Management of remnant prairie ecosystems: Soil transfer, fire, and exotic species invasion

Adam R Warrix, Purdue University

Abstract

Property management is an important aspect in sustaining the Earth’s ecosystems. Anthropogenic changes to the planet have made conservation important in maintaining species abundance and diversity as well as limit damages to sensitive ecosystems. Invasive species have become a standard, consistent problem in managed ecosystems. Such species often invade into disturbed areas, which commonly are a result of restoration or other management activities. In dredging open water bodies at Eagle Marsh Nature Preserve (Allen County, IN), artificial mounds were constructed with the soil removed. This movement of soil created a disturbance which facilitated for the recruitment and colonization of invasive species. The purpose of this study was to quantify the effectiveness of transferring a native seed bank in a mesic prairie to the artificial mounds as a method of controlling invasive species. The native seed bank in the mesic prairie would be lost due to additional management. This study was conducted with greenhouse and field experimentation. Soil samples containing the seed bank were moved to a greenhouse to quantify plant emergence following different intact and mixed soil treatments. All emerging plant species were identified and counted. All treatment methods contained a high diversity of native species and a low diversity of invasive species with the exception of the seed bank soil mixed with soil from the mounds. The mound mixed soil contained a higher diversity of invasive species than other treatments. A plant survey of the mounds was conducted in July 2014. In October 2014, 960 m2 of soil was transferred from the donor site to the mounds. A post-move survey conducted in July 2015 indicated the native species diversity increased while the diversity of invasive species decreased. Soil transfer as a management strategy was appropriate in this situation where a large native seed bank in a donor region existed. By moving soil from one location to another, we were able to promote native plant establishment and reduce invasive species emergence. While soil transfer is effective, other management strategies may not have the same results. Callery pear (Pyrus calleryana) is an invasive tree introduced to North America as an ornamental from southwest Asia. It easily invades disturbed areas, causing a disruption to mid- to late-successional species establishment. The purpose of this study was to assess Callery pear demographics in a managed prairie and quantify the effects of a prescribed fire management strategy on Callery pear density and recruitment. This study was conducted at Arrowhead Prairie (Allen County, IN), managed by Little River Wetlands Project (LRWP). Before 2009, Arrowhead Prairie was primarily used for agriculture. Following LRWP acquisition, the property has undergone active management including native plant seeding and prescribed fire. The prairie was divided into a north and south section using a historic ditch, with the south section burned in April 2014 and the north section burned in May 2015. Bare seeds, fruit, first-year seedlings, and second-year seedlings were also burned in a separate controlled experiment. Fire in both years top killed Callery pear individuals, with 100% of surveyed trees producing epicormic shoots and 83% producing more than one epicormic sprout. First-year seedlings exposed to the fire had a 3% resprout rate while all seconds-year seedlings resprouted. In contrast, 13% of individuals at Arrowhead Prairie had epicormic shoots without fire. Trees were significantly shorter post-burn than prior to the burn; however, root collar diameter was not different, suggesting that resources were used in primary growth. While fire did reduce stem height, it did increase the number of stems occurring within the burned section due to epicormic sprouting. Root stored reserves provided necessary energy to produce numerous sprouts by the majority of pear trees, although no trees produced flowers during the duration of the study. Plant age likely plays an important role in response to fire, with seeds and fruits succumbing. However, older seedlings may survive with increased epicormic shoot production. Multiple techniques combined with relevant studies allows for land managers to make appropriate decisions in terms of management. Although many of these techniques are not universal, a wide range of researched techniques provides multiple avenues of approach when managing a parcel of land.

Degree

M.S.

Advisors

Marshall, Purdue University.

Subject Area

Plant biology|Ecology|Plant sciences

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