Effects of thinning on microsites and natural regeneration in a Larix olgensis plantation in mountainous regions of eastern Liaoning Province, China

In order to understand the effects of thinning on microsite conditions and natural regeneration in the larch plantation, thinning experiment was conducted in a 40-year-old Larix olgensis plantation in Qingyuan County in eastern Liaoning Province, China in 2003-2004 Five thinning treatments （0%, 10.2%, 19.8%, 29.7% and 40.3% thinned） were designed on the same site. After thinning, canopy openness and the microsite conditions such as photosynthetic photon flux density （PPFD）, soil moisture content, and soil temperature were measured in one growing season. Meanwhile, the investigation of natural regeneration was conducted at the end of the growing season. The results showed that the canopy openness increased with the increase of thinning intensities. PPFD and soil temperature and soil moisture content in different soil layers were positively relative with canopy openness after thinning. The richness of regenerating tree species did not significantly increase （p=0.30） after one growing season since thinning, but the regeneration density and frequency of tree species increased significantly （p〈0.05）. In addition, the number of regenerating tree species increased, and the increment was correlated with the characteristics of iudividual tree species. The increasing percentage of regenerating seedlings of the shade-intolerant tree species was more than that of shade-tolerant tree species. Among the investigated regeneration species, the biggest response of seedling emergency to the canopy openness was Phellodendron amurense. This paper confirmed the following conclusions： after thinning, the variety of regenerating tree species was correlative with the characteristics of regenerating tree species, and the distribution of unthinned trees and the site conditions in the investigated larch plantation were the additional factors influencing, the regeneration.

Explaining First-Year Seedling Survival from Quality Distributions of Bare-Root Seedlings and Microsites in Industrial Plantations

First-year seedling survival impacts all subsequent management planning in plantation forestry. Descriptive statistics of first-year seedling survival data from the Louisiana Department of Agriculture and Forestry (LDAF) indicated that survival success reaches a plateau at between 79% - 85% under normal weather conditions. We provide an explanation for this plateau based on an analysis of seedling and microsite qualities involved in operational pine plantations by: 1) using a conceptual model demonstrating how variation in seedling quality and microsite quality interact to determine plantation survival, 2) presenting an example to characterize quality distributions of seedling and microsite qualities, and 3) comparing model outcomes based on measured distributions to realistic values of first-year survival. Simulation results indicated that consistent survival could result from random pairings of initial seedling and site quality distributions. LDAF data analysis indicated that 72% of seedlings were associated with the most frequent quality class that comprised seedlings with stem caliper between 3.2 to 4.7 mm and average stem height and volume of 25.75 cm and 3.43 cm3, respectively. Similarly, assessment of microsites at planting sites in Southeast Louisiana indicated that 48% of planted seedlings were associated with the most frequent microsite quality class which supported first-year height increment between 9 to 29 cm. Modelling of current operational practice indicated that using seedlings with larger caliper size would increase first year survival, but would result in higher establishment costs. The conceptual model could be modified to for use in other regions regardless of species types involved.

周边建筑对目标建筑顶面风力机微观选址的影响

为分析周边建筑物对目标建筑物顶面风流场特性的影响,以内蒙古工业大学学生宿舍为目标建筑物,并以其为中心,分别对五种不同半径范围内的周边建筑物进行模拟计算,分析盛行和非盛行风向下五种几何模型中目标建筑物顶面的风场特征,结果表明,所考虑周边建筑物的范围尺寸对目标建筑物顶面风场特征影响较大,随着考虑周边建筑物范围尺寸的扩大,目标建筑物顶面的减速现象越明显,且强湍流区域越大。由于不同尺寸范围内周边建筑形态、布局、高度等差异,仅考虑盛行风向不能准确判断目标建筑周围风场特征,需根据周边建筑的结构和分布特征对多个风向情况进行分析。

