Are Dams Regulating Diversity of Riparian Forests?

Transcription

1 Are Dams Regulating Diversity of Riparian Forests? Functional trade-offs and synergies in Mediterranean Europe* Francisca C. Aguiar, Maria João Martins, Maria Dolores Bejarano, ChristerNilsson, Maria Manuela Portela, Pedro Segurado, David M. Merritt *under the Project OASIS: How to run regulated rivers in semi-arid regions? PTDC/AAC-AMB/120197/2010 Session 1D, 1 September 2014, Perth

2 OBJECTIVE understand the adaptive strategies of riparian plant communities to regulated flows assess the influence of different flow components on ecological responses of riparian vegetation

3 BACKGROUND alteration of flow regimes causes shifts in the composition and diversity as well as the trait syndromes of streamside plant communities most of works are focused on the effects of a single dam and in other communities (fish) there is still a limited knowledge of riparian strategies to streamflow regulation and moreover to different dam operations, especially in Mediterranean rivers

4 STUDY AREA free-flowing rivers Portugal Number of ecoregions Average of free-flowing watercourses (%)

5 STUDY AREA Run-off Precipitation

6 STUDY AREA Reservoir, water transferred to another basin Run-of-river dam

7 METHODS SPATIAL APPROACH Floristic data upstream free-flowing FF Field surveys at riparian zones 20 locations FF+ 11 REG Woody species cover (%) downstream regulated REG

8 METHODS FUNCTIONAL TRAIT APPROACH 26 traits mostly recorded from FLOWBASE Canopy height; life span Duration of seed bouyancy; diaspore type Physical defenses; tolerance to anoxia

9 METHODS Leaf anatomy 0. scleromorphic or coriaceous 1. hygromorphic or mesomorphic Root morphology 0. horizontal or fasciculated 1. taproot Seed bank longevity 1. Transient(<1y) 2. Short-term persistent(0-5y) 3.Long-term persistent(>5y) Reproduction type 0.By seeds 1. By seeds and/or vegetatively Tolerance to waterlogging 1.low 2. medium 3. high Seed buoyancy h Leaf pubescence 0. No or lightly hairy in nerves 1. yes Physical defense 0. no 1.yes Leaf phenology 0. deciduous 1. evergreen Tolerance to water stress 1.low 1. medium 1. high Rooting depth 1. shallow 2. medium deep 3. deep Connection to riparian zone 0. no 1. yes Max canopy heigth m Diaspore type 0. fruit 1. seed Dispersal vector 0. other 1. hydrochory Life span 1.short-lived perennials(5-50y) 2. medium-lived(>50-<150y) 3.Long-lived (>150y) Seed weight mg Leaf width cm Light requirements 1. low 2. medium 3. high Fruit type 0. dry 1. fleshy Strategy_CRS 0. no 1. yes

10 METHODS Deriving Riparian Guilds to express trait syndromes data riparian woody flora (species; % cover) alocate traits for each species/taxa 60 S a li_ a t ro c S a li_ s a lv F ra n g _ a ln u A ln u _ g lu t S a li_ a lb a S a li_ n e o t R u b u _ u lm i R u b u s la in z ii R u b u _ v a g a R u b u _ b r ig a R u b u _ g e n e R u b u _ ra d u A ila _ a lt i R o b i_ p s e u U le _ m in o D it t_ v is c R o s a _ c a n i R o s a _ p o u z P ru n _ a v iu P y ru _ c o rd Q u e r _ s u b e Q u e r_ p y re A c e r _ p s e u Q u e r_ f a g i J u g l_ r e g i F r a x _ a n g u C a s t _ s a t i Q u e r _ ro b u P la t_ h is p P o p u _ c a n a V it _ v in i Ile x _ a q u i C r a t_ m o n o C o ry _ a v e l S a m b _ n ig r B e t u _ c e lt L a u r_ n o b i P h il_ a n g u D a p h _ g n id P h il_ la t i S o r b _ a u c u A r b u _ u n e d F ic u _ c a r i E r ic _ a u s t E r ic _ c in e E r ic _ a rb o E ric _ c ili A c a c _ d e a l A c a c _ m e la H e d e _ h ib e M y rt _ c o m m V a c _ m y r t F lu e _ t in c C a ll_ v u lg H y p e _ a n d r H y p _ h u m i C y ti_ s c o p C y t i_ s tr i S e s a _ s u f f L a v a _ s to e L ith _ p ro s P in u _ p in a C is t _ p s il E r ic _ te t r G e n i_ flo r riparian guilds classification using Gower similarity measure and Group Average clustering method 70 S im ila rity Samples validation ANOSIM (Analysis of Similarities) Principal Coordinate Analysis (PCoA)

