The retrieval of the nonlinear random waves from the non-Gaussian characteristics of the sea surface elevation distribution

In this paper, without recourse to the nonlinear dynamical equations of the waves, the nonlinear random waves are retrieved from the non-Gaussian characteristic of the sea surface elevation distribution. The question of coincidence of the nonlinear wave profile, spectrum and its distributions of maximum (or minimum) values of the sea surface elevation with results derived from some existing nonlinear theories is expounded under the narrow-band spectrum condition. Taking the shoaling sea wave as an example, the nonlinear random wave process and its spectrum in shallow water are retrieved from both the non-Gaussian characteristics of the sea surface elevation distribution in shallow water and the normal sea waves in deep water and compared with the values actually measured. Results show that they can coincide with the actually measured values quite well, thus, this can confirm that the method proposed in this paper is feasible.

Surface Elevation Distribution of Sea Waves Based on the Maximum Entropy Principle

A probability density function of surface elevation is obtained through improvement of the method introduced by Cieslikiewicz who employed the maximum entropy principle to investigate the surface elevation distribution. The density function can be easily extended to higher order according to demand and is non-negative everywhere, satisfying the basic behavior of the probability, Moreover because the distribution is derived without any assumption about sea waves, it is found from comparison with several accepted distributions that the new form of distribution can be applied in a wider range of wave conditions, In addition, the density function can be used to fit some observed distributions of surface vertical acceleration although something remains unsolved.

Distribution Pattern of Vascular Plant Species of Mountains in Nepal and their Fate Against Global Warming

This study aims to find the altitudinal distribution pattern of vascular plant species reported from high mountain of Nepal(Manang) along the whole Himalayan elevation gradient, and evaluate their fate against climate change. Data was gathered from multiple sources, field investigations, literatures, and herbarium specimens. Altogether, 303 vascular plant species were reported from Manang. We used a published data to calculate distribution range of each species by interpolating between its upper and lower elevation limits. The relationship between elevation and species richness is elucidated by generalized linear model. The consequence of global warming upon Manang's vascular plant species was estimated based on projected temperature change for next century and adiabatic lapse rate along the elevation gradient of the Himalayas. The vascular plant species richness has a unimodel relationship with elevation along the whole elevation gradient of Nepal as well as in three biogeographical regions of Nepal. Vascular plants of Manang are found distributed from low land Terai to high alpine regions of Nepal and their elevation distribution range varies from 200 to 4700 m. Out of 303 vascular plants of Manang, only seven species might be affected if temperature increase by 1.5°C, whereas at least 70 species will be affected with 5°C temperature increased. However, the majority of species(233 species) have wider distribution range(> 1000 m) and more than 5°C temperature tolerance range, thus they are likely to be less affected from global warming by the end of 21 st century.

Elevational distribution of forests and its spatiotemporal dynamics in subtropical China from 2000 to 2019

The subtropical region of China possesses abundant forest resources and features a mountainous terrain.Under the implementation of policies such as natural forest protection,the Grain for Green Project,and other initiatives since the beginning of the 21st century,coupled with climate change,the forest resources in this region have undergone significant changes compared to historical periods.In addition,forest resources distributing mainly in mountainous areas also implies that these changes may vary significantly with elevation.To explore the spatiotemporal dynamics of forest distribution in subtropical China since 2000,especially the trend of changes with elevation,we analyzed the data from two land cover products focusing on forest cover and forest types.We used a hierarchical approach,in which coarse-classification forest cover data with relatively small uncertainties impose constraints on forest type data with larger uncertainties,to achieve a reasonable balance between obtaining more details and reducing data uncertainty.We first divided the forest cover data into‘unchanged'and‘changed'categories.With the constraints by the forest cover results,we further analyzed the‘unchanged'and‘changed'forest types.The results indicated that,since the implementation of ecological engineering and management policies,54%of the area in the subtropical region had maintained unchanged forest cover attributes over the past 20 years,which implied the good state of ecological environment.The results also showed that dynamic conversions existed in the long term between forests and lands for essential production needs like croplands.The elevational variations of forest cover suggested that the dominant changes came from the conversion between forests and croplands in low-elevation regions below 700 m,the conversion between forests and shrublands in mid-elevation regions of 700–1500 m,and the conversion between forests and grasslands in high-elevation regions above 2000 m.In the regions with unchanged forest cover,96%exhibited unchanged forest types as well.Evergreen broad-leaved forests(EBF)were most widely distributed below 1700 m,while evergreen needle-leaved forests(ENF)dominated above 1700 m.There was still a large area of ENF and EBF undergoing dynamic conversions from/to transitional forest types such as mosaic of tree,shrub,and herbaceous cover(T-S-H)and mosaic of natural vegetation and cropland(NV-CRO).ENF almost unidirectionally transformed into T-S-H in low-elevation regions below 1000 m,and transformed from NV-CRO in mid-and high-elevation regions above1000 m.EBF experienced an areal decrease and transformed into T-S-H in low-elevation regions,but the areal increase in mid-to low-elevation regions mainly transformed from NV-CRO.These variations with elevation may involve the impacts of specific human activities and climate change,and will provide a vertical dimension of information and perspectives for an in-depth exploration of the evolving ecosystem services of forest resources in subtropical China.

