Artemisia tridentata Salix exigua Lepidospartum sq. Populus fremontii Salix laevigata Arundo do. Floodplain scrub Floodplain herb. Salix lucida Salix ex.-Arundo Baccharis pilularis Populus balsamifera Salix lasiolepis Mixed willow forest Artemisia californica Mixed willow scrub Salix exigua-Baccharis salicifolia Introduced herbaceous Baccharis salicifolia Mixed riparian scrub HIGH RELATIVE ELEVATION INLAND NOT RECENTLY FLOODED GAINING COASTAL LOSING RECENTLY FLOODED LOW RELATIVE ELEVATION The lower Santa Clara River and its floodplain have been significantly altered by flood control, land use pracces, and invasion by Arundo donax that have disrupted natural processes and resulted in riparian habitat loss. Despite these alteraons, the lower river presents a unique opportunity to conserve and restore remaining riparian funcons and ecosystems. To this end, the California State Coastal Conservancy is establishing the Santa Clara River Parkway by acquiring and enhancing floodplain habitat and flood-prone property. This poster presents a subset of the analycal tools, understanding of vegetaon dynamics and physical process linkages, and Arundo donax (giant reed) treatment and other strategies developed and used to assist with acquiring, managing, and restoring Parkway lands. BACKGROUND For more informaon, please visit: www.santaclarariverparkway.org 0 10 20 30 40 50 1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Water Year Precipitation (inches) Dry Years Wet Years 0 10 20 30 40 50 1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Water Year Precipitation (inches) Dry Years Wet Years 0 10 20 30 40 50 1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Water Year Precipitation (inches) Dry Years Wet Years a) b) 0 25,000 50,000 75,000 100,000 125,000 150,000 175,000 200,000 Salix lasiolepis Baccharis pilularis Artemisia californica Artemisia ca- Eriogonum fasc Mixed willow forest Mixed willow scrub Salix exigua - Baccharis salic Mixed riparian scrub Populus balsamifera Mixed scrub Non-native grasses and forbs Salix lucida Eucalyptus spp. Baccharis salicifolia Salix exigua - Arundo donax Riverwash scrub Riverwash herbaceous Arundo donax Mixed riparian forest Salix laevigata Floodplain wetland Lepidospartum squamatum Salix exigua Artemisia tridentata Populus fremontii Tamarix spp. Distance from river mouth (ſt) Treat arundo in the spring/summer following major floods to take advantage of the removed biomass. Control arundo in an upstream to downstream direction and from tributaries. Control arundo in and adjacent to fire-prone shrub lands. In monospecific stands of arundo, or where it occurs with immature native vegetation, use more economical mowing techniques to remove biomass prior to treatment. Use hand-removal techniques around mature native trees and patches of native vegetation to enhance ability of native vegetation to recruit naturally after treatment. The vegetaon dynamics-physical process linkages described above, as well as recent research by Coffman et al. (2010) on the ecology and impact of arundo on the lower Santa Clara River, provides guidelines for priorizing arundo treatment projects: Promote and implement sensible revegetation The nature of flooding and vegetaon reset along the lower river should determine the area where acve planng is implemented, to avoid the loss of expensive acve revegetaon efforts. Where acve planng is reasonable, the riparian dynamics analysis results can be used to inform select plan species that are most likely to be successful at a given site. Allow natural recruitment in the active floodplain. Focus active revegetation in areas not subject to frequent, resetting floods. Actively revegetate sites following arundo removal. Differences between the coastal fog belt and the arid inland porons of the watershed are at least partly responsible for the correlaon between distance from river mouth and plant species distribuons, although arundo occurs throughout the watershed. Riparian vegetaon along the lower Santa Clara River is sub- ject to infrequent but dramac resets during large flood events, parcularly during El Niño-Southern Oscillaon (ENSO) events, which are characterized by relavely high rainfall and, as a result, high flood magnitudes. (LEFT) Riparian vegetation conditions before (June 2002), immediately after (February 2005), and nine months following the 2005 high-flow event (September 2005). (RIGHT) Average time since last flood (± 1 SE) of vegetation alliances in the analysis area. Time since last flood and relave elevaon above the channel were two of the strongest correlates with vegetaon alliance distribuon. This sug- gests that the extent and distribuon of riparian vegetaon is closely linked to the dramac scouring of vegetaon during ENSO cycles, and the progression of seral stages thereaſter. Arundo is more common on surfaces that have been flooded within the past 40 years. Vegetation Distribution Correlations Canonical correspondence analyrsis (CCA) was used to idenfy the environ- mental variables most affecng the distribuon of vegetaon alliances (list- ed below). Univariate analysis was then used to examine differences in re- laonships based on the most important environmental variables idenfied through CCA. This analysis idenfied linkages between physical processes and the establishment and maintenance of riparian vegetaon and assisted in predicng how riparian vegetaon may establish and persist on restored floodplains within the study area. Linking Vegetation Dynamics with Physical Processes to Develop Arundo Control and Riparian Restoration Strategies for a Semi-arid River and its Floodplain Zooey Diggory 1* , Bruce Orr 1 , Amy Merrill 1 , Gretchen Coffman 2 , William Sears 1,3 , and Peter Brand 4 INFORMED ARUNDO TREATMENT and RESTORATION STRATEGIES ANALYTICAL TOOLS Accurate and current mapping of riparian vegetaon, including invasive species, was a crucial first step in river corridor manage- ment and restoraon planning. This project followed the State of California standard vegetaon classificaon system, mapping to the vegetaon alliance level, and included focused percent-cover mapping for invasive arundo and tamarisk. Changes in the extent of riparian veg- etaon along the lower Santa Clara River were quanfied by mapping highly vegetated, parally vegetated and scoured areas on overlays of aer- ial photographs taken soon aſter six major floods. 