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Individual study: Conservation of the critically endangered Bakersfield saltbush Atriplex tularensis, Kern Lake Preserve, California, USA

Published source details

Freas K.E. & Murphy D.D. (1988) Taxonomy and the conservation of the critically endangered Bakersfield saltbush, Atriplex tularensis. Biological Conservation, 46, 317-324

Summary

The Bakersfield saltbush Atriplex tularensis is a salt-tolerant, monoecious annual of an alkali plant community once widespread in southern San Joaquin Valley, California. Due to extensive conversion of habitat to agriculture, only a single population now persists at Kern Lake Preserve. In 1986, despite much rain and flooding (expected to favour germination and survival), only 89 seedlings were found and most died without setting seed. Seed bank status, germination requirements and artificial propagation were investigated to determine the most effective conservation strategy. Results of propagation trials are summarised here.

In June 1987, 13 poorly developed plants (<3 cm tall) insufficiently mature to be identified as A. tularensis or A. serenana (a widespread, closely related species) were discovered. Due to dryness of the soil it was unlikely that any would survive (eight already showing signs of senesce) therefore, they were transferred with soil to a greenhouse (Stanford University). Plants were watered daily, exposed to natural light, and a 14/10h light/dark schedule (under 'Gro Lux' bulbs). Temperatures were similar to field conditions (15-32°C).

Precise determination of germination requirements requires that a large number of seeds are exposed to various combinations of soil moisture, temperature and pretreatment conditions. In this present study, no such experiment was undertaken. Seeds from 30 mature were planted in October 1987 in sterile soil, watered daily for 30 days and subject to ambient greenhouse temperatures. There was no pre-treatment to enhance germination prior to planting.

 

The eight individuals that had begun to senesce prior to transplanting all died during the subsequent two weeks. The five survivors however grew well, branching extensively (50-100 stems/plant), with inflorescences on most branches and numerous axillary flowers. Thousands of fruits were produced. In the germination trial, 15 of 30 seeds germinated, all in the first 8 days.
Results suggest that provision of water to Kern Lake Preserve are key to Bakersfield saltbush conservation and this will help safeguard the entire alkali sink scrub plant community.
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