scholarly journals Frugivore loss limits recruitment of large-seeded trees

2011 ◽  
Vol 278 (1723) ◽  
pp. 3345-3354 ◽  
Author(s):  
Debra M. Wotton ◽  
Dave Kelly
Keyword(s):  
New Zealand ◽  
Plant Regeneration ◽  
Seed Dispersal ◽  
Seed Predation ◽  
Tree Species ◽  
Seedling Survival ◽  
Fruit Pulp ◽  
Synergistic Interactions ◽  
Local Plant ◽  
Pulp Removal

Although global declines in frugivores may disrupt seed dispersal mutualisms and inhibit plant recruitment, quantifying the likely reduction in plant regeneration has been difficult and rarely attempted. We use a manipulative factorial experiment to quantify dependence of recruitment on dispersal (i.e. fruit pulp removal and movement of seed away from parental area) in two large-seeded New Zealand tree species. Complete dispersal failure would cause a 66 to 81 per cent reduction in recruitment to the 2-year-old seedling stage, and synergistic interactions with introduced mammalian seed and seedling predators increase the reduction to 92 to 94 per cent. Dispersal failure reduced regeneration through effects on seed predation, germination and (especially) seedling survival, including distance- and density-dependent (Janzen–Connell) effects. Dispersal of both species is currently largely dependent on a single frugivore, and many fruits today remain uneaten. Present-day levels of frugivore loss and mammal seed and seedling predators result in 57 to 84 per cent fewer seedlings after 2 years. Our study demonstrates the importance of seed dispersal for local plant population persistence, and validates concerns about the community consequences of frugivore declines.

scholarly journals Fire suppression and seed dispersal play critical roles in the establishment of tropical forest tree species in southeastern Africa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tomohiro Fujita
Keyword(s):  
Seed Dispersal ◽  
Tree Species ◽  
Seedling Survival ◽  
Fire Suppression ◽  
Forest Tree ◽  
Tree Seedlings ◽  
Seedling Mortality ◽  
Forest Tree Species ◽  
Seed Deposition ◽  
Syzygium Guineense

AbstractThis study examined the mechanisms of facilitation and importance of seed dispersal during establishment of forest tree species in an Afrotropical woodland. Seedling survival of Syzygium guineense ssp. afromontanum was monitored for 2.5 years at four different microsites in savannah woodland in Malawi (southeastern Africa) under Ficus natalensis (a potential nurse plant), Brachystegia floribunda (a woodland tree), Uapaca kirkiana (a woodland tree), and at a treeless site. The number of naturally established forest tree seedlings in the woodland was also counted. Additionally, S. guineense ssp. afromontanum seed deposition was monitored at the four microsites. Insect damage (9% of the total cause of mortality) and trampling by ungulates (1%) had limited impact on seedling survival in this area. Fire (43%) was found to be the most important cause of seedling mortality and fire induced mortality was especially high under U. kirkiana (74%) and at treeless site (51%). The rate was comparatively low under F. natalensis (4%) and B. floribunda (23%), where fire is thought to be inhibited due to the lack of light-demanding C4 grasses. Consequently, seedling survival under F. natalensis and B. floribunda was higher compared with the other two microsites. The seedling survival rate was similar under F. natalensis (57%) and B. floribunda (59%). However, only a few S. guineense ssp. afromontanum seedlings naturally established under B. floribunda (25/285) whereas many seedlings established under F. natalensis (146/285). These findings indicate that the facilitative mechanism of fire suppression is not the only factor affecting establishment. The seed deposition investigation revealed that most of the seeds (85%) were deposited under F. natalensis. As such, these findings suggest that in addition to fire suppression, dispersal limitations also play a role in forest-savannah dynamics in this region, especially at the community level.

scholarly journals Native seed dispersal by rodents is negatively influenced by an invasive shrub

2021 ◽  
pp. 53-67
Author(s):  
A. F. Malo ◽  
A. Taylor ◽  
M. Díaz
Keyword(s):  
Seed Dispersal ◽  
Seed Predation ◽  
Seedling Survival ◽  
Apparent Competition ◽  
Acer Pseudoplatanus ◽  
Pedunculate Oak ◽  
Seed Fate ◽  
Factors Affecting ◽  
Native Seed ◽  
Open Woodland

