Riparian Grazing Strategies and their impact on riparian health

Transcription

1 Riparian Grazing Strategies and their impact on riparian health Theresa A. Becchetti, Kenneth W. Tate, Edward R. Atwill, David F. Lile,, Don L. Lancaster, Neil McDougald, Sheila Barry, Roger S. Ingram, Holly A. George, Wayne J. Jensen, William E. Frost, Royce Larsen, Ralph Phillips, Mark Horny, John Harper, Gary G. Markegard,, Stephanie Larson, Rick Delmas,, James Farley, Larry Forero UCCE Rangeland Watershed Group

2 Grazing and Riparian Health?

3 Background Review of literature base (Allen( Allen-Diaz et al. 1999, Belsky et al. 1999, Larsen et al. 1998, Rinne 1999). Critical study components undefined such as stocking rates, physical characteristics, and grazing system. Experiments compare grazing to no grazing. Sparse information on direct links of grazing and fisheries.

4 Background Lacking in literature: Toolbox of tested, site-specific specific grazing recommendations. Needs: Data driven, management scale project to identify feasible grazing management that enhances riparian resources.

5 Riparian Grazing Project Objectives: Cross-sectional sectional survey of California s rangeland riparian areas. Identify grazing management and site characteristics associated with high and low riparian health. Synthesize data for site specific recommendations. Publish and extend information. Utilize sites to develop set of case studies.

6 Study Sites

7 Survey Tools Habitat Assessments Hydrologic Condition EPA NRCS BLM NRCS Stream Visual Assessment Protocol Site: Channel condition tural channel; no Evidence of past channel alteration, Altered channel; <50% of the reach Channel is actively downcutting uctures, dikes. No but with significant recovery of with riprap and/ or channelization. or widening. >50% of the reach dence of down-cutting channel and banks. Any dikes or Excess aggradation; braided channel. with riprap or channel-ization. excessive lateral levies are set back to provide access Dikes or levees restrict flood plain Dikes or levees prevent access to ting. to an adequate flood plain. width. the flood plain Hydrologic alteration ooding every 1.5 to 2 years. Flooding occurs only once Flooding occurs only once No flooding; channel deeply incised or dams, no water every 3 to 5 years; limited every 6 to 10 years; channel structures prevent access to flood plain or hdrawals, no dikes or other channel incision. deeply incised. dam operations prevent flood flows. uctures limiting the stream's Or Or or ess to the flood plain. Withdrawals, although Withdrawals significantly Withdrawals have caused severe loss of low annel is not incised. present, do not affect affect available low flow flow habitat. available habitat for biota. habitat for biota Or Flooding occurs on a 1-year rain event or less Riparian zone tural vegetation Natural vegetation extends Natural Natural vegetation extends Natural vegetation less than a third of the ends at least two one active channel width vegetation a third of the active channel active channel width on each side. ive channel on each side. extends half of width on each side. or dths on each side. Or the active Or Lack of regeneration. If less than one width, channel width Filtering function or covers entire flood plain. on each side. moderately compromised. Filtering function severely compromised Bank stability nks are stable; banks are low Moderately banks unstable; be Unstable; banks may be low, but stable; are Moderately banks may elevation of active flood low (at elevation of active low, but typically are high (flooding typically are high; some straight in); 33% or more of eroding flood plain); less than 33% of occurs 1 year out of 5 or less reaches and inside edges of bends face area of banks in outside eroding surface area of banks frequently); outside bends are are actively eroding as well as nds is protected by roots that in outside bends is protected actively outside bends (overhanging end to the by roots that extend to the eroding (overhanging vegetation at vegetation at top of bare bank, se-flow elevation. baseflow elevation. top of bank, some mature trees numerous falling into steam annually, some mature trees falling into stream slope failures apparent). annually, numerous slope failures apparent) Water appearance ry clear, or clear but Occasionally cloudy, Considerable cloudiness most of the Very turbid or muddy appearance most of -colored; objects visible especially after storm event, time; objects visible to depth 0.5 to the time; objects visible to depth < 0.5 ft; depth 3 to 6 ft (less if but clears rapidly; objects 1.5 ft; slow sections may appear peagreen; slow moving water may be bright-green; ghtly colored); no oil visible at depth 1.5 to 3 ft; bottom rocks or submerged other obvious water pollutants; floating een on surface; no may have slightly green objects covered with heavy green or algal mats, surface scum, sheen or heavy ticeable film on color; no oil sheen on water olive-green film. coat of foam on surface. bmerged objects or surface. or or ks. Moderate odor of ammonia or rotten Strong odor of chemicals, oil, sewage, other eggs. pollutants Nutrient enrichment ear water along entire reach; diverse Fairly clear or slightly Greenish water along entire reach; Pea green, gray, or brown water uatic plant community includes low greenish water along overabundance of lush green along entire reach; dense stands of antities of many species of entire reach; moderate macrophytes; abundant algal growth, macrophytes clog stream; crophytes; little algal growth present. algal growth on stream especially during warmer months. severe algal blooms create thick substrates. algal mats in stream Barriers to fish movement barriers Seasonal water withdrawals Drop structures, culverts, dams, structures, dams, Drop structures, Drop culverts, culverts, inhibit movement within the or diversions (< 1 foot drop) or diversions (> 1 foot drop) dams, or diversions (> 1 reach within the reach within 3 miles of the reach foot drop) within the reach Site Characterization Management Survey

