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.     

Relations between apical structure and growth patterns in Pinus halepensis Mill,seedlings

Abstract

The process of primary growth in 2-year-old seedlings of 11 populations of Pinus halepensis Mill. is described. At the end of the first growing season one type of apical structure was observed: type-1, a tuft of primary needles placed close together, surrounding and protecting a meristematic apex.

At the end of the 2nd growing season, three types of apical structure were observed: type-1; type-2, a terminal winter bud; and type-3; a «bud» with characteristics of both type-1 and type-2.

Morphological observation along with an anatomical examination of the winter bud led to the conclusion that the definitive growth pattern in juvenile P. halepensis is monocyclic with a variable number of summer shoots. This growth pattern is reached by some P. halepensis populations in 3–4 years, by contrast, in other pine species two years are usually needed.

The populations studied differed both in growth potential (differences in number of cycles, ratio of first cycle to total growth, growth rates) and in the developmental stages of the apical meristem.

Four groups could be identified: (i) Morocco and Spain, (a limited growth, few cycles, a high ratio of 1st cycle to total growth, and growth in 2nd season almost entirely due to free growth); (ii) Algeria and Greece, (moderate to low growth, a large number of cycles, a low ratio of 1st cycle to total growth, and very early formation of apical structure with preformed primordia); (iii) Israel and Central Italy (a high growth, a large number of cycles, a medium ratio of 1st cycle to total growth, and early formation of apical structure with preformed primordia); (iiii) Greece, France and Italy, which was intermediate between group (i) and the other 2 groups.     

Species dynamics and colonization patterns in an abandoned forest in an urban landscape

Species dynamics in an abandoned urban forest of Central Japan is described in this paper. The dominant species in the urban plantation were Cryptomeria japonica and Chamaecyparis obtusa. A variety of eight patches of the canopy was produced by previous forest management practices. Progressive and retrogressive species dynamics within these eight patches are investigated in this paper. The study elucidates the deterministic role of patchiness in the nature of species colonization and the maintenance of species diversity in an urban forest. Altogether 139 native and/or naturalized species, including 23 shrub and 35 tree species, were recorded in the study area of 3.2 ha. The performance of species varied according to their successional attributes indicating a selective canopy influence. Twenty percent of the tree species were shade-intolerant pioneers (e.g. Cornus spp., Rhus javanica var. roxburghii) re-established under selective tree-felling. Thirty percent were shade-tolerant climax species (e.g. Neolitsea sericea, Persea thunbergii) dominant in remnant closed patches. The remaining 50% belonged to various seral types with aggressive deciduous species (e.g. Aphananthe aspera, Celtis sinensis) in most of the patches. Some ruderal herbaceous species dominated heavily disturbed clear-felled patches. This study suggests that canopy modification influences the subsequent colonization pattern. Furthermore, heterogeneous patches contribute to greater species diversity and dynamics in isolated woodlands.     

Reproductive strategy, clonal structure and genetic diversity in populations of the aquatic macrophyte Sparganium emersum in river systems

Many aquatic and riparian plant species are characterized by the ability to reproduce both sexually and asexually. Yet, little is known about how spatial variation in sexual and asexual reproduction affects the genotypic diversity within populations of aquatic and riparian plants. We used six polymorphic microsatellites to examine the genetic diversity within and differentiation among 17 populations (606 individuals) of Sparganium emersum, in two Dutch-German rivers. Our study revealed a striking difference between rivers in the mode of reproduction (sexual vs. asexual) within S. emersum populations. The mode of reproduction was strongly related to locally reigning hydrodynamic conditions. Sexually reproducing populations exhibited a greater number of multilocus genotypes compared to asexual populations. The regional population structure suggested higher levels of gene flow among sexually reproducing populations compared to clonal populations. Gene flow was mainly mediated via hydrochoric dispersal of generative propagules (seeds), impeding genetic differentiation among populations even over river distances up to 50 km. Although evidence for hydrochoric dispersal of vegetative propagules (clonal plant fragments) was found, this mechanism appeared to be relatively less important. Bayesian-based assignment procedures revealed a number of immigrants, originating from outside our study area, suggesting intercatchment plant dispersal, possibly the result of waterfowl-mediated seed dispersal. This study demonstrates how variation in local environmental conditions in river systems, resulting in shifting balances of sexual vs. asexual reproduction within populations, will affect the genotypic diversity within populations. This study furthermore cautions against generalizations about dispersal of riparian plant species in river systems.     

