The impact of increasing fire frequency on forest transformations in southern Siberia

2016 ◽  
Vol 382 ◽  
pp. 225-235 ◽  
Author(s):  
Elena A. Kukavskaya ◽  
Ludmila V. Buryak ◽  
Evgeny G. Shvetsov ◽  
Susan G. Conard ◽  
Olga P. Kalenskaya
2017 ◽  
Vol 209 (2) ◽  
pp. 1265-1286 ◽  
Author(s):  
V V Shcherbakova ◽  
A J Biggin ◽  
R V Veselovskiy ◽  
A V Shatsillo ◽  
L M A Hawkins ◽  
...  

Abstract Defining variations in the behaviour of the geomagnetic field through geological time is critical to understanding the dynamics of Earth's core and its response to mantle convection and planetary evolution. Furthermore, the question of whether the axial dipole dominance of the recent palaeomagnetic field persists through the whole of Earth's history is fundamental to determining the reliability of palaeogeographic reconstructions and the efficacy of the magnetosphere in shielding Earth from solar wind radiation. Previous palaeomagnetic directional studies have suggested that the palaeofield had a complex configuration in the Devonian period (419–359 Ma). Here we present new high-quality palaeointensity determinations from rocks aged between 408 and 375 Ma from the Minusa Basin (southern Siberia), and the Kola Peninsula that enable the first reliable investigation of the strength of the field during this enigmatic period. Palaeointensity experiments were performed using the thermal Thellier, microwave Thellier and Wilson methods on 165 specimens from 25 sites. Six out of eight successful sites from the Minusa Basin and all four successful sites from the Kola Peninsula produced extremely low palaeointensities (<10 μT). These findings challenge the uniformitarian view of the palaeomagnetic field: field intensities of nearly an order of magnitude lower than Neogene values (except during relatively rare geomagnetic excursions and reversals) together with the widespread appearance of strange directions found in the Devonian suggest that the Earth's field during this time may have had a dominantly multipolar geometry. A persistent, low intensity multipolar magnetic field and associated diminished magnetosphere would increase the impact of solar particles on the Earth's magnetosphere, ionosphere and atmosphere with potential major implications for Earth's climate and biosphere.


2008 ◽  
Vol 24 (3) ◽  
pp. 269-279 ◽  
Author(s):  
Thomas A. Groen ◽  
Frank van Langevelde ◽  
Claudius A.D.M. van de Vijver ◽  
Navashni Govender ◽  
Herbert H.T. Prins

Abstract:In this paper, we investigate which factors determine tree clustering in Southern African savannas. This was tested by measuring clustering of trees using the T-squared sampling method in plots of the Kruger National Park experimental burning programme in South Africa. Fire return interval is the main treatment in these plots, but also several auxiliary determining parameters like clay content in the soil, diameter of tree canopies, understorey composition, tree species diversity and average annual rainfall were measured while sampling. In the Kruger National Park 48 plots distributed over four different landscape types and with three different burning treatments (never, once every 3 y and annually) were sampled. First, we related the clustering of trees to these environmental variables. When looking at the most abundant species in each plot, the analysis revealed that clustering is mainly correlated with clay content in the soil. This analysis also showed that fire frequency had a positive effect on the clustering of tree species that are not very abundant. We suggest that less abundant species might be less resistant to fire and therefore adopt a mechanism of clustering to exclude grass fires under their canopy. Finally, we tested the effect of clustering on the impact of fire on trees by analysing the relationship between the distance of a tree to its nearest neighbour and its canopy diameter. We found that clustering reduces the damaging effect of fire on trees. Our study contributes to understanding of savanna functioning by showing which processes are relevant in the distribution of savanna trees.


2013 ◽  
Vol 10 (10) ◽  
pp. 15735-15778 ◽  
Author(s):  
W. Knorr ◽  
T. Kaminski ◽  
A. Arneth ◽  
U. Weber

Abstract. Human impact on wildfires, a major Earth system component, remains poorly understood. While local studies have found more fires close to settlements and roads, assimilated charcoal records and analyses of regional fire patterns from remote-sensing observations point to a decline in fire frequency with increasing human population. Here, we present a global analysis using three multi-year satellite-based burned-area products combined with a parameter estimation and uncertainty analysis with a non-linear model. We show that at the global scale, the impact of increasing population density is mainly to reduce fire frequency. Only for areas with up to 0.1 people per km2, we find that fire frequency increases by 10 to 20% relative to its value at no population. The results are robust against choice of burned-area data set, and indicate that at only very few places on Earth, fire frequency is limited by human ignitions. Applying the results to historical population estimates results in a moderate but accelerating decline of global burned area by around 14% since 1800, with most of the decline since 1950.


