scholarly journals Measuring the pulse of trees; using the vascular system to predict tree mortality in the 21st century

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Timothy J Brodribb ◽  
Herve Cochard ◽  
Celia Rodriguez Dominguez
Keyword(s):  
Tree Mortality ◽  
Vascular System ◽  
Warming Trend ◽  
Physiological Basis ◽  
Mesic Forest ◽  
Species Survival ◽  
Urgent Task ◽  
Dry Conditions ◽  
Plant Water Transport ◽  
Distributional Limits

Abstract Tree mortality during hot and dry conditions presents a stark reminder of the vulnerability of plant species to climatic extremes. The current global warming trend makes predicting the impacts of hot/dry events on species survival an urgent task; yet, the standard tools for this purpose lack a physiological basis. This review examines a diversity of recent evidence demonstrating how physiological attributes of plant vascular systems can explain not only why trees die during drought, but also their distributional limits according to rainfall. These important advances in the science of plant water transport physiology provide the basis for new hydraulic models that can provide credible predictions of not only how but when, where and which species will be impacted by changes in rainfall and temperature in the future. Applying a recently developed hydraulic model using realistic parameters, we show that even apparently safe mesic forest in central France is predicted to experience major forest mortality before the end of the century.

A multi-proxy reconstruction of climate during the late-Pleistocene to early Holocene transition in the northeastern, USA

2021 ◽  
pp. 1-17
Author(s):  
Laurie D. Grigg ◽  
Kevin J. Engle ◽  
Alison J. Smith ◽  
Bryan N. Shuman ◽  
Maximilian B. Mandl
Keyword(s):  
Late Pleistocene ◽  
Climatic Variability ◽  
Warming Trend ◽  
Early Holocene ◽  
Individual Species ◽  
Environmental Preferences ◽  
The North ◽  
Show Evidence ◽  
Dry Conditions ◽  
Components Analysis

Abstract A multiproxy record from Twin Ponds, VT, is used to reconstruct climatic variability during the late Pleistocene to early Holocene transition. Pollen, ostracodes, δ18O, and lithologic records from 13.5 to 9.0 cal ka BP are presented. Pollen- and ostracode-inferred climatic reconstructions are based on individual species’ environmental preferences and the modern analog technique. Principal components analysis of all proxies highlights the overall warming trend and centennial-scale climatic variability. During the Younger Dryas cooling event (YD), multiple proxies show evidence for cold winter conditions and increasing seasonality after 12.5 cal ka BP. The early Holocene shows an initial phase of rapid warming with a brief cold interval at 11.5 cal ka BP, followed by a more gradual warming; a cool, wet period from 11.2 to 10.8 cal ka BP; and cool, dry conditions from 10.8 to 10.2 cal ka BP. The record ends with steady warming and increasing moisture. Post-YD climatic variability has been observed at other sites in the northeastern United States and points to continued instability in the North Atlantic during the final phases of deglaciation.

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.

scholarly journals Non-structural carbohydrates mediate seasonal water stress across Amazon forests

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Caroline Signori-Müller ◽  
Rafael S. Oliveira ◽  
Fernanda de Vasconcellos Barros ◽  
Julia Valentim Tavares ◽  
Martin Gilpin ◽  
...  
Keyword(s):  
Water Stress ◽  
Tree Species ◽  
Tree Mortality ◽  
Soluble Sugar ◽  
Dry Season ◽  
Future Climate Change ◽  
Wet Season ◽  
Dry Conditions ◽  
Almost All

AbstractNon-structural carbohydrates (NSC) are major substrates for plant metabolism and have been implicated in mediating drought-induced tree mortality. Despite their significance, NSC dynamics in tropical forests remain little studied. We present leaf and branch NSC data for 82 Amazon canopy tree species in six sites spanning a broad precipitation gradient. During the wet season, total NSC (NSCT) concentrations in both organs were remarkably similar across communities. However, NSCT and its soluble sugar (SS) and starch components varied much more across sites during the dry season. Notably, the proportion of leaf NSCT in the form of SS (SS:NSCT) increased greatly in the dry season in almost all species in the driest sites, implying an important role of SS in mediating water stress in these sites. This adjustment of leaf NSC balance was not observed in tree species less-adapted to water deficit, even under exceptionally dry conditions. Thus, leaf carbon metabolism may help to explain floristic sorting across water availability gradients in Amazonia and enable better prediction of forest responses to future climate change.

