Differential effects of native and invasive algal wrack on macrofaunal assemblages inhabiting exposed sandy beaches

Many sandy beaches worldwide receive large amounts of drift seaweed, known as wrack, from offshore algal beds and closer rocky intertidal shores. Despite the important influence of algal wrack on macrofaunal assemblages from different coastal systems, relatively little attention has been paid to the macrofaunal responses in sandy beaches to macrophyte wrack supplies. Algal wrack is a key resource, i.e. for food and/or refuge, for beach invertebrates while its availability can affect diversity and abundance of intertidal animals including shorebirds, but the role of certain types of wrack and its location on the shore has not been examined experimentally to date. In this paper, we use experimental manipulation of two species of brown seaweeds, i.e. artificial wrack patches made up of the native macroalgae Saccorhiza polyschides and the invasive species Sargassum muticum, to test hypotheses about influences on macrofaunal assemblages inhabiting the drift line and supratidal levels of exposed beaches. Results pointed out that different types of wrack deposits were not used uniformly by invertebrates. Nutritional value differed between the two species of wrack. In most cases, the carbohydrates, lipids and organic carbon content were greater in patches of S. muticum than in patches of S. polyschides. Data also provided evidences that nutritional content and microclimatic conditions of wrack deposits, i.e. temperature and humidity, might affect macrofaunal assemblages.     

Effects of sandblasting and salt spray on inland plants transplanted to coastal sand dunes

A transplant experiment was conducted on a sandy beach to elucidate whether salt spray and sandblasting are the major factors inhibiting inland plants from becoming established on coastal sand dunes. Potted inland plants of Miscanthus sinensis and Imperata cylindrica var. koenigii were transplanted in two zones on the beach and in one area far inland from the beach. One zone on the beach (sea side) was located on a front dune that was occupied by native sand-dune plants; the other zone (land side) was located behind the sand dunes, where grassland comprised both sand-dune and inland species. To assess the condition of transplants, we measured changes in the canopy leaf area periodically at all sites. The final dry weight at each site was determined at the end of the experiment. Seasonal changes in sandblasting and salt spray intensities were evaluated periodically at the sites by measurement of the opaqueness of exposed transparent plastic sheets and the amount of sodium trapped in exposed filter papers, respectively. All transplants died in the sea-side zone, where both salt spray and sandblasting were most frequent and intense. The final dry weight was greatest at the inland site, which lacked salt spray and sandblasting. Although salt spray was intense in the land-side zone, the canopy leaf area decreased considerably only in seasons during which salt spray was accompanied by intense sandblasting. We concluded that sandblasting accompanied by salt spray is one of the main factors inhibiting the survival and growth of inland plants on coastal sand dunes.     

Monitoring sandy desertification of Otindag Sandy Land based on multi-date remote sensing images

Sandy desertification is now the main ecological problem in the Otindag Sandy Land. In order to reveal the process of land degradation, especially the latest situation of sandy desertification, a method integrating remote sensing, Geographic Information System (GIS) and field survey was employed to build a sandy desertification dataset for analysis. Remote sensing images included the Landsat Thematic Mapper (TM) image in 1987, the Enhanced Thematic Mapper Plus (ETM⁺) image in 2000, and the image with the Charge-Coupled Device Camera (CCD) on the China-Brazil Earth Resources Satellite (CBERS) in 2006. Five land-cover classes, including active sand dunes, fixed sand dunes, semi-fixed sand dunes, inter-dune grassland and wetlands, were identified. Results showed that the Otindag Sandy Land has been suffering sandy desertification since 1987 with 2 different desertified stages. The first stage from 1987 to 2000 was a severe sandy desertification period, characterized by the fixed sand dunes decreasing at a high speed, and the semi-fixed and active sand dunes increasing remarkably. The second stage spanned from 2000 to 2006 and the sandy desertification was weakened greatly. Although a large area of fixed sand dunes were transformed to other types, fixed sand dunes were still the dominant type in the Ointdag region at 2006. Spatial change detection based on active sand dunes showed that the expansion area was much larger than the reversion area in the past two decades, and that several active sand belts had been formed, suggesting that sandy desertification controlling of the Otindag Sandy Land will be a long-term task.     

