Environmental Conditions Of Habitats Research Articles

Taxonomic Diversity and Ecological Characteristics of Chlorophyta and Charophyta in the Water Bodies of the Kuyalnyk Estuary (Ukraine, the Black Sea Northwestern Coast)

Results of analysis of original data obtained in 2001-2018 on the ecology and biogeographic distribution of 40 species (45 infraspecific taxa) of Chlorophyta of the orders Cladophorales (8), Ulotrichales (4), Ulvales (6), Chlo-rellales (1), Chlamydomonadales (6), and Sphaeropleales (20) and 7 species of Charophyta of the orders Zygnematales (2), Desmidiales (4), and Charales (1) of the hyperhaline Kuyalnyk estuary, its main tributaries and various water bodies located within the two-kilometer water protection zone are given in the paper. The ecological characteristics (relationship to pH, water salinity, organic matter content, and ecotopic confinement) and the environmental conditions of habitats (temperature, water salinity, pH, and the content of inorganic compounds of nitrogen and phosphorus) are given in the paper. In the hyperhaline Kuyalnyk estuary, the concentration of nutrients (nitrogen and phosphorus) was high during all water periods. The increase in water salinity up to 200-320‰ resulted in the decrease in species diversity, changes in the structure of algal communities, and also in a predominance of species ofthe genus <i>Dunaliella</i> Teod. (Chlorophyta).

Variations in phenotypic plasticity in a cosmopolitan copepod species across latitudinal hydrographic gradients

Studies assessing latitudinal variations in habitat conditions and phenotypic plasticity among populations yield evidence of the mechanisms governing differentiation in the potential to adapt to current/future habitat changes. The cosmopolitan copepod species Acartia tonsa thrives across ocean clines delimiting Seasonal (30–40° S) and Permanent (10–30° S) Upwelling coastal provinces established during the middle–late Pliocene (3.6–1.8 Ma) alongshore the South East Pacific (SEP), nowadays exhibiting contrasting variability features related to several ocean drivers (temperature, salinity, pH, and food availability). Latitudinal variation across the range of environmental conditions of the coastal provinces can contribute toward shaping divergent A. tonsa’s phenotypes, for example, through specific patterns of phenotypic plasticity in morphological and physiological traits and tolerance to environmental drivers. With the aim of contributing to the understanding of these adaptive processes in a relatively little studied oceanic region, here we compared the expression of parental (i.e., adult size, egg production, and ingestion rate) and offspring (i.e., egg size) traits in relation to variation in environmental habitat conditions across different cohorts of two distant (> 15° latitude) A. tonsa populations inhabiting estuarine and upwelling habitats located in the Seasonal and Permanent Upwelling province, respectively. Mean conditions and ranges of variability in the habitat conditions and phenotypic plasticity of parental and offspring traits within and among cohorts of A. tonsa populations varied significantly across the different examined regions (i.e., Seasonal vs. Permanent). We also found significant differences in the coupling of habitat variability and trait expression, suggesting that the differences in trait expressions might be related to habitat variability. The phenotypic divergence was translated to cohort-related patterns of trait trade-offs regulating reproduction and tolerance of egg production efficiency that can jointly determine the level of plasticity, genetic structure, or local adaptation. The current findings provide novel evidence of how divergent phenotypes might sustain A. tonsa populations across variable coastal provinces of the SEP.

Homogenization of bryophyte species after alpine grassland restoration.

