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News Article

Conifers in Patagonia react differently to climate change


Populations of the same species show variable growth responses depending on location

Models predicting vegetative response to climate change are regularly used to create projections of ecosystem productivity; however, they often rely on species exhibiting a consistent response to changes in their environment. But a recent paper by Portland State University, published in the Journal of Biogeography, has revealed that populations of the same tree species display a variable growth rate in response to climate change along the latitudinal gradient of their range.

Pilgerodendron uviferum is the world’s most southern conifer tree species and can be found in a north-south spread across Patagonia in southern South America. This made it a suitable test species for researchers to understand how its growth is impacted by climate change across this region. The samples used for this study were distributed over northern, central and southern Patagonia with a drought severity index (scPDSI) used as an indicator of environmental change. The sampling ranged from 1900-1993, focussing in on the significant climate shifts which occurred in the 1950s and 1970s. The authors used tree-ring radial growth chronologies for this study; an established method for monitoring historical changes in growth response in tree species.

Both northern and southern edges of the sampling range experience drier conditions during the spring and summer and so when these regions are wetter there was increased tree growth recorded. But surprisingly, in the wettest sample region, central Patagonia, growth was increased by drier and sunnier conditions

Results showed that trees initially responded similarly to climate shifts at both poles of the sampling range however in the second half of the 20th century the responses began to diverge as southern South America became warmer. In the 1950s there was an upward trend in Antarctic Oscillation (Southern Annular Mode) which pushed storm tracks north meaning central and southern Patagonia became wetter, resulting in trees here reversing their pre-1950 trend and favouring drier, sunnier conditions

Andrés Holz PSU geography professor and faculty fellow in PSU's Institute for Sustainable Solutions said: "We found that not only can we see different populations of a widely distributed species respond differently to natural climate variability in a given region, but also over time within each of these regions and because climate variability is amplified by climate change, their tree growth responses to climate can change from a bit to a lot,"

One variable per species or population is not a reliable method to understand species growth. For models of ecosystem productivity this will be important to consider as there would appear to be different and non-stationary responses between populations along latitudinal gradients, especially in common and widely spread species.

 

Read the original press release here: https://www.pdx.edu/clas/news/populations-widely-spread-tree-species-respond-differently-climate-change-psu-study-finds

 

Read the full paper here:

Holz, A., Hart, S.J., Williamson, G.J., Veblen, T.T. and Aravena, J.C., 2018. Radial growth response to climate change along the latitudinal range of the world's southernmost conifer in southern South America. Journal of Biogeography45(5), pp.1140-1152. https://doi.org/10.1073/pnas.1800182115

 

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(“growth ring*" OR "dendrochronology" OR "dendroclimatology" OR "dendroecology" OR "annual ring*" OR "tree ring*" OR "seasonal growth") AND ("climate chang*" OR "climatic season*" OR "global warming" OR "climatology" OR "general circulation models")