Introduction
Material and Validity of Data
Results
The largest number of species was found in montane forests (358 spp.) and mixed floodplain forests (326 spp.). This is reflected in the rarefaction curves which show an increase in species with an increase in the number of individuals (Fig. 16.5).
Discussion
The vegetation of the mixed floodplain forest represents an ecotone with characteristic tree species from the whitewater and/or blackwater region of Central Amazonia (Amaral et al. 1997). Aggregate distribution observed for some dominant herbivorous beetle species in the mixed floodplain forest suggests preference for certain tree species.
Introduction
Anatomical Classification of Tree-Ring Structures
Often this type is characterized by many and/or large vessels at the beginning of the ring, but other species show the largest vessels in the middle of the ring. In order to detect all boundaries within a sample, it is therefore important to consider changes in the general pattern of.
Macroscopical Variability of the Visibility of Rings within Species
Within a stem disk, rings may only tend to wedge in the outer parts when the tree begins to form buttresses (Fig. 17.8). This genus forms defined tree-ring boundaries in general (Fig. 17.2), but these are not evident over the entire cross-section.
Structure and Ecological Function of Xylem Elements in Growth Zones
Abrupt changes are of particular importance in dendrochronological studies, as they can be used to date and analyze the impact of certain events, such as extreme climatic events or suppression and release effects (Schöngart et al. 2004; Brienen et al. 2006). Given that fiber cells are the main cost of xylem production, it is not surprising that an individual from a nutrient-rich várzea can invest the most in fiber cells (53.38%) and less in axial (28%) and radial (7, 96%) parenchyma.
How to Measure Growth Dynamics in Tropical Trees
Another artificial marker is radiocarbon dating of individual growth zones based on the effect of nuclear weapons (Worbes and Junk 1989). Tree ring dating is also possible based on fire scars or tree rings with observable characteristics that differ from neighboring rings (years of indicators) by exogenous factors such as fire or extreme climatic events (Worbes 1999).
Discussion and Conclusions
An example is the reconstruction of the Southern Oscillation effect (ENSO) with tree ring data for the nineteenth century using the tree species Piranhea trifoliata in the várzea (Schöngart et al. 2004). However, comparisons of the wood densities of tree species in the várzea, igapó and terra firme yielded statistically. From this model, C sequestration is derived as the annual change in the C stock of the AGWB (dashed line).
We found significant correlations between C sequestration in AGWB and stand structural parameters. For old-growth forests along the flood gradient in the Peruvian várzea, Nebel et al. An increase in temperature in the Amazon basin could exacerbate the effects of drought by accelerated evaporation (White et al. 1999).
Marengo etc. 2008) and will probably affect forest dynamics and carbon cycling in the AGWB of floodplain forests. Approximately 350 tree species of the Amazon basin are used as timber sources and 34% of them occur in floodplains (Martini et al. 1998). Consequently, floodplain forests are one of the most stressed and threatened forest ecosystems in the Amazon.
Introduction
History of Human Occupation of the Amazon River Floodplain
The highly productive floodplain of the Amazon River consistently had the highest human population density in the entire region (Meggers 1984). Roosevelt (1999) postulated that indigenous kingdoms in the lower Amazon consisted of many thousands of people living in settlements of many square kilometers on the highest points of the várzea or at strategic points nearby. Export-oriented, unsustainable exploitation of the area's natural resources has replaced the sustainable subsistence systems of the Amazon Indians.
After World War II, valuable timber resources were increasingly exploited, and large parts of the floodplain forest of the lower Amazon River were destroyed for jute plantations and cattle ranching. In addition to environmental concerns, socio-economic and legal issues challenge the sustainable use of várzea.
Ecological Characterization of the Várzea and Igapó Based
The fish biomass is about one fifth of the várzea biomass (Saint-Paul et al. 2000). Given the high biodiversity of the igapó forest, the most appropriate management of the igapó is through extensive fishing, ecotourism and sustainable extraction of non-timber products. This favors the adaptation of plants and animals to the transition between aquatic and terrestrial phases and allows organisms sufficient time to exploit the resources of the floodplain.
Its recognition of the events associated with rising and falling water levels supports the FPC's use as the scientific basis for broader concepts dealing with the sustainable management of várzea. Destruction of the floodplain forest reduces the availability of food for many commercially important fish species.
A New Model for Water-Level Prediction as a Prerequisite
An accurate forecast of the hydrograph is essential for the riverine population to adjust their activities accordingly and to minimize losses. Since 1989, monthly forecasts of the maximum water level have been made from March to May by the Serviço Geológico do Brazil (CPRM). This method incorporates the fact that rainfall in the Amazon basin is influenced by El Niño and La Niña events, which can be predicted by sea surface temperature (SST) anomalies in the tropical Pacific.
The predicted and observed maximum water levels for the past five years are shown in Figure 1. The correlation between the minimum water level and monthly SST anomalies in the TNA is evident for eleven consecutive months before the minimum water level appears (Schöngart et al., submitted) .
