Differential tree mortality in response to severe drought: evidence for long-term vegetation shifts

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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Impacts of an Extreme Early-Season Freeze Event in the Interior Pacific Northwest (30 October–3 November 2002) on Western Juniper Woodlands

Journal of Applied Meteorology ◽

10.1175/jam2261.1 ◽

2005 ◽

Vol 44 (7) ◽

pp. 1152-1158 ◽

Cited By ~ 5

Author(s):

Paul A. Knapp ◽

Peter T. Soulé

Keyword(s):

Pacific Northwest ◽

Tree Mortality ◽

Extended Period ◽

Severe Drought ◽

Cold Spell ◽

Cold Event ◽

Western Juniper ◽

Synoptic Conditions ◽

Temperature Records

Abstract In mid-autumn 2002, an exceptional 5-day cold spell affected much of the interior Pacific Northwest, with minimum temperatures averaging 13°C below long-term means (1953–2002). On 31 October, minimum temperature records occurred at 98 of the 106 recording stations, with records lowered in some locations by 9°C. Calculation of recurrence intervals of minimum temperatures shows that 50% of the stations experienced a >500-yr event. The synoptic conditions responsible were the development of a pronounced high pressure ridge over western Canada and an intense low pressure area centered in the Intermountain West that promoted strong northeasterly winds. The cold spell occurred near the end of the growing season for an ecologically critical and dominant tree species of the interior Pacific Northwest—western juniper—and followed an extended period of severe drought. In spring 2003, it became apparent that the cold had caused high rates of tree mortality and canopy dieback in a species that is remarkable for its longevity and resistance to climatic stress. The cold event altered western juniper dominance in some areas, and this alteration may have long-term impacts on water budgets, fire intensities and frequencies, animal species interrelationships, and interspecific competition among plant species.

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Differential impact of severe drought on infant mortality in two sympatric neotropical primates

Royal Society Open Science ◽

10.1098/rsos.200302 ◽

2020 ◽

Vol 7 (4) ◽

pp. 200302 ◽

Cited By ~ 2

Author(s):

Fernando A. Campos ◽

Urs Kalbitzer ◽

Amanda D. Melin ◽

Jeremy D. Hogan ◽

Saul E. Cheves ◽

...

Keyword(s):

Infant Mortality ◽

Tree Mortality ◽

Natural Populations ◽

Dry Forest ◽

Primate Species ◽

Spider Monkeys ◽

Severe Drought ◽

Climate Conditions ◽

Fruit Abundance

Extreme climate events can have important consequences for the dynamics of natural populations, and severe droughts are predicted to become more common and intense due to climate change. We analysed infant mortality in relation to drought in two primate species (white-faced capuchins, Cebus capucinus imitator, and Geoffroy's spider monkeys, Ateles geoffroyi ) in a tropical dry forest in northwestern Costa Rica. Our survival analyses combine several rare and valuable long-term datasets, including long-term primate life-history, landscape-scale fruit abundance, food-tree mortality, and climate conditions. Infant capuchins showed a threshold mortality response to drought, with exceptionally high mortality during a period of intense drought, but not during periods of moderate water shortage. By contrast, spider monkey females stopped reproducing during severe drought, and the mortality of infant spider monkeys peaked later during a period of low fruit abundance and high food-tree mortality linked to the drought. These divergent patterns implicate differing physiology, behaviour or associated factors in shaping species-specific drought responses. Our findings link predictions about the Earth's changing climate to environmental influences on primate mortality risk and thereby improve our understanding of how the increasing severity and frequency of droughts will affect the dynamics and conservation of wild primates.

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Quantifying whole tree non-structural carbon dynamics under long-term experimental drought using radiocarbon

10.5194/egusphere-egu21-3330 ◽

2021 ◽

Author(s):

Drew Peltier ◽

Mariah Carbone ◽

Christopher Ebert ◽

Xiaomei Xu ◽

Henry Adams ◽

...

