Patterns of post‐drought recovery are strongly influenced by drought duration, frequency, post‐drought wetness, and bioclimatic setting

Global Change Biology, Journal Year: 2021, Volume and Issue: 27(19), P. 4630 - 4643

Published: July 6, 2021

Abstract Understanding vegetation recovery after drought is critical for projecting dynamics in future climates. From 1997 to 2009, Australia experienced a long‐lasting known as the Millennium Drought (MD), which led widespread reductions productivity. However, post‐drought and its determinants remain unclear. This study leverages remote sensing products from different sources—fraction of absorbed photosynthetically active radiation (FPAR), based on optical data, canopy density, derived microwave data—and random forest algorithms assess over Australian natural during 20‐year period centered MD. Post‐drought was prevalent across continent, with 6 out 10 events seeing full within about months. Canopy density slower recover than leaf area seen FPAR. The probability most strongly controlled by return interval, hydrological condition, length. Full seldom observed when occurred at intervals 3 months or less, moderately dry (standardized water balance anomaly [SWBA] [−1, −0.76]) conditions resulted less complete wet (SWBA > 0.3) conditions. Press droughts, are long term but not extreme, delayed more pulse droughts (short extreme) higher frequency persistent decline. Following press decline differed little among biome types peaked semi‐arid regions aridity levels. Forests savanna required longest times drought, while grasslands were slowest drought. provides quantitative thresholds that could be used improve modeling ecosystem post‐drought.

Language: Английский

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Vulnerability of European ecosystems to two compound dry and hot summers in 2018 and 2019

Earth System Dynamics, Journal Year: 2021, Volume and Issue: 12(4), P. 1015 - 1035

Published: Oct. 15, 2021

Abstract. In 2018 and 2019, central Europe was affected by two consecutive extreme dry hot summers (DH18 DH19). The DH18 event had severe impacts on ecosystems likely vegetation activity in the subsequent year, for example through depletion of carbon reserves or damage from drought. Such legacies drought heat stress can further increase susceptibility to additional hazards. Temporally compound extremes such as DH19 can, therefore, result an amplification due preconditioning effects past disturbance legacies. Here, we evaluate how these impacted responses first (DH18) modulated second (DH19). To quantify changes vulnerability each event, train a set statistical models period 2001–2017, which are then used predict enhanced index (EVI) anomalies MODIS. These estimates correspond expected EVI based sensitivity climate. Large departures predicted values indicate conditions be identify modulating composition other environmental factors observed impacts. We find regions (DH) events were significantly stronger than those previous climate–vegetation relationships. One region, largely dominated grasslands crops, showed much both DH their drought, possibly linked changing background CO2 temperature conditions. A forests grasslands, browning DH19, even though partly alleviated 2019. This trajectory mainly explained role interannual legacy increased biotic disturbances, also promoted warm Dry become more frequent coming decades, posing major threat stability European forests. show that state-of-the-art process-based could not represent decline response because they missed gaps may overestimation resilience temperate future model projections.

Language: Английский

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Tree Vitality and Forest Health: Can Tree-Ring Stable Isotopes Be Used as Indicators?

Current Forestry Reports, Journal Year: 2021, Volume and Issue: 7(2), P. 69 - 80

Published: Feb. 27, 2021

Abstract Purpose of Review Society is concerned about the long-term condition forests. Although a clear definition forest health still missing, to evaluate health, monitoring efforts in past 40 years have concentrated on assessment tree vitality, trying estimate photosynthesis rates and productivity. Used decline Central Europe since 1980s, crown foliage transparency has been commonly believed be best indicator relation air pollution, although annual variations appear more closely related water stress. not good rates, defoliation one most used indicators vitality. Tree rings often as However, growth trends are difficult interpret because sampling bias, ring width patterns do provide any information physiological processes. Recent Findings In two decades, tree-ring stable isotopes only reconstruct impact climatic events, such drought, but also study induced by pollution episodes, other natural disturbances environmental stress, pest outbreaks wildfires. They proven useful tools for understanding processes response stress factors. Summary Tree-ring integrate transpiration may enhance our promising We call use future programmes.

