松嫩草原火干扰状况研究

松嫩草原自然状态下火周期为４年，最易着火的季节—时间是每年４月和１０月，以４月份最为敏感。松嫩草原火提高的地下０．５ｃｍ处土壤温度与燃掉的可燃物量成直线正相关。燃烧指数以每年的４月份最高，大于６０，形成炙热速进火。草原火管理工作中，应着重加强对每年４月份的警戒。     

Burial rates of surrogate seeds in arable fields

The probability of seed consumption by surface-dwelling predators depends on the duration of seed exposure on the soil surface. We investigated seed burial using painted ceramic beads as surrogate seeds. Fifty beads of three size classes each were applied to small arenas within crop fields and their fates were followed from August to October. New sets of beads were applied as soon as most beads had disappeared from the soil surface. Bead availability on the soil surface declined immediately after placement, and then declined steadily over time, with increased loss during rain and management practices. Smaller beads were incorporated into the soil/litter matrix more easily than larger beads. Bead burial differed considerably among crop environments, with more burial in forage crops (red clover, lucerne) than in row crops (soyabean, maize). The fact that seed availability differed among crop environments suggests that it can be manipulated to maximise predation risk.     

环境因素对淡水浮丝藻生长及产生嗅味的影响

浮丝藻(Planktothrix) 是一种在我国水域中普遍存在, 可以引起蓝藻水华的水华藻之一,其代谢生成的二-甲基异莰醇 (2-methylisoborneol, 2-MIB) 可导致水体产生令人厌恶的嗅和味,从而使饮用水感官质量下降。本文探讨了温度 (15-30℃),BG11营养盐浓度 (20-100% (w/v))和光照强度 (1000-4000 Lux)对分离于巢湖的浮丝藻(Planktothrix sp.) FACHB-1372生长密度,总2-MIB生成量及胞外2-MIB分泌量的影响。研究结果表明在所述实验条件范围内,温度对浮丝藻生长密度,总2-MIB生成量及胞外2-MIB分泌量影响最显著。25 ℃是浮丝藻最适宜的生长温度,最高细胞密度可达6.04×10_⁵ cell?ml_^-1,30 ℃是其最适宜的产2-MIB温度,总2-MIB生成量和胞外2-MIB分泌量最高分别可达3.64×10_³ ng?L_^-1和2.78×10_³ ng?L_^-1；其次为营养盐浓度,增大BG-11营养盐浓度,浮丝藻生长密度和总2-MIB生成量会随之增加,但实验发现低浓度营养盐时,胞外2-MIB分泌量所占比例较高,表明低浓度营养盐更有利于浮丝藻进行胞外2-MIB分泌；光照对浮丝藻生长及产嗅味物质影响较小,强光照可促进2-MIB胞外释放,4000 Lux时其胞外2-MIB分泌量达最高。最后,依据实验结果为控制和预警浮丝藻过渡繁殖和嗅味物质释放提出了应对方法。     

Management of Grazing Intensity in the Semi‐Arid Rangelands of Southern Australia: Effects on Soil and Biodiversity

Overgrazing contributes to rangeland degradation altering plant community composition, erosion and biodiversity. Little unanimity in the literature exists on the effects of livestock grazing on soil carbon and biodiversity, in part, due to uncontrolled grazing pressure from native and feral animals. Paired paddock contrasts at three, long‐term (>8 years) study locations in the southern Australian rangelands were used to examine the effects of managing grazing intensity through the use of exclusion fencing and rotational grazing on soil organic carbon (SOC), soil nitrogen (TN), ground cover and biodiversity (flora and invertebrates). Grazing management had no effect on SOC or TN on grey soils (Vertisols), but for red soils (Lixisols), significantly higher levels of SOC were found for both the 0 to 5 and 5 to 10‐cm soil depths (0·3% and 0·27% respectively) and associated with increased TN. We found strong and consistent relationships among SOC and higher perennial (p < 0·001), higher litter (p < 0·05) cover and close proximity to trees (p < 0·05). Managing grazing intensity resulted in significantly higher perennial ground cover (p < 0·001) on Vertisols (8·9 to 11%) and Lixisols (12·5 to 15%) and higher plant diversity (both native and exotic) but negatively impacted invertebrate diversity, indicating trade‐offs between production and resources. We provide evidence that the effects of grazing management on SOC are mediated by ground cover and increased organic matter supply and/or reduced soil carbon redistribution (erosion), which indicates that the management of grazing intensity may provide a tool to avoid soil carbon loss in rangelands. Copyright © 2016 John Wiley & Sons, Ltd.     

