Geoscience Reference
In-Depth Information
Table 16.1
Variables and critical values used for the evaluation of specific indicators within the conservation status
evaluation system for alder-ash alluvial forest (
*
91E0, Annex I, Habitats Directive) and Atlantic salmon in the
Natura 2000
river network, Cantabria, northern Spain.
Diagnosis
Specific Indicators
Favourable
Inadequate
HABITATS
Area
Percentage area covered in each
assessment unit
Observed relative area
≥
Expected
Observed relative area
<
Expected
Structure & Composition
Invasive species
Absent / Spaced plants
Patches
Transformer species
*
Absent
Spaced plants / Patches
Organic matter (plant debris)
Abundant / Present
Absent
Fragmentation degree
Absent / Present
Abundant
Regeneration
Seedlings and saplings present
Seedlings and saplings absent
Disease (physiological state)
Absent
Present
Vulnerability
Overlap between observed area and
area covered by high and medium
pressure influence zone
Vegetation polygon overlaps
<
10%
Vegetation polygon overlaps > 10%
with high or > 20% with medium
intensity influence zone
with high or
20% with medium
pressure influence zone
<
SPECIES
Distribution Range
River length (km)
Occupied length
≥
60% reference
Occupied length
<
60% reference
Structure & Composition
Population Size
Observed population size
≥
Observed population size
<
3 generations ago
3 generations ago
a
1SW / MSW ratio
≤
0.1
>
0.1
Female / Male ratio
≥
0.3
<
0.3
Productivity (Individuals m
−2
)
≥
0.01
<
0.01
Vulnerability
Overlap between distribution range
(DR) and length covered by high
and medium pressures influence
zone
DR overlaps
<
20% with high or
DR overlaps
>
20% with high or
<
40% with medium intensity
pressure layer
>
40% with medium intensity
pressure layer
*
Transformer species are a subset of invasive plants which change the character, condition, form or nature of ecosystems
over substantial areas relative to the extent of that ecosystem (Richardson
et al.
, 2000).
a
1SW: one sea-winter fish; MSW: multi-sea-winter fish.
