When is an island not an island? Insular effects and their causes in fynbos shrublands

Summary According to the equilibrium theory of island biogeography, insularisation will lead to species loss from habitat remnants. Extinctions will continue untill species number equilibrates at a level appropriate for the size and isolation of the island remnants. We tested whether insularisation leads to species loss by comparing plant species numbers on islands of fynbos shrublands surrounded by Afrotemperate evergreen forest with extensive mainland tracts of fynbos. Species area curves for islands and subsamples of mainland had significantly different slopes (z _island=0.43, z _mainland=0.16). Small islands had the fewest species (less than one fifth) relative to mainland samples of similar size. The species area curves intersect at 590 ha so that reserve sizes of this order of magnitude are needed to avoid species losses relative to extensive areas of fynbos.We compared traits of species on islands and mainlands to determine processes most affected by insularisation. Island floras did not differ from the mainland in the mix of dispersal types, pollinator syndromes or proportion of dioecious species. Islands did have significantly fewer species of low stature and significantly more species that survive fire only as seed and not by resprouting. We infer that the main cause of species loss is change in disturbance frequency. Islands have fewer fires and lose species dependent on frequent fires. We predict that island effects could be reduced by judicious fire management of small reserves.     

On the relationship between two indices (“Bulk density” and “dry-matter content”) of dry-matter accumulation in plant organs

“Bulk density” and “dry-matter content” are useful indices of dry-matter accumulation in plant organs. A theoretical equation describing the relationship between these two indices was put forward. To examine the reliability of this equation, the seasonal changes of these two indices were investigated in the leaves and stems of different ages ofAucuba japonica. In each organ both indices varied seasonally almost parallel to each other, but the seasonal changes of dry-matter content were less obvious than those of bulk density. The observed bulk density was always larger than that calculated from the observed dry-matter content by the theoretical equation. A drying experiment showed that this discrepancy was caused by the decrement of the volume of the plant material by water loss during the period from the weight measurement to the volume measurement. When the water loss was negligible, the equation described well the relationships between the two indices of the experimental materials. It was also shown that this equation was useful for the estimation of the amount of air space in plant materials.     

鼎湖山森林群落演替之研究

鼎湖山森林群落在自然状态下遵循一定的客观规律向更优化的气候顶极群落演变。本文分析其1955年至1989年(35年)来的演替结果,总结出鼎湖山森林群落演替的进程和模式,进一步应用植物群落演替系统的线性模型和非线性模型对演替进程进行定量研究,并做出相应的演替进程的数量预测。     

Fishing spots and sea tenure: Incipient forms of local management in Atlantic forest coastal communities

Recent work has dealt with the local management of aquatic resources as an alternative to Hardin's (1968) tragedy of the commons. In communities with no formal management of resources, informal ownership of fishing spots or conflicts with outside competitors may determine the basis for future local management. In this study, I analyze the use of aquatic resources by five fishing communities on the Atlantic Forest coast of southeast Brazil: Búzios Island, Puruba, and Picinguaba in São Paulo State, and Jaguanum and Itacuruçá Islands at Sepetiba Bay in Rio de Janeiro State. Informal ownership of fishing spots, used for set gillnet fishing, is regulated by kin ties at Búzios Island. The artisanal fishers of Sepetiba Bay, especially those from Jaguanum Island, have a conflict with Bay intruders, such as the shrimp and herring trawlers. Two coastal communities, Puruba and Picinguaba, have conflicts with fishing regulations from a State Park (Parque Estadual da Serra do Mar),created in 1977. The transformation of populated areas of the Atlantic Forest to Extractive Reserves might be a way to avoid conflicts with intruders and with governmental agencies, and to involve local populations in management. Kinship rules at Búzios Island and the territorial behavior of fishers at Sepetiba Bay may form a basis for local organization.     

