Effects of forest cover types and environmental factors on soil respiration dynamics in a coastal sand dune of subtropical China

Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for secondary natural Litsea forest and plantations of casuarina,pine, acacia and eucalyptus. Results show that significant diurnal variations of Rsoccurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of Rswere found in all five forest stands. Rschanged exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of Rs variations. Positive relationships between seasonal Rsand soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter(Q10 value) of Rsranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual Rswas highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter,and soil properties(pH, total N, available P, and exchangeable Mg) were also significant factors.

Habitat Use, Home Range, and Hibernaculum of the Mongolian Racerunner, Eremias argus (Lacertidae, Reptilia) in a Coastal Sand Dune in South Korea

Information on habitat use is critical in sizing protected areas for endangered reptile species. To investigate habitat use, home range, and hibernaculum of the endangered Mongolian Racerunner(Eremias argus), we radio-tracked 40 specimens in a coastal sand dune in South Korea. Of the 163 locations recorded during the breeding season, 150(92.0%) were in grass sand dunes, and the rest(8.0%), all associated with the same lizard, were in shrub sand dunes. All of the 123 locations recorded during the non-breeding season were in grass sand dunes. No lizards were found in the grasslands abutting the dunes. The four lizards with identifiable hibernation sites were found under an average of 17.8 cm of sand and were all located in grass sand dunes. The lizards moved approximately 5 m daily and used 162 m2of home range(computed by minimum convex polygon, MCP) during the breeding season, and they moved approximately 2 m and used 68 m2of home range during the non-breeding season. However, the mean daily moved distances and MCP home ranges were not statistically significantly different between the seasons or between males and females. Our results suggest that in coastal sand dunes, E. argus uses grass sand dunes as its main habitat throughout the year. This finding could be used to determine the appropriate habitat size and to designate for the conservation of this endangered species.

Endophytic fungi of wild legume Sesbania bispinosa in coastal sand dunes and mangroves of the Southwest coast of India

Evaluation of 450 surface sterilized tissue segments of a seasonal wild legume, Sesbania bispinosa （Jacq.）, of coastal sand dunes and mangroves of southwest India yielded 546 isolates comprising 39 endophytic fungi with six dominant taxa （Aspergillus flavus, Aspergillus niger, Cladosporium tenuissimum, Fusarium moniliforme, Penicillium chrysogenum and morpho sp. 1）. A consortium of saprophytic, pathogenic and toxigenic fungi exists as endophytes in S. bispinosa. Number of segments colonized, number of isolates obtained, species richness and diversity were higher in S. bispinosa in mangroves compared to coastal sand dunes. Seeds yielded more fungal isolates, but species richness and diversity were low. In spite of low fungal colonization in root segments, the diversity was high. Up to 30-40 % endophytic fungi of S. bispinosa differed between coastal sand dunes and mangroves revealing partial host- and habitat-specificity. As S. bispi- nosa is extensively used as green manure and forage in southwest India, further studies especially on the bioactive compounds of its endophytic fungi might broaden its range of uses. In addition to conventional morphologicaltechniques, molecular tools would provide precise insight on the endophytic fungi of coastal sand dunes and mangroves.

Chronology of coastal aeolian deposition and its paleo-environmental implications on the Liuao Peninsula of South China

Coastal dunes are a common geomorphic type in sandy coastal zones.They are a record of the coupled evolutionary processes of the wind and ocean waves.Many coastal dune fields have developed on the east coast of Fujian China and now occur as widespread typical coastal aeolian sand landforms on the Liuao Peninsula,Gulei Peninsula and Dongshan Island,but it is difficult to evaluate the dynamic geomorphologic process of sandy coast due to the lack of systematic and accurate chronological data.In this study,we selected the Hutoushan(HTS)aeolian dune on the Liuao Peninsula as the research object.Optical dating and grain-size analysis were applied to sand samples from the aeolian sequence of a profile of the HTS dune.The results show that the ages of seven samples of this profile were in the range of 37.8–0.19 ka from 4.0 to 0.2 m deep.These correspond to the Marine Isotope Stage 3(MIS3),abrupt climatic change events of 4.2 and 1.1 ka and the Little Ice Age(LIA),respectively.These samples displayed evidence of a longer-term climate trend in this area.The period of formation of this coastal aeolian dune corresponds to a cold and arid climate associated with the East Asia Winter Monsoon(EAWM).Periods of dune fixation and rubification are evidence of a hot and humid climate.Mobilization and stabilization of the aeolian dune is an important characteristic of the coastal evolution in South China since the late Pleistocene.

