Years Of Vegetation Change Research Articles

Tracing 40,000 years of vegetation change in the Baetic-Rifan biodiversity hotspot

This study presents a 40,000-year-old pollen record from Los Tollos Lake in the Baetic-Rifan region of southernmost Spain. The data offer insights into the past ecosystems of a current biodiversity hotspot situated at the ecotone between the Atlantic and the Mediterranean. This new sequence encompasses Mediterranean and Ibero-North African sclerophylls, broad-leaf trees, conifers, and Tertiary relicts. The full-glacial abundance of mesothermophytes, particularly oaks, is among the highest recorded for the European Quaternary. Notably, the presence of ecologically significant pollen taxa, which are poorly dispersed and currently occur outside the study area, suggests that this biodiversity hotspot was more extensive in the Pleistocene. During the period of c. 40.8–36.5 ka, three Artemisia maxima at 40.6, 38.9, and 36.9 ka coincide with decreases in Quercus, indicating the spread of steppes in response to the abrupt coolings of the GS10, GS9 (HS4), and GS8 events. Similarly, increases in Quercus around 41, 40, and 37.2–38.3 ka parallel the GI10, GI9, and GI8 warm events. A forested period from 36.5–32 ka includes oak expansions during the GI7 and GI6 interstadials. From 32 to 19.2 ka, more xerophytic vegetation is observed, including the HS3, GS5-GS3, HS2, and GS2.1b-c cold spells, although the correlation with vegetation changes is not synchronous. As early as approximately 21 ka, Artemisia definitively declines, while the region was reforesting, likely due to the presence of stationary populations of broadleaf trees and conifers in the southern Baetic mountains. From approximately 12 ka onwards, the highest values of angiosperm trees are recorded, with oaks dominating throughout most of the Holocene. The pollen record and the correlation with marine records suggest a more intense hydrological regime during the first half of the Holocene, but there is also archaeobotanical evidence for human activity during the second half, resulting in a more open landscape, making it difficult to discriminate the impact of each factor. Some abrupt aridity events during the Holocene coincide with small variations in tree cover, particularly at 9.2, 8.2, 6.8, 5.5–4.8, 4.2, and 2.8 ka. Since the Neolithic and during the metallurgic stages, forest species, especially broad-leaf trees, experienced range retraction accompanied by population extinctions. The region's plant communities have been subject to fire regimes since the Pleistocene, seemingly dependent on the available tree biomass.

Seventy-five years of vegetation change after fire in Tasmanian alpine heathland

Context Alpine ecosystems are threatened by warming and an associated increase in fire frequency. There is a gap in our knowledge of succession in Tasmanian alpine heath more than 50 years after fire. The literature suggests that the alpine successional progression usually involves decreasing rates of change, decreasing differences among fire ages, ongoing transitions among shrub species, ongoing transitions from some lifeforms/species to others, and that warming results in increases in species richness. Aims We test for these tendencies up to 75 years from fire in alpine vegetation on kunanyi/Mount Wellington, Tasmania, Australia. Methods We documented the changes in vegetation structure and composition between 1998 and 2022 in plots on either side of an alpine fire boundary in the alpine heathland and used earlier data and observations to extend the record of change after fire to 75 years. We put these changes in the context of the only area of alpine vegetation that was not burnt in 1947 or later. Key results The area last burnt in 1947 exhibited declines in all lifeform covers between 1998 and 2022. All lifeforms except tall shrubs and mat shrubs declined in cover in the area last burnt in 1962. By 2022, shrub cover in the 1962-burnt area had not attained equivalence with the area last burnt in 1947. Herbs had the most dramatic decline in both fire-age classes. There were few shrub seedlings in 2022. All but six taxa, three being exotic, were observed in both the plots and previous broader surveys. Increases in species richness caused by the upward migration of lower-elevation species were not observed. The long-unburnt patch lacked the major dominant of the 1947-burnt plots, namely Orites acicularis, and was dominated by a gymnosperm absent from most of the mountain. Conclusions Succession follows the initial floristic composition model. The differences in trajectories from the 1947 and 1962 fires could possibly be due to desiccation or abrasion damage from increasing wind speeds and temperatures. There are strong indications of further potential change in the absence of fire. Implications The slow rate of recovery and its on-going nature emphasise the importance of keeping fire out of this vegetation type.

