Effects of Tanglehead ( contortus ) Invasion on Soil Microbial Communities in the Coastal Sandsheet

Joshua Grace 1 Invasive Grass Research Specialist

D. B. Wester 1, V. Acosta-Martinez 2, S. Rideout-Hanzak 1, J.A. Ortega-S1

1 Caesar Kleberg Wildlife Research Institute, Texas A&M University-Kingsville, TX 2 USDA-ARS-Cropping Systems Research Laboratory, USDA, Lubbock, TX Introduction

• Biological species invasion poses a great threat to biodiversity – Exotic species – Native species acting invasively

• Grasses – Competitive dominance ↓ Nave growth ↓ Species diversity ↓ Species richness Introduction Cascading effects on ecosystems • South Texas – Old World bluestem – Buffelgrass – Kleingrass – Lehmann’s lovegrass Potential impacts on livestock production – Guineagrass

Tanglehead ( [L.] Link) Introduction • Tanglehead (Heteropogon contortus [L.] Link) • Native, warm season, perennial bunchgrass • Dense monotypic stands/ litter accumulation • Provides key wildlife habitat • Unique situation for So. Texas landowners

– Bobwhite Quail http://www.texasbeyondhistory.netl – Whitetail Deer CKWRI Tanglehead Research

• Current Research – Control and management – Production and phenology – Seed viability and longevity – Ecosystem processes • Nutrient processes • Soil microbial dynamics – Community Size (biomass C, N) – Community Composition Study Area

• CKWRI cooperating ranch – Jim Hogg County – Approx. 29 miles south of Hebbronville, TX

Native Community Tanglehead/Native Mix Tanglehead Dominated

8 Native, 7 Mix, 3 Invaded ( n = 18) Methodology

• Collected 3 soil cores from each site – A-Horizon (0-10”), Delmita and Nueces – Mixed to form 1, 450 g combined sample from each site (n=18) for analysis – 2013, 2014, 2015

Native Community Tanglehead/Native Mix Tanglehead Dominated Methodology—Soil Analyses

• Microbial Biomass Carbon ( MBC ) and Nitrogen ( MBN) – Chloroform fumigation extraction-method • (Brookes et al. 1985 & Vance et al. 1987) – mg C kg -1 soil , and mg N kg -1 soil

• Microbial Community Composition – Fatty Acid Methyl Ester ( FAME ) profiling • (Schutter& Dick 2000) – Fatty acids identified & compared by retention times and peak areas to components of MIDI standards – %; based on nmol g-1 soil Results- Microbial Community Size

1. Repeated Measures, Mixed Model ANOVA

• MBC: Treatment x Year: P = 0.0077 – Treatment x Year interaction Treatment x Year: P = 0.0077 soil)

1 P = 0.0001 P = 0.0263 – In 2013 & 2015, MBC was − lower in invaded sites than P = 0.9053 native sites a b c a a a a ab ab 0 100 200 300 MBC (mg kg MBC (mg 2013 2014 2015

Tanglehead Mixture • MBN: Native – Very weak interaction effects Treatment x Year: P = 0.0688 soil) P = 0.1320 1 – MBN was greater in native − P = 0.0039 P = 0.7978 sites than invaded sites

during 2013 a a b a a a a a a 0 2 4 6 8 MBN (mg kg MBN (mg 2013 2014 2015 Results- Microbial Community Composition

• Nonmetric Multidimensional Scaling Ordination • Using microbial indicators • G+, G-, Actinomycetes, Fungi

2013 2014 2015 MDS Axis 2 MDS Axis 2 MDS Axis 2 -0.2 -0.1 0.0 0.1 0.2 -0.2 -0.1 0.0 0.1 0.2 -0.2 -0.1 0.0 0.1 0.2

-0.2 -0.1 0.0 0.1 0.2 -0.2 -0.1 0.0 0.1 0.2 -0.2 -0.1 0.0 0.1 0.2 MDS Axis 1 MDS Axis 1 MDS Axis 1 Results- Microbial Community Composition

• Nonmetric Multidimensional Scaling Ordination

2013 Gn 2014 2015

N M T M T GPAc FUN N M T MDS MDS 2 Axis MDS Axis 2 Axis MDS N 2013 2014 2015 -0.2 -0.1 0.0 0.1 0.2 -0.2 -0.1 0.0 0.1 0.2

-0.2 -0.1 0.0 0.1 0.2 -0.2 -0.1 0.0 0.1 0.2 MDS Axis 1 MDS Axis 1

2013 ‰2014 ‰2015 Native ‰Mixture ‰Tanglehead Results- Microbial Community Comp.

Multivariate Analyses • MANOVA Fu Fungi – Treatment: P = 0.0487

• Invaded = Native: P = 0.0120 G+Gpeg – Year: P < 0.0001

Ac

G-Gneg 0.10.1 0.2 0.2 0.3 0.3 0.4 0.4 0.5 0.5

1 2 3 Fu Fungi 2013 2014 2015

2013 ‰ 2014 ‰ 2015 G+Gpeg • G+, Actinomycetes, and fungi increase • Likely a precipitation factor AcAc

G-Gneg Native ‰ Mixture ‰ Tanglehead 0.10.1 0.2 0.2 0.3 0.3 0.4 0.4 0.5 0.5 1 2 3 • G+ and Actinomycetes decrease and fungi Heco Mixture Native increases Results- Fungi:Bacteria Ratio Repeated Measures, Mixed Model ANOVA

• Fungi:Bacteria Ratio

Fungi:Bacteria Ratio • Treatment effects ( P = 0.0183) – Invaded = Mixture Native Mixture – Invaded > Native Heco – Mixture > Native a b b 0.60 0.70Native 0.80 Mixture Heco • Year effects ( P = 0.0001) – 2013 = 2014 20132013 – 2015 > 2013 20142014 20152014 – 2015 > 2014 a a b 0.5 0.7 0.9 201320122014 20132015 2014 Conclusions

• Along this invasion gradient: Microbial Community size and composition differed in tanglehead vs. native sites

• Tanglehead-invaded sites showed lower microbial biomass C and N in 2 of the 3 years • (smaller microbial community size) • Implications on soil health and functions (soil respiration, soil productivity, and health) Conclusions

• Along our invasion gradient, we did see differences in microbial community size and composition in tanglehead sites vs. native sites

– Had higher fungi:bacteria ratios than native sites • Shift to more fungi-dominated microbial communities may represent changes in nutrient levels • Can result in shifting of the system, including conditions favoring invasive Conclusions

• We observed changes in mean microbial composition

Native Mixture Tanglehead

G+, Actinomycetes Fungi ↑MBC and MBN ↓MBC and MBN • Patterns in variation of microbial composition – Both a “year” and “invasion” pattern – Invasion pattern consistent within years – Left-to-right gradient Conclusions

• Soil organisms: – Play vital roles in carrying out ecosystem processes such as decomposition and nitrogen cycling – Changes in soil community composition and size may be particularly important in S. TX ecosystems due to fluctuations in resource availability – Compositional changes may indicate changes in microbial diversity

• Results indicate negative changes in soil quality and microbial functioning that are key factors when undergoing restoration practices Current Research

• What causes this change in microbial communities? – Residual dry matter? – Introduction of individual plant?

• How can we manage and control? – Grazing, burning, disking, herbicide? – All of the above? Acknowledgements

• USDA-ARS-CSR Laboratory • The Rotary Club of Corpus Christi-Harvey Weil • Mr. Henry Hammon • Mr. Renee’ Barrientos • The Coates family • South Texas Quail Coalition • The Brown Foundation Questions?