Herbivory, hunting, and long-term vegetation change in degraded savanna

Understanding long-term (centennial–millennial scale) ecosystem stability and dynamics are key to sustainable management and conservation of ecosystem processes under the currently changing climate. Fossil pollen records offer the possibility to investigate long-term changes in vegetation composition and diversity on regional and continental scales. Such studies have been conducted in temperate systems, but are underrepresented in the tropics, especially in Africa. This study attempts to synthesize pollen records from Nigeria (tropical western Africa) and nearby regions to quantitatively assess Holocene regional vegetation changes (turnover) and stability under different climatic regimes for the first time. We use the squared chord distance metric (SCD) to assess centennial-scale vegetation turnover in pollen records. Results suggest vegetation in most parts of Nigeria experienced low turnover under a wetter climatic regime (African Humid Period), especially between ~8000 and 5000 cal year BP. In contrast, vegetation turnover increased significantly under the drier climatic regime of the late-Holocene (between ~5000 cal year BP and present), reflecting the imp role of moisture changes in tropical west African vegetation dynamics during the Holocene. Our results are consistent with records of vegetation and climatic changes in other parts of Africa, suggesting the Holocene pattern of vegetation change in Nigeria is a reflection of continental-scale climatic changes.

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Vegetation change (1988–2010) in Camdeboo National Park (South Africa), using fixed-point photo monitoring: The role of herbivory and climate

Koedoe ◽

10.4102/koedoe.v55i1.1127 ◽

2013 ◽

Vol 55 (1) ◽

Cited By ~ 5

Author(s):

Mmoto L. Masubelele ◽

Michael T. Hoffman ◽

William Bond ◽

Peter Burdett

Keyword(s):

South Africa ◽

Fixed Point ◽

National Parks ◽

Vegetation Cover ◽

National Park ◽

Vegetation Change ◽

Growth Form ◽

Annual Rainfall ◽

Management Interventions

Fixed-point photo monitoring supplemented by animal census data and climate monitoring potential has never been explored as a long-term monitoring tool for studying vegetation change in the arid and semi-arid national parks of South Africa. The long-term (1988–2010), fixed-point monitoring dataset developed for the Camdeboo National Park, therefore, provides an important opportunity to do this. Using a quantitative estimate of the change in vegetation and growth form cover in 1152 fixed-point photographs, as well as series of step-point vegetation surveys at each photo monitoring site, this study documented the extent of vegetation change in the park in response to key climate drivers, such as rainfall, as well as land use drivers such as herbivory by indigenous ungulates. We demonstrated the varied response of vegetation cover within three main growth forms (grasses, dwarf shrubs [< 1 m] and tall shrubs [> 1 m]) in three different vegetation units and landforms (slopes, plains, rivers) within the Camdeboo National Park since 1988. Sites within Albany Thicket and Dwarf Shrublands showed the least change in vegetation cover, whilst Azonal vegetation and Grassy Dwarf Shrublands were more dynamic. Abiotic factors such as drought and flooding, total annual rainfall and rainfall seasonality appeared to have the greatest influence on growth form cover as assessed from the fixed-point photographs. Herbivory appeared not to have had a noticeable impact on the vegetation of the Camdeboo National Park as far as could be determined from the rather coarse approach used in this analysis and herbivore densities remained relatively low over the study duration.Conservation implications: We provided an historical assessment of the pattern of vegetation and climatic trends that can help evaluate many of South African National Parks’ biodiversity monitoring programmes, especially relating to habitat change. It will help arid parks in assessing the trajectories of vegetation in response to herbivory, climate and management interventions.

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Unravelling long-term vegetation change patterns in a binational watershed using multitemporal land cover data and historical photography

2011 6th International Workshop on the Analysis of Multi-temporal Remote Sensing Images (Multi-Temp) ◽

10.1109/multi-temp.2011.6005058 ◽

2011 ◽

Author(s):

Miguel L. Villarreal ◽

Laura M. Norman ◽

Robert H. Webb ◽

Diane E. Boyer ◽

Raymond M. Turner

Keyword(s):

Land Cover ◽

Vegetation Change ◽

Land Cover Data

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Recruitment patterns following a severe drought: long-term compositional shifts in Patagonian forests

Canadian Journal of Forest Research ◽

10.1139/x08-149 ◽

2008 ◽

Vol 38 (12) ◽

pp. 3002-3010 ◽

Cited By ~ 80

Author(s):

María L. Suarez ◽

Thomas Kitzberger

Keyword(s):

Vegetation Change ◽

Forest Canopy ◽

Tree Mortality ◽

Forest Composition ◽

Future Climate Change ◽

Severe Drought ◽

Climate Change Scenarios ◽

Recruitment Pattern ◽

Recruitment Patterns

Severe droughts have the potential of inducing transient shifts in forest canopy composition by altering species-specific adult tree mortality patterns. However, permanent vegetation change will occur only if tree recruitment patterns are also affected. Here, we analyze how a massive mortality event triggered by the 1998–1999 drought affected adult and sapling mortality and recruitment in a mixed Nothofagus dombeyi (Mirb.) Blume – Austrocedrus chilensis (D. Don) Flor. et Boult. forests of northern Patagonia. Comparing drought-induced and tree-fall gaps, we assessed changes in forest composition, microenvironments, and seedling density and survival of both species. Drought-kill disturbance shifted species composition of both canopy and sapling cohorts in favour of A. chilensis. Drought gaps were characterized by a shadier and more xeric environment, affecting the recruitment pattern of N. dombeyi seedlings. The seedling cohort was composed mostly of A. chilensis, and its survival was always higher than that of N. dombeyi. Additionally, A. chilensis seedlings showed higher plasticity than N. dombeyi seedlings, increasing its root to shoot ratios in drought gaps. The results suggest that extreme drought itself is a strong driving force in forest dynamics, with important imprints on forest landscapes. Future climate-change scenarios, projecting an increased in frequency and severity of droughts, alert us about expected long-term compositional shifts in many forest ecosystems.