Degradation of the endosperm cell walls of Lactuca sativa L., cv. grand rapids in relation to the mobilisation of proteins and the production of hydrolytic enzymes in the axis,cotyledons and endosperm

The timing of changes in total nitrogen and soluble amino nitrogen content, and in the activities of proteinase (pH 7.0), isocitrate lyase, catalase, phytase, phosphatase (pH 5.0), -galactosidase and -mannosidase were studied in extracts from the cotyledons, axis and endosperms of germinating and germinated light-promoted lettuce seeds. The largest amount of total nitrogen (2.7% seed dry weight) occurs within the cotyledons, as storage protein. As this decreases the total nitrogen content of the axis increases and the soluble amino nitrogen in the cotyledons and axis increases. Proteinase activity in the cotyledons increases coincidentally with the depletion of total nitrogen therein. Enzymes for phytate mobilisation and for gluconeogenesis of hydrolysed lipids increase in activity in the cotyledons as the appropriate stored reserves decline. Beta-mannosidase, an enzyme involved in the hydrolysis of oligo-mannans released by the action of endo--mannase on mannan reserves in the endosperm, arises within the cotyledons. This indicates that complete hydrolysis of mannans to the monomer does not occur within the endosperm. Mobilisation of all cotyledon reserves occurs after the endosperm has been degraded, providing further evidence that the endosperm is an early source of food reserves for the growing embryo.Abbreviations HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulphonic acid - EDTA ethylenediamine tetraacetic acid disodium salt - TCA trichloroacetic acid Part 2 of a series, of which the first was published in Planta 139, 1–8 (1978)     

Kinetics of the cooperativity of the Ca2+-transporting adenosine triphosphatase of sarcoplasmic reticulum and the mechanism of the ATP interaction.

The extent of the negative cooperativity with MgATP of the Ca²⁺-stimulated ATPase activity of sarcoplasmic reticulum has been studied with various membrane preparations and under various conditions. Preparations studied were fragmented sarcoplasmic reticulum vesicles, deoxycholate-solubilized and fractionated ATPase, triton extracted reticulum, vesicles reconstituted from either detergent, and limited trypsin digests of the reticulum. Conditions studied were suboptimal, optimal, and inhibitory Ca²⁺ concentrations; temperatures from 13 to 46 °C; 1 or 5 mm MgCl₂; 0.1 m KCl, 0.1 m NaCl, or no added salt; and Triton or deoxycholate present in the assay. With preparations in which vesicles could accumulate Ca²⁺ ion, the ionophore A23187 was added to prevent inhibition by internal Ca²⁺ ions. Under all circumstances, the negative cooperativity of MgATP was present (Hill coefficient of 0.2 to 0.8), indicating the persistence of the properties of the enzyme molecule and its lipid environment giving rise to kinetic negative cooperativity. Attempts to measure the number of ATP sites by protection against N-ethylmaleimide inactivation and by binding of an analog suggested, but did not prove, that there was only one specific, active ATP binding site below 0.5 mm. These results are interpreted to be consistent with either of two mechanisms for ATP cooperativity of the Ca²⁺-stimulated ATPase activity of sarcoplasmic reticulum: (a) a single, high affinity ATP active site and a second, lower affinity “allosteric” activator site; or (b) a single ATP site which demonstrates two affinities through some kinetic mechanism such as a substrate-induced, slow transition.     

Preparation, characterization, and functions of rabbit lymph node populations. III. Antigen-induced uptake of thymidine and dibutyryl cyclic AMP: inhibition of thymidine uptake by cholera toxin and dibutyryl cyclic AMP.

Keyhole limpet hemocyanin (KLH)-primed lymph node cell (LNC) populations were incubated with various amounts of KLH and the cellular incorporation of tritiated thymidine ([³H]TdR) or tritiated N⁶, O^2′ dibutyryl cyclic AMP ([³H]DbcAMP) was determined. T LNC responded more vigorously than did complement receptor lymphocytes (CRL), i.e., B cells, at all KLH concentrations, during all time intervals examined, and in the presence or absence of normal rabbit serum (NRS). The depletion of adherent cells from KLH-primed LNC resulted in no significant decrease in KLH-induced incorporation of either [³H]TdR or [³H]DbcAMP in any of the LNC populations. Thus it appeared that variation among LNC populations in the incidence of macrophages did not account for the marked variation in their responses. Cultures containing equal numbers of T and CRL were induced to incorporate more [³H]TdR or [³H]DbcAMP than either population cultured separately or the sum of their individual responses. It was concluded that KLH-induced incorporation of these substances into primed, isolated LNC, was primarily manifested in the T-cell population. The synergism seen in cultures containing mixtures of T and CRL suggested that B cells are induced to incorporate [³H]TdR or [³H]DbcAMP in the presence of antigen and T-cell product(s). KLH-induced incorporation of [³H]TdR into KLH-primed LNC was inhibited by cholera enterotoxin (CT) and DbcAMP as previously reported. However, CT or DbcAMP inhibited this incorporation into T LNC to a greater extent than into CRL or unfractionated LNC.     