Coastal Dunes Mobility Integration and Characterization:Developing of a Flexible Volume Computing Method

Coastal dunes are among the most complex interfaces to study in the world. Improving the knowledge of their morphodynamics is essential to better understand the present evolutions and try to anticipate future. The recent use of the new vectors that are drones, UAV and UAS, improves the temporal and spatial resolutions of geomatic data acquired on these environments. Many studies attempt to measure the sedimentary variations that occur from one date to another by the use of differential volumes. In particular, they make it possible to understand the roles of storms, sometimes erosive, as well as the possible morphological responses of associated reconstruction periods. One of the primary methods for calculating volume evolutions is the assessment of a vertical delimitation of the dune toe. However, it is difficult to limit mobile and variable environment, temporally and spatially, to a simple vertical topographic delimitation. This study was realized to estimate the error induced by the use of the vertical threshold method. In the examples that were done, this error was far from being negligible and might in some cases exceed the evolutions of measured volumes. In overcoming this problem, an alternative method was developed. It was the seemingly better adaptability to these mobile environments that are the coastal dunes.

Effects of Forest Types and Environmental Factors on Soil Microbial Biomass in a Coastal Sand Dune of Subtropical China

Coastal sand dune ecosystems generally have infertile soil with low water-holding capacity and high salinity. However, many plant species have adapted to the harsh sand environment along the southeastern coast of China. Studying the microbial biomass in such an ecosystem can improve our understanding of the roles that microbes play in soil fertility and nutrient cycling. We investigated the differences in soil microbial biomass carbon(MBC) and nitrogen(MBN) contents and their seasonal dynamics in five forest types(a secondary forest and plantations of Casuarinas, Pine, Acacia, and Eucalyptus). The results indicated that the seasonal variations of soil MBC and MBN contents in all five forest stands were higher in spring and winter, but lower in summer and autumn. The MBC content was lower in the Casuarinas plantation than in the other plantations in the same soil layer. However, no significant differences were observed in MBN contents among the different forest types. The MBC and MBN concentrations were positively correlated with soil moisture, but negatively correlated with soil temperature. The MBC and MBN contents also decreased with increasing soil depth. Across all soil layers, secondary forest had the highest MBC and MBN concentrations. Our study also showed that the MBC and MBN contents were positively affected by total soil carbon(TC), pH, and litter N content, but were negatively impacted by soil bulk density and litter C content. Moreover, the MBN content was positively correlated with root N content. In summary, environmental factors and the differences in litter and fine roots, soil nutrient contents, as well as the soil physical and chemical properties caused by different tree species collectively affected the concentrations of the soil MBC and MBN.

A PRELIMINARY STUDY ON FORMATION OF THE SAND DUNE SYSTEMS IN THE NORTHERN AUSTRALIAN COASTAL ZONE

Ⅰ. INTRODUCTIONDune activity across northern Australia is currently the focus of a joint research project between the Australian National University and the Xi’an Laboratory of Loess and Quaternary Geology, Academia Sinica. Although the project is not yet completed, there is sufficient data available to allow discussion of the general setting of the dune fields studied to date. These include the dune fields near Shelbume Bay and Cape Flattery, eastern Cape York, Cobourg Peninsula, Arnhemland, and Groote Eylandt, Gulf of Carpentaria(Fig. 1).

