This study evaluates the secondary successional pathways of Hawaiian lowland rainforest following anthropogenic disturbance. Whereas primary succession on lava flows has been well studied in Hawaii, ...secondary successional dynamics on disturbed habitats in the presence of nonnative species has been poorly researched and documented. Our study was based on two vegetation sampling efforts conducted on 200-400-year-old lava flows 2 and 27 years following a 400-hectare clearcutting operation in the Puna District of the southeast quadrant of Hawaii Island. Intact forest adjacent to the clearcut area provided a baseline to compare against succession dynamics in the clearcut area. The most important trees of the uncut primary forest, based on frequency, density, and dominance, were keystone Hawaiian forest species Metrosideros polymorpha, followed by Psychotria hawaiiensis, Psidium cattleianum, Ciboteum glaucum, and Cibotium chamissoi. Whereas early successional nonnative species dominated the initial vegetation colonizing the clearcut site, M. polymorpha, P. cattleianum, and Cibotium species were also present. Twenty-seven years later we found the clearcut site colonized by two distinct secondary forest types: M. polymorpha-dominated forest and Falcataria moluccana-dominated forest. Whereas M. polymorpha maintained a similar level of dominance in uncut primary forest and M. polymorpha-dominated secondary forest stands, it was nearly absent from F. moluccana-dominated secondary forest stands. Results demonstrated that the keystone Hawaiian native tree species can effectively reestablish across disturbed landscapes, but are unable to outcompete in areas where fast growing nonnative trees become established. This underscores the critical need to suppress early nonnative tree establishment in disturbed habitats if the objective is to reestablish Hawaiian native forests.
BACKGROUND: The Andes-Amazon basin of Peru and Bolivia is one of the most data-poor, biologically rich, and rapidly changing areas of the world. Conservation scientists agree that this area hosts ...extremely high endemism, perhaps the highest in the world, yet we know little about the geographic distributions of these species and ecosystems within country boundaries. To address this need, we have developed conservation data on endemic biodiversity (~800 species of birds, mammals, amphibians, and plants) and terrestrial ecological systems (~90; groups of vegetation communities resulting from the action of ecological processes, substrates, and/or environmental gradients) with which we conduct a fine scale conservation prioritization across the Amazon watershed of Peru and Bolivia. We modelled the geographic distributions of 435 endemic plants and all 347 endemic vertebrate species, from existing museum and herbaria specimens at a regional conservation practitioner's scale (1:250,000-1:1,000,000), based on the best available tools and geographic data. We mapped ecological systems, endemic species concentrations, and irreplaceable areas with respect to national level protected areas. RESULTS: We found that sizes of endemic species distributions ranged widely (< 20 km² to > 200,000 km²) across the study area. Bird and mammal endemic species richness was greatest within a narrow 2500-3000 m elevation band along the length of the Andes Mountains. Endemic amphibian richness was highest at 1000-1500 m elevation and concentrated in the southern half of the study area. Geographical distribution of plant endemism was highly taxon-dependent. Irreplaceable areas, defined as locations with the highest number of species with narrow ranges, overlapped slightly with areas of high endemism, yet generally exhibited unique patterns across the study area by species group. We found that many endemic species and ecological systems are lacking national-level protection; a third of endemic species have distributions completely outside of national protected areas. Protected areas cover only 20% of areas of high endemism and 20% of irreplaceable areas. Almost 40% of the 91 ecological systems are in serious need of protection (= < 2% of their ranges protected). CONCLUSIONS: We identify for the first time, areas of high endemic species concentrations and high irreplaceability that have only been roughly indicated in the past at the continental scale. We conclude that new complementary protected areas are needed to safeguard these endemics and ecosystems. An expansion in protected areas will be challenged by geographically isolated micro-endemics, varied endemic patterns among taxa, increasing deforestation, resource extraction, and changes in climate. Relying on pre-existing collections, publically accessible datasets and tools, this working framework is exportable to other regions plagued by incomplete conservation data.
This study evaluates the secondary successional pathways of Hawaiian lowland rainforest following anthropogenic disturbance. Whereas primary succession on lava flows has been well studied in Hawaii, ...secondary successional dynamics on disturbed habitats in the presence of nonnative species has been poorly researched and documented. Our study was based on two vegetation sampling efforts conducted on 200–400-year-old lava flows 2 and 27 years following a 400-hectare clearcutting operation in the Puna District of the southeast quadrant of Hawaii Island. Intact forest adjacent to the clearcut area provided a baseline to compare against succession dynamics in the clearcut area. The most important trees of the uncut primary forest, based on frequency, density, and dominance, were keystone Hawaiian forest species Metrosideros polymorpha, followed by Psychotria hawaiiensis, Psidium cattleianum, Ciboteum glaucum, and Cibotium chamissoi. Whereas early successional nonnative species dominated the initial vegetation colonizing the clearcut site, M. polymorpha, P. cattleianum, and Cibotium species were also present. Twenty-seven years later we found the clearcut site colonized by two distinct secondary forest types: M. polymorpha-dominated forest and Falcataria moluccana-dominated forest. Whereas M. polymorpha maintained a similar level of dominance in uncut primary forest and M. polymorpha-dominated secondary forest stands, it was nearly absent from F. moluccana-dominated secondary forest stands. Results demonstrated that the keystone Hawaiian native tree species can effectively reestablish across disturbed landscapes, but are unable to outcompete in areas where fast growing nonnative trees become established. This underscores the critical need to suppress early nonnative tree establishment in disturbed habitats if the objective is to reestablish Hawaiian native forests.
This study evaluates the secondary successional pathways of Hawaiian lowland rainforest following anthropogenic disturbance. Whereas primary succession on lava flows has been well studied in Hawaii, ...secondary successional dynamics on disturbed habitats in the presence of nonnative species has been poorly researched and documented. Our study was based on two vegetation sampling efforts conducted on 200-400-year-old lava flows 2 and 27 years following a 400-hectare clearcutting operation in the Puna District of the southeast quadrant of Hawaii Island. Intact forest adjacent to the clearcut area provided a baseline to compare against succession dynamics in the clearcut area. The most important trees of the uncut primary forest, based on frequency, density, and dominance, were keystone Hawaiian forest species Metrosideros polymorpha, followed by Psychotria hawaiiensis, Psidium cattleianum, Ciboteum glaucum, and Cibotium chamissoi. Whereas early successional nonnative species dominated the initial vegetation colonizing the clearcut site, M. polymorpha, P cattleianum, and Cibotium species were also present. Twenty-seven years later we found the clearcut site colonized by two distinct secondary forest types: M. polymorpha-dominated forest and Falcataria moluccana-dominated forest. Whereas M. polymmpha maintained a similar level of dominance in uncut primary forest and M. polymorpha-dominated secondary forest stands, it was nearly absent from F. moluccana-dominated secondary forest stands. Results demonstrated that the keystone Hawaiian native tree species can effectively reestablish across disturbed landscapes, but are unable to outcompete in areas where fast growing nonnative trees become established. This underscores the critical need to suppress early nonnative tree establishment in disturbed habitats if the objective is to reestablish Hawaiian native forests.
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.
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.
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