scholarly journals Severe fires alter the outcome of the mutualism between ants and a Neotropical savanna tree

2020 ◽  
Vol 131 (3) ◽  
pp. 476-486
Author(s):  
Heraldo L Vasconcelos ◽  
Elmo B A Koch ◽  
Flávio Camarota ◽  
Richard Tito ◽  
Lino A Zuanon ◽  
...  
Keyword(s):  
Plant Protection ◽  
Insect Herbivory ◽  
Fire Disturbance ◽  
Insect Herbivores ◽  
Extrafloral Nectary ◽  
Neotropical Savanna ◽  
Ant Community ◽  
Nesting Habits ◽  
In Fire ◽  
The Relationship

Abstract Physical disturbances, such as fire, may affect the relationship between ants and plants. We evaluated the extent to which severe fires alter the protective effect of ants against the herbivores of an extrafloral-nectary bearing tree. We performed an ant removal experiment and sampled the ant fauna from the same trees over 4 years: the pre-fire year, the fire-year, and again 1 and 2 years later. Ants reduced insect herbivory in the pre-fire year and in the fire-year but failed to provide any plant protection in the two years after fire. The magnitude of the ant effect on herbivory did not differ between the pre-fire year and the fire-year. Fire reduced the abundance of ants with strictly arboreal-nesting habits. However, in the fire year (but not in the subsequent ones), this decline was compensated by an increase in the abundance of arboreal generalists and ground-nesting ants foraging in trees. Our results indicate that severe fires can affect the strength and direction of the ant effects on herbivory by altering the structure of the arboreal ant community and the abundance of insect herbivores. Fire disturbance is thus an important factor of conditionality of ant-plant mutualisms in fire-prone habitats, like the Cerrado savannas.

scholarly journals Tropical Dry Forest Resilience to Fire Depends on Fire Frequency and Climate

2021 ◽  
Vol 4 ◽  
Author(s):  
Maximilian Hartung ◽  
Geovana Carreño-Rocabado ◽  
Marielos Peña-Claros ◽  
Masha T. van der Sande
Keyword(s):  
Tropical Forests ◽  
Tropical Dry Forest ◽  
Remote Sensing Data ◽  
Fire Frequency ◽  
Dry Forest ◽  
Fire Disturbance ◽  
Fire Intensity ◽  
Forest Resilience ◽  
Landsat Satellite ◽  
In Fire

Wildfires are becoming increasingly frequent and devastating in many tropical forests. Although seasonally dry tropical forests (SDTF) are among the most fire-threatened ecosystems, their long-term response to frequent wildfires remains largely unknown. This study is among the first to investigate the resilience in response to fire of the Chiquitano SDTF in Bolivia, a large ecoregion that has seen an unprecedented increase in fire intensity and frequency in recent years. We used remote sensing data to assess at a large regional and temporal scale (two decades) how fire frequency and environmental factors determine the resilience of the vegetation to fire disturbance. Resilience was measured as the resistance to fire damage and post-fire recovery. Both parameters were monitored for forested areas that burned once (F1), twice (F2), and three times (F3) between 2000 and 2010 and compared to unburned forests. Resistance and recovery were analyzed using time series of the Normalized Burn Ratio (NBR) index derived from Landsat satellite imagery, and climatic, topographic, and a human development-related variable used to evaluate their influence on resilience. The overall resilience was lowest in forests that burned twice and was higher in forests that burned three times, indicating a possible transition state in fire resilience, probably because forests become increasingly adapted during recurrent fires. Climatic variables, particularly rainfall, were most influential in determining resilience. Our results indicate that the Chiquitano dry forest is relatively resilient to recurring fires, has the capacity to recover and adapt, and that climatic differences are the main determinants of the spatial variation observed in resilience. Nevertheless, further research is needed to understand the effect of the higher frequency and intensity of fires expected in the future due to climate change and land use change, which may pose a greater threat to forest resilience.

scholarly journals Does insect herbivory suppress ecosystem productivity? Evidence from a temperate woodland