Importance of methodological pluralism in deriving counterfactuals for evidence-based conservation.

Most protected area impact research that uses counterfactuals draws heavily on quantitative methods, data, and knowledge types, making it valuable in producing generalizations but limited in temporal scope, historical detail, and habitat diversity and coverage of ecosystem services. We devised a methodological pluralistic approach, which supports social science qualitative methods, narratives, mixed methods, and interdisciplinarity, to fully unlock the potential of counterfactuals in ensuring a place-based and detailed understanding of the socioecological context and impacts of protected areas. We applied this approach to derive possible counterfactual conditions for the impact of a montane protected area on 40years of vegetation change in the Cape Floristic Region-a global biodiversity hotspot and UNESCO World Heritage Site in South Africa. We incorporated diverse methods, knowledge, and information sources, drawing on before-after protected area comparisons for inside and outside the protected area. A significant increase in shrubland vegetation (17-30%) was observed and attributed primarily to a decline in frequent burning for grazing. This also occurred outside the protected area and was driven by socioeconomic drivers and not by concerns over biodiversity conservation or land degradation. Had the protected area not been established the area would have seen intensification of cultivation and increased road networks, buildings, and water storage in dams. Our approach increased historical temporal coverage of socioecological change and contextualized assumptions around causality. Protected area impact evaluation should reengage in place-based research that fully incorporates pluralism in methodologies for constructing counterfactuals in a way that builds regional and global understanding from the local level upward. We devised 10 key principles for deriving counterfactuals grounded in methodological pluralism, covering aspects of collaboration, cocreation, inter- and transdisciplinarity, diverse values and lived experiences, multiple knowledge types, multiple possible causal mechanisms, social science qualitative methods, perceptions, perspectives, and narratives.

Trends in Woody and Herbaceous Vegetation in the Savannas of West Africa

We assess 32 years of vegetation change in the West African Sudano-Sahelian region following the drought events of the 1970s and 1980s. Change in decadal mean rain use efficiency is used to diagnose trends in woody vegetation that is expected to respond more slowly to post-drought rainfall gains, while change in the slope of the productivity–rainfall relationship is used to infer changing herbaceous conditions between early and late periods of the time series. The linearity/non-linearity of the productivity–rainfall relationship and its impact on the interpretation of overall greening trends, and specific woody and herbaceous vegetation trends, is also examined. Our results show a mostly positive association between productivity and rainfall (69% of pixels), which can be best described as linear (32%) or saturating (37%). Choosing the ‘best’ model at a specific location using Akaike Information Criterion has no discernible effect on the interpretation of overall greening or herbaceous trends, but does influence the detection of trends in woody vegetation. We conclude that widespread recovery in woody vegetation is responsible for the post-drought greening phenomenon reported elsewhere for the Sahel and Sudanian sub-regions. Meanwhile, trends in herbaceous vegetation are less pronounced, with no consistent indication towards either herbaceous degradation or recovery.

Forty years of vegetation change in former coppice‐with‐standards woodlands as a result of management change and N deposition

