Using a dark enclosed chamber technique, the fluxes of CO2, N2O and CH4 from nature and disturbed grassland were measured on the spot in Inner Mongolian Temperate Grassland along the annual rainfall gradient section r...Using a dark enclosed chamber technique, the fluxes of CO2, N2O and CH4 from nature and disturbed grassland were measured on the spot in Inner Mongolian Temperate Grassland along the annual rainfall gradient section ranging from 450 to 200 mm. The results showed that the measured mean fluxes of CO2, N2O and CH4were (1 180.4 ±308.7), (0.010 ± 0.004) and (-0.039 ± 0.016) mg · m-2/h, respectively. The decrease of the fluxes of CO2, N2O and CH4 follows with that of annual rainfall gradient in the measurement area. Human activities, such as grazing and reclamation are also critical factors to affect the fluxes of these gases from grassland. Daily continuous measurement of CO2, N2O and CH4 fluxes showed a strong diurnal variation with higher emission in the daytime. A good relationship between the fluxes of CO2, N2O, CH4 and temperature was exposed in this study.展开更多
Above-and belowground biomass allocation not only influences growth of individual plants,but also influences vegetation structures and functions,and consequently impacts soil carbon input as well as terrestrial ecosys...Above-and belowground biomass allocation not only influences growth of individual plants,but also influences vegetation structures and functions,and consequently impacts soil carbon input as well as terrestrial ecosystem carbon cycling.However,due to sampling difficulties,a considerable amount of uncertainty remains about the root:shoot ratio(R/S),a key parameter for models of terrestrial ecosystem carbon cycling.We investigated biomass allocation patterns across a broad spatial scale.We collected data on individual plant biomass and systematically sampled along a transect across the temperate grasslands in Inner Mongolia as well as in the alpine grasslands on the Tibetan Plateau.Our results indicated that the median of R/S for herbaceous species was 0.78 in China's grasslands as a whole.R/S was significantly higher in temperate grasslands than in alpine grasslands(0.84 vs.0.65).The slope of the allometric relationship between above-and belowground biomass was steeper for temperate grasslands than for alpine.Our results did not support the hypothesis that aboveground biomass scales isometrically with belowground biomass.The R/S in China's grasslands was not significantly correlated with mean annual temperature(MAT) or mean annual precipitation(MAP).Moreover,comparisons of our results with previous findings indicated a large difference between R/S data from individual plants and communities.This might be mainly caused by the underestimation of R/S at the individual level as a result of an inevitable loss of fine roots and the overestimation of R/S in community-level surveys due to grazing and difficulties in identifying dead roots.Our findings suggest that root biomass in grasslands tended to have been overestimated in previous reports of R/S.展开更多
