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1.
凋落物物理阻隔对格氏栲种子萌发及胚根生长的影响   总被引:1,自引:0,他引:1  
朱静  刘金福  何中声  邢聪  王雪琳  江蓝 《生态学报》2020,40(16):5630-5637
为了探讨凋落物物理阻隔对格氏栲天然林自然更新状况的影响,通过模拟野外凋落物覆盖,设置格氏栲种子上层覆盖厚0 cm(CK)、2 cm(D2)、4 cm(D4)、6 cm(D6)、8 cm(D8)及种子下层铺垫厚2 cm(U2)、4 cm(U4)凋落物等7个处理,分析凋落物覆盖方式及厚度对格氏栲种子萌发及胚根生长的影响。结果表明:(1)凋落物覆盖方式及厚度对种子萌发进程存在显著影响。CK萌发持续时间最长,上层覆盖处理(D)次之,下层铺垫处理(U)的种子起始萌发时间显著滞后。(2)CK种子萌发率最高,其次D6处理发芽速度较快,发芽整齐;U处理较D处理的发芽率及发芽势均显著降低,且萌发抑制率显著增加。(3)D处理的种子胚根生长速度快,胚根长度大于CK;U处理的种子胚根生长速度呈先慢后快趋势。可见,凋落物是影响格氏栲种子萌发及胚根生长的重要因素,主要通过阻碍种子与土壤接触而抑制萌发,影响格氏栲林更新。  相似文献   

2.
格氏栲天然林林窗和林下种子散布及幼苗更新研究   总被引:1,自引:0,他引:1  
以格氏栲(Castanopsis kawakamii)天然林为研究对象,探讨了林窗和林下格氏栲种子雨、种子库的分布特征及幼苗更新状况。结果表明:林窗种子雨总量和完好种子密度高于林下,未成熟种子比例低于林下;林窗和林下种子雨高峰期掉落数量分别占种子雨总量的77.13%和74.5%;林窗种子库储量低于林下,种子库中以全食或捡拾种子比例最高,其中种子库储量垂直分布表现为枯落物层(约占2/3)>腐殖质层(0~5 cm)(约占1/3)>心土层(5~10 cm)(小于1%),以格氏栲种子占绝对优势;格氏栲从种子到幼苗的转化率低,林窗中格氏栲完好种子密度与幼苗密度均高于林下。林窗微生境提高了种子散布过程中格氏栲成熟种子的密度和比例,有利于促进格氏栲的幼苗更新,表明林窗在格氏栲种群恢复过程中扮演着重要角色。  相似文献   

3.
探讨格氏栲(Castanopsis kawakamii)天然林林窗数量特征及其空间分布对预测森林种群动态变化及演替具有重要意义。该文采用无人机航拍获取格氏栲天然林正射影像图并结合野外调查,通过提取林窗特征参数和计算植被覆盖率来探讨林窗空间分布及其影响因素。结果表明:(1)保护区内格氏栲天然林植被覆盖率为75.53%,部分地区出现一定面积裸露土地。(2)研究区林窗空隙率为2.40%,密度为6.50ind.·hm-2,平均林窗面积为36.86 m2。(3)研究区林窗数量随林窗面积增加呈负指数分布,以微、小和中型林窗为主,面积100 m2以上的林窗数量较少。(4)低海拔林冠层覆盖度好,中海拔地区林窗个体数和平均林窗面积较大,高海拔地区林窗密度和空隙率相对较大。林窗主要分布在缓坡和斜坡上,其平均面积、密度和林窗空隙率也明显较高。西和南方位林窗数量较多,北、西北和东南方向林窗密度和空隙率相对较大。格氏栲天然林植被覆盖率较高,以微、小和中型林窗为主,地形因子通过改变林窗面积、林窗密度和林窗空隙率特征驱动了格氏栲天然林林窗数量与空间分布格局。  相似文献   

