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1.
Abstract Measuring the fate of seeds between seed production and seedling establishment is critical in understanding mechanisms of recruitment limitation of plants. We examined seed fates to better understand the recruitment dynamics of four resprouting shrubs from two families (Fabaceae and Epacridaceae) in temperate grassy woodlands. We tested whether: (i) pre‐dispersal seed predation affected seed rain; (ii) post‐dispersal seed predation limited seed bank accumulation; (iii) the size of the seed bank was related to seed size; and (iv) viable seeds accumulated in the soil after seed rain. There was a distinct difference in seed production per plant between plant families with the legumes producing significantly more seeds per individual than the epacrids. Seed viability ranged from 43% to 81% and all viable had seed or fruit coat dormancy broken by heat or scarification. Pre‐dispersal predation by Lepidopteran larvae removed a large proportion of seed from the legume seed rain but not the epacrids. Four species of ants (Notoncus ectatomoides, Pheidole sp., Rhytidoponera tasmaniensis and Iridomyrmex purpureus) were major post‐dispersal seed removers. Overall, a greater percentage of Hardenbergia (38%) and Pultenaea (59%) seeds were removed than the fleshy fruits of Lissanthe (14%) or Melichrus (0%). Seed bank sizes were small (<15 seeds m?2) relative to the seed rain and no significant accumulation of seed in the soil was detected. Lack of accumulation was attributed to seed predation as seed decay was considered unlikely and no seed germination was observed in our study sites. Our study suggests that seed predation is a key factor contributing to seed‐limited recruitment in grassy woodland shrubs by reducing the number of seeds stored in the soil. 相似文献
2.
河岸带生态系统退化机制及其恢复研究进展 总被引：22，自引：3，他引：22
恢复和重建自然和人为干扰导致的退化河岸带生态系统是目前恢复生态学、流域生态学等学科研究的重要内容之一．对河岸带生态系统的干扰表现在河流水文特征改变、河岸带直接干扰和流域尺度干扰3个方面,分别具有不同的影响机制．河流水文特征改变通过改变河岸土壤湿度、氧化还原电位、生物生存环境以及沉积物传输规律对河岸带生态系统产生影响;河岸带直接干扰通过人类活动及外来物种入侵而直接影响河岸带植被多样性;流域尺度干扰则主要表现在河道刷深、河道淤积、河岸带地下水位降低和河流冲刷过程改变等．河岸带生态恢复评价对象包括河岸带生态系统各要素,评价指标已从单一的生态指标转向综合性指标．河岸带生态恢复应在景观或者流域尺度上进行考虑,识别对其影响的生物和物理过程以及导致其退化的干扰因子,通过植被重建与水文调控来进行．扩展研究尺度和研究对象及采用多学科的研究方法将是今后相关研究中的重要问题． 相似文献
3.
Karen A. Esper‐Reyes Néstor A. Mariano Raúl E. Alcalá Jaime R. Bonilla‐Barbosa Gabriel Flores‐Franco Elisabet V. Wehncke 《植被学杂志》2018,29(1):62-73
Aims
Rivers are important corridors for the movement, migration and dispersal of aquatic organisms, including seeds from riparian plants. Although tropical dry forests (TDF) are among the most extensive and floristically rich ecosystems of tropical habitats, and the most globally endangered ecosystem, less attention has been given to riparian corridors within this ecosystem. Although most TDFs manifest peak seed dispersal during dry seasons, we hypothesized that riparian corridors may show a dispersal peak during the rainy season, due to an anticipated ‘sweep or drag effect’, resulting from river overflow and bank erosion. Our main aims were to investigate whether there were any differences in the seed communities transported by the river to sites in rainy as opposed to dry seasons, and to evaluate any possible relationship between the riparian seed community and river flow.Location
Amacuzac River, drainage of the Balsas basin, State of Morelos, Mexico.Methods
To evaluate the above assumption, we associated Amacuzac River flow with the number of species and seeds dispersed by water. We also characterized and evaluated differences between seed communities transported by the river during the rainy and dry seasons, and between four different sites located along the river. We used univariate and ordination NMDS techniques to evaluate patterns between seasons at the community level.Results
Forty‐five plant species were identified from 909 seeds collected from the river. The composition of riparian seed communities was markedly different between seasons but not between sites. Seed abundances were significantly higher in the rainy than in the dry season and varied between sites. Seed species diversity in the river (H’ = 1.6–1.9) showed no significant differences between seasons or sites, but species assemblages and dominance varied according to season. Ordination techniques and subsequent fitting analyses showed that seed species composition was positively associated with river flow.Conclusions
Seed dispersal patterns generated by rivers are significant mechanisms for structuring the composition and distribution of the riparian plant community in Mexican TDF. Varying species assemblages and seed abundance dispersed by the river throughout the year is a relevant and until now unknown consequence that may affect the dynamics and composition of riparian plant communities in this region. This study initiative will promote new avenues of research regarding plant establishment and succession. 相似文献4.
