Understanding and mitigating soil legacies to improve restoration success. Christine V. Hawkes University of Texas at Austin

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1 Understanding and mitigating soil legacies to improve restoration success Christine V. Hawkes University of Texas at Austin

2 Targeting legacies in restoration Ecosystem Attributes Intact Native Site Attempt to ameliorate legacy effects that impede restoration Degraded, Some Invasion Degraded, Extreme Invasion Ecosystem State Modified from Whisenant 1999

3 Need to target legacy effects explicitly Heneghan et al. 28 Rest Ecol

4 Can we change rate of legacy decay? Legacy development Legacy decay Strength of Legacy Invader introduction Invader removal Goal is to increase the rate of decay Time

5 Native Scrub Disturbed Scrub Scrub Converted to Pasture

6 Ecosystem State Targeting legacies in restoration Ecosystem Attributes Native Scrub Œ Natives Δ Soil microbes Ø C,N Disturbed Scrub No natives Ø Δ Soil microbes Ø C,N Δ Structure Invasive Removal, Microbial Inoculation, Native Seed Addition Scrub Converted to Pasture

7 Restoration community & ecosystem goals Mitigate structural, biogeochemical, and microbial legacies Initiate self-sustaining native populations

8 Restoration sites -disturbed -pasture Native sites -undisturbed scrub patches

9 Restoration treatments: herbicide Credit: Archbold Biological Station

10 Restoration treatments: soil microbial addition Credit: B. Sikes Credit: T. Eisner Credit: T. Eisner

11 Restoration experiment Native Scrub Disturbed Scrub Pasture Plots were set up in fall 26 and tracked through spring 21. Control Control Herbicide Microbial Addition

12 Measuring restoration success Return site characteristics? Reduce nutrient legacies? Improve plant recovery?

13 Measuring restoration success Return site characteristics? Reduce nutrient legacies? Improve plant recovery?

14 Success on some (visible) fronts: plant removals largely restore structure Non-native Cover (% ± 1SE) Soil Aggregation (mm ± 1SE) C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE Bare Ground (% ± 1SE) Litter Cover (% ± 1SE) C +M C +M +H +HM C +M +H +HM C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE

15 Success on some (visible) fronts: plant removals largely restore structure Non-native Cover (% ± 1SE) Soil Aggregation (mm ± 1SE) C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE Bare Ground (% ± 1SE) Litter Cover (% ± 1SE) C +M C +M +H +HM C +M +H +HM C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE

16 Success on some (visible) fronts: plant removals largely restore structure Non-native Cover (% ± 1SE) Soil Aggregation (mm ± 1SE) C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE Bare Ground (% ± 1SE) Litter Cover (% ± 1SE) C +M C +M +H +HM C +M +H +HM C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE

17 Success on some (visible) fronts: plant removals largely restore structure Non-native Cover (% ± 1SE) Soil Aggregation (mm ± 1SE) C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE Bare Ground (% ± 1SE) Litter Cover (% ± 1SE) C +M C +M +H +HM C +M +H +HM C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE

18 Success on some (visible) fronts: plant removals largely restore structure Non-native Cover (% ± 1SE) Soil Aggregation (mm ± 1SE) C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE Bare Ground (% ± 1SE) Litter Cover (% ± 1SE) C +M C +M +H +HM C +M +H +HM C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE NATIVE DISTURBED PASTURE

19 Success on some (visible) fronts: plant removals largely restore structure Non-native Cover (% ± 1SE) Soil Aggregation (mm ± 1SE) C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE Bare Ground (% ± 1SE) Litter Cover (% ± 1SE) C +M C +M +H +HM C +M +H +HM C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE NATIVE DISTURBED PASTURE

20 Success on some (visible) fronts: plant removals largely restore structure Non-native Cover (% ± 1SE) Bare Ground (% ± 1SE) Soil Aggregation (mm ± 1SE) Litter Cover (% ± 1SE) C +M C +M +H +HM C +M +H +HM C +M C +M +H +HM C +M +H +HM NATIVE DISTURBED PASTURE NATIVE DISTURBED PASTURE

21 Measuring restoration success Return site characteristics? Yes, site cover, openness, & soil crust aggregation were improved in degraded sites Reduce nutrient legacies? Improve plant recovery?

22 Measuring restoration success Return site characteristics? Yes, degraded site cover, openness, & soil crust aggregation were improved Reduce nutrient legacies? Improve plant recovery?

