Browsing by Subject "boreal"

Global biodiversity continues to decline. Recent reports of decline in insect abundance and biomass are concerning, given the crucial roles insects play in multiple ecosystem processes, such as pollination, nutrient cycling and as a food resource for higher trophic levels. Based on the current state of the literature, it appears that total insect abundance and biomass are in decline, but there is considerable variation in trajectories in different regions and taxa. Many studies report on either aggregated community abundance or biomass, but few have examined how closely these two variables are correlated. For example, declining trends in large-bodied species could have disproportionately large effects on total biomass, even if total abundance remained stable. This, in turn, could have substantial consequences for predators dependent on insect biomass for food. Whether studying total abundance or biomass, long-term monitoring data are essential for robust estimation of temporal trends. In my thesis, I investigated trends in macro-moth abundance and biomass using data from the Finnish moth monitoring scheme (Nocturna) over a period of 24 years (1993-2016). My main objectives were to explore whether total abundance and biomass have changed over the timeframe examined, and to estimate the degree of correlation between the two variables in these data. As is typical for monitoring programs, only counts of moth individuals have been recorded. In order to obtain information on biomass, I created a predictive model for converting the recorded abundance counts to dry biomass based on species mean wingspan and body robustness. I weighed museum collection specimens of common moth species of variable sizes, and used these data for fitting the model. Additionally, I also investigated how local weather (thermal and precipitation) conditions during the growing season and winter relate to interannual variation in total abundance. Finally, I analysed potentially informative species traits (e.g., wingspan, voltinism, overwintering stage) in relation to population trends of individual species, because such associations could be underlying change in total abundance or biomass. There was no long-term change in total macro-moth abundance or biomass over the 24-year monitoring period. Abundance and biomass were very highly correlated (r > 0.9). In terms of interannual variation, total moth abundance and biomass showed a distinctive pattern suggestive of periodicity, with peaks at approximately 10-year intervals. Local weather conditions were very weakly associated with annual change rates of total abundance, leaving the interannual pattern unexplained. Lichen-feeding and multivoltinism (multiple generations per year) were positively related to population trends, supporting earlier findings. Especially relevant to potential trends in biomass, wingspan showed no relationship with positive or negative trends, which is in line with the high correlation between abundance and biomass in this dataset. My results imply that the total abundance and biomass trends in boreal Europe diverge from those commonly reported from temperate Europe. Further research is required to shed light on factors underlying total insect abundance and biomass trends. The method I developed for converting moth abundance to biomass is applicable to similar work elsewhere.

Vegetation maps and bioclimatic zone classifications communicate the vegetation of an area and are used to explain how the environment regulates the occurrence of plants on large scales. Many practises and methods for dividing the world's vegetation into smaller entities have been presented. Climatic parameters, floristic characteristics, or edaphic features have been relied upon as decisive factors, and plant species have been used as indicators for vegetation types or zones. Systems depicting vegetation patterns that mainly reflect climatic variation are termed 'bioclimatic' vegetation maps. Based on these it has been judged logical to deduce that plants moved between corresponding bioclimatic areas should thrive in the target location, whereas plants moved from a different zone should languish. This principle is routinely applied in forestry and horticulture but actual tests of the validity of bioclimatic maps in this sense seem scanty. In this study I tested the Finnish bioclimatic vegetation zone system (BZS). Relying on the plant collection of Helsinki University Botanic Garden's Kumpula collection, which according to the BZS is situated at the northern limit of the hemiboreal zone, I aimed to test how the plants' survival depends on their provenance. My expectation was that plants from the hemiboreal or southern boreal zones should do best in Kumpula, whereas plants from more southern and more northern zones should show progressively lower survival probabilities. I estimated probability of survival using collection database information of plant accessions of known wild origin grown in Kumpula since the mid 1990s, and logistic regression models. The total number of accessions I included in the analyses was 494. Because of problems with some accessions I chose to separately analyse a subset of the complete data, which included 379 accessions. I also analysed different growth forms separately in order to identify differences in probability of survival due to different life strategies. 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. Exceptionally mild and wet winters during the study period may have killed off hemiarctic plants. Some winters may have been too harsh for temperate accessions. Trees behaved differently: they showed an almost steadily increasing survival probability from temperate to northern boreal origins. Various factors that could not be controlled for may have affected the results, some of which were difficult to interpret. This was the case in particular with herbs, for which the reliability of the analysis suffered because of difficulties in managing their curatorial data. In all, the results gave some support to the BZS, and especially its hierarchical zonation. However, I question the validity of the formulation of the hypothesis I tested since it may not be entirely justified by the BZS, which was designed for intercontinental comparison of vegetation zones, but not specifically for transcontinental provenance trials. I conclude that botanic gardens should pay due attention to information management and curational practices to ensure the widest possible applicability of their plant collections.