The causes of decreasing plant species richness include abandonment of traditional management and the spread of invasive species, even in alpine habitats. Studies on the restoration and management of alpine habitats are predominantly focused on vascular plants, although an important part of alpine vegetation and its diversity is formed by bryophytes. We used bryophytes to indicate changes that occur after the clearcutting of nonindigenous dwarf pine (Pinus mugo Turra) and attempted to reveal the community to which the development of bryophyte species structure was directed. We compared species richness and composition between surveys to test for changes in spatial heterogeneity bryophyte communities. We also tried to reveal the main ecological drivers of the restoration process. The study was performed in the (sub)alpine area of the Eastern High Sudetes Mts. (the Czech Republic). We estimated bryophyte species cover and compared the composition of the bryophyte community in autochthonous grassland areas, areas under the dwarf pine canopy, and clearcut areas to reveal the pattern of shifts 9 years after the treatment. We also measured soil characteristics to reveal the environmental habitat conditions. Evidence of taxonomic homogenization of habitat after dwarf pine removal was found. Light conditions and attributes of litter were the driving factors of successional changes in the bryophyte communities, which led to taxonomic homogenization. This finding explains the slow restoration process due to dwarf pine legacy on the clearcut area. The succession trends were also shaped by unobserved factors, such as climate change and environmental eutrophication. We highly recommended active management and long-term monitoring.

Влияние экологических условий на виталитетную структуру ценопопуляций доминантов древесного яруса в лесах южной части Приволжской возвышенности

The vitality structure of cenopulations of woody plants is formed under the influence of ecological, cenotic and anthropogenic influences. The study of the nature and degree of influence of the ecological parameters of the habitat will make it possible to predict the formation of the vitality structure of woody plants. The objects of study are individuals of the generative age state of three species of woody plants: Quercus robur, Tilia cordata, Acer platanoides. Environmental conditions of habitat were assessed by using range ecological scales. Vitality was assessed by three key determinative morphometric parameters. Correlation analysis was carried out to establish the impact of environmental conditions on the indicators of the vitality of cenopopulations. Both direct and inverse relationships (with a correlation coefficient of 0.5 and above) between ecological conditions and vitality of the studied species were noted. The vitality of Tilia cordata is more influenced compared to other studied species.

Field studies on breeding sites of CulicoidesLatreille (Diptera: Ceratopogonidae) in agriculturally used and natural habitats

Culicoides are vectors of pathogens mainly of veterinary importance. To establish targeted vector control measures, it is paramount to comprehend the ecological factors determining their distribution. Therefore, we used emergence traps to sample eight biotopes and assess their potential as breeding sites. Part one of the study investigates agricultural habitats, part two compares four biotopes of a forest-dominated area with less anthropogenic influence, including a physicochemical analysis of soil moisture, pH value and organic content. Thirteen culicoid species were collected, with a strong dominance of the Obsoletus Complex on meadows, and with Culicoides punctatus (Meigen), Culicoides pictipennis (Staeger) and the Obsoletus Complex, to be the most abundant species in the natural habitats. Several co-existing species were found, some of them not having been described before. Our results suggest that ungrazed meadows seem unsuitable as breeding sites. Only the influence of livestock creates adequate conditions for certain midge species. The alder on fen site contained most culicoid species with the highest species diversity. Our study clearly indicates that knowledge of species-specific preferences for environmental habitat conditions (choice of breeding site) in connection to soil conditions is crucial to understand the biology and phenology of midges and their role as vectors of pathogens.

Can we predict which species win when new habitat becomes available?

Land cover change is a key component of anthropogenic global environmental change, contributing to changes in environmental conditions of habitats. Deforestation is globally the most widespread and anthropogenically driven land cover change leading to conversion from closed forest to open non-forest habitat. This study investigates the relative roles of geographic features, characteristics of species climatic niche and species traits in determining the ability of open-habitat plant species to take advantage of recently opened habitats. We use current occurrence records of 18 herbaceous, predominantly open-habitat species of the genus Acaena (Rosaceae) to determine their prevalence in recently opened habitat. We tested correlation of species prevalence in anthropogenically opened habitat with (i) geographic features of the spatial distribution of open habitat, (ii) characteristics of species climatic niche, and (iii) species traits related to dispersal. While primary open habitat (naturally open) was characterised by cold climates, secondary open habitat (naturally closed but anthropogenically opened) is characterised by warmer and wetter conditions. We found high levels of variation in the species prevalence in secondary open habitat indicating species differences in their ability to colonise newly opened habitat. For the species investigated, geographical features of habitat and climatic niche factors showed generally stronger relationships with species prevalence in secondary open habitat than functional traits. Therefore, for small herbaceous species, geographical features of habitat and environmental factors appear to be more important than species functional traits for facilitating expansion into secondary open habitats. Our results suggested that the land cover change might have triggered the shifts of factors controlling open-habitat plant distributions from the competition with forest trees to current environmental constraints.