4.
The aim of this study is to analyze the effects of forest gaps on the variations of soil properties in Castanopsis kawakamii natural forest. Soil physical and chemical properties in various sizes and development stages were studied in C. kawakamii natural forest gaps. The results showed that forest gaps in various sizes and development stages could improve soil pore space structure and water characteristics, which may effectively promote the water absorbing capacity for plant root growth and play an important role in forest regeneration. Soil pore space structure and water characteristics in small gaps showed more obvious improvements, followed by the medium and large gaps. Soil pore space structure and water characteristics in the later development stage of forest gaps demonstrated more obvious improvements, followed by the early and medium development stages. The contents of hydrolysable N and available K in various sizes and development stages of forest gaps were higher than those of non-gaps, whereas the contents of total N, total P, available P, organic matter, and organic carbon were lower. The contents of total N, hydrolysable N, available K, organic matter, and organic carbon in medium gaps were higher than those of large and small gaps. The disturbance of forest gaps could improve the soils’ physical and chemical properties and increase the population species’ richness, which would provide an ecological basis for the species coexistence in C. kawakamii natural forest.  相似文献   

5.
ABSTRACT

The canopy disturbance, the gap environment, gap regeneration and maintenance of tree species diversity in the lower subtropical evergreen broad-leaved forest (LSEBF) of South China were studied in this paper. The most common manner of gap formation in the forest was by stem breakage. Most gaps were formed by two gap makers. The sizes of most expanded gaps (EG) and canopy gaps (CG) were in the range of 100 – 300 m2 and 50 – 100 m2, respectively. The ecological factors in gaps were analysed on the basis of contrasting measurement of the microclimatic regimes in gaps of different sizes and in non-gap stands. Tree species in the LSEBF were classified into 5 ecological species groups on the bases of their changes in order of importance values in gaps and in non-gap stands. Most of the species reached their peak of regeneration density around the gap sizes of 100 m2 and 500 m2. The curves of regeneration density vs. gap age for major species revealed two types. Regeneration densities of most species, and species diversity indices in gaps were greater than those in non-gap stands.  相似文献   

6.
Decoated pepper (Capsicum annuum L. cv Early Calwonder) seeds germinated earlier at 25°C, but not at 15°C, compared to coated seeds. The seed coat did not appear to impose a mechanical restriction on pepper seed germination. Scarification of the endosperm material directly in front of the radicle reduced the time to germination at both 15°C and 25°C.

The amount of mechanical resistance imposed by the endosperm on radicle emergence before germination was measured using the Instron Universal Testing Machine. Endosperm strength decreased as imbibition time increased. The puncture force decreased faster when seeds were imbibed at 25°C than at 15°C. The reduction in puncture force corresponded with the ability of pepper seeds to germinate. Most radicle emergence occurred at 15°C and 25°C after the puncture force was reduced to between 0.3 and 0.4 newtons.

Application of gibberellic acid4+7 (100 microliters per liter) resulted in earlier germination at 15°C and 25°C and decreased endosperm strength sooner than in untreated seeds. Similarly, high O2 concentrations had similar effects on germination earliness and endosperm strength decline as did gibberellic acid4+7, but only at 25°C. At 15°C, high O2 concentrations slowed germination and endosperm strength decline.

  相似文献   

7.
Abstract. We conducted a study in the laurel forest of Tenerife (Canary Islands, Spain) to describe the characteristics of natural gaps and to assess the role of treefall gaps in forest dynamics. Very little is left of the natural laurel forest with i.a. Laurus azorica, Ilex canariensis and Prunus lusitanica. We looked for treefall gaps in 80 randomly located 2500 m2 plots. These plots represented ca. 1% of the remaining and protected laurel forest of Tenerife. We recorded the characteristics of the species causing the gaps, gap architecture and gap age in all observed gaps larger than 10 m2. We inventoried the regeneration in each gap and in a neighbouring control plot with the same topography. Large gaps (>75 m2) were not common in the laurel forest. The absence of large gaps could be due to the physiognomy of the vegetation, the mild weather or the rarity of disturbances. Instead of forming gaps, many trees decompose in place and branches from neighbouring trees and suckers from the decomposed trees occupy the free space. Also, the high rate of asexual regeneration could contribute to the fast closing of the gap. The number of gaps created by Prunus lusitanica was higher than expected (based on canopy composition) while Ilex canariensis and Laurus azorica created fewer gaps. In this evergreen forest, differences between gap and non-gap conditions are not as distinct as in other forest types. Only 0.4% of the canopy is in the gap phase (0.6% including gaps smaller than 10m2). No differences were found in patterns of regeneration between gap and non-gap phases in the forest. Gaps do not explain the persistence of pioneer species in the laurel forest.  相似文献   

8.

