Collaborative Research: Dynamic Roots as the Biophysical Link Between Deep Moisture and the Atmosphere

合作研究：动态根作为深层水分与大气之间的生物物理联系

基本信息

批准号：
1852707
负责人：
Ying Fan Reinfelder
金额：
$ 23.34万
依托单位：
Rutgers University New Brunswick
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-07-01 至 2025-06-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1852707&HistoricalAwards=false
关键词：
Collaborative Research Dynamic Roots Biophysical

项目摘要

Plants play an important role in moving water across the land surface between the atmosphere above and the soil below. Some plants can extend their roots substantially below the surface to take advantage of ground water, giving them a moisture reservoir that persists through dry seasons and droughts. When plants tap into this reservoir they transpire moisture through their leaves, providing a source of moisture to the atmosphere at a time when the air may be at its driest. The extent to which this transpired groundwater influences meteorological conditions such as precipitation, cloudiness, and atmospheric stability is not known, nor is its dependence on region, season, and other factors.The transpiration of groundwater involves a complex set of biological and physical processes which are difficult to observe and simulate. But the PIs have developed a scheme in which the bulk effect of these processes can be approximated using two observationally-motivated assumptions. First, the extent to which plants extend their roots to tap groundwater depends on their position relative to the local topography. In dry or seasonally dry climates plants on a hilltop are typically too high above the water table to effectively access groundwater, so we can assume that they rely exclusively on near-surface soil moisture. At the valley floor the water table can be so close to the surface that plant roots have to be shallow to avoid excessive salinity and waterlogging, so they also rely exclusively on near-surface moisture. Thus maximum groundwater uptake occurs at mid-hillslope locations, and groundwater usage depends on the Height Above Nearest Drainage (HAND). The PIs have developed a "giant hillslope" method to quantify this dependence in terms of a five-bin representation of small-scale HAND topography.Second, roots respond dynamically to the vertical profile of soil water. The PIs argue that root dynamics can be simply represented by assuming that roots actively extend to reach available groundwater, taking up water from whatever level offers the greatest moisture access for the least effort. This assumption is formalized using a scheme in which the transport of moisture through roots is analogous to the movement of electric current in a circuit: the roots act as "wires", through which a "current" of moisture flows from a specific soil layer to the plant leaves, driven by the "voltage" difference (i.e. water potential difference) between plant leaves and the soil layer tapped by the roots. The flow of moisture from a soil layer to the surface is then given by the ratio of the layer-to-leaves voltage drop to the resistance of the wire, in exact analogy to Ohm's law (electric current equals voltage divided by resistance).The PIs implement their root-groundwater scheme in the Noah land-surface model, which is coupled to the Weather Research and Forecasting (WRF) model to form a coupled land-atmosphere model. The model is then used to test the impact of groundwater transpiration on the continental-scale hydrological cycle. Among the scientific questions to be addressed is the extent to which groundwater transpiration promotes precipitation, both by making a substantial contribution to the moisture available for precipitation, and by reducing atmospheric stability.The research has societal value due to the importance of the hydrological cycle for water resources. The work is of particular value for building bridges between the research communities concerned with the separate but closely connected fields of land surface hydrology, continental-scale hydroclimate, and plant ecology. The implementation of the new scheme in the WRF model will make it available for operational use, as WRF is widely used for weather forecasting. The PIs also conduct educational and outreach activities in K-12 schools, and the project supports two graduate students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

植物在陆地表面上层大气和下层土壤之间输送水分方面发挥着重要作用。有些植物可以将根部延伸到地表以下，以利用地下水，为它们提供一个在旱季和干旱期间持续存在的水分储存库。当植物进入这个水库时，它们会通过叶子蒸发水分，在空气最干燥的时候为大气提供水分来源。地下水蒸腾作用对降水、云量和大气稳定性等气象条件的影响程度尚不清楚，其对地区、季节和其他因素的依赖性也不得而知。地下水蒸腾涉及一系列复杂的生物和物理过程，难以观察和模拟。但 PI 开发了一种方案，其中可以使用两个基于观察的假设来近似这些过程的总体效应。首先，植物根系向地下水延伸的程度取决于它们相对于当地地形的位置。在干燥或季节性干燥的气候下，山顶上的植物通常高于地下水位太高，无法有效获取地下水，因此我们可以假设它们完全依赖于近地表土壤水分。在谷底，地下水位可能非常接近地表，植物的根部必须很浅，以避免盐分过高和涝渍，因此它们也完全依赖于近地表的水分。因此，最大的地下水吸收发生在山坡中部位置，地下水的使用取决于最近排水系统之上的高度（HAND）。 PI 开发了一种“巨型山坡”方法，以小规模 HAND 地形的五箱表示来量化这种依赖性。其次，根系对土壤水的垂直剖面动态响应。 PI 认为，根部动态可以简单地表示为假设根部主动延伸以到达可用的地下水，从任何能以最少的努力提供最大水分获取的水平吸收水分。这一假设是使用一种方案形式化的，其中水分通过根部的传输类似于电路中电流的运动：根部充当“电线”，水分“电流”通过它从特定的土壤层流向植物叶子，由植物叶子和根部轻触的土壤层之间的“电压”差（即水势差）驱动。然后，水分从土壤层到表面的流量由层到叶子的电压降与导线电阻的比率给出，这与欧姆定律完全相似（电流等于电压除以电阻）。 PI 在 Noah 陆地表面模型中实施其根地下水方案，该方案与天气研究和预报 (WRF) 模型耦合形成陆地-大气耦合模型。然后该模型用于测试地下水蒸腾对大陆尺度水文循环的影响。要解决的科学问题之一是地下水蒸腾在多大程度上促进降水，既通过对降水可用的水分做出重大贡献，又通过降低大气稳定性。由于水文循环对降水的重要性，这项研究具有社会价值。水资源。这项工作对于在涉及陆地表面水文学、大陆尺度水文气候和植物生态学等独立但密切相关领域的研究界之间架起桥梁具有特别价值。由于 WRF 广泛用于天气预报，因此在 WRF 模型中实施新方案将使其可供业务使用。 PI 还在 K-12 学校开展教育和外展活动，该项目支持两名研究生。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，认为值得支持。

项目成果

期刊论文数量（3）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Coupled whole‐tree optimality and xylem hydraulics explain dynamic biomass partitioning

耦合整树最优性和木质部水力学解释了动态生物量分配

DOI：
10.1111/nph.17242
发表时间：
2021-03
期刊：
New Phytologist
影响因子：
9.4
作者：
Potkay, Aaron;Trugman, Anna T.;Wang, Yujie;Venturas, Martin D.;Anderegg, William R. L.;Mattos, Caio R. C.;Fan, Ying
通讯作者：
Fan, Ying

Spatiotemporal origin of soil water taken up by vegetation

植被吸收土壤水的时空来源