scholarly journals Short-term effects of drought on tropical forest do not fully predict impacts of repeated or long-term drought: gas exchange versus growth

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170311 ◽  
Author(s):  
Patrick Meir ◽  
Maurizio Mencuccini ◽  
Oliver Binks ◽  
Antonio Lola da Costa ◽  
Leandro Ferreira ◽  
...  
Keyword(s):  
Tropical Forest ◽  
El Niño ◽  
Tree Mortality ◽  
El Nino ◽  
Short Term ◽  
Sapwood Area ◽  
Plant Hydraulics ◽  
Trade Offs ◽  
The Impact

Are short-term responses by tropical rainforest to drought (e.g. during El Niño) sufficient to predict changes over the long-term, or from repeated drought? Using the world's only long-term (16-year) drought experiment in tropical forest we examine predictability from short-term measurements (1–2 years). Transpiration was maximized in droughted forest: it consumed all available throughfall throughout the 16 years of study. Leaf photosynthetic capacity was maintained, but only when averaged across tree size groups. Annual transpiration in droughted forest was less than in control, with initial reductions (at high biomass) imposed by foliar stomatal control. Tree mortality increased after year three, leading to an overall biomass loss of 40%; over the long-term, the main constraint on transpiration was thus imposed by the associated reduction in sapwood area. Altered tree mortality risk may prove predictable from soil and plant hydraulics, but additional monitoring is needed to test whether future biomass will stabilize or collapse. Allocation of assimilate differed over time: stem growth and reproductive output declined in the short-term, but following mortality-related changes in resource availability, both showed long-term resilience, with partial or full recovery. Understanding and simulation of these phenomena and related trade-offs in allocation will advance more effectively through greater use of optimization and probabilistic modelling approaches. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

scholarly journals Modelling tropical forest responses to drought and El Niño with a stomatal optimization model based on xylem hydraulics

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170315 ◽  
Author(s):  
Cleiton B. Eller ◽  
Lucy Rowland ◽  
Rafael S. Oliveira ◽  
Paulo R. L. Bittencourt ◽  
Fernanda V. Barros ◽  
...  
Keyword(s):  
Tropical Forest ◽  
El Niño ◽  
Optimization Model ◽  
El Nino ◽  
Soil Drought ◽  
Forest Sites ◽  
Dynamic Global Vegetation Models ◽  
Vegetation Models ◽  
Global Vegetation

The current generation of dynamic global vegetation models (DGVMs) lacks a mechanistic representation of vegetation responses to soil drought, impairing their ability to accurately predict Earth system responses to future climate scenarios and climatic anomalies, such as El Niño events. We propose a simple numerical approach to model plant responses to drought coupling stomatal optimality theory and plant hydraulics that can be used in dynamic global vegetation models (DGVMs). The model is validated against stand-scale forest transpiration ( E ) observations from a long-term soil drought experiment and used to predict the response of three Amazonian forest sites to climatic anomalies during the twentieth century. We show that our stomatal optimization model produces realistic stomatal responses to environmental conditions and can accurately simulate how tropical forest E responds to seasonal, and even long-term soil drought. Our model predicts a stronger cumulative effect of climatic anomalies in Amazon forest sites exposed to soil drought during El Niño years than can be captured by alternative empirical drought representation schemes. The contrasting responses between our model and empirical drought factors highlight the utility of hydraulically-based stomatal optimization models to represent vegetation responses to drought and climatic anomalies in DGVMs. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

Tropical forest dynamics across a rainfall gradient and the impact of an El Niño dry season

2004 ◽  
Vol 20 (01) ◽  
pp. 51-72 ◽  
Author(s):  
Richard Condit ◽  
Salomon Aguilar ◽  
Andres Hernandez ◽  
Rolando Perez ◽  
Suzanne Lao ◽  
...  
Keyword(s):  
Tropical Forest ◽  
El Niño ◽  
Forest Dynamics ◽  
El Nino ◽  
Dry Season ◽  
Rainfall Gradient ◽  
Tropical Forest Dynamics ◽  
The Impact

scholarly journals Ecological responses to El Niño–induced surface fires in central Brazilian Amazonia: management implications for flammable tropical forests

