The northern Humboldt Current System (nHCS) is an area with high environmental variability that impacts key demographic and community-scale processes. Understanding the role and ecological implications of these interannual or long-term events is crucial in describing the dynamics of the nHCS community. Using catch data from pelagic assessment surveys from 1983 to 2019 and the community trajectory analysis framework, we tested and characterised the patterns and compositional dynamics of the nHCS pelagic fish community over space and time. Spatially, changes were evaluated for ecological regions with similar community composition identified through hierarchical clustering with spatial constraint. We found that the community is in constant inter-annual variability consistent with the long-term warm and cold periods of the system. A long trajectory segment suggests a community regime shift between 1994 and 1999, years associated with a change in the average oceanographic conditions in the system and an extreme El Niño event (1997-98). After 1999, we identified a period where the community was constantly changing and dominated by coastal species. These long-term community changes were not homogeneous over the ecological areas, finding a lower temporal variability in the coastal area than in the northern and offshore. The main factor controlling the spatial and temporal dynamics of the nHCS pelagic fish community seems to be the long and short-term environmental conditions in the system. This study helps to understand the magnitude and direction of pelagic fish community changes and define the community’s recovery process after an event-driven change.

Climate change and shrub encroachment affect nematode biodiversity, although shrub species had different effects on below-ground community. Yet, the consequences of shrub species on the nematode beta diversity under future climate change scenarios remain insufficiently explored. Here, we studied the dominant shrub effects on the beta diversity of soil nematode communities along climate gradients on the Qinghai-Tibet Plateau. We investigated soil nematode communities in 31 sites of alpine meadow ecosystems across a 1200 km × 1200 km area with widespread shrub on the Qinghai-Tibet Plateau. We found that shrubs decreased the nematode beta diversity through decreasing the nestedness component at local and landscape scales. Leguminous shrubs had stronger effects on the nematode beta diversity than non-leguminous shrub types at landscape scale. MAP and MAT both significantly increased the negative shrub effects on the nematode beta diversity, but they remained constant for leguminous shrub. The pSEM analysis showed that shrubs had direct and indirect effects on nematode beta diversity via plant species turnover. Our results showed that shrub encroachment, particularly leguminous shrubs, leads to the homogenization of nematode communities. The “warming-wetting” trend will exacerbate shrub effects on the homogenization of nematode communities on the Qinghai-Tibet Plateau. Our study provides insight into the ecological processes that maintain soil biodiversity and biogeographic patterns of soil communities on the Qinghai-Tibet Plateau.