Effects of fire and agricultural practices on neotropical ant communities

Fire is extensively used in agricultural management in Mexico. There is little information on the effects of those practices on the abundance and diversity of animals that live within these forest soils. We studied the effect of slashing, burning and land use in a tropical deciduous forest on ant communities in the State of Jalisco, Mexico. The original vegetation (tropical deciduous forest) was modified into a corn field. Sampling was carried out in five stages: before slashing, after slashing, after burning, after seeding and after harvest. We found that very severe fires greatly reduced ant diversity. The most important effect of fire was the reduction of ant density, and the change of species composition and trophic guilds. These changes are relevant in the recycling process of energy in the ecosystem.     

Export of chloride after clear-cutting in the Hubbard Brook sandbox experiment

The objective of this study was to discern the source of higher than usual concentrations of chloride in drainage water collected from experimental forest plots after clear-cutting. When the sandbox experiments were initiated at the Hubbard Brook Experimental Forest Station three vegetation types were established: red pine, grass, and minimally vegetated (scattered lichens and bryophytes) as the bare control plot. After 15 years of growth the trees were cut down and above-ground biomass removed from the red pine sandbox. For several years prior to the cut, high concentrations ( 75 M) of dissolved Cl^– in drainage waters occurred in November/December. This is attributed to the buildup of rainfall-derived Cl^– due to evapotranspiration that depletes soil moisture to low levels resulting in a lack of drainage during this period. The excess Cl^– is quickly flushed out by subsequent drainage over a few weeks and Cl^– concentrations return to values characteristic of rainfall and throughfall. After the trees were removed in May, 1998, Cl^– continued to be leached from the system. The concentration of Cl^– peaked (175 M) in Sept. 1998 and did not return back to base level concentration until Dec. 1999. The Cl^– release pattern is distinctly different from that of dissolved NO₃ ^–, which peaked about one year later than Cl^–. An excess (over that of the control sandbox) of 78 g Cl^– was released in the 1.5 year period after clear-cut, showing that a large amount of leachable chloride is stored in the bulk soil/root/organic matter fraction. Lack of uptake by trees may be part of the reason for this chloride pulse. But an analysis of chloride content in roots and litter indicates that as much as 50% of the chloride leached from the sandbox may have come from the decaying roots and litter. Additional chloride may have been released from the soil organic matter by decomposition. The biochemical behavior of Cl^– in systems such as this should be evaluated before assuming Cl^– to be conservative for purposes of hydrological transport or soil weathering studies.     

澳大利亚森林火灾的管理与火生态的研究

澳大利亚是火灾频发的地区．每年因森林火灾的危害都要造成相当的社会、经济损失及生态环境的破坏,故火生态的研究及火的管理在澳大利亚的生态学研究中一直占有重要地位．本文主要讨论了澳洲森林大火起燃的物理过程和机制、可燃物的特征、林火的特点、习性及对生态环境的影响和如何控制和减少火灾的危害性,达到对火进行利用、控制和管理的目的．     

Long‐term forest structure and regeneration after wildfire in Russian Karelia

We examined forest structure and regeneration in a 350‐ha forest dominated by Pinus sylvestris 31 yr after a wildfire in the Vienansalo wilderness, Russian Karelia. In most parts of the area, the 1969 fire was not stand replacing but had left larger trees alive so that the area generally remained forest covered. In some localities, however, all trees apparently died and distinct gaps were formed, suggesting that the fire severity varied considerably, contributing to increased variation in stand structure. Living and dead wood volumes were similar, 112 and 96 m³.ha^‐1, respectively. The tree species proportions of dead vs living wood indicated that prior to fire disturbance Picea was more common in the area. Regeneration was abundant (saplings, ca. 14 000 ind.ha^‐1, height 20 ‐200 cm) and tree seedling recruitment had occurred over a long period of time. Regeneration density was highest on the mesic Vaccinium‐Myrtillus forest site type, decreasing towards nutrient‐poor site types. The most common regeneration microsites were level ground (56% of saplings), immediate surroundings of decayed wood (23%) and depressions (11%). The high proportion of saplings on level ground suggests that after the fire regeneration conditions have been favourable across the whole forest floor. Nevertheless, the areas in the vicinity of decayed wood have been particularly important microsites for seedling establishment. The results provide an example of the effects of wildfire on forest structure in a natural Pinus sylvestris dominated forest, demonstrating the non stand replacing character of fire, high variability in stand structure and the abundance of post‐fire regeneration.     

