Microclimate feedbacks sustain power law clustering of encroaching coastal woody vegetation

AbstractThe spatial pattern of vegetation patchiness may follow universal characteristic rules when the system is close to critical transitions between alternative states, which improves the anticipation of ecosystem-level state changes which are currently difficult to detect in real systems. However, the spatial patterning of vegetation patches in temperature-driven ecosystems have not been investigated yet. Here, using high-resolution imagery from 1972 to 2013 and a stochastic cellular automata model, we show that in a North American coastal ecosystem where woody plant encroachment has been happening, the size distribution of woody patches follows a power law when the system approaches a critical transition, which is sustained by the local positive feedbacks between vegetation and the surrounding microclimate. Therefore, the observed power law distribution of woody vegetation patchiness may be suggestive of critical transitions associated with temperature-driven woody plant encroachment in coastal and potentially other ecosystems.

Download Full-text

Continental-scale modelling of the effects of climatic and non-climatic disturbances on woody plant encroachment in the grasslands of Africa

10.5194/egusphere-egu21-7425 ◽

2021 ◽

Author(s):

Francesco D'Adamo ◽

Rebecca Spake ◽

James Bullock ◽

Booker Ogutu ◽

Jadunandan Dash ◽

...

Keyword(s):

Soil Moisture ◽

Woody Plant ◽

Population Change ◽

Sub Saharan Africa ◽

Woody Vegetation ◽

Woody Plant Encroachment ◽

Continental Scale ◽

Wide Range ◽

Sub Saharan ◽

Climatic Disturbances

<p>Grasslands cover ca. 7% (2,100,000 km2) of the African continent. They provide a wide range of ecosystem services (e.g., forage, water, recreational spaces, carbon sequestration), and host large wildlife communities. Despite their importance, African grasslands are reported to be suffering from degradation and, perhaps more worryingly, have received little consideration within international policies (e.g., United Nations Sustainable Development Goals). A key issue at present is widespread woody plant encroachment (WPE), which it is shifting African grassland from a grassy- to a (less palatable) woody-dominated biome. However, the way climatic (e.g., precipitation, soil moisture) and non-climatic disturbances (e.g., fire, population density) affect WPE is still poorly understood, particularly at large spatiotemporal scales. Here we identified grasslands in sub-Saharan Africa according to the ESA Climate Change Initiative (CCI) land cover product and use vegetation optical depth (VOD) from passive microwave observations as a proxy for woody vegetation change between 1992 and 2011. We then use independent climatic (precipitation and soil moisture) and non-climatic (burn intensity, population change) data to assess how both spatiotemporal variations and interactions between climatic and non-climatic drivers controlled rates of VOD increase during 1992-2011. We consider not only annual precipitation, soil moisture, fire, and population data, but also integrated and lagged precipitation data (both up to five years ahead of VOD) in these models. Preliminary results reveal a large overall increase in woody vegetation in sub-Saharan Africa grasslands as well as considerable spatiotemporal variation in VOD change that is not due to climatic factors alone.</p>

Download Full-text

Temperature and precipitation controls over leaf- and ecosystem-level CO2 flux along a woody plant encroachment gradient

Global Change Biology ◽

10.1111/j.1365-2486.2011.02599.x ◽

2011 ◽

Vol 18 (4) ◽

pp. 1389-1400 ◽

Cited By ~ 45

Author(s):

Greg A. Barron-Gafford ◽

Russell L. Scott ◽

G. Darrel Jenerette ◽

Erik P. Hamerlynck ◽

Travis E. Huxman

Keyword(s):

Woody Plant ◽

Co2 Flux ◽

Woody Plant Encroachment ◽

Temperature And Precipitation ◽

Ecosystem Level

Download Full-text

Social and Ecological Dimensions of Urban Conservation Grasslands and Their Management through Prescribed Burning and Woody Vegetation Removal

Sustainability ◽

10.3390/su12083461 ◽

2020 ◽

Vol 12 (8) ◽

pp. 3461 ◽

Cited By ~ 3

Author(s):

Alison Farrar ◽

Dave Kendal ◽

Kathryn J. H. Williams ◽

Ben J. Zeeman

Keyword(s):

Native Species ◽

Prescribed Burning ◽

Woody Plant ◽

Community Education ◽

Woody Vegetation ◽

Woody Plant Encroachment ◽

Management Actions ◽

Grassland Conservation ◽

Natural Grasslands ◽

Eastern Australia

Natural grasslands are threatened globally. In south-eastern Australia, remnants of critically endangered natural grasslands are increasingly being isolated in urban areas. Urbanisation has led to reduced fire frequency and woody plant encroachment in some patches. Grasslands are currently being managed under the assumption that desirable management actions to address these threats (prescribed burning and removing woody vegetation) (1) lead to improved conservation outcomes and (2) are restricted by negative public attitudes. In this study, we tested these two assumptions in the context of native grassland conservation reserves in Melbourne, Australia. Firstly, we investigated differences in species and functional trait composition between patches that had been recently burnt, patches that were unburnt and patches subject to woody vegetation encroachment. We found that the functional traits of species converged in areas subject to woody plant encroachment and areas frequently disturbed by fire. Burning promoted native species, and patches of woody plants supressed the dominant grass, providing a wider range of habitat conditions. Secondly, we surveyed 477 residents living adjacent to these grassland conservation reserves to measure values, beliefs and attitudes and the acceptance of prescribed burning and removing woody vegetation. We found conflict in people’s attitudes to grasslands, with both strongly positive and strongly negative attitudes expressed. The majority of residents found prescribed burning an acceptable management practice (contrary to expectations) and removing trees and shrubs from grasslands to be unacceptable. Both cognitive factors (values and beliefs) and landscape features were important in influencing these opinions. This research provides some guidance for managing urban grassland reserves as a social–ecological system, showing that ecological management, community education and engagement and landscape design features can be integrated to influence social and ecological outcomes.

