Tree diversity,composition, forest structure and aboveground biomass dynamics after single and repeated fire in a Bornean rain forest

Forest fires remain a devastating phenomenon in the tropics that not only affect forest structure and biodiversity, but also contribute significantly to atmospheric CO2. Fire used to be extremely rare in tropical forests, leaving ample time for forests to regenerate to pre-fire conditions. In recent decades, however, tropical forest fires occur more frequently and at larger spatial scales than they used to. We studied forest structure, tree species diversity, tree species composition, and aboveground biomass during the first 7 years since fire in unburned, once burned and twice burned forest of eastern Borneo to determine the rate of recovery of these forests. We paid special attention to changes in the tree species composition during burned forest regeneration because we expect the long-term recovery of aboveground biomass and ecosystem functions in burned forests to largely depend on the successful regeneration of the pre-fire, heavy-wood, species composition. We found that forest structure (canopy openness, leaf area index, herb cover, and stem density) is strongly affected by fire but shows quick recovery. However, species composition shows no or limited recovery and aboveground biomass, which is greatly reduced by fire, continues to be low or decline up to 7 years after fire. Consequently, large amounts of the C released to the atmosphere by fire will not be recaptured by the burned forest ecosystem in the near future. We also observed that repeated fire, with an inter-fire interval of 15 years, does not necessarily lead to a huge deterioration in the regeneration potential of tropical forest. We conclude that burned forests are valuable and should be conserved and that long-term monitoring programs in secondary forests are necessary to determine their recovery rates, especially in relation to aboveground biomass accumulation.     

Estimation of aboveground biomass and net biomass increment in a cool temperate forest on a landscape scale

I clarified aboveground biomass (AGB), net biomass increment (NBI) and its spatial heterogeneity in a cool temperate forest on a landscape scale (>2,200 ha). The relationships among AGB, NBI, and the size frequency distribution of trees of each stand were examined by combining an analysis of vegetation using aerial photographs, and data from 146 inventory plots (28.8 ha in total). This area included natural broad-leaved stands, harvested broad-leaved stands, and artificial conifer plantations. A –3/2 power distribution density function was applied to the individual mass frequency distribution of each plot. Estimated AGB in carbon (C) equivalent was 480–5,615 g C m^–2 (3,130 g C m^–2 on average), and NBI was –98 to 436 g C m^–2 year^–1 (83.0 g C m^–2 year^–1 on average). NBI had a single significant relationship with the reciprocal of theoretical maximum individual mass, while NBI was not significantly related to AGB. My results showed that, on a landscape scale, AGB and NBI strongly depend on the size structure of forest stands.     

森林景观的历史变域研究进展

历史变域概念产生于20世纪90年代,是森林生态系统管理的重要概念之一,可以为生态系统管理提供参考和目标。总结了历史变域领域近期的研究热点:火烧的历史变域研究从定量化火烧特征开始,进而探讨火烧特征的影响因素,并且从火烧特征的单一影响因素向多影响因素、从单一尺度向多时空尺度研究发展;森林景观历史变域研究由描述景观的单一结构特征深入到揭示综合结构特征及功能特征。方法的新进展包括:评估历史数据的误差、探索采样和数据分析方法、重视火疤木数据的多时空特征、以及发掘整合多种来源的历史数据。模拟自然干扰的森林管理是历史变域概念的重要应用之一,最近的研究集中在为森林管理提供更加全面的模拟自然干扰的干扰参数,并且强调这些参数的空间异质性;同时,该管理模式也面临挑战和质疑:气候变化条件下历史变域的概念是否仍旧适用?森林管理是否能够真正达到自然干扰的效果?分析了我国的研究现状,提出发展建议。     

遥感在森林地上生物量估算中的应用

生物量是地表C循环研究的重要组成部分,生物量研究有助于深入认识区域乃至全球的C平衡。森林作为地球最重要的陆地生态系统,区域乃至全球尺度的森林地上生物量估算一直是生态学研究的难点之一。在大的空间尺度上,遥感技术是估算森林地上生物量的有效手段。TM、AVHRR、SAR等数据以及多源数据的融合在森林生物量估算方面广泛应用,并取得了显著效果。运用遥感技术进行森林生物量估算时,所采用的数据源不同,分析方法也不相同,主要分析方法有:相关分析、多元回归分析、神经网络和数学模型模拟等。随着测定不同空间、时间和波谱分辨率的各种传感器的广泛使用,以及生物量遥感估算模型的进一步发展和完善,大尺度森林生物量的遥感估算研究必将向前迈进一大步。     

