Biocrusts (topsoil communities formed by mosses, lichens, bacteria, fungi, algae, and cyanobacteria) are a key biotic component of dryland ecosystems. Whilst climate patterns control the distribution of biocrusts in drylands worldwide, terrain and soil attributes can influence biocrust distribution at landscape scale. Multi-source unmanned aerial vehicle (UAV) imagery was used to map and study biocrust ecology in a typical dryland ecosystem in central Spain. Red, green and blue (RGB) imagery was processed using structure-from-motion techniques to map terrain attributes related to microclimate and terrain stability. Multispectral imagery was used to produce accurate maps (accuracy > 80%) of dryland ecosystem components (vegetation, bare soil and biocrust composition). Finally, thermal infrared (TIR) and multispectral imagery was used to calculate the apparent thermal inertia (ATI) of soil and to evaluate how ATI was related to soil moisture (r² = 0.83). The relationship between soil properties and UAV-derived variables was first evaluated at the field plot level. Then, the maps obtained were used to explore the relationship between biocrusts and terrain attributes at ecosystem level through a redundancy analysis. The most significant variables that explain biocrust distribution are: ATI (34.4% of variance, F = 130.75; p < 0.001), Elevation (25.8%, F = 97.6; p < 0.001), and potential solar incoming radiation (PSIR) (52.9%, F = 200.1; p < 0.001). Differences were found between areas dominated by lichens and mosses. Lichen-dominated biocrusts were associated with areas with high slopes and low values of ATI, with soil characterized by a higher amount of soluble salts, and lower amount of organic carbon, total phosphorus (P_tot) and total nitrogen (N_tot). Biocrust-forming mosses dominated lower and moister areas, characterized by gentler slopes and higher values of ATI with soils with higher contents of organic carbon, P_tot and N_tot. This study shows the potential to use UAVs to improve our understanding of drylands and to evaluate the control that the terrain has on biocrust distribution.

中文翻译：

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无人机RGB、热红外和多光谱图像用于研究地形对旱地生物结皮空间分布的控制

生物结皮（由苔藓、地衣、细菌、真菌、藻类和蓝藻形成的表土群落）是旱地生态系统的关键生物成分。虽然气候模式控制着全球旱地生物结皮的分布，但地形和土壤属性会影响景观尺度上的生物结皮分布。多源无人机 (UAV) 图像用于绘制和研究西班牙中部典型旱地生态系统中的生物地壳生态学。红色、绿色和蓝色 (RGB) 图像使用基于运动的结构技术进行处理，以绘制与微气候和地形稳定性相关的地形属性。多光谱图像用于生成旱地生态系统组成部分（植被、裸土和生物地壳成分）的准确地图（精度 > 80%）。最后，r ²  = 0.83）。土壤特性与无人机衍生变量之间的关系首先在田间地块水平上进行评估。然后，通过冗余分析，利用获得的地图在生态系统层面探索生物地壳与地形属性之间的关系。解释生物地壳分布的最重要变量是：ATI（方差的 34.4%，F  = 130.75；p  < 0.001）、海拔（25.8%，F  = 97.6；p  < 0.001）和潜在的太阳入射辐射 (PSIR) (52.9 %, F  = 200.1; p < 0.001)。在地衣和苔藓占主导地位的地区之间发现了差异。以地衣为主的生物结皮与高坡度和低 ATI 值的区域相关，土壤的特征是可溶性盐含量较高，有机碳、总磷 (P _tot ) 和总氮 (N _tot )含量较低。形成生物结皮的苔藓在较低和较潮湿的地区占主导地位，其特点是坡度较缓，ATI 值较高，土壤有机碳、P _tot和 N _tot含量较高。这项研究显示了使用无人机来提高我们对旱地的了解并评估地形对生物地壳分布的控制的潜力。