Vegetation and Soil Surface Arthropods in Mediterranean Vineyards with Different Interrow Cover Crop Combinations

Interrow cover crops have been increasingly adopted in Mediterranean vineyards to improve soil conservation and other ecosystem services. However, their long-term effects on vegetation dynamics and soil surface arthropod communities remain poorly understood. A study was conducted over three sampling years (2017, 2018 and 2023) in the Douro Demarcated Region (northeastern Portugal) to evaluate, one, two, and seven years after establishment, differences associated with two sown cover crop mixtures, namely a sown legume mixture (LEG) and a sown mixture of legumes and grasses (LEGRA) and spontaneous vegetation (SPONT) in vegetation dynamics and the activity density, richness, diversity, and stability of soil surface arthropod communities. Vegetation was assessed through floristic surveys, and arthropods were sampled using pitfall traps. Vegetation composition and soil surface arthropods community structure varied among sampling years, indicating that temporal variation also contributed to differences in both communities. LEG consistently maintained the highest vegetation cover, whereas LEGRA showed the lowest plant richness. Despite species turnover, LEG and LEGRA retained their functional identity, while SPONT exhibited greater temporal variation in floristic composition. Cover crop treatments were associated with differences in soil surface arthropod activity density, diversity, and community stability. LEGRA showed the highest activity density, whereas higher diversity and evenness were observed in LEG. SPONT presented intermediate values, differing significantly from LEGRA only in Shannon Wiener diversity index. All treatments maintained a relatively balanced trophic structure, suggesting a potential for natural regulation of herbivore population. Vegetation cover and plant richness were positively associated with soil surface arthropod diversity, highlighting the importance of vegetation characteristics for that communities in Mediterranean vineyards.