Patricia A. Fleming Hannah Anderson Amy S. Prendergast Michael R. Bretz Leonie E. Valentine Giles E. StJ. Hardy 《Mammal Review》2014,44(2):94-108
- Despite once being described as common, digging mammal species have been lost from the Australian landscape over the last 200 years. Around half of digging mammal species are now extinct or under conservation threat, and the majority of extant species have undergone marked range contractions.
- Our aim is to identify the role of digging mammals in ecosystem processes throughout Australia. We highlight how the actions of digging mammals are vital for maintaining ecosystem functioning and how their extirpation has led to loss of ecosystem functions.
- A review of the literature indicates that many aspects of the influence of bioturbation on ecosystem functioning have been studied. The role of digging mammals in arid and semi‐arid zones has been previously established. We collate and review a broader scope of studies, including those carried out in the mesic woodlands and forests of Australia. We identify roles of digging mammals in the context of ecosystem functioning and conservation management.
- Bioturbation significantly alters soil processes, increasing soil turnover and altering the chemical and structural properties of soil. Greater water infiltration and decreased surface run‐off and erosion alter soil hydrophobicity and increase soil moisture. Diggings capture organic matter, provide habitat for a diversity of microscopic and macroscopic organisms, and increase nutrient cycling. Mycophagous mammals disperse fungi (e.g. mycorrhizae), while all diggings can create suitable sites for fungal growth. Diggings also capture plant seeds, increasing seedling germination, recruitment and plant growth. The overall effect of mammal diggings is therefore increased plant vigour and resilience, increased biodiversity and consequently improved ecosystem functioning.
- We propose that the loss of digging mammals has contributed to the deterioration of ecosystems in Australia. Recognising the roles of digging mammals will inform potential management options such as species translocations or reintroductions.
5.
Miriam Paul Carla P. Catterall John Kanowski Peter C. Pollard 《Ecological Management & Restoration》2012,13(2):144-152
Summary Seed availability is a major factor limiting the recruitment of rain forest to cleared land, but little is known about the composition of the soil seed bank under different reforestation pathways. We quantified changes in the viable soil seed bank following rain forest clearing and pasture establishment and subsequent reforestation in subtropical eastern Australia. Major reforestation pathways in the region include planting of a diverse suite of native trees for ecological restoration purposes, autogenic regrowth dominated by the non‐native tree Camphor Laurel (Cinnamomum camphora) and management of this regrowth to accelerate the development of a native tree community. These pathways differ considerably in cost: restoration plantings are expensive, autogenic regrowth is free, whilst managing regrowth generally costs much less than restoration plantings. We surveyed five sites within each of three reforestation pathways as well as reference sites in remnant rain forest and pasture. The composition of the seed bank was determined by germinating plants from soil samples collected from each site. Germinants were classified into several functional groups according to life form, origin, dispersal mode and successional stage. The majority of functional groups varied significantly in abundance or richness between rain forest and pasture sites. Most of the functional groups that varied between rain forest and pasture were restored to values similar to rain forest by at least one of the three reforestation pathways examined. The species richness of native woody plants in the soil seed bank was slightly higher in restoration plantings than in autogenic or managed regrowth; nevertheless, the species richness and abundance of native woody plants and vines were higher in the seed bank of autogenic regrowth than pasture, and both attributes were enhanced by the management of regrowth sites. The results of this study show that autogenic regrowth can make an important contribution to rain forest restoration at a landscape scale. The optimal reforestation approach or mix of approaches will depend on the desired rate of recovery and the resources available for restoration. 相似文献
6.