AbstractQuestionDid vegetation of former coppice‐with‐standards woodlands, which were in conversion towards high forest for about 100 yrs, change over the last 41 yrs (1970–2011)? What were the main drivers of vegetation change?LocationDransfeld Plateau, central Germany.MethodsRepetition of 85 historical semi‐permanent vegetation plots located in 13 forest patches on limestone soil. Differences in species composition and plant functional types between historical and recent plots were analysed using a block multi‐response permutation procedure (bMRPP), NMDS, indicator species analysis (ISA) and ANOVA.ResultsWe found significant changes in all vegetation layers. In the tree layer, Fagus sylvatica and Hedera helix had increased, while Quercus robur and Carpinus betulus had decreased. In the understorey, tree regeneration had strongly increased. In the herbaceous layer, species richness had decreased from 30 to 24 species per 100 m², and the abundance of plant functional types had changed: the proportion of geophytes and therophytes had increased, while the proportion of hemicryptophytes had decreased. Spring‐green species (i.e. species active mainly before tree foliation) had increased, while summer‐green species had decreased. In addition, the estimated mean SLA of herbaceous species had increased. The proportion of closed‐forest species had slightly increased, while the proportion of species of forest edges and clearings had decreased. NMDS ordination separated the herbaceous layers from 1970 and 2011 along the second axis, which correlated with the indicator values for continentality (decrease over time) and N (increase over time).ConclusionsAlthough the stands still shared many characteristics of coppice‐with‐standards woodlands, the vegetation had clearly shifted towards that of darker and more nutrient‐rich forest. This indicates both a marked legacy of historic coppice management and a strong influence of recent high forest management, as well as N deposition.

Thirty years of vegetation change in the coastal Santa Cruz Mountains of Northern California detected using landsat satellite image analysis

The Santa Cruz Mountains is a coastal landscape with a history of extensive forest logging, and a future with projected climate warming that may alter vegetation cover and surface water runoff in new ways. Results from Landsat satellite image time-series analysis since 1983 of this study area showed gradual, statistically significant increases in the normalized difference vegetation index (NDVI) in more than 90 % of the (predominantly second-growth) evergreen forest locations sampled. The cumulative distribution of NDVI values in 2013 was significantly different and higher overall from the cumulative distribution of NDVI values in 1983. The extreme drought year of 2013 (and other previous years of low precipitation) did not affect average NDVI growth rates in most drainage basins of the study area, with the exception of four relatively small basins that had less than 30 % forested land cover. Notably different patterns of NDVI change were detected in areas burned by wildfires in recent years. Within the perimeters of the 2008 Summit Fire and the 2009 Lockheed Fire, NDVI showed notable declines from pre-fire levels to those calculated in 2013 Landsat imagery. In contrast to these recent fires, the burned area from the 1985 Lexington Fire showed the highest rate of NDVI increase (over 27 years of regrowth) of any relatively large contiguous area within the Santa Cruz Mountains.

Historical and recent fragmentation of temperate floodplain grasslands: Do patch size and distance affect the richness of characteristic wet meadow plant species?

Patch size and isolation are thought to have a large influence on the extinction risk of specialist plant species in grassland fragments in the modern agricultural landscape. We combined a re-sampling study in semi-permanent floodplain grassland plots with a GIS-based analysis of historical (1950s/1960s) and recent landscape patterns. Based on historical and recent vegetation maps and releves from six study areas (plus a protected reference area) covering 50–60 years of vegetation change following agricultural intensification, we aimed at analysing the importance of fragmentation on the diversity of potentially sensitive specialist species of wet floodplain meadows in northern Germany. On the plot scale, we found 30–66 % reductions in species richness of these characteristic wet meadow plant species over time and an associated increase in the fragmentation of grassland habitats. Distance to the nearest suitable habitat had a modest negative effect on modern plot-scale richness, while the other tested landscape metrics (total meadow area, mean patch size and landscape proximity index distribution) had no significant influence. There was also no evidence for a legacy of historical landscape structure on current richness of specialist species. Instead, management intensity and its change over the past decades, as indicated by altered Ellenberg indicator values for nutrients and moisture, had a strong influence on plot-scale diversity. The results suggest that fragmentation is not the proximate cause of impoverishment and point to habitat deterioration as a main driver. We conclude that conservation measures in Central-European floodplain meadows should not only focus on large continuous grassland areas, but should also consider small meadow patches if they remained species-rich.

