Home – Home – Jornals – Flora and Vegetation of Asian Russia 2010 number 2

The need for separating such terms as «fluctuations» and «successions» for assessing consequences of climatically induced vegetation changes is emphasized. Despite significance, the ambiguity of these terms meaning is noted. The ambiguity is connected with existing different mechanisms of vegetation dynamics, which, in general, are described by two concepts — holistic and individualistic. Attempting to analyze some of terms (e.g., fluctuations, successions, chronosequences, successional step, successional threshold) commonly applied to vegetation dynamics performance, we assume that they are relevant to a holistic concept. In case of vegetation dynamics going as described by an individualistic concept, the phenomenological immanence of the above mentioned terms disappears. They turn into «just terms» and should be only implicated for pragmatic reasons. Besides, we could conclude that chronosequence analysis gives opportunity to reveal a dynamic process as a succession properly. From the other side, in order to determine the direction of dynamic processes, analysis of ecological groups and functional plant types is appropriate.

In the forest-steppe ecotone in Inner Mongolia of China, different tree-species are distributed with different MAP range in the forest-steppe ecotone. Both modern vegetation pattern and the Holocene vegetation development
show that Chinese pine was the most drought tolerant tree species and can resist long-term climate drying. Strong human impact on vegetation was constrained to the West Liao River basin over thousands of years of sedentary agriculture.

A range of key testing sites was used to show the capabilities of different methods of vegetation dynamics
analysis. Recognition of vegetation according to direct features and comparison of maps are applied with space photos made at different time. The indirect methods of analysis also provide a wide spectrum of possibilities.
Such a work is based on study of spatial structure of vegetation cover. The analysis of space photo patterns with further field verification works well. Application of topo-ordination schemes of vegetation allows to forecast
plant community changes.

Activity indices of plant species in altitudinal zonal elements of the flora were analyzed. As a result, displacement of forest-steppe species by true steppe species in Cleistogenetea squarrosae communities was revealed. Comparison of these tendencies with those in forest vegetation in Baikal Region suggests that ridge slopes are characterized by increasing of humidity. On the contrary, aridization process is observed in basins. Both alternatively oriented trends are inspired by general climate warming. Due to temperature increase, the permafrost existing on the forested slopes is gradually melting and provides additional soil moisturing. At the same time, the steppe ecosystems suffer a loss of the soil water supply as well as air moisture affected by climate warming.

Accurate reconstruction of past vegetation based on pollen data needs understanding of the relationships between pollen and vegetation. For this aim we placed traps and collected surface samples in typical communities in Hulun Buir steppe. A (association index), O (over-representation index), and U (under-representation index), which measure pollen representation to vegetation, were calculated when combining pollen data with vegetation data. The results suggest that the pollen produced by dominant plants, such as Artemisia, Poaceae, Rosaceae, Asteraceae, Cyperaceae and Ranunculaceae, Chenopodium is well represented and indicates the plant species growing around. It seems there is no significant correlation between the pollen productivity and pollen dispersal. Although pollen assemblages can reflect plant communities in Hulun Buir steppe, the coefficient of similarity was only 0.6, which revealed a high effect of background pollen components on the accuracy of pollen representation to vegetation in this study area.

The small patches of relict Chinese pine forests in the Ortindag Sand Land in North China are at their northern
distribution limits. Herein we summarized achievements of the recent study of cambial activity as well as tree growth and regeneration dynamics of Chinese pine populations, climate reconstructions from tree rings up to
ecosystem dynamics in the Ortindag Sand Land and their implications for ecosystem management.

The carbon flux in grassland ecosystems of different bioclimatic zones within the Transbaikal region has been studied. The extra-arid steppe (Selenginskoye middle mountain area: sedge-grass-herbage community on meadow-chestnut soil), moderately arid forest-steppe (the Selenga River delta: herbage-grassy community on meadow-subsaline soil), cryoarid forest-steppe (Vitimskoye plateau: grass-herbage community on meadowchernozem cryosoils) were among them. NPP values in all ecosystems were low: 2404 g/m² per year in the forest-steppe zone, 1407 in the arid steppe zone, and 1540 in the cryoarid ecosystem. Prevalence of the below-ground part in the total biomass structure was revealed for all communities of continental territories. On account of short warm period the total CO₂ emission is low. It is maximal from the meadow-subsaline soil in moderately arid forest-steppe and evaluated as equal 1163 g C/m². The CO₂ emission from the meadow-chestnut soil is much lower (633 g C/m²), and falls to the minimal value (353 g C/m²) in the meadow-chernozem cryosoils. The soils appear as the significant depositary of the carbon.

