Fungi were isolated using a rose bengal chloramphenicol agar as the culture medium. Congo red staining was used on sodium carboxymethyl cellulose medium to screen fungal strains that have potential to produce cellulolytic enzymes according to the cellulolytic index (CI). The ability of these isolates to break down holocellulose in three forest litter substrates (broad-leafed: Juglans mandshurica; coniferous: Larix gmelinii; broadleaf-conifer mixed: J. mandshurica and L. gmelinii) was tested over 80 days of incubation. The holocellulose content and the decomposition rule were studied. The strain with the most efficient degradation effect on natural cellulose in forest litter was selected. The growth of fungi was observed by scanning electron microscopy (SEM). The hydrolytic circles indicated the activity of cellulase produced by the fungi, and it implied that the fungi could degrade cellulose. The results showed that eight strains were able to degrade cellulose. The strain A2 (Peniophora incarnate) showed the highest CI, while A4 (Sarocladium strictum) was most capable of degrading holocellulose in various litter substrates. The SEM micrographs revealed that A4 had the ability to invade leaf tissue and degrade holocellulose in leaves. This study could be helpful for forest litter management, which provides a new way to cleanup forest litter using cellulose-degrading fungi.

Wildfire is an important factor in the evolution of terrestrial organisms, and fires assist in maintaining the structure and function of the global ecosystem. Knowledge of fire severity is indispensable for understanding the ecological significance of wildfire. Therefore, quantifying fire severity is an important aspect of studying the response mechanism of terrestrial ecosystems to wildfire, and it is of great significance to fire ecology. In this paper we comprehensively introduce and compare the classification and quantification methods for fire severity; we discuss the development and application status of various methods, and we elucidate their existing problems. We analyze each method in terms of the relevant ecosystem, the fire behavior, time, and the relationship between fire severity and ecosystem response in order to provide a reference basis for proposing and developing new severity measurement methods. The current methods for describing fire severity include four main types: 1) According to features of the burned area, fire severity can be classified as light, moderate, and heavy. 2) Using composite burn index (CBI) to quantify and record the fire severity. 3) In quantifying fire severity with vegetation change, there are certain limitations and theoretical problems to be solved. 4) Remote sensing could very well be an important means of measuring fire severity in the future, but there are still many problems that need to be solved before the remote sensing index can become a global fire severity indicator. Fire severity is a latent variable in ecosystem. Only by clarifying the relationship between fire behavior, fire severity, time related variables and the pre-and post-fire ecosystem can the existing models be perfected or new, better fire severity measurement models be proposed for broad applications.

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Wildfires and pests are natural disturbance agents in many forest ecosystems that often contribute to ecological succession, nutrient cycling, and forest species composition. Mongolian pine (Pinus sylvestris var. mongolica) is a coniferous species that plays an important role as an ecological barrier, and is widely spread in northern China. Its wood is loose; its branches, leaves, and cones contain a high level of resin and volatile oils that make the species highly flammable and the stands dominated by the species are very vulnerable to fire. Recently, resinosis on boles of Pinus sylvestris became an epidemic in China. To explore the potential effects of pests on fire, we compared the flammability of Mongolian pine barks with or without resinosis on boles using a cone calorimeter and several combustion analyses. We found that the barks from boles with resinosis had a greater oil content than the healthy trees. The study also indicated that the ignition times of the barks from boles with and without resinosis were 6.00 s (±1.73) and 22.67 s (±1.15), respectively, and that the heat release rate curves were parabolic, with peaks 225.19 and 75.27 kW/m2, respectively, for the two bark types. Additionally, because resinosis was on the low- to mid-bole of infested trees, the barks from boles with resinosis tended to be ignited much easier than those without resinosis. This clearly evidenced that pests could affect fire severity and behavior by increasing forest flammability. More information about the role that pests play in the different forest cover types is needed to increase our understanding of fire danger and to develop sound forest management policies.

Background and aimBoreal forests account for one third of terrestrial carbon stock. Wildfires are an important perturbation of this carbon pool, affecting in particular the litter layer. After forest fires, the litter layers may possess shifting chemical property and decomposition dynamics due to the changes in post-fire vegetations succession and abiotic factors.MethodsWe measured water-soluble organic carbon (WSOC) and water-soluble nitrogen (WSN) in the litter layers of Oi and Oe horizons in boreal forests along a gradient of fire history in northeastern China. ResultsWe found that WSOC and WSN concentrations in the Oi layer were higher than those in the Oe layer. The concentrations were markedly altered by fires and showed different responses to the ecological succession. The time since fire had significant positive correlations with WSOC in Oi and Oe layers. The distance-based redundancy analysis and the structural equation model analysis suggested that factors additional to the time since fire also influenced the litter water-soluble matter (WSM) properties. Biotic factors were more strongly correlated with the litter WSM properties in the Oe layer than in the Oi layer. Although biotic factors contributed less than abiotic factors to the WSM properties, they still play significant roles in litter WSM in burned area. ConclusionsOur results show that manipulating biotic factors can be an important management strategy for litter WSM restoration, which can assist the overall ecological restoration in burned forests faced with the increasing danger of wildfires in the changing global climate.