Simulating dynamic and mixed-severity fire regimes: A process-based fire extension for LANDIS-II

Fire regimes result from reciprocal interactions between vegetation and fire that may be further affected by other disturbances, including climate, landform, and terrain. In this paper, we describe fire and fuel extensions for the forest landscape simulation model, LANDIS-II, that allow dynamic interactions among fire, vegetation, climate, and landscape structure, and incorporate realistic fire characteristics (shapes, distributions, and effects) that can vary within and between fire events. We demonstrate the capabilities of the new extensions using two case study examples with very different ecosystem characteristics: a boreal forest system from central Labrador, Canada, and a mixed conifer system from the Sierra Nevada Mountains (California, USA). In Labrador, comparison between the more complex dynamic fire extension and a classic fire simulator based on a simple fire size distribution showed little difference in terms of mean fire rotation and potential severity, but cumulative burn patterns created by the dynamic fire extension were more heterogeneous due to feedback between fuel types and fire behavior. Simulations in the Sierra Nevada indicated that burn patterns were responsive to topographic features, fuel types, and an extreme weather scenario, although the magnitude of responses depended on elevation. In both study areas, simulated fire size and resulting fire rotation intervals were moderately sensitive to parameters controlling the curvilinear response between fire spread and weather, as well as to the assumptions underlying the correlation between weather conditions and fire duration. Potential fire severity was more variable within the Sierra Nevada landscape and also was more sensitive to the correlation between weather conditions and fire duration. The fire modeling approach described here should be applicable to questions related to climate change and disturbance interactions, particularly within locations characterized by steep topography, where temporally or spatially dynamic vegetation significantly influences spread rates, where fire severity is variable, and where multiple disturbance types of varying severities are common.     

低C/N比污水生物脱氮所需外加碳源量的确定

利用中试规模实验装置,探讨了现有活性污泥工艺改造成间歇曝气生物脱氮工艺的实践中,碳氮比(C/N)对废水生物脱氮效率、脱氮反应速度的影响,分析了脱氮容量,确定了所需外加碳源量.      

考虑开挖扰动和基质吸力影响的基坑边坡安全性研究

在传统的边坡安全性分析中 ,人们都不考虑开挖扰动和基质吸力的影响。笔者通过试验 ,研究了开挖扰动对土体工程性质的影响 ,并且建立了考虑开挖扰动和基质吸力影响的基坑边坡安全性分析模型 ,还给出了计算实例。研究结果表明 ,开挖扰动和基质吸力对边坡安全系数有较大的影响。     

太湖地区农田NO排放不连续测量最佳时间

以我国南方太湖地区稻麦轮作生态系统的旱地阶段为例,在通过自动连续测量揭示ＮＯ排放的时间变异规律性基础上,讨论了ＮＯ排放不连续测量结果矫正及最佳观测时间选择．根据自动连续测量结果,ＮＯ排放表现出日间极大值型和夜间极大值型２种规律性日变化形式．前者发生在温度比较适宜,但植物生长较弱的情况下,此日变化形式直接与温度有关;后者发生在植物旺盛生长的情况下,且主要取决于植物对铵态氮的吸收,而与温度没有直接关系．在植物生长强弱变换的过渡期,日变化的规律性不明显．不连续测量结果的矫正因子也因植物生长状况而异．当观测时间选择不当,又不进行任何矫正处理时,根据不连续测量结果估计的ＮＯ排放可能偏高１２％ ～４７％ 或偏低１８％ ～６８％ ．无论哪种植物生长情形,１５ｖ００～１６ｖ００都是ＮＯ排放不连续测量的最佳观测时间．这时的观测结果不需要日变化矫正,能直接用来代表日平均排放量.     

过去20年气候变暖对我国冬季采暖气候条件与能源需求的影响

20世纪80年代中期以来,我国气候变暖,尤其是90年代中期以来的显著变暖,对我国冬季采暖气候条件和能源需求产生了很大影响。论文以全国458个气象台站逐日平均气温为基础,对其影响进行了分析。依照《采暖通风与空气调节设计规范G(B50019-2003)》的规定,确定了采暖初(终)日及集中(过渡)采暖期的划分方法,并采用度日法分析了采暖强度。结果发现与1980年以前时段相比,1985-2004年以及1995-2004年间,我国集中采暖区和过渡采暖区的界线明显北移,尤其110E°以东地区北移最大达2～3个纬距;北方大部地区采暖期长度缩短5～15d,长江以南地区缩短最大达30d以上;北方采暖强度普遍减小200℃以上;理论上由气候变暖导致的我国北方地区冬季采暖耗能降低了5%～30%,长江中下游地区冬季采暖耗能降低了30%以上。     

