<meta charset="utf8"></head><body>用于古气候和古生态重建的数字叶面学

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			<td>Copy stand or tripod</td>
			<td></td>
			<td></td>
			<td>For fossil photography</td>
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			<td>Digital camera</td>
			<td></td>
			<td></td>
			<td>For fossil photography, high resolution camera preferred</td>
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			<td>Image editing software&#160;</td>
			<td></td>
			<td></td>
			<td>For digital preperation. Examples include Adobe Photoshop and GIMP, the latter of which is free (https://www.gimp.org/)</td>
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			<td>ImageJ software</td>
			<td>IJ1.46pr</td>
			<td></td>
			<td>For making digital measurments, free software (https://imagej.net/ij/index.html)</td>
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			<td>Microsoft Excel</td>
			<td>Microsoft</td>
			<td></td>
			<td>Or similar software for data entry</td>
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			<td>R software</td>
			<td>The R foundation</td>
			<td></td>
			<td>For running provided R script (https://www.r-project.org/). R studio offers a user friendly R enviornment (https://posit.co/download/rstudio-desktop/). Both are free.</td>
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			<td>dilp R Package</td>
			<td></td>
			<td></td>
			<td>Can be installed following instructions here: https://github.com/mjbutrim/dilp</td>
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reconstructing terrestrial paleoclimate and paleoecology with fossil leaves using digital leaf physiognomy and leaf mass per area

Leaves are fundamental production units that facilitate the exchange of energy (e.g., light, heat) and matter (e.g., carbon dioxide, water vapor) between the plant and its surrounding environment1,2. To perform these functions, leaves must mechanically support their own weight against gravity in still and windy air 3,4. Because of these intrinsic links, several aspects of the size, shape, and toothiness of leaves (physiognomy) reflect the details of their function and biomechanics and provide insight into their environment and ecology. Prior work has quantified relationships between leaf physiognomy, climate, and ecology across the modern world to establish proxies that can be applied to fossil leaf assemblages5,6. These proxies provide important opportunities to reconstruct paleoclimate and paleoecology and contribute to a greater understanding of the complex interplay between various systems of the planet throughout its history. This article details the methods necessary for the use of two proxies: 1) the leaf mass per area reconstruction method to elucidate paleoecology, and 2) digital leaf physiognomy to reconstruct paleoclimate.
Leaf dry mass per area (MA) is a frequently measured plant trait in both neo- and paleobotany. The primary value of MA, especially for fossil reconstructions, is that it is part of the leaf economics spectrum, a coordinated axis of well-correlated leaf traits that includes leaf photosynthetic rate, leaf longevity, and leaf nutrient content by mass7. The ability to reconstruct MA from fossils provides a window into these otherwise inaccessible metabolic and chemical processes and ultimately can reveal useful information about plant ecological strategy and ecosystem function.
Royer et al.5 developed a method to estimate the MA of woody non-monocotyledonous (dicot) angiosperm fossil leaves based on the area of the leaf blade and the width of the petiole. Theoretically, the leaf petiole acts as a cantilever, holding the weight of the leaf in the optimal position3,4. The cross-sectional area of the petiole, which makes up the most significant component of beam strength, should, therefore, be strongly correlated with the mass of the leaf. By simplifying the shape of the petiole into a cylindrical tube, the cross-sectional area of the petiole can be represented with the petiole width squared, allowing leaf mass to be estimated from a two-dimensional fossil (for more detail, see Royer et al.5). Leaf area can be measured directly. Together, petiole width squared divided by leaf area (i.e., the petiole metric; Table 1) provides a good proxy for fossil MA and allows paleobotanists to step into modern trait-based ecology. MA reconstruction methods have also been expanded to broadleaf and petiolate gymnosperms5,8, herbaceous angiosperms8, and ferns9, which produced relationships that differ from the relationships observed for woody dicot angiosperms and from each other. An expanded woody dicot dataset and new regressions equations for reconstructing the variance and mean of MA at the site level allow the inference of the diversity of leaf economic strategies and what strategies are most prevalent, among woody dicot angiosperms in fossil floras10.
The relationship between physiognomic leaf traits and their climate has been noted for over a century11,12. Specifically, the physiognomy of woody dicot angiosperm leaves is strongly correlated with temperature and moisture13. This relationship has formed the basis for numerous univariate14,15,16,17 and multivariate6,18,19,20,21,22 leaf physiognomic proxies for terrestrial paleoclimate. Both univariate and multivariate leaf physiognomic paleoclimate methods have been widely applied to angiosperm-dominated fossil floras across all continents spanning the last ~120 million years of Earth&#39;s history (Cretaceous to modern)23.
Two fundamental observations utilized in leaf physiognomic paleoclimate proxies are 1) the relationship between leaf size and mean annual precipitation (MAP) and 2) the relationship between leaf teeth (i.e., outward projections of the leaf margin) and mean annual temperature (MAT). Specifically, the average leaf size of all woody dicot angiosperm species at a locality is positively correlated with MAP, and the proportion of woody dicot angiosperm species at a locality with toothed leaves, in addition to the size and number of teeth negatively correlate with MAT6,12,13,14,15,16,24.
A functional link between these leaf physiognomy-climate relationships is strongly supported by both theory and observation1,2,25. For example, although larger leaves provide greater photosynthetic surface area, they require greater support, lose more water through transpiration, and retain more sensible heat due to a thicker boundary layer 1,26,27. Thus, larger leaves are more common in wetter, hotter environments because water loss through increased transpiration effectively cools leaves and is less problematic. In contrast, smaller leaves in drier hot climates reduce water loss and avoid overheating instead by increasing sensible heat loss28,29. Details of what factors, or combination of factors, contribute most strongly to explaining functional links remain enigmatic for other leaf traits. For example, there have been several proposed hypotheses to explain the leaf teeth-MAT relationship, including leaf cooling, efficient bud packing, enhanced support and supply of thin leaves, guttation through hydathodes, and enhanced early season productivity30,31,32,33.
Most leaf physiognomic paleoclimate proxies rely on categorical division of leaf traits rather than quantitative measurements of continuous variables, leading to several potential shortcomings. The categorical approach excludes the incorporation of more detailed information captured by continuous measurements that are strongly correlated with climate (e.g., number of teeth, leaf linearity), which can reduce the accuracy of paleoclimate estimates6,20,34. Additionally, in some of the leaf trait scoring methods, the traits being categorically scored can be ambiguous, leading to issues in reproducibility, and some traits have limited empirical evidence to support their functional link to climate6,15,16,35,36.
To address these shortcomings, Huff et al.20 proposed digitally measuring continuous leaf traits in a method known as digital leaf physiognomy (DiLP). A key advantage of DiLP over previous methods is its reliance on traits that 1) can be measured reliably across users, 2) are continuous in nature, 3) are functionally linked to climate, and 4) display phenotypic plasticity between growing seasons6,37. This has led to more accurate estimates of MAT and MAP than previous leaf physiognomic paleoclimate methods6. In addition, the method accommodates the imperfect nature of the fossil record by providing steps to account for damaged and incomplete leaves. The DiLP method has been successfully applied to a range of fossil floras from multiple continents spanning a large range of geologic time6,38,39,40,41,42.
The following protocol is an expansion of that described in earlier work5,6,20,34. It will explain the procedures necessary to reconstruct paleoclimate and paleoecology from woody dicot angiosperms fossil leaves using the DiLP and MA reconstruction methods (see Table 1 for an explanation of the variables measured and calculated through the use of this protocol). In addition, this protocol provides steps to record and calculate leaf traits not included in DiLP or MA analysis but that are easy to implement and provide useful characterizations of leaf physiognomy (Table 1). The protocol follows the following format: 1) Imaging fossil leaves; 2) leaf digital preparation, organized into five possible preparation scenarios; 3) leaf digital measurement, organized into the same five possible preparation scenarios; and 4) DiLP and MA analyses, using the R package dilp10.
The protocol for MA reconstructions is embedded within the DiLP protocol because both are convenient to prepare for and measure alongside each other. If a user is interested in MA analyses only, they should follow the preparation steps described in DiLP preparation scenario 2, whether or not the leaf margin is toothed, and the measuring steps describing petiole width, petiole area, and leaf area measurements only. A user can then run the appropriate functions in the dilp R package that performs the MA reconstructions.

