农牧交错带土地沙化的本质及其形成研究

通过对陕北农牧交错带不同类型沙化土地土体构型、土壤质地、元素组成和理化性质的分析,研究了土地沙化的本质。结果表明：受风沙作用影响,土壤中细粒物质逐渐减少,颗粒组成变粗;表层消失,最终被流沙所取代,原土壤剖面被覆盖在沙层之下;土壤有机质及养分含量减少,保水保肥性能降低,生产力不断下降;现代土壤形成过程以侵蚀和风沙沉积为主,物质淋溶和化学风化微弱。研究区土地沙化可划分为：风沙侵蚀为主、风沙蚀积平衡、风沙沉积为主和土壤形成发育4个阶段;沙化土地的类型有：肥力衰退质地粗化、表层剥蚀、片沙覆盖、流动沙丘与固定沙丘等5种。     

Organic phosphorus in soil water under a European beech (Fagus sylvatica L.) stand in northeastern Bavaria, Germany: seasonal variability and changes with soil depth

Organically bound phosphorus (P) is a mobile form of phosphorus in many soils and thus its dynamics relevant for the leaching and cycling of this element. Despite its importance, little is known about the chemical composition of dissolved organic P. We studied the concentrations, fluxes, and chemical composition of organic P in forest floor leachates and soil solutions in a Rendzic Leptosol under a 90-year-old European beech (Fagus sylvatica L.) forest over a 27-month period (1997–1999). The chemical composition of organic P was analysed using XAD-8 fractionation and ³¹P-nuclear magnetic resonance (NMR) spectroscopy. Organic P was the dominant P form in forest floor leachates as well as in porewaters of the mineral soil. The largest concentrations of organic P were observed during summer and peaked (330–400 g dissolved organic P l^–1) after rain storms following short dry periods, concurrently with the concentrations of organic carbon (OC). Because of high rainfall, fluxes of organic P (and C) were greatest in autumn although concentrations of organic C and P were lower than in summer. In forest floor leachates, the hydrophilic fraction of dissolved organic matter contained 83 ± 13% of the bulk organic P. In soil solutions from 90 cm depth, organic P was almost exclusively in the hydrophilic fraction. Because of the low retention of the hydrophilic fraction of dissolved organic matter in the mineral soils, concentrations of organic P in soil water remained almost constant with depth. Consequently, organic P contributed > 95% of the total P leached into deeper subsoils. The overall retention of organic P in the weakly developed mineral soils was little and so the average annual fluxes of organic P in subsoils at 90 cm depth (38 mg m^–2) comprised 67% of those from the forest floors (57 mg m^–2) during the study period. Hence, organic P proved to be mobile in the studied soil. ³¹P-NMR spectroscopy confirmed the dominance of organic P species in soil water. Signals due to inorganic P occurred only in spectra of samples collected in winter and spring months. Spectra of samples from summer and autumn revealed traces of condensed phosphates. Due to low P contents, identification of organic P species in samples from winter and spring was not always possible. In summer and autumn, monoester and diester phosphates were the dominant organic species and varied little in their relative distributions. The distribution of organic species changed little from forest floor leachates to the subsoil solutions indicating that the composition of P-containing compounds was not influenced by sorptive interactions or biological transformation.     

稳定同位素分析在鸟类食性及营养级结构中的应用

稳定同位素分析(stable isotope analysis,SIA)自20世纪70年代末引入鸟类生态学领域以来,在研究鸟类食性和营养级结构方面展现了强大的发展潜力和广泛的应用前景。总结了该技术在鸟类食源组成和营养级结构方面研究的前期准备、实验流程、数据分析和研究进展等,重点阐述了其在鸟类保护与管理方面的应用。鉴于稳定同位素在生物体内存在分馏现象,从鸟类不同组织和部位对营养级富集因子、转化周期、同位素印记的差异,提出了完善该方法的建议和应用前景。     

黑曲霉发酵过程中菌体形态的分析方法建立及应用

丝状真菌(Filamentous fungi)的发酵生产通常具有较高的工业应用价值,但其菌体形态是一个区别于其他非丝状菌的一个重要发酵指标。针对目前形态分析的瓶颈,本研究使用琼脂糖凝胶对黑曲霉菌形进行固定,利用平板实现菌球样本的大量制备,并结合图形处理软件自建自动化处理程序,实现了大量准确可靠的菌体形态参数的获得,大大增加了形态数据处理通量及准确度。应用该方法于黑曲霉发酵生产糖化酶过程中不同供氧水平及剪切水平下菌体形态的研究,通过大量形态数据定量阐明了黑曲霉在不同剪切水平下的分区域形态分布特性,为进一步工业过程的形态优化提供了重要的研究方法。     

