scholarly journals Rainfall patterns after fire differentially affect the recruitment of three Mediterranean shrubs

2011 ◽  
Vol 8 (3) ◽  
pp. 5761-5786 ◽  
Author(s):  
J. M. Moreno ◽  
E. Zuazua ◽  
B. Pérez ◽  
B. Luna ◽  
A. Velasco ◽  
...  
Keyword(s):  
Seedling Recruitment ◽  
Soil Seed Bank ◽  
Rainfall Variability ◽  
Seedling Emergence ◽  
Fire Season ◽  
First Year ◽  
Mediterranean Shrubs ◽  
Rainfall Patterns ◽  
Fire Characteristics ◽  
Projected Changes

Abstract. In fire-prone environments, the "event-dependent hypothesis" states that plant population changes are driven by the unique set of conditions of a fire (e.g., fire season, climate). Climate variability, in particular changes in rainfall patterns, can be most important for seeder species, since they must regenerate after fire from seeds, and for Mediterranean shrublands, given the high yearly variability of rainfall in these ecosystems. Yet, the role of rainfall variability and its interaction with fire characteristics (e.g., fire season) on plant populations has received little attention. Here we investigated the changes in seedling emergence and recruitment of three seeder species (Cistus ladanifer, Erica umbellata and Rosmarinus officinalis) after fires lit during three different years and at two times during the fire season (early and late in the fire season) to account for potential changes in the soil seed-bank during the year. Three plots were burned at each season, for a total of 18 plots burned during the three years. After fire, emerged seedlings were tallied, tagged and monitored during three years (two the last burning year). Rainfall during the study period was rather variable, and in some years was well below average. Seedling emergence after fire varied by a factor of 3 to 10, depending on the species and on the burning year. The bulk of seedling emergence occurred in the first year after fire, and seedling recruitment at the end of the study period was tightly correlated with this early emergence. Seedling emergence in E umbellata and R officinalis, but not in C ladanifer, were correlated with precipitation in the fall and winter immediately after the fire, being E umbellata most sensitive to low rainfall. Fire season was generally not an important factor in controlling emergence and recruitment. We discuss how projected changes in rainfall patterns with global warming can alter the balance of species in this shrubland, and can drive some species to near local extinction.

scholarly journals Rainfall patterns after fire differentially affect the recruitment of three Mediterranean shrubs

2011 ◽  
Vol 8 (12) ◽  
pp. 3721-3732 ◽  
Author(s):  
J. M. Moreno ◽  
E. Zuazua ◽  
B. Pérez ◽  
B. Luna ◽  
A. Velasco ◽  
...  
Keyword(s):  
Seedling Recruitment ◽  
Rainfall Variability ◽  
Seedling Emergence ◽  
Fire Season ◽  
First Year ◽  
Mediterranean Shrubs ◽  
Rainfall Patterns ◽  
Fire Characteristics ◽  
Projected Changes ◽  
In Fire

Abstract. In fire-prone environments, the "event-dependent hypothesis" states that plant population changes are driven by the unique set of conditions of a fire (e.g. fire season, climate). Climate variability, in particular changes in rainfall patterns, can be most important for seeder species, since they regenerate after fire from seeds, and for Mediterranean shrublands, given the high yearly variability of rainfall in these ecosystems. Yet, the role of rainfall variability and its interaction with fire characteristics (e.g. fire season) on plant populations has received little attention. Here we investigated the changes in seedling emergence and recruitment of three seeder species (Cistus ladanifer, Erica umbellata and Rosmarinus officinalis) after fires lit during three different years and at two times (early and late) during the fire season. Three plots were burned at each season, for a total of 18 plots burned during the three years. After fire, emerged seedlings were tallied, tagged and monitored during three years (two in the last burning year). Rainfall during the study period was rather variable and, in some years, it was well below average. Postfire seedling emergence varied by a factor of 3 to 12, depending on the species and on the burning year. The bulk of seedling emergence occurred during the first year after fire; seedling recruitment at the end of the study period was tightly correlated with this early emergence. Emergence in Erica and Rosmarinus, but not in Cistus, was correlated with precipitation in the fall and winter immediately after fire, with Erica being the most sensitive to reduced rainfall. Fire season was generally neither an important factor in controlling emergence nor, in particular, recruitment. We discuss how projected changes in rainfall patterns with global warming could alter the balance of species in this shrubland, and could drive some species to near local extinction.

