辽西低山棕壤丘陵区小流域泥沙连通性与土壤侵蚀的空间分布特征

了解土壤侵蚀和泥沙连通性的空间分布特征对制定流域综合管理措施具有重要作用。本研究以辽西低山棕壤丘陵区二道岭小流域为对象,基于InVEST泥沙输移比模型,引入连通性指数和土壤流失模型作为泥沙连通性和土壤侵蚀强度空间分布特征的衡量指标,通过探究不同泥沙连通性等级和土壤侵蚀强度下坡度、坡向和土地利用特征,分析地形、土地利用类型、泥沙连通性和土壤侵蚀之间的关系。结果表明：二道岭小流域泥沙连通性平均值为-3.79,平均土壤侵蚀量为614 t·km²·a^-1;高连通性主要出现在坡耕地中,较低的连通性主要分布在林草地中;93.3%流域面积的土壤侵蚀强度在中度以下,极强烈以上侵蚀面积仅占流域面积的1.1%。泥沙连通性等级越高,<5°坡度的面积所占比例越高,其余坡度的面积占比相对稳定;耕地面积占比增加,林草地面积占比减少;阴坡面积占比降低,阳坡面积占比增加。随着土壤侵蚀强度的递增,<8°坡度的面积占比增加,其余坡度的面积占比相对稳定;林草地面积占比减少,其他土地利用面积占比增加;阳坡面积占比总体增加,阴坡面积占比总体降低。土地利用是影响该流域土壤侵...     

基于RUSLE模型的珊溪水库流域土壤侵蚀定量估算

土壤侵蚀是当今世界面临的主要问题之一,其中水库流域的土壤侵蚀将会直接影响水库库容和水环境安全。本文以温州珊溪水库流域为研究区域,基于美国农业部开发的修正通用土壤流失方程(RUSLE),并结合地理信息系统(GIS)和遥感技术,评估研究区流域土壤侵蚀现状,并借助GIS空间叠加分析功能,定量分析流域土地利用类型、坡度与土壤侵蚀强度之间的关系。结果表明:该流域年均土壤侵蚀模数为3085.76 t·km-2·a-1,属于中度侵蚀;在土壤侵蚀强度上,微度侵蚀区域面积占流域面积的49.42%,极强度侵蚀和剧烈侵蚀区域面积占流域面积的10.93%。在土壤侵蚀量上,微度侵蚀区域侵蚀量仅占流域侵蚀总量的0.8%,极强度侵蚀和剧烈侵蚀区域侵蚀量占流域侵蚀总量的62.15%;林地面积最大,占流域面积70.21%,且林地的土壤侵蚀量占流域侵蚀量的70.92%,是研究区土壤侵蚀量的主要来源;将研究区划分为7个坡度带,其中[15!,25!)和[25!,35!)坡度带侵蚀面积和侵蚀量达55.12%和61.35%;研究还发现,土壤侵蚀强度与滑坡的发生存在一定的相关性,土壤侵蚀强度大的地方发生滑坡的可能性越大。因此,针对该研究区侵蚀强度较大的小面积区域,加强水土保持力度能有效改善整个研究区域的土壤侵蚀现状。     

基于GIS和RUSLE的滇南山区土壤侵蚀时空演变——以云南省元阳县为例

滇南山区土壤侵蚀时空演变研究对于水土保持规划及世界文化遗产区的生态保护具有重要意义。本研究基于RUSLE模型和GIS/RS空间信息技术,分析元阳县2005—2015年间土壤侵蚀状况的时空变化趋势,以及其侵蚀成因和影响机理。结果表明: 研究期间,元阳县土壤侵蚀空间分异显著,流失区主要集中于县域东南部、西南部,藤条江沿岸区域侵蚀广泛,极强度和剧烈侵蚀呈点状分布。元阳县2005—2015年平均土壤侵蚀模数为11.06 t·hm^-2·a^-1,微度和轻度侵蚀所占面积比例近80%,而轻度和中度侵蚀则构成了近50%的全年土壤侵蚀总量,是县域水土流失治理的重点侵蚀级别。研究期间,随着森林覆盖率的提高,县域水土流失有减缓趋势。元阳县地形复杂多变,土壤侵蚀分布与海拔、坡度有很大的相关性,这种分布格局的形成受自然和人为因素的共同影响,海拔500 m以下、1500 m以上且坡度25°～45°的山地区是水土防护治理的重点区域。     