Effects of prescribed fire on an ant community in Florida pine savanna

Abstract.  1. The effects of prescribed fire on ant community structure were examined in a regenerating longleaf pine savanna in Florida, U.S.A. The presence of ants on 20, 10 × 10 m plots was determined by baiting every 1–3 months from 18 months before a fire until 6 months afterwards.
2. Expected species richness (based on rarefaction) and species density 6 months post-fire were significantly lower than for the same month (September) 6 months before the fire.
3. Cluster analysis revealed that the effects of fire were far less important predictors of ant community structure than seasonality and unexplained inter-annual variation. Thus, overall, the impacts of fire were relatively minor and short term at the community level.
4. Different functional groups of ants (as defined by Andersen, 1997) responded to fire in strikingly different ways. Generalised Myrmicinae (e.g. Pheidole spp., Monomorium viride ) were affected more severely by fire than were the other functional groups. In contrast, the dominant Dolichoderinae ( Forelius pruinosus ) exhibited a large increase after the fire and seemed to be responsible for the decline in abundance of several species.
5. A strong negative correlation between F. pruinosus and other groups of ants immediately after the fire suggested more intense competition among ants at that time. Six months post-fire, the abundance of F. pruinosus decreased markedly and the abundance of other species rebounded.
6. The rapid post-fire recovery of the ant community probably reflects adaptations of ants to a chronic fire regime.     

Effects of repeated burning on Mediterranean communities of the northeastern Iberian Peninsula

Question: In relation to a single fire, do repeated wildfires in Mediterranean type ecosystems (1) reduce plant species richness or diversity; (2) modify patterns of abundance or dominance of plant species or (3) alter plant composition? Location: Pinus halepensis dominated communities of Catalonia, northeastern Iberian Peninsula, western Mediterranean Basin. Methods: Regional, paired design with 14 study sites, each consisting of a once burnt area (1994) and a twice burnt area (1975–1993 and 1994). Ten years after the last fire, we recorded all vascular plant species present in nested plots and quantified their relative abundances on transects. We compared species richness, diversity, dominance and relative abundance and species‐area correlations between paired once and twice burnt areas and assessed their floristic composition similarity. Results: No statistically significant differences were found in species richness or diversity. Slopes of species‐area correlations were higher in once burnt areas. In twice burnt areas, dominance by one or two species was higher. P. halepensis showed lower relative abundance and nanophanerophytes showed higher relative abundance. No differences were found for resprouter, seeder or resprouter‐seeder species. Floristic composition similarity between paired areas tended to be higher in less productive sites. Conclusions: Fire recurrence had contrasting effects on species richness at different spatial scales. Repeated burning reduced the relative abundance of the dominant tree species, which resulted in a higher relative abundance of shrubs. It also promoted the dominance of herbs, particularly Brachypodium retusum. However, it did not change the relative abundance of regenerative groups. Paired areas were more similar as they were more Mediterranean in terms of climatic conditions.     

Host identity affects the response of mycorrhizal fungal communities to high severity fires in Alaskan boreal forests

Ongoing climate change in the boreal forests of western North America is associated with wildfires which are increasing in extent and severity, thus impacting mycorrhizal fungal communities through fungal mortality and shifts in host species and age. We planted three native tree species, Picea mariana, Picea glauca, and Populous tremuloides, and non-native Pinus contorta var. latifolia at 22 post-fire sites, encompassing wide variation in fire severity and environmental gradients, across Interior Alaska. We characterized fungal community composition using Illumina MiSeq. Fire severity had a greater impact on fungal composition than the environmental variables we considered. There were large shifts in fungal Phyla and guilds with high severity, but these shifts were dependent on host tree species. We also found pine-specific fungi on Pinus contorta var. latifolia. These data suggest that shifts in mycorrhizal fungal communities from increases in fire severity may be exacerbated by associated changes in plant successional trajectories and host composition.     