Soil is the main predictor of secondary rain forest estimated aboveground biomass across a Neotropical landscape

We studied the relative effects of landscape configuration, environmental variables, forest age, and spatial variables on estimated aboveground biomass (AGB) in Costa Rican secondary rain forests patches. We measured trees ≥5 cm dbh in 24, 0.25 ha plots and estimated AGB for trees 5–24.9 cm dbh and for trees >25 cm dbh using two allometric equations based on multispecies models using tree dbh and wood‐specific gravity. AGB averaged 87.3 Mg/ha for the 24 plots (not including remnant trees) and 123.4 Mg/ha including remnant trees (20 plots). There was no effect of forest age on AGB. Variation partitioning analysis showed that soils, climate, landscape configuration, and space together explained 61% of tree AGB variance. When controlling for the effects of the other three variables, only soils remained significant. Soil properties, specifically K and Cu, had the strongest independent effect on AGB (variation partitioning, R² = 0.17, p = 0.0310), indicating that in this landscape, AGB variation in secondary forest patches is influenced by soil chemical properties. Elucidating the relative influence of soils in AGB variation is critical for understanding changes associated with land cover modification across Neotropical landscapes, as it could have important consequences for land use planning since secondary forests are considered carbon sinks. Abstract in Spanish is available with online material.     

Process-centred restoration in a fire-adapted ponderosa pine forest

Accurate and ecologically meaningful characterisation of reference conditions is a fundamental premise of restoration ecology. Restoration practice and research commonly define reference conditions in terms of compositional and structural elements. We propose a “process-centred” framework that places central emphasis on ecological functions and ecosystem processes. A wide variety of processes is central to the functioning and dynamics of ecological systems, and can be placed at the foundation of restoration research and practice. A process-centred approach allows the definition of “reference dynamics”, where spatial and temporal variability and underlying mechanisms of change are primary. We illustrate this approach using a 303-yr reconstruction of the natural surface fire regime to guide restoration of a Pinus ponderosa forest in the Jemez Mountains of southwestern North America. Fire occurrence varied over space and time during the period of record, with ecologically significant variation in fire intervals (yr fire⁻¹) governed by process–structure interactions. We defined a variety of reference variables for reintroduction of fire as the keystone ecological process, along with related structural variation. A process-centered approach and the reference dynamics paradigm can replace a more static concept of reference conditions in defining restoration baselines and provide an improved standard of comparison for restoration ecology.     

Three centuries of fire in montane pine‐oak stands on a temperate forest landscape

Question: What was the role of fire in montane pine‐oak (Pinus‐Quercus) stands under changing human land uses on a temperate forest landscape in eastern North America? Location: Mill Mountain in the central Appalachian Mountains, Virginia, US. Methods: A dendroecological reconstruction of fire history was generated for four stands dominated by xerophytic pine and oak species. The fire chronology began under presettlement conditions following aboriginal depopulation. Subsequent land uses included European settlement, iron mining, logging, and US Forest Service acquisition and fire protection. Results: Fires occurred approximately every 5 years until 1930 without any evidence of a temporal trend in fire frequency. Burning ceased after 1930. Area‐wide fires affecting multiple pine stands were common, occurring at intervals of approximately 16 years. Most living pines became established during the late 1800s and early 1900s. Dead pines indicated that an older cohort established ca. 1730. Most hardwoods were established between the 1920s and 1940s. Conclusions: Except for fire protection, changes in land use had no discernible influence on fire frequency. Lightning ignitions and/or large fire extent may have been important for maintaining frequent burning in the 1700s, while fuel recovery may have constrained fire frequency during later periods. The disturbance regime appears to be characterized by frequent surface fires and occasional severe fires, insect outbreaks or other disturbances followed by pine recruitment episodes. Industrial disturbances appear to have had little influence on the pine stands. The greatest impact of industrial society is fire exclusion, which permitted hardwood establishment.     

Fire increases aboveground biomass, seed production and recruitment success of Molinia caerulea in dry heathland

During the last decades, the perennial tussock grass Molinia caerulea has shown an increased abundance in European heathlands, most likely as a result of increased nitrogen deposition and altered management schemes. Because of its deciduous nature, Molinia produces large amounts of litter each year, which may affect the intensity and frequency of accidental fires in heathlands. These fires may influence plant population dynamics and heathland community organization through their effects on plant vital attributes and competitive interactions. In this study, fire-induced changes in competitive ability and invasiveness of Molinia through changes in biomass production, seed set and seed germination under both natural and laboratory conditions were investigated. We found that fire significantly increased aboveground biomass, seed set and germination of Molinia. Seed set was twice as high in burned compared to unburned heathland. Two years after fire, seedling densities in natural conditions were on average six times higher in burned than in unburned heathland, which resulted in increased abundance of Molinia after burning. The seed germination experiment indicated that seeds harvested from plants in burned heathland showed higher germination rates than those from unburned heathland. Hence, our results clearly demonstrate increased invasive spread of Molinia after large and intense fires. Active management guidelines are required to prevent further encroachment of Molinia and to lower the probability of large fires altering the heathland community in the future.     

