Gunta Cekstere

Influence of De-Icing Salt on K Supply and Street Trees Ecological Status in Riga, Latvia

The study was conducted to evaluate the toxic effect of soil and plant pollution with Na and Cl− on K supply and ecological condition of the street trees (Tilia × vulgaris H.) in Riga during 2005 and 2007. The results revealed that the ecological status of street trees could be characterized as seriously injured due to high concentrations of Na and Cl− in soil (maxNa 1,568.1 mg/kg; maxCl 744.9 mg/kg) and lime leaves (maxNa 1.93%; maxCl 3.00%). The concentrations of Na and Cl− in lime leaves demonstrated a marked tendency to increase during summer, while the concentrations of K in leaves decreased (min. 0.15%). There were close correlations between the concentration of Na and Cl− in lime leaves and the extent of leaf necrosis, although unfavorable K/Na ratio has additive negative impact.

Effect of Humic Substances on Nutrient Status and Yield of Onion (Allium Cepa L.) in Field Conditions

Humic substances (HS) extracted from various organic materials have been shown to stimulate plant growth. However, scarce information is available on the impact of different methods of application of HS on nutrient status of vegetable species, especially in soil and climate conditions of the temperate zone. The goal of the present study was to evaluate the effect of pre-plant (bulblet soaking) and foliar application of commercially-produced peat and vermicompost-derived HS preparations on nutrient status and yield of onion (Allium cepa L.) in field experiments using two farming systems - conventional and organic. Although the effect was variable between nutrients, dependent on timing, application methods and farming systems, pre-plant and foliar HS tested was hardly effective in preventing nutrient (S, Zn, B) deficiencies limiting onion yield. Moreover, HS induced changes that significantly reduced nutrient status of organically grown onion and had detrimental effect on yield. Although one-year results did not suggest a benefit from HS application, further studies are necessary to evaluate the possible effectiveness of peat and vermicompost extracts on onion production in Latvia.

Mineral Nutrition of Young Ash in Latvia

Abstract The research objectives were: 1) to determine healthy young ash supply with nutrients and their concentrations in natural growth conditions; 2) to estimate nutrient balance and inter-correlations within a system “soil-plants”; and 3) to determine the potential effect of environmental conditions (forest type, plant phytosociological group, soil group, etc.) on nutrient accumulation in soil and leaves of young ash. The investigation was conducted in 28 different forest sites with young ash in Latvia. The results demonstrated that young ash grows well on a wide range of site types in terms of soil composition, forest type and phytosociological tree group. Although highly heterogeneous, soil in ash stands in Latvia can provide a sufficient supply of nutrients. Therefore, the nutrient status of healthy young ash leaves can be characterized as sufficient, although low levels of P, Zn, and K in leaves was found for most sites. Significant impact of soil group and forest type was found on nutrient composition of ash soil, while leaf nutrient concentrations were more dependent on the forest type and phytosociological tree group. The obtained results confirmed the ability of ash to accumulate nutrients within a certain range from soils of different fertility, organic matter content and soil reaction in Latvia.

Chemical Composition of Scots Pine Bark as a Bioindicator of Environmental Quality in Riga, Latvia / Priežu Mizu ķīmiskais Sastāvs Kā Vides Stāvokļa Bioindikators Rīgā (Latvija)

Abstract The chemical composition of pine bark was used for the determination of environmental quality in Rīga. Bark samples were collected at 54 sites in Rīga differing in vegetation and building area characteristics (urban forests, parks and cemeteries, dwelling houses, and streets and railway zones) and at 52 sites from rural areas in Latvia (background level). Concentrations of Ca, Mg, Na, K, Fe, Mn, Zn, Ni, Cu, Cd, Pb, and pH was determined in the samples. The results showed significantly higher concentrations of chemical elements in pine bark collected in Rīga, compared to background levels: Fe and Cu concentrations three times higher, and other elements - up to 1.8 times. The highest element concentrations in Rīga were near streets (Sarkandaugava, Jaunmīlgrāvis, Daugavgrīva, Čiekurkalns, Imanta area, etc.). Element concentration and pH was significantly dependent on the distance from the closest street. The lowest element concentrations were found in urban forests (Jugla, Biķernieki, Beberbeķi) and parks and cemeteries (I Forest Cemetery, Jaunciema Cemetery). Mežaparks (forest), Sarkandaugava, Jaunmīlgrāvis, and Vecmīlgrāvis together formed the most polluted area in Rīga due to the close location near and downwind from the harbour. Vides stāvokļa novērtēšanai Rīgā kā bioindikators izmantots priedes mizas ķīmiskais sastāvs. Paraugi tika ievākti 54 vietās pilsētā atkarībā no veģetācijas un apbūves īpatnībām: urbānie meži, parki un kapsētas, dzīvojamās mājas un ielu malas un dzelzceļa zonas. Fona līmeņa raksturošanai izvēlētas 52 vietas Latvijā ārpilsētas mežos. Visos paraugos noteikta Ca, Mg, Na, K, Fe, Mn, Zn, Ni, Cu, Cd, Pb koncentrācija un pH. Rezultāti parādīja, ka Rīgā, salīdzinot ar fona līmeni, bija lielāka visu priedes mizā analizēto ķīmisko elementu vidējā koncentrācija. Fe un Cu koncentrācija pilsētvidē bija trīs reizes, bet pārējo ķīmisko elementu koncentrācija - līdz 1,8 reizes lielāka, salīdzinot ar lauku vidi. Pilsētvidē lielākās ķīmisko elementu koncentrācijas konstatētas gar brauktuvēm (Sarkandaugavā, Jaunmīlgrāvī, Daugavgrīvā, Èiekurkalnā, Imantā un citur). Konstatēts, ka ķīmisko elementu koncentrācijas būtiski izmainās, attālinoties no brauktuves. Viszemākās ķīmisko elementu koncentrācijas priedes mizā bija pilsētmežos (Jugla, Biķernieki, Beberbeķi), kā arī parkos un kapsētās (I Meža kapi, Jaunciema kapi). Tomēr Mežaparks (mežs) līdz ar Sarkandaugavu, Jaunmīlgrāvi un Vecmīlgrāvi bija stiprāk piesārņotais Rīgas rajons, jo tas atrodas ostas kompleksa un valdošo rietumu vēju tiešā ietekmes zonā.

