Recipient Organization
SOUTH DAKOTA STATE UNIVERSITY
PO BOX 2275A
BROOKINGS,SD 57007
Performing Department
Natural Resource Management
Non Technical Summary
Non-native plant invasions create significant ecological and economic impacts. Biological invasions occur when a non-native species is introduced to a new environment, grows into a sustained population, and this population creates problems. Ecologically, invasive species alter community structure, alter ecosystem processes such as hydrology, nutrient cycling, and fire regimes. Specifically, invasive plants in South Dakota have been observed to decrease wildlife habitat quality, substantially lower native species diversity, and reduce forage abundance for livestock. Beyond ecological impacts, species invasions generate economic impacts estimated to be greater than $100 billion annually in the US as a result of costs to control the invasion, reduced recreational and aesthetic opportunities, and lost livestock and crop production. Identification of traits that contribute to invasion enable more informed and precise management of invasive species. Competitive ability is often a trait that enables newly introduced species to become dominant in a new environment. Competitive ability encompasses both direct and indirect effects of the invader on neighbors. The hypothesis that invasive species have higher competitive ability than co-occurring native species is long standing with documented support in many ecosystems. An invader with a large competitive effect (i.e., ability to suppress neighbors) and a large competitive response (i.e., avoidance of suppression due to neighbors) will have a high potential to become invasive. It is worthy to note that allelopathy, or the direct chemical inhibition of one by plant by another, is not a mechanism of competition. A species with higher competitive ability may be more likely to invade resource rich sites and sites with higher biodiversity than species without this ability. South Dakota grasslands tend to be fairly resource rich and biodiverse and therefore may be especially vulnerable to invasion of species with high competitive ability. Crown vetch (Securigera varia synonym Coronilla varia) is a non-native perennial legume that has been planted for erosion control or as forage. Crown vetch can become invasive, spreading from where it was planted both by seed and rhizome. The dense monospecific stands created by crown vetch decrease native plant richness, performance, and biomass; modify soil nutrient cycling; and alter available fuel loads. Crown vetch has very high competitive ability, even outcompeting Canada thistle (Cirsium arvense) in some settings. Russian olive (Elaeagnus angustifolia) was introduced in the early 1900's as a horticulture tree from central Asia to the United States. Russian olive now occurs in rangelands and riparian areas in the Great Plains, the Intermountain West, and western Canada. Federal programs between 1930 and 2002 encouraged land managers to plant Russian olive in US grasslands to provide windbreak and stabilize soils. However, ecological research suggests that Russian olive creates negative ecological impacts. Russian olive has been observed to alter vegetation dynamics by limiting recruitment of shade-intolerant native tree and shrub species. In riparian areas of southeastern Alberta and north-central Montana, Russian olive has almost completely replaced the native Plains cottonwood (Populus deltoides). Russian olive has also been observed to alter the soil microbial community and alter nutrient cycles in both terrestrial and aquatic systems.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The major goal of this project is to elucidate the competitive ability of two non-native plants in South Dakota that have previously received little research attention. The supporting objectives are:Determine the competitive ability of non-native crown vetch (Securigera varia) compared to co-occurring native plants.Determine if soil solarization effectively reduces the seedbank of non-native crown vetch (Securigera varia).Determine the competitive ability of non-native Russian olive (Elaeagnus angustifolia) compared to native riparian species.
