An integrated watershed modelling framework to explore the covariation between sediment connectivity and soil erosion

Quantitative identification of the covariation between sediment connectivity and soil erosion can contribute to provide the key information for watershed sediment management. However, this covariation and its spatiotemporal response mechanisms are still unclear, especially whether this covariation can be used as a basis for identifying critical source areas of sediment in large-scale ecological restored watersheds. In this study, an integrated methodology framework by the revised universal soil loss equation (RUSLE), index of connectivity (IC) and sediment delivery ratio (SDR) was proposed to visually assess the spatiotemporal characteristics of erosion and sediment yield processes in the Yanhe Watershed with large-scale ecological restoration from 1985 to 2020 and to identify the covariation between sediment connectivity and erosion in subbasins. The soil erosion estimated by RUSLE has decreased by over 80% since 1985 owing to increased vegetation cover and the effective implementation of soil conservation measures, but the upper reaches still have high erosion intensity due to differences in specific controlling factors such as topographic conditions and land cover, requiring focused soil conservation practice. The IC results showed that as the vegetation restoration and soil conservation measures in the Yanhe Watershed varied from year to year, their spatial and temporal patterns had a strong influence on the distribution of sediment connectivity, and some local areas in the middle reaches showed local minima of IC in 1995, 1998 and 2010 mainly due to the implementation of long-term ecological restoration project. The developed IC-Erosion maps indicated that areas with high connectivity but low erosion accounted for over 60% of the total watershed area from 1985 to 1999, demonstrating a reverse correlation between sediment connectivity and erosion. Meanwhile, over 40% of the erosion occurred in a few areas (approximately 20%) with high connectivity and high erosion from 2000 to 2004, which can be characterized as the critical areas of erosion. The methods and results of this study provide ideas for separately defining both erosion and connectivity and quantifying bi-variable erosion–connectivity classification, which can be easily viewed on a scatterplot.     

棉铃虫精子的超微结构及对其辐照后变化的初步观察

利用透射电子显微镜技术,研究了棉铃虫（ＨｅｌｉｃｏｖｒｐａａｒｍｉｇｅｒａＨｕｅｂｎｅｒ）真核精子和无核精子的超微结构,比较了在经γ射线照射的棉铃虫精子与未照射虫精子结构的差异,结果表明,棉铃虫真核精子和无核精子的顶体结构有较大差异。真核精子有核,呈半月形,鞭毛线粒体衍生物与微管系统紧密结合,从头到尾在质膜上都覆盖许多特定结构的外长物;无核精子没有核,顶体和鞭毛通微管连接,鞭毛缄粒体衍生物与微管系     

Soil nutrient changes due to land use changes in Northern China: a case study in Zunhua County, Hebei Province

Abstract. Since the 1980s, land use in rural areas of China has changed greatly as the result of political initiatives. These changes have caused soil nutrient changes which are examined in this paper for Zunhua County, northern China from 1980 to 1999. The areas of farmland, grassland, and paddy decreased greatly and were replaced by increases in forest and residential land. The soils under forest in 1999 transformed from farmland in 1980 increased in organic matter by 21%, total nitrogen by 18%, available nitrogen by 65%, available phosphorus by 17% and available potassium by 17%. Similarly, in the area which was converted from farmland in 1980 to grassland in 1999, soil organic matter, total nitrogen, available nitrogen, available phosphorus, and available potassium increased by 38%, 37%, 71%, 2% and 28%, respectively. Changes from farmland to forest and grassland not only changed land cover but also improved soil fertility and probably reduced soil nutrient losses.     

玉米根系形态对光照、氮水平反应的基因型差异

用溶液培养的方法 ,研究了光照、以及氮水平对不同氮效率玉米自交系根系形态养分吸收的影响 ,研究结果表明 ,提高光照水平有助于光合产物向根系分配 ,表现为总根长、根体积、根系重量等显著增加。在不同光照水平低氮胁迫时 ,氮低效品种白瓷与其它三个品种相比 ,根系的形态指标均有不同程度的降低。在高光强 ,0 .4 mmol/ L氮水平胁迫时 ,与氮高效品种 4 78相比 ,根系体积减少 2 7.54% ,根干重减少 2 1.2 4 % ,并降低了根系的吸收效率 ,同时也表明 ,光照与氮水平对光合产物的分配具有耦合效应     

浅谈水土保持产业化经营的理论依据

水土保持产业化需要有坚实的理论来作指导。市场经济要求一切生产经营活动都要遵循市场经济理论 ,实行适应市场要求的产业化经营。水土保持产业化经营要用生态经济学理论作指导 ,使产业化建设和运行达到经济、生态和社会效益的持久统一。扩大经营主体的规模、实行产业群体内部各经济主体的联合 ,是实现水土保持产业化经营的两条重要途径     

Responses of soil dissolved organic matter to long-term plantations of three coniferous tree species

