Vpliv presihanja na aktivnost in primarno produkcijo vrst Phragmites australis in Carex elata na Cerkniškem jezeru : magistrsko delo

Rudolf, Mojca (author), Gaberščik, Alenka (mentor)

Aktivnost in primarna produkcija prevladujočih rastlinskih vrst na Cerkniškem jezeru navadnega trsta Phragmites australis in togega šaša Carex elata sta odvisni od sprememb vodostaja. Naš namen je bil raziskati vlogo teh vrst pri pretoku energije in kroženju vode v odvisnosti od presihajočega vodnega režima. Hkrati smo želeli poudariti tudi njuno vlogo iz vidika ekosistemskih storitev in vidika varstva narave. Aktivnost preučevanih vrst smo ugotavljali z merjenjem fotokemične učinkovitosti FSII, fotosinteze in transpiracije. Izračunali smo učinkovitost izrabe vode. Merili smo tudi parametre primarne produkcije. Pri navadnem trstu smo ugotavljali velikost in gostoto rastlin, število internodijev, bazalni diameter in število cvetočih rastlin, pri šašu pa velikost in število listov. Pri obeh vrstah smo dolocili indeks listne površine in suho maso rastlin. Ob meritvah na terenu smo spremljali tudi abiotske dejavnike - fotosintezno aktivno sevanje, vlažnost zraka in temperaturo. Ugotovili smo, da imata navadni trst in togi šaš pomembno vlogo pri kroženju vode in vnosu energije v ekosistem. Potencial rastlin kot nosilcev pretoka energije in kroženja vode se ni dosti spreminjal in ni bilo opaziti večjih odstopanj med posameznimi leti. Cas in dolžina poplav sta vplivala na uspevanje navadnega trsta bolj kot pa na uspevanje togega šaša. Trst, ki je uspeval na kopnem, in tudi trst v vodi sta bolje izkoristila svetlobno energijo v času nizkega vodostaja, kar odraža negativna korelacija med vodostajem in fotokemično učinkovitostjo FSII, medtem ko pri togem šašu korelacija ni bila značilna. Vrednosti potencialne fotokemične učinkovitosti so bile nad vrednostjo 0,8 in se niso značilno razlikovale, iz cesar lahko sklepamo, da rastline niso bile podvržene vecjemu stresu. Nivo fotosinteze odraža variabilnost razmer na rastišču. Pri trstu v vodi in pri šašu smo ugotovili značilno pozitivno korelacijo med vodostajem in fotosintezo, medtem ko pri trstu v vodi povezava ni bila značilna. Razlike v vrednostih transpiracije pri trstu so bile ugotovljene med posameznimi leti, med posameznimi rastišči pa večjih odstopanj ni bilo. Pozitivna korelacija med transpiracijo in vodostajem je bila ugotovljena pri trstu na kopnem in vodi, medtem ko pri šašu povezava ni bila značilna. Učinkovitost izrabe vode je bilavečja v bolj sušnih razmerah, ker mora rastlina omejiti izgube vode. Suha masa trsta na kopnem je znašala v povprečju 1194 g/m2 (leto 2005) in nekoliko manj v letu 2006 (748 g/m2). Nekoliko nižjo primarno produkcijo je imel trst, ki je uspeval v vodi (720 g/m2 in 838 g/m2). Vrednosti pri togem šašu se niso dosti spreminjale in so znašale v povprečju 333 g/m2 in 383 g/m2 v sezoni 2005in 2006. Pri primerjavi višine rastlin so opazne razlike na kopnem in v vodi, kjer je uspeval v povprečju višji trst. Dejavniki primarne produkcije pri togem šašu se niso dosti spreminjali v posameznih sezonah. Uspešnost obeh vrst je indikator okoljskih razmer v določenem letu. Naše raziskave kažejo veliko prožnost trsta in šaša pri odzivih na spremembe vodostaja, kar pomeni nemotene ekosistemske storitve (vnos energije in kroženje vode), vključno z ustreznostjo habitatov za ostale vrste. Ohranjanje naravnega vodnega režima jeključni dejavnik za vzdrževanje optimalnih razmer na rastišču in posledično pretoka energije, visoke biodiverzitete in nemotenih ekosistemskih storitev.

• Language: Slovenian
• Keywords: spremembe vodostaja, Phragmites australis, Carex elata, fotosinteza, transpiracija, fotokemična učinkovitost FSII, primarna produkcija, ekosistemske storitve, varstvo narave
• Work type: Master's thesis
• Typology: 2.09 - Master's Thesis
• Organization: BF - Biotechnical Faculty
• Place of publishing: Ljubljana
• Publisher: [M. Rudolf]
• Year: 2008
• Number of pages: XI, 86 str.
• PID: 20.500.12556/RUL-15546
• UDC: 581.16+502.51:(285 Cerkniško jezero)(497.4)(043.2)=163.6
• COBISS.SI-ID: 2200486
• Publication date in RUL: 11.07.2014

Secondary language

• Language: English

Abstract

Activity and primary production of two prevailing species Phragmites australis and Carex elata was studied in relation to water level fluctuations on Cerknica Lake. The aim of our research was to examine the role of Phragmites australis and Carex elata in through flow of energy and water cycling in relation to intermittent water regime. On the basis of this research we also wanted to point out the role of both species for the selected ecosystem services and nature conservation aspects. The activity of studied species was monitored measuring photochemical efficiency of PSII, photosynthesis and transpiration rate. On the basis of the latter two we calculated water use efficiency. At the end of the season we performed growth analysis. In Phragmites australis we measured height and density of plants, number of internodes, basal diameter and the number of flowering plants, whilein Carex elata we measured the length and number of leaves. In both we determined leaf area index and dry mass of aboveground plant parts. During field measurements we monitored abiotic parameters such as photosintetically active radiation, relative humidity and air temperature. The study revealed that Phragmites australis and Carex elata played an important role in water cycling and input of energy into the ecosystem. The changes in duration and extent of flooding affected the Phragmites australis to higher extend than Carex elata. Terrestrial reed, as well as reed in water exhibited higher lightuse efficiency during low water level as revealed by negative correlation between photochemical efficiency of PSII and water level. In sedge no difference comparing three seasons were found. Values of potential photochemical efficiency of PSII were not significantly different (near 0.8), that revealed that plants were not under irreversible stress. The level of photosynthesis express growth conditions at the certain time. In littoral reedand in sedge we calculated positive correlation among photosynthesis and water level, while in terrestrial reed the correlation was not significant. The differences in transpiration in terrestrial and littoral reed occurred among different seasons. Positive correlation between transpiration rate and water level was established in both terrestrial and aquatic reeds, while it was not significant in sedge. The results showed that water use efficiency increased under lower water availability. Dry mass of terrestrial reed was in average 1194 g/m2 (year 2005) and somewhat less in 2006 (748 g/m2). Lower production was measured in littoral reed (720 g/m2 and 838 g/m2, respectively). The values in sedge were in average 333 g/m2 and 383 g/m2. The habitus of plants differed among years and locations. In years 2005 and 2006 littoral reed was higher than terrestrial reed. Primary productivity parameters in sedge did not vary among seasons. Three years studies revealed great plasticity of both species to water level fluctuations, that assure undisturbed ecosystem services (input of energy and water cycling), including habitats for other species. Therefore regular water regime is of primary importance for maintenance of favorable growth conditions and consequently the through flow of energy, biodiversity and undisturbed ecosystem services.