Roadfill Revegetation in Semiarid Mediterranean Environments. Part II: Topsoiling, Species Selection, and Hydroseeding

Erosion is one of the main problems in roadfill restoration. Revegetation is widely used as a method to reduce erosion rates, and it is often carried out through hydroseeding. In semiarid Mediterranean conditions, this approach to revegetation often produces poor results due to climatic limitations. We evaluated whether (1) spreading topsoil and (2) hydroseeding with local rather than commercial species mixtures could improve the vegetative cover of roadfills. The study was carried out in 24 plots over a 20‐month period. At the end of the study, vegetation cover was higher in topsoiled plots (38.8%) than in nontopsoiled plots (21.5%). Locally selected species produced higher vegetative cover (61.1%) than did standard commercial species (52.2%). After 20 months, the erosion index was not different among any treatment probably due to the low sensitivity of this variable. These results suggest that amendment of soils through the addition of topsoil is an important technique in roadfill revegetation in Mediterranean environments. Additionally, hydroseeding with local species will produce better vegetative cover on roadfills than does hydroseeding with available commercial species.     

Factors Affecting Revegetation of Oil Field Access Roads in Semiarid Grassland

We assessed vegetation recovery on access roads removed after well abandonment in an active oil‐producing region of northern Great Plains grasslands. We compared extant vegetation on 58 roads, restored 3–22 years previously, to records of species seeded on each and to adjacent, undisturbed prairie, to evaluate main differences between the restored and adjacent community and to explore patterns in the restored plant community over time. The restored plant community was dominated by low richness of seeded non‐native and native grasses and forbs, whereas adjacent prairie had numerous, abundant native graminoids and shrubs and higher richness of native forbs. Cover of seeded species on roads was double that of colonizing species. Disparity in cover of dominant native grasses between the adjacent community and relatively narrow restored roadway suggests that conditions for germination and survival in roadbeds are poor. This is at least partly due to persistence of seeded species. Differences in restored plant composition over time were best explained by changes in species seeded, from non‐natives to natives, and secondarily by successional shifts from ruderal to perennial non‐seeded species. Of the 30 species seeded at least once on these roads, only 10 were commonly used. The long‐term influence of seeding choices in grassland road restorations implies that improvements in these practices will be critical to reversing ecological impacts of roads.     

油菜3个栽培种发芽期耐盐性评价

对油菜种质资源进行耐盐性评价是培育耐盐油菜品种的基础性工作。本研究在室内分别采用3种盐(NaCl)浓度(86 mmol/L、170 mmol/L、256 mmol/L)对芥菜型油菜(Brassica juncea)、白菜型油菜(B.rapa)和甘蓝型油菜(B.napus)等3个栽培种的203份种质资源进行盐胁迫,结果表明盐胁迫对各栽培种的发芽率有不同程度抑制作用,白菜型油菜表现最好,甘蓝型油菜次之,芥菜型油菜最差。基于发芽率筛选出14份优异种质。进一步利用梯度浓度盐(NaCl)溶液对其进行胁迫,发现各栽培种发芽率均随着盐浓度的升高呈下降趋势,符合Boltzmann曲线,但白菜型油菜下降最为缓慢。通过比较盐胁迫下各栽培种6个性状值(胚轴长、根长、总鲜重、地上部分鲜重、总叶绿素含量和电导率)后发现,白菜型油菜发芽期耐盐性优于甘蓝型油菜和芥菜型油菜。对170 mmol/L NaCl胁迫下14份种质各性状值的主成分分析表明,白菜型油菜Br2、甘蓝型油菜Bn1和Bn3为最耐盐种质,可用于耐盐油菜品种的培育。     

The Potential Role of Stream Habitat Restoration in Facilitating Salmonid Invasions: A Habitat‐Hydraulic Modeling Approach

