ADAPTIVE GRAZING on Semi-arid Range

Transcription

1 ADAPTIVE GRAZING on Semi-arid Range

2 Rotational Grazing [SYSTEMS] as a means to increase vegetation and animal production has been subjected to as rigorous a testing as any hypothesis in the rangeland profession, and it has been found to convey few, if any, consistent benefits over continuous grazing (Briske et al. 2008).

3 Does it Matter? TEMPORAL DISTRIBUTION Species composition of plant communities can be modified in response to the frequency, intensity, and seasonality of grazing. Rest and deferment to promote plant growth is the most fundamental and long-standing corollary of the unifying principles (Briske et al. 2008)

4 Experimental grazing research embodies a fundamental tradeoff between a robust assessment of ecological processes and the ability to mimic the responses associated with adaptive management (Briske et al. 2011). Adaptive Management = Plan monitor Re-plan (Savory 1988)

5 WHY DO GRAZING SYSTEMS FAIL WHERE ADAPTATION WORKS? WHAT ADAPTATIONS ARE MANAGERS MAKING?

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7 Economic, Grazing, and Precipitation Data: Stocking Rate (AUD/ha) Annual Precipitation (cm) Cattle Percent Return on Investment (ROI) Overstocked Avg. Precip. Avg. Stocking Rate ROI Cattle Length of Deferral Adaptation Process-based Grazing Avg. Precip. Avg. Precip. Avg. Stocking Rate Maximize stocking rate to Avg. Stocking Rate Time (years) Management Paradigm: Production/Cattle Focus cover high overhead Deferral Length (days)

8 Conclusions from Early Years: 1) High stocking won t fix high overhead. 2) Grazing Systems do not mitigate overstocking. 3) Economic review works.

9 ADAPTATION #1 Action: Change to Ecological management paradigm (mental model) Goal: Improve secondary production through ecological health (Hypothesis) Mechanism: Unknown

10 The move to an ecological focus was driven by a failed grazing system. All private managers are adaptive but not necessarily with an ecological paradigm.

11 2000 Ecological Appraisal: 1) Low Residual, low litter Poor capture and retention of water Poor mineral Cycle 2) Gramma Grass Dominated <20% cool-season grasses ranch wide Winterfat and 4 wing Salt bush only in specific locations Blue Stem, Vine Mesquiteonly specific locations Green Needle not observed 1999

12 ADAPTATION #2: Action: Decrease Stocking Rate ( ) Goal: Improved water cycle Mechanism: 1. Improved animal performance from decreased competition for forage 2. Increased residuals cause improved water capture and infiltration

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14 Economic, Grazing, and Precipitation Data: Stocking Rate (AUD/ha) Annual Precipitation (cm) Cattle Percent Return on Investment (ROI) Overstocked Avg. Precip. Avg. Stocking Rate ROI Cattle Length of Deferral Adaptation Avg. Precip. Avg. Stocking Rate Process-based Grazing Avg. Precip. Avg. Stocking Rate animal performance and water Time (years) Management Paradigm: Ecological Reduced stocking to improve cycle Deferral Length (days)

15 Adaptation #3 Cross fence to increase stock density ( ) 1.Ecological goal = improved mineral cycle 2.Ecological process intervention = space/time density of manure and urine

16 MONITORING OBSERVATIONS: No change in spatial manure density 2.Minimal recovery of flagged defoliated plants If you can t see change, it s not there -- statistics are not necessary!

17 1) Focus on plant health and diversity versus mineral cycle. A) Look at plant monitoring B) Look at scientific literature C) Education from other producers/technicians

18 1. Plant growth is sporadic (Torell et al. 2011) 2. Short grass = < 1cm/week maximum 3. Mid-grasses = > 3cm/week maximum 4. Dry year = <5% seed production 5. Normal year = 20-40% seed production 6. 1 defoliation = no seed production

19 Was species mix ( <20% cool-season) driven by grazing? Large body of data (e.g., Hart and Ashby, 1998) : 1) Blue Gramma increased with grazing intensity 2) Western Wheat and Needle and Thread decreased with grazing intensity 3) Neighbors water limited pastures 50-60% cool-season 4) Technicians suggested day recovery Most grazing studies were May or June to Oct. grazing they missed most cool-season consumption.

