Effects of high Ca and Mg stress on plants water use efficiency in a Karst ecosystem

Abstract

Background Karst ecosystems are widely distributed in the world, with one of the largest continuous Karst landforms in Southwest China. Karst regions are characterized by water shortage, high soil calcium (Ca) and magnesium (Mg) content, and soil nutrient leaching, resulting in drought stress and growth limitation of plants. Methods This study compared nitrogen (N), phosphorus (P), potassium (K), Ca, and Mg of herbaceous and woody plants in a small Karst ecosystem in Southwest China. The indexes of water use efficiency (WUE) were calculated to identify the drought stress of plants in this Karst ecosystem. Meanwhile, the relationship between Ca and Mg accumulation and WUE was evaluated in herbaceous and woody plants. Results Herbaceous plants showed a higher content of leaf N (13.4 to 40.1 g·kg−1), leaf P (2.2 to 4.8 g·kg−1) and leaf K (14.6 to 35.5 g·kg−1) than woody plants (N: 10.4 g to 22.4 g·kg−1; P: 0.4 to 2.3 g·kg−1; K: 5.7 to 15.5 g·kg−1). Herbaceous plants showed a significantly positive correlation between WUE and K:Ca ratio (R = 0.79), while WUE has a strongly positive correlation with K:Mg ratio in woody plants (R = 0.63). Conclusion Herbaceous plants suffered from nitrogen (N) limitation, and woody plants were constrained by P or N+P content. Herbaceous plants had higher leaf N, P, and K than woody plants, while Ca and Mg showed no significant differences, probably resulting from the Karst environment of high Ca and Mg contents. Under high Karst Ca and Mg stress, herbaceous and woody plants responded differently to Ca and Mg stress, respectively. WUE of herbaceous plants is more sensitive to Ca stress, while that of woody plants is more sensitive to Mg stress. These findings establish a link between plant nutrients and hydraulic processes in a unique Karst ecosystem, further facilitating studies of the nutrient-water cycling system in the ecosystem.

Driving Forces and Ecological Restoration Revelation in Southwest China Based on the Divergence Characteristics of Ecosystem Compound Use Efficiency

“…Meanwhile, it integrates several key factors of the watercarbon-light cycle, including soil moisture, photosynthetic rate, plant biomass, carbon assimilation and respiration, etc., making it more representative than a single index. Until now, existing studies have employed quantitative statistical methods [13] and partial correlation analyses [14] to uncover how factors such as climate [15,16], geological conditions [17], and nutrient absorption affect resource use processes [18][19][20]. However, these studies primarily emphasized the natural driving forces, and the pattern of the water, carbon, and light use efficiency is the outcome of interactions between natural ecological and socio-cultural processes at different spatiotemporal scales; that is, human activities, primarily land use change, and ecological restoration also have an important influence on the water-carbon-light cycles [21][22][23].…”