Low water conservation ability of carbonate limits vegetation growth in karst landscape has been commonly recognized, but how bedrock mediates the effect of precipitation on vegetation growth remains unclear. We studied the spatio-temporal differences of vegetation growth in Guizhou Province of China by dividing the study region into three types of lithological region based on stream sediment geochemical data. The differences of precipitation-vegetation growth relationship among them were assessed. The results show that in months with low precipitation (0-150 mm), lower vegetation growth occurs in regions where the bedrock has higher calcium (Ca) content, whereas in months with high precipitation (150-250 mm), significant differences are not observed in the vegetation growth among various lithological regions. Extremely high amount of precipitation (>250 mm) can even benefit vegetation growth on the karst landscape. Our findings highlight that there is a threshold of precipitation amount for limiting vegetation growth in the karst landscape, which should be taken into account when studying responses of vegetation growth to climate change in the karst landscape.

The role of bedrock geochemistry in vegetation growth within karst areas has been examined in recent works, implying that the approach of the critical zone (CZ) extending from the canopy to the groundwater bottom enhances the understanding of vegetation ecology. In this paper, the research progress of vegetation ecology associated with bedrock features in the karst CZ in subtropical Southwest China is systematically reviewed. There are great differences in soil formation and soil features (water-holding capacity, particle size, and soil chemistry) between karst and non-karst regions, even between dolomite and limestone within a karst region. Water and soil are easily leached due to the connected underground crevices in karst, particularly in limestone-dominated regions, leading to water deficits in karst CZ plants in subtropical Southwest China. The development of plant roots in crevices affects the water and nutrient absorption by plants and microbial activities in the soil, which form the basis for vegetation distribution and growth in the karst CZ. The organic acids from plants also increase weathering rates. As extensive human activities have accelerated vegetation degradation and soil erosion and further led to rocky desertification characterized by increasing areas of rock exposure, state-of-the-art knowledge about the effects of bedrock-associated belowground and aboveground interactions can guide the implementation of vegetation restoration and the control of further rocky desertification in the subtropical karst CZ.

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Crown architecture is a critical component for a tree to interact with the ambient environment and to compete with neighbors. However, little is known regarding how climate variability may shape crown architecture traits across large geographical extents and whether crown architecture traits have coordinated variations with trunk and leaf traits to climate gradients. Here we used Quercus mongolica trees as an example, used the cutting‐edge terrestrial laser scanning technique to accurately characterize their crown architecture traits, and explored their variabilities along with environmental variability across large climate gradients in northern China. Our results showed that there are significant spatial variations in trunk, crown, and leaf traits even for the same genetic group across large environmental gradients. Tree height and leaf size had tight covariations with precipitation (|R|> 0.8, p < 0.01). We also observed coordinated variations among crown architecture traits related to canopy shape (e.g., primary branch insertion angle, chord length ratio), trunk traits (e.g., tree height), leaf traits (e.g., specific leaf area), and climate variability, highlighting there are likely fundamental evolutionary strategies regulating these covariations. With a projected drier and hotter climate scenario in this region, our results further suggest trees are expected to transit from a “tree shape” to a “shrub shape,” with large ecological and ecophysiological impacts on this region.