Monitoring results of salt marshes basing on remote sensing data

Yury Moskalenko, AZBOS

Dynamics of the condition of salt marshes natural complexes was estimated in the territory of the Black Sea Biosphere Reserve (section "Yahorlytskyi Bay") for the period since the early 1980s on the example of 9 control plots (fig.1, Table 1) basing on Landsat satellite images freely distributed by the United States Geological Survey (USGS) through GLOVIS web service (USGS Global Visualization Viewer http://glovis.usgs.gov)

Fig 1. Scheme of location of control plots on the peninsula

 

Table 1. Brief general characteristics of control monitoring plots on Yahorlytskyi Peninsula

No. of plot

Protection regime

Key determinant for hydrological regime

Estimated area, ha

1

А

Wind-driven phenomena

86

2

B

Atmospheric precipitation

131

3

B

Atmospheric precipitation

66

4

B

Atmospheric precipitation

146

5

B

Wind-driven phenomena

138

6

А

Atmospheric precipitation

101

7

B

Atmospheric precipitation, wind-drivenphenomena in case of considerable driven tides in the eastern part of Tendrivskyi Bay

238

8

А

Wind-driven phenomena

75

9

B

Wind-driven phenomena

107

Notes: А – in the old protected part of Yahorlytskyi Peninsula, B – in the territory joined to the reserve in 1998 (a liquidated aviation testing ground).

Control plots (1, 5, 8, 9) which dynamics of moisture depends predominantly from wind-driven tides in the eastern part of Tendrivskyi Bay are similar in vegetation type (fig. 2.)

In the control plot 7 there are considerable areas of drying up lakes overgrown by Salicornia along the periphery (fig. 3). These areas are subject to flooding during strong wind-driven tides in the eastern part of Tendrivskyi Bay. Therefore, key determinants of hydrological regime of this plot are both atmospheric precipitation and wind-driven phenomena.

 

Fig. 2. Typical landscape of salt marshes within control plots 1, 5, 8, 9

Fig. 3 . Dry lake within control plot 7

Fig. 4. Peripherial part of the salt marsh within control plot 2

Fig. 5. Central part of the salt marsh on a sample plot 2 in the end of May 2011.

 

Plots 2, 3, 4 and 6 are located in an axial elevated part of the peninsula. Salt marshes, located within them, are represented by depression with well-expressed relief. Along the periphery these salt marshes, as a rule, are surrounded by rather a wide strip of bare ground somewhere covered with spots of Halocnemum (fig. 4.). In the central part the vegetation is usually continuous, of meadow type. In the deepest part there are drying up lakes, sometimes reedbeds. In extremely wet years these depressions can be filled with water almost completely.

LONG-TERM DYNAMICS OF SURFACE AREAS OF SALT MARSHES

Carried out for those control plots, where atmospheric precipitation is a key determinant in hydrological regime, for the period from 2004 to 2011.

In the studied years there were no changes in contours of salt marshes, at least to the extent which could have influenced on the data of remote sensing with 15 m/pixel resolution. We suppose that during the considered period of time these changes did not take place in a lesser extent either. It is connected with the fact that these salt marshes are located in the depressions with well-expressed relief where changes occur in a much greater period of time than we can consider.

LONG-TERM DYNAMICS OF THE STATE OF SALT MARSHES

Carried out for those control plots, where atmospheric precipitation is a key determinant in hydrological regime, for the period since the early 1980s.

Extremely dry years

For the studied period of 30 years the driest were the years 1993-1994 and 2006-2007. The salt marshes, not connected with Tendrivskyi Bay, dried up.  (fig. 6).

See map:

  • Fig 6: 16 July 1993. Water content – 0 points.

Extremely wet years

Among extremely wet years we succeeded to analyze the years 2004 and 2010.

Both years are characterized by a high amount of precipitation in winter/spring period and in early summer, also rather a hot August with small precipitation amount. As a result, in spring and early summer the salt marshes were extremely watered. When August starts, the surface of salt marshes is getting intensively dry that leads to considerable reduction in the salt marshes water content by the end of this month (fig. 7-8).

See map:

  • Fig. 7:  04 May 2010. Water content– 4 points.
  • Fig. 8:  15 July 2010. Water content – 1 point.

Years with normal moisture in vegetation period

Unfortunately, for years with normal amount of moisture in vegetation period we succeed to receive remote sensing data only for the year 1987.

On 13 May 1987 the salt marshes of Yahorlytskyi Peninsula were enough watered (fig. 9). However, already by the end of June all continental salt marshes had dried up. In spite that precipitation amount in August and September corresponded to the average long-term norm, the continental salt marshes of the peninsula still remained dry by late October (fig. 10).

