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1.
    
The increasing number of stresses on coastal dune ecosystems requires the use of more effective restoration strategies to enhance dune‐building and increase vegetation reestablishment. In this study, the use of a wheat straw as a surrogate wrack was an effective method to improve growth of spring planted Uniola paniculata (sea oats). Approximately 1,000 U. paniculata plugs were planted within 21 × 4 m plots at six replicate sites. Two weeks later, plantings were divided into 11 × 4 m subplots with half of the subplots receiving five bales of wheat straw and the remaining subplots receiving no wheat straw. This surrogate wrack layer measured approximately 10 cm in depth. Mean aboveground biomass of U. paniculata 6 months after planting with surrogate wrack was 9.25 ± 1.00 g compared with 2.18 ± 0.24 g without surrogate wrack. Number of tillers, tiller height, and basal width were also greater at the end of the first growing season for plants treated with surrogate wrack (p < 0.05). Two years after planting, significantly more inflorescences occurred and aboveground biomass (g/m2) was greater with than without surrogate wrack. Sand accumulation was notably greater with surrogate wrack (11.16 cm) than without wrack (7.78 cm) 8 months after planting (p = 0.1093). However, relative sand accumulation was significantly greater with than without surrogate wrack 2 years after planting. Increased sand accumulation suggests surrogate wrack either directly or indirectly traps more sand by creating an additional obstacle or promoting the growth of dune grasses.  相似文献   

2.
    
Due to their position at the land–sea interface, barrier islands are vulnerable to both oceanic and atmospheric climate change‐related drivers. In response to relative sea‐level rise, barrier islands tend to migrate landward via overwash processes which deposit sediment onto the backbarrier marsh, thus maintaining elevation above sea level. In this paper, we assess the importance of interior upland vegetation and sediment transport (from upland to marsh) on the movement of the marsh–upland boundary in a transgressive barrier system along the mid‐Atlantic Coast. We hypothesize that recent woody expansion is altering the rate of marsh to upland conversion. Using Landsat imagery over a 32 year time period (1984–2016), we quantify transitions between land cover (bare, grassland, woody vegetation, and marsh) and the marsh–upland boundary. We find that the Virginia Barrier Islands have both gains and losses in backbarrier marsh and upland, with 19% net loss from the system during the timeframe of the study and increased variance in marsh to upland conversion. This is consistent with recent work indicating a shift toward increasing rates of landward barrier island migration. Despite a net loss of upland area, macroclimatic winter warming resulted in 41% increase in woody vegetation in protected, low‐elevation areas, introducing new ecological scenarios that increase resistance to sediment movement from upland to marsh. Our analysis demonstrates how the interplay between elevation and interior island vegetative cover influences landward migration of the boundary between upland and marsh (a previously underappreciated indicator that an island is migrating), and thus, the importance of including ecological processes in the island interior into coastal modeling of barrier island migration and sediment movement across the barrier landscape.  相似文献   

3.
    
The continued increase in the number of tourists visiting the Northern Gulf Coast (NGC), USA, in the last century, and the resulting sprawl of large cities along the coast, has degraded and fragmented the available habitat of Arctosa sanctaerosae, a wolf spider endemic to the secondary dunes of the white sandy beaches of the NGC. In addition to anthropogenic disturbance to this coastal region, hurricanes are an additional and natural perturbation to the ecosystem. The data presented here explore the status of populations of this species spanning the entire known range and the factors influencing population demography including anthropogenic disturbance and severe tropical storms. Using microsatellite markers, we were able to document the genetic structure of A. sanctaerosae, including current and historic patterns of migration. These results combined with ecological and census data reveal the characteristics that have influenced population persistence: ecological variables affecting the recovery of the population clusters after severe tropical storms, genetic fragmentation due to anthropogenic disturbance, and their interaction. These findings demonstrate the significance that the high traffic beach communities of the NGC and their impact on the once intact contiguous dune ecosystem have on recovery after severe tropical storms. Contemporary modeling methods that compare current and historic levels of gene flow suggest A. sanctaerosae has experienced a single, contiguous population subdivision, and the isolates reduced in size since the onset of commercial development of the NGC. These results point to the need for monitoring of the species and increased protection for this endangered habitat.  相似文献   

