青藏高原灌丛土壤碳氮含量及其相关功能基因分布特征
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第二次青藏高原综合科学考察项目(2019QZKK0306,2019QZKK0308);国家自然科学基金项目(42007077)


Distribution characteristics of carbon and nitrogen contents and related functional genes in shrub soils of the Tibetan Plateau
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    摘要:

    在微生物的代谢活动下,土壤中有机态碳氮化合物矿化分解释放矿质养分和二氧化碳,深刻影响着自然生态系统土壤碳、氮等元素的循环转化、土壤的养分供应和有机质的更新,并对地上植被的演替和分布有极为重要的意义。青藏高原灌丛面积分布广泛,地形和气候条件复杂,但目前对灌丛分布地区土壤碳氮含量、矿化作用强度及其影响因素等的认识较少。研究结合土壤理化分析和高通量定量PCR(quantitative microbial element cycling, QMEC)技术研究了青藏高原喜马拉雅山-冈底斯山地区不同类型灌丛土壤碳氮含量、碳氮矿化速率和相关功能基因的分布特征及其与植被、气候和土壤因子间的耦联关系。结果表明,不同类型灌丛土壤的有机碳、全氮含量、CO2释放速率、净氮矿化速率、碳氮矿化基因的丰度有显著差异。其中,位于青藏高原东南部的雪层杜鹃和香柏灌丛分布区土壤有机碳和全氮含量、CO2释放速率、净氮矿化速率显著高于位于中西部的变色锦鸡儿、金露梅和砂生槐灌丛地区,并与年平均降雨量显著正相关。然而,碳、氮矿化基因丰度分布趋势与之相反,在雪层杜鹃和香柏灌丛分布区丰度显著低于中西部的三类灌丛,且与年平均降雨量呈显著负相关,但与土壤pH呈显著正相关。同时pH与年平均降水量、湿润指数和土壤含水率均为显著负相关。这些结果表明降水可通过增加盐基离子淋溶,使土壤盐基饱和度下降、氢饱和度增加,引起土壤酸化,进而影响碳氮循环过程,导致不同类型灌丛土壤碳氮元素的赋存及其周转速率差异。同时,碳、氮矿化相关功能基因丰度各类群间呈现显著的正相关关系,表明土壤碳氮循环过程间紧密的耦联关系。这些结果为准确评估青藏高原土壤碳、氮库及其动态平衡提供了重要信息和参考依据。

    Abstract:

    Under the effect of microbial metabolic activities, the mineralization and decomposition of organic carbon and nitrogen compounds in the soil release mineral nutrients and carbon dioxide, which profoundly affects the circulation and transformation of soil C, N, and other elements in the natural ecosystem, the supply of soil nutrients and the renewal of organic matter, and is of great significance to the succession and distribution of aboveground vegetation. Combined with soil physicochemical analysis and High throughput quantitative PCR(quantitative microbial element cycling, QMEC) technology, this study investigated the content of soil organic C and total N, soil respiration rate, net N mineralization rate and the abundance of C and N mineralization genes, and further explored their correlation with vegetation, climate, and soil factors in alpine shrub soils across the Himalayan-Gangdise regions on the Tibetan Plateau. The results showed that there were significant differences in the content and mineralization rate of C and N elements, and the abundance of C and N mineralization genes in the soils of different shrub types. Among them, soil respiration rate, net N mineralization rate, soil organic C and total N content in the Rhododendron nivale and Juniperus pingii var. wilsonii shrub areas were significantly higher than those in the Caragana versicolor, Dasiphora fruticose, and Sophora moorcroftian shrub areas, but the abundance of C and N mineralization genes was on the reverse. Soil respiration rate, net N mineralization rate, soil organic C and total N content were positively correlated with the mean annual precipitation. However, the abundance of C and N mineralization genes was negatively correlated with the mean annual precipitation, but positively correlated with the soil pH. Meanwhile, pH was negatively correlated with the mean annual precipitation, humidity index, and soil water content. All these results indicated that precipitation could reduce soil base saturation and increase soil hydrogen saturation by increasing the leaching of base ion, causing soil acidification and affecting the process of C and N cycle, thus affecting the turnover of C and N elements and determining the storage of C and N elements in the soils of different shrub types. Further, a significantly positive correlation was observed between the abundance of C and N mineralization genes, suggesting the close coupling relationship between soil C and N cycling processes. These results provide important information and reference basis for the accurate assessment of soil C and N pools and their dynamic balance of storage on the Tibetan Plateau.

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李传虹,张林,刘四义,韩丽丽,姚保民,申聪聪,郝志鹏,张丽梅.青藏高原灌丛土壤碳氮含量及其相关功能基因分布特征.生态学报,2024,44(1):392~404

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