23 Soil N differs among veg types 5 4 Total Inorganic N ug g Microbial Biomass N 25 ug g Control Control Control NATIVE SCRUB DISTURBED SCRUB CONVERTED PASTURE Hamman & Hawkes 213 Rest Ecol

24 Microbial additions have little effect on N 5 4 Total Inorganic N ug g Microbial Biomass N 25 ug g Control +Mic Control +Mic Control +Mic NATIVE SCRUB DISTURBED SCRUB CONVERTED PASTURE Hamman & Hawkes 213 Rest Ecol

25 High N persists after veg removal 5 4 Total Inorganic N ug g Microbial Biomass N 25 ug g Control +Mic Control +Mic +Herb Control +Mic +Herb NATIVE SCRUB DISTURBED SCRUB CONVERTED PASTURE Hamman & Hawkes 213 Rest Ecol

26 Treatments do not change N legacies 5 4 Total Inorganic N ug g Microbial Biomass N 25 ug g Control +Mic Control +Mic +Herb +Mic NATIVE SCRUB DISTURBED SCRUB +Herb Control +Mic +Herb +Herb +Mic CONVERTED PASTURE Hamman & Hawkes 213 Rest Ecol

27 Measuring restoration success Return site characteristics? Yes, degraded site cover, openness, & soil crust aggregation were improved. Reduce nutrient legacies? No. May need more time. Possibly remove topsoil if N reduction is necessary. Improve plant recovery?

28 Measuring restoration success Return site characteristics? Yes, degraded site cover, openness, & soil crust aggregation were improved. Reduce nutrient legacies? No. May need more time. Possibly remove topsoil if N reduction is necessary. Improve plant recovery?

29 The cast of characters Hypericum cumulicola*** Eryngium cuneifolium*** Lechea cernua* Lechea deckertii Polygonella basiramia*** Paronychia chartacea**

30 More germination in native sites Proportion Germination (± 1 SE) Control Control Control NATIVE SCRUB DISTURBED SCRUB CONVERTED PASTURE

31 More germination in native sites Proportion Germination (± 1 SE) Control +Mic Control Control NATIVE SCRUB DISTURBED SCRUB CONVERTED PASTURE

32 Microbial additions alone do not improve germination Proportion Germination (± 1 SE) Control +Mic Control +Mic Control +Mic NATIVE SCRUB DISTURBED SCRUB CONVERTED PASTURE

33 Plant removals improve germination only in pastures Proportion Germination (± 1 SE) Control +Mic Control +Mic +Herb Control +Mic NATIVE SCRUB DISTURBED SCRUB +Herb CONVERTED PASTURE

34 Plant removals with microbial additions recover germination in disturbed sites Proportion Germination (± 1 SE) Control +Mic Control +Mic +Herb +Herb Control +Mic +Mic NATIVE SCRUB DISTURBED SCRUB +Herb CONVERTED PASTURE +Herb +Mic

35 Substantial native background recruitment, but not in pastures Recruitment (num m -2 ± 1 SE) Control +Mic Control +Mic +Herb +Herb Control +Mic +Herb +Herb +Mic +Mic NATIVE SCRUB DISTURBED SCRUB CONVERTED PASTURE Open space, moisture, and non-native veg cover explain 38% of variation in recruitment

36 Cnidosculus stimulosus Background recruitment of non-targeted species Stipulicida setacea Polanisia tenuifolia Polygonella robusta

37 Opportunities created for recruitment of non-targeted species in pastures Recruitment (num m -2 ± 1 SE) Control +Mic Control +Mic +Herb +Herb Control +Mic +Mic NATIVE SCRUB DISTURBED SCRUB +Herb CONVERTED PASTURE +Herb +Mic Open space and soil aggregation explain 43% of variation in non-target recruitment

38 What does this mean for population viability? Demographic modeling of taxa to estimate population growth rates Started with one of the most abundant plant species, Polygonella basiramia

39 Polygonella population growth rates increased with restoration treatments VEGETATION TREATMENT Δ LAMBDA RELATIVE TO CONTROLS Disturbed Scrub Microbes Herbicide Herbicide+Microbes +2.8% Converted Pasture Microbes Herbicide +2.5% Herbicide+Microbes +1.1%

40 Measuring restoration success Return site characteristics? Yes, degraded site cover, openness, & soil crust aggregation were improved. Reduce nutrient legacies? No. May need more time. Possibly remove topsoil if N reduction is necessary. Improve plant recovery? Yes, but veg-specific effects on germination, establishment, and population trajectories.

41 The probability of successful restoration differs among sites Native Scrub Ecosystem Attributes Invasive Plant Removal & Soil Inoculation Disturbed Scrub Invasive Plant Removal Scrub Converted to Pasture Ecosystem State

42 Can we open up the soil black box? How do microbial communities differ among native, disturbed, and pasture sites? Do those differences persist? Can we use what we learn to further enhance restoration success?

43 Focus on fungi Root fungi Involved in nutrient and water uptake Soil fungi Responsible for decomposition and nutrient recycling in soil Both abundant in this ecosystem and should play important functional roles given the low nutrient, xeric soils

44 Can we open up the soil black box? How do fungal communities differ among native, disturbed, and pasture sites? Do those differences persist? Can we use what we learn to further enhance restoration success?