Denitrification and the challenge of scaling microsite knowledge to the globe

Our knowledge of microbial processes—who is responsible for what,the rates at which they occur,and the substrates consumed and products produced—is imperfect for many if not most taxa,but even less is known about how microsite processes scale to the ecosystem and thence the globe.In both natural and managed environments,scaling links fundamental knowledge to application and also allows for global assessments of the importance of microbial processes.But rarely is scaling straightforward:More often than not,process rates in situ are distributed in a highly skewed fashion,under the influence of multiple interacting controls,and thus often difficult to sample,quantify,and predict.To date,quantitative models of many important processes fail to capture daily,seasonal,and annual fluxes with the precision needed to effect meaningful management outcomes.Nitrogen cycle processes are a case in point,and denitrification is a prime example.Statistical models based on machine learning can improve predictability and identify the best environmental predictors but are—by themselves—insufficient for revealing process-level knowledge gaps or predicting outcomes under novel environmental conditions.Hybrid models that incorporate well-calibrated process models as predictors for machine learning algorithms can provide both improved understanding and more reliable forecasts under environmental conditions not yet experienced.Incorporating trait-based models into such efforts promises to improve predictions and understanding still further,but much more development is needed.

Saxicolous lichen communities in three basins associated with mining activity in northwestern Argentina

Mining activity affects the vegetation and soils of the ecosystems.However,the effects of mining activity on saxicolous lichen communities are less concerned.Thus,the aim of this study was to characterize saxicolous lichen communities in three basins(Vis-Vis River basin,Poteros River basin,and Capillitas River basin)surrounding metalliferous mining projects of different types of operation and at different stages of exploitation.A large-scale mine(Bajo de la Alumbrera)with more than 25 a of open-pit mining located in the Vis-Vis River basin(CRV).A pre-exploitation mine(Agua Rica)located in the Poteros River basin(CRP),and a small-scale mine(Minas Capillitas)with more than 160 a of underground mining located in the Capillitas River basin(CAC).In each basin,species richness,cover,and frequency of lichen communities were measured on 40 rock outcrops.Also,explanatory variables were recorded,i.e.,altitude,slope,aspect,vegetation cover,rock,and soil cover around the rocky area sampled.Richness and total cover of lichen communities were analysed using linear models,and species composition was explored using multivariate ordination analysis.Results showed that a total of 118 lichen species were identified.The species richness differed among basins and the lichen composition present in areas close to mining sites responded mainly to basins,altitude,and microsite variables.The lichen cover showed no difference among basins,but it changed under different rock and vegetation cover.It was not possible to quantify the effects of mining activity on species richness and composition.However,the low richness values found in the downstream of Minera Alumbrera could be associated with the negative impact of open-pit mining.Moreover,the effects of large-scale mining activity on lichen communities needs more investigation.

Synergies between microsites of plant communities and steady-stage alpine meadows on the Qinghai-Tibetan Plateau

Background:Due to the effects of climate change and overgrazing in recent decades,alternative stable states in the alpine Kobresia meadow degradation process have coexisted in the same geographical and climatic environment,with variations occurring among microsites.Methods:We used a space-for-time substitution approach to explore the synergies of microsite variation according to its numerical characteristics and the proportion of each stable state at various stages of succession in alpine Kobresia meadows on the Qinghai-Tibetan Plateau.Results:(1)The highest average aboveground biomass in summer was 196.2±20.3 gm^(-2),with significantly higher levels of biomass in≤3.65 sheep unit ha^(-1) than in other levels of grazing intensity,while the parameters showed no significant differences among grazing intensity levels in>3.65 sheep unit ha^(-1).(2)The importance of plant functional groups,aboveground biomass,and niche breadth of Poaceae and Cyperaceae significantly decreased as the grazing intensity increased.(3)The effects of≥0°C accumulated temperature,total precipitation,altitude,longitude,and latitude cumulatively contributed less than 20%of the variation in the distribution of functional group characteristics across microsites.Conclusions:(1)Overgrazing decreases primary production in alpine Kobresia meadows,but ecosystem responses regulate plant community structure and botanical components so as to partially counteract grazing disturbance.(2)Overgrazing changed the proportion of microsites,which in turn led to regime shift in the plant community and subsequent synergies between the microsites of plant communities and their stable states.

