The persistence and germination of fern spores in fire-prone, semi-arid environments

2014 ◽  
Vol 62 (6) ◽  
pp. 518 ◽  
Author(s):  
Sarah K. Paul ◽  
Kingsley W. Dixon ◽  
Ben P. Miller
Keyword(s):  
Soil Surface ◽  
Arid Environment ◽  
Spore Density ◽  
Temperature Extremes ◽  
Arid Environments ◽  
Fibrous Root ◽  
High Germination ◽  
Plant Persistence ◽  
Spore Longevity ◽  
In Fire

In addition to population regeneration, the spore phase provides ferns with a capacity for dispersal through space and time (if spores are able to survive for long periods), and buffers their populations against environmental extremes. Inhabiting dry and fire-prone environments provides specific challenges to ferns, and the traits of fern spores in relation to these challenges are not well understood. Their shallow, dense and fibrous root networks mean that the loss or establishment of fern populations in disturbed ecosystems may influence soil stability, and indicate a keystone role in ecosystem function and ecological restoration. Here, we examine the requirements for, and limits of, spore persistence and germination of three Cheilanthes Syn.Fil. (Pteridaceae) species, namely, optimal conditions for spore germination and prothallial growth, sensitivity to temperature extremes and spore longevity. Viability of fresh spores was assessed following exposure to temperature extremes (–20 to 250°C) or after incubation at a range of temperatures (10−35°C) and in light or dark conditions. Viability of spores from herbarium voucher specimens was also assessed, covering 3–65 years of storage. Maximal germination occurred among spores incubated between 20°C and 30°C in light. Further temperature variation within this range resulted in a ×10 difference in prothallial size. Germination was unaffected by 10 min of exposure to temperatures up to 100°C, but was reduced after exposure to temperatures of −20°C and 110°C. Germination of herbarium-stored spores demonstrated longevity of up to 15 years. This longevity, combined with high spore density in field soils (including at depth to at least 10 cm), very high germination under ideal conditions, and microscopic size, describes a disturbance-mediated propagule persistence strategy. Spores are non-persisting and will germinate if exposed to light and water, but do persist if buried. Germinable spore can be found 5 cm below the soil surface, and can persist for at least 15 years, but the light requirement for germination means that persistent spores can achieve germination only if exhumed. Elucidating these traits reveals a unique pathway for plant persistence, and contributes to the development of the restoration capacity of arid-environment ferns.

Seed dormancy in four Tibetan Plateau Vicia species and characterization of physiological changes in response of seeds to environmental factors

2013 ◽  
Vol 23 (2) ◽  
pp. 133-140 ◽  
Author(s):  
Xiaowen Hu ◽  
Tingshan Li ◽  
Juan Wang ◽  
Yanrong Wang ◽  
Carol C. Baskin ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Seed Dormancy ◽  
Germination Rate ◽  
Soil Surface ◽  
The Tibetan Plateau ◽  
Physical Dormancy ◽  
High Germination ◽  
One Year ◽  
Hydrotime Model ◽  
Aba Biosynthesis

AbstractAlthough seed dormancy of temperate legumes is well understood, less is known about it in species that grow in subalpine/alpine areas. This study investigated dormancy and germination of four Vicia species from the Tibetan Plateau. Fresh seeds of V. sativa were permeable to water, whereas those of V. angustifolia, V. amoena and V. unijuga had physical dormancy (PY). One year of dry storage increased the proportion of impermeable seeds in V. angustifolia, but showed no effect on seed coat permeability in V. amoena or V. unijuga. Seeds of all four species also had non-deep physiological dormancy (PD), which was especially apparent in the two annuals at a high germination temperature (20°C). After 1 year of storage, PD had been lost. The hydrotime model showed that fresh seeds obtained a significantly higher median water potential [Ψb(50)] than stored seeds, implying that PD prevents germination in winter for seeds dispersed without PY when water availability is limited. After 6 months on the soil surface in the field, a high proportion of permeable seeds remained ungerminated, further suggesting that PD plays a key role in preventing germination after dispersal. Addition of fluridone, an inhibitor of abscisic acid (ABA) biosynthesis, evened-out the differences in germination between fresh and stored seeds, which points to the key role of ABA biosynthesis in maintaining dormancy. Further, fresh seeds were more sensitive to exogenous ABA than stored seeds, indicating that storage decreased embryo sensitivity to ABA. On the other hand, the gibberellic acid GA3 increased germination rate, which implies that embryo sensitivity to GA is also involved in seed dormancy regulation. This study showed that PY, PD or their combination (PY+PD) plays a key role in timing germination after dispersal, and that different intensities of dormancy occur among these four Vicia species from the Tibetan Plateau.