Carbon and nutrient dynamics in relation to growth rhythm in the giant bamboo Phyllostachys pubescens

The carbon and nutrient dynamics in relation to growth rhythm in the giant bamboo Phyllostachys pubescens on Mount Jinyun, Chongqing, China, was studied during 1993–1996. Concentrations of TNC (total non-structural carbohydrates), N, P, and K all showed the same distribution pattern among organs: leaves > branches rhizomes stems roots. The rapid spring growth of new shoots noticeably reduced the concentration of TNC in the rhizomes, in which a large amount of carbohydrates was stored. The N concentration of the rhizomes did not decrease, however. Nutrient concentration of new (1st-year) leaves was significantly higher than that of old (2nd-year) leaves. Although the density of adult shoots was almost the same during 1994–1996, the low ratio of the number of adult shoots with new to that with old leaves from June 1994 to April 1995 resulted in a low TNC concentration in the rhizomes in early spring (April) 1995. This led to a low production of new shoots in the spring of 1995, their number being only ca. 10% of that in 1994 and 1996. Before old leaves were shed, a large amount of nutrients was remobilized and translocated to other plant parts to support further growth. Fertilization with NPK significantly increased the concentrations of N and P in leaves and subsequently increased the number of emerging new shoots.     

Forest regeneration in abandoned coffee plantations and pastures in the Cordillera Central of Puerto Rico

Forest structure and species composition were described in abandonedshade and sun coffee plantations and abandoned pastures in Puerto Rico. Foreststructural characteristics were similar to older forest sites afterapproximately 30 yr of recovery. The historical presence of shadecoffee plantations as the dominant agricultural activity in the region hasresulted in the homogenization of secondary forest composition. The continuousdominance of Coffea arabica and species used for shade inabandoned shade coffee contributed to a slower rate of species compositionchange in comparison to abandoned pastures. Abandoned pastures were initiallycolonized by a group of light demanding and/or wind dispersed species and thenby shade tolerant species characteristic of abandoned shade coffee plantations,suggesting that the secondary forests of abandoned shade coffee plantation arethe major source of species in this landscape. The presence of a few isolatedbig trees in sun coffee plantations appeared to facilitate colonization ofwoodyspecies similar in composition to abandoned shade coffee plantations. In amultivariate analysis, time since abandonment and elevation were the variablesthat explained the majority of variability in species composition among sites.However, a few native species (e.g. Guarea guidonia,Casearia sylvestris, Ocotealeucoxylon) were common regardless of land use history or elevation.In contrast, important old forest species (e.g. Sloaneaberteriana, Dacryodes excelsa,Manilkara bidentata) were rare or absent from most of thesecondary forest stands suggesting the need to reintroduce these species. Landmanagement and conservation efforts can be improved by incorporating theeffectsof land use history on secondary forest dynamics.     

Hyaloscyphaceae in Japan (6): the genus Hyphodiscus in Japan and its anamorph Catenulifera gen. nov.

