Unburnt Areas Research Articles

Differential responses of the acidobacterial community in the topsoil and subsoil to fire disturbance in Pinus tabulaeformis stands.

Acidobacteria is found to be dominant and abundant in forest soil, and performs specific ecological functions (such as cellulose decomposition and photosynthetic capacity, etc.). However, relative limited is known about its changing patterns after a fire interruption. In this study, the response of soil Acidobacteria to a wildfire disturbance was investigated using the Illumina MiSeq sequencing system. The research area was classified by different severities of fire damage (high, moderate, and low severity, and an unburnt area), and samples were collected from various soil layers (0–10 cm as topsoil; 10–20 cm as subsoil). We obtained a total of 986,036 sequence reads; 31.77% of them belonged to Acidobacteria. Overall, 18 different Acidobacteria subgroups were detected, with subgroups 4, 6, 1, 3, and 2 the most abundant, accounting for 31.55%, 30.84%, 17.42%, 6.02%, and 5.81% of acidobacterial sequences across all samples, respectively. Although no significant differences in acidobacterial diversity were found in the same soil layer across different fire severities, we observed significantly lower numbers of reads, but higher Shannon and Simpson indices, in the topsoil of the high-severity fire area than in the subsoil. Non-metric multidimensional scaling (NMDS) analysis and permutational multivariate analysis of variance (PERMANOVA) also revealed significant differences in the acidobacterial community structure between the two soil layers. Soil pH, total nitrogen, NH4+-N, the Shannon index of understory vegetation and canopy density were the major drivers for acidobacterial community structure in the topsoil, while soil pH and organic matter were significant factors in the subsoil. A variance partitioning analysis (VPA) showed that edaphic factors explained the highest variation both in the topsoil (15.6%) and subsoil (56.3%). However, there are large gaps in the understanding of this field of research that still need to be explored in future studies.

A study of soil erosion rates using 239Pu, in the wet-dry tropics of northern Australia

The Daly River drains a large (52500 km2) and mainly undisturbed catchment in the Australian wet–dry tropics. The basin landscapes are mantled by a thick veneer of kandosol soil which has developed under varying rates of erosion, uplift, bedrock type and climate and has been identified as being suitable for agriculture. Commencement of large scale clearing and cropping since 2002 have raised concerns about the increased loss of top soil from the land clearing and cultivation activities adjacent to the Daly River. This study was undertaken to determine the modern soil loss rates which can be used to develop a sustainable soil conservation strategy for this catchment. 239Pu, released in the 1950s and 1960s by atmospheric nuclear weapons tests, is used to obtain a quantitative assessment of recent rates of soil loss. Soil cores 30–40 cm deep have been collected from fields with various land uses including peanut and hay cropping and cattle grazing. Cores taken from undisturbed and unburnt areas in open eucalypt woodland have been used as reference sites. The soil loss rates have been established by comparing the excess or deficiency of the 239Pu tracer over that of the reference sites. Since land use practices in the catchment are similar, it is likely that the measured soil loss rates are indicative of soil loss rates over the Daly Basin as well.The development of 239Pu as a soil tracer represents a viable alternative to the traditionally used 137Cs tracer. This also represents a new tool in the quantification of catchment soil loss and the adoption of appropriate soil conservation strategies for the tropical regions and regions where increasing settlement and agriculture are encroaching on catchment slopes.

Vegetation structure across fire edges in a Neotropical rain forest

Human-induced wildfires are one of the greatest threats to tropical forest and are predicted to increase in importance due to altered regimes associated with climate change. Wildfires promote high tree mortality, thus modifying forest structure and composition, and lead to habitat loss and fragmentation. Wildfires may also have effects on the adjacent unburnt areas due to edge influence; conversely, proximity to unburnt forest stands may favor regeneration in the burnt areas. We evaluated wildfire effects on the forest structure of Brazilian Atlantic forest remnants. We established 244 plots along eight 360 m-long transects distributed among three burnt patches, where we measured structural attributes of overstory, understory, and deadwood. The wildfire promoted very high mortality of trees, saplings, and lianas, changing substantially the forest structure. Our analyses showed clear differences between the burnt and unburnt areas but no clear gradients, highlighting the incipient stage of edge influence-related processes. The Neotropical bracken fern Pteridium arachnoideum was dominant in the burnt areas, which can possibly arrest secondary succession. Our results highlight the importance of wildfires as a menace to Brazilian Atlantic Forests remnants, as well as to tropical rainforests elsewhere - an ever-rising concern in a future of increased fire frequency.