Resilience of floodplain ecosystems in a semi-arid environment

2010 ◽  
Vol 32 (3) ◽  
pp. 305 ◽  
Author(s):  
Matthew J. Colloff ◽  
Darren S. Baldwin
Keyword(s):  
Stable State ◽  
Arid Environment ◽  
Ecosystem Functions ◽  
Arid Environments ◽  
Ecosystem Resilience ◽  
Floodplain Ecosystems ◽  
Murray Darling Basin ◽  
Single State ◽  
Floods And Droughts ◽  
Semi Arid

Implicit to loss of ecosystem resilience is that systems can shift from one stable state to another as a result of disturbance. We present a conceptual model of ecosystem resilience of floodplains and wetlands in semi-arid environments like those of the Murray–Darling Basin. The model is based on a single state characterised by fluctuating wet and dry phases driven by episodic floods and droughts. It might appear that such a single state is inherently unstable, but stability, and the measure of resilience, is conferred by the capacity of floodplains and wetlands to undergo drought and yet return to a functioning wet phase following inundation as well as to undergo flooding and return to the dry phase following flood recession. Floodplains and wetlands are driven by strong, periodic abiotic disturbances and their ecosystem functions and biogeochemical processes are highly rate-limited, spatiotemporally variable and driven by relatively species-poor assemblages of plants and animals adapted to withstand drought and flooding. Extreme drying due to climatic change and over-allocation of water resources represents the primary mechanism via which resilience is lost.

scholarly journals Linking Termite Feeding Preferences and Soil Physical Functioning in Southern-Indian Woodlands

Insects ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 4 ◽  
Author(s):  
Sougueh Cheik ◽  
Rashmi Ramesh Shanbhag ◽  
Ajay Harit ◽  
Nicolas Bottinelli ◽  
Raman Sukumar ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Deciduous Forest ◽  
Soil Surface ◽  
Soil Bulk Density ◽  
Water Infiltration ◽  
Arid Environments ◽  
Feeding Preferences ◽  
Soil Hydraulic Conductivity ◽  
Odontotermes Obesus ◽  
Soil Hydraulic

Termites are undoubtedly amongst the most important soil macroinvertebrate decomposers in semi-arid environments in India. However, in this specific type of environment, the influence of termite foraging activity on soil functioning remains unexplored. Therefore, this study examines the link between the quality of litter and the functional impact of termite feeding preferences on soil properties and soil hydraulic conductivity in a deciduous forest in southern India. Different organic resources (elephant dung: “ED”, elephant grass: “EG”, acacia leaves: “AL” and layers of cardboard: “CB”) were applied on repacked soil cores. ED appeared to be the most attractive resource to Odontotermes obesus, leading to a larger amount of soil sheeting (i.e., the soil used by termites for covering the litter they consume), more numerous and larger holes in the ground and a lower soil bulk density. As a consequence, ED increased the soil hydraulic conductivity (4-fold) compared with the control soil. Thus, this study highlights that the more O. obesus prefers a substrate, the more this species impacts soil dynamics and water infiltration in the soil. This study also shows that ED can be used as an efficient substrate for accelerating the infiltration of water in southern-Indian soils, mainly through the production of galleries that are open on the soil surface, offering new perspectives on termite management in this environment.

scholarly journals Comparison of Rain Effects on Splash Dispersal of Three Colletotrichum Species Infecting Strawberry

1999 ◽  
Vol 89 (7) ◽  
pp. 555-563 ◽  
Author(s):  
N. Ntahimpera ◽  
L. L. Wilson ◽  
M. A. Ellis ◽  
L. V. Madden
Keyword(s):  
Flux Density ◽  
Soil Surface ◽  
Selective Medium ◽  
Spore Density ◽  
Deposition Flux ◽  
Closely Related Species ◽  
Colletotrichum Species ◽  
Splash Dispersal ◽  
Significant Difference ◽  
The Media

