Savanna burning and the assessment of long-term fire experiments with particular reference to Zimbabwe

Long-term fire experiments in savannnas are rare, given the difficulties and demands of operation. Controlled fire experiments date from colonial times in West Africa, although the largest and best-known is located in the Kruger National Park, South Africa. The achievements of these experiments are assessed from examples in Africa, South America and Australia. A less well-known experiment in Zimbabwe was sited at the Marondera Grassland Research Station and ran from 1953 to 1991. Some of the preliminary results on the impact of fire on vegetation are analysed and compared with further vegetation surveys in 2007. Studies on tree growth in this miombo savanna woodland indicate that the plots burned at three- and four-year intervals recovered to greater mean heights than the unburned control plots. There was no significant variation between treatments, suggesting that the few trees that did survive in the frequently burned plots were large specimens. Brachystegia and Julbernadia dominated the plots throughout and after the experiment. Basal area and stocking density were highest in the four-yearly burned plots but there was a high variability throughout the experiment, suggesting that many trees may have attained heights and bark thicknesses sufficient to protect from fire damage. Fire also affected the composition of the herbaceous plant community, but not the number of species. By the end of the experiment some grass and sedge species had flourished while others revealed greater susceptibility to fire, and fire-tolerant species predominated in the most frequently burned areas. The experimental design appeared to cope well with the variability between plots and indicated the soundness of the initial design and its implementation.

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Long-term effects of thinning and fertilization on growth of red fir in northeastern California

Canadian Journal of Forest Research ◽

10.1139/x05-048 ◽

2005 ◽

Vol 35 (6) ◽

pp. 1285-1293 ◽

Cited By ~ 7

Author(s):

Jianwei Zhang ◽

William W Oliver ◽

Robert F Powers

Keyword(s):

Basal Area ◽

Basal Area Increment ◽

Stand Development ◽

Long Term Effects ◽

Annual Increment ◽

Fourth Period ◽

Abies Magnifica ◽

The Impact ◽

Second Period

To determine the impact of fertilization and thinning on growth and development of red fir (Abies magnifica A. Murr.) stands, we established an experiment in a 60-year-old stand using a 2 × 3 factorial design with nitrogen-fertilized and nonfertilized treatments and three stocking levels. Plots were established in 1976 and were measured every 5 years for 26 years. The periodic annual increment in basal area was 97%, 51%, 38%, and 33% greater in fertilized trees than in nonfertilized trees during the first, second, third, and fourth 5-year periods, respectively. After 20 years, annual basal area increment was greater in nonfertilized trees. The response of annual volume increment to fertilization was not statistically significant until the fourth period. Yet, volume increases of the fertilized plots were 25%92% greater than those of the nonfertilized plots from 1976 to 1996. Similarly, basal area increment was greater in lightly thinned plots than in unthinned plots from the second period on, until heavy mortality during 19962002. Basal area increment was greater in the heavily thinned plots from the fourth period on. Results indicate that red fir can respond to fertilization and thinning quickly and that both treatments speed stand development. In addition, fertilization increases the stand's carrying capacity. Therefore, forest managers can use these silvicultural practices to improve stand growth, to reduce fire fuels, and to accelerate stand development.

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The impact of burning on lion Panthera leo habitat choice in an African savanna

Current Zoology ◽

10.1093/czoolo/59.3.335 ◽

2013 ◽

Vol 59 (3) ◽

pp. 335-339 ◽

Cited By ~ 12

Author(s):

Stephanie Eby ◽

Anna Mosser ◽

Ali Swanson ◽

Craig Packer ◽

Mark Ritchie

Keyword(s):

National Park ◽

Habitat Choice ◽

Territory Size ◽

Short Term ◽

Data Set ◽

Burned Areas ◽

The Impact ◽

Term Data ◽

Prey Attraction

Abstract Carnivores play a central role in ecosystem processes by exerting top-down control, while fire exerts bottom-up control in ecosystems throughout the world, yet, little is known about how fire affects short-term carnivore distributions across the landscape. Through the use of a long-term data set we investigated the distribution of lions, during the daytime, in relation to burned areas in Serengeti National Park, Tanzania. We found that lions avoid burned areas despite the fact that herbivores, their prey, are attracted to burned areas. Prey attraction, however, likely results from the reduction in cover caused by burning, that may thereby decrease lion hunting success. Lions also do not preferentially utilize the edges of burned areas over unburned areas despite the possibility that edges would combine the benefit of cover with proximity to abundant prey. Despite the fact that lions avoid burned areas, lion territory size and reproductive success were not affected by the proportion of the territory burned each year. Therefore, burning does not seem to reduce lion fitness perhaps because of the heterogeneity of burned areas across the landscape or because it is possible that when hunting at night lions visit burned areas despite their daytime avoidance of these areas.