福建海岸沙地5种防护林土壤微生物群落特征

[目的]探明福建海岸沙地不同防护林对土壤微生物群落的影响及机制,为海岸带防护林森林质量提升提供科学依据。[方法]选择5种主要防护林为对象,分别为次生林、木麻黄(Casuarina equisetifolia)人工林、湿地松(Pinus elliottii)人工林、厚荚相思(Acacia crassicarpa)人工林和尾巨桉(Eucalyptus urophylla×E.grandis)人工林,采用磷脂脂肪酸法(Phospholipids fatty acid, PLFA)比较了不同防护林的土壤微生物群落结构。[结果](1)海岸沙地不同防护林土壤中共检测到18种PLFA生物标记,在尾巨桉和次生林中种类最多,湿地松和厚荚相思人工林最少。(2)土壤总磷脂脂肪酸、革兰氏阳性细菌和革兰氏阴性细菌含量均表现为尾巨桉和次生林较高,厚荚相思和木麻黄人工林较低,土壤真菌含量为尾巨桉林最高,丛枝菌根菌含量为次生林最高,真菌和丛枝菌根菌含量在其他防护林间无显著差异。(3)次生林的土壤微生物多样性和均匀度均高于4种人工林。(4)土壤pH、细根碳氮含量为土壤微生物群落的主要影响因子,其次为土壤全氮和硝态氮含量以及凋落物木质素/氮和细根碳氮比。[结论]不同防护林对土壤微生物群落的影响存在显著差异,在海岸带木麻黄防护林中引种尾巨桉和乡土树种,可以增加土壤微生物多样性,提高森林生态功能。

<i>Rhynchostegium megapolitanum</i>(Web. et Mohr) B.S.G.—A Rare Bryophyte in Dune Ecosystems of Zealand, Denmark

Rhynchostegium megapolitanum was observed during a study of the effects of the invasive nonnative Rosa rugosa in a sand dune. The vascular as well as the epiphytic and epigeic cryptogam vegetation was recorded., and soil properties were measured. Epihytic lichens were abundant on dead or dying branches of Rosa rugosa scrubs, under which the stable substrate and high light exposure provided growth conditions for an epigeic community dominated by lichens and bryophytes. The occurrence of the rare bryophyte Rhynchostegium megapolitanum is discussed.

Evidence of functional and structural changes in the microbial community beneath a succulent invasive plant in coastal dunes

Coastal dunes represent priority habitats for conservation due to the provision of valuable ecosystem services such as land protection,water supply or biodiversity conservation.Soil microbial communities are of crucial importance to maintain plant diversity due to harsh environmental conditions,water limitation and nutrient scarcity.Invasive alien plants represent a major threat to ecosystem conservation.Here,we explored different impacts of Carpobrotus edulis,a succulent plant invading coastal areas worldwide,on the function and structure of bacterial communities.Sand represents a challenging substrate due to low organic matter content and limited microbial activity.We optimized bacterial extraction for functional evaluation before assessing ecosystem impacts produced by C.edulis.We compared 12 extracting procedures combining different soil storage,sample amount and extracting solutions on the functional activity of sand communities through the community-level physiological profile.We further explored the function(using Biolog Ecoplates)and structure[using polymerase chain reaction–denaturing gradient gel electrophoresis(PCR-DGGE)]of bacterial communities from dunes invaded by C.edulis.Saline solution consistently increased bacterial cells detected by cytometry(P≤0.001).Principal component analysis suggested a limited temporal framework(0–24 h)in which community function can be explored without significant alterations in C substrate consumption.Changes under C.edulis invasion exhibited a different pattern of C substrate utilization comparing native and non-native zones(interspecific),but also between native zones(intraspecific),suggesting that functional impacts are site-dependent.Complementary,results obtained from PCR-DGGE indicated that the bacterial community structure of native dunes significantly differed from dunes invaded by C.edulis.