羌塘国家级自然保护区地表土壤冻结天数时空变化特征

利用1981—2018年羌塘自然保护区周边5个气象台站的地表逐日最低温度和平均气温资料,采用线性回归和Mann-Kendall非参数检验方法,分析了近38 a以及全球变暖1.5℃和2℃阈值时羌塘自然保护区地表土壤冻结天数的时空变化特征。结果表明:(1)近38 a近地表土壤冻结开始日期呈推迟趋势,变化率为7.72 d·10 a^-1,冻结终止日期以8.17d·10 a^-1的速率显著提早;冻结持续时间和冻结天数均呈显著缩短趋势,平均每10年分别缩短14.69和11.19 d;同时段内,自然保护区大部分土壤冻结参数的变化率均大于青藏高原。(2)在年代际变化上,自然保护区呈现土壤冻结开始日期推迟、冻结终止日期提前、冻结持续时间和冻结天数缩短的变化特征。(3)土壤冻结参数在21世纪初均发生了气候突变,较青藏高原土壤冻融时间的突变点偏晚。(4)在全球变暖1.5℃时,RCP4.5和RCP8.5情景下的自然保护区土壤冻结参数变化值相同,冻结开始日期推迟25 d,冻结终止日期提早22 d,冻结持续时间和冻结天数分别缩短46和28 d;变暖2.0℃时,RCP4.5...     

若尔盖人-狼冲突现状与管理研究

大中型食肉动物肇事事件导致人类与野生动物关系恶化,给生物多样性保护工作带来巨大的挑战。若尔盖湿地是我国三大湿地之一,湿地、草原分布广泛,生物多样性丰富,畜牧业发达,但近年来狼(Canis lupus)捕杀牲畜的肇事事件时有发生。为了解若尔盖野生狼肇事件的空间分布以及牧民对人-狼冲突管理的看法,本研究于2022年对若尔盖县13个乡镇83个行政村进行走访调查。结果表明：(1)多数受访者(66.0%)认为在过去5年内,若尔盖县野生狼数量有所增加;(2)狼肇事事件具有明显的空间分异性,最严重的是包座乡。包座乡临近山区,该区域牧场面积广阔、牧民饲养牲畜数量多等原因导致该镇发生狼肇事事件较多;(3)对于狼肇事,绝大多数牧民(85.0%)更希望采取经济补偿或者驱赶措施,只有少数牧民(9.4%)希望采取捕杀的措施;(4)影响牧民对狼肇事管理措施的偏好因子中,受教育程度、年龄、民族以及被杀牲畜数量有显著影响。建议加强狼种群监测管理,采取措施减少狼捕杀牲畜,优化补偿机制,缓解当地牧民与狼之间的矛盾。本研究为当前若尔盖县野生动物保护和管理决策提供了依据,对其他地区大型食肉动物与当地居民冲突管理具有借鉴意义。     

鼎湖山植物群落α多样性与环境的关系

用样带取样法,来研究不同取样尺度和不同取样尺度条件下的多个环境因子与鼎湖山植物群落α多样性的关系.取样尺度分别为10、20、40、80m和160m.涵盖鼎湖山主要的植被类型：季风常绿阔叶林、针阔混交林、沟谷常绿阔叶林和针叶林.相关分析和主成分分析结果表明,环境因子对各层次的α多样性的影响程度各不相同,达到显著相关性的取样尺度也不一样,表现出较大的复杂性,同时也表明样带上的环境异质性较高.因此,用海拔梯度作为主要的环境梯度来研究鼎湖山植物群落多样性具有合理性.海拔高度与乔木层多样性的关系在所有取样尺度上都较密切,这说明海拔高度可能是影响乔木层α多样性的最重要环境因子.