Many successful invasions have taken place in systems where harmful disturbance has changed habitat conditions. However, less attention has been paid to the role of habitat restoration, which modifies habitats and thus also has the potential to facilitate invasions. We examined whether in‐stream habitat restorations have the potential to either facilitate or resist invasion by two widely introduced non‐native stream salmonids, Salvelinus fontinalis Mitchill and Oncorhynchus mykiss Walbaum, in Finland. A physical habitat simulation system was used to calculate whether the habitat area for the target species increased or decreased following the restorations. For comparison, we also reported results for four native stream fish species. The simulations showed that the restored streams provided the highest amount of usable habitat area for the native species, particularly for Salmo salar L. and Gottus gobio L. However, it was interesting to note that the restorations significantly increased habitat quality for the two non‐native species, especially at low flows. Nevertheless, the non‐native species had the lowest amount of usable habitat area overall. The modeling results indicated that not only habitat destruction but also habitat restoration could contribute to the spread of non‐native species. Fisheries and wildlife managers should be aware of the possibility, when restoring habitats in order to preserve native ecosystems, that non‐native species could manage to gain a foothold in restored habitats and use them as population sources for further spread. Knowing the widespread negative effect of non‐native species, this risk should not be underestimated.     

Invasive plant feedbacks promote alternative states in California vernal pools

Invasive species have the potential to create positive feedbacks and push an ecosystem into an alternative state through a variety of mechanisms. Unless the drivers behind these feedbacks are understood, restoring a system to a more desirable state may not be possible. We used a long‐term vernal pool restoration project based out of Travis Airforce Base, Fairfield, CA, U.S.A. to examine natural pools dominated by either invasive or native plant communities, and restored pools predominately composed of invasive plants. We determined that plant community structure is drastically altered towards invasive grasses with the addition of a single centimeter of litter. In the absence of this litter layer, community structure was driven by a non‐native forb rather than native species. We also found that native plant‐dominated vernal pools have a longer inundation duration and are deeper compared to invasive‐dominated pools, regardless of construction status. These results suggest that once invasive grasses establish through lower inundation depths, their litter deposition can initiate a positive feedback to maintain an invasive alternative state. However, even after litter removal, non‐native forbs can replace the grasses causing a second alternative state still separate from the most desirable native dominated state. This study directly demonstrates that invasive species, and their positive feedbacks, may limit the success of ecological restoration. To effectively restore a system all constraints must be identified and removed before successful restoration can occur.     

Reducing Biotic and Abiotic Land‐Use Legacies to Restore Invaded,Abandoned Citrus Groves

Land‐use legacies associated with agriculture, such as increased soil fertility and elevated soil pH, promote invasions by non‐native plant species on former agricultural lands. Restoring natural soil conditions (i.e. low fertility and low pH) may be an effective, long‐term method to control and reduce the abundance of non‐native and ruderal species that invade abandoned agricultural lands. In this study, we examined how soil manipulation treatments of lowering soil fertility with carbon additions and lowering soil pH by applying sulfur affect non‐native and ruderal native plant species abundance in two former citrus groves in central Florida. Non‐native plant biomass was removed by one of two methods (tilling or topsoil removal), and was combined with a soil amendment of sulfur, carbon, sulfur + carbon, or none. The biomass removal treatments significantly decreased non‐native abundance, with topsoil removal as the most effective. Carbon additions did not affect soil fertility or vegetation. Sulfur and sulfur + carbon additions significantly decreased soil pH in both groves for at least 1 year post‐treatment; however, we did not see a significant vegetation response. Overall, our results suggest that removing vegetation by tilling and topsoil removal is an effective method for reducing non‐target species cover. Although we did not see a response of vegetation to our treatments, we were able to restore the initial soil characteristics, which can be a first step toward complete restoration.     

