Rainfall during the first three years of the Land Retirement Demonstration Project was below average. In contrast, winter rainfall for the 2002-03 growing season was predicted to be fairly high (i.e., mild El Niņo conditions were predicted). In anticipation of these wetter conditions, an experiment-the Section 23 Restoration Trial-was developed in which various species could be evaluated during an above-average rainfall year. In this experiment, two species mixtures were compared. The first mixture, the "traditional mix" was composed of a subset (9 of 13) of the species that were imprinted on the HRS Plots. The second mixture, the "experimental mix" incorporated various species that had been used to some success in other restoration trials at Tranquillity, augmented by a few species that had demonstrated restoration potential elsewhere in California.

The Section 23 restoration trial occupied an area of approximately 28.3 ha (70 ac). This area had received some weed control and was the largest contiguous block of "unassigned" land remaining on the Tranquillity site. Plots were ca.3.0 ha (7.5 ac) in size; a complete randomized block design was applied, with treatments replicated four times. Micro-topographic contours (berms) were installed in all plots. Berms were aligned east to west and were the full length of the plot. Berm spacing was 30-ft, such that part of a flat and half of a berm would be imprinted in a single pass and with a final pass through the middle of a flat, there would be no overlap in seeding. In this manner, the berms were also compacted slightly. Berms were constructed on 11 December 2002. Imprinting was scheduled to follow immediately thereafter; however, rainfall during this period precluded the use of heavy equipment throughout December and imprinting was postponed until 28-31 January 2003.

Table 1. Species planted in the Section 23 Restoration Trial, including Family, common name, and seeding rate. Seeding rates are expressed in gross (i.e., not lbs. pure live seed) pounds per acre. Key to treatments: TRAD, Traditional; EXP, Experimental.

TaxonFamilyCommon NameTRADEXP
Allenrolfea occidentalisChenopodiaceaeiodinebush9.49.4
Aristida ternipes var. hamulosaPoaceaeSpreading threeawn-6.1
Atriplex polycarpaChenopodiaceaeallscale saltbush10.34.7
Bromus carinatusPoaceaeCalifornia brome8.5-
Frankenia salinaFrankeniaceaealkali heath6.2-
Gilia tricolorPolemoniaceaebird's-eye gilia-20.5
Grindelia camporumAsteraceaegumplant-11.8
Hemizonia pungensAsteraceaecommon spikeweed1.51.4
Lasthenia californicaAsteraceaeCalifornia goldfields29.235.4
Lupinus bicolorFabaceaebicolored lupine-3.4
Nassella pulchraPoaceaepurple needlegrass-8.9
Phacelia ciliataHydrophyllaceaeGreat Valley phacelia-1
Sporobolus airoidesPoaceaealkali sacaton15-
Suaeda moquiniiChenopodiaceaebush seepweed1.9-
Vulpia microstachysPoaceaesmall fescue18.2-

Page created: March 1, 2005; Last updated: Dec. 20, 2005