1973 ◽  
Vol 3 (3) ◽  
pp. 496-513 ◽  
Author(s):  
Bruce M. Kilgore

AbstractThe impact of fire on the environment of the various Sierran conifer forests varies with intensity and frequency. Generally, however, fire (1) prepares a seedbed; (2) cycles nutrients within the system; (3) adjusts the successional pattern; (4) modifies conditions affecting wildlife; (5) influences the mosaic of age classes and vegetation types; (6) alters the numbers of trees susceptible to disease and insects; and (7) both reduces and creates fire hazards. Natural fire frequency apparently coincides with levels of fuel accumulation that result in burns of relatively low intensity at frequent intervals. This may average 8 yr in mixed conifer forests, although frequencies from 4 to 20 yr or more are found in particular sites.In all probability, giant sequoia and various pines of the Sierra survive today because of the role fire plays in the various forest types. National Park Service management policies are aimed at restoring fire, as nearly as possible, to its natural role in Sierran conifer forests. This is being accomplished by prescribed burning at lower and middle elevation types and by allowing lightning fires to burn in higher elevation forests.


Koedoe ◽  
2000 ◽  
Vol 43 (1) ◽  
Author(s):  
V.W. Meyer ◽  
L.E.O. Braack ◽  
H.C. Biggs

This paper provides fundamental information on distribution and density of the genus Cubitermes, Wasm. quantified for future monitoring. After distribution trends have been established, changes in Cubitermes density over time can be brought into contention with other factors in the Kruger National Park, such as the impact of fire frequency, water distribution, and elephant density on these insects. At least ten 2 ha belt-transects were undertaken in each of the 20 northern landscape zones of the KNP. Termite mounds were recorded and their activity within was determined. Cubitermes accounts for 29.8% of all active termite mounds in the northern KNP, with an average density of 0.33 mounds/ha. Cubitermes favours the Nwambiya Sandveld (zone 32). These termites occur in high density in the Klipkoppies 1 land type (Gorge), but in low densities in the Phalaborwa 10-12, Bulweni 1-3, Letaba 1-7 and Pafuri 3-6 land types. Cubitermes mounds tend to occur in high numbers on the Nzhelele formation (Mn) (sandstones; quartzite; basalt). Mounds of this genus in the Far North are highly concentrated on the Gaudam and Moriah soil series of the Hutton form, suggesting that these termites prefer very sandy soils with medium to coarse particles.


2021 ◽  
Vol 83 (11) ◽  
Author(s):  
Alanna Hoyer-Leitzel ◽  
Sarah Iams

AbstractSavanna ecosystems are shaped by the frequency and intensity of regular fires. We model savannas via an ordinary differential equation (ODE) encoding a one-sided inhibitory Lotka–Volterra interaction between trees and grass. By applying fire as a discrete disturbance, we create an impulsive dynamical system that allows us to identify the impact of variation in fire frequency and intensity. The model exhibits three different bistability regimes: between savanna and grassland; two savanna states; and savanna and woodland. The impulsive model reveals rich bifurcation structures in response to changes in fire intensity and frequency—structures that are largely invisible to analogous ODE models with continuous fire. In addition, by using the amount of grass as an example of a socially valued function of the system state, we examine the resilience of the social value to different disturbance regimes. We find that large transitions (“tipping”) in the valued quantity can be triggered by small changes in disturbance regime.


Author(s):  
Marina V. Fonti ◽  
Elena A. Babushkina ◽  
Dina F. Zhirnova ◽  
Eugene A. Vaganov