2004 ◽  
Vol 359 (1443) ◽  
pp. 367-380 ◽  
Author(s):  
Jos Barlow ◽  
Carlos A. Peres
Keyword(s):  
Tropical Forest ◽  
Tropical Forests ◽  
Forest Fires ◽  
Forest Structure ◽  
El Niño ◽  
Tree Mortality ◽  
El Nino ◽  
Recovery Process ◽  
Management Implications ◽  
Brazilian Amazonia

Over the past 20 years the combined effects of El Niño–induced droughts and land–use change have dramatically increased the frequency of fire in humid tropical forests. Despite the potential for rapid ecosystem alteration and the current prevalence of wildfire disturbance, the consequences of such fires for tropical forest biodiversity remain poorly understood. We provide a pan–tropical review of the current state of knowledge of these fires, and include data from a study in a seasonally dry terra firme forest of central Brazilian Amazonia. Overall, this study supports predictions that rates of tree mortality and changes in forest structure are strongly linked to burn severity. The potential consequences for biomass loss and carbon emissions are explored. Despite the paucity of data on faunal responses to tropical forest fires, some trends are becoming apparent; for example, large canopy frugivores and understorey insectivorous birds appear to be highly sensitive to changes in forest structure and composition during the first 3 years after fires. Finally, we appraise the management implications of fires and evaluate the viability of techniques and legislation that can be used to reduce forest flammability, prevent anthropogenic ignition sources from coming into contact with flammable forests and aid the post–fire recovery process.

Impact of severe drought associated with the 1997–1998 El Niño in a tropical forest in Sarawak

2000 ◽  
Vol 16 (3) ◽  
pp. 355-367 ◽  
Author(s):  
Michiko Nakagawa ◽  
Kenta Tanaka ◽  
Tohru Nakashizuka ◽  
Tatsuhiro Ohkubo ◽  
Tsuyoshi Kato ◽  
...  
Keyword(s):  
Tropical Forest ◽  
El Niño ◽  
El Nino ◽  
Basal Area ◽  
Size Class ◽  
Severe Drought ◽  
Drought Period ◽  
Composition And Structure ◽  
Log Linear ◽  
The Impact

The impact of the unusually severe drought associated with the 1997–1998 El Niño on tropical forest dynamics in Sarawak, Malaysia was examined. Mortality during the non-drought period (1993–1997) in a core plot (1.38 ha) was 0.89 % y−1, while that during the drought period (1997–1998) in the same plot and a peripheral plot was 6.37 and 4.35 % y−1, respectively. The basal area lost in the drought interval was 3.4 times that of the annual incremental basal area in 1993–1997. Drought mortality was higher for the smaller trees, though it was less size dependent than the non-drought mortality. Dipterocarpaceae, which is the dominant family in the study plot, had a mortality 12–30 times higher in the drought than the non-drought period. There were no significant differences in mortality among the topographic types. From the results of a log-linear model (multi-factored contingency table), the death of trees was correlated with size class, indicating a change in the size-class structure of the forest. Thus, both the species composition and structure are totally affected by such an episodic drought even in a per-humid tropical forest.

scholarly journals Inter-comparison and assessment of gridded climate products over tropical forests during the 2015/2016 El Niño

2018 ◽  
Vol 373 (1760) ◽  
pp. 20170406 ◽  
Author(s):  
C. Burton ◽  
S. Rifai ◽  
Y. Malhi
Keyword(s):  
Southeast Asia ◽  
Tropical Forest ◽  
Tropical Forests ◽  
Air Temperature ◽  
El Niño ◽  
El Nino ◽  
Congo Basin ◽  
Wide Range ◽  
Spatio Temporal ◽  
The Impact

