© Photos and content by Meghann Jarchow and Alexa Kruse. 

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Sampling Methods

 

The tallgrass prairie is a rapidly declining ecosystem. In order to better understand the ecology of this important ecosystem, the productivity of the ecosystem needs to be measured. One way to measure the productivity of an ecosystem is to measure the aboveground biomass. This thesis develops a model to allow for more efficient sampling of the tallgrass prairie ecosystem through a non-destructive method of estimation of aboveground biomass. The point-intercept method (PIM) is a commonly used technique to non-destructively sample herbaceous the vegetation. The PIM records the number of times a plant crosses the pin (a thin metal rod), which is quantified as a hit, to calculate the plant abundance and species diversity in an area.

 

A vegetative survey was conducted using the PIM and clipping of aboveground biomass to determine the relationship between aboveground biomass and total hits in May, July, and September. Because plants have different growth forms, which affects the relationship between the number of hits and the amount of aboveground biomass produced, the morphology of the plants sampled needs to be considered. In order to strengthen the relationship between number of hits and aboveground biomass, several different morphological characteristics were sampled: leaf width, leaf thickness, leaf angle, plant height and stem diameter for three to ten representative species from the main prairie functional groups: C3 grasses, C4 grasses, non-leguminous forbs, and legumes.

 

Principle Component Analysis (PCA) showed that functional group identity alone did not separate the species into distinct groups. Leaf width and growth form (grass versus forbs) were chosen as the grouping variables because combining these two plant characteristics separated the species into distinct groups. This resulted in five plant categories: narrow-leaved grasses, wide-leaved grasses, narrow-leaved forbs, medium-leaved forbs, and wide-leaved forbs. July had the strongest relationship between the number of hits and aboveground biomass for most of the groups. However, the relationship between the number of hits and aboveground biomass was strongest for narrow-leaved grasses and wide-leaved grasses in September and May, respectively.

 

The regression equations produced through this research provide a more accurate method to estimate aboveground biomass in restored tallgrass prairies using a non-destructive sampling method.

 

Peer-reviewed article from the experiment:

Davis, A.C. and M.E. Jarchow (submitted) Non-destructive estimation of plant biomass in the tallgrass prairie ecosystem. American Midland Naturalist.