Plant-Soil-Microbial Stoichiometric Characteristics and Driving Mechanisms During Lithophytic Moss Succession in Karst Rocky Desertification Regions

Lithophytic
mosses are key pioneers initiating soil formation and nutrient accumulation in
karst rocky desertification ecosystems, yet the mechanisms linking moss
succession with the stoichiometric dynamics of the plant–soil–microbial system
remain poorly understood. Here, we investigated changes in community
composition, C, N and P concentrations, and ecological stoichiometry of mosses,
soils, and extracellular enzymes across four successional stages of lithophytic
moss patches (ST1, 0–10 cm; ST2, 10–20 cm; ST3, 20–30 cm; ST4, >30 cm in
diameter) under sun-exposed and shaded habitats. Moss communities exhibited a
clear successional progression from random colonization characterized by high
diversity (ST1), to competitive exclusion resulting in diminished diversity
(ST2–ST3), and finally to niche complementarity that
reinstated diversity (ST4). This change was intricately linked to advanced
canopy development and soil accumulation. Moss colonization enhanced soil
organic carbon (SOC) by 212.25–263.97% compared to bare rock. Soil carbon,
nitrogen, and phosphorus increased by 78.08–79.32%, 105.70–112.86%, and
55.79–67.07%, respectively, along the successional gradient across habitats.
Phosphorus limitation exacerbated as soil C:N ratios diminished and N:P ratios
increased. Notwithstanding substantial elevations in tissue nitrogen and
phosphorus contents, mosses preserved essentially constant C:N:P ratios,
signifying robust stoichiometric homeostasis. The activities of
β-1,4-glucosidase and urease exhibited a considerable increase with succession,
but alkaline phosphatase remained comparatively stable. The enzyme N:P ratios
decreased by 32.97–33.11% from the early to late stages, and vector-based
ecoenzymatic stoichiometry indicated widespread microbial co-limitation of
carbon and nitrogen. Mantel testing and structural equation modeling indicated
that SOC and total soil nutrients predominantly govern soil C:N:P
stoichiometry, while plant phosphorus significantly influences moss
stoichiometry. Urease further modulated the enzyme C:N:P by reducing enzyme N:P
ratios and mitigating microbial nitrogen constraint. Lithophytic moss
succession modifies ecosystem stoichiometry by changing soil resource pools and
microbial enzyme distribution, ultimately improving soil fertility, and
facilitating ecological restoration in karst rocky deserts habitats.