Terrestrial Ecosystems Dynamic
Ecological systems are dynamic by nature and constantly feel the influence of climate variability. Since the structure and functioning of forest ecosystems are controlled by climatic factors through metabolic function, it may change in the future dynamics of forest restoration, growth, progress and growth of tree mortality, as well as the relationship of rocks. It is expected that climate change will be faster than the rate at which ecosystems can adapt and repair itself.
Ecosystems of the North must first of all respond to possible global warming because of climate-driven ecosystem response reveals itself most clearly. At high latitudes, with the growth temperature to be increased one-year rainfall due to the fact that during warm periods path cyclones shifted to the north.
We should expect significant movement boundaries of vegetation. It is believed that the rate of migration of various species of trees in the past was of the order of 4-200 km per century. In regard to the regions in the middle latitudes, the average warming 1-3, 5 ° C over the next 100 years would mean moving existing geographical zones with temperatures in the same direction around the poles, or moving 150-550 km height approximately 150-550 m.
In Finland, the next century estimated temperature rise at high latitudes 2-4 ° C (to be regarded as elongation factor growing season), as well as increasing the number of annual precipitation of 10-15% allows timbers extend their ranges to the north at a rate 10-45 km per century (Year Book, 1996)
Global warming and a decrease (or complete cessation) grazing in alpine meadows in Austria led to the emergence of numerous trees in the band of 100 meters above the forest (Stutzer, 1999). Many of these trees are damaged as a result of freezing and drying icing. In the future, we should expect raising edge of the forest 50 m, as in this band trees differ satisfactory growth and fruit. However, climatic conditions are so severe that the trees are primarily distributed through the vegetative propagation.
Accordingly, the composition of species in forests is likely change. In some regions may disappear entirely whole forest types, and at the same time there can be new assemblages of species and hence new ecosystems. A substantial part of the existing forest areas of the globe (on average around the globe at one third of the territory with variations by region from one-seventh to two-thirds) as one of the consequences of possible changes in temperature and in the presence of water in equilibrium with the equivalent of twice the CO2 content major changes in the common vegetation types; with the greatest changes occur at high latitudes and the least – in the tropics.
A direct impact on ecosystems will provide increase of CO2 (and some other gases) in the atmosphere, which can lead to increased productivity and efficiency of water use by some plant species. Secondary effects of climate change can be manifested in changes in soil characteristics and environmental violations (e. g. occurrence of fires, pests and diseases) that are more favorable for some species than others, and will, as a result, changes in species composition and ratio in ecosystems.
Adaptation options for ecosystems are limited, and their effectiveness is questionable. Relevant options include promoting the establishment of corridors to facilitate the ” migration” of ecosystems, land use management, actively promoting natural regeneration, forest plantations and artificial restoration of degraded areas.
Since the predicted rate of climate change will be greater than the speed with which different species can adapt (including movement range), as well as because of the isolation and fragmentation of many ecosystems, the presence of conjugated impact factors (natural resources, industrial pollution, human carelessness) and limited adaptation options ecosystems (especially forest systems, mountain ranges and coral reefs) are quite vulnerable to the impacts of climate change.
As in the scenarios of climate change in the projections of forest occur as optimistic as pessimistic scenarios. Special studies and model calculations carried out at the Institute of Global Climate and Ecology showed that in the next 50 years, the impact of climate change on forest growth in general will be small – on the order of magnitude smaller than that of the non-equilibrium distribution of forest age, formed under the influence of intensive logging of previous years. The author can accept only if one considers only the direct effects of climate change. But the destruction of forest stands combination of adverse climatic factors, leading to a weakening of the plants or the creation of optimal conditions for the development of pests, diseases, fires a weak signal. The situation is even in relatively prosperous 20th century testifies to the huge destructive role of pests, diseases, fires in boreal forests.
Some studies temperate ecosystems Asia (between 18 ° N and the Arctic Circle, including: Japanese islands. The Korean peninsula, Mongolia, most of China and the Russian Siberia), based on the use of different models, give reason to believe that climate conditions equivalent to a doubling of CO2 will significantly decrease in the area (50%) and productivity of boreal forests (mainly in the Russian Federation), accompanied by a significant expansion of grazing areas and shrubs. There will be also a decrease in the area of tundra (up to 50%), accompanied by the release of methane from deep horizons of peatlands and the increase (25%) emissions CO2. What will also be an additional factor contributing to the increase in the greenhouse effect.
Permafrost, Tundra, Swamps
If warming enhanced plant growth, wherein the carbon dioxide is absorbed by the atmosphere cannot compensate for the accelerated decomposition of organic substances. Since when significant climate warming is predicted in the northern and arctic regions, where large areas are occupied by tundra and wetlands. In turn, the permafrost from thawing ice more peat is exposed to microorganisms decomposing organic matter and a large selection of CO2 and CH4 in the atmosphere. It is estimated that with an increase in summer temperatures in the tundra at 4 ° C in the atmosphere to allocate an additional 50% of carbon from peat, despite more intensive growth of plants is not intended to compensate.