Changes in grassland bird communities and breeding success after a fire in the Argentinian Pampas

Fire is responsible for the structure and composition of the biological communities in grasslands, despite this, few studies evaluate the effects of fire on bird communities, especially in the southern cone of South America. We compared the structure and composition of vegetation, bird communities, density of nests and predation rates between burnt and unburnt areas in grassland habitats in the Argentine Pampas during two reproductive seasons following a fire. The abundance, richness and diversity of birds were lower in the burnt areas and followed a pattern of interannual recovery associated with the increase in vegetation cover. The density of nests and the number of nesting species was higher in the controls only during the first season. The risk of predation of artificial nests in burnt areas was greater 1 year after the fire in respect to the controls, this difference decreased over time in inverse relationship with the percentage of plant cover surrounding the nests. Our results highlight the importance of a good vegetation structure and cover to support abundant and species-rich bird communities, as well as high values of nest density and reproductive success, and the ability of vegetation and bird communities to recover after the fire. However, this successional and temporary loss of habitats of high nesting value should be analyzed on a larger scale in order to consider the effect of the total reduction, and the fragmentation of the grasslands in a good state of conservation, on the population dynamics of grassland birds.

Assessing the resistance of a breeding amphibian community to a large wildfire

Socioeconomic and global climate changes are modifying fire regimes towards larger and more intense fires. Studying the response of organisms to the occurrence of large fires is crucial to anticipate shifts in patterns of biodiversity in fire-prone regions. Amphibia is the most threatened terrestrial vertebrate taxon, although it is also the least studied in relation to its response to fire. We evaluated the resistance to fire (similarity in species composition before and after fire) and reproductive success during the first breeding season after a fire of an amphibian community at the Mediterranean basin. We sampled 33 aquatic habitats, including ponds and streams located inside and outside the perimeter of the fire, and reported the presence of adult amphibians and their reproductive success. The community composition in burnt and unburnt areas was compared by similarity analysis. Generalized Linear Models were used to test the effects of fire (burnt or unburnt area), habitat type (stream or pond), distance to the perimeter of the wildfire, and altitude on total and breeding species richness. We did not find significant differences in amphibian community composition between burnt and unburnt areas, or in total species richness per water point. Of the 12 species found in the study area, only frogs of the genus Hyla declined in the burnt area due to the destruction of their preferred microhabitat, i.e. vegetation surrounding ponds. In contrast, breeding occurrence and breeding species richness declined in burnt streams and ponds. These results suggest a high amphibian resistance to fire at the community level, although the reduction of breeding activity can threaten the persistence of a rich community in future scenarios of increased recurrence of megafires.