20 ADAPTATION #4 Action: Plan for minimum 100-day recovery periods (facilitated by cross fencing) Goal: Improve plant diversity (specifically cool-season grasses) 1) Mechanism: Leave a large portion of the plants on the ranch undefoliated each growing season. A) Assume seed production and seedling/tiller survival are limiting processes. B) Assume plant maturity would promote vegetative and sexual reproduction.

21 Strategy: Defer to allow reproduction Increase Deferral to minimum 100 days 9 Pastures to 36 Pastures 36 pastures allowed 100-day recovery with reasonably short graze periods. (Recall 3cm/week)

22 Corollaries before monitoring results: Long deferral was a landmark, but it misses the point Key Point: plant physiology, not time, measures recovery. Corollary Adaptation #1: Return to pastures is measured by ecological criteria: 1. Plant physiology of desired plants 2. Residual and litter cover 3. Seasonality of previous graze period 4. Weather events Grazing Response Index (Reed et al. 1999)

23 Corollary #2: Animal selection matters Corollary #3: Seasonality matters Corollary #4: Variable stocking rates help (mix cow-calf, yearling, custom graze) Monitoring Data:

24 % Plants Defoliated in a Graze Period (Averaged by Month 2010) ADAPTATION #2: SEASONAL DEFOLIATION PATTERNS Jan April Western Wheat Month Blue Gramma Nov

25 March 19, 2008 Early March defoliation 2007 Fall/Dormant defoliation 2007 (120 days deferral)

26 Selectivity and seasonality make grazing processes plant specific, so grazing strategies and variables must be plant specific. 1. Annual stocking rate is an important variable, but it is a simple variable in a complex system. 2. Selectivity and seasonality require variables like seasonspecific and species-specific grazing intensity. All grazing is targeted, so management must be targeted.

27 Continuous grazing at moderate stocking allows adequate deferral of plants. Deferral occurs because 50% of the plants remain undefoliated. What about diversity and animal selection?

28 % Plants Defoliated in a Graze Period (Averaged by Month 2010) Jan Species Abundance Threshold April Squirrel Tail Western Wheat Month Winterfat Blue Gramma Nov

29 April, 2008

30 October, 2008

31 Percent plants with Seed Production Pastures Grazed Before June 30, 2010 Pastures Grazed after June 30, 2010 Seed production data gathered Fall 2010.

32 Timing of 2007 grazing related to plant recruitment Spring % Young (<7cm) Plants Fall Grazed Jan. Feb Grazed March April 2007 Grazed May June 2007 Grazed July, Aug., Sept. 2007

33 Management can prepare for weather events, but palatability is a function of abundance San Louis Valley and 4 Wing Salt Bush.

34 Economic Response of Process-based Adaptations?

35 Economic, Grazing, and Precipitation Data: Stocking Rate (AUD/ha) Annual Precipitation (cm) Cattle % Return on Investment (ROI) Overstocked Avg. Precip. Avg. Stocking Rate ROI Cattle Length of Deferral Adaptation Avg. Precip. Avg. Stocking Rate Process-based Grazing Avg. Precip. Avg. Stocking Rate YEAR Deferral Length (days)

36 Did we achieve the Ecological Goal?

37 % Western Wheat >50% Western Wheat Species composition of plant communities can be modified in response to the frequency, intensity, and seasonality of grazing (Briske et al. 2008).

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39 Typical Winterfat occurrence late1990s

40 Rest and deferment to promote plant growth (reproduction) is the most fundamental and long-standing corollary of the unifying principles (Briske et al. 2008) Area close to previous slide 2010

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42 Reversible State-transition: Blue Gramma + Filaree +- Western Wheat Silver Bluestem Side Oats Vine Mesquite Green Needle Grass Western Wheat Blue Gramma

43 Conclusions from Case Study 1) A Grazing System was ineffective: Grazing systems are a simple solution to a complex problem 2) Process-based scientifically-sound adaptations were effective: Recovery based on plant physiology to allow reproduction Varying defoliation patterns through seasonal grazing AND

44 3) grazing experiments indicate that if ecological benefits can be directly achieved in these [rotational] systems (Teague et al. 2008), they require very nuanced and specific grazing patterns (Briske et al. 2011).

