Provenance effects on tree seed quality in the face of climate change

CARÓN, MARIA MERCEDES; DE FRENNE, PIETER; VERHEYEN, KRIS

Bruselas

Congreso; Starters day - Starters in het natuur- en bosonderzoek; 2012

Climate warming is already today affecting plant population dynamics across the globe. Particularly the sexual reproductive phase of plants is expected to be vulnerable to global warming. However, the reproductive phase also provides plants with an opportunity to adapt or to migrate in response to environmental changes. The survival of young seedlings in more extreme conditions not only depends on the availability of seed resources but it has also been demonstrated the temperature during the maternal reproduction can affects the progeny performance. Hence, studying the variation in characteristics of seeds developed under different climatic conditions along a latitudinal gradient might provide us with important information on the future impact of climate change on tree species regeneration from seed. We studied sycamore maple (Acer pseudoplatanus), which is an important tree species in European deciduous forests. Furthermore, given the climatic tolerance of this species, its importance is expected to increase in the future. The main goal of this study was to analyze morphological and physiological characteristics of Acer pseupolatanus seeds developed in 9 different regions along a 2200km long European latitudinal gradient ranging from Italy to Norway. In each region, mature seeds of A. pseudoplatanus were collected from 3 adult trees located in different forest patches. In addition, in each site environmental and population variables were recorded. The following morphological characteristics were determined: length of the samara (wing), wet seed mass, dry seed mass and bare seed mass (i.e. without dispersal structures). Finally, the viability of individual seeds was analyzed with the Tetrazolium salt test. All these characteristics are closely related with the dispersal and establishment success of the seeds. We found a strong positive correlation between the samara length and the seed mass (wet and dry), but not between the samara length and the bare seed mass. The differences in seed mass and samara length were not strongly linked to geographical factors such as latitude and longitude; however, it was a tendency to increase towards the north. In some replications there was a trade off between the bare seed mass and the samara length, heavier seeds were linked to smaller samaras. There were significant regional differences in terms of the dry seed mass, bare seeds mass and samara length. The southern provenances always showed a clear differentiation from the northern provenances. Seed viability did not show significant differences among the provenances. Nevertheless, seed viability was generally higher and more stable (lower among-tree variation) in seed lots sampled in central provenances than in southern as well as northern seed lots. To conclude, our preliminary results indicate that latitudinal climatic variation, along with other factors, has an important influence on the samara size and seed mass of sycamore maple. The presence, in some cases, of a trade off between samara size and bare seed mass supports the theory of dispersal vs. establishment trade-off. The latitudinal variation in this trade-off indicates that different tree provenances are exhibiting contrasting strategies in terms of establishment vs. dispersal. This could be important in the context of climate change as this is directly linked to the migration capacity of populations or the provision of extra resources to seedlings in the face of a changing environment.