Air and soil temperature across fire-created edges in a Neotropical rainforest

Anthropogenic fires have strong impacts in tropical rainforests that are not necessarily restricted to the burnt areas, as edge influence from the burnt patch may significantly alter the unburnt vegetation. Conversely, the remaining forest patches may mitigate changes in microclimate in the adjacent burnt areas. We studied variation in air and soil temperature in burnt and unburnt areas in the Atlantic forest of southern Bahia, Brazil. In November-December 2017, approx. two years after a series of wildfires, we sampled six transects at three burnt-unburnt edges, placing soil and temperature data loggers at the edge and at 20, 60, and 120 m into the burnt and unburnt areas and keeping them there for seven days. One data logger of each pair was buried at a depth of 3 cm and the other was kept at a height of 1 m above ground in a protective case. Air in the burnt area was cooler than in the forest at night and warmer in the morning, whereas soil was cooler than in the forest at night and early morning and warmer in the afternoon. We did not observe gradients in air or soil temperature, but soil temperature was more variable in the burnt area than in the unburnt forest. Conversely, notwithstanding the differences between diurnal and noctural temperatures, daily average, minimum and maximum air temperature varied little between the environments, possibly due to shading by bracken fern in the burnt areas. The variation in soil temperature is likely due to changes in vegetation structure, as the bracken fern does not provide as much shade and temperature control as the native forest canopy. Thus, even in the absence of strong effects on air temperature, changes in the temporal and spatial variability of soil temperature may be observed, with possible consequences for plant recruitment and soil organisms.

Relative spatial differences in sediment transport in fire-affected agricultural landscapes: A field study

Abstract Fires can considerably increase wind erosion risk in dryland agricultural regions. While wind erosion post-fire has been extensively studied in rangeland and grazing landscapes, limited work has considered post-fire erosion on annual plant communities and annual crops. Here we evaluated the relative spatial differences in patterns of sediment transport between burnt and unburnt crop stubble sites. Following a severe wildfire, we studied the spatio-temporal pattern of aeolian sediment transport with an array of Modified Wilson and Cooke (MWAC) dust samplers on adjacent burnt and unburnt wheat stubble. Sediment collection was conducted during nine weeks over an area of 3 ha. Collection rates were converted to horizontal sediment flux to derive spatial distribution maps and perform statistical analysis. Compared to the unburnt plot, we observed that sediment transport was up to 1000 times higher within the burnt area. This could lead to damages to emerging annual crops sown after the fire if no management strategy was applied. There was only negligible sediment flux in areas with shallow and low-density stubble, which gradually increased with distance from the unburnt area. These results suggest that strips of remaining unburnt stubble could provide a potential benefit to adjacent burnt or bare plots. Patterns of sediment transport were consistent in all sampling periods and were observed at a spatial scale undetectable in wind tunnel studies, indicating that field observations could complement fine-scale experimental studies to assess environmental processes in real-life conditions.

Post-burn and long-term fire effects on plants and birds in floodplain wetlands of the Russian Far East

Wildfires affect biodiversity at multiple levels. While vegetation is directly changed by fire events, animals are often indirectly affected through changes in habitat and food availability. Globally, fire frequency and the extent of fires are predicted to increase in the future. The impact of fire on the biodiversity of temperate wetlands has gained little attention so far. We compared species richness and abundance of plants and birds in burnt and unburnt areas in the Amur floodplain/Russian Far East in the year of fire and 1 year after. We also analysed vegetation recovery in relation to time since fire over a period of 18 years. Plant species richness was higher in burnt compared to unburnt plots in the year of the fire, but not in the year after. This suggests that fire has a positive short-term effect on plant diversity. Bird species richness and abundance were lower on burnt compared to unburnt plots in the year of the fire, but not in the year after. Over a period of 18 years, high fire frequency led to an increase in herb cover and a decrease in grass cover. We show that the effects on biodiversity are taxon- and species-specific. Fire management strategies in temperate wetlands should consider fire frequency as a key driving force of vegetation structure, with carry-over effects on higher trophic levels. Designing fire “refuges”, i.e., areas that do not burn annually, might locally be necessary to maintain high species richness.

Extending wire method for field assessment of surface peat thickness loss due to peat fire incidence in oil palm plantations

This paper contributes the development of a research method for the assessment of surface peat thickness loss due to peat fire incidence in oil palm plantation, since there are oil palm tree stumps still standing in the field after a fire. Peat thickness loss due to peat fire in June 2013 was assessed in an oil palm plantation in Rokan Hilir, Riau Province in April and November of 2015. The total burnt area of up to 114 ha and the surrounding areas that were burned was estimated to be more than 3,000 ha. In order to assess the loss of the surface thickness due to peat fire, the length of rooting system of the oil palm plants above ground was measured. The length of roots is a key parameter of measurement for this study. Since there were parts of the oil palm that was unburned at the burned site the different length of oil palm rooting system above ground was compared between the burnt and unburnt areas. The comparison was conducted with a total of 3,789 sample points of measurement. The result showed that the surface thickness loss is 7 mm in the total burned area.

