IMPACT OF GRAZING AND ENVIRONMENT ON SOIL CARBON IN RECLAIMED URANIUM
MINES TAILINGS: A REGION SPECIFIC STUDY IN WYOMING
Abstract
Grassland ecosystems, which cover over one-third of the Earth’s land
area, store 10-30% of global soil carbon (C). However, these ecosystems
face substantial impacts from human activities, including mining. This
study investigates the spatial distribution of soil C and related
environmental factors in reclaimed grasslands on former uranium mine
sites in Wyoming. We hypothesized that grazing duration and
environmental factors would influence soil C levels. Interactions
between topography, vegetation diversity, soil properties, and soil C in
the context of grazing management in both natural and reclaimed
grasslands from of a wide range of periods from 1 year to 100 years were
analyzed using Geographically Weighted Regression models. Data collected
from 2022-23 showed that total carbon was consistently higher in natural
grasslands (1.2-4.9%) than in reclaimed grasslands (0.8-1.3%).
Additionally, soil C was significantly higher in natural grasslands
grazed for 1 year compared to those grazed for 100 years. In contrast,
reclaimed grasslands had lower soil C in areas grazed for 1 year
compared to those grazed for 7 or 14 years. The absolute values of
coefficients from environmental covariates indicated that areas grazed
for a shorter duration (~1 year) were more influenced by
biotic and abiotic factors than areas grazed for longer periods
(>7 years). Our findings show moderate grazing increases the
resiliency of grassland ecosystem when grazed 7 years or longer and
acknowledge the roles of topographic, soil, and vegetative factors in
enhancing soil C concentration and developing sustainable land
management practice in rangeland conditions.