Climate change and terrestrial biodiversity

Rachel Warren , ... Rhosanna Jenkins , in The Impacts of Climate change, 2021

i Introduction

The Earth'southward regional climate determines the geographical location of tropical forests, deserts, tundra, temperate woodland, and all other ecosystems. Information technology also constrains the geographical range of many individual species. Hence, it is not surprising that the 1°C global warming that has and then far occurred has already affected biodiversity with the effects of climate change on biodiversity and ecosystems already detected on every continent. At the species level, this includes observed changes in species' geographical ranges, changes in the timing of seasonal events (called phenology), and population declines. The first species extinction, attributable to anthropogenic climate change has already been observed. At the ecosystem level, some ecosystems take begun to transform, and the frequency of fires has increased in some areas. The furnishings are non uniform around the earth—with particularly large effects detected already in the Arctic for example. With farther climate change, much greater effects are projected upon species and ecosystems, with large scale species losses expected from many areas, resulting in the potential collapse of ecosystem functioning and a cascade of species extinctions. Every bit well equally the Arctic ecosystem, Mediterranean-type ecosystems, and biodiversity hotspots are especially at risk.

Humans depend on nature in ways that many people are unaware of. Biodiversity performs natural processes resulting in the pollination of many of our crops, the breakdown of much of our waste, the purification of air and water, and the maintenance of the Earth's geochemical cycles. This last process includes the sequestration of around a half of the carbon dioxide that nosotros accept emitted into the atmosphere within terrestrial and marine ecosystems. Natural systems provide timber, food and cobweb, and they frequently buffer settlements confronting the impacts of extreme weather events such as floods and storm surges. They regulate soil erosion and disease outbreaks, while providing health, recreational, and spiritual benefits. Thus, if terrestrial ecosystem functioning is diminished it places man civilisation at greater and greater risk (see Chapter 5 for a discussion of marine ecosystems, with which terrestrial systems obviously interact at coastal zones).

The management of land is ane necessary part of the solution to the climate alter problem. Poor land direction results in an escalation of climatic change impacts on biodiversity. For example, to reduce (mitigate) the amount of global climate change, free energy could be produced from energy crops. Withal, in this case if land is used on a large calibration to grow energy crops in identify of cropland or protected ecosystems, this can have deleterious effects on biodiversity and ecosystems that may be comparable with those caused by climate change itself. In that location are win-win solutions: ecosystems themselves may be restored in order to increase the sequestration of carbon past the biosphere, and carefully tailored utilize of energy crops and agronomical practices, together with changes in diet, tin reduce the land employ footprint of our society. In this mode, careful land direction tin synergistically address the goals of the United Nations (Un) Framework Convention on Climate Change, the Un Convention on Biological Diversity, and the Un Convention to Combat Desertification (CCD).

Read full affiliate

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B9780128223734000252

DETRITUS: ORGANIC CARBON CYCLING AND ECOSYSTEM METABOLISM

ROBERT G. WETZEL , in Limnology (Tertiary Edition), 2001

C. Detrital Dynamic Structure in River Ecosystems

The construction of biomass or carbon fluxes in flowing waters is much less well documented. From a detailed budget of the boilerplate daily biomass catamenia in a temperate woodland stream, information technology was estimated that 25–xxx% of the particulate biomass input flowed through and was decomposed past the benthic animals, assuming an average absorption rate of twoscore% for non-predators ( Cummins, 1972). Allochthonous and autochthonous inputs of dissolved organic affair, which found at least five times and probably 10 times that of the POC, were not considered in this budget.

The dissolved organic matter, as in lakes, drives the metabolism of streams and rivers. It is common for >90% of the annual organic carbon movement in streams and rivers to be in the dissolved class (due east.chiliad., Table 23-18). Experimental analyses in bogus streams have demonstrated that a big portion (>50%) of this DOM can be rapidly degraded (24–48 h) by planktonic and attached bacteria under optimal conditions. Nether natural atmospheric condition, some of the Medico being transported is photolysed by natural sunlight either completely to CO2 or partially with the generation of substrates available for bacterial deposition.The amount of DOC that is converted to POM via flocculation, especially in hardwater streams every bit discussed earlier, or that enters bacterial biomass that is and so partially degraded past animals is unclear. This area is of bully interest and is in need of further research. Less than 1% of detrital organic inputs was estimated to be metabolized past macroinvertebrate fauna of a mount stream in New England (Fisher and Likens, 1973). The role of animals in comparison to microflora in decomposition of POM varies widely, and may be even more variable in streams than in lakes, just is certainly small-scale.

