Effect of fire intensity on active organic and total soil carbon in a Larix gmelinii forest in the Daxing'anling Mountains,Northeastern China

Studying contents and seasonal dynamics of active organic carbon in the soil is an important method for revealing the turnover and regulation mechanism of soil carbon pool. Through 3 years of field sampling and lab analysis, we studied the seasonal variations, content differences, and interrelationships of total organic carbon （TOC）, light fraction organic carbon （LFOC）, and particulate organic carbon （POC） of the soil in the forest areas burned with different fire intensities in the Daxing＇anling Mountains. The mean TOC content in the low-intensity burned area was greater than that in the unburned area, moderate-intensity, and high-intensity burned areas in June and November （P 〈 0.05）. LFOC and POC in the low-intensity burned area were greater than that in either moderate-intensity or high-intensity burned areas, with significant differences in LFOC in September and November （P 〈 0.05）. A significant difference in LFOC between the unburned and burned areas was only found in July （P 〈 0.05）. However, the differences in POC between the unburned and burned areas were not significant in all the whole seasons （P 〉 0.05）. Soil LFOC and POC varied significantly with the seasons （P 〈 0.05） in the Daxing＇anling Mountains. Significant linear relationships were observed between soil TOC, LFOC, and POC, which were positively correlated with soil nitrogen and negatively correlated with soil temperature in the Daxing＇anling Mountains.

Short term effects of fire intensity and fire regime on vegetation dynamic in a tropical humid savanna(Lamto,central Cote d’Ivoire)

We tested the effects of different fire regimes (with different fire date and fuel load) on grass growth, tree debarking and topkill in a Guinea savanna of West Africa. Different fire intensities were simulated on two plots of 3.72 ha each, delimited in two shrubby savanna of the Lamto reserve (C?te d’Ivoire). Two fire regimes were applied, the mid-season fire (January) and the late fire (April). Two fuel levels (single: C1 and double: C2) have been used. For each fire regime, fire intensity was determined. It increases with the fuel quantity (1259 ± 356 kW·m–1 and 3380 ± 1472 kW·m–1 respectively for C1 and C2). The regrowth speed of grasses is also dependent on the fuel quantity (grasses). It increases with it and is higher after the mid-season fire than the late fire. The average intensity of the mid-season fire (2966 ± 2233 kW·m–1) is not significantly different from that of the late fire (1673 ± 1124 kW·m–1). Damages or debarking caused by fire on adult trees were recorded and are linked to fire intensity. Those damages appear to initiate the external cavity observed on trees, known to be detrimental to tree trunk mechanical resistance. They generally affect adult trees of Crossopteryx febrifuga species which is also the most commonly hollowed species. Mid-season fire remains the recommanded fire regime because it insures a faster regrowth of grasses which leads to the maintenance of equilibrium between grasses and trees.

Spatial and temporal distribution of forest fire frequency and forest area burnt in Jilin Province, Northeast China

Forest fires caused by natural forces or human activities are one of the major natural risks in Northeast China.The incidence and spatial distribution of these fires vary over time and across the forested areas in Jilin Province,Northeast China.In this study,the incidence and distribution of 6519 forest fires from 1969 to 2013 in the province were investigated.The results indicated that the spatiotemporal distribution of the burnt forest area and the fire frequency varied significantly by month,year,and region.Fire occurrence displayed notable temporal patterns in the years after forest fire prevention measures were strictly implemented by the provincial government.Generally,forest fires in Jilin occurred in months when stubble and straw were burned and human activities were intense during traditional Chinese festivals.Baishan city,Jilin city,and Yanbian were defined as fire-prone regions for their high fire frequency.Yanbian had the highest frequency,and the fires tended to be large with the highest burned area per fire.Yanbian should thus be listed as the key target area by the fire management agency in Jilin Province for better fire prevention.

黑龙江省夏季林火火焰高度和火强度的研究

介绍了黑龙江省夏季森林火灾的种类,其包括地表火、地下火、树冠火三种。分析了这三种林火蔓延方式之间的相互演变关系,阐述了火强度的研究方法并给出了平均火强度值。

Quantifying fire severity:a brief review and recommendations for improvement

Introduction: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.Results: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.Discussion and Conclusion: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.

Long-term effects of fire frequency and season on herbaceous vegetation in savannas of the Kruger National Park,South Africa

Aims:The long-term effects of changing fire regimes on the herbaceous component of savannas are poorly understood but essential for understanding savanna dynamics.We present results from one of the longest running(>44 years)fire experiments in savannas,the experimental burn plots(EBPs),which is located in the Kruger National Park(South Africa)and encompasses four major savanna vegetation types that span broad spatial gradients of rainfall(450–700 mm)and soil fertility.Methods:Herbaceous vegetation was sampled twice in the EBPs using a modified step-point method,once prior to initiation of the experiment(1954)and again after 44–47 years.Different combinations of three fire frequency(1-,2-and 3-year return intervals)and five season(before the first spring rains,after the first spring rains,mid-summer,late summer and autumn)treatments,as well as a fire exclusion treatment,were applied at the plot level(;7 ha each),with each treatment(n=12 total)replicated four times at each of the four sites(n=192 plots total).The effects of long-term alterations to the fire regime on grass community structure and composition were analyzed separately for each site.Important Findings:Over the 44+years duration of the experiment,fires were consistently more intense on sites with higher mean annual rainfall(>570 mm),whereas fires were not as intense or consistent for sites with lower and more variable rainfall(<510 mm)and potentially higher herbivory due to greater soil fertility.Because the plots were open to grazing,the impacts of herbivory along with more variable rainfall regimes likely minimized the effects of fire for the more arid sites.As a consequence,fire effects on grass community structure and composition were most marked for the higher rainfall sites and generally not significant for the more arid sites.For the high-rainfall sites,frequent dry season fires(1-to 3-year return intervals)resulted in high grass richness,evenness and diversity,whereas fire exclusion and growing season fires had the lowest of these measures and diverged the most in composition as the result of increased abundance of a few key grasses.Overall,the long-term cumulative impacts of altered fire regimes varied across broad climatic and fertility gradients,with fire effects on the grass community decreasing in importance and herbivory and climatic variability likely having a greater influence on community structure and composition with increasing aridity and soil fertility.