Saccharum spontaneum biomass and associated soil and foliar nutrient data

Invasive C4 grasses that colonize tropical landscapes abandoned from use
for intensive grazing and agriculture can inhibit natural regeneration of
secondary forest. In Panama, dense stands of Saccharum spontaneum require
active forest restoration to re-establish successional processes. In this
region, restoration strategies typically involve clearing grass cover and
applying fertilizer prior to planting tree seedlings. However, if
fertilizers alleviate nutrient limitation in the grasses and enhance their
competition with tree seedlings, it can add to costs for manual
maintenance of the sites free of Saccharum. Here we evaluated how S.
spontaneum responds to nitrogen and phosphorus addition in the field to
determine whether S. spontaneum is nutrient limited in this system. S.
spontaneum was both nitrogen and phosphorus as revealed through increased
foliar nutrient concentrations. S. spontaneum biomass was significantly
greater in both nitrogen and phosphorus addition plots after both the
first growth period (early rainy season) and second growth period (late
rainy season), with release from co-limitation of N and P, and the overall
impact of N, greater during the second growth period. Nutrient limitation
in S. spontaneum and seasonal shifts in resource allocation suggest
caution when fertilizing areas under restoration that were previously
dominated by exotic grasses.