闽江口海岸沙丘的形成与演化

闽江口海岸沙丘的物质来源于以闽江泥沙为沙源的海滩沙，宽广的海滩、强劲的向岸风与干旱的时空耦合，适宜的地形空间构成了海岸沙丘发育的基本条件。海岸沙丘起源于约２５００ａＢ．Ｐ．，其活动是多幕次的，唐、宋及近代几次气候干冷期的出现，人口陡增以及垦荒规模扩大等人为因素，促进了海岸沙丘的发育进程。海岸沙丘从海向陆按雏形沙丘，岸前沙丘，横向沙丘及沙丘链，圆形、抛物线型或Ｕ型沙丘及风积平原依次演化。

中国海岸风成沙ESR测年的研究

介绍ESR测年的基本原理，并讨论风成沙Ge心测年的可行性、风成沙E’心的特征、测年误差及可靠性等问题。1992－1993年在渤、黄、东、南海沿岸采集的100余个风成沙样品ESR测年实验表明，绝大部分海岸风成沙的年龄为1－7万年。

长乐东部沿海海岸风沙区域分异探讨

根据长乐东部沿海不同岸段风沙的化学成份、矿物成份、沙色、粒度特征和风沙地貌特征等研究结果，阐明了由于沙源、向岸风与岸线夹角、原始地形和海滩坡度等因素在时空组合上的不同，使得海岸风沙的堆积特征、发育模式、地貌类型及其组合在不同岸段显示出明显的区域分异性。邻近河口的北段沙源充足，风沙地貌类型多，沙丘带规模大，堆积特征接近于河口沙。中段沙源枯竭，有效风能大，地貌类型单一，堆积物具有二次搬运和分选的特征。南段则介于上述两者之间。

海岸沙丘表面不同部位风沙流中不同粒径沙粒垂向分布的变化

河北昌黎黄金海岸典型沙丘的实地观测表明,风沙流中中沙与细沙输沙量的垂向分布在沙丘表面不同部位的变化并无本质性差别但有一定变化幅度的差异,如绝对输沙量均在迎风坡至丘顶增加、丘顶至背风坡坡脚减小,但中沙输沙量在迎风坡增加的幅度小于细沙、在背风坡减少的幅度大于细沙;相对输沙量在沙丘不同部位的变化趋向类似,但细沙的变化幅度要小于中沙;中沙的垂向分布模式均为幂函数,细沙则表现为指数分布(0～10cm高度内)和幂函数分布(10～30cm高度内)。

地中海沿岸沙丘种子大小对植物及其种子多度的影响

分析了地中海沿岸沙丘3种微生境(灌丛下、灌丛之间的开阔地、路径)以及整个沙丘生态系统的种子大小与土壤种子库中休眠种子的数量、土壤种子库中总种子的数量、地上植被中各个植物种的个体数量和幼苗数量、每种植物在小样方中的出现频率等方面之间的关系,也分析了种子尺寸(长、宽、高之和的平均值)与土壤种子的长久性、土壤种子库中休眠种子数量之间的关系;还分析了具有不同种子大小的植物在沙丘生态系统和各微生境的分布比率,验证了生活周期短的植物的种子在土壤中更长久和被干扰的微生境具有更多的休眠种子这种假说。结果发现,在地中海沿岸沙丘生态系统中,具有特别大的种子和特别小种子的植物种类都很少,不同植物种子的大小呈现近正态分布,但绝大多数植物的种子重量都不超过10 mg;微生境影响种子尺寸与种子长久性的关系,在灌丛下、开阔地区域等两个微生境以及整个的沙丘生态系统都呈现显著的正向关系(p<0 .0 5 ) ,而在路径这种关系不很明显;种子多度与植被物种出现频率呈现强烈的正相关(p<0 .0 5 ) ,没有发现种子大小与土壤种子库中休眠种子数量、种子库中总的种子数量、植被物种出现频率、植被的物种多度、幼苗植物多度等方面有显著的关系;具有中度大小种子(0 .1～10 mg)的植物在总的土壤种子库、休?

