97 resultados para farmland ponds

em Chinese Academy of Sciences Institutional Repositories Grid Portal


Relevância:

20.00% 20.00%

Publicador:

Resumo:

The temporal and vertical fluctuations of size fractionated alkaline phosphatase activity (APA) and kinetics parameters as well as orthophosphate (o-P) and chlorophyll concentrations were investigated after bloom disappearance in two shallow ponds A and B from 27 October 2001 to 15 April 2002. Pond A (Microcystis) bloomed seriously but pond B did not. The data of o-P and chlorophyll suggested that phosphorus was the principal limiting nutrimental element and its vertical flux should be regarded as an important driving factor for algal growth. In pond A, the accumulation of algae-derived detritus after bloom disappearance in overlying water stimulated excretion of algal fraction APA, mainly produced by attached bacteria responsible for detritus decomposition, whereas bacterial fraction APA preferred to function in surface water. Interestingly, completely contrary phenomena were observed in pond B. In season, even though no obvious difference for size-fractionated APA in both ponds, the total APA in pond A peaked earlier showing higher activity and efficiency (low K-m and high V-max values) as a result of algal-derived detritus input. In summary, it is suggested that the excretion of alkaline phosphatase with strongly catalyzing efficiency and high activity should be taken as important contributor to algal-derived detritus decomposition, further fueling nutrient recycle and accelerating algal development next year. Furthermore, some inhibitors and surfactants were testified to be good tools to identify the origin of dissolved alkaline phosphatase.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

National Natural Science Foundation of China [40201005]; Knowledge Innovation Project of Chinese Academy of Sciences [KZCX3-SW-321, KZCX2-314, KZCX1-SW-321-4]

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The interactions among industrial development, land use/cover change (LUCC), and environmental effects in Changshu in the eastern coastal China were analyzed using high-resolution Landsat TM data in 1990, 1995, 2000, and 2006, socio-economic data and water environmental quality monitoring data from research institutes and governmental departments. Three phases of industrial development in Changshu were examined (i.e., the three periods of 1990 to 1995, 1995 to 2000, and 2000 to 2006). Besides industrial development and rapid urbanization, land use/cover in Changshu had changed drastically from 1990 to 2006. This change was characterized by major replacements of farmland by urban and rural settlements, artificial ponds, forested and constructed land. Industrialization, urbanization, agricultural structure adjustment, and rural housing construction were the major socio-economic driving forces of LUCC in Changshu. In addition, the annual value of ecosystem services in Changshu decreased slightly during 1990-2000, but increased significantly during 2000-2006. Nevertheless, the local environmental quality in Changshu, especially in rural areas, has not yet been improved significantly. Thus, this paper suggests an increased attention to fully realize the role of land supply in adjustment of environment-friendly industrial structure and urban-rural spatial restructuring, and translating the land management and environmental protection policies into an optimized industrial distribution and land-use pattern.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Two new urostylid ciliates, Metaurostylopsis songi n. sp. and Metaurostylopsis salina n. sp. and Metaurostylopsis marina (Kahl 1932) are investigated using live observation and protargol impregnation. These species were isolated in Korea from intertidal sediments, saline ponds, and coastal waters. Metaurostylopsis songi is in vivo about 120 pm x 25 mu m, has a slenderly ellipsoidal body, colorless cortical granules in rows on ventral and dorsal body sides, about 54 macronuclear nodules, 28-47 adoral membranelles, five frontal, two or three frontoterminal and six or seven transverse cirri, and 9-12 midventral cirral pairs followed posteriorly by 1-3 single cirri. In vivo M. salina is about 60 pin x 25 mu m, has a pyriform body, colorless cortical granules irregularly arranged, about 45 macronuclear nodules, 18-23 adoral membranelles, three frontal, three to five frontoterminal and two to five transverse cirri, and four or five midventral cirral pairs followed posteriorly by five to seven single cirri. Both species have three marginal cirral rows on each body side and 3 long dorsal kineties. The Korean specimens of M. marina match the Chinese population in all main features. Metaurostylopsis songi differs from M. marina by the more slender body, the number of frontal cirri (invariably five vs. four), and the arrangement of cortical granules (in rows on dorsal and ventral cortex vs. only along dorsal kinetics and anterior body margin). Metaurostylopsis salina differs from its congeners by the distinctly smaller size, the pyriform body shape, the scattered cortical granules (vs. in rows), and number of frontal cirri. It differs from M. marina also by the number of midventral cirral pairs (four or five vs. seven to 11).