Refuge–mediated apparent competition is the mechanism by which invasive plants increase pressure on native plants by providing refuge for generalist consumers. In the UK, the invasive Rhododendron ponticum does not provide food for generalist seed consumers like rodents, but evergreen canopy provides refuge from rodent predators, and predation and pilferage risk are key factors affecting rodent foraging and caching behaviour. Here we used a seed removal/ seed fate experiment to understand how invasion by an evergreen shrub can alter seed dispersal, seed fate and early recruitment of native trees. We used seeds of four species, small and wind–dispersed (sycamore maple Acer pseudoplatanus and European ash Fraxinus excelsior) and large and animal–dispersed (pedunculate oak Quercus robur and common hazel Corylus avellana), and monitored seed predation and caching in open woodland, edge habitats, and under Rhododendron. In the open woodland, wind–dispersed seeds had a higher probability of being eaten in situ than cached seeds, while the opposite occurred with animal–dispersed seeds. The latter were removed from the open woodland and edge habitats and cached under Rhododendron. This pattern was expected if predation risk was the main factor influencing the decision to eat or to cach a seed. Enhanced dispersal towards Rhododendron cover did not increase the prospects for seed survival, as density of hazel and oak saplings under its cover was close to zero as compared to open woodland, possibly due to increased cache pilferage or low seedling survival under dense shade, or both. Enhanced seed predation of ash and sycamore seeds close to Rhododendron cover also decreased recruitment of these trees. Rhododendron patches biased rodent foraging behaviour towards the negative (net predation) side of the conditional rodent / tree interaction. This effect will potentially impact native woodland regeneration and further facilitate Rhododendron spread due to refuge–mediated apparent competition.

scholarly journals Fire Suppression as Well as Seed Dispersal Play Critical Role in the Establishment of Forest Tree Species in Tropical Woodland

2021 ◽  
Author(s):  
Tomohiro Fujita
Keyword(s):  
Seed Dispersal ◽  
Tree Species ◽  
Seedling Survival ◽  
Fire Suppression ◽  
Critical Role ◽  
Forest Tree ◽  
Forest Tree Species ◽  
Natural Establishment ◽  
Tropical Woodland ◽  
Syzygium Guineense

Abstract This study examined the mechanisms of facilitation and importance of seed dispersal during establishment of forest tree species in a tropical woodland. Seedling survival of Syzygium guineense ssp. afromontanum seedling (forest tree species) was monitored for 2.5 years in four different microsites in savannah-woodland in Malawi under Ficus natalensis (a potential nurse plant), Brachystegia floribunda (a woodland tree), and Uapaca kirkiana (a woodland tree), and in a treeless site. S. guineense ssp. afromontanum seed deposition was also monitored in the four sites, and the natural establishment of forest tree species was observed to confirm the importance of seed dispersal. Protection from fire was found to be the most important facilitation mechanism in this area, with a total fire-induced mortality rate of 43%. However, the rate was comparatively low under F. natalensis, where fire is thought to be inhibited due to the lack of light-demanding C4 grasses. B. floribunda also offered protection from fire, and seedling survival did not differ between these two microsites. However, only a few individual forest tree species naturally established under B. floribunda, indicating that the facilitative mechanism of fire suppression is not the only factor affecting establishment in this tropical woodland. A higher rate of seed dispersal was also observed under F. natalensis compared with the other three microsites, suggesting that dispersal processes are also critical for the establishment of forest tree species in woodland in this region.

scholarly journals Secondary seed removal in a degraded forest habitat in Madagascar

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paula M. A. Fiedler ◽  
Alice De Lapparent ◽  
Jeremie Razafitsalama ◽  
Justin Sanamo ◽  
Kim J. E. Steffens ◽  
...  
Keyword(s):  
Seed Dispersal ◽  
Seed Predation ◽  
Tree Species ◽  
Natural Regeneration ◽  
Forest Restoration ◽  
Forest Degradation ◽  
Degraded Forest ◽  
Seed Removal ◽  
Forest Habitat ◽  
Removal Experiments

AbstractForest restoration is a prime goal within the 2021–2030 UN “Decade of Ecosystem Resoration”. As part of these activities, natural regeneration has to be promoted for biological as well as for economic reasons. For this, the processes of seed dispersal, seed predation and germination have to be understood in the original as well as in degraded vegetation formations. We used seed removal experiments to assess post-dispersal processes that influence recruitment along a gradient of forest degradation in Madagascar analyzing seeds of three animal dispersed tree species. The percentage of seeds consumed or dispersed, declined from forest (28.6%) to degraded forest (17.2%) to savanna (10.8%). Only three out of 1080 seeds were cached and remained intact during the 14-day experiment. All three seeds were cached in the forest habitat and none in the degraded forest and savanna. The low percentage of seeds removed may be due to the lack of endemic rodents caching seeds, as only introduced rats were recorded in the area. The species-poor fauna of potential secondary seed dispersers of the region and especially in the degraded areas might represent an obstacle for diverse regeneration in degraded regions of Madagascar.

scholarly journals Fungi and insects compensate for lost vertebrate seed predation in an experimentally defaunated tropical forest