The Potential of Fisheries and Fish Culture
Fisheries
From 1950 to 2005, the minimum water level at the port of Manaus shows a significant correlation with monthly SST anomalies in the tropical North Atlantic (TNA, 05°–20° N/60°–30°W). More than half of the catch is caught by artisanal fishermen and riverine communities for their own consumption. Part of the region's production is sold either in small local markets or to professional fishermen and shipowners who bring the fish to urban centers.
Therefore, from the early 1990s, the Federal Brazilian Environmental Agency (IBAMA) chose to decentralize participatory fisheries management (Fisher et al. 1992; McGrath et al. IBAMA Ruffino 1996; Isaac et al. 1998), transferring some of the responsibilities and rights for local communities, who helped control the lakes in their territories and were granted fishing rights in some of the lakes. The time span and the difference between the forecast and the occurrence of the maximum water level are shown.
Fish Culture
Thus, hybrid breeding in Amazonian fish culture requires intensive research aimed at avoiding these problems, eg, by producing mono-sex hybrids or triploids. It can be argued that fish culture on a large scale is economically unsustainable, as long as there is productive fishing for the same species. Today, fish culture in Amazonia remains a complementary activity to fishing, providing high-quality fish at reasonable prices throughout the year.
The Várzea plays a minor role in fish culture, not only because of direct competition with regional fisheries, but also because of fluctuations in water levels in large water bodies, which create serious technological problems. Nevertheless, the availability of cheap fish as food for highly valued carnivorous species, such as pirarucu and large catfish, may provide opportunities in specially adapted lakes.
The Role of Agriculture
The highest water level is reached about 3 weeks after the beginning of the dry season. An economic analysis of the agrarian production systems in várzea identified two different approaches. Over the past several years, efforts have been made to overcome the periodicity of the productive cycle.
For example, in the middle of the last century, large areas were deforested for the cultivation of the fiber crops jute (Corchorus capsularis L. [Tiliaceae]) and, to a lesser extent, mallow (Urena lobata L. [Malvaceae]) (Homma 1998). This experience supports the need to protect at least part of the várzea alta due to its importance for biodiversity (see below).
The Impact of Cattle- and Buffalo-Ranching
Farming in areas near urban centers should be restricted to favor farmers who produce perishable goods for the local market. Increases in beef production should be achieved through intensification rather than through expansion of farm size, e.g. through better adapted and specialized breeding stocks for milk and meat as well as improvements in reproduction rates, animal health (including the establishment of an efficient veterinary system), pasture utilization (through rotational grazing and adequate livestock numbers), the management capabilities of farmers and farm staff, and slaughter, processing and marketing facilities. Forests growing below the 25 m water level (measured at Manaus harbor) must be protected from transformation into pastures, because the utility of such pastures is low, but the environmental impact of forest destruction is serious.
Water buffalo should only be kept in small numbers and under human control to avoid environmental destruction. Alternative economically viable feeding systems should be developed during the high water period to reduce animal weight loss, e.g.
The Potential of Forestry
In the várzea, low-density tree species exceed the MLD of 45 cm much faster than high-density species (Fig. 23.5). If current forest management practices continue, the wood stocks of high-density forest in the várzea will be overexploited, while the growth potential of low-density wood in várzea floodplain forests will not be used efficiently. To achieve a higher level of sustainability, Schöngart (2008) developed a management concept based on the wood stocks and growth rates of the different successive stages in the várzea.
Sustainable use of timber reserves in nutrient-poor igapó is, under current management options, infeasible due to the low growth rate of its tree species (Schöngart et al. Therefore, forests of igapó floodplains should be excluded from forest management and, instead, protected in perpetuity.
The Impact of Different Management Options on Biodiversity
Our list of floodplain forest trees includes over 900 species (Wittmann et al., this volume), that of herbaceous plants about 400 species (Junk and Piedade 1993). This hinders speciation due to the lack of genetic isolation. 1998) stated that speciation occurs mainly in the headwaters and that species trickle downstream, where they become established or disappear. There is also lateral immigration of terrestrial organisms from the adjacent upland, as shown by Wittmann et al. (this volume) for trees from the floodplain forest.
About a third of the approximately 900 tree species recorded in the várzea forests of the Amazon basin also occur in highland forests (Wittmann et al. 2006a). Of the tree species common to both ecosystems, approximately 70% are restricted to the tall várzea.
Management Options and the Carbon Cycle in a Changing Global Climate
The composition of tree species varies considerably along the course of the river in the high várzea - which is flooded at a height of up to 3 m, which corresponds to less than 50 days per year - 1 - because in the adjacent highlands many species that have flooded a little. -tolerant ecotypes colonize these areas. The predominance of widely distributed low tree species is explained by the longitudinal connectivity of forest communities through seed dispersal by rivers. Moreover, it reflects selection pressure in response to extreme environmental conditions in highly flooded sites, which lead to a limited number of highly flood-tolerant tree species.
In addition to adding a large number of tree species to the species list, it provides specific habitats for many types of animals. Below: General tree species similarity (Sørensen 1948 fehlt!!) (n= 918 várzea tree species) between low várzea forests, high várzea forests and terrafirme forests of the Amazon basin (Wittmann et al.
Discussion and Conclusions
