Bioenergy production may reduce the emission of CO2 which contributes to climate change,
particularly when management strategies are adopted that promote soil carbon (C) sequestration in
bioenergy cropping systems. Planting perennial native grasses, such as switchgrass (Panicum virgatum L.)
and big bluestem (Andropogon gerardii Vitman) may be used as a strategy to enhance soil C
accumulation owing to their extensive root systems. Fertilizer use may further promote soil C
sequestration, because of its positive impacts on plant production and soil C input. However, the
influence of fertilizer addition on soil C accumulation is variable across bioenergy cropping
systems, and fertilizer can negatively impact the environment. Increasing plant diversity may be
used as a strategy to enhance soil C accumulation while augmenting other ecosystem properties such
as soil biodiversity. The present study evaluates how inter- and intra- specific plant community
diversity and N addition influence soil C storage and soil biodiversity. Soil was collected from a
long-term (9 growing seasons) field experiment located at the Fermilab National Environmental
Research Park in Illinois, USA. Treatments included [1] three cultivars of big bluestem and three
cultivars of switchgrass cultivars grown in monoculture, [2] plant community diversity manipulated
at both the species- and cultivar level, and [3] nitrogen (N) applied annually at two levels (0 and 67
kg ha-1). The soil at the site was dominated by C3 grasses for 30 years before
replacement with C4 bioenergy grasses, which enabled quantification of plant-derived C
accumulation owing to the natural difference in isotopic signature between C3 and
C4 grasses. Soil samples were analyzed for [1] soil C and its δ13C isotopic
signature, and [2] nematode and soil bacterial diversity. Our results indicate that both plant
diversity and N addition influence soil community structure but not soil C storage or soil nematode
biodiversity. However, the addition of big bluestem to the plant species mixes enhanced plant-derived
C storage. In summary, our findings suggest that plant species identity can control soil C accumulation
in the years following land conversion, and that manipulating plant community structure in bioenergy
cropping systems may have a greater positive impact on soil C accumulation than N fertilization.
Relationship between ecological stoichiometry and plant community diversity in the upper reaches of Tarim River, northwestern China