Leena Lindén

Using a botanic garden collection to test a bioclimatic hypothesis

Bioclimatic hypotheses are used to explain how climate regulates the occurrence of species. A derivative of these hypotheses is that plants moved between corresponding bioclimatic areas should thrive, whereas plants moved to a different zone should languish. This principle is routinely applied in forestry and horticulture but actual tests of the hypotheses seem scanty. We carried out a test on the Finnish system of bioclimatic vegetation zoning using the plant collection of Helsinki University Botanic Garden in Kumpula, which is situated at the northern limit of the hemiboreal zone. We aimed to test how the plants’ survival depends on their provenance with the expectation that plants from the hemiboreal or southern boreal zones should do best in Kumpula. Probability of survival was estimated using collection database information of 379 plant accessions of known wild origin, and logit models. Different growth forms were analysed separately. In most analyses accessions of temperate and hemiarctic origin showed lower survival probability than those originating from any of the boreal subzones, which among them exhibited rather evenly high probabilities. Trees were an exception showing an almost steadily increasing survival probability from temperate to northern boreal origin. In all, the results gave some support to the tested hypothesis, but the various factors that could not be controlled for produced results that were difficult to interpret. We conclude that botanic gardens should pay due attention to information management and curational practices to ensure widest possible applicability of their plant collections.

Urban wetland parks in Finland: improving water quality and creating endangered habitats

Urbanization changes water balance, degrades water quality and disrupts habitats. Wetlands offer storm water volume and flow control, water pollution mitigation, and rich land–water interphase habitats. In the present case study, urban wetlands were designed and implemented to provide multiple functions, including water quality improvement and the establishment of critically endangered clay stream habitat, along a revived urban stream within the Baltic Sea watershed in Southern Finland. The primary water quality concern in the recipient lake is algal bloom controlling and clay particle-carried phosphorus. Wetlands were monitored for functioning over five calendar years. At a wetland monitored for 5 years, herbaceous vegetation was well self-established in the second year, and reached 102 species, of which 97% were native, in the fifth growing season. Successful breeding of amphibians and water birds occurred right after construction. Continuous water quality monitoring over the fourth year at this wetland, with 0.1% area of its watershed, revealed seasonal and event-based differences: for total phosphorus, an annual 10% average with lower removal rates outside, and up to 71% event reductions during the growing season, while highest load reductions occurred during heavy rain and snowmelt events outside the growing season. The created wetlands provided critical habitat and beneficial functions and thus compensated partly for urbanization.

Flower Bud Cold Hardiness of ‘Muskoka’ Red Raspberry as Related to Water Content in Late Winter

Abstract ‘Muskoka’ red raspberry (Rubus idaeus L.) canes were sampled from a field (latitude 60°10′N) at 2- to 3-week intervals from February to April to examine whether the loss of cold hardening capacity in late winter is connected to the increase in bud water content, or to the increased ability of buds to absorb water. Bud base vascular tissue lost its hardening capacity earlier than floral primordia and was injured at warmer temperatures. Cold hardiness was more closely correlated with bud water content than with water potential. Both low water content and low water potential indicated the ability of tissue to harden at low temperatures. All determined parameters except hardening capacity were positively correlated with mean air temperature during a 2-day period preceding sampling. Loss of bud base vascular tissue hardening capacity coincided with increases in bud water content, maximal water content and water potential in the beginning of April, after diurnal mean temperature had risen above 0°C.