Ecology of testate amoebae in an Amazonian peatland and development of a transfer function for palaeohydrological reconstruction

Tropical peatlands represent globally important carbon sinks with a unique biodiversity and are currently threatened by climate change and human activities. It is now imperative that proxy methods are developed to understand the ecohydrological dynamics of these systems and for testing peatland development models. Testate amoebae have been used as environmental indicators in ecological and palaeoecological studies of peatlands, primarily in ombrotrophic Sphagnum-dominated peatlands in the mid- and high-latitudes. We present the first ecological analysis of testate amoebae in a tropical peatland, a nutrient-poor domed bog in western (Peruvian) Amazonia. Litter samples were collected from different hydrological microforms (hummock to pool) along a transect from the edge to the interior of the peatland. We recorded 47 taxa from 21 genera. The most common taxa are Cryptodifflugia oviformis, Euglypha rotunda type, Phryganella acropodia, Pseudodifflugia fulva type and Trinema lineare. One species found only in the southern hemisphere, Argynnia spicata, is present. Arcella spp., Centropyxis aculeata and Lesqueresia spiralis are indicators of pools containing standing water. Canonical correspondence analysis and non-metric multidimensional scaling illustrate that water table depth is a significant control on the distribution of testate amoebae, similar to the results from mid- and high-latitude peatlands. A transfer function model for water table based on weighted averaging partial least-squares (WAPLS) regression is presented and performs well under cross-validation (r 2apparent=0.76,RMSE=4.29;r2jack=0.68,RMSEP=5.18. The transfer function was applied to a 1-m peat core, and sample-specific reconstruction errors were generated using bootstrapping. The reconstruction generally suggests near-surface water tables over the last 3,000 years, with a shift to drier conditions at c. cal. 1218-1273 AD

Quaternary pollen analysis: recent progress in palaeoecology and palaeoclimatology

During the last decade Quaternary pollen analysis has developed towards improved pollen-taxonomical precision, automated pollen identification and more rigorous definition of pollen assemblage zones. There have been significant efforts to model the spatial representation of pollen records in lake sediments which is important for more precise interpretation of the pollen records in terms of past vegetation patterns. We review the difficulties in matching modelled post-glacial plant migration patterns with pollen-based palaeorecords and discuss the potential of DNA analysis of pollen to investigate the ancestry and past migration pathways of the plants. In population ecology there has been an acceleration of the widely advocated conceptual advance of pollen-analytical research from vaguely defined ‘environmental reconstructions’ towards investigating more precisely defined ecological problems aligned with the current ecological theories. Examples of such research have included an increasing number of investigations about the ecological impacts of past disturbances, often integrating pollen records with other palaeoecological data. Such an approach has also been applied to incorporate a time perspective to the questions of ecosystem restoration, nature conservation and forest management. New lines of research are the use of pollen analysis to study long-term patterns of vegetation diversity, such as the role of glacial-age vegetation fragmentation as a cause of Amazonian rain forest diversity, and to investigate links between pollen richness and past plant diversity. Palaeoclimatological use of pollen records has become more quantitative and has included more precise and rigorous testing of pollen-climate calibration models with modern climate data. These tests show the approximate nature of the models and warn against a too straightforward climatic interpretation of the small-scale variation in reconstructions. Pollenbased climate reconstructions over the Late Glacial–early Holocene boundary have indicated that pollen-stratigraphical changes have been rapid with no evidence for response lags. This does not rule out the possibility of migrational disequilibrium, however, as the rapid changes may be mostly due to nonmigrational responses of existing vegetation. It is therefore difficult to assess whether the amplitude of reconstructed climate change reflects real climate change. Other outstanding problems remain the obscure relationship of pollen production and climate, the role of human impact and other nonclimatic factors, and nonanalogue situations.

Neotropical refugia

Patterns of endemism in the Neotropics have been explained by restriction of forest to ‘refugia’ in arid cold-stages of the Quaternary (Haffer J (1969)
Speciation in Amazonian forest birds. Science 165: 131–137). The palaeoecological record, however, shows no such forest contraction. We review
palaeoecological and phylogenetic data on the response of Neotropical taxa and communities to climatic changes of the Cenozoic. Solar insolation varies
over this period with latitude and geography, including shifts in opposite directions between high and low latitudes. In the Neotropics, distribution and
abundance patterns originate on a wide range of timescales through the Cenozoic, down to the currently dominant precession forcing (20 kyr). In contrast,
distributions and abundances at higher latitudes are controlled by obliquity forcing (40 kyr). The patterns observed by Haffer (1969) are likely derived
from pre-Quaternary radiations and are not inconsistent with palaeoecological findings of continuous forest cover in major areas of the Neotropics
during the Quaternary. The relative proportions of speciation processes have changed through time between predominantly sympatric to predominantly
allopatric depending on the prevailing characteristics of orbitally forced climatic changes. Behaviour of Neotropical organisms and ecosystems on long
timescales may be influenced much more by precessional forcing than by the obliquity forcing that controls high-latitude climate change and glaciations.

Control of wild rubber extraction in the forests of northeast India, 1850-1880

This paper uses the history of rubber extraction to explore competing attempts to control the forest environments of Assam and beyond in the second half of the nineteenth century. Forest communities faced rival efforts at environmental control from both European and Indian traders, as well as from various centres of authority within the Raj. Government attempts to regulate rubber collection were undermined by the weak authority of the Raj in these regions, leading to widespread smuggling. Partly in response to the disruptive influence of rubber traders on the frontier, the Raj began to restrict the presence of outsiders in tribal regions, which came to be understood as distinct areas outside British control. When rubber yields from the forests nearest the Brahmaputra fell in the wake of intensive exploitation, India's scientific foresters demanded and from 1870 obtained the ability to regulate the Assamese forests, blaming indigenous rubber tapping strategies for the declining yields and arguing that Indian rubber could be ‘equal [to] if not better' than Amazonian rubber if only tappers would change their practices. The knowledge of the scientific foresters was fundamentally flawed, however, and their efforts to establish a new type of tapping practice failed. By 1880, the government had largely abandoned attempts to regulate wild Indian rubber, though wild sources continued to dominate the supply of global rubber until after 1910.