Seed germination at different temperatures and seedling emergence at different depths of Rhamnus spp

2014 ◽  
Vol 9 (5) ◽  
pp. 569-578 ◽  
Author(s):  
Hanan Aou-ouad ◽  
Hipólito Medrano ◽  
Ahmed Lamarti ◽  
Javier Gulías
Keyword(s):  
Seed Germination ◽  
Seedling Recruitment ◽  
Seedling Emergence ◽  
Burial Depth ◽  
Temperature Regimes ◽  
Mediterranean Shrubs ◽  
Different Temperatures ◽  
Temperature Ranges ◽  
Different Depths ◽  
Rhamnus Alaternus

AbstractRhamnus alaternus and R. ludovici-salvatoris, two Mediterranean shrubs with different geographic distributions, have shown important differences in seedling recruitment capacity. The objectives of this work were to determine the ability of these species to germinate seeds under different temperature ranges, as well as the capacity of seedlings to emerge from different burial depths, in order to better understand their regeneration processes. Two different experiments were performed. In the first one, seed germination was studied in Petri dishes and in the dark at different temperature regimes: a) 5–15°C, b) 10–20°C and c) 15–25°C (12h/12h). In the second experiment, seedling emergence capacity from different burial depths (0.5, 2 and 5 cm) was tested. R. ludovici-salvatoris showed a significantly higher final germination rates, a lower dormancy period, and average time response at 10–20°C than at other temperature ranges, although differences were much greater when seeds were subjected to the 5–15°C temperature regime. By contrast, R. alaternus did not show significant differences between treatments (5–15°C and 10–20°C) in germination behavior. Seedling emergence of both species was lower and slower when seeds were buried at 5 cm. However, R. ludovici-salvatoris always showed a lower seedling emergence capacity than R. alaternus at any burial depth. The low ability of R. ludovici-salvatoris to germinate seeds and emerge between 5–15°C, even from shallow depths, is discussed in relation to its low regeneration capacity and declining geographic distribution.

Ecological Studies of the Endangered Rutidosis Leptorrhynchoides .I. Seed Production, Soil Seed Bank Dynamics, Population Density and Their Effects on Recruitment

1995 ◽  
Vol 43 (1) ◽  
pp. 1 ◽  
Author(s):  
JW Morgan
Keyword(s):  
Population Density ◽  
Seed Production ◽  
Seed Bank ◽  
Seedling Recruitment ◽  
Fire Regime ◽  
Seedling Survival ◽  
Soil Seed Bank ◽  
Seedling Emergence ◽  
Seed Bank Dynamics ◽  
The Impact

The seasonal dynamics of the soil seed bank of Rutidosis leptorrhynchoides F.Muell. were studied by the seedling emergence technique. Seed longevity in soil was quantified in a seed burial and retrieval experiment. The importance of annual seed production to recruitment was also determined over a 2-year-period, as was the impact of conspecific neighbour density on seed production per inflorescence. Rutidosis leptorrhynchoides appears to form a transient seed bank with little capacity to store germinable seeds in the soil from year to year. No seedlings were observed in soil sampled after the autumn germination pulse and no viable seed was present in the soil within 16 weeks of burial. The rate of seed loss was similar when seed was buried under all intact grassland canopy and in 0.25m2 canopy gaps. It appears that most seeds simply rot in moist soil or are predated by soil invertebrates. Seedling recruitment was at least 15 times greater in plots where natural seed input occurred than where it was curtailed. Less than 10% of seed shed resulted in seedling emergence. It is suggested that recruitment in the large populations studied was limited by germination rather than by microsite availability for seedling survival. Population density had an impact on seed production with sparsely distributed individuals producing fewer seeds per inflorescence than plants from denser colonies, although there was much variation. Sparse plants produced significantly fewer seeds per inflorescence than hand crosspollinated heads suggesting reduced pollinator efficacy in these colonies relative to larger colonies where there was no such difference. Rutidosis leptorrhynchoides is dependent on the maintenance of the standing population for recruitment. Any factors that influence flowering and subsequent seed production will limit the ability of the species to regenerate. Over sufficient time, this could lead to the localised extinction of the species and may explain why R. leptorrhynchoides has failed to reappear in remnants where a suitable fire regime has been re-implemented after a period of management unfavourable to the survival, flowering and regeneration of this species.

Seedling Emergence of Winter Annual Grasses as Affected by Limited Tillage and Crop Canopy

1998 ◽  
Vol 12 (2) ◽  
pp. 262-267 ◽  
Author(s):  
R. L. Anderson
Keyword(s):  
Cultural Practices ◽  
Soil Seed Bank ◽  
Seedling Emergence ◽  
First Year ◽  
Downy Brome ◽  
Crop Canopy ◽  
Proso Millet ◽  
Jointed Goatgrass ◽  
Annual Grasses ◽  
Tillage Operation