Some wetlands will become a forest or heath. Woody plants growing on the permafrost will be subjected to significant impacts in the process of melting. The initial overall impact of warming on carbon accumulation in the high ecosystems is likely to be negative, since the processes of decay in the beginning will go faster reproduction (Technical summary climate change 2001: A Report of Working Group II, 2001). In these systems, changes in albedo and energy absorption during winter will act as a positive makeup regional warming as a result of early snow melt and, in the course of decades and centuries, the forest boundary will move to the North Pole. Most processes in wetland areas depend on hydrological conditions (drainage); therefore adaptation to alleged climate change may be practically impossible. Arctic and subarctic bog communities on permafrost, as well as the more southern depression wetlands with small drainage areas, are likely to be most sensitive to climate change. In some cases, changing drainage may be accompanied by fires in peatlands.
For example, areas of permafrost currently hold 58% of the territory of Russia. In the Moscow State University of Lomonosov was the prognosis changes the southern boundary of the permafrost for 2100. Vast areas of Russia in the next century will be in areas of permafrost degradation. In the southern regions of the Urals and Siberia permafrost border will move by 2100 to 300-400 km to the north.
Currently tundra soils behave as follows: during periods of waterlogging – the source of methane during drought. About the reaction of the tundra climate change, there are different forecasts: so if climate change will lead to a reduction in rainfall in the summer, the tundra will be a drain methane, on the other hand, there are mechanisms that stabilize the soil moisture and temperature, which compensate for this effect. Thus, if climate change does not stimulate any successional changes in the tundra landscape, the average flow of the tundra will be about the same.
Studies show that the potential wetlands are highly vulnerable. Now as a result of the process of peat accumulation, they are a net carbon sink. He is estimated to be approximately 150 million tonnes of C02 equivalent per year. Even small anthropogenic climate impacts on the large flow can lead to significant emissions.
Studies of the Institute of Atmospheric Physics, Russian Academy of Sciences In the short time scale of the flow of methane from the tundra can be very responsive to variations in climatic parameters, since the functioning of micro-organisms and is strongly dependent on temperature and soil moisture. In general, in the long term, the melting of permafrost is expected to strengthen methane emissions.
There are currently no unequivocal opinion about the direction of the West Siberian nature. Most modern scholars believe that there is a progressive hydromorfization. However, there is another point of view, according to which water logging in the region to date has stabilized and in some areas is replaced by the reducing of swamps. The reason for these differences lies in the fact that the territorial and temporal changes of forests and wetlands are complex and non-unidirectional process which is determined by factors both local and global order, changing both in space and in time. This statement is consistent with our observations.
Permafrost degradation western boreal forest of Canada due to climate warming, while due to rising water swamp forests are replaced by treeless oligotrophic. Since the Little Ice Age degraded only 9% of the permafrost, so most of the sites are in relict state. However, the condition of 22% preserved permafrost is unstable. It is assumed that the operating environment will be further loss of forest areas in the boreal continental zone to the west of the country, with the projected increase in the long accumulation of organic matter by another 11%.
Influence of rainfall variability on growth conifer species seen in many parts of the Subarctic. However, it is more varied, depending on the conditions of habitats and is less pronounced compared to the influence of temperature. Often this effect is mediated by soil hydrological and thermal regimes.
We also should not exclude the possibility that an increase in winter precipitation, later snow cover will be accompanied by a shift to later date cambium activation despite an increase in summer temperatures.
Spatial and temporal distribution of rainfall and temperature – the main factors determining the distribution of woody plants in the world. Air temperature affects the physiological processes in plants and, in the long term, the population and the level of social development. Temperature determines the yield and quality of seeds and fruits, influencing processes such as flowering, budding, ripening fruits and cones (Kozlowski, Pallardi, 1997). Spring and autumn air temperature changes also affect the softening and hardening of the needles (Guak et al., 1998). Temperature determines the level of ecosystem processes, such as degradation and mineralization of soil. Indirect effects associated with heating can be even more noticeable than a direct connection with the increase in temperature of plants – in the subpolar biological communities where heat is likely permafrost layer (Mooney et al., 1999). Local forests are adapted to the local climate characteristics. However, in case of significant climate change, adaptation to local unchanging climate can play a negative role for stability.
Lack or excess of water is determined for the most important processes related to food biochemistry. In particular, swamp forests are sensitive to changes in the hydrological regime. Since forest ecosystems usually occupy regions where the lack of moisture has no (or almost no) place, the distribution of water resources in space and time seems critical for the carbon balance and is one of the main components of the models used to predict global climate change.
