Ecological processes affecting weed communities in Nova Scotian wild blueberry fields

Ecological gradients and processes are known to play a key role in determining weed community composition in agroecosystems. The present study investigated whether climatic, topographical, and soil edaphic factors were associated with weed species occurrences and abundances in wild blueberry fields. A plant survey of 165 wild blueberry fields in the Canadian province of Nova Scotia was conducted and combined with climatic, topographical, and soil edaphic data collected from Federal databases. Linear mixed models and multivariate analyses were used to disentangle the relationship between weed species occurrences, species-species interactions, and environmental covariates in wild blueberry fields. The surrounding weed species diversity in fields had the strongest association with wild blueberry stem density with increasing species richness driving a decrease in stem density regardless of weed density. Weed diversity was affected by accumulated growing degree days, topographical position index, and topographical wetness index. The occurrence and abundance of many common weed species was positively associated with wild blueberry and accumulated growing degree days. The relative importance of niche-based assembly rules for overall weed species composition in wild blueberry fields, however, was minimal. Yet several species showed high correlation with environmental cofactors. These results stress the importance of local stochasticity and species-species interactions in determining weed communities in wild blueberry fields and the challenge with predicting weed communities in perennial agroecosystems.