草地退化对三江源国家公园高寒草甸表层土壤有机碳、全氮、全磷的空间驱动
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中国科学院-青海省人民政府三江源国家公园联合研究专项(LHZX-2020-07);国家林业和草原局经济发展研究中心业务委托项目(JYFL-2021-00020);国家重点研发计划项目(2017YFA0604802);国家自然科学基金项目(41877547)


Spatial response of topsoil organic carbon, total nitrogen, and total phosphor content of alpine meadows to grassland degradation in the Sanjiangyuan National Park
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    摘要:

    草地退化显著削弱了三江源高寒草甸的土壤肥力及生态承载功能,但空间尺度上的驱动强度和环境调控尚不清晰。在2020年7-8月,基于三江源国家公园高寒草甸典型分布区原生植被和退化植被的60个配对采样,研究表层(0-30 cm)土壤有机碳(SOC)、全氮(TN)和全磷(TP)含量对草地退化的空间响应特征。三江源国家公园高寒草甸原生植被SOC和TN含量分别为(2.45±2.05)%(平均值±标准差,下同)和(0.25±0.20)%,配对样本t-检验的结果表明草地退化导致SOC和TN分别极显著(P<0.001)下降了44.0%和35.6%。TP对草地退化无显著响应(P=0.22)。原生植被的土壤C : N : P平均为59.6 : 6.2 : 1.0,草地退化导致化学计量值平均下降28.3%。一般线性模型的结果表明草地退化对SOC和TN及土壤生态化学计量特征的空间降低强度主要取决于纬度和海拔(P<0.01),与经度和土壤深度关系较弱(P>0.30),即低纬度高海拔的高寒草甸响应相对强烈。草地退化导致三江源国家公园高寒草甸土壤碳氮损失严重,降低了土壤生态化学计量。研究结果可为三江源退化高寒草甸土壤营养功能的治理和恢复提供理论支撑。

    Abstract:

    Alpine meadows constitute approximately 23% of the Qinghai-Tibetan Plateau surface and are vital to ecosystem services and human well-being. Under the context of unprecedented climate warming and heavy grazing practices, alpine grasslands have been undergoing serious and extensive degradation for the past decades. Grassland degradation substantially weakened soil nutrients status and ecological carrying capacity of alpine meadows, but their spatial driving magnitudes and environmental controls remain unclear in the Three Rivers Source. From July to August in 2020, based on 60 paired soil samples of native and degraded alpine meadows in the Sanjiangyuan National Park, the spatial response of topsoil (0-30 cm) organic carbon content (SOC), total nitrogen content (TN), and total phosphorus content (TP) to grassland degradation was quantified, as well as the underlying environmental controls. The contents of SOC and TN in native alpine meadows were (2.45±2.05)% (Mean±Standard deviation, the same below) and (0.25±0.20)%, respectively. The results of the paired-samples t-test showed that the content of SOC and TN in degraded alpine meadows were significantly (P<0.001) decreased by 44.0% and 35.6%, compared to native alpine meadows. The degradation induced-loss in topsoil density of SOC and TN was 2.23 kg/m2 and 0.16 kg/m2, respectively, given that marginally significant (P=0.06) difference between bulk density in native (0.93 g/cm3) and degraded alpine meadows (1.12 g/cm3). The content of TP exhibited no significant (P=0.22) response to grassland degradation, because soil phosphor comes mainly from rock weathering, which was strongly affected by soil parent materials. The C:N:P of native and degraded alpine meadows averaged 59.6:6.2:1.0 and 35.6:4.2:1.0, respectively. And it was remarkably reduced by 28.3% due to grassland degradation, which might alleviate the nutrient limitations on plant growth. The difference of soil nutrients and stoichiometry between native and degraded alpine meadows was used as an indicator for the spatial effects of grassland degradation. And the general linear model analysis revealed that the spatial magnitudes of grassland degradation on SOC, TN, and soil stoichiometry were significantly related to latitude and elevation (P<0.01), rather than longitude and soil depth. This finding suggested that the response to degradation could be much stronger in alpine meadows of lower latitude and higher elevation. Therefore, grassland degradation caused serious losses of topsoil carbon and nitrogen and decreased soil stoichiometry of alpine meadows in the Sanjiangyuan National Park. These results can provide a theoretical basis for the rehabilitation and management of the soil nutrient function of the degraded alpine meadows in the Sanjiangyuan National Park.

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张法伟,李红琴,仪律北,罗方林,张光茹,王春雨,杨永胜,李英年.草地退化对三江源国家公园高寒草甸表层土壤有机碳、全氮、全磷的空间驱动.生态学报,2022,42(14):5586~5592

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