Premium
M editerranean and temperate treelines are controlled by different environmental drivers
Author(s) -
Piper Frida I.,
Viñegla Benjamín,
Linares Juan C.,
Camarero J. Julio,
Cavieres Lohengrin A.,
Fajardo Alex
Publication year - 2016
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1111/1365-2745.12555
Subject(s) - temperate climate , twig , temperate rainforest , mediterranean climate , basal area , zoology , growing season , biology , temperate forest , ecology , botany , ecosystem
Summary The growth limitation hypothesis ( GLH ) is the most accepted explanation for treeline formation, but it has been scarcely examined in Mediterranean regions, where treelines are located at lower elevations than in temperate regions. The GLH states that low temperature is the ultimate environmental driver for treeline formation, constraining C ‐sinks (i.e. tissue formation) more than C ‐sources. The GLH predicts similar or increasing (but not decreasing) non‐structural carbohydrate ( NSC ) concentrations with elevation throughout the course of the growing season. We hypothesized that elevational trends in growth and NSC in M editerranean regions are not determined by low temperature alone. We tested the GLH by examining the mean annual basal area and NSC concentrations in developing (new twigs) and ripened tissues (branch, stem) of trees growing at three elevations in three M editerranean and three temperate treelines in the C hilean southern A ndes (33° S, K ageneckia angustifolia ; 36, 40 and 46° S, N othofagus pumilio ) and in S pain (36° N, P inus sylvestris ; 42° N, Pinus uncinata ). Samples for NSC were taken at the onset of summer and autumn, which represent periods of contrasting drought intensities in M editerranean regions. Tree growth decreased significantly with elevation in temperate treelines but not in M editerranean treelines. In M editerranean treelines, new twig NSC concentrations increased significantly with elevation in the early summer but not in the early autumn. In temperate treelines, in contrast, no elevational or seasonal variation (or interaction between them) was observed in new twig NSC concentrations. The NSC concentrations of the branches and stems from both climates showed no elevational trends. The soluble sugars' NSC fraction increased over the season in M editerranean treelines and decreased in temperate treelines. Synthesis . Although we found support for the growth limitation hypothesis ( GLH ) in temperate and M editerranean treelines, our study shows that the tree growth and C balance in M editerranean treelines are not controlled by low temperature alone. We suggest that environmental factors other than temperature explain the lower global elevation of M editerranean treelines when compared to temperate treelines.