Rain simulation studies were performed to compare splash dispersal of three Colletotrichum species: C. acutatum (C. acutatum-O isolate from Ohio and C. acutatum-M isolate from Mississippi), C. fragariae (isolate from Mississippi), and C. gloeosporioides (isolate from Florida). Conidial dispersal was assessed by counting colonies formed from spore-bearing splash droplets deposited in sheltered petri plates containing a selective medium. Colonies were converted to number of conidia based on germination rates of spores on the media. The interpolated total number of dispersed conidia over a 61 min rain and 72 cm from the point source (Σ) was calculated. For all species, a rain intensity of 30-mm/h resulted in significantly greater dispersal than an intensity of 11-mm/h. C. fragariae had the lowest amount of spore dispersal, and C. acutatum-O had the highest dispersal. C. acutatum-M and C. gloeosporioides were intermediate in magnitude of conidial splash dispersal. However, differences were directly attributed to differences in spore density per fruit at the source. When Σ was corrected for source strength (Σr), the species were very similar, with only C. acutatum-M having a mean Σr significantly less than the others. Proportions and rates of spore removal (per minute) from source fruits were higher for C. acutatum-O and C. gloeosporioides than for other isolates. Wash-off rates of conidia deposited on healthy fruits were the same for all species. Deposition flux density of spores that had been uniformly sprayed over the entire soil surface of the experimental area was affected by species. A significant difference in means was observed between C. acutatum and C. fragariae—the latter had a somewhat lower flux density. This is the first demonstration that closely related species infecting the same plant species are similar in terms of splash dispersal.

Differences in germination response to smoke and temperature cues in ‘pyrophyte’ and ‘pyrofuge’ forms of Erica coccinea (Ericaceae)

2018 ◽  
Vol 27 (8) ◽  
pp. 562 ◽  
Author(s):  
Jenny Leonard ◽  
Adam G. West ◽  
Fernando Ojeda
Keyword(s):  
South African ◽  
Incubation Temperature ◽  
Fire Regimes ◽  
Smoke Exposure ◽  
The South ◽  
Natural Fire ◽  
Germination Response ◽  
High Germination ◽  
Germination Success ◽  
In Fire

Many plants in fire-prone ecosystems produce seeds that are cued to germinate after fire. However, fire is not uniform in the landscape, and there are often refugia where fire does not reach, like rocky outcrops or moist valleys. Erica coccinea, a heath shrub from the South African fynbos, has two distinct pyrophyte forms (a resprouter and a seeder) as well as a ‘pyrofuge’ form that only occurs in fire refugia. We measured germination response to smoke and incubation temperature in seeds from pyrophyte (resprouter and seeder) and pyrofuge populations to determine whether these forms responded differently to a fire-cue (smoke) and a general germination cue (temperature). We found that seeds from pyrofuge plants had high germination success (80.9–92.0%) at the lowest incubation temperature (15/8°C 12h day/night cycle) regardless of smoke exposure. In contrast, seeds from pyrophytes (resprouters and seeders) responded strongly to the smoke cue (71.2–95.0%) and were not as limited by temperature. These results show that fire presence and absence is driving divergence of the primary germination cue in Erica coccinea. Given the patchiness of many natural fire regimes worldwide, we expect there may be pyrofuge populations exhibiting a similar divergence of traits in other species and other fire-prone ecosystems.

A new approach for biocrust and vegetation monitoring in drylands using multi-temporal Sentinel-2 images

2019 ◽  
Vol 43 (4) ◽  
pp. 496-520 ◽  
Author(s):  
Cinzia Panigada ◽  
Giulia Tagliabue ◽  
Eli Zaady ◽  
Offer Rozenstein ◽  
Roberto Garzonio ◽  
...  
Keyword(s):  
Vascular Plant ◽  
Temporal Distribution ◽  
Soil Surface ◽  
Absorption Feature ◽  
Arid Environments ◽  
Vegetation Monitoring ◽  
Rainfall Gradient ◽  
The North ◽  
Multi Temporal ◽  
Sentinel 2

Drylands, one of the planet’s largest terrestrial biomes, are suggested to be greatly threatened by climate change. Drylands are usually sparsely vegetated, and biological soil crusts (biocrusts) – that is, soil surface communities of cyanobacteria, mosses and/or lichens – can cover up to 70% of dryland cover. As they control key ecosystem processes, monitoring their spatial and temporal distribution can provide highly valuable information. In this study, we examine the potential of European Space Agency’s (ESA) Sentinel-2 (S2) data to characterize the spatial and temporal development of biocrust and vascular plant greening along a rainfall gradient of the Negev Desert (Israel). First, the chlorophyll a absorption feature in the red region (CRred) was identified as the index mostly sensitive to changes in biocrust greening but minimally affected by changes in soil moisture. This index was then computed on the S2 images and enabled monitoring the phenological dynamics of different dryland vegetation components from August 2015 to August 2017. The analysis of multi-temporal S2 images allowed us to successfully track the biocrust greening within 15 days from the first seasonal rain events in the north of Negev, and to identify the maximum development of annual vascular plants and greening of perennial ones. These results show potential for monitoring arid and semi-arid environments using the newly available S2 images, allowing new insights into dryland vegetation dynamics.