南方山区典型小流域桉树人工林种植对水土流失的影响

南方山区人工林的不合理开发导致严重的水土流失。典型人工林小流域土壤侵蚀时空变化研究对于人工林种植和山区生态环境可持续发展具有重要意义。本研究利用地理信息系统结合修正通用土壤流失方程，分析了粤西山区大顶山小流域土壤侵蚀的时空变化及关键驱动机制。结果表明：大顶山小流域侵蚀模数为1948.1 t·km^-2·a^-1,属于轻度侵蚀，但空间变异十分剧烈，变异系数为5.12,最大值可达191127 t·km^-2·a^-1。微度侵蚀(<500 t·km^-2·a^-1)面积占流域总面积的80.6%,中度及以上侵蚀(>2500 t·km^-2·a^-1)主要分布在植被覆盖度小于30%的桉树人工林幼林区，贡献了流域总侵蚀量的75.7%。2014—2019年间，大顶山小流域平均侵蚀年际变化不大，但土壤侵蚀空间分布变化较大，植被覆盖度、坡度和降雨是关键影响因素。桉树人工林种植导致自然植被破坏是引发造林区土壤侵蚀的首要原因。幼林区土壤侵...     

基于RUSLE-SMA的黄土丘陵沟壑区土壤侵蚀评价及景观格局分析——以庆城县蔡家庙流域为例

以甘肃省庆城县蔡家庙小流域为例,运用混合光谱线性分解(SMA)从Landsat遥感影像提取植被覆盖度,获取流域的植被覆盖因子,借助通用土壤侵蚀方程RUSLE计算了2003和2010年土壤侵蚀量,分析了土壤侵蚀与土地利用和地形因子之间的关系,并对流域土壤侵蚀景观格局变化进行了研究.结果表明:7年间,蔡家庙小流域土壤侵蚀量由3.61×106 t·a-1增加到4.48×106 t·a-1,增加了24％;平均侵蚀强度由8590.23 t·km-2增加到10652.01 t·km-2.不同土地利用类型的侵蚀状况差异较大,未利用地、草地、园地的侵蚀状况严重;坡度大于15°、高程低于1395 m以及坡向朝西的区域,土壤侵蚀较严重.研究区整体侵蚀景观高度破碎,斑块总数减少,破碎度变小,景观异质性减小,整体形状趋于规则;除微度侵蚀景观外,其余景观类型趋于简单化.     

万山汞矿区表层土壤汞迁移

水土流失是土壤退化的根本原因,是最严重的生态环境问题之一。目前对喀斯特山区土壤侵蚀研究已经进入成熟阶段,但对以典型喀斯特山区为背景、汞污染严重地区因土壤侵蚀发生的汞迁移的研究却很少。本文基于GIS平台,借助通用土壤流失方程(RU-SLE)模型评估研究区侵蚀强度,对万山汞矿区(167.4km2)因土壤侵蚀造成的汞迁移进行了研究。结果表明,万山土壤侵蚀模数为0～600884t·km-2·a-1,微度侵蚀和剧烈侵蚀面积占全区总面积的76.6%,其中剧烈侵蚀对土壤总侵蚀量的贡献率达到90.5%。全区因土壤侵蚀发生的土壤汞(THg)流失量高达505kg·a-1,迁移速率为3.02kg·km-2·a-1。土地利用方式和坡度是影响汞流失的重要因素。旱地和灌木林最易发生汞流失,流失量分别为175和319kg·a-1。本研究不仅为当地治理水土流失、制定水土保持方案奠定了可靠的科学依据,也为当地环境汞污染治理提供了有力的数据支持。     

