Combined heat and drought affect the abundance, composition and diversity of subalpine surface‐active soil arthropod communities

Abstract Alpine and subalpine ecosystems are predicted to have increased temperature and altered seasonal rainfall and snow cover duration as climate change progresses, potentially changing the communities of these ecosystems. Soil arthropods facilitate key environmental processes that determine ecosystem function and stability; however, little is known about how warming and drought conditions impact soil arthropod communities in the field. This study aimed to assess the effects of soil warming and drought conditions on the abundance and diversity of soil arthropod communities. Climate‐controlled shelters manipulated soil temperature and incoming precipitation in a factorial experiment (FutureClim) in a subalpine grassy herbfield in Australia. Surface‐active arthropods were sampled from climate‐controlled shelters using pitfall traps in January, March and April 2023 and were identified to order. Abundance, diversity and community composition changed significantly across the sampling period. Diversity was lowest in all warming and drought treatments in April relative to control, while community composition was significantly driven by temperature and moisture but also was highly variable across the site. The effects of warming and drought on abundance differed substantially between arthropod taxa, with opposing effects on mesofauna and macrofauna. Two Collembola orders, which comprised a large proportion of the arthropod community, were more abundant in heated shelters during the cooler months. In contrast, Hymenoptera (mostly driven by the dominant alpine ant Iridomyrmex alpinus ), Hemiptera and Diptera were more abundant in drought and heat‐drought conditions, but larvae were scarce in droughted treatments. Collectively, this study suggests that the abundance, composition and possibly diversity of surface‐active mesofauna and macrofauna will likely change in the future. Focus on phenological shifts of communities over both short and long timescales, coupled with vegetation and soil changes, is needed to better understand potential ecological changes associated with soil warming and drying.