The life history and ecology of the millipede Tymbodesmus falcatus (Polydesmida: Gomphoclesmidae) in northern Nigeria with notes on Sphenodesmus sheribongensis

The life history of the gomphodesmid millipede Tymbodesmus falcatus in Zaria, Nigeria is described. Larvae of stadia I to VI are soil-dwelling, stadium VII and adults are surface active.
Tymbodesmus probably completes its life cycle in two years; the adults are relatively shortlived and die before the onset of the dry season. The species survives the dry season as dia-pausing larvae in moulting chambers in the soil.
The biology of Sphenodesmus is, in general, similar to that of Tymbodesmus.
Body form in the species is described and compared with that found in other polydesmoids. A possible relationship between brood size and the degree of surface activity in polydesmoids is discussed.     

Stable soil pH of thai mangroves in dry and rainy seasons and its relation to zonal distribution of mangroves

Soil characteristics of mangrove forests at Amphur Laemngob, Trat Province, east Thailand were investigated in both dry andrainy seasons. Sonneratia alba, Avicennia alba andRhizophora mucronata mainly grew as seaward mangroves.Rhizophora apiculata, Ceriops tagal, Excoecaria agallocha andBruguiera gymnorrhiza grew as meso mangroves in most cases.Lumnitzera racemosa was found as a landward mangrove. The salinity of the soil in which these 8 species grew was significantly higher in the dry season than in the rainy season. Soil pH did not change irrespective of the season. Each species seemed to grow at inherent soil pH. Bruguiera gymnorrhiza, Sonneratia alba andAvicennia marina were found both in Japan and Thailand. The soil pH of each mangrove species was similar in Japan and Thailand. The soil salinity of each mangrove species in Japan was similar to that in Thailand in the dry season. It was suggested that soil pH and salinity in the dry season are the important factors governing the zonal distribution of mangroves.     

Effect of the spatial and seasonal soil heterogeneity over arbuscular mycorrhizal fungal spore abundance in the semi-arid valley of Tehuacán-Cuicatlán, Mexico

Recent studies have shown that some species of Mimosa (Leguminosae-Mimosoideae) create resource islands (RI), rich in soil organic matter and nutrients, as well as in arbuscular mycorrhyzal fungal (AMF) spores, in the semi-arid Valley of Tehuacán-Cuicatlán. The relevance of this fact is that arid and semi-arid regions are characterized by low fertility soils and scarce precipitation, limiting plant species growth and development; this explains why the presence of AM fungi may be advantageous for mycorrhizal desert plants. Fluctuations in AMF spore numbers could be related to environmental, seasonal and soil factors which affect AMF sporulation, in addition to the life history of the host plant. The aim of this study was to asses the impact of spatial (resource islands vs open areas, OA) and seasonal (wet season vs start of dry season vs dry season) soil heterogeneity in the distribution and abundance of AMF spores in four different study sites within the Valley. We registered AMF spores in the 120 soil samples examined. Significant differences in the number of AMF spores were reported in the soil below the canopy of Mimosa species (RI) comparing with OA (RI > OA), and between Mimosa RI themselves when comparing along a soil gradient within the RI (soil near the trunk > soil below the middle of the canopy > soil in the margin of the canopy > OA); however, there were no significant differences between the soil closest to the trunk vs middle, and margin 's OA. Finally, more spores were reported in the soil collected during the wet season than during the dry season (wet > start of dry > dry). Therefore, the distribution of AMF spores is affected by spatial and seasonal soil heterogeneity. This study points out the relevance of Mimosa RI as AMF spore reservoirs and the potential importance of AM fungi for plant species survivorship and establishment in semi-arid regions. AM fungi have recently been recognized as an important factor determining plant species diversity in arid and temperate ecosystems.     

Leaf shedding and weather in tropical dry-seasonal forest shape the phenology of fungi – Lessons from two years of monthly surveys in southwestern Panama

In the present study, conducted in a secondary dry-seasonal forest in the pacific lowlands of southwestern Panama over 2 years, fungal diversity is linked to plant phenology, litter, and climatic data. Agaricales fungi showed maximum species richness at the beginning of rainy seasons, probably due to the important litter accumulation during the dry season and the increase in humidity favoring fungal growth. Species richness declined during the wet season possibly due to torrential rains, moulds, and decreasing availability of nutrients. Occurrence of foliar pathogenic microfungi correlated negatively with flushing of new leaves at the beginning of the rainy season. Their incidence increased during the wet season and remained high during the dry season. Synchronization of leaf shedding in most tree species significantly reduced the yearly incidence of foliar pathogenic fungi causing an annual turn-over of fungal pathogens that probably contributes to maintain a high diversity of plant pathogenic species.     

