THE ABIOTIC GRIM REAPER: DETERMINING THE SURVIVAL OF SALT
MARSH VEGETATION
Schwarz C hristian 1, Tom Ysebaert1, Liquan Zhang2, Zhenchang Zhu2 and Peter Herm an1
1 Netherlands Institute o f Ecology (NIOO), PO Box 140, 4400 AC Yerseke, the Netherlands
E-mail: C.Schwarz@ nioo.knaw.nl
2 State Key Laboratory o f Estuarine and Coastal Research, East China Normal University, 3663
Zhongshan Road North, Shanghai 200062, China
The co lonization and spreading behaviour o f marsh plants is s tro n g ly linked to th e ir interactions
w ith the a biotic environm ent. The outcom e o f these interactions fo rm s the basis to evaluate,
explain and predict d istrib u tio n patterns and therefore the a b ility to su pp ort policy makers in the
decision m aking processes fo r tid al w etland management.
The aim o f th is study is to evaluate the influence o f a biotic param eters (hydrodynam ic and sedim ent
properties) on the survival and lateral expansion o f tw o salt marsh pioneer plants (S partina
a lte rn iflo ra , Scirpus m ariquter), in order to fin d m echanistic explanations fo r patterns observed on
a larger scale. These tw o species co-occur in the lower pioneer zone o f salt marshes in the Yangtze
Estuary, China; d iffe rin g th ro u g h th e ir m orph olo gy does the native species Scirpus m a riq u e te r
e x h ib it a small and fle xib le habitus, the invasive species S p artin a a lte rn iflo ra a s tiff and tail.
D iffe re nt size classes o f dispersal units (seedlings, rhizom e fragm ents and tussocks) were planted
at three d iffe re n t locations in the salt marsh pioneer zone o f eastern C hongm ing Island, Yangtze
Estuary, China. The planting date and period was chosen, to have a su fficie n t size and num ber o f
dispersal units (rig h t after the grow th spurt in early spring) on the one hand, and to include a
period o f high p recipitation and strong w inds (disturbed scenario: plum rain, around July) on the
other. The locations were chosen accordingly to d iffe re n t sedim ent and hydrodynam ic properties,
which at the spot resulted in d iffe re n t patterns o f the developing vegetation fron t.
Our results indicate the existence o f a size threshold enabling these tw o ecosystem engineers to
survive the disturbed scenario and therefore fo rm in g a selective m echanism. Further, we were
confronted w ith an unexpected lower survival o f the stronger ecosystem engineer S partina
a lte rn iflo ra . This indicates th a t even th ough S p artin a a lte rn iflo ra co nstitu te s the stronger
ecosystem engineer (higher grow th rate, earlier start-, longer vegetation period and higher
sedim ent tra p p in g a bility) the s tiffe r aboveground parts and, com pared to Scirpus m a riq u e te r the
lower investm ent in the below ground parts are e x h ib itin g a serious v ia b ility disadvantage.
The im plications o f these fin d in g s not o nly help to explain the vegetation d is trib u tio n patterns on
C hongm ing Island, but also give im p o rta n t insights in the interaction m echanisms between plants
and th e ir a biotic environm ents including the perspective to explain patterns on a larger scale.
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