Language: Английский

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Ecological mechanisms underlying aridity thresholds in global drylands

Functional Ecology, Journal Year: 2021, Volume and Issue: 36(1), P. 4 - 23

Published: Oct. 30, 2021

Abstract With ongoing climate change, the probability of crossing environmental thresholds promoting abrupt changes in ecosystem structure and functioning is higher than ever. In drylands (areas where it rains <65% what could be potentially evaporated), recent research has shown how three aridity [at (1‐Aridity Index) values 0.54, 0.70 0.80] leads to on structural functional attributes. Despite importance these findings their implications develop effective monitoring adaptation actions combat change desertification, we lack a proper understanding mechanisms unleashing shifts. Here review multiple that may explain existence observed across global drylands, discuss potential amplification underpin hypothetical temporal shifts with change. We propose each threshold caused by different specific mechanisms. The first mainly physiological plant water shortages. second unleashed involving soil processes plant–soil interactions such as erosion, community nutrient cycling circulation. collapse vegetation once third (0.8) crossed related survival limits plants cause sudden cover diversity losses plant–atmospheric feedbacks link further aridification. By identifying, revising linking relevant observed, provide set hypotheses identify knowledge gaps concerning study emergence drylands. were also able establish plausible factors are context dependent influence occurrence time. Our help focus future efforts strategies monitor, adapt or even revert A free Plain Language Summary can found within Supporting Information this article.

Language: Английский

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Assessing the impacts of drought on net primary productivity of global land biomes in different climate zones

Ecological Indicators, Journal Year: 2021, Volume and Issue: 130, P. 108146 - 108146

Published: Aug. 26, 2021

Drought is the most widespread event under climate change and projected to lead high uncertainties in quantifying terrestrial carbon exchange. However, considering complexity of drought quantification differences physiological responses among different vegetation types, potential mechanisms response across regions their at varying time scales remain unclear globally. Here, we analyzed activity determined scale dominating drought-induced variations, then explored its driving factors (temperature, precipitation, evapotranspiration, water balance) climatic conditions types from 2000 2015 using Standardized Precipitation Evapotranspiration Index (SPEI) Net Primary Productivity (NPP). Our results indicated that NPP-SPEI correlation was stronger arid semi-arid compared humid sub-humid zones Vegetation mainly responded short medium shortest observed for deciduous needle-leaf forests closed shrublands, which located southeastern Australia, central Africa, southern Russia. Moreover, grassland cropland ecosystems were found be also highly vulnerable globe. Analysis effects various meteorological on timescales showed balance predominant factor affecting drought. In particular, increase significantly reduced intensity prolonged timescales. time-scales reduces prolongs time-scales. Therefore, identification dominant mostly impact land biomes assist assessing stability ecosystem thus support mitigation reduce degradation.

Language: Английский

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Life after recovery: Increased resolution of forest resilience assessment sheds new light on post‐drought compensatory growth and recovery dynamics

Journal of Ecology, Journal Year: 2021, Volume and Issue: 109(9), P. 3157 - 3170

Published: Jan. 17, 2021

Abstract Understanding the impacts of extreme drought on forest productivity requires a comprehensive assessment tree and resilience. However, current approaches to quantifying resilience limit our understanding response dynamics, recovery trajectories legacies by constraining temporal scale resolution assessment. We compared individual growth histories with forecasted using dynamic regression at an annual resolution, allowing impact stand level dynamics be assessed relative scenario where no occurred. The novel application this approach allowed us quantify cumulative legacy radial multiple stem heights different densities. show that choice pre‐ post‐drought periods over which is can lead systematic bias in both estimates interpretations indices. In contrast, measuring annually revealed clear nonlinearities trajectories. Furthermore, we demonstrate influence pre‐drought attributes such as size, rates densities were only detectable certain stages recovery. Importantly, become positive for some individuals, extending up 9 years after event post‐recovery result reclamation lost basal area. Synthesis . importance increasing order understand patterns drivers highlight shortcomings collapsing into single average value how persist phase, even positively impacting trees. If unaccounted for, phase underestimation overestimation above‐ground losses productivity, highlighting considering longer‐term compensatory

Language: Английский

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Satellite data reveal differential responses of Swiss forests to unprecedented 2018 drought

Global Change Biology, Journal Year: 2022, Volume and Issue: 28(9), P. 2956 - 2978

