RM Congress - Presentation - 09 Campana

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