青藏高原高寒草甸罂粟科植物种子萌发特性研究

对9种罂粟科植物种子在5个温度(5℃、10℃、15℃、20℃、25℃)下的萌发特性进行了研究.结果显示:(1)采自低海拔的小果博落回、秃疮花和白屈菜在15～25℃的萌发率高于5～10℃;采自高海拔的全缘叶绿绒蒿和多刺绿绒蒿达到最大萌发率的温度分别为5℃和10℃;而采自高海拔的红花绿绒蒿和五脉绿绒蒿只有通过5℃冷处理后才能萌发,表明种子的最佳萌发温度与采集地海拔相关.(2)萌发速率随温度升高增大,秃疮花和苣叶秃疮花在25℃萌发速率最大,其余种25℃的萌发速率略小于20℃的萌发速率.(3)萌发时滞表现出随温度升高而缩短的趋势,秃疮花、白屈菜和苣叶秃疮花在25℃萌发时滞最短,其余种25℃萌发时滞又长于20℃萌发时滞.(4)一年生植物多刺绿绒蒿在所有温度下的萌发率和萌发速率均最高,而萌发时滞最短,这可能是一年生植物适应特殊环境的一种对策.     

Restoration of Wet Fen Meadows by Topsoil Removal: Vegetation Development and Germination Biology of Fen Species

The present investigation was part of a fen restoration project, which deals with the rehabilitation of a deeply drained peat land used for intensive agriculture for more than 200 years. Consequently, the conditions for restoration are unfavorable. The hay of well‐developed fen meadows from nature reserves in the region appeared to contain enough viable seeds to act as a source for the development of target communities when spread out on bare peat after topsoil removal. Repeated vegetation analysis showed that a combination of topsoil removal and hay transfer resulted in the establishment of new populations in the target area for 70% of the species of the donor area. Germination conditions of fen species were investigated to determine the optimal combination for stimulating germination rates. Most fen species were found to be dormant, and it was shown that dormancy could be broken with fluctuating light and temperature cycles and stratification pre‐treatment.     

Food Resource Partitioning between Two Invasive Gobiid Species (Pisces,Gobiidae) in the Littoral Zone of the River Danube,Hungary

At present, the invasive round and bighead gobies are the most abundant benthic fish species in the near shore zone of the Middle Danube. We compared their diet seasonally in natural and artificial habitats and contrasted it with the food supply. The composition of the macroinvertebrate community was determined mainly by seasonal changes, whereas habitat type had smaller effect. Round gobies followed these changes flexibly. They consumed mainly chironomids in the spring, whilst amphipods and molluscs in the summer and autumn. Bighead gobies relied on amphipods in each season and in both habitats, and consumed fish, too, including round goby (intraguild predation). Diet overlap was determined by the morphological differences of the species allowing a varying degree of differentiation according to the seasonally changing food supply. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

南亚热带森林木本植物种子萌发和储存

研究了南亚热带森林 90种木本植物的种子和果实的大小、含水量等特征及种子萌发 ,并对其中有足够萌发个体的种 (45种 )进行了萌发分析和对有足够萌发个体和足够种子的种 (41种 )进行了种子或果实储存对萌发影响的研究。肉质果实种子和肉质种子萌发率较干燥种子高 ,两者差异显著。大多数种播种 6 0d内萌发。肉质果实的种子和肉质种子较干燥种子的休眠期长 ,留土萌发种子较出土萌发种子休眠期长。大种子种与小种子种之间、夏季成熟的肉质果实的种子与冬季和春季成熟的肉质果实的种子之间休眠期长短差异不显著。萌发率与新鲜种子含水量无显著的相关 ,但种子中水分含量的减少明显影响萌发率 ,尤其是在种子自然干燥的最初 3d。当种子的水分含量减至 2 0 % (约在种子自然干燥 10～ 14d)时 ,种子萌发率降至很低。萌发率随储存时间 (密封 ,(4± 1)℃ )而下降 ,但储存一个月下降不大 (- 8.3% ) ,储存 3个月后 ,显著下降。果实储存与种子储存之间、大种子种与小种子种储存之间、肉质果实的种子和肉质种子储存与干燥种子储存之间 ,萌发率差异一般不显著。     

