Modeling fire susceptibility in west central Alberta, Canada

Strategic modification of forest vegetation has become increasingly popular as one of the few preemptive activities that land managers can undertake to reduce the likelihood that an area will be burned by a wildfire. Directed use of prescribed fire or harvest planning can lead to changes in the type and arrangement of forest vegetation across the landscape that, in turn, may reduce fire susceptibility across large areas. While among the few variables that fire managers can influence, fuel conditions are only one of many factors that determine fire susceptibility. Variations in weather and topography, in combination with fuels, determine which areas are more likely to burn under a given fire regime. An understanding of these combined factors is necessary to identify high fire susceptibility areas for prioritizing and evaluating strategic fuel management activities, as well as informing other fire management activities, such as community protection planning and strategic level allocation of fire suppression resources across a management area. We used repeated fire growth simulations, automated in the Burn-P3 landscape-fire simulation model, to assess spatial variations in fire susceptibility across a 2.4 million ha study area in the province of Alberta, Canada. The results were used to develop a Fire Susceptibility Index (FSI). Multivariate statistical analyses were used to identify the key factors that determine variation in FSI across the study area and to describe the spatial scale at which these variables influence fire susceptibility at a given location. A fuel management scenario was used to assess the impact of prescribed fire treatments on FSI. Results indicated that modeled fire susceptibility was strongly influenced by fuel composition, fuel arrangement, and topography. The likelihood of high or extreme FSI values at a given location was strongly associated with the percent of conifer forest within a 2-km radius, and with elevation and ignition patterns within a 5-km radius. Results indicated that prescribed fire treatments can be effective at reducing forest fire susceptibility in community protection zones and that simulation modeling is an effective means of evaluating spatial variation in landscape fire susceptibility.     

From guiding principles for the conservation of forest biodiversity to on-ground practice: Lessons from tree hollow management in Tasmania

A useful theoretical approach in the literature for those trying to conserve forest biodiversity involves a number of strategies to achieve maintenance of habitat for different species across multiple spatial and temporal scales. This approach emphasises the importance of implementing measures in off-reserve areas to complement reserve systems. This contrasts with both the traditional ‘set-aside’ approach to conservation and the primary aim of production forestry. Translating this risk-spreading approach into on-ground practice is often a difficult task.     

Effects of landscape composition and configuration on northern flying squirrels in a forest mosaic

Habitat loss and sometimes habitat fragmentation per se affect species survival, reproduction, dispersal, abundance and distribution. However, understanding the independent effects of fragmentation (i.e., landscape configuration) has been limited because it is frequently confounded with landscape composition (i.e., habitat amount). We assess the independent effects of landscape composition and configuration on the occurrence of northern flying squirrels (Glaucomys sabrinus) in New Brunswick, Canada after controlling for local site conditions. We measured landscape structure using an “organism-based” approach; landscape structure was characterized quantitatively using a spatially explicit local-scale distribution model for northern flying squirrels.     

Spatial and temporal patterns in structure and diversity of Mediterranean forest of Quercus pyrenaica in relation to fire

The main objective of this work is to analyze the spatial and temporal response of Q. pyrenaica community to fire. In order to do so, an ecological characterization of 15 forests in different succession stages (5 Initial: 0–20 years, 5 Medium: 20–60 years and 5 Mature: over 60 years), paying special attention to structural and diversity features, was carried out. The results show that temporal changes are very important, and particularly affect the structure and relative abundance of the vegetation. The main differences consist in the change from a homogenous structure, with high cover and overlayering of woody species, at Initial stage, to a more pluristratified, complex and organized structure, with lower cover and overlayering of woody species at Mature stage. The changes in abundances showed a decrease in shrubby species, such as the Erica australis, Genista florida and Erica arborea at Initial stage, and the incorporation of tree species, such as Crataegus monogyna, Acer pseudoplatanus and Alnus glutinosa at Mature stage. However, there are no significative differences between stages for specific richness and diversity values. Spatial heterogeneity is high and similar in all three defined stages.     

Spatial distribution,architecture, and development of the root system of Pinus banksiana Lamb. in natural and planted stands

In the province of Québec, Canada, the majority of planted jack pine (Pinus banksiana Lamb.) seedlings are produced in rigid wall containers. More than 95% of them exhibit deformations of the root system which may induce stem instability. Studies of the root architecture of planted jack pine have been limited to a 30 cm radius from the stem, as barely any studies have been devoted to naturally regenerated stands. Moreover, only a few researches have focused on temporal evolution of root systems. The aim of the present study was to characterize the architectural, spatial, and temporal development of jack pine roots in natural and planted stands. Study sites were located in the continuous boreal forest of Quebec. The plantation was done in 1987, so that the trees were 15 years old at the time of sampling. Trees from natural stand had regenerated after a fire in 1983 and were 13–16 years old. The root systems of 14 jack pine trees per site were manually excavated up to a <5 mm diameter, without regard to their distance from the stem. The number, length, diameter, and the spatial and temporal development of roots were analyzed according to three scales of root architecture: the root system, axes, and segments. Overall, the numbers and lengths of roots were higher with planted pines. However, naturally regenerated trees displayed a better distribution of their roots around the stem and at depth, combined with more rapid length growth during the first years. In natural stands, all the trees had a taproot and 30% of the main roots originated at a depth of more than 20 cm, and they are regularly distributed around the stems. Planted trees did not present a taproot and 97% of the main roots originated in the first 20 cm beneath the soil surface. Moreover, 50% of root length was located in one-third of the area surrounding the stems, an area that corresponded to the furrow. Finally, the annual development of lateral roots in planted stand displayed a 5-year delay when compared with natural stand, which also affected maximum growth length and development of the branching pattern. Root distribution and temporal development are known to play a major role in the stability of aerial parts. Seedling production methods, container type, site preparation and planting techniques need to be examined in greater detail in order to assess their effect throughout the development of the root system. It is necessary to compare different sylvicultural practices and with natural/planted stands to gain a clearer understanding of this problem.     

