Big, ancient trees are organisms that have a peculiar esthetic and moral impact on those who can see and feel. Nature lovers know this, but until now they had problem confronting the utilitarians for whom a tree is only worth what can be defined in a quantitative manner — e.g. it was difficult to contradict those stating that a few new trees were ecologically equivalent to an old, big tree. But there is more and more research demonstrating the uncomparable contribution to ecosystems of these towering or spreading giants. See articles mentioned in the post

Major loss of large trees with cavities — Bittar, Gabriel 2013.01.07

In the following research, it is found that the increase in a tree’s total leaf area so much outpaces decline in productivity per unit of leaf area, that a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree.

In an interview, lead author Stephenson declares that trees accelerate their growth as they get older and bigger: “This finding contradicts the usual assumption that tree growth eventually declines as trees get older and bigger. (…) In absolute terms, trees 100 cm in trunk diameter typically add from 10-200 kg dry mass each year averaging 103 kg per year. This is nearly three times the rate for trees of the same species at 50 cm in diameter, and is the mass equivalent to adding an entirely new tree of 10-20 cm in diameter to the forest each year (…)

Extraordinary growth of some species, such as Eucalyptus regnans (the Australian mountain ash) and Sequoia sempervirens (the North-American coast redwood) is not limited to a few species: “Rapid growth in giant trees is the global norm, and can exceed 600 kg per year in the largest individuals”.

This article will make date in ecology:

Rate of tree carbon accumulation increases continuously with tree size

Nature (2014) doi:10.1038/nature12914

It can be found at

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12914.html

Summary

Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle—particularly net primary productivity and carbon storage—increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age. Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree. The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-leveland stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.