Use of auto-germ to model germination timing in the sagebrush-steppe.

William C Richardson,Nicholas S Barney,Dallin R Whitaker,Bruce A Roundy,Zachary T Aanderud,Matthew D Madsen,Ryan S Call,Kyler P Sant

doi:10.1002/ece3.4591

Abstract

Germination timing has a strong influence on direct seeding efforts, and therefore is a closely tracked demographic stage in a wide variety of wildland and agricultural settings. Predictive seed germination models, based on soil moisture and temperature data in the seed zone are an efficient method of estimating germination timing. We utilized Visual Basic for Applications (VBA) to create Auto‐Germ, which is an Excel workbook that allows a user to estimate field germination timing based on wet‐thermal accumulation models and field temperature and soil moisture data. To demonstrate the capabilities of Auto‐Germ, we calculated various germination indices and modeled germination timing for 11 different species, across 6 years, and 10 Artemisia‐steppe sites in the Great Basin of North America to identify the planting date required for 50% or more of the simulated population to germinate in spring (1 March or later), which is when conditions are predicted to be more conducive for plant establishment. Both between and within the species, germination models indicated that there was high temporal and spatial variability in the planting date required for spring germination to occur. However, some general trends were identified, with species falling roughly into three categories, where seeds could be planted on average in either fall (Artemisia tridentata ssp. wyomingensis and Leymus cinereus), early winter (Festuca idahoensis, Poa secunda, Elymus lanceolatus, Elymus elymoides, and Linum lewisii), or mid‐winter (Achillea millefolium, Elymus wawawaiensis, and Pseudoroegneria spicata) and still not run the risk of germination during winter. These predictions made through Auto‐Germ demonstrate that fall may not be an optimal time period for sowing seeds for most non‐dormant species if the desired goal is to have seeds germinate in spring.

Highlights

Seed germination timing strongly impacts the success of direct seeding efforts in wildland systems by influencing exposure to pathogens, nutrients and soil moisture, temperature, light, her‐ bivory, and other biotic and abiotic factors (Gornish et al, 2015; James & Carrick, 2016)
Our objectives were to provide instructions on how to use Auto‐ Germ and demonstrate the utility of the program through a case study that (a) calculated various germination indices under different constant temperatures on 10 different species commonly used for restoration projects in the Great Basin and (b) for these same spe‐ cies model seed germination timing across 6 years and 10 Artemisia‐ steppe sites to estimate the planting date required for 50% or more of the simulated population of seeds to germinate in spring (March 1st or later) when conditions are predicted to be more conducive for plant establishment
For all species except A. tridentata and L. cinereus, 50% or more of the required planting dates for spring germination occurred by November or later

Summary

Introduction

Seed germination timing strongly impacts the success of direct seeding efforts in wildland systems by influencing exposure to pathogens, nutrients and soil moisture, temperature, light, her‐ bivory, and other biotic and abiotic factors (Gornish et al, 2015; James & Carrick, 2016). For these reasons, several studies have tracked germination timing in the field to better understand. Knowledge gained from short‐term field germination studies is often lacking due to high annual variability in weather conditions at the time of the experiment (Hardegree, Jones, Roundy, Shaw, & Monaco, 2016). To gain general inferences from germination studies, labor‐intensive studies need to be repeated for multiple years

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