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Rete Montagna  Interna,onal  Congress   Eurac  Conven,on  Center  -­‐  Bolzano/Bozen  -­‐  IT  November,  6th  -­‐  8th  2014

How sensi)ve  is  riparian  vegeta)on  to  river   morphological  changes?  A  case  study  in  the  Italian  Alps     DANIELA  CAMPANA,  FRANCESCO  COMITI,   FRANCESCO  GIAMMARCHI,  GIUSTINO  TONON  

Free University  of  Bozen-­‐Bolzano,  Faculty  of  Science  and  Technology,  Bolzano,  Italy


2014


How sensiJve  is  riparian  vegetaJon  to  river   morphological  changes?  A  case  study  in  the  Italian  Alps  

Daniela Campana,  Francesco  ComiJ,  Francesco  Giammarchi,  GiusJno  Tonon   Free  University  of  Bozen-­‐Bolzano,  Faculty  of  Science  and  Technology,  Bolzano,  Italy  

INTERNATIONAL CONFERENCE     Eurac  ConvenJon  Center  –  November  6th  –  8th  2014  


OUTLINE

•  Study area     •  Aims  of  the  research     •  Methods   •  Climate  and  hydrological  regime   •  Tree  growth  paVerns   •  RestoraJon  effects  on  tree  growth     •  Conclusions  


STUDY AREA •  With a  iver   length   of  about   50  knm   and  a   Ahr  R flows   in  the   orth-­‐east    2  is  the  most   watershed   o f   6 30   k m of  the  province  of  Bozen/ important  tributary  of  Rienz  River  

Bolzano

•  25 km2  of  glaciers   responsible  of   the  nivo-­‐glacial   regime  

Study area  


STUDY AREA Mühlen in  Taufers  

Past river  degrada)on   •  Narrowing  of  riverbed   •  Incision  (gravel  mining)   •  Bed  armouring    

UMenheim

•  DisconJnuity between  channel  and   floodplain  (inundated  for  Q>30  yr)   •  Poor  connecJon  of  riparian   vegetaJon  (dominated  by  Alnus   incana)  to  river  dynamics    

Gais Study  area  


STUDY AREA Mühlen in  Taufers  

Restora)on    

•  River restoraJon  program  since  2003   by  the  Department  of  Hydraulic   works  of  the  Autonomous  Province   of  Bozen  (restoraJon  14,9  km  in   length)   UMenheim  

ü  Widening of  the  riverbed     ü  Removal  of  the  bank  protecJon   ü  Raise  riverbed  elevaJon   Gais   Study  area  


STUDY AREA Mühlen in  Taufers  (restored  in  2004-­‐2006)   2003  

2008  

Photos by  Autonomous  Province  of  Bolzano   Study  area  


STUDY AREA Gais (restored  in  2007-­‐2011)   2004  

2011

Photos by  Autonomous  Province  of  Bolzano  

Study area  


AIMS OF THE RESEARC Address  the  growth  response  of  the  riparian  forest  along  the  Ahr   River  to  river  morphological  changes  

Assess the  linkage  among  environmental  factors  and  riparian  forest   growth               We  expected  an  enhanced  tree  growth  ader  the  river  restoraJon   works   Aims  


METHODS •  Riparian forest  mostly  formed   by  Alnus  incana,  locally   associated  with  Fraxinus   excelsior  and  Picea  abies   •  Trees  about  20  m  high,  with   85%  of  coverage   •  2  samplings  (October  2011-­‐ October  2012)   •  37  Alnus  incana  and  6   Fraxinus  excelsior     Mühlen

Gais

Methods

•  2 cores  sampled  from  each   individual  with  a  5  mm   increment  borer    


METHODS •  Annual ring  width  (resoluJon  of   1/100  mm)  and  age  measured   with  a  dendrochronograph   RINNTECH  LINTAB  6       •  Cross-­‐daJng  among  each  single   tree  in  order  to  remove  errors   due  to  the  presence  of  false   rings  or  missing  rings   •  StandardizaJon  through  a   negaJve  exponenJal  in  order  to   remove  the  juvenile  growth   trend  and  a  calculaJon  of  an   adjusted  Tree  Ring  Index  (TRI)   Methods


Rein in Taufers

METHODS •  Temperature data  at  Mühlen  in  Taufers   since  1992     •  PrecipitaJon  data  at  Mühlen  in  Taufers   since  1972;  at  Rein  in  Taufers  used  for   analyzing  long-­‐term  tree  growth  (data   since  1921)    

Mühlen in Taufers

•  Water discharge  at  St.  Georgen  since   1986   •  ElevaJon  of  groundwater  table  since   March  2002  at  3  piezometers  near  Gais  

