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Peter B Reich - One of the best experts on this subject based on the ideXlab platform.
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Seed Rain, safe sites, competing vegetation, and soil resources spatially structure white pine regeneration and recruitment
2020Co-Authors: Martin Doviak, Peter B Reich, Lee E FrelichAbstract:Abstract: We tested the effects of Seed Rain, safe sites, soil depth, overstory, and shrub layer on the establishment and recruitment of white pine (Pinus strobus L.) in aspen mixedwoods of the western Great Lakes region, U.S.A. Germinant and Seedling densities were positively related to Seed Rain and safe site characteristics that indicate moist conditions: high overstory basal area, decaying wood, and moss cover. Germinant and Seedling densities were highest under dense overstory (>16 m 2 /ha) and were unrelated to shrub cover. Sapling recruitment was greatest under low overstory density (<16 m 2 /ha) and low shrub cover (<55%). On shallow soil (~14 cm), germinants and Seedlings commonly occurred on soil depths <5 cm, but large saplings almost always occurred on soil depths >5 cm. On deeper soil (~21 cm), overstory white pines occupied the shallowest soils (~18 cm) of all major overstory species, indicating that competition may cause white pine recruitment into the canopy to be lower on deeper soils. White pine populations in the study were initially spatially structured by Seed Rain and safe sites but sapling growth and recruitment was structured by overstory density, shrub cover, and soil depth. Résumé : Nous avons testé les effets de la dispersion aérienne des gRaines, des refuges, de l'épaisseur du sol, de l'étage dominant et de la strate arbustive sur l'établissement et le recrutement du pin blanc (Pinus strobus L.) dans une forêt mixte de peuplier de l'ouest de la région des Grands Lacs, aux États-Unis. La densité des germinats et des semis était positivement reliée à la dispersion aérienne des gRaines et aux caractéristiques des refuges indicatrices de conditions humides : surface terrière élevée de l'étage dominant, bois en décomposition et tapis de mousses. La densité des germinats et des semis était la plus forte sous un étage dominant dense (>16 m 2 /ha) et n'était pas influencée par le couvert d'arbustes. Le recrutement de gaules était le plus élevé sous un étage dominant de faible densité (<16 m 2 /ha) et un faible couvert d'arbustes (<55 %). Sur sol mince (~14 cm), les germinats et les semis se trouvaient le plus souvent sur des sols de moins de 5 cm d'épaisseur mais les gaules de forte dimension se trouvaient presque toujours sur des sols de plus de 5 cm d'épaisseur. Sur les sols plus profonds (~21 cm), les pins blancs de l'étage dominant occupaient les sols les plus minces (~18 cm) comparativement à toutes les principales espèces de l'étage dominant, indiquant que la compétition peut être responsable du plus faible recrutement du pin blanc dans le couvert sur les sols plus profonds. Dans cette étude, la dispersion aérienne des gRaines et les refuges déterminaient initialement la structure spatiale des populations de pin blanc mais le recrutement et la croissance des gaules étaient déterminés par la densité de l'étage dominant, le couvert d'arbustes et la profondeur du sol. [Traduit par la Rédaction] Doviak et al. 190
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pathways in old field succession to white pine Seed Rain shade and climate effects
Ecological Monographs, 2005Co-Authors: Martin Dovciak, Lee E Frelich, Peter B ReichAbstract:Trees slowly colonize old fields on sandy outwash in the prairie-forest eco- tone of the north-central United States, and in the absence of fire, succession is expected to proceed toward oak woodland. We analyzed whether a case of unusually rapid and spatially extensive invasion by white pine (Pinus strobus) could be explained by the pres- ence of specific temporal or spatial opportunity windows suitable for such invasion. We tested whether the invasion was temporally restricted to the period immediately after aban- donment or to periods of favorable climate, and whether it was spatially restricted to areas of high Seed Rain or high forest-edge shade. White pine invasion into the field occurred in two waves separated from each other by a 1987-1989 drought period. The first wave (1980- 1985) occurred during a period of average climate and led to the establishment of dense sapling patches in shade near forest edges. The second wave (1991-1994) occurred during a period of high precipitation and cooler than normal temperature, and resulted in colo- nization of the unshaded field center. In addition to the two temporal windows, white pine invasion occurred within two spatial windows: in areas highly sheltered by forest edge and in areas receiving high white pine Seed Rain. Overall these windows produced three different successional pathways: (1) a slow, creeping white pine invasion into highly shaded areas with low Seed Rain near forest edges; (2) a rapid, discrete-step invasion in areas where Seed Rain was abundant enough to overcome mortality in lower shade and where early arrivals facilitate filling in by later arrivals; and (3) a deferred invasion in the field center where low Seed Rain and lack of shade allowed the persistence of a grassland stage until favorable climate resulted in a white pine recruitment pulse. Temporal variation in climate can ac- celerate or decelerate any of the three successional pathways.