See map:

  • Fig. 9:  13 May 1987. Water content – 2 points.
  • Fig. 10:  4 October 1987. Water content – 0 points.

Years with non-compensated deficit of moisture after the previous draught

The situation of 2008 deserves a separate consideration. The preceding year, 2007, was very dry, with extremely severe summer draught induced by deficit of summer precipitation and very high temperatures. It leads to powerful drying-out of salt marsh complexes.

In spite of rather big seasonal precipitation sum of autumn-2007 the consequences of drying-out were compensated only to a very small extent. As a result, at the end of November 2007 a part of salt marshes remained completely dry, and in other salt marshes the percentage of watered areas did not exceed 10-30% of their total size. The next premise for the situation development in 2008 was an abnormally dry winter 2007/2008 with only 31.7 mm of precipitation during the winter season. In spite of the fact that the spring was characterized by 132% of average long-term precipitation norm, very warm weather conditions of the spring season (average seasonal temperature 1.21º C exceeded the norm) favoured evaporation of moisture. As a consequence, by the end of this spring all the salt marshes, not connected with the bay, became absolutely dry (fig. 10). So, in spite of rather high annual precipitation sum and hydrothermal coefficient of 2008 the water content of salt marshes in this year was extremely low.

See map:

  • Fig. 11:  Water content of salt marshes in Yahorlytskyi Peninsula in late spring 2008 (satellite image: 30 May 2008 ). Water content – 1 point.

DYNAMICS OF BIRDS SPECIES COMPISITION AND NUMBER DEPENDING ON THE STATE OF SALT MARSHES

Breeding period 2008. Plots 2 and 3.

Since the salt marshes within control plots in the beginning of breeding season-2008 were completely dry, we did not record any waterbirds during counts except for the Shelduck (3 individuals, Plot 3).

Breeding period 2010. Plots 2 and 3.

The year 2010 was abnormally wet and the salt marshes in an axial part of the peninsula in the breeding period were very watered (4 points, fig. 6). By the start of the breeding season both plots had very well-developed water table, which covered a considerable part of the salt marshes surface area. There were recorded 126 individuals of 9 species, of them 5 species were breeding.

Breeding period 2011. All plots.

After the extremely wet year of 2010, in spring-2011 the salt marshes of Yahorlytskyi Peninsula still remained very watered but already to early June the water content decreased up to 2 points. At the moment of counts almost all control salt marshes, located in an axial part of the peninsula, were without water table.

There were recorded 24 species of waterbirds, with a total number of 2302 individuals.

The salt marshes of an axial part of the peninsula (plots 2, 3 and 6) were characterized by low species diversity (see fig. 12, 13). The highest concentration of birds was registered within Plot 2 where a small lake still remained. The salt marshes in low peripheral parts of the peninsula (control plots 1,5,7 and 9) were much more abundant both in species diversity and summarized number of waterbirds.

 

See map:

Fig. 12. Species diversity of waterbirds in control plots in May 2011.

Fig. 13. Number of waterbirds (individuals) in control plots in May 2011.

 

Breeding period 2012. All plots.

Salt marshes complexes of the peninsula were very dry. As a result there were registered 26 species of waterbirds.

The salt marshes complexes, containing the lakes connected with waters of Tendrivskyi Bay (i.e. control plots 1,5 and 9) were the most abundant both in species diversity and general numbers of waterbirds (fig. 14, 15)

See map:

Fig. 14. Species diversity of waterbirds in control plots in May 2012.

Fig. 15. Number of waterbirds (individuals) in control plots in May 2012.

 

Conclusions

Therefore, the most favourable conditions for birds in a breeding season are formed in the period of maximal water content in salt marshes of the peninsula. At the same time, there are premises to believe that in this case the waterbirds, that breed on the peninsula, prefer breeding on the salt marshes of an axial part of the peninsula and also on those located in a lower part of the peninsula but to some extent distanced from the lakes connected with the bay.

In dry years the water birds practically have no possibility to breed on central (continental) salt marshes of the peninsula. They are used as breeding habitats by only a limited number of waterbird species (Kentish Plover and Collared Pratincole). The latter gives grounds to state that even in dry years these salt marshes have certain significance for bird conservation.

In a period of autumn migration the coastal salt marshes biotopes, which hydrological regime is predominantly determined by wind-driven phenomena, are crucial for birds. Central (continental) salt marshes get dry by autumn (no matter how wet they were before it) and have no value for birds.

In a period of spring migration the central (continental) salt marshes can be used by birds only in wet years or in years with normal precipitation amount.