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Peter Jeffrey Williams ◽  
Robert C. Ong ◽  
Jedediah F. Brodie ◽  
Matthew Scott Luskin
Keyword(s):  
Seed Dispersal ◽  
Seed Predation ◽  
Tree Species ◽  
Species Interactions ◽  
Simulation Models ◽  
Tree Species Composition ◽  
Exclusion Experiment ◽  
Complex Species ◽  
Seed Mortality ◽  
Plant Animal Interactions

AbstractOverhunting reduces important plant-animal interactions such as vertebrate seed dispersal and seed predation, thereby altering plant regeneration and even above-ground biomass. It remains unclear, however, if non-hunted species can compensate for lost vertebrates in defaunated ecosystems. We use a nested exclusion experiment to isolate the effects of different seed enemies in a Bornean rainforest. In four of five tree species, vertebrates kill many seeds (13–66%). Nonetheless, when large mammals are excluded, seed mortality from insects and fungi fully compensates for the lost vertebrate predation, such that defaunation has no effect on seedling establishment. The switch from seed predation by generalist vertebrates to specialist insects and fungi in defaunated systems may alter Janzen–Connell effects and density-dependence in plants. Previous work using simulation models to explore how lost seed dispersal will affect tree species composition and carbon storage may require reevaluation in the context of functional redundancy within complex species interactions networks.

Bigleaf maple seedling establishment and early growth in Douglas-fir forests

1988 ◽  
Vol 18 (10) ◽  
pp. 1226-1233 ◽  
Author(s):  
Jeremy S. Fried ◽  
John C. Tappeiner II ◽  
David E. Hibbs
Keyword(s):  
Seed Predation ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Early Growth ◽  
Douglas Fir ◽  
Stand Development ◽  
Size Distributions ◽  
Canopy Density ◽  
Successful Establishment ◽  
Survival Of Seedlings

Survival, age and height distributions, and stocking of bigleaf maple (Acermacrophyllum Pursh) seedlings were studied in 1- to 250-year-old Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) stands in western Oregon to identify the stages in stand development in which bigleaf maple is most likely to establish successfully from seed. Maple seedling emergence averaged 30–40% where seeds were planted and protected from rodents but was typically <2% for unprotected seeds. Seedling survival after 2 years was highly dependent on canopy density, measured by percent sky. Average 1st-year survival of seedlings originating from planted, protected seeds was highest in clearcuts (1–2 years old, 36% survival, 56% sky) and pole-size stands (41–80 years old, 30% survival, 17% sky) with sparse understories and canopies. It was lowest in young stands with dense canopies (20–40 years old, 4% survival, 8% sky) and old stands (81–250 years old, 14% survival, 13% sky) with dense understories. Naturally regenerated populations of bigleaf maple seedlings, which occurred in aggregations (0.005–0.04 ha in area), were most abundant (up to 10 000/ha) in pole-size Douglas-fir stands. Although seedling size distributions within stands had a strongly inverse J shaped form, size distributions within aggregations appeared more normal (bell-shaped). Seedling age rarely exceeded 15 years. Seedlings grew slowly in the understory, often reaching only 25 cm in height after 8–10 years, and were intensively browsed by deer. Naturally regenerated seedlings were virtually absent from clearcuts, probably because of dense competing vegetation and lack of seed caused by poor dispersal and seed predation. The "window" for the most successful establishment of bigleaf maple seedlings appears to begin after canopy thinning and end before forbs and shrubs invade.

Dispersal ofAcaciaseeds by ungulates and ostriches in an African savanna

1996 ◽  
Vol 12 (3) ◽  
pp. 345-356 ◽  
Author(s):  
Maxine F. Miller
Keyword(s):  
South Africa ◽  
Seed Dispersal ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Crown ◽  
African Savanna ◽  
Large Herbivores ◽  
Mammalian Herbivores ◽  
Open Environments ◽  
Presence And Absence

ABSTRACTThe dispersal of AfricanAcaciaseeds in the presence and absence of large mammalian herbivores and ostriches was assessed in a savanna ecosystem in South Africa. In the absence of large herbivores,A. tortilisandA. niloticapods were mainly dispersed in the shade, directly beneath the tree crown and seeds remained in pods for over 18 months. In the presence of large herbivores,A. tortilis, A. niloticaandA. karrooseeds were freed from pods and were dispersed into open, non-shaded habitats. Impala dispersed mostA. tortilisseeds (18,900 ha−1), giraffe mostA. niloticaseeds (1060 ha−1) and giraffe and kudu mostA. karrooseeds (452 and 448 ha−1, respectively). Seedling survival in dung in open environments may exceed that of seedlings in soil shaded beneath the tree crown. It appears that seed dispersal by large herbivores may be advantageous to future seedling recruitment.

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