Investigating the contribution of the coarse fraction to total pyrogenic carbon stocks in forest soil

Pyrogenic carbon (PyC) quantification methods based on visual identification typically measure only the PyC particles >0.5 mm, whereas oxidative methods are usually conducted on the <2 mm soil fraction. To reconcile the discrepancy between these two methods, we used the weak nitric acid digestion method to quantify the PyC mass in the <2 mm soil, and in the charcoal particles >2 mm, in a California dry mixed conifer forest spatially heterogeneous in fire severity. We found that charcoal particles >2 mm represented 5–10% of mineral soil PyC in recently burned areas (three years post-fire in our study) and 3% in the unburnt areas (>100 years since the last fire). We, therefore, stress the importance of considering the size fraction of the charcoal quantified.

Location of long‐term communal burrows of a threatened arid‐zone lizard in relation to soil and vegetation

AbstractThe great desert skink (Liopholis kintorei) of the Egerniinae subfamily (Reptilia: Scincidae) is a communal burrowing lizard that inhabits arid spinifex grasslands in central Australia. Great desert skink activity is centred in and around the burrows which are inhabited for many years. However, it is not known whether skinks select burrow sites with specific attributes or how continuing occupancy of burrows is influenced by the surrounding habitat; especially post‐fire, when plant cover is reduced. Here, we test whether great desert skink burrows in areas burnt 2 years previously and in longer unburnt areas are associated with particular habitat attributes, and whether there are differences between occupied and recently abandoned burrow sites. Vegetation composition, cover and soil surface characteristics at 56 established great desert skink burrows, including occupied and recently unoccupied burrows, were compared with 56 random nearby non‐burrow control sites. Burrow sites had higher plant cover compared with the surrounding landscape in both recently burnt and longer unburnt areas and were more likely to be associated with the presence of shrubs. Soil stability and infiltration were also higher at burrow sites. However, we found no evidence that burrows with lower cover were more likely to be abandoned. Our results suggest that great desert skinks may actively select high cover areas for burrow construction, although differences between burrow and control sites may also partly reflect local changes to plant cover and composition and soil properties resulting from burrow construction and long‐term habitation of a site. Further research should determine if burrows with shrubs or higher plant cover provide greater protection from predators, more structural stability for burrow construction, increased prey abundance or other benefits. We recommend that maintenance of areas with relatively higher plant cover be prioritized when managing great desert skink habitat.

Differential pollinator response underlies plant reproductive resilience after fires.

Assessing the resilience of plant-animal interactions is critical to understanding how plant communities respond to habitat disturbances. Most ecosystems experience some level of natural disturbance (e.g. wildfires) to which many organisms are adapted. Wildfires have structured biotic communities for millennia; however, the effects of fire on interactions such as pollination have only recently received attention. A few studies have shown that generalist plants can buffer the impact of fires by pollinator replacement, suggesting that the resilience to disturbance could depend on the level of specialization of the interactions. Here, we hypothesize that (1) fires could impose negative effects on plants with specialized pollination systems, and (2) in large wildfires, these negative effects will be stronger with increasing distance inside the burnt area because pollinators will need more time to recolonize. These questions were tested in the specialized pollination system of a widespread Mediterranean palm, Chamaerops humilis. The post-fire pollination resilience was assessed in replicated wildfires representing three post-fire ages by measuring the abundance of beetle pollinators and by estimating fruit set (i.e. the proportion of flowers setting fruits) in burnt and unburnt areas. To test for distance effects, plants were sampled along transects inside the burnt area. Despite a marked post-fire decline in the specialist pollinator, exacerbated by the distance from the fire's edge, the palm's fruit set was barely affected. The temporary replacement by a sap beetle at burnt sites - an effective pollinator that had not been previously recognized - provided post-fire reproductive resilience. Differential pollinator responses to disturbance can ensure plant success even in plants with only two functionally similar pollinators. This highlights the importance of pollinator replacement and dynamics for the resilience of interactions and ultimately of plant reproduction in disturbance-prone ecosystems.