4.
Hamburg is a small borough located in Berks County, Pennsylvania. During the 1940s and 1950s, crushed automobile battery casings, containing high levels of lead, were used as fill in and around Hamburg. Several of the fill areas were along the eastern bank of the Schuylkill River and the Schuylkill River Canal. To reduce exposure to human and ecological receptors, the United States Environmental Protection Agency (U.S. EPA) initiated actions at several of the fill areas. Remediation actions at three of these fill areas, the Berry Property, the Hamburg Playground City Playground, and the Port Clinton Avenue site, utilized native plants, slope stabilization, and soil caps.

The Berry Property consisted of a flat, wooded area adjacent to the river. The Hamburg Playground consisted of a steep wooded slope between the river and the parking lot for the municipal park. The Port Clinton Avenue site consisted of flat and sloped, wooded, and old-field areas between the canal and Port Clinton Avenue. At each of the three sites, some of the contaminated soils were excavated and the remainder was graded and capped. The clean soil cap was then covered with an erosion control mat, seeded with native grasses, and planted with native shrubs. At the Hamburg Playground and Port Clinton Avenue site, the existing trees and much of the existing vegetation were maintained to preserve the slope stability and the natural environment. Great care was taken to ensure community access to the municipal park. Some of the important considerations included retaining the existing trees, dealing with invasive species, maintaining the plants during a drought, and channeling storm-water runoff. The work was coordinated with the Hamburg Borough Council, the Schuylkill River Greenway Association, and the Pennsylvania Department of Environmental Protection (PADEP).

The actions resulted in a stabillized slope with channelized storm water to control erosion and protect the river, a clean soil and plant cover that eliminates exposure to human and animal receptors, and an aesthetically pleasing and usable area that meets the needs of the community and the local conservation/environmental organization.  相似文献   


5.
    
Throughout the northern Great Plains of North America, there are large tracts of vegetation‐stabilized aeolian dune fields; some have transformed from desert‐like conditions to grassland only within the last 200 years. Here, we examine how this transformation has affected vadose zone hydrology by comparing infiltration and soil moisture on stabilized and active dunes at a dune field in Saskatchewan, Canada. At one active and one stabilized dune, we measured soil moisture dynamics throughout the 2010 growing season with time‐domain reflectometry sensors installed at four depths down to 200 cm below the surface. We also acquired soil samples from two active and two stabilized dunes ten times throughout the 2010 growing season to measure soil moisture dynamics down to 500 cm below the surface. Results indicate that while soil moisture was elevated at 25 cm depth in the stabilized dunes during the 2010 growing season, below that level soil, moisture was significantly lower than the active dunes and also more variable down to 500 cm. A comparison of surface hydraulic conductivity between one active dune and one stabilized dune showed that it was more than one order of magnitude greater at the former, presumably due to the elevated levels of silt, clay, and organics at the surface of the stabilized dune, which reduce the infiltration rate. Overall, we interpret the main difference in soil moisture dynamics to be caused by the presence of transpiring vegetation, as well as changes in soil properties attributed to the establishment of vegetation. Therefore, the results of this study suggest that during dune stabilization, the establishment of vegetation reduces profile soil moisture recharge. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

6.
Abstract To interpret broad-scale erosion and accretion patterns and the expansion and contraction of shrub thickets in response to sea level rise for a coastal barrier system, we examined the fine-scale processes of shrub recruitment and mortality within the context of the influence of ocean current and sediment transport processes on variations in island size and location. We focused on Myrica cerifera shrub thickets, the dominant woody community on most barrier islands along the coastline of the southeastern USA. Observations suggest that M. cerifera, a salt-intolerant species, is increasing in cover throughout the Virginia barrier islands, yet rising sea level in response to climate change is increasing erosion and reducing island area. Our objective was to explain this apparent paradox using pattern–process relationships across a range of scales with a focus on ocean currents and sediment transport interacting with island characteristics at intermediate scales. Multi-decadal comparisons across scales showed a complex pattern. At the scale of the entire Virginia barrier complex, modest decreases in upland area were accompanied by large increases in shrub area. Responses were more variable for individual islands, reflecting inter-island variations in erosion and accretion due to differences in sediment transport via ocean currents. Several islands underwent dramatic shrub expansion. Only for within-island responses were there similarities in the pattern of change, with a lag-phase after initial shrub colonization followed by development of linear, closed canopy thickets. Understanding the fine-scale processes of shrub seedling establishment and thicket development, in conjunction with the influence of ocean currents and sediment transport, provides a framework for interpreting island accretion and erosion patterns and subsequent effects on shrub thicket expansion or contraction across scales of time and space.  相似文献   

