Scientific results of the Bryotrop expedition to Zaire and Rwanda : 7., life strategies of epiphytic bryophytes from tropical lowland and montane forests, ericaceous woodlands and the Dendrosenecio subpáramo of the eastern Congo basin and the adjacent mountains (Parc National de Kahuzi-Biega/Zaire, Forêt de Nyungwe/Rwanda)

Life strategies of epiphytic bryophytes are studied along an altitudinal gradient from the eastern Congo basin (tropical lowland zone) to the mountains of the East-African graben (tropical subalpine/alpine Zone; BRYOTROP III-transect). Three strategies, Colonists, Perennial shuttle species and Perennial stayers can be observed, which are further subdivided according to their reproduction tactic (high sexual reproductive effort, high asexual reproductive effort, moderately or low sexual and asexual reproductive effort). Of these, only taxa with a long life span (perennials) are of importance, indicating the unchanging and constant ecological conditions and long-lasting microsites, provided by the epiphytic habitats. The basis for the life strategy pattern analysis along the altitudinal gradient were plant sociological investigations and the determination of the mean percentage cover values for the different life strategy categories. By this, the distribution and occurrence of the different strategies within the communities and the altitudinal zones can be shown

Diversity and altitudinal niche width characteristics for 35 taxa of the Papua New Guinea Frullania flora with consideration of sibling pairs

The Frullania taxa on Mount Albert Edward, Papua New Guinea, form many associations that suggest a high degree of niche similarity, but at different altitudes, different associations form. The species diversity of the genus is greatest at the middle altitudes and least in the dry lowlands. This altitudinal separation is apparent in the niche widths of the taxa. The members of the four sibling taxa pairs examined exhibit distinct altitudinal niches, suggesting that the sibling taxa are distinct, with different niche optima

Tropical rainforest bird community structure in relation to altitude, tree species composition, and null models in the Western Ghats, India

Studies of species distributions on elevational gradients are essential to understand principles of community organisation as well as to conserve species in montane regions. This study examined the patterns of species richness, abundance, composition, range sizes, and distribution of rainforest birds at 14 sites along an elevational gradient (500-1400 m) in the Kalakad-Mundanthurai Tiger Reserve (KMTR) of the Western Ghats, India. In contrast to theoretical expectation, resident bird species richness did not change significantly with elevation although the species composition changed substantially (<10% similarity) between the lowest and highest elevation sites. Constancy in species richness was possibly due to relative constancy in productivity and lack of elevational trends in vegetation structure. Elevational range size of birds, expected to increase with elevation according to Rapoport's rule, was found to show a contrasting inverse U-shaped pattern because species with narrow elevational distributions, including endemics, occurred at both ends of the gradient (below 800 m and above 1,200 m). Bird species composition also did not vary randomly along the gradient as assessed using a hierarchy of null models of community assembly, from completely unconstrained models to ones with species richness and range-size distribution restrictions. Instead, bird community composition was significantly correlated with elevation and tree species composition of sites, indicating the influence of deterministic factors on bird community structure. Conservation of low- and high-elevation areas and maintenance of tree species composition against habitat alteration are important for bird conservation in the southern Western Ghats rainforests.Comment: 36 pages, 5 figures, two tables (including one in the appendix) Submitted to the Journal of the Bombay Natural History Society (JBNHS

Diversity and composition of cactus species along an altitudinal gradient in the Sierras del Norte Mountains (Córdoba, Argentina)

Cacti are important elements of the flora in many ecosystems of the Americas. However, the factors that determine their richness and composition are not well known, particularly at the regional scale. The aim of this work was to study the patterns of cactus richness (both species and growth forms) and composition in the Sierras del Norte mountain range (Córdoba Province, Argentina). Species presence was recorded at 55 sites covering an altitudinal gradient from 203 to 970 m. Twenty four species from eight genera were recorded in the area. Total species richness and growth form richness decreased with increasing altitude. The richness of columnar and short columnar species decreased with increasing altitude, whereas richness of globose species increased. Opuntioid richness did not respond to altitude. Species composition was strongly related to altitude. Gymnocalycium bruchii and Parodia erinacea occurred at sites located at higher altitudes, whereas at sites at lower altitudes, Gymnocalycium schickendantzii, Stetsonia coryne and Cleistocactus baumannii, among other species, were present. Our results highlight the importance of altitude in shaping the distribution of species and growth forms in the Sierras del Norte Mountains.Fil: Gurvich, Diego Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Zeballos, Sebastián Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; ArgentinaFil: Demaio, Pablo Horacio. NGO Ecosistemas Argentinos; Argentin

