Renner, Maralyn A. .
Persistence of small populations of Sidalcea malachroides (H. & A.) Gray, Malvaceae: Seven years of survey, mitigation, and monitoring on managed timberlands in northwestern California.
SIDALCEA malachroides is a short-lived pioneer sub-shrub typically found in disturbed habitats along the northern California coast, such as on roadsides and skid roads, and in recent silvicultural thinning and clear-cut areas. Most known populations are on private timberlands subjected to periodic disturbance over the past century. The species is polygamous, with the majority of plants being either staminate or pistillate and the few perfect (hermaphrodite) plants appearing to be functionally staminate. In surveys from 1999 to 2004, 81 of the 116 groups located had 30 or fewer plants. Groups with >100 plants were only found in areas recently disturbed by logging operations. In 2005 I revisited 60 groups and classified them as either small (≤30 plants, n=49) or large (>30 plants, n=11). I recorded numbers by age class and sex, and vigor and environmental characteristics. I hypothesized that small groups were more likely to have skewed sex ratios resulting in a shortage of pollen-producing members, which would lower seed set and endanger persistence. I found a correlation between the original size of the group and the ability of that group to persist: single plants were likely to disappear, while groups of 2 or more were likely to be relocated. I found that mitigation that avoided impacts to the sites, thus allowing competing vegetation to invade, resulted in fewer plants in following years. Without factors that maintain open canopy and disturbed soils, competing vegetation crowded out most of the Sidalcea malachroides plants in as few as six to seven years. New swarms of plants have appeared in areas disturbed by logging and other land management activities wherever a seed bank existed, with high initial numbers that decreased over time from competition and shading. Without repeated disturbance, these populations are at risk of existing entirely within the seed bank.
Log in to add this item to your schedule
1 - Scotia Pacific Company, LLC., Botany Department, P. O. Box 712, 121 Main St., Scotia, California, 95565, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Tuesday, August 1st, 2006
Time: 11:30 AM