南亚热带森林木本植物种子萌发和储存

研究了南亚热带森林90种木本植物的种子和果实的大小、含水量等特征及种子萌发,并对其中有足够萌发个体的种(45种)进行了萌发分析和对有足够萌发个体和足够种子的种(41种)进行了种子或果实储存对萌发影响的研究.肉质果实种子和肉质种子萌发率较干燥种子高,两者差异显著.大多数种播种60 d内萌发.肉质果实的种子和肉质种子较干燥种子的休眠期长,留土萌发种子较出土萌发种子休眠期长.大种子种与小种子种之间、夏季成熟的肉质果实的种子与冬季和春季成熟的肉质果实的种子之间休眠期长短差异不显著.萌发率与新鲜种子含水量无显著的相关,但种子中水分含量的减少明显影响萌发率,尤其是在种子自然干燥的最初3 d.当种子的水分含量减至20%(约在种子自然干燥10～14 d)时,种子萌发率降至很低.萌发率随储存时间(密封,(4±1) ℃)而下降,但储存一个月下降不大(-8.3%),储存3个月后,显著下降.果实储存与种子储存之间、大种子种与小种子种储存之间、肉质果实的种子和肉质种子储存与干燥种子储存之间,萌发率差异一般不显著.     

Identifying potentially invasive non‐native marine and brackish water species for the Arabian Gulf and Sea of Oman

Invasive non‐native species (NNS) are internationally recognized as posing a serious threat to global biodiversity, economies and human health. The identification of invasive NNS is already established, those that may arrive in the future, their vectors and pathways of introduction and spread, and hotspots of invasion are important for a targeted approach to managing introductions and impacts at local, regional and global scales. The aim of this study was to identify which marine and brackish NNS are already present in marine systems of the northeastern Arabia area (Arabian Gulf and Sea of Oman) and of these which ones are potentially invasive, and which species have a high likelihood of being introduced in the future and negatively affect biodiversity. Overall, 136 NNS were identified, of which 56 are already present in the region and a further 80 were identified as likely to arrive in the future, including fish, tunicates, invertebrates, plants and protists. The Aquatic Species Invasiveness Screening Kit (AS‐ISK) was used to identify the risk of NNS being (or becoming) invasive within the region. Based on the AS‐ISK basic risk assessment (BRA) thresholds, 36 extant and 37 horizon species (53.7% of all species) were identified as high risk. When the impact of climate change on the overall assessment was considered, the combined risk score (BRA+CCA) increased for 38.2% of all species, suggesting higher risk under warmer conditions, including the highest‐risk horizon NNS the green crab Carcinus maenas, and the extant macro‐alga Hypnea musciformis. This is the first horizon‐scanning exercise for NNS in the region, thus providing a vital baseline for future management. The outcome of this study is the prioritization of NNS to inform decision‐making for the targeted monitoring and management in the region to prevent new bio‐invasions and to control existing species, including their potential for spread.     

Comparisons of Mycorrhizal Responsiveness with Field Soil and Commercial Inoculum for Six Native Montane Species and Bromus tectorum

Reestablishing native perennial plants and reducing invasive species are pivotal for many ecological restoration projects. The interactions among plant species, arbuscular mycorrhizal fungi, and soil P availability may be critical determinants of the success of native and non‐native plants in restoration and species invasions. Here we assessed mycorrhizal responsiveness for three late‐successional and three early‐successional plant species native to Rocky Mountain National Park and for the non‐native Downy brome, cheatgrass (Bromus tectorum L.) using field soil and commercial inoculum. Factorial greenhouse experiments were conducted to compare biomass of plant species with and without field soil and commercial inoculum treatments along a phosphorus (P) gradient, which ranged from ambient field levels to 12% of field levels, using dilutions of native soils. The two field soil inoculum treatments resulted in significant biomass differences for all species studied. Late‐successional species responded positively to field inoculum, whereas early‐successional species responded negatively. The two commercial inocula had low colonization rates (14 of 166 inoculated plants). The commercial inocula substrates had significant treatment effects on five of seven species included in the study in the apparent absence of mycorrhizal symbiosis. Soil P levels influenced mycorrhizal responsiveness in only one species, Smooth blue aster (Aster laevis L.). Our results show that, at least for the species studied here, locally collected field inoculum is the best choice for reestablishment of late‐successional native plant species.     