Changes in the distribution and abundance of plant and animal species are recorded in the levels of fertility and mortality, particularly the growth and spread of individuals in the population. Climate and soil determine the presence and growth of plants. Climate influences the distribution and abundance of species, determining the availability of resources, fertility and survival (Hansen, Rotella, 1999). Changes in the mode of action, as well as competition and cooperation with other species also affect the distribution of animals and plants. The vital role played by human activity also.
Global climate change could primarily entail changing the relationship between the rocks. Most likely, these changes will be shown on the stage of regeneration in the area of boreal forests. On the northern border larch forests is a pioneer, but high demands on lighting conditions does not give her a chance to compete with other species in areas where they have an acceptable climate and soil conditions. Therefore, when climate change larch on part of its range may be replaced by spruce and fir, and in some cases, and pine. Spruce global temperature increase by itself would not be able to change the conditions of growth and reproduction. However, changes in precipitation can have a negative impact on her, especially in areas of southern taiga and mixed forests. For hardwood probable climate change will be less significant than for conifers – for immediate impact. However, the destruction of conifers, stimulated by climate change (outbreaks of pests and diseases, fires, etc..), Frees up space for the development of aspen, birch, alder, willow (indirect effects).
In the study of the influence of climate change on forests and natural protected areas in Mexico, the deterioration of the conditions for the existence of vegetation (increasing aridity) (Villers-Ruiz, Trejo-Vazquez, 1998). Expected disappearance of 13% of the forests is moderately cold and moderately hot climate. On the other hand, will increase the share of tropical dry forest and rainforest humid and sub-humid.
Vertical subalpine fir promotion and Engelmann spruce is celebrated on well warmed up the slopes of New Mexico (Dyer, Moffett, 1999). Evaluation was carried out using a series of aerial photographs from the 1930s. On the northeast slope of the mountain boundary of the forest and meadows relatively stable.
In the simulation of climatic changes in the French Alps and the French Mediterranean (average temperature increase of 3 ° C and a slight increase in precipitation) to 5 radial growth of trees in 24 populations found that only a few of the 24 populations were vulnerable to climate change (Keller et al ., 2000). All are located on the border of their ecological range and may be divided into two groups. The first consists of alpine populations and reacts increasing growth induced climate warming during the growing season. The second consists of a single population of Scots pine in the Mediterranean and reacts strong decrease in growth due to summer water stress. However, the individual response of the trees in the form of radial growth without cenotic and ecosystem linkages can well predict the dynamics of the population. This is especially true of populations included in the first group.
In the study of plant responses to climate change is extremely important phenological response. In the literature, there is a lack unambiguous expected response to global warming.
It should be borne in mind established in provenance (Kortkeros, northern Russia) pattern – the development of seeds in the northern populations of Scots pine and Norway spruce is slightly faster than in southern populations (Fedorkov, 2001). According to the model Sarvas trees, transferred from the colder regions with a short growing season in warmer regions with a longer growing season develop floral authorities before transferred from warmer regions or local breeds.
In general, there is a number of parameter responses of forest ecosystems to climate change:
– Displacement of including in the mountains;
– Forest loss is accompanied by a certain damage to hydrological systems, increased soil erosion;
– The destruction of forests, which causes the release of carbon into the atmosphere, may contribute to global warming;
– Loss of biodiversity;
– Change in productivity;
– Increase in extreme moisture (water logging, draining);
– Height fire hazard;
– Reduction in the quantity and quality of seeds;
– Impact on the renewal (particularly conifers);
– Increasing the severity of diseases and pests;
– Reduced resistance because of the increased frequency of adverse short-term effects (periods of abnormally warm weather and frosts, strong winds, snow, etc.);
Climate change affects the frequency, intensity, time and / or spatial localization shocks. Many of the potential effects of future climate change can be mitigated adaptation of forest communities to natural climate variations. However, the body of research suggests that, as a result of the emergence of new modes of exposure to climate change may be significant changes in the forest with long-term environmental and socio-economic consequences.
Natural shocks superimposed on the effects of human activity, such as air pollution, cultivation and harvesting, agricultural and urban development, recreation in nature. And we are not talking about the usual summation.
Natural impacts associated with climate stem from insects, diseases introduced by species, fires, droughts, heavy snowfalls, hurricanes, landslides, storm wind and icing. In each geological epoch local, regional and global changes in temperature and precipitation affect the frequency and intensity of such natural factors.
The impact of these shocks is seen in a wide range of scales, from the leaf of the tree and the forest and forest landscape. Their result can manifest itself in: loss of foliage color and reduce the period of its operation; deformation of the structure of the tree – windfall, windbreak, broken branches or loss of the crown; increased mortality of trees or chronic stress, which leads to their death; dysfunction regeneration – loss of seed stock; degradation of the physical environment, including soil erosion; imbalance in the turnover of biomass and nutrients; Impact on the surface organic layers of soil and underground plant roots and reproductive tissues; and the growing heterogeneity of the landscape (separation, increase the free space between forest communities).
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