Land Retirement Demonstration Project

Native plant restoration through seeding method and soil type study

Presented To:

Society for Ecological Restoration, California (SERCAL)
Bass Lake, California 2005

by

Emily M. Magill1¹, John V. H. Constable¹, and Nur P. Ritter²
1. Department of Biology, California State University Fresno, CA.
2. C.S.U. Stanislaus, Endangered Species Recovery Program, Fresno, CA.

Abstract

Establishment of native plant communities on retired agricultural soils in the San Joaquin Valley has been problematic due to lack of effective seeding strategy and invasive species dominance. During the 2003-2004 field season, three seeding methods (broadcasting, drilling, and imprinting) were evaluated for their establishment success. We hypothesized that broadcasting would result in the greatest establishment as it most closely mimicked the natural history of many native species. Due to unusually low rainfall, establishment of just two species (Phacelia ciliata and Hemizonia pungens) warranted monitoring. Phacelia had highest percent cover when imprinted (41.5%) and broadcast (40.1%) over being drilled (33.7%; p=0.04). Hemizonia grew more poorly than Phacelia; percent cover was significantly greater when broadcasted (4.4%) as opposed to being imprinted (2.4%; p = 0.02) but had no significant difference from being drilled (4.1%; p=.33). In a greenhouse trial, the photosynthetic and growth rates of Phacelia and an invasive grass (Bromus madritensis) were compared. We hypothesized that Phacelia would exhibit optimal growth on native soil and Bromus on retired agricultural soil, respectively. Phacelia and Bromus were planted in a 2x2 experimental design incorporating the two soil types. Bromus had 400% higher photosynthetic rates than Phacelia on native soils (p> 0.01), but showed no significant difference from Phacelia on retired soil. Bromus had root to shoot ratios 220% larger than Phacelia (p> 0.01). Dominance of Bromus in many field locations may result from the high R/S ratio facilitating water uptake and early season germination which may constrain growth of native species such as Phacelia.