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Salinity and nutrient distribution in soil profiles of long-term crop rotations

Canadian Journal of Soil Science ◽

10.4141/cjss94-031 ◽

1994 ◽

Vol 74 (2) ◽

pp. 229-234

Author(s):

G. J. Beke ◽

H. H. Janzen ◽

T. Entz

Keyword(s):

Root Zone ◽

Soil Depth ◽

Crop Rotations ◽

Research Station ◽

Nitrate N ◽

Cropping Sequence ◽

Extractable P ◽

The Impact ◽

Semi Arid

The effect of cropping systems on salt and nutrient movement in soil has been studied mainly at relatively short-term (< 20 yr) experimental sites or at commercial sites without documented history. This study investigated the impact of two similar, unfertilized, long-term crop rotation experiments, differing in duration and experimental design, on soil EC (salinity), sodium adsorption ratio (SAR), nitrate-N, and extractable-P distributions in semi-arid southern Alberta. The experiments, established in 1911 and 1951 at the Lethbridge Research Station on moderately well drained soils, included continuous spring wheat (Triticum aestivum L.) fallow-wheat-wheat and fallow-wheat cropping sequences. Regardless of length of experiment or cropping sequence, the salinity and SAR values increased with soil depth. Leaching of salts had occurred to a minimum depth of 150 cm, depending on the nature of the parent material and soil-drainage volumes. Within the 90- to 150-cm depth, most salt leaching had taken place under the fallow-wheat rotation and least under the continuous-wheat cropping sequence. Downward movement of nitrate-N generally peaked in the lower root zone, regardless of cropping system or duration of the experiment. Deep leaching of nitrate-N had occurred in the fallow-wheat soil. Movement of extractable P was restricted to the 0- to 30-cm depth. Significant deep leaching of salts had taken place over the 35-yr period of the 1951 experiment whereas the longer, 75-yr period of the 1911 experiment was required to cause significant deep leaching of nitrate-N and of extractable P movement in the 0- to 30-cm depth. Key words: Dryland crop rotations, summerfallow, semi-arid region, soil salinity, soil nitrate and phosphate

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Long-term effects of peatland black spruce regeneration treatments in northeastern Ontario

The Forestry Chronicle ◽

10.5558/tfc81042-1 ◽

2005 ◽

Vol 81 (1) ◽

pp. 42-49 ◽

Cited By ~ 8

Author(s):

Arthur Groot ◽

Michael J Adams

Keyword(s):

Picea Mariana ◽

Black Spruce ◽

Stocking Density ◽

Basal Area ◽

Long Term Effects ◽

Seeding Rate ◽

Site Class ◽

Advance Regeneration ◽

Rate Effects

Studies of black spruce (Picea mariana (Mill.) BSP) broadcast seeding and of harvest methods for advance regeneration protection were remeasured 17 to 20 years after establishment on peatland sites in northeastern Ontario. The effects of seeding rate on black spruce stocking, density or basal area were apparent at two study locations 20 years after treatment, but high levels of advance regeneration masked seeding rate effects at two other study locations. The effects of different harvest methods on black spruce stocking, density and basal area, which were evident at earlier ages, were no longer statistically significant 17 to 19 years after treatment. Black spruce density increased moderately with time because of gradual recruitment of new seedlings. Density of black spruce stems taller than 1.3 m tall exceeded 4000 ha-1 for nearly all treatments, but these stems were spatially aggregated at the 4-m2 scale. The stand characteristics of these regenerated peatland stands are consistent with site class 2 stands in the Ontario normal yield tables. Key words: black spruce; Picea mariana; advance regeneration; direct seeding; regeneration; peatland; stand dynamics

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The Impact of Availability Territory and Terrain Characteristics on Location of Burnt Areas in Dark Coniferous Forests Pechora-Ilych Nature Reserve

Forestry Engineering Journal ◽

10.12737/article_59c227c2d0b820.11924404 ◽

2017 ◽

Vol 7 (3) ◽

pp. 49-58

Author(s):

Алексей Алейников ◽

Aleksey Aleynikov ◽

Ольга Лисицына ◽

Ol'ga Lisicyna ◽

Надежда Владимирова ◽

...