Forest dynamics after drought-induced mortality: a global assessment

2020 ◽  
Author(s):  
Enric Batllori Presas ◽  
Francisco Lloret Maya
Keyword(s):  
Forest Dynamics ◽  
Global Assessment ◽  
Temperate Forest ◽  
Tree Mortality ◽  
Forest Ecosystems ◽  
Species Traits ◽  
Short Term ◽  
Management Intensity ◽  
Dry Conditions ◽  
Study Sites

<p>Forest mortality related to extreme drought has been reported worldwide, affecting all biomes and plant types (angiosperm vs. gymnosperms, evergreen vs. deciduous). The forecasted increased frequency and intensity of drought events as a consequence of anthropogenic climate change could promote an increasingly widespread drought-induced mortality in the future. However, little understanding exists on ecological trajectories or the replacement processes after drought-induced mortality events. We assess (through a collaborative initiative) the extent of short-term self-replacement patterns in temperate forest ecosystems worldwide (N = 131 sites) in relation to: species traits, the major bioclimatic characteristics of reporting sites, and past management and disturbance legacies in the affected sites. We found that alternate species replaced pre-drought dominant tree species in ~70% of the examined cases, whereas in ~10% of the study sites there was no replacement by woody vegetation. Replacement was influenced by management intensity, and post-drought shrub dominance was higher when pathogens acted as co-drivers of tree mortality. No significant replacement patterns were found in relation to the bioclimatic characteristics of the reporting sites (environmental location) or of the dominant species (bioclimatic ‘niche’). Shifts to both more xeric and to moister communities were observed. These changes were driven by species with higher limits of tolerance to dry conditions and by species with wider bioclimatic ranges, respectively. Overall, our findings highlight the potential for major forest ecosystem reorganization in the coming decades.</p>

Prediction of temperate broadleaf tree species mortality in arid limestone habitats with stomatal safety margins

2019 ◽  
Vol 39 (8) ◽  
pp. 1428-1437 ◽  
Author(s):  
Zhicheng Chen ◽  
Shan Li ◽  
Junwei Luan ◽  
Yongtao Zhang ◽  
Shidan Zhu ◽  
...  
Keyword(s):  
Tree Species ◽  
Tree Mortality ◽  
Vascular System ◽  
Stomatal Closure ◽  
Survival Rates ◽  
Safety Margin ◽  
Xylem Embolism ◽  
Safety Margins ◽  
Broadleaf Tree ◽  
Embolism Resistance

Abstract A growing body of evidence highlights the occurrence of increased widespread tree mortality during climate change-associated severe droughts; however, in situ long-term drought experiments with multispecies communities for the prediction of tree mortality and exploration of related mechanisms are rather limited in natural environments. We conducted a 7-year afforestation trial with 20 drought-resistant broadleaf tree species in an arid limestone habitat in northern China, where the species displayed a broad range of survival rates. The stomatal and xylem hydraulic traits of all the species were measured. We found that species’ stomatal closure points were strongly related to their xylem embolism resistance and xylem minimum water potential but not to their survival rates. Hydraulic failure of the vascular system appeared to be the main cause of tree mortality, and the stomatal safety margin was a better predictor of tree mortality than the traditionally considered xylem embolism resistance and hydraulic safety margin. We recommend the stomatal safety margin as the indicator for predicting drought-induced tree mortality and for selecting tree species in future forest restorations in arid regions.

Late-Glacial Vegetation and Climate Change in Western Oregon

1998 ◽  
Vol 49 (3) ◽  
pp. 287-298 ◽  
Author(s):  
Laurie D. Grigg ◽  
Cathy Whitlock
Keyword(s):  
Pacific Northwest ◽  
Younger Dryas ◽  
Late Glacial ◽  
Warming Trend ◽  
Cascade Range ◽  
Subalpine Forest ◽  
Coast Range ◽  
The Pacific ◽  
Dry Conditions ◽  
Vegetation And Climate