Fifty years of vegetation change in oceanic-montane liverwort-rich heath in Scotland

Background: Liverwort heath is considered in Scotland to be one of the vegetation types most vulnerable to environmental change, yet detailed insights into its dynamics are lacking.Aims: To assess the nature and extent of plant compositional changes in liverwort heath over 50 years and relate this to environmental change drivers.Methods: Vegetation plots previously recorded 20 and 50 years ago were re-surveyed to assess changes in species composition, plot-level species richness and between-plot variability, using several β-diversity indices and partitioning. The environmental indicator values of the species that showed most change were used to identify the environmental drivers of change.Results: Liverwort heath in north-west Scotland has undergone compositional changes over 50 years, becoming more heterogeneous, and losing some of its distinct character. Dwarf shrubs and specialist liverworts have decreased, while graminoids have increased. Partitioning of change in β diversity indicated that mainly changes in species richness, rather than species turnover, have driven the taxonomic differentiation over time. Grazing, eutrophication and warmer and drier conditions were found to be potentially important drivers of the observed vegetation change.Conclusions: Our results highlight the vulnerability of liverwort heath to environmental change.

Historia del fuego y la vegetación en una secuencia holocena del Pirineo central: la Basa de la Mora

The importance of studying past fire regimes is derived from the need to understand the effects of current Global Change on present and future fire activity. Studying the relationship between long-term fire ecology, ecosystems and climate allows us to understand how vegetation responds to this perturbation and to define the thresholds triggering irreversible changes in the vegetation. This work presents the last 10 000 years of vegetation change and fire activity on a high altitude ecosystem from the Pyrenees range: the mountain lake Basa de la Mora located in the central southern Pyrenees. Holocene fire activity has been inferred through fossil carbon particle identification in the sedimentary sequence obtained in this lake. We observe that the strongest Holocene fire activity in the area occurred between 8.1 and 4 cal Kyr BP. This period was followed by a phase, between 3.2 and 1.7 cal Kyr BP, where almost no fire activity was recorded. These changes seem to be due to biomass availability and fire-conductive climate conditions. Positive correlation has been found between fire activity and Betula, Corylus, as the key fueling taxa and groups of ariditytolerant taxa. Additionally, fire dynamics seems coupled to higher anthropogenic activities after 1.7 cal Kyr BP.

800 years of vegetation change, fire and human settlement in the Sierra Nevada of California, USA

A combination of pollen and sedimentary charcoal stratigraphies are used in conjunction with historical records to determine the relationships between climate, vegetation change and changing disturbances over the last 800 years in the Sierra Nevada, California. This period witnessed significant climate variability (the ‘Medieval Climate Anomaly’ followed by the ‘Little Ice Age’), as well as expansion of Native American, then Euro-American, populations. From c. ad 1300 to about ad 1800, the meadow was surrounded by a Pinus ponderosa–mixed conifer forest. The abundance of charcoal and carbonaceous spheres in the sediments suggests fire repeatedly burned across the meadow between c. ad 1300 and c. ad 1550, suggesting frequent surface fires. A similar pattern was noted previously in nearby Yosemite Valley, associated with a proto-historic Miwok population expansion (Anderson and Carpenter, 1991). Subsequently, cooler conditions with greater meadow soil moisture prevailed during the LIA, but with little decline in burning. We interpret this as evidence for continued Native American burning. Beginning in the mid-19th century ce, pine pollen percentages declined substantially, then rebounded somewhat during the 20th century. Grass pollen increases, and introduced herbs ( Erodium, Plantago, Rumex, Zea) increase, documenting Euro-American settlement of the local Wawona area, with harvesting of economically important trees, livestock grazing and small-scale farming. These changes are consistent with the historical record. The sedimentary record largely confirms the fire scar record, documenting the anomalous nature of the absence of fire in the vicinity, which is critical to our understanding of the importance of this process on pre-European landscapes.