Returning home after fire: how fire may help us manage the persistence of scrub-steppe specialist bird populations

Semi-natural open habitats have drastically changed in the last few decades due to agricultural intensification and rural depopulation. Steppe-birds, and especially those adapted to primary stages of vegetation succession, are threatened by an increase in scrub cover, and management actions are being applied to reverse scrub encroachment and restore habitat suitability in semi-natural open habitats. In this paper we evaluated for the first time, the long-term effects of a wildfire on habitat structure, vegetation productivity, and the associated response of an endangered scrub-steppe specialist bird, the Dupont’s Lark Chersophilus duponti. Wildfire occurred in a Mediterranean steppe of central Spain dominated by permanent community of dwarf cushions scrubs. Bird abundance was evaluated by line transects in the burnt and unburnt areas 3 years prior to the fire and 4 and 7 years after the fire. We quantified changes in habitat structure at fine scale level through vegetation sampling points and in vegetation productivity by estimating the Normalized Difference Vegetation Index (NDVI). Fire had strong effects for at least up to 4 years after the fire, when lower NDVI values, less scrub cover and fewer, but not significant, number of males were detected in the burnt area with respect to the pre-fire conditions. Seven years after fire most vegetation variables measured did not differ between areas, number of males detected within the burnt area was recovered and NDVI values in burnt area were slightly recovered but were significantly lower than in control area. Slow regeneration of the scrub cover after fire explained the unsuccessful occupation of the burnt area by the Dupont’s Lark up to several years after fire. The more dispersed and shorter habitat created by fire 7 years after the fire seems to be more suitable for the species than that in control areas. The large number of males around the burnt area may have played a role in the recolonization process. In sum, vegetation recovery and the presence of a low scrub-steppe specialist, as the Dupont’s lark, suggests that fire management could be integrated into conservation plans to effectively manage scrub encroachment processes in Mediterranean scrub-steppes.

The effects of fires on plants and wildlife species diversity and soil physical and chemical properties at Aberdare Ranges, Kenya

Njeri WF, Githaiga JM, Mwala AK. 2018. The effects of fires on plant and wildlife species diversity and soil physical and chemical properties at Aberdare Ranges, Kenya. Asian J For 2: 25-38. This study was aimed to determine the effects of fires on species diversity (plants, animals, birds), and soil physical and chemical properties at the Aberdare Ranges forest, Kenya. Data were collected on five sites that experienced fires in 2002, 2009, 2012, 2013, and 2014 from both burnt and unburnt areas. Point Centered Quarter and quadrant methods were used for woody vegetation sampling and herbaceous vegetation sampling, respectively. Foot count was done for animal census and point count for birds. The data showed that the herbaceous vegetation in burnt sites had significantly higher species diversity than the unburnt sites in the areas that experienced fire before 2014. The fire had triggered the regeneration of the herbaceous plants. The burnt sites had a significantly higher percentage cover. The fire has an immediate adverse effect on the population of animals as demonstrated on the site consumed in 2014. No animal species was found on the site seven days after the fire when data was collected. The animal diversity was proportional to the vegetation density caused by the vegetation regeneration due to fires. All the burnt sites had fewer birds than the unburnt sites. Effects of fires were prominent in the upper layer of the soil for all the soil properties under study. Burning caused an increase in pH, potassium, organic carbon and cation exchange capacity. The study demonstrated that fires lead to an immediate adverse effect on vegetation, wildlife and soil chemical properties. Postfire management is necessary on sites that have recently experienced fires to rehabilitate them. Authorities responsible for the management of forests must ensure that people are kept out of those sites to allow vegetation to recover without interference. Reforestation can also be done on the burnt sites to increase plant and habitat for the wildlife.