Spatial and temporal variability in fire occurrence within the Las Bayas Forestry Reserve, Durango, Mexico

Patterns of fire occurrence within the Las Bayas Forestry Reserve, Mexico are analyzed in relation to variability in climate, topography, and human land-use. Significantly more fires with shorter fire return intervals occurred from 1900 to 1950 than from 1950 to 2001. However, the frequency of widespread fire years (25% filter) was unchanged over time, as widespread fires were synchronized by climatic extremes. Widespread fire years occurred during dry years that lagged wet years. Widespread fire years lagged the negative El Niño phase (wet winters) of the Southern Oscillation by 1 year, but were not synchronized by the positive, La Niña phase (dry winters) of the Southern Oscillation. The smaller, localized fires that occurred more frequently during the first half of the 20th century were attributed to changes in land tenure with the introduction of the ejido system in the early 1950s. Ejido management strategies lowered fire frequencies by suppressing fires and reducing anthropogenic fires. There were likely more ignitions prior to the arrival of the ejido system as fires were ignited by lightning and indigenous people. As the movement of indigenous peoples across the landscape has been restricted by changes in land tenure, numbers of human-ignited fires subsequently decreased post 1950. After 1950, fires occurred less frequently, were more synchronized, and more restricted to years of extreme climate.     

Review of forest landscape models: Types, methods, development and applications

Forest landscape models simulate forest change through time using spatially referenced data across a broad spatial scale (i.e. landscape scale) generally larger than a single forest stand. Spatial interactions between forest stands are a key component of such models. These models can incorporate other spatio-temporal processes such as natural disturbances (e.g. wildfires, hurricanes, outbreaks of native and exotic invasive pests and diseases) and human influences (e.g. harvesting and commercial thinning, planting, fire suppression). The models are increasingly used as tools for studying forest management, ecological assessment, restoration planning, and climate change. In this paper, we define forest landscape models and discuss development, components, and types of the models. We also review commonly used methods and approaches of modeling forest landscapes, their application, and their strengths and weaknesses. New developments in computer sciences, geographic information systems (GIS), remote sensing technologies, decision-support systems, and geo-spatial statistics have provided opportunities for developing a new generation of forest landscape models that are increasingly valuable for ecological research, restoration planning and resource management.     

Review of forest landscape models: Types, methods, development and applications

Forest landscape models simulate forest change through time using spatially referenced data across a broad spatial scale (i.e. landscape scale) generally larger than a single forest stand. Spatial interactions between forest stands are a key component of such models. These models can incorporate other spatio-temporal processes such as natural disturbances (e.g. wildfires, hurricanes, outbreaks of native and exotic invasive pests and diseases) and human influences (e.g. harvesting and commercial thinning, planting, fire suppression). The models are increasingly used as tools for studying forest management, ecological assessment, restoration planning, and climate change. In this paper, we define forest landscape models and discuss development, components, and types of the models. We also review commonly used methods and approaches of modeling forest landscapes, their application, and their strengths and weaknesses. New developments in computer sciences, geographic information systems (GIS), remote sensing technologies, decision-support systems, and geo-spatial statistics have provided opportunities for developing a new generation of forest landscape models that are increasingly valuable for ecological research, restoration planning and resource management.     

Persistence of resprouting species after fire in natural and post‐mine restored shrublands in southwestern Australia

