Plant: consumer interactions as cause and consequence of long-term BEF relationships

Biodiversity is essential for providing ecosystem services and functions, yet species are being lost at an alarming rate. While species loss has immediate effects on ecosystem functioning, long-term species interactions strengthen biodiversity's role over time. Habitat loss is difficult to reverse, as ecosystem recovery can take decades due to their historical legacies. Shifts in biodiversity-ecosystem functioning (BEF) relationships are frequently observed in plants and may cascade to consumers, with plant-consumer feedbacks potentially enhancing plant diversity effects. In this dissertation, I explored temporal trends in plant diversity effects on consumer communities and their functions (Manuscript 1, Manuscript 5), examined mechanisms driving this variability (Manuscript 1, Manuscript 2, Manuscript 4), analysed consumer feedback effects on plants (Manuscript 2), and provided a comprehensive list of consumer species traits (Manuscript 3). In summary, I demonstrated that the effects of plant diversity on consumers and their functions strengthen over time, primarily through the interplay of plant traits, community structure, feedback mechanisms, and climate, rather than plant productivity alone. Specifically, feedback effects appear to prevent consumer loss at high plant diversity while accelerating declines at low diversity. These concerning results highlight the urgent need to integrate long-term dynamics into conservation strategies, as declines in consumer populations cascade through food webs, restrict energy flows from plants to higher trophic levels, and reduce ecosystem multi-functionality and stability. However, significant gaps remain in our understanding of how variations in consumer communities and their functions are shaped by plant-consumer interactions and their interplay with climate. Ultimately, addressing these gaps is crucial to halt the ongoing biodiversity crisis and ensure the continued provision of vital ecosystem services.