Darren P. Giling Michael R. Grace Ralph Mac Nally Ross M. Thompson 《Freshwater Biology》2013,58(12):2601-2613
- The effectiveness of revegetation is usually gauged by responses in biodiversity, which may differ between isolated replanted patches. The ecological value of revegetation may be detected more effectively by monitoring ecosystem processes. In‐stream metabolism has been much modified by the degradation of riparian vegetation in agricultural landscapes around the world. We sought to determine whether the spatial scale typical of most riparian replanting projects (i.e. <1 km long) influences stream metabolism.
- Metabolism is a functional measure that incorporates gross primary production (GPP), ecosystem respiration (ER) and the difference between them [net ecosystem productivity (NEP)]. We hypothesised that replanted reaches would have lower GPP (due to greater canopy shading) and greater ER (governed by larger terrestrial energy inputs) compared with pasture reaches.
- We measured metabolism in paired reaches within four agricultural streams. Two streams had an untreated pasture reach contrasted with a reach replanted with native woody vegetation >17 years ago. The other two streams had similar riparian vegetation condition adjacent to both reaches, to act as reference sites.
- Mean daily GPP (0.27–4.9 g O2 m?2 day?1) and ER (1.1–22 g O2 m?2 day?1) were within the range of values recorded previously in agricultural streams elsewhere. Replanted reaches had rates of NEP lower than upstream untreated reaches at treatment sites, but NEP was similar between reaches at reference sites.
- The effects of replanting on stream ecosystem processes are detectable even when the spatial scale of restoration is relatively small in a whole‐of‐catchment context. Land managers can protect and restore vegetation at feasible spatial scales and benefit ecosystem processes. Ecosystem metabolism should be included in the range of responses that need to be monitored to provide a complete picture of the effectiveness of stream restoration.
7.
The fire avoidance hypothesis proposes that a benefit of seed dispersal by ants (myrmecochory) is to protect seeds from being killed during fire and to facilitate post‐fire germination of seeds that require heat shock to break their physical dormancy. The aim of this study was to quantify the effect of fire and seed burial by a predominant seed‐dispersing ant, Rhytidoponera metallica (subfamily: Ectatomminae) on germination levels of three ant‐dispersed legume species (Pultenaea daphnoides, Acacia myrtifolia and Acacia pycnantha). Experimental burial of seeds within aluminium cans at a site prior to being burnt and at an adjacent unburnt site showed that fire increased germination levels, particularly for seeds buried at 1‐ and 2‐cm deep and that overall, germination levels differed among the three plant species. To quantify seed burial depths and post‐fire germination levels facilitated by R. metallica ants, seeds were fed to colonies prior to fire at the burnt and unburnt sites. Of the seeds buried within nests that were recovered, between 45% and 75% occurred within the upper 6 cm of the soil profile, although unexpectedly, greater percentages of seeds were recovered from the upper 0–2 cm of nests in the unburnt site compared with nests in the burnt site. Germination levels of buried seeds associated with R. metallica nests ranged from 21.2% to 29.5% in the burnt site compared with 3.1–14.8% in the unburnt site. While increased seed germination levels were associated with R. metallica nests following fire, most seeds were buried at depths below those where optimal temperatures for breaking seed dormancy occurred during the fire. We suggest that R. metallica ants may provide fire avoidance benefits to myrmecochorous seeds by burying them at a range of depths within a potential germination zone defined by intra‐ and inter‐fire variation in levels of soil heating. 相似文献
8.
