Reductions in grassland species evenness increase dicot seedling invasion and spittle bug infestation

Previous experiments that tested whether diverse plant communities have lower invasibility have all varied species richness. We experimentally varied evenness of four grassland species (three grasses and one forb) by planting a field experiment in Texas, and monitored the number of unplanted dicot and monocot species that invaded plots for two growing seasons. By varying evenness, we eliminated any sampling effect in our diversity treatment, because all plots contained the same plant species. Experimentally reducing evenness led to a greater number of dicot invaders, which emerged in plots throughout the growing season, but had less of an effect on monocot invaders, which emerged in flushes when experimental plants were semi-dormant. Frequency of Solidago canadensis (altissima) stems with spittle bugs significantly increased with reductions in evenness during the first year, apparently because the greater number of Solidago stems in high evenness plots diluted the spittle-bug effect. These results support the view that higher diversity plant communities are more resistant to dicot invaders and insect herbivores

Season progression, ontogenesis, and environment affect Lespedeza cuneata herbage condensed tannin, fiber, and crude protein concentrations

© Crop Science Society of America. Sericea lespedeza [Lespedeza cuneata (Dumont de Courset) G. Don., SL] is a perennial, warm-season forage legume with wide adaptation, freeze tolerance, establishment ease, and persistence under grazing. It has high condensed tannin (CT) concentrations (g kg−1), which could be useful for methane mitigation and rumen bypass protein, as well as insect pest and gastro-intestinal nematode suppression. However, CT concentration is variable. Our objective was to test CT, crude protein (CP), and fiber concentrations at five locations (Georgia, Alabama, North Carolina, Louisiana, and Texas) during a growing season. Established ‘AU Grazer’ SL regrowth and accumulated herbage in separate trials was sampled starting late April 2010 every 35 d for four dates. Regrowth CP concentration ranged (P ≤ 0.05) from 127 g kg−1 in North Carolina on date 3 up to 221 g kg−1 in Alabama on date 1. Sericea lespedeza regrowth in the warmest latitude (Louisiana) consistently contained among the greatest (P ≤ 0.05) acid detergent fiber. In regrowth herbage, we recorded a wide (P ≤ 0.05) total CT range, from 133.5 mg kg−1 in Texas on date 3 to 46.1 mg kg−1 in Louisiana on date 1, reflecting variability in fiber-bound, protein-bound, and especially extractible CT. Results from accumulated herbage reflected (P ≤ 0.05) herbage ontogenesis with less CP and greater fiber concentration with maturity but showed the same lack of CT concentration pattern as the regrowth herbage. These results indicate that SL herbage nutritive value and CT concentration is variable, so that any hay or pellets sold commercially for CT content should be assayed by environment and crop maturity