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Seed Rain safe sites competing vegetation and soil resources spatially structure white pine regeneration and recruitment
Canadian Journal of Forest Research, 2003Co-Authors: Martin Dovciak, Peter B Reich, Lee E FrelichAbstract:We tested the effects of Seed Rain, safe sites, soil depth, overstory, and shrub layer on the establishment and recruitment of white pine (Pinus strobus L.) in aspen mixedwoods of the western Great Lakes region, U.S.A. Germin- ant and Seedling densities were positively related to Seed Rain and safe site characteristics that indicate moist condi - tions: high overstory basal area, decaying wood, and moss cover. Germinant and Seedling densities were highest under dense overstory (>16 m 2 /ha) and were unrelated to shrub cover. Sapling recruitment was greatest under low overstory density ( 5 cm. On deeper soil (~21 cm), overstory white pines occupied the shallowest soils (~18 cm) of all major overstory species, indicating that competition may cause white pine recruitment into the canopy to be lower on deeper soils. White pine populations in the study were initially spatially structured by Seed Rain and safe sites but sapling growth and recruitment was struc - tured by overstory density, shrub cover, and soil depth.
Margaret M Mayfield - One of the best experts on this subject based on the ideXlab platform.
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landscape structure mediates zoochorous dispersed Seed Rain under isolated pasture trees across distinct tropical regions
Landscape Ecology, 2019Co-Authors: Lachlan S Charles, John M Dwyer, Hazel M Chapman, Biplang G Yadok, Margaret M MayfieldAbstract:Isolated pasture trees play an important role in forest recovery within fragmented tropical landscapes by attracting Seed dispersers and facilitating Seedling growth. However, studies with conflicting results have led to confusion about what drives variation in zoochorous-dispersed Seed Rain patterns under isolated tree canopies. To assess the role of landscape and biological factors impacting zoochorous-dispersed Seed Rain under isolated pasture trees across three tropical regions of the world. We measured Seed dispersal under 144 isolated pasture trees found in 12 fragmented tropical and sub-tropical landscapes in Australia, Colombia and Nigeria. Using linear mixed effect models, we modeled Seed diversity, abundance, richness and evenness as functions of the biological features and landscape context of isolated trees. Throughout all regions, the amount of woody vegetation surrounding trees in pastures was negatively related to Rainforest Seed diversity, evenness and abundance. Seed diversity and evenness increased significantly with the distance of isolated trees to forest fragments in the Australian sub-tropics, but elsewhere, Seed diversity and evenness tended to decline with distance to forest, though not significantly. Our results suggest that the tree composition of landscapes surrounding isolated pasture trees is important for influencing zoochorous-dispersed Seed Rain, regardless of the region studied. Our study highlights the prominent role of landscape-scale, rather than local-scale factors on Seed dispersal to isolated pasture trees, while providing strong evidence that early stage successional processes involving isolated pasture trees are similar throughout global tropical regions.