Tree-ring formation studies are important for assessing the impact of environmental factors on tree growth at intra-seasonal resolution. This information is necessary for understanding plant acclimatization to current and expected climate changes. Little is still known about how tree age may affect the duration and rate of annual ring formation. In this study, we investigated tree-ring formation in Scots pine (Pinus sylvestris L.) trees of different ages (30- and 95-year-old trees) from the foreststeppe zone in Southern Siberia. The main objectives were 1) to estimate the timing of cambial activity by distinguishing the phases of division, enlargement, wall thickening, and maturation of tracheids and 2) to compare the anatomical structure of the tracheids forming the annual rings of the differently aged trees. Stem tissue was sampled weekly from April to September 2014. The results showed a 1-2 week difference in duration of the phases of xylem formation between the groups; in addition, the ring width of the young trees was slightly narrower. The size of the tracheids of the entirely formed ring (i.e. the results of the enlargement phase) did not differ between the groups whereas the dynamics of the cell-wall thickness showed significant differences. The data obtained in the present study can provide references to calibrate process-based models linking environment to wood formation. These data can be used to benchmark time-explicit simulated measurements of annual ring increment and cell anatomical structure against the corresponding parameters of mature trees growing under natural conditions


2011 ◽  
Vol 41 (10) ◽  
pp. 2031-2039 ◽  
Author(s):  
Amy E. Hessl ◽  
Tom Saladyga ◽  
Thomas Schuler ◽  
Peter Clark ◽  
Joshua Wixom

The impact of settlement era fires on Appalachian forests was substantial, but whether these fires affected the extent of fire-adapted ridgetop plant communities is poorly understood. Here we present fire history and stand structure of an Appalachian ridgetop (Pike Knob, West Virginia) based on fire scars from three species (Pinus pungens Lamb., Pinus resinosa Soland., and Quercus rubra L.) and stand structure from two species (P. pungens and P. resinosa). Our research objectives are to determine (i) the degree to which the fire frequency on Pike Knob was affected by European American settlement (~1780–1900) and (ii) how the history of fire on Pike Knob shaped the current age structure of P. resinosa and P. pungens. All three species documented fire activity beginning in the mid- to late 1800s and continuing into the middle of the 20th century, when pasture lands were most active. The majority of P. pungens and P. resinosa established during or shortly after the ~85-year period of fires (1868–1953), suggesting a strong influence of past land use on current forest composition. Ridgetop pine communities have been resilient to both the absence of fire and frequent fire, indicating that pine communities will also be resilient to modern fire management, whether fire is excluded or re-introduced.


Forests ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 274 ◽  
Author(s):  
Víctor Fernández-García ◽  
Elena Marcos ◽  
Otilia Reyes ◽  
Leonor Calvo

Global change is altering fire frequency and severity in many regions across the world. In this work, we studied the impact of different frequency and severity regimes on the soil biochemical properties in burned areas with different environmental conditions. We selected three sites dominated by pine ecosystems along a Mediterranean-Transition-Oceanic climatic gradient, where we determined the fire frequency, and severity of the last wildfire. Four years after the last wildfire, we established 184 4 m2 plots. In each plot, we collected a composed soil sample from a 3 cm depth, and measured several ecological variables potentially affected by the fire frequency and severity (cover of bare soil, cover of fine and coarse plant debris, cover of vegetation, and vegetation height). From each soil sample, we analyzed the enzymatic activities corresponding to the biogeochemical cycles of carbon, nitrogen, and phosphorus (β-glucosidase, urease, and acid-phosphatase, respectively), and the microbial biomass carbon. The results indicated that fire frequency only played a significant role in soil biochemical properties at the Mediterranean and Transition sites. Specifically, we found that increases in frequency contributed to increased urease and phosphatase activities (at the Transition site), as well as microbial biomass carbon (at the Mediterranean and Transition sites). In relation to burn severity, we found opposite patterns when comparing the Mediterranean and Oceanic sites. Specifically, increased severity significantly decreased β-glucosidase, urease, and microbial biomass carbon at the Mediterranean site, whereas at the Oceanic one, severity significantly increased them. Burn severity also decreased microbial biomass carbon at the Transition site. Our results also indicated that, overall, fire frequency determined the studied ecological variables at the Mediterranean and Transition sites, but clear indirect effects on biochemical properties due to changes in ecological variables were not found. This study adds to the knowledge on the impact of shifts in fire regimes on soils in the current context of change.


