Abstract: Global species losses are being exacerbated by climate change and growing anthropogenic impacts, and pose a critical threat to ecosystem function and processes. Yet, because ecosystems are noisy and measurement instruments are limited, spurious trends frequently are captured, making it difficult to separate genuine signals of change. We previously developed an analytical approach that mines long term and legacy data to detect frequency, magnitude, and other characteristics of spurious trends within that type of data, and found that in single-population studies, spurious trends were common in short (< 5 year) observation periods, and populations occurring in more thermally heterogeneous environments were more prone to spurious trends. To better understand how patterns of change (and noise) propagate through trophic levels, we developed an extension of our previous tool that allowed us to directly examine trends across temporal resolutions at multiple trophic levels, as well as quantify lags and asynchronies between trophic levels.et.. This investigates how different trophic levels synchronize with one another and additionally examines the challenge of defining synchrony, which is generally how fluctuations within one population correlate with other populations, and what results would need to occur in order to justify synchronization. This project used data from the US Long Term Ecological Research data repository. We identified four different LTER sites meeting our criteria of long term and continuous data collection of three interacting trophic levels,with 12 years of overlapping data across the study sites. Consistent with previous work, when considered individually, most time series included in the present study reached a convergent population trend within 10 years. However, when evaluating convergent trends between trophic levels, patterns were less defined, which can be explained by differing ecological traits between and at each of the trophic levels. Similar to examining a single trophic level, studying tritrophic trends also requires a study duration larger than what is standard to truly understand the synchronies across trophic levels, and may require even greater context to interpret when any of these trophic levels are subject to transitory dynamics. Among patterns of synchrony, we observed lags between population trends of upper and lower trophic levels. By researching the population dynamics of trophic levels on smaller scales like it is done in this study, inferences are made regarding biodiversity trends and implications over time in an increasingly anthropogenically impacted world.
