Canopy modification of acid neutralizing capacity of atmospheric base
cations in a temperate pine plantation
Abstract
11institutetext:
Knowledge-based Systems and Document Processing Research Group
Faculty of Computer Science
Otto-von-Guericke-University Magdeburg
11email:
[email protected]
Chemical changes of base cations in bulk precipitation ( BP)
induced by canopy alteration significantly influence the buffer action
against soil acidification and the consequent biogeochemical processes
in forest ecosystems. However, the underlying mechanisms that influence
the varying magnitudes and directions of acid neutralizing capacities
(ANC) in BP during canopy passage remain less understood. Here,
we investigated the chemical compositions of base cations (potassium (K
+), calcium (Ca 2+), magnesium (Mg
2+) and sodium (Na +)), the capacity
of individual alkaline ions to neutralize acidity, in addition to their
spatio-temporal variabilities outside and beneath the canopies of
Chinese pine plantation ( Pinus tabuliformis Carr.) throughout
2019 growing season with a large proportion of annual rainfall. Results
showed that volume-weighted mean concentrations of base cations in
throughfall ( TF) were significantly increased with the highest
enrichment ratio by K +, followed by Mg
2+, Ca 2+ and Na
+. Canopy leaching mainly occurred for K
+ (59.06%) and Mg 2+ (54.20%)
whereas dry deposition of Ca 2+ (57.27%) were the
dominant net throughfall flux component. TF ANC was significantly
higher than BP, indicating that rainwater beneath the pine canopy
became less acidic. Ca 2+ was the predominant acid
neutralizing component, followed by K + and Mg
2+ in both BP and TF. However, the
capacity of Ca 2+ for neutralizing acidity was
weakened whereas K + and Mg 2+ were
enhanced in TF compared to BP. Additionally, the
concentrations of TF base cations were significantly negatively
or positively correlated to canopy cover and TF amount, with
exception of TF K +. Antecedent dry period and
rainfall intensity were the most influential meteorological parameters
affecting the intra-event variation trend and magnitude of TF
base cations. Our findings contribute to understanding the controlling
processes and underlying mechanisms that drive the complex interactions
between base cations nutrients and forest ecosystem.