Rangeland Health Assessments: Vegetation
Rangeland Health Assessments: Vegetation
Rangeland assessments can be an incredibly valuable tool to not only gauge but improve the health of your grasslands. We use them regularly to give both us and the landowner information regarding their current state of their land and they can be instrumental in helping us choose techniques to improve and maintain the health of them but what actually goes into an assessment?
Before even stepping foot in the field, preliminary mapping will done to determine the specific ecoregion of the site such as moist-mixed grasslands or cypress uplands and that give us more information regarding the general climatic conditions. From there, we further differentiate into ecosites on the land of interest. Ecosites give us more information regarding the soil types, productivity of the land and its ability to respond the changes in management. These can include but are not limited to loam, badlands, sandy loam, thin and solonetzic. Armed with this information, it gives us expected plant communities to see and how different stress and management factors affect them.
Plants species can tell us a lot about the land and the management. Some species are more adapted to above or below average moisture conditions, some plants prefer different types of soil and some species tolerate grazing pressure better than others. For example, species like northern wheatgrass or porcupine grass are a preferred species and under continual heavy grazing pressure tend to decline. We call these decreaser plants and they are typically highly productive and highly palatable. On the other hand, there are increaser plants like pasture sage that will increase under heavy grazing pressure and are generally avoided by grazers. While they are native, they do hold little grazing value compared to the decreaser plants. Other species are opportunistic and establish quickly in recently disturbed areas and are classified as invaders.
To assess the plant community, we look at the individual plant species that make up the site and use quadrats that are 0.25m2 to identify each plant located within the quadrat. We will also break it down into what percentage of overall vegetation each plant makes up within the quadrat. It’s vital to complete multiple quadrats for the assessment and then averaged together to get a more complete look at the rangeland plant inventory that best captures what the land looks like.
After that we can compare the plant species in the area to the one in the reference community for that site. If the plant community at the site has any degree of alterations or changes, the score will change accordingly because it can be sign of disturbance such as drought or heavy grazing pressure with inappropriate rest. Plant communities can be vital to understand because the diversity and species of plants that make up grassland communities directly correlate with forage production and nutrients available for livestock.
For the vegetation component, we also evaluate the layers that are present. Grasslands are known for their incredible diversity and host a variety of plants that differ in size, structure, height and depth/composition of roots. Due to these various characteristics, they form layers and the layers greatly contribute to the overall diversity of the landscape.
The lichen and club moss cover on grasslands is also considered a layer because they contribute to the soil armour and the ability for the soil to hold water. When layers are missing, it can indicate stress from disturbance or grazing. It is also important to note if there are changes due to natural disturbance such as damage from wildlife or insects.
The third vegetation question asks if there are any invasive species present. Recording the types of invasive species, density and distribution is important for not only controlling the spread on that pasture but to decrease the chance of infestation to other pastures. Common invasive species noted are Leafy Spurge, Common Burdock and Canada Thistle but currently also include non-native grasses such as Crested Wheatgrass and Kentucky Bluegrass. Management for these non-native grasses are approached differently than the other typical weeds. In regards to Kentucky Bluegrass, it is not native but still serves purpose as a grazing resource and elimination is nearly impossible. You cannot selectively graze or spray it so we accept its presence but also acknowledge it does decrease the overall biodiversity of the native grasslands.
Once we collect all this information, we can move onto the next step of the rangeland assessment to look at the hydrologic function and soil erosion which we will cover in our next blog post!
Photo credit: Rangeland Health Assessment Native Grassland Booklet
Author: Mindy Hockley-Anderson