quantifying the spatial impact of exotic plant invasion on ecosystem functioning-from the leaf to the landscape level

外来入侵物种极大地改变了生态系统的生物地球化学循环，对生态系统的功能产生了重大影响，是对地球生物多样性的重大威胁。然而，到目前为止，明确量化这些影响仍然具有挑战性。一个原因是缺乏适当的方法来捕捉与生物入侵相关的生态系统变化的空间维度。传统的生态生理学方法在很大程度上局限于比较邻近的植物个体，往往忽视了空间维度。景观生态学虽然在更大的空间尺度上运作，但通常仅限于测量生物层面以上的模式和过程，如物种分布和繁殖速度。该项目的中心目标是将生态生理学与景观生态学联系起来，从而对植物入侵的空间方面进行综合理解，从而量化外来物种在空间尺度上的影响。解决这一问题的一种非常合适的技术是高光谱遥感，它允许使用光谱测量在叶片水平上量化本地物种生物化学的变化，同时允许使用航空图像扩大到景观水平。本文以固定氮的豆科植物长叶合欢（Acacia longifolia）为研究对象，研究了植物入侵后从叶片到景观尺度的生态系统功能变化的新方法：(1)通过叶片水平的光谱特征校准叶片生理生化特性和叶片13C和15N稳定同位素特征；(2)利用光谱法在林分水平上评价长叶刺槐对周边植被的影响阈值；(3)利用高光谱航空影像在景观尺度上绘制金针叶和优势原生植被类型的分布图。最后，我们将把我们的发现综合到一个预测模型中，该模型将使我们能够在景观尺度上评估入侵物种对本地物种生理和生态系统功能的影响。该项目建立在广泛的数据集之上，包括2011年EUFAR在研究地点进行的高光谱航空图像和激光雷达数据。此外，从10多年的前期研究中，我们对入侵的长叶橐吾和地中海原生植被有了广泛的了解。我们的跨学科方法将使科学在评估入侵物种影响的空间维度和量化生态系统功能变化方面取得显著进展。此外，通过将景观生态学和生态生理学联系起来，该项目与入侵生物学以外的植物生态学高度相关，将大大丰富我们对生态学研究中考虑空间尺度的重要性的理解。

Exotic invasive species represent a major threat to earths biodiversity, since they substantially alter biogeochemical cycles of ecosystems with large impacts on ecosystem functioning. However, to date, explicitly quantifying such impacts remains challenging. One reason is the lack of adequate methodology to capture the spatial dimension of ecosystem changes associated with biological invasion. Conventional ecophysiological approaches are largely restricted to comparing neighbouring plant individuals and tend to neglect the spatial dimension. Landscape ecology, although operating on larger spatial scales, is typically limited to measurements of patterns and processes above the organism level, such as species distribution and propagation speed.The central aim of this project is to link ecophysiology with landscape ecology, thus moving towards an integrated understanding of the spatial aspect of plant invasions, enabling the quantification of exotic species impacts across spatial scales. A highly suitable technology to address this purpose is hyperspectral remote sensing, which allows for quantifying alterations in native species biochemistry on the leaf level using spectral measurements while allowing to scale up to the landscape level using aerial images.Utilizing the case study of the N2-fixing leguminous tree Acacia longifolia, a problematic invader in coastal regions of Portugal and many ecosystems worldwide, we will develop new methodology for quantifying changes in ecosystem functioning after plant invasion from the leaf to the landscape scale, by: (1) calibrating physiological and biochemical leaf properties and foliar 13C and 15N stable isotopic signatures with spectral characteristics at the leaf level; (2) assessing the threshold of impact of A. longifolia in the surrounding vegetation at the stand-level using spectral methods; and (3) mapping the distribution of A. longifolia and dominant native vegetation types on the landscape scale using hyperspectral aerial images. Finally (4), we will synthesize our findings in a predictive model which will enable us to assess the impact of an invasive species on native species physiology and on ecosystem functioning at the landscape scale.This project builds on an extensive data set including hyperspectral aerial images and LiDAR data from a EUFAR flight campaign at the study site in 2011. Moreover, extensive knowledge on the invasive A. longifolia and native Mediterranean vegetation is available from over 10 years of prior research.Our interdisciplinary approach will bring science significantly further in evaluating the spatial dimension of invasive species impacts and in quantifying changes in ecosystem functioning. Furthermore, by linking landscape ecology and ecophysiology, this project is highly relevant for plant ecology beyond invasion biology and will significantly enrich our understanding of the significance of accounting for spatial scales in ecological studies.