Data from: Spatiotemporal patterns of rising annual plant abundance in grasslands of the Willamette Valley, Oregon (USA)

<p dir="ltr"><b>Context</b><br>Plant communities are undergoing compositional changes that affect ecosystem function. These changes are not always uniform across the landscape due to heterogenous topographic and edaphic conditions. To predict areas most at risk of change, it is necessary to identify the landscape drivers affecting plant abundance.</p><p dir="ltr"><b>Objectives</b><br>Annual plants are increasing across the western USA, largely driven by non-native annual invasions. Here, we quantified change in annual plant abundance and identified landscape factors contributing to that change over the past 35 years.</p><p dir="ltr"><b>Methods</b><br>We focused on Willamette Valley (Oregon) grasslands because they represent a new example in this phenomenon. To understand the spatiotemporal patterns of annual plant abundances between 1986 and 2020, we combined a remote-sensing vegetation cover dataset from the Rangeland Analysis Platform with gridded soils data and topographic variables. We determined the rate of change in percent cover for each 30 × 30 m pixel and regressed cover against heat load, soil depth and sand content for > 5975 hectares to determine areas most sensitive to rising annual cover.</p><p dir="ltr"><b>Results</b><br>We found a tendency toward increasing annual cover, with a median gain of + 15% cover among significantly increasing pixels. However, change was uneven across the landscape, with annual cover increasing markedly in areas with high heat load and shallower soils.</p><p dir="ltr"><b>Conclusions</b><br>We identified steep, south-facing slopes as being particularly sensitive to rising annual cover. Annual plant invasions may be lagging in this region compared to elsewhere in the Western USA, but trends here suggest it may just be a matter of time.</p><p><br></p><p dir="ltr">This dataset hosted on Dryad provides all necessary variables (as .csv tables) to perform our analyses, as well as a shapefile for the study area:</p><ol><li>"<b>df_RAP.csv</b>": Annual forb and grass (AFG) and perennial forb and grass (PFG) cover data collected directly from the Rangeland Analysis Platform public datasets via Google Earth Engine. Total (herbaceous) cover was calculated by adding AFG and PFG cover.</li><li>"<b>df_ratechange.csv</b>": Rate of change data calculated from linear regressions of AFG cover against year from the "<b>df_RAP.csv</b>" dataset.</li><li>"<b>df_xvars.csv</b>": Soil and topographic variables collected/calculated directly from public platforms.</li><li>"<b>sites16shape</b>": Zipped folder containing shapefiles for the 16 study sites of interest.</li></ol><p dir="ltr">For a detailed description of the datasets, please refer to the README.txt file associated with the Dryad data.</p>