The relative importance of plant-pollinator network parameters in maintaining seed productivity varies between years

Human activities have caused biodiversity loss and climate change, altering critical ecosystem functions. Numerous empirical studies have focused on the relationship between plant diversity and primary productivity or its stability. However, ecosystem functions such as pollination and nutrient cycling would be regulated by biological interactions among multiple trophic levels. Here, we examined the relationship between plant diversity, pollination attributes, and seed productivity in a biodiversity experiment conducted in Inner Mongolia in 2018 and 2019, differing in intra-annual precipitation patterns. We found that pollinator visitation frequency did not affect seed productivity in both years. In 2018, we observed that flowering plant richness and flower vulnerability had positive effects on seed productivity. In 2019, however, only network evenness had a negative effect on seed productivity. The consistent effect of pollination network structure but not visitation frequency on seed productivity across two growing seasons suggests that complementary plant-pollinator interactions rather than mass effects of pollinator visitation regulate plant reproduction in the studied system. Since the relative contributions of flowering plant richness and plant-pollinator interactions on seed productivity would vary due to intra-annual precipitation patterns, as presented here, observations across multiple years should be required to fully reveal the ecosystem consequences of plant-pollinator interactions.