2000—2018年西北砒砂岩区植被覆盖度与地形效应

利用2000—2018年的MODIS-EVI数据,基于像元二分模型计算植被覆盖度,利用数字高程模型(DEM)数据从高程、坡度和坡向等方面分析西北砒砂岩区植被覆盖度的地形效应。结果表明: 2000—2018年西北砒砂岩区植被覆盖度(FVC)相对较低,平均按2.43·a^-1的速率递增,FVC正距平年主要有12年,其中以2018年和2013年相对最高,负距平年主要有7年,其中以2001年和2000年相对最低。砒砂岩区FVC空间分布由东南向西北逐渐降低,但不同类型砒砂岩区FVC存在较大差异,其中裸露砒砂岩区FVC相对最低,覆沙砒砂岩区次之,覆土砒砂岩区相对最高;2000—2018年砒砂岩区FVC的平均变化率为0.0031,植被生长状况趋于改善。高程-坡向效应表明,裸露砒砂岩和覆沙砒砂岩区坡向分别在高程≤1000 m和>1500 m处对FVC的影响较大,覆土砒砂岩区坡向对FVC的影响较小,但在高程1200～1300 m处影响较大。坡度-坡向效应表明,砒砂岩在坡度≤15°时,FVC的坡度坡向效应不明显,坡度＞25°时裸露砒砂岩和覆沙砒砂岩的阴坡和半阴坡FVC大于阳坡和半阳坡;覆土砒砂岩坡度＞15°时,半阴坡和半阳坡的FVC大于阴坡和阳坡。     

黄丘区特色治理开发小流域土壤侵蚀变化对景观格局演变的响应

研究土壤侵蚀与景观格局变化的关系对小流域的治理开发具有重要的指导意义。本研究以实施退耕还林草、生态农业、生态旅游及科技示范的黄土高原安塞南沟特色治理小流域为研究对象,基于GIS平台和通用土壤流失方程,分析小流域1981—2018年景观格局和土壤侵蚀量的时空演化特征,并利用主成分回归法,从斑块类型水平和景观水平两个尺度分析土壤侵蚀模数与3类9个景观格局指标的关系。结果表明: 研究期间,在5种景观类型中,耕地和林地面积的时空变化主导了南沟小流域景观格局的演化,并且影响整个小流域的聚集分散程度;南沟小流域的土壤侵蚀量逐年减少,1981—2018年土壤侵蚀面积减少29.7%,侵蚀模数减少61.2%,且有73.4%的区域土壤侵蚀强度减轻;耕地和林地面积的变化决定了整个小流域土壤侵蚀模数的变化,其景观格局指数的变化方向与该景观类型土壤侵蚀的变化方向一致;退耕还林草工程是流域景观格局变化、土壤侵蚀减轻的主要原因,特色开发治理可以减弱局部地区土壤侵蚀强度。景观类型的合理化配置能有效地防治小流域土壤侵蚀,将其与特色治理开发相结合有助于实现小流域可持续高质量发展。     

地形因子对黄土高原山杏叶片功能性状的影响

坡向和坡度是重要的地形因子,调控水、热组合可以影响植物生长及叶片功能性状,研究叶片功能性状对不同地形因子的响应,有助于了解植物对环境的适应策略.以阳坡(半阳坡)和阴坡(半阴坡)2个坡向,以及15°~20°、21°~25°和26°~30°3个坡度为环境梯度,对比研究了其对黄土高原主要造林树种山杏叶片功能性状(包括叶面积、比叶面积、叶干物质含量和叶片含水量)的影响,结果表明:1)坡向与坡度分别对所有叶片功能性状的影响均显著,坡向和坡度仅对叶片含水量具有交互作用.2)坡向梯度上,阳坡叶片的叶面积与阴坡相当,但叶干物质含量(0.24 g·g^-1)和叶片含水量(59.6%)均小于后者(0.27 g·g^-1和67.0%);阳坡叶片的比叶面积显著高于阴坡,其值分别为183.72和163.05 cm2·g^-1.3)坡度梯度上,叶片的比叶面积和叶面积均随坡度增大呈先减后增趋势,二者分别在15°~20°和26°~30°上达最大值,分别为184.04 cm^2·g^-1和21.14 cm2.4)除15°~20°与26°~30°的土壤水分无差异外,其余坡度以及坡向之间的土壤水分均存在显著差异,且土壤水分是造成叶片功能性状差异的主要原因之一,其中0~10 cm土层含水量对叶片功能性状的影响最大.5)叶片比叶面积与叶片含水量、叶干物质含量呈负相关,与叶面积呈正相关;叶干物质含量与叶片含水量呈正相关,与叶面积呈负相关;土壤含水量仅与叶片含水量呈正相关,与其他叶片功能性状均不相关.     

