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Dynamics of Soil Moisture in Some Meadow Communities in Northwestern Croatia

Ljudevit Ilijanić ; Hrvatska

Sažetak

The study gives the results of a two-year investigation of the water regimen of soil in the meadow communities Succisa pratensis-J uncus conglomeratus and Deschampsietum cespitosae (Molinietalia, Table 1), and Bromo-Cynosuretum cristati and Ononido-Arrhenatheretum elatioris (Arrhenatheretalia, Table 2) in Northwestern Croatia (Fig. 1). The climat in this region is humid (Fig. 2) ; phytogeographically this part of Croatia belongs to the vegetation zone of the alliance Carpinion betuli illyricum (Horvat et al. 1974).
The moisture was determined by drying the soil at 100—105°C up to a constant weight, and it is expressed in % of dry soil. The samples were taken with a »Dutch borer« once a month (from March 1967 to February 1969) from the surface down to a depth of 250 cm, or to the level of ground-water if the latter was nearer the surface. Comparative graphs (Figs. 3—10) show the changes in soil moisture in the above mentioned period.
In the first year of investigation, owing to the larger amount of precipitation, the soil moisture during the vegetation period, especially in the surface layer, was higher than in the second year. (An exception was one stand of the association Ononido-Arrhenatheretum (Fig. 1. locality 7 ; Fig. 9 ; Table 3, locality 7) which was irrigated during the dry period of the second year; this resulted in higher soil moisture as compared with the previous year).
The greatest oscillation in moisture was recorded in the layer of the soil at 0 to 35 depth. In deeper layers, the variations over the year were considerably smaller. This was particularly evident in the soil profiles where ground-water lay lower, so that soil moisture in deeper layers below 70 (100) cm remained practically unchanged throughout the vegetation period, corresponding to field capacity. Accordingly, it may be concluded that the water regim in the surface layer of the soil, where the main portion of underground parts of plants is found, is decisive for the development of vegetation in the meadow stands investigated. The moisture dynamics in that layer depends primarily on the precipitation and occasionally on flood waters. Ground-water plays no decisive role in most stands.
It should be emphasized that the floristic differences in the three stands of the association Bromo-Cynosuretum cristati (Arrhenatherion) investigated were clearly influenced by the water regim, particularly in the surface layer of the soil. In other words, two stands (Tab. 2, relevé 1 and 2) are more similar in soil moisture to the community Succisa pratensis-Juncus conglomeratus (Molinion) and the association Deschampsietum cespitosae (Deschampsion), while only the third stand (Table 2, relevé 3) is in the water regim of the surface layer of the soil more similar to the association Ononido-Arrhenatheretum (Arrhenatherion) (cf. Figs. 3—10; Table 3). Hence the conclusion that the association Bromo-Cynosuretum cristati as described by Horvatić was understood too broadly; therefore a more detailed comparative phytocoenological (syntaxonomic) analysis of this community on the whole of its area is required.
The stands of the association Ononido-Arrhenatheretum (Table 2, rel. 4—6) showed a markedly greater mutual similarity of the water regimen of the soil on the one hand, and on the other a clear difference from the other communities (Figs. 3—10; Table 3). The lower soil moisture during the vegetation period and a more equalized water regim, or lesser oscillation in the soil moisture than in the other communities investigated, are essential ecological features of this community. In the lowlands of this country, the association Ononido-Arrhenatheretum elatioris makes exceptionally valuable meadow vegetation from the economic point of view. These meadows are mown twice a year as a rule, and depending on the rainfall during the summer months, even three times, yielding high quality forage.
Owing to extensive irrigation works after World War II and to the effects of fertilization, this community keeps spreading in the lowland regions of Croatia, while the surfaces of more moist and marsh meadows retreat. Thereby this region is becoming impoverished in its flora and fauna, a fact that should be particularly taken into consideration in the projects of the protection of ecosystems.

Ključne riječi

Hrčak ID:

159766

URI

https://hrcak.srce.hr/159766

Datum izdavanja:

31.12.1992.

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