数字化视域下的生物可渗透性建筑外墙设计研究

近年,全球绿色建筑产业现代化进程不断提速,垂直绿化作为最广泛的生态设计手段却有明显缺点,如传统的绿植幕墙本质上需要昂贵的结构系统进行支撑和维护。文章将针对此现象,基于生物可渗透性设计概念,结合生物学和建筑学的方向,探索让生物自然生长在建筑表面的低维护、低损耗的自适应式建筑外墙系统。

核桃园行内地面覆盖的土壤微域生态效应

为了探明核桃园行内地面覆盖的土壤微域生态环境效应、确立核桃园科学省力的土壤管理措施,以盛果期早实薄皮核桃‘绿岭’为试材,通过连续4 a的行内地面覆盖,研究了园地土壤的水分、通气、矿质营养及三大微生物区系等微域生态环境的状况,结果表明:通过连续四年覆盖,0—20 cm土层,覆盖牛粪、碎木屑、苜蓿处理及CK 2014年核桃生长期的土壤平均质量含水量的变异系数分别为9.27%、10.27%、12.15%和13.96%,最大变幅分别为1.86%、1.95%、2.17%和2.63%;20—40 cm土层,覆盖牛粪、碎木屑、苜蓿处理及CK的土壤平均质量含水量分别为13.23%、12.46%、11.77%和11.43%。覆盖牛粪、碎木屑、苜蓿及CK的0—60 cm土层的平均土壤容重为1.34、1.38、1.43 g/cm^3和1.48 g/cm^3,3类微生物总量分别为430.94×10~4、208.87×10~4、183.42×10~4个/g和160.46×10~4个/g。通过主成分分析对覆盖牛粪、碎木屑、苜蓿处理及CK的土壤肥力进行综合评价,得分分别为0.61、0.26、0.09和-0.96,各因子对土壤肥力水平的综合效应排序为:土壤有机质含量>全氮含量>全钾含量>全磷含量>土壤质量含水量>孔隙度>细菌数量>真菌数量>放线菌数量>土壤容重。

林隙微生境及更新研究进展

系统评述了国内外关于林隙干扰及更新的最新研究进展。林隙是一种经常发生的小规模干扰,是森林群落时空格局变化的驱动力。不同的林隙干扰状况导致了林隙内光照的差异,进一步造成林隙内温度、湿度、土壤理化性质的变化,形成了微生境的时空异质性。林隙干扰通过改变微生境而对幼苗的出土、存活、定居和生长产生重要影响。林隙内种子库的物种丰富度变化很大,是幼苗分布格局的重要影响因子。更新幼苗的存活率和生长量受林隙大小及幼苗在林隙中位置的影响。指出了这一领域今后的研究方向。

微立地土壤水分-物理性质差异及对水曲柳幼林生长的影响

采用较小立地尺度对土壤水分物理性质的变化及与水曲柳生长的关系进行研究 .结果表明 ,除传统尺度立地上土壤水分 物理性质存在较大差异外 ,该尺度立地内部微立地间亦存在较大的变化 ,一些指标如非毛管孔隙度、土壤通气度和土壤渗透系数等在微立地间的变化甚至超出立地间的变化 .土壤水分 物理性质的差异 ,使得不同微立地间水曲柳生长存在较大差异 ,同一立地内不同微立地间林木生长差异明显高于不同立地间的差异 .土壤水分 物理性质及林木生长受到局部地段微立地的影响 .微立地的研究对进一步实现适地适树具有重要意义 .

