scholarly journals Minimal mortality and rapid recovery of the dominant shrub Larrea tridentata following an extreme cold event in the northern Chihuahuan Desert

2019 ◽  
Vol 30 (5) ◽  
pp. 963-972
Author(s):  
Laura M. Ladwig ◽  
Scott L. Collins ◽  
Dan J. Krofcheck ◽  
William T. Pockman
Keyword(s):  
Chihuahuan Desert ◽  
Larrea Tridentata ◽  
Rapid Recovery ◽  
Cold Event ◽  
Extreme Cold

scholarly journals Changes in extreme temperature over China when global warming stabilized at 1.5 °C and 2.0 °C

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Cenxiao Sun ◽  
Zhihong Jiang ◽  
Wei Li ◽  
Qiyao Hou ◽  
Laurent Li
Keyword(s):  
Global Warming ◽  
Return Period ◽  
Extreme Temperature ◽  
Cmip5 Models ◽  
The Tibetan Plateau ◽  
Cold Event ◽  
Southeast China ◽  
Transient Simulations ◽  
Cold Events ◽  
Extreme Cold

Abstract The 1.5 °C global warming target proposed by the Paris Agreement has raised worldwide attention and inspired numerous studies to assess corresponding climate changes for different regions of the world. But CMIP5 models based on Representative Concentration Pathways (RCP) are ‘transient simulations’ and cannot reflect the response of climate warming stabilized at 1.5 °C. The current work presents an assessment of extreme temperature changes in China with simulations from ‘Half a degree Additional warming, Prognosis and Projected Impacts’ (HAPPI) project specially conceived for global warming levels stabilized at 1.5 °C and 2.0 °C. When global warming stabilizes at 1.5 °C/2.0 °C, the areal-mean temperature for whole China increases by about 0.94 °C/1.59 °C (relative to present period, taken from 2006–2015). Notable increase regions are mainly found in Northwest and Northeast-North China, but warm spell duration increases mostly in Southeast China. The effect of the additional 0.5 °C warming is particularly investigated and compared between the transient and stabilized simulations. Changes of mean and extreme temperature are larger in transient simulations than in stabilized simulations. The uncertainty range is also narrower in stabilized simulations. Under stabilized global warming scenario, extreme hot event with return period of 100 years in the present climate becomes event occurring every 4.79 (1.5 °C warming level) and 1.56 years (2.0 °C warming level), extreme cold event with return period of 10 years becomes event occurring every 67 years under 1.5 °C warming and is unlikely to occur under 2.0 °C warming. For geographic distribution, the occurrence probabilities of extreme (hot and cold) events mainly change in the Tibetan Plateau, and the extreme cold events also change in Northeast and Southeast China.

Dietary selection by goats and the implications for range management in the Chihuahuan Desert: a review

2016 ◽  
Vol 38 (4) ◽  
pp. 331 ◽  
Author(s):  
M. Mellado
Keyword(s):  
Chihuahuan Desert ◽  
Good Condition ◽  
Secondary Compounds ◽  
Field Studies ◽  
Arid Environment ◽  
Larrea Tridentata ◽  
Desert Rangelands ◽  
Lactating Goats ◽  
Varied Diet ◽  
Sources Of Variation

Field studies characterising the forage resources of mixed-breed goats on Chihuahuan Desert rangelands were reviewed and the principal sources of variation in their diet choices discussed. Goats eat a varied diet comprising at least 126 plant species in this landscape. Goats are highly selective feeders, changing their diet from predominantly forbs (8–64%) to browse (35–88%). Graminoids make up only ~5% of the diet, but grasses could be important dietary components on rangelands in good condition. Feed intakes range between 0.8% and 3.4% of bodyweight, depending