Ecosystem Metabolism in Piedmont Streams: Reach Geomorphology Modulates the Influence of Riparian Vegetation 总被引：1，自引：0，他引：1
We measured the impact of riparian zone vegetation on ecosystem metabolism in paired forested and meadow reaches on 13 streams
in southeastern Pennsylvania and Maryland, USA. Metabolism estimates were based on open-system measurements of dissolved oxygen
changes, with reaeration determined from propane evasion. Daily gross primary productivity (GPP) in meadow and forested reaches
averaged 2.85 and 0.86 g O2 m−2 d−1, respectively, at water temperatures of 12°C or greater when the forest canopy was developed and 1.74 and 1.09 g O2 m−2 d−1, respectively, at temperatures below 12°C when the canopy was bare. Community respiration (CR24) also was greater in meadow reaches than in forested reaches, averaging 5.58 and 3.57 g O2 m−2 d−1, respectively, in the warm season and 4.87 and 2.88 g O2 m−2 d−1, respectively, during the cold season. Thus, both meadow and forested reaches were heterotrophic. Forested reaches were always
wider and nearly always shallower than companion meadow reaches. When ecosystem function was assessed per unit of stream length,
the difference in average GPP between meadow and forested reaches was reduced from three-fold to 1.9-fold in the warm season,
and mean GPP was greater in the forested reaches during the cold season. Mean CR24 per meter stream length was greater in forested reaches during both seasons. Even though riparian shading reduced primary
productivity per unit area of streambed, the greater stream width of the forested reaches counteracted that reduction in part.
Thus, when rates of ecosystem function were expressed per length of stream, differences between reaches were always smaller
than when expressed per area, and activity per unit stream length was sometimes greater in forested reaches than in meadow
reaches. 相似文献
9.
Resilient systems can absorb disturbance and persist despite variability as long as the capacity of the system to adapt is not exceeded. Riparian plant communities of dryland alluvial rivers are expected to be naturally resilient systems because they persist in the highly variable floodplain. River modification has altered the flow regime on many dryland rivers, in some cases exceeding the adaptive capacity of the riparian vegetation, but these changes may be readily reversible. The Salt River in Phoenix, Arizona has been impounded, dewatered, channelized, but also re‐watered with urban effluent and storm drain runoff. To determine whether riparian vegetation is resilient to these various perturbations, paired comparisons were made in the vegetation and seed bank between a non‐diverted reference reach, a diverted reach, and a re‐watered urban reach. In the diverted reach, composition had shifted to that of a stress tolerant xeroriparian shrubland with low diversity in both the seed bank and extant vegetation. Most surprisingly, few differences were observed in the composition and structure of the vegetation and soil seed banks between the reference reach and the urban reach, particularly in the wet patches, suggesting that hydric riparian plant communities have the capacity to adapt to these modified conditions. These results provide support for a process‐oriented approach to restoration on the Salt River and other urban dryland rivers using patches of persisting vegetation as models for achievable restoration targets. 相似文献
10.
Invasive plants are a serious threat to biodiversity. Yet, in some cases, they may play an important ecological role in heavily modified landscapes, such as where fleshy‐fruited invasive plants support populations of native frugivores. How can such conservation conflicts be managed? We advocate an approach in which native fleshy‐fruited plants are ranked on their ability to provide the fruit food resources for native frugivores currently being provided by invasive plants. If these native taxa are preferentially used, where ecologically appropriate, in plantings for restoration and in park and garden settings, they could help support native frugivore populations in the event of extensive invasive plant control. We develop and critically examine six approaches to selecting candidate native plant taxa: a multivariate approach based on the frugivore assemblage, a scoring model, and several multivariate approaches (including trait combinations having the greatest correlation with the diet of the native frugivore assemblage) based on the functional traits of fruit morphology, phenology, conspicuousness, and accessibility. To illustrate these approaches, we use a case study with Bitou bush (Chrysanthemoides monilifera subsp. rotundata) (Asteraceae), an Australian Weed of National Significance. The model using a dissimilarity value generated from all available traits identified a set of species used by the frugivores of C. monilifera more than null models. A replacement approach using species ranked by either all traits available or the frugivore community appears best suited to guide selection of plants in restoration practice. 相似文献
11.