Seed Ecology of Woody Species in a Caribbean Dry Forest

Peak flowering activity among woody species in the tropical dry forests of St. John, U.S. Virgin Islands, coincided with the brief spring rainy season but continued at moderate levels for six months, abating with the autumn rains. Fruit maturation showed a major peak in the long winter dry season and a minor crest during the summer dry season. Seeds of wind-dispersed species disseminated mainly during the winter dry season, while animal dispersal of seeds (74% of all woody species) followed the bimodal pattern (for wet and dry seasons) described for the community as a whole. Under shadehouse conditions, most dry forest tree species germinated well (> 80%) and emerged promptly (within four weeks of planting) and synchronously (90% emergence within a four-week interval). Nine of 29 species tested in the shadehouse manifested dormancy of at least six weeks. Seed germinability varied among tree species, and the viability of most species began to decline following six months of dry storage. Few species retained high germinability after nine months of dry storage. The species composition of soil seed banks did not correspond closely with above-ground communities on three forested sites of varying stand age. In the youngest stand (35 years old), dominated by the weedy, arborescent legume Leucaena leucocephala, the soil seed bank was also dominated by this species, but no seeds of any other tree species were found in the soil samples. Seeds of native trees were scarcely encountered (only one indigenous species) in soil seed bank samples of three forest sites. Local seed rain from less disturbed forest may not be sufficient for prompt recovery of the dry forest community on degraded sites.     

南亚热带森林不同演替阶段土壤种子库的初步研究

本文对鼎湖山不同演替阶段的森林（马尾松林、针阔叶混交林、季风常绿阔叶林）的土壤种子库进行了初步研究．分别从各个阶段的样地内抽取４或８个１×１ｍ的小样地,分三层（共１０ｃｍ厚）采集土样,带回实验室,通过萌发法观察记录其土壤种子库状况．通过统计分析,其结果如下：１．种子数量和物种多样性一般随演替发展而减少,种子数目以３—５ｃｍ厚土层为最多．２．各演替阶段土壤种子库的种类组成均以草本植物为主．３．在光照和湿度基本一致的情况下,萌发种子数与温度成正相关．４．雨季取的种子数目较旱季多,且种类组成有所不同．这是因为南亚热带森林内植物种子的休眠期短,在旱季采集土样时许多种的种子尚未下落．５．种子库组成与地上植物相关性不明显,但演替早期阶段的相关性比演替后期更密切。     

The life histories and distribution of the centipedes Rhysida nuda togoensis and Ethmostigmus trigonopodus (Scolopendromorpha: Scolopendridae) in Nigeria

Observations on populations of Rhysida nuda togoensis and Ethmostigmus trigonopodus in Zaria, Nigeria, show that growth rates are very rapid and life cycles shorter than in centipedes from temperate regions. R. nuda togoensis reproduces when one year old and, in all probability, E. trigonopodus does so as well.
It is suggested that both species are enabled to continue feeding in damp areas after the rains have ended by virtue of their mobility and large size (with consequent greater resistance to desiccation). Increasing aridity drives them into crevices in the soil where a relatively rich fauna may persist through the dry season. The young appear at the beginning of the rains, thereby having the entire rainy season available for feeding.
The taxonomy of R. nuda togoensis is discussed and the distribution of both species in Nigeria is described. They are virtually absent from the dry sudan savanna vegetation belt.     

Fire regime shifts affect bird species distributions

Aim Fire is a major driver of ecosystem structure and process, and shifts in fire regimes are implicated in the decline of many species. Shifting fire regimes have been documented around the world, and fire frequency and extent is predicted to increase in many areas because of changes in both climate and land management. Here, we evaluate how predicted increases in fire frequency are likely to impact on species distributions. Location The tropical savannas of northern Australia. Methods We developed distribution models for 44 bird species using the modelling algorithm Maxent. Our models incorporated bird locality records and environmental variables including climate, total fire frequency and the subset of fire frequency occurring late in the dry season. We investigated the effect of increasing total fire frequency and increasing fire late in the dry season, on species distributions by projecting species model algorithms onto scenarios of incrementally increased total fire frequency. Results The probability of presence for most species was higher when fire frequency late in the dry season was low. Species showed a mixed response to an overall increase in total fire frequency, with one‐third predicted to increase in distribution. However, almost all species (98%) showed a decrease in predicted range with increased late‐dry season fire, and species distribution area was generally negatively correlated with an increase in late‐dry season fire. Main conclusions Our study highlighted the array of responses of species to increasing fire frequency and suggested that increased fire frequency late in the dry season is detrimental to most savanna‐restricted bird species. The understanding of individual species’ preferences for particular fire frequencies is important for informed conservation planning.     

