General Discussion And Conclusions

Perhaps the major feature of the Quaternary history of far eastern rainforest is that there has been little overall change in gross distribution over most of the area and through most of the period. Rainforest has shown tremendous resilience in the face of increasingly variable climatic conditions that have seen its partial replacement by more open vegetation types during drier and cooler glacial phases. The major spatial exception to this pattern is in tropical Australia, where the extensive...

Diversity in relation to precipitation and geology

Gamma Diversity Tropical Rainforest

In the current analysis, alpha diversity shows broad correlations with both precipitation patterns and geology Figure 10.5a-d, see color section . Total precipitation amount is positively correlated with diversity Figure 10.5a and average length of dry season negatively correlated Figure 10.5d . Both reproduce the basic pattern of high average diversity in central and western Amazonia, and along the main stem of the Amazon, though with notable discrepancies. Strong gradients in alpha diversity...

Precipitation and diversity

Gamma Diversity Tropical Rainforest

Diversity is clearly correlated with climatic stability, and the plateau in Amazonian diversity from 1 N to 5 S falls squarely on the area with no predictable dry season, and the lowest variability in climate over time Figures 10.5b, c . Both local and regional diversity in all data sets analyzed showed this trend. Diversity may also appear anomalously low in areas with a shorter dry season as calculated through the number of months that average below 100 mm, especially if the timing of...

Altitudinal Variations

Massenerhebung

On tropical mountains, there are marked altitudinal changes of vegetation Troll, 1959 . The concept of an actual zonation is rather too strict to be useful, but there is no doubt that as one ascends a mountain there are gradual changes. Most tree species have an ecological amplitude in terms of mean annual temperature MAT , of about 6 C van Steenis, 1934-36 . There are some conspicuous exceptions to this, but it applies to many species. There is thus a continuum of change seen as the climber...

The early evidence for human occupation

Map Caverna Pedra Pintada

As elsewhere, there are formidable holes in the archeological records relating to initial human entrance into the now-humid Neotropics, and new evidence tends to accumulate slowly because early human groups were small and often highly mobile, leaving behind few tangible remains. Nonetheless, we know considerably more about the subject now than we did 10 to 15 years ago. There is convincing evidence of human occupation dating to the Late and terminal Pleistocene periods between c. 15.2 kcal. yr...

Geology and diversity

The current study shows that, for South American tropical forests, tree alpha diversity is also associated with geological age of substrate. While subsidiary to rainfall effects, alpha diversity tended to be higher on younger substrates, which in turn were more fertile substrates, even after accounting for precipitation variability Figure 10.5d . This is almost certainly not an effect of age per se, but rather due to the correlation between age and fertility in Amazonian surface geology. This...

Changes in the hydrology of the Amazon River Basin

Macroscale hydrological models, which model the land-surface hydrological dynamics of continental-scale river basins, have rapidly developed during the last decade Russell and Miller, 1990 Marengo et al., 1994 Miller et al., 1994 Nijssen et al., 1997, 2001 . These models can act as links between global climate models and water resource systems on large spatial scales and long-term timescales. Predictions of river discharge in the Amazon Basin for present climates and 2 x CO2 future scenarios...

Precipitation patterns

Tropical Rainforest Precipitation

Patterns of precipitation amount and variability in Amazonia change with both latitude and longitude. Analysis of TRMM data shows average annual precipitation in the Amazonian lowlands peaks at 2-4 S latitude, with a broad plateau from 4 N to 4 S of the equator. Precipitation decreases steadily to the south and north Figure 10.3e . Precipitation at low latitudes can be either high or low, while sites to the north and south have more uniformly low rainfall. Precipitation variability, measured as...

Trends In Rainforest Diversity Based On The Palynological Record

Obtaining meaningful data regarding palynomorph diversity, which can be interpreted in terms of species diversity of vegetation, is fraught with difficulties, and so is rarely attempted Birks and Line, 1990 . Differences in depositional environment, as well as taphonomic factors, have a significant effect on such estimates, making number of pollen types, or pollen diversity indices difficult to interpret. Also, individual analysts may have different concepts of what constitutes a pollen type...

Differences Between Quaternary And Tertiary Megathermal Forests

Refuge Hypothesis

Using Quaternary analogs to interpret ecological and climatic successions from the Tertiary raises two main issues 1 was there a fundamental difference between Quaternary and Tertiary rainforests and 2 were Tertiary species compositions so different from the Quaternary as to make comparison fruitless With respect to the first of these issues, it is now clear that there was one major difference between Quaternary rainforests, and those from the Miocene and Early Pliocene. Over the last 2.8 Myr,...

