Relationship between leaf mineral elements and soil nutrients of Barringtonia racemosa and its growth response in different community types

To investigate the variation in mineral element contents in leaves and rhizosphere soil of Barringtonia racemosa across different community types, and to analyze the correlation between mineral elements and soil factors, so as to provide a scientific basis for the management and conservation of B. racemosa growth in different habitats.

Three community types along the Tiaofeng river in Guantian village, Suixi County, Zhanjiang City were selected: a pure B. racemosa community (T1), a mixed Acrostichum aureum-B. racemosa community (T2), and a mixed Sonneratia apetala-B. racemosa community (T3). Soil physicochemical properties, growth traits (tree height and diameter at breast height, DBH), and mineral element contents in leaves and rhizosphere soil were measured. Principal component analysis (PCA) was employed to explore the relationship between leaf and soil mineral elements and their variations among communities.

1) Significant differences were observed in soil properties and mineral elements among the communities. Soil pH, salinity, and available potassium (AK) were significantly higher in T2 and T3 than in T1 (P < 0.05). Soil organic carbon, total nitrogen (TN), total potassium (TK), calcium (Ca), and iron (Fe) were significantly higher in T3 than in T1 and T2 (P < 0.05); 2) Soil mineral elements significantly influenced the growth of B. racemosa. The pure community (T1) showed the highest leaf total phosphorus (TP), sodium (Na), iron (Fe), and manganese (Mn) contents, as well as significantly greater tree height and DBH, indicating that lower interspecific competition contributed to its superior growth; 3) PCA revealed that PC1(69.04% variance explained) and PC2(24.77%) collectively accounted for 94.81% of the total variance. PC1 was positively driven by TP, Fe, Mn, DBH, and tree height, while PC2 showed significant positive correlations with TK, magnesium (Mg), and zinc (Zn). The T1 community scored highest in comprehensive evaluation (T1> T3> T2), reflecting its soil nutrient advantages and low competitive pressure. High organic carbon and TN in T2 did not mitigate the inhibitory effect of high Na (salinity), and although T3 had higher Ca and K contents, strong competition from S. apetala restricted B. racemosa growth. PCA further identified P, Fe, Mn, K, Mg, and Zn as key promoting factors, while organic carbon, TN, and Na exerted context-dependent limiting effects.

Significant differences in mineral element contents were detected in both leaves and rhizosphere soil of B. racemosa across different communities. Soil pH, salinity, available potassium, and sodium were key limiting factors. Resource competition from A. aureum and S. apetala in mixed communities (T2 and T3) suppressed B. racemosa growth. The growth variation was influenced by both species competition and topographic conditions. PCA effectively revealed inter-community differences, providing a scientific basis for the management of B. racemosa.