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Rainforest Seed Rain into abandoned tropical australian pasture is dependent on adjacent Rainforest structure and extent
Austral Ecology, 2017Co-Authors: Lachlan S Charles, John M Dwyer, Margaret M MayfieldAbstract:It is well known that the recovery of abandoned tropical pastures to secondary Rainforest benefits from the arrival of Seeds from adjacent Rainforest patches. Less is known, however, about how the structural attributes of adjacent Rainforest (e.g. tree density, canopy cover and tree height) impact Seed Rain patterns into abandoned pastures. Between 2011 and 2013, we used Seed traps and ground Seed surveys to track the richness and abundance of Rainforest Seeds entering abandoned pastures in Australia's wet tropics. We also tested how Seed Rain diversity is related to the distance from forest, the proportion of forest cover in the landscape and several structural attributes of adjacent forest patches, specifically average tree height, canopy cover, tree species richness and density. Almost no Seeds were captured in elevated pasture Seed traps, even near forest remnants. Abundant forest Seeds were found in ground surveys but only within 10 m of forest edges. In ground surveys, Seeds from wind-dispersed species were more abundant, but less species rich, than animal-dispersed species. A survey of pasture Seedling recruits suggested that some forest Seeds must be dispersing more than 10 m into pasture at very low frequencies, but only a few species are establishing there. Recruits were predominantly animal-dispersed not wind-dispersed species. In addition to distance from forest and the proportion of forest within a 100- to 200-m radius of sampling sites, the richness and density of adjacent forest trees were the most important factors for explaining the probability of Seed occurrence in abandoned pastures. Results suggest that without some restoration assistance, the recovery of abandoned pastures into secondary Rainforest in Australia's tropical Rainforests will likely be limited, at least in part, by a very low rate of Seed dispersal away from forest edges and by the diversity and density of trees in adjacent remnant forests.
Lee E Frelich - One of the best experts on this subject based on the ideXlab platform.
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Seed Rain, safe sites, competing vegetation, and soil resources spatially structure white pine regeneration and recruitment
2020Co-Authors: Martin Doviak, Peter B Reich, Lee E FrelichAbstract:Abstract: We tested the effects of Seed Rain, safe sites, soil depth, overstory, and shrub layer on the establishment and recruitment of white pine (Pinus strobus L.) in aspen mixedwoods of the western Great Lakes region, U.S.A. Germinant and Seedling densities were positively related to Seed Rain and safe site characteristics that indicate moist conditions: high overstory basal area, decaying wood, and moss cover. Germinant and Seedling densities were highest under dense overstory (>16 m 2 /ha) and were unrelated to shrub cover. Sapling recruitment was greatest under low overstory density (<16 m 2 /ha) and low shrub cover (<55%). On shallow soil (~14 cm), germinants and Seedlings commonly occurred on soil depths <5 cm, but large saplings almost always occurred on soil depths >5 cm. On deeper soil (~21 cm), overstory white pines occupied the shallowest soils (~18 cm) of all major overstory species, indicating that competition may cause white pine recruitment into the canopy to be lower on deeper soils. White pine populations in the study were initially spatially structured by Seed Rain and safe sites but sapling growth and recruitment was structured by overstory density, shrub cover, and soil depth. Résumé : Nous avons testé les effets de la dispersion aérienne des gRaines, des refuges, de l'épaisseur du sol, de l'étage dominant et de la strate arbustive sur l'établissement et le recrutement du pin blanc (Pinus strobus L.) dans une forêt mixte de peuplier de l'ouest de la région des Grands Lacs, aux États-Unis. La densité des germinats et des semis était positivement reliée à la dispersion aérienne des gRaines et aux caractéristiques des refuges indicatrices de conditions humides : surface terrière élevée de l'étage dominant, bois en décomposition et tapis de mousses. La densité des germinats et des semis était la plus forte sous un étage dominant dense (>16 m 2 /ha) et n'était pas influencée par le couvert d'arbustes. Le recrutement de gaules était le plus élevé