Monitoring ecosystem functioning is a significant step towards detecting changes in ecosystem attributes that could be linked to land degradation and desertification in drylands worldwide. Remote sensing-based vegetation indices (VIs) and land surface albedo are two favorite indicators to monitor desertification process due to their close relationship with ecosystem status and to their increasing applicability over multiple spatiotemporal scales. While VIs are routinely used to monitor ecosystem attributes and functions such as vegetation cover and productivity, no previous study has evaluated whether remote sensing-measured albedo is related to the simultaneous provision of multiple ecosystem functions (multifunctionality) in global drylands. In this study, we evaluated the correlation of six albedo metrics (shortwave black-sky albedo, shortwave white-sky albedo, visible black-sky albedo, visible white-sky albedo, near-infrared black-sky albedo and near-infrared white-sky albedo) and two VIs (Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI)) with multifunctionality indices related to carbon, nitrogen and phosphorus cycling measured in 61 dryland ecosystems from all continents except Antarctica. We found a negative relationship between land surface albedo and multifunctionality. Black-sky albedo had a stronger correlation with multifunctionality than white-sky albedo. Visible black-sky albedo showed the strongest correlation with multifunctionality (MUL, -0.314), as well as with functions related to carbon (CCY, -0.216) and nitrogen cycling (NCY, -0.410), while near-infrared (-0.339) and shortwave black-sky albedo (-0.325) showed stronger correlations with functions related to phosphorus cycling (PCY) than visible black-sky albedo (-0.233) did. VIs showed significant positive correlations with MUL, CCY, and NCY, and the magnitudes were higher than those observed between albedo metrics and the multifunctionality indices. However, VIs were not correlated with PCY, which had significant correlations with both shortwave and near-infrared albedo. Though the magnitudes of the correlations observed were not high, which may result from the wide variability in soil and vegetation types in our dataset, our findings indicate that remotely sensed albedo correlates to multifunctionality, which has been linked to alternative states in global drylands. As such, albedo has the potential to monitor changes in dryland ecosystem functioning, which can inform us about the onset of desertification in these areas.

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遥感估算的反照率与全球旱地生态系统多功能性相关

监测生态系统功能是检测生态系统属性变化的重要一步，这些变化可能与全世界旱地的土地退化和荒漠化有关。基于遥感的植被指数（VI）和地表反照率是监测荒漠化过程的两个最受欢迎的指标，因为它们与生态系统状况密切相关，并且在多个时空尺度上的适用性不断增强。虽然VI通常用于监测生态系统属性和功能，例如植被覆盖和生产力，但之前没有研究评估遥感测量的反照率是否与全球旱地同时提供多种生态系统功能（多功能性）有关。在这项研究中，我们评估了六种反照率指标（短波黑天反照率、短波白天反照率、可见黑天反照率、可见白天反照率、近红外黑天反照率和近红外白天反照率）的相关性。天空反照率）和两个 VI（归一化植被指数 (NDVI) 和增强型植被指数 (EVI)），其中包含与碳、氮和磷循环相关的多功能指数，在除南极洲以外的所有大陆的 61 个旱地生态系统中进行测量。我们发现地表反照率和多功能性之间存在负相关关系。黑天反照率与多功能性的相关性比白天反照率更强。可见黑天反照率与多功能性（MUL，-0.314）以及与碳（CCY，-0.216）和氮循环（NCY，-0.410）相关的功能表现出最强的相关性，而近红外（-0.339）短波黑天反照率（-0.325）与磷循环（PCY）相关函数的相关性比可见黑天反照率（-0.233）更强。VI 与 MUL、CCY 和 NCY 呈显着正相关，并且其幅度高于反照率指标和多功能指数之间观察到的幅度。然而，VI 与 PCY 不相关，而 PCY 与短波和近红外反照率均具有显着相关性。尽管观察到的相关性幅度并不高，这可能是由于我们数据集中土壤和植被类型的广泛变化造成的，但我们的研究结果表明，遥感反照率与多功能性相关，而多功能性与全球旱地的替代状态有关。因此，反照率有潜力监测旱地生态系统功能的变化，这可以让我们了解这些地区荒漠化的发生。