Nitrogen fertilization has a small but detectable effect on the spectral properties of needles in Norway spruce

IF 3.7 2区农林科学 Q1 FORESTRY

Forest Ecology and Management Pub Date : 2025-09-16 DOI:10.1016/j.foreco.2025.123170

Jussi Juola , Miina Rautiainen , Heli Peltola , Samuli Launiainen , Aarne Hovi

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引用次数: 0

Abstract

Optical remote sensing has been proposed as a tool to guide precise application of fertilizers; however, the effects of nitrogen (N) fertilization on the spectral properties of coniferous needles from mature forests are not known. In this extensive pilot study, we present how N fertilization affects the spectral properties, nutrient content, and morphological properties of Norway spruce needles collected from a controlled fertilization experiment in Finland. We found small mean differences (<3 % across the 400–2500 nm range) in reflectance, transmittance, and albedo spectra between the needles collected from fertilized and unfertilized plots. In addition, the results suggest a saturation in the spectral changes beyond moderate (<200 kg N ha⁻¹) levels of N fertilization. The needle spectra enabled predicting morphological properties using partial least squares regression. Specific leaf area and water content showed moderate-to-good generalization (R² values of 0.7 and 0.8, respectively) with low-to-very-low relative RMSEP-% values (6.2 % and 2.2 %, respectively) and narrow confidence intervals (4.8–7.4 % and 1.5–2.8 %, respectively). Nitrogen fertilization had a statistically significant effect on spectra only in current-year needles. We found that an absorption feature centered between 1112–1272 nm showed the best accuracy (83.3 %) in differentiating current-year needles collected from fertilized and unfertilized plots. Our results highlight that N fertilization has a small yet detectable effect on the spectral properties of needles in Norway spruce trees which could be used to develop remote sensing applications for assessing N fertilization in forests.

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氮肥对挪威云杉针叶的光谱特性有微小但可检测的影响

光学遥感已被提出作为指导肥料精确施用的工具；然而，氮肥对成熟森林针叶光谱特性的影响尚不清楚。在这项广泛的试点研究中，我们介绍了氮肥如何影响芬兰对照施肥试验中收集的挪威云杉针叶的光谱特性、养分含量和形态特性。我们发现，在400-2500 nm范围内，从施肥地块和未施肥地块收集的针叶在反射率、透射率和反照率光谱上存在很小的平均差异（<3 %）。此外，结果表明，超过中等（<200 kg N ha−1）施氮水平后，光谱变化趋于饱和。针状光谱利用偏最小二乘回归预测形态特性。比叶面积和含水量具有中等到较好的通用性（R²值分别为0.7和0.8），相对RMSEP-%值从低到极低（分别为6.2 %和2.2 %），置信区间较窄（分别为4.8-7.4 %和1.5-2.8 %）。氮肥仅对当年针叶的光谱有统计学显著影响。结果表明，以1112 ~ 1272 nm为中心的吸收特征在区分施肥和未施肥地块的当年针上具有最高的准确度（83.3 %）。研究结果表明，氮肥对挪威云杉针叶光谱特性的影响虽小，但可检测到，可用于开发森林氮肥遥感评估应用。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Forest Ecology and Management 农林科学-林学

CiteScore

7.50

自引率

10.80%

发文量

665

审稿时长

39 days

期刊介绍： Forest Ecology and Management publishes scientific articles linking forest ecology with forest management, focusing on the application of biological, ecological and social knowledge to the management and conservation of plantations and natural forests. The scope of the journal includes all forest ecosystems of the world. A peer-review process ensures the quality and international interest of the manuscripts accepted for publication. The journal encourages communication between scientists in disparate fields who share a common interest in ecology and forest management, bridging the gap between research workers and forest managers. We encourage submission of papers that will have the strongest interest and value to the Journal''s international readership. Some key features of papers with strong interest include: 1. Clear connections between the ecology and management of forests; 2. Novel ideas or approaches to important challenges in forest ecology and management; 3. Studies that address a population of interest beyond the scale of single research sites, Three key points in the design of forest experiments, Forest Ecology and Management 255 (2008) 2022-2023); 4. Review Articles on timely, important topics. Authors are welcome to contact one of the editors to discuss the suitability of a potential review manuscript. The Journal encourages proposals for special issues examining important areas of forest ecology and management. Potential guest editors should contact any of the Editors to begin discussions about topics, potential papers, and other details.