sous un étage dominant de faible densité (<16 m 2 /ha) et un faible couvert d'arbustes (<55 %). Sur sol mince (~14 cm), les germinats et les semis se trouvaient le plus souvent sur des sols de moins de 5 cm d'épaisseur mais les gaules de forte dimension se trouvaient presque toujours sur des sols de plus de 5 cm d'épaisseur. Sur les sols plus profonds (~21 cm), les pins blancs de l'étage dominant occupaient les sols les plus minces (~18 cm) comparativement à toutes les principales espèces de l'étage dominant, indiquant que la compétition peut être responsable du plus faible recrutement du pin blanc dans le couvert sur les sols plus profonds. Dans cette étude, la dispersion aérienne des gRaines et les refuges déterminaient initialement la structure spatiale des populations de pin blanc mais le recrutement et la croissance des gaules étaient déterminés par la densité de l'étage dominant, le couvert d'arbustes et la profondeur du sol. [Traduit par la Rédaction] Doviak et al. 190
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pathways in old field succession to white pine Seed Rain shade and climate effects
Ecological Monographs, 2005Co-Authors: Martin Dovciak, Lee E Frelich, Peter B ReichAbstract:Trees slowly colonize old fields on sandy outwash in the prairie-forest eco- tone of the north-central United States, and in the absence of fire, succession is expected to proceed toward oak woodland. We analyzed whether a case of unusually rapid and spatially extensive invasion by white pine (Pinus strobus) could be explained by the pres- ence of specific temporal or spatial opportunity windows suitable for such invasion. We tested whether the invasion was temporally restricted to the period immediately after aban- donment or to periods of favorable climate, and whether it was spatially restricted to areas of high Seed Rain or high forest-edge shade. White pine invasion into the field occurred in two waves separated from each other by a 1987-1989 drought period. The first wave (1980- 1985) occurred during a period of average climate and led to the establishment of dense sapling patches in shade near forest edges. The second wave (1991-1994) occurred during a period of high precipitation and cooler than normal temperature, and resulted in colo- nization of the unshaded field center. In addition to the two temporal windows, white pine invasion occurred within two spatial windows: in areas highly sheltered by forest edge and in areas receiving high white pine Seed Rain. Overall these windows produced three different successional pathways: (1) a slow, creeping white pine invasion into highly shaded areas with low Seed Rain near forest edges; (2) a rapid, discrete-step invasion in areas where Seed Rain was abundant enough to overcome mortality in lower shade and where early arrivals facilitate filling in by later arrivals; and (3) a deferred invasion in the field center where low Seed Rain and lack of shade allowed the persistence of a grassland stage until favorable climate resulted in a white pine recruitment pulse. Temporal variation in climate can ac- celerate or decelerate any of the three successional pathways.
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Seed Rain safe sites competing vegetation and soil resources spatially structure white pine regeneration and recruitment
Canadian Journal of Forest Research, 2003Co-Authors: Martin Dovciak, Peter B Reich, Lee E FrelichAbstract:We tested the effects of Seed Rain, safe sites, soil depth, overstory, and shrub layer on the establishment and recruitment of white pine (Pinus strobus L.) in aspen mixedwoods of the western Great Lakes region, U.S.A. Germin- ant and Seedling densities were positively related to Seed Rain and safe site characteristics that indicate moist condi - tions: high overstory basal area, decaying wood, and moss cover. Germinant and Seedling densities were highest under dense overstory (>16 m 2 /ha) and were unrelated to shrub cover. Sapling recruitment was greatest under low overstory density ( 5 cm. On deeper soil (~21 cm), overstory white pines occupied the shallowest soils (~18 cm) of all major overstory species, indicating that competition may cause white pine recruitment into the canopy to be lower on deeper soils. White pine populations in the study were initially spatially structured by Seed Rain and safe sites but sapling growth and recruitment was struc - tured by overstory density, shrub cover, and soil depth.
Karen D. Holl - One of the best experts on this subject based on the ideXlab platform.