Relevância:

10.00% 10.00%

Publicador:

Resumo:

生物多样性的维持、监测、保育与恢复是生物多样性科学的核心研究内容( DIVERSITAS)。作为世界上典型的植被类型,常绿阔叶林以其丰富的生物多样性而倍受世人关注。我国的常绿阔叶林是全球分布面积最大,发育最为典型的常绿阔叶林,其分布区多为农业区,与长江流域的生态安全密切相关:伴随着人们的生产活动,生境的岛屿化与破碎化问题越来越突出,常绿阔叶林的合理保育问题和生态恢复问题已成为大家关注的焦点。本研究“常绿阔叶林恢复生态学研究初报”正是在这种背景下开展的,主要实验研究工作与结果如下: 1.系统综述了生态系统退化程度的诊断指标体系、途径与方法,绘制了生态系 统退化程度的概念模型,为恢复生态学研究和生态恢复实践提供参考。 2.固定样地的建立:为深入开展生物多样性与恢复生态学研究,本研究建立了一系列固定样地(常绿阔叶林固定样地、常绿落叶阔叶林固定样地、退化生态系统恢复与重建实验样地等),这些样地的建立为进一步深化研究奠定了坚实基础。 3.种群大小级结构特征:对栲树Castanopsis fargesii和油茶Camellia oleifera种 群大小级结构特征研究表明,栲树种群大小级结构(高度级和胸围级)呈弱双峰型分布,油茶种群大小级结构呈倒“J”型分布。对树木大小级划分标 准的比较研究表明划分标准的选择应基于研究目的和物种性质。作者认为应深入研究干扰特别是生境的岛屿化与破碎化对常绿阔叶林稳定性的影响。 4.种子扩散与种群维持:种子扩散是种群维持的一个关键阶段,而建群种的维持机制可在一定程度上反映群落的维持机理。对都江堰常绿阔叶林固定样地的主要建群种栲树种子扩散的研究表明,种子雨密度、种子在地上保留密度以及种子丢失状况是个动态过程,种子雨在2001年持续了约3个月的时间,种子年产量达到每平方米73.37个正常种子;研究发现栲树种子下落后能在地上保留一段相当长的时间(捕食者饱和现象“predator satiation"),这为种子萌发提供了更多的时间和机会,从而使得栲树种群能通过大年(the mast year)的高种子产量与捕食者饱和现象顺利完成自然更新;捕食者饱和现象有助于解释栲树的优势种群地位和稳定机制,以及对整个生态系统稳定性的贡献;作者提出了一个描述栲树种子扩散命运的概念模型,该模型表明种子雨与种子丢失的不同阶段是在不同程度上以不同方式贡献于栲树的自然更新。总之,栲树自然更新伴随着一个复杂的种子扩散过程。 5.光因子调控与生态恢复:光是影响植物生长的一个重要生态因子。研究了三种不同遮荫处理(100% PAR、40% PAR和22% PAR)对青冈Cyclobalanopsis glauca幼苗在亚热带弃耕地上的影响作用,两年的研究结果显示:青冈幼苗 可以在弃耕地上正常生长:两种遮荫处理(40% PAR和22% PAR)对青冈的萌芽和幼苗生长有正效应,并且22% PAR遮荫处理有明显的促进作用;本研究也说明了植物在不同的遮荫处理作用下有不同的生长策略。关于在生态恢复中如何利用光因素对植物生长的影响以及遮荫的复合效应问题值得深入研究。 6.种间关系与生态恢复:杂草竞争是植被恢复中的一个重要问题。对两种常绿阔叶树种(青冈和石栎Lithocarpus glaber)在不同坡位(坡上位、中位、下位)和有无地上杂草竞争的情况下的对比研究表明:不同物种在不同坡位,其幼苗生长对杂草竞争的反应是不同的;在坡上位和下位,除草处理能显著地提高青冈幼苗的田间保存率、苗高、基径和冠幅的生长,而在中位,除草处理的效果不显著;但是对于石栎来说,除草处理仅能显著地提高坡中位幼苗基径的生长量;研究说明了(地上)杂草竞争对植物生长的影响(程度)因物种而异,因而除草处理并不是对所有常绿阔叶树种的幼苗生长有促进作用,杂草竞争也不是一切常绿阔叶树种在弃耕地上建立与定居的障碍因子。作者建议在生态恢复实践中应根据具体情况选择除草与否,关于杂草竞争/除草在植被恢复中的作用值得进一步研究。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