Forty Years of Vegetation Change on the Missouri River Floodplain

Comparative inventories in 1969 and 1970 and in 2008 of vegetation from 30 forest stands downstream of Garrison Dam on the Missouri River in central North Dakota showed (a) a sharp decline in cottonwood regeneration; (b) a strong compositional shift toward dominance by green ash; and (c) large increases in invasive understory species, such as smooth brome, reed canary grass, and Canada thistle. These changes, and others discovered during remeasurement, have been caused by a complex of factors, some related to damming (altered hydrologic and sediment regimes, delta formation, and associated wet–dry cycles) and some not (diseases and expansion of invasive plants). Dominance of green ash, however, may be short lived, given the likelihood that the emerald ash borer will arrive in the Dakotas in 5–10 years, with potentially devastating effects. The prospects for recovery of this valuable ecosystem, rich in ecosystem goods and services and in American history, are daunting.

Twelve years of vegetation change in an artificial marsh after the transfer of plants and hydrological restoration

For 12 years starting from 1991, we performed vegetation surveys every 2–3 years at permanent plots located in an artificial marsh which was constructed in former rice paddies through sod transplantation from a natural marsh. Management of the artificial marsh was conducted to maintain the condition of the donor vegetation by removing unnecessary plants and ensuring a water supply of constant quality and quantity. However, the structure and floristic composition of the donor vegetation were destroyed during sod transplantation, and eutrophic water was supplied before the construction of a well in year 5. The transition of communities identified in the artificial marsh was monitored periodically at 34 fixed plots established three years after transplantation, with a further two plots added in year 7. Seasonal changes in surface water chemistry were also monitored. While the main communities of the artificial marsh resembled that of the donor marsh, two other communities were also identified at arid or muddy sites, where dominant plants had grown from seeds or propagules. After 12 years, we identified three communities (with one community containing two subunits), the dominance of which changed among the plots over the years. The communities developed along two main gradients, dry to wet and secondary succession. The first gradient was characterized by species groups favoring dry conditions, while the second gradient was characterized by species groups favoring disturbed conditions. The original composition recorded for donor marsh plants was not established by year 12 after transplantation to the artificial marsh.

Twenty-five years of vegetation change along a putative successional chronosequence on the Tanana River, AlaskaThis article is one of a selection of papers from The Dynamics of Change in Alaska’s Boreal Forests: Resilience and Vulnerability in Response to Climate Warming.

Along the Tanana River floodplain, several turning points have been suggested to characterize the changes in ecosystem structure and function that accompany plant community changes through primary succession. In the past, much of this research focused on a presumed chronosequence that uses space for time substitutions. Within this chronosequence, permanent vegetation plots repeatedly measured over time provide an excellent test of the turning points model. We analyzed both canopy and understory vegetation data collected since 1987 in the Bonanza Creek Experimental Forest at the Bonanza Creek Long Term Ecological Research site to address the following questions: (i) Do long-term changes in the densities of seedling, sapling, and mature trees and shrubs of the dominant woody taxa at each successional stage support the turning points model? (ii) How does the entire plant community change with time at each hypothesized turning point? (iii) Do we see evidence of directional and synchronous shifts in species composition across successional stages? We conclude that some aspects of vegetation change during the last 25 years were consistent with the turning points model; however, many changes were not consistent, indicating the potential roles of biological, environmental, landscape, and climate controls in vegetation patterns.

Facilitation drives 65 years of vegetation change in the Sonoran Desert

Ecological processes of low-productivity ecosystems have long been considered to be driven by abiotic controls with biotic interactions playing an insignificant role. However, existing studies present conflicting evidence concerning the roles of these factors, in part due to the short temporal extent of most data sets and inability to test indirect effects of environmental variables modulated by biotic interactions. Using structural equation modeling to analyze 65 years of perennial vegetation change in the Sonoran Desert, we found that precipitation had a stronger positive effect on recruitment beneath existing canopies than in open microsites due to reduced evaporation rates. Variation in perennial canopy cover had additional facilitative effects on juvenile recruitment, which was indirectly driven by effects of density and precipitation on cover. Mortality was strongly influenced by competition as indicated by negative density-dependence, whereas precipitation had no effect. The combined direct, indirect, and interactive facilitative effects of precipitation and cover on recruitment were substantial, as was the effect of competition on mortality, providing strong evidence for dual control of community dynamics by climate and biotic interactions. Through an empirically derived simulation model, we also found that the positive feedback of density on cover produces unique temporal abundance patterns, buffering changes in abundance from high frequency variation in precipitation, amplifying effects of low frequency variation, and decoupling community abundance from precipitation patterns at high abundance. Such dynamics should be generally applicable to low-productivity systems in which facilitation is important and can only be understood within the context of long-term variation in climatic patterns. This predictive model can be applied to better manage low-productivity ecosystems, in which variation in biogeochemical processes and trophic dynamics may be driven by positive density-dependent feedbacks that influence temporal abundance and productivity patterns.