Eleven years of recovery dynamic after experimental burning and cutting in two Cistus communities

Recovery after cutting and burning in two series of experimental shrubland plots dominated by Cistus laurifolius and Cistus ladanifer, respectively, was studied over 11 years. The two communities tend to recover by an autosuccession process after disturbances, with Cistus species being dominant from the first or second year. The greatest diversity is recorded in the first few years after the disturbances, with higher species richness, basically herbaceous ones, and lower dominance effect. Cover by woody species tends to increase but from the fourth year the differences are not significant. The highest herbaceous cover is after one year and the peak is more marked in the cut plots. Herbaceous species cover decreases afterwards and there are small changes in the different years but without clear trends. When all the samplings are compared by a TWINSPAN, the first division separates both communities and the  second division the initial and the final phases from each community. The separation between cut and burnt plots is only observed in the final phases.     

Effects of forest disturbance on the structure of ground-foraging ant communities in central Amazonia

This study evaluates biotic responses, using ants as bio-indicators, to relatively recent anthropogenic disturbances to mature forest in central Amazonia. The structure of the ground-foraging ant community was compared in four habitats that represented a gradient of disturbance associated with differences in land use. Ants were collected in undisturbed, mature forest, in an abandoned pasture, in a young regrowth forest (situated in a former pasture area), and in an old regrowth forest (established where mature forest was just cleared and abandoned). More ant species were found in mature and old regrowth forest than in the abandoned pasture. By contrast, ant abundance tended to decrease with forest maturity. Both pasture and young regrowth forest exhibited a distinct ant species composition compared to mature forest, whereas species composition in the old regrowth forest showed greater similarity to that of mature forest. In spite of differences in fallow time between former pasture areas and non-pasture areas, there is evidence that different land-management practices do result in different rates of recovery of the ant forest fauna after land abandonment. In any case, recuperation of the ground-foraging ant fauna appears to be faster than regeneration of the woody-plant community. In this sense, regrowth forests may be valuable for the conservation of ground-foraging ants and perhaps for other components of mature-forest leaf-litter fauna within the context of a fragmented landscape.     

Effects of late growing-season and late dormant-season prescribed fire on herbaceous vegetation in restored pine-grassland communities

Abstract. We compared the effects of late dormant-season and late growing-season prescribed fires on herbaceous species in restored shortleaf pine- (Pinus echinata) grassland communities in the Ouachita Highlands of western Arkansas. Herbaceous species richness, diversity, and total forb and legume abundance increased following fire. Late growing-season burns reduced distribution and abundance of panicums (primarily Panicum boscii, P. dichotomum, and P. linearifolium) while late dormant-season burns increased Panicum distribution and abundance. Density of legumes (such as Stylosanthes biflora) increased following frequent or annual dormant-season fires. However, season of fire influenced the distribution and abundance of fewer than 10 % of the species. Fire plays an essential role in pine-grassland communities by creating and maintaining open canopy conditions that perpetuate understory herbaceous plant communities.     

Impact of secondary forest management on ant assemblage composition in the temperate region in Japan

In Japan, the impacts of human disturbance on ant assemblages have been intensively studied mainly in suburban areas. In contrast, the impact on ant assemblages of long-term human management and abandonment of forests is not well studied even though forestry is viewed as a process that seriously impacts ant assemblages. Besides, the studies focused on the relationship between secondary forest management for producing the firewood and charcoal which is considered to be characteristic of Japan and ant assemblage is not well studied. Do the long-term impacts on the secondary forest alter the ant composition? The effects of forest management on ant assemblages were studied through comparisons of managed, unmanaged and clear cut forest plots in secondary tree stands that had been used previously for producing firewood and charcoal. Ant species richness did not differ among forest categories, but ant species composition varied among forest categories. The absence or presence of openland and woodland ant specialist species is considered a good indicator for secondary forest management.     

