The long-term effect of gap size on soil invertebrates in subalpine forest

Abstract

Frequent extreme climate events cause large-scale forest mortality, forming canopy gaps of various sizes that affect plant renewal and soil hydrothermal conditions. However, their long-term effects on soil invertebrate communities, particularly in fragile subalpine forests, remain understudied. Here we established a long-term monitoring platform in Picea asperata plantations to simulate natural gap disturbance across a gradient of control and artificially created gaps: small (74 m²), medium (109 m²), and large (196 m²) gap. After a 12-year period following gap formation, we assessed the Collembola, one of the most abundant and diverse soil invertebrates. Our results indicate that gap formation overall decreased the Collembola abundance by 43.7 %, with little effect on species richness. Gap sizes influenced Collembola community composition among small, medium, and large sizes, while large gap assembled similar composition with control plots, presumably attributed to similar abiotic condition i.e., litter phosphorus and litter-layer moisture. Further, gap formation caused shifts Collembola community towards smaller body sizes and increased sexual reproduction, indicating resource limitations probable due to litter deprivation after gap formation. Our study suggests an overall negative long-term effects of gap formation on abundance and trait performances, but large gaps showed a relatively promising future as they inhabited a faster recovery at least in abiotic condition. Given that our findings are based on a single sampling event, future studies would benefit from repeated sampling campaigns to capture temporal variability and offer valuable insights for long-term forest management strategies.