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 1938 1969 1978 1992 1995 2005 Scoured Channel Bed Partially Vegetated Floodplain Highly Vegetated Floodplain 0 10 20 30 40 50 60 70 80 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 Percent Vegetated Flood Magnitude (cfs) Acres Percent Vegetated Flood Magnitude (cfs) Year 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 11,000 12,000 13,000 14,000 15,000 1938 1969 1978 1992 1995 2005 Scoured Channel Bed Partially Vegetated Floodplain Highly Vegetated Floodplain 0 10 20 30 40 50 60 70 80 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000 180,000 Percent Vegetated Flood Magnitude (cfs) Acres Percent Vegetated Flood Magnitude (cfs) Year Year Flow (cfs) Flood Recurrence Interval 1938 120,000 14 year 1969 165,000 24 year 1978 102,200 11 year 1992 104,000 12 year 1995 110,000 13 year 2005 136,000 16 year Vegetation Mapping Climate Flood Dynamics Arundo has invaded, and in many areas replaced, nave riparian vegetaon in the watershed. In addion to reducing riparian habitat quality and quanty, accumulated arundo biomass increases the suscepbil- ity of the lower Santa Clara River riparian corridor to fire, and post-fire condions further promote arundo growth rates by elevang nutrient levels and eliminang compeon from nave species (Coffman et al. 2010). Floodplain Development Our historical flood mapping demonstrates the dramac effect of le- vees and development in constraining the floodplain and liming ri- parian vegetaon. In the lowest reaches of the river where levees are most extensive, the riparian corridor has been reduced by nearly 70% compared with condions in 1938. Plant communies differ between gaining and losing groundwater reaches, with species such as Salix (willow) and Populus (coonwood) occurring more frequently in gaining reaches, and Artemisia tridentata (sagebrush) and Lepidospartum squamatum (scalebroom) occurring more frequently in drier, losing reaches. Arundo is established and survives in both gaining and losing reaches. VEGETATION-PROCESS LINKAGES Prevenng development in the floodplain and increasing floodplain width and connecvity with the river will ameliorate some of the most significant impacts on the lower Santa Clara River and promote a greater extent of nave riparian vegetaon. Increase and improve floodplain connectivity Invasion by Arundo Implement strategic actions to control arundo 0 10 20 30 40 50 60 Floodplain wetland Riverwash scrub Mixed willow scrub Salix exigua - Arundo donax Salix laevigata Mixed willow forest Arundo donax Salix lucida Baccharis salicifolia Populus fremontii Salix lasiolepis Populus balsamifera Salix exigua Artemisia californica - Eriogonum fasc Mixed riparian forest Lepidospartum squamatum Tamarix spp. Mixed riparian scrub Salix exigua - Baccharis salic Non-native grasses and forbs Artemisia californica Artemisia tridentata Mixed scrub Baccharis pilularis Eucalyptus Alliance Time since last flood (yrs with SE bars) (BELOW) Flood events with corresponding aerial photographs used to examine changes in the extent of riparian vegetation in the lower Santa Clara River. Historical Changes in Riparian Vegetation Extent Riparian corri- dor conditions at river mile 11 in 1938 and 2005. 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Mixed scrub Populus balsamifera Salix lasiolepis Populus fremontii Salix exigua - Arundo donax Mixed riparian scrub Mixed willow scrub Eucalyptus Salix laevigata Baccharis pilularis Riverwash scrub Salix lucida Riverwash herbaceous Floodplain wetland superalliance Mixed willow forest Salix exigua - Baccharis salicifolia Arundo donax Baccharis salicifolia Non-native grasses and forbs Artemisia californica Mixed riparian forest Salix exigua Artemisia tridentata Lepidospartum squamatum % o f p l o t s w i t h i n g a i n i n g o r l o s i n g r e a c h e s % occurring in losing reaches % occurring in gaining reaches Percentage of plots within each vegetation alliance that occurs in gaining (blue) versus losing (orange) reaches. Overall, 54% of the reaches (red line) in the 1,490 alliance vegetation plots were in gaining reaches. Extent of the 1938 and 2005 floods. Reach 6 enlarged The extent and density (percent cover) of arundo infestations in the lower river. Groundwater Availability (BELOW) a) Distribution of mean annual precipitation based on data from the period 1900–1960; b) Precipitation records indicate peri- ods of cumulatively wetter (blue) and drier (orange) periods in the watershed. Distribution of gaining and losing reaches in the lower Santa Clara River watershed. Land cover types within the lower Santa Clara River watershed. Example of the detailed vegeta- tion mapping used for the lower Santa Clara River. The Santa Clara River watershed. (BELOW) Area of vegetated and unvegetated floodplain affected by selected floods. Average longitudinal position (± 1 SE) of vegetation alliances in the analysis area. Acquire land for conservation through purchase or easements. Remove or stop repairing unnecessary berms and levees. Replace bank-edge levees with setback levees. 1 Sllwater Sciences, 2855 Telegraph Avenue, Suite 400, Berkeley, California 94705; 2 Riparian Invasive Research Laboratory, Marine Science Instute, University of California, Santa Barbara, CA 93106-6150; 3 San Francisco Public Ulity Commission, 1145 Market Street, 4th Floor, San Francisco, California 94103; 4 California Coastal Conservancy, 1330 Broadway, 11th Floor, Oakland, California 94612; *Send correspondance to [email protected] Species distribuon and vegetaon reset Species distribuon Species distribuon and vegetaon structure Vegetaon extent Nave vegetaon extent The four physical variables most significantly correlated with vegetation types from the CCA.