Topsoil is a valuable resource for revegetation of mine sites as it contains seeds of plant species indigenous to the local environment. As mine site restoration is undertaken after the completion of mining, it is a common practice to stockpile topsoil in preparation for restoration activities. While many studies have found a decrease in seedling emergence with increasing stockpile age in temperate regions around the world, a few examine the effect of stockpile age on topsoil seed bank and seedling recruitment in arid environments. Seed longevity is promoted under dry conditions whereas viability loss is increased under warm and moist conditions. Here in a study in Australia's Great Sandy Desert, the effect of topsoil storage age and method of storing topsoil (under‐cover and exposed) on seedling recruitment was examined for a major gold mining site. There was a trend for lower seedling emergence (68% lower) and species richness (30% lower) from topsoil stored for 2 years than from topsoil direct returned and topsoil stored for 1 year. Seedling emergence from topsoil stockpiled for 2 years was more than 3.5‐fold higher from covered topsoil stockpiles than uncovered topsoil stockpiles. For two ecologically dominant species, after 2 years of storage, seedling emergence of the grass Triodia basedowii was 13% of direct returned topsoil and seedling emergence of the shrub Acacia stellaticeps was 68% of direct returned topsoil. The implication of the decline in seedling emergence from topsoil stockpiling on mine site revegetation in a biodiverse arid region is discussed. 相似文献
12.
Lassina Sanou;Patrice Savadogo;Didier Zida;Adjima Thiombiano; 《Nordic Journal of Botany》2022,2022(5):e03304
Soil seed bank (SSB) characteristics may vary with habitat heterogeneity. We investigated the SSB density in three microhabitats (under canopy, eroded soil and bare soil) in five vegetation types (abandoned farm, dense woodland, gallery forest, grassland and open woodland) at varying soil depths (0–5, 5–10 and 10–15 cm) in a savanna-woodland in Burkina Faso, West Africa. Total germinable SSB densities varied between 4 and 308 seeds per dm3 of soil. Herbaceous taxa were the major constituent of the germinable SSB across the microhabitats, regardless of vegetation type. Seedlings of 30 species emerged from the SSB, of which 24 were annual species and only 4 woody species, indicating that natural regeneration of woody species via seed dispersal is limited. Both microhabitat and vegetation type contributed to the variation in taxa richness, and germinable seed density and diversity. There was a significant difference in SSB density and richness between microhabitats in the different vegetation types (p < 0.05). The SSB densities were higher under tree canopies than outside tree canopies (eroded soil and bare soil) and highest in the upper soil layers in all vegetation types. The aboveground vegetation (AGV) and flora within the SSB shared many herbaceous species but many woody species present in the AGV were absent in the SSB. Under tree canopies are the ecological niches that favor accumulation of a diversity of seeds, suggesting the preservation and conservation of adult trees in savanna-woodland ecosystems is critical to facilitating the restoration of these ecosystems. 相似文献
13.
Vibrans H 《American journal of botany》1999,86(4):476-481
The diaspores of the 50 most important maize field weed species (agrestals) in a traditional maize-growing area of south-central Mexico (region of Puebla and Tlaxcala) were analyzed for morphological adaptations to long-distance dispersal. Adaptations to wind-dispersal were absent and to endozoochory were minimal. Most species had no visible adaptations and are presumably transported with mud. However, about one-quarter of the taxa, particularly the tall and dominant ones, relied at least partially on burrs with hooks or awns. The possible vectors for these exo- or epizoochorous species are discussed: the most likely regular dispersers are humans (epianthropochory). Interviews with farmers confirm this conclusion. Using humans as vectors allows the plant to transport relatively large seeds to favorable habitats (directed dispersal). The importance of this relatively rare dispersal adaptation in Mexican maize field weeds leads to questions on the origin and evolution of these agrestals. 相似文献
14.
Rowena L. Long Marta J. Gorecki Michael Renton John K. Scott Louise Colville Danica E. Goggin Lucy E. Commander David A. Westcott Hillary Cherry William E. Finch‐Savage 《Biological reviews of the Cambridge Philosophical Society》2015,90(1):31-59
Seed persistence is the survival of seeds in the environment once they have reached maturity. Seed persistence allows a species, population or genotype to survive long after the death of parent plants, thus distributing genetic diversity through time. The ability to predict seed persistence accurately is critical to inform long‐term weed management and flora rehabilitation programs, as well as to allow a greater understanding of plant community dynamics. Indeed, each of the 420000 seed‐bearing plant species has a unique set of seed characteristics that determine its propensity to develop a persistent soil seed bank. The duration of seed persistence varies among species and populations, and depends on the physical and physiological characteristics of seeds and how they are affected by the biotic and abiotic environment. An integrated understanding of the ecophysiological mechanisms of seed persistence is essential if we are to improve our ability to predict how long seeds can survive in soils, both now and under future climatic conditions. In this review we present an holistic overview of the seed, species, climate, soil, and other site factors that contribute mechanistically to seed persistence, incorporating physiological, biochemical and ecological perspectives. We focus on current knowledge of the seed and species traits that influence seed longevity under ex situ controlled storage conditions, and explore how this inherent longevity is moderated by changeable biotic and abiotic conditions in situ, both before and after seeds are dispersed. We argue that the persistence of a given seed population in any environment depends on its resistance to exiting the seed bank via germination or death, and on its exposure to environmental conditions that are conducive to those fates. By synthesising knowledge of how the environment affects seeds to determine when and how they leave the soil seed bank into a resistance–exposure model, we provide a new framework for developing experimental and modelling approaches to predict how long seeds will persist in a range of environments. 相似文献
15.