scholarly journals Rain Splash Dispersal of Gibberella zeae Within Wheat Canopies in Ohio

2004 ◽  
Vol 94 (12) ◽  
pp. 1342-1349 ◽  
Author(s):  
P. A. Paul ◽  
S. M. El-Allaf ◽  
P. E. Lipps ◽  
L. V. Madden
Keyword(s):  
Flux Density ◽  
Soil Surface ◽  
Selective Medium ◽  
Gibberella Zeae ◽  
Spore Density ◽  
Rain Intensity ◽  
Head Blight ◽  
Splash Dispersal ◽  
Rain Splash ◽  
Maize Kernels

Rain splash dispersal of Gibberella zeae, causal agent of Fusarium head blight of wheat, was investigated in field studies in Ohio between 2001 and 2003. Samplers placed at 0, 30, and 100 cm above the soil surface were used to collect rain splash in wheat fields with maize residue on the surface and fields with G. zeae-infested maize kernels. Rain splash was collected during separate rain episodes throughout the wheat-growing seasons. Aliquots of splashed rain were transferred to petri dishes containing Komada's selective medium, and G. zeae was identified based on colony and spore morphology. Dispersed spores were measured in CFU/ml. Intensity of splashed rain was highest at 100 cm and ranged from 0.2 to 10.2 mm h-1, depending on incident rain intensity and sampler height. Spores were recovered from splash samples at all heights in both locations for all sampled rain events. Both macroconidia and ascospores were found based on microscopic examination of random samples of splashed rain. Spore density and spore flux density per rain episode ranged from 0.4 to 40.9 CFU cm-2 and 0.4 to 84.8 CFU cm-2 h-1, respectively. Spore flux density was higher in fields with G. zeae-infested maize kernels than in fields with maize debris, and generally was higher at 0 and 30 cm than at 100 cm at both locations. However, on average, spore flux density was only 30% lower at 100 cm (height of wheat spikes) than at the other heights. The log of spore flux density was linearly related to the log of splashed rain intensity and the log of incident rain intensity. The regression slopes were not significantly affected by year, location, height, and their interactions, but the intercepts were significantly affected by both sampler height and location. Thus, our results show that spores of G. zeae were consistently splash dispersed to spike heights within wheat canopies, and splashed rain intensity and spore flux density could be predicted based on incident rain intensity in order to estimate inoculum dispersal within the wheat canopy.

Fire responses and survival strategies of mistletoes (Loranthaceae) in an arid environment in Western Australia

2011 ◽  
Vol 59 (6) ◽  
pp. 533 ◽  
Author(s):  
A. N. Start
Keyword(s):  
Host Specificity ◽  
Western Australia ◽  
Seed Storage ◽  
Fire Risk ◽  
Fire Regimes ◽  
Arid Environment ◽  
Survival Strategies ◽  
Fresh Seed ◽  
Acacia Aneura ◽  
In Fire

Between 1982 and 2008, data were collected on Loranthaceous mistletoes, their hosts and the fire responses of both, in and adjacent to the Pilbara, an arid region in Western Australia where hummock grasslands (dominated by Triodia sp. R.Br., Poaceae) and mulga woodlands (dominated by Acacia aneura Benth., Mimosaceae) are widespread. Hummock grasslands are fire prone and highly flammable. Mulga woodlands are less so, except in an inter-zone where Triodia in the understorey may be sufficiently dense to carry fire. The foliage (and fresh seed) of all mistletoe species was killed if scorched. Moreover, none had any means of long-term, in situ seed-storage. Three fire-survival strategies were observed across the 16 mistletoe taxa. One species (two varieties) was a resprouter. The other 14 were obligate seeders. Post-fire regeneration of those taxa depended on fresh seed being imported and deposited in suitable host canopies by birds. Twelve of them reduced fire risk by varying degrees of host specificity, favouring hosts that grew in fire-sheltered sites. However, two species had very low host specificity and grew on fire-vulnerable hosts in fire-prone hummock grasslands. Their low host specificity increased the likelihood that imported seed would be deposited on suitable hosts. Since pastoral settlement, fire regimes have changed and current regimes are eroding many mistletoe populations. None of the species occurring in the study area is threatened at bioregional or National levels. Nevertheless, the outlook is bleak for mistletoes growing in areas dominated by hummock grasslands, subregional extinction is likely and there are broader implications for biodiversity.