受人类活动和气候变化的影响,大气氮(N)沉降日益加剧,使得草地生态系统正从自然N限制转向富营养化甚至饱和,进而影响了草地的生长。然而,关于优势种植物在N添加下的光合生理潜在机制的研究仍然不足。该研究以内蒙古温带典型草原优势种...受人类活动和气候变化的影响,大气氮(N)沉降日益加剧,使得草地生态系统正从自然N限制转向富营养化甚至饱和,进而影响了草地的生长。然而,关于优势种植物在N添加下的光合生理潜在机制的研究仍然不足。该研究以内蒙古温带典型草原优势种植物为研究对象,通过不同水平的N养分添加实验,探讨优势种羊草(Leymus chinensis)对N添加的光合生理响应机制。结果表明:地上生物量随着N添加先增加后降低,以10 g N·m^(–2)·a^(-1)处理增加最多。尽管25 g N·m^(–2)·a^(-1)处理出现下降趋势,但与对照相比仍然显著增加了地上生物量。低N时,植物通过把较少的N分配给羧化系统,并降低比叶质量(LMA)使叶片获得更多的光能来适应低N生境。适量的N添加通过增加总叶绿素(Chl)的含量,降低Chl a/b的比值来捕获更多光能;同时增加LMA、羧化效率、最大羧化速率(Vcmax)、最大电子传递速率(Jmax),并降低Jmax/Vcmax,把更多的N分配给羧化系统,提高羧化能力;通过增加实际光化学效率、电子传递效率和光化学猝灭系数,提高了光系统II(PSII)的光化学活性。过量的N添加对羊草的生理指标有一定抑制作用,羧化能力降低,导致净光合速率有所降低,在一定程度上抑制PSII的光化学活性,而非光化学猝灭系数以及类胡萝卜素增加起到了耗散过剩激发能的作用。N添加对羊草光合特性的影响总体表现为"适量促进,过量抑制"。该地区羊草最适的N添加范围是5–10 g N·m^(–2)·a^(-1)。展开更多
氮素矿化是决定土壤供氮能力的重要生态过程,也是目前国内外土壤氮循环研究的重点。养分添加在调节土壤的氮转化方面起着重要的作用。该文以内蒙古锡林河流域温带典型草原为研究对象,通过不同水平的氮(N)和磷(P)养分添加实验,利用树脂...氮素矿化是决定土壤供氮能力的重要生态过程,也是目前国内外土壤氮循环研究的重点。养分添加在调节土壤的氮转化方面起着重要的作用。该文以内蒙古锡林河流域温带典型草原为研究对象,通过不同水平的氮(N)和磷(P)养分添加实验,利用树脂芯原位培养法分析研究不同水平施氮、施磷对生长季草地土壤氮矿化的影响。结果表明:高氮处理对草地土壤硝态氮(NO3--N)、铵态氮(NH4+-N)及无机氮都有明显的影响,其中25 g N·m-2·a-1和10 g N·m-2·a-1高氮处理显著提高了无机氮含量,25 g N·m-2·a-1高氮处理显著增加土壤的NO3--N及NH4+-N含量。与施氮相比,施磷处理对土壤NO3--N、NH4+-N及无机氮的影响较为有限,只有12.5 g P2O5·m–2·a–1的磷处理显著促进了NO3--N及无机氮含量。高氮处理对草地土壤氮素转化有明显影响,其中25 g N·m-2·a-1高氮处理对净硝化速率、氨化速率及矿化速率都有显著的促进作用,说明高梯度的施氮处理有利于提高土壤的供氮能力。氮是内蒙古锡林河流域草原生态系统有机氮矿化的限制因子。与施氮相比,施磷处理对草地土壤氮转化的作用较为有限,仅有12.5 g P2O5·m–2·a–1+2 g N·m-2·a-1处理显著促进生长季中期的净氨化速率。说明施磷对土壤氮转化的影响弱于施氮的影响。养分添加显著提高了草地的地上生物量。养分添加情景下,土壤湿度与净矿化速率极显著相关,表明湿度是影响该区域温带草原土壤氮矿化的主效因素。环境因子(如有机碳含量、土壤全氮及土壤C/N)与不同氮处理下的净矿化速率之间显著相关,而土壤微生物碳、氮含量与土壤氮矿化均没有显著相关性。展开更多
基于6年模拟氮沉降试验平台研究了氮沉降对温带草原凋落物质量的影响。采集对照(0 g N·m^(-2)·a^(-1))、低氮(5 g N·m^(-2)·a^(-1))、中氮(10 g N·m-2·a-1)和高氮(15g N·m^(-2)·a^(-1))4个氮...基于6年模拟氮沉降试验平台研究了氮沉降对温带草原凋落物质量的影响。采集对照(0 g N·m^(-2)·a^(-1))、低氮(5 g N·m^(-2)·a^(-1))、中氮(10 g N·m-2·a-1)和高氮(15g N·m^(-2)·a^(-1))4个氮添加梯度,混合和单一两种凋落物类型,测定了凋落物纤维素、半纤维素、木质素、全碳、全氮和全磷含量。结果表明:长期模拟氮沉降降低了2种凋落物中纤维素、半纤维素、木质素含量及其与N素的比值;氮沉降对凋落物C含量无明显影响,降低了凋落物N、P含量以及C/N和C/P比值。由于氮沉降增加了凋落物N、P元素含量,同时降低了难分解的结构性物质含量,因此可能会对凋落物分解产生促进作用。展开更多
基于374个高寒草原和温带草原土壤样品的测试结果,运用多元逐步回归分析模型定量评估了土壤环境因子对土壤有机碳(SOC)含量的影响。结果表明:高寒草原土壤有机碳含量(20.18 kg C/m2)高于温带草原(9.23 kg C/m2)。土壤理化生物学因子对...基于374个高寒草原和温带草原土壤样品的测试结果,运用多元逐步回归分析模型定量评估了土壤环境因子对土壤有机碳(SOC)含量的影响。结果表明:高寒草原土壤有机碳含量(20.18 kg C/m2)高于温带草原(9.23 kg C/m2)。土壤理化生物学因子对高寒草原和温带草原SOC含量(10 cm)变化的贡献分别是87.84%和75.00%。其中,土壤总氮含量和根系对高寒草原SOC含量变化的贡献均大于对温带草原SOC含量变化的相应贡献。土壤水分是温带草原SOC含量变化的主要限制性因素,其对SOC含量变化的贡献达33.27%。高寒草原土壤C/N比显著高于温带草原土壤的相应值,揭示了青藏高原高寒草原较高的SOC含量是由于较低的土壤微生物活性所导致。展开更多
Numerous studies have focused on vegetation traits and soil properties in grassland, few of which concerned about effects of human utilization patterns on grassland yet. Thus, this study hypothesized that human distur...Numerous studies have focused on vegetation traits and soil properties in grassland, few of which concerned about effects of human utilization patterns on grassland yet. Thus, this study hypothesized that human disturbance(e.g., grazing, mowing and fencing) triggered significant variation of biomass partitioning and carbon reallocation. Besides, there existed some differences of species diversity and soil fertility. To address these hypotheses of grassland with diverse utilization patterns in Hulun Buir City, Inner Mongolia, China, we sampled in situ about aboveground biomass(AGB) and belowground biomass(BGB) to