Forest succession trajectories after fi res in valleys and on slopes in the Greater Khingan Mountains,China

Accurate assessment of postfire vegetation recovery is important for forest management and the conservation of species diversity.Topography is an important factor aff ecting vegetation recovery but whether species composition varies with diff erent recovery stages and between valleys and slopes is unclear.Using fi eld data and a space-for-time substitution method,we quantifi ed species richness and diversity to obtain the successional trajectories of valleys and slopes.We surveyed the species of 10 burned areas from 1986 to 2010 in the Greater Khingan Mountains in northeastern China,and found that with increasing postfi re recovery time,species richness in both valleys and slopes gradually decreased.However,species richness in valleys was relatively higher.Shrubs recovered rapidly in the valleys,and species diversity maximized approximately 11 years after fi re.However,it maximized 17–18 years after fi re on the slopes.Numerous shade-tolerant species were present in the valleys 11 years after fi re but not until after 18 years on slopes.Larch appeared earlier than 11 years after fi re and its recovery was slow in the valleys but appeared quickly on slopes and established dominance early.Our study provides some new insights into vegetation succession after fi re at local scales.After fi re,the vegetation recovery processes diff er with topography and it aff ects the initial rate of recovery and species composition at diff erent successional stages.

Analysis on Natural Regeneration Characteristics and Growth Factors of Two Cut-over Lands of Larix gmelini Forests in Greater Khingan Mountains

[Objective] This study aims to analyze the natural regeneration characteristics and growth factors of two cut-over lands of Larix gmelini forests in Greater Khingan Mountains. [Method] A database was established based on the information of natural regeneration cut-over sample plots of Larix gmelini forests in Greater Khingan Mountains. Natural regeneration characteristics of clear-cutting sample plot and shelterwood-cutting sample plot of Larix gmelini in the northern regions of Greater Khingan Mountains were investigated by programming analysis. [Result] The natural regeneration of two principal felling systems was both good, and that of shelterwood-cutting sample plot was better. There were significant linear regression relationships among various growth factors of naturally regenerated plants. [Conclusion] This study provided scientific theoretical guidance for subsequent deforestation and regeneration in Greater Khingan Mountains.

The driving factors and their interactions of fire occurrence in Greater Khingan Mountains, China

Fire is an important disturbance in terms of forest management.A comprehensive understanding of the relationships between the spatial distribution of fire occurrence and its driving factors are critical for effective forest fire management.To reveal biogeoclimatic and anthropogenic influences,this study introduced a geographical detector model to quantitatively examine the effects of multiple individual factors and their combinations on spatial patterns of fire occurrence in the Greater Khingan Mountains between 1980 and 2009.The geographical detector computes the explanatory power(q value)to measure the connection between driving factors and spatial distributions of fire occurrence.Kernel density estimation revealed the spatial variability of fire occurrence which was impacted by bandwidth.30 km might be the optimal bandwidth in this study.The biogeoclimatic and anthropogenic effects were explored using topography,climate,vegetation,and human activity factors as proxies.Our results indicated that solar radiation had the most influence on the spatial pattern of fire occurrence in the study area.Meanwhile,Normalized Difference Vegetation Index,temperature,wind speed,and vegetation type were determined as the major driving factors.For various groups of driving factors,climate variables were the dominant factors for the density of fire occurrence,while vegetation exerted a strong influence.The interactions between the driving factors had a more significant impact than a single factor.Individually,the factors in the topography and human activity groups exhibited weaker influences.However,their effects were enhanced when combined with climate and vegetation factors.This study improves our understanding of various driving factors and their combined influences on fire occurrences of the study area in a spatial context.The findings of this study verify that the geographical detector is applicable in revealing the driving factors of fire occurrence.

The Discovery of the Bivalve Fossil Arguniella from the Lower Cretaceous Shangkuli Formation in Northern Greater Khingan Mountains, China: Implications for Stratigraphic Correlation

Objective Typical Early Cretaceous non-marine bivalve fossils from Eastern Asia are represented by the Arguniella-Sphaerium assemblage,and they were important members of the Jehol Biota.Historically,the genus Arguniella in western Liaoning had been mistakenly identified as the Jurassic Ferganoconcha,re-identified as Arguniella with。

The climate change variations in the northern Greater Khingan Mountains during the past centuries

The Greater Khingan Mountains （Daxinganling） are China＇s important ecological protective screen and also the region most sensitive to climate changes. To gain an in-depth understanding and reveal the climate change characteristic in this high-latitude, cold and data-insufficient region is of great importance to maintaining ecological safety and corre- sponding to global climate changes. In this article, the annual average temperature, precipi- tation and sunshine duration series were firstly constructed using tree-ring data and the me- teorological observation data. Then, using the climate tendency rate method, moving-t-testing method, Yamamoto method and wavelet analysis method, we have investigated the climate changes in the region during the past 307 years. Results indicate that, since 1707, the annual average temperature increased significantly, the precipitation increased slightly and the sun- shine duration decreased, with the tendency rates of 0.06~C/10a, 0.79 mm/10a and -5.15 h/10a, respectively （P〈~0.01）. Since the 21 st century, the period with the greatest increase of the annual average temperature （also with the greatest increase of precipitation） corresponds to the period with greatest decrease of sunshine duration. Three sudden changes of the an- nual average temperature and sunshine duration occurred in this period while two sudden changes of precipitation occurred. The strong sudden-change years of precipitation and sunshine duration are basically consistent with the sudden-change years of annual average temperature, suggesting that in the mid-1860s, the climatic sudden change or transition really existed in this region. In the time domain, the climatic series of this region exhibit obvious local variation characteristics. The annual average temperature and sunshine duration exhibit the periodic variations of 25 years while the precipitation exhibits a periodic variation of 20 years. Based on these periodic characteristics, one can infer that in the period from 2013 to 2030, the temperature will be at a high-temperature stage, the precipitation will be at an abundant-precipitation stage and the sunshine duration will be at an less-sunshine stage. In terms of spatial distribution, the leading distribution type of the annual average temperature in this region shows integrity, i.e：, it is easily higher or lower in the whole region; and the second distribution type is more （or less） in the southwest parts and less （or more） in the northeast parts. Precipitation and sunshine duration exhibit complex spatial distribution and include four spatial distribution types. The present study can provide scientific basis for the security in- vestigation of homeland, ecological and water resources as well as economic development programming in China＇s northern borders.