The third Chinese National Arctic Research Expedition （3rd CHINARE-Arctic in 2008） was carried out from July to September 2008. During the survey, numerous sea water samples were taken for CO2 parameter measurement ...The third Chinese National Arctic Research Expedition （3rd CHINARE-Arctic in 2008） was carried out from July to September 2008. During the survey, numerous sea water samples were taken for CO2 parameter measurement （including total alkalinity TA and total dissolved inorganic carbon DIC）.The distribution of COs parameters in the Western Arctic Ocean was determined, and the controlling factors are addressed. The ranges of summertime TA, normalized TA （nTA）, DIC and normalized DIC （nDIC） in the surface seawater were 1 757 2 229 umol.kg 1 2 383-2 722 umol.kg-1, 1 681 2 034 pmol.kg 1, 2 119--2 600 umol.kg-1, respectively. Because of dilution from ice meltwater, the surface TA and DIC concentrations were relatively low. TA in the upper 100 m to the south of 78°N had good correlation with salinity, showing a conservative behavior. The distribution followed the seawater-river mixing line at salinity 〉30, then followed the seawater mixing line （diluted by river water to salinity = 30） with the ice meltwater. The DIC distribution in the Chukchi Sea was dominated by biological production or respiration of organic matter, whereas conservative mixing dominated the mixed layer TA distribution in the ice-free Canada Basin.展开更多
Tropical waters show different regional aspects due to specificities in their nutrient biogeochemical cycles, which can affect the carbon system and influence their regional role as sinks or sources of CO<sub>2&...Tropical waters show different regional aspects due to specificities in their nutrient biogeochemical cycles, which can affect the carbon system and influence their regional role as sinks or sources of CO<sub>2</sub>. This study was performed on particular tropical areas that present a different seasonal behaviour related to the carbon cycle observed in the late rainy season (July 2013). Understanding the CO<sub>2</sub> drawdown and outgassing potential in these areas is needed to call attention to more long-term monitoring efforts and protect understudied tropical coastal systems more efficiently. This study is focused on nutrient values, hydrological data, biogeochemical carbon behaviour linked to the carbonate system and includes estimates of CO<sub>2</sub> fluxes in three contrasting areas off the northeastern Brazilian shelf: 1) an urbanised estuary (Recife-REC), 2) a coastal Island (Itamaracá-ITA) and 3) an oceanic archipelago (Fernando de Noronha-FN). In general, REC acted as a source, while ITA and FN as carbon sinks. In ITA, despite the high DIC and Total Alkalinity observed (mean ~2360 μmol·kg<sup>-1</sup>), the sink is associated with an effective cascading of atmospheric CO<sub>2</sub> associated with turbulent shallow waters coupled with biogenic removal of and precipitation of CaCO<sub>3</sub> by coralline algae. FN acted as a sink, linked to minor decreases in Total Alkalinity (mean~2295 μmol·kg<sup>-1</sup>) influenced by ammonium-based primary production, nitrogen fixation and sporadic entrainment of nutrient rich waters in the upper thermocline. More studies in different western tropical Atlantic coastal systems can improve the knowledge of tropical shelf seas and their contribution to the ocean carbon budget under specific regional trophic regimes.展开更多