Jointed goatgrass and downy brome continue to plague winter wheat producers in the western United States. Because there are no effective herbicides for in-crop control of these weeds, producers are seeking cultural practices that stimulate seed germination and deplete the soil seed bank. We determined the effect of limited tillage and crop canopy on seedling emergence of these grasses. One tillage operation with a sweep plow increased jointed goatgrass seedling emergence 74% in the first year but did not affect emergence in later years. Downy brome emergence was not affected by tillage. Jointed goatgrass seedlings emerged over 5 yr, whereas downy brome did not emerge after 3 yr. Seedling emergence of both species was two times greater in corn and barley than in proso millet. Producers will accrue more benefit for seedbank management with cultural strategies such as alternative rotations and competitive wheat canopies than with limited tillage using a sweep plow.

scholarly journals Relating Rainfall Patterns to Agricultural Income: Implications for Rural Development in Mozambique

2014 ◽  
Vol 6 (2) ◽  
pp. 218-237 ◽  
Author(s):  
Julie A. Silva ◽  
Corene J. Matyas
Keyword(s):  
Rainfall Variability ◽  
Rural Households ◽  
Well Being ◽  
First Year ◽  
Agricultural Income ◽  
Growing Seasons ◽  
Rainfall Patterns ◽  
Crop Agriculture ◽  
Staple Crop ◽  
Normal Rainfall

Abstract Rural farmers in Mozambique rely on rain-fed agriculture for food and income, yet they experience high rainfall variability ranging from extreme drought to flooding rainfall from tropical cyclone systems. To explore linkages between rainfall and agriculture, the authors regress changes in annual household per capita agricultural income on reliance on staple food crops, agricultural and demographic characteristics, and rainfall patterns using longitudinal data for rural households for 2002 and 2005. They characterize rainfall patterns by defining nine rainfall zones using the percent of normal rainfall received in each month of three agricultural growing seasons and rainfall from two tropical cyclones that occurred during the study period. Results show that in a period where monthly rainfall seldom occurred in normal amounts, most households experienced decreases in agricultural income. Even after controlling for rainfall patterns, they find that greater household dependency on staple crop agriculture is associated with declining annual agricultural income. They also find that areas affected by both wet and dry rainfall extremes in the first year of the study had decreases in the well-being of rural households when measured two years later. Taken together, their findings suggest that antipoverty policies focused on increasing agricultural income seem likely to fail in countries characterized by highly variable rainfall and exposure to extreme events, particularly when coupled with high levels of poverty and widespread dependence on rain-fed agriculture.

Biology and control of Reseda lutea L. 2. Life cycle: seedling emergence, recruitment, and vegetative reproduction

1997 ◽  
Vol 48 (4) ◽  
pp. 517 ◽  
Author(s):  
J. W. Heap
Keyword(s):  
Life Cycle ◽  
Seedling Recruitment ◽  
Vegetative Reproduction ◽  
Seedling Emergence ◽  
Soil Surface ◽  
First Year ◽  
Shoot Production ◽  
Tap Root ◽  
And Control ◽  
Fluctuating Temperatures

The reproductive biology of Reseda lutea L. was studied in the laboratory and field in southern Australia. Seedling emergence was greatest from 5 mm depth (57%) to 10 mm (53%) but also occurred from 80 mm. Seeds on the soil surface did not germinate. Following cultivation of a field population, seedling emergence was high (144/m2) in the first winter and recruitment to the perennial population was estimated at 10·2%. Seedling emergence in subsequent winters was low. Perennial shoot numbers increased gradually in the first year after cultivation, from seedling recruitment and daughter shoots, and then stabilised at around 28/m2. Shoots formed on root fragments at a range of constant and fluctuating temperatures between 10° and 35°C, with a maximum of 17·3 shoots per 50-mm fragment at 15°C. Shoot production increased with root fragment length and diameter. Shoots were produced on root fragments as short as 10 mm and as thin as 1 mm. Fragments from the upper tap root produced more shoots than those from further down the tap root, or from laterals. An illustrated model of the life cycle of R. lutea in Australia is presented.

Impact of sowing, canopy cover and litter on seedling dynamics of two Polylepis species at upper tree lines in central Ecuador

2007 ◽  
Vol 23 (3) ◽  
pp. 309-318 ◽  
Author(s):  
Arne Cierjacks ◽  
Juan Enrique Iglesias ◽  
Karsten Wesche ◽  
Isabell Hensen
Keyword(s):  
Linear Models ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Seedling Emergence ◽  
Canopy Cover ◽  
Climatic Conditions ◽  
First Year ◽  
Tree Line ◽  
Seedling Dynamics ◽  
Log Linear