Background and Aims

In neotropical forests, very small-seeded pioneer species (<0·1 mg seed mass) recruit preferentially in small tree fall gaps and at gap edges, but large-seeded pioneers do not. Since water availability is related to gap size, these differences in microsite preference may reflect in part species-specific differences in germination at reduced water potentials.

Methods

For 14 neotropical pioneer species, the hypothesis is tested that small-seeded species, with shallow initial rooting depths, reduce the risks associated with desiccation by germinating more slowly and at higher water potentials than large-seeded species.

Key Results

Germination occurred both more quickly and at lower water potentials with increasing seed mass. For example, Ochroma pyramidale (seed mass 5·5 mg) had a time to 50 % germination (T50) of 2·8 d and a median base potential for germination (ψb50) of −1·8 MPa while Clidemia quinquenervia (seed mass 0·017 mg) had a T50 of 17·6 d and ψb50 of −1·1 MPa.

Conclusions

These data suggest that small-seeded species germinate only in comparatively moist microsites, such as small canopy gaps, which may reduce the risk of drought-induced mortality. Conversely, large-seeded species are able to germinate in the drier environment of large gaps, where they benefit by enhanced seedling growth in a high irradiance environment. The positive association of seed size and canopy gap size for optimal seedling establishment is maintained by differential germination responses to soil water availability coupled with the scaling of radicle growth rate and seed size, which collectively confer greater drought tolerance on large-seeded species.Key words: Germination, seed size, Panamá, neotropical, pioneer, water potential  相似文献   

9.
Loosening of cell walls is an important developmental process in key stages of the plant life cycle, including seed germination, elongation growth, and fruit ripening. Here, we report direct in vivo evidence for hydroxyl radical (·OH)-mediated cell wall loosening during plant seed germination and seedling growth. We used electron paramagnetic resonance spectroscopy to show that ·OH is generated in the cell wall during radicle elongation and weakening of the endosperm of cress (Lepidium sativum; Brassicaceae) seeds. Endosperm weakening precedes radicle emergence, as demonstrated by direct biomechanical measurements. By 3H fingerprinting, we showed that wall polysaccharides are oxidized in vivo by the developmentally regulated action of apoplastic ·OH in radicles and endosperm caps: the production and action of ·OH increased during endosperm weakening and radicle elongation and were inhibited by the germination-inhibiting hormone abscisic acid. Both effects were reversed by gibberellin. Distinct and tissue-specific target sites of ·OH attack on polysaccharides were evident. In vivo ·OH attack on cell wall polysaccharides were evident not only in germinating seeds but also in elongating maize (Zea mays; Poaceae) seedling coleoptiles. We conclude that plant cell wall loosening by ·OH is a controlled action of this type of reactive oxygen species.  相似文献   

10.
The seed dispersal mechanisms and regeneration of various forest ecosystems can benefit from the actions of carnivores via endozoochory. This study was aimed to evaluate the role of carnivores in endozoochory and diploendozoochory, as well as their effect on seed viability, scarification, and germination in two forest ecosystems: temperate and tropical dry forest. We collected carnivore scat in the Protected Natural Area of Sierra Fría in Aguascalientes, Mexico, for 2 years to determine the abundance and richness of seeds dispersed by each carnivore species, through scat analysis. We assessed seed viability through optical densitometry using X‐rays, analyzed seed scarification by measuring seed coat thickness using a scanning electron microscope, and evaluated seed germination in an experiment as the percentage of seeds germinated per carnivore disperser, plant species, and forest type. In the temperate forest, four plant species (but mainly Arctostaphylos pungens) were dispersed by four mammal species. The gray fox dispersed the highest average number of seeds per scat (66.8 seeds). Bobcat dispersed seeds through diploendozoochory, which was inferred from rabbit (Sylvilagus floridanus) hair detected in their scats. The tropical dry forest presented higher abundance of seeds and richness of dispersed plant species (four species) than in the temperate forest, and the coati dispersed the highest number of seeds (8,639 seeds). Endozoochory and diploendozoochory did not affect viability in thick‐testa seeds (1,480 µm) in temperate forest and thin‐testa seeds (281 µm) in tropical dry forest. Endozoochory improved the selective germination of seeds. Nine plant species were dispersed by endozoochory, but only one species (Juniperus sp.) by diploendozoochory. These results suggest that carnivores can perform an important ecological function by dispersing a great abundance of seeds, scarifying these seeds causing the formation of holes and cracks in the testas without affecting viability, and promoting the selective germination of seeds.  相似文献   

