Relationship between herbicide use intensity and floristic diversity in smallholder rubber plantations in South Cameroon

Herbicides are frequently used in smallholder rubber plantations to manage weeds; however, their ecological impacts on floristic diversity in tropical agroecosystems are inadequately documented. That is why the relationship between herbicide use intensity and floristic diversity in smallholder rubber plantations in Niété, South Cameroon, was evaluated in this study. To achieve that purpose, a survey was administered to 100 producers. Floristic inventories were performed using 66 quadrats, including 33 in rubber plantations and 33 in adjacent fallows. Species richness, Shannon diversity, and Simpson index were calculated to compare plant communities between environments. The relationships between herbicide intensity and biodiversity indices were evaluated using Spearman analysis. Results revealed that most of the producers have an old rubber farm of 20.3 ± 12.6 years measuring 4.40 ± 3.96 ha. The average age of producers is 52.3 ± 13.7 years, and 25.5% of them are members of a producer association using an average herbicide application rate of 4.73 L/ha/year. Fallows had a higher species richness (13.4 ± 4.6 species) than plantations (10.5 ± 2.8), although the difference was not statistically significant (p > 0.098). Significant negative correlations were observed between herbicide intensity and species richness, Shannon diversity, and Simpson index. PCA suggested greater floristic homogenization in plantations compared with fallows. It can be concluded that increasing herbicide use intensity was linked to poorer biodiversity indices and reduced floristic homogeneity, emphasizing the need for weed-management practices for maintaining floristic diversity in smallholder rubber agroecosystems.