Research about Yazoo National Wildlife Refuge

USGS1990

Establishment of bottomland oak plantations on the Yazoo National Wildlife Refuge complex

Stocking, height and diameter growth, and invasion of both herbaceous and woody plant species are reported for 5 direct seeded and 5 planted seedling stands of bottomland oaks, all of which were between 4 and 8 years old. Stocking was generally higher in the planted seedling stands. Both height and diameter growth were substantially higher in the planted seedling stands. Low stocking and poor growth, especially for the direct seeded stands, was associated with medium-textured soils and a heavy cover of Johnson grass ( Sorghum halepense ) and goldenrod ( Solidago altissima ). Invasion of woody species was heavily dominated by light-seeded species, and was highest in stands close to mature trees.

Mississippi↗

USGS1988

Pesticide contamination and hatching success of waterbirds in Mississippi

Waterfowl wintering on the Yazoo National Wildlife Refuge (NWR) were contaminated (ltoreq 4 ppm wet wt) with dichloro diphenyl trichloroethane (DDT) and 1,1-dichloro-2,2-bis-(p-chlorophenyl) ethylene (DDE), but residues were below levels known to affect waterfowl. Eggs of some nesting waterbirds contained higher than expected levels of DDE, especially those of green-backed herons ( Butorides striatus ), ranging up to 43 ppm wet weight. Hatching success (P < 0.05) and eggshell thickness (P < 0.05) in green-backed herons and anhingas ( Anhinga anhinga ) were negatively correlated with DDE in the eggs, and shell thinning (P < 0.05) was evident 12-13 years after DDT was banned in the United States. The threshold level of DDE determined necessary for reduced hatching success in green-backed heron eggs was 5.1-10 ppm wet weight. These results further increase our ability to interpret DDE concentrations in waterbirds and predict their potential effects on productivity.

Mississippi↗