Socio-Economics and Vegetation Change in Urban Ecosystems: Patterns in Space and Time

By 2050, 70% of the Earth’s human population will live in urban areas. Urbanization can have a devastating impact on local ecosystems, but these impacts vary across time and space. Identifying links between spatiotemporal change in urban ecosystems and neighborhood socio-economics is crucial to management aimed at maintaining flora and fauna in urban areas. Here, we tracked 20 years of socio-economic change and 15 years of vegetation change in 32 residential neighborhoods in south-eastern Australia. Regression models that explicitly accounted for a time lag between neighborhood socio-economic characteristics and vegetation response explained more variation in vegetation cover than models that ignored the effects of time. Also, relationships between vegetation and socio-economic factors were stronger in later years for the same neighborhoods suggesting the influence of socio-economics is more readily identified in established neighborhoods. Socio-economic variables alone, or in combination with biophysical variables, were better predictors of vegetation cover than only biophysical variables. Across space, vegetation cover had a negative quadratic relationship with neighborhood housing density, peaking at mid-density values, and a positive relationship with education level and immigration status (the percentage of residents with a non-Australian background). Over time, housing density had a positive relationship with vegetation cover, reflecting an increase in vegetation as neighborhoods develop. Our results highlight the need to understand temporal context when attempting to explain contemporary patterns in vegetation cover and the increasing importance of socio-economic factors in influencing cover as neighborhoods become established.

15,000 Years of vegetation change in the Bonneville basin: the Blue Lake pollen record

This paper contributes to the emerging picture of late Pleistocene and Holocene environmental change in the Bonneville basin, western North America, through analysis of pollen and sediments from the Blue Lake marsh system, a major wetland area located on the western margin of the Great Salt Lake desert. Analyses of data obtained from the upper 4 m of the Blue Lake core suggest that during the latest Pleistocene, when Lake Bonneville covered the Blue Lake site, pine and sagebrush dominated terrestrial plant communities. These steppe-woodland taxa declined in abundance after ∼12 cal ka BP. Wetland plant communities developed at or nearby Blue Lake by ∼11.9 cal ka BP and bulrush-dominated marshes were established no later than 10.8 cal ka BP. The Blue Lake wetlands largely desiccated during a dry and warm early middle Holocene ∼8.3–6.5 cal ka BP. Climatic amelioration starting ∼6.5 cal ka BP is marked principally by a local return of marshes at the expense of playa and grass meadow communities, and a regional increase in sagebrush relative to other dryland shrubs. Singleleaf pinyon pine migrated into the nearby Goshute Mountains after ∼8 cal ka BP. Late Holocene fluctuations include cool intervals from ∼4.4 to 3.4 and ∼2.7 to 1.5 cal ka BP and warmer conditions from 3.4 to 2.7 cal BP and after 1.5 cal ka BP.

