Valdo Kuusemets

Nutrient runoff dynamics in a rural catchment: Influence of land-use changes, climatic fluctuations and ecotechnological measures

Abstract The main trend in land-use changes in the Porijogi River catchment, south Estonia, is a significant increase in abandoned lands (from 1.7% in 1987 to 10.5% in 1997), and a decrease in arable lands (from 41.8 to 23.9%). Significant climatic fluctuations occurred during the last decades. Milder winters (increase of air temperature in February from −7.9 to −5.5°C during the period 1950–1997) and a change in the precipitation pattern have influenced the mean annual water discharge. This results in more intensive material flow during colder seasons and decreased water runoff in summer. During the period 1987–1997 the runoff of total-N, total-P, SO4, and organic material (after BOD5) decreased from 25.9 to 5.1, from 0.32 to 0.13, from 78 to 48, and from 7.4 to 3.5 kg ha−1 year−1, respectively. Most significant was a 4–20-fold decrease in agricultural subcatchments while in the forested upper-course catchment the changes were insignificant. Variations of total-N, and total-P runoff in both the entire catchment and its agricultural subcatchments are well described by the change of land use (including fertilization intensity), soil parameters and water discharge. In small agricultural subcatchments the rate of fertilization was found to be the most important factor affecting nitrogen runoff, while land-use pattern plays the main role in larger mosaic catchments. Ecotechnological measures (e.g. riparian buffer zones and buffer strips, constructed wetlands) to control nutrient flows from agricultural catchments are very important.

Impact of climatic fluctuations and land use change on runoff and nutrient losses in rural landscapes

Results on the influence of land use and climatic changes on nutrient losses in the Porijogi river catchment, south Estonia, are presented, The main tendency in land use changes is a significant increase in abandoned lands (from 1.7% in 1987 to 12.5% in 1994), and a decrease in arable lands (from 41.8 to 22.5%). Significant climatic fluctuations were observed from 1951-1994. Warmer winters (increase from -7.9 to -5.8°C from 1950-1994) and a change in the precipitation pattern have influenced the mean annual water discharge. This results in more intensive material flow during colder seasons and decreased water runoff in summer. Changes in water discharge and land use are also reflected in the mean annual runoff of total inorganic nitrogen (TIN) and total-P which decreased from 15.6 to 2.7 kg N ha -1 yr -1 (83%) and 0.32 to 0.21 kg P ha -1 yr -1 (34%), respectively during this period. However, nutrient losses from the forest subcatchment (upper course) did not change significantly. In contrast, the mean annual runoff of water, organic matter (after biological oxygen demand: BOD 5 ), TIN, total-P and SO 4 from cultivated subcatchments showed a significant decrease.

Nutrient dynamics of riparian ecotones: A case study from the Porijo˜gi River catchment, Estonia

The transformation of nitrogen and phosphorus was studied in various riparian ecotones of the moraine plain and moraine-hilly landscapes in the Porijo˜gi River catchment area, southern Estonia. Soil water and ground water samples were collected once per month between 1992 and 1993 from piezometers installed between plant communities located along topo-edaphic gradients from moraine uplands to stream valleys at six sites. The production rate, as well as the N and P content in plant biomass from the 1 m2 plots located near the piezometers was analyzed. Results show that various riparian ecotones had a significant influence on soil water quality. In the arable land, the mean annual concentration of total inorganic nitrogen (NH4+NO2+NO2) in piezometer water was 3–40 mg N1−1, but in the grey alder forest (Alnus incana) total inorganic nitrogen never exceeded 1 mg N1−1. The most significant reduction was in the average concentration of NO3-N content which was reduced from 25 mg 1−1 under the arable land to 0.5 mg 1−1 within the alder forest. The average total phosphorus (orthophosphate phosphorus + organic phosphorus) concentration also decreased under the alder stands, being 0.2-1.5 mg P1−1 in the arable land and less than 0.2 mg P 1−1 in the alder forest (less than 0. l mg P1−1 in loamy soils and 0.2 mg P1−1 in sandy soils). Wetland herb communities (Carex elata association and Filipendula ulmaria-Cirsium oleraceum-Aegopodium podagraria community) also had a significant influence on soil water quality. Plant biomass (sum of above- and below-ground biomass) of riparian and wetland communities accumulates up to 70 g N m−2 and up to 6 g P m−2during the growth season. Harvesting of riparian herbaceous communities may remove 20–30% of nutrient input. In the cultivated grasslands on sandy colluvial soils with a deep humus layer and sedge fens the content of NH4-N and total-P in groundwater toplayer significantly increased, rising to 3 mg and 0.5 mg−1, respectively. Also, it has been assumed that vertical penetration of deep groundwater (contaminated with nitrate and phosphate), may increase the nutrient load to surface water bodies, despite the physical presence of a wide buffer zone (e.g. sedge fen) along the river corridor. From the observations of this work, alder forests and/or willow bushes as buffer strips on and adjacent to the stream banks are recommended to control diffuse water quality.