延胡索酸酶的结构和功能研究进展

延胡索酸酶在三羧酸（TCA）循环中催化延胡索酸和L-苹果酸之间的可逆水合反应,根据不同的来源、空间结构以及生化性质,延胡索酸酶可分为二聚体的第一类延胡索酸（ClassI fumarase）和四聚体的第二类延胡索酸酶（ClassII fumarase）。目前C1assI fumarase的研究较少,本文对C1assII fumarase的结构、功能和作用机理的研究进展进行了综述。     

雷公山水青冈林乔木层主要植物种群空间分布格局

应用立木大小级对水青冈群落中的水青冈(Fagus longipetiolata)和青冈栎(Cyclobalanopsis glauca)两个优势种群径级结构进行了对比分析,同时采用方差/均值的t检验法、Morisita指数Iq的F检验法、丛生指数I、负二项式指数K、平均拥挤系数m*和聚块性指数m*/m判定并检验了两种优势种群的分布格局,并按径级分样地进行了格局类型及强度的比较。结果表明,在分布格局上,水青冈种群V级占优势,在3个样地中分别达到52%,49.1%,49.4%,Ⅰ级没有,Ⅱ级较少,表现为衰退种群;青冈栎种群Ⅳ级较多,Ⅰ、V级在个体数量比水青冈种群多;群落中两优势种群均呈集群分布。分析径级结构得出,随径级增大,水青冈种群由随机分布向集群分布过渡,而青冈栎种群则由集群分布向随机分布过渡。     

莱州湾小拟哲水蚤(Paracalanus parvus)丰度分布周年变动

利用2011年5月?2012年4月(除冰期12月和翌年1?2月外)在渤海莱州湾逐月由底至表垂直拖网(网孔目160μm)获得的浮游动物样品,开展小拟哲水蚤丰度分布周年季节变动研究。结果显示,小拟哲水蚤季节变化呈单峰型,7?10月份丰度较高,高峰值出现在8月份;水平分布以湾中部偏东侧丰度较集中,其次为湾口站位,湾顶站位为相对低值区。应用 Primer 6.0软件中的 BIOENV程序分析发现,小拟哲水蚤总丰度的月变化主要受水温影响、特别是1月前的水温,可能还受黄河径流量的间接影响;水平分布则与盐度、水深关系密切。     

中国草地样带植物氮磷元素空间格局及其与气候因子的关系

在横穿内蒙古和青藏高原的中国草地样带中,设置了132个采样样地,采集到138种、329个植物叶片样品。在对植物样品进行化学元素分析的基础上,分析了植物叶片氮磷元素空间格局及其与气候因子的关系,试图为全球气候变化条件下草地的C,N,P元素循环研究以及草地生态系统对全球气候变化的响应和适应研究提供依据,同时也为相关生态学模型提供基础数据。结果表明：青藏高原地区植物N,P含量均高于内蒙古地区。随着年均温的增加,植物叶片N元素含量呈降低趋势,P元素含量和N/P变化不明显;随着年均降水量的增加,植物叶片N,P元素含量均略呈增加的趋势,而N/P变化不明显。上述研究结果验证了温度-植物生理假说（TPPH）,同时,还支持土壤年龄假说和生长速率假说。然而,地带性气候因子对植物叶片N,P元素变异的解释率并不高,这表明草地植被N,P元素变化的格局、规律和机制仍需进一步深入研究。     

杭州市耕地土壤有机质状况及时空变化特点

为了解杭州市耕地土壤有机质状况,笔者利用近期获得的耕地土壤肥力测试数据,统计分析了全市耕地土壤有机质的变化特征。结果表明：杭州全市耕地土壤有机质以中量水平为主,大部分土壤的有机质在20~40 g/kg 之间,约有1/4(27.00%)的土壤有机质偏低。土壤有机质平均含量以水网平原最高,其次为丘陵区和河谷平原区,滨海平原最低。第二次土壤普查以来,全市水田土壤有机质平均含量趋于下降,而旱地土壤有机质含量呈现增加趋势。杭州市耕地土壤有机质区域变异大,高低差异明显;应增加水田土壤有机肥料的投入,防止水田土壤有机质的进一步下降,并重视滨海平原区耕地土壤有机质的提升。