TABLE 23-18. Almanac Hateful Concentrations of Organic Matter in Send in the Fifth-to Sixth-Order Ogeechee River, Georgia a

Mean (mg AFDW liter −1) Full organic affair (%)
Dissolved organic affair 25.iv 96.three
Particulate organic matter
 Amorphous fabric (bacteria) 0.xxx 1.xiv
 Baggy textile (protozoans) 0.04 0.15
 Amorphous material (other) 0.52 i.98
 Vascular plant detritus 0.03 0.11
 Algae (generally diatoms) 0.06 0.23
 Fungi 0.014 0.05
 Animals 0.002 0.01
Total particulate organic thing 0.97 3.7
Full organic matter in transport 26.37 100.0
a
From information of Benke and Meyer (1988).

These relationships are exemplified in an annual organic carbon budget for a section of a small river in Nihon (Table 23-19). Dissolved organic affair and fine particulate organic matter fabricated upwards >88% of the inputs of organic carbon. Total community respiration constituted for <5% utilization of the organic matter loading. The remainder was either stored briefly or largely exported as fine POC and more often than not every bit DOC.

TABLE 23-nineteen. Annual Organic Carbon Budget Estimates in a 500-m Segment of the Kogesawa River, Uratakao, Japan a

Organic matter kg C yr −i Percent (%)
Inputs
 Primary product 100 5.1
 Litterfall into stream 90 4.half dozen
 Lateral movement to stream 38 ane.9
 Fine particulate organic matter 480 24.v
 Dissolved organic matter 1170 59.8
 Groundwater inflow, DOC eighty 4.one
  Subtotals 1958 100.0
Outputs:
 Community respiration 77 4.ane
 Fine particulate organic matter 620 32.seven
 Dissolved organic matter 1200 63.ii
  Subtotal 1897 100.0
a
Extracted from information of Yasuda et al. (1989).

Information technology is of the utmost importance to emphasize that these examples of the functional construction of lake and stream ecosystems are only preludes to the important underlying questions of what parameters control the observed structural integrity of the system. Analyses of structure and dynamics of ecosystems are a prerequisite to analyses of factors regulating the observed and irresolute structure. But such analyses must non become an end in themselves. Sufficient underlying similarities between the structure and dynamics of ecosystems probably exist that will permit generalizations to emerge with less rigorous analyses. As a result, more try could be devoted to experimental evaluation of control mechanisms. It is critical that the regulatory mechanisms of natural ecosystems be understood before human perturbations of the systems tin exist effectively evaluated and minimized. Meaningful applied enquiry and wise direction of aquatic resources cannot be undertaken effectively without a basic agreement of functional command mechanisms.

Read full affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9780080574394500277

TROPICAL ECOSYSTEMS | Eucalypts

R.J.East. Wiltshire , in Encyclopedia of Forest Sciences, 2004

Flowering Phenology and Pollination

The bulk of eucalypts produce small white or cream flowers grouped into large inflorescences, which are visited primarily by insects, a range of birds, and bats. Others develop fewer larger, colored flowers that are especially attractive to birds. Many temperate forest and woodland eucalypts rely on opportunist pollination, primarily past a diverse insect beast, with patchy bird and mammal pollination. In contrast, many mallees and tropical woodland eucalypts appear to exist adapted to pollination by nectar-seeking birds or mammals.

Specialization and coevolution with one type of pollinator (insect, bird, or mammal) undoubtedly has consequences for pollen-dispersal distances (and outcrossing rates), and flowering intensity and phenology. For example, in bird-specialist eucalypts with relatively low flowering intensity, visitors are encouraged to motion between trees. Such a strategy may be associated with eucalypts with clumped, patchy, or disjunct distributions. However, a universal strategy appears to be production of many inflorescences, each presenting flowers at unlike phases, encouraging repeated visits by a multifariousness of vectors.

Read full affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B0121451607001885

Fires, Ecological Furnishings of

William Bail , in Encyclopedia of Biodiversity, 2001

II. World Biomes and Burn down Incidence and Influence

Fires are rare only at the extremes of the climatic continuum. Neither the most humid tropical and temperate forests nor the driest deserts experienced fire every bit a major factor. However, between these 2 extremes, fire has influenced the extent and composition of a great variety of ecosystems, including boreal forests, dry conifer forests, many grasslands (especially those dominated by tall grasses), temperate woodlands, tropical savannas, Mediterranean-type shrublands, heathlands, and eucalypt woodlands. Forests with mast-flowering bamboo understories are also prone to burning later on the bamboos bloom and dice, creating massive fuel loads. Humans take changed mural patterns of called-for. Fifty-fifty humid tropical forests are showtime to burn every bit a result of logging. All these biomes experience fires of widely differing frequency and severity which help shape ecosystem structure and office.