<meta charset="utf8"></head><body>作者聚焦：用于现代和古代植物群落气候和生态重建的叶性状分析

使用数字叶面学和单位面积的叶质量用化石叶重建陆地古气候和古生态学

Our research is focused on understanding the relationship between plant traits and climate and ecology in modern plants. Then using these relationships, we can develop proxies or models that we can use to reconstruct climate and ecology in ancient plant communities. Recent research has focused on understanding the biological, physiological, evolutionary underpinnings of the relationship between plant traits and climate and ecology, today and in the past.This research has shown that plant traits respond to climate and ecology, both in the lifetime of a single plant and in evolutionary time scales. Our research has demonstrated that despite the complex factors that influence plant traits, there are very strong empirical relationships between leaf traits and climate and ecology. We've used these relationships to develop models for reconstructing climate and ecology that have been applied in a variety of settings through Earth history.These methods refine the reconstruction of paleoclimate and paleoecology to provide a much more comprehensive understanding of terrestrial ecosystems and climate than is available by just studying our modern Earth. Such a perspective is critical in understanding what our future Earth holds as climates and ecosystems respond to anthropogenic impact. This is a leaf-physionomy-based approach, meaning that it does not require an accurate taxonomic identification.In addition, DiLP uses digital measurements of continuous leaf characters as opposed to qualitative and categorical, which allows for greater reproducibility, and these leaf characters have a functional relationship to climate.

Climate and environment strongly influence the size, shape, and toothiness (physiognomy) of plants&#39; leaves. These relationships, particularly in woody ...

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Reconstructing Terrestrial Paleoclimate and Paleoecology with Fossil Leaves Using Digital Leaf Physiognomy and Leaf Mass Per Area

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1.9K 次观看.  University of Washington. 我们的研究重点是了解现代植物植物性状与气候和生态之间的关系。然后利用这些关系，我们可以开发代理或模型，用于重建古代植物群落的气候和生态。最近的研究集中在了解当今和过去植物性状与气候和生态之间关系的生物学、生理学、进化基础。这项研究表明，植物性状对气候和生态做出反应，无论是在单一植物的生命周期还是在进化时...