Сhanges in zonal and intrazonal ecosystems (meadow, steppe and plavni communities)
Sergey Podorozhny, Elena Zhmud, AZBOS
Plant communities of zonal (meadows, steppes) and intrazonal (wetlands vegetation communities) ecosystems were estimated on several model plots, presented in Figure 1.
|Figure 1. Model plots to study zonal and intrazonal ecosystems|
1 - Syvash (Kutara Cape); 2 - Syvash (Mytrofanivka-Kutara); 3 - Syvash (Zentiup Site 1); 4 - Syvash (Zentiup Site 2); 5 - Syvash (near Vesnianka Village); 6 - Utliukskyi Liman (near Ozeriany Village); 7 - Utliukskyi Liman (near Volchie Village); 8 - Lower reaches of Malyi Utliuh River; 9 - Molochnyi Liman (near Yefremivka Village); 10 - Molochnyi Liman (near Sheliuhi Village); 11 - Molochnyi Liman (Sheliuhivskyi Depression); 12 - Molochnaya River Mouth; 13 - Dalni Makorty; 14 - Novopetrivskyi control plot.
Meadow vegetation communities
Phytomass of meadow vegetation communities were studied on two sample plots (fig. 1), 30 to 100 m2 in size. The plots were described according to standard geobotanical methods. Plot 1 (point 9 in the map). Located on slopes of Molochnyi Liman, near Yefremivka Village. Meadows are represented by monodominant communities of Elytrigia repens (Fig.2).
|Fig. 2. Quackgrass meadows from Elytrigia repens in a lowering at the liman terrace (near Yefremivka Village, July 2011).|
Plot 2 (point 6 in the map). Located on slopes of Utliukskyi Liman (near Ozeriany Village). Meadows are represented by monodominant communities from Elytrigia repens and fragments of monodominant communities of Elytrigia elongatа (fig. 3).
|Fig. 3. Quackgrass meadows from Elytrigia repens near Ozeriany Village, July 2011.|
For two years (2010-2011) of observation the phytomass of meadow communities with dominance of Elytrigia repens had a growing trend from 4.2 to 22.0 %.
Comparison of phytomass growth rate with main climate indices – air temperature and precipitation amount - has shown that the main factor influencing on phytomass growth of meadow communities of Elytrigia elongatа as well as those of Elytrigia repens is precipitation amount.
Air temperature influences on meadow coenoses to a lesser extent since a majority of meadow plants actively vegetate in a wide temperature range. Possible changes in composition of meadow communities of Elytrigia repens with increase of air temperature and decrease of precipitation amount are shown in Fig. 4.
|Fig. 4. Changes of meadows from Elytrigia repens against the trend of air temperature and precipitation amount|
Due to increase of climate aridity the productivity of meadows is declining and further they transform in halophytic coenoses with the dominance of Lepidum latifolium and Tripolium vulgaris. At the last stages of succession there are formed more "aridizated" halophytic coenoses with the dominance of lignificated species - Artemisia santonica and Limonium caspium.
Changes in meadow communities of Puccinellia gigantea in case of Scenario 1 are presented in fig. 5. With increase of climate aridity they are transforming in low productive coenoses with the dominance of Artemisia santonica, Limonium caspium, etc. Other intermediary stages as opposed to quackgrass meadows are absent there.
|Fig. 5. Changes of meadows from Puccinellia gigantea against the trend of air temperature and precipitation amount|
An important factor influencing on the condition of meadow communities of Puccinellia gigantea is a relief along with socio-economical factors: grazing and haymaking.
Changes in the structure of steppe vegetation communities
According to research results in 2007-2011 there is a trend of "meadowfication" of steppe communities at the expense of increase in them of phytocoenotical role of Elytrigia repens, Cynodon dactylon (on light and dark chestnut soils with low fertility).
Besides, there is a clear trend of increasing phytomass of steppe communities with the dominance of Stipa capillata for the period from 1952 to 2011. Phytomass growth is a direct consequence of increase of precipitation amount and air temperature. If the trend of increasing precipitation amount and air temperature continues it may lead to "meadowfication of southern steppes.
Changes in the structure of wetlands vegetation communities of small rivers in the Azov area
Due to reduction of river runoff and general water content, the following changes can go in wetland communities. The most watered monodominant coenoses from Phragmites australis will be replaced with high-grass marshy meadows with the dominance of Carex acuta and Eleocharis palustris. Further, with reducing water content and increasing mineralization of river waters the high-grass marshy meadows will be transformed in halophytic large-grass meadows with the dominance of Carex distanis and Bolboschoenus maritimus.Possible changes in the composition of wetland vegetation communities with increasing air temperature and decreasing precipitation amount is shown in fig. 6.
|Fig. 6. Possible succession changes of wetland vegetation communities in mouths of Berda River and Molochna River against the trend of air temperature and precipitation amount.|
At the rivers with lesser volume of annual runoff than Berda and Molochna and, correspondingly, with higher water mineralization (Malyi Utliuh) the succession changes most of all will be characterized by absence of a stage of high-grass marshy meadows and halophytic large-grass meadows (fig.7).Productivity of wetland communities in the process of reduction of river runoff can decline 80-90 times (in Salicornia coenoses it amounts to only 2 hwt/ha, and productivity of modern reed communities is 159 to 177.5 hwt/ha of air-dry phytomass).Increase of precipitation amount along with increase of air temperatures will hardly be accompanied by an essential transformation of wetland communities in the region.
|Fig. 7. Succession changes of wetland vegetation communities of Malyi Utliuh river mouth, with high water mineralization.|