Bat activity before and after a severe wildfire in Pilliga forests: Resilience influenced by fire extent and landscape mobility?

AbstractWildfires are becoming increasingly severe and common in many parts of the world, yet their effects on certain taxa remain poorly studied. In November 2006, a major wildfire occurred in the Pilliga forests of north‐west New South Wales, Australia. This fire was severe and extensive, burning more than 120 000 ha. Prior to the fire, we conducted a study in the affected area assessing bat activity in relation to flyway size and riparian zones, allowing us to opportunistically compare before – and – after effects of wildfire on bats in burnt and unburnt areas. We assessed how bat activity and bat composition changed from 1 year pre‐fire to 1 year post‐fire and 4 years post‐fire, accounting for the effects of flyway size. A BACI analysis showed that there was an effect of time (year) on bat activity, with activity markedly reduced in both burnt and unburnt sites in the year post‐ fire, before recovering 4‐years post‐fire to levels that approached pre‐burn activity. However, there was no treatment or interaction effect, indicating fire alone did not affect bat activity at our sites. Activity was 50% lower at supplementary sites more remote (~5 km) from the fire edge. Multi‐dimensional scaling and permanova described a strong effect of year but no evidence of fire or stream size‐mediated effects on species composition. The drop in activity post‐fire coincided with a period of drought that subsequently broke in the year prior to our survey 4 years post‐fire. Some species‐specific responses to the fire were evident and depended on the proximity to unburnt forest. We suggest the potential for landscape re‐assortment, whereby some species may move from the unburnt landscape into the burnt landscape, possibly in response to a resource pulse of insects. A landscape pattern of movement could obscure the detection of direct fire effects on mobile bats. We suggest fire extent, proximity to unburnt vegetation and severity are key considerations when interpreting the response of bats to wildfire.

The threatened status of the hollow dependent arboreal marsupial, the Greater Glider ( Petauroides volans ), can be explained by impacts from wildfire and selective logging

Abstract Logging and fires represent the major disturbance regimes in Eucalyptus forests and these can have varying effects on populations of forest fauna depending on their intensity and/ or frequency. Knowledge of the effects of fires on arboreal marsupials is limited and to the best of our knowledge no previous research has considered the effect of fire frequency on populations of these species. The aim of this study was to examine the effects of fire frequency (canopy-consuming wildfires) and logging intensity on the Greater Glider, Petauroides volans, a species of hollow dependent gliding possum that has recently been listed as vulnerable to extinction under Australian biodiversity law. Surveys were completed across a selective logging intensity and fire frequency gradient in tall wet (WSF) and tall dry sclerophyll forests (DSF) in north-eastern New South Wales, Australia. Generally, P. volans was restricted to WSF, where even a single fire, 10 years prior, significantly reduced the density of P. volans in comparison to unburnt areas. Significant negative impacts from intensive logging were also detected. These effects may explain observed declines in the abundance of P. volans over much of its range as well as its scarcity in the more fire prone DSF. To counteract these effects, we recommend not implementing prescribed fire under high or greater fire weather danger conditions near high-density populations of this species, along with increased retention of hollow-bearing trees during timber harvesting and/ or wider riparian buffers in areas where high density populations of P. volans occur.

Importance of internal refuges and the external unburnt area in the recovery of rodent populations after wildfire

