[MCN] When drought follows fire, tree seedlings die

Lance Olsen lance at wildrockies.org
Mon Jan 16 09:10:59 EST 2017

When and where a forest fire is followed by drought, recovery from 
fire becomes harder, thanks to seedling failure, a loss of the 
youngest age class (Kueppers et al 2016, Harvey et al 2016, and Welch 
et al 2016).

Kueppers and colleagues approached the question of seedling survival 
in a common garden experiment, using limber pine and Engelmann spruce 
to test outcomes. Harvey et al looked at post-fire conifer seedling 
survival in the US Rockies. Welch et al eyed post-fire conifer 
seedling survival in the Sierra Nevadas.

A basic finding was common to all three 2016 studies: Seedlings need water.

Drought makes a difference to the forest's youngest trees in any 
circumstance, and now including the difference drought makes to the 
young when it comes on the heels of a fire.

These three findings of 2016 look all the more compelling because 
they confirm an earlier, 2013 finding:
"We examined conifer regeneration a decade following complete 
stand-replacing wildfire in dry coniferous forests spanning a 700 m 
elevation gradient where low elevation sites had relatively high 
moisture stress due to the com- bination of high temperature and low 
precipitation. Conifer regeneration varied strongly across the 
elevation gradient, with little tree regeneration at warm and dry low 
elevation sites" (Dodson and Root 2013).

Dodson and Root. Conifer regeneration following stand-replacing 
wildfire varies along an elevation gradient in a ponderosa pine 
forest, Oregon, USA. Forest Ecology and Management 2013

Harvey, Donato, and Turner. High and dry: post-fire tree seedling 
establishment in subalpine forests decreases with post-fire drought 
and large stand-replacing burn patches. Global Ecology and 
Biogeography 2016

Kueppers et al. Warming and provenance limit tree recruitment across 
and beyond the elevation range of subalpine forest. Global Change 
Biology (2016)

Welch, Safford, and Young. Predicting conifer establishment 
post-wildfire in mixed conifer forests of the North American 
Mediterranean-climate zone. Ecosphere 2016.
"Oxygen in the atmosphere might be reduced several percent below the 
present level without adverse effects."

"Free oxygen not only supports life; it arises from life. The oxygen 
now in the atmosphere is probably mainly, if not wholly, of 
biological origin."

Preston Cloud and Aharon Gibor. The Oxygen Cycle. 
Scientific American, September 1970
"We found that tree mortality rates increased by an overall average 
of 4.7%yr from 1963 to 2008, with higher mortality rate increases in 
western regions than in eastern regions (about 4.9 and 1.9% yr , 
respectively). The water stress created by regional drought may be 
the dominant contributor to these widespread increases in tree 
mortality rates across tree species, sizes, elevations, longitudes 
and latitudes. Western Canada seems to have been more sensitive to 
drought than eastern Canada" (Peng et al 2011).
"We contend that traditional approaches to forest conservation and 
management will be inadequate given the predicted scale of 
social-economic and biophysical changes in the 21st century."

Forest Ecology and Management Accepted 7 October 2015
Review and synthesis
Achievable future conditions as a framework for guiding forest 
conservation and management
S.W. Golladay, K.L. Martin, J.M. Vose, D.N. Wear, A.P. Covich, R.J. 
Hobbs, K.D. Klepzig, G.E. Likens, R.J. Naiman, A.W. Shearer 
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