Data from: "Moisture rivals temperature in limiting photosynthesis by trees establishing beyond their cold-edge range limit under ambient and warmed conditions"

This archive contains data files that were used to draw conclusions in “Moisture rivals temperature in limiting photosynthesis by trees establishing beyond their cold-edge range limit under ambient and warmed conditions”, by Moyes et al., 2015. All field research was completed in common garden plots set up as part of the Alpine Treeline Warming Experiment (ATWE) on Niwot Ridge, Colorado, USA. There are two main data file formats in this archive: comma-separated values (.csv), and Microsoft Excel (.xls and .xlsx). .xlsx files can be read using Microsoft Excel and Google Sheets, and .csv files can be read using any simple text editor program, such as TextEdit (Mac) and Notepad (Windows). This .pdf data user’s guide can be read using Adobe Acrobat Reader, or any other compatible software. Seedling photographs and their corresponding leaf area-processed images are available in .jpg/.JPG image format, and can be opened using Preview (Mac) and Photos (Windows). To provide additional spatial context, two types of geospatial files are also published in this data package: ESRI shapefiles (.shp) and .kml files. Shapefiles are compatible with any GIS software able to read the file type (such as QGIS or ESRI’s ArcGIS suite), and .kml files can be opened with Google Earth or Google Maps. Figures 3 and 4 in the publication contain data from Moyes et al. 2013. This publication is cited in the References section in this archive, and data files can be accessed via the Alpine Treeline Warming Experiment project portal on ESS-DIVE. --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- - Climate change is altering plant species distributions globally, and warming is expected to promote uphill shifts in mountain trees. However, at many cold-edge range limits, such as alpine treelines in the western United States, tree establishment may be colimited by low temperature and low moisture, making recruitment patterns with warming difficult to predict. - We measured response functions linking carbon (C) assimilation and temperature- and moisture-related microclimatic factors for limber pine (Pinus flexilis) seedlings growing in a heating × watering experiment within and above the alpine treeline. We then extrapolated these response functions using observed microclimate conditions to estimate the net effects of warming and associated soil drying on C assimilation across an entire growing season. - Moisture and temperature limitations were each estimated to reduce potential growing season C gain from a theoretical upper limit by 15–30% (c. 50% combined). Warming above current treeline conditions provided relatively little benefit to modeled net assimilation, whereas assimilation was sensitive to either wetter or drier conditions. - Summer precipitation may be at least as important as temperature in constraining C gain by establishing subalpine trees at and above current alpine treelines as seasonally dry subalpine and alpine ecosystems continue to warm.

本归档文件包含支撑Moyes等人2015年发表的论文《在自然与增温环境下突破低温边界分布范围的树木光合作用受水分限制程度不亚于温度》的实验数据文件。所有野外研究均在美国科罗拉多州尼沃特岭（Niwot Ridge）的高山林线增温实验（Alpine Treeline Warming Experiment, ATWE）项目所设置的共同花园样地中完成。
本归档包含两种主流数据文件格式：逗号分隔值文件（comma-separated values, .csv）以及微软Excel文件（.xls与.xlsx）。其中.xlsx格式文件可通过Microsoft Excel与Google Sheets读取，.csv格式文件则可通过任意简易文本编辑器打开，例如Mac系统的TextEdit以及Windows系统的记事本（Notepad）。
本PDF格式的数据用户指南可通过Adobe Acrobat Reader或其他兼容软件读取。幼苗照片及其配套的叶面积处理图像采用.jpg/.JPG格式存储，可通过Mac系统的预览（Preview）与Windows系统的照片（Photos）应用打开。
为提供额外的空间背景信息，本数据包还包含两类地理空间文件：ESRI形状文件（ESRI shapefiles, .shp）与.kml文件。形状文件可兼容所有支持该格式的地理信息系统（GIS）软件（例如QGIS或ESRI的ArcGIS套件），.kml文件则可通过Google Earth或Google Maps打开。
论文中的图3与图4采用了Moyes等人2013年的实验数据。该文献已收录于本归档的参考文献部分，数据文件可通过ESS-DIVE平台上的高山林线增温实验项目门户获取。
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- 气候变化正在全球范围内改变植物物种的分布格局，预计增温将推动山地树木向高海拔区域迁移。然而在诸多低温边界分布极限处，例如美国西部的高山林线，树木定植过程可能同时受低温与低水分的共同限制，这使得增温背景下的种群补充模式难以预测。
- 本研究针对生长在高山林线内外的柔枝松（Pinus flexilis）幼苗，通过增温×控水实验测定了碳（C）同化速率与温度、水分相关微气候因子之间的响应函数。随后基于实测微气候条件对该响应函数进行外推，以估算整个生长季内增温及伴随的土壤干旱对碳同化速率的净效应。
- 研究估算显示，水分与温度限制分别会使理论上限下的生长季碳增益降低15%~30%（两者共同限制的总降幅约为50%）。在现有林线以上区域实施增温对模型模拟的净碳同化速率提升效果有限，而碳同化速率对湿润或干旱条件均较为敏感。
- 随着季节性干旱的亚高山与高山生态系统持续增温，在当前高山林线及以上区域定植的亚高山树木，其碳增益所受的夏季降水限制作用可能至少与温度相当。