Establishment and Growth of Living Fence Species: An Overlooked Tool for the Restoration of Degraded Areas in the Tropics

Numerous tree species can establish by vegetative means in the tropics. Many are used in agriculture as living fences and in alley cropping and could also be used in a restorational setting. However, little is known about their establishment ability. This study evaluated the establishment ability and cover development of multiple species in three separate field trials in northern Honduras. First, 11 species were evaluated for their ability to establish in a common garden experiment. Second, of the former species, Bursera simaruba and Gliricidia sepium were evaluated for 2 years for their ability to establish vegetatively and develop cover at three deforested sites. Lastly, a study examined whether greater initial stake height and diameter at breast height increased the establishment success and crown development of G. sepium stakes. First, five species, Erythrina berteroana, Erythrina fusca, Jatropha curcas, G. sepium, and B. simaruba, had high establishment success. Others showed promise but may have been planted in the wrong season. Second, establishment for G. sepium was nearly 100% at all sites, whereas B. simaruba ranged from 30–50%. Gliricidia sepium stakes developed more rapidly and attained greater cover than B. simaruba. Dry season planting may increase the establishment success of both species. Lastly, greater initial stake height and diameter at breast height each resulted in greater crown development for G. sepium. The use of living fence species as a restorational tool has been overlooked. Aside from the advantages of planting tree species vegetatively, species can act as seed recruitment foci by attracting seed dispersers and provide shade to improve microclimatic conditions for seedling establishment. The technique described is simple and could have broad application throughout tropical regions.     

Climate controls the distribution of a widespread invasive species: implications for future range expansion

相似文献   

A Protocol for Integrated Management, Monitoring, and Enhancement of Degraded Themeda triandra Grasslands based on Plantings of Indicator Species

Abstract Lowland temperate grasslands dominated by Themeda triandra (kangaroo grass) are an endangered ecosystem in southeastern Australia. Grass biomass must be removed frequently to maintain plant diversity, but few studies of the impacts of different biomass removal techniques have been undertaken, and no rapid monitoring schemes have been developed. Low species densities in many reserves (due to past stock grazing) make it difficult to assess the effects of management regimes on plant diversity. Management impacts could be assessed by planting indicator species in replicated enhancement plots and subjecting these plots to adaptive management trials. A protocol for selecting potential indicator species is described, based on a regional quadrat database, using clearly defined criteria. Potential indicator species need to be conspicuous, easy to identify and abundant in high quality diverse grassland remnants, to have relatively broad ecological tolerances, to occur in sites that are relatively species rich and have a comparatively low cover of dominant exotic species, to commonly persist at low densities in long‐grazed reserves, to be responsive to changes in management, and to have been studied ecologically. Only three species from western Victorian grasslands satisfied these criteria: Calocephalus citreus (lemon beauty‐heads), Chrysocephalum apiculatum (common everlasting), and Leptorhynchos squamatus (scaly buttons). All are widespread, herbaceous, hemicryptophytic daisies. Despite a number of caveats, the scheme has the potential to provide a more clearly focused framework for grassland ecosystem management than currently exists.     