长白落叶松（Larix olgensis）工业人工林的模拟间伐

应用马尔柯夫过程理论,在获得林分直径转移概率的基础上,采用间伐最小径阶林木,最大径阶林木,中间径阶林木三种间伐方式,在保留不同密度情况下对长白落叶松工业人工林进行模拟间伐,提出了适宜的保留密度和相应的抚育间伐对象。结果表明：马尔柯夫过程确能反映长白落叶松工业人工林的直径转移过程,利用马尔可夫过程理论对长白落叶松工业人工林进行模拟间伐实现了依据培育时间来确定间伐方法和措施,提高了长白落叶松工业人工林经营管理的精准性;长白落叶松工业人工林成林后的间伐无论从培育森林方面,还是从取得木材、加大林分收益方面考虑,都应该以间伐小径阶的林木为主,注重培育I、II级木,间伐III, IV级木;20～25 a长白落叶松工业人工林间伐后的保留经营密度以0.7为宜。     

Sulfate Reduction Potential in Sediments in the Norilsk Mining Area,Northern Siberia

Abstract

The purpose of this study was to characterize the distribution and activity of sulfate-reducing bacteria in tailings and sediments impacted by effluents from mining and smelting operations in the Norilsk area in northern Siberia. The Norilsk mining complex involves three smelter operations, a hydrometallurgical plant, and extensive tailings areas located in the permafrost zone. Sulfate reduction rates measured with a ³⁵SO₄ ^2? tracer technique under various in-situ conditions ranged from 0.05 to 30 nmol S cm^?3 day^?1. Acetate and glucose addition greatly stimulated sulfate reduction, whereas lactate had less effect. The most pronounced stimulation of sulfate reduction (6.5-fold) was observed with phosphate amendment. Most-probable-number (MPN) counts of sulfate-reducing bacteria in media with glucose, ethanol, lactate, and acetate as electron donors were generally highest at around 10⁷ cells ml^?1. The actual MPN counts varied with the sample, electron donor, and incubation conditions (pH 7.2 vs. pH 3.5; 28°C vs. 4°C). Enrichment cultures of sulfate-reducing bacteria were established from a sample that showed the highest rate of sulfate reduction. After multiple serial transfers, the dominant sulfate-reducers were identified by fluorescence in situ hybridization using genus and group-specific 16S rRNA-targeted oligonucleotide probes. Desulfobulbus spp. prevailed in ethanol and lactate enrichments and the Desulfosarcina-Desulfococcus group dominated in acetate and benzoate enrichments. Psychrophilic Desulfotalea-Desulfofustis and moderately psychrophilic Desulforhopalus spp. were identified in enrichments incubated at 4°C, but they were also found in mesophilic enrichments.     

马占相思人工林和果园地表径流规律的对比研究

基于连续 5年的观测 ,对比研究了马占相思人工林和果园两种地表类型上地表径流的各自特点 ;讨论了季节性地表径流的差异与系统水分结构问题 ;探讨了根据实际资料求取发生地表产流的降雨量临界值的方法 ,此方法以综合考虑未发生产流的最大降雨量和已发生产流的最小降雨量为基础 ;并得到了如下的一些结果 :1)本区域不同强度的大气降水频度分布比较均匀 ,但降水量主要由少数几场特大降水带来 ,并且降水量的季节分配极不平均 ,湿季 (4～ 9月 )降水量占全年的 85 .5 %。 2 )地表径流的季节差异更大 ,果园在湿季的地表径流量占全年的93.8% ,马占相思林占 95 .1% ,作者认为在降水量存在较大干湿季差别的地区 ,对于越难于发生地表径流的下垫面 ,这个值会越高。3)马占相思地表径流系数在逐年减小 ,果园的变化较大。4)一次性降雨量对地表径流量的影响在这两种地表类型上都很明显 (r>0 .85 ) ;一次性降雨强度对地表径流的影响只有在中等降雨量 (6～ 16 mm)下才表现明显 (r>0 .87) ,对于较小和较大降水量 ,径流量与降雨强度关系都不大 ;径流系数受一次性降雨强度的影响很明显 (林地 r>0 .92 ,果园 r>0 .77)。 5 )马占相思和果园一次性“最大可能”地表径流产流的雨量临界值 ,分别为5 .1m m和 2 .8mm。     

Statistical method for prediction of gait kinematics with Gaussian process regression

We propose a novel methodology for predicting human gait pattern kinematics based on a statistical and stochastic approach using a method called Gaussian process regression (GPR). We selected 14 body parameters that significantly affect the gait pattern and 14 joint motions that represent gait kinematics. The body parameter and gait kinematics data were recorded from 113 subjects by anthropometric measurements and a motion capture system. We generated a regression model with GPR for gait pattern prediction and built a stochastic function mapping from body parameters to gait kinematics based on the database and GPR, and validated the model with a cross validation method. The function can not only produce trajectories for the joint motions associated with gait kinematics, but can also estimate the associated uncertainties. Our approach results in a novel, low-cost and subject-specific method for predicting gait kinematics with only the subject's body parameters as the necessary input, and also enables a comprehensive understanding of the correlation and uncertainty between body parameters and gait kinematics.