Tree species have significant effects on the availability and dynamics of soil organic matter. In the present study, the pool sizes of soil dissolved organic matter (DOM), potential mineralizable N (PMN) and bio-available carbon (C) (measured as cumulative CO₂ evolution over 63 days) were compared in soils under three coniferous species — 73 year old slash (Pinus elliottii), hoop (Araucaria cunninghamii) and kauri (Agathis robusta) pines. Results have shown that dissolved organic N (DON) in hot water extracts was 1.5–1.7 times lower in soils under slash pine than under hoop and kauri pines, while soil dissolved organic C (DOC) in hot water extracts tended to be higher under slash pine than hoop and kauri pines but this was not statistically significant. This has led to the higher DOC:DON ratio in soils under slash pine (32) than under hoop and kauri pines (17). Soil DOC and DON in 2 M KCl extracts were not significantly different among the three tree species. The DOC:DON ratio (hot water extracts) was positively and significantly correlated with soil C:N (R² = 0.886, P < 0.01) and surface litter C:N ratios (R² = 0.768, P < 0.01), indicating that DOM was mainly derived from litter materials and soil organic matter through dissolution and decomposition. Soil pH was lower under slash pine (4.5) than under hoop (6.0) and kauri (6.2) pines, and negatively correlated with soil total C, C:N ratio, DOC and DOC:DON ratio (hot water extracts), indicating the soil acidity under slash pine favored the accumulation of soil C. Moreover, the amounts of dissolved inorganic N, PMN and bio-available C were also significantly lower in soils under slash pine than under hoop and kauri pines. It is concluded that changes in the quantity and quality of surface litters and soil pH induced by different tree species largely determined the size and quality of soil DOM, and plantations of hoop and kauri pine trees may be better in maintaining long-term soil N fertility than slash pine plantations.     

仿自然鱼道水力及过鱼性能物理模型试验

仿自然鱼道是具有一定自然特征的过鱼设施,适用于中低水头工程,是目前鱼道形式研究热点之一。为了获得一种具有综合生态功能的鱼道,该文提出了一种利用芦苇模块构建的植物型鱼道,并通过物理模型试验对其水力特性和过鱼性能进行了研究。结果表明:选取芦苇为基本单元构建植物型鱼道是合适的。植物模块交错布置的植物鱼道内可形成蜿蜒的水流,流态丰富,过鱼通道内流速均小于1.1 m/s,满足过鱼要求。过鱼试验表明,过鱼对象可以在该鱼道内顺利上溯,植物模块下游侧可形成低流速的鱼类休息区,验证了鱼道体型的合理性。该文提出的植物型鱼道丰富了鱼道的形式,具有一定创新性,对今后类似鱼道的设计和建设具有一定的指导意义。     

有机固废堆肥过程的水分平衡模型研究进展

畜禽粪便等有机固体废物堆肥过程中水分含量影响堆肥反应过程,并最终影响堆肥产品质量和后续的产品加工,建立堆肥过程中的水分平衡模型有利于深入理解堆肥过程并优化堆肥过程的工艺参数。该文基于国内外研究进展,对堆肥模型建立基础、水分模型及有机质降解模型研究现状进行综述,概括了堆肥过程中水分迁移转化的主要途径,明确了堆肥过程有机质降解产生的水分是水分平衡模型的重要组成部分。同时,提出可以根据物料平衡思想建立堆肥过程中质量平衡模型,由此分析了堆肥过程中水分平衡模型和有机质降解模型。现在的水分质量平衡模型考虑了堆肥过程中通风对流、水汽蒸发以及微生物作用有机质降解产水对水分的影响,将水分模型分为对流模型、反应—对流模型、反应—蒸发模型和反应—对流—扩散模型4种模型。堆肥产水过程中的有机质降解模型主要有一阶动力学模型、Monod模型和经验模型。     

不同含水率对谷子籽粒压缩力学性质与摩擦特性的影响

为了探明不同含水率谷子籽粒的物理机械性质,减少谷子籽粒在播种、碾米加工及储运等过程中受到压缩载荷及摩擦而产生的机械损伤,该文针对不同含水率的谷子籽粒进行压缩力学性质与摩擦特性试验。研究了谷子籽粒的挤压破碎过程,获得不同含水率谷子籽粒的力-位移（变形）曲线,破坏力、变形量及破坏能。随着含水率升高,破坏力减小,变形量和破坏能呈现先降低后升高的变化规律。同时采用赫兹接触理论,得到谷子籽粒单向表观弹性模量和许用挤压应力,结果表明二者都随含水率升高线性降低。分别测定了谷子籽粒与钢板和铝板间的滑动摩擦系数,随含水率升高,谷子与该2种材料的摩擦系数均增大,且与铝板的摩擦系数要高于钢板。根据试验结果,分别拟合得到了压缩和摩擦力学性能指标与谷子含水率的关系方程,为谷子播种、仓储、加工等装备设计及参数优化提供了基础依据。     

Genetic Relationships of some PCNA Persimmons (Diospyros kaki Thunb.) from China and Japan revealed by SRAP analysis

Sequence-related amplified polymorphism (SRAP) marker was employed to analyze genetic relationships of 10 Chinese, 11 Japanese varieties of persimmon and its 6 relatives. Twenty out of 72 primer combinations could amplify clearly and consistently. Just only one primer set could discriminate all the genotypes used in this study. The genetic relationships were analyzed using unweighted pair-group method of arithmetic average cluster analysis (UPGMA) and principal coordinated analysis (PCOA). The results showed: Chinese varieties were grouped into two clusters, while the Japanese varieties were grouped into one cluster with two subgroups. The persimmon relatives were clustered together. Probably, Chinese and Japanese Pollination-constant and Non-astringent (PCNA) persimmons had different genetic background. ‘Eshi No.1’ from Hubei province was close to Male type 6. ‘Xiangxitianshi’ from Xiangxi municipality, Hunan province, had a high similarity coefficient with ‘Maekawa-Jirou’ and was clustered in the Japanese varieties group, indicating that ‘Xiangxitianshi’ maybe close to the Japanese variety in terms of genetic background. The Chinese Pollination-constant and Astringent (PCA) and PCNA persimmons were not distinctly distinguished implying that the non-astringent trait of Chinese PCNA type might result from the PCA type.