Questions: Is post‐fire persistence of resprouting species lower in restored sites, and is survival related to lignotuber size? Location: Southwestern Australia, Eneabba, 300 km north of Perth. Methods: Post‐fire persistence of 10 lignotuberous shrub species was compared between three sites restored 8–24 years ago after mineral‐sand mining and three surrounding natural shrubland sites (8–24 years since previous fire). Results: Overall persistence of species was 11–93% in restored sites (mean 52%) and 79–100% in natural sites (mean 96%). Persistence increased with time since rehabilitation for five species with <25% of individuals in three species surviving in the youngest stand. For equivalent crown size, average lignotuber circumferences were 50% smaller at restored sites and this probably accounted for their higher post‐fire mortality. Apart from differences in the age of plants, restored sites had lower soil penetrability than natural sites, which may have restricted rootstock development. A tradeoff favoring a higher crown volume to lignotuber size ratio was apparent in nine of the ten species with greater crown volumes (by 37%) and smaller lignotubers (by 36%) in restored sites. Two resprouting species for which crown seed store was quantified had much higher fecundity in restored sites. Conclusions: Fires reduced resprouter persistence in restored sites owing to poor development/insufficient size of lignotubers. Further management after fires is required, including application of resprouter seeds/seedlings on restored topsoil, transplanting adult resprouters (where viable) from natural areas ahead of the mining front. Low intensity/patchy fires are recommended on long unburnt sites. Resprouter survival would have likely been much greater in the first place if a deeper sandy soil profile was rehabilitated, thereby providing a more suitable medium for lignotuber development.     

黑龙江省黑河地区森林地上生物量和NPP估测及时空格局

根据黑龙江省黑河地区2005和2010年1390块固定样地数据和东北地区树种生物量异速模型,估算各样地单位面积森林地上生物量(AGB)和净初级生产力(NPP).结合该地区2005和2010年两期ETM⁺遥感图像,运用地统计克里格与协同克里格法对AGB和NPP进行插值,比较多种方差函数的拟合效果,并用最佳插值方法得出该地区AGB和NPP的分布图;通过两期分布图的对比,分析该区域AGB和NPP随时间和空间的动态变化趋势,及其与地形因子(坡向、坡度、海拔)和不同林分类型的时空变化规律.结果表明: 2005—2010年,黑河地区AGB呈现增加趋势,高于40 t·hm^-2的生物量面积明显增加;NPP有所下降,出现高NPP地区向低NPP地区转变的现象.AGB和NPP与各地形因子均有一定的相关性,其中,与海拔的相关性明显,说明AGB和NPP的分布受海拔影响显著.研究期间,AGB在各个坡向均有所提高,NPP则降低;AGB和NPP随着坡度增大、海拔增高有增加趋势;常绿针叶林AGB和NPP增长最多,针阔混交林AGB增长最少,落叶阔叶林NPP增长最少.     

Sulfur speciation and distribution in soils and aboveground biomass of a boreal coniferous forest

Major sulfur pools are quantified in soils and aboveground biomass of a coniferous boreal forest. Total ecosystem S averages 1395 kg·ha⁻¹ of which 98% is found in the soil, with 89% being in the mineral horizons. Organic S dominates in soil, tree parts (trunks, branches + foliage, roots) and litterfall, ranging from 77 to 99% of total S concentration. Carbon-bonded S, ester sulfate and SO₄-S in soil profiles range respectively from 51–68%, 29–37% and 1–14% of total S concentrations and account respectively for 57, 33 and 10% of total S on an areal basis. Adsorbed SO₄ accounts for 82% of total SO₄, and can be predicted from Al bound to organic matter, amorphous Al and pH (r^{2 = 0.81}). There is a strong relationship between % carbon and carbon-bonded S in 4 of the 5 soil horizons studied which represent over 95% of the total soil organic matter, whereas ester sulfate is related to % carbon in 3 soil horizons representing only 37% of the soil organic matter. An analysis of atmospheric S loading and S data for 10 forested sites in Europe and North America suggests that the size of the organic S pool in forested systems is independent of atmospheric loading.     

Diversity and aboveground biomass in three tropical forest types in the Dja Biosphere Reserve,Cameroon

We present tree community diversity, species composition, basal area and aboveground biomass of three forest types in the Dja Biosphere Reserve, in South‐East Cameroon, part of the contiguous tropical forest of the Congo Basin. A total of fourteen, 1 ha, plots were established in heterogeneous terra firme forests (TFF), Gilbertiodendron dewevrei forests (GDF) and periodically flooded forests (PFF). A total of 281 tree species with diameter ≥10 cm were recorded. The Shannon diversity index was significantly higher in TFF (5.7 ± 0.28) and PFF (5.6 ± 0.23) than in GDF (2.29 ± 0.48) (ANOVA, F_2,11 = 139.75, P < 0.001). While tree density did not differ between forest types (F_2,11 = 3.50, P = 0.06), basal area differed significantly (F_2,11 = 7.38, P = 0.009), as did aboveground biomass (F_2,11 = 17.95, P < 0.001). Mean AGB values were respectively, 596.1 ± 62.24, 401.67 ± 58.06 and 383.14 ± 61.91 Mg ha^?1 in GDF, TFF and PFF. Variation in the abundance of trees with large diameter was the main reason for these differences. Few dominant species made the greatest contribution to the AGB. G. dewevrei, accounted for 83% of AGB in GDF, Penthaclethra macrophylla for 9.9% in TFF and Uapaca heudolotii for 10.6% in PFF. The importance of preserving G. dewevrei forest in the context of ‘Reducing Emissions from Deforestation and forest Degradation’ (REDD) policies is discussed.     