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Seed dispersal limitations shift over time in tropical forest restoration
Ecological Applications, 2015Co-Authors: Karen D. Holl, Leighton J Reid, Rakan A ZahawiAbstract:Past studies have shown that tropical forest regeneration on degraded farmlands is initially limited by lack of Seed dispersal, but few studies have tracked changes in abundance and composition of Seed Rain past the first few years after land abandonment. We measured Seed Rain for 12 months in 10 6-9-year-old restoration sites and five mature, reference forests in southern Costa Rica in order to learn (1) if Seed Rain limitation persists past the first few years of regeneration; (2) how restoration treatments influence Seed community structure and composition; and (3) whether Seed Rain limitation is contingent on landscape context. Each restoration site contained three 0.25-ha treatment plots: (1) a naturally regenerating control, (2) tree islands, and (3) a mixed-species tree plantation. Sites spanned a deforestation gradient with 9-89% forest area within 500 m around the treatment plots. Contrary to previous studies, we found that tree Seeds were abundant and ubiquitous across all treatment plots (585.1 ± 142.0 Seeds · m(-2) · yr(-1) [mean ± SE]), indicating that lack of Seed Rain ceased to limit forest regeneration within the first decade of recovery. Pioneer trees and shrubs comprised the vast majority of Seeds, but compositional differences between restoration sites and reference forests were driven by rarer, large-Seeded species. Large, animal-dispersed tree Seeds were more abundant in tree islands (4.6 ± 2.9 Seeds · m(-2) · yr(-1)) and plantations (5.8 ± 3.0 Seeds · m(-2) · yr(-1)) than control plots (0.2 ± 0.1 Seeds · m(-2) · yr(-1)), contributing to greater tree species richness in actively restored plots. Planted tree species accounted for < 1% of Seeds. We found little evidence for landscape forest cover effects on Seed Rain, consistent with previous studies. We conclude that Seed Rain limitation shifted from an initial, complete lack of tree Seeds to a specific limitation on large-Seeded, mature forest species over the first decade. Although total Seed abundance was equal among restoration treatments, tree plantations and tree islands continued to diversify Seed Rain communities compared to naturally regenerating controls. Compositional differences between regenerating plots and mature forests suggest that large-Seeded tree species are appropriate candidates for enrichment planting.
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Seed Rain under tree islands planted to restore degraded lands in a tropical agricultural landscape
Ecological Applications, 2010Co-Authors: Rebecca J Cole, Karen D. Holl, Rakan A ZahawiAbstract:Planting native tree Seedlings is the predominant restoration strategy for accelerating forest succession on degraded lands. Planting tree ''islands'' is less costly and labor intensive than establishing larger plantations and simulates the nucleation process of succession. Assessing the role of island size in attracting Seed dispersers, the potential of islands to expand through enhanced Seed deposition, and the effect of planting arrangements on Seed dispersal by birds and bats informs restoration design. Determining the relative importance of local restoration approach vs. landscape-level factors (amount of surrounding forest cover) helps prioritize methods and locations for restoration. We tested how three restoration approaches affect the arrival of forest Seeds at 11 experimental sites spread across a gradient of surrounding forest cover in a 100-km 2 area of southern Costa Rica. Each site had three 50 3 50 m treatments: (1) control (natural regeneration), (2) island (planting tree Seedlings in patches of three sizes: 16 m 2 ,6 4 m 2 , and 144 m 2 ), and (3) plantation (planting entire area). Four tree species were used in planting (Terminalia amazonia, Vochysia guatemalensis, Erythrina poeppigiana, and Inga edulis). Seed Rain was measured for 18 months beginning ;2 years after planting. Plantations received the most zoochorous tree Seeds (266.1 6 64.5 Seedsm � 2 � yr � 1 (mean 6 SE)), islands were intermediate (210.4 6 52.7 Seedsm � 2 � yr � 1 ), and controls were lowest (87.1 6 13.9 Seedsm � 2 � yr � 1 ). Greater tree Seed deposition in the plantations was due to birds (0.51 6 0.18 Seedsm � 2 � d � 1 ), not bats (0.07 6 0.03 Seedsm � 2 � d � 1 ). Seed Rain was primarily small- Seeded, early-successional species. Large and medium islands received twice as many zoochorous tree Seeds as small islands and areas away from island edges, suggesting there is a minimum island size necessary to increase Seed deposition and that Seed Rain outside of planted areas is strongly reduced. Planting design was more important for Seed deposition than amount of forest cover within the surrounding 100- and 500-m radius areas. Establishing plantations and large islands facilitates the arrival of early-successional tree Seeds and represents a broadly applicable strategy for increasing Seed Rain on abandoned agricultural lands. However, more intensive restoration approaches may be necessary for establishment of dispersal-limited species.