11 METHODS Hydrologic data SPATIAL APPROACH Daily flow data from gauging stations pre-dam and post-dam indices for 9 case studies 33 Indicators of Hydrologic Alteration (IHA7.1 software) expressing different characteristics of the flow regime Regime features G1=Group 1 Magnitude Timing G2=Group 2 Magnitude Duration G3=Group 3 Timing G4=Group 4 Frequency Duration Hydrological parameters Magnitude of monthly water conditions Magnitude/Duration of annual extreme water conditions Timing of annual extreme water conditions Frequency/Duration of high/low pulses G5=Group 5 Rates of change Frequency Rate/Frequency of Change

12 STUDY AREA Run-of-river dam 1,0 12 0,8 0,6 11 0,4 0,2 10 0,0 1 2 free-flowing regulated GROUP 1: Montly flows Reservoir dam ,0 0,8 2 0,6 0,4 0,2 0,

13 METHODS Relating guilds variation with hydrologic alterations Ordination method: Redundancy Analysis (RDA) Canoco 5 Functional diversity indices were calculated for FF and REG sites R package FD

14 RESULTS 6 riparian guilds at 65% of similarity level (Global R ANOSIM =0.66) Guild a mostly obligate riparian species, competitors, evergreen hygromorphic leaves, high waterlogging tolerance, with hydrochoric dispersal Guild b facultative riparian, with physical defences, high tolerance to water stress, tap roots Guild e Guild f facultative riparian or non-riparian, vegetative reproduction, evergreen, mostly short-lived perennials, dry fruits

15 RESULTS PCoA ordination (66 riparian woody species; 26 functional plant traits; 6 guilds a-f) Axes 1, 2: 48% of total variation Axis 1: Leaf phenology, Tolerance to drought, CRS strategies, Maximum height (axis1) Axis 2: Diaspore and Fruit type, Seed bank longevity

16 RESULTS Redundancy analysis (RDA) IHA10 Magnitude of flows separate most of sites with low alterations (run-of-river dams; dams with powerhouses at the dam-toe) from those with higher water storage capacity IHA30 Duration of high flows segregates free-flowing rivers from downstream dam sites. FF free-flowing REG regulated October median flows_iha10 High pluse duration_iha30

17 RESULTS Guild a was more abundant in natural hydrographs than in dam-regulated rivers Guild f abundant in FF rivers, reflect the widespread terrestrialization of Mediterranean rivers. FF free-flowing REG regulated

18 variables account for only16.6% of variation...! RESULTS

19 DISCUSSION geomorphology upstream downstream

20 DISCUSSION N Touvedo Lima River land-use Campo do Gerês Fronhas Fronhas Example: Fronhas (construction date: 1985) Portugal Vilarinho das Furnas Atlantic Ocean Touvedo (Salvador)

21 DISCUSSION land-use species has to to cope with hydrological constrains and land-use disturbance

22 CONCLUSIONS regulated flows especially in rivers with reservoir dams favour alien species cover, and wide range of riparian guilds. widespread terrestrialization was observed both in natural hydrographs and in hydropower rivers disturbance by land-use create some noise in data analysis future work is required to extract/add this effect allowing occasional high flows from reservoir dams, more seasonal variability, and varying interannual flows would favour establishment of riparian pioneer species and a better functioning riparian ecosystem.

23 Thank you very much for your attention Terceira Dimensão Fotografia Aérea