临安次生灌丛植物多样性对林火烈度空间异质性的响应

以同一过火3a后临安市太阳镇天然次生灌丛为对象,采用样地调查法按不同林火烈度设置火干扰样地进行植物群落调查,以检验林分内部的林火烈度异质性是否与局部的植物多样性变化相关。结果表明:研究区共有高等植物83种,分属于38科67属,群落区系组成以亚热带科属为主,表现出常绿阔叶林已退化过渡到位于演替早期阶段的落叶次生灌丛群落的性质;低林火烈度对灌木层的树种组成有影响,但不明显;中烈度林火对灌木层的物种组成影响较大;低、中林火烈度下草本层的物种组成变化都很明显;灌木层的物种数和多样性指数都表现出低烈度火未火烧中烈度火的趋势;草本层的物种数、多样性指数和均匀度指数表现出中烈度火低烈度火未火烧的趋势;草本层的物种组成和多样性受林火烈度的影响较灌木层更大。研究表明次生灌丛群落过火区内部林火烈度异质性在初期会引起植物多样性的响应差异;低烈度火干扰可以增加次生灌丛生物多样性、促进群落更新;中烈度火干扰下木本植物物种多样性丧失较大,而草本植物多样性显著增加,不利于群落的正向演替。     

Effects of Wolbachia on mtDNA variation in two fire ant species

Wolbachia are endosymbiotic bacteria that infect arthropods. As they are maternally transmitted, the spread of Wolbachia variants within host populations may affect host mtDNA evolution. We sequenced a portion of the mitochondrial cytochrome oxidase I gene from numerous individuals of two Wolbachia-infected fire ant species, Solenopsis invicta and S. richteri, to determine how these bacteria influence patterns of mtDNA variation. As predicted, there was a strong association between Wolbachia strain and host mtDNA lineage within and between these fire ant species. However, there was no consistent association between the presence of Wolbachia and a reduction in mtDNA diversity. Moreover, patterns of mtDNA variation within Wolbachia-infected populations did not differ consistently from neutral expectations, despite our prediction that strong positive selection acting on Wolbachia influences the evolutionary dynamics of other cytoplasmic genomes. Specifically, while values of Tajima's D consistently were less than zero for all six samples of fire ants harbouring Wolbachia, MacDonald-Kreitman tests suggested that the patterns of variation were different from those expected under neutrality in only two of the samples. We conclude that these neutrality tests do not unambiguously reveal a clear effect of Wolbachia infection on patterns of mtDNA variation and substitution in fire ants. Finally, consistent with an earlier study, our data revealed the presence of two divergent mtDNA haplotype lineages and Wolbachia strains within S. invicta. Recognition of these two lineages has important consequences for interpreting patterns of mtDNA evolution and genetic differentiation between conspecific social forms of this species.     

Biodiversity and resilience of arthropod communities after fire disturbance in temperate forests

Changes in ecosystem functions following disturbances are of central concern in ecology and a challenge for ecologists is to understand the factors that affect the resilience of community structures and ecosystem functions. In many forest ecosystems, one such important natural disturbance is fire. The aim of this study was to understand the variation of resilience in six functional groups of invertebrates in response to different fire frequencies in southern Switzerland. We measured resilience by analysing arthropod species composition, abundance and diversity in plots where the elapsed time after single or repeated fires, as determined by dendrochronology, varied. We compared data from these plots with data from plots that had not burned recently and defined high resilience as the rapid recovery of the species composition to that prior to fire. Pooling all functional groups showed that they were more resilient to single fires than to repeated events, recovering 6–14 years after a single fire, but only 17–24 years after the last of several fires. Flying zoophagous and phytophagous arthropods were the most resilient groups. Pollinophagous and epigaeic zoophagous species showed intermediate resilience, while ground-litter saprophagous and saproxylophagous arthropods clearly displayed the lowest resilience to fire. Their species composition 17–24 years post-burn still differed markedly from that of the unburned control plots. Depending on the fire history of a forest plot, we found significant differences in the dominance hierarchy among invertebrate species. Any attempt to imitate natural disturbances, such as fire, through forest management must take into account the recovery times of biodiversity, including functional group composition, to ensure the conservation of multiple taxa and ecosystem functions in a sustainable manner.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .     

