DOI: 10.5061/dryad.9s4mw6msf
title: Plant functional traits of 337 native Texas grasses

description: Premise: Understanding relationships among grass traits, fire, and
 herbivores may help improve conservation strategies for savannas that are
 threatened by novel disturbance regimes. Emerging theory, developed in
 Africa, emphasizes that functional traits of savanna grasses reflect the
 distinct ways that fire and grazers consume biomass. Specifically,
 functional trade-offs related to flammability and palatability predict
 that highly flammable grass species will be unpalatable, while highly
 palatable species will impede fire. Methods: We quantified six culm and
 leaf traits of 337 native grasses of Texas—a historical savanna region
 that has been transformed by fire exclusion, megafaunal extinctions, and
 domestic livestock. Results: Multivariate analyses of traits revealed
 three functional strategies. ‘Grazer grasses’ (n=50) had culms that were
 short, narrow, and horizontal, and leaves with high width:length and low
 C:N—trait values that attract grazers and avoid fire. ‘Fire grasses’
 (n=104) had culms that were tall, thick, and upright, and leaves that were
 thick, with low width:length, and high C:N—trait values that promote fire
 and discourage grazers. ‘Generalist tolerators and generalist avoiders’
 (n=183) had trait values that were intermediate to the other groups.
 Conclusions: Our findings confirm that the flammability-palatability
 trade-offs that operate in Africa also explain correlated suites of traits
 in Texas grasses. This highlights that the grass flora of Texas bears the
 signature of Pleistocene megafauna and the influence of fires that predate
 human arrival. We suggest that grass functional classifications based on
 fire and grazer traits can improve prescribed fire and livestock
 management of savannas of Texas and globally.
description: # Plant functional traits of 337 native Texas grasses
 [https://doi.org/10.5061/dryad.9s4mw6msf](https://doi.org/10.5061/dryad.9s4mw6msf) ## Description of the data and file structure *Maximum culm height*—(cm) is the maximum attainable height of the grass culm. Because maximum culm height for many species is not accurately reflected in herbarium specimens, we extracted data from Silveus (1933), Gould (1975), Shaw (2011) and Clayton et al. (2016). *Culm diameter*—(mm) is the diameter of the internode of the culm at its widest point. At the S. M. Tracy herbarium, Texas, we measured one randomly selected culm per specimen using a digital micrometer (Mitutoyo 293-344-30 Digimatic Micrometer, 0.001 mm precision) positioned at the thickest part of the second long internode following standard protocols (Wigley et al., 2020). In cases where the culm was not round, we measured the shortest dimension. *Culm angle*—(no units, categorical variable) is the angle between the grass culm and the soil surface. We extracted culm angle data from published literature [Silveus (1933), Gould (1975), Shaw (2011) and Clayton et al. (2016)]. From the species’ descriptions, we coded the culm angles following the classification of Hempson et al. (2022): ‘spreading’, ‘creeping’, ‘prostrate’ = 1; ‘spreading to ascending’, ‘spreading to geniculate’, ‘creeping to ascending’, ‘creeping to geniculate’ = 2; ‘geniculately ascending’, ‘decumbent’, ‘geniculately ascending and/or decumbent’, ‘erect or spreading’, ‘erect or prostrate’ = 3; ‘erect or geniculately ascending’, ‘erect or decumbent’ = 4; ‘erect’ = 5. Thus, culm angle values range from 1 to 5, representing prostrate horizontal angle (1) to an erect vertical angle (5). *Leaf W:L *(no units)—*is the ratio of the width measured at the widest portion of the leaf to the maximum length of the leaf. Because literature-derived measurements are a good proxy for (and ultimately derived from) herbarium specimens (as in Jardine et al., 2020), we extracted leaf dimensions from published literature [Silveus (1933), Gould (1975), Shaw (2011) and Clayton et al. (2016)].*  *Leaf thickness *(mm)— is the distance between adaxial and abaxial surfaces of the leaf measured just near (not at) the midrib. From each specimen we rehydrated leaf sections for 24 hours in distilled water (Jardine et al., 2020) and then measured the thickness with a digital micrometer (*Mitutoyo 293-344-30 Digimatic Micrometer, least count = 0.001 mm*). *Leaf C:N *(no units)—is the ratio of carbon to nitrogen in leaves. Due to the large number of samples (N= 996), we contracted four labs [Stable Isotopes for Biosphere Science Lab, Texas A&M University (427 samples); Cornell Isotope Lab, Cornell University (104 samples); Stable Isotope Ratio Facility for Environmental Research, The University of Utah (289 samples); Boston University Stable Isotope Laboratory, Boston University (176 samples)] to measured leaf C and N of leaf sections taken from herbarium specimens at the S. M. Tracy Herbarium.