7.
Summary A palynological investigation was conducted on sediments from three small floodplain swamps on upper Wollombi Brook in the Hunter Valley NSW in order to reconstruct pre-European riparian vegetation composition and community structure. Pre-European riparian plant communities on upper Wollombi Brook were characterized by wet sclerophyll forest associations with rainforest elements (most likely close to the channel). Major changes in both the nature and extent of riparian vegetation have been associated with European settlement. The pre-European pollen spectra assists the identification of a suite of native taxa potentially suitable for use in riparian revegetation operations, particularly in highly cleared streambank sites where protection of water quality and aquatic habitat is an important goal but where insufficient local remnants are available to indicate pre-existing plant species. The research emphasizes the use of palaeoenvironmental evidence as a tool for contemporary environmental management.  相似文献   

8.
试验于2001年8月17日至9月30日在中国科学院沙坡头沙漠试验研究站进行,主要利用时域反射仪(TDR)连续测量土壤剖面水分含量的方法,观测受植物根系吸水,蒸散作用影响下的人工植被荒漠灌木柠条(Caragana korshinskii)群落区固定沙丘降水入渗与再分配过程。土壤体积含水率由水平埋设在植物根系剖面内12个深度层次(5~200cm)的时域反射仪探头每小时自动测定1次。天然降水条件下的土壤入渗速率由入渗深度与相应的入渗时间之比值计算得到。结果表明:在7次不连续降水过程中,土壤入渗速率与降水强度呈简单线性相关关系,土壤入渗速率约为降水强度的10倍强。然而当次降水过程中降水强度小于0.46mm/h时,土壤入渗速率约为0cm/h,此时的降水对人工植被固定沙丘区的土壤基本上没有水分补给作用。受荒漠灌木柠条根系吸水作用的影响,其根系密集剖面深度40~140cm内降水水分入渗积累不明显。降水入渗速率及入渗深度受土壤剖面初始含水率多寡而变化,干燥土壤剖面有助于提高入渗速率及入渗深度。降水以后随着时间的推移,区域环境内空气温度、湿度等气象条件适宜,柠条生长进入相对旺盛阶段,其根系密集层140cm深度处土壤含水率在总体上下降的过程中,表现出昼消夜长的趋势,翌日8:00土壤含水率值略高于前一日20:00水分值0.1%~0.3vol.%。  相似文献   

9.
    
Aim To document long‐term rates of immigration, extinction and turnover in insular floras and evaluate the relative impacts of recent hurricane activity and climate change. Location Three archipelagos of small islands, in the Exuma Cays, Andros and Abacos, Bahamas. Methods I surveyed the floras of 194 vegetated islands in three archipelagos over several multi‐year periods, spanning up to 17 years. Changes in abundance (foliar cover) of persistent populations were measured on a subset of 14 islands in the Exuma Cays over a 9‐year period. Results Rates of plant turnover were generally low compared with other organisms, but varied among archipelagos and time periods. Turnover rates were usually higher in the second decade of this study, and extinction rates were often dramatically higher than immigration rates in the second decade, resulting in overall decreases in species richness. Turnover did not differ significantly among island types based on generalized location and surrounding water depths, and extinctions were not more likely to occur on more exposed islands. The abundance (foliar cover) of populations that did not go extinct decreased steadily over the second decade of this study, indicating, along with higher extinction rates, a generalized decline in these insular floras. Main conclusions Although some islands may have been at or near a state of dynamic equilibrium in the first decade of this study, average species richness declined in all three archipelagos during the second decade, when extinctions greatly outnumbered immigrations. Four major hurricanes affected the study archipelagos in the second decade of this study, although the available evidence suggests that the hurricanes were not directly responsible for the declines. Indirect effects of hurricanes such as increased herbivory and possible decreased nutrient availability, along with a long‐term (25 years) increase in temperature and decline in rainfall are likely contributing factors.  相似文献   

10.
    