Alternative Filter Media for Phosphorous Removal in a Horizontal Subsurface Flow Constructed Wetland

Abstract During the study period from 1997 to 2002 the purification efficiency of phosphorus in the horizontal subsurface flow (HSSF) constructed wetland (CW) in Kodijärve, has been quite high (63–95%). However, slowly increasing trend in outlet P concentrations and decreasing annual P removal rate are obviously the indicators that show possible saturation processes in filter media. To search for potential filter media with high phosphorus sorption capacity, sorption characteristics and particle size distribution of several local sands, gravels, glauconite-sandstone, LWA, and calcareous waste products from oil-shale industry were investigated. The average P sorption capacity for best materials (crashed ash block, oil, shale fly ash and the sediment from oil shale ash plateau) was higher than 96% and estimated design capacity was around 4–5 g P kg−1. According to results, sediment from oil shale ash plateau was considered as perspective filter media for P retention. In Summer 2002 experimental sedimentation filter, filled with the sediment from oil shale ash plateau, was installed in the outlet from the Kodijärve HSSF CW. According to preliminary results the average P removal in the sedimentation filter was 52%.

Nutrient flows and management of a small watershed

Nutrient leaching from agricultural areas is one of the main concerns of watershed management. The paper examines nitrogen and phosphorus leaching from different parts of small agricultural watershed (378 ha) that was divided into 6 subcatchments. The calculations of nutrient outflow are based on the detailed measurement at the time of intensive agricultural activities during 5 years (1987–1991). The results show that nutrient leaching can vary very much even in such a small catchment area. The retention of nitrogen and phosphorus took place in the storage lake: 3,900 and 2.2 kg ha−1 year−1, respectively. At the same time, in the small subcatchment with high shallow groundwater outflow value, the nitrogen and phosphorus outflow was 233 and 0.90 kg ha−1 year−1, respectively. The most effective mitigation method is establishing buffer zones on the banks of the stream. A buffer zone of 460 m length would remove 2,200 to 2,640 kg N and 12 to 15 kg P a year, a constructed wetland on the stream would remove 1,660 to 2,760 kg N and 3 to 4.5 kg P a year. The detailed study gives good opportunity to estimate most critical areas where application of mitigation methods is most needed and ecologically and economically effective.

Experimentally constructed wetlands for wastewater treatment in Estonia

Abstract This work presents preliminary results from two constructed wetlands for municipal wastewater treatment in Estonia: (1) a free water surface constructed wetland (a cascade of 4 serpentine ponds in which Typha latifolia and Phragmites australis have been planted (total area about 1.2 ha, mean depth of the ponds 0,5 m) for secondary treatment of waste water from the town of Põltsamaa with about 5,000 inhabitants and from a food processing factory, and (2) a two‐chamber horizontal‐flow sand‐plant filter (two chambers, 30x6.25x1.0 m, each) filled with coarse sand, one planted with Typha latifolia, and the other with Iris pseudacorus and Phragmites australis, receiving a septic tank effluent of about 40 population equivalents in Kodijärve. The horizontal flow sand‐plant filter showed satisfactory purification efficiency in terms of BOD7 and phosphorus (66–95% and 63–96%, respectively). However, nitrogen removal was relatively low, varying from 12 to 85%. In the cascade of free water surface wetlands, the most critical parameter is phosphorus retention. Mean purification efficiency observed was about 73% for nitrogen, 68% for BOD7 and 24% for phosphorus. Purification efficiency in both wetland systems did not decrease during the cold season.

Nitrogen and Phosphorus Accumulation and Biomass Production by Scirpus sylvaticus and Phragmites australis in a Horizontal Subsurface Flow Constructed Wetland

Abstract We studied plant biomass production and nutrient accumulation by wood club-rush (Scirpus sylvaticus) and reed (Phragmites australis) in a horizontal subsurface flow constructed wetland in 2001 and 2002. The wetland consists of two beds, one with dry and another with wetter conditions. From both beds, 5 above-ground, below-ground, and litter samples were taken in the summer, during the maximum flowering period of the dominant species. The average dry biomass of whole plant and litter was considerable higher in 2002 (3071 g m− 2) than in 2001 (620 g m− 2) due to the climatic conditions. The average dry weight biomass of 5 plots in 2001 was 513 g m−2 in the dry bed and 729 g m− 2 in the wet bed. In 2002 these values were 2,520 and 3,765, respectively. Variations in biomasses will also appear in values for nutrient accumulation, in all cases the N and P accumulation was higher in 2002. The average nitrogen accumulation by plants was 16.6 g m− 2 in the wet and 10.7 g m− 2 in the dry bed in 2001, and 51.7 and 83.5 g m− 2 in 2002 respectively. Phosphorus accumulation was higher in the wet bed during 2001—2.8 g m− 2, in the dry bed this value was 1.9 g m− 2. In 2002, the phosphorus accumulation was higher in the dry bed—12.8 g m− 2, in the wet bed it was 12.43 g m− 2. The total biomass at the same conditions in the wet bed was slightly higher in case of wood club-rush—765 g m− 2 in 2001 and 3846 g m− 2 in 2002, same values for reed were 674 g m− 2 and 3,646, respectively.

