Baltimore Ecosystem Study: Increased diversity of the regional species pool via seeding augments establishment of native species in experimental vacant lot restorations

The harsh geophysical template characterized by the urban environment
combined with people’s choices has led ecologists to invoke
environmental filtering as the main ecological phenomena explaining
urban biodiversity patterns. Yet, dispersal is often overlooked as a
driving factor, especially on expanding vacant land. Does overcoming
dispersal limitation by seeding native species in urban environments
and increasing the functional or phylogenetic diversity of the seeding
pool increase native plant species diversity and abundance in urban
vacant land? We took an experimental approach to learn how different
dimensions of plant biodiversity within an augmented regional species
pool, via seed additions, can explain variation in community structure
over a 3-year period. Vacant lots were cleared and manipulated with
seeding treatments of high or low phylogenetic and functional
diversities from a pool of 28 native species. Establishment success,
total native cover and native species richness were followed and
compared to cleared, unseeded control lots as well as un-manipulated
lots. Seeding increased native plant abundance and richness over
uncleared plots, as well as cleared and unseeded control plots.
Phylogenetically diverse seed mixtures had greater establishment
success than mixtures composed of closely related species.
Diversifying seed mixtures increased the likelihood of including
species that are better able to establish on vacant land. However,
there were no differences in varying levels of either functional or
phylogenetic diversity. Augmenting the regional species pool via
diverse seed mixtures can enhance native plant cover and richness
under the harsh environmental conditions conferred by land
abandonment.