B soil crusts, or biocrusts, are major contributors to the biodiversity and ecosystem functions of deserts, semideserts, woodlands, and grasslands worldwide (Belnap 2003; Weber et al. 2016). Biocrust communities contain a diverse assemblage of cyanobacteria, algae, lichens, and bryophytes, as well as bacteria, archaea, fungi, and other associated soil organisms. Collectively, biocrust organisms influence erosion rates, water infiltration, nutrient cycling, carbon (C) storage, and vascular plant composition, among other ecological attributes (Weber et al. 2016). Increasing recognition of the pivotal role that biocrusts play in dryland ecosystems has spurred calls for greater appreciation, protection, and restoration of these communities (Belnap 2003; Bowker 2007; Ferrenberg et al. 2017). Although attention and research have overwhelmingly focused on biocrusts in arid and semiarid climates, biocrusts frequently occur in more humid regions as well (eg Eldridge 1999; Thiet et al. 2014; Schulz et al. 2016). In wetter climates, the open canopy and sparse litter that biocrust communities require are usually restricted to areas where vascular plant primary productivity is low (Eldridge et al. 2000; Büdel et al. 2014). The particular habitats that support biocrusts also often support a broader diversity of distinctive plants and animals absent from the more typical habitats of their region (eg forests; Eldridge 1999; Eldridge et al. 2000; Büdel et al. 2014), and biocrusts can therefore be thought of as “islands” in a sea of surrounding landscape. Such biocrust islands include barrens, sand plains, alvar communities, sparse grasslands, and sand dunes (Table 1) that are often appreciated and managed for their conservation value at regional and global scales. The presence of biocrusts in these ecosystems makes them even more biodiverse than is commonly recognized. Diverse biocrusts dominated by algae, cyanobacteria, bryophytes, and lichens have been documented in the US Midwest (eg Iowa [Schulten 1985], northwestern Ohio [Neher et al. 2003], northern Indiana [Thiet et al. 2005], and Wisconsin [WDNR 2015]), the US Northeast (eg Cape Cod [Smith et al. 2004; Thiet et al. 2014], New Jersey’s Pinelands [Sedia and Ehrenfeld 2005], and New York [Gilman 1995; Stergas and Adams 1989]), Florida (Hawkes and Flechtner 2002), and temperate regions of Europe (eg Sparrius 2011; Büdel et al. 2014; Schulz et al. 2016) as well as temperate Australia (Eldridge 1999; Eldridge et al. 2000; O’Bryan et al. 2009). We suspect that a lack of recognition of the status of temperate biocrusts as a discrete community with ecological importance has resulted in numerous additional sites worldwide going unnoticed. Here, we review what is known about biocrusts in temperate regions where they have been studied (primarily North America, Europe, and Australia), with a focus on the unique Temperate biocrusts: mesic counterparts to their betterknown dryland cousins

中文翻译：

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温带生物结皮：它们更知名的旱地表亲的中等对应物

B 土壤结皮或生物结皮是全球沙漠、半沙漠、林地和草原的生物多样性和生态系统功能的主要贡献者（Belnap 2003；Weber 等人，2016）。生物地壳群落包含蓝藻、藻类、地衣和苔藓植物以及细菌、古生菌、真菌和其他相关土壤生物的多样化组合。总的来说，生物外壳生物影响侵蚀率、水渗透、养分循环、碳 (C) 储存和维管植物组成，以及其他生态属性（Weber 等人，2016 年）。越来越多地认识到生物结皮在旱地生态系统中发挥的关键作用，促使人们呼吁更多地了解、保护和恢复这些群落（Belnap 2003；Bowker 2007；Ferrenberg 等人，2017）。尽管注意力和研究压倒性地集中在干旱和半干旱气候中的生物结皮上，但生物结皮也经常发生在更潮湿的地区（例如 Eldridge 1999；Thiet 等人，2014 年；Schulz 等人，2016 年）。在较潮湿的气候中，生物结皮群落所需的开放树冠和稀疏凋落物通常仅限于维管植物初级生产力低的地区（Eldridge 等人，2000 年；Büdel 等人，2014 年）。支持生物结皮的特定栖息地通常也支持更广泛的多样性独特的植物和动物，而这些植物和动物在其地区更典型的生境中缺乏（例如森林；Eldridge 1999；Eldridge 等人，2000 年；Büdel 等人，2014 年），因此生物结皮可以被认为是周围景观海洋中的“岛屿”。这种生物壳岛包括贫瘠之地、沙地平原、阿尔瓦群落、稀疏草原、和沙丘（表 1），它们通常因其在区域和全球范围内的保护价值而受到赞赏和管理。这些生态系统中生物结壳的存在使它们的生物多样性比人们普遍认为的还要多。在美国中西部（例如爱荷华州 [Schulten 1985]、俄亥俄州西北部 [Neher et al. 2003]、印第安纳州北部 [Thiet et al. 2005] 和威斯康星州 [ WDNR 2015]）、美国东北部（例如 Cape Cod [Smith et al. 2004; Thiet et al. 2014]、新泽西州的 Pinelands [Sedia and Ehrenfeld 2005] 和纽约 [Gilman 1995; Stergas and Adams 1989]），佛罗里达（Hawkes 和 Flechtner 2002）、欧洲温带地区（例如 Sparrius 2011；Büdel 等人 2014；Schulz 等人 2016）以及澳大利亚温带地区（Eldridge 1999；Eldridge 等人 2000；奥布莱恩等人。2009）。我们怀疑，由于缺乏对温带生物结皮作为具有生态重要性的离散群落的地位的认识，导致全球许多其他地点被忽视。在这里，我们回顾了对温带地区（主要是北美、欧洲和澳大利亚）的生物结皮进行研究的已知情况，重点是独特的温带生物结皮：它们更广为人知的旱地表亲的中等对应物