Given the broad geographic extent of ecosystems that burn down, burn influences the distribution and abundance of many species. Some ecosystems are dominated by species that depend on fire to consummate their life cycles. Others are dominated by species that tolerate burning just accept no direct dependence on fire. Ecosystems that seldom or never burn, except when disturbed by human being activity, contain mixtures of species that fortuitously tolerate burning and species extremely intolerant of burn down. The impact of burning on biodiversity varies profoundly among these different types of ecosystems and species-response patterns.

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B012226865200119X

Temporary Waters

E.A. Colburn , in Encyclopedia of Ecology (2d Edition), 2008

Community Environmental

Community studies include questions about local and regional biodiversity; customs limerick and structure in relation to environmental and biological variables and disturbances; patterns of colonization and extinction; predator–prey, host–parasite, and competitive interactions between species; and food webs.

Comparable temporary waters differ in their biota. Distributions of species, and thus community limerick, shift along gradients of size, hydroperiod, predictability, and salinity, with richness increasing with decreasing stress. Community composition may change betwixt years, and it can as well vary seasonally, with a succession of new hatches and migrants inbound waters over time. The presence of potential community members every bit unhatched propagules in the sediment complicates assessments of community composition and structure.

Community theory

The theory of island biogeography postulates that species richness in isolated habitats is regulated by local extinction and colonization and should vary with habitat size and proximity to potential sources of colonizers. The intermediate disturbance hypothesis predicts high richness in communities field of study to a moderate degree of disturbance or stress; according to this model, high stress leads to mortality in all merely fast-growing individuals, and under depression stress, inter- and intraspecific interactions such as competition and predation decide community construction. Other models expect at resources and habitat division/niche diversification, temporal offsets in life histories, and other mechanisms controlling community composition and structure. Studies of amphibians, plants, invertebrates, and algae in temperate woodland pools, Mediterranean temporary pools, Negev and Namibian desert pools, Scandinavian rockpools, Chill snowmelt pools, and other areas testify complex relationships betwixt customs composition and habitat variables such as size, hydroperiod, frequency of flooding, hydrologic predictability, altitude from other waters, and salinity. The information advise that customs richness is related to both degrees of disturbance and the predictability of disturbance. Isolation is too of import, with greater richness in waters that are connected to larger bodies (e.thousand., in floodplains) merely likewise fewer taxa specifically adapted to temporary habitats. Species pools in individual water bodies are poor in comparison to the regional set up of species ( Table 6), and experimental assemblages comprised of larger subsets of available species office differently than the smaller natural communities.

Table 6. Regional species pools (β multifariousness) are greater than local species pools (α diversity), as illustrated by numbers of non-dipteran macroinvertebrates establish in early on bound from nine adjacent temporary pools on Cape Cod, Massachusetts, Usa

Water body Number of taxa
Pool one 34
Pool 2 22
Puddle three 24
Pool four 37
Pool 5 12
Pool 6 38
Pool seven 48
Pool 8 28
Pool 9 22
Full species 89

Modified from fig. ii in Colburn, E.A., 2004. Vernal Pools: Natural History and Conservation. Blacksburg, VA: McDonald and Woodward.

Interspecific interactions

Nutrient web manipulations allow examination of relationships amongst species and testify interesting relationships. For instance, algae grow improve when grazed by tadpoles than alone. Some potential competitors avoid conflict by preferentially choosing waters with different hydrologic or other characteristics when the other species are nowadays. The survival outcomes for some species of amphibians and insects when they co-occur with competitors depend on which species becomes established first.

Sure aquatic insects, crustaceans, and vertebrates can survive in pools with long flood durations, but they are typically found only at the more ephemeral terminate of the flooding continuum. They are excluded from the longer hydroperiod pools by predators such every bit amphibian larvae, tadpole shrimp, and water bugs. The ovipositing females of some species explicitly avoid pools with predators. For example, vulnerable species of mosquitoes avoid laying eggs in pools containing predatory backswimmers, whereas predation-resistant midge larvae do not; American toads (Bufo americanus) avoid temporary pools with omnivorous wood frog tadpoles (Rana sylvatica).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780444637680003619

Genus Melampyrum: Threatened Hemiparasites With an Important Ecological Role to Play

Sarah Eastward. Dalrymple , in Reference Module in Earth Systems and Environmental Sciences, 2021

Conservation status

There are no formal extinction risk assessments of whatsoever of the species of Melampyrum in the IUCN Red List. However, this lack of evaluation at global level should not be interpreted to mean that all species are of low business organisation with regards to endangerment – diverse species have fabricated it on to regional Cherry Lists that place declines within countries and/or ecoregions. M. arvense, M. nemorosum and 1000. pratense are three of the well-nigh widespread European representatives of the genus just are classified as being rare or endangered in Germany (Karlík and Poschlod, 2019), Romania (Mihaela, 2007) and Republic of iceland (Wąsowicz, 2020) respectively. In the latter instance, M. pratense, English name the 'common cow-wheat,' is now recognized to exist not so common – in the Great britain the species has undergone a 28% decline over the time menstruation 1987–2004 (Braithwaite et al., 2006).

