JOBBAGY GAMPEL Esteban Gabriel
Global controls of forest line elevation in the northern andsouthern hemispheres
EG JOBBÁGY; RB JACKSON
GLOBAL ECOLOGY AND BIOGEOGRAPHY
Lugar: United Kingodm; Año: 2000 vol. 9 p. 253 - 268
1.We explored whether the independent evolutionaryhistory of extratropical forests in thesouthern and northern hemispheres affects thetemperatureelevation relationship of mountainforest lines. We compiled 115 forest line descriptionsfrom the literature, covering the majorextratropical mountain ranges of the world. Werelated forest line elevation to thermal regimesusing mean annual temperature adjusted to sealevel (MAT) and seasonal thermal amplitude(STA, mean of the warmest month minus themean of the coldest) obtained from a globalclimate database.2.Thermal variables explained 79% of the globalvariability of forest line elevation, whichincreased approximately 130 m for every 1 K ofMAT and for every 2 K of STA. After consideringSTA, there was no significant effect of hemisphereon forest line elevation. MAT-elevationrelationships for sites with STA < 15 K were thesame between hemispheres.3.Sites dominated by different tree life formshad similar mean temperatures for the warmestmonth (differences < 3 K), but contrasting meantemperatures for the coldest (differences > 30 K).Along a gradient of increasing STA anddecreasing winter temperatures, forest lines werefirst dominated by evergreen broadleaf trees,followed by deciduous broadleaf species, evergreenconifers, and finally deciduous conifers.4.Our results suggest that temperatures duringthe warm part of the year are the main control offorest line elevation in extratropical regionswhile temperatures during the cold part of theyear affect the dominant life form of trees. Thereis a high degree of convergence in adaptationto mountain climates between trees species ofboth hemispheres. This convergence suggeststhat there is not a wide vacant altitudinal beltfor introduced forest line species of the northernhemisphere into the southern hemisphere.