Author(s):  
Виктория Викторовна Ростовцева ◽  
Анна Александровна Мезенцева ◽  
Марина Львовна Бутовская

В настоящей работе мы представляем результаты экспериментального исследования влияния вербальной коммуникации на кооперативные процессы в мужских коллективах. Коэволюция кооперации и вербальной коммуникации составляет важный аспект эволюционной антропологии, поскольку человек, как вид, отличается особыми кооперативными и коммуникативными (язык) способностями. Мужская кооперация представляет особый интерес. Исторически так сложилось, что именно мужчины были всегда вовлечены в деятельность, связанную с необходимостью в групповой кооперации (военное дело, охота). Важную роль в укреплении мужской кооперации играла и повсеместно распространенная патрилокальность, при которой мужчины, в отличие от женщин, на протяжении всей жизни оставались в кровнородственных мужских коллективах (мощный фактор укрепления мужской кооперации согласно теории родственного альтруизма У. Гамильтона). Модельной группой нашего исследования стали молодые мужчины бурятской национальности (104 участника; возраст 20±2 года) – традиционно кочевые скотоводы с ярко выраженной патриархальной культурой; жители г. Улан-Удэ. Склонность к про-социальному поведению участников оценивалась в групповой экспериментальной игре «Общественное благо», которая проводилась в группах из 4 человек, в условиях взаимодействий «лицом к лицу». Суть игры заключалась в том, что участникам предлагалось вынести несколько последовательных решений о том, сколько собственных денежных средств (предоставленных каждому игроку в личное распоряжение) он желает вложить в «общий проект», а сколько оставить при себе. Сумма вложенных в «общий проект» средств в последствии удваивалась и распределялась поровну между всеми четырьмя участниками группы. Эта игра позволяет определить индивидуальную склонность к кооперации, обману, альтруистичному поведению. Эксперимент проводился в 2 раунда: (1) при отсутствии какой-либо коммуникации между участниками; (2) при условии возможности переговоров. Важно отметить, что в обоих случаях решения о вложении средств в «общий проект» принимались участниками секретно, так что другие участники группы не могли проверить, кто сколько вложил (даже несмотря на договорённости, присутствовавшие во втором раунде игры). В результате исследования было установлено, что вербальная коммуникация между участниками оказывает колоссальный положительный эффект на проявления кооперативного поведения, способствует сдвигу поведения в сторону интересов группы, а не индивидуальной выгоды. Повышенная индивидуальная вербальная экспрессивность была свойственна высоко-кооперативным участникам. Однако небольшая часть участников характеризовалась антисоциальным поведением (применением стратегии обмана). К нашему удивлению, им была свойственна еще большая степень вербальной экспрессивности. Мы склонны полагать, что полученный результат свидетельствует об использовании обманщиками сверхстимула, для расположения к себе других участников группы, что является необходимым условием для успешного обмана. Результаты обсуждаются с эволюционной точки зрения. Here we report on the results of the experimental study investigating an impact of verbal communication on male group cooperation. The coevolution of cooperation and verbal communication makes up a special interest within evolutionary anthropology, since Homo sapiens is distinguished by outstanding cooperative and communicative (language) abilities. Male cooperation is of particular interest. Historically emerged so that activities, which require high group-cooperation skills (warfare, big-game hunting), are predominantly or exclusively male occupations. Maintaining high level of cooperation among males, in contrast to females, was also encouraged by widely spread patrilocality tradition, meaning that males were closely genetically related with each other during the whole life-span (a powerful factor for enhancement of cooperation according to Hamilton’s kin-selection theory). Participants of our study were young men of Mongolian origin (Buryats of Southern Siberia), whose traditional culture involved nomadic pastoralism and patrilocality. Individual predispositions for pro-social behavior were assessed via group cooperation game – “Public Goods Game”, which was played in groups of four participants, under condition of the “face-to-face” interactions. In this game each participant was asked to decide how much of his own funds (real monetary equivalents were given to his disposal by the experimenter) he was willing to invest into a “common project” (not invested funds were kept by a participant). The sum of investments into “common project” was then doubled and distributed equally between all four group members. This game allows estimating individual predispositions for cooperation, cheating, and altruistic behavior. The experiment was conducted in 2 rounds: (1) under condition of absence of any intentional communication between participants; (2) with verbal negotiations option. Worth noting that all investment decisions in both rounds were made privily, so that other group members had no information on investments of their partners (even despite any verbal agreements in the second round). Our results have demonstrated that verbal communication has a crucial positive impact on cooperative behavior, shifts individual behavior towards maximizing group benefits as opposed to immediate personal gain. Increased individual verbal expressiveness was characteristic of highly pro-socially oriented subjects. However a small fraction of our participants was characterized by anti-social behavior (employing cheating strategy), and these subjects were even more talkative than others. This result suggests that cheaters have applied exaggerated (supernatural) stimulus to build own trustworthiness in a group, which is a prerequisite of successful cheating. The results are discussed from evolutionary perspective.


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