Individual study: Grassland compost amendments increase plant production without changing plant communities
Ryals R., Eviner V.T., Stein C., Suding K.N. & Silver W.L. (2016) Grassland compost amendments increase plant production without changing plant communities. Ecosphere, 7, e01270-n/a
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Other biodiversity: Add compost to the soil
A replicated, randomized, controlled study in 2008–2012 in two grazed grasslands in California, USA, found more plant biomass in plots with added compost. Sixteen species of rare plants were found only in plots with added compost. Plants: Before grazing, more plant biomass was found in plots with added compost, compared to plots without it (coastal prairie: 41% more; valley grassland: 71% more). Higher plant diversity was found in plots with added compost, compared to plots without it, in one of eight comparisons (coastal prairie, 2009: 7.5 vs 6 species/m2; Shannon evenness index). In the valley grassland, increases in the relative abundance of three grass species, and decreases in that of two forb and one bulb species, were found in plots with added compost, compared to plots without it. In the coastal prairie, sixteen rare species (<5% of observations) were found only in plots with added compost. The abundance of an invasive grass (medusahead Elymus caput-medusae) was lower in plots with added compost, in one of four comparisons (13% lower abundance in plots with compost), but that of an invasive forb (Carthamus lanatus) was no different. Methods: In December 2008, composted green waste (7 kg dry matter/m2, 129 g N/m2, C to N ratio of 11) was added to three plots at each of two sites (one valley grassland and one coastal prairie, both dominated by non-native annuals), but compost was not added to three control plots at each site. All plots (25 x 60 m plots) were in cattle-grazed paddocks (15 ha, rotationally grazed to 84 g standing/m2).