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.

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.

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.

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.

scholarly journals Fire Seasonality, Seasonal Temperature Cues, Dormancy Cycling, and Moisture Availability Mediate Post-fire Germination of Species With Physiological Dormancy

2021 ◽  
Vol 12 ◽  
Author(s):  
Berin D. E. Mackenzie ◽  
Tony D. Auld ◽  
David A. Keith ◽  
Mark K. J. Ooi
Keyword(s):  
Seedling Recruitment ◽  
Fire Severity ◽  
Seedling Emergence ◽  
Seasonal Temperature ◽  
Soil Heating ◽  
Fire Seasonality ◽  
Moisture Availability ◽  
Wide Range ◽  
Physiological Dormancy ◽  
In Fire

Fire seasonality (the time of year of fire occurrence) has important implications for a wide range of demographic processes in plants, including seedling recruitment. However, the underlying mechanisms of fire-driven recruitment of species with physiological seed dormancy remain poorly understood, limiting effective fire and conservation management, with insights hampered by common methodological practices and complex dormancy and germination requirements. We sought to identify the mechanisms that regulate germination of physiologically dormant species in nature and assess their sensitivity to changes in fire seasonality. We employed a combination of laboratory-based germination trials and burial-retrieval trials in natural populations of seven species of Boronia (Rutaceae) to characterize seasonal patterns in dormancy and fire-stimulated germination over a 2-year period and synthesized the observed patterns into a conceptual model of fire seasonality effects on germination. The timing and magnitude of seedling emergence was mediated by seasonal dormancy cycling and seasonal temperature cues, and their interactions with fire seasonality, the degree of soil heating expected during a fire, and the duration of imbibition. Primary dormancy was overcome within 4–10 months’ burial and cycled seasonally. Fire-associated heat and smoke stimulated germination once dormancy was alleviated, with both cues required in combination by some species. For some species, germination was restricted to summer temperatures (a strict seasonal requirement), while others germinated over a broader seasonal range of temperatures but exhibited seasonal preferences through greater responses at warmer or cooler temperatures. The impacts of fires in different seasons on germination can vary in strength and direction, even between sympatric congeners, and are strongly influenced by moisture availability (both the timing of post-fire rainfall and the duration soils stay moist enough for germination). Thus, fire seasonality and fire severity (via its effect on soil heating) are expected to significantly influence post-fire emergence patterns in these species and others with physiological dormancy, often leading to “germination interval squeeze.” Integration of these concepts into current fire management frameworks is urgently required to ensure best-practice conservation. This is especially pertinent given major, ongoing shifts in fire seasonality and rainfall patterns across the globe due to climate change and increasing anthropogenic ignitions.

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.

scholarly journals Twenty-first century droughts have not increasingly exacerbated fire season severity in the Brazilian Amazon

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
R. Libonati ◽  
J. M. C. Pereira ◽  
C. C. Da Camara ◽  
L. F. Peres ◽  
D. Oom ◽  
...  
Keyword(s):  
Forest Fires ◽  
Brazilian Amazon ◽  
First Century ◽  
Fire Season ◽  
Fire Intensity ◽  
Amazon Forest ◽  
Active Fire ◽  
Fire Activity ◽  
Twenty First Century ◽  
In Fire

AbstractBiomass burning in the Brazilian Amazon is modulated by climate factors, such as droughts, and by human factors, such as deforestation, and land management activities. The increase in forest fires during drought years has led to the hypothesis that fire activity decoupled from deforestation during the twenty-first century. However, assessment of the hypothesis relied on an incorrect active fire dataset, which led to an underestimation of the decreasing trend in fire activity and to an inflated rank for year 2015 in terms of active fire counts. The recent correction of that database warrants a reassessment of the relationships between deforestation and fire. Contrasting with earlier findings, we show that the exacerbating effect of drought on fire season severity did not increase from 2003 to 2015 and that the record-breaking dry conditions of 2015 had the least impact on fire season of all twenty-first century severe droughts. Overall, our results for the same period used in the study that originated the fire-deforestation decoupling hypothesis (2003–2015) show that decoupling was clearly weaker than initially proposed. Extension of the study period up to 2019, and novel analysis of trends in fire types and fire intensity strengthened this conclusion. Therefore, the role of deforestation as a driver of fire activity in the region should not be underestimated and must be taken into account when implementing measures to protect the Amazon forest.

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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