Distribution and range expansion of deer in Ireland

• 1 Throughout Europe, the range of many deer species is expanding. We provide current distribution maps for red deer Cervus elaphus, sika Cervus nippon, fallow deer Dama dama and muntjac deer Muntiacus sp. in Ireland, and estimates of range expansion rates for red deer, sika and fallow deer.
• 2 There was a considerable expansion in the ranges of red deer, sika and fallow deer between 1978 and 2008. The compound annual rate of expansion was 7% for red deer, 5% for sika and 3% for fallow deer. The total range increase was 565% for red deer, 353% for sika and 174% for fallow deer. The potential implications of these expansions are discussed.
• 3 There are unknown numbers of red‐sika hybrid deer in some parts of Ireland. Range expansion is likely to lead to further hybridizations with implications for the genetic integrity of deer stocks.
• 4 Sightings of free‐roaming muntjac deer were first recorded in 2007. The distribution of confirmed sightings of single and multiple animals in the eastern region of Ireland suggests multiple releases.
• 5 Deer are already impacting on both the economic and biodiversity values of habitats in Ireland, where, at present, no sustainable deer management policy exists.

     

Predicting invasion risk of 16 species of eucalypts using a risk assessment protocol developed for Brazil

Risk analyses are predictive systems designed to detect the risk of invasion by non‐native species. Although eucalypts are often considered moderately invasive given the extent of cultivation on a global scale, some species are widely recognized as invasive for transforming and impacting natural areas in several countries. These problems may be due to propagule pressure derived from human interest in forest production and aesthetic values. Risk analyses were carried out for 16 eucalypt species cultivated in Brazil using a protocol adapted from an Australian model to Brazilian conditions. The species were: Corymbia citriodora, Corymbia maculata, Corymbia torelliana, Eucalyptus benthamii, Eucalyptus brassiana, Eucalyptus camaldulensis, Eucalyptus cloeziana, Eucalyptus dunnii, Eucalyptus globulus, Eucalyptus grandis, Eucalyptus pellita, Eucalyptus robusta, Eucalyptus saligna, Eucalyptus tereticornis, Eucalyptus urophylla and Eucalyptus viminalis. Results indicate high risk for seven species, moderate risk for eight species and low risk for one species. The only low risk species is E. dunnii, while the highest risk scores refer to C. torelliana, E. tereticornis and E. grandis. These results are consistent with the history of invasion of the species around the world and should be considered for plantations especially when investment capacity to prevent and permanently control spread is low or not associated with forest certification standards. Risk analysis is a valid tool for discriminating between species and making decisions on species to be introduced or cultivated. The results of this study show that there are many species that can be cultivated without incurring biological invasions.     

Factors Affecting the Early Survival and Growth of Native Tree Seedlings Planted on a Degraded Hillside Grassland in Hong Kong, China

Abstract The effects of seasonal drought, belowground competition, and low soil fertility on the survival and growth over 2 years of four native tree species planted on a degraded hillside grassland in Hong Kong were studied in a field transplant experiment using three‐way analysis of variance. The tree species were Schima superba (Theaceae), Castanopsis fissa (Fagaceae), Schefflera heptaphylla (Araliaceae), and Sapium discolor (Euphorbiaceae), and the treatments were dry season irrigation, herbicide, and fertilizer. Each species responded differently to the treatments. Sapium had a very low survival rate as a result of wind damage at the exposed study site. All three treatments significantly reduced the survival rate of Castanopsis seedlings, whereas herbicide reduced it for Sapium but increased it for Schefflera. The significant effects on seedling growth were all positive, except for a strong negative effect of herbicide on Castanopsis growth. Overall, the results suggest that all three factors—seasonal drought, belowground competition, and low soil nutrients—can significantly impair seedling growth on a degraded hillside site in Hong Kong but that their relative importance differs among species. The growth benefits of the three treatments were largest and most consistent for Schima, which as a mature forest dominant would be expected to be particularly sensitive to the environmental conditions on degraded open sites. This study highlights the fact that more systematic planting trials are needed to identify suitable native tree species for cost‐effective reforestation on degraded hillsides in Hong Kong and South China.