自然界木本植物在某些情况下可能面对淹水带来的胁迫伤害,木本植物对淹水的生理生态响应及适应机制的研究,不仅可以从机理上解释河岸带和消落区树种分布的规律,对于大型水库消落区的治理也能起到理论依据的作用,因此,木本植物对淹水的生理生态响应及适应机制历来是植物生理生态研究领域的热点问题之一。 三峡水库蓄水造成库区部分陆地岛屿化,这将对岛屿优势植物带来深远影响。短柄枹栎(Quercus glandulifera)、栓皮栎(Quercus variabilis)、马尾松(Pinus massoniana)是这些岛屿上的三种优势树种。在岛屿形成初期,应用生理生态学手段,在7月和9月分别对其水势和叶绿素荧光进行了野外测定,从而为岛屿化对植物生理生态影响的研究和监测提供重要的本底数据。研究结果表明马尾松较其它两种植物更耐旱。水势和Fv/Fm在清晨高中午低,经过一个晚上可以基本恢复,因此就目前状况看岛上的三种优势植物均生长健康。但是库区蓄水后,在淹水胁迫下植物的生理生态过程将如何变化,还需要后期的连续观测。 枫杨(Pterocarya stenoptera)、池杉(Taxodium ascendens)和栓皮栎(Quercus variabilis)是三峡库区河岸带和库塘消落区常见的植物,对于河岸带和库塘消落区的水土保持和水源涵养具有十分重要的作用。通过设计模拟淹水实验,研究了这三种植物对淹水的生理生态响应及适应机制。淹水对枫杨和栓皮栎生理生态过程的早期影响是快速降低了二者的最大净光合速率、气孔导度、最大光化学量子效率(Fv/Fm)。但经过最初的下降后,枫杨的最大净光合速率、气孔导度和最大光化学量子效率逐渐恢复,而栓皮栎的则持续下降。在试验过程中,枫杨和池杉均产生了有利于吸收氧气的不定根和肥大的皮孔,而栓皮栎没有产生不定根。随淹水时间的增加枫杨的叶绿素含量与对照没有显著差异;而栓皮栎的叶绿素含量在第33天后大幅降低,Chla/Chlb的比值下降。淹水后第10天和70天测定的清晨水势,受淹栓皮栎比对照高,而受淹枫杨比对照低。淹水导致池杉和栓皮栎的根/茎/叶膜质过氧化状态均呈现动态变化。淹水处理的栓皮栎根的MDA含量低于对照而池杉的高于对照,比如:淹水24天后,栓皮栎根的丙二醛含量是对照的73%;而池杉是对照的111.5%。淹水处理第10天和第24天两个种的叶和茎MDA含量均高于对照但第50天则略低于对照。淹水导致池杉和栓皮栎两个种的根/茎/叶可溶性糖含量呈现动态变化。持续淹水导致栓皮栎叶片可溶性糖含量相比于对照先略下降后上升,茎可溶性糖含量显著上升而根可溶性含量先下降后上升。而池杉根/茎/叶可溶性糖含量对照和处理之间差异不显著。淹水导致栓皮栎的比叶重(Leaf dry mass per area)持续升高,池杉的与对照没有显著差异。淹水导致栓皮栎的根系活力持续下降,池杉则开始时下降后又升高,这可能与池杉在淹水过程中产生了有利于吸收氧气的不定根,而栓皮栎没有产生不定根有关。 以上生理生态的实验结果说明相对枫杨和池杉,栓皮栎应属于对淹水较敏感的树种。并得到以下一些结论:1)间接支持了“长期淹水导致不耐淹种(如栓皮栎)库量减小,进而导致光合速率下降的负反馈效应”假说;2)淹水对不耐淹种光合速率下降的影响至少包括气孔开度降低、光化学量子效率降低和库尺寸下降导致的光合速率下调的负反馈效应(长期)三个生理生态原因;3)淹水对水势的影响与树种相关;4)淹水并未导致不耐淹种(如栓皮栎)根膜质过氧化状态上升,而是导致其下降。导致其下降的主要原因是根系缺氧造成的;5)淹水胁迫初期耐淹种(如枫杨和池杉)和不耐淹种(栓皮栎)均出现部分生理生态过程的下调,持续时间大概在1-10天内。随后耐淹种生理过程逐渐恢复而不耐淹种在略为恢复1-2天后逐渐下降到较低水平。耐淹种恢复的关键原因可能是不定根和肥大的皮孔的出现。 令人意外的是70天的淹水过程并没有导致栓皮栎的死亡,这说明该树种对淹水具有一定的忍耐能力。因此,栓皮栎分布于河岸带和消落区较高海拔处并很少受到季节性淹水影响的生理生态原因可能还包括其他方面。淹水后可能要面对土壤透气性恢复带来的生理干旱胁迫可能对栓皮栎的生理过程造成影响。因此进一步研究淹水后恢复过程中三个种的生理生态过程对于深刻理解河岸带和消落区树种分布的生理生态原因无疑具有十分重要的理论意义。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