Testing non-equilibrium theories in savannas: 1400 years of vegetation change in Tsavo National Park, Kenya

Non-equilibrium processes in savannas are poorly understood because little data is available on how tree abundance has changed over long periods of time. Here I analyse fossil pollen and charcoal from Kanderi Swamp in Tsavo National Park, Kenya in order to investigate patterns of vegetation change over the past 1400 years. I compare the results with the predictions of cyclical, phase and transition and stochastic non-equilibrium models. Fourier analysis of the pollen data provides evidence of cyclical changes in tree abundance with a periodicity of 250–500 years, but the pollen data also suggests that the vegetation surrounding Kanderi swamp remained in a prolonged woodland phase, as predicted by phase and transition models, from approximately 770–1520 a. d. In addition, the results provided evidence of much shorter term changes in tree/grass abundance, perhaps reflecting stochastic variations in rainfall. The charcoal data suggests a link between vegetation change and fire history, possibly mediated through the effects of rainfall variation on the accumulation of combustible biomass in the herb layer. There was also evidence of extreme fires occurring twice in the past 1400 years. The results suggest that at the local scale, the vegetation near Kanderi Swamp has been mainly influenced by localised disturbance, rather than climatic shifts or the Rinderpest epidemic, and that elements of cyclical, phase and transition and stochastic models are needed in order to fully understand the observed pattern of vegetation change.

65,000 years of vegetation change in central australia and the australian summer monsoon

Carbon isotopes in fossil emu (Dromaius novaehollandiae) eggshell from Lake Eyre, South Australia, demonstrate that the relative abundance of C4 grasses varied substantially during the past 65,000 years. Currently, C4 grasses are more abundant in regions that are increasingly affected by warm-season precipitation. Thus, an expansion of C4 grasses likely reflects an increase in the relative effectiveness of the Australian summer monsoon, which controls summer precipitation over Lake Eyre. The data imply that the Australian monsoon was most effective between 45,000 and 65,000 years ago, least effective during the Last Glacial Maximum, and moderately effective during the Holocene.

Preservation Island, Furneaux Group: Two hundred years of vegetation change

Preservation Island was the first area south of Sydney to experience the impact of European settlement. A recent survey of the vegetation resulted in the inventory of 140 plant species, 49 of these being introduced to the island. Ten vegetation types were mapped, some of these being disturbance disclimax communities. The island has a flora typical of many of the Furneaux Outer Islands. Since 1797, Allocasuarina verticillata, once the likely dominant tree on the island, has been depleted almost to extinction and grassland with a high proportion of exotic species has expanded to cover more than a third of the island. Exotic species propagules have been associated with human activity on the island but also with birds and by sea drift. The high levels of natural and human-related disturbance have encouraged establishment of introduced plants. Some obligate-seeding species on the island have been reduced to either precariously low numbers (Acacia ?genistifolia) or extinction (Callitris rhomboidea) by a high fire frequency. The biological productivity of the island was high at the time of initial human settlement because there was an extremely large muttonbird rookery, penguins, macropods and other animals. Scrub and low closed forest were more extensive. Most of the biological capital was exhausted within 30 or 40 years. The significance of the island in post-contact Australian history means that more historical remarks are recorded than would otherwise be expected for such an isolated place.

A combined pollen and phytolith record for fourteen thousand years of vegetation change in northeastern Thailand

Pollen and phytolith analyses of a 6.18 m core (3KUM) extracted from Lake Kumphawapi, northeastern Thailand provide the oldest continuous sequence of vegetation change for continental Southeast Asia. The combined microbotanical data suggest human/environment interaction from at least the Early Holocene to the present. An amelioration of arid Late Pleistocene environments in this region is indicated by the development of herbaceous swamp and swamp forest communities at the core site. Early Holocene vegetation changes reflect the rapid expansion and diversification of mixed-deciduous forests, which may also have been disturbed by anthropogenic burning. The Late Holocene reduction in dry-land forest and the subsequent establishment of secondary-growth forests, suggests a further change to burning regimes. Changes in both human subsistence strategies as well as climate occurred during this period, including the critical transition to rice agriculture. These changing subsistence patterns are reflected in the Kumphawapi record by evidence of shifting burning regimes, including indirect evidence of agricultural activities in the Middle Holocene. The timing and nature of agricultural development indicated by the archaeological data for northeastern Thailand needs to be re-evaluated in order to account for the burning regimes and vegetation changes evident in the 3KUM microfossil record.