To understand the impacts of extreme climate events, it is first necessary to understand the spatio-temporal characteristics of the event. Gridded climate products are frequently used to describe climate patterns but have been shown to perform poorly over data-sparse regions such as tropical forests. Often, they are uncritically employed in a wide range of studies linking tropical forest processes to large-scale climate variability. Here, we conduct an inter-comparison and assessment of near-surface air temperature fields supplied by four state-of-the-art reanalysis products, along with precipitation estimates supplied by four merged satellite-gauge rainfall products. Firstly, spatio-temporal patterns of temperature and precipitation anomalies during the 2015–2016 El Niño are shown for each product to characterize the impact of the El Niño on the tropical forest biomes of Equatorial Africa, Southeast Asia and South America. Using meteorological station data, a two-stage assessment is then conducted to determine which products most reliably model tropical climates during the 2015–2016 El Niño, and which perform best over the longer-term satellite observation period (1980–2016). Results suggest that eastern Amazonia, parts of the Congo Basin and mainland Southeast Asia all experienced significant monthly mean temperature anomalies during the El Niño, while northeastern Amazonia, eastern Borneo and southern New Guinea experienced significant precipitation deficits. Our results suggest ERA-Interim and MERRA2 are the most reliable air temperature datasets, while TRMM 3B42 V7 and CHIRPS v2.0 are the best-performing rainfall datasets. This article is part of a discussion meeting issue ‘The impact of the 2015/2016 El Niño on the terrestrial tropical carbon cycle: patterns, mechanisms and implications’.

scholarly journals Resistance of African tropical forests to an extreme climate anomaly

2021 ◽  
Vol 118 (21) ◽  
pp. e2003169118
Author(s):  
Amy C. Bennett ◽  
Greta C. Dargie ◽  
Aida Cuni-Sanchez ◽  
John Tshibamba Mukendi ◽  
Wannes Hubau ◽  
...  
Keyword(s):  
Tropical Forests ◽  
El Niño ◽  
Tree Mortality ◽  
El Nino ◽  
Southern Oscillation ◽  
Carbon Sink ◽  
El Niño Event ◽  
Dry Conditions ◽  
Carbon Losses

The responses of tropical forests to environmental change are critical uncertainties in predicting the future impacts of climate change. The positive phase of the 2015–2016 El Niño Southern Oscillation resulted in unprecedented heat and low precipitation in the tropics with substantial impacts on the global carbon cycle. The role of African tropical forests is uncertain as their responses to short-term drought and temperature anomalies have yet to be determined using on-the-ground measurements. African tropical forests may be particularly sensitive because they exist in relatively dry conditions compared with Amazonian or Asian forests, or they may be more resistant because of an abundance of drought-adapted species. Here, we report responses of structurally intact old-growth lowland tropical forests inventoried within the African Tropical Rainforest Observatory Network (AfriTRON). We use 100 long-term inventory plots from six countries each measured at least twice prior to and once following the 2015–2016 El Niño event. These plots experienced the highest temperatures and driest conditions on record. The record temperature did not significantly reduce carbon gains from tree growth or significantly increase carbon losses from tree mortality, but the record drought did significantly decrease net carbon uptake. Overall, the long-term biomass increase of these forests was reduced due to the El Niño event, but these plots remained a live biomass carbon sink (0.51 ± 0.40 Mg C ha−1 y−1) despite extreme environmental conditions. Our analyses, while limited to African tropical forests, suggest they may be more resistant to climatic extremes than Amazonian and Asian forests.