Ecological, phylogenetical, and pharmacognostical characteristics of Aconitum kiyomiense endemic to Hida highlands, Takayama city, Gifu Prefecture, Japan.

Aconitum kiyomiense Kadota (Ranunculaceae) is endemic to Takayama city, Gifu Prefecture, central Japan. We collected specimens from marshes and flood plains at altitudes ranging from 852 to 1085m and from a new habitat consisting of a mesic meadow in the subalpine belt (1681m). Glabrous pedicels and flowering sequence of inflorescence were used for identification, but intra-species variations in the pilus of pedicels (glabrous, pilose, and chimeric types) were observed. Although the flowering sequence has been reported as both indeterminate and determinate, all specimens in the present study were determinate. No intra-species variation was detected via partial nuclear internal transcribed space, and sequences did not match another 17 East Eurasian continent subgenus Aconitum species. The chloroplast trnL-trnF intergenic spacer region (trnL-trnF) showed three different haplotypes. The trnL-trnF dominant haplotype sequence was identical to that of A. kusnezoffii growing on the Eurasian continent, suggesting that A. kiyomiense is more primitive than other Japanese aconitum and a relic species of the Eurasian continent. We report the first detection of aconitine alkaloids in the tuberous roots, which exhibited aconitine alkaloid contents varying from 0.32 to 4.05mg/g dry weight (mg/g) for aconitine, 0.02 to 4.12mg/g for hypaconitine, undetectable to 0.05mg/g for jesaconitine, and 0.42 to 3.76mg/g for mesaconitine. The variation of aconitine alkaloid components and contents appeared to be random and did not vary with inflorescence phenotype, trnL-trnF haplotype, environmental habitat conditions, or the geographic region of the collection sites. Since most populations showed no genetic intra-variation, it will be necessary to maintain the continuity of habitats and designate areas for conservation of genetic diversity at the population level.

Functional traits and environmental conditions predict community isotopic niches and energy pathways across spatial scales

Abstract Despite ongoing research in food web ecology and functional biogeography, the links between food web structure, functional traits and environmental conditions across spatial scales remain poorly understood. Trophic niches, defined as the amount of energy and elemental space occupied by species and food webs, may help bridge this divide. Here, we ask how the functional traits of species, the environmental conditions of habitats and the spatial scale of analysis jointly determine the characteristics of trophic niches. We used isotopic niches as a proxy of trophic niches, and conducted analyses at spatial scales ranging from local food webs and metacommunities to geographically distant sites. We sampled aquatic macroinvertebrates from 104 tank bromeliads distributed across five sites from Central to South America and compiled the macroinvertebrates’ functional traits and stable isotope values (δ15N and δ13C). We assessed how isotopic niches within each bromeliad were influenced by the functional trait composition of their associated invertebrates and environmental conditions (i.e., habitat size, canopy cover [CC] and detrital concentration [DC]). We then evaluated whether the diet of dominant predators and, consequently, energy pathways within food webs reflected functional and environmental changes among bromeliads across sites. At last, we determined the extent to which the isotopic niches of macroinvertebrates within each bromeliad contributed to the metacommunity isotopic niches within each site and compared these metacommunity‐level niches over biogeographic scales. At the bromeliad level, isotopic niches increased with the functional richness of species in the food web and the DC in the bromeliad. The diet of top predators tracked shifts in prey biomass along gradients of CC and DC. Bromeliads that grew under heterogeneous CC displayed less trophic redundancy and therefore combined to form larger metacommunity isotopic niches. At last, the size of metacommunity niches depended on within‐site heterogeneity in CC. Our results suggest that the trophic niches occupied by food webs can predictably scale from local food webs to metacommunities to biogeographic regions. This scaling process is determined by both the functional traits of species and heterogeneity in environmental conditions. A plain language summary is available for this article.