利用微米木纤维定向重组技术形成超高强度纤维板的细胞裂解理论研究

采用人造板微观力学和木材细胞学理论，提出了一种利用定向重组微米木纤维技术形成超高强度人造板的细胞裂解理论和强度参数预测方法。应用提出的理论，可以根据纤维、木质素、细胞直径和排列的程度，建立理想状态下微米重组高强度定向纤维板木纤维细胞在定向重组微米技术形成超高强度人造板的细胞裂解理论，为人造板力学运用数学手段深入到细胞结构研究的深度提供了一种新的理论和方法。     

庞泉沟自然保护区优势种种群竞争关系及其动态预测

利用Hegyi单木竞争指数模型对庞泉沟自然保护区优势种群的种内、种间竞争关系进行了定量分析。结果表明:种内和种间竞争强度随着林木径级的增大而逐渐减小,种内竞争较之与其伴生树种间的竞争剧烈。华北落叶松种内、种间竞争强度大小顺序为:种内>云杉>红桦>白桦>关帝柳>花楸>山杨。竞争强度与对象木胸径之间存在显著的幂函数非线性回归关系,回归结果与林分实际相符,从而为庞泉沟自然保护区混交林理论研究和合理经营提供了科学依据。     

福建柏人工林不同间伐强度效应试验

通过对福建省永春大荣国有林场16年生福建柏人工林进行间伐强度效应试验,结果表明:强度间伐对胸径和单株材积生长效应最佳,弱度间伐后的蓄积量最大;不同间伐强度对树高生长、单位面积蓄积量及林分总收获量无显著影响。     

蒸腾速率、阻力与叶内外水势和光强关系的研究

本文采用ＬＩ一１６００稳态气孔计和压力室测定了杨柴的蒸腾速率、阻力、叶水势及其环境因子的日变化，分析结果表明：当０～２ｍ土层内土壤平均水势在－０．０４～－０．２０ＭＰａ时，光照强度是影响杨柴等树木蒸腾速率的主要因子，它主要是通过影响蒸腾阻力所致。光照强度（Ｌｉ）与蒸腾阻力（Ｄｒ）的关系符合方程Ｄｒ＝ａｅｂ／Ｌｉ。这样，根据光照强度对阻力的影响过程，把光照强度与蒸腾速率（Ｔｒ）的关系分成３个区段：①弱光照区，Ｔｒ＝Ｋ／Ｄｒ；②过渡区，Ｔｒ＝Ｋ·ψＬ－Ａ／Ｄｒ；③光饱和区，Ｔｒ＝ａ·ψＬ－Ａ＋ｂ，其中ａ、ｂ和Ｋ是系数。     

林火对土壤氮含量的扰动作用

通过对大兴安岭地区新林林业局 2 0a内不同年份间隔的 11块火烧迹地土壤进行调查取样和室内实验分析 ,发现火烧后不同年限、不同强度的火烧迹地 ,土壤全氮与有效氮含量变化情况如下 :低强度火烧后 9d ,土壤全氮和有效氮含量均比未烧前低 ,这与中、高强度火烧后的情况正好相反。火烧后 4a内 ,土壤氮的含量基本都比未烧林地有所下降 (中强度火烧迹地土壤有效氮含量除外 )。以后有逐年增加的趋势。火烧迹地降第一场雨后 ,低强度火烧迹地土壤全氮比降雨前减少 ,有效氮增加 ;中强度火烧迹地土壤全氮和有效氮均比降雨前增加 ;高强度火烧迹地土壤全氮和有效氮均比降雨前有所下降。连年火烧迹地土壤全氮减少 ,有效氮增加