2021 ◽  
Author(s):  
Kristiina Visakorpi ◽  
Sofia Gripenberg ◽  
Yadvinder Malhi ◽  
Terhi Riutta
Keyword(s):  
Gas Exchange ◽  
Leaf Area ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Leaf Gas Exchange ◽  
Insect Herbivory ◽  
Ecosystem Productivity ◽  
Area Loss ◽  
Leaf Area Loss ◽  
The Relationship

AbstractOur current understanding of the relationship between insect herbivory and ecosystem productivity is limited. Previous studies have typically quantified only leaf area loss, or have been conducted during outbreak years. These set-ups often ignore the physiological changes taking place in the remaining plant tissue after insect attack, or may not represent typical, non-outbreak herbivore densities. Here, we estimate the amount of carbon lost to insect herbivory in a temperate deciduous woodland both through leaf area loss and, notably, through changes in leaf gas exchange in non-consumed leaves under non-outbreak densities of insects. We calculate how net primary productivity changes with decreasing and increasing levels of herbivory, and estimate what proportion of the carbon involved in the leaf area loss is transferred further in the food web. We estimate that the net primary productivity of an oak stand under ambient levels of herbivory is 54 - 69% lower than that of a completely intact stand. The effect of herbivory quantified only as leaf area loss (0.1 Mg C ha−1 yr−1) is considerably smaller than when the effects of herbivory on leaf physiology are included (8.5 Mg C ha−1 yr−1). We propose that the effect of herbivory on primary productivity is non-linear and mainly determined by changes in leaf gas exchange. We call for replicated studies in other systems to validate the relationship between insect herbivory and ecosystem productivity described here.

scholarly journals Satellite-Based Assessment of Grassland Conversion and Related Fire Disturbance in the Kenai Peninsula, Alaska

2019 ◽  
Vol 11 (3) ◽  
pp. 283 ◽  
Author(s):  
Katherine Hess ◽  
Cheila Cullen ◽  
Jeanette Cobian-Iñiguez ◽  
Jacob Ramthun ◽  
Victor Lenske ◽  
...  
Keyword(s):  
Land Cover ◽  
Land Cover Change ◽  
Landsat Imagery ◽  
Fire Danger ◽  
Fire Disturbance ◽  
Time Step ◽  
Kenai Peninsula ◽  
Spruce Beetle ◽  
Grassland Conversion ◽  
The Relationship

Spruce beetle-induced (Dendroctonus rufipennis (Kirby)) mortality on the Kenai Peninsula has been hypothesized by local ecologists to result in the conversion of forest to grassland and subsequent increased fire danger. This hypothesis stands in contrast to empirical studies in the continental US which suggested that beetle mortality has only a negligible effect on fire danger. In response, we conducted a study using Landsat data and modeling techniques to map land cover change in the Kenai Peninsula and to integrate change maps with other geospatial data to predictively map fire danger for the same region. We collected Landsat imagery to map land cover change at roughly five-year intervals following a severe, mid-1990s beetle infestation to the present. Land cover classification was performed at each time step and used to quantify grassland encroachment patterns over time. The maps of land cover change along with digital elevation models (DEMs), temperature, and historical fire data were used to map and assess wildfire danger across the study area. Results indicate the highest wildfire danger tended to occur in herbaceous and black spruce land cover types, suggesting that the relationship between spruce beetle damage and wildfire danger in costal Alaskan forested ecosystems differs from the relationship between the two in the forests of the coterminous United States. These change detection analyses and fire danger predictions provide the Kenai National Wildlife Refuge (KENWR) ecologists and other forest managers a better understanding of the extent and magnitude of grassland conversion and subsequent change in fire danger following the 1990s spruce beetle outbreak.

