Sven Mutke

Population divergence for heteroblasty in the canary island pine (Pinus canariensis, Pinaceae)

A heteroblastic (or vegetative phase) change is an abrupt manifestation in the general heteroblastic development during the ontogeny of plants. The Canary Island pine undergoes an especially marked and delayed heteroblastic change, including both the formation of secondary needles on dwarf shoots and the onset of preformed growth. To assess genetic and environmental effects on the heteroblastic change in this species, we followed plants from 19 populations at a dry site and a wetter site. Comparing juvenile and adult needles from the same individuals, the adult had a significantly lower rate of water loss and higher leaf mass per area. Pooling data from all seed sources, the heteroblastic change took place when plants reached a critical height, on average, at 4 years of age at the dry site and 1 year earlier at the wet site. Within a subsample of individuals of equal size, mortality was significantly higher in juvenile plants than in mature plants. However, the juvenile phase was longer in plants from dry regions when compared to plants from highly productive, wet regions. This apparent contradiction might be explained through differential resource allocation and the cost of sclerophylly and resprouting ability. Considering the life strategy of the Canary Island pine, we interpret the prolonged juvenile phase as an unavoidable trade-off for the high tolerance of adults to harsh environments.

Cone Yield Characterization of a Stone Pine (Pinus pinea L.) Clone Bank

Abstract In spite of the use of the edible kernels of Stone pine (Pinus pinea L.) gathered from Mediterranean pine forests, the species remains a genuine forest tree that has never been domesticated as an orchard crop. In the last decades, some efforts have been made to select valuable genotypes for exploring the possibilities of Stone pine as an orchard crop. The present paper characterizes the cone yield of a grafted clone bank in order to elucidate the relevance of genetic and environment factors for seed-yield quantity and quality and for sequential transition rates of the development from pollinated conelets to ripe cones. Individual tree size and cone yield were separated in their genetic and environmental components, in order to estimate phenotypic, genetic and environmental correlations. A statistical model for logtransformed individual cone yield was adjusted, ranking the tested genotypes by their estimated clonal value after adjustment for tree size covariables. The degree of genetic determination for adjusted cone yield was estimated in 15%, the expected genetic gain by selection of the top 10% of tested genotypes would be 12%. Genetic correlation between genetic values for cone yield and cone and seed size were weak but significantly positive (r = 0.27 and 0.17), hence the lack of trade-offs between crop quantity and quality will allow a combined selection.

Crown architecture of grafted Stone pine (Pinus pinea L.): shoot growth and bud differentiation

The singular umbrella-like crown shape of Stone pine can be interpreted as a consequence of primary shoot-growth patterns and posterior axis differentiation due to differential secondary growth and down-bending of branches. This paper centres on the first aspect, analysing the growth, branching and flowering behaviour of about 5,000 individual shoots on 27 grafted Stone pines. The data measurement on standing trees allowed to study correlations of topologic and geometric variables in the shoot and their ancestors. The only significant correlations were found with parameters of the mother shoot formed the previous year and with the number of cones born 3 years before by the respective ancestor. The fitted relationships between geometric and topologic shoot and branch variables are the first step of a structural model construction that can be completed with functional components like a radiation and a carbon allocation submodel, stressing the importance of the heavy Stone pine cones as carbon sinks, with a total annual allocation similar to stem wood. In conclusion, the Stone pine crown shape emerges as consequence of the lack of initial vigour differentiation between stem and main-branch apical meristems that favour the generalized sylleptic reiteration in the open-grown trees.

Cone morphology variation in Pinus canariensis Sm.

Abstract. Morphological variation of Pinus canariensis cones was studied, based on a sample of 891 cones collected at 23 populations covering the entire natural range of distribution of the species. Both categorical and quantitative traits were used for the analyses. The categorical traits of the apophysis and umbo were subjected to Multiple Correspondence Analysis (MCA). The categories related to apophysis type were found to be the most important variables for ordination. Three cone groups were defined through clustering, generally differentiated according to apophysis prominence. Approximately half of the studied cones were classified within one group, denominated form gibba and corresponding to the majority of previous descriptions of the species. In addition, we found some other, less frequent cone forms (called plana, gibberosa protuberans and reflexa), which have not been traditionally considered in Pinus canariensis. Cones and seeds were larger in stands at higher altitude, possibly adapted to unfavourable (cold and dry) environment. No clear geographical structure was found in the studied traits at the population level. However, variation of cone morphology among islands was found to be related to the extension of pine forests.

Resin-tapped pine forests in Spain: Ecological diversity and economic valuation

Abstract Since ancient times, Mediterranean pine forests have been habitat for human activity, providing a wide range of goods such as timber, seeds, resin and derived products. Among them, tar and resin have played an historical role on the interaction between human activity and forests. In Spain, the resin played an important role in the economic and social development in rural areas during 20th century. But after 1980, resin production plummeted and the virtual disappearance of resin tapping caused the abandonment of traditional forest activities and the subsequently losses of ecosystem forest services (provision, regulation and cultural). This paper deals with some of the ecosystem services provided by resin tapped pine forests and shows how the abandonment of this traditional forestry activity would lead to a loss of social welfare beyond the economic activity. Among these ecosystem services, special attention is paid to the biodiversity of the pine forests. For that purpose, a stratified vegetation sampling was conducted in the leading resin-tapping Spanish region. Ecological analysis was therefore compared with the social preferences for several attributes associated to resin-tapped pine forests in Spain, including the biodiversity of flora.