Abstract:

Biological soil crusts （BSC）， especially moss crusts as an advanced successional stage， play a critical role in soil stabilization and ecological function restoration in arid and semi-arid ecosystems. To clarify the relationship between moss crust biomass and physiological indicators and explore reasonable methods for biomass measurement， this study systematically quantified the correlations between moss crust biomass and key morphological/physiological indicators （thickness， chlorophyll content， chlorophyll fluorescence kinetics parameters， and gross primary productivity） in the western Loess Plateau through field sampling， laboratory analysis， and structural equation modeling （SEM）. The results showed that BSC thickness was significantly linearly correlated with biomass （R²=0.805， β=0.90）， serving as a reliable morphological proxy for rapid biomass assessment. In contrast， physiological indicators exhibited nonlinear dynamics： chlorophyll content per unit area and maximum photochemical quantum yield showed quadratic relationships with biomass （R²=0.645 and 0.490， respectively）， while chlorophyll concentration per unit mass decreased in a power function pattern with increasing biomass （R²=0.607）. SEM further revealed that gross primary productivity （GPP） directly drives biomass accumulation （β=0.44）， whereas chlorophyll content indirectly affects biomass through GPP mediation. This study identifies thickness as the optimal indicator for field biomass assessment and emphasizes the need to integrate environmental stress factors to optimize predictive models， providing a methodological basis for BSC monitoring and ecological restoration practices.

Key words: biological soil crust （BSC）, moss crust, biomass, Loess Plateau