The impact of El Niño on mast fruiting in Sumatra and elsewhere in Malesia

2000 ◽  
Vol 16 (4) ◽  
pp. 563-577 ◽  
Author(s):  
S. A. Wich ◽  
C. P. Van Schaik
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Fruit Production ◽  
Forest Community ◽  
Tropical Rain Forests ◽  
Mast Fruiting ◽  
Oscillation Phenomenon ◽  
The Impact

Long-term data on flower and fruit production of the forest community in two lowland tropical rain forests in north-western Sumatra are presented. The proportion of years with mast fruiting was found to be similar to that found elsewhere in Malesia. However, masting at the two sites, 70 km apart, did not coincide, and showed no correlation with the El Niño–Southern Oscillation phenomenon (ENSO). Comparisons with other sites in Malesia suggest a general waning of ENSO's impact toward western Malesia. Spatial variation at various scales in the timing of masting events was noted in Sumatra and elsewhere. This suggests that additional factors to ENSO play a role in determining forest-level mast fruiting, and we hypothesize that frugivorous animals have the opportunity to track mast fruiting. It is hypothesized that asynchrony between nearby areas in masting increases toward the western edge of Malesia.

Trust in the executive

2018 ◽  
Vol 55 (5) ◽  
pp. 609-624 ◽  
Author(s):  
Thomas Clark Durant ◽  
Michael Weintraub ◽  
Daniel Houser ◽  
Shuwen Li
Keyword(s):  
Time Horizon ◽  
Medium Term ◽  
Short Term ◽  
Promising Alternative ◽  
Trade Offs ◽  
Turn Taking ◽  
Institutional Types ◽  
Winner Takes All ◽  
The Impact

Why is it so hard to get opposing elites to work together rather than to seek partisan gains and/or political survival? While the credible commitment problem is widely known, there are a number of lesser known obstacles to building trust and trustworthiness between opposing elites. This article presents an account of how some of those obstacles interact through time. Common institutional types, particularly winner-takes-all and power-sharing institutions, force trade-offs between agile responses in the short term and medium-term trust between elites, on the one hand, and between trust among elites in the medium term and the adaptability of agreements in the long term, on the other. We call this the ‘time horizon trilemma’. As an alternative approach, we consider a variant on the two-person consulate used by the Roman Republic for more than 400 years as Rome rose to prominence. In our variant, a ‘turn-taking institution’, opposing executives take short alternating turns as the ultimate decisionmaker within one term. We conduct behavioral games in the experimental lab to provide an initial estimate of the impact of these institutional types – winner-takes-all, requiring consensus only, requiring turn-taking only, or requiring both – on overcoming obstacles to agile responses in the short term, trust among elites in the medium term, and adaptability of agreements in the long term. We find that turn-taking is a promising alternative to solving the time horizon trilemma.

Modulation of Atlantic Basin Tropical Cyclone Activity by the Madden–Julian Oscillation (MJO) from 1905 to 2011

2014 ◽  
Vol 28 (1) ◽  
pp. 204-217 ◽  
Author(s):  
Philip J. Klotzbach ◽  
Eric C. J. Oliver
Keyword(s):  
Tropical Cyclone ◽  
Time Scales ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Atlantic Multidecadal Oscillation ◽  
Madden Julian Oscillation ◽  
Atlantic Basin ◽  
The Impact

Abstract The Madden–Julian oscillation (MJO) has been demonstrated to play a role in tropical cyclone (TC) activity around the globe in a number of recent studies. While the impact of the MJO on TCs in the Atlantic basin since the mid-1970s has been well documented, a newly developed 107-yr-long index for the MJO allows for additional analysis of the impacts of the MJO on Atlantic TC activity. TC activity in the Atlantic increases when MJO-related convection is enhanced over Africa and the Indian Ocean, while TC activity in the Atlantic is suppressed when the MJO enhances convection over the western Pacific. This long-term record of the MJO also allows for the analysis of how the MJO’s impacts may be modulated by other climate modes, such as the El Niño–Southern Oscillation (ENSO) over interannual time scales and the Atlantic multidecadal oscillation (AMO) over multidecadal time scales. When climatologically unfavorable conditions such as an El Niño event or a negative AMO phase are present, even TC-favorable MJO conditions are not enough to generate statistically significant increases in TC activity from the long-term average across the Atlantic basin. However, climatologically favorable conditions during a La Niña event or a warm AMO phase act to enhance the modulation of TC activity over the Atlantic basin by the MJO.

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