基于多时相遥感影像的浑善达克沙地沙漠化监测

沙漠化是浑善达克沙地面临的主要环境问题.为了揭示该地区沙漠化过程,特别是其最新状态,利用1987年和2000年的Landsat TM/ETM 及2006年的中巴资源卫星CCD数据,在地面考察资料及地理信息系统(GIS)的支持下,提取了固定沙地、半固定沙地、流动沙地、丘间草原及湿地5种地表覆被类型,建立了浑善达克沙地沙漠化数据库.结果表明浑善达克沙地在过去20a里发生了沙漠化,但是可分为两个阶段.第一阶段从1987年到2000年,为沙漠化快速发展期,固定沙地面积显著减少,而半固定沙地和流动沙地则明显增加;第二阶段从2000年到2006年,为沙漠化缓减期.尽管发生了沙漠化,但固定沙地仍然是浑善达克沙地面积最大的类型.针对流动沙地的空间变化检测表明在过去20a里沙地恶化的面积远远大于逆转的面积,并且已经形成了几条流动沙带,这意味着浑善达克沙地沙漠化的遏制是一个长期的过程.     

Spontaneous and initiated succession on unvegetated slopes in the abandoned lignite‐mining area of Goitsche,Germany

Abstract. In this study, we examined the colonization of unvegetated, dry slopes in the lignite‐mining area of Goitsche, Germany. The plots, characterized by different habitat conditions, were studied from 1994–2000. The vegetation development on treated plots was compared to untreated plots showing spontaneous succession. For initial treatments we used fresh plant clippings from a species‐rich sandy grassland (Armerion elongatae) mowed at the end of July. Soil seed bank samples, taken at the beginning of the experiments and cultivated for 18 months, confirmed that the vegetation development on the slopes started with primary succession. Because seed rain is considered to be an important factor in primary succession, we also studied the diaspore input during the first year. The hospitable Quaternary substrate of Site I (pH = 4.1–4.7, 92 % sand) supports fast vegetation development on treated and untreated plots. On treated plots, we have identified plant assemblages similar to initial stages of the Armerion elongatae community. On control plots, Coryne‐phorion communities have established spontaneously. At Site II (mixed Quaternary and Tertiary substrate, pH = 3.0–3.5,40 % sand) the total cover and number of psammophytic species was low. Treated plots showed development towards ruderal sandy grassland, but the establishment of Calamagrostis epigejos would eventually lead to monodominant stands. Untreated control plots showed basically the same pattern, however the development was slower. At Site III (pH = 1.8–2.8, 34 % sand), the hostile Tertiary substrate impeded the succession on both treated and untreated plots because low pH and therefore high amounts of Al³⁺ produced elemental toxicity to plants. The application of plant clippings accelerated the vegetation development in sites with a pH exceeding 3. On plots with the initial treatment, vegetation cover and total number of species were higher than on untreated plots. The application of fresh plant clippings from areas with similar habitat conditions appears to be a viable alternative to traditional restoration methods.     

干湿交替对科尔沁沙地人工林叶凋落物分解和养分释放的影响

在干旱/半干旱地区,土壤干湿交替现象非常明显.在全球气候变化背景下,预测未来科尔沁沙地的土壤干湿交替变化强度将进一步加剧.本研究采用室内原位土柱培养方法,模拟干湿交替对科尔沁沙地小叶杨和樟子松叶凋落物分解速率及养分释放的影响.试验设置3个处理:恒湿处理(CM)、轻度干湿交替处理(DW₁,10 d干燥+20 d湿润)和重度干湿交替处理(DW₂,20 d干燥+10 d湿润).整个培养试验共处理180 d,其中进行4次干湿交替循环处理,并在干湿交替处理结束后,将各处理置于相同土壤水分条件(60%田间持水量)延时培养60 d.结果表明: 小叶杨和樟子松叶凋落物分解及养分释放对干湿交替的响应一致.在干湿交替期间,DW₂处理显著抑制叶凋落物分解及叶凋落物C、木质素和总酚释放;与CM相比,DW₂处理叶凋落物质量、C、木质素和总酚残留率分别增加17.4%、23.8%、35.2%和32.7%,而干湿交替对叶凋落物N和P养分释放无显著影响.干湿交替处理结束和延时培养结束时,不同干湿处理叶凋落物分解及养分残留率的变化具有一致性.而延时培养期间DW₂处理凋落物分解速率、叶凋落物C和木质素释放加快,表明干湿交替对叶凋落物分解及养分释放具有短期延时效应.     