Notes on phenology and abundance of Psocoptera from primary and secondary dryland forest in Central Amazonia,Brazil

Psocoptera were collected from soil (by Kempson extraction) and from tree trunks (by arboreal photoeclectors) at two contrasting sites near Manaus, Brazil, for one year. The predominant soil taxa were Epipsocetae, especially Isthmopsocus, and a number of minor constituents are probably casual litter‐frequenters. Tree trunks yielded several taxa absent from soil. Soil in a secondary forest site yielded about four times as many psocids as a primary forest site and psocids were more abundant in the dry season than in the rainy season. Arboreal photoeclectors collected more psocids in the primary forest, but catches at both sites were larger in the dry season than in the rainy season. About 81 per cent of the psocids were immature stages.     

Responses of Tropical Understory Plants to a Severe Drought: Tolerance and Avoidance of Water Stress1

Shade-tolerant understory shrubs and subcanopy trees constitute most of the woody species in Neotropical moist forest, but studies demonstrating physiological differences among these species are few. Shade-tolerant species that coexist in the forest understory exhibit differences in leaf life span that have been associated with variation in physiological traits. We hypothesized that water relations of understory species with widely divergent leaf life spans differ in response to drought. Although severe drought is infrequent in Neotropical moist forest, we studied the water relations of shade-tolerant understory species with short or long leaf life spans during the severe 1991-1992 dry season on Barro Colorado Island, Panama. The predawn leaf water potential declined to -2.8 and -3.6 MPa during the dry season in Hybanthus prunifolius and Psychotria horizontalis, respectively, two species with short leaf life spans, but remained above -1.3 MPa in two species with long leaf life spans, Swartzia simplex and Ouratea lucens. The midday leaf water potential dropped as low as -3.4 and -4.5 MPa for H. prunifolius and P. horizontalis, respectively. The osmotic potential of H. prunifolius and P. horizontalis and another species with short leaf life span, Alms blackiana, decreased early in the dry season, a period during which all three had substantially negative predawn water potential. In contrast, the osmotic potential of S. Simplex, O. lucens, and Licania platypus, a third species with long leaf life span, declined late in the dry season, even though we observed little change in predawn water potential for S. simplex and O. lucens. We conclude that the variable and potentially severe dry season in Neotropical moist forest can be sufficiently intense to severely limit soil moisture availability for understory plants. H. prunifolius and P. horizontalis tolerated dehydration, whereas S. simplex and O. lucens postponed dehydration.     

Aspects of community ecology of amphibians and reptiles at Bonny Island (Nigeria), an area of priority relevance for petrochemical industry

Finima Nature Park, situated in Bonny Island (Niger Delta, Nigeria), is a protected forested area placed within one of the most industrially developed (and environmentally polluted) regions of the whole African continent. Amphibian and reptile community composition in relation to season and microhabitat characteristics was studied, by a combination of field techniques, during the wet and dry seasons of 2007 and 2008. Overall, a total of 21 species of reptiles from nine families (with 668 individuals caught) and eight amphibian species from five families (492 individuals caught) were recorded. Nearly 94% of the amphibian individuals and most of the species were recorded, especially during the wet season, whereas most of the reptiles were found with no inter‐seasonal differences. However, Agama agama and Mabuya affinis were found especially during the dry season. As for microhabitat use, the reptile species showed a clear, aggregated preference for two microhabitat types (dry leaves and under logs), which are probably crucial when these animals need to lose body temperature to avoid overheating. Concerning amphibians, the various species used the available microhabitats in a way expectable from their main ecological traits, with toads differing from aquatic frogs, and these differing from arboreal frogs.     

