Hubbard Brook Experimental Forest: Seedling bank – watershed 1 and watershed 6 (2018)

The understory layer is complex and includes groups of stems with
distinctly different chances of survival and recruitment to the
sapling size class. We explored how calcium amendment has impacted the
trajectory of the seedling bank at Hubbard Brook Experimental Forest.
The density of all tree stems in the seedling bank in 2018 (19 years
after treatment) was greater in CAL (Watershed 1; calcium treatment)
than REF (Waterhsed 6; reference) and beech was more abundant than
sugar maple in both watersheds. In terms of relative abundance, the
treatment had the opposite effects on the two species: the relative
density of sugar maple was significantly greater in CAL than REF while
the relative density of beech was significantly less. In terms of
beech stem origin, Beech sprouts were more abundant than seedlings on
both watersheds; however, beech stems of seed origin were more
abundant on CAL (mean±1SE: 4.06±0.49 seedlings m-2) than REF
(2.98±0.42), while sprouts were fewer (CAL: 14.4±1.30; REF: 20.5±1.47)
resulting in the seedling to sprout ratio on CAL (1:3.5) being half
that on REF (1:7). The influence on the seedling bank on future
composition of these forests remains to be seen.

These data were gathered as part of the Hubbard Brook Ecosystem Study
(HBES). The HBES is a collaborative effort at the Hubbard Brook
Experimental Forest, which is operated and maintained by the USDA
Forest Service, Northern Research Station.