Three Hyphodiscus species are described and illustrated: Hyphodiscus otanii sp. nov., Hyphodiscus hymeniophilus, and H. theiodeus, which is new to Japan. Culture studies revealed Phialophora-like anamorphs. Catenulifera gen. nov. is proposed for the anamorph of Hyphodiscus. The history of the genus is reviewed. Hyphodiscus can be delimited to members with gelatinized excipulum, Cistella-like hairs with more coarse granulation, small asci, ascospores with conspicuous globules, cylindrical, flexuous paraphyses, and a Catenulifera anamorph. Received: September 6, 2001 / Accepted: October 4, 2001     

Fish community structure and environmental correlates in the highly altered southern Sacramento-San Joaquin Delta

We sampled 11 sites in the southern Sacramento-San Joaquin Delta from 1992–1999, to characterize fish communities and their associations with environmental variables. Riparian habitats were dominated by rock-reinforced levees, and large water diversion facilities greatly influenced local hydrodynamics and water quality. We captured 33 different taxa, only eight of which were native. None of the native species represented more than 0.5% of the total number of individuals collected. The abundance of native species was consistently low but typically peaked during high outflow periods. Fish communities were predominantly structured along environmental gradients of water temperature and river flow. Native species (tule perch, Hysterocarpus traski, & Sacramento sucker, Catostomus occidentalis) were associated with conditions of high river flow and turbidity, while the majority of the non-native species were associated with either warm water temperature or low river flow conditions. The exceptions were the non-native striped bass, Morone saxatilis, and white catfish, Ameiurus catus, which were positively associated with relatively high river flow. Variation in fish community structure was greater among river locations within years than within river locations among years, thus fish communities at each river location were consistently different each year. Differences in fish communities among river locations were correlated with river flow and turbidity. We predict that the fish communities of this region will remain numerically dominated by non-native species if the environmental conditions we observed persist in the future.     

Interannual fluctuations in recruitment and growth of the sardine,Sardinops melanostictus,in the sea of Japan and adjacent waters

Recruitment and growth of the sardineSardinops melanostictus fluctuated markedly in the Sea of Japan and adjacent waters between 1978 and 1993. Stock size was calculated using Virtual Population Analysis and average body length in each age class was determined by the number of annual rings on the scales. There is an inverse correlation between average water temperature at a depth of 50 m in the coastal area of the mainland of Japan in winter (January to March) and recruitmentR defined as the number of individuals at 1 year old. There is also an inverse correlation between spawning stock sizeE and reproductive success in (R/E). A multiple regression model using spawning stock size and water temperature in winter as independent variables can explain 73% of variance in reproductive success. It suggests that both density-dependent and density-independent factors perform important roles determining reproductive success. There is an inverse correlation between body length and stock size and this suggests that there is a density-dependent effect on the growth of the sardine.     

Stand structure and growth patterns of understorey trees in a coniferous forest,Taisetsuzan National Park,northern Japan

Stand structure was studied with special reference to growth and mortality patterns of sapling and understorey trees in a coniferousPicea jezoensis andAbies sachalinensis forest in Taisetsuzan National Park, Hokkaido, northern Japan.Picea jezoensis was dominant in the basal area, whileA. sachalinensis was abundant in large numbers in the canopy. Estimated mortalities increased significantly with diameter at breast height (DBH) for bothP. jezoensis andA. sachalinensis in the canopy, but the tendency was different between the two species.Picea jezoensis had a lower mortality rate thanA. sachalinensis, especially at small DBH classes. The spatial distribution of understorey individuals ofA. sachalinensis did not show any significant correlation with the spatial distribution of canopy gaps, but that ofP. jezoensis showed a significant correlation.Abies sachalinensis can grow higher thanP. jezoensis under suppressed conditions; whileP. jezoensis requires canopy gaps for steady height growth. This growth pattern leads to a different waiting height in the understorey (≥2 m in height and 10 cm in diameter at breast height).Abies sachalinensis waited for an improvement in light conditions at higher strata (max. 7 m), whileP. jezoensis waited at lower strata (max. 3 m). The estimated mortality of understoreyA. sachalinensis increased with size, while that of understoreyP. jezoensis decreased. Therefore,P. jezoensis gives priority to survival whileA. sachalinensis gives priority to understorey growth. The difference in the ‘waiting pattern’ between the two species in the understorey was considered a significant feature for the canopy recruitment process ofP. jezoensis andA. sachalinensis.     

