[MCN] Forest mortality trends extends to beech systems, too

[Lance Olsen]

Forest Ecology and Management Volume 358, 15 December 2015, Pages 130-138

Stand dieback and collapse in a temperate forest and its impact on 
forest structure and biodiversity
Philip A. Martin, Adrian C. Newton, Elena Cantarello, Paul Evans

Highlights
*There is global concern about forest dieback which may result in forest loss.

*We examine a forest undergoing dieback using a dataset collected 
over 50 years.

*Basal area declined, with a transition to a grass-dominated system 
in some areas.

*The decline may have been driven by interactions between drought and 
overgrazing.

*Resilience of the forest is low and management is needed to improve 
the situation.

Abstract
http://www.sciencedirect.com/science/article/pii/S037811271500465X

Concern is increasing about large-scale dieback that is occurring in 
many forest ecosystems. However, understanding of the processes of 
dieback and its potential impacts is limited, partly owing to the 
lack of long-term monitoring data for forest stands in which dieback 
has occurred. Here we present monitoring data collected over 50 years 
along two transects in a temperate forest ecosystem, in which the 
canopy dominant beech (Fagus sylvatica L.) has demonstrated 
significant dieback. Our results show that basal area in the forest 
has declined by 33%, and juvenile tree densities have also been 
reduced by approximately 70%. Growing season temperatures have 
steadily increased and there have been a number of droughts causing 
climatic water deficits in recent decades, particularly in 1995. We 
hypothesise that these droughts may have interacted with novel 
pathogenic fungi to cause mortality of large trees. Curvilinear 
responses to BA loss were observed in tree community change, ground 
flora species richness, and percentage cover of grass, providing 
evidence of thresholds associated with stand dieback. Evidence also 
suggested that BA failed to recover once it declined. Critical values 
of basal area for a change in ground flora species richness and grass 
cover were around 40% decline from initial values. While these 
changes are dramatic, they cannot be considered a regime shift as the 
pressures that may have contributed to the ecosystem transition, 
drought, pathogenic fungi and overgrazing, are on-going. While 
managers might consider accepting forest dieback as part of an 
adaptive response of the system to novel environmental conditions, 
this would likely be associated with significant change in 
biodiversity and ecosystem service provision.

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"The growth in CO2 emissions closely follows the growth in Gross 
Domestic Product (GDP) corrected for improvements in energy 
efficiency."

P. Friedlingstein, et al. "Update on CO2 emissions."
Nature Geoscience. Published online: 21 November 2010
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"An impressive study across all of northern Russia from 1953-2002 
showed a shift in tree allometries. In areas where summer 
temperatures and precipitation have both increased, a general 
increase in biomass (up 9%) is primarily a result of increased 
greenery (33% more carbon in leaves and needles), rather than woody 
parts (roots and stem). In areas that have experienced warming and 
drying trends, greenery has decreased, and both roots and stems have 
increased (Lapenis et al. 2005)."

"  ...  there is little theoretical or experimental support to 
suggest that climate warming will cause absolute climatic tolerances 
of a species to evolve sufficiently to allow it to conserve its 
geographic distribution."

Camille Parmesan. "Ecological and Evolutionary Responses to Recent 
Climate Change." Annual Review of Ecol. Evol. & Systematics  2006. 
37:637-69


















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