Responses of tundra plants to experimental warming: Meta-analysis of the international tundra experiment

Am. Arft et al., Responses of tundra plants to experimental warming: Meta-analysis of the international tundra experiment, ECOL MONOGR, 69(4), 1999, pp. 491-511
Citations number
Categorie Soggetti
Journal title
ISSN journal
0012-9615 → ACNP
Year of publication
491 - 511
SICI code
The International Tundra Experiment (ITEX) is a collaborative, multisite ex periment using a common temperature manipulation to examine variability in species response across climatic and geographic gradients of tundra ecosyst ems. ITEX was designed specifically to examine variability in arctic and al pine species response to increased temperature. We compiled from one to fou r years of experimental data from 13 different ITEX sites and used meta-ana lysis to analyze responses of plant phenology, growth, and reproduction to experimental warming. Results indicate that key phenological events such as leaf bud burst and flowering occurred earlier in warmed plots throughout t he study period; however, there was little impact on growth cessation at th e end of the season. Quantitative measures of vegetative growth were greate st in warmed plots in the early years of the experiment, whereas reproducti ve effort and success increased in later years. A shift away from vegetativ e growth and toward reproductive effort and success in the fourth treatment year suggests a shift from the initial response to a secondary response. T he change in vegetative response may be due to depletion of stored plant re serves, whereas the lag in reproductive response may be due to the formatio n of flower buds one to several seasons prior to flowering. Both vegetative and reproductive responses varied among life-forms; herbaceous forms had s tronger and more consistent vegetative growth responses than did woody form s. The greater responsiveness of the herbaceous forms may be attributed to their more flexible morphology and to their relatively greater proportion o f stored plant reserves. Finally, warmer, low arctic sites produced the str ongest growth responses, but colder sites produced a greater reproductive r esponse. Greater resource investment in vegetative growth may be a conserva tive strategy in the Low Arctic, where there is more competition for light, nutrients, or water, and there may be little opportunity for successful ge rmination or seedling development. In contrast, in the High Arctic, heavy i nvestment in producing seed under a higher temperature scenario may provide an opportunity for species to colonize patches of unvegetated ground. The observed differential response to warming suggests that the primary forces driving the response vary across climatic zones, functional groups, and thr ough time.