Biodiversity–ecosystem functioning relationships under multi-scale fragmentation pressures in natural forests along an elevational gradient

Habitat fragmentation has contributed significantly to biodiversity loss and ecosystem degradation in many regions over the past decades. Forest fragmentation is increasing in more than half of the world’s forests, and over 70% of the global forest area is situated within one kilometer of the nearest forest edge. Although biodiversity can be a stabilising force for ecosystem functioning, it is unclear whether and how above- and belowground biodiversity can buffer forest ecosystem functioning under fragmentation-induced pressures in heterogeneous mountain landscapes.

In this study, we investigated 260 forest plots distributed across 26 fragmented patches of temperate coniferous forests and mixed conifer–broadleaf forests in northwestern Yunnan, China. These forest patches span an elevational range from ca. 2,180 to 3,840 m and represent diverse fragmentation pressures, including road edges, farmland boundaries, fire-affected areas, plantations, and natural meadow transitions. Within each patch, 10 × 10 m plots were established at 10 m intervals along transects extending from the forest edge to 100 m inside the forest. This design allowed us to study both the strength of edge effects and the impacts of different types of fragmentation.

Plant community composition, soil samples, and UAV hyperspectral imagery were collected for all plots. Taxonomic, functional, and phylogenetic plant diversity was determined, as well as soil microbial diversity using eDNA metabarcoding. Ecosystem functioning was assessed using above-ground biomass, as well as soil carbon and nitrogen pools. We use mixed-effects models and structural equation modelling to disentangle direct fragmentation effects from biodiversity-mediated modulation of ecosystem functioning. Our analyses will specifically focus on (i) how different fragmentation pressures affect multi-dimensional biodiversity; (ii) how fragmentation types and edge-to-interior intensity gradients influence ecosystem functioning; and (iii) whether above- and below- ground biodiversity modulate the impacts of fragmentation stress on forest functioning and sensitivity.

By integrating multi-scale fragmentation pressures with above- and belowground biodiversity and functioning assessments, this study provides novel insights into biodiversity–ecosystem functioning relationships under environmental stress.

Keywords: forest fragmentation; biodiversity-ecosystem functioning; edge effects; ecosystem multifunctionality; functional and phylogenetic diversity; soil microbial