Assal, T. J. | Search bioRxiv

bioRxiv2025

Estimating rangeland fractional cover and canopy gap size class with Sentinel-2 imagery

Rangelands are extensive ecosystems, providing important ecosystem services while undergoing continuous change. As a result, improved monitoring technologies can help better characterize vegetation change. Satellite remote sensing has proven effective in this regard, tracking vegetation dynamics at broad and fine scales. We leveraged the spatial, spectral, and temporal resolution of Sentinel-2 satellites to estimate fractional cover and canopy gap across rangelands of the western United States. We produced annual, 10 m spatial resolution estimates of fractional cover and canopy gap size class for years 2018 to 2024. Fractional cover estimates include that of common plant functional types (annual forb and grass, bareground, littler, perennial forb and grass, shrub, tree) and select genera (including invasive annual grass species, pinyon-juniper species, and sagebrush species); canopy gap size classes include gap sizes 25 to 50, 51 to 100, 101 to 200, and greater than 200 cm. We make these data available as Cloud Optimized GeoTIFFs, organized as 75x75 km tiles covering the 17 western states of the United States.

ecology↗

bioRxiv2022

Landscape change and alien invasions drive shifts in native lady beetle communities over a century

AimUnderstanding drivers of insect population declines is essential for the development of successful conservation plans, but data limitations restrict assessment across spatial and temporal scales. Museum records represent a unique source of historical data that can be leveraged to investigate temporal trends in insect communities. Native lady beetle decline has been attributed to competition with established alien species and landscape change, but the relative importance of these drivers is difficult to measure with short-term field-based studies. Here we assessed distribution patterns for native lady beetle species over 12 decades using museum records and evaluated the relative importance of alien species and landscape change as long-term drivers contributing to changes in lady beetle communities. LocationOhio, USA. MethodsWe compiled occurrence records for 28 lady beetle species collected in Ohio, USA from 1900-2018. Incidence-based measures of taxonomic beta-diversity were used to evaluate changes in lady beetle community composition over time. To evaluate the relative influence of temporal, spatial, landscape, and community drivers on the captures of native lady beetles, we constructed negative binomial generalized additive models. ResultsWe report evidence of declines in captures for several native species, including Adalia bipunctata, Coccinella novemnotata, Hippodamia convergens, and Coleomegilla maculata. Importantly, the timing, severity, and drivers of these documented declines were species-specific. Changes in lady beetle species composition began in the 1980s, when processes of species loss/gain and turnover shifted communities towards dominance by a few alien lady beetle species. Land cover change also was associated with declines in captures, particularly for C. novemnotata which declined prior to the arrival of alien species in the state. Main conclusionsOur study documented shifts in Ohios lady beetle communities beginning in the 1980s as alien species supplanted natives. Drivers of declines in captures of native lady beetle species were highly species-specific, emphasizing that mechanisms driving population losses cannot be generalized even among closely related species. These findings also indicate the importance of museum holdings and the analysis of species-level data when studying temporal trends in insect populations.

ecology↗