Successional processes ultimately determine and define carbon accumulations in forested ecosystems. Although primary succession on wholly new substrate occurs across the globe, secondary succession, ...often following storm events or anthropogenic disturbance, is more common and is capable of globally significant accumulations of carbon (C) at a time when offsets to anthropogenic carbon dioxide (CO2) emissions are critically needed. In Hawai'i, prior studies have investigated ecosystem development during primary succession on lava flows, including estimates of C mass accumulation. Yet relatively little is known regarding secondary succession of Hawaii's native forests, particularly regarding C mass accumulation. Here we documented aboveground C mass accumulation by native‐ and nonnative‐dominated second‐growth forests following deforestation of mature native lowland rainforests in the Puna District of Hawai'i Island. We characterized species composition and stand structure of three distinct successional forest stand types: those dominated by the native tree, Metrosideros polymorpha (ʻŌhiʻa), and those dominated by invasive nonnative trees, Falcataria moluccana (albizia) and Psidium cattleianum (strawberry guava). We compared M. polymorpha‐dominated and F. moluccana‐dominated second‐growth forests to adjacent mature M. polymorpha‐dominated forests as well as young M. polymorpha‐dominated forests undergoing initial stages of primary succession on 36‐years‐old lava fields. Aboveground carbon density (ACD) values of mature primary forest stands (171 Mg/ha) were comparable to those of mature continental tropical forests. M. polymorpha‐dominated second‐growth stands attained nearly 50% of ACD values of mature primary forests after less than 30 years of post‐disturbance succession and exhibited aboveground carbon accumulation rates of ~3 Mg C·ha−1·year−1. Such rates were comparable to those of second‐growth forests in continental tropics. Rates of ACD accumulation by second‐growth forests dominated by nonnative F. moluccana stands were similar, or slightly greater than, those of M. polymorpha‐dominated stands. However, M. polymorpha individuals were virtually absent from stands dominated by either P. cattleianum or F. moluccana. Taken together, results demonstrated that re‐establishment and rapid accumulation of C mass by M. polymorpha stands during secondary succession is certainly possible, but only where populations of nonnative species have not already colonized areas during early stages of secondary succession.
Abstract
Successional processes ultimately determine and define carbon accumulations in forested ecosystems. Although primary succession on wholly new substrate occurs across the globe, secondary ...succession, often following storm events or anthropogenic disturbance, is more common and is capable of globally significant accumulations of carbon (C) at a time when offsets to anthropogenic carbon dioxide (CO
2
) emissions are critically needed. In Hawai'i, prior studies have investigated ecosystem development during primary succession on lava flows, including estimates of C mass accumulation. Yet relatively little is known regarding secondary succession of Hawaii's native forests, particularly regarding C mass accumulation. Here we documented aboveground C mass accumulation by native‐ and nonnative‐dominated second‐growth forests following deforestation of mature native lowland rainforests in the Puna District of Hawai'i Island. We characterized species composition and stand structure of three distinct successional forest stand types: those dominated by the native tree,
Metrosideros polymorpha
(ʻŌhiʻa), and those dominated by invasive nonnative trees,
Falcataria moluccana
(albizia) and
Psidium cattleianum
(strawberry guava). We compared
M. polymorpha
‐dominated and
F. moluccana
‐dominated second‐growth forests to adjacent mature
M. polymorpha
‐dominated forests as well as young
M. polymorpha
‐dominated forests undergoing initial stages of primary succession on 36‐years‐old lava fields. Aboveground carbon density (ACD) values of mature primary forest stands (171 Mg/ha) were comparable to those of mature continental tropical forests.
M. polymorpha
‐dominated second‐growth stands attained nearly 50% of ACD values of mature primary forests after less than 30 years of post‐disturbance succession and exhibited aboveground carbon accumulation rates of ~3 Mg C·ha
−1
·year
−1
. Such rates were comparable to those of second‐growth forests in continental tropics. Rates of ACD accumulation by second‐growth forests dominated by nonnative
F. moluccana
stands were similar, or slightly greater than, those of
M. polymorpha
‐dominated stands. However,
M. polymorpha
individuals were virtually absent from stands dominated by either
P. cattleianum
or
F. moluccana
. Taken together, results demonstrated that re‐establishment and rapid accumulation of C mass by
M. polymorpha
stands during secondary succession is certainly possible, but only where populations of nonnative species have not already colonized areas during early stages of secondary succession.