8 Habitat Features

9 Hydrologic Function

10 Physical Characteristics

11 Data Collected: # of # of Hydrologic # of Site # of Habitat Function Characterization # of Management Sites Questions Questions Covariates Questions

12 Pearson Correlation Coefficients (r): EPA PFC PFC NRCS EPA NRCS

13 Significant Physical Parameters EPA NRCS PFC Entrenchment Slope n.s n.s. Substrate 0.04 < % Run n.s. <0.001 n.s. % Riffle <0.001 n.s. n.s. % Pool <0.001 n.s. n.s. % Canopy <0.001 < R Significant p values reported

14 Rosgen Stream Morphology Components Level I Entrenchment ratio Width to Depth ratio Slope Sinuosity Level II above plus Substrate Size

15 Rosgen Classification

16 Analysis How best can we get site specific results? 19 a ab ab b 16 EPA c c A B C E F G Rosgen

17 Analysis Examine current management practices (as person days per year) at various Levels of detail. Level 1 n=128 Level 2, s n=75 Level 2, w n=55 Level 3, s AB n=8 Level 3, s CE n=67 Level 3, w AB n=35 Level 3, w CE n=20

18 A and B Streams Steep gradient Limited Floodplain Bedrock and Boulder

19 C and E Streams Low Gradient Large Floodplain Lots of Meanders

20 Independent Variables: Growing Season Grazing (Early, Late, or Entire Season, Dormant Season) Stock Density (Number of head per acre) Animal Unit per Acre per Year (No. of animals/acre/year) Rest Provided (Yes/No) Rest Between Grazing (Days) Frequency (Number of times per year pasture is grazed) Herding (Man Days per Year) Off-Site Attractant Provided (Yes/No) Off-Site Attractant Time (Man Days per Year) Fencing (Yes/No) Fencing Time (Man Days per Year)

21 Results: Level 1- EPA = (Stock Density) 0.332(Frequency) (Rest Between Grazing) (Herding) (Off- Site Attractant Time) (Frequency*Stock Density) n=128, R 2 = 0.20

22 Results: Level 2, s- EPA = (Rest Between Grazing) (Herding) (Off-Site Attractant Time) n=75, R 2 = 0.19

23 Results: Level 2, w- EPA = (Stock Density) n=55, R 2 = 0.10

24 Results: Level 3, s AB- Sample Size too small to analyze. n=8

25 Results: Level 3, s CE- EPA = (Rest Between Grazing) (Herding) (Off-Site Attractant Time) n=67, R 2 = 0.24

26 Results: Level 3, s CE, PFC Herding OA Time Rest between Grazing β P

27 Results: Level 3, s CE, PFC Herding OA Yes/ No β P

28 Predicting EPA through Management: (Level 3, s CE streams) 20 OATime = 5 days EPA Rest Between Grazing Herding = 5 days Herding = 15 days Herding = 30 days

29 Results: Level 3, w AB streams- No terms were significantly associated with EPA. n=35

30 A and B Streams

31 Results: Level 3, w CE streams- EPA = (Stock Density) n=20, R 2 = 0.18

32 Results: Level 3, w CE streams, PFC- Stock Density β P

33 Predicting EPA through Management (Level 3, w CE streams) EPA Stock Density

34 Off-Site Attractant Time Across Three Levels Level Coefficient n p values R 2 Level Level 2, summer Level 3, summer CE streams

35 Conclusions Underlying factors interact with management regimes. However- we are identifying feasible grazing management practices

36 Questions?