Māra Pakalne’s scientific contributions

Slitere National Park in Latvia is home to rich fens with many endangered and threatened plant species. This study aims to address how the hydrological systems affect vegetation biodiversity (cf. Wolejko et al. 2019) in the mire systems of the National Park: the base-rich inter-dune mires and extremely base-rich calcareous fens. Groundwater samples from these areas were collected for measurements of ion composition and natural isotopes of C, H and O. Also, we simulated groundwater flow paths from the highest local topographical point (a nearby sandy plateau) to the sea, and calculated the residence times of these groundwater flows. The results show that the inter-dune mires are supplied by a mixture of local and regional groundwater systems. The groundwater supply at one of the inter-dune mires was dominated by local groundwater flow from adjacent dunes, but we also detected a small input of calcareous water. This dominance of local groundwater may have resulted from the presence of drainage ditches and a small stream that drains into the Baltic Sea. In contrast, the extremely base-rich fens were found to be solely dependent on regional groundwater which is likely to discharge at the plateau foothills due to the presence of fault structures. Thus, the mires in Slitere National Park are not as undisturbed as was previously believed. Drainage may have affected the original hydrological flow paths. Further research on the extent of these changes is recommended to preserve the endangered species and high biodiversity of these fens. Also, in order to trace the origin of groundwater flows, further investigation into the larger landscape beyond the plateau might be required.

Calcareous fen succession in Lake Engure Nature Park, Latvia, on the former bottom of Lake Engure (water table significantly lowered in 1842). In our study, vegetation data from the same transect in 1988 and 2018 are compared. The results suggest that Schoenetum ferruginei community is being gradually replaced by Cladietum marisci community.

Bryophytes are pioneer species that occupy degraded sites, both after natural disturbances (e.g. fire) and human impact (e.g. logging). Post-harvested peatlands can be inhabited by bryophyte species that are adapted to extreme conditions such as drought, exposure to high sun radiation, wind erosion, etc. Still, bryophyte richness is higher in intact or less affected peatlands-raised bogs, transition mires and fens with different ecological niches. The role of bryophytes, especially Sphagnum, in mires involves also peat formation and carbon sequestration. Climate change mitigation by reducing greenhouse gas (GHG) emissions, low groundwater fluctuations are only some functions that are strongly related to processes in intact peatlands. To study bryophyte species composition in peatlands with different management history, data were collected in eight sites: three peatlands with minor drainage impact in Latvia and five significantly drained, post-harvested peatlands in Lithuania. Vegetation cover (bryophytes, lichens, herbs, shrubs, trees) and physical parameters (degree of site degradation, soil moisture) were recorded in 269 plots in 2017–2018 during the LIFE Peat Restore project (LIFE15 CCM/DE/000138). Additionally, vegetation data together with environmental parameters were used for indirect GHG emission assessment applying the recently developed GEST (Greenhouse Gas Emission Sites Types) approach. In all sites, 382 species were recorded, including 85 bryophyte species (10 liverworts and 75 mosses, including 19 Sphagnum species). Bryophyte species richness showed moderate positive correlation with total species richness (r S =0.53, p<0.001), weak correlation with moisture (r S =0.34, p<0.001) and herb cover/species richness (r S =0.24, p<0.001; r S =0.28, p<0.001, respectively). Bryophyte species richness was best explained by total number of species per plot, bare peat and bryophyte species cover and was site-specific. Species composition significantly differed between degraded and near-natural sites. From all recorded bryophytes, 24 species were related to one of four previously defined degradation classes using indicator-species analysis. Campylopus introflexus, Pleurozium schreberi, Pohlia nutans, Polytrichum spp. were indicators of the most degraded sites, while Cephalozia bicuspidata, Dicranum bonjeanii, Mylia anomala, Sphagnum angustifolium were found only in sites with minor drainage impact. The results suggest that bryophytes can be used as indicators to assess the degradation of peatlands.