45 Soil fungi had little overlap among veg types regardless of treatment NMS Axis 2 (r 2 = 36) Native Disturbed Pasture NMS Axis 1 (r 2 =.6) Glinka & Hawkes, in review

46 Native sites have lower diversity and fewer fungi NMS Axis 2 (r 2 = 36) Native Increasing fungal richness & abundance Disturbed Pasture NMS Axis 1 (r 2 =.6) Fungal Richness (# OTUs ± 1 SE) Hyphal abundance (mm g -1 soil ± 1 SE) Glinka & Hawkes, in review

47 Strongest fungal legacy in pastures Native Disturbed Pasture NMS Axis 2 (r 2 = 36) NMS Axis 1 (r 2 =.6) Glinka & Hawkes, in review

48 Can we open up the soil black box? How do fungal communities differ among native, disturbed, and pasture sites? Do differences persist? Yes! There are strong differences over three years, likely related to changes in soil organic matter. Can we use what we learn to further enhance restoration success?

49 Can we open up the soil black box? How do fungal communities differ among native, disturbed, and pasture sites? Do those differences persist? Yes! There are strong differences over three years, likely related to changes in soil organic matter. Can we use what we learn to further enhance restoration success?

50 Manipulating specific fungi

51 Cultured fungi reflect whole community patterns Native Disturbed Pasture Sikes & Hawkes, unpublished

fungi 98 96 1 1 99 99 94 95 98 79 89 93 1 93 1 1 85 89 92 99

52 93 Cultured root fungi and soil fungi are phylogenetically distinct Credit: S/ Taghavi Root fungi Soil fungi Sikes & Hawkes, unpublished

53 Select fungi for amendments Fungi selected for variable function based on prior tests of competition and decomposition 8 root and 5 soil fungal isolates per site type

54 Testing fungal effects on restoration efforts Disturbed Pasture Control Control Herbicide Control Root fungi Soil fungi Home Site Fungi Native Scrub Fungi

55 Overall native plant germination was dominated by three species Palafoxia feayi % 1% 9% Polygonella robusta Lechea cernua Sabal etonia 17% Schizachyrium niveum 13% 6% Aristida gyrans

56 No variation in Aristida in the absence of fungi 2 Germinants 15 1 Control 5 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

57 Fungal effects on Aristida were highly 2 context dependent Germinants 15 1 Control 5 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

58 Aristida germination inhibited in disturbed sites by fungi from native scrub Germinants Root fungi Control home native Soil fungi 5 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

59 Fungi from pastures improved Aristida germination in pastures with veg removed Germinants Root fungi Control home native Soil fungi 5 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

60 Fungi had no effect on Aristida germination in pastures when grasses were not removed Germinants Root fungi Control home native Soil fungi 5 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

61 Without fungi, Schizachyrium germination varied little across sites Germinants Root fungi Control home native Soil fungi 1 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

62 Fungi from disturbed sites improved Schizachyrium germination in disturbed sites Germinants Root fungi Control home native Soil fungi 1 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

63 In pastures, root fungi from native scrub improved Schizachyrium germination Germinants Root fungi Control home native Soil fungi 1 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

64 Palafoxia germination lower in pastures without fungi Germinants Root fungi Control home native Soil fungi 2 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

65 Fungal effects on Palafoxia are also highly context dependent Germinants Root fungi Control home native Soil fungi 2 DISTURBED PASTURE +Herbicide PASTURE Sikes et al. unpublished data

66 Can we open up the soil black box? How do fungal communities differ among native, disturbed, and pasture sites? Do those differences persist? Yes! There are strong differences over three years, likely related to changes in soil organic matter. Can we use what we learn to further enhance restoration success? Potentially, but it is not straightforward and may be both species- and site-specific

67 Different approaches overcome legacies Native Scrub to different degrees Ecosystem Attributes Invasive Plant Removal + Soil Inoculation Specific microbe additions for some species Disturbed Scrub Invasive Plant Removal Scrub Converted to Pasture Ecosystem State

68 When should we address legacy effects? Amount of effort should be based on the balance of resources required, potential efficacy, and degree of need Many new studies coming out manipulating microbes and finding improved restoration, but the field is still in its infancy Development Decay General rules? Strength of Legacy Time

69 Hawkes Lab Erin Brault Clare Glinka Nick Johnson Ben Sikes Archbold Biological Station Eric Menges Hilary Swain Patrick Bohlen Stacy Smith USDA NRI Managed Ecosystems Program Smith Fellows Program Thank you!

70 Four of these species were also differentially sensitive to microbes Proportion of germination (± 95% CI) no crust (autoclaved) crust (not autoclaved) Eryngium Hypericum Paronychia Polygonella Species Hawkes 24 Plant Ecology

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