Soil respiration (SR) is the primary pathway by which plant-fixed CO₂ is released back to the atmosphere. Recent studies suggested that aboveground photosynthesis activity may affect as strongly as or more strongly on SR than soil temperature. We conducted a preliminary study to explore the effect of short-term assimilate supply on SR and to estimate the contribution of root-derived respiration to SR across 6 ecosystems in a foreststeppe ecotone, north China.

Description of the ecotone strip between the forest and high-mountain belts is given in the article. The main
structural ecotone elements as synusia and community are singled out. Different types of ecotone strips are described, their indicative significance is substantiated.

Floristic and geographical distinctions between meadow steppes of the order Festucetalia valesiacae and true
steppes of the order Helictotricho-Stipetalia in the South Urals were studied. The geographical differentiation of
the communities of the orders is difficult due to the complexity of the relief and strong fragmentation of the steppes. The
floristic differentiation is possible in the absence in Helictotricho-Stipetalia communities of a diagnostic combination
of meadow steppe species represented by the alliance Festucion valesiacae.

Flora of halophytic vegetation within Western Zabaikaliye is overviewed. Three hundred thirty six species and
subspecies of vascular plants from 163 genera and 52 families have been registered. The distinct specificity of
flora is a high rank of Chenopod family in the families’ spectra, and Chenopodium, Suaeda, as well as Plantago,
Puccinellia — in the genera’ spectra. Enrichment of the saline habitat flora is achieved mostly due to numerous
glycophytes tolerant to substrate salinity. Despite it, plant communities in saline habitats are always predominating
by halophytes. The preliminary classification of halophytic plant communities in accordance with Braun-Blanquet approach is
proposed. As a result 3 orders, 4 alliances, 14 associations, 4 subassociations, and 11 variants, belonging to the
classes Scorzonero-Juncetea gerardii and Thero-Salicornietea, are distinguished. The first class contains the majority
of recognized syntaxa. Such features as great variability of synmorphology, widely fluctuating physiognomic
aspects, and mostly low species richness have been noted as typical of halophytic plant communities.

The results of study of bryophytes in the moderately dry oak-woods (all. Lathyro-Quercion roboris), pine forests
(all. Caragano fruticis-Pinion sylvestris) and larch-birch forests (all. Veronico teucrii-Pinion sylvestris) of the South
Urals are discussed. Eighty moss species and 8 liverworts have been revealed. Forty nine percent of bryophyte
species have low constancy. The lowest diversity of bryophytes is characteristic of larch-birch forests (23 species)
and oak-woods (32 species), the highest — of pine forests (83 species). Species that grow on the bases of
tree trunks and on the rotten wood (Pylaisia polyantha, Pseudoleskeella nervosa, Stereodon pallescens, Sciuro-hypnum
reflexum, Brachytheciastrum velutinum, Plagiomnium cuspidatum, Platygyrium repens) have high constancy. In the
forest communities which are developed on the slopes, epilythic bryophytes of carbonate rocks (Tortella tortuosa,
Schistidium apocarpum s.l., Pseudoleskeella tectorum) and ground light-loving species (Abietinella abietina,
Ceratodon purpureus, Rhytidium rugosum, Syntrichia ruralis) are abundant. In comparison with moderately dry
forests of the Russian Plain, communities from the South Urals are distinguished by almost complete absence
of ruderal moss species. This indicates low disturbance and natural character of the Urals communities and
emphasizes their high conservation value.

Populations of East-Asian species (Sсutellaria baicalensis, Sophora flavescens, and Astragalus membranaceus) in the
territory of Zabaikaliye, the Russian Far-East and Inner Mongolia were studied. A total of 363 relevees were
processed using the ecological scales, and ranges of environmental conditions were evaluated. To assess population
optimum, the individual and cenopopulation features were taken into account. As the most appropriate,
the ecological scales method proposed by I.A. Tsatsenkin et al. (1978) for analyzing forest-steppe communities
was used. By integrating data on plant communities and populations the optimal conditions for each species
were revealed. Generally, habitats of South and South-Eastern part of Zabaikaliye and the Russian Far-East are
the most favorable for the species under study. We conclude that moisture might be the key factor for functioning
of populations of East-Asian species.

Indices of temperature, precipitation and relative evapotranspiration (RET) for the last 51 years in the borderland
between Shaanxi and Gansu Provinces, and Ningxia Hui Autonomous Region (BSGNAR) were calculated
to analyze the climate change in this area. During the past 50 years, the average temperature increased
significantly, while precipitation decreased slightly with regional differences. RET change was not so distinct
in general, but had a minor increase at the late stage of the study period. Under such circumstances, climate
change had clear effects on distribution of potential vegetation in the area, with a tendency to transit to warming
and drying vegetation types.