Lesson 32 Mineral Cycling - Alaska Geobotany Center

Ecosystem pools and fluxes of potassium at
Hubbard Brook
• In the 1960s and 1970s Bormann and
Likens worked out the biogeochemistry
of potassium, a very easily leached
element in forests at Hubbard Brook.
• K is the most abundant cation in
throughfall at HBEF, representing 33%
of the total during the growing season.
• K is added to the system through wet
and dry deposition, where it enters the
available pool directly or is washed into
the soils through the forest canopy.
Weathering is another important input.
• K is moved within the system
(intrasystem cycling) by throughfall,
stemflow, nutrient uptake, plant
assimilariotn and use, resorption and
biological decomposition.
• K departs the system through the
dissolved fraction and particulate
fraction in streams.
• The ecosystem is thus connected to
the larger biogeochemical cycles by
meteorologic, geologic, and biologic
vectors that move nutrients across
ecosystem boundaries.
Modified from Likens et al. 1977. Biogeochemistry of a Forested Ecosystem.