scholarly journals PATTERNS OF STORAGE AND FIBROUS ROOT DEVELOPMENT IN SEVERAL SWEETPOTATO CULTIVARS AND THEIR PROGENIES

HortScience ◽  
1992 ◽  
Vol 27 (11) ◽  
pp. 1172c-1172
Author(s):  
N. Bidiaka ◽  
V.A. Khan ◽  
C.K. Bonsi ◽  
C. Stevens ◽  
E. G. Rhoden ◽  
...  
Keyword(s):  
Field Trial ◽  
Inverse Relationship ◽  
Block Design ◽  
Soil Surface ◽  
Maximum Level ◽  
Regression Equations ◽  
Stem Cuttings ◽  
Fibrous Root ◽  
Storage Roots ◽  
Randomized Block Design

In 1991 leafless stem cuttings 7 nodes long from 4 maternal parents (`Carver', Carver ii', `TU-1892' and `Georgia-Jet') and their progenies (MP/P) were planted 3 nodes deep in greenhouse benches filled with Jiffy-Mix to determine if any similarity in storage (SR) or fibrous root (FR) patterns could be used to identify high yielding cultivars in a breeding program. The experiment was planted in a complete randomized block design with 7 replications for each treatment and the total number of SR and FR data were collected over a 9 wk period with weekly sampling. The results indicated that SR initiation was a continuos process and took from 5-9 wk before reaching a maximum level for some MP/P. There was a significant inverse relationship between SR and FR numbers, as SR increased FR decreased. SR for most MP/P were initiated at the underground node closest to the soil surface and FR at the lower two nodes. When regression equations were used on the greenhouse data to predict total number of SR that would be produced in a field trial, no significant differences were found between the number of SR initiated in the greenhouse and field trial 80 days after transplanting by some of these MP/P. However, cultivars with the highest number of storage roots in the field trial did not have the highest number of marketable roots or yield and this was probably due to differences among MP/P in the rate of root enlargement.

scholarly journals Microbial and geo-archaeological records reveal the growth rate, origin and composition of desert rock surface communities

2021 ◽  
Vol 18 (11) ◽  
pp. 3331-3342
Author(s):  
Nimrod Wieler ◽  
Tali Erickson Gini ◽  
Osnat Gillor ◽  
Roey Angel
Keyword(s):  
Growth Rate ◽  
Archaeological Site ◽  
Arid Environment ◽  
Building Stone ◽  
Rock Surface ◽  
Arid Environments ◽  
Oxygen Isotope Ratios ◽  
Carbon And Oxygen Isotope ◽  
Dating Method ◽  
First Time

Abstract. Biological rock crusts (BRCs) are ubiquitous features of rock surfaces in drylands composed of slow-growing microbial assemblages. BRC presence is often correlated with rock weathering, soiling effect or mitigating geomorphic processes. However, their development rate is still unknown. In this work, we characterised and dated BRCs in an arid environment, under natural conditions, by integrating archaeological, microbiological and geological methods. To this end, we sampled rocks from a well-documented Byzantine archaeological site and the surrounding area located in the central Negev, Israel. The archaeological site, which is dated to the fourth to seventh centuries CE, was constructed from two lithologies, limestone and chalk. BRC started developing on the rocks after being carved, and its age should match that of the site. Using stable carbon and oxygen isotope ratios, we confirmed the biogenic nature of the crusts. The BRC samples showed mild differences in the microbial community assemblages between the site and its surroundings, irrespective of lithology, confirming the dominance of aeolian inoculation sources. All BRCs were dominated by Actinobacteria, Cyanobacteria and Proteobacteria. We further measured the BRC thickness on 1700-year-old building stone blocks and determined it to be 0.1–0.6 mm thick. Therefore, a BRC growth rate was estimated, for the first time, to be 0.06–0.35 mm kyr−1. Our dating method was then validated on a similar archaeological site located ca. 20 km away, giving comparable values. We propose that BRC growth rates could be used as an affordable yet robust dating tool in archaeological sites in arid environments.

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