evaluate their biomass allocation. Species diversity and soil properties were also investigated. Subsequently, we discussed the relationship of species diversity with environmental conditions, using data collected from 23 sites during the ecological project period of Returning Grazing Lands to Grasslands(RGLG) program. The results were as follows: 1) both AGB and BGB were lower on grazing regime than those on fencing and mowing, but the ratio of root-to-shoot(R/S) was higher on grazing regime than the other two utilization patterns; 2) neither of evenness and Simpson Index was different significantly among all grassland utilization patterns in desert, typical, and meadow grassland at 0.05. In meadow grassland, species richness of fencing pattern was significantly higher than that of grazing pattern(p < 0.05); 3) both of soil organic carbon content and soil available phosphorous content were increased significantly on fencing pattern than grazing pattern(p < 0.05) in desert grassland, and mowing patterns increased the soil nutrients(soil organic carbon, soil total phosphorous, soil available phosphorous, and soil total nitrogen) significantly compared with grazing patterns(p < 0.05) in typical grassland. However, there were no significant differences among utilization patterns in meadow grassland. In conclusion, both of AGB and BGB were increased significantly by fencing. Moreover, species diversity and so展开更多
为了解大气氮沉降和降水格局改变对草原生物量的影响,在内蒙古温带典型草原开展氮、水添加控制试验.试验设置对照(CK),氮素添加(10 g m^(-2) a^(-1)),水分添加(60 mm m^(-2) a^(-1)),氮、水同时添加(N 10 g m^(-2) a^(-1)+水60 mm m^(-2...为了解大气氮沉降和降水格局改变对草原生物量的影响,在内蒙古温带典型草原开展氮、水添加控制试验.试验设置对照(CK),氮素添加(10 g m^(-2) a^(-1)),水分添加(60 mm m^(-2) a^(-1)),氮、水同时添加(N 10 g m^(-2) a^(-1)+水60 mm m^(-2) a^(-1))4种处理.经过两年试验处理,结果显示:(1)较对照处理,氮添加处理下总生物量(403.03 g/m^2)、地上生物量(279.97 g/m^2)、地下生物量(123.07 g/m^2)和禾类草地上生物量(165.35 g/m^2)均显著增加,而杂类草地上生物量变化不显著.(2)水添加较对照显著增加了地上生物量(200.93 g/m^2)、杂类草地上生物量(177.82 g/m^2),但显著降低了地下生物量(-110.39 g/m^2),而总生物量与禾类草地上生物量变化不显著.(3)氮添加处理下,水添加显著增加了地下生物量与禾类草地上生物量,但对总生物量、地上生物量、杂类草地上生物量没有显著影响.进一步分析显示,在不添加水分条件下,氮添加较对照显著增加禾类草地上生物量(107.15 g/m^2)与地下生物量(5.43 g/m^2);而在水分添加条件下,氮添加较对照分别增加58.2 g/m^2和117.64 g/m^2.本研究结果表明,禾类草地上生物量与其氮含量呈正相关关系,杂类草地上生物量与土壤含水量呈正相关关系,这可能是氮素添加提高禾类草地上生物量和水分添加提高杂类草地上生物量的重要机制之一;在内蒙古干旱半干旱地区仅氮素添加(10 g m^(-2) a^(-1))的措施可显著增加禾类草的地上生物量,有利饲草产量的增加,如需增加菊科、豆科等其他杂草的生物量,可考虑水分的补给.展开更多
文摘Using a dark enclosed chamber technique, the fluxes of CO2, N2O and CH4 from nature and disturbed grassland were measured on the spot in Inner Mongolian Temperate Grassland along the annual rainfall gradient section ranging from 450 to 200 mm. The results showed that the measured mean fluxes of CO2, N2O and CH4were (1 180.4 ±308.7), (0.010 ± 0.004) and (-0.039 ± 0.016) mg · m-2/h, respectively. The decrease of the fluxes of CO2, N2O and CH4 follows with that of annual rainfall gradient in the measurement area. Human activities, such as grazing and reclamation are also critical factors to affect the fluxes of these gases from grassland. Daily continuous measurement of CO2, N2O and CH4 fluxes showed a strong diurnal variation with higher emission in the daytime. A good relationship between the fluxes of CO2, N2O, CH4 and temperature was exposed in this study.