Abandoned pastures and secondary forests are increasingly prominent features of tropical landscapes. Forest regrowth on abandoned pastures is generally slow and virtually limited to regeneration from seeds from external sources, since agricultural activities alter site conditions. We hypothesize that seed availability is a major limiting factor in forest recovery on abandoned pastures. This hypothesis was tested by studying the seed bank, seed rain, and seed predation in a small pasture (1 ha) situated in a forest‐pasture mosaic in northwestern Costa Rica. The tree seed density in the pasture seed bank was much lower (21/m2) than the density in the seed bank of a neighboring secondary forest (402/m2). Within a period of five weeks, 23 tree seeds entered the pasture by seed rain. This number is low compared to densities found in closed forests but higher than densities reported in other studies where virtually no seeds were found beyond 20 m from the forest edge. Possibly the small size of the pasture with seed sources nearby and the small‐scale landscape mosaic enhance seed dispersal. Predation limits the seed density in pastures, with 42% of the woody species consumed by predators. The low seed density in the seed bank, and hampered recruitment combined with significant losses, pose severe restrictions to forest recovery on abandoned pastures. Moderate land use, and small sized clearings with seed sources nearby may increase the pace of recovery. Nevertheless, forest establishment may still take a considerable time. Thus, enlarging the available pool of species may be a worthwhile management strategy. 相似文献
16.
用芦苇恢复受损河岸生态系统的工程化方法 总被引：17，自引：1，他引：17
我国中小河流的护岸工程只考虑工程的耐久性多采用混凝土护岸。忽略了河流的生态功能,破坏了河流的各种生态过程,导致河流污染严重,生态作用越来越小。本研究提出一种用芦苇恢复受损河岸的工程化方法,以解决恢复受损河岸时成本高,破坏了芦苇原生地的生态环境和芦苇不便于运输的问题。其优点在于：在保证能够达到防止河岸崩塌及侵蚀的同时,在河岸工程设计中纳入生态学原理．创造出动植物及微生物能够生存的多孔隙河岸工程生态结构;可以减少对芦苇原生地的破坏。并且能够快速、大量繁殖芦苇幼苗。快速恢复受损河岸的芦苇群落及其生态环境;此方法在减少劳力、时间和成本的基础上,能够更容易恢复浅水带和河岸缓冲带芦苇群落,构建出一个芦苇繁茂的水域。 相似文献
17.
Alexandra J. R. Carthey Kirstie A. Fryirs Timothy J. Ralph Haiyan Bu Michelle R. Leishman 《Freshwater Biology》2016,61(1):19-31
- Many plants disperse their seeds in waterbodies via hydrochoric transport. Despite a growing body of research into hydrochory, little is known about the fundamental seed traits that determine floatation ability or hydrochoric transport behaviour more generally. Seeds are transported in fluvial systems in one of three phases: surface transport, within the flow or incorporated in bedload. Seeds are often categorised as buoyant or non‐buoyant based on density, with little consideration of the morphological traits that determine how long seeds spend in each transport phase.
- We investigated the seed traits that best predict time spent floating under laboratory conditions, using sixty species of riparian plants from south‐eastern Australia. We measured and calculated key physical attributes (length, width, volume, surface area, mass, density, sphericity, roundness and shape category) and categorised seeds according to their primary dispersal modes (water/wind, vertebrate, adhesion, ants and unassisted).
