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111.
Owing to the continuously increasing concentration of atmospheric CO2, it has become a priority to understand if soil organic matter (SOM) will behave as a sink or a source of CO2 under future environmental changes. Although many studies have addressed this question, a clear understanding is still missing, particularly with respect to long-term responses. In this study, we quantified soil C stores and dynamics in relationship to soil aggregation and pool composition in a Californian chaparral ecosystem exposed for 6 years to a gradient of atmospheric CO2 concentrations, ranging from pre-industrial levels 250 to 750 μl l−1 CO2. Fossil fuel-derived CO2 depleted in 13C was used for the fumigation, thus providing a tracer of C input from the vegetation to the soil.Long-term CO2 exposure invariably affected soil aggregation, with a significant decrease in the macroaggregate fraction at highest CO2 levels relative to the other two size fractions (i.e. microaggregates and silt and clay). This soil structural change most likely reduced the stability and protection of SOM, and C content generally decreased in most fractions over the CO2 treatments, and induced faster turnover of recently fixed C at high CO2 levels. The strongest response was found in the C content of the microaggregates, which decreased significantly (P<0.05) with rising levels of CO2. We conclude that increasing atmospheric CO2 concentrations will decrease soil C in chaparral ecosystems, and that the microaggregate fraction is the most responsive to increasing concentrations of atmospheric CO2. 相似文献
112.
西伯利亚落叶松树轮稳定碳同位素对气候的响应 总被引:2,自引:0,他引:2
利用采自阿尔泰山南坡东段正格采点的西伯利亚落叶松树轮样本,建立树轮宽度年表,对比宽度年表,按照树轮稳定碳同位素研究步骤,提取树轮稳定碳同位素序列(δ13C)和去趋势序列(DS)。分析表明:阿尔泰山南坡东部近160 a西伯利亚落叶松树轮δ13C变化于-22.8‰~-25.4‰,平均值为-24.0‰,变差系数-0.017。相关分析表明:正格采点树轮宽度序列对各气候要素相关不显著;树轮去趋势序列(DS)对前期气候因子的响应也不敏感;在生长季内(5~9月),树轮去趋势序列(DS)与富蕴气象站平均气温、平均最高气温和平均相对湿度有较好的相关性,树木生长季内的平均气温、平均最高气温与树轮去趋势序列(DS)显著正相关,6~7月平均最高气温与去趋势序列(DS)相关达到0.611(P<0.000 001);与生长季内平均相对湿度呈负相关关系,其中6~7月相对湿度与去趋势序列(DS)相关最高(r=-0.493, P<0.001),与7月降水量呈负相关关系(r=-0.459, P<0.01)。生长季内的平均最高气温和相对湿度对阿尔泰山西伯利亚落叶松树轮δ13C的响应最为敏感,阿尔泰山西伯利亚落叶松树木碳同位素分馏的主要控制因子为6~7月的平均最高气温,降水对树轮稳定碳同位素影响不大,相对湿度对树轮稳定碳同位素没有直接影响。 相似文献
113.
中国西北中小型盆地天然地下水水化学特征——以公婆泉盆地为例 总被引:2,自引:1,他引:2
研究分析干旱气候条件下甘肃北山公婆泉盆地天然地下水水化学成分特征,结合水文地质条件与水化学特征Piper三线图表明:研究区存在4种类型地下水,白垩系深层水中钙镁离子含量相对高于其他类型水.地下水氚同位素结合水化学特征较好地区分了水源点的水文地质属性.氢氧同位素表明,该区地下水来源于大气降水,第四系浅层水受到强烈的蒸发作用,发生了一定程度的氧漂移,并影响"混合水"的同位素组成.最后分析了地下水主要离子的来源,以及地下水形成过程中所受到的溶滤、沉积和蒸发等水文地球化学作用. 相似文献
114.