Keyword(s):

Forest Cover ◽

Nature Reserve ◽

Functional Organization ◽

Local Population ◽

Selective Logging ◽

Burned Areas ◽

Burnt Areas ◽

The Impact ◽

Succession Processes

Fires – one of the most important factors in catastrophic transformation of natural forest cover. Destroying whole ecosystems, fires, at the same time, start long-term succession processes. The study of the causes of fires makes a significant contribution to understanding structural and functional organization and dynamics of modern forests. The article examines the impact of availability of the territory and landscape-topographical features on the distribution and size of burnt areas formed in the last 150 years, in the foothill area of Pechora-Ilych Nature Reserve. The peculiarity of the territory is a complete lack of roads; the only roads are the rivers: Pechora, Ilych and their major tributaries. Analysis of the location of burned areas showed that significant influence on the occurrence of fire is provided by proximity of navigable rivers, since the greatest number of fires during studied period occurred at a distance of up to 3 km from navigable rivers, along which local population actively explores the territory (building of hunting shacks, gathering pine nuts, selective logging, etc.). Size of the fire is connected with proximity to navigable rivers: the largest fires is confined to the river banks and are likely to be only of anthropogenic origin. Small fires occurred at different distances from navigable rivers, could be both natural and anthropogenic ones. Settlements that existed before the formation of reserve had substantial and statistically significant effect on the occurrence of fire. Statistically significant associations of burnt areas with absolute altitude (the vast majority of burned areas are located on surfaces below 400 m) indirectly confirms that fires occurred at intensively developed parts of forests along the rivers.

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Decadal changes in fire frequencies shift tree communities and functional traits

10.1101/2020.07.22.216226 ◽

2020 ◽

Author(s):

Adam F. A. Pellegrini ◽

Tyler Refsland ◽

Colin Averill ◽

César Terrer ◽

A. Carla Staver ◽

...

Keyword(s):

Environmental Conditions ◽

Fire History ◽

Vegetation Type ◽

Basal Area ◽

Fire Regimes ◽

Fire Frequency ◽

Tree Communities ◽

In Fire ◽

The Impact

Global change has resulted in chronic shifts in fire regimes, increasing fire frequency in some regions and decreasing it in others. Predicting the response of ecosystems to changing fire frequencies is challenging because of the multi-decadal timescales over which fire effects emerge and the variability in environmental conditions, fire types, and plant composition across biomes. Here, we address these challenges using surveys of tree communities across 29 sites that experienced multi-decadal alterations in fire frequencies spanning ecosystems and environmental conditions. Relative to unburned plots, more frequently burned plots had lower tree basal area and stem densities that compounded over multiple decades: average fire frequencies reduced basal area by only 4% after 16 years but 57% after 64 years, relative to unburned plots. Fire frequency had the largest effects on basal area in savanna ecosystems and in sites with strong wet seasons. Analyses of tree functional-trait data across North American sites revealed that frequently burned plots had tree communities dominated by species with low biomass nitrogen and phosphorus content and with more efficient nitrogen acquisition through ectomycorrhizal symbioses (rising from 85% to nearly 100%). Our data elucidate the impact of long-term fire regimes on tree community structure and composition, with the magnitude of change depending on climate, vegetation type, and fire history. The effects of widespread changes in fire regimes underway today will manifest in decades to come and have long-term consequences for carbon storage and nutrient cycling.

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Suppressed, but Not Forgotten

Swiss Journal of Psychology ◽

10.1024/1421-0185/a000033 ◽

2011 ◽

Vol 70 (1) ◽

pp. 5-11 ◽

Cited By ~ 8

Author(s):

Beat Meier ◽

Anja König ◽

Samuel Parak ◽

Katharina Henke

Keyword(s):

Memory Trace ◽

Thought Suppression ◽

Test Phase ◽

Indirect Test ◽

Final Test ◽

Test Experiment ◽

And Control ◽

Cue Words ◽

The Impact

This study investigates the impact of thought suppression over a 1-week interval. In two experiments with 80 university students each, we used the think/no-think paradigm in which participants initially learn a list of word pairs (cue-target associations). Then they were presented with some of the cue words again and should either respond with the target word or avoid thinking about it. In the final test phase, their memory for the initially learned cue-target pairs was tested. In Experiment 1, type of memory test was manipulated (i.e., direct vs. indirect). In Experiment 2, type of no-think instructions was manipulated (i.e., suppress vs. substitute). Overall, our results showed poorer memory for no-think and control items compared to think items across all experiments and conditions. Critically, however, more no-think than control items were remembered after the 1-week interval in the direct, but not in the indirect test (Experiment 1) and with thought suppression, but not thought substitution instructions (Experiment 2). We suggest that during thought suppression a brief reactivation of the learned association may lead to reconsolidation of the memory trace and hence to better retrieval of suppressed than control items in the long term.

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