Calcium content and high calcium adaptation of plants in karst areas of southwestern Hunan, China

Abstract

Abstract. Rocky desertification is a major ecological problem of land degradation in karst areas. In these areas, the high soil calcium (Ca) content has become an important environmental factor that can affect the restoration of vegetation. Consequently, the screening of plant species that can adapt to high Ca soil environments is a critical step in vegetation restoration. In this study, three grades of rocky desertification sample areas were selected in karst areas of southwestern Hunan, China (LRD: light rocky desertification; MRD: moderate rocky desertification; and IRD: intense rocky desertification). Each grade of these sample areas had three sample plots in different slope positions, each of which had four small quadrats (one in rocky-side areas, three in non-rocky-side areas). We measured the Ca content of leaves, branches, and roots from 41 plant species, as well as soil total Ca (TCa) and exchangeable Ca (ECa) at depths of 0–15, 15–30, and 30–45 cm in each small quadrat. The results showed that the soil Ca2+ content in rocky-side areas was significantly higher than that in non-rocky-side areas (p<0.05). The mean soil TCa and ECa content increased gradually along with the grade of rocky desertification, in the order IRD > MRD > LRD. For all plant functional groups, the plant Ca content of aboveground parts was significantly higher than that of the belowground parts (p<0.05). The soil ECa content had significant effects on plant Ca content of the belowground parts but had no significant effects on plant Ca content of the aboveground parts. Of the 41 plant species that were sampled, 17 were found to be dominant (important value > 1). The differences in Ca2+ content between the aboveground and belowground parts of the 17 dominant species were calculated, and their correlations with soil ECa content were analyzed. The results showed that these 17 species can be divided into three categories: Ca-indifferent plants, high-Ca plants, and low-Ca plants. These findings provide a vital theoretical basis and practical guide for vegetation restoration and ecosystem reconstruction in rocky desertification areas.

The Characteristics of Soil C, N, and P Stoichiometric Ratios as Affected by Geological Background in a Karst Graben Area, Southwest China

“…The classification of the severity of rocky desertification referred to the method of Jiang et al (2014) [2], which has been classified into four categories according to the rock exposure rate in China: (1) No rocky desertification with a rock exposure rate <30% of the land; (2) LRD (light rocky desertification with a rock exposure rate ranging from 30% to 50%); (3) MRD (moderate rocky desertification with a rock exposure rate ranging from 50% to 70%); and (4) SRD (severe rocky desertification with a rock exposure rate >70%).…”

“…Soil pH can affect the forms and transformation of C, N, and P elements in the soil by changing the geochemical environment and microbial abundance, community, and activity. In addition, soil with a high Ca concentration in rock desertification areas has become the most important environmental factor affecting the local plant physiological characteristics and distribution [1]. In this study, although the correlations between pH and C, N, and P stoichiometry were highly significant (zero-order correlations in Figure 5), the Pearson correlation coefficients between pH and C:P, N:P, C:AvP, and N:AvP decreased significantly when Ca was used as a control variable ( Figure 5).…”

“…Karst, which accounts for 12% of the world's total land area, is a calcium (Ca)-rich environment and a unique ecological system [1]. China has approximately 3.44 million km 2 of karst areas, including buried, covered, and exposed carbonate rock areas, accounting for 15.6% of all karst areas in the world [2].…”

Increase in leaf organic acids to enhance adaptability of dominant plant species in karst habitats

“…We found that the effect of habitat on leaf traits was associated with the differences in leaf [Ca] between the habitats (Figure 6), indicating plants are substantially affected by high soil [Ca]. Therefore, the significantly higher leaf [Ca], [Min], and [OA] in karst than in nonkarst habitats (Figure 4) partly reflects the effects of habitat properties, especially high soil [Ca] (Hao et al, 2015;Wei et al, 2018). The high leaf [OA] was likely a consequence of high leaf [Ca] in karst habitats (Triplett et al, 1980).…”

Reduced Organic Carbon Content during the Evolvement of Calcareous Soils in Karst Region

“…Karst accounts for 12% of the world's total land area [7], and China has approximately 3.44 million km 2 of karst areas, including buried, covered, and exposed carbonate rock areas, accounting for 15.6% of all karst areas in the world [8]. Karstification has a profound impact on global change.…”