Upload
melnhe
View
246
Download
0
Embed Size (px)
Citation preview
Co-limitation in BEF: N affects P resorption and P affects N resorption Kara Phelps SUNY ESF
Why should we study?
• Unintentional fertilization of ecosystems over last 150 years ▫ Doubling in
atmospheric nitrogen concentrations
▫ About 400% increase in global phosphorus cycle
• Realization that ecosystems are often co-limited ▫ Not limited by single
least available nutrient ▫ Result = synergistic
ecosystem response to addition of multiple nutrients
Justus von Liebig http://todayinsci.com/L/Liebig_Justus/LiebigJustus-Quotations.htm
How can we study?
• Foliar resorption ▫ Translocation of
foliar nutrients prior to leaf senescence
▫ Result = nutrient conservation and recycling within the plant
How do we measure resorption?
Efficiency Proficiency • The percent difference
between nutrient concentrations of litterfall and green leaves
• The concentration to which nutrients have been reduced in litter
Previous studies • Elements in isolation
▫ Attempts to link P resorption to soil P and green leaf P
▫ Ditto for N
What do we expect? • Single element
limitation: ▫ Resorption of an
element is more efficient when that element is in low supply
▫ Low P efficiency with high soil P
What do we expect? • Multiple element
limitation: ▫ Resorption of an
element is driven by supply of other elements
▫ High P efficiency with high soil N
What have we seen so far? Pre-Treatment: See et al., 2014
• P efficiency and proficiency improved with increasing soil N content across six stands
• No detectable correlation between soil P and P resorption!
Whoa…
See, Yanai, Fisk, Vadeboncoeur, Quintero, and Fahey 2014
• Strong positive correlation between total soil N and P resorption efficiency ▫Across six sites ▫Among 4 of 6
species studied
What did we do? In the field
• Three young stands in Bartlett Experimental Forest ▫ C1, C2, and C3 ▫ 25-35 years old ▫ Four plots in each stand
N, P, NP, Control • Green leaves collected in C2
in August 2014 ▫ American beech, pin
cherry, white birch, yellow birch, red maple
• Litter collected in C1, C2, C3 in October 2014
What did we do?
In the lab: • All leaves were:
▫ Dried ▫ Ground ▫ Analyzed for C and N (CN
analyzer) ▫ Ashed and digested ▫ Analyzed for Al, Ca, Mg, Mn, P,
K, Na, Sr, and S (ICP-OES)
C:N ratios
Green Leaves – C2
• Green leaf N content and green leaf N concentration ▫ Highest in N-
fertilized plot of C2
▫ Soil N highest in NP plot
• P efficiency highest in N fertilized plot • N efficiency highest in P-fertilized plot
October P resorption proficiency
N efficiency correlation with green leaf P
N efficiency correlated with green leaf P concentrations, but not with green leaf N
P efficiency did not depend upon green leaf P concentrations, but was correlated with green leaf N concentrations
Resorption Efficiency
Green Leaf Concentrations Nitrogen Phosphorus
Nitrogen ρ = 0.19 p = 0.43
ρ = 0.54 p = 0.02
Phosphorus ρ = 0.48 p = 0.03
ρ = -0.14 p = 0.56
N efficiency correlated with green leaf P concentrations, but not with green leaf N
P efficiency did not depend upon green leaf P concentrations, but was correlated with green leaf N concentrations
Resorption Efficiency
Green Leaf Concentrations Nitrogen Phosphorus
Nitrogen ρ = 0.19 p = 0.43
ρ = 0.54 p = 0.02
Phosphorus ρ = 0.48 p = 0.03
ρ = -0.14 p = 0.56
N efficiency correlated with green leaf P concentrations, but not with green leaf N
P efficiency did not depend upon green leaf P concentrations, but was correlated with green leaf N concentrations
Resorption Efficiency
Green Leaf Concentrations Nitrogen Phosphorus
Nitrogen ρ = 0.19 p = 0.43
ρ = 0.54 p = 0.02
Phosphorus ρ = 0.48 p = 0.03
ρ = -0.14 p = 0.56
Next steps…• Compare with
pretreatment data • Same methods, more
stands to compare: ▫ Age ▫ Treatment, including Ca
plots
Ruth Yanai Adam Wild Craig See B9 Bunch
Thank you to: