An experimental augmentation of Arabis koehleri var. koehleri was outplanted in fall 2007 on land owned and managed by the BLM, and has been monitored twice yearly, spring and fall. This project is designed to see if it is more effective in terms of establishment, survival and/or growth, to use seeds or small plants as founders (Guerrant, 1996; Guerrant and Kaye, 2007). Secondary questions include possible genetic effects among 55 maternal plants available for use as seed donors, as well as of habitat characteristics that were recorded at planting (e.g. slope (over 1 dm and 1 m), aspect, planting substrate, plant size), which, with potential block (replicate) effects, are intended yield information on microhabitat characteristics that might influence survival. Three people participated in the outplanting, and possible effects of planter were also examined.
The basic experimental design is a randomized complete block design (Yandell, 1997). This is a balanced design, insofar as each block has equivalent numbers and kinds of experimental units (i.e. seeds and plants). Each block (i.e. experimental replicate) was designed to be comprised of 64 Experimental Units 32 plants and 32 groups of 3 seeds, from a variable number of maternal lines. Thus, a block is comprised of a total of 128 propagules (32 plants, and 96 seeds, in 32 batches of three each). A total of 6 blocks, or replicates, were planted, each on a different ‘hill’ or rocky outcrop. Because some seeds were lost, a total of 748 propagules were planted.
By the first spring after outplanting, seventy three of the 190 plants placed out in the field (38%) and zero seeds (i.e. seedlings from seeds) were alive. Only 7 (4%) of the plants survived their first summer. Similar to the 2001 outplanting, propagule type had a profound effect on establishment and survival. Coincidentally, the summers of 2002 and 2008 were by far the driest in the period 2001 through 2008, which may have been an important causal factor in low seedling establishment and plant survivorship. Effects on survival of replicate (fall), slope 1M (fall), and substrate (spring) were seen during one monitoring period. Maternal parent (spring) and slope 1M (fall) had an effect on growth during one monitoring period. There were significant researcher effects on survival in spring and fall, and an effect on growth rate in the spring but not fall. Experience appears to have been an important contributing factor.