- We used Cox's proportional hazards modelling to reveal that seed density and volume : surface area ratio were the physical traits that best predicted time spent floating. Volume : surface area ratio represents both seed size and shape, as it increases with size and sphericity. Our results showed that denser, larger and/or more spherical seeds (i.e. higher volume : surface area ratio) were poor floaters. They are therefore more likely to be transported in subsurface flow or as bedload.
- We combined our data with geomorphic models of sediment transport in flow to develop a biophysical process model of how hydrological forces and seed physical traits determine hydrochorous seed transport behaviour in rivers. The model describes how surface tension, buoyancy and flow velocity act on seed density and volume : surface area ratio to characterise time spent floating. We extrapolate from our data to conceptualise how these traits predict transitions between surface, subsurface and bedload transport. Hydrochoric seed transport behaviour and deposition are both threshold‐driven and multidirectional.
- Our process model is likely to be applicable across a range of different seed types in a range of rivers. It substantially increases our understanding of hydrochoric processes in rivers, lakes and lotic wetlands and will help illuminate the links between seed traits, hydrochoric transport and patterns of riparian vegetation and species composition.
18.
Rosa Menéndez;Geoff B. Monteith;Penny van Oosterzee;Noel D. Preece; 《Restoration Ecology》2024,32(4):e14104
With less than half of the world's tropical forests remaining, ecological restoration is urgently needed to halt biodiversity loss. However, the efficacy of different active reforestation methods remains largely untested particularly with respect to the recovery of fauna during the early years of restoration. Here, we present the results of a long-term restoration project in the Australian Wet Tropics after 6 years of planting. Using dung beetles as bioindicators of restoration success, we investigated how the diversity and density of trees in experimental plots influence the recovery of dung beetle diversity and their ecological functions (dung removal and secondary seed dispersal). We found that after only 6 years since planting, a native dung beetle community, representing around 41% of the species found in the adjacent rainforest, has colonized the experimental plots. Plots with the highest diversity of trees (24 species planted) showed higher dung beetle diversity, dung removal, and seed dispersal but only when the density of trees on the plots was low. These plots also have higher species richness, diversity, and abundance of rainforest species, while the opposite trend was found for open-habitat species. Therefore, planting a higher diversity of trees appears to be the best method for the early recovery of rainforest dung beetle communities and their functions. This is particularly crucial at low tree density, which is a common issue in active restoration projects as tree mortality is relatively high in the early years. 相似文献
19.
20.
Weed invasion success is strongly influenced by availability of seed dispersal vectors, which may include animals. We examined the potential of several small introduced mammals (mice, kiore, ship rats and possums) to disperse germinable seeds in New Zealand. Captive animals were fed fleshy fruit of weeds (Berberis glaucocarpa, Cotoneaster spp., Crataegus monogyna, Ilex aquifolium, Leycesteria formosa, Ligustrum sinense, Lonicera japonica, Passiflora mollissima, Pyracantha angustifolia, Sorbus hupehensis) and native species (Coprosma spp., Prumnopitys ferruginea and Solanum aviculare). We recorded the percentage of fruit consumed, seed ingested and gut passage time. Faeces were collected and the seeds extracted and tested for germination potential in an unheated glasshouse (two weed species) or under controlled conditions (11 species). The smallest rodents (mice and kiore) generally destroyed all seeds eaten. Large numbers of viable seeds of the small‐seeded (<1 mg) species, L. formosa and S. aviculare, passed through ship rats. Possums consumed the seeds of all adventive and native fruits except P. ferruginea. The proportion of seeds recovered intact from possum faeces varied with plant species and ranged from 6 to 83%. The time required for 50% of all seeds to be passed by possums ranged from 2.5 to 5.5 days with an average of 3.7 days, and was generally unrelated to simple fruit parameters such as percentage pulp and moisture content. For seeds where germination also occurred in the uneaten controls, the germination of seed from possums ranged from 3 to 78%. Germination was mostly lower in seeds from possums than in the controls, where differences were significant. Possums have major potential to disperse a wide range of fleshy fruit‐producing native and introduced plant species. Ship rats have the potential to disperse those with very small seeds. 相似文献