Observed increasing water constraint on vegetation growth over the last three decades

Jiao, Wenzhe; Wang, Lixin; Smith, William K.; Chang, Qing; Wang, Honglang; D’Odorico, Paolo

doi:10.1038/s41467-021-24016-9

Cited by 336 publications

(228 citation statements)

References 71 publications

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“…A positive correlation means ET increases with water availability, and the higher the correlation, the more sensitive ET is to dry periods and droughts. A negative correlation means ET decreases with increasing water availability, which is typically due reduced temperature and solar radiation associated with high levels of precipitation (Jiao et al, 2021). A lack of correlation implies ET is not responsive to water availability.…”

Section: Correlation Of Et and Spimentioning

confidence: 99%

“…Observed increases in forest WUE show that under elevated CO 2 concentrations, forests are able to maintain productivity using less water, allowing them to become less coupled with water availability(Keenan et al, 2013), but changes in WUE at the local scale are less conclusive. Interestingly, a recent study identi ed an increasing water constraint on vegetation growth across the extra-tropical northern hemisphere over the past 30 years and found that water savings from increased CO 2 did not offset the increasing water constraint(Jiao et al, 2021). In a more water limited Rocky Mountain watershed, the water savings attributed to stomatal closure associated with elevated CO 2 , were offset by increased lateral ow, largely ameliorating the bene t to local vegetation (Tai, Venturas, Mackay, Brooks, & Flanagan, 2021).…”

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confidence: 99%

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Forest water use is increasingly decoupled from water availability even during severe drought

2022

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Context: Key to understanding forest water balances is the role of tree species regulating evapotranspiration (ET), but the synergistic impact of forest species composition, topography, and water availability on ET and how this shapes drought sensitivity across the landscape remains unclear.Objectives: Our aims were to quantify (1) the effect of forest composition and topography including elevation and hillslope gradients on the relationship between ET and water availability, and (2) whether the relationship has changed over time.Methods: We used remotely sensed Landsat and MODIS ET to quantify forest ET across the Blue Ridge ecoregion of the southeastern USA. Then quanti ed metrics describing ET responses to water availability and trends in responses over time and assessed how these metrics varied across elevation, hillslope, and forest composition gradients.Results: We demonstrated forest ET is becoming less constrained by water availability at the expense of lateral ow. Drought impacts on ET diverged along elevation and hillslope gradients, and that divergence was more pronounced with increasingly severe drought, indicating high elevation and drier, upslope regions tend to maintain ET rates even during extreme drought. We identi ed a decoupling of ET from water availability over time, and found this process was accelerated at higher elevations and in areas with more diffuse-porous trees.Conclusions: Given the large proportion of forests on the landscape distributed across high elevation and upslope positions, reductions in downslope water availability could be widespread, amplifying vulnerability of runoff, the health of downslope vegetation, and aquatic biodiversity.

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Section: Correlation Of Et and Spimentioning

confidence: 99%

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confidence: 99%

Forest water use is increasingly decoupled from water availability even during severe drought

2022

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“…Vegetation growth is expected to become more water constrained because global warming results in an increase in vapor pressure deficit and possible reductions in soil moisture [ 6 ]. Understanding how vegetation responds to water availability in the context of global warming results in larger concerns [ 7 , 8 ]. However, quantifying vegetation response to water availability at large spatial and temporal scales is challenging as vegetation development response to water availability is influenced by many interacting factors including geomorphology and soils, vegetation types, and time scales [ 7 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

Assessment of Climate Change and Human Activities on Vegetation Development in Northeast China