Numerous threats can be attributed to causing local losses beyond the Melampyrum genus. For many species, the reliance on item host plants, and short dispersal distances mean that habitat loss and fragmentation result in isolated populations that are genetically impoverished (due east.yard. Melampyrum sylvaticum; Crichton et al., 2016 ). This problem affects temperate woodlands and grasslands in particular as it is these productive habitats that are more likely to have been exploited for intensive agriculture. Changes in agricultural exercise may likewise have affected species that are thought to be weeds of depression-intensity arable cropping systems e.g. Yard. nemorosum may be quickly eradicated from mown grasslands if mowing occurs earlier in mid-summer rather than late summertime considering seeds have not withal ripened (Blažek et al., 2016). Climate modify is likely to impact Melampyrum due to the low water use efficiency and consequent sensitivity to drought that results from the hemiparasitic strategy. The mount endemics such every bit M. indicum, restricted to the Assam region of the southern Himalaya (Hassler, 2021), and M. herbichii and M. saxosum, high meridian species of the Romanian Carpathians, are all likely candidates for climate-induced range contractions.

Ex situ conservation is the preservation of threatened plant species in facilities such as botanic gardens and seed banks. According to the PlantSearch facility hosted by Botanic Garden Conservation International, 31 species of Melampyrum take been listed but only 20 of these are held in ex situ facilities (Tabular array i). Xvi species are known to exist held at simply ane facility and information technology is unclear whether these are living plants or seed collections. Annual plants present problems when stored as living collections because they demand to collected as seed and reshown every year. In addition, several species of Melampyrum exhibit an unusual germination wheel that involves the emergence of the radicle (the starting time root) prior to the onset of winter. The first leaves (cotyledons) sally only once weather condition amend in the following spring. This prolonged germination means that seeds cannot be disturbed in the soil once the radicle has emerged – to do and so would risk dissentious the root and killing the seed. In add-on, parasites must be grown with suitable hosts, further complicating the requirements for supporting living collections. For these reasons, it is not surprising that the genus appears to exist poorly represented in ex situ facilities. The only species that may be in a more than favorable status with regard to ex situ provision are One thousand. pratense and M. arvense, held in xvi and xiv ex situ collections respectively.

Read full chapter

URL:

https://world wide web.sciencedirect.com/scientific discipline/article/pii/B9780128211397001574

Stream Ecosystem Functioning in an Agricultural Landscape

Sally Hladyz , ... Guy Woodward , in Advances in Ecological Enquiry, 2011

B Impacts of Riparian Clearance on Stream Ecosystem Functioning: Detrital Decomposition, Chief Production and Consumption Rates

Detritus dominates the basal resources of many stream food webs, particularly in the upper reaches of river networks (Cummins et al., 1989; Wallace et al., 1999; Webster and Benfield, 1986; Woodward et al., 2005). It is derived generally from allochthonous subsidies of riparian leaf litter, which are broken down to produce CO2 and other inorganic compounds, dissolved and fine-particulate organic affair, and consumer biomass (Gessner et al., 1999). The principal biological agents of litter decomposition are detritivorous invertebrate 'shredders' and microbial decomposers (leaner and aquatic hyphomycete fungi; Hieber and Gessner, 2002), and decomposition rates are mediated via the combined influences of resource quality, temperature, and consumer abundance (Effigy 2; Boyero et al. 2011; Gessner et al., 2010; Hladyz et al., 2009; Reiss et al., 2010 ). Shredders oft account for the majority of leafage mass loss, at to the lowest degree in the temperate woodland streams that accept been most intensively studied ( Hieber and Gessner, 2002; Hladyz et al., 2009; Irons et al., 1994); their affluence and activity are determined by the quality, quantity and timing of litter inputs. At that place are, however, suggestions that microbial decomposers can exist more important in pasture streams because invertebrate shredders may be deficient or absent, even though total decomposition (i.e. consumption past invertebrates   +   microbes) rates may be like to those in woodland streams (Hladyz et al., 2010).

