5.1. Assessment of management effects on wetland vegetation

One of the main actions in the LIFE Prespa Waterbirds project is the management of the littoral zone in Lesser Prespa Lake, in order to restore wet meadow vegetation that was displaced by reedbeds during the previous absence of management, both traditional and conservation-driven. Towards this aim, mowing using specialised machinery and grazing have been used since 2018.

In order to monitor the effects of this management, 24 transects of varying size, distributed in eight blocks of three, were established in 2018, using a randomly stratified sampling strategy. In every block, the middle transect were left intact (control – no management), while the other two, placed to the left and right of the control at 20 m distance, were mowed every management season. The vegetation in each transect was monitored on a yearly basis. Each transect was divided into 5 equal parts, creating 6 sampling points (one at the beginning and one at the end of each sub-transect). At every sampling point 4 nested quadrats of 0.4 m x 0.4 m were established, one in each corner of a 1 m x 1 m quadrat. Each 1 m x 1 m quadrat was sampled in July 2018 prior to the first year of mowing (baseline year) and in July 2019 & 2020. The mowing was implemented between July to November 2018 and July to November 2019. The density of stems (culms), the height and diameter of the highest stem and of a random stem were recorded. Water level was also recorded, when present.

Map: Transects established in the NW part of the Lesser Prespa Lake reedbeds for the purpose of monitoring management.

During the first year of management implementation (2018-2019), no general significant effects of management were detected in the density, height or diameter of P. australis and T. angustifolia. However, starting in the second year (2019-2020), statistically significant effects were observed in the structural parameters of the vegetation. P. australis showed an overall 23% increase in its density (p<0.05) in the management transects, which was accompanied by a decrease in its maximum height (p<0.05), but not in its diameter. At the same time, T. angustifolia density and diameter decreased (p<0.05), although no effect was detected in its maximum height.

The absence of a strong negative effect on the structural parameters of reedbeds can be attributed to the absence of subsequent submergence of the mowed shoots since the period between the two samplings was characterised by very low water levels in Lesser Prespa Lake (see also Step 3.2). In addition, previous studies have demonstrated that the reedbeds of Prespa are of high productivity, thus, in the absence of a significant stressor factor, such as flooding, the harvesting of reeds had a limited impact on the regrowth of the reedbed. The continuation of the management practices during the years following the LIFE Prespa Waterbirds project is of high priority for the successful restoration of wet meadow vegetation.

Please refer to the results of the monitoring study in the following link:

Monitoring of the impact of management on the structural parameters of the reedbed in Lesser Prespa Lake (2018 – 2020)