生态安全条件下土地利用格局优化——以皇甫川流域为例

在人类活动导致的生态环境问题中,土地利用格局变化对区域生态安全起着决定性作用。选择我国乃至在世界上都罕见的多沙、粗沙、强烈水土流失的黄河皇甫川流域作为研究区域,针对土壤侵蚀和生态用水这两大影响流域生态安全的关键问题,开展土地利用变化模拟、土壤侵蚀3S监测、适宜植被盖度估算、土壤侵蚀情景模拟、土地利用格局优化等方面的综合研究。结果表明:(1)土地利用格局变化是导致土壤侵蚀变化的重要因素。从1987年到2015年,建筑用地、林地和灌丛面积增加,水域、沙地和裸砒砂岩面积减少,导致流域年平均土壤侵蚀模数由16160.72 t km-2a-1降至9710.72 t km-2a-1。(2)土地利用类型与土壤侵蚀模数密切相关并存在一定规律。6种不同土地利用类型多年平均土壤侵蚀模数的大小顺序为:裸砒砂岩沙地耕地草地林地灌丛,表明灌、林措施是流域植被恢复和土壤侵蚀减少的首选。(3)土地利用结构和空间格局优化有助于提升区域生态安全水平。在优化格局下,2007年和2015年土壤侵蚀模数比优化前分别减少5469.57 t km-2a-1和5432.77 t km-2a-1,优化后2015年土壤侵蚀模数仅为4277.95 t km-2a-1,低于流域自然侵蚀临界值或允许土壤侵蚀模数5300 t km-2a-1,优化土地利用格局成为加强流域生态环境建设的重要途径。     

DNA synthesis in vivo in Bacillus subtilis

DNA polymerase III is the enzyme responsible for deoxynucleotide addition to nascent DNA fragments in Bacillus subtilis protoplasts. Nascent single-stranded fragments separated from bulk DNA by hydroxyapatite chromatography cannot self-anneal. Partial inhibition of DNA polymerase III by 6-(hydroxyphenylazo)-uracil, a specific inhibitor, slows the rate of nascent fragment synthesis but has no effect on final size. Neither DNA polymerase I nor II can elongate nascent fragments in protoplasts when DNA polymerase III is completely inhibited.     

Alterations in central and peripheral adrenergic receptors in deoxycorticosterone/salt hypertensive rats

The treatment of uninephrectomized rats with deoxycorticosterone (DOCA) and salt for 6 weeks caused a significant systolic hypertension and cardiac and renal hypertrophy. There was a significant decrease in the density of cardiac α₁- and β-, and renal α₁-adrenoceptors in DOCA/salt hypertensive rats, as compared to uninephrectomized salt loaded control rats. In contrast, the cerebral cortex, corpus striatum, hippocampus and hypothalamus/thalamus of hypertensive rats showed a significant increase in adrenoceptor binding in these hypertensive rats. In contrast, muscarinic cholinergic receptors and [³H]yohimbine binding sites were not altered in most tissues of the hypertensive rats. The present study suggests an important role for central and peripheral α₁- and β-adrenoceptors in the pathogenesis of hypertension.     

Photosynthesis research in India: transition from yield physiology into molecular biology

Photosynthesis research in India can be traced back several thousand years, with the mention of the Sun energizing the plants, which form food for all living creatures on the earth (from the Mahabharata, the great epic, ca. 2600 B.C.) and the report of Sage Parasara (ca. 100 B.C.) on the ability of plants to make their own food, due to their pigments. With the pioneering studies by Sir Jagdish Chandra Bose, work on photosynthesis proceeded steadily during the first half of the 20th century. Some of the classic reports during this period are: malate metabolism in Hydrilla, spectrophotometric estimation of chlorophylls, importance of spectral quality for photosynthesis – an indication of two photosystems, photoinactivation of photosynthesis, and importance of flag leaf photosynthesis to grain yield. After the 1960s, there was a burst of research in the areas of physiology and biochemistry of carbon assimilation and photochemistry. A significant transition occurred, before the beginning of new millennium, into the area of molecular biology of chloroplasts, regulation of photosynthesis and stress tolerance. Future research work in India is geared to focus on the following aspects of photosynthesis: elucidation/analysis of genes, molecular biology/evolution of enzymes, development/use of transgenics and modeling. This revised version was published online in August 2006 with corrections to the Cover Date.     