11.
Stevia rebaudiana (Bert.) is an emerging sugar alternative and anti-diabetic plant in Pakistan. That is why people did not know the exact time of propagation. The main objective of the present study was to establish feasible propagation methods for healthy biomass production. In the present study, seed germination, stem cuttings and micropropagation were investigated for higher productivity. Fresh seeds showed better germination (25.51–40%) but lost viability after a few days of storage. In order to improve the germination percentage, seeds were irradiated with 2.5, 5.0, 7.5 and 10 Gy gamma doses. But gamma irradiation did not show any significant change in seed germination. A great variation in survival of stem cutting was observed in each month of 2012. October and November were found the most suitable months for stem cutting survival (60%). In order to enhance survival, stem cuttings were also dipped in different plant growth regulators (PGRs) solution. Only indole butyric acid (IBA; 1000 ppm) treated cutting showed a higher survival (33%) than control (11.1%). Furthermore, simple and feasible indirect regeneration system was established from leaf explants. Best callus induction (84.6%) was observed on MS-medium augmented with 6-benzyladenine (BA) and 2,4-dichlorophenoxyacetic acid (2,4-D; 2.0 mg l−1). For the first time, we obtained the highest number of shoots (106) on a medium containing BA (1.5 mg l−1) and gibberellic acid (GA3; 0.5 mg l−1). Plantlets were successfully acclimatized in plastic pots. The current results preferred micropropagation (85%) over seed germination (25.51–40%) and stem cutting (60%).  相似文献   

12.
Mast seeding, the synchronized interannual variation in seed production of trees, is a well‐known bottom‐up driver for population densities of granivorous forest rodents. Such demographic effects also affect habitat preferences of the animals: After large seed production events, reduced habitat selectivity can lead to spillover from forest patches into adjacent alpine meadows or clear‐cuts, as has been reported for human‐impacted forests. In unmanaged, primeval forests, however, gaps created by natural disturbances are typical elements, yet it is unclear whether the same spillover dynamics occur under natural conditions. To determine whether annual variation in seed production drives spillover effects in naturally formed gaps, we used 14 years of small mammal trapping data combined with seed trap data to estimate population densities of Apodemus spp. mice and bank voles (Myodes glareolus) on 5 forest sites with differing disturbance history. The study sites, located in a forest dominated by European beech (Fagus sylvatica), Norway spruce (Picea abies), and silver fir (Abies alba), consisted of two primeval forest sites with small canopy gaps, two sites with larger gaps (after an avalanche event and a windthrow event), and a managed forest stand with closed canopy as a control. Hierarchical Bayesian N‐mixture models revealed a strong influence of seed rain on small rodent abundance, which were site‐specific for M. glareolus but not for Apodemus spp. Following years of moderate or low seed crop, M. glareolus avoided open habitat patches but colonized those habitats in large numbers after full mast events, suggesting that spillover events also occur in unmanaged forests, but not in all small rodents. The species‐ and site‐specific characteristics of local density responding to food availability have potentially long‐lasting effects on forest gap regeneration dynamics and should be addressed in future studies.  相似文献   