Published: Feb. 19, 2022

Extreme events such as the summer drought of 2018 in Central Europe are projected to occur more frequently future and may cause major damages including increased tree mortality negative impacts on forest ecosystem services. Here, we quantify response >1 million pixels 10 × m across Switzerland terms resistance, recovery, resilience. We used Normalized Difference Water Index (NDWI) derived from Sentinel-2 satellite data a proxy for canopy water content analyzed its relative change. calculated NDWI change between 2017 pre-drought years (indicating resistance), 2019 post-drought recovery), 2017-2019 resilience). Analyzing this large natural experiment, found that 4.3% Swiss declined 2018, indicating areas with low resistance effects. While roughly 50% area recovered, 2.7% forested continued decline 2019, suggesting prolonged effects or delayed damage. differential responses associated site topographic characteristics stand characteristics, lesser extent climatic conditions interactions these drivers. Low high recovery were most prominent at edges, but also south-facing slopes lower elevations. Tree functional type was important driver resilience, damage stands conifer abundance. Our results demonstrate suitability satellite-based quantification drought-induced spatial resolution areas. Such information is predict how local impact vulnerability extreme help search appropriate adaptation strategies.

Language: Английский

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What happens after drought ends: synthesizing terms and definitions

New Phytologist, Journal Year: 2022, Volume and Issue: 235(2), P. 420 - 431

Published: April 4, 2022

Drought is intensifying globally with climate change, creating an urgency to understand ecosystem response drought both during and after these events end limit loss of functioning. The literature replete studies how ecosystems respond drought, yet there are far fewer focused on dynamics ends. Furthermore, while the terms used describe can be variable inconsistent, so those that responses following drought. With this review, we sought evaluate create clear definitions ecologists use post-drought responses. We found legacy effects, resilience recovery were most commonly respect responses, but variable. Based our review literature, propose a framework for generalizing ends, which refer as 'the period'. suggest future papers need clearly characteristics imposed encourage authors term period general encompasses ends other more specific descriptors period.

Language: Английский

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Phenological physiology: seasonal patterns of plant stress tolerance in a changing climate

New Phytologist, Journal Year: 2022, Volume and Issue: 237(5), P. 1508 - 1524

Published: Nov. 14, 2022

Summary The physiological challenges posed by climate change for seasonal, perennial plants include increased risk of heat waves, postbudbreak freezing (‘false springs’), and droughts. Although considerable work has shown that the traits conferring tolerance to these stressors – thermotolerance, cold hardiness, water deficit stress, respectively are not static in time, they frequently treated as such. In this review, I synthesize recent literature on predictable seasonal therefore, phenological patterns acclimation deacclimation heat, cold, water‐deficit stress perennials, focusing woody native temperate climates. highlight promising, high‐throughput techniques quantifying drought tolerance. For each forms tolerance, summarize current balance evidence regarding temporal over course a year suggest characteristic scale responses environmental stress. doing so, offer synthetic framework ‘phenological physiology’, which understanding leveraging seasonally recurring (phenological) can facilitate adaptation mitigation.

Language: Английский

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Central European 2018 hot drought shifts scots pine forest to its tipping point

Plant Biology, Journal Year: 2022, Volume and Issue: 24(7), P. 1186 - 1197

Published: July 23, 2022

The occurrence of hot drought, i.e. low water availability and simultaneous high air temperature, represents a severe threat to ecosystems. Here, we investigated how the 2018 drought in Central Europe caused tipping point tree ecosystem functioning Scots pine (Pinus sylvestris L.) forest southwest Germany. Measurements stress indicators, such as needle potential, carbon assimilation volatile organic compound (VOC) emissions, dominant P. trees were deployed evaluate during drought. Ecosystem impact recovery assessed exchange, normalized difference vegetation index (NDVI) from satellite data mortality data. During summer 2018, potentials dropped minimum values -7.5 ± 0.2 MPa, which implied hydraulic impairment sylvestris. Likewise, VOC emissions strongly declined after mid-July. Decreasing NDVI August onwards detected, along with defoliation sylvestris, impairing flux 2019, shifting into year-round source. A total 47% all monitored (n = 368) died by September 2020. recovered pre-2018 levels likely emerging broadleaved understorey species. had negative impacts on co-occurrence unfavourable site-specific conditions recurrent droughts resulted accelerated mortality. Thus, pushed stand towards its point, subsequent shift broadleaf-dominated forest.

Language: Английский

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