Rodent populations respond quickly to changes in habitat structure and composition resulting from disturbances such as wildfires. Rodents may recolonise burnt areas from individuals that survived the wildfire in ‘internal refuges’ or from the surrounding unburnt area (i.e. external colonisation). With the aim of assessing the relative role of both hypotheses on rodent abundance and foraging behaviour after fire, four Mediterranean burnt areas were studied using sampling stations at increasing distances from the perimeter of the burnt area. In the first 18 months after fire, the abundance of wood mice (Apodemus sylvaticus) and seed removal activity were highest near the perimeter. This suggests the weight of external sources (i.e. from unburnt areas) in the recolonisation process is higher than that of internal refuges. Algerian mice (Mus spretus) colonised the burnt areas from external sources. Vegetation cover was the most important variable affecting the relative abundance of rodents in recently burnt areas. After some months of vegetation recovery, rodent individuals that had dispersed from the unburnt area were likely to take advantage of sparsely occupied habitat with sufficient resources and, at this time, might use internal refuges. Therefore, understanding recolonisation dynamics is fundamental to anticipate biodiversity patterns and promote adaptive management.

中度火干扰对兴安落叶松林土壤呼吸的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 中度火干扰对兴安落叶松林土壤呼吸的影响 DOI: 10.5846/stxb201705311005 作者: 作者单位: 东北林业大学林学院,东北林业大学林学院,东北林业大学林学院 作者简介: 通讯作者: 中图分类号: 基金项目: 中央高校基本科研业务费专项资金项目（2572015DA01）；国家自然科学基金项目（31470657） Effects of fire disturbances on soil respiration in Dahurian Larch (Larix gmelinii) forests Author: Affiliation: Faculty of Forestry,Northeast Forestry University,Faculty of Forestry,Northeast Forestry University,Faculty of Forestry,Northeast Forestry University Fund Project: Fundamental Research Funds for the Central Universities (2572015DA01); National Natural Science Foundation (31470657) 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:通过测定中度火干扰后塔河地区兴安落叶松（Larix gmelinii）林生长季土壤呼吸（Rs），并进一步探究火干扰后影响土壤呼吸变化的主要环境因子。选择在塔河林业局火烧4年后兴安落叶松林中度火烧迹地设置样地，选择临近未过火区域设置对照样地。土壤呼吸通量用LI-8100进行测量，土壤异养呼吸（Rh）采用壕沟法进行测量。火烧迹地与未火烧对照样地生长季土壤呼吸速率平均值分别为（3.67±1.03）μmol CO2 m-2 s-1，（4.21±1.25）μmol CO2 m-2 s-1。火烧迹地土壤呼吸速率显著降低（P<0.05）。生长季土壤呼吸组分的动态变化表明，土壤呼吸速率的降低是因为土壤自养呼吸（Ra）显著降低导致的（P<0.05）。温度是控制这一地区生长季土壤呼吸变化的主要环境因子。与对照样地相比，火烧迹地土壤呼吸的变化与土壤温度具有更强的相关性。塔河地区兴安落叶松林火烧迹地和未火烧对照样地Q10分别为5.85±1.06，4.25±1.19，火干扰后Q10显著增加（P<0.05）。研究结果表明：在全球气候变化的背景下火干扰后中国塔河地区兴安落叶松林生态系统对温度的变化更为敏感。本研究结果将为研究中国塔河地区火干扰后碳循环变化提供数据支持。 Abstract:This study investigated the increasing seasonal soil respiration (Rs) in the Dahurian Larch (Larix gmelinii) forests after fire disturbance in the Tahe area, and identified the main environmental factors influencing soil respiration changes after fires. Plots that had been under fire disturbance over four years in the Tahe forestry bureau were selected for this investigation, and the nearby unburnt area was selected for the control plots. The Rs was measured by using an Li-8100, and the trench method was used to measure the soil heterotrophic respiration (Rh). The mean Rs of post-fire plots and unburnt control plots was (3.67±1.03)μmol CO2 m-2 s-1 and (4.21±1.25)μmol CO2 m-2 s-1, respectively. The Rs in the post-fire plots was significantly lower than that in the unburnt control plots (P < 0.05). We quantified the Rs component changes after fire disturbance. The decrease in Rs was mainly due to a significantly decreased autotrophic respiration (Ra) rate (P < 0.05). Soil temperature was the dominant environmental factor influencing soil respiration variability in this area. Compared with the unburnt control plots, the Rs in the post-fire plots had a much stronger correlation with soil temperature. The temperature sensitivity index (Q10) of Rs in the post-fire plots and unburnt control plots was 5.85±1.06 and 4.25±1.19, respectively. The Q10 value significantly increased after fire disturbance (P < 0.05). In view of the global climate change, the results of this study demonstrate that the Dahurian Larch (L. gmelinii) forest ecosystem in the Tahe area of China is sensitive to temperature change. Our findings provide scientific basis for research on carbon cycling after fire disturbance in the Tahe area of China. 参考文献 相似文献 引证文献

