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Flora of the Oker river
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Riparian flora of the Oker system

Riverbanks are characterized by high species richness, which is mainly based on habitat diversity in cross-section and periodic disturbances, such as floods. Total species richness of a given river depends on the habitat diversity in longitudinal direction
also. For example 546 vascular plant species were found along the Oker river (cf. Flora of the Oker River). This number represents nearly a third of the Lower Saxonian Flora. Only 80 to 90% of species of the Oker tributaries are present at the Oker too. Therefore 700 species at least occur at the riverbanks of the Oker system. The lower factor of community "Jaccard-Index" results from the exclusive occurrence of many species at the Oker riverbanks.

Species richness of the riparian flora
River:
Length in [km]
Number of
sampling sites
Number of
species
Common species
with the Oker
Factor of
community
Oker
125
107
546
[546]
[100%]
Radau
21
19
292
255 (87,3%) 
43,7 
Ecker
19
18
255
229 (89,8%)
40,0
Ilse
42
41
380
332 (87,4%)
55,9
Altenau
23
12
167
 151 (90,4%)
 26,9
Wabe
28
28
367
296 (80,7%)
48,0
Schunter
57
59
420
336 (80,0%)
53,3
The following table consists 77 species which were recorded in more than 60% of sampling sites of one river at least. The species are sorted according to total frequency. Only Urtica dioica, Ranunculus repens, Dactylis glomerata and Galium aparine were found with high frequency in sampling sites of all rivers. Most species are showing a frequent occurrence only at one or few rivers. In some cases the calculated species frequencies revealed floristic differences for the different rivers.

High frequent species of the Oker system
River:
Oker
Radau
Ecker
Ilse
Altenau
Wabe
Schunter
Number of sampling sites:
107
19
18
41
12
28
59
 
 
 
 
 
 
 
