Science Considerations in Functional Restoration: Soils

1. Science Considerations in Functional Restoration: Soils Mac A. Callaham, Jr. Center for Forest Disturbance Science Southern Research Station USDA Forest Service 04 February 2013

2. What is soil? Soil is: A dynamic reactor of variable volume, situated on or near the Earth’s surface, consisting of chemical, biological, and physical components, and with integral linkages to atmospheric, geologic, and hydrologic characteristics of the local ecosystem. What are its functions? • To support plants • To support a community of soil organisms • To serve as a reservoir of resources (water, nutrients, energy) • To buffer systems against environmental change

3. Background “Restoration ecology has been largely a botanical science, perhaps because natural communities are composed largely of plants, and plants are the basis of most ecosystems” T.P. Young, et al. (2005) Ecology Letters 8:662-673 “Soils are the central organizing entities in terrestrial ecosystems” Coleman and Whitman (2005) Pedobiologia 49:479-497 “This is funny. Soils and plants are inextricably linked, right? Where would each be without the other? Soil is a function of the plants that are there, and the plants that are present are a function of the soil characteristics, and, and, and,…” Callaham (2005-2013) Journal of Late Night Ponderings 2:47-497

4. History and a Major Premise: The restoration and conservation movements in North America were precipitated by massive soil degradation associated with the drought and Dust Bowl of the 20’s and 30’s

5. Recent History Tony Bradshaw (1983) makes a famous proposition: “ Restoration is the acid test of ecology.” And, in this paper, he discusses at length the importance of getting the soil right as it relates to the ultimate success in restoration projects Bradshaw, A.D. (1983) J. of Appl. Ecol. 20:1-17

6. But then, what happened? “Restoration ecology has been largely a botanical science…” T.P. Young, et al. (2005) Ecology Letters 8:662-673 And that’s not all… If one takes the time to look through recent texts on the subject of restoration ecology, one finds that soil is generally treated in terms of being simply a medium for plant growth. Also, in the peer reviewed literature…

7. We surveyed the contents of the journal Restoration Ecology (1993-2006). Titles contained soils terms about 1/3 of the time • - This information fell into three categories (site conditions, restoration treatments, and edaphic responses) • Site condition information was used to develop a baseline or target for soil variables • Fertilization was the most common treatment in studies where soil variables were manipulated. • Soil nutrient status was most common response measured, and inverts often were used as indicators Modified from Callaham et al. 2008

8. Why not more soil work? Soil is opaque and relatively difficult to study Benchmarks for soil properties have been difficult to identify (faunal indicators, key processes, etc.) Soil processes and/or communities develop over a wide range of time-scales, including some that may be too long to be practical to study by normal standards Soils can be quite variable spatially and may or may not be correlated with variation in aboveground vegetation Restoration Ecology is a relatively new discipline

9. Context and Definitions All of the terms used (by me) should be interpreted broadly For example, restoration = enhancement of any kind And not per SER guidelines: “Restoration attempts to return an ecosystem to its historic trajectory, i.e., to a state that resembles a known prior state or to another state that could be expected to develop naturally within the bounds of the historic trajectory.”

10. ? Endpoint Objective B A3 Enhancement/Restoration/Succession A2 Over-exploitation/Degradation A1 FUNCTION C Degraded System ? STRUCTURE Modified from Bradshaw, 1987; Stanturf, 2005

11. Native Soil Ecosystem Agriculture Forestry Urbanization Pollution Managed Soil Ecosystem Physical Disturbance Habitat fragmentation Fertilization Herbicide/Pesticide Species extinctions Species introductions Vegetation Soil Function: chemical, physical, biological Abandonment Restoration or Time Plant inputs Soil microbial and faunal communities structure and abundance Species extinctions Species introductions Altered Soil Ecosystem New plant and animal species composition New soil properties New biogeochemical relationships Modified from Callaham et al. (2006) Biol. Inv. 8:1317-1329

12. Bradshaw 1987

13. Physical Environment Vegetative Manipulation Holistic Management Whisenant 1999 Hobbs & Harris 2001 Functionality Objective Degraded Bradshaw 1987

14. Heneghan et al. 2008 Physical Environment Vegetative Manipulation Holistic Management Whisenant 1999 Hobbs & Harris 2001 Functionality Objective Degraded Bradshaw 1987

15. Proceedings from our conference in Chicago appear in Restoration Ecology

16. Points of Departure? Soils are Heterogeneous Soils Have History Soils Are Alive Soils Are Complex

17. Points of Departure? Soils are Heterogeneous Soils Have History Soils Are Alive Soils Are Complex Soils Are Particular, Peculiar, and Idiosyncratic (and they make a difference…) From Callaham et al. (2008) Rest. Ecol. 16:604-607

18. “Soils are heterogeneous” Therefore, homogenization of soil can hinder restoration Examples: Sedimentation, erosion, cultivation (plowing/tilling), plant invasion, cropping/fertilization, other engineering… Solutions: Do not homogenize, or dehomogenize when possible (manipulate resources, add topographic or textural features)

19. “Soils have history” This may be the most important consideration when planning restorations Examples: Sedimentation, erosion, cultivation (plowing/tilling), invasions, extinctions, cropping, fertilization, pollution Solutions: Be informed about site history, be realistic about what can inhabit a given soil, be patient, manipulate resources…

20. “Soils are alive” There is remarkable diversity in soil organisms occupying any given volume of soil, and they are all doing something! Examples: Bacteria, fungi (saprobes and mycorrhizae), microarthropods, macroarthropods, earthworms, beneficials and bad actors, ecosystem engineers, we know that disturbances affect the community composition of soil organisms Solutions: Know the difference between good and bad actors, consider transplants of native organisms

21. Ecosystem Engineers “…are organisms that affect other organisms by creating, modifying, maintaining or destroying habitats.” Jones et al., 1994 Oikos 69:373-386

22. Alternative Stable States Redrawn from Scheffer et al. (2001) Nature 413:591-595 Ecosystem State Conditions Ecosystem State Ecosystem State Conditions Conditions

23. Abiotic State Biotic State Biotic State Redrawn and modified from Byers, et al. (2006), TREE 21:493-500

24. “Soils are complex” In other words, soils are heterogeneous, living and breathing entities (with a past!) Examples: Soils that have only “natural” history are the most heterogeneous, diverse, and functionally complicated. Perturbations usually result in simplification of these systems. Solutions: Experimentation is the best way forward. Full restoration of soil diversity and function remains an elusive goal.

25. To Conclude… • Question: • What are the most appropriate measures of success for ecosystem restoration from the perspective of a soil ecologist? • Some Answers: • Nutrient mineralizaton • Organic matter cycling (decomp, respiration, accumulation) • Soil microbial community characteristics and functions • Soil invertebrate community composition. • Other suggestions? • Problems: • A no-analog future • Alternative stable states • Moving targets…

26. Thanks for your attention! Acknowledgements: Dave Coleman John Stanturf Joan Ehrenfeld Sara Baer Ralph Boerner Dan Richter Liam Heneghan Chuck Rhoades Valerie Eviner