45 Hypothesis from Case Study 1) Species diversity varies positively with economic return. Ecological health can drive secondary production. (See Jacobo et al and Kothman et al 1971) 2) Length of deferral vs. diversity is complex:

46 Definition of Complexity Inflection related to a change of underlying processes Variable Y Complexity = Multiple relationships between variables Variable X

47 Length of Deferral vs. Species Diversity Inflection related to reproduction processes Species Diversity short duration grazing Complexity = Multiple relationships between variables 100 Days 1 Year Length of Deferral

48 % of 24 Studies with Diversity Data 70% 60% % Studies Rotation > Continuous 50% 40% 30% 20% 10% 0% Studies with Rest Periods > 89 Days (13) Studies with rest periods < 90 Days (11)

49 % Studies Rotation > Continuous 120% 100% 80% 60% 40% 20% 0% % of 24 Studies with Diversity Data Initial Seral State Low (6) Initial Seral State High (10) Initial Seral State Unknown (8)

50 Length of Deferral vs. Species Diversity High Initial Diversity Species Diversity Low Initial Diversity History matters in complex systems 100 Days 1 Year Length of Recovery

51 Length of Deferral vs. Species Diversity Species Diversity short duration grazing Inflection related to reproduction processes Rotation vs Continuous trials are not process-based quantitative science (Provenza 1991). continuous grazing 100 Days 1 Year Length of Recovery

52 Conclusion: Seasonality and return interval are important grazing variables. Complex problems require: 1) Process-based science 2) Adaptive management 3) Effective communication between science and management (Boyd and Svejcar 2009) We pay lip service to complexity but we ignore it in the rotational grazing controversy.

53 Adaptive Grazing on Semi-arid Range Grady C. Grissom and Tim Steffens Introduction This presentation is a log of adaptive management decisions and their outcomes over 16 years. The thought processes behind the management decisions and the economic data were gleaned from manager s reports written one to four times annually. The story documents a change of management paradigm from focus on economics to focus on ecology. Initial application of a calendar-driven grazing system failed ecologically and economically. However, my observations of plantanimal interactions during the early years of rotation sparked an interest in ecology. Specifically, I came to understand that maximum economic returns on rangelands require maximum ecological health. On this hypothesis, I began to adapt the grazing system in a variety of ways to fit my environment, infrastructure, and management abilities. The case study is framed in the context of the ongoing rotational grazing debate. This debate, spanning the last 25 years, generally puts ranchers anecdotal evidence of good results from rotating cattle (like this case study) against a large body of controlled scientific studies that show inconsistent results at best. Managers certainly do not need the approval of scientists to do things that work. However, the resolution of this debate is important. The future health of our rangelands will require good management, good science, and good communication between the two. 1 To a large extent the grazing debate has broken down good communication. Rangeland systems are complex, which means that variable relationships change with location and through time. Reductionist science has limited abilities to deal with complex systems. This observation is at the heart of the grazing debate. Managers that constantly adapt to their environment can accomplish outcomes that controlled studies cannot mimic. This case study essentially shows that both sides are right. Hopefully, it makes a small contribution to ending the conflict and restoring confidence and communication between land managers and range scientists. 39

54 Slide 1: Title. Slide Descriptions Slide 2: A quote from Briske et al 2 that summarizes inconsistent results from controlled grazing studies. This quote infers that stocking rate is the only grazing variable that matters. Slide 3: Yet, the same paper summarizes scientific conclusions that the frequency, seasonality, and deferment of grazing are important management controlled variables. If so, rotational grazing that provides deferment and varies the frequency and intensity of grazing should be effective. Slide 4: A 2011 Briske et al paper 3 concludes that adaptive managers may be doing things differently than controlled grazing studies. It is ironic that the scientific world has concluded that Allan Savory s grazing practices are not effective but that adaptive management is. Savory s core message has always been about adaptive management, not grazing protocols. Slide 5: This presentation will attempt to answer these two questions. Slide 6: Rancho Largo is 14,020 acres 25 miles NE of Walsenburg, CO (60 miles SE of Pueblo, CO). Average annual precipitation is 11 on loamy plains and sandy plains soils. The ranch is primarily short grass steppe with Pinon-Juniper habitat around small canyons in the Dakota sandstone. I arrived as manager in late 1995 and have been there since. Slide 7: This graph will appear in a number of slides. It shows years on the horizontal axis beginning in 1996 and running through Three time periods are shown at the top of the slide but here the second two are blocked out. This slide shows only the early years ( ). The graph shows average precipitation (cm), average stocking rate (AUD/ha), return on investment (ROI) for cattle ($), and length of deferral between graze periods (days). The key points for are: 1) Precipitation was above average. 2) Stocking rates were high. 3) ROI cattle was negative. 4) Deferral between graze periods was short. Table 1 (below) also shows that animal performance as measured by conception rate was low. 40

