I studied the distribution and abundance of the plant species of forests in central Iowa, emphasizing the effect of cattle grazing on the vegetation. I used traits to identify groups of species that may function as guilds, and to address whether species' frequency was related to traits. To understand the difference between species that were common compared to those relatively less common (restricted species), I examined whether the two groups differed in reproductive output and allocation, seed viability, and seedling emergence;Understory species and canopy trees were generally distributed along the same environmental gradients. These were landform, soil phosphorous and nitrogen content, and disturbance and woodland size. I identified a distinct group of understory species associated with ungrazed and grazed plots. Species associated with ungrazed woods included many anecdotally to be typical of high quality woodlands. The strongest effect of grazing on tree species was the reduction in number of seedlings found in grazed woods. Traits associated ungrazed plots included preference for undisturbed, moist and low light habitats, low stature, flowering in the earliest part of spring, presence of root storage and ant dispersal. The species with the following traits had on average much higher frequency of occurrence compared to species that lacked the traits: diaspore dispersal by ants and by attachment to animals, and species that are native, flower in spring and prefer closed canopy (low light) and undisturbed habitats;Common species produced an order of magnitude greater but smaller seeds compared to congeneric or confamilial restricted species. They also produced more viable seed and had greater emergence rates than related restricted species. Seedlings of all 17 species emerged in sites currently occupied by each species suggesting that seed availability limits recruitment. In sum, the evidence suggests that restricted species have a more limited ability to migrate and recruit compared to related common species because they produce fewer and bigger (and therefore less dispersible seeds), and they have lower viability and emergence rates.