Feeding ecology of sesarmid crabs in mangroves

相手蟹科物种是红树林湿地的主要底栖动物类群,在生态系统中起着重要的作用。我国大陆地区目前已记录的相手蟹科物种数量为12种,低于其它红树林地区(国内常用的采样方法会造成螃蟹物种数量和密度的低估),其中褶痕相手蟹(SESArMA PlICATA)、无齿相手蟹(S.dEAAnI)和双齿相手蟹(S.bIdEnS)等是常见种。红树植物叶片是相手蟹科动物的主要食物来源,相手蟹科动物通过地表摄食和洞穴贮存的形为消耗了大量的红树植物凋落叶,使这些凋落叶的有机质和营养元素得以保留在生态系统内,在凋落叶的周转和物质归还方面起到重要的作用。它们同时也摄食红树植物的繁殖体并且对不同物种的繁殖体具有摄食偏好,这可能对一些红树物种的植被更新能力和红树植被群落结构产生影响。相手蟹科动物对不同物种和不同状态的红树叶片也存在摄食偏好,通常对腐烂的叶片摄食偏好较强;螃蟹的摄食偏好与叶片的营养成份、粗纤维和单宁含量以及C/n比等性质有关;但在恶劣的野外环境下,螃蟹则会表现出随机性摄食。目前关于相手蟹科动物生态学作用的认识仍不充分,例如它们的种群大小和对凋落物的转化作用等,有待于进一步研究。Sesarmid crabs,common macro invertebrates in mangrove ecosystems,influence the structure and function of mangrove habitats through their burrowing activities and processing of leaf litter.A total of 12 sesarmid species have been recorded in mainland China,which may be an underestimate since more sesarmid species have been reported in Hong Kong and other tropical mangrove regions.( The reason for this underestimation could be due to the method commonly used to locate the crabs within mainland China.The most common method used is to place plot frame on the soil surface and simply dig to about 20—30 cm,and sift through the soil to locate crabs which could allow sesarmid crabs to escape deeper into the soil during the digging.) The most common sesarmid species in China are Sesarma plicata,S.deaani and S.bidens,while Neosarmatium meinerti is widely recorded in tropical areas of Australia and Kenya.Mangrove plant tissues,mainly leaves,are the main food source of sesarmid crabs,but crabs also feed on sediment detritus and faunal tissue to supplement the nutrient limited mangrove leaves.Some dietary specializations among different mangrove crabs have been recognized.Some crabs feed on only live leaves obtained by climbing into trees,while some species feed only on dead leaves on the mangrove floor.Crabs also have frequently been observed burying fallen mangrove leaves,to enhance leaf nutrition quality,prevent leaf litter from being removed by tidal flushing and avoid competition and predation when food or time available for collectingfood is limited,and predator abundance is high.The feeding preference of sesarmid crabs for mangrove leaves with different conditions or from different mangrove species also has been reported from the laboratory and the field research.For example,sesarmid crabs in China prefer leaves of Kandelia candel over those of Bruguiera gymnorrhiza and Aegiceras corniculatum.Leaf characteristics such as C /N ratio,tannin,water and crude fiber contents determine the feeding preferences.Generally,sesarmid crabs prefer decomposed leaves,ascribed to the decreased tannin content and C /N ratio,and increases in water during leaf decomposition.It also has been suggested that crabs need to consume more decomposed leaves to obtain adequate C and N since they have lower C and N assimilation rates from those leaves.Feeding preferences have been more often demonstrated in laboratory studies while some field studies have revealed a lack of selective feeding of different mangrove species.This is probably due to the environmental stresses in field like predation,limited feeding time,and limited food availability.The ability of sesarmid crabs to remove leaf litter has been studied frequently in the past decades,and crabs have been shown to consume a large proportion of annual leaf fall production,far in excess of the local production in some mangrove forests.The ability of crabs to remove litter seems to be stronger in tropical areas than in subtropical or warm temperate areas.In subtropical areas like China,removal of leaf litter is affected by temperature and showed significant seasonal variation.Not only sesarmid crabs but some snails( e.g.Terebralia palustris) and ocypodoid /grapsid crabs( e.g.Helograpsus haswellianus and Ucides cordatus) also have been reported to consume mangrove leaves.Direct grazing of leaf litter by crabs accounts for a small proportion of leaf litter removed from mangrove floor in China,while the stocking of leaves in crab burrows for later consumption is the key way by which leaf litter is retained in the ecosystem,preventing tidal export.Through shredding and grazing of leaf litter,crabs also initiate and enhance the breakdown of mangrove detritus and recycling of nutrients.Sesarmid crabs also have been found to graze mangrove propagules and seeds,thus play a critical role in determining seedling recruitment and vegetation regeneration.It also has been suggested that the predation preference on some non-dominant mangrove species regulates their distribution with the vegetation community.The feeding ecology of sesarmid crabs and its involvement of in mangrove restoration,their retention of C and nutrients in mangrove soils and predation of seeds /propagulse are worthy further studies.国家自然科学基金项目(41206108;41076049); 福建省自然科学基金项目(2011J05111); 海洋公益性行业科研专项项目(201205008