Download Full-text

How widespread is woody plant encroachment in temperate Australia? Changes in woody vegetation cover in lowland woodland and coastal ecosystems in Victoria from 1989 to 2005

Journal of Biogeography ◽

10.1111/j.1365-2699.2009.02255.x ◽

2010 ◽

Vol 37 (4) ◽

pp. 722-732 ◽

Cited By ~ 45

Author(s):

Ian D. Lunt ◽

Lisa M. Winsemius ◽

Simon P. McDonald ◽

John W. Morgan ◽

Remy L. Dehaan

Keyword(s):

Vegetation Cover ◽

Woody Plant ◽

Coastal Ecosystems ◽

Woody Vegetation ◽

Woody Plant Encroachment

Download Full-text

Conservation and Restoration of Grasslands

10.1093/oso/9780198744511.003.0008 ◽

2018 ◽

Author(s):

Brian J. Wilsey

Keyword(s):

Community Assembly ◽

Woody Plants ◽

Woody Plant ◽

Priority Effects ◽

Woody Plant Encroachment ◽

Humpty Dumpty ◽

Alternate States ◽

Density And Biomass ◽

Acid Test ◽

Stocking Rates

Conservation programs alter herbivore stocking rates and find and protect the remaining areas that have not been plowed or converted to crops. Restoration is an ‘Acid Test’ for ecology. If we fully understand how grassland systems function and assemble after disturbance, then it should be easy to restore them after they have been degraded or destroyed. Alternatively, the idea that restorations will not be equivalent to remnants has been termed the ‘Humpty Dumpty’ hypothesis—once lost, it cannot be put back together again. Community assembly may follow rules, and if these rules are uncovered, then we may be able to accurately predict final species composition after assembly. Priority effects are sometimes found depending on species arrival orders, and they can result in alternate states. Woody plant encroachment is the increase in density and biomass of woody plants, and it is strongly affecting grassland C and water cycles.

Download Full-text

The structure of co-publications multilayer network

Computational Social Networks ◽

10.1186/s40649-021-00089-w ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Ghislain Romaric Meleu ◽

Paulin Yonta Melatagia

Keyword(s):

Power Law ◽

Degree Distribution ◽

Preferential Attachment ◽

Small World ◽

Generation Model ◽

Small World Network ◽

Power Law Distribution ◽

Multilayer Networks ◽

Multilayer Network ◽

Scientific Papers

AbstractUsing the headers of scientific papers, we have built multilayer networks of entities involved in research namely: authors, laboratories, and institutions. We have analyzed some properties of such networks built from data extracted from the HAL archives and found that the network at each layer is a small-world network with power law distribution. In order to simulate such co-publication network, we propose a multilayer network generation model based on the formation of cliques at each layer and the affiliation of each new node to the higher layers. The clique is built from new and existing nodes selected using preferential attachment. We also show that, the degree distribution of generated layers follows a power law. From the simulations of our model, we show that the generated multilayer networks reproduce the studied properties of co-publication networks.

Download Full-text

Power-law behavior of transcription factor dynamics at the single-molecule level implies a continuum affinity model

Nucleic Acids Research ◽

10.1093/nar/gkab072 ◽

2021 ◽

Author(s):

David A Garcia ◽

Gregory Fettweis ◽

Diego M Presman ◽

Ville Paakinaho ◽

Christopher Jarzynski ◽

...

Keyword(s):

Transcription Factor ◽

Single Molecule ◽

Power Law ◽

Dwell Time ◽

Specific Binding ◽

Power Law Distribution ◽

Single Molecule Level ◽

Binding Behavior ◽

Chromatin Template ◽

Nuclear Domains

Abstract Single-molecule tracking (SMT) allows the study of transcription factor (TF) dynamics in the nucleus, giving important information regarding the diffusion and binding behavior of these proteins in the nuclear environment. Dwell time distributions obtained by SMT for most TFs appear to follow bi-exponential behavior. This has been ascribed to two discrete populations of TFs—one non-specifically bound to chromatin and another specifically bound to target sites, as implied by decades of biochemical studies. However, emerging studies suggest alternate models for dwell-time distributions, indicating the existence of more than two populations of TFs (multi-exponential distribution), or even the absence of discrete states altogether (power-law distribution). Here, we present an analytical pipeline to evaluate which model best explains SMT data. We find that a broad spectrum of TFs (including glucocorticoid receptor, oestrogen receptor, FOXA1, CTCF) follow a power-law distribution of dwell-times, blurring the temporal line between non-specific and specific binding, suggesting that productive binding may involve longer binding events than previously believed. From these observations, we propose a continuum of affinities model to explain TF dynamics, that is consistent with complex interactions of TFs with multiple nuclear domains as well as binding and searching on the chromatin template.

Download Full-text