In the LIFE REstore project, vegetation was surveyed in 32 extracted peatlands in the period from 2016 to 2018. The surveyed peatlands included both former block-cut and vacuum harvested areas. Typical vegetation types occurring in the former peat extraction areas were identified, and influence of drainage, water table and other factors was evaluated. The results of LIFE REstore inventory were supplemented with data from similar studies carried out in Latvia. In total, results from 39 cutaway peatland areas in Latvia have been included in this study. Several scenarios of spontaneous revegetation were identified. They were distinguished by dominant properties of residual peat layer, peat extraction methods, and moisture conditions. Each scenario includes several succession stages. Overall, the results describe the process of spontaneous revegetation in various conditions in Latvia, although not all variations could be included in this overview. The main factors determining the course of spontaneous revegetation in cutaway peatlands are groundwater table, type and properties of residual peat, its physical and chemical properties, as well as hydro-chemical parameters of water bodies. The restoration of peat-forming mire vegetation and hence the peat accumulation process is possible only in wet conditions, which is important when planning rehabilitation for mire ecosystem and its functions, including carbon sequestration, regulation of water and nutrient cycling, and soil formation. The results of this inventory were used to identify the factors which should be taken into account in planning rehabilitation of peatlands damaged by peat extraction, i.e. restoration of peat-forming vegetation. Abandonment of such degraded peatlands leading to natural succession cannot be considered rehabilitation in cases when the impact of drainage system is not eliminated.

2016.–2018. gadā LIFE Restore projektā veikta veģetācijas inventarizācija 32 kūdras ieguves ietekmētās teritorijās. Apmeklētas teritorijas, kur kūdra iegūta gan ar karjeru, gan griešanas, gan frēzēšanas metodi. Dokumentēti teritorijās raksturīgie veģetācijas tipi, novērtēta meliorācijas sistēmu ietekme, mitruma apstākļi un citi ietekmējošie faktori. LIFE Restore inventarizācijas rezultāti papildināti ar citu Latvijā veiktu līdzīgu pētījumu datiem, tādējādi nodaļa ietver rezultātus no 39 teritorijām visā Latvijā. Konstatēti vairāki veģetācijas pašatjaunošanās scenāriji, kuri nodalīti pēc palikušā kūdras slāņa ominējošām īpašībām, kūdras ieguves metodes, mitruma apstākļiem un katrs ietver vairākas veģetācijas attīstības stadijas. Kopumā rezultāti raksturo veģetācijas pašatjaunošanās gaitu dažādos apstākļos Latvijā. Galvenie faktori, kas nosaka veģetācijas raksturu kūdras ieguves ietekmētās teritorijās, ir ūdens līmenis, palikušās kūdras tips un tās fizikāli ķīmiskās īpašības, kā arī ūdens hidroķīmiskie rādītāji ūdenstilpēs. Purva veģetācijas un līdz ar to arī kūdras uzkrāšanās procesa atjaunošanās iespējama tikai mitros apstākļos, kas ir būtiski arī, plānojot renaturalizāciju, lai atjaunotu purva ekosistēmas funkcijas – oglekļa uzkrāšanu, ūdens un vielu aprites regulēšanu un augsnes veidošanos. Inventarizācijas rezultāti izmantoti, lai vērtētu renaturalizācijas iespējas un būtiskos faktorus, kurus, plānojot purvu veģetācijas atjaunošanu kūdras ieguves ietekmētās teritorijās, būtu jāņem vērā, lai rezultāts būtu sekmīgs. Par renaturalizāciju nevar uzskatīt teritorijas atstāšanu veģetācijas dabiskai attīstībai, ja netiek likvidēta meliorācijas sistēmas ietekme.

During the previous decades the Latvian peatlands are influenced by drainage and peat harvesting. To restore the drained and degraded peatlands and to diminish the greenhouse gas (GHG) emissions, within the LIFE Peat Restore project (LIFE15 CCM/ DE/000138) re-establishment of natural carbon sink function of peatlands is planned in three sites in Latvia. Additionally, GHG emissions are being measured before and after restoration to demonstrate the role of peatland restoration in mitigation of climate change. Since the LIFE Peat Restore project is international (involves partners from Latvia, Estonia, Lithuania, Germany, and Poland), the results can be compared at international level. The aim of the LIFE Peat Restore project is improving the functioning of mire ecosystems, including carbon sequestration capability.

The first study about bryophytes in Lielie Kangari was published by Austra Āboliņa in 1982, where 144 species were found. The present study was conducted in the southern part of Lielie Kangari Nature Reserve in spring of 2016, where 148 bryophyte species and one bryophyte variety were found. In total 19 bryophyte species had conservation status in Latvia and 29 species were found for the first time in the Reserve. Bryophytes were found mostly on soil, peat, and dead wood substrates.