为开展碳、氮、氢、氧(C、H、O、N)稳定同位素鉴别库尔勒香梨产地的可行性研究,明确新疆库尔勒香梨δ13C、δ15N、δ2H、δ18O值,本研究以甘肃香梨和陕西红香酥梨作为对照,采用稳定同位素比值质谱仪(IRMS)分析新疆库尔勒香梨与对照样品的δ13C、δ15N、δ2H、δ18O值,并采用正交校正的偏最小二乘判别分析(OPLS-DA) 鉴别新疆库尔勒香梨产地真实性。结果表明,新疆、甘肃两个产区香梨与陕西产区红香酥梨的δ13C、δ15N、δ2H、δ18O值存在显著差异(P<0.05)。新疆产区的66份库尔勒香梨判别准确率为95.45%;甘肃产区的20份香梨样品判别准确率为60%;陕西产区的23份红香酥梨样品判别准确率为95.65%。C、N、H、O 4种稳定同位素可有效鉴别新疆库尔勒香梨和陕西红香酥梨,但在新疆库尔勒香梨与甘肃香梨鉴别方面,误判率较高,如果能结合其他鉴别技术,则有可能出现较好的鉴别效果。本研究为库尔勒香梨产地真实性鉴别提供了科学依据。 相似文献
115.
Relationship between stable carbon isotope discrimination and water use efficiency under regulated deficit irrigation of pear-jujube tree 总被引:2,自引:0,他引:2
Ningbo Cui Taisheng Du Shaozhong Kang Fusheng Li Xiaotao Hu Mixia Wang Zhijun Li 《Agricultural Water Management》2009,96(11):1615-1622
To investigate the relationship between stable carbon isotope discrimination (Δ) of different organs and water use efficiency (WUE) under different water deficit levels, severe, moderate and low water deficit levels were treated at bud burst to leafing, flowering to fruit set, fruit growth and fruit maturation stages of field grown pear-jujube tree, and leaf stable carbon isotope discrimination (ΔL) at different growth stages and fruit stable carbon isotope discrimination (ΔF) at fruit maturation stage were measured. The results indicated that water deficit had significant effect on ΔL at different growth stages and ΔF at fruit maturation stage. As compared with full irrigation, the average ΔL at different growth stages and ΔF at fruit maturation stage were decreased by 1.23% and 2.67% for different water deficit levels, respectively. ΔL and ΔF among different water deficit treatments had significant difference at the same growth stage (P < 0.05). Under different water deficit conditions, significant relationships between the ΔL and WUEi (photosynthesis rate/transpiration rate, Pn/Tr), WUEn (photosynthesis rate/stomatal conductance of CO2, Pn/gs), WUEy (yield/crop water consumption, Y/ETc) and yield, or between the ΔF and WUEy and yield were found, respectively. There were significantly negative correlations of ΔL with WUEi, WUEn, WUEy and yield (P < 0.01) at the fruit maturation stage, or ΔL with WUEi and WUEn (P < 0.01) over whole growth stage, respectively. ΔF was negatively correlated with WUEy, WUEn and yield (P < 0.05), but positively correlated with ETc (P < 0.01) over the whole growth stage. Thus ΔL or ΔF can compare WUEn and WUEy, so the stable carbon isotope discrimination method can be applied to evaluate the water use efficiency of pear-jujube tree under the regulated deficit irrigation. 相似文献
116.
Thanh Thuy Nguyen Tu Céline Egasse Gérard Bardoux Jean-François Ponge Sylvie Derenne 《Soil biology & biochemistry》2011,43(11):2222-2228
We monitored the carbon isotope composition of bulk leaves and specific long-chain alkanes during a four-year litterbag experiment using 13C-labelled leaves and unlabelled reference leaves of the European beech tree (Fagus sylvatica L.). Whereas the isotope composition of alkanes from 13C-enriched leaves exhibited a marked decrease in 13C-content, the isotope composition of unlabelled reference leaves remained nearly constant. We interpreted this difference as evidence for a microbial contribution to the long-chain alkane pool of the decomposing leaves and related it to the progressive invasion of leaves by soil organisms which was revealed upon microscopic examination. These results suggest that long-chain alkanes may not provide an unaltered record of organic carbon isotope composition in soils and sediments. 相似文献
117.