55 Average Annual Grazing Periods per pasture Planned growing season deferral (Days) Year Precipitation RF and Fowler (inches) Stocking Rate (acres/auy) RLCC Stocking Rate (AU/year) Stocking Rate per unit Precipitation (AUY/inch) Cow Herd Conception Rate (%) Yearling Daily Gain (Lbs/day) PP PP PP PP PP PP PP PP Table 1. Annual precipitation, stocking rate, livestock performance, and rotation characteristics from 1996 to Precipitation was averaged from the Rocky Ford, CO and Fowler, CO weather stations. Stocking rates are based on a 1000-pound standard animal unit (SAU) for 1 year (AUY). After 2004 recovery was measured in plant physiology (PP) and available forage. Slide 8: 1) Our management paradigm in the early years was focused on cattle and production. We expected a relatively small ranch to support a family and pay on a land mortgage (i.e., overheads were high). We tried to overcome high overhead by running at a high stocking rate. The problem was, high stocking rates resulted in poor animal performance. Pregnancy rates in the cow herd averaged 80%. 2) The initial grazing system was method driven with no explicit mental model of plant-animal interactions, no goals, and no monitoring protocol to guide livestock movements. Our desired outcome, high livestock production, was economic, with no reference to ecological conditions or processes. Deferral periods of 40-days in the spring and 60-days in the summer provided insufficient recovery for defoliated plants. We assumed that utilizing compensatory regrowth by rotating 41

56 animals among pastures and grazing multiple times in a growing season facilitated higher stocking rates. We were wrong. 3) Overstocking results in a quickly returned economic message to managers. Within a year poor animal performance causes poor economic returns. The economic message usually precedes extensive ecological damage. This is why ranching is inherently ecologically sustainable. Successful ranches are almost always in fair to good ecological condition. Slides 9-10: The economic message was clear; our current business plan was unsustainable. Observations from grouping cattle and moving them on the landscape led to an interest in grazing ecology. In the early 2000s we indulged our interest in grazing ecology through seminars, management publications, scientific literature, and interactions with progressive grazing managers. Research provided a working hypothesis: Ecosystem function is the key to increased livestock production from rangelands. This is the most important and the only universal point in this presentation. All other adaptations are subject to the complexity of ecological systems. The variable relationships that drive the management strategies will change with location and/or time. However, success in adaptive grazing absolutely requires a commitment from management to ecological diversity and health. Slide 11: Our hypothesis that profit is driven by ecological health required knowledge of our current ecological condition. We began a baseline ecological survey in Slide 12: Our baseline showed low residual forage and low litter, indicating a poor water cycle. We chose to decrease stocking rate to improve water cycle and animal performance. Decreased stocking became extensive in the drought of 2002 (Table 1). Slide 13: Example of how residual grass slows evaporation. Slide 14: Between 2000 and 2003 we reduced stocking rates to moderate levels. Even with less rainfall (drought 2002), conception rates (Table 1) and ROI eventually improved. Slide 15: The traditional Savory approach (A good starting point) Slide 16: We did not see changes in manure distribution or breakdown. Manure was still heavy at water points and sparse in uplands. It is likely that we never reached high enough stock densities to see Mob Grazing type results. We chose to drop the mineral cycling goal and focus on plant diversity. Key point is: If you can t see the changes, go another direction. One doesn t need transects and statistics to manage adaptively. Slides 17-20: While looking for mineral cycling, we saw that plants were not recovering in the days between graze periods. Through our observations and research, we decided that we could grow more western wheatgrass with 100-day recovery periods. 42

