Spatial aspects of tree mortality strongly differ between young and old-growth forests.

Rates and spatial patterns of tree mortality are predicted to change during forest structural development. In young forests, mortality should be primarily density dependent due to competition for light, leading to an increasingly spatially uniform pattern of surviving trees. In contrast, mortality in old-growth forests should be primarily caused by contagious and spatially autocorrelated agents (e.g., insects, wind), causing spatial aggregation of surviving trees to increase through time. We tested these predictions by contrasting a three-decade record of tree mortality from replicated mapped permanent plots located in young (< 60-year-old) and old-growth (> 300-year-old) Abies amabilis forests. Trees in young forests died at a rate of 4.42% per year, whereas trees in old-growth forests died at 0.60% per year. Tree mortality in young forests was significantly aggregated, strongly density dependent, and caused live tree patterns to become more uniform through time. Mortality in old-growth forests was spatially aggregated, but was density independent and did not change the spatial pattern of surviving trees. These results extend current theory by demonstrating that density-dependent competitive mortality leading to increasingly uniform tree spacing in young forests ultimately transitions late in succession to a more diverse tree mortality regime that maintains spatial heterogeneity through time.

[1]  Robert J. Pabst,et al.  Testing predictions of forest succession using long‐term measurements: 100 yrs of observations in the Oregon Cascades , 2015 .

[2]  S. Acker,et al.  Recent tree mortality and recruitment in mature and old-growth forests in western Washington , 2015 .

[3]  Jiquan Chen,et al.  Spatially nonrandom tree mortality and ingrowth maintain equilibrium pattern in an old-growth Pseudotsuga-Tsuga forest. , 2014, Ecology.

[4]  P. Diggle,et al.  On tests of spatial pattern based on simulation envelopes , 2014 .

[5]  T. Aakala,et al.  Long-term mortality rates and spatial patterns in an old-growth forest , 2013 .

[6]  Jürgen Bauhus,et al.  Many ways to die – partitioning tree mortality dynamics in a near‐natural mixed deciduous forest , 2013 .

[7]  T. Aakala,et al.  Spatially random mortality in old-growth red pine forests of northern Minnesota , 2012 .

[8]  Jerry F. Franklin,et al.  Causes and implications of the correlation between forest productivity and tree mortality rates , 2011 .

[9]  John J. Battles,et al.  The contribution of competition to tree mortality in old-growth coniferous forests , 2011 .

[10]  J. Franklin,et al.  The tree mortality regime in temperate old-growth coniferous forests: the role of physical damage , 2010 .

[11]  S. Fraver,et al.  Natural development and regeneration of a Central European montane spruce forest , 2010 .

[12]  T. Wiegand,et al.  Evidence for the spatial segregation hypothesis: a test with nine-year survivorship data in a Mediterranean shrubland. , 2010, Ecology.

[13]  A. Larson,et al.  Spatial patterns of overstory trees in late- successional conifer forests , 2008 .

[14]  Thorsten Wiegand,et al.  Heterogeneity influences spatial patterns and demographics in forest stands , 2008 .

[15]  J. Battles,et al.  Spatial elements of mortality risk in old-growth forests. , 2008, Ecology.

[16]  Thorsten Wiegand,et al.  Spatial patterns and competition of tree species in a Douglas-fir chronosequence on Vancouver Island , 2006 .

[17]  E. D. Ford,et al.  Statistical inference using the g or K point pattern spatial statistics. , 2006, Ecology.

[18]  Charles B. Halpern,et al.  TREE MORTALITY DURING EARLY FOREST DEVELOPMENT: A LONG-TERM STUDY OF RATES, CAUSES, AND CONSEQUENCES , 2006 .

[19]  A. Wolf.  Fifty year record of change in tree spatial patterns within a mixed deciduous forest , 2005 .

[20]  R. Parish,et al.  The tree seedling bank in an ancient montane forest: stress tolerators in a productive habitat , 2005 .