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Landscape Change and Trade in Ancient Greece: Evidence from Pollen Data

The Economic Journal ◽

10.1093/ej/ueaa026 ◽

2020 ◽

Vol 130 (632) ◽

pp. 2596-2618

Author(s):

Adam Izdebski ◽

Tymon Słoczyński ◽

Anton Bonnier ◽

Grzegorz Koloch ◽

Katerina Kouli

Keyword(s):

Environmental History ◽

Agricultural Production ◽

Landscape Change ◽

Vegetation Change ◽

Structural Changes ◽

Ancient Greece ◽

Pollen Data ◽

Trade Expansion ◽

Southern Greece

Abstract In this article we use pollen data from six sites in southern Greece to study long-term vegetation change in this region from 1000 BCE to 600 CE. Based on insights from environmental history, we interpret our estimated trends in the regional presence of cereal, olive and vine pollen as proxies for structural changes in agricultural production. We present evidence that there was a market economy in ancient Greece and a major trade expansion several centuries before the Roman conquest. Our results are consistent with auxiliary data on settlement dynamics, shipwrecks and ancient oil and wine presses.

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Kentucky Bluegrass Invasion Alters Soil Carbon and Vegetation Structure on Northern Mixed-Grass Prairie of the United States

Invasive Plant Science and Management ◽

10.1017/inp.2016.2 ◽

2017 ◽

Vol 10 (01) ◽

pp. 9-16 ◽

Cited By ~ 6

Author(s):

Matt A. Sanderson ◽

Holly Johnson ◽

Mark A. Liebig ◽

John R. Hendrickson ◽

Sara E. Duke

Keyword(s):

Vegetation Structure ◽

Native Species ◽

Vegetation Change ◽

Kentucky Bluegrass ◽

The United States ◽

Total Carbon ◽

Stocking Rate ◽

Soil C ◽

Exotic Grasses

Invasive nonnative grasses pose a significant threat to rangelands of the Northern Great Plains. Long-term data from a grazing experiment near Mandan, ND (46°46′11.43″N, 100°54′55.16″W) revealed the invasion of native prairie by Kentucky bluegrass, an exotic grass. We hypothesized that bluegrass invasion altered soil13C and15N levels, tracking the increased abundance of invasive cool-season grass aboveground. In 2014, soil samples were collected to depths of 0 to 7.6 cm and 7.6 to 15.2 cm in pastures grazed similarly since 1916. Samples were analyzed for total carbon (C) and nitrogen (N) and13C and15N isotopes and compared against archived samples from 1991. Vegetation change from native to exotic grasses changed the isotopic composition of soil C. The soil δ13C at the 0- to 7.6-cm depth became more negative between 1991 and 2014. Soil δ13C became less negative with increasing stocking rate at both soil depths. Soil δ15N values at the 0- to 7.6-cm depth decreased between 1991 and 2014. Soil δ15N increased with increasing stocking rate at the 0- to 7.6-cm depth in 2014. Soil C and N concentrations at 0 to 7.6 cm increased by 35% (12 g C kg−1) and 27% (0.9 g N kg−1), respectively, from 1991 to 2014; however, concentrations at the 7.6- to 15.2-cm depth did not change. The shift from native C4to invasive C3grass did not reduce soil C storage in the long-term prairie pastures. The more deleterious effect of invasion, however, may have been the buildup of dead biomass, which alters vegetation structure and may reduce native species’ diversity and abundance.

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Links between spring snow cover and long-term alpine vegetation change

10.5194/egusphere-egu2020-8737 ◽

2020 ◽

Author(s):

Shengwei Zong ◽

Christian Rixen

Keyword(s):

Remote Sensing ◽

Snow Cover ◽

Plant Species ◽

Climate Warming ◽

Vegetation Change ◽

Alpine Vegetation ◽

Alpine Ecosystems ◽

Snow Cover Extent ◽

The Relationship

Snow is an important environmental factor determining distributions of plant species in alpine ecosystems. During the past decades, climate warming has resulted in significant reduction of snow cover extent globally, which led to remarkable alpine vegetation change. Alpine vegetation change is often caused by the combined effects of increasing air temperature and snow cover change, yet the relationship between snow cover and vegetation change is currently not fully understood. To detect changes in both snow cover and alpine vegetation, a relatively fine spatial scales over long temporal spans is necessary. In this study in alpine tundra of the Changbai Mountains, Northeast China, we (1) quantified spatiotemporal changes of spring snow cover area (SCA) during half a century by using multi-source remote sensing datasets; (2) detected long-term vegetation greening and browning trends at pixel level using Landsat archives of 30 m resolution, and (3) analyzed the relationship between spring SCA change and vegetation change. Results showed that spring SCA has decreased significantly during the last 50 years in line with climate warming. Changes in vegetation greening and browning trend were related to distributional range dynamics of a dominant indigenous evergreen shrub Rhododendron aureum, which extended at the leading edge and retracted at the trailing edge. Changes in R. aureum distribution were probably related to spring snow cover changes. Areas with decreasing R. aureum cover were often located in snow patches where probably herbs and grasses encroached from low elevations and adjacent communities. Our study highlights that spring SCA derived from multi-source remote sensing imagery can be used as a proxy to explore relationship between snow cover and vegetation change in alpine ecosystems. Alpine indigenous plant species may migrate upward following the reduction of snow-dominated environments in the context of climate warming and could be threatened by encroaching plants within snow bed habitats.

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