Ecology of bryophytes along altitudinal and latitudinal gradients in New Zealand

Six altitudinal transects through temperate rain forests were studied at different latitudes in the South and North Island of New Zealand with respect to species numbers of bryophytes, cover and phytomass of epiphytic bryophytes, composition of life forms and ratio liverworts : mosses. Phytodiversity of bryophytes is almost constant from the lowlands to the high montane belt but decreases in the subalpine belt. Similarly, phytomass and cover increase with elevation but decrease in the subalpine belt. The percentage of liverworts increases accordingly and can reach maxima of 80-90%. The most significant life forms are tails and wefts characteristic for hyperhygric conditions, pendents for cloud belts and cushions for subalpine belts. The altitudinal gradient is much stronger then the latitudinal gradient, that means the differences between the elevations within a transect are more important than the differences between the transects. They are attributed to the humidity. The temperate rain forests of New Zealand have similar bryological characteristics as the tropical rain forests in equatorial latitudes in 2000 – 3000 m altitude but differ in the drier subalpine belt and higher phytomass

Höhengradienten in der Biodiversitäts-Forschung: eine Übersicht unter Berücksichtigung des Klimawandels

Mountains, with their isolated position and altitudinal belts, are hotspots of biodiversity. Their flora and fauna have been observed worldwide since the days of Alexander von Humboldt, which has led to basic knowledge and understanding of species composition and the most important driving forces of ecosystem differentiation in such altitudinal gradients. Systematically designed analyses of changes in species composition with increasing elevation have been increasingly implemented since the 1990s. Since global climate change is one of the most important problems facing the world this century, a focus on such ecosystem studies is urgently needed. To identify the main future needs of such research we analyze the studies dealing with species changes of diverse taxonomical groups along altitudinal gradients (0 to 6,400 m a.s. l.) on all continents, published during the past one to two decades. From our study we can conclude that although mountains are powerful for climate change research most studies have to face the challenge of separating confounding effects driving species assemblages along altitudinal gradients. Our study therefore supports the view of the need of a global altitudinal concept including that (1) not only one or a few taxonomical groups should be analyzed, but rather different taxonomical groups covering all ecosystem functions simultaneously; (2) relevant site conditions should be registered to reveal direct environmental variables responsible for species distribution patterns and to resolve inconsistent effects along the altitudinal gradients; (3) transect design is appropriate for analyzing ecosystem changes in site gradients and over time; (4) both the study design and the individual methods should be standardized to compare the data collected worldwide; and (5) a long-term perspective is important to quantify the degree and direction of species changes and to validate species distribution models. (6) Finally we suggest to develop experimental altitudinal approaches to overcome the addressed problems of biodiversity surveys.Gebirge mit ihrer mehr oder weniger isolierten Lage und ihren vielfältigen Höhenstufen stellen „Hotspots der Biodiversität“ dar. Ihre Flora und Fauna wird seit den ersten Beschreibungen durch Alexander von Humboldt immer wieder untersucht. Systematisch angelegte Studien zur räumlichen Verteilung von Arten bzw. Artengruppen in Höhengradienten erlangen eine zunehmend größere Bedeutung seit den 1990iger Jahren, insbesondere im Rahmen der Klimafolgenforschung. Um für die zukünftige Biodiversitätsforschung die heute als wesentlich angesehenen Forschungsansätze zu identifizieren, wurden in dieser Studie Literaturangaben der letzten zwei Jahrzehnte über die sich verändernden Artenzusammensetzungen in Höhengradienten aus allen Kontinenten, verschiedenen Artengruppen und einem Höhenbereich von 0 bis 6.400 m ü. NN ausgewertet. Diese Zusammenstellung zeigt, dass Untersuchungen der Muster der Biodiversität von Höhengradienten in Gebirgen einen wichtigen Beitrag für das Verständnis der Herausbildung und Änderung von Biodiversitätsmustern gerade im Rahmen des zu erwartenden Klimawandels leisten können. Die Musterbildung im Höhengradienten ist für verschiedene Artengruppen durchaus unterschiedlich. Diese Literaturauswertung macht aber auch die Notwendigkeit eines weltweit einheitlichen Konzeptes für die Forschung in Höhengradienten deutlich. Ein solches Konzept sollte folgende Gesichtspunkte beinhalten: (1) Nicht nur ausgewählte Artengruppen, sondern mehrere verschiedene Artengruppen gemeinsam analysieren; nur so lassen sich die vielfältigen Ökosystemfunktionen und Prozesse berücksichtigen. (2) Begleitend möglichst viele Umweltfaktoren erfassen, um herausarbeiten zu können, welche der Umweltfaktoren für die Musterbildung wirklich maßgeblich sind. (3) Die Transekte so anlegen, dass sie nicht nur eine einmalige räumliche Analyse ermöglichen, sondern auch zukünftig im Sinne von Zeitreihen zur Verfügung stehen. (4) Sowohl das Erhebungsflächendesign als auch die Aufnahmemethoden für die einzelnen Artengruppen standardisieren, um die Daten weltweit vergleichen zu können. (5) Langzeitstudien starten; denn nur sie bieten die Möglichkeit, erwartete oder aus Modellen abgeleitete Veränderungen der Artenzusammensetzungen bzw. von Verschiebungen von einzelnen Arten im Höhengradienten zu validieren. (6) Gezielt konzipierte Experimente einsetzen, um offene Fragen zur Verteilung der Arten in Höhengradienten untersuchen zu können

