Abstract
Cypress (Cupressus funebris Endl.) is an important tree species in the subtropical regions of China; it is also a major tree species for afforestation and forest land restoration under low-fertility soil conditions. Cypress is considered a calcicolous tree, and its growth and development can be promoted significantly by exchangeable calcium (Ca2+) in the soil. However, most of the subtropical regions have low-fertility acidic soils, in which Ca2+ gradually becomes a limiting element for Cypress growth. In this study, different concentrations of Ca2+ fertilizer were added under fertile soil (3 g·kg-1 NPK fertilizer added) and low-fertility soil (0 g·kg-1 NPK fertilizer added) conditions. Cypress clones responded differently to Ca2+ addition in different soil conditions. The seedling height and dry matter quality of Cypress in fertile soil were significantly greater than those in low-fertility soil, but plant height and dry biomass did not differ significantly among Ca2+ treatments. The accumulation efficiencies of nitrogen (N), phosphorous (P) and Ca all differed significantly among the Ca2+ treatments. In low-fertility soil, the addition of 3 g·kg-1 Ca2+ significantly promoted development of roots 0.5–2 mm in diameter, and both the C1 and C2 clones achieved their highest N, P and Ca accumulation efficiencies. When the Ca2+ concentration increased to 6 g·kg-1, the seedling height, dry matter quality and root development were lower than those of the 3 g·kg-1 Ca2+ treatment. In the fertile soil, the addition of Ca2+ significantly inhibited development of roots 0.5–1 mm in diameter. The highest N accumulation efficiency was achieved under the 0 g·kg-1 Ca2+ treatment, and the highest Ca accumulation efficiency was achieved under the 6 g·kg-1 Ca2+ treatment. Seedling height, root dry weight, roots 0–1.5 mm in diameter and Ca accumulation showed a significant interaction effect between NPK fertilizer and Ca2+. Therefore, Ca accumulation was more efficient in low-fertility soils. Under low-fertility soil conditions, the addition of CaSO4 can promote the root development of seedlings and advance and prolong the fast growth period of seedling height. Cypress clones can be used as an important tree species for afforestation under low-fertility soil conditions, especially under calcareous soil conditions.
Highlights
Calcium (Ca2+) is an essential nutrient required for plant growth and development (Kudla et al, 2010; Rashid et al, 2020)
In the low-fertility soil, the fast growth period for seedling height began at 76 days after the addition of 3 g kg−1 Ca2+ (T5); the beginning date was advanced by 5 days, while the duration of the fast growth period was prolonged by 6 days compared to that of the 0 g kg−1 Ca2+ (T4) treatment
The fast growth period for seedling height began at 82 days after the addition of 6 g kg−1 Ca2+ (T6); the beginning date was delayed by 1 day, while the duration of the fast-growth period was prolonged by 4 days compared with that of the 0 g kg−1 Ca2+ treatment (T4)
Summary
Calcium (Ca2+) is an essential nutrient required for plant growth and development (Kudla et al, 2010; Rashid et al, 2020). The root is an important organ of plants for resource acquisition, and the spatiotemporal distribution of plant roots determines the amounts of water and nutrients that are absorbed for photosynthesis and harvest products (Hodge, 2004; Mommer et al, 2012; Rogers & Benfey, 2015). Fine roots are defined as all roots ≤ 2 mm in diameter, and these roots are important organs that allow trees to absorb water and nutrients (Meinen et al, 2009). Absorptive fine roots represent the most distal roots, which are involved primarily in the acquisition and uptake of soil resources, whereas transport fine roots are more common in the branching hierarchy and serve primarily structural and transport functions with some additional capacity for storage. It is assumed that roots ≤ 1.0 mm in diameter are absorptive roots and roots
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