磷在潮土肥际微域中的迁移和转化

采用室内土柱实验研究了磷在潮土肥际微域中的迁移和形态转化。结果表明,磷在潮土中的移动距离很短,经过7 d和28 d的迁移,磷的迁移距离仅为8～14 mm。施入的磷主要固定在紧靠施肥点2 mm土体范围内,随距施肥点距离的增加,土壤水溶性磷、酸溶性磷和有效磷的含量呈指数曲线迅速降低。磷在施肥后7 d内的迁移量较大,迁移进入土壤的磷绝大部分被吸附固定。施肥量对不同形态磷在肥际微域中的迁移量产生显著影响;但培养时间只明显影响了水溶性磷的迁移量。

钾在潮土肥际微域中的迁移与转化

采用室内土柱实验研究了钾在潮土肥际微域中的迁移和形态转化。结果表明,在室温25℃、土壤含水量332 g/kg和容重1.22 g/cm^3的条件下,经过7 d和28 d的扩散,钾在潮土中的迁移距离为40-75 mm,前期移动较快。在迁移距离内,土壤水溶性钾和交换性钾含量与距施肥点距离呈极显著线性负相关。施肥量和培养时间对水溶性钾和交换性钾含量在肥际微域中的分布均有显著影响,但对非交换性钾含量没有显著影响。外源钾进入土壤后在肥际微域中被固定的部分仅占5.6%-21.5%,绝大部分仍以有效态存在。

基于数值模拟的复杂地形风场风资源评估方法

与采用线性模型的WAsP软件相比,CFD方法具有可以逼真模拟复杂地形三维风场大气流动的优势,因此成为了复杂地形风场风资源评估的发展方向。为了把CFD软件包FINE/TURBO和带有壁面函数的k-ε湍流模型用于复杂地形地貌风电场的风资源评估和微观选址中去,本文以南澳岛风场作为研究对象,在中性大气条件假设下,对风场区域以30°风向为间隔进行数值模拟。研究采用不同入口边界条件对数值计算结果的影响。比对模拟结果发现,风场中的风加速与湍流强度基本上不随来流条件发生变化。基于这一规律,结合全年测风数据评估风场的风资源分布状况,建立了一套风资源评估的数值模拟及后处理方法,为工程实际提供了有力参考。

基于改进差分进化算法的潮流发电机组微观选址

针对潮流能发电机组布局依赖经验法、缺乏自主优化而导致微观选址难度大的问题,提出了一种基于差分进化算法并结合流场仿真模型的微观选址优化方法。通过对流场的有限元仿真,获取选址区域在原始状态下的流速分布;在充分考虑地形、潮汐和尾流效应等因素的前提下,以仿真结果为依据,以潮流发电机组群输出功率最大为优化目标,以机组间距及水深限制为约束,建立微观选址优化的数学模型;采用差分进化算法进行模型求解,同时为更利于最优解的搜索,提出了对其变异算子及参数设置的改进策略。以龟山水道为例进行微观选址优化计算,验证了所提模型的准确性与算法的高效性。

微立地土壤物理性质差异及对脂松幼林生长的影响

为探索微立地对脂松幼林生长的影响,采用较小尺度,测定与单株林木生长空间相关的土壤物理性质,并通过方差分析方法分析了脂松幼林期间的树高和胸径的生长量。结果表明:不同微立地类型上土壤物理性质差异显著,微立地地形因子对脂松幼林的树高生长和胸径生长都有显著影响,其中凹地形和伐桩对脂松的树高和胸径的生长是负影响,而且与普通地形上的林木长势差异显著;凸地形对脂松的树高和胸径的生长是正影响,但与普通地形上的林木长势差异不显著。

磷在红壤肥际微域中的迁移和转化

采用室内土柱实验研究了磷在红壤肥际微域中的迁移和形态转化。结果表明,相同施量的磷在7天和28天时的迁移距离相同,施用磷酸二氢钙(MCP)0 2g和0 5g时的迁移距离分别为1 4cm和2 0cm。磷在施肥7天内的迁移量较大,然后只发生少量迁移。迁移进入土壤的磷86 3%～94 2%被吸附固定,64 1%～72 2%仍以有效态存在。在迁移距离内,土壤水溶性磷、酸溶性磷和有效磷含量与距施肥点距离呈极显著直线负相关。施肥量对水溶性磷、酸溶性磷和有效磷在肥际微域中的含量分布有显著影响;但培养时间只对水溶性磷含量分布有显著影响。

