https://doi.org/10.25338/B8S63T
Data collected by Steven Haring, UC Davis sharing@ucdavis.edu
Design and oversight by Amélie Gaudin and Brad Hanson

Description of the data and file structure

EXPERIMENT DESCRIPTION: The data in this dataset come from plant community surveys undertaken within a cover cropping experiment that took place in commercial almond orchards in Central California, USA from 2018 to 2020. The experiment was set up at three locations, one each in Tehama, Merced, and Kern Counties in California. Each location had four repetitions of the experiment at each year, and the experiment was repeated at each location (i.e. six site-years total, with two years at each of three locations). Each site had two cover crop treatments (i.e. pollinator, soil) and one bare ground treatment. The Kern and Merced sites also had a more intensive (i.e. all vegetation controlled) treatment.

NONE in the species column is associated with bare ground. Other values are five-character Bayer Codes, which are also known as EPPO Codes. Bayer Codes typically use the first three letters of genus and first two letters of specific epithet. The Weed Science Society of America maintains a Composite List of Weeds, which may be used to verify Bayer codes.

In this study, the pollinator mix was planted with SINAL, BRSNC, and RAPSR. The soil mix was planted with SINAL, RAPSR, VICVI, TRFRE, and SECCE. If these cover crop species are found in a plot from a different treatment, they are likely to be volunteer plants or resident plants from the existing soil seed bank. All other species are considered to be weedy or resident vegetation.

DETAILED METHODS: Data collection was repeated seasonally throughout each year of the experiment. Each experimental plot at each survey timing was surveyed with 50-meter long point-intercept transects. Each plot had a transect across the middle of the plot (i.e. alley) and one transect in the tree strip, where cover crops are not planted and intensive herbicide programs are applied. Ground cover was identified at each of 50 points evenly spaced along each transect (i.e. observations within each zone of each plot at each timing should sum to 50). The intercepts column shows how many points along the transect were associated with the vegetation type identified in the species column.

DATA COLUMNS:

• Year: The year in which data were collected the field
• Month: The month in which data were collected the field
• Day: The day in which data were collected in the field
• ObservationTiming: The relative timing (season) in which data were collected. Simpler to use than dates, because we were interested in seasonal variation in plant communities
• Location: The county from which data were collected, corresponding with one of our three experimental sites (Kern, Merced, or Tehama Counties in California, USA)
• Rep: The replicate or block. There were four replicates at each site. Replicates were numbered arbitrarily, and replicate IDs stayed consistent throughout the experiment
• Treatment: The groundcover treatment applied to each plot
• OrchardZone: The management zone where data were collected, either the STRIP at the base of the trees (associated with irrigation and higher-intensity management) or the ALLEY between tree rows (covering most of the orchard area)
• Species: Lists Bayer codes (described above) identifying observed plants, or NONE to represent bare ground
• Intercepts: A count of the number of times a plant species was identified along a 50-m-long, 50-point transect