Aim To document long‐term rates of immigration, extinction and turnover in insular ant faunas and evaluate the relative impacts of recent hurricane activity and climate change. Location Small islands in the Exuma Cays, Andros and Abaco archipelagos of the Bahamas. Methods I surveyed the ant faunas of > 140 small islands in three archipelagos of the Bahamas over several multi‐year periods, spanning up to 17 years, by recording species attracted to baits. Immigrations, extinctions and species turnover were documented, as were the relative abundances of species. Four major hurricanes affected the study archipelagos in the second decade of this study. Results Rates of ant turnover were generally low among archipelagos and time periods. Immigrations outnumbered extinctions in the first decade of this study, although this pattern was reversed in the second decade. General physical characteristics of the islands were not significant predictors of the occurrence of extinctions. The relative abundance (based on proportion of baits occupied) of persistent populations of the two most common species both declined in the second decade, indicating, along with higher extinction rates, a generalized decline in these insular ant faunas. Main conclusions The available evidence suggests that hurricanes were not directly responsible for the observed declines in the ant faunas. Regional changes in insular ant species richness, however, are correlated with generalized North Atlantic hurricane activity over the last half century. Indirect effects of hurricanes on the vegetation of these islands, such as increased herbivory and possible decreased nutrient availability, along with a long‐term (quarter century) increase in temperature and decline in rainfall, are possible contributing factors to the changing ant turnover dynamics.  相似文献   

11.
人工樟子松—差不嗄蒿植被及其固沙作用   总被引:4,自引:2,他引:4  
李进 《生态学杂志》1992,11(3):17-21,27
植物固沙是整治沙漠和沙漠化土地的一种有效措施。人工植被的建立是植物固沙的必然结果。人工植被的演替、稳定性及其对环境的影响直接关系到流沙的固定程度。因此,本文旨在探讨人工樟子松(Pinus sylvestris var.  相似文献   

12.
    
Aim To investigate species compositions, rates of species turnover, species–area and species–distance relationships and patterns of nestedness in the floras of small Bahamian islands, by comparing two groups of islands that had been differentially affected by two hurricanes. Location Small islands occurring on either side of Great Exuma near Georgetown, Bahamas. Methods We surveyed the plant species of 44 small islands over a 5‐year period from 1998 to 2002. Hurricanes Lili and Michelle occurred in 1996 and 2001, respectively; both storms affected small islands on the more exposed south‐west side of Great Exuma to a greater degree than small islands on the more protected north‐east side. A set of 27 islands was surveyed in 1998 and 2002 to evaluate species turnover. Stepwise multiple linear regression analyses and an information‐theoretic approach (the Akaike information criterion) were used to elucidate the importance of area and distance as predictors of plant species number. We compared a piecewise linear regression model with a simple linear regression of species number against area to determine whether a small island effect existed. Nestedness patterns were evaluated by Wilcoxon two‐sample tests to analyse occurrence sequences. Results Species turnover was low in an absolute sense (overall = 0.74% year?1), yet was over three times higher than that documented in a nearby archipelago in the absence of hurricanes. Both vegetated area and distance were important predictor variables for exposed islands but not for protected islands. Some support was found for a small island effect for the exposed islands based on a piecewise linear regression model. Both island groups revealed significant nestedness at the level of the assemblage (both P < 0.001). On exposed islands, 65–79% (depending upon the method of calculation) of all species were significantly nested, but only 47% of all species were significantly nested on protected islands. Main conclusions Overall, these insular floras seem highly resistant to hurricane‐force disturbances. Species turnover was low (< 1% year?1) in an absolute sense, particularly in comparison with rates for other taxa. Higher degrees of nestedness and significant species–area and species–distance relationships for exposed islands indicated stronger patterns of community assembly. It is likely that disturbance is a major structuring force for the exposed islands, although the type of disturbances that mediate these patterns may not be primarily hurricane‐force storms.  相似文献   