Pollen records from two sites in western Oregon provide information on late-glacial variations in vegetation and climate and on the extent and character of Younger Dryas cooling in the Pacific Northwest. A subalpine forest was present at Little Lake, central Coast Range, between 15,700 and 14,850 cal yr B.P. A warm period between 14,850 and 14,500 cal yr B.P. is suggested by an increase in Pseudotsuga pollen and charcoal. The recurrence of subalpine forest at 14,500 cal yr B.P. implies a return to cool conditions. Another warming trend is evidenced by the reestablishment of Pseudotsuga forest at 14,250 cal yr B.P. Increased haploxylon Pinus pollen between 12,400 and 11,000 cal yr B.P. indicates cooler winters than before. After 11,000 cal yr B.P. warm dry conditions are implied by the expansion of Pseudotsuga. A subalpine parkland occupied Gordon Lake, western Cascade Range, until 14,500 cal yr B.P., when it was replaced during a warming trend by a montane forest. A rise in Pinuspollen from 12,800 to 11,000 cal yr B.P. suggests increased summer aridity. Pseudotsuga dominated the vegetation after 11,000 cal yr B.P. Other records from the Pacific Northwest show an expansion of Pinus from ca. 13,000 to 11,000 cal yr B.P. This expansion may be a response either to submillennial climate changes of Younger Dryas age or to millennial-scale climatic variations.

scholarly journals Bark Transpiration Rates Can Reach Needle Transpiration Rates Under Dry Conditions in a Semi-arid Forest

2021 ◽  
Vol 12 ◽  
Author(s):  
Anna Lintunen ◽  
Yakir Preisler ◽  
Itay Oz ◽  
Dan Yakir ◽  
Timo Vesala ◽  
...  
Keyword(s):  
Transpiration Rate ◽  
Water Loss ◽  
Tree Mortality ◽  
Pinus Halepensis ◽  
Water Status ◽  
Stomatal Closure ◽  
Total Water ◽  
Evaporative Demand ◽  
Dry Conditions ◽  
Semi Arid

Drought can cause tree mortality through hydraulic failure and carbon starvation. To prevent excess water loss, plants typically close their stomata before massive embolism formation occurs. However, unregulated water loss through leaf cuticles and bark continues after stomatal closure. Here, we studied the diurnal and seasonal dynamics of bark transpiration and how it is affected by tree water availability. We measured continuously for six months water loss and CO2 efflux from branch segments and needle-bearing shoots in Pinus halepensis growing in a control and an irrigation plot in a semi-arid forest in Israel. Our aim was to find out how much passive bark transpiration is affected by tree water status in comparison with shoot transpiration and bark CO2 emission that involve active plant processes, and what is the role of bark transpiration in total tree water use during dry summer conditions. Maximum daily water loss rate per bark area was 0.03–0.14 mmol m−2 s−1, which was typically ~76% of the shoot transpiration rate (on leaf area basis) but could even surpass the shoot transpiration rate during the highest evaporative demand in the control plot. Irrigation did not affect bark transpiration rate. Bark transpiration was estimated to account for 64–78% of total water loss in drought-stressed trees, but only for 6–11% of the irrigated trees, due to differences in stomatal control between the treatments. Water uptake through bark was observed during most nights, but it was not high enough to replenish the lost water during the day. Unlike bark transpiration, branch CO2 efflux decreased during drought due to decreased metabolic activity. Our results demonstrate that although bark transpiration represents a small fraction of the total water loss through transpiration from foliage in non-stressed trees, it may have a large impact during drought.

scholarly journals Anomalous glacier responses to 20th century climatic changes in Darwin Cordillera, southern Chile

1995 ◽  
Vol 41 (139) ◽  
pp. 465-473 ◽  
Author(s):  
Per Holmlund ◽  
Humberto Fuenzalida
Keyword(s):  
20Th Century ◽  
General Trend ◽  
Warming Trend ◽  
Turn Of The Century ◽  
Aerial Photographs ◽  
The North ◽  
Asymmetric Pattern ◽  
Dry Conditions ◽  
Northern Side ◽  
Wind Activity

AbstractThere is an asymmetric pattern response of glaciers in Darwin Cordillera (54–55° S, 69–71° W) to the climate of the 20th century. This asymmetry is suggested here as a cause of an increased wind activity which has a pronounced orographic effect. Although climatic records for the last 50 years show a warming trend, as well as no trend in precipitation in the area, some glaciers are advancing. The area is characterized by strong climatic gradients, with high rates of precipitation on the southwestern side of the range and dry conditions on the northern side. Glaciers on the northern and eastern sides show a general trend of receding fronts. With a few exceptions, these glaciers have gradually and uninterruptedly been shrinking since the turn of the century. On the southern rim, the present extents of some glaciers are similar to their 20th century maximum extents. These are, in turn, similar or close to the Holocene maximum. The most extreme sites are the glaciers on either side of Mount Darwin, which is 2469 m high. The north-facing glacier Ventisquero Marinelli has retreated several hundred metres per year over the last two decades, while the south-facing glaciers in the Pahia Pia basin have advanced during the same period.In this study, the frontal changes over the last 50 years of 20 glaciers have been analysed. Aerial photographs (verticals) from 1943 and 1984 have been used, as well as oblique aerial photographs from 1993. The general result is that glaciers with accumulation areas facing south and west show somewhat stable fronts, while glaciers facing east and north show receding fronts.