Leaf micromorphological adaptation of Pogostemon spp. (section Eusteralis) in Thailand

Pogostemon section Eusteralis is comprised of diverse taxa found in a range of habitats, from terrestrial to aquatic/marshland. However, few studies have examined the leaf micromorphology of Pogostemon and the micromorphological adaptations of this section to their habitats. Therefore, leaf micromorphological characters of the section Eusteralis in Thailand were investigated to assess the relationships between leaf micromorphological characters and environmental conditions and to explore alternative taxonomic characters for supporting the infrageneric classification. Common leaf micromorphological characters of this section were striate cuticular ornamentation, capitate trichomes with two apical cells, peltate trichomes with a large head cell, a convex outline of the abaxial side of the midrib and crescent collateral vascular bundles with a parenchymatous sheath. Variable leaf micromorphological characters were observed and appeared to be associated with environmental habitat conditions. The correlation between leaf micromorphology and environmental factors were considered and it was suggested that the major factor causing different leaf micromorphology is water availability. The important leaf micromorphological trait of Eusteralis that can distinguish this section from the section Pogostemon is the type of non-glandular trichomes; the section Eusteralis possesses only simple unicellular and bicellular trichomes, but no simple multicellular trichomes were found in the section Eusteralis, unlike in the section Pogostemon. This might be used as an additional character to define the infrageneric classification of Pogostemon.

Studies on Isozyme Variations and Morphometric Relationship among three Populations of Austruca sindensis (Alcock 1900) from Pakistan

The isozyme variability and morphometric analysis were examined in three populations of the fiddler crab, Austruca sindensis. The crab samples were collected from the three populations of A. sindensis (Sandspit, Sonari, and Sonmiani) along the coast of Pakistan. Three different enzymes, Catalase (CAT), Carbonate dehydratase (CD), Amylase (Amy) and a general protein pattern were investigated. Two isozymes were identified to be useful for the populations differentiation of A. sindensis along the coast of Pakistan. POPGENE software was used for the analysis of banding pattern, polymorphic loci, allelic frequency, heterozygosity and genetic distance of three populations of A. sindensis; while, Minitab and MS-Excel was used for the analysis of morphometric analysis. Four polymorphic loci, CAT-I, CAT-II, CD-I and CD-II were interpretable in muscle with Polyacrylamide Gel Electrophoresis (PAGE), the allele frequency differs significantly, detected in population of the Sonmiani Bay as compared with Sonari and Sandspit. The morphometric analysis showed low level of variability among the three studied populations when total 8 selected morphometric traits were analyzed (wet weight (WW), carapace length (CL), carapace width (CW), abdominal length (AL), abdominal width (AW), enlarged chela length (EL), enlarged chela width (EW), pleopode length (PL)). Multiple statistical approaches applied; regression analysis, ANOVA and Discriminant function analysis (DFA). Among all the statistical analysis used total three traits, showed significant variations among three populations (CW, EL and AL). The result of this study indicated that not only the morphological difference reflects the environmental conditions of habitat, but also the biochemical variations can be considered as the indicator of specific population dispersal.

Macrobenthic biomass and production in a heterogenic subarctic fjord after invasion by the red king crab