13.
Plant populations were reintroduced to the coastal dune bar of the Devesa de Albufera from 1988 to 2004; different coastline sections received different species composition and cover. With the aim to detect spatial and temporal variation of floristic diversity, we compared current species composition and cover across the length of the Devesa and across the dune bar with those imposed at the time of restoration. Non-metric multidimensional scaling (NMDS) detected significant differences both across the dune faces and across the coast sections. Differences across the dune faces reflect the sea-inland ecological gradient and resulted from a spatial rearrangement of plant populations: Calystegia soldanella, Achillea maritima and Polygonum maritimum prefer the windward face; Malcolmia littorea and Lagurus ovatus the leeward. Differences across coast sections are related to those at restoration time, with a slow trend towards the homogenization of plant communities. At the current level of anthropic pressure, the plant cover is likely to evolve following the trends pointed out in this research.  相似文献   

14.
杨淑萍  危常州  梁永超 《生态学报》2010,30(9):2322-2331
采用水培试验,分析了不同浓度的NaCl(0、50、100、150、200、250 mmol.L-1)处理对两个海岛棉品种新海28号(XH28,耐盐基因型)和新海21号(XH21,盐敏感基因型)植株生长、生物量分配、蛋白质含量、脯氨酸(Pro)含量以及过氧化物酶(POD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)等生理生态指标的影响。研究发现:(1)盐胁迫对海岛棉幼苗鲜重的影响大于干重,对茎叶的影响大于根系;(2)盐处理引起海岛棉幼苗根叶脯氨酸含量的增加;(3)低浓度NaCl处理(≤50 mmol.L-1)显著增加耐盐品种XH28的根长、株高及单株鲜干重;(4)盐胁迫引起海岛棉幼苗根系中可溶性蛋白质含量下降,相反叶片中可溶性蛋白质含量上升;(5)盐胁迫下耐盐品种XH28幼苗中的POD、CAT、APX酶活性明显高于盐敏感品种XH21,但GR活性显著低于XH21。研究表明,低浓度NaCl处理刺激了棉株生长,增加了生物量;盐胁迫下叶内蛋白质、脯氨酸含量明显增加,POD、CAT、APX酶活力升高是海岛棉耐盐品种XH28的基本特征。  相似文献   

15.
16.
A survey of soils and trees was conducted on Syunkunitai coastal sand dune in eastern Hokkaido to clarify the relationships between the soil properties and the plant cover type. A belt transect of 360m in length was established across the dune. Three community types, that is, a Picea glehnii forest, an Abies sachalinensis forest, and a salt marsh were recognized. Soil types at the study area were determined to be sandy immature soil and peat soil. Their horizon sequences were described as A0–V–C or T–V–C layers (A0, T, V, and C indicate layers of leaf litter, peat, volcanic deposit, and parent material, respectively). The Abies sachalinensis forest was characterized by a relatively high calcium concentration in the surface soil layer and a tendency for podzolization in the volcanic deposit layer. The Picea glehnii forest was characterized by peat accumulation because of the high ground water table, volcanic deposits in the soil profile, and the strong influence of sea salt on the soil chemistry. The roots in the Picea glehnii forest were distributed more shallowly than those in the Abies sachalinensis forest, thus avoiding the high water table level as well as the influence of seawater in the soil. The salt marsh showed an extremely high sodium concentration and base saturation, indicating that this area was directly affected by seawater. Recently, the periphery of the Picea glehnii forest on Syunkunitai sand dune has been declining because of seawater inundation caused by ground subsidence.  相似文献   