scholarly journals Identification of a Disease on Cocoa Caused by Fusariumin Sulawesi

2013 ◽  
Vol 29 (3) ◽  
Author(s):  
Ade Rosmana ◽  
Hikmawati Hikmawati ◽  
Asman Asman
Keyword(s):  
Tree Mortality ◽  
Vascular Tissue ◽  
Disease Incidence ◽  
Fusarium Species ◽  
Dry Conditions ◽  
Causal Pathogen ◽  
Fusarium Sp ◽  
Theobroma Cacao L ◽  
Cocoa Seedlings ◽  
Apparently Healthy

A disease presumed to be caused by Fusarium was observed in cocoa open fields with few or without shade trees. Within the population of cocoa trees in the field, some trees had died, some had yellowing leaves and dieback, and the others were apparently healthy. In order to demonstrate Fusarium species as the causal pathogen and to obtain information concerning the incidence of the disease, its distribution and its impact on sustainability of cocoa, isolation of the pathogen, inoculation of cocoa seedlings with isolates and a survey of disease has been conducted. Fusarium was isolated from roots and branches, and inoculated onto cocoa seedlings (one month old) via soil. Symptoms appeared within 3-4 weeks after infection. These symptoms consisted of yellowing of leaves beginning from the bottom until the leaves falldown, and browning internal of vascular tissue. Darkened vascular traces in the petiole characteristic of vascularstreak dieback infection were absent. The occurrence of Fusarium in the field was characterized by the absence of obvious signs of fungal infestation on root of infected trees, yellowing of leaves on twigs, dieback, and tree mortality in severe infestations. Disease incidence could reach 77% and in this situation it was difficult for trees recover from heavy infections or to be regenerated in the farm. The study proves that Fusarium is a pathogen causing dieback and the disease is called as Fusarium vascular dieback (FVD). Its development is apparently enhanced by dry conditions in the field. Key words: Fusarium sp., vascular disease, dieback, FVD, Theobroma cacao L.

scholarly journals Anomalous glacier responses to 20th century climatic changes in Darwin Cordillera, southern Chile

1995 ◽  
Vol 41 (139) ◽  
pp. 465-473 ◽  
Author(s):  
Per Holmlund ◽  
Humberto Fuenzalida
Keyword(s):  
20Th Century ◽  
General Trend ◽  
Warming Trend ◽  
Turn Of The Century ◽  
Aerial Photographs ◽  
The North ◽  
Asymmetric Pattern ◽  
Dry Conditions ◽  
Northern Side ◽  
Wind Activity

AbstractThere is an asymmetric pattern response of glaciers in Darwin Cordillera (54–55° S, 69–71° W) to the climate of the 20th century. This asymmetry is suggested here as a cause of an increased wind activity which has a pronounced orographic effect. Although climatic records for the last 50 years show a warming trend, as well as no trend in precipitation in the area, some glaciers are advancing. The area is characterized by strong climatic gradients, with high rates of precipitation on the southwestern side of the range and dry conditions on the northern side. Glaciers on the northern and eastern sides show a general trend of receding fronts. With a few exceptions, these glaciers have gradually and uninterruptedly been shrinking since the turn of the century. On the southern rim, the present extents of some glaciers are similar to their 20th century maximum extents. These are, in turn, similar or close to the Holocene maximum. The most extreme sites are the glaciers on either side of Mount Darwin, which is 2469 m high. The north-facing glacier Ventisquero Marinelli has retreated several hundred metres per year over the last two decades, while the south-facing glaciers in the Pahia Pia basin have advanced during the same period.In this study, the frontal changes over the last 50 years of 20 glaciers have been analysed. Aerial photographs (verticals) from 1943 and 1984 have been used, as well as oblique aerial photographs from 1993. The general result is that glaciers with accumulation areas facing south and west show somewhat stable fronts, while glaciers facing east and north show receding fronts.

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