Pest Plant Score of Alien Robinia Pseudoacacia in Rīga (Latvia) and Kaunas (Lithuania) / Svešzemju Sugas Robinia Pseudoacacia Invazitātes Novērtējums Rīgā (Latvija) Un Kauņā (Lietuva)

Abstract Robinia pseudoacacia is an alien tree species that has wide distribution in green areas of Rīga and Kaunas. In recent years, the spread and invasion of this species was observed. The aim of this study was to determine the relative importance of invasiveness of R. pseudoacacia in Rīga and Kaunas. The degree of species invasion was estimated by applying the Pest Plant Prioritization Process, which is based on the Analytic Hierarchy Process method. The results showed that the invasive degree of R. pseudoacacia was near medium (0.4); the present compared to potential distribution rating was medium (0.57) and the social, environmental and economic impact score was very low (0.17). The Final Pest Plant Score for R. pseudoacacia was near medium (0.426). The obtained estimates indicated that black locust was medium invasive, and that well-lit conditions favour its establishment. Robinia pseudoacacia ir svešzemju koku suga, kas plaši izplatīta Rīgas un Kauņas zaļajā zonā, kur pēdējos gados novērojama šīs sugas izplatīšanās un invāzija. Pētījuma mērķis bija novērtēt R. pseudoacacia invazitātes relatīvo nozīmi Rīgā un Kauņā. Sugas invāzijas pakāpe tika novērtēta, izmantojot Pest Plant Prioritization Process, kas pamatojas uz Analytic Hierarchy Process Method. Rezultāti parādīja, ka R. pseudoacacia invazitātes pakāpe bija vērtējama kā zemāka par vidējo (0,4); pašreizējā izplatības intensitāte salīdzinājumā ar potenciālo izplatības intensitāti vērtējama kā vidēja (0,57), savukārt sociālās, vides un ekonomiskās ietekmes novērtējums bija ļoti zems (0,17). Līdz ar to gala novērtējums R. pseudoacacia saskaņā ar Final Pest Plant Score bija tuvu vidējam (0,426). Iegūtais novērtējums norādīja, ka R. pseudoacacia ir vidējA invazitāte, bet piemērotos apstākļos, piemēram, gaismas palielināšanās gadījumā, tās izplatība pieaug.

Structure and dynamics of oligomesic dry pine forests in land zones of the Lake Engure catchment area

Abstract Investigation of species composition, soil physical and chemical properties, as well as forest productivity of oligomesic dry pine forests (Vacciniosa and Myrtillosa forest types) was carried out in six dry land zones differing in age of the Lake Engure catchment area (sediment zones of the drained lakebed, Mia, Limnea, Litorina Sea, Baltic Ice Lake and glaciofluvial sediment zone in Northern Kursa Upland). Higher species diversity in the tree layer and a more typical podzolisation process was found in the older dry land zones (sediments of the Baltic Ice Lake, Northern Kursa Upland), while higher species diversity in the field layer (higher proportion of grasses and sword grasses), more intensive gleying process in soils, as well as considerably higher stand productivity was observed in the younger dry land zones (the drained lakebed, Mia, Limnea and Littorina Sea stages). Characteristic species of the Vaccinio-Piceetea class were dominant in the pine forests of older dry land zones, whereas species of the Pulsatillo-Pinetea class were typical in the sea coastal pine forests. Abstract in Latvian Engures ezera sateces baseina sešās sauszemes vecuma zonās (nosusinātās ezerdobes, Mia, Limnejas, Litorīnas jūras, Baltijas ledus ezera un Ziemeļkursas augstienes glaciofluviālo nogulumu zona) pētīts oligomezotrofo sauso priežu mežu (Vacciniosa un Myrtillosa) sugu sastāvs, augsnes fizikālās un ķīmiskās īpašības, kā arī mežu produktivitāte. Vecākās sauszemes vecuma zonās (Baltijas ledus ezera nogulumi, Ziemeļkursas augstiene) ir lielāka sugu dažādība koku stāvā un augsnēm izteiktāks podzolēšanās process, savukārt jaunākās sauszemes vecuma zonās (nosusinātā ezerdobe, Mia, Limnejas un Litorīnas jūras stadijas) ir lielāka sugu dažādība zemsedzē (lielāks graudzāļu un grīšļu īpatsvars), augsnēm raksturīgs izteiktāks glejošanās process, kā arī ievērojami augstāka kokaudzes produktivitāte. Vecāko sauszemes zonu priežu mežos dominē klases Vaccinio-Piceetea rakstursugas, turpretim jūras piekrastes priežu mežiem (Mia nogulumu zona) raksturīgas klases Pulsatillo-Pinetea sugas.