Figure 2. Within-stream constraints on foliage-litter decomposition rates. 91% of variance in litter decomposition rates within a single woodland stream as a function of resources quality for invertebrate shredders, every bit measured by the degree of microbial conditioning and C:N content of litter—91% of the variance is deemed for by these two variables alone. Redrawn after Hladyz et al. (2009).

In theory, because pasture streams lack a dense, overhanging canopy and pregnant leafage litter inputs (Campbell et al., 1992; Reid et al., 2008), algal production could underpin a greater proportion of secondary product, via autochthonous-based pathways in food webs, relative to the role of detritus in woodland streams (Effigy i; Delong and Brusven, 1998; Hladyz et al., 2011). In this way, pasture systems could retain the potential to procedure leafage litter (Gessner et al., 1998), even though that ability might not unremarkably exist expressed (Hladyz et al., 2011). Although leaf litter per se may exist scarce, these systems can receive appreciable terrestrial inputs of grass litter as an alternative detrital resource (Hladyz et al., 2011; Leberfinger and Bohman, 2010; Menninger and Palmer, 2007). Surprisingly, trivial is known most how grass litter is candy in pasture streams (just run across Menninger and Palmer, 2007; Young et al., 1994), but there are indications that it is used primarily by microbes rather than invertebrate consumers (Dangles et al., 2011; Hladyz et al., 2010; Niyogi et al., 2003). This suggests a primal shift in the driving agents of decomposition in item and overall ecosystem functioning in general, in terms of reliance on autochthonous versus allochthonous pathways, at the base of the food web (Hladyz et al., 2010). In other words, the construction and dynamics of these systems might exist very different from their woodland counterparts.

One of the primary aims in this affiliate was to compare litter decomposition rates in a set of 100 European streams, half of which were reference sites bordered by native vegetation, and the other half had altered riparian vegetation. These were selected to correspond the major types of riparian alteration, on a continental-scale, with the 10 regions representing the major European ecoregions equally defined in the WFD: the alterations investigated included riparian zones that had been cleared for pasture (in Ireland, Romania and Switzerland) or forestry (N. Sweden), and a range of depression diversity plantations (e.1000. monospecific beech forests in France; eucalypt plantations in Portugal and Espana). Nosotros so sought to characterise community structure and ecosystem functioning in a set of nine pasture streams in Ireland, to gain a better understanding of how these systems operate in their own correct, using a combination of survey and experimental approaches (Table ane; Figure 3).

Tabular array 1. Outline of the tiered approach to the study, ranging from an extensive pan-European field bioassay experiment (Tier I) through to increasingly more controlled field-based (Tiers II–III) and laboratory studies (Tier IV)

Tier I Tier Two Tier III Tier IVa Tier IVb
Number of written report sites 100 9 1 north/a n/a
Water chemistry characterised/controlled ✓/× ✓/× ✓/✓ ✓/✓ ✓/✓
Oak litter decomposition ✓ ✓ ✓ × ✓
Grass litter decomposition × ✓ ✓ ✓ ✓
Grass litter quality controlled × × ✓ ✓ ✓
1° consumer aggregation composition characterised/controlled ×/× ✓/× ✓/✓ ✓/✓ ✓/✓
1° consumer affluence characterised/controlled ×/× ✓/× ✓/✓ ✓/✓ ✓/✓
1° consumer—basal resource stable isotope signatures characterised × ✓ × × ×
two° consumer aggregation composition characterised/controlled ×/× ✓/× ✓/✓ ×/× ×/×

Tier I: RIVFUNCTION pan-European study (including 15 pasture streams—5 in Ireland); Tier II: Irish multiple sites field experiments; Tier III: Irish single site (Dripsey River) field experiments; Tier IVa: Irish gaelic laboratory mesocosm experiment (multiple-choice feeding trial); Tier IVb: Irish gaelic laboratory microcosm experiment (single-option feeding trial). Come across Section Ii for full details and Effigy 3 for a schematic delineation of the connections betwixt the drivers and responses for Tiers Ii–IV.

Figure 3. Generalised schematic representation of the putative main drivers of customs structure and ecosystem functioning in the intensive studies carried out in the Irish pasture streams (Tiers Two–IV of the study design—see Table 1 for details).

Read total chapter

URL:

https://www.sciencedirect.com/science/commodity/pii/B9780123747945000043

The Ancient Human Occupation of Britain

Ian Candy , ... Jonathan Lee , in Developments in Quaternary Sciences, 2011

2.4.ii.3 Group three: Temperate climates with evidence for conditions cooler than the present day

Deposits correlated with this group contain evidence for climatic conditions that were libation than the present day. Criteria used for allocating deposits to this group are (ane) proxy bear witness for summer and/or wintertime temperatures that are lower than the present solar day, and (ii) evidence for a vegetation aggregation deficient in warm temperate tree species. Key sites in Group 3 include Happisburgh Site 1 and High Lodge.