We studied the macrobenthic fauna and their production potential in Porsangerfjord, Northern Norway, in relation to environmental gradients and the recent invasion by the predatory red king crab into the outer fjord. The study area is characterized by a distinct along-fjord temperature gradient, with the influence of warmer Atlantic water in the outer fjord and year-round bottom temperatures around zero in the inner fjord. Benthic organisms can play a crucial role in ecosystem energy flow. Despite this, our knowledge of factors regulating benthic secondary production in high latitude ecosystems is limited. Macrobenthic abundance, biomass (B), production (P) and production-to-biomass ratio (P/B) were estimated from grab samples collected in 2010. Annual P/B ratios were calculated using a multi-parameter artificial neural network (ANN) model by Brey (2012). The mean abundance, biomass, production and P/B were 4611ind.m−2 (95% CI=3994, 5316), 65gwwm−2 (95% CI=51, 82), 174kJm−2y−1 (95% CI=151, 201) and 1.02y−1, respectively. Benthic biomass and production in the fjord were dominated by polychaetes. Spatial variability in P/B and production was mainly driven by community structure and differences in environmental habitat conditions. The inner basins of the fjord were characterized by high total production (439kJm−2y−1), attributable to high standing stock biomass and community structure, despite cold bottom temperatures. In the middle and outer fjord, smaller taxa with low individual body masses increased the P/B ratios, but they did not compensate for the low biomass, thereby resulting in lower total production in these areas. The low biomass and the sparseness of large taxa in the outer and middle fjord may already be a result of predation by the invasive red king crab resulting in an overall lower macrobenthic production regime.

Environmental drivers of macroinvertebrate communities in high Arctic rivers (Svalbard)

Summary The impacts of climate‐induced environmental changes on freshwater biodiversity are not well understood in Arctic regions. We quantified water source contributions (meltwater, ground water), environmental habitat conditions and benthic macroinvertebrate community dynamics in north‐west Svalbard. The aim was to use contemporary findings to infer how future environmental change may affect these Arctic river ecosystems. Water source dynamics played an important role in influencing environmental habitat conditions; meltwater contributions to flow were related significantly to discharge, channel stability, electrical conductivity and pH. Low regional benthic macroinvertebrate diversity relative to other Arctic regions was attributed to harsh winter conditions and biogeographical dispersal constraints associated with the Svalbard archipelago. Generalised estimating equations and multivariate ordination models showed benthic macroinvertebrate diversity and abundance were influenced significantly by several environmental habitat variables. Rivers in non‐glacierised basins typically supported more diverse and abundant communities than those in glacierised basins, most likely as a consequence of the warmer water temperature and less‐disturbed habitat conditions associated with these systems. Consequently, shifts in water source contributions driven by changes in climate may alter environmental habitat conditions in Svalbard rivers and could lead to an increase in abundance and diversity among some freshwater macroinvertebrate communities.

Seaweed communities on abrasion platforms along the Newe Yam Island, in the north of Israel

The current study presents an analysis of seaweed communities of Newe Yam, a small island of rocky platforms in the north of Israel. The scope of this research was to evaluate the effect of wave action upon abrasion platforms, including tidal pools and potholes, on the distribution of marine macroalgae species thriving on natural substrates. At the study site there are two major processes operating in opposing directions. One is destruction by natural forces (wave action and chemical and physical constraints) and the other is construction by marine life. The research studies the distribution of algae species as a function of geographical conditions in the examined region. The abiotic environmental habitat conditions include: topography, the width of the abrasion platforms, the presence of potholes and rims, and the orientation of the platform. Concomitantly, the algae community was also studied. This was done along transects perpendicular to the shoreline. The local relationship between various biotic com...

Effects of gamete behavior and density on fertilization success in marine green algae: insights from three-dimensional numerical simulations

We developed a numerical simulation of mating experiment to study effects of phototactic gamete behavior and density on fertilization success, using the C++ programming language, and pseudo-parallelization methods with input parameters based on experimental data. In our experiments, we found that gametes with positive phototaxis are favored, particularly in shallow water, because they can search for potential mates on the two-dimensional (2-D) water surface rather than randomly in three dimensions. We also found evidence that sperm (male gametes) limitation might not be the dominant selective force in the evolution of isogamous or slightly anisogamous marine green algae because almost all of female gametes can be fertilized on the 2-D water surface meaning they might not be under sperm limited conditions. Gamete density also appears to affect mating success seriously. These findings were produced by some technical progress made recently to rapidly and correctly count the numbers of zygotes formed calculating the locations of huge numbers of male and female gametes in the test tank. Both gamete behavior and density might be determined by environmental conditions of habitat, particularly the depth of water.