Oxalis debilis in China: distribution of flower morphs, sterile pollen and polyploidy

BACKGROUND AND AIMS: Oxalis debilis is a South American tristylous species that is currently naturalizing in China. Based on field observations and herbarium data a report is made on its pollination, morph frequencies, pollen viability, seed set and chromosome number. In addition, a new chromosome count for the species in Africa is provided. METHODS: Field observations were conducted in six provinces in south-east China. Flower visitors were recorded and nectar sugar was measured with a refractometer. The species' compatibility system was determined by carrying out experimental self- and cross-pollinations on bagged inflorescences. Stigma receptivity and pollen viability was determined using the MTT test. KEY RESULTS AND CONCLUSIONS: Populations of O. debilis in China contain either the mid-style-length morph or the short morph, but not both. Pollination is by nectar- and pollen-foraging bees; pollen viability is low; and seed set in natural and experimentally self- or cross-pollinated flowers is extremely low. Chromosome counts indicate that O. debilis contains diploid and tetraploid forms in its native as well as introduced range, which does not support a previous hypothesis that the predominant vegetative reproduction in this species is an escape from pentaploidy.     

Different biomass-allocation patterns among four tree species in heavily disturbed sites on a volcanic mountain in Hokkaido,northern Japan

We have compared biomass-allocation patterns and frequency of sprouting among saplings of four tree species (Larix kaempferi, Betula platyphylla var. japonica, Populus maximowiczii, and Populus sieboldii) growing on a volcanic mountain in Hokkaido, northern Japan. Growing conditions were very harsh on the mountainside. Leaf mass and fine root mass relative to root mass were larger in L. kaempferi, and L. kaempferi root mass was less than for the other species. Sprouting ratios were high for the broadleaved species. Different allometries and sprouting ratios among species suggest that survival strategies for L. kaempferi were different from those for the broadleaved species. L. kaempferi has greater ability to increase leaf mass under harsh growing conditions; this probably results in large photosynthetic production by L. kaempferi on the volcano. In contrast, the two Populus species and Betula platyphylla seem to maintain populations through their ability to produce sprouts from large root systems.     

Effects of scale-dependent factors on herbaceous vegetation patterns in a wetland,northern Japan

Herbaceous vegetation was examined in an Otanoshike wetland in northern Japan to clarify the relationships between vegetation patterns and environmental factors with different scales. Alders (Alnus japonica) have recently invaded and might modify the herbaceous vegetation. In total, 150 50×50cm plots were established on the transitional areas between alder thickets and grassy marshland. Cover was measured for the vascular plant taxa, and canopy area, number of stumps, number of mounds, water depth, elevation difference, litter thickness, soil organic matter, and soil pH were measured in each plot. TWINSPAN cluster analysis classified four vegetation groups: (i), grasslands represented by Phragmites australis, Trientalis europaea, Lythrum salicaria, and Hosta rectifolia; (ii), Calamagrostis langsdorfii, and Polygonum thunbergii grasslands with Spiraea salicifolia; (iii), reed swamp dominated by Phragmites australis, and (iv), marshland dominated by Carex lyngbyei. Canonical correspondence analysis indicated that water depth primarily divided vegetation groups 1–2 and 3–4. Alder established in drier sites mostly by re-sprouting, and the canopy affected light and soil conditions on the ground surface. The second axis of canonical correspondence analysis was related to the canopy area and soil pH, and explained the vegetation differentiation between groups 1 and 2, and groups 3 and 4. In conclusion therefore, scale-dependent or hierarchical variables affected the vegetation patterns in different ways, that is, the herbaceous vegetation was first differentiated by water depth that was corresponding to alder establishment on a large scale, and subsequent light and soil conditions were second determinants on a small scale.     