输沙量对海岸沙丘表面风沙流中不同粒径沙粒垂向分布的影响

在我国海岸沙丘的典型分布区河北昌黎黄金海岸，对不同输沙量下海岸沙丘表面风沙流中不同粒径组沙粒垂向分布的变化进行了野外观测。结果表明，在风速相近、物质组成一致和下垫面性质相同情况下，随着风沙流总输沙量的增加，在非均匀沙床面上不同粒径组沙粒的垂向分布呈现出了不同的变化特点。其中，随总输沙量增加粗沙输沙量总量并无增加，其输沙量下层减少、中层增加、上层减少，垂向分布转变为典型负幂函数模式；中沙在不同高度的绝对输沙量均有增加，相对输沙量下层（0～4cm）减少、上层（4～60cm）增加或基本持平，其垂向分布基本符合指数递减规律，尤其是在0～60cm高度内的分布随总输沙量的增加由负幂函数转变为指数函数；细沙输沙量总量和不同高度的输沙量均有不同程度的增加，相对输沙量下层（0～6cm）减少、上层（6～60cm）基本持平或增加，垂向分布符合典型的指数函数布模式。究其原因，主要应与不同风速气流的携沙极限以及不同粒径组沙粒的运动方式密切相关。

长乐东部沿海及海坛岛风沙地貌发育条件分析

本文探讨长乐东部沿海及海坛岛两地海岸风沙地貌的成因,作者根据野外调查结果分析得出风况、沙源和地形空间是长乐东部沿海及海坛岛风沙地貌发育的基本条件,认为气候变干的趋势和人类活动因素是加速海岸风沙地貌形成的触发因素。

南亚热带海岸沙地不同树种叶片化学计量学季节动态研究

养分贫瘠是南亚热带海岸沙地植物生长与分布的主要限制因子之一。本文以南亚热带海岸沙地5种树种的叶片和凋落叶为研究对象,通过对其碳、氮、磷含量及生态化学计量学特征的研究,从树种水平上分析了不同树种鲜叶与凋落叶养分浓度及重吸收率的动态变化,探讨了不同树种的叶片化学计量特征及与养分含量的关系,以科学评判不同树种对海岸沙地贫瘠立地的适应性,为沿海防护林的可持续经营提供理论依据。结果表明:海岸沙地上5个树种叶片碳含量普遍较高,而氮、磷含量在不同树种间差异较大,且均呈显著的季节变化。不同树种的平均氮、磷重吸收率变化范围分别为25.0%～54.4%和52.1%～78.1%,其中固氮树种的平均氮重吸收率低于非固氮树种,而其磷重吸收率高于非固氮树种。在不同季节,不同树种受不同的养分限制。尾巨桉在春秋季为氮限制,在夏冬季为磷限制;厚荚相思和木麻黄在不同季节均为磷限制;湿地松在春季为氮磷共同限制,夏季为氮限制,秋冬季为磷限制;而潺槁木姜子在春季为氮限制,夏季为氮磷共同限制,秋冬季节为磷限制。

海岸沙丘沙运动特征若干问题的研究──以闽江口南岸为例

在海岸带，沙粒粒径和水分含量是决定沙粒起动风速的最主要因素。闽江口南岸海滩沙的平均粒径为２．０Φ，水分含量多在０．３％～１．０％之间。运用Ｊｏｈｎｓｏｎ的经验公式，可计算出海滩沙的起动风速为６～７ｍ／ｓ。这一结果与实际观测值十分吻合。由于海岸环境因素的影响，使得同等条件下海岸带沙粒的起动风速明显大于内陆沙漠沙，而风沙流的输沙率明显小于内陆沙漠沙。海岸带是风速剧变带，在引用陆地气象台站的风速记录分析海岸风况和研究风沙运动规律时。

粤琼海岸沙丘砂石英颗粒的表面结构特征

本文通过对广东和海南海岸沙丘砂石英颗粒的扫描电镜分析,认为其表面结构特征,既具有典型的风成环境特征.又有继承和改造了的海滩砂的特征.风成环境特征的机械撞击痕迹和化学作用痕迹都很明显.