Response of vegetation fine root functional traits to karst rocky desertification

Fine roots, among the more physiologically active underground plant parts, contribute significantly to understanding critical ecological processes in terrestrial ecosystems and the mechanisms of plant adaptation to the environment. Karst rocky desertification (KRD) is a severe ecological problem triggered by human disturbances, and characterized by surface vegetation degradation, severe soil erosion, extensive bedrock exposure, and the formation of desert-like landscapes. To elucidate plant adaptation strategies and driving mechanisms in response to KRD, a severe form of terrestrial ecosystem degradation, a typical KRD ecosystem in southwestern China was selected and a space-for-time substitution approach was be used to study the responses of fine root biomass, morpho-, and chemo-functional traits of woody and herbaceous plants to the KRD process. The main results and conclusions are as follows: (1) During the KRD evolution, significant changes occurred in the morpho- and chemo-functional traits of fine roots in both woody and herbaceous plants, with distinct response laws observed between the two plant types. For herbaceous plants, fine root biomass reached its peak at the severe rocky desertification (SRD) stage, while the contents of fine root nitrogen (N), phosphorus (P), and silicon (Si) were lowest at the SRD stage. For woody plants, specific root length and specific root surface area of fine roots significantly decreased at the SRD stage, but the contents of fine root carbon (C), N, P, and Si did not show a significant reduction. (2) Soil physicochemical properties were significantly correlated with fine root functional traits. Soil total C and total P were the very important factors influencing fine root functional traits. Soil nutrients, rather than soil moisture, were the primary limiting factors for plant growth in the karst environments. (3) Fine roots in both woody and herbaceous plants maintained relatively consistent root survival and defense strategies during the KRD process. This study provides important scientific insights into the adaptation strategies of plants to KRD environments and offers scientific support for the development of vegetation restoration measures in KRD control.