Experimental reintroduction and restoration outplantings from 2003-2006 have included the greenhouse propagation of Tahoe yellow cress and the installation of over 7,500 container-grown plants at 11 sites around the lake. During that time, Lake Tahoe has gone from a low lake elevation of 6,222.6ft [LTD] (Lake Tahoe Datum) in the fall of 2004 to the maximum legal limit of 6,229.1 ft in July, 2006. This tremendous fluctuation has made ideal research conditions for investigating the effects of lake level on many aspects of Tahoe yellow cress demography and habitat characteristics.
Obtain technical reports on research activities from the TYC Virtual Library.
- Avalanche beach, Emerald Bay (CDPR)
- Ebright Beach (USFS)
- Hidden Beach (NDSL)
- Nevada Beach (USFS)
- Lester Beach, D.L. Bliss State Park (CDPR)
- Pope Beach (USFS)
- Sand Harbor (NDSL)
- Taylor & Tallac Creek, Baldwin Beach (USFS)
- Upper Truckee East (CTC)
- Zephyr Cove (USFS)
- Can TYC occupy any site around the lake that provides habitat?
- Are there ecosystem factors that affect TYC performance within a site or microhabitat?
- Can TYC populations be created or enlarged in order to restore the species?
- Can any TYC genotype or gene pool perform equally well at any appropriate site?
- Can TYC microhabitats be found or created that won't conflict with shoreline activity?
- Overall site suitability, as indicated by the performance of outplanted TYC, tended to support the priority site rankings presented in the CS, i.e. performance at Core and High Priority Restoration Sites (Avalanche, UTE, Tallac, Taylor, Nevada) exceeded that at Medium, Low and Unranked Priority sites (D.L. Bliss, Ebright, Hidden Beach, Pope, Sand Harbor). Therefore managers cannot assume site equivalency.
- Plant performance varies in microhabitats at different distances and elevations above Lake Tahoe. In general, lower elevation microhabitats (those closer to the shoreline) supported better plant performance than did high elevation microhabitats.
- Data from 2006 and past years suggest that genetics do not have a detectable role in the performance of outplanted Tahoe yellow cress.
- Outplantings in 2003 to 2005 may have successfully created new populations and enhanced existing ones. However, high lake level in 2006 inundated all of the persisting two and three year-old outplanted individuals.Observations during 2007 suggest that plants from the submerged cohorts may have reappeared at 2 of the 8 sites that experienced inundation. Although it is not possible to determine the exact mechanism for a site,the reappearances could be from four sources:
1) emergence of rootstock from naturally occurring plants or outplanted founders that survived inundation
2) the progeny of seed subsequently produced by those naturally occurring plants or founders
3) from seed deposited from offsite or
4) some combination of the three. - Estimated annual seed production in the outplanting from 2003 to 2006 suggest that these cohorts produced nearly 1.4 million seed over the last four years. A lack of information on the seed bank dynamics of the species makes it impossible to speculate on the fate of these seeds, but the sheer numbers suggest that the outplantings must have made some significant contribution to the persistence of local subpopulations.
Obtain technical reports on research activities from the TYC Virtual Library.