清栓酶治疗儿童脑动脉炎和脑血栓形成31例

用清栓酶治疗儿童脑动脉炎和脑血栓形成３１例,其中急性期２２例、恢复期５例、后遗症期４例,有效率分别为９Ｏ．９％、８０．０％和８７．１％．总有效率为８７．１％。脑动脉炎可导致血小板聚集性增高、血管闭塞和血栓形成,清栓酶可降低血小板聚集性,具有扩张血管,溶解血栓之作用,故可以使临床表现得以好转。     

四种云杉的核型分析

首次报道了中国珍稀濒危保护植物长叶云杉 ( P. smithiana ( Wall.) Boiss.)和康定云杉 ( P. likian-gensis( Franch.) Pritz.var.montigena( Mast.) Cheng ex Chen)及我国特产的青海云杉 ( P.crassif oliaKom.)和林芝云杉 ( P.likiangensis( Franch.) Pritz.var.linzhiensis Cheng et L.K.Fu)的核型。它们的核型公式都是 K( 2 n) =2 4 =2 2 m+2 sm (林芝云杉有 1条 B染色体 ) ,染色体相对长度组成分别为 2 n=1 4 M2 +8M1 +2 S,2 L+1 2 M2 +6M1 +4S,2 L +1 0 M2 +1 0 M1 +2 S,和 2 L+1 2 M2 +6M1 +4S.均为 2 A (除青海云杉 1 A外 )核型类型。     

Diurnal variations in learning performance in chickens

Diurnal variations in the learning performance of young chicks were investigated using a visual discrimination task which requires birds to discrminate grains from a background of pebbles. Chicks accustomed to receiving fresh food daily in the morning were found to learn well during the day, in that they pecked almost exclusively at grains; but during the night they pecked indiscriminately at grains and pebbles. This occurred even though food was available ad libitum. Chicks accustomed to receiving fresh food daily in the evening learnt the task during the day, and also late at night. Thus the shape of the performance cycle depends in part on environmental factors. Other factors, such as activity, which may contribute to, or co-vary with, this variation in learning performance were investigated.     

Opioid receptor agonists in the rabbit colon: comparison of in vivo and in vitro studies

Myoelectrical activity was recorded in the proximal and distal colon of rabbits using chronically implanted electrodes. The motility in both the proximal and distal colon was inhibited by the intravenous (IV) administration of the following opioid agonists for mu receptors: morphine and fentanyl, kappa receptors: ethylketazocine (EKC) and U 50 488 H, and delta receptors: D-Ala2 D-Leu5-enkephalin (DADLE) and D-Ser2 Leu-enkephalin-Thr6 (DSLET). In contrast, the myoelectric activity in the distal colon was increased during the infusion of an endogenous kappa opioid agonist, dynorphin (DYN). All of these effects were prevented by naloxone pretreatment. During in vitro studies using extraluminal force transducers, fentanyl, U 50 488 H and DSLET inhibited spontaneous contractions of the proximal colon, but U 50 488 H and DSLET caused a substantial increase in the motility of the distal colon. The observed motor responses in the proximal and distal colon following opioid agonist administration indicate that the control of these two intestinal segments may be different. It is suggested that the stimulatory effect of dynorphin on the distal colon is peripherally-mediated while inhibition of the whole colon by opioid agonists regardless of subtypes seems to be centrally-mediated.     

Chlorophyll isolation,structure and function: major landmarks of the early history of research in the Russian Empire and the Soviet Union

This paper covers major events of the early history of chlorophyll research in the Russian Empire and the Soviet Union from 1771 until 1952, when the modern period of studies on photosynthesis began in full swing. Short biographical sketches of key scientists, reviews of their major research contributions and some selected photographs are included. This revised version was published online in August 2006 with corrections to the Cover Date.     

Endocytosis in Chinese hamster fibroblasts : Inhibition by glucose

Endocytosis in Chinese hamster ovary fibroblasts was investigated by measuring the rate of uptake of ³H-sucrose, which is known to enter cells only by endocytosis. Serum, polyvinylpyrrolidone (PVP), adenosine triphosphate, insulin, and cyclic 3′,5′-adenosine monophosphate, all of which are known to increase the rate of endocytosis by other cell systems, had no effect on Chinese hamster fibroblasts. However, medium in which these cells had been maintained for several days, referred to as conditioned medium, had a profound effect on endocytosis. These cells endocytosed 3 to 5 times as rapidly in conditioned medium as in fresh medium. A logarithmic inhibition of this effect was observed with increasing -glucose concentrations, however, glucose-free medium did not produce as great an effect as conditioned medium. This suggests that these cells may endocytose in response to their nutritional requirements.