1.00, whereas the n/ia in sandy loam soil (4.36) was significantly higher than that in silt loam soil (3.08). This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil, and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO3– leaching. Under aerobic conditions, both nitrification and denitrification made contributions to N2O emissions. Nitrification was the dominant pathway leading to N2O production in soils and was responsible for 82.0% of the total emitted N2O in sandy loam soil, which was significantly higher than that in silt loam soil (71.7%). However, the average contribution of denitrification to total N2O production in sandy loam soil was 17.9%, which was significantly lower than that in silt loam soil (28.3%). These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions. gross N transformation rates 15N tracing N2O emission sources sandy loam silt loam semi-arid region 期刊： Journal of Arid Land 分类： 地球科学 >> 地理学 引用： ChinaXiv:202106.00012 (或此版本 ChinaXiv:202106.00012V1 ) DOI:10.1007/s40333-021-0098-x CSTR:32003.36.ChinaXiv.202106.00012.V1 推荐引用方式： LANG Man,LI Ping,WEI Wei.(2021).Gross nitrogen transformations and N2O emission sources in sandy loam and silt loam soils.Journal of Arid Land.doi:10.1007/s40333-021-0098-x 版本历史 [V1] 2021-06-04 18:51:53 ChinaXiv:202106.00012V1 下载全文