科尔沁沙地草地营造樟子松人工林对土壤化学和生物学性状的影响

以科尔沁沙地东南缘沙质草地和不同年龄樟子松（Pinus sylvestris var. mongolica）人工林（15、24和30年生）为对象,研究草地造林对土壤pH,土壤C、N、P含量,无机N（铵态氮、硝态氮）含量,C、N矿化速率,微生物生物量C含量以及土壤酶（脲酶、转化酶和过氧化氢酶）活性的影响.结果表明：草地造林初期,林地土壤C、N、P含量逐渐降低,随着林龄增加而逐渐恢复;与草地相比,24年生樟子松人工林土壤C、N、P含量最低,分别下降29%、34%和33%,而30年生樟子松人工林土壤C和N含量与草地差异不显著.草地造林能够影响土壤无机N存在形式,使土壤铵态氮含量逐渐增加,硝态氮含量下降.草地造林对土壤潜在N矿化速率和硝化速率影响不显著,但能够改变土壤C矿化速率,不同林龄樟子松人工林土壤C矿化速率依次为：24年生>30年生>草地>15年生.草地造林初期,土壤微生物生物量C含量和土壤转化酶活性明显降低,随着林龄的增加又逐渐增加;草地造林对土壤脲酶活性影响不显著,而使土壤过氧化氢酶活性逐渐增加.科尔沁沙地草地造林能够显著改变土壤化学和生物学性状,且随着林龄的变化而有所差异.     

Swimming ability and burrowing time of two cirolanid isopods from different levels of exposed sandy beaches

Most of the macroinfauna from sandy beaches is highly mobile, emerging out of the sediment when the tide rises, and using the swash to migrate up and down the beach face or feed (searching for prey or carrion). After swash excursions, they usually burrow back into the sediment, maintaining zonation at low tide. Therefore, the different species abilities to emerge, move around and burrow under different swash climates and sediment conditions are expected to influence observed distribution patterns. Nonetheless, few attempts have been made to understand behavioral mechanisms of these organisms in moving fluids.In this study, we used a flume tunnel to investigate the orientation, swimming ability and burrowing time of two similar species of cirolanid isopods, Excirolana armata Dana and Excirolana braziliensis Richardson, under current velocities ranging from 5 to 30 cm·s⁻¹. E. armata inhabits middle levels of dissipative to intermediate beaches, while E. braziliensis is found towards the upper level of a wider range of beach states. Both species oriented countercurrent above a threshold velocity, which turned out to be significantly lower for E. armata than for E. braziliensis. E. armata proved to be a stronger swimmer as shown by the higher velocities surmounted, and the less drags experienced at the highest current velocity. E. armata also burrowed faster than E. braziliensis. Burrowing time was affected by sediment grain size and water content, but not by water flow. Once organisms managed to begin burrowing under different flow conditions, they were not affected by current velocity. Nonsaturated sand precluded burial, while coarse sand retarded it. Differences in the observed patterns of across-beach distribution may thus be the result of species-specific behavioral responses to swash climate, manifested in swimming ability, burying and orientation in directional flows.     

沙地土壤种植杨树-刺槐混交林后持水特性变化的研究

通过对比法研究了沙地土壤种杨树刺槐混交林后持水特性的变化。结果表明,沙地土壤种植杨树,刺槐纯林和混交林后,土壤持水特性,孔隙分布状况和水容量得到了改善和提高,提高和改善的幅度均以混交林最大,无林地植被覆盖后土壤持水性能改善的根本原因在于土壤有机质含量的增加,从而改善了土壤的孔隙状况。     

科尔沁沙地围封沙质草甸土壤种子库特征的研究

科尔沁沙地沙质草甸围封 5年后土壤种子库中植物种类有 38种 ,其中一、二年生草本植物 2 4种 ,多年生草本植物 9种 ,灌木 5种。土壤种子库密度为 (1385 5± 16 5 1)粒·m-2 ,其中 ,一、二年生草本植物所占的比例最大为 96 5 8% ,前 5种一、二年生草本植物黄蒿、灰绿藜、猪毛菜、狗尾草和画眉草占总数的 87 2 0 % ,而多年生草本植物和灌木类种子库密度分别占0 94 %和 2 4 8%。若以单子叶和双子叶植物统计 ,单子叶植物种子数占 13 13% ,双子叶植物的种子数占 86 87% ,其中豆科植物仅占 2 83%。土壤种子库中所有植物种的密度与其相对应的地面植物种的密度呈显著非完全相关性 ,其关系可用三次曲线来表示。从种子库组成分析 ,已围封 5年的沙质草甸植被仍处在黄蒿 -杂类草混合植被阶段。