Keyword(s):

Stress Responses ◽

Tree Mortality ◽

Carbon Dynamics ◽

Severe Drought ◽

Mature Trees ◽

Coarse Roots ◽

Additional Information ◽

Structural Carbon ◽

Whole Tree

<div> <div> <div> <p>Under increasingly frequent, persistent, and severe drought events, predicting future forest carbon dynamics necessitates quantitative understanding of the physiological processes leading to tree mortality and physiological impairment. The responses of non-structural carbon (NSC; primarily sugars and starch) pools in mature trees is particularly important, as dynamics in NSC interact with hydraulic damage to perturb future tree growth. However, NSC concentration measurements alone are not suUcient to understand the stress responses of tree NSC pools formed over years to decades. Thus, we are using radiocarbon (14C) to quantify the age of NSC stored within, and used by, pi&#241;on pine trees exposed to either severe or long-term drought stress at the Sevilleta LTER, in New Mexico, USA. Measuring the age of NSC allows inference on the storage history of a tree, and how different NSC pools may be altered by drought. Experimental plots are subjected to either 0% (control) or 90% reduction in precipitation. A 45% precipitation reduction plot has also been in place since 2009, offering a chance to study the impacts of a decade of drought. We are measuring &#916;14C of NSC in twigs, bole sapwood, and coarse roots, as well as in CO2 respired from the bole and branches. Our goal is to quantify the role of different-aged NSC pools across tree organs in driving whole-tree physiological responses to drought. Preliminary results show that the long-term droughted trees store and respire on average younger NSC than control trees. Ongoing drought treatments and sampling will provide additional information on how NSC dynamics in these trees are influenced by drought.</p> </div> </div> </div>

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Development and Verification of the Available Number of Water Intake Days in Ungauged Local Water Source Using the SWAT Model and Flow Recession Curves

Water ◽

10.3390/w13111511 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1511

Author(s):

Jung-Ryel Choi ◽

Il-Moon Chung ◽

Se-Jin Jeung ◽

Kyung-Su Choo ◽

Cheong-Hyeon Oh ◽

...

Keyword(s):

Water Supply ◽

Water Intake ◽

Water Resource Management ◽

Assessment Tool ◽

Swat Model ◽

High Water ◽

Coefficient Of Determination ◽

Severe Drought ◽

Regional Government

Climate change significantly affects water supply availability due to changes in the magnitude and seasonality of runoff and severe drought events. In the case of Korea, despite high water supply ratio, more populations have continued to suffer from restricted regional water supplies. Though Korea enacted the Long-Term Comprehensive Water Resources Plan, a field survey revealed that the regional government organizations limitedly utilized their drought-related data. These limitations present a need for a system that provides a more intuitive drought review, enabling a more prompt response. Thus, this study presents a rating curve for the available number of water intake days per flow, and reviews and calibrates the Soil and Water Assessment Tool (SWAT) model mediators, and found that the coefficient of determination, Nash–Sutcliffe efficiency (NSE), and percent bias (PBIAS) from 2007 to 2011 were at 0.92, 0.84, and 7.2%, respectively, which were “very good” levels. The flow recession curve was proposed after calculating the daily long-term flow and extracted the flow recession trends during days without precipitation. In addition, the SWAT model’s flow data enables the quantitative evaluations of the number of available water intake days without precipitation because of the high hit rate when comparing the available number of water intake days with the limited water supply period near the study watershed. Thus, this study can improve drought response and water resource management plans.

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Estimating long-term tree mortality rate time series by combining data from periodic inventories and harvest reports in a Bayesian state-space model

Forest Ecology and Management ◽

10.1016/j.foreco.2012.12.022 ◽

2013 ◽

Vol 292 ◽

pp. 64-74 ◽

Cited By ~ 7

Author(s):

Katalin Csilléry ◽

Maëlle Seignobosc ◽

Valentine Lafond ◽

Georges Kunstler ◽

Benoît Courbaud

Keyword(s):

Time Series ◽

Mortality Rate ◽

State Space ◽

Tree Mortality ◽

State Space Model ◽

Space Model ◽

Combining Data

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Landscape-scale disturbances and regeneration in semi-arid woodlands of southwestern Australia

Pacific Conservation Biology ◽

10.1071/pc940214 ◽

1994 ◽

Vol 1 (3) ◽

pp. 214 ◽

Cited By ~ 44

Author(s):