At Happisburgh Site i, early Middle Pleistocene deposits record a climate characterised by summer and winter temperatures that were cooler than the present day; the landscape was dominated by open grassland and boreal woodland (Coope, 2006; Ashton et al., 2008). The protrude assemblage (Coope, 2006) indicates summer temperatures of 12–15   °C (at least i–4   °C lower than present), while winter temperatures lay between −   eleven and −   iii   °C (at least 6   °C lower than nowadays).

The deposits at Loftier Lodge are sedimentologically complex, having undergone intensive glaciotectonics (Ashton et al., 1992). The coleopteran assemblage from the early on Middle Pleistocene deposits suggests summer temperature reconstructions (15–sixteen   °C) that are broadly consistent, or peradventure a degree or so lower, than nowadays-twenty-four hours conditions (Coope, 2006), while mean wintertime temperatures lay between −   iv and +   i   °C (2–7 °C lower than the present day). The pollen assemblage supports this interpretation, indicating the being of a vegetation cover dominated by pine with pocket-sized bandbox, juniper, herbs and heath plants, just defective warm temperate woodland species ( Hunt, 1992).

While Waverley Wood (Shotton et al., 1993) is an important early on Middle Pleistocene site, whether it should exist included with Grouping two or 3 deposits is not clear. This dubiety stems from the fact that (1) the sedimentary sequence at Waverley Woods is complex, comprising multiple aqueduct in-fill deposits, and (2) there is evidence for meaning climatic oscillations during the accumulation of these aqueduct fills. The climatic succession consists of a deterioration followed by an amelioration (Shotton et al., 1993; Coope, 2006). The assemblage of coleopteran species indicates oscillations between summertime temperatures consistent with present-day values (xv–17   °C) and summer temperatures significantly lower than the nowadays (8–12   °C), while winter temperature estimates vary between those that overlap with modern-day levels (+   three to –7   °C) and those that are significantly lower (−   9 to −   25   °C) (Shotton et al., 1993; Coope, 2006). Many of the mammalian remains, notwithstanding, record fully temperate conditions (due east.chiliad. mole, Talpa europaea, which cannot survive within even seasonally frozen ground, and straight-tusked elephant, Palaeoloxodon antiquus), a suggestion supported by the molluscan assemblages which indicate that '… for the most role the regional climate …' of the early on Eye Pleistocene deposits at Waverley Forest '… could not take been much colder than the English Midlands at the present' (Shotton et al., 1993, 303). This picture strongly contrasts with the palynological prove which indicates boreal woodland and open grassland. The deposits are characterised by low affluence of temperate tree pollen, and it has been suggested that they probably correlate with the end of an interglacial reflecting deposition during a mail service-temperate episode (Shotton et al., 1993).

Finally, all-encompassing palaeoenvironmental prove comes from littoral/terrestrial deposits at Boxgrove, on the Sussex coastal plain (Roberts and Parfitt, 1999). The sequence at Boxgrove records a high body of water-level stand followed by regression during which freshwater deposits and incipient palaeosols adult, followed in turn by a menstruation of extreme climatic cooling characterised past the deposition of periglacial slope deposits (Bates et al., 1997; Roberts and Parfitt, 1999). In the freshwater/palaeosol units faunal and ostracod assemblages, together with oxygen isotopic data from ostracod tests, suggest a climate which was interglacial in aspect but slightly cooler than the present day (Holmes et al., 2009). The mammal fauna indicates a cooler climate, possible more continental than the present (Preece and Parfitt, 2000), while the ostracod and isotopic results point summer temperatures comparable to present-solar day levels merely winter temperatures that were slightly lower (Holmes et al., 2009). Mean annual air temperature was likewise likely to have been lower than at present (Holmes et al., 2009).