D. A. Ramírez J. L. Rolando W. Yactayo P. Monneveux R. Quiroz 《Journal of Agronomy and Crop Science》2015,201(6):410-418
Selection for drought tolerance entails prioritizing plant traits that integrate critical physiological processes occurring during crop growth. Discrimination against 13C (?) in leaflets (?leaflet) and tubers (?tuber) was compared under two water regimes in two potato‐improved varieties selected to maintain yield under drought conditions (Unica and Sarnav) and one drought susceptible European cultivar (Désirée). In the control treatment, soil water content was kept at field capacity over the whole growth cycle, while in the drought treatment water supply was restricted after tuber initiation (50 % of field capacity). Gas exchange and N content per unit leaf area (Narea) as well as ? were assessed at different stages. Sarnav showed the highest tuber yield in both water conditions, suggesting that yield in the water restriction treatment was largely driven by yield potential in this genotype. Higher stomatal conductance (gs) and Narea and lower ?leaflet in well‐watered Sarnav suggested higher photosynthetic capacity. Under water restriction, Sarnav maintained higher gs indicating that carbon diffusion was a key factor for biomass accumulation under water restriction. Our results suggest the use of ? determined after tuber initiation as an indirect selection indicator for tuber yield under both well‐watered and restricted soil water availability conditions. 相似文献
118.
Under Mediterranean conditions, drought affects cereals production principally through a limitation of grain filling. In this study, the respective role of post‐anthesis photosynthesis and carbon remobilization and the contribution of flag leaf, stem, chaff and awns to grain filling were evaluated under Mediterranean conditions in durum wheat (Triticum turgidum var. durum) cultivars. For the purpose, we examined the effects of shading and excision of different parts of the plant and compared carbon isotope discrimination (Δ) in dry matter of flag leaf, stem, chaff, awns and grain at maturity and in sap of stem, flag leaf, chaff and awns, this last measurement providing information on photosynthesis during a short period preceding sampling. Source–sink manipulations and isotopic imprints of different organs on final isotope composition of the grain confirmed the high contribution of both carbons assimilated by ears and remobilized from stems to grain filling, and the relatively low contribution of leaves to grain filling. Grain Δ was highly and significantly associated with grain yield across treatments, suggesting the utilization of this trait as an indicator of source–sink manipulations effects on grain yield. Chaff and awns Δ were better correlated with grain Δ than stem and leaf Δ, indicating that chaff were more involved in grain filling than other organs. Moreover, in chaff, sap Δ was highly significantly correlated with dry matter Δ. These results suggest the use of Δ for a rapid and non‐destructive estimation of the variation in the contribution of different organs to grain filling. 相似文献
119.
Distinctive diet‐tissue isotopic discrimination factors derived from the exclusive bamboo‐eating giant panda 下载免费PDF全文
Han HAN Wei WEI Yonggang NIE Wenliang ZHOU Yibo HU Qi WU Fuwen WEI 《Integrative zoology》2016,11(6):447-456
Stable isotope analysis is very useful in animal ecology, especially in diet reconstruction and trophic studies. Differences in isotope ratios between consumers and their diet, termed discrimination factors, are essential for studies of stable isotope ecology and are species‐specific and tissue‐specific. Given the specialized bamboo diet and clear foraging behavior, here, we calculated discrimination factors for carbon and nitrogen isotopes from diet to tissues (tooth enamel, hair keratin and bone collagen) for the giant panda (Ailuropoda melanoleuca), a species derived from meat‐eating ancestors. Our results showed that carbon discrimination factor obtained from giant panda tooth enamel (ε 13Cdiet‐enamel = 10.0‰) and nitrogen discrimination factors from hair keratin (Δ15Ndiet‐hair = 2.2‰) and bone collagen (Δ15Ndiet‐collagen = 2.3‰) were lower, and carbon discrimination factors from hair keratin (Δ13Cdiet‐hair = 5.0‰) and bone collagen (Δ13Cdiet‐collagen = 6.1‰) were higher than those of other mammalian carnivores, omnivores and herbivores. Such distinctive values are likely the result of a low‐nutrient and specialized bamboo diet, carnivore‐like digestive system and exceptionally low metabolism in giant pandas. 相似文献
120.