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.