Read full chapter

URL:

https://www.sciencedirect.com/scientific discipline/article/pii/B9780444535979000029

ARCHAEOLOGICAL RECORDS | Global Expansion 300000–8000 Years Agone, Asia

G.D. Petraglia , R. Dennell , in Encyclopedia of Quaternary Science (2d Edition), 2013

The Replacement of Indigenous Populations of Neanderthals, H. erectus and H. floresiensis past Modern Humans

The prevailing view among many geneticists and paleoanthropologists is that all living humans in Asia today are descended from a relatively small population which originally arose in Africa (east.g., Ingram et al. (2000)). Based on slight and by and large ambiguous fossil and archaeological testify, it has been argued that modern humans reached the Levant by 100   ka, and afterwards, other populations traveled (perhaps along the Indian Ocean rim) to reach Australasia by 45–60   ka (Lahr and Foley, 1994; Field and Lahr, 2006) ( Figure vii ). An alternative scenario is that our species entered the Levant and Arabia past OIS 5 (Petraglia et al., 2011). Whichever model is preferred, mod humans replaced Neanderthals in Southwest and Key Asia, indigenous populations (blazon(s) unknown in Due south Asia), populations of H. erectus in Eastern Asia, and ultimately, H. floresiensis in the island of Flores, Indonesia.

Figure 7. Potential routes of anatomically mod humans during OIS 4, showing routes and barriers.

 Adapted from Field JS and Lahr MM (2006) Cess of the southern dispersal: GIS-based analyses of potential routes at oxygen isotopic stage 4. Journal of Earth Prehistory, figure 14.

The appearance of anatomically modern humans in Africa is accompanied by a diverseness of economic, social, and symbolic traits that are ofttimes associated with modernistic human civilisation, although the materialization of such traits is temporally and geographically patchy over the last 250   ka (McBrearty and Brooks, 2000), and few of these traits are both widespread and exclusive to modern humans.

The menstruum betwixt 45 and 30   ka in the Levant is marked past the extinction of the Neanderthals and the expansion of modern humans equipped with Upper Paleolithic adaptations (Shea, 2003 ). Neanderthals throughout western and Central Eurasia appear to have been well-adapted to temperate woodlands and cold steppes, with adaptations geared toward meat acquisition. Economic intensification in later Neanderthal adaptations in the Levant are sindicated by multiseasonal site occupations, a broadening of the subsistence base, and production of spear points to procure prey ( Shea, 2003). Though Neanderthals may have had circuitous social and economic behaviors, small behavioral and adaptive advantages on the role of modern humans may accept somewhen led to their replacement by modern humans.

In addition to the expansion of modern humans into the Levant, populations may take used the Bab al Mandab strait beyond the southern terminate of the Carmine Sea for expansions during OIS v, every bit is exemplified by the presence of Middle Paleolithic sites in southern Arabia with Northeast African affinities (Petraglia and Alsharekh, 2003; Rose, 2004). Though information technology is clear that modernistic humans reached Australia by 45–42   ka and possibly before (Bowler et al., 2003; O'Connell and Allen, 2004), the spread of mod humans across Asia has not been documented from skeletal evidence or archaeological assemblages, and remains at present a hypothesis based largely on modern genetic bear witness. Y-chromosome and MtDNA data suggest the colonization of South asia by mod humans originating in Africa, quondam between 73 and 55   ka (Kivisild et al., 2003). The genetic data advise a unmarried, early migration was responsible for the initial settlement toward South Asia and toward the east (Thangaraj et al., 2005). Information technology has been suggested that modern movements into South asia may take originally been accompanied by a Center Paleolithic technology, presenting issues in discriminating such assemblages from those being used by resident populations of archaic hominins (James and Petraglia, 2005). Though modern humans were probably present in Southern asia sometime after 70   ka, prove for mod human beliefs develops slowly and such signs are temporally and spatially patchy. Because stone tool assemblages in Bharat earlier the great Toba volcanic eruption of 74   ka are like to subsequent ones that were likely made by H. sapiens, it is possible that our species was already in Southern asia before 74   ka (Petraglia et al., 2007). The development of new cultural innovations in the Tardily Paleolithic of South Asia may be related, in function, to fluctuations in the environs and demographic changes, indicating that it may be difficult to discern movements of modern humans. Modern humans probably reached east and southward East asia by 40   ka, as indicated by the remains of modern humans at Tianyuandong Cavern, North Mainland china (Shang et al., 2010) and Niah Cave, Borneo (Barker, 2002), both dated at ca. twoscore–43   ka. Even before indications of H. sapiens in Eastern asia include a metatarsal from Callao Cavern, the Philippines (Mijares et al., 2010) and a cranium from Tam Pa Ling, Laos, that has been directly dated at ca. 63   ka (Demeter et al., 2012). Though encounters between archaic and modern humans are unclear beyond nigh of Asia, the replacement of indigenous primitive populations was probably completed by 18   ka, with the extinction of hominins such every bit H. floresiensis (Chocolate-brown et al., 2004) in remote island settings. In Java, H. erectus may have been extinct before the inflow of H. sapiens, as the Ngandong assemblage of H. erectus has recently been re-dated to 143–546   ka (Indriati et al., 2011).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780444536433003460