13.
To promote the natural regeneration of secondary forests under gap disturbance is one of important approaches for realizing their restoration and sustainable management. However, soil seed bank, one of regeneration strategies, is poorly understood in gaps of secondary forests. Objectives of the study were to evaluate the effects of sizes of experimentally created gaps on seed distribution in soil, and of seed banks on vegetation recovery at early formation stage of gaps in temperate secondary forests, Northeast China. It was found that with increasing gap size, species richness in the seed bank significantly increased (r?=?0.691, P?<?0.05, n?=?10), but correspondence in species-composition of seed reservoir between gaps and canopies adjacent to gaps decreased (r?=??0.83, P?<?0.01, n?=?10). Gap size and soil depth and their two-way interactions had significant differences on the distribution of seed bank density (F?=?4.101, P?<?0.05; F?=?34.483, P?<?0.01; F?=?5.232, P?<?0.01, respectively). The Sokal and Sneath similarity indices in species-composition between extant and potential (seed bank) vegetation were generally low, ranging from 0.06 (interior of large gaps) to 0.24 (canopies adjacent to large gaps). From the view of seed bank to restore temperate secondary forests, establishment of medium-sized artificial gaps (i.e., gap size with 500–150 m2) could be more feasible for seed invasion. To conclude, the regeneration potential out of soil seed banks is limited, and the restoration of gaps at early formation stage may be mostly dependent on other reproductive strategies (e.g., vegetative propagation of species).  相似文献   

14.
Among coastal plant species at risk from rapid environmental changes is the North American Great Lakes dune endemic Cirsium pitcheri. Despite being listed as federally threatened, little is known about how C. pitcheri seed attributes influence germination and dormancy‐break patterns in the context of climate change. Following a previous work where we found differences in the number and weight of C. pitcheri seeds among capitulum positions and study sites, here we examine the effects of seed attributes (capitulum position, seed weight, and site of origin) on the proportion and timing of C. pitcheri seed germination under temperature treatments that simulate projected warming in the Great Lakes (20/10, 25/10, and 30/10°C day/night). Our results demonstrate that C. pitcheri produces diverse cohorts of seeds with seed attributes that significantly influence the timing and probability of germination over a 3‐year soil seed bank. Cirsium pitcheri seed germination proportions were highest at 20°C and decreased successively at 25 and 30°C. Seeds from terminal capitula also had higher germination proportions and took longer to germinate than those from secondary capitula. Lastly, the effect of seed weight on germination probability depended on site of origin and capitulum position, with all effects varying in size and significance over time. Ultimately, our results highlight the considerable differences in germination patterns exhibited by seeds from different capitulum positions and sites of origin and provide insight into the dormancy‐break patterns that C. pitcheri might experience under predicted temperature rise in the Great Lakes region of North America.  相似文献   

15.
Agricultural biotechnology is very familiar with the properties of nanomaterial and their potential uses. Therefore, the present experiment was conducted to test the beneficial effects of nanosilicon dioxide (nSiO2: size- 12 nm) on the seed germination of tomato (Lycopersicum esculentum Mill. cv Super Strain B). Application of nSiO2 significantly enhanced the characteristics of seed germination. Among the treatments, 8 g L−1 of nSiO2 improved percent seed germination, mean germination time, seed germination index, seed vigour index, seedling fresh weight and dry weight. Therefore, it is very clear that nSiO2 has a significant impact on the seed germination potential. These findings could provide that alternative source for fertilizer that may improve sustainable agriculture.  相似文献   

16.
Two tomato (Lycopersicon esculentum Mill.) lines with greatly different capabilities to germinate at 10°C were compared with respect to sensitivity to experimental treatments which affect the water status of the embryo. Germination rates and final percentages could be drastically changed (at 25°C) by (a) removing the mechanical constraint from the radicle tip, (b) imposing water stress by an osmoticum, (c) stress hardening of the seeds through osmotic pretreatment, and (d) inhibiting embryo expansion by abscisic acid (ABA). All treatments showed a similar difference in germination vigor between the two lines indicating that cold sensitivity is in fact a matter of water relations rather than of phase transitions in membrane lipids. Inhibition of germination by ABA was completely abolished by removing the mechanical constraint from the radicle tip. Osmotic stress of −3 bar which quantitatively replaced this constraint in inhibiting germination also restored the sensitivity to ABA. It is concluded that all these treatments act on the balance between the hydraulic extension force of the embryo radicle and the opposing force of the seed layers covering the radicle tip. The difference in cold sensitivity between the two seed lines resides either in the osmotic potential or the pressure potential of the germinating embryo.  相似文献   

