Top-down and bottom-up controls limit woody encroachment into persistent temperate rainforest meadows

These data describe soils, woody plant seedlings, and ungulate herbivory in and around temperate montane meadows in the Oregon Coast Range, USA. Meadows such as these are a global study system for the accelerating phenomenon of woody encroachment, but study this phenomenon into meadows in western Oregon has been conducted almost entirely in the western and High Cascades, with only two extant observational studies of grassy balds in the Coast Range. These data describe factors limiting woody encroachment into meadows in the Oregon Coast Range, including bottom-up control by soil properties, plant-plant interactions, and top-down control by large herbivores. I measured chemical and physical properties of soils (depth of organic layer; bulk density of top 3 cm of mineral soil; and mineral soil profiles: particle size distribution, pH, % total C, % total N) to a depth of 50 cm in meadow and forest. I recorded community, density, and proportion browsed for shrubs, conifers, and deciduous trees ≤2 m tall along transects from meadow into forest. I experimentally planted 20 Pseudotsuga menziesii (Douglas-fir) seedlings in each of five meadows (n = 100) and factorially manipulated aboveground neighboring plant presence and ungulate herbivore access. I found that meadow soils were lower in C and C:N; slightly lower in N, and similar in plant-available water (derived from particle size distribution) and pH relative to forest soils. Shrubs were most dense, but experienced the lowest browse pressure, near the meadow edge; while trees were sparse and varied by site—although at one site, browse pressure was heavier in meadow than forest. Seedling survival and growth varied by site, herbivory reduced growth, and total soil N best explained residual variation in seedling growth among sites. My findings indicate that ungulate herbivores exert top-down control on woody encroachment into temperate montane meadows, perhaps in concert with local N-limitation.