POLLEN Analysis, PRINCIPLES

H. Seppä , in Encyclopedia of Quaternary Science (2d Edition), 2013

Establish–Pollen Representation

The results of the pollen counts are usually presented in pollen diagrams showing the percent values of all or selected pollen types. It is important to annotation that well-nigh pollen grains cannot exist identified to the species level. Near are identified either to the genus or family level only. Palynologists working in a given region may come to recognize ii or more types of pollen within a genus or family that are specific to that region and can identify these on the basis of identification keys. Pollen of all grass species are identified at the family level (Poaceae), pollen of unlike pine species at the generic level (Pinus), and the three common North-European birch species cannot exist distinguished from each other.

Since the first comparisons of pollen diagrams and modern plant abundances, information technology has been known that pollen records do non directly reflect plant abundances because some taxa are overrepresented and others underrepresented in pollen samples. A potential style to transform the fossil pollen percentage values to correspond more precisely with existent relative plant abundances is to use various types of statistical correction factors adult individually for each pollen type. In order to obtain such factors, it is necessary to study the pollen–plant relationships by comparing modern plant abundances and modern pollen values within forests. Foundations for this piece of work were laid in the temperate woodlands in N America and Europe in the 1960s. Davis (1963) defined an index, termed the R-value, for describing the ratio between pollen and vegetation percentages and used the R-value to catechumen the original pollen sums to reverberate the vegetation percentages. In contrast, Andersen (1970) compared absolute pollen aggregating values analyzed from moss polsters with the vegetation percentages of corresponding tree species in the same woodland. Significantly, he showed that models describing pollen input cannot consist just of multiplying terms that reverberate the relative productivity differences but must as well include additive terms to business relationship for the background pollen component originating outside the vegetation area used for calibration purposes. The relationship between pollen per centum values and the vegetation percentage can therefore exist depicted as a linear regression bend in which the slope indicates the pollen productivity of the given species and the y-axis intercept shows the amount of background component of the same species transported from outside the study surface area.

An improvement combining features of both the R-value method and Andersen's linear regression method is an extended R-value (ERV) method, which is based on the percentage values but takes into business relationship the background pollen input (Prentice, 1988; Prentice and Parsons, 1981). In improver, the ERV method includes a site factor that ensures that the corrected percentages at each site total 100%. The ERV model presents the relationship betwixt the pollen percent and the surrounding vegetation as:

p = ik α 5 i f ik + grand z i

where p ik is the pollen percentage of the taxon i at site k and v ik is the abundance of the taxon in the vegetation. α is a coefficient describing the pollen product of taxon i, and z i is the groundwork component of pollen coming from exterior the report surface area. f grand is the site factor ensuring that the correct-paw side of the equation will total 100%. Information technology is of import to notation that these taxa have to be identified at the aforementioned taxonomic level. Thus, if the pollen taxon is Pinus, then the vegetation taxon must also be Pinus (genus level) and would include all the pine species in the area, subsumed at that taxonomic level. There is frequently confusion on this indicate, whereby people talk almost Pinus (pollen taxon, genus level) and then beginning discussing pine species individually.

The site gene tin be expressed equally:

f = one thousand one / ∑ j α j five jk 1 − ∑ j x j

Due to the inclusion of the site gene, ERVs also account for the Fagerlind effect (Prentice and Parsons, 1981), a nonlinearity typical of pollen percentage data. The linear regression methods assume a linear relationship between the pollen values and institute abundance. However, the percentage pollen data are not linear, because they must full 100%. Therefore, an increase in the pollen type of one taxon must be accompanied by a decrease of some other, even if the actual abundances of the other taxa remain abiding. In general, the ERVs give a markedly better fit to pollen percent-institute abundance data than do the classical linear regression models.

Although valuable and rational in principle, the generation of reliable correction factors is a complicated process, and their use is never unproblematic or straightforward. Withal, when the representation differences between the chief plant taxa are meaning, the corrected values undoubtedly oft reflect the original plant abundances more closely than the uncorrected values. Nevertheless, information technology is important to think that the linear models for pollen input presume abiding groundwork pollen and abiding pollen productivity for whatever given taxon, whenever it appears, implying that the use of correction factors is constrained in space and time to the overall vegetation type for which they were originally generated. Vegetation changes during the Holocene have been of such magnitude that the background pollen input has undoubtedly changed, and the linear relationship obtained from modern samples is therefore not a reliable approximate for correcting the fossil pollen values on millennial or longer timescales.

Read total chapter

URL:

https://world wide web.sciencedirect.com/science/article/pii/B9780444536433001710