Land-use changes, especially the conversion of native forest vegetation to cropland and plantations in tropical region, can alter soil C and N pools and N availability for plant uptake. Deforestation, followed by shif...Land-use changes, especially the conversion of native forest vegetation to cropland and plantations in tropical region, can alter soil C and N pools and N availability for plant uptake. Deforestation, followed by shifting cultivation and establishment of rubber tree plantation, is a common land-use change in Xishuangbanna, southwest China. However the influence of this kind of land-use change on soil C and N dynamics in this region remains poorly understood. This study was conducted to assess the effects of land-use change on soil C and N pools. Soil samples were collected on five adjacent plots, which belong to three land-use types including secondary forest-an acuminate banana(Musa itinerans) secondary forest and a male bamboo(Dendrocalamus membranaceae) secondary forest, shifting cultivation, and rubber tree (Hevea brasiliensis (H.B.K.) Muell. Arg.) plantation(one plot is 3-year-old, and another is 7-year-old). We measured soil bulk density (BD), pH value, moisture content and concentrations of soil organic carbon(SOC), total soil nitrogen(TSN), and inorganic N(NO - 3-N and NH + 4-N ) at 0—3, 3—20, 20—40 and 40—60 cm depths, and calculated C and N pools in 0—20, 20—40, 40—60, and 0—60 cm soil layers. Compared with the adjacent secondary forests, shifting cultivation and establishment of rubber tree plantations resulted in significant decline in concentrations and stocks of SOC and TSN in 0—20 and 0—60 cm soil layers, and increase in pH and bulk density at 0—3, 3—20, and 20—40 cm depths. Soil moisture content decreased only in 0—20 cm surface soils in shifting cultivation and plantations. The dynamics of mineral N was much more complex, which had different trends among depths and ecosystems. Compared with the secondary forests, SOC stocks in 0—20 cm surface soils in shifting cultivation and rubber tree plantations(3-year-old plantation and 7-year-old plantation) decreased by 34.0%, 33%, and 23%; and TSN stocks decreased by 32 2%, 20.4%, and 20.4%, respectively, whereas the decreases of SOC and TSN stocks in 0—60 cm soil layers were much less. The results indicated that C and N losses were mainly occurred in 0—20 cm surface soil, followed by 20—40 cm layer.展开更多
【目的】提高土壤碳固持,特别是增加有机碳累积、减少碳损失,对于提高旱地土壤肥力、缓解大气温室效应具有重要意义。黄土高原旱地土壤有机碳含量低,增施氮肥是这一地区重要的作物增产措施,但氮肥投入对土壤碳的影响如何,一直没有报道...【目的】提高土壤碳固持,特别是增加有机碳累积、减少碳损失,对于提高旱地土壤肥力、缓解大气温室效应具有重要意义。黄土高原旱地土壤有机碳含量低,增施氮肥是这一地区重要的作物增产措施,但氮肥投入对土壤碳的影响如何,一直没有报道。【方法】利用黄土高原旱地持续23年的长期定位试验,在每年施磷39 kg P2O5·hm-2条件下,设置0、45、90、135、180 kg N·hm-2 5个氮水平种植冬小麦,在小麦收获期采集0—40 cm不同土层的土壤样品,研究长期施用不同用量的氮肥对旱地土壤总碳、有机碳、轻质有机碳及无机碳的影响,分析不同氮肥用量引起的土壤有机碳、轻质有机碳及无机碳累积量的变化,定量分析氮肥用量对旱地土壤不同形态碳的影响。【结果】随氮肥用量增加,旱地土壤不同土层总碳无显著变化,但0—30 cm土层有机碳含量却随之增加,与不施氮肥相比,增幅可达7%—28%;0—40 cm土层轻质有机碳含量也增加,增幅达31%—106%,但施氮量过高不利于有机碳累积。对不同形态土壤碳累积量与氮肥用量的回归分析表明,施氮量120 kg N·hm-2时,0—30 cm土层有机碳累积量达最高值36.6 Mg;施氮量161 kg N·hm-2时,0—40 cm土层轻质有机碳累积量达最高值2.69 Mg;每千克肥料氮每年可使土壤有机碳增加1.34 kg·hm-2,轻质有机碳增加0.31 kg·hm-2;0—20 cm表层土壤轻质有机碳占有机碳的百分比也随施氮量增加而升高。相反,5—20 cm土层土壤无机碳含量却随氮肥用量增加而显著降低,施氮量180 kg N·hm-2时,无机碳累积量比不施氮减少2.8 Mg,每千克肥料氮每年可使无机碳减少0.67 kg·hm-2。【结论】在黄土高原旱地长期施用不同用量的氮肥虽不显著影响土壤的总碳数量,却显著地改变了旱地土壤碳的组成,即通过增加土壤的轻质有机碳,增加了土壤的有机碳累积量,同时降低了土壤的无机碳累积。因此,合理调控氮肥用量,不仅是旱地作物增产的关键措施,对增加土壤有机碳固持、培肥土壤也有重要意义。同时,施用氮肥引起的土壤无机碳损失不容忽视,其潜在的农业、生态与环境效应需引起大众关注。展开更多
