DOI: 10.5061/dryad.k3j9kd5fh
title: Establishment from seed is more important for exotic than for native plant species

description: Climate change has initiated the movement of both native and non-native
 (exotic) species across the landscape.  Exotic species are
 hypothesized to establish from seed more readily than comparable native
 species.  We tested the hypothesis that seed limitation is more
 important for exotic species than native grassland species.  We
 compared seed limitation and invasion resistance over three growing
 seasons between 18 native and 18 exotic species, grown in both
 monocultures and mixtures in a field experiment.  Half of the
 plots received a seed mix of the contrasting treatment (i.e. exotic
 species were seeded into native plots, and native species were seeded into
 exotic plots), and half served as controls. We found that 1) establishment
 in this perennial grassland is seed limited, 2) establishment from seed is
 greater in exotic than native species, and 3) community resistance to
 seedling establishment was positively related diversity of extant species,
 but only in native communities.  Native-exotic species diversity
 and composition differences did not converge over time.  Our
 results imply that native-to-exotic transformations occur when diversity
 declines in native vegetation and exotic seeds arrive from adjacent sites,
 suggesting that managing for high diversity will reduce transformations to
 exotic dominance.
description: Experiment established in 2008 compared all native vs. all exotic
 plant communities and monocultures, with and without summer irrigation
 (128 mm per year), called MEND (Maintenance of Exotic vs. Native
 Diversity).  In October 2016, a seed addition experiment was conducted on
 this experiment. Number of seedlings were measured in each plot (seeded
 and controls), number of plant species was recorded over time.
description: # Establishment from seed is more important for exotic than for native
 plant species Four data
 sets, all csv files. **CSV File Name - repeated_S_with19.csv.** Block:
 October 2007, or March 2008 planting date Column: Plot location on grid
 Row: Plot location on grid Origin: Native or Exotic REP: Replicate Irrig:
 Irrigated with 128 mm of water or 0 mm of water Seed: Seeds added or not
 draw: Replicate draw S708: Richness in first week in July, 2008 S1008:
 Richness in October 2008 S609: Richness in June 2009 S1009: Richness in
 October 2009 S610: Richness in June 2010 S1010: Richness in October 2010
 S1011: Richness in October 2011 S612: Richness in June 2012 S1012:
 Richness in October 2012 S613: Richness in June 2013 S1013: Richness in
 October 2013 S614: Richness in June 2014 S1014: Richness in October 2014
 S615: Richness in June 2015 S1015: Richness in October 2015, when seed
 additions were made S616: Richness in June 2016 S1016: Richness in October
 2016 S617: Richness in June 2017 S1017: Richness in October 2017 S618:
 Richness in June 2018 S1018: Richness in October 2018 S619: Richness in
 June 2019 **CSV File Name: mixtures.csv** Data collected from mixture
 plots. Columns: Added: Seed added or not Block: Plot location on a grid
 Column: Plot location on a grid Row: Plot location on a grid Origin:
 Native or Exotic Irrig: Irrigated with 128 mm per year or 0 mm per year
 draw: Replicate draw Date: Month and year Rich: Number of plant species
 AddRich: Number of new plant species from seed additions Count: Number of
 seedlings in plot TotalRich: Total species richness **CSV File Name:
 Monocultures.csv** Data collected from monoculture plots. Columns: id:
 Observation number Block: Planted in October 2007 or March 2008 C: Plot
 location in a grid (Column) R: Plot location in a grid (Row) Origin:
 Native or Exotic Irrig: Irrigated with 128 mm or 0 mm per year Added:
 Seeds added or not Pair: Species phylogenetic pair Treat: Species added
 (seeds added) or not (no seeds added) Ct617: Seedling count in June 2017
 Ct1017: Seedling count in October 2017 Ct618: Seedling count in June 2018
 Ct1018: Seedling count in October 2018 Ct619: Seedling count in June 2019
 **CSV file name nbe.csv ** **Columns:** Plot: Observation number Block:
 Planted in Oct. 2007 or March 2008 C: Plot location in a grid (Column) R:
 Plot location in a grid (Row) Origin: Native or Exotic Irrig: Irrigated
 with 128 mm or 0 mm per year Date: Month and Year Draw: Replicate draw
 Added: Seeds added (Y) or Not (N) sumO: sum seedlings observed sumE:
 expected number of seedlings OvsE: sumO - sumE sign: sign lnOvsE: ln
 transformed OvsE lOvsE: ln transformed OvsE with original sign