17.
哀牢山中山湿性常绿阔叶林林窗更新研究   总被引:21,自引:2,他引:19  
对云南哀牢山中山湿性常绿阔叶林林窗更新状况的调查结果表明,林内优势树种在林窗阶段不占优势,其在林窗内的重要值显著低于成熟林分;林窗内外的乔木幼苗在组成上存在较大差异,林窗内的幼苗多样性(H=2.73,D=0.89)高于林冠下(H=2.25,D=0.82),二者的Jaccard相似系数只有0.6.许多树种的幼苗只出现在林窗内;林窗内的乔木幼苗密度(38636株·hm2)远远高于林冠下(17323株·hm2).林窗内和林冠下的乔木幼苗(H≤50cm)均以高度为11~20cm幼苗的在数量上占优势,但林窗内高度超过20cm的幼苗比例明显高于林冠下;林窗大小对乔木幼苗更新有重要影响,不同树种的幼苗密度高峰出现在不同大小级别的林窗内.  相似文献   

18.
To explore within-gap spatial patterns of soil surface CO2 flux, we measured instantaneous soil surface CO2 flux, soil surface temperature, and soil moisture in north–south transects across canopy gaps and in adjacent contiguous forest from April to November 2010 in a second-growth northern hardwood forest in Wisconsin, USA. Throughout the growing season, soil surface CO2 flux was higher in the northern 1/3 and northern edge of gaps compared to the central and southern portions. These patterns were driven primarily by within-gap variation in soil temperature, which was itself driven by within-gap patterns of insolation. Most locations in the northern 1/3 and northern edge of gaps had significantly higher modeled total growing season C flux (mean 725 g C m−2) compared to the contiguous forest (mean 706 g C m−2), whereas C flux in the central and southern portions of gaps (mean 555 g C m−2) was significantly lower than both the contiguous forest and the northern portions of gaps.  相似文献   

19.
Seed recruitment is a major driver of mangrove restoration globally. It is hypothesized that soil condition and channel hydrology can accelerate seedling recruitment and regeneration after a major disturbance. Species abundance, diversity indices, microbial and chemical concentrations in sand‐filled mangrove forest was studied. Eight plots measuring 487.77 m2 each were established with ten transects in each plot in a random block design to investigate the effect of soil conditions on seedling growth. A total of 1,886 seedlings were counted. Seedling abundance was significantly different between red (Rizophora racemosa), white (Laguncularia racemosa), and black (Avicennia germinans) mangroves, and nypa palm (nypa fruticans). The most dominant species was black mangrove, and the least dominant species was nypa palm. Muddy soils had the most abundant species (n = 994) followed by sandy (n = 457) and semi‐muddy (435) soils. Furthermore, sandy soils had the highest species diversity (H = 0.896) followed by semi‐muddy (H = 0.876) and muddy (H = 0.583) soils. The soil metal concentration has no correlation with seed abundance and occur in the order Iron > Nitrate > Copper > Cadmium. Soil with high species diversity had high soil microbial population; however, seedling abundance was correlated with soil nutrients and not heavy metals. Small seeds are easily recruited while good soil condition plus existing hydrological connection facilitated natural seedling regeneration in the disturbed mangrove forest.  相似文献   

20.
Ramonda serbica and Ramonda nathaliae are rare and endemo relict plant species from Balkan Peninsula. An efficient micro propagation and in vitro conservation method via direct and indirect organogenesis from seed and leaf explants, respectively, was established in this study. The seed of both Ramonda species were collected from different populations in Kosovo, and were germinated in nutrient media JG-B without any phytohormone. The highest number of shoots and multiplication rate was observed on JG-B medium supplemented with BAP and IAA (0.5 mg l−1 each), whereas the highest number of leaves per plantlets was found on WPM and RA medium supplemented with BAP and IAA (0.1 mg l−1 each). During this stage of micro propagation some significant differences were observed in plantlets from different populations. The indirect organogenesis from parts of leaves of natural plants was not successful due to unavailability of established protocol for disinfections of the plant material. On other hand, parts of leaves from micro propagated plantlets, cultured on MS medium supplemented with different ratio of BAP and NAA, resulted in the highest efficiency for shoot regeneration. In vitro conservation of micro propagated plants at the lower temperature (4 °C) had a significantly positive effect for storage of more than 12 months.  相似文献   

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