Patterns and processes of global shrub expansion

Naito, Adam T.; Cairns, David M.

doi:10.1177/0309133311403538

Cited by 202 publications

(153 citation statements)

References 162 publications

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“…This 'shrubification' is consistent with that previously reported in Alaska 5 and across the Arctic in general 6 . Such increases in shrub abundance might boost the productivity and CO 2 uptake of tundra ecosystems.…”

Section: Long-term Effects Of Permafrost Thawsupporting

confidence: 91%

Long-term effects of permafrost thaw

Zona

2016

Nature

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Section: Long-term Effects Of Permafrost Thawsupporting

confidence: 91%

Long-term effects of permafrost thaw

Zona

2016

Nature

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“…Another possibility is shrub encroachment, a widespread phenomena in both temperature and moisture limited grasslands where native grasses are being progressively replaced by shrub vegetation (e.g., [78]). Shrub encroachment has been documented in many regions dominated by pasture ecosystems, including North America, Africa, Australia, and South America (see [79] for a review). Initial research indicated that shrub encroachment caused reduced productivity and an overall loss of ecosystem function [18,80].…”

Section: Discussionmentioning

confidence: 99%

A Global Assessment of Long-Term Greening and Browning Trends in Pasture Lands Using the GIMMS LAI3g Dataset

Cook

Pau

2013

Remote Sensing

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Pasture ecosystems may be particularly vulnerable to land degradation due to the high risk of human disturbance (e.g., overgrazing, burning, etc.), especially when compared with natural ecosystems (non-pasture, non-cultivated) where direct human impacts are minimal. Using maximum annual leaf area index (LAImax) as a proxy for standing biomass and peak annual aboveground productivity, we analyze greening and browning trends in pasture areas from 1982-2008. Inter-annual variability in pasture productivity is strongly controlled by precipitation (positive correlation) and, to a lesser extent, temperature (negative correlation). Linear temporal trends are significant in 23% of pasture cells, with the vast majority of these areas showing positive LAImax trends. Spatially extensive productivity declines are only found in a few regions, most notably central Asia, southwest North America, and southeast Australia. Statistically removing the influence of precipitation reduces LAImax trends by only 13%, suggesting that precipitation trends are only a minor contributor to long-term greening and browning of pasture lands. No significant global relationship was found between LAImax and pasture intensity, although the magnitude of trends did vary between cells classified as natural versus pasture. In the tropics and Southern Hemisphere, the median rate of greening in pasture cells is significantly higher than for cells dominated by natural vegetation. In the Northern Hemisphere extra-tropics, conversely, greening of natural areas is 2-4 times the magnitude of greening in pasture areas. This analysis presents one of the first global assessments of greening and browning trends in global pasture lands, including a comparison with vegetation trends in regions dominated by Remote Sens. 2013, 5 2493 natural ecosystems. Our results suggest that degradation of pasture lands is not a globally widespread phenomenon and, consistent with much of the terrestrial biosphere, there have been widespread increases in pasture productivity over the last 30 years.

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“…The proliferation of woody plants (encroachment or thickening) has been widely documented across many of the world's drylands (Ravi et al, 2009;Naito and Cairns, 2011). Encroachment has substantial effects on ecosystem properties and functions including soil hydrological properties and water balance (Nie et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Spatial patterns of infiltration vary with disturbance in a shrub-encroached woodland

Daryanto

Eldridge²,

Wang

2013

Geomorphology

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Woody plant encroachment is known to have substantial effects on a range of ecosystem processes. Research worldwide indicates that the area around shrubs and trees has higher levels of infiltration than the interspaces. Little is known, however, about the hydrological consequences of shrub removal on infiltration, and how this might be influenced by grazing. We examined the spatial patterns of infiltration across three treatments relating to shrub removal and grazing: (i) undisturbed (ungrazed, unploughed), (ii) grazed but unploughed, and (iii) grazed and ploughed. In general we found that disturbance was associated with a greater cover of bare soil but lower infiltrability, our laboratory-based measure of infiltration. At the undisturbed site, bare soil was patchy and localized, with an autocorrelation range or connectivity of 1.4 m. The autocorrelation range of infiltrability at this site (A0 = 3 m) was larger than would be predicted from the size of the shrub canopy, and this was attributed to the presence of a well-developed understorey layer and biological soil crust community. At both grazed sites, infiltration was confined to the immediate canopy area of the remaining shrubs (A0 = 1.2 m in the unploughed-grazed site). Additionally, there was increasing connectivity of bare soil with disturbance, up to 6.8 m at the ploughed-grazed site. With increasing disturbance, resource-rich shrub patches are likely to become more developed, further reinforcing their growth and persistence at the expense of the bare interspaces. Our results indicate the importance of shrubs for maintaining landscape connectivity, and the long-term unsustainable practice of removal by ploughing, which is likely to promote shrub dominance rather than suppression.

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Patterns and processes of global shrub expansion

Cited by 202 publications

References 162 publications

Long-term effects of permafrost thaw

Long-term effects of permafrost thaw

A Global Assessment of Long-Term Greening and Browning Trends in Pasture Lands Using the GIMMS LAI3g Dataset

Spatial patterns of infiltration vary with disturbance in a shrub-encroached woodland

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