Facultative Altitudinal Movements by Mountain White-Crowned Sparrows (Zonotrichia Leucophrys Oriantha) in the Sierra Nevada

Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) winter in Mexico and often arrive in the vicinity of their breeding grounds in the Sierra Nevada well before nesting is possible. Arrival at Tioga Pass, California (elevation 3,030 m), usually occurs in early May, but residual winter snow and adverse weather can delay nesting for weeks. We used radiotelemetry to determine whether prebreeding Mountain White-crowned Sparrows engaged in weather-related altitudinal movements during the waiting period between the end of spring migration and onset of breeding during 1995-2001, with a range of residual winter snowpacks. Interannual variation in arrival date and onset of egg laying was 18 and 41 days, respectively. We tracked females for two years and males for all seven years. During spring snowstorms (which occurred in four years), radiomarked individuals moved to lower elevation sites, where they often remained for several days. Departing birds left Tioga Pass by early afternoon and returned early in the morning after storms. More frequent storms during tracking increased the likelihood of facultative altitudinal movements, but heavier residual winter snowpack did not. Warm days increased the likelihood of birds returning to Tioga Pass from low elevation. This study demonstrates that facultative altitudinal movement behavior can be a common feature of spring arrival biology in montane-breeding birds. Received 1 November 2002, accepted 30 June 2004.Integrative Biolog

Structure and Dynamics of Tree Stands at the Upper Timberline in the Western Part of the Putorana Plateau

Analysis of the age structure of Dahurian larch (Larix gmelinii Rupr.) forests in the western part of the Putorana Plateau (Sukhie Gory Range) and comparison of diachronous topographic maps and satellite images have revealed changes in the altitudinal position of the upper boundary of tree vegetation. the most significant changes occurred on south- and southwest-facing slopes. Correlations of trunk diameters with the phytomass of trees and its fractions have been found. the course of changes in the structure and phytomass of tree stands in the upper timberline over the past centuries has been reconstructed. Forest expansion has been facilitated by the general change in climate conditions (warming) in the study area.This study was supported by the Russian Science Foundation, project no. 17-14-01112