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Effect of shrubs on tree Seedling establishment in an abandoned tropical pasture
Journal of Ecology, 2002Co-Authors: Karen D. HollAbstract:Summary 1 The objective of this study was to evaluate whether early successional shrubs facilitate, tolerate or inhibit different stages of tree establishment in abandoned tropical pasture. 2 Seed Rain, Seed predation, Seed germination and Seedling survival of tropical forest trees in pasture grass, below small ( 40 m 2 ) shrub patches, were compared in one abandoned pasture in Costa Rica over 2 years. 3 Seed Rain of animal-dispersed trees was higher below both large and small shrub patches than below grass. Seed Rain of wind-dispersed trees did not differ in the three patch types. 4 Predation of all animal-dispersed Seeds combined and of three individual species was significantly higher below large and small shrub patches compared with below grass; predation of five species did not differ significantly in the three patch types. 5 Germination did not differ significantly in the three patch types for any of the species. 6 Seedling survival was highest below large shrub patches for three of four species. 7 Computer simulations of probabilities of Seeds arriving in the pasture and surviving to the Seedling stage suggest that early successional shrubs have a net facilitative effect on the early stages of forest tree Seedling establishment compared with areas without shrubs in the pasture studied, although variance was high. Shrubs may facilitate, inhibit and tolerate different stages of tree Seedling establishment.
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factors limiting tropical Rain forest regeneration in abandoned pasture Seed Rain Seed germination microclimate and soil1
Biotropica, 1999Co-Authors: Karen D. HollAbstract:Vegetation, Seed Rain, Seed germination, microclimate, and soil physical and chemical parameters were measured in a recently abandoned pasture and adjacent primary Rain forest in southern Costa Rica. The goal of this study was to assess the importance of these factors in limiting forest regeneration in abandoned pastures. Seed Rain of animal dispersed species decreased dramatically in the pasture >5 m from the forestlpasture edge; fewer wind dispersed Seeds fell in the pasture than in the forest, but the difference was much less than for animal dispersed Seeds. Percent Seed germination of most species studied was similar in the forest and in pasture with grasses; Seed germination was lower during the dry season in areas of pasture cleared of grasses. Air temperature, vapor pressure deficit (VPD), and photon flux density (PFD) were much higher in the pasture than in the forest at 1 m above the ground. VPD and PFD at ground level and soil temperature were similar in the pasture and the forest, indicating that pasture grasses strongly modify microclimatic conditions near the soil surface. The lowest gravimetric water content recorded in the pasture during the dry season was 0.5 and leaf relative water contents of the two species measured in the forest and pasture were identical, suggesting that plants in the pasture were not water stressed. Levels of most soil nutrients were lower in the pasture as compared to the forest; however, aboveground and root biomass for Seedlings grown in pasture and forest soils did not differ significantly. Although a number of factors impede forest recovery in abandoned pastures, these results suggest that the most important limitation is lack of Seed dispersal.
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do bird perching structures elevate Seed Rain and Seedling establishment in abandoned tropical pasture
Restoration Ecology, 1998Co-Authors: Karen D. HollAbstract:Lack of Seed dispersal has been shown to be a major factor limiting tropical forest recovery in abandoned pasture land. The goal of this work was to determine whether bird perching structures serve to enhance Seed dispersal and Seedling establishment in an abandoned pasture in Costa Rica. Two types of perching structures (crossbar and branch) were tested. Bird visitation rates were significantly higher on branch than on crossbar perches. The number of animal-dispersed Seeds was significantly higher below branch perches than below crossbar perches or in open pasture. Despite differences in Seed Rain, percent cover of animal-dispersed plants and the number of Seedlings of animal-dispersed plant species were similar below both perch types and in open pasture. Baiting perches with bananas did not increase either bird visitation rates or Seed Rain. These results suggest that, although bird perching structures increase Seed dispersal, they do not overcome other barriers to tropical forest recovery such as Seed predation and low Seed germination.
