Scott A. Davis and Dr. Bruce Roundy, Plant and Animal Sciences
The invasion of non-native species, mainly cheatgrass (Bromus tectorum), into our rangelands, especially following the destruction caused by wildfires, has made it necessary to find viable options for the restoration of native plant species to these areas. The aim of this project was to determine whether or not it is possible to create models for the germination and seminal root growth of a suite of species using heat accumulation models. By creating these models, we hope to be able to discover other native species that not only compete with cheatgrass through early establishment, but provide a quality food source for native animals in varying climates as well.
Much progress has been made over the past year. However, as occurs with any new experimental design, we have encountered setbacks and were required to make modifications not only to the timetable, but to our experimental design. For example, growth chambers originally intended to be used in the seminal root growth phase of this study were unable to maintain consistent temperatures with the higher than normal humidity levels caused by excess water from the soil tubes. Data from these failed incubators was thrown out and a new chamber was located for use in this phase of the experiment. Unfortunately, after repeated attempts and consultations with the manufacturer of the unit, as well as other service professionals, the large walk-in chamber is not yet ready for use. These events have made it impossible to this point to progress with the second half of the study.
Despite these setbacks, the study proceeded to gather information on a suite of seven species under diurnal temperature curves including: cheatgrass (Bromus tectorum), blue bunch wheatgrass (Psuedoroegneria spicata), crested wheatgrass (Agropyron desertorum), common yarrow (Achillea millefolium), native flax (Linum lewisii), longspur lupine (Lupinus arbustus), and nakedstem sunray (Enceliopsis nudicaulis).
A year ago, germination models were created by gathering data on these species from growth chambers that were programmed to maintain constant temperatures of five degree intervals between five and 30 degrees Celsius. Each species had 25 seeds placed in a Petri dish on each of the four shelves of a total of six growth chambers. Every day for two weeks and then every other day for an additional two weeks, seeds that had germinated were removed from the Petri dishes and tallied. Following the germination trials, these data were compiled and then analyzed to show the number of days required to reach 50% germination, days to 50% germination of the germinable seeds, accumulated degree hours to 50% germination, and lastly the average degree hours required to reach 50% germination at each temperature for each species. Using this information and simple regression analysis, models were created that predict the amount of time needed for 50% germination of the germinable seeds for each of the above named species.
In order to test the accuracy of these models, growth chambers were programmed to follow diurnal (fluctuating) temperature curves created from data collected from the field. Each species had 25 seeds placed in a Petri dish on each of the four shelves of the growth chamber. Every day for two weeks and then every other day for an additional three weeks, seeds that had germinated were removed from the Petri dishes and tallied. This process was repeated for three diurnal curves resembling field temperatures for early spring, late spring, and early fall. After analyzing these numbers to determine the number of days required to reach 50% germination, days to 50% germination of the germinable seeds, accumulated degree hours to 50% germination, and lastly the average degree hours required to reach 50% germination at each temperature for each species, actual outcomes observed under diurnal curves will be compared with those predicted by the models that were previously created. Statistical analysis of the differences or similarities will indicate the success of the models in predicting germination under field conditions.
Next we will attempt to create a model of the seminal root growth of each of these species. Four containers have been constructed to hold 20-cm tubes at a 45 degree angle to ensure that the seminal root will grow along the clear side of the tube, allowing measurement and observation of their growth. Four of these containers containing five tubes of each species will be placed on separate shelves in the walk-in growth chamber that will be programmed to hold constant temperatures of five degree intervals between five and 30 degrees Celsius. By measuring the days to germination and then the days to 15 cm root depth over a two month period, we will create a model to predict the amount of degree hours necessary to reach 15 cm of seminal root depth.
Following the creation of the seminal root growth model, these same containers will then be placed into the same growth chamber that will be programmed to maintain the same early spring, late spring, and early fall diurnal temperature regimes used in the constant temperature germination phase of the experiment. Measuring the days to 50% germination and then the days to 15 cm seminal root depth over a two month period, we will then determine the degree hours necessary for both germination and seminal root growth. We will then compare these observed outcomes with those predicted by the seminal root growth model in an effort to determine the model’s viability.
The germination models created earlier in the study were presented at the international conference of the Society for Range Management held in Vancouver, British Colombia in February of 2006. Interest was shown in the early results of these models and others expressed interest in the outcome of further testing. Following the compilation and analysis of data from the diurnal curve germination studies and the statistical analysis of the observed outcomes versus those predicted by our models, this study will be sent for publication in a professional journal.