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

Abstract

Hard limestone substrates, which are extensively distributed, are believed to exacerbate drought and increase the difficulty of restoration in vulnerable karst regions. Fissures in such substrates may alleviate the negative effect of drought on plants, but the underlying mechanisms are remains poorly understood. In a two-way factorial block design, the growth and photosynthesis of two-year-old Phoebe zhennan seedlings were investigated in two water availabilities (W100% and W30%) and three stimulated fissure habitat groups: control soil habitat (S group, CK), soil-filled fissure habitat (SF group), and non-soil-filled fissure habitat (F group). Moreover, the fissure treatments included both small and large fissures. Compared to S group, F group decreased the total biomass, root biomass, total root length, and the root length of fine roots in the soil layer at both water availabilities, but increased photosynthetic rate (Pn) and remained at stable water use efficiency (WUE) at W30%. However, there was no significant differences between SF group and S group in the biomass accumulation and allocation as well as Pn. Nevertheless, the SF group lowered the root distribution in total and in the soil layer, also increased WUE at W30%. Across all treatments, fissure sizes had no effect on plant growth or photosynthesis. Karst fissures filled with soil can alleviate drought impacts on plant root growth, which involves adjusting root distribution strategies and increasing water use efficiency. Rock fissures can be involved in long-term plant responses to drought stress and vegetation restoration in rocky mountain environments under global climate change.