A framework for habitat monitoring and climate change modelling: construction and validation of the Environmental Stratification of Estonia

Environmental stratifications provide the framework for efficient surveillance and monitoring of biodiversity and ecological resources, as well as modelling exercises. An obstacle for agricultural landscape monitoring in Estonia has been the lack of a framework for the objective selection of monitoring sites. This paper describes the construction and testing of the Environmental Stratification of Estonia (ESE). Principal components analysis was used to select the variables that capture the most amount of variation. Seven climate variables and topography were selected and subsequently subjected to the ISODATA clustering routine in order to produce relatively homogeneous environmental strata. The ESE contains eight strata, which have been described in terms of soil, land cover and climatic parameters. In order to assess the reliability of the stratification procedure for the selection of monitoring sites, the ESE was compared with the previous map of Landscape Regions of Estonia and correlated with five environmental data sets. All correlations were significant. The stratification has therefore already been used to extend the current series of samples in agricultural landscapes into a more statistically robust series of monitoring sites. The potential for applying climate change scenarios to assess the shifts in the strata and associated ecological impacts is also examined.

Pollinator richness and abundance in Northeast Estonia: bumblebees, butterflies and day-flying moths

Pollinator richness and abundance in Northeast Estonia: bumblebees, butterflies and day-flying moths We studied diversity and abundance of three groups of pollinators: bumblebees, butterflies and day-flying moths, in Ida-Viru County, Estonia. The field work was done during the summers of 2008 and 2009, in 22 semi-natural meadows located across Northeast Estonia. In total, we found 22 species of bumblebees (gen. Bombus), including 5 species of cuckoo bumblebees, 56 species of butterflies and 42 species of day-flying moths. We recorded 597 individuals of bumblebees, 768 individuals of butterflies and 330 individuals of day-flying moths in our study sites. We analysed differences between years (2008 and 2009) for the species richness and abundance of bumblebees, butterflies and day-flying moths; the relationships between insect species richness and area of meadow, the total number of species per meadow and the local abundance of each species separately. We found significant differences between bumblebee richness and abundance in 2008 and 2009, and between butterfly abundance at the same years. These differences may be due to more favourable conditions: warmer and dryer weather in the second year. We found no significant relationships between area of meadow and species richness of bumblebees, butterflies and day-flying moths; however, when we analysed the abundance of each species separately, we found that two species of bumblebees, i.e. B. pascuorum and B. schrencki, and one species of day-flying moths, i.e. Chiasmia clathrata, were negatively related with area of meadow. Although, Northeast Estonia is a region that has been environmentally affected by mining activities and the presence of power plants, it could be considered an important area that supports a significant richness and abundance of pollinators across its territory. Kolme tolmeldajaterühma: kimalased, päevaliblikad ja päeval aktiivsed hämarikuliblikad, liigirikkus ja arvukus Ida-Virumaal Töö eesmärgiks oli uurida kolme tolmeldajate rühma: kimalased, päevaliblikad ja päeval aktiivsed hämarikuliblikad, liigirikkust ja arvukust Ida-Virumaal. Välitööd tehti aastatel 2008 ja 2009 22-1 poollooduslikul niidul. Kimalasi leiti 22 liiki (gen. Bombus), sealhulgas 5 liiki kägukimalasi (subgen. Psithyrus), 597 isendit. Kõige arvukamad liigid olid B. pascuorum, B. lucorum and B. ruderarius. Päevaliblikaid leiti 56 liiki ja 768 isendit, kõige arvukamad liigid olid Coenonympha glycerion, Aphantopus hyperantus ja Thymelicus lineola. Päeval aktiivseid hämarikuliblikaid leidsime 42 liiki ja 330 isendit, kõige arvukamad liigid olid Siona lineata ja Scopula immorata. Kimalaste liigirikkus ja arvukus ning liblikate arvukus erinesid statistiliselt oluliselt aastatel 2008 ja 2009. See võis olla põhjustatud erinevate aastate ilmastikutingimuste erinevustest, kuivõrd 2009. aasta oli kuivem ja soojem. Elupaiga suurus ei avaldanud statistiliselt usaldusväärset mõju uuritud tolmeldajate rühmade liigirikkusele. Samas omas elupaiga suurenemine negatiivset mõju mõningate liikide, nagu B. pascuorum, B. schrencki ja Chiasmia clathrata arvukusele.