基金supported by the National Natural Science Foundation of China (Grant No. 30870381)the Key Project of Scientific and Technical Supporting Programs Funded by the Ministry of Science & Technology of China (Grant No. 2007BAC06B01)
文摘Above-and belowground biomass allocation not only influences growth of individual plants,but also influences vegetation structures and functions,and consequently impacts soil carbon input as well as terrestrial ecosystem carbon cycling.However,due to sampling difficulties,a considerable amount of uncertainty remains about the root:shoot ratio(R/S),a key parameter for models of terrestrial ecosystem carbon cycling.We investigated biomass allocation patterns across a broad spatial scale.We collected data on individual plant biomass and systematically sampled along a transect across the temperate grasslands in Inner Mongolia as well as in the alpine grasslands on the Tibetan Plateau.Our results indicated that the median of R/S for herbaceous species was 0.78 in China's grasslands as a whole.R/S was significantly higher in temperate grasslands than in alpine grasslands(0.84 vs.0.65).The slope of the allometric relationship between above-and belowground biomass was steeper for temperate grasslands than for alpine.Our results did not support the hypothesis that aboveground biomass scales isometrically with belowground biomass.The R/S in China's grasslands was not significantly correlated with mean annual temperature(MAT) or mean annual precipitation(MAP).Moreover,comparisons of our results with previous findings indicated a large difference between R/S data from individual plants and communities.This might be mainly caused by the underestimation of R/S at the individual level as a result of an inevitable loss of fine roots and the overestimation of R/S in community-level surveys due to grazing and difficulties in identifying dead roots.Our findings suggest that root biomass in grasslands tended to have been overestimated in previous reports of R/S.
文摘受人类活动和气候变化的影响,大气氮(N)沉降日益加剧,使得草地生态系统正从自然N限制转向富营养化甚至饱和,进而影响了草地的生长。然而,关于优势种植物在N添加下的光合生理潜在机制的研究仍然不足。该研究以内蒙古温带典型草原优势种植物为研究对象,通过不同水平的N养分添加实验,探讨优势种羊草(Leymus chinensis)对N添加的光合生理响应机制。结果表明:地上生物量随着N添加先增加后降低,以10 g N·m^(–2)·a^(-1)处理增加最多。尽管25 g N·m^(–2)·a^(-1)处理出现下降趋势,但与对照相比仍然显著增加了地上生物量。低N时,植物通过把较少的N分配给羧化系统,并降低比叶质量(LMA)使叶片获得更多的光能来适应低N生境。适量的N添加通过增加总叶绿素(Chl)的含量,降低Chl a/b的比值来捕获更多光能;同时增加LMA、羧化效率、最大羧化速率(Vcmax)、最大电子传递速率(Jmax),并降低Jmax/Vcmax,把更多的N分配给羧化系统,提高羧化能力;通过增加实际光化学效率、电子传递效率和光化学猝灭系数,提高了光系统II(PSII)的光化学活性。过量的N添加对羊草的生理指标有一定抑制作用,羧化能力降低,导致净光合速率有所降低,在一定程度上抑制PSII的光化学活性,而非光化学猝灭系数以及类胡萝卜素增加起到了耗散过剩激发能的作用。N添加对羊草光合特性的影响总体表现为"适量促进,过量抑制"。该地区羊草最适的N添加范围是5–10 g N·m^(–2)·a^(-1)。
文摘氮素矿化是决定土壤供氮能力的重要生态过程,也是目前国内外土壤氮循环研究的重点。养分添加在调节土壤的氮转化方面起着重要的作用。该文以内蒙古锡林河流域温带典型草原为研究对象,通过不同水平的氮(N)和磷(P)养分添加实验,利用树脂芯原位培养法分析研究不同水平施氮、施磷对生长季草地土壤氮矿化的影响。结果表明:高氮处理对草地土壤硝态氮(NO3--N)、铵态氮(NH4+-N)及无机氮都有明显的影响,其中25 g N·m-2·a-1和10 g N·m-2·a-1高氮处理显著提高了无机氮含量,25 g N·m-2·a-1高氮处理显著增加土壤的NO3--N及NH4+-N含量。与施氮相比,施磷处理对土壤NO3--N、NH4+-N及无机氮的影响较为有限,只有12.5 g P2O5·m–2·a–1的磷处理显著促进了NO3--N及无机氮含量。高氮处理对草地土壤氮素转化有明显影响,其中25 g N·m-2·a-1高氮处理对净硝化速率、氨化速率及矿化速率都有显著的促进作用,说明高梯度的施氮处理有利于提高土壤的供氮能力。氮是内蒙古锡林河流域草原生态系统有机氮矿化的限制因子。与施氮相比,施磷处理对草地土壤氮转化的作用较为有限,仅有12.5 g P2O5·m–2·a–1+2 g N·m-2·a-1处理显著促进生长季中期的净氨化速率。说明施磷对土壤氮转化的影响弱于施氮的影响。养分添加显著提高了草地的地上生物量。养分添加情景下,土壤湿度与净矿化速率极显著相关,表明湿度是影响该区域温带草原土壤氮矿化的主效因素。环境因子(如有机碳含量、土壤全氮及土壤C/N)与不同氮处理下的净矿化速率之间显著相关,而土壤微生物碳、氮含量与土壤氮矿化均没有显著相关性。