Relationships between drosophilids (Diptera, Drosophilidae) and the environment in two contrasting tropical vegetations

Although natural populations of drosophilid flies have been the subject of ecological studies, the population ecology of these insects in the tropics is still poorly known. This paper discusses aspects of the relationship between drosophilids and their environment, based on 28 monthly collections made in two contrasting vegetations of the Brazilian Cerrado biome: gallery forest and savanna. Exotic species were found in both types of environment; but 14 of the 30 captured Neotropical species occurred exclusively in the gallery forests, probably because of their climatic stability and greater environmental heterogeneity. Even though some endemic species were more abundant in the dry and cold months, most populations exhibited peaks of abundance in the wet season. The species diversity indexes (H' and D), higher in the dry season, were probably affected by increased evenness at this time of year, when the populations of practically all the species are greatly reduced. As species richness in the savanna vegetation clearly decreased in the dry season, increasing again in the wet season, it is suggested that some drosophilids migrate to the forests when climatic conditions are too stressful in the savannas.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 233–247.     

西双版纳地区不同植被亚型蚁科昆虫群落研究

研究了西双版纳地区１６各被亚型蚂蚁的特有种、优势种、物种多样性指数、均匀度指数、优势度指数和相似性系数。所采蚂蚁分隶于８亚科６６属２２０种。雨季的季节性十麻蚂蚁物种多样性指数最大,为２．９０８;旱季的茶园中多样性指数最小,为０．１１４。以山地雨林和季风常绿阔叶林蚂蚁物各组成相似性系数最大,为０．３５６;以温暖性叶阔叶林和茶园相似性系数最小,为０．０１７。１６种植被亚型均有特有种,其中半常绿季雨林特     

Principles of Natural Regeneration of Tropical Dry Forests for Restoration

Tropical dry forests are the most threatened tropical terrestrial ecosystem. However, few studies have been conducted on the natural regeneration necessary to restore these forests. We reviewed the ecology of regeneration of tropical dry forests as a tool to restore disturbed lands. Dry forests are characterized by a relatively high number of tree species with small, dry, wind‐dispersed seeds. Over small scales, wind‐dispersed seeds are better able to colonize degraded areas than vertebrate‐dispersed plants. Small seeds and those with low water content are less susceptible to desiccation, which is a major barrier for establishment in open areas. Seeds are available in the soil in the early rainy season to maximize the time to grow. However, highly variable precipitation and frequent dry spells are important sources of mortality in seeds and seedlings. Collecting seeds at the end of the dry season and planting them when soil has sufficient moisture may increase seedling establishment and reduce the time they are exposed to seed predators. Germination and early establishment in the field are favored in shaded sites, which have milder environment and moister soil than open sites during low rainfall periods. Growth of established seedlings, however, is favored in open areas. Therefore, clipping plants around established seedlings may be a good management option to improve growth and survival. Although dry forests have species either resistant to fire or that benefit from it, frequent fires simplify community species composition. Resprouting ability is a noticeable mechanism of regeneration in dry forests and must be considered for restoration. The approach to dry‐forest restoration should be tailored to this ecosystem instead of merely following approaches developed for moister forests.     

Timing of seed dispersal generates a bimodal seed bank depth distribution

The density of soil seed banks is normally highest at the soil surface and declines monotonically with depth. Sometimes, for a variety of reasons, peak density occurs below the surface but, except in severely disturbed soils, it is generally true that deeper seeds are older. In seasonally dry habitats that develop deep soil cracks during the dry season, it is possible that some seeds fall down cracks and rapidly become deeply buried. We investigated this possibility for three dominant clonal perennials (Scirpus maritimus, S. litoralis, and Juncus subulatus) in the Do?ana salt marsh, a nontidal marsh with a Mediterranean climate located in southwest Spain. Two species, which shed most of their seed during the dry season and have seeds with low buoyancy, had bimodal viable seed depth distributions, with peak densities at the surface and at 16-20 cm. A third species, which shed most seeds after soil cracks had closed and had seeds with high buoyancy, had viable seeds only in surface soil. Bimodal seed bank depth distributions may be relatively common in seasonally dry habitats with fine-textured soils, but their ecological significance has not been investigated.     

