Biomass Allocation, Root Spatial Distribution, and the Physiological Response of Dalbergia odorifera Seedlings in Simulated Shallow Karst Fissure-Soil Conditions

Abstract

Karst rocky desertification (KRD) is a typical fragile ecological environment with its key and difficult management point being vegetation restoration. Therefore, it is crucial to determine the adaptation mechanisms of suitable plants for ecological restoration in KRD areas. D. odorifera is a tall leguminous, woody plant with high medicinal and wood value. This study aimed to explore the adaptation strategy of the D. odorifera root system to the shallow karst fissure-soil (SKF-S) habitats. The growth, biomass, spatial root distribution, morphological characteristics, and physiological responses of D. odorifera seedlings under different treatments were studied in pots simulating SKF-S habitats. Through the experiments conducted, the following conclusions were obtained: (I) D. odorifera enhanced its ability to acquire limited resources through an allocation adjustment strategy (adjusting the biomass allocation strategy, increasing the root shoot ratio, prioritizing organ leaves and 3-level roots), which effectively offset some of the adverse effects; (II) with an increase in the stress severity, D. odorifera improved its resource acquisition adaptive strategy by reducing the root diameter and increasing the contact area with soil; (III) the spatial development characteristics of its root system were mainly manifested in the ability to grow vertically, deeper, compared to a horizontal extension; (IV) D. odorifera did not passively endure rocky desertification stress but actively improved its metabolism through root metabolic activity and SOD enzyme activity.

Karst fissures mitigate the negative effects of drought on plant growth and photosynthetic physiology

“…Soil nutrients are at risk of vertically leaching to deeper layers, while vegetation root systems promote the absorption and utilization of soil nutrients in karst ssures (Witty et treatments in uenced the biomass accumulation of each organ (except stems), but the interaction between water and habitat treatments did not affect the biomass accumulation of each organ. This observation con rms the complementary effects of karst ssures and water de cits on plant biomass accumulation (Tariq et al 2017;Yu et al 2022b).…”

“…At both W100% and W30%, P. zhennan seedlings increased the relative investment into ne roots (including root length, surface area, volume, and biomass) in the soil layer, as it provides ample water supply for plant uptake, re ecting the "hydrophilic" characteristics of plant roots (Shipley and Meziane 2002;Zhao et al 2017;Yu et al 2022b). However, under drought condition (at W30%), the SF group attempted to enhance the distribution of ne roots in the ssure layer by reducing their allocation in the soil layer.…”

“…However, under drought condition (at W30%), the SF group attempted to enhance the distribution of ne roots in the ssure layer by reducing their allocation in the soil layer. This response likely helps to utilize the limited water retained in the soil-lled karst fractures (Zhao et al 2017;Yu et al 2022b). In contrast, in the F group, more ne roots were allocated to the soil layer rather than to the karst fracture layer under drought conditions.…”

“…This is because the karst ssure layer without soil not only lacks water and nutrient storage capacity but also experiences higher water and nutrient loss rates (Peng et al 2019;Yan et al 2019). Therefore, P.zhennan seedlings show responses that avoid making ineffective attempts to access resources in the karst ssure layer (Yu et al 2022b).…”