Driftskontroll av kalkdoseringsanlegg i Mandalsvassdraget Avviksrapport 2011

Driftskontroll av kalkdoseringsanleggene i Mandalsvassdraget gjennomføres for å avdekke effektiviteten til de enkelte anleggene i vassdraget. Avviksrapporten er en sammenfatning av hendelser i rapporteringsperioden. Den foreslår også tiltak for optimalisering av rutiner, installasjoner og kalkingsstrategi. Den daglige driftskontrollen av Smeland doseringsanlegg måtte tidvis opphøre på grunn av mange svikt i telelinjen. Det var lav dosering fra anlegget. Håverstad doseringsanlegg hadde god driftssikkerhet gjennom hele året. Bjelland doseringsanlegg kalket tilfredsstillende, men det var en del mangler ved pH-målingene. Årsakene var ofte stopp i gjennomstrømmingen av pH-kyvetta, men også feil på måleutstyret. Logåna-anlegget hadde også for mange stopp i vanngjennom-strømmingen. Det foreslås tiltak for å bedre disse forholdene. Fisk kan ha tatt skade av for surt vann på grunn av manglende vannglass når behovet oppsto. pH-målet for lakseførende strekning av elva ble opprettholdt kontinuerlig i hele periodenSamarbeid om kalking av Mandalsvassdraget, MANKALK (Audnedal, Evje- og Hornnes, Mandal, Marnardal, Songdalen og Åseral kommune)

Tree mold evidence of Loulu Palm (Pritchardia sp.) Forest on the Kona Coast, Hawai'i

Lava flows at Pu'uhonua o Honaunau National Historical Park on the island of Hawai'i contain tree molds identified as native loulu (Pritchardia sp.) palms on the basis of gross morphology and surface features and patternings. The vegetation is reconstructed as loulu forest with an admixture of dicot species, represented by branched molds. Occurrence of loulu forest at ∼1000 B.P. (calibrated radiocarbon dates on charcoal from beneath the flow) suggests that these palms persisted into the early period of Polynesian settlement on the Kona coast and that Pritchardia was an important component of precontact vegetation in this area

Population Dynamics of Marsilea villosa (Marsileaceae) on O‘ahu, Hawai‘i

v. ill. 23 cm.QuarterlyMarsilea villosa Kaulfuss is an endemic Hawaiian fern with a very small, fragmented natural range and an ephemeral habit that makes it difficult to assess population health. Its sporocarps are presumed to remain viable for many years, allowing it to survive periods of drought and then sexually reproduce when there is sufficient precipitation to cause them to be submerged in standing water. Surveys of plant cover at ‘Ihi‘ihilaua¯kea Crater, where the largest and best-protected stand was located, have shown that vigorous growth of the species occurs after the crater floor is flooded. This study documents dramatic decline over the last 8 yr, during which growth has been largely vegetative. Analyses of rainfall records suggest that events producing long-duration floods occur on average every 6.5 yr, yet 13 yr have elapsed since the last one. Although this may in part explain the poor condition of the population, other ecological changes have occurred including decline of the dominant trees and invasion of alien grasses that may influence flooding frequency. Marsilea villosa may be able to avoid extinction because flooding caused by rare climatic events will kill off the competitors that have encroached on its former ecological space. However, it is predicted to be a less-conspicuous part of the ecosystem most of the time unless management can effectively suppress invaders