Elevation patterns of woody taxa richness in the evergreen Afromontane vegetation of Ethiopia

Plant species distributions show patterns along elevation gradients. Regardless of the diverse Afromontane vegetation in Ethiopia (AFE), studies of elevation patterns of woody plants are limited and they are restricted to small areas or single/few Mountains. Moreover, there is no general consensus on the patterns of woody taxa distribution by elevation. The objectives of this study were to examine the elevation patterns of woody taxa richness and their relationship with elevation in the AFE. Data were collected and compiled from the Flora of Ethiopia and Eritrea (Vols. 1-7). About 5918 plant species of 243 families were examined and their elevational distributions were recorded. The distributional ranges of woody taxa were aggregated at 19 points (sites) at 100 m intervals starting from 1500 to 3400 m a.s.l. Single-factor analysis of variance (one-way ANOVA) was used to test the hypothesis that mean species richness of woody taxa decreases from the lower to the upper limit of AFE. Simple linear correlation and regression were used to show the relationships of woody taxa richness with elevation. We documented the presence of 505 woody taxa (441 species, 31 subspecies and 33 varieties) representing 267 genera and 90 families in the AFE. In terms of habit, 279 taxa are shrubs, 178 are trees and 48 are lianas. The distribution of woody taxa (trees, shrubs and lianas) showed a slight increase at the lower portion and a monotonic decline with increasing elevation. Species richness of trees, shrubs and lianas was negatively and significantly correlated with elevation (r = −0.985, −0.984, −0.981, respectively; all p < 0.001). Our hypothesis was accepted because mean richness significantly decreased from the lower to the upper limit of AFE (p < 0.001). Generally, monotonic patterns of decline in richness were observed for trees, shrubs and lianas. The contribution of shrubs to total richness increased with increasing elevation whereas that of trees and lianas decreased.

Human activities and elevational constraints restrict ranging patterns of snub-nosed monkeys in a mountainous refuge

Both natural conditions and anthropogenic factors affect the survivability,distribution,and population density of wildlife.To understand the extent and how these factors drive species distributions,a detailed description of animal movement patterns in natural habitats is needed.In this study,we used satellite telemetry to monitor elevational ranges favored by endangered golden snub-nosed monkeys(Rhinopithecus roxellana),in the Qinling Mountains,central China.We investigated the abundance and distribution of food resources through sampling vegetation quadrats at different elevations and sampled anthropogenic activities using field surveys.Our results indicated that although there was no significant variation in food resources between low-(<1500 m)and middle-elevations(1500–2200 m),monkeys were found most often in areas above 1500 m,where there was less anthropogenic development(e.g.houses and roads);however,monkeys rarely ranged above 2200 m and had limited food availability at this altitude.There was limited human disturbance at this elevation.We suggest that both human activity and ecological constraints(i.e.food resources)have considerable effects on elevational use of R.roxellana in the Qinling Mountains.This study highlights the critical roles these factors can play in shaping the vertical distribution of high-altitude primates.This research provides useful insights for habitat-based conservation plans in which human disturbance management and habitat restoration should be prioritized.

Strong partitioning of soil bacterial community composition and co-occurrence networks along a small-scale elevational gradient on Zijin Mountain

The elevational distributions of bacterial communities in natural mountain forests,especially along large elevational gradients,have been studied for many years.However,the distributional patterns that underlie variations in soil bacterial communities along small-scale elevational gradients in urban ecosystems are not yet well understood.Using Illumina MiSeq DNA sequencing,we surveyed soil bacterial communities at three elevations on Zijin Mountain in Nanjing City:the hilltop(300 m a.s.l.),the hillside(150 m a.s.l.),and the foot of the hill(0 m a.s.l.).The results showed that edaphic properties differed significantly with elevation.Bacterial community composition,rather than alpha diversity,strongly differed among the three elevations(Adonis:R2=0.12,P<0.01).Adonis and DistLM analyses demonstrated that bacterial community composition was highly correlated with soil pH,elevation,total nitrogen(TN),and dissolved organic carbon(DOC).The degree scores,betweenness centralities,and composition of keystone species were distinct among the elevations.These results demonstrate strong elevational partitioning in the distributions of soil bacterial communities along the gradient on Zijin Mountain.Soil pH and elevation together drove the smallscale elevational distribution of soil bacterial communities.This study broadens our understanding of distribution patterns and biotic co-occurrence associations of soil bacterial communities from large elevational gradients to short elevational gradients.

Influence of complex topography on global solar radiation in the Yangtze River Basin

Global solar radiation（GSR） is the most direct source and form of global energy, and calculation of its quantity is highly complex due to influences of local topography and terrain inter-shielding. Digital elevation model（DEM） data as a representation of the complex terrain and multiplicity condition produces a series of topographic factors（e.g. slope, aspect, etc.）. Based on 1 km resolution DEM data, meteorological observations and NOAA-AVHRR remote sensing data, a distributed model for the calculation of GSR over rugged terrain within the Yangtze River Basin has been developed. The overarching model permits calculation of astronomical solar radiation for rugged topography and comprises a distributed direct solar radiation model, a distributed diffuse radiation model and a distributed terrain reflectance radiation model. Using the developed model, a quantitative simulation of the GSR space distribution and visualization has been undertaken, with results subsequently analyzed with respect to locality and terrain. Analyses suggest that GSR magnitude is seasonally affected, while the degree of influence was found to increase in concurrence with increasing altitude. Moreover, GSR magnitude exhibited clear spatial variation with respect to the dominant local aspect; GSR values associated with the sunny southern slopes were significantly greater than those associated with shaded slopes. Error analysis indicates a mean absolute error of 12.983 MJm-2 and a mean relative error of 3.608%, while the results based on a site authentication procedure display an absolute error of 22.621 MJm-2 and a relative error of 4.626%.