Seasonal diet changes in elephant and impala in mopane woodland

Elephant and impala as intermediate feeders, having a mixed diet of grass and browse, respond to seasonal fluctuations of forage quality by changing their diet composition. We tested the hypotheses that (1) the decrease in forage quality is accompanied by a change in diet from more monocots in the wet season to more dicots in the dry season and that that change is more pronounced and faster in impala than in elephant; (2) mopane (Colophospermum mopane), the most abundant dicot species, is the most important species in the elephant diet in mopane woodland, whereas impala feed relatively less on mopane due to the high condensed tannin concentration; and (3) impala on nutrient-rich soils have a diet consisting of more grass and change later to diet of more browse than impala on nutrient-poor soils. The phosphorus content and in vitro digestibility of monocots decreased and the NDF content increased significantly towards the end of the wet season, whereas in dicots no significant trend could be detected. We argue that this decreasing monocot quality caused elephant and impala to consume more dicots in the dry season. Elephant changed their diet gradually over a 16-week period from 70% to 25% monocots, whereas impala changed diets rapidly (2?C4?weeks) from 95% to 70% monocots. For both elephants and impala, there was a positive correlation between percentage of monocots and dicots in the diet and the in vitro digestibility of these forage items. Mopane was the most important dicot species in the elephant diet and its contribution to the diet increased significantly in the dry season, whereas impala selected other dicot species. On nutrient-rich gabbroic soils, impala ate significantly more monocots than impala from nutrient-poor granitic soils, which was related to the higher in vitro digestibility of the monocots on gabbroic soil. Digestibility of food items appears to be an important determinant of diet change from the wet to the dry season in impala and elephants.     

The taxonomy, distribution and ecology of centipedes of the genus Asanada (Scolopendromorpha:Scolopendridae) in Nigeria

The distribution and variation of Asanada spp. in Nigeria is described. Three forms are recognized and their relationship with other African populations of Asanada is discussed. An account of the biology of A. sokotrana in Nigeria is given. During the rainy season the species is characteristically found in deserted mounds of Trinervetermes spp. but disappears from this habitat in the dry season, presumably retreating into the soil. Egg-laying and brooding take place at the latter end of the dry season and the young appear at the beginning of the rains. Males live for only one year but some females live for longer than this. Growth continues through the dry season.     

Soil extracellular enzyme activities correspond with abiotic factors more than fungal community composition

Soil extracellular enzymes are the proximal drivers of decomposition. However, the relative influence of climate, soil nutrients and edaphic factors compared to microbial community composition on extracellular enzyme activities (EEA) is poorly resolved. Determining the relative effects of these factors on soil EEA is critical since changes in climate and microbial species composition may have large impacts on decomposition. We measured EEA from five sites during the growing season in March and 17 sites during the dry season in July throughout southern California and simultaneously collected data on climate, soil nutrients, soil edaphic factors and fungal community composition. The concentration of carbon and nitrogen in the soil and soil pH were most related to hydrolytic EEA. Conversely, oxidative EEA was mostly related to mean annual precipitation. Fungal community composition was not correlated with EEA at the species, genus, family or order levels. The hyphal length of fungi was correlated with EEA during the growing season while relative abundance of taxa within fungal phyla, in particular Chytridiomycota, was correlated with the EEA of beta-glucosidase, cellobiohydrolase, acid phosphatase and beta-xylosidase in the dry season. Overall, in the dry season, 35.3 % of the variation in all enzyme activities was accounted for by abiotic variables, while fungal composition accounted for 27.4 %. Because global change is expected to alter precipitation regimes and increase nitrogen deposition in soils, EEA may be affected, with consequences for decomposition.     

Importance of soil moisture and its interaction with competition and clipping for two montane meadow grasses

Meadow classification studies have demonstrated the importance of water table fluctuation patterns in determining plant community composition in the western United States. However, a mechanism causing an overall increase in Poa pratensis ssp. pratensis populations and local declines in Deschampsia cespitosa populations in western montane meadows over the past century has not been defined. In order to better understand plant species interactions in these often highly grazed systems, we observed aboveground responses of Poa and Deschampsia to changes in species composition, soil moisture gradients, and clipping in the field. As well, we conducted a factorial greenhouse experiment, varying plant density, water availability, and clipping. While Poa is adapted to dry meadows and Deschampsia to wet meadows, their ranges overlap in wet conditions where soil moisture averages 50% in the early growing season. Deschampsia appears to be excluded from dry meadows where Poa is prevalent and soil moisture is closer to 30% water content in the early growing season. Our greenhouse experiment revealed that Deschampsia’s competitive ability decreases, while Poa’s increases, at soil moistures of 19%. However in more mesic conditions (50% soil moisture), each species aboveground biomass, tillering, and inflorescence weight was adherent to soil moisture conditions, and species interactions were less important. Our early growing season clipping treatments significantly reduced biomass of both grasses, but did not appear to favor one species over the other. This work points to the importance of soil water content in determining the performance of each plant species and the level of species interactions in montane meadows.