Colin J. Yates ◽

Richard J. Hobbs ◽

Richard W. Bell

Keyword(s):

Tree Mortality ◽

Landscape Scale ◽

Eucalyptus Species ◽

Natural Ecosystems ◽

Fragmented Landscapes ◽

The Past ◽

Adult Tree ◽

Western Australian ◽

Semi Arid

Woodlands dominated by Eucalyptus salmonophloia occur both in the fragmented landscapes of the Western Australian wheatbelt and in the adjacent unfragmented goldfields area. We examined the responses of the unfragmented woodlands to landscape-scale disturbances caused by fire, floods, windstorms and drought. Sites known to have experienced disturbances of these types over the past 50 years all had cohorts of sapling-stage E. salmonophloia and other dominant Eucalyptus species. Sites disturbed either by fire, flood or storm during 1991-92 displayed adult tree mortality and extensive seedling establishment, although rates of establishment and survival varied between sites. No regeneration was observed at equivalent undisturbed sites. These results indicate that landscape-scale disturbances of several types are important drivers of the dynamics of these semi-arid woodlands. Lack of regeneration of fragmented woodlands in the wheatbelt is likely to be due to changed disturbance regimes coupled with altered physical and biotic conditions within remnants. We argue that it may be difficult to identify processes which are important for the long-term persistence of natural ecosystems in fragmented landscapes without reference to equivalent unfragmented areas.

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How does water yield respond to mountain pine beetle infestation in a semiarid forest?

Hydrology and Earth System Sciences ◽

10.5194/hess-25-4681-2021 ◽

2021 ◽

Vol 25 (9) ◽

pp. 4681-4699

Author(s):

Jianning Ren ◽

Jennifer C. Adam ◽

Jeffrey A. Hicke ◽

Erin J. Hanan ◽

Christina L. Tague ◽

...

Keyword(s):

Mountain Pine Beetle ◽

Tree Mortality ◽

Hydrologic Model ◽

Water Yield ◽

Driving Mechanisms ◽

Mountain Pine ◽

Pine Beetle ◽

Interannual Climate Variability ◽

Hydrologic Responses

Abstract. Mountain pine beetle (MPB) outbreaks in the western United States result in widespread tree mortality, transforming forest structure within watersheds. While there is evidence that these changes can alter the timing and quantity of streamflow, there is substantial variation in both the magnitude and direction of hydrologic responses, and the climatic and environmental mechanisms driving this variation are not well understood. Herein, we coupled an eco-hydrologic model (RHESSys) with a beetle effects model and applied it to a semiarid watershed, Trail Creek, in the Bigwood River basin in central Idaho, USA, to examine how varying degrees of beetle-caused tree mortality influence water yield. Simulation results show that water yield during the first 15 years after beetle outbreak is controlled by interactions between interannual climate variability, the extent of vegetation mortality, and long-term aridity. During wet years, water yield after a beetle outbreak increased with greater tree mortality; this was driven by mortality-caused decreases in evapotranspiration. During dry years, water yield decreased at low-to-medium mortality but increased at high mortality. The mortality threshold for the direction of change was location specific. The change in water yield also varied spatially along aridity gradients during dry years. In wetter areas of the Trail Creek basin, post-outbreak water yield decreased at low mortality (driven by an increase in ground evaporation) and increased when vegetation mortality was greater than 40 % (driven by a decrease in canopy evaporation and transpiration). In contrast, in more water-limited areas, water yield typically decreased after beetle outbreaks, regardless of mortality level (although the driving mechanisms varied). Our findings highlight the complexity and variability of hydrologic responses and suggest that long-term (i.e., multi-decadal mean) aridity can be a useful indicator for the direction of water yield changes after a disturbance.

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Crop responses to lime in long-term pasture-crop rotations in a high rainfall area in south-eastern Australia

Australian Journal of Agricultural Research ◽

10.1071/ar00087 ◽

2001 ◽

Vol 52 (3) ◽

pp. 329 ◽

Cited By ~ 16

Author(s):

G. D. Li ◽

K. R. Helyar ◽

M. K. Conyers ◽

B. R. Cullis ◽

P. D. Cregan ◽

...