The relationship between stem-galling wasps and mycorrhizal colonization of Quercus turbinella

2005 ◽  
Vol 83 (10) ◽  
pp. 1349-1353 ◽  
Author(s):  
Rebecca C. Mueller ◽  
Christopher M. Sthultz ◽  
Theodore Martinez ◽  
Catherine A. Gehring ◽  
Thomas G. Whitham
Keyword(s):  
Plant Species ◽  
Insect Herbivory ◽  
Arbuscular Mycorrhizas ◽  
Mycorrhizal Colonization ◽  
Dynamic Relationship ◽  
Live Oak ◽  
The Relationship

While numerous studies have examined the relationship between herbivory and mycorrhizal colonization, few studies have been undertaken on plant species such as oaks that can be dually colonized by both arbuscular mycorrhizas (AM) and ectomycorrhizas (EM). We examined the relationship between insect herbivory by a stem-galling wasp (Cynipidae) and the mycorrhizal colonization of shrub live oaks ( Quercus turbinella Greene). We found that oaks with high numbers of galls had 2.4 times higher levels of branch die-back and were 2.3 times more water stressed than oaks with low numbers of galls. Oaks with high numbers of galls supported 21% higher levels of AM colonization but had 53% lower levels of EM colonization than oaks with low numbers of galls. In addition, AM colonization was positively correlated with the number of galls per tree, while EM colonization was negatively correlated with the number of galls per tree. These findings suggest that there is a dynamic relationship between stem-galling wasps and the AM and EM mutualists of shrub live oak.

Geographic variation in extrafloral nectaries in the ant-associated plant genus Adriana (Euphorbiaceae) and its relationship to water availability

2007 ◽  
Vol 55 (5) ◽  
pp. 568 ◽  
Author(s):  
M. A. Whalen ◽  
D. A. Mackay
Keyword(s):  
Water Stress ◽  
Geographic Variation ◽  
Water Availability ◽  
Secretory Activity ◽  
Climatic Variation ◽  
Extrafloral Nectaries ◽  
Climatic Variables ◽  
Extrafloral Nectary ◽  
Effect Of Water ◽  
The Relationship

The relationship between geographic variation in extrafloral nectary size and climatic variation was assessed in three taxa within Adriana (Euphorbiaceae). In each taxon, there was a significant association between gland size and moisture-related climatic variables. A glasshouse experiment was conducted to examine the effect of water stress on nectary longevity, and it was found that the secretory activity of nectaries declined more rapidly on drought-stressed plants than on watered plants.

scholarly journals Rhizosphere microbes and host plant genotype influence the plant metabolome and reduce insect herbivory

2018 ◽  
Author(s):  
Charley J. Hubbard ◽  
Baohua Li ◽  
Robby McMinn ◽  
Marcus T. Brock ◽  
Lois Maignien ◽  
...  
Keyword(s):  
Secondary Metabolites ◽  
Flea Beetle ◽  
Insect Herbivory ◽  
Amplicon Sequencing ◽  
Plant Performance ◽  
Insect Herbivores ◽  
List Type ◽  
Plant Genotype ◽  
Herbivore Resistance ◽  
Rhizosphere Microbiome

SummaryRhizosphere microbes affect plant performance, including plant resistance against insect herbivores; yet, the relative influence of rhizosphere microbes vs. plant genotype on herbivory levels and on metabolites related to defense remains unclear.In Boechera stricta, we tested the effects of rhizosphere microbes and plant genotype on herbivore resistance, the primary metabolome, and select secondary metabolites.Plant populations differed significantly in the concentrations of 6 glucosinolates (GLS), secondary metabolites known to provide herbivore resistance in the Brassicaceae, and the population with lower GLS levels experienced ~60% higher levels of aphid (Aphis spp.) attack; no effect was observed of GLS on damage by a second herbivore, flea beetles (Altica spp.). Rhizosphere microbiome (intact vs. disrupted) had no effect on plant GLS concentrations. However, aphid number and flea beetle damage were respectively ~3-fold and 7-fold higher among plants grown in the disrupted rhizosphere microbiome treatment, and distinct (as estimated from 16s rRNA amplicon sequencing) intact native microbiomes also differed in their effects on herbivore damage. These differences may be attributable to shifts in primary metabolic pathways.The findings suggest that rhizosphere microbes can play a greater role than plant genotype in defense against insect herbivores, and act through mechanisms independent of plant genotype.

scholarly journals Comparing Exogenous Methods to Induce Plant-Resistance Against a Bark-Feeding Insect

