influence of chinese privet (ligustrum sinense lour.) on floodplain productivity and regeneration...
TRANSCRIPT
Influence of Chinese privet (Ligustrum sinense Lour.) on floodplain productivity and regeneration
Eve Brantley, Jennifer Mitchell, and B. Graeme LockabyAuburn University School of Forestry and Wildlife SciencesCenter for Forest Sustainability
Ligustrum sinense Lour.• Often forms dense thickets, particularly in bottomland
forests and along fencerows
• Shade and flood tolerant
• Aggressive colonizer - spreads locally by root sprouts and widely by abundant bird- and other animal-dispersed seeds.
Invasive Plants of the Eastern United States
• Present in all of the southeastern states and ranges north to Massachusetts
Objectives• To determine how increasing densities of Chinese privet
influence aboveground and belowground net primary productivity.
• Investigate influence of Chinese privet density on native plant regeneration
Study Sites• 16 - 0.04 ha study sites selected in West Georgia
• Southern Piedmont
• Floodplains occupied by deciduous forests, closed canopy
ÊÚ
ÊÚ
ÊÚÊÚÊÚ
ÊÚ
ÊÚ
ÊÚÊÚ
ÊÚ
ÊÚ
ÊÚ
ÊÚÊÚ
ÊÚ
ÊÚ
ÊÚ
ÊÚÊÚ
ÊÚ
Georgia, USA
Columbus GA
LaGrange GA
Study Sites
• Sites represent a continuum of understory Chinese privet stem density (0 – 100%)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
BLN
1
BLN
2
BLN
3
MU
3
RB1
SC2
SC1
MU
2
RB3
SB2-
1
SB2-
2
MU
1
RB2
SB4-
3
SB4-
1
SB4-
2
Prop
ortio
n of
ste
ms
as C
hine
se p
rivet
Study sites
To determine how increasing densities of Chinese privet influence above- and belowground net primary productivity.
Aboveground productivity:• Monthly collection of litterfall (3 -.25 m2 traps per site)
• Litterfall samples dried, weighed and analyzed for C, N, P
• Diameter at breast height (DBH) recorded annually for all stems greater than 10 cm DBH and used to estimate stem annual increment
To determine how increasing densities of Chinese privet influence above- and belowground net primary productivity.
Belowground productivity:• Two fine root samples collected every 6-8 weeks using
soil core method (Vogt and Persson 1991, Anderson and Ingram 1993, Bledsoe et al. 1999)
• Samples collected to a depth of 11 cm and sorted size classes by live and dead fractions
• Samples dried, weighed
and analyzed for C and N
Investigate influence of Chinese privet density on native plant regeneration
Regeneration:• 12 – 1 m2 plots established at 3, 6 and 9M from site
center on north, south, east, and west ordination
• After spring leaf out, vegetation in each regen plot less than 10 cm DBH will be identified to species and its height recorded
Statistics• SAS version 9.1
• Linear and non-linear regression
• All differences below p < 0.10 reported
Year 1 Results
Increasing privet understory
Net Primary Productivity, Year 1
0
500
1000
1500
2000
2500
3000
3500
BLN
1
BLN
2
BLN
3
MU
13
RB
1
SC
2
SC
1
MU
12
RB
3
SB
21
SB
22
MU
11
RB
2
SB
43
SB
41
SB
42
g/m
2/yr
Roots Stem NPP Litterfall
Year 1 Results
• Chinese privet presence measured by proportion of understory - percent of understory that is Chinese privet (0 – 100%)
• Curvilinear and linear relationships between Net Primary Productivity and privet invasion
• Strong, negative relationship between Chinese privet invasion and native plant regneration
Net Primary Productivity and Chinese privet understory proportion
Significant curvilinear relationship between
– Total NPP & proportion of understory as privet
(P < 0.008 R2 .5821)
0
500
1000
1500
2000
2500
3000
3500
0 20 40 60 80 100
% understory privet 2004
tota
l npp
g/m
2/yr
Net Primary Productivity and Chinese privet understory proportion
Significant curvilinear relationship between
– Aboveground NPP & proportion of understory as privet
(P < 0.05 R2 .4133)
0
500
1000
1500
2000
2500
0 20 40 60 80 100
% understory privet 2004
tota
l ab
ove
gro
un
d n
pp
g/m
2/yr
Net Primary Productivity and Chinese privet understory proportion
Significant nonlinear relationship between
– Belowground NPP & proportion of understory as privet
(P < 0.01 R2 .5311)
0
200
400
600
800
1000
1200
0 20 40 60 80 100
% understory privet 2004
bel
ow
gro
un
d n
pp
g/m
2/yr
Regeneration
% Chinese Privet Understory (2004) compared with % Chinese Privet in Regeneration Layer (2005)
y = 0.9688x + 5.9086 (p < 0.001 R2 = 0.933)
0
20
40
60
80
100
0 20 40 60 80 100
% Understory Chinese Privet 2004
% R
eg
en
era
tion
Ch
ine
se P
rive
t 2
00
5
Regeneration
% Chinese Privet Understory (2004) compared with % Native Species in Regeneration Layer (2005)
y = -0.9641x + 94.115 (p < 0.001 R2 = 0.9472)
0
20
40
60
80
100
0 20 40 60 80 100
% Understory Chinese Privet 2004
% R
egen
erat
ion
Nat
ive
Spe
cies
20
05
Year 1 Conclusions - NPP
• In southeastern Piedmont riparian areas Chinese privet appears to influence
– Net Primary Productivity
– Native species regeneration
As Chinese privet stem densities rise:
• ANPP is the greatest at medium levels of Chinese privet understory proportion (40-80%)
• ANPP is lower at the low (0-40%) and high (80-100%) levels of Chinese privet understory proportion
As Chinese privet stem densities rise:
• BNPP is the greatest at medium levels of Chinese privet understory proportion (40-80%)
• BNPP is lower at the low (0-40%) and high (80-100%) levels of Chinese privet understory proportion
Year 1 Conclusions – Regeneration
• Proportion of Chinese privet in the understory is strongly related to the regeneration layer
– Increase in Chinese privet regeneration with increasing proportion of understory Chinese privet
– Decrease in native species regneration with increasing proportion of understory Chinese privet
~ 50% understory privet, native regen drops below 40%
Acknowledgements
• Dr. B. Graeme Lockaby• Dr. Kathryn Flynn• Dr. William Conner• Dr. James E. Hairston
• Jennifer Mitchell• Don Vestal• Robin Governo• Lena Polyakova• Rachel Jolley• Jackie Crim• Emile Elias
Auburn University School of Forestry and Wildlife Sciences, Center for Forest Sustainability