环境因子和火干扰因子对喀纳斯泰加林柳兰分布的影响

喀纳斯泰加林植被的生长和分布受火干扰和环境因子的共同作用,为了解喀纳斯泰加林林下柳兰分布与生态因子的关系,促进种群扩繁,共设置了35个样地进行调查和分析。建立柳兰重要值与生态因子矩阵,利用CCA分析法对不同火烧林分中柳兰的生长分布状况与林火烈度、火后时间、海拔、坡度、坡向、郁闭度、土壤pH值、速效钾、土壤有机质、灌木层盖度、草本层盖度和草本层物种多样性指数等20个生态因子的关系进行了分析。结果显示,第一轴主要反映林火烈度、海拔、坡向,灌木层盖度、pH值、有机质、全钾和速效钾的变化;第二轴主要反映林火烈度、火后时间、草本层盖度、坡向、坡位、土壤容重、电导率、有机质、有效磷和全氮的变化。对柳兰分布有显著影响的生态因子是林火烈度、有机质、海拔、坡向、灌木层盖度、土壤容重、全钾和速效钾,前两轴的累计贡献率为72.48%。柳兰适合在土壤呈弱酸性、海拔低、阳坡、土壤容重小、土壤有机质、全钾和速效钾含量高的环境中生长。柳兰是阳性植物,是火烧后的先锋植物。对影响柳兰分布的生态因子进行定量分离,结果发现环境因子和火干扰因子对柳兰样地物种分布的解释能力为88.2%,显示出较好的排序效果。喀纳斯泰加林受人为...     

周期性的温度扰动对藻类群落结构演替的影响

为了研究水库生境扰动对藻类水华的作用机制,以中度扰动理论为基础,结合藻类群落生境选择学说和藻类生态功能组,开展了不同温度扰动周期、相同扰动幅度下藻类多样性变化特性和群落结构演替特征的室内控制实验.结果表明:1适度的扰动会促进藻类的生长且增加其多样性.中度扰动组Δ22℃/48 h藻类生物量最大,但多样性最高,不存在绝对占优藻种,而高频次扰动组Δ22℃/24 h生物多样性较小,但可降低藻类生物量.2温度的周期性变化对浮游藻类群落的演替有明显的影响,优势种也呈现一定的差异性.藻类优势功能组演替基本规律为:X_1(小球藻)→J(栅藻)→S_1(席藻)或X_2(衣藻),群落结构呈现出C/CR型藻类先行占优向R型演替的趋势.高温扰动频繁时,R型藻类(S_1)明显占优;无扰动或低扰动时,群落结构组成特点以C/R策略为主.适度的扰动组Δ22℃/48 h形成了多种生长策略的藻类共存的格局,且耐受高温胁迫的S策略藻类(L_0)开始出现.     

Termite assemblages in a West-African semi-deciduous forest and teak plantations

Responses of termite assemblages to the conversion of semi-deciduous forest into teak plantations were studied in the Lama Forest Reserve in Benin, West Africa. Four belt transect surveys were run in each of the two forest types, adopting a modified termite diversity assessment protocol. Termite assemblages were remarkably species-poor in both forest types, with only 19 species encountered altogether. The low species richness was due to the rarity of soil-feeders of the soil/humus interface and the absence of true soil-feeders in the compact vertisol soil. Species richness was significantly higher in semi-deciduous forest than in teak plantations, but termite encounters were significantly lower. Termite assemblage and feeding group structure differed significantly among forest types. Wood-feeders were recorded only in semi-deciduous forest. In contrast, fungus-growers were more species-rich and about four times more abundant in teak plantations, mainly due to one Ancistrotermes species. The humification score, which depicts the position of termite assemblages along a gradient of increasing humification of their food substrate, was significantly higher in teak plantations, due to the absence of wood-feeders and the preponderance of fungus-growers. Combined principal components and multiple regression analysis identified two significant predictors of termite assemblages, soil water content and leaf litter biomass. The abundance of fungus-growers in teak plantations seemed to be mainly related to the high leaf litter biomass. Indirect evidence also suggests that lower predation pressure by ants on termites in teak plantations may have contributed to the abundance of termites.     

低负荷间歇运行燃煤锅炉烟尘排放规律的探讨

通过对不同负荷情况下运行的燃煤锅炉烟尘排放浓度测试，探讨了低负荷间歇运行燃煤锅炉的烟尘排放规律。随着锅炉负荷的降低，过量空气系数变大，烟尘排放浓度和排放量也变大。在相近低负荷条件下运行的不同出力的锅炉，额定出力大的锅炉烟尘排放量大。在燃煤量相近而在不同负荷状态下运行的两台锅炉，额定出力大的锅炉烟尘排放量大。对于常年低负荷运行时的锅炉，环境管理部门在对其烟尘排放进行监督管理时宜以低负荷运行时的烟尘测试数据为依据。     

Landscape ecological characteristics in temporal changes of riverside open space in urbanized area

１ＩｎｔｒｏｄｕｃｔｉｏｎＲｅｃｅｎｔｌｙｉｎＪａｐａｎ，ｔｈｅｒｉｖｅｒｓｐａｃｅｉｎｕｒｂａｎａｒｅａｓｉｓｃｈａｎｇｉｎｇｉｎｔｏｒｉｖｅｒｐａｒｋｓ，ｒｉｖｅｒｏｐｅｎｓｐａｃｅａｎｄｎａｔｕｒｅｏｒｉｅｎｔｅｄｂａｎｋ．Ｃｏｎｓｅｑｕｅｎ...