STRUCTURAL ATTRIBUTES OF SCHIZACHYRIUM SCOPARIUM IN RESTORED TEXAS BLACKLAND PRAIRIES

Authors: Derner, Justin; Polley, Herbert; Johnson, Hyrum; Tischler, Charles

Submitted to: Journal of Restoration Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2003
Publication Date: 3/1/2004
Citation: Derner, J.D., Polley, H.W., Johnson, H.B., Tischler, C.R. 2004. Structural attributes of Schizachyrium scoparium in restored Texas blackland prairies. Restoration Ecology. 12(1):80-84.

Interpretive Summary: Many previously cultivated lands are being restored to prairies in the Southern Great Plains. These restoration efforts utilize a single planting of seeds of desired plant species that results in plants being of similar age. Therefore, the entire population of plants in these restored prairies may be more susceptible to disease and disturbance than populations of plants in native prairies that have many different aged plants. We measured the physical structure of little bluestem, a dominant perennial grass in the tallgrass prairie, in prairies differing in time since restoration and in a native tallgrass prairie. Most of the plants in the oldest restored area were physically separating into several, smaller plants, suggesting that most individuals were of similar age. Plants in the youngest restored prairie were smaller and did not exhibit the pattern of fragmenting associated with older plants. Surprisingly, plants in the native prairie were physically similar to the younger plants in the recently restored prairies. Results indicate that there is considerable risk to population dynamics of little bluestem associated with restoring tallgrass prairie with a single seeding. Populations with single-aged plants are likely more susceptible to disease, pathogen injury and severe disturbances. Producers attempting restoration efforts in tallgrass prairie need to be aware of the economical and ecological risks associated with disturbance and similar-aged plants.

Technical Abstract: There is a paucity of information on how the physical structure of the C4, perennial bunchgrass little bluestem [Schizachyrium scoparium (Michx.) Nash] in restored prairies may be affected by the time since restoration. We hypothesized that tiller density would be lower, and size and occurrence of "hollow crowns" and degree of plant fragmentation would be greater as time since restoration increased. One hundred plants in a native tallgrass prairie, and 8-, 17-, and 23-year old restored tallgrass prairies were assessed for: presence/absence of a "hollow crown" (i.e., dead center portion), degree of fragmentation, plant height, tiller density and diameter of the "hollow crown". Tiller density was lower and the size and occurrence of "hollow crowns", and degree of plant fragmentation was greater in older restored prairies. Surprisingly, physical structure of little bluestem plants in the native prairie was similar to that of plants in more recently restored prairies (8-yr and 17-yr), which may indicate that little bluestem plants in the native prairie are fragments of previous large plants. Responses of little bluestem to time since restoration were consistent with the pattern of architectural development in bunchgrasses, indicating that plantings resulting in a single cohort of little bluestem may render populations in restored prairies particularly susceptible to severe disturbances.