水肥耦合对黄泛平原砂地毛白杨水氮吸收与利用的调控机制

Water and fertilizer coupling has been widely applied in the plantations cultivation around the world, but the understanding of the coupling effects of water and fertilizer on water and nitrogen uptake and utilization of poplar and its mechanism was still limited, and there are few related systemetic researches. To solve scientific questions about the long-term variation of water and nitrogen movement and distribution in poplar root-zone, and the variation of root-zone water and nitrogen uptake and utilization and its mechanism under different combinations of water and fertilizer application parameters, a research will be conducted in triplod Populus tomentosa plantations in Yellow River Flooding Plain, and different water and fertilizer coupling treatments will be set up. Meanwhile, tree growth, ecophysiological characteristics, root-zone water and nitrogen dynamics, and environmental factors will be monitored consecutively or regularly. Besides, research methods of numerical simulation, field experiment research and theoretical analysis will be applied in this project. Four research contents will be investigated in this project: 1) the dynamics and spatial distribution of water and nitrogen in the root-zone, 2) the coupling effects of water and fertilizer on the morphology and temporal and spatial distribution of fine roots, 3) the relationship between the spatial distribution of water and nitrogen in root-zone and the root water and nitrogen absorption characteristics, and 4) the response of plant water and nitrogen utilization to the coupling of water and fertilizer and its mechanism. The results of this project will reveal the regulation mechanism of water and fertilizer coupling on water and nitrogen movement, absorption and utilization in the system of ‘root zone-fine roots-tree’. Besides, they will also provide the science foundation for establishing high-efficient water and fertilizer coupling strategies in Populus tomentosa plantation.

水肥耦合在国内外虽已广泛应用于人工林培育，但关于其对杨树水氮吸收和利用的调控效应和机制目前尚了解不足，且相关研究几为空白。本项目拟针对不同水肥耦合方式下杨树根区水氮运移和分布的长期规律、水肥耦合参数变化时杨树根区水氮吸收和利用特征的变化规律与机制等科学问题，以栽植于黄泛平原砂地上的三倍体毛白杨人工林为研究对象，在设置不同水肥耦合处理，并对林木生长和生理生态特征、根区水氮动态以及环境因子进行连续监测的基础上，运用数值模拟、田间试验研究以及理论分析的方法，研究根区水氮动态及空间分布特征；水肥耦合对吸收根形态与时空分布的调控效应；根区水氮空间分布与根系水氮吸收特征的相关关系；林木水氮利用特征对水肥耦合的响应规律与机制。通过以上研究，不仅将揭示水肥耦合对毛白杨“根区—吸收根—林木”系统内水氮运移、吸收与利用的调控机制，还可为毛白杨人工林高效水肥耦合策略的制定提供科学依据。

水肥耦合在国内外虽已广泛应用于人工林培育，但关于其对杨树水氮吸收和利用的调控效应和机制目前尚了解不足，且相关研究几为空白。本项目针对不同水肥耦合方式下杨树根区水氮运移和分布的长期规律、水肥耦合参数变化时杨树根区水氮吸收和利用特征的变化规律与机制等科学问题，以栽植于黄泛平原砂地上的三倍体毛白杨人工林为研究对象，设置不同水肥耦合处理，并在对林木生长和生理生态特征、根区水氮动态以及环境因子进行连续监测的基础上，运用数值模拟、田间试验研究以及理论分析的方法，阐明了砂地条件下滴灌、沟灌与降雨协同影响杨树人工林根区水氮分布与促进林木生长的规律：灌溉主要影响湿润区浅土层土壤水氮的动态变化，降雨引起干燥区土壤含水率波动，二者协同改善林地水分条件，促进林木生长和林地生产力提高。滴灌和沟灌湿润体的差异是影响两种灌溉方式下土壤水分和氮素运移的关键因素。揭示了水肥耦合下毛白杨人工林细根“觅食”策略和林木水氮利用规律，细根“觅食”策略：形态可塑性＞生长可塑性，即林木主要通过改变不同土层细根分布及部分形态特征，而非改变细根生长，以适应水氮资源的变化。水肥耦合措施定向调控器官生物量分配及林木水氮利用规律：高肥缺水和充分灌溉分别显著提高林木地上部分和茎干生物量的分配比例，降低灌溉频率和减少施氮量能提高林木水氮利用效率。阐明了砂地条件下S86三倍体毛白杨人工林滴灌和沟灌“根区—吸收根—林木”水氮运移、吸收与利用的水肥调控机制：水是关键调控因子，水氮交互作用未发挥；高灌溉频率和强降雨有利于促进林木生长、改善水氮吸收利用，但易形成深层水氮渗漏；高灌溉或高施肥处理显著影响器官生物量分配，中、低灌溉频率水肥利用效率显著提高。