2021 ◽  
Vol 12 ◽  
Author(s):  
Yayuan Chen ◽  
Adriana Puentes ◽  
Christer Björkman ◽  
Agnès Brosset ◽  
Helena Bylund
Keyword(s):  
Plant Defenses ◽  
Plant Protection ◽  
Insect Herbivory ◽  
Mechanical Damage ◽  
The Other ◽  
Early Exposure ◽  
Protection Measure ◽  
Seedling Resistance ◽  
Pine Weevil ◽  
Late Exposure

Exogenous application of the plant hormone methyl jasmonate (MeJA) can trigger induced plant defenses against herbivores, and has been shown to provide protection against insect herbivory in conifer seedlings. Other methods, such as mechanical damage to seedlings, can also induce plant defenses, yet few have been compared to MeJA and most studies lack subsequent herbivory feeding tests. We conducted two lab experiments to: (1) compare the efficacy of MeJA to mechanical damage treatments that could also induce seedling resistance, (2) examine if subsequent insect damage differs depending on the time since induction treatments occurred, and (3) assess if these induction methods affect plant growth. We compared Scots pine (Pinus sylvestris) seedlings sprayed with MeJA (10 or 15 mM) to seedlings subjected to four different mechanical bark damage treatments (two different bark wound sizes, needle-piercing damage, root damage) and previous pine weevil (Hylobius abietis) damage as a reference treatment. The seedlings were exposed to pine weevils 12 or 32 days after treatments (early and late exposure, hereafter), and resistance was measured as the amount of damage received by plants. At early exposure, seedlings treated with needle-piercing damage received significantly more subsequent pine weevil feeding damage than those treated with MeJA. Seedlings treated with MeJA and needle-piercing damage received 84% less and 250% more pine weevil feeding, respectively, relative to control seedlings. The other treatments did not differ statistically from control or MeJA in terms of subsequent pine weevil damage. For the late exposure group, plants in all induction treatments tended to receive less pine weevil feeding (yet this was not statistically significant) compared to control seedlings. On the other hand, MeJA significantly slowed down seedling growth relative to control and all other induction treatments. Overall, the mechanical damage treatments appeared to have no or variable effects on seedling resistance. One of the treatments, needle-piercing damage, actually increased pine weevil feeding at early exposure. These results therefore suggest that mechanical damage shows little potential as a plant protection measure to reduce feeding by a bark-chewing insect.

scholarly journals Examining the Relationship between Fire Interest and Firesetting: Contributions of Previous Experience with Fire and Self and Emotional Regulation

2021 ◽  
Author(s):  
Rosalie Sherrell
Keyword(s):  
Regression Analysis ◽  
Emotional Regulation ◽  
Sensation Seeking ◽  
Economic Cost ◽  
Emotional Dysregulation ◽  
Previous Exposure ◽  
Unique Predictor ◽  
In Fire ◽  
The Relationship

<p>Deliberate firesetting is an international problem with significant personal and economic cost. Interest in fire has previously been identified as a unique predictor of deliberate firesetting, however little is known about how fire interest interacts with other factors to produce firesetting. This research aimed to gain a deeper understanding of the role of fire interest by exploring how this construct interacts with previous exposure to fire and aspects of self and emotional regulation, and how this relates to firesetting behaviour. Two anonymous online studies were conducted among New Zealand adult community samples: Study 1 examined the relationship between fire interest, previous exposure to fire, emotional dysregulation, impulsivity, and sensation seeking (N = 146); Study 2 replicated the first study and explored the relationship between these factors and engagement in deliberate firesetting (N = 149). Results from both studies showed that only previous exposure to fire and sensation seeking were consistently positively correlated with fire interest, however, when other variables were controlled for via multiple regression analysis, the thrill/adventure seeking facet of sensation seeking was the only significant predictor of fire interest. In Study 2, logistic regression showed that only fire interest and impulsivity were significant predictors of deliberate firesetting. Moderation analyses indicated that thrill/adventure seeking moderates the relationship between fire interest and firesetting behaviour, while impulsivity does not. These findings extend previous research and theory by providing an initial understanding of how various factors may influence an individual’s level of fire interest and their engagement in deliberate firesetting. </p>

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