[21]  Daniel M. Kashian,et al.  VARIABILITY AND CONVERGENCE IN STAND STRUCTURAL DEVELOPMENT ON A FIRE-DOMINATED SUBALPINE LANDSCAPE , 2005 .

[22]  J. Worrall,et al.  Forest dynamics and agents that initiate and expand canopy gaps in Picea–Abies forests of Crawford Notch, New Hampshire, USA , 2005 .

[23]  Adrian Baddeley,et al.  spatstat: An R Package for Analyzing Spatial Point Patterns , 2005 .

[24]  William A. Bechtold,et al.  Largest-Crown- Width Prediction Models for 53 Species in the Western United States , 2004 .

[25]  Jerry F. Franklin,et al.  Spatial Aspects of Structural Complexity in Old-Growth Forests , 2004, Journal of Forestry.

[26]  Thorsten Wiegand,et al.  Rings, circles, and null-models for point pattern analysis in ecology , 2004 .

[27]  R. Pélissier,et al.  Avoiding misinterpretation of biotic interactions with the intertype K12-function: population independence vs. random labelling hypotheses , 2003 .

[28]  F. He,et al.  Density‐dependent effects on tree survival in an old‐growth Douglas fir forest , 2000 .

[29]  N. Kenkel,et al.  A long‐term study of Pinus banksiana population dynamics , 1997 .

[30]  Jan Lepš,et al.  Spatial dynamics of forest decline: the role of neighbouring trees , 1996 .

[31]  George R. Parker,et al.  Long-term spatial dynamics in an old-growth deciduous forest , 1996 .

[32]  S. Acker,et al.  Spatial patterns of tree mortality in an old-growth Abies-Pseudotsuga stand , 1996 .

[33]  J. Franklin,et al.  Recent mortality and decline in mature Abiesamabilis: the interaction between site factors and tephra deposition from Mount St. Helens , 1994 .

[34]  Alan Boyde,et al.  Analysis of a three-dimensional point pattern with replication , 1993 .

[35]  E. David Ford,et al.  A Model of Competition Incorporating Plasticity through Modular Foliage and Crown Development , 1993 .

[36]  N. C. Kenkel,et al.  Pattern of Self‐Thinning in Jack Pine: Testing the Random Mortality Hypothesis , 1988 .

[37]  C. T. Dyrness,et al.  Natural Vegetation of Oregon and Washington , 1988 .

[38]  Norman L. Christensen,et al.  Competition and Tree Death , 1987 .

[39]  Jerry F. Franklin,et al.  Tree Death as an Ecological Process , 1987 .

[40]  C. Oliver,et al.  Disturbance patterns and forest development in a recently deglaciated valley in the northwestern Cascade Range of Washington, U.S.A. , 1985 .

[41]  Peter J. Diggle,et al.  Competition for Light in a Plant Monoculture Modelled as a Spatial Stochastic Process , 1981 .

[42]  K. Vogt,et al.  Biomass distribution and above- and below-ground production in young and mature Abiesamabilis zone ecosystems of the Washington Cascades , 1981 .

[43]  R Core Team,et al.  R: A language and environment for statistical computing. , 2014 .

[44]  T. Aakala,et al.  Long-term mortality rates and spatial patterns in an old-growth Pinus resinosa forest , 2013 .

[45]  T. Kuuluvainen,et al.  Trees dying standing in the northeastern boreal old-growth forests of Quebec: spatial patterns, rates, and temporal variation , 2007 .

[46]  W. Keeton,et al.  Disturbances and structural development of natural forest ecosystems with silvicultural implications, using Douglas-fir forests as an example , 2002 .

[47]  J. Agee.  Fire Ecology of Pacific Northwest Forests , 1993 .

[48]  A. M. Laessle,et al.  Spacing and Competition in Natural Stands of Sand Pine , 1965 .