M B Bush W D Gosling and P A Colinvaux Introduction

Data from palynology, taxonomy and isotopic analyses, allied to climate models, reveal the complexity of the history of Amazon ecosystems. Evidence from these records suggests that Pleistocene climatic change was neither uniform nor synchronous across the basin, but that its effects were pervasive. A major obstacle to Amazon paleoecology is paucity of lakes containing uninterrupted sedimentary sequences spanning one or more glacial cycles. To date, the only fossil pollen records from lowland...

Subject index

Measuring C4 and C3 abundance, 339 8180 data, 64 Huascaran ice core, 44 Climate Observational Study edaphic and secondary grassland Africa , 121 adiabatic lapse rate, see lapse rates aerosol, 250, 252 African rainforest, see Guineo-Congolian rainforest Afromontane evergreen forests, 121-122 Amazon Basin agricultural pressure, 211 Amazon Basin crop origins, 203 cultivation of crops, Holocene, 201-206 domesticated crops, Holocene, 201-206 Central America, 204-205 South America, 203-205 during the...

Detected and projected changes in precipitation

Ccsr Nies Uncertainty

The IPCC Third Assessment Report IPPC, 2001 has shown no clear signs of negative trends in Amazonia due to increased deforestation as one would expect Section 9.2.3 . Section 9.2.5 describes trends and long-term variability in observed mean seasonal and annual rainfall and discharges. The magnitude and size of the trends depend on rainfall data sets, length of records, etc. and the uncertainty is high since Figure 9.7. Air temperatures in the Amazon region as simulated by five IPCC models R30...

Biosphere Modeling

Factors Determining Climate Scenarios

Vegetation is a major factor affecting land surface processes Figure 6.3 , and a good measure of ambient climate and change in this. Therefore, a central part of understanding climate change impact is to understand the correspondence between climate and the distribution of vegetation, both in terms of major vegetation formations, or biomes, and individual plants or species. Modeling the biosphere is not a new field of research. Initial attempts were carried out by Kostitzin 1935 . Working on...

Atmospheric and hydrological water balance

The hydrological cycle of the Amazon region is of great importance since the region plays an important role in the functioning of regional and global climate. Variations in its regional water and energy balances at year-to-year and longer timescales are of Figure 9.3. Seasonal cycle of river discharges and levels in northern and southern Amazonia. Levels are in cm Rio Negro at Manaus . Discharges from the Amazon, Madeiras, and Tocantins Rivers are in 103 m3 s_1. Source M. Costa and M. Coe....

Litter Inputs

Tropical Rainforest Precipitation

Alterations to the amount and timing of rainfall in tropical forests may significantly affect nutrient-cycling via litter production, although the relationship between climate Anthropogenic Increased Nitrogen Deposition Precipitation NH4 Anions NO3- Cations Leaching losses increase Figure 11.4. The potential effects of anthropogenic nitrogen deposition and increased precipitation in tropical forests. Increased inputs of ammonium could stimulate ammonium-leaching in variable charge soils, and...

Biome modeling

Cross Section Plants

A continental-scale study the VEMAP project VEMAP members, 1995 demon-strated the interdependence of biogeographical and biogeochemical aspects of the ecological response to climate change assessing how global change will affect ecosystems and must therefore include both aspects. Such a combined approach is exemplified by the process-based equilibrium terrestrial biosphere model BIOME-3 that simulates vegetation distribution and biogeochemistry Haxeltine and Prentice, 1996 . BIOME-3 predicts...

Tropical Rainforest References

B., Aravena, R., Wolfe, A. P., and Seltzer, G. O. 2000 Holocene hydrological reconstructions from stable isotopes and paleolimnology, Cordillera Real, Bolivia. Quaternary Science Reviews 19, 1801-1820. Abbott, M. B., Wolfe, B. B., Wolfe, A. P., Seltzer, G. O., Aravena, R., Mark, B. G., Polissar, P. J., Rodbell, D. T., Rowe, H. D., and Vuille, M. 2003 Holocene paleohydrology and glacial history of the central Andes using multiproxy lake sediment studies....

Spatial Patterns And Recent Trends In The Climate Of Tropical Rainforest Regions

J., Steudler, P., and Melillo, J. M. 1989 Nitrogen saturation in northern forest ecosystems. Bioscience 39, 378-386. Aerts, R. 1997 Climate, leaf litter chemistry, and leaf litter decomposition in terrestrial ecosystems A triangular relationship. OIKOS 79, 439-449. Andreae, M. O., Talbot, R. W., Beresheim, H., and Beecher, K. M. 1990 Precipitation chemistry in Central Amazonia. Journal of Geophysical Research 95, 16987-16999. Arnone III, J. A. and Korner, C. 1995...

The Massenerhebung Effect

Before And After The Rain Forest

As usually defined, the Massenerhebung or mountain mass elevation effect means the occurrence of physiognomically and sometimes floristically similar vegetation types at higher altitudes on large mountain masses than on small isolated peaks, especially those in or near the sea. Although the effect was first reported in the European Alps Schroeter, 1908 and in North America where it is known as the Merriam effect Martin, 1963 , it is best known in the tropics. Perhaps its clearest expression is...