Project Methods
Objective 1: Determine the competitive ability of non-native crown vetch (Securigera varia) compared to co-occurring native plants. A standard 'cage-match' design will be used to determine the competitive ability of crown vetch compared with co-occurring natives (options include Echinacea angustifolia, Dalea purpurea, Monarda fistulosa, Cleome serrulata, Ratibida columnifera, Liatris aspera, Gaillardia aristata, and Aster ericoides). In this experiment, growing with a neighbor will be considered the 'treatment' and plants growing alone will be considered the 'control'. Within a greenhouse located at South Dakota State University's main campus in Brookings, SD, crown vetch and native seeds will be planted in containers (Deepot 40, Steuwe and Sons, Corvallis OR) containing field-collected topsoil. The goal of the cage-match design is to have one crown vetch individual and one native individual in each pot. In case germination of the seeds is not 100%, several seeds of each species will be planted per pot to ensure that at least one plant of each species establishes. Within each treatment pot, multiple seeds of crown vetch will be seeded in the center of the pot and multiple seeds of one native species will be planted 2.5 cm from the center. The first emergent crown vetch seedling and the first emergent native seedling will be allowed to grow, and all subsequent seedlings will be removed. Control pots with one plant of each species (crown vetch and each native species) growing alone will also be planted. Ten (10) replicate pots for each treatment combination and of each individual species growing alone will be established. Because I am measuring competition as the effect of one individual on another individual, the number of seeds germinating is not important. The only important factor is to have one plant of each species per treatment pot. Greenhouse temperature will be maintained between 10-20 °C and ambient light will be used. Pots will be kept near field capacity with careful and attentive watering. Plants will be allowed to grow for a 5 month growing season after which aboveground biomass will be removed. Biomass from each individual plant will immediately be placed in envelopes, labeled, and placed in a drying oven set at 60 °C until constant weight is achieved. Biomass will then be weighed. Response variables include: 1) biomass of plants growing with and without a neighbor; and 2) a relative interaction index. The relative interaction index that will be used is Rii= (Bw-B0)/(Bw+B0) where Bw is plant biomass produced with competition (growing with a neighbor) and B0 is plant biomass produced without competition (growing alone). This index has strong mathematical properties (i.e., it is linear, has no discontinuities in its range, and is symmetrical around zero) and reflects the competitive ability of crown vetch. Data will be analyzed in JMP Pro 12 (JMP Pro, Version 10. SAS Institute Inc., Cary, NC, 2012).Objective 2: Determine if soil solarization effectively reduces the seedbank of non-native crown vetch (Securigera varia). Solarization is a method of placing plastic film on the soil surface during the summer to control plant invasions. The basic premise is that the heat that accumulates under the solarization treatment during the entire summer kills seeds in the seedbank. Solarization uses minimal labor, does not introduce chemicals into the environment, nor cause large disturbance. This method has been shown to be effective in controlling plant invasions in southwestern rangelands. We will adapt this method as a potential strategy for controlling crown vetch invasion in South Dakota. Because crown vetch is a recent invader to South Dakota, patches that are large and dense enough to adequately replicate our treatments are rare. Therefore, this field experiment will take place at the Murfield Waterfowl Production Area managed by US Fish and Wildlife Service. Crown vetch was first recorded at Murfield in 2014 and has since experienced substantial population growth. In this experiment, the solarization film will be considered the 'treatment', and areas adjacent to and outside the film will be considered the 'control'. Twenty 1m X 1m squares of 60 μm thick black polyethylene film will be deployed on patches of crown vetch at Murfield for an entire summer season. The film will be placed in the field early in the season but after crown vetch plants can be identified. The film will be held in place with landscape fabric staples. We will check the film every 10 days and replace any staples that have been lost and replace any film that has been damaged. Film will be removed late in the season after plants senesce. Seed bank samples will be collected: 1) from both the treated plots and control plots before the film is deployed; 2) from both the treated plots and control plots immediately after the film is removed; and 3) from the control plots later in the season after seed shatter. Seed banks will be examined using methods described in Espeland, Perkins, and Leger, 2010. The objective of this study is to examine if a season-long solarization treatment will eliminate the seed bank of crown vetch, thus the response variable will be crown vetch germination from the seed bank samples. The efficacy of the treatments will be determined by the difference in crown vetch germinants from samples collected from under the treatments and from control areas. Data will be analyzed in JMP Pro 12 (JMP Pro, Version 10. SAS Institute Inc., Cary, NC, 2012).Objective 3: Determine the competitive ability of non-native Russian olive (Elaeagnus angustifolia) compared to a native riparian species. The competitive ability of Russian olive will be determined using cage match methods similar to those for objective 1 with some modification. The invasive species will be Russian olive and the native species could include (Salix exigua, Salix amygdaloides, or Populus deltoids). Large containers will be used (Deepot 60, Steuwe and Sons, Corvallis OR). Each cage match container will be planted with one field-collected cutting of Russian olive and one field-collected cutting of the native species. The cuttings will be placed in the container 10 cm apart. Control pots with one individual of each species growing alone will also be planted. The replication level will be 10. In this experiment, growing with a neighbor will be considered the 'treatment' and plants growing alone will be considered the 'control'. Careful and attentive watering will keep the pots near field capacity. Greenhouse temperature will be maintained between 10-20 °C and ambient light will be used. Plants will be allowed to grow for a 5 month growing season after which aboveground biomass will be removed. Biomass from each individual plant will immediately be placed in bags and labeled. Biomass will then be placed in a drying oven set at 60 °C until constant weight is achieved. Biomass will then be weighed. Response variables include: 1) biomass of plants growing with and without a neighbor; and 2) a relative interaction index. The relative interaction index that will be used is Rii= (Bw-B0)/(Bw+B0) where Bw is plant biomass produced with competition (growing with a neighbor) and B0 is plant biomass produced without competition (growing alone). This index has strong mathematical properties (i.e., it is linear, has no discontinuities in its range, and is symmetrical around zero) and reflects the competitive ability of Russian olive. Data will be analyzed in JMP Pro 12 (JMP Pro, Version 10. SAS Institute Inc., Cary, NC, 2012).