茂金属催化剂体系及其丙烯聚合性能调控

国内聚丙烯的生产基本上使用传统的Ziegler-Natta催化剂,国外已经使用茂金属催化剂.茂金属催化剂生产的聚丙烯提升了产品性能,市场需求份额逐年增加,国内需要开发茂金属催化剂并拓展工业应用.茂金属催化剂与传统的Ziegler-Natta催化剂相比,结构类型丰富,反应调控能力强,可以催化生成结构多样的聚丙烯.以茂金属催化剂的发展为主线,探讨催化剂结构对反应性能的影响;分析体系中多种因素如温度、压力、催化剂浓度、助剂等对反应活性的调控;讨论催化反应机理.中国石化茂名石化公司基金;;聚烯烃催化技术与高性能材料国家重点实验室基金;;上海市聚烯烃催化技术重点实验室基金(Nos.201501-PT-C01-005,沪CXY-2015-003,16DZ2270800,16DZ2290700);;国家自然科学基金(Nos.21473142,20673191);;教育部创新团队基金(No.IRT_14R31)资助项目~

a practical hierarchical key management scheme based on one-way hash function

针对等级角色的权限管理和访问控制,形式化地定义与分析了等级密钥管理问题,提出了一个基于单向散列函数的实用的等级密钥管理方案.该方案允许各等级角色自主选择主密钥,并利用安全的单向散列函数和公开的辅助参数构造角色间的等级权限关系,其密钥生成与密钥推导过程简单快捷,能够有效地满足等级系统权限管理的安全需求.与目前已有的等级密钥管理方案相比较,密钥推导效率及存储开销均有所优化,同时能够更好地适应等级角色访问控制的动态变化

密度制约对宝天曼落叶阔叶林锐齿栎死亡前后分布格局的影响

为了在温带和亚热带的过渡带中验证森林树木死亡是否受密度制约的影响,我们在宝天曼国家级自然保护区选择1个100 m×100 m的暖温带落叶阔叶林样地,用双变量函数g(r)(the pair-correlation function)研究了锐齿栎(Quercus aliena var.acuteserrata)死亡前(活树和枯木统称为死亡前树木)和死亡后(活树为死亡后树木)的分布格局。把样地中的锐齿栎分为幼树(1 cm≤DBH5 m尺度呈聚集分布,死亡后幼树(1 cm≤DBH5 m的尺度呈聚集分布;(2)采用随机标签零模型和案例–对照设计的方法,排除生境异质性影响后,将幼树和小树的分布格局作为案例,将成年树的分布格局作为对照,并代表生境异质性的作用,通过小径级树木与成年树分布格局的对比发现,密度制约效应对死亡前后的锐齿栎分布格局均具有影响;(3)幼树和小树在成年树周围的分布死亡前为显著聚集分布格局,死亡后剩余树木的聚集强度下降;随着与成年树之间距离的增加,死亡后的幼树(仅包括现存的活树)逐渐向随机分布格局演替。本研究初步表明锐齿栎空间格局受生境异质性的影响并呈现出显著的聚集效应,排除生境异质性影响后,锐齿栎死亡前后的空间格局受到密度制约的影响,这一结果为Janzen-Connell假说提供了支持

暖温带–北亚热带过渡带落叶阔叶林群落不同径级系统发育结构的变化

群落的系统发育结构能够有效地反映各种生态过程对群落组成的影响,通过研究群落系统发育结构能推断出其形成的生态过程,对于揭示群落动态具有重要意义。作者将宝天曼1 ha落叶阔叶林样地分为10 m×10 m、20m×20 m、25 m×25 m三个尺度的样方,将样地内乔木个体划分为小径级(1 cm≤DB

母乳中1,3-二不饱和脂肪酸-2-棕榈酸甘油三酯的组成及其功能特性研究进展Composition of 1,3-diunsaturated fatty acid-2-palmitin triacylglycerols in human milk and their functions: a review