John M Dwyer - One of the best experts on this subject based on the ideXlab platform.
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landscape structure mediates zoochorous dispersed Seed Rain under isolated pasture trees across distinct tropical regions
Landscape Ecology, 2019Co-Authors: Lachlan S Charles, John M Dwyer, Hazel M Chapman, Biplang G Yadok, Margaret M MayfieldAbstract:Isolated pasture trees play an important role in forest recovery within fragmented tropical landscapes by attracting Seed dispersers and facilitating Seedling growth. However, studies with conflicting results have led to confusion about what drives variation in zoochorous-dispersed Seed Rain patterns under isolated tree canopies. To assess the role of landscape and biological factors impacting zoochorous-dispersed Seed Rain under isolated pasture trees across three tropical regions of the world. We measured Seed dispersal under 144 isolated pasture trees found in 12 fragmented tropical and sub-tropical landscapes in Australia, Colombia and Nigeria. Using linear mixed effect models, we modeled Seed diversity, abundance, richness and evenness as functions of the biological features and landscape context of isolated trees. Throughout all regions, the amount of woody vegetation surrounding trees in pastures was negatively related to Rainforest Seed diversity, evenness and abundance. Seed diversity and evenness increased significantly with the distance of isolated trees to forest fragments in the Australian sub-tropics, but elsewhere, Seed diversity and evenness tended to decline with distance to forest, though not significantly. Our results suggest that the tree composition of landscapes surrounding isolated pasture trees is important for influencing zoochorous-dispersed Seed Rain, regardless of the region studied. Our study highlights the prominent role of landscape-scale, rather than local-scale factors on Seed dispersal to isolated pasture trees, while providing strong evidence that early stage successional processes involving isolated pasture trees are similar throughout global tropical regions.
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Rainforest Seed Rain into abandoned tropical australian pasture is dependent on adjacent Rainforest structure and extent
Austral Ecology, 2017Co-Authors: Lachlan S Charles, John M Dwyer, Margaret M MayfieldAbstract:It is well known that the recovery of abandoned tropical pastures to secondary Rainforest benefits from the arrival of Seeds from adjacent Rainforest patches. Less is known, however, about how the structural attributes of adjacent Rainforest (e.g. tree density, canopy cover and tree height) impact Seed Rain patterns into abandoned pastures. Between 2011 and 2013, we used Seed traps and ground Seed surveys to track the richness and abundance of Rainforest Seeds entering abandoned pastures in Australia's wet tropics. We also tested how Seed Rain diversity is related to the distance from forest, the proportion of forest cover in the landscape and several structural attributes of adjacent forest patches, specifically average tree height, canopy cover, tree species richness and density. Almost no Seeds were captured in elevated pasture Seed traps, even near forest remnants. Abundant forest Seeds were found in ground surveys but only within 10 m of forest edges. In ground surveys, Seeds from wind-dispersed species were more abundant, but less species rich, than animal-dispersed species. A survey of pasture Seedling recruits suggested that some forest Seeds must be dispersing more than 10 m into pasture at very low frequencies, but only a few species are establishing there. Recruits were predominantly animal-dispersed not wind-dispersed species. In addition to distance from forest and the proportion of forest within a 100- to 200-m radius of sampling sites, the richness and density of adjacent forest trees were the most important factors for explaining the probability of Seed occurrence in abandoned pastures. Results suggest that without some restoration assistance, the recovery of abandoned pastures into secondary Rainforest in Australia's tropical Rainforests will likely be limited, at least in part, by a very low rate of Seed dispersal away from forest edges and by the diversity and density of trees in adjacent remnant forests.