17.
The vertical flux of water, ammonium, and phosphatewas measured from two developing barrier islandmarshes; Hog Island, VA (1.3 m tidal range) andPritchards Island, SC (2.5 m tidal range). Verticalflow and nutrient concentrations from the deposit weremeasured using seepage meters placed on the surface ofthe marsh. Measured water flow was not significantlydifferent between the sites (average = 60.1 and 57.4l m-2h-1for the VA and SC marsh). Verticalflow, calculated from piezometric head gradients andhydraulic conductivity, only accounted for 15 and 4%of measured flow at the VA and SC marshes,respectively. Horizontal flow, calculated as thedifference between measured total flow and calculatedvertical flow, was larger at the SC marsh. Therefore,tidal range seems to influence the direction(horizontal vs. vertical), but not the magnitude oftotal water flow from these developing marshes.Despite a lower tidal range, phosphate flux wassignificantly higher at the VA marsh (69 mmol m-2yr-1) relative to the SC marsh (11 mmol m-2yr-1) probably because of higher porewaterphosphate concentrations. Measured ammonium flux wasnot significantly different between the sites (194 and174 mmol m-2yr-1for the VA and SC marsh).Nutrient concentration must be considered togetherwith tidal range when assessing nutrient export. Thisstudy represents one of few that quantify nutrient andwater export from naturally-developing marshes.Although young marshes are thought to export smallquantities of nutrients and other materials, rates ofnutrient export from these developing marshes weresimilar to rates measured in older marshes. Therelatively high export rates from these developingmarshes were attributed to high rates of subsurfaceflow and high nutrient input from a buried marsh ormudflat located one meter below the present marshsurface. These results have implications fordevelopment of created or restored marshes especiallywhere the goals of those activities are to maximizewetland functions such as nutrient exchange.  相似文献   

18.
长春花(Catharanthus roseus)是夹竹桃科的一种亚灌木植物,具有重要的药用价值和观赏价值,在前期的试验性种植中,发现长春花对热带珊瑚岛环境有很强的适应性。为了探讨长春花对热带珊瑚岛环境的生理生态适应性,该文以移植到热带珊瑚岛的长春花和生长于海南省文昌市苗圃的长春花为研究对象,对其叶片的形态解剖结构、生理学特征、营养元素含量等进行了分析。结果表明:(1)与苗圃生长的长春花和其他耐胁迫的植物相比,移植到热带珊瑚岛上的长春花具有叶片厚、栅栏组织发达、比叶面积小等形态解剖特征,这些特征有利于其光能吸收、水分储存和对环境资源的利用。(2)长春花的超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性较高,表现出较强的抗氧化性和抗胁迫能力。(3)长春花的叶绿素a和叶绿素b含量较低,可以减少过多的光能进入叶绿体光合系统,防止过剩的光能对光合系统产生伤害。(4)热带珊瑚岛土壤养分含量低,但生长在岛上的长春花叶片的营养元素含量高,表现出很强的养分吸收和利用能力。因此,长春花对干旱、贫瘠等恶劣生境具有很好的适应能力,可以作为热带珊瑚岛植被恢复工具种。  相似文献   

19.
以海岛棉‘新海21号’为试验材料,根据陆地棉GhTCP14基因序列,设计1对引物,通过RT-PCR技术获得海岛棉GbTCP14核苷酸序列,开放阅读框长1 221bp,编码406个氨基酸,分子式C1892H2950N572O620S16,预测分子量为44.134 6kD,等电点为6.88,氨基酸序列包含1个高度保守的TCP结构域及4个低丰度复杂区。GbTCP14蛋白氨基酸序列与其他物种TCP14氨基酸序列比对表明,海岛棉GbTCP14蛋白与其他植物中的TCP14蛋白共同具有一个高度保守的TCP结构域,序列之间的一致性较高。进化树分析表明,海岛棉GbTCP14基因与木本棉GaTCP14基因分布在同一分支上。实时荧光定量PCR表明,海岛棉GbTCP14基因在开花后第15天时表达量最高,在第5~20天时相对表达量比其他时期较高,第25天时相对表达量最低。在不同组织中花瓣和花萼中表达量较高,根和茎中表达量一般,叶组织中表达量最低。通过酵母系统转录激活分析显示,GbTCP14蛋白不具有转录活性。  相似文献   

20.
《Science activities》2013,50(4):133-136
Profiling landforms actively involves students in measuring the topography of landforms such as beaches, hillsides, and stream embankments. In this activity, the author describes how to set up an inquiry situation in which students can ask questions, seek answers, and develop explanations about seasonal or weather-related changes in the landscape.  相似文献   

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