利用RS和GIS手段相结合的方法研究了塔里木河下游的植被和景观变化,并分析了由于历史时期塔里木河水流量的变化而导致的地下水位变化、环境因子和人类活动对植被及景观格局的影响。 对环境因子与植被覆盖变化关系的分析结果发现: ⑴在1987年至2004年占研究区总面积26%的景观发生变化;而植被和水体的变化最大;植被的变化中荒漠化和转化为农田是其主要的变化类型。1987年至2004年,仅有占总面积39%的植被没有发生变化,而发生荒漠化和盐碱化的植被仅有少数能够恢复。 ⑵在选取的环境因子中,植被缀块的起始NDVI和植被缀块距河道的距离对植被变化的影响最大,其次为海拔、坡度、缀块形状和缀块距离居民点的距离;而坡向和缀块面积与植被变化的关系较小。发生荒漠化的植被缀块距离河道较远且自身的NDVI较低,表明这些植被缀块的变化主要是受到水资源的限制;而转化为农田的植被缀块自身的NDVI较高且距河道较近,表明人类的开垦活动主要在植被生长较好的地区进行。研究期间内能够保持的植被距河道较近且NDVI较低,这与能够保留的植被主要是较稀疏的胡杨林有关。 ⑶植被缀块距河道的距离在1987年至1999年间与植被的变化显著相关,而在1999年至2004年相关不显著,这表明影响植被变化的影响环境因子随时间变化。 ⑷虽然所选取的环境因子对植被变化的解释力偏低,但在某些时间段对植被变化的解释力可以达到40%。如果增加环境因子,使用梯度分析的方法可以较好的解释环境及其它因子对植被变化的影响。 对地下水位变化对植被及景观时空格局变化的研究结果发现: ⑴在地下水水位剧烈下降的1986年至1999年,植被面积减少30%,距离河道最近的区域减少最多,植被占总面积的比例和植被的减少随距离河道距离的增加而减小;平均NDVI降低;荒漠面积增加4.8%,年均增加1338公顷;盐碱地面积增加。由于生态应急输水工程的实施,1999年至2004年期间沿塔里木河道地下水位回升,植被面积增加48%,距离河道最近的区域面积增加最明显,植被面积增加的增幅随距离河道距离的增加而减小;荒漠面积减少8.3%,年均减少6280公顷;平均NDVI升高;荒漠面积减少;盐碱地面积在某些区段增加,某些区段减少。 ⑵1986年至1999年胡杨林、柽柳灌丛和盐生草甸缀块密度增加,植被趋于破碎化;总体上胡杨林、柽柳灌丛和盐生草甸的缀块形状变得规则,而盐生草甸在某些区段趋于不规则;景观的聚集度在河道左侧增加而右侧减小;景观多样性和均匀性均下降。