Gais

•  Data analyzed  for  the  whole  year  and   for  the  growing  season  (April-­‐ September)  

St. Georgen Bruneck Methods


CLIMATE AND HYDROLOGICAL REGIM •  Seasonal paVern  of  water  discharge  with  highest  values  between  May-­‐September   •  Groundwater  table  level  between  -­‐3,77  m  and  -­‐2,53  m   •  Water  table  rose  slightly  in  the  years  2008-­‐2012    

•  Simple regression  shows  a  relaJonship  between  water  discharge  and   groundwater  table  level  (R2  =  0.62  for  annual  data  and  R2=0.37    for  seasonal  data)   -­‐2  

Mean daily  water  table  

70

-­‐3

60 -­‐4  

50 40  

-­‐5

30

-­‐6

20 -­‐7  

apr-­‐12

lug-­‐11

oV-­‐10

gen-­‐10

apr-­‐09

lug-­‐08

oV-­‐07

apr-­‐06

gen-­‐07

lug-­‐05

oV-­‐04

gen-­‐04

lug-­‐02

apr-­‐03

oV-­‐01

gen-­‐01

apr-­‐00

oV-­‐98

Hydrology

lug-­‐99

gen-­‐98

apr-­‐97

oV-­‐95

lug-­‐96

gen-­‐95

apr-­‐94

lug-­‐93

oV-­‐92

gen-­‐92

apr-­‐91

lug-­‐90

oV-­‐89

apr-­‐88

gen-­‐89

lug-­‐87

0

oV-­‐86

10

-­‐8

Water table  (m  below   surface  level)  

Mean monthly  water  discharge  

gen-­‐86

Water discharge  (m3/s)  

80


CLIMATE AND HYDROLOGICAL REGIM

Hydrology

• 

No relaJonship  between   temperature  and  water   discharge  

• 

RelaJonship between   precipitaJon  and  water   discharge  (R2=0.84  for   annual  data  and  R2=0.56   for  seasonal  data)    

• 

PrecipitaJon influence   groundwater  table  level   (R2=0.47  for  annual  data   and  R2=0.54  for  seasonal   data)  


TREE GROWTH PATTERN •  Forward stepwise   analysis  

1,6

Alnus

1,2 1,0   0,8  

2010

2001

1998

1995

1992

1989

1986

1983

1980

1977

1974

1971

1968

1965

1962

1959

1956

1953

1950

1947

1941

1944

1938

0,4

2007

RR

0,6

2004

TREE RING  INEX  

1,4

1,6

Fraxinus

1,2 1,0   0,8  

2010

2007

2001

1998

1995

1992

1989

1986

1983

1980

1977

1974

1971

1968

1965

1962

1959

1956

1953

1950

1947

1941

1944

0,4

2004

RR

0,6

1938

TREE RING  INDEX  

1,4

Tree growth

•  Alnus: groundwater   table  level  of  the   growing  season   (R2=0.51)   •  Fraxinus:  mean  annual   water  discharge                (R2  =  0.61)   •  Absence  of  a   relaJonship  between   precipitaJon  and  tree   growth  


RESTORATION EFFECTS ON TREE GROW

•  Gravel mining  in  the  1970s   with  a  decrease  in  average   width     •  Minimum  width  in  2000   •  Riverbed  width  and   elevaJon  increased  ader   restoraJon  works  

•  Does riverbed  raise   corresponds  to  an   increased  groundwater   table  ?  

Gais

Mühlen in  Taufers  

(Campana et  al.,  2014)  

Restoration


RESTORATION EFFECTS ON TREE GROW

•  Segmented linear   regression   •  Break-­‐point  at  year   2009  for  groundwater   table  depth  (whole  year   and  growing  season)  

Annual values  

Growing season  values  

Annual values  

Growing season  values  

•  Break-­‐point at  year   2007  for  annual  water   discharge  values  and  at   year  2008  for  growing   season  values   Restoration


RESTORATION EFFECTS ON TREE GROW

Alnus

•  Segmented linear   regression   •  Break-­‐point  at  year   2009  for  Alnus   Fraxinus  

•  Break-­‐point at  year   2009  for  Fraxinus  

Restoration


CONCLUSIONS

ü  Water discharge  and  groundwater  table  depth  influence   riparian  vegetaJon  growth   ü  Water  discharge  and  groundwater  table  depth  respond  to   restoraJon  changes   ü  Riparian  vegetaJon  respond  to  restoraJon  works   ü  Fraxinus  beVer  responds  to  river  morphological  changes   than  Alnus     ü  Further  monitoring  is  needed  for  a  beVer  understanding  of   tree  growth  trend   Conclusions


THANK YOU FOR YOUR ATTENTION!

QUESTIONS ARE WELCOME


2014

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