文摘基于6年模拟氮沉降试验平台研究了氮沉降对温带草原凋落物质量的影响。采集对照(0 g N·m^(-2)·a^(-1))、低氮(5 g N·m^(-2)·a^(-1))、中氮(10 g N·m-2·a-1)和高氮(15g N·m^(-2)·a^(-1))4个氮添加梯度,混合和单一两种凋落物类型,测定了凋落物纤维素、半纤维素、木质素、全碳、全氮和全磷含量。结果表明:长期模拟氮沉降降低了2种凋落物中纤维素、半纤维素、木质素含量及其与N素的比值;氮沉降对凋落物C含量无明显影响,降低了凋落物N、P含量以及C/N和C/P比值。由于氮沉降增加了凋落物N、P元素含量,同时降低了难分解的结构性物质含量,因此可能会对凋落物分解产生促进作用。
文摘基于374个高寒草原和温带草原土壤样品的测试结果,运用多元逐步回归分析模型定量评估了土壤环境因子对土壤有机碳(SOC)含量的影响。结果表明:高寒草原土壤有机碳含量(20.18 kg C/m2)高于温带草原(9.23 kg C/m2)。土壤理化生物学因子对高寒草原和温带草原SOC含量(10 cm)变化的贡献分别是87.84%和75.00%。其中,土壤总氮含量和根系对高寒草原SOC含量变化的贡献均大于对温带草原SOC含量变化的相应贡献。土壤水分是温带草原SOC含量变化的主要限制性因素,其对SOC含量变化的贡献达33.27%。高寒草原土壤C/N比显著高于温带草原土壤的相应值,揭示了青藏高原高寒草原较高的SOC含量是由于较低的土壤微生物活性所导致。
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05060100)National Natural Science Foundation of China(No.41105117)
文摘Numerous studies have focused on vegetation traits and soil properties in grassland, few of which concerned about effects of human utilization patterns on grassland yet. Thus, this study hypothesized that human disturbance(e.g., grazing, mowing and fencing) triggered significant variation of biomass partitioning and carbon reallocation. Besides, there existed some differences of species diversity and soil fertility. To address these hypotheses of grassland with diverse utilization patterns in Hulun Buir City, Inner Mongolia, China, we sampled in situ about aboveground biomass(AGB) and belowground biomass(BGB) to evaluate their biomass allocation. Species diversity and soil properties were also investigated. Subsequently, we discussed the relationship of species diversity with environmental conditions, using data collected from 23 sites during the ecological project period of Returning Grazing Lands to Grasslands(RGLG) program. The results were as follows: 1) both AGB and BGB were lower on grazing regime than those on fencing and mowing, but the ratio of root-to-shoot(R/S) was higher on grazing regime than the other two utilization patterns; 2) neither of evenness and Simpson Index was different significantly among all grassland utilization patterns in desert, typical, and meadow grassland at 0.05. In meadow grassland, species richness of fencing pattern was significantly higher than that of grazing pattern(p < 0.05); 3) both of soil organic carbon content and soil available phosphorous content were increased significantly on fencing pattern than grazing pattern(p < 0.05) in desert grassland, and mowing patterns increased the soil nutrients(soil organic carbon, soil total phosphorous, soil available phosphorous, and soil total nitrogen) significantly compared with grazing patterns(p < 0.05) in typical grassland. However, there were no significant differences among utilization patterns in meadow grassland. In conclusion, both of AGB and BGB were increased significantly by fencing. Moreover, species diversity and so
