Data from: Temporal dynamics of snowmelt nutrient release from snow–plant residue mixtures: an experimental analysis and mathematical model development

Reducing eutrophication in surface water is a major environmental
challenge in many countries around the world. In cold Canadian prairie
agricultural regions, part of the eutrophication challenge arises during
spring snowmelt when a significant portion of the total annual nutrient
export occurs, and plant residues can act as a nutrient source instead of
a sink. Although the total mass of nutrients released from various crop
residues has been studied before, little research has been conducted to
capture fine-timescale temporal dynamics of nutrient leaching from plant
residues, and the processes have not been represented in water quality
models. In this study, we measured the dynamics of P and N release from a
cold-hardy perennial plant species, alfalfa (Medicago sativa L.), to
meltwater after freeze–thaw through a controlled snowmelt experiment.
Various winter conditions were simulated by exposing alfalfa residues to
different numbers of freeze–thaw cycles (FTCs) of uniform magnitude prior
to snowmelt. The monitored P and N dynamics showed that most nutrients
were released during the initial stages of snowmelt (first 5 h) and that
the magnitude of nutrient release was affected by the number of FTCs. A
threshold of five FTCs was identified for a greater nutrient release, with
plant residue contributing between 0.29 (NO3) and 9 (PO4) times more
nutrients than snow. The monitored temporal dynamics of nutrient release
were used to develop the first process-based predictive model controlled
by three potentially measurable parameters that can be integrated into
catchment water quality models to improve nutrient transport simulations
during snowmelt.

减少地表水富营养化（eutrophication）是全球许多国家面临的重大环境挑战。在加拿大寒冷的草原农业区，富营养化挑战的一部分源于春季融雪期——此时年总养分输出的很大一部分发生，且植物残体可作为养分源而非汇。尽管此前已对不同作物残体释放的养分总质量进行过研究，但针对植物残体养分淋溶的精细时间尺度动态变化的研究较少，且这些过程尚未在水质模型中得到体现。本研究通过控制性融雪实验，测定了耐寒多年生植物紫花苜蓿（Medicago sativa L.）残体在冻融后向融水释放磷（P）和氮（N）的动态变化。在融雪前，通过将紫花苜蓿残体置于不同次数的等强度冻融循环（freeze–thaw cycles, FTCs）中，模拟了多种冬季条件。监测到的磷和氮动态显示，大部分养分在融雪初期（前5小时）释放，且养分释放量受冻融循环次数影响。研究发现，5次冻融循环是养分大量释放的阈值，此时植物残体贡献的养分是雪的0.29倍（硝酸根，NO3）至9倍（磷酸根，PO4）。基于监测到的养分释放时间动态，开发了首个基于过程的预测模型，该模型由三个可潜在测量的参数控制，可整合到流域水质模型中，以改进融雪期养分迁移模拟。