Keyword(s):

Crop Production ◽

Acid Soils ◽

Crop Rotations ◽

Severe Drought ◽

High Rainfall ◽

South Eastern ◽

Permanent Pasture ◽

Eastern Australia ◽

South Eastern Australia

A long-term trial, known as ‘managing acid soils through efficient rotations’ (MASTER), commenced in 1992 to develop and demonstrate a cropping system that is economically viable on the highly acid soils of the traditional permanent pasture region in south-eastern Australia, so that their fertility is sustained or improved. There were 2 permanent pasture systems and 2 pasture–crop rotations, each with and without lime. This paper reports the effect of lime on crop production over the first cycle (6 years). On annual pasture–crop rotations, lime significantly increased the dry matter production at anthesis and grain yields of wheat (cv. Dollarbird) compared with the unlimed treatments. Averaged across years from 1992 to 1997 (excluding the severe drought year 1994), wheat crops produced 1.6 t/ha more grain on the limed treatments than on the unlimed treatments (3.6 v. 2.0 t/ha). On perennial pasture–crop rotations, the lime effects varied with crops grown at each phase and year. For example, despite being tolerant of acidity, oats (cv. Yarran) responded to lime in 1996. Likewise, triticale (cv. Abacus) responded to lime in 1997. Wheat (cv. Dollarbird) that is moderately tolerant to acidity responded to lime in phase 6 from 1992 to 1997 excluding 1994 (3.5 v. 1.7 t/ha). Acid-tolerant wheat varieties, triticale, and narrow-leaf lupins are considered the most viable crops for the soil and climatic conditions encountered in this high rainfall (5000—800 mm per annum) area of south-eastern Australia.

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Compound Drought-Flood Events in Fragile Contexts: Examples from the Horn of Africa

10.5194/egusphere-egu21-10148 ◽

2021 ◽

Author(s):

Alessia Matano ◽

Anne Van Loon ◽

Marleen de Ruiter ◽

Johanna Koehler ◽

Hans de Moel ◽

...

Keyword(s):

Warning Signs ◽

Security Level ◽

Severe Drought ◽

Flood Events ◽

Horn Of Africa ◽

Long Term Effects ◽

Mental Maps ◽

Humanitarian Crises ◽

Compound Events

<p>Humanitarian crises often result from a combination of multiple physical and societal processes, rather than independently from a single driver. The combination of processes leads to &#8220;compound events&#8221;, whose socio-economic impacts could be larger than those expected by analysing each driver individually. In recent years, the Horn of Africa has been increasingly exposed to compound events. Frequent extreme wet and dry conditions often compound with its fragile context characterized by internal ethnic conflicts, unstable governments, and high levels of poverty, resulting in impacts usually larger than anticipated. An improved understanding of the drivers and their interactions can help to reduce future risks associated with compound events.</p><p>Here, we conducted a retrospective analysis of the humanitarian crises that occurred in Kenya and Ethiopia in 2017-2018. In this period, a severe drought that occurred over the span of around 18/24 months, was followed by extensive flooding during the 2018 March-May rainy season. The impacts and their related drivers were explored, first through a review of the literature, and then through a survey and semi-structured interviews with several stakeholders from national agencies, civil societies, and NGOs. The approach resulted in a participatory co-creation of causal loop diagrams used as qualitative mental maps of the perceived drivers and interactions. These were then used as a basis for the semi-quantitative analysis of driver-interactions, modelling the impacts of immediate and long-term effects of the compound events.</p><p>The analysis disentangles the spatial-temporal feedback of drought and flood events, and their interconnections with societal forces. We found both negative and positive feedback on the food security level of the Kenyan and Ethiopian population. For instance, the flood initially exacerbated food insecurity caused by the long drought, but in the long term, it helped alleviate related water shortages. The results show the importance of taking drought response actions that first do not increase the risk related to subsequent floods (e.g., encouraging the allocation of people in lowland areas), but also that can boost the positive impacts of above-average rainfall on drought effects. Moreover, we investigated potential early warning signs and explored the impacts of several measures, identifying windows of opportunity for interventions.</p>

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