GROWTH AND PHYSIOLOGY OF PICEA-ABIES POPULATIONS FROM ELEVATIONAL TRANSECTS - COMMON GARDEN EVIDENCE FOR ALTITUDINAL ECOTYPES AND COLD ADAPTATION

1. There are conflicting reports concerning the adaptive features of t ree populations originating from cold, high-altitude environments. We hypothesize that such trees will possess adaptive features that will b e demonstrated in a common environment, such as elevated rates of net CO2 exchange, elevated needle nitrogen concentration and high proporti onal biomass allocation to roots. To test this hypothesis we measured tree and seed properties of 54 populations of Norway spruce [Picea abi es (L.) Karst.] located along eight altitudinal transects (from c. 600 to 1500 m) in southern Poland. We also measured growth, biomass parti tioning, net photosynthetic capacity (A(max)), needle dark respiration (RS) and carbohydrate, nitrogen (N) and chlorophyll concentration of seedlings originating from these populations grown for 2 to 7 years in a common garden at 150 m elevation. Measured in situ along the elevat ional transects, there were linear declines in seed mass, average d.b. h. and height growth increment of seed trees with increased altitude o r lower mean annual temperature. 2, In the common garden, the Norway s pruce populations from colder, high-altitude habitats had higher N con centration in needles than those from low altitudes. Both A(max) and n eedle RS increased with altitude of seed origin and were significantly related to needle N concentration. High-altitude populations also had higher concentrations of chlorophyll and carotene than those from low elevations. Despite higher photosynthetic rates in high-altitude popu lations, seedling height and dry mass in the common garden declined wi th altitude of seed origin. Proportional dry mass partitioning to root s nearly doubled with increasing altitude of origin, while the length of the shoot-growth period was reduced. The high respiration rates, hi gh allocation to roots and reduced shoot-growth period are probably re sponsible for the low growth rate potential of high-altitude populatio ns, more than offsetting their higher photosynthetic rates.3, The resu lts of this study showed that Norway spruce populations from cold moun tain environments are characterized by several potentially adaptive fe atures. Because these were similar to conifer population responses alo ng a latitudinal gradient of origin, they are probably driven by clima te. These climate-driven differences were common to all transects: for a given altitude or mean annual temperature, plant traits were indepe ndent of mountain range of origin. However, populations originating fr om cold high-elevation sites often differed per unit change in altitud e or mean annual temperature more than did low elevation populations. The scaling of nitrogen, CO2 exchange and biomass and allocation patte rns may be useful in modelling Norway spruce response on montane fores t ecosystems under changing environments.