Spectroscopic Analysis of Canopy Nitrogen and Nitrogen Isotopes in Managed Pastures and Hay Land
Spectroscopic Analysis of Canopy Nitrogen and Nitrogen Isotopes in Managed Pastures and Hay Land
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DOI：
10.1109/tgrs.2011.2104964
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发表时间：
2011-07-01
影响因子：
8.2
通讯作者：
Craine, Joseph M.
中科院分区：
文献类型：
--
作者：
Elmore, Andrew J.;Craine, Joseph M.
改善流域养分预算、生态系统模型以及我们对土地利用管理对生态系统功能影响的理解，取决于能够预测氮 (N) 循环各个方面的遥感方法的发展。对于温带管理的草原来说尤其如此，这些草原占农业用地的很大一部分，有时会向水生系统和大气中输出大量的氮。尽管叶面 N 通常是遥感的，但我们探索使用光谱学来预测叶面 N-15 与 N-14 的同位素比率，即 delta N-15。全球调查和特定地点研究表明，叶面 Delta N-15 可以反映氮的可用性和流失到大气中的氮量。我们建立了管理牧场和干草地的树冠反射率数据集，然后收集这些数据进行实验室分析。对于干燥和研磨样品的光谱，我们计算了最有可能与 delta N-15 相关的三个吸收特征的归一化带深度 (NBD)。在这些数据中，叶面 N 和 Delta N-15 不相关，我们发现已知与叶面 N 相关的 2100 nm 特征的 NBD 的 Delta N-15 线性模型较弱，但显着。与干燥和地面样品的光谱相比，冠层光谱本质上反映了植被结构，与 Delta N-15 的相关性更好。这些结果表明，估计 Delta N-15 和牧场管理方式方面的近期进展可能与植被结构的量化有关，或包括植被结构的量化。
Improving watershed nutrient budgets, ecosystem models, and our understanding of the impact of land-use management on ecosystem functioning depends on the development of remote sensing methods that can predict aspects of the nitrogen (N) cycle. This is particularly true for temperate managed grasslands, which constitute a large portion of agricultural land and, at times, export a significant amount of N to aquatic systems and the atmosphere. Although foliar N is often remotely sensed, we explore the use of spectroscopy to predict the foliar isotopic ratio of N-15 to N-14, i.e., delta N-15. Foliar delta N-15 has been shown in global surveys and site-specific studies to reflect N availability and the amount of N lost to the atmosphere. We built a data set of the canopy reflectance of plots in managed pastures and hay lands, which we then harvested for laboratory analysis. For the spectra of dried and ground samples, we calculated the normalized band depth (NBD) of three absorption features most likely to correlate with delta N-15. In these data, foliar N and delta N-15 were not correlated, and we found weak, but significant, linear models with delta N-15 for the NBD of the 2100-nm feature known to relate to foliar N. The canopy spectra, which inherently reflect the vegetation structure, correlated better with delta N-15 than the spectra of dried and ground samples. These results suggest that near-term advances in estimating delta N-15 and aspects of pasture management style are likely to be related to, or to include, the quantification of the vegetation structure.