Dung beetle assemblages in primary forest and disturbed habitats in a tropical dry forest landscape in western Mexico

Dung beetles (Scarabaeinae) are conspicuous components in most terrestrial ecosystems, performing important ecological functions and services. Being sensitive to several types of disturbance, they have been successfully used as indicators of habitat change. Dung beetle communities in tropical rainforests have been well studied, but considerably less information is available for tropical dry forests. In this study I sampled dung beetles in two undisturbed habitats, deciduous forest and semideciduous forest, and two disturbed habitats, secondary forest and open area habitat, in the Chamela-Cuixmala region of western Mexico. Dung beetle species with high indicator value for each habitat were identified. Beetle abundance, observed species richness and estimated species richness were similar in the three forest habitats, but significantly lower in the open area habitat. A more detailed analysis of species-specific abundances in the three forest habitats revealed some differences. Transects of one of the undisturbed habitats, the deciduous forest, were more similar to the non-adjacent transects of disturbed secondary forest, than to the adjacent undisturbed semideciduous forest transects. Unlike studies in other tropical sites that have found a decrease in equitability in Scarabaeinae assemblages between undisturbed forest and disturbed habitat (particularly open habitats), in the Chamela-Cuixmala region all four habitats showed similar low equitability in community structure, with two or three very dominant species.     

Characterization of tree macroremains production in a recently burned conifer forest in northern Québec,Canada

The production of plant macroremains was studied in a conifer forest twomonths after it burned in 1996 in northern Québec. The proportions ofvarious types of charred and uncharred pieces (needles, cones andwood) produced by black spruce (Piceamariana) and jack pine (Pinusbanksiana) were determined by sampling around individual trees.Both species produced equivalent masses of charred material, but pieces of woodcharcoal from jack pine are generally larger that those of black spruce. Theproportion of charred versus uncharred needles is the bestindicator of the species dominance in the forest. Although the fall of uncharredneedles is delayed from the time of a fire, they contribute to more than half ofall remains produced. Jack pine cones remain on the tree for a long time after afire, while charred cones of black spruce are dehiscent (cones come off thebranches easily). Trees are poor wood charcoal producers compared toundergrowth shrubs. As a result, the macroremains assemblage associated with afire event is made up of large amount of uncharred material from trees and alarge proportion of charred pieces produced by undergrowth vegetation. Modernassemblages of plant macroremains indicate that in order to reconstruct pastvegetation associated with fire disturbance, it is important to distinguishbetween the various types of remains, because wood charcoal is mainly producedby material that is already dead.     

Standing crop and aboveground biomass partitioning of a dwarf mangrove forest in Taylor River Slough,Florida

The structure and standing crop biomass of a dwarf mangrove forest, located in the salinity transition zone ofTaylor River Slough in the Everglades National Park, were studied. Although the four mangrove species reported for Florida occurred at the study site, dwarf Rhizophora mangle trees dominated the forest. The structural characteristics of the mangrove forest were relatively simple: tree height varied from 0.9 to 1.2 meters, and tree density ranged from 7062 to 23 778 stems ha^–1. An allometric relationship was developed to estimate leaf, branch, prop root, and total aboveground biomass of dwarf Rhizophora mangle trees. Total aboveground biomass and their components were best estimated as a power function of the crown area times number of prop roots as an independent variable (Y = B × X^–0.5083). The allometric equation for each tree component was highly significant (p<0.0001), with all r² values greater than 0.90. The allometric relationship was used to estimate total aboveground biomass that ranged from 7.9 to 23.2 ton ha^–1. Rhizophora mangle contributed 85% of total standing crop biomass. Conocarpus erectus, Laguncularia racemosa, and Avicennia germinans contributed the remaining biomass. Average aboveground biomass allocation was 69% for prop roots, 25% for stem and branches, and 6% for leaves. This aboveground biomass partitioning pattern, which gives a major role to prop roots that have the potential to produce an extensive root system, may be an important biological strategy in response to low phosphorus availability and relatively reduced soils that characterize mangrove forests in South Florida.