1999年至2004年,总体上胡杨林、柽柳灌丛和盐生草甸的缀块密度减小,植被趋于整合;胡杨林、柽柳灌丛和盐生草甸缀块形状变得不规则,但盐生草甸在某些区段变得相对规则;景观聚集度指数变化没有明显的规律;景观多样性和均匀性均增加。 ⑶除植被占总面积的比例在沿河道由上段到中断到下段方向上呈现减少的趋势,其它植被及景观特性在沿河道纵向上变化规律不明显;而在沿河道垂直方向上,植被及景观特性的变化表现出与距离河道的距离相关,表明该地区的植被及景观特性是受到地下水控制的。 ⑷在塔里木河实施的生态应急输水工程对当地植被的恢复起到了一定的作用,但主要局限在沿河道附近的区域。对于干旱区植物的保护,合理使用径流水资源,保证水资源的供应畅通是更好和更长远的发展策略。 对人类活动对景观的影响的研究发现: ⑴1987年至1999年,农田面积增加4240公顷,年均增加353公顷;植被面积减少4884公顷,年均减少407公顷。1999年至2004年,农田面积增加4568公顷,年均增加913公顷;植被面积减少8487公顷,年均减少1697公顷,远大于农田面积的增加。 ⑵农田平均缀块面积和农田最大缀块面积从1987年至1999年至2004年增加;聚集度指数在1987年至1999年降低,而1999年至2004年升高。最大植被缀块面积、平均形状指数和聚集指数从1987年至1999年至2004年均下降;其它植被及农田景观指数在1987年至1999年和1999年至2004年间变化不一致。在距河道1km的范围内,农田缀块数、农田面积、最大农田缀块面积、平均缀块面积、平均形状指数以及聚集度指数在从1987年至1999年至2004年一直升高;距河道1km范围内的景观多样性和均匀度指数和平均形状指数在1987年至1999年至2004年增加,而聚集度指数和最大缀块指数在1987年至1999年至2004年一直减小。 ⑶研究结果表明人类活动-主要是开垦农田-导致了当地植被面积的减少,并导致植被破碎化。受到径流来水量减少的影响,人类开垦活动正在逐渐向距离河道近的区域转移,并导致植被向退化的方向发展,河道附近的区域是塔里木河下游植被分布的主要区域,这对该地区植被的维持和保护非常不利。 在塔里木河下游,地下水位的下降和人类活动都导致植被趋于退化,人工输水虽然能够恢复植被,但其效应主要集中在河道附近的地区,对于该生态关键地区植被的保护,合理的使用水资源并适当的进行人类活动才是植被及生态保护的根本。