基金funded from the National Natural Science Foundation of China (Grant no. 40976116)the Scientific Research Foundation of Third Institute of Oceanography,SOA (Grant nos. 2010011, 2010001)+1 种基金sponsored by the China Program for International Polar Year 2007–2008the Special Research Foundation for Public Welfare Marine Program(Grant no. 201105022–2)
文摘The third Chinese National Arctic Research Expedition （3rd CHINARE-Arctic in 2008） was carried out from July to September 2008. During the survey, numerous sea water samples were taken for CO2 parameter measurement （including total alkalinity TA and total dissolved inorganic carbon DIC）.The distribution of COs parameters in the Western Arctic Ocean was determined, and the controlling factors are addressed. The ranges of summertime TA, normalized TA （nTA）, DIC and normalized DIC （nDIC） in the surface seawater were 1 757 2 229 umol.kg 1 2 383-2 722 umol.kg-1, 1 681 2 034 pmol.kg 1, 2 119--2 600 umol.kg-1, respectively. Because of dilution from ice meltwater, the surface TA and DIC concentrations were relatively low. TA in the upper 100 m to the south of 78°N had good correlation with salinity, showing a conservative behavior. The distribution followed the seawater-river mixing line at salinity 〉30, then followed the seawater mixing line （diluted by river water to salinity = 30） with the ice meltwater. The DIC distribution in the Chukchi Sea was dominated by biological production or respiration of organic matter, whereas conservative mixing dominated the mixed layer TA distribution in the ice-free Canada Basin.
文摘Tropical waters show different regional aspects due to specificities in their nutrient biogeochemical cycles, which can affect the carbon system and influence their regional role as sinks or sources of CO<sub>2</sub>. This study was performed on particular tropical areas that present a different seasonal behaviour related to the carbon cycle observed in the late rainy season (July 2013). Understanding the CO<sub>2</sub> drawdown and outgassing potential in these areas is needed to call attention to more long-term monitoring efforts and protect understudied tropical coastal systems more efficiently. This study is focused on nutrient values, hydrological data, biogeochemical carbon behaviour linked to the carbonate system and includes estimates of CO<sub>2</sub> fluxes in three contrasting areas off the northeastern Brazilian shelf: 1) an urbanised estuary (Recife-REC), 2) a coastal Island (Itamaracá-ITA) and 3) an oceanic archipelago (Fernando de Noronha-FN). In general, REC acted as a source, while ITA and FN as carbon sinks. In ITA, despite the high DIC and Total Alkalinity observed (mean ~2360 μmol·kg<sup>-1</sup>), the sink is associated with an effective cascading of atmospheric CO<sub>2</sub> associated with turbulent shallow waters coupled with biogenic removal of and precipitation of CaCO<sub>3</sub> by coralline algae. FN acted as a sink, linked to minor decreases in Total Alkalinity (mean~2295 μmol·kg<sup>-1</sup>) influenced by ammonium-based primary production, nitrogen fixation and sporadic entrainment of nutrient rich waters in the upper thermocline. More studies in different western tropical Atlantic coastal systems can improve the knowledge of tropical shelf seas and their contribution to the ocean carbon budget under specific regional trophic regimes.
