PARENT SESSION
Poster Session # 15: Plant Ecology.
Wednesday, August 6 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Seedlings of desert agave grow better in sandy than in rocky soil.
Threat, Calvin1, North, Gretchen*,1, 1 Occidental College, Los Angeles, CA, USA
ABSTRACT- In the northwestern Sonoran Desert, Agave deserti occurs primarily in rocky microhabitats and only infrequently in sandy soil. A previous study indicated that the shoot growth and root production of mature agaves were greater, however, in sandy soil, suggesting that seedling growth and requirements might account for greater plant frequency in rocky soil. In one experiment, root and shoot growth were measured for seedlings in containers of field-collected sandy or rocky soil during 30 d of watering followed by 30 days without water. Seminal root length was nearly two times greater in sandy than in rocky soil at the end of 60 days, and only seedlings in sandy soil produced adventitious roots. Root dry weight was two times greater for seedlings in sandy soil, although shoot dry weights were similar. Shoot growth over the 60 days was higher for seedlings in sandy than in rocky soil, although the pattern was reversed in the last week of the experiment. Therefore, we are currently investigating the effects of more prolonged soil drying. In a second experiment, the effect on seedling growth of the shade provided by rocks was examined. Three sets of containers filled with sandy soil were planted with seedlings 1) adjacent to rocks, 2) adjacent to plastic screens of similar projected areas as rocks, or 3) unshaded. Containers were placed in full sun outdoors in late summer and fall for 45 days without watering, with rocks and screens on the south side of seedlings. Despite record-breaking heat in Los Angeles, seedling growth was not improved by shade. We are now investigating whether rocks in the soil improve seed germination and the anchorage of newly germinated seeds.
Key words: root growth, agave deserti, seedling establishment, soil type