不同土壤和供肥模式对磷在肥际微域中的迁移和转化的影响

采用室内土柱实验研究了单施磷酸二氢铵（MAP）、磷酸二氢铵配施草酸（MAP＋OA）和包膜磷酸二氢铵（包膜MAP）3种施肥模式下磷在潮土和水稻土肥际微域中的迁移和形态转化。结果表明,磷在土壤中的迁移距离较短,磷在潮土中的迁移距离较水稻土短,配施草酸处理可增加磷在土壤中的迁移距离,包膜MAP处理磷的迁移距离最短且释放量少。磷在施肥60 d内的迁移量较大,然后只发生少量迁移,迁移进入土壤的磷60.2%~80.3%被吸附固定,15.4%~42.9%仍以有效态存在,配施草酸处理可降低土壤对磷的固定作用,包膜MAP处理缓慢释放磷肥可能会增强土壤对磷的固定作用。

帽儿山实验林场白桦人工幼林适宜微立地研究

在相同立地上的不同类型的微立地环境中,测定白桦幼树生长指标和土壤含水率,并以邻近微环境外的4株白桦作为对照,分析微立地环境对白桦幼树生长的影响。研究结果表明:由伐根和倒木等粗大木质残体构成的微立地对白桦幼树的生长均产生明显的促进作用。凸凹地形微立地对幼树生长的作用因所处立地条件而异,凸地形、凹地形分别在下坡位和上坡位有利于白桦幼树生长。灰烬堆微立地在上坡位不利于白桦的生长,中、下坡有利。白桦人工造林时,根据立地条件科学选择微立地作为栽植点可以有效改善幼林的生长表现。

子午岭三种生境下辽东栎幼苗定居限制

辽东栎(Quercus wutaishanica)是子午岭地区的乡土乔木树种,也是该地区气候顶极群落的建群种,其幼苗的补充更新影响着森林群落的结构及物种组成。在3种典型生境(辽东栎林、人工油松林、灌草丛)中,设置3因素(种子、干扰、遮荫)两水平的野外播种实验(随机区组设计),记录辽东栎幼苗出苗量,并监测幼苗同生群在3种生境中3a间的生长状况,以确定种子及微生境在辽东栎幼苗补充过程中的限制作用。播种实验样方大小30cm×30cm,共计216个样方。结果显示,在辽东栎林及油松林内,增加种子和干扰强度(去除枯落物),能引起出苗量和幼苗补充量的显著增加,且2种处理方式间存在交互作用,表明在郁闭林冠下,辽东栎幼苗的补充受到了种子和微生境的双重限制,枯落物是导致微生境限制的主要因素之一。在灌草丛生境,各种处理方式均不能增加幼苗的补充量,表明辽东栎无法在开阔生境(强光照、干旱)中完成实生幼苗的补充更新。3种生境中的幼苗同生群生存分析表明,辽东栎幼苗在森林群落中存活率显著高于灌草丛群落。根据幼苗生长指标判断,在3种生境中,人工油松林是辽东栎幼苗定居的最佳场所。与实验预期相反,灌木对辽东栎幼苗的补充无显著影响。

动态评价粒子群优化及风电场微观选址

提出了动态评价方法处理一类约束优化问题.将目标函数值和约束违反量进行动态归一化处理,再进行加权求和,动态评价解的优化性能.不仅解决了惩罚因子确定困难的问题,而且增加了优化算法的多样性,提高了优化算法搜索全局最优解的能力.将动态评价方法引入粒子群算法,求解风电场微观选址优化问题.仿真结果表明,动态评价方法提高了风电场发电量和风能利用效率.此外,该方法可广泛应用于其他优化算法以求解约束优化问题.