Relevância:

10.00% 10.00%

Publicador:

Resumo:

1. The stripe-backed weasel Mustela strigidorsa is one of the rarest and least-known mustelids in the world. Its phylogenetic relationships with other Mustela species remain controversial, though several unique morphological features distinguish it from congeners. 2. It probably lives mainly in evergreen forests in hills and mountains, but has also been recorded from plains forest, dense scrub, secondary forest, grassland and farmland. Known sites range in altitude from 90 m to 2500 m. Data are insufficient to distinguish between habitat and altitudes which support populations, and those where only dispersing animals may occur. 3. It has been confirmed from many localities in north-east India, north and central Myanmar, south China, north Thailand, north and central Laos, and north and central Vietnam. Given the limited survey effort, the number of recent records shows that the species is not as rare as hitherto believed. Neither specific nor urgent conservation needs are apparent.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Habitat use by wintering Ruddy Shelduck (Tadorna ferruginea) in Lijiang Lashihai Lake of southwest China was studied from 1 November 1999 to 29 April 2000. We divided habitats into five types-deep water, shallow water, mudflat, grassland and farmland. Shallow water and grassland, with rich food and easily accessible water, were preferred by wintering Ruddy Shelducks, Farmland was preferred in mid-winter but avoided in early winter and late winter. Even in mid-winter, the feeding Ruddy Shelduck on farmland were not equally distributed in fields and preferred wet fields (just irrigated) and avoided dry fields. In dry fields, the distances to water sources had great impact on the feeding distribution. Mudflats were only selected in later winter, coinciding with the growth of water-weeds. Deep-water areas were always avoided. Prohibition of human disturbance and retaining shallow water areas and grassland are important measures to mitigate conflict between Ruddy Sheldruck and local people.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

One of the most endangered populations of Black-necked Cranes (Grus nigricollis), the central population, is declining due to habitat loss and degradation, but little is known about their space use patterns and habitat preferences. We examined the space use and habitat preferences of Black-necked Cranes during the winter of 2007-2008 at the Napahai wetland in northwest Yunnan, China, where approximately 300 Black-necked Cranes (>90% of the total central population) spent the winter. Euclidean distance analysis was employed to determine the habitat preferences of Black-necked Cranes, and a local nearest-neighbor, convex-hull construction method was used to examine space use. Our results indicate that Black-necked Cranes preferred shallow marsh and wet meadow habitats and avoided farmland and dry grassland. Core-use areas (50% isopleths) and total-use areas (100% isopleths) accounted for only 1.2% and 28.2% of the study area, respectively. We recommend that habitat protection efforts focus on shallow marsh and wet meadow habitats to maintain preferred foraging sites. Core-use areas, such as the primary foraging areas of Black-necked Cranes, should be designated as part of the core zone of the nature reserve. Monthly shifts in the core-use areas of the cranes also indicate that the reserve should be large enough to permit changes in space use. In addition to preserving habitat, government officials should also take measures to decrease human activity in areas used by foraging Black-necked Cranes.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Nutrient-rich effluents caused rising concern due to eutrophication of aquatic environment by utilization of a large amount of formula feed. Nutrient removal and water quality were investigated by planting aquatic vegetable on artificial beds in 36-m(2) concrete fishponds. After treatment of 120 days, 30.6% of total nitrogen (TN) and 18.2% of total phosphorus (TP) were removed from the total input nutrients by 6-m(2) aquatic vegetable Ipomoea aquatica. The concentrations of TN, TP, chemical oxygen demand (COD) and chlorophyll a in planted ponds were significantly lower than those in non-planted ponds (P<0.05). Transparency of water in planted ponds was much higher than that of control ponds. No significant differences in the concentration of total ammonia nitrogen (TAN), nitrate nitrogen (NO3-N) and nitrite nitrogen (NO2--N) were found between planted and non-planted ponds. These results suggested that planting aquatic vegetable with one-sixth covered area of the fishponds could efficiently remove nutrient and improve water quality.