Thermostability of Irreversible Unfolding α-Amylases Analyzed by Unfolding Kinetics

For most multidomain proteins the thermal unfolding transitions are accompanied by an irreversible step, often related to aggregation at elevated temperatures. As a consequence the analysis of thermostabilities in terms of equilibrium thermodynamics is not applicable, at least not if the irreversible process is fast with respect the structural unfolding transition. In a comparative study we investigated aggregation effects and unfolding kinetics for five homologous alpha-amylases, all from mesophilic sources but with rather different thermostabilities. The results indicate that for all enzymes the irreversible process is fast and the precedent unfolding transition is the rate-limiting step. In this case the kinetic barrier toward unfolding, as measured by unfolding rates as function of temperature, is the key feature in thermostability. The investigated enzymes exhibit activation energies (E(a)) between 208 and 364 kJmol(-1) and pronounced differences in the corresponding unfolding rates. The most thermostable alpha-amylase from Bacillus licheniformis (apparent transition temperature, T(1/2) approximately 100 degrees C) shows an unfolding rate which is four orders of magnitude smaller as compared with the alpha-amylase from pig pancreas (T(1/2) approximately 65 degrees C). Even with respect to two other alpha-amylases from Bacillus species (T(1/2) approximately 86 degrees C) the difference in unfolding rates is still two orders of magnitude.

Breeding biology and population structure of the intertidal crab Petrolisthes laevigatus (Anomura: Porcellanidae) in central-southern Chile

The present study describes the seasonal reproductive cycle and population structure of the porcellanid crab Petrolisthes laevigatus, a typical inhabitant of the rocky intertidal. A total of 960 individuals (including 372 females) was collected in monthly samples from October 1993 to December 1994 in central-southern Chile. Ovigerous females were present between August and December, and were absent between January and July. The breeding season started during late winter (August), and females with embryos close to hatching occurred between October and end of spring (December). Considering the gonadosomatic index and the duration of the incubation period, it is concluded that P. laevigatus has a markedly seasonal breeding period with probably two successive spawnings per female per season. Our results compared with previous studies in temperate intertidal porcellanids suggest a lower structural variability of the population during the sampling period, but a pronounced seasonal variation in both sex ratio and abundance. The influence of environmental habitat conditions (i.e. temperature) is suggested to be responsible for the lower variation in the crab population size structure in ovigerous females, and the almost constant size distribution observed in males.

Conspecific thistle plant selection by a herbivorous ladybird beetle, Epilachna pustulosa

AbstractHost selection by Epilachna pustulosa Kôno (Coleoptera: Coccinellidae) was surveyed in an area of about 130 ares, focusing on the role of the spatial distribution pattern of the host plant, thistle Cirsium kamtschaticum Ledeb. (Asteraceae) and the environmental conditions of habitats where thistle plants were growing. A total of 198 thistle clones were found in the area studied, and approximately 40% showed some degree of E. pustulosa infestation by July. Eggs were only oviposited on thistle clones that were fed on by adults. Adult beetles and egg masses of E. pustulosa showed an aggregated distribution in the earlier season (June) among thistle clones. The distribution of adults became more random (but still aggregated) by the later season (July), along with an increase in the number of infested clones. Multiple logistic regression analyses revealed that clone size and soil moisture were consistently important for the beetle's choice of clones to feed on. The other logistic regression analyses indicated that thistle‐clone size and sunlight condition influenced egg distribution. Thistle clone selection by E. pustulosa changed with season from a rather strict selection in June to a more obscure one in July, expanding the range of thistle clones used as feeding and oviposition substrate.

