DEVELOPMENTAL PLASTICITY ALLOWSBETULA NANATO DOMINATE TUNDRA SUBJECTED TO AN ALTERED ENVIRONMENT

Abstract

We investigated how three co‐dominant arctic shrubs (Betula nana, Salix pulchra, and Ledum palustre ssp. decumbens) responded to long‐term treatment with N+P fertilizers and greenhouses in a factorial field experiment at Toolik Lake, Alaska. Our goal was to understand the relationship between growth of individuals and species abundance in the community, and the mechanism by which one species achieves dominance under changed environmental conditions. We compared aboveground growth and allocation patterns in individual ramets 15 yr of age with community abundance measured by quadrat harvests. Ramets of all three species substantially increased their stem biomass with fertilization, but the increase was much larger for Betula than for the other two species. In quadrat sampling, only Betula appreciably increased its biomass per unit area with fertilization or greenhouse treatment. For Salix in all treatments, and Ledum in the two fertilizer treatments, ramet density per unit area decreased more than growth of surviving 15‐yr‐old ramets was promoted, so community biomass of these species declined. In contrast, Betula increased its ramet density in all treatments by producing new shoots from stems older than 15 yr, even though stem mortality was also increased in the two fertilizer treatments. Betula increased its growth in part by a major change in allocation, from producing mostly short shoots to producing many more long shoots. As a result, the number of branches and the rate of production of new meristems greatly increased. This developmental plasticity allowed extensive growth that led to development of a dense canopy and imposed light limitation on the other species. The flexible growth strategy of Betula points to the importance of meristem availability and developmental constraints in determining plant response to environmental change. Developmental controls over meristem availability are not usually considered in ecological paradigms for allocation, but they may be useful for predicting plant response to changes in nutrient availability in other ecosystems.

Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra

“…The soil heat flux, on the other hand, depended strongly on soil thermal properties. This is in contrast to the studies by Blok et al (2010) and Briggs et al (2014), which identified soil shading as important control of local permafrost thaw. A schematic of the differences we found between key components of the dwarf shrub and wet sedge system can be found in Fig.…”

Complex effects of mammalian grazing on extramatrical mycelial biomass in the Scandes forest‐tundra ecotone

“…It could also have to do with the fact that B. nana is able to allocate large proportions of its biomass belowground and can translocate substantial amounts of nutrients between plant parts during the season (Chapin, Johnson, & McKendrick, 1980). This high plasticity helps it to respond quickly to altered environmental conditions (Bret-Harte et al, 2001). Therefore, when B. nana is suppressed by grazers, it is possible that comparatively more C is allocated to the roots, which may stimulate fungal growth.…”

Tree Height-Diameter Relationships in the Alpine Treeline Ecotone Compared with Those in Closed Forests on Changbai Mountain, Northeastern China

“…In previous studies, Betula nana L., and other birch species (Betula populifolia Marsh., Betula papyrifera Marsh., Betula alleghaniensis Britt.) have been found to show a higher degree of plasticity than other species found at higher altitudes [44,45]. While larch with an upright tree form grew faster than birch, larch with a 'cushion' or more stunted form grew more slowly than birch [46].…”