 
Urtica dioica
 91%
 95%
 72%
 93%
 92%
 100%
 100%
Ranunculus repens
 90%
 79%
 83%
 83%
 75%
 96%
 93%
Poa trivialis
 91%
 79%
 56%
 59%
 92%
 100%
 100%
Dactylis glomerata
 70%
 63%
 67%
 73%
 92%
 100%
 98%
Galium aparine
 69%
 74%
 61%
 73%
 67%
 96%
 95%
Arrhenatherum elatius
 79%
 32%
 28%
 76%
 92%
 93%
 92%
Agrostis stolonifera agg.
 94%
 53%
 67%
 44%
 42%
 89%
 95%
Heracleum sphondylium
 67%
 53%
 33%
 68%
 75%
 85%
 90%
Alliaria petiolata
 45%
 68%
 50%
 80%
 42%
 96%
 88%
Lamium maculatum
 59%
 68%
 28%
 78%
 50%
 81%
 88%
Calystegia sepium
 73%
 32%
 28%
 59%
 83%
 85%
 88%
Aegopodium podagraria
 45%
 68%
 50%
 71%
 42%
 81%
 85%
Artemisia vulgaris
 84%
 53%
 39%
 71%
 33%
 63%
 78%
Stachys sylvatica
 19%
 68%
 89%
 61%
 75%
 59%
 32%
Elymus repens
 72%
 11%
 17%
 46%
 75%
 89%
 93%
Glechoma hederacea
 75%
 58%
 44%
 54%
 8%
 74%
 85%
Epilobium hirsutum
 58%
 32%
 22%
 39%
 75%
 74%
 92%
Phalaris arundinacea
 66%
 21%
 28%
 54%
 58%
 63%
 93%
Lapsana communis
 17%
 32%
 50%
 68%
 58%
 67%
 83%
Anthriscus sylvestris
 69%
 11%
 22%
 63%
 42%
 81%
 78%
Cirsium arvense
 49%
 16%
 22%
 63%
 58%
 63%
 86
Geum urbanum
 9%
 68%
 44%
 61%
 33%
 89%
 37%
Taraxacum officinale agg.
 30%
 79%
 0%
 49%
 8%
 81%
 88%
Geranium robertianum
 13%
 79%
 78%
 37%
 42%
 63%
 22%
Holcus lanatus
 66%
 47%
 56%
 24%
 17%
 48%
 69%
Fraxinus excelsior
 20%
 47%
 44%
 49%
 67%
 67%
 32%
Ranunculus ficaria
 17%
 68%
 33%
 15%
 0%
 93%
 98%
Rumex obtusifolius
 67%
 53%
 44%
 59%
 0%
 26%
 61%
Scrophularia umbrosa
 49%
 16%
 28%
 27%
 92%
 41%
 53%
Stellaria aquatica
 64%
 47%
 39%
 61%
 8%
 26%
 59%
Silene dioica
 77%
 79%
 56%
 66%
 17%
 0%
 8%
Valeriana officinalis agg.
 30%
 42%
 56%
 2%
 50%
 52%
 66%
Stellaria media
 36%
 53%
 22%
 59%
 8%
 41%
 78%
Veronica hederifolia
 15%
 63%
 11%
 46%
 0%
 81%
 76%
Galeopsis tetrahit
 70%
 68%
 61%
 78%
 8%
<21%
<21%
Poa pratensis
 33%
 5%
 0%
 37%
 42%
 81%
 81%
Scrophularia nodosa
 76%
 53%
 72%
 24%
 8%
 15%
 31%
Galium album
 64%
 16%
 28%
 39%
 42%
 30%
 46%
Festuca rubra
 61%
 21%
 17%
 24%
 33%
 41%
 58%
Festuca gigantea
 4%
 74%
 67%
 49%
 25%
 19%
 17%
Alnus glutinosa
 37%
 58%
 89%
 37%
 33%
 v
 v
Lamium album
 70%
 11%
 6%
 63%
 0%
 33%
 69%
Bromus sterilis
 7%
 32%
 6%
 46%
 8%
 78%
 73%
Poa nemoralis
 7%
 63%
 83%
 39%
 8%
 26%
 8%
Deschampsia cespitosa
 41%
 79%
 72%
 17%
 25%
 v
 v
Elymus caninus
 5%
 79%
 67%
 32%
 25%
 22%
 2%
Lycopus europaeus
 74%
 16%
 33%
 22%
 8%
 30%
 49%
Carduus crispus
 64%
 16%
 33%
 41%
 17%
 4%
 53%
Achillea millefolium agg.
 75%
 11%
 22%
 49%
 17%
 11%
 41%
Myosotis palustris agg.
 46%
 16%
 22%
 12%
 25%
 63%
 41-60%
Lolium perenne
 25%
 26%
 11%
 37%
 8%
 63%
 41-60%
Acer pseudoplatanus
 15%
 37%
 61%
 34%
 8%
 44%
 20%
Epilobium ciliatum
 63%
 47%
 28%
 17%
 8%
 32%
 20%
Impatiens parviflora
 7%
 47%
 61%
 46%
 17%
 21%
 10%
Solanum dulcamara
 61%
 5%
 22%
 37%
 42%
<21%
 41-60%
Poa annua
 17%
 16%
 11%
 51%
 17%
 74%
 21-40%
Poa palustris
 20%
 21%
 17%
 7%
 17%
 37%
 80%
Brachypodium sylvaticum
 0%
 58%
 83%
 17%
 25%
 7%
 7%
Alopecurus pratensis
 34%
 0%
 6%
 2%
 42%
 37%
 71%
Senecio ovatus
 19%
 84%
 83%
 2%
 0%
 v
 3%
Stellaria holostea
 1%
 63%
 44%
 39%
 17%
 15%
 14%
Tripleurospermum perforatum
 71%
 11%
 22%
 37%
 0%
 7%
 39%
Plantago major
 25%
 32%
 22%
 61%
 25%
 41-60%
 21-40%
Bromus inermus
 13%
 0%
 6%
 39%
 33%
 <21%
 86%
Rumus conglomeratus
 6%
 11%
 22%
 22%
 8%
 33%
 66%
Rubus ideaus
 15%
 47%
 72%
 12%
 17%
 v
 v
Luzula sylvatica
 7%
 63%
 78%
 12%
 0%
 0%
 0%
Stachys palustris
 70%
 0%
 6%
 5%
 8%
 19%
 47%
Chaerophyllum hirsutum
 12%
 74%
 67%
 0%
 0%
 0%
 0%
Impatiens noli-tangere
 9%
 47%
 67%
 15%
 8%
 4%
 3%
Rubus fruticosus agg.
 13%
 26%
 67%
 24%
 8%
 v
 v
Athyrium filix-femina
 14%
 47%
 61%
 12%
 0%
 v
 3%
Mycelis muralis
 11%
 32%
 61%
 17%
 0%
 11%
 2%
Rumex sanguineus
 1%
 11%
 6%
 2%
 33%
 74%
 <21%
Polygonum cuspidatum
 13%
 63%
 17%
 15%
 0%
 0%
 0%
Bidens frondosa
 61%
 0%
 17%
 5%
 0%
 0%
 8%
Galium sylvaticum
 1%
 0%
 67%
 0%
 0%
 4%
 2%
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