57 Slide 21: We increased pasture numbers to 36 so we could have reasonably short grazing periods (2 weeks) and long ( days) deferrals. Slides 22-25: Season-long recovery was a management change that started positive ecological response to grazing management. However, we continued to adapt management in response to monitoring information. Before 2005, one annual graze plan was developed each year, assuming that a given period of time allowed adequate recovery. After 2005, management chose pastures available for grazing several times a year based on monitoring of plant physiology and available forage. A key criterion for return to a pasture was whether species of interest had completed their life cycle (produced seed) since the last graze period. This adaptation continued to increase recovery period length through Planning based on plant physiology also requires seasonal considerations. For instance, a late May defoliation followed by October defoliation allows no recovery for cool-season plants. Late May is the end of the spring growth period and October is the beginning of the fall growth period. Hence, 120 days of grazing deferment in summer allows no physiological recovery for cool-season plants. The same concept applies to a fall graze period followed by a spring graze period for cool-season species. The realization that animals graze plants, not pastures, led us to monitor the percentage of each plant species defoliated in a graze period. The species-specific grazing intensity information highlighted changes in seasonal animal selectivity. For instance, at RLCC cattle seldom defoliate western wheatgrass from June through September. Hence, cattle can occupy a pasture in mid-summer while still deferring western wheatgrass. We found that most species have significant seasonal variation in demand. Grazing management considerations also fostered changes of the cattle business. Cow numbers were reduced and yearling and custom grazing enterprises were added to facilitate flexibility for managing forage demand within a year. This allowed us to retain or sell calves, buy or sell yearlings, or to take in custom cattle in response to markets and precipitation. Slides 26-33: Recovery based on plant physiology, seasonal grazing plans, and a diversified cattle business were fundamental long-term adaptations. We also identified a number of short-term adaptations that nuanced grazing practices for specific plant species, grazing seasons, or cattle behavior (Table 2). These adaptations resulted largely from short-term ecological assessments of cattle diet selection. 43

58 Year Hypothesis and/or Assessment Observation 2005 Plant selection by cattle varies drastically with grazing season. Western wheatgrass is heavily defoliated in the spring or fall (if green) and rarely defoliated in the summer or dormant season to 2008 Yearlings in summer begin to graze less, stay at water points longer, and look less full when 50% of the blue gramma plants are defoliated Plant species respond differently to defoliation and seasonal grazing. Typically 80-90% of the winterfat plants in pastures grazed before July 1 produce seed. Only 10-20% of the plants grazed after July 1 produced seed Four wing saltbush was not responding to deferral of even 300 days. We were not losing plants but saw no evidence of recruitment. Adaptive Management Response A pasture grazed in the spring year one, the summer year two, and the spring or fall year 3 will give 2 years between defoliation of western wheatgrass. (ie. One can graze a pasture in the summer and still allow coolseason grasses to recover) Over several years we found that moving yearlings at 50% blue gramma defoliation resulted in good daily gains. In 2008 we grazed to 60 or 65% defoliation and yearling gains were only 1.0 lb/day. In locations where winterfat recruitment is desired graze before mid-summer. Tried 2-year deferral in some pastures with good potential for four wing saltbush recruitment. Follow-up Assessment and Action Observed recruitment of coolseason grasses so management action continued. Continued practice after Observed higher percentage of young plants in pastures grazed before mid-summer so management action continued. Modest success with a few new plants in pastures of acres. Continued 2-year deferrals when possible but it is economically difficult to defer for 2 years regularly. Table 2. Summary short-term grazing adaptations. Slides 34-35: After these adaptations, we ran more cattle on less rainfall with good animal performance (Table 1) and much-improved ROI. Slides 36-42: Western wheatgrass increased by a factor of 3 from the early years to the late years. We also saw a variety of other mid-grasses increase significantly. These included galletta, green needle grass, silver bluestem, vine mesquite, and sideoats grama. Winterfat went from rare patches on a 10m scale to a widespread forb. Some patches reached a 500m scale. The increase of mid-grasses resulted in higher residual cover and litter in the late years even with higher stocking rates (Table 1). We felt that the increased residuals and litter improved the water cycle and made higher sustainable stocking possible. Slides 43-44: Management adaptations that alter the key goal-related ecological processes will produce desired outcomes. For us the key process was western wheat reproduction. The management action was to provide full recovery, defined by plant physiology rather than time. Adaptations must be nuanced for a specific climate and set of soils, plants, and animals. Most likely, our methods would be worthless in Nebraska. That is why grazing systems don t work and that is why controlled experiments cannot reproduce what adaptive managers do. 44

59 Slides 45-52: A written description of these would cause the speaker/author severe brain damage. They will be explained during my talk. Editor s Note: Tables, included with permission, are from: "Case Study: Adaptive Grazing Management at Rancho Largo Cattle Co., Rangelands 35(5), October 2013 (in press) 45