酸雨对红壤区茶园根际中微量元素转化与茶叶自然品质的影响

As a global envrionmental issues, acid rain can increase soil acidification and affect the crop output and quality. Trace elements are the important indicators of tea quality, and their transformations in soil and uptake by plants can be influenced by acid environment. Rhizosphere is a key zone of plant and soil interaction, but how acid rain affects the transformation and absorption of trace elements in rhizosphere soil of tea plantation is unclear as well as their coupling mechanisms with tea quality. We will use a simulatating experiment by running 5 years with 4 treatments of pH 2.5, 3.5, 4.5 acid rain and control (water) to study the responses of rhizosphere trace element cycling and leaf quality in the tea plantation of 25 year-old. Rhizoshpere and bulk soils will be collected using hand shaking method to study the transformations of Al, Ca, Mg, Fe, Mn and Zn measured by sequencing extraction and ICP-AES and their rhizosphere effects, and rhizosphere microbical diversity using proysequencing methods. Roots from different functional module and their secretions will be collected using mining, pruning and negative pressure methods, respectively to measure the concentrations of trace elements using acid digestion and atomic absorption methods, metal chelation and micro positioning techniques. Additionally, tea chemical quality will be meausured by biochemical analysis. These results will reveal how different intensity acid rain affects the cycling of trace elements and leaf quality in tea plantation, and their coupling mechanisms. Our results can contribute to establish regulation and management theory of trace element cycling in tea plantation, and provide technological support to deal with acid rain stress in red soil region.

酸雨是全球性的环境问题，会加剧红壤酸化，影响作物产量与品质。中微量元素是茶叶重要品质指标，其土壤转化与植物吸收受酸化环境等调控。根际是植物-土壤互作的关键区域，酸雨对茶树根际中微量元素转化吸收的影响机制及与茶叶品质的耦合效应不清楚。以红壤区25年生茶园为对象，依托已连续5年开展pH 2.5、3.5、4.5酸雨和对照4种处理试验平台，采用抖落法采集不同层次根际和非根际土壤，挖掘法和负压法收集不同功能模块根系和根系分泌物，应用连续浸提-等离子体发射光谱、高通量测序、酸消煮-原子吸收、金属螯合、显微定位、生化分析等方法，研究铝钙镁铁锰锌形态转化及根际效应、根际微生物功能群多样性、根系及分泌物中微量元素含量、运输、分配、茶叶自然品质等，揭示不同强度酸雨胁迫根系-土壤-微生物中微量元素转化与茶叶品质的耦合机制。结果有助于建立茶园中微量元素循环与调控理论，为红壤区作物应对酸沉降提供技术支撑。

酸雨是全球性的环境问题，加剧红壤酸化，从而具有影响茶叶产量与品质的潜在性。Ca、Al、Fe、Mn、Cu、Zn、Se等中微量元素是茶叶重要品质指标，其土壤转化与植物吸收受酸化环境等调控，且茶叶中这些微量元素含量与其茶多酚、可溶性糖等指标密切相关。本项目依托红壤区25 年生茶园开展pH 2.5、3.5、4.5酸雨和对照4种处理的试验平台，定期采集根际和非根根际土壤、老枝、新枝、成熟叶、茶叶等样品，测定其主要元素的含量及茶叶自然品质。结果表明，试验处理第3年根际土壤可提取态Al先随pH降低到3.5时增加然而至2.5下降，而硝态N、矿质N和有效P一直随pH降低而下降；植株体全Al和全P含量分别随pH降低而上升和下降；茶叶可溶性糖和自由氨基酸均受酸雨强度的影响，且与Al/N、Al/P、N/P等呈显著相关（p<0.05）。试验处理第4年，土壤有效Mg和Ca含量分别表现为根际负效应和正效应，但两者的含量均随酸雨加重而下降；植株体Mg和Ca平均含量也均随酸雨加重而下降，而Al含量正好相反；小枝和根系Al/Mg 和Al/Ca随酸雨加重而升高，而N/Al下降，且酸雨影响茶叶N/Al，P/Ca和N/P；不同组织不同元素含量之间存在协同和拮抗现象。此外，发现茶树地上和地下组织Zn和Se及Ca、Al、Fe、Mn、Cu对N、P、Zn、Se添加的响应具分异性，培育高品质锌硒茶及营建生态高值茶园具有可行性。总之，酸雨的加重改变根际土壤和植物体Al和养分含量及其化学计量比，且高强度的酸雨将显著影响茶叶自然品质。酸雨加重将加强茶园茶树体Al循环而降低Mg和Ca在土壤和根系之间的交换。研究结果增进了我们对植物适应酸沉降的理解，建议采取有效措施，如施石灰等缓解土壤过度酸化，从而保障茶园健康可持续经营。