Lin

Kappas

Wyss

et al. 2022

Sensors

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Vegetation in Northeast China (NEC) has faced dual challenges posed by climate change and human activities. However, the factors dominating vegetation development and their contribution remain unclear. In this study, we conducted a comprehensive evaluation of the response of vegetation in different land cover types, climate regions, and time scales to water availability from 1990 to 2018 based on the relationship between normalized difference vegetation index (NDVI) and the standardized precipitation evapotranspiration index (SPEI). The effects of human activities and climate change on vegetation development were quantitatively evaluated using the residual analysis method. We found that the area percentage with positive correlation between NDVI and SPEI increased with time scales. NDVI of grass, sparse vegetation, rain-fed crop, and built-up land as well as sub-humid and semi-arid areas (drylands) correlated positively with SPEI, and the correlations increased with time scales. The negatively correlated area was concentrated in humid areas or areas covered by forests and shrubs. Vegetation water surplus in humid areas weakens with warming, and vegetation water constraints in drylands enhance. Moreover, potential evapotranspiration had an overall negative effect on vegetation, and precipitation was a controlling factor for vegetation development in semi-arid areas. A total of 53% of the total area in NEC showed a trend of improvement, which is mainly attributed to human activities (93%), especially through the implementation of ecological restoration projects in NEC. The relative role of human activities and climate change in vegetation degradation areas were 56% and 44%, respectively. Our findings highlight that the government should more explicitly consider the spatiotemporal heterogeneity of the influence of human activities and water availability on vegetation under changing climate and improve the resilience of regional water resources. The relative proportions and roles map of climate change and human activities in vegetation change areas provide a basis for government to formulate local-based management policies.

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“…Despite these optimistic predictions of afforestation potential, there is evidence that global drylands have expanded into neighboring forests over the last 50 years (Huang et al, 2016; Zhang, Zhang, et al, 2020). Although trends and projections of dryland expansion are still debated (Berg & McColl, 2021; Huang et al, 2016; Jiao et al, 2021; Lian et al, 2021; McDermid et al, 2021), potential expansion could result in a net release of carbon dioxide through vegetation degradation and cause a positive feedback to climatic warming (Huang et al, 2016).…”

Section: Effects Of Afforestation In Drylandsmentioning

confidence: 99%

Nature‐based framework for sustainable afforestation in global drylands under changing climate

Liu

Hartmann

et al. 2022

Global Change Biology

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Drylands cover more than 40% of Earth's land surface and occur at the margin of forest distributions due to the limited availability of water for tree growth. Recent elevated temperature and low precipitation have driven greater forest declines and pulses of tree mortality on dryland sites compared to humid sites, particularly in temperate Eurasia and North America. Afforestation of dryland areas has been widely implemented and is expected to increase in many drylands globally to enhance carbon sequestration and benefits to the human environment, but the interplay of sometimes conflicting afforestation outcomes has not been formally evaluated yet. Most previous studies point to conflicts between additional forest area and water consumption, in particular water yield and soil conservation/desalinization in drylands, but were generally confined to local and regional scales. Our global synthesis demonstrates that additional tree cover can amplify water consumption through a nonlinear increase in evapotranspiration-depending on tree species, age, and structure-which will be further intensified by future climate change. In this review we identify substantial knowledge gaps in addressing the dryland afforestation dilemma, where there are trade-offs with planted forests between increased availability of some resources and benefits to human habitats versus the depletion of other resources that are required for sustainable development of drylands. Here we propose a method of addressing comprehensive vegetation carrying capacity, based on regulating the distribution and structure of forest plantations to better deal with these trade-offs in forest multifunctionality. We also recommend new priority research topics for dryland afforestation, including: responses and feedbacks of dryland forests to climate change; shifts in the ratio of ecosystem ET to tree cover; assessing the role of scale of afforestation in influencing the trade-offs of dryland afforestation; and comprehensive modeling of the multifunctionality of dryland forests, including both ecophysiological and socioeconomic aspects, under a changing climate.

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Observed increasing water constraint on vegetation growth over the last three decades

Cited by 336 publications

References 71 publications

Forest water use is increasingly decoupled from water availability even during severe drought

Forest water use is increasingly decoupled from water availability even during severe drought

Assessment of Climate Change and Human Activities on Vegetation Development in Northeast China

Nature‐based framework for sustainable afforestation in global drylands under changing climate

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