Vegetation structure in relation to micro-landform in an evergreen broad-leaved forest on Amami Ohshima Island,south-west Japan

The relationship between micro-landform and vegetation structure was studied in a plot that was established on a slope from the ridge to the valley bottom in an evergreen broad-leaved forest on Amami Ohshima Island, south-west Japan. Five micro-landform units recognized in the plot were grouped into the upper and lower slopes by their location in relation to the erosion front, and plant distributions and vegetation structure were compared between them. Although small trees with d.b.h. less than 10 cm occurred almost all over the plot, the occurrence of larger trees was limited mostly to the upper slope. Based on the spatial distribution pattern in the plot, woody species are classified into three groups: group A mostly or strictly confined to the upper slope; group B confined to the lower slope; and group C associated statistically with neither slope. A well-developed forest stand, whose dominant species wereCastanopsis sieboldii ssp.lutchuensis andSchima wallichii, was seen on the upper slope, whereas only a poorly developed stand was seen on the lower slope. The difference in stability of the land surface is likely to be the major cause of the observed differences in stand structure between the upper and lower slopes. It is suggested that the erosion front is important as a line demarcating different habitats within a slope from the ridge to the valley bottom.     

Development of microsatellite markers for the dwarf bamboo species Sasa cernua and Sasa kurilensis (Poaceae) in northern Japan

Ten polymorphic microsatellite markers were isolated from the dwarf bamboo species Sasa cernua and Sasa kurilensis. The applicability of these markers was confirmed by genotyping of open‐pollinated seeds and leaf samples from natural populations. Genotypes of seeds from each culm shared at least one allele from the maternal parent without contradiction. All 10 loci were polymorphic in S. cernua with 2–15 alleles (average H_E = 0.532). Eight loci were polymorphic in S. kurilensis with 2–10 alleles (average H_E = 0.532). These markers will be useful in detailing the extent of clonal and sexual reproduction in these species.     

Habitat expansion of an exotic lace bug, Corythucha marmorata (Uhler) (Hemiptera: Tingidae), on the Kii Peninsula and Shikoku Island in western Japan

Habitat expansion of an exotic lace bug Corythucha marmorata (Uhler) was observed on the Kii Peninsula in 2003–2004, and on Shikoku Island between 2004 and 2007. The bug was first sighted in Nishinomiya City in Hyogo Prefecture in 2000, and then further south in central Kii Peninsula in 2003 before reaching the southern tip of the peninsula by 2004. The bug was first observed in the Tokushima and Ehime Prefectures of Shikoku Island in 2004, after which the range expanded and extended across the entire island by 2007. In this study, six wild Asteraceae species were identified as the host plants to the lace bug.     

Morphological structure and functional patterns of Keratella cochlearis (Gosse) populations in stratified lakes

Vertical distribution of the rotifer Keratella cochlearis in stratified water columns of mesotrophic and eutrophic lakes during summer stagnation has been studied. Coexisting morphs K. cochlearis hispida (Lauterborn, 1898), K. c. tecta (Gosse, 1851) and K. c. cochlearis (Gosse, 1851) inhabit different layers in the water column and are vertically subdivided. The distribution of morph abundance and reproductive potential indicate that substitution of morphs within the vertical water column may be due to trophic conditions. The maximum population productivity is observed at the epi-metalimnion border. The maximum density zone lies below the zone of the highest productivity. The principle of sliced functioning is used to explain the adaptive significance of the morphological structure of populations under heterogeneous environmental conditions.     

陕北烟田多异瓢虫空间分布型与抽样技术研究

根据1995年烟田多异瓢虫Hippodamiavariegats（Goeze）调查,计算了6种分布型指数,以及频次拟合优度检验,结果表明：该虫幼虫、蛹在陕北烟田里聚集分布,其聚集强度随种群密度增加而降低,聚集原因是环境差异;卵块分布同时具有聚集和随机的趋势,成虫为随机分布。同时建立了各虫态的理论抽样量公式,估测种群密度公式。