The effects of forestry on carabid beetles (Coleoptera: Carabidae) in boreal forests

As compared to natural forests, managed boreal forests are younger, more homogeneous in terms of tree age and species composition, and consist of smaller fragments. Here we examine the effects of such characteristics caused by forestry on carabid beetles (Coleoptera, Carabidae) in the boreal region. The main results are the following. (1) Fragmentation of forests and the size of a fragment appear not to be crucial for the survival of the majority of forest carabids, as they tend to be distributed over various successional stages, but species requiring old-growth habitats suffer. (2) For carabids there appear to be no or very few edge specialist species, and forest-open land edges appear to be effective barriers for species associated with forest or open habitat. However, generalist species easily cross the edge, and edges of forest fragments may be invaded by species from the surrounding open habitat. (3) Habitat change following clear-cutting dramatically changes the composition of carabid assemblages: species restricted to mature forests disappear and open-habitat species invade, while habitat generalists survive at least in the short term. Carabid diversity can probably best be maintained if forest management mimics natural processes, maintains natural structures and includes the natural composition of vegetation and other structural elements (such as dead wood) within the stands, provided that these forest features can be maintained and recreated through forest management practices. At a larger scale, the whole spectrum of forest types and ages (especially old-growth forests), and different successional processes (especially fire) should be maintained. These require the development and use of innovative logging methods, and the planning, implementation, and assessment of landscape-scale ecological management strategies.     

蚂蚁-紫胶虫兼性互利关系对蚂蚁群落多样性的影响

为了探讨蚂蚁-紫胶虫兼性互利关系对树冠上蚂蚁群落多样性的影响,作者于2009年12月至2010年5月,采用目光搜寻的方法调查了不同紫胶虫数量样地(样地Ⅰ有效枝条寄生率为60％、样地Ⅱ为30％、样地Ⅲ为10％、样地Ⅳ不放养紫胶虫)中钝叶黄檀(Dalbergia obtusifolia)树冠蚂蚁群落的多样性.结果显示,兼性互利关系能够显著提高树冠蚂蚁群落多度及物种丰富度,改变树冠上蚂蚁的群落结构;由紫胶虫数量高低导致的蜜露产量的多寡对树冠上蚂蚁的多度和群落结构均具有显著影响,但对物种丰富度无显著影响;同时紫胶虫的个体发育阶段也是影响树冠上蚂蚁多度的重要因素.本研究证明,紫胶虫对于提高树冠上蚂蚁的多样性具有显著的正面影响,紫胶林对蚂蚁多样性保护有利.     

Effects of regeneration burning on the properties of forest soils in southern Tasmania: Comments on recent study by Elliset al. (1982)

Summary Important methodological factors which should be considered when attempting to measure and interpret the effects of hot slash fires on the properties of forest surface soils are briefly discussed. Soil properties cannot be assumed to be similar, prior to cutting and burning of forest, on coupes located several kilometres apart in dissected terrain. In order to study the effects of forest treatment on soil properties, sites should either be closely adjacent or preferably measurements should be taken before and after treatment on the same experimental area.It is argued that the conclusions reached by Elliset al. regarding the effects of regeneration burning on soil properties in southern Tasmania are unjustified because of the use of inappropriate experimental methods.     

Chronosequential change in a butterfly community after clear-cutting of deciduous forests in a cool temperate region of central Japan

Transect counts of butterflies were conducted in the northern part of Ibaraki, central Japan, from 1997 to 2001 at 11 census sites, composed of successive stages of deciduous forest development: grassland (one site, early abandoned stage); cutover land (one site, 1–5 years after clear‐cutting); secondary forests (very young (two sites, 6–9 years), middle (two sites, 16–22 years) and old (two sites, 47–51 years)) and old‐growth natural forests (three sites, ≥124 years old). A total of 86 species and 8858 individual butterflies were recorded by 29 sets (406 times) of transect counts. The species richness (number of species), abundance (number of individuals) and diversity indices (Shannon–Wiener H′ and Simpson's 1–λ) of butterflies were high in the early stages (grassland, cutover land and very young secondary forests) of secondary succession. Typical natural forest species increased with the progress of succession, and the old secondary forests and old‐growth natural forests had similar species composition. In contrast, most of the typical natural grassland species were recorded only in the grassland site. In the cutover land site, the number of individuals of grassland species considerably decreased from the first to the second year; furthermore, only one typical natural grassland species was recorded. Thus, the suitable stage for grassland butterfly species lasts for only 1–2 years after clear‐cutting. Old secondary forests (approximately>50 years old) would be able to give refuge to the forest butterfly species, including typical natural forest species. Based on the results, a practical, forestry‐based plan to conserve butterfly diversity was proposed.