The Response Mechanism of Plants Under Rock Stress in Karst Ecosystem: A Study Based on the Effects of Aboveground Rocks on Root Phenotypes and Leaf Water Potential

This study focused on the response mechanism of plants in karst ecosystems under rock stress, and explored the influence of aboveground rocks on the root phenotype and leaf water potential of plants. By quantifying the root characteristics of a total of 9 plant species in 3 types of vegetation areas, this study found: (1) The root biomass of grassland plants (Heteropogon contortus, Bidens pilosa, and Imperata cylindrical) in the near-rock area was on average 17.2% higher than that in the far-rock area. The lateral extension of roots was 27.8% lower, the vertical extension was on average 16.9% higher, and the total root bifurcation ratio (Rb) was on average 11.5% higher, respectively, compared to the far-rock area. (2) The root biomass of shrubland plants (Rubus mesogaeus, Spiraea martini, and Pyracantha fortuneana) in the near-rock area was on average 14.5% higher than the far-rock area. The average lateral extension of the root system was on average 17.5% lower, while there was no significant difference in the vertical extension. The Rb was on average 10.5% higher. (3) The root characteristics of forestland trees (Pistacia weinmanniifolia, Pinus yunnensis, and Carpinus turczaninowii) were significantly different from those of grassland and shrubland (p < 0.001), but the differences between the near-rock area and the far-rock area were not significant. The predawn and midday leaf water potential data showed that the plants in near-rock area of the grassland were 0.07 ± 0.03 (mean ± SD) MPa and 0.16 ± 0.07 MPa higher than those in the far-rock area, respectively, and the shrubland area was 0.12 ± 0.06 MPa and 0.20 ± 0.08 MPa higher, while there was no significant difference in the forestland. This study confirmed that aboveground rocks significantly enhanced the leaf water status of plants in arid environments by influencing root biomass, extension, and bifurcation ratio. This discovery provides a new perspective for understanding the survival mechanism of plants in karst areas.