Differences in soil chemistry remain following wildfires on temperate heath and blanket bog sites of conservation concern

Wildfires have the potential to change the physico-chemical characteristics of soils, and further research is required to establish the nature, extent and duration of these impacts. The extent to which the impacts of wildfires differ from the more frequently studied prescribed burns is an active area of investigation with serious implications for landscape managers and conservation biologists. Here, we take advantage of multiple large wildfires which occurred in vulnerable upland habitats of conservation importance, to measure in-situ differences in soil conditions between burnt and unburnt areas ca. 1.5years and 3.5years after fires. There were no detectable differences in pH, total nitrogen, total carbon, potassium or magnesium concentrations between burnt and unburnt locations 15–18months after wildfires, suggesting that these were either unaffected by the fires, or more likely, as suggested by previous research, had exhibited transient differences immediately after the wildfires which had returned to baseline conditions within 1.5years. By contrast, burnt and unburnt locations differed with respect to phosphorus and calcium concentrations which remained elevated up to 3.5years post-fire. Calcium concentrations remained greater in burnt plots across all three habitat types, whilst available phosphorus concentrations remained elevated in blanket bog but returned to the same level as unburnt control plots in wet and dry heath. Taken together, our findings suggest that there is the potential for wildfires to have longer-lasting effects on phosphorus and calcium concentrations in some temperate European Annex I habitats of conservation concern, particularly blanket bog, than previously expected based on results of studies of experimental burning or wildfires in other habitat types. The magnitude and duration of fire impacts on soils depends largely on the environmental and meteorological characteristics of the region. Hence, this study highlights the need for more research across a broader range of sites taking advantage of unexpected wildfires, to assess the extent to which their impacts may differ between habitat types and from those of experimental or controlled burning.

Synergistic effects of the components of global change: Increased vegetation dynamics in open, forest-steppe grasslands driven by wildfires and year-to-year precipitation differences.

Climate change and land use change are two major elements of human-induced global environmental change. In temperate grasslands and woodlands, increasing frequency of extreme weather events like droughts and increasing severity of wildfires has altered the structure and dynamics of vegetation. In this paper, we studied the impact of wildfires and the year-to-year differences in precipitation on species composition changes in semi-arid grasslands of a forest-steppe complex ecosystem which has been partially disturbed by wildfires. Particularly, we investigated both how long-term compositional dissimilarity changes and species richness are affected by year-to-year precipitation differences on burnt and unburnt areas. Study sites were located in central Hungary, in protected areas characterized by partially-burnt, juniper-poplar forest-steppe complexes of high biodiversity. Data were used from two long-term monitoring sites in the Kiskunság National Park, both characterized by the same habitat complex. We investigated the variation in species composition as a function of time using distance decay methodology. In each sampling area, compositional dissimilarity increased with the time elapsed between the sampling events, and species richness differences increased with increasing precipitation differences between consecutive years. We found that both the long-term compositional dissimilarity, and the year-to-year changes in species richness were higher in the burnt areas than in the unburnt ones. The long-term compositional dissimilarities were mostly caused by perennial species, while the year-to-year changes of species richness were driven by annual and biennial species. As the effect of the year-to-year variation in precipitation was more pronounced in the burnt areas, we conclude that canopy removal by wildfires and extreme inter-annual variability of precipitation, two components of global environmental change, act in a synergistic way. They enhance the effect of one another, resulting in greater long-term and year-to-year changes in the composition of grasslands.