1,3-二不饱和脂肪酸-2-棕榈酸甘油三酯（UPU）是指甘油骨架的sn-1、sn-3位连接不饱和脂肪酸、sn-2位连接棕榈酸的一类甘油三酯的总称，其在母乳脂肪中含量最高，可为婴儿提供更加均衡的脂肪酸和甘油三酯，对婴儿生长发育有特殊的生理功能。为对开发新型母乳结构脂肪提供理论支持，系统介绍了不同国家、地区母乳脂肪中3种sn-2棕榈酸甘油三酯UPU、UPS、SPS的含量，我国成熟期母乳中UPU的组成和含量，从降低婴儿粪便硬度、促进脂肪和矿物质吸收、保护肠道健康，提供更多种类、比例更稳定均衡的脂肪酸等方面，论述了UPU的功能作用及其消化和吸收特性，另外对比了市售营养强化剂OPO与母乳中UPU组成的差异，通过分析提出LC-MS方法更适合婴儿配方奶粉中OPO含量的测定。 1,3-Diunsaturated fatty acid-2-palmitin triacylglycerols (UPU) are the triacylglycerols that unsaturated fatty acids combined at sn-1 or 3 position, and palmitic acid located at the sn-2 position. UPU has the highest content in human milk fat, providing infant balanced fatty acids and triacylglycerols which are important for infant growth. In order to provide the scientific basis for the development of novel human milk fat substitutes, the contents of three sn-2 palmitate triglycerides UPU, UPS and SPS in human milk fat in different countries and regions, and the composition and contents of UPU in maturing human milk in China were systematically introduced, the function of UPU in terms of reducing fecal hardness, promoting fat and mineral absorption, protecting intestinal health of infants, providing a wider variety of fatty acids in a more stable and balanced ratio, and its digestive and absorption properties were discussed, and the differences in the composition of commercially available nutritional fortifier OPO and UPU in human milk were compared.The LC-MS method was proposed to be more suitable for the determination of OPO content in infant formula

中国母乳多不饱和脂肪酸组成、特点与其满足 婴儿膳食营养素摄入量的比较分析 Composition and characteristics of polyunsaturated fatty acids in human milk in China and its comparative analysis of meeting the dietary nutrient intake of infants

脂肪是母乳的重要组分，母乳中的脂肪酸是母乳脂肪中变化较大的常量营养素，尤其是多不饱和脂肪酸(PUFA)，在婴儿营养、免疫及神经认知功能上发挥着重要作用。旨在为更科学合理的母乳喂养提供营养策略，综述了中国母乳中n-6 PUFA、n-3 PUFA、亚油酸(LA)、α-亚麻酸(ALA)、花生四烯酸(ARA)、二十二碳六烯酸(DHA)的含量以及LA/ALA比值，并根据 0~6月龄婴儿PUFA的参考摄入量，分析中国母乳中PUFA的组成及特点。我国母乳成熟乳中LA含量偏高，ARA含量相对稳定，ALA和DHA含量偏低且波动范围大，LA/ALA比值在4.25～33.44之间。可通过膳食干预改善母乳中PUFA组成，提高母乳喂养婴儿生长发育所需的PUFA含量。 Fat is an important component of human milk. Fatty acids in human milk are macronutrients with great changes, especially polyunsaturated fatty acids (PUFA), which play an important role in infant nutrition, immunity and neurocognitive function.In order to provide nutritional strategies for more scientifically sound breast feeding, the contents of n-6 PUFA, n-3 PUFA, linoleic acid(LA), α-linolenic acid(ALA), arachidonic acid(ARA), docosahexaenoic acid(DHA) and LA/ALA ratio in human milk in China were reviewed, and the composition and characteristics of PUFA in human milk in China were analyzed according to the reference intake of PUFA for infants from 0 to 6 months of age.The mature human milk in China contained high levles of LA, relatively stable levels of ARA, low and fluctuating levels of ALA and DHA, and the LA/ALA ratio ranged from 4.25 to 33.44. The PUFA composition of human milk can be improved by dietary intervention so as to increase the PUFA content required for the growth and development of breastfed infants

荒漠地区公路建设环境保护与生态恢复技术

《荒漠地区公路建设环境保护与生态恢复技术》项目组通过资料收集、理论分析、室内外试验和工程实践,系统开展了荒漠地区公路建设与自然环境相互影响、荒漠地区公路建设的生态环境敏感性、荒漠地区公路建设环境保护与生态恢复技术集成以及典型区域公路建设环保与生态建设示范四方面研究,取得了如下主要创新性成果： 1．分析揭示了荒漠地区公路与环境的相互影响关系,建立了公路建设环境保护与生态恢复的基础平台。 2. 提出了荒漠地区公路路域生态功能重要性、环境敏感性和景观类型区划的原则与方法,建立了相应的区划体系。 3．构建了荒漠地区公路路域生态修复技术评价指标体系和评价数学模型。 4．提出了荒漠..