Failure of reproduction is hypothesized as being a main reason for the formation of upper tree lines but there is, as yet, little supportive evidence of such. This study investigates the effects of experimental sowing, canopy cover and litter depth on seedling emergence and survival of Polylepis incana and Polylepis pauta at the upper distribution limit of the species in the Páramo de Papallacta, central Ecuador. We established 18 study plots located in the interior, at the edge and at the exterior of closed forests at the upper tree line and analysed seedling dynamics for 1 y following experimental sowing with four different litter treatments. For both species, seedling numbers were significantly higher in the forest interior than outside, and higher in the treatments with the litter layer removed. In P. pauta, sowing significantly increased seedling number, which was more pronounced within and at the edge of the forest than outside. In contrast, there was no impact of sowing on seedling emergence in P. incana. First-year seedling survival and mean growth rate per month were low in both species. Log-linear models did not reveal significant interactions between survival and canopy cover or litter removal. Our data show that seedling recruitment is limited at the upper tree line – presumably due to extreme climatic conditions – which indicates the importance of constraints in sexual regeneration for tree-line formation in central Ecuador.

scholarly journals Differential Influences of Teleconnections from the Indian and Pacific Oceans on Rainfall Variability in Southeast Asia

Atmosphere ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 886
Author(s):  
Abdul Azim Amirudin ◽  
Ester Salimun ◽  
Fredolin Tangang ◽  
Liew Juneng ◽  
Muhamad Zuhairi
Keyword(s):  
Indian Ocean ◽  
Southeast Asia ◽  
El Niño ◽  
El Nino ◽  
Rainfall Variability ◽  
June July August ◽  
Rainfall Patterns ◽  
Negative Impacts ◽  
The Individual ◽  
June July

This study investigates the individual and combined impacts of El Niño and the positive Indian Ocean Dipole (IOD) on the Southeast Asia (SEA) rainfall variability. Using composite and partial correlation techniques, it is shown that both inter-annual events have individually distinct impacts on the SEA rainfall anomaly distribution. The results showed that the impacts of the co-occurrence of El Niño and IOD events are significant compared to the individual effects of pure El Niño or pure IOD. During June-July-August and September-October-November, the individual impacts of the pure El Niño and IOD events are similar but less significant. Both events caused negative impacts over the southern part of SEA during June-July-August (JJA) and propagated northeastward/eastward during September-October-November (SON). Thus, there are significant negative impacts over the southern part of SEA during the co-occurrence of both events. The differential impacts on the anomalous rainfall patterns are due to the changes in the sea surface temperature (SST) surrounding the region. Additionally, the differences are also related to the anomalous regional atmospheric circulations that interact with the regional SST. The anomalous Walker circulation that connects the Indian Ocean and tropical Pacific Ocean also plays a significant role in determining the regional anomalous rainfall patterns.

Variation in vegetation cover and seedling performance of tree species in a forest-savanna ecotone

2019 ◽  
Vol 35 (2) ◽  
pp. 74-82 ◽  
Author(s):  
Hamza Issifu ◽  
George K. D. Ametsitsi ◽  
Lana J. de Vries ◽  
Gloria Djaney Djagbletey ◽  
Stephen Adu-Bredu ◽  
...  
Keyword(s):  
Vegetation Cover ◽  
Seedling Recruitment ◽  
Seedling Survival ◽  
Tree Cover ◽  
First Year ◽  
Transplant Experiment ◽  
Tree Seedling ◽  
Savanna Woodland ◽  
Specific Effects ◽  
Species Specific

AbstractDifferential tree seedling recruitment across forest-savanna ecotones is poorly understood, but hypothesized to be influenced by vegetation cover and associated factors. In a 3-y-long field transplant experiment in the forest-savanna ecotone of Ghana, we assessed performance and root allocation of 864 seedlings for two forest (Khaya ivorensis and Terminalia superba) and two savanna (Khaya senegalensis and Terminalia macroptera) species in savanna woodland, closed-woodland and forest. Herbaceous vegetation biomass was significantly higher in savanna woodland (1.0 ± 0.4 kg m−2 vs 0.2 ± 0.1 kg m−2 in forest) and hence expected fire intensities, while some soil properties were improved in forest. Regardless, seedling survival declined significantly in the first-year dry-season for all species with huge declines for the forest species (50% vs 6% for Khaya and 16% vs 2% for Terminalia) by year 2. After 3 y, only savanna species survived in savanna woodland. However, best performance for savanna Khaya was in forest, but in savanna woodland for savanna Terminalia which also had the highest biomass fraction (0.8 ± 0.1 g g−1 vs 0.6 ± 0.1 g g−1 and 0.4 ± 0.1 g g−1) and starch concentration (27% ± 10% vs 15% ± 7% and 10% ± 4%) in roots relative to savanna and forest Khaya respectively. Our results demonstrate that tree cover variation has species-specific effects on tree seedling recruitment which is related to root storage functions.

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