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Abstract:
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Grassland restoration projects are designed to restore native habitats on former
agricultural land on the Mid-Atlantic Coastal Plain and other areas with the support of the
Conservation Reserve Program (CRP) and the Conservation Reserve Enhancement
Program (CREP). Land once farmed for 60 years in Queen Anne’s County, Maryland,
was used for a grassland restoration project. The 92-ha of land was drilled-seeded with
warm-season grasses, such as little bluestem, big bluestem and eastern gamagrass and
sectioned off into 12 representative fields. The Ultisol soils on the Eastern Shore of
Maryland are characterized by being low in nutrients, low in organic matter and
moderately acidic. Prescribed burning was selected to help aid in maintaining the
grassland restoration process. The burns increase productivity of grasses by allowing
more available light and allow more nutrients to be released into the soil for plant uptake.
Soil core samples, 10 cm in depth, were taken from 9 locations within a 13-ha field 1 day
before, 11 days after and 1 year after a first prescribed burn, and 12 days after a third
prescribed burn. Total soil organic matter (SOM) content was determined by loss-onignition
method and total soil cation exchange capacity (CEC) was determined by the
barium compulsive exchange method. Total SOM content increased from pre-burn
values in samples taken 12 days after the third burn. These increases could have been due
to the fact that a year after the first burn, total SOM content did not fall below pre-burn
values, so a small build-up of ash is present after each burn. Total available CEC sites
were determined via weight of the soil during the compulsive exchange procedure and by
atomic absorption spectrophotometry. The two methods gave different results for CEC,
suggesting that the weight method is not as accurate. Overall CEC data shows a decrease
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both a year after the first burn and 12 days after the third burn as compared to pre-burn
conditions in all three layers. In the bottom layer, the CEC following the third burn was
overall lower than a year after the first burn. These decreases after the third burn could
have been because of the functional groups believed to exist on the ash were still
protonated, which prohibited any cations to bind to those sites. This was likely affected
by the decreases in soil pH values found at these times. After the third burn, the
relationships between CEC, SOM and extractable cations Ca2+, Mg2+ and K+ were still
correlated, although the relationships had changed. Results have shown that annual burns
provide increase production in the grassland restoration projects. |