Quaternary History

Photos Quaternary Lake Cores

Despite recent progress and new fossil pollen sequences obtained by coring swamps and lakes in Africa, it is not possible to reconstruct the Quaternary history of all the different forest units described in Section 5.2. Not all of them being documented yet, the presentation of fossil pollen records follows a chronological order, starting with the last glacial period, and then discussing the last 10,000 years of the Holocene. The list of sites where fossil pollen are available is given in Table...

Holoceneforest Cover Congo Basin

Forest Semideciduous Phytoliths

Simplified pollen diagram from Ngamakala, presented according to depth Congo, after Elenga et al., 1994 a arboreal and climber taxa b herbaceous taxa c synthetic diagram calculated versus pollen sum including all identified taxa, aquatics, and spores . 1 1 Syzygium rT-i NAP I Other AP gS53 Spores I I Unknown 1 1 Syzygium rT-i NAP I Other AP gS53 Spores I I Unknown Figure 5.9. Simplified pollen diagram from Ngamakala, presented according to depth Congo, after Elenga et al., 1994 a...

Late Cretaceous Expansion Of Megathermal Forests

Angiosperms, which dominate megathermal rainforests today, first radiated during the Early Cretaceous from mid- to low latitudes Crane et al., 1995 Hickey and Doyle, 1977 in response to climatic stress Stebbins, 1974 Doyle and Donaghue, 1987 . They are unlikely to have become initially established in a closed, rainforest setting as previously inferred by Takhtajan 1969 and Thorne 1976 on the assumption that primitive angiosperms such as members of Winteraceae, Trochodendron and Tetracentron...

Megathermal Rainforests During The Early Tertiary Period Of Greenhouse Climate

Climate During The Tertiary Period

At the beginning of the Tertiary, megathermal rainforests were thus established in three parallel latitudinal zones Figure 1.4 . In the northern hemisphere, Northern Megathermal termed Boreotropical in Morley, 2000a mesic and monsoonal forests extended from North America and Europe, to East Asia, Southern Megathermal forests were present in mid-latitude South America, Australasia and southern Africa, and equatorial forests of the Palmae province were well-developed in northern South America,...

Modern Pollen Sampling

Some basis for interpretation of Quaternary palynological records is derived from examination of patterns and processes of modern pollen deposition recorded in pollen traps and surface sediments. Such sampling examines deposition both within the rainforest and outside the rainforest in lake, swamp, and marine environments used for reconstructions of vegetation history. The first quantitative study of pollen deposition in rainforest was by Flenley 1973 . In the lowland rainforest of Malaysia he...

Maintenance of humidity and importexport of moisture in the Amazon Basin

Great Plains Low Level Jet

Under the present climate the Amazon Basin behaves as a moisture sink P gt E , and therefore the basin receives moisture from sources such as the tropical rainforest by means of intense recycling and by transport from the tropical Atlantic by near-surface easterly flows or trade winds. The former has generated plenty of concern due to the possible impact of deforestation on the hydrological cycle of the basin see Section 9.2.5 . In this context, water that evaporates from the land surface is...

Age years BP

Rates The Tropical Rainforest

Selected vegetation records derived from pollen diagrams from tropical Southeast Asia and the West Pacific. Only the last 30,000 years are shown. Human impact is omitted. References to individual sites are as follows Summit, Brass, Imbuka, Komanimambuno Hope, 1976 , Inim Flenley, 1972 Walker and Flenley, 1979 , Sirunki Walker and Flenley, 1979 , Draepi Powell et al., 1975 , Di-Atas Newsome and Flenley, 1988 , Sipinggan Maloney, 1981 , Bayongbong Stuijts, 1984 Stuijts et al., 1988 ....

Nutrient Uptake

Not surprisingly, the impact of climate change on below-ground ecology has received far less attention than above-ground effects. In order to stimulate more research, Norby and Jackson 2000 produced an excellent review of the data currently available on root responses to elevated C02 and climate changes. Plant uptake of essential nutrients is highly sensitive to soil temperature, moisture, and aeration, and thus is likely to be affected by climate change, but measured changes in nutrient uptake...

The Later Pleistocene

Australia Rainforest Climate Diagram

A more spatially representative picture of changes in the distribution and composition of rainforest can be constructed for the later part of the Pleistocene from a greater number of sites that, in addition to those from ODP Sites 1144 and 820, provide continuous or near-continuous palynological records through at least the last glacial cycle Figure 4.1 . The record from core SHI-9014 in the Banda Sea van der Kaars et al., 2000 provides the most substantial evidence of vegetation change in the...