文摘Land-use changes, especially the conversion of native forest vegetation to cropland and plantations in tropical region, can alter soil C and N pools and N availability for plant uptake. Deforestation, followed by shifting cultivation and establishment of rubber tree plantation, is a common land-use change in Xishuangbanna, southwest China. However the influence of this kind of land-use change on soil C and N dynamics in this region remains poorly understood. This study was conducted to assess the effects of land-use change on soil C and N pools. Soil samples were collected on five adjacent plots, which belong to three land-use types including secondary forest-an acuminate banana(Musa itinerans) secondary forest and a male bamboo(Dendrocalamus membranaceae) secondary forest, shifting cultivation, and rubber tree (Hevea brasiliensis (H.B.K.) Muell. Arg.) plantation(one plot is 3-year-old, and another is 7-year-old). We measured soil bulk density (BD), pH value, moisture content and concentrations of soil organic carbon(SOC), total soil nitrogen(TSN), and inorganic N(NO - 3-N and NH + 4-N ) at 0—3, 3—20, 20—40 and 40—60 cm depths, and calculated C and N pools in 0—20, 20—40, 40—60, and 0—60 cm soil layers. Compared with the adjacent secondary forests, shifting cultivation and establishment of rubber tree plantations resulted in significant decline in concentrations and stocks of SOC and TSN in 0—20 and 0—60 cm soil layers, and increase in pH and bulk density at 0—3, 3—20, and 20—40 cm depths. Soil moisture content decreased only in 0—20 cm surface soils in shifting cultivation and plantations. The dynamics of mineral N was much more complex, which had different trends among depths and ecosystems. Compared with the secondary forests, SOC stocks in 0—20 cm surface soils in shifting cultivation and rubber tree plantations(3-year-old plantation and 7-year-old plantation) decreased by 34.0%, 33%, and 23%; and TSN stocks decreased by 32 2%, 20.4%, and 20.4%, respectively, whereas the decreases of SOC and TSN stocks in 0—60 cm soil layers were much less. The results indicated that C and N losses were mainly occurred in 0—20 cm surface soil, followed by 20—40 cm layer.
文摘【目的】提高土壤碳固持,特别是增加有机碳累积、减少碳损失,对于提高旱地土壤肥力、缓解大气温室效应具有重要意义。黄土高原旱地土壤有机碳含量低,增施氮肥是这一地区重要的作物增产措施,但氮肥投入对土壤碳的影响如何,一直没有报道。【方法】利用黄土高原旱地持续23年的长期定位试验,在每年施磷39 kg P2O5·hm-2条件下,设置0、45、90、135、180 kg N·hm-2 5个氮水平种植冬小麦,在小麦收获期采集0—40 cm不同土层的土壤样品,研究长期施用不同用量的氮肥对旱地土壤总碳、有机碳、轻质有机碳及无机碳的影响,分析不同氮肥用量引起的土壤有机碳、轻质有机碳及无机碳累积量的变化,定量分析氮肥用量对旱地土壤不同形态碳的影响。【结果】随氮肥用量增加,旱地土壤不同土层总碳无显著变化,但0—30 cm土层有机碳含量却随之增加,与不施氮肥相比,增幅可达7%—28%;0—40 cm土层轻质有机碳含量也增加,增幅达31%—106%,但施氮量过高不利于有机碳累积。对不同形态土壤碳累积量与氮肥用量的回归分析表明,施氮量120 kg N·hm-2时,0—30 cm土层有机碳累积量达最高值36.6 Mg;施氮量161 kg N·hm-2时,0—40 cm土层轻质有机碳累积量达最高值2.69 Mg;每千克肥料氮每年可使土壤有机碳增加1.34 kg·hm-2,轻质有机碳增加0.31 kg·hm-2;0—20 cm表层土壤轻质有机碳占有机碳的百分比也随施氮量增加而升高。相反,5—20 cm土层土壤无机碳含量却随氮肥用量增加而显著降低,施氮量180 kg N·hm-2时,无机碳累积量比不施氮减少2.8 Mg,每千克肥料氮每年可使无机碳减少0.67 kg·hm-2。【结论】在黄土高原旱地长期施用不同用量的氮肥虽不显著影响土壤的总碳数量,却显著地改变了旱地土壤碳的组成,即通过增加土壤的轻质有机碳,增加了土壤的有机碳累积量,同时降低了土壤的无机碳累积。因此,合理调控氮肥用量,不仅是旱地作物增产的关键措施,对增加土壤有机碳固持、培肥土壤也有重要意义。同时,施用氮肥引起的土壤无机碳损失不容忽视,其潜在的农业、生态与环境效应需引起大众关注。