Seed size, shape and persistence in dry Mediterranean grass and scrublands

AbstractSeed size and shape, measured as the variance of the three main dimensions, have been proposed as good indicators for predicting seed persistence. We tested whether these variables were robust predictors of seed persistence in the soil for 58 abundant herbaceous species, primarily annuals, in grass and scrubland of central Spain. Seed persistence was estimated from data on germinable seed banks, while seed weight and shape were measured using fresh seeds collected in the study area. There was a significant tendency for species with persistent seeds to have smaller seeds than species with transient seeds. Seed shape was not, however, related to persistence and we did not find any clear seed weight/shape threshold for predicting persistence. The binary logistic model of seed bank type as a function of seed weight was significant and explained 67% of total variability. Supplementary information about dormancy, environmental conditions of habitat, predation and attack by pathogens has to be used to elaborate more accurate general predictive models of seed persistence.

The valley of Shimshal – a geographical portrait of a remote high mountain settlement and its pastures with reference to environmental habitat conditions in the North-West Karakorum (Pakistan)

This article presents observations on the natural hazard potential for permanent and seasonal mountain settlements and infrastructure such as routeways and irrigation canals in the North-West Karakorum. The remote high mountain settlement Shimshal (3080 m), located in the upper Shimshal valley and surrounded by three potential natural glacier dams, is of particular interest. The permanent settlement of Shimshal and its seasonal pasture settlements in the Shimshal Pamir at heights of 3200 and 4600 m respectively, reach the upper limits for permanent and temporary settlement. The choice of location for settlement and agricultural activities is already dictated by relief conditions. Primary settlement areas are the sediment accumulations in the valley floors. The wide distribution of unconsolidated screes in particular prevents settlement expansion upwards along the valley slopes. Glacial outburst floods as well as seasonal flooding events further reduce the scanty settlement area, as well as being among the most devastating sources of danger. The production of debris and the supply of loose material deposits induced in connection with the glaciation history of the area becomes a permanent source of danger for human settlement through resedimentation in the form of rockfall or mudflow. Furthermore, canal systems essential for the survival of oasis settlements suffer annual destruction through mass movements on the slopes, induced by the glacially pre-formed relief. Thus the adaptation of settlement locations to a glacially formed mountain relief will be examined in this study, with particular reference to the geomorphological landscape situation. What makes the Shimshal settlement particularly interesting is its very isolated location at a distance of 80 km from the Hunza valley which contains the main settlement concentration of the North-West Karakorum. Traditional ways of life can be expected to be well protected from outside influences. In the North-West Karakorum we find a debris landscape which differs greatly in its development and distribution from that of the Himalayas, influenced particularly in the lower valley locations between 1000 and 3000 m by the different climatic situation, and where therefore in comparison with the Himalayas a completely different pattern of natural hazards arises.

Optimal Reproductive Strategy of Plants, with Special Reference to the Modes of Reproductive Resource Allocation

Abstract A growth model for reproductive energy allocation pattern and schedule is proposed. Assumptions are as follows: (1) the assimilation rate for an individual is given by a logistic curve of vegetative dry weight; (2) size variability is expressed by the parameter W of the logistic curve (asymptotic value of vegetative dry weight); (3) a plant controls allocation of the assimilate to vegetative and reproductive structures so as to maximize the reproductive energy investment at the end of the growth period. The models were analyzed in comparison with field and experimental observations and gave reasonable explanations for the reproductive allocation pattern of individuals which reflects ecological preferences and life history characteristics, such as environmental conditions of habitats (stable or changing), length of life span (annual, biennial or perennial) and growth form (erectophile or planophile). Decreasing RA (reproductive allocation) with individual size and delayed switchover time from vegetative to reproductive growth were found in plants which occur in stable environments and have a more or less fixed growth period; in those which occur in changing environments where growth period depends on individual size, RAs that remain constant or increase with variations in individual size and early switchover time were detected. Most perennials conform to the former case, but annuals and biennials conform to the latter case. Under extremely overcrowded conditions, planophiles, which are much more subject to crowding effect than erectophiles, tend to have increasing RA with increasing size, while erectophiles tend to have almost constant RA irrespective of size. These trends are discussed in the light of the life history characteristics and ecological distribution of plant species studied.