•Ceratocystis fimbiata routinely found associated with rapidly dying ‘ōhi‘a.•Distribution and impact of this newly described disease shown.•Elevated mortality in 30% of total area classified as ...‘ōhi‘a in our study area.•High annual ‘ōhi‘a mortality rates, 28% on average and as high as 46%.•No correlation between Psidium cattleianum and ‘ōhi‘a mortality rates.
Pests or pathogens that affect trees have the potential to fundamentally alter forest composition, structure and function. Throughout the last six years, large areas of otherwise healthy ‘ōhi‘a (Metrosideros polymorpha) trees have been dying rapidly (typically within weeks) in lowland tropical wet forest on Hawai‘i Island, USA. This mortality is quite distinct from previous well-documented ‘ōhi‘a dieback episodes driven by cohort senescence. Ceratocystis fimbiata was identified and routinely found associated with rapidly dying individuals of ‘ōhi‘a, Hawai‘i’s most widespread native tree. Pathogenicity of this fungus was proven and M. polymorpha was recorded as a new host for C. fimbiata. Mortality of ‘ōhi‘a at this scale is of great concern as the understory in these forests is often occupied by invasive non-native plants capable of severely limiting ‘ōhi‘a regeneration. Imagery of ‘ōhi‘a mortality obtained in 2012 revealed large expanses of greater than expected mortality (i.e., ≥10%) across 1600ha. By 2014 ‘ōhi‘a mortality levels ≥10% had spread to 6403ha, or 30% of total area classified as ‘ōhi‘a in our study area. Further, levels of ‘ōhi‘a mortality in field plots established within the study region averaged 39%, and mortality levels were comparable across size classes and forest compositions. Results from a subset of field plots re-inventoried one year after plot establishment revealed average annual ‘ōhi‘a mortality rates of 24% and 28% based on basal area and stem density measures, respectively; mortality rates were as high as 47% in some field plots. The dearth of ‘ōhi‘a seedling recruitment and characteristic understory dominance of non-native species documented within our research plots, coupled with the lethality of C. fimbriata to ‘ōhi‘a, suggest that these forests likely will be dominated by non-native species in the future.
Pests or pathogens that affect trees have the potential to fundamentally alter forest composition, structure and function. Throughout the last six years, large areas of otherwise healthy 'hi'a ...(Metrosideros polymorpha) trees have been dying rapidly (typically within weeks) in lowland tropical wet forest on Hawai'i Island, USA. This mortality is quite distinct from previous well-documented 'hi'a dieback episodes driven by cohort senescence. Ceratocystis fimbiata was identified and routinely found associated with rapidly dying individuals of 'hi'a, Hawai'i's most widespread native tree. Pathogenicity of this fungus was proven and M. polymorpha was recorded as a new host for C. fimbiata. Mortality of 'hi'a at this scale is of great concern as the understory in these forests is often occupied by invasive non-native plants capable of severely limiting 'hi'a regeneration. Imagery of 'hi'a mortality obtained in 2012 revealed large expanses of greater than expected mortality (i.e., greater than or equal to 10%) across 1600ha. By 2014 'hi'a mortality levels greater than or equal to 10% had spread to 6403ha, or 30% of total area classified as 'hi'a in our study area. Further, levels of 'hi'a mortality in field plots established within the study region averaged 39%, and mortality levels were comparable across size classes and forest compositions. Results from a subset of field plots re-inventoried one year after plot establishment revealed average annual 'hi'a mortality rates of 24% and 28% based on basal area and stem density measures, respectively; mortality rates were as high as 47% in some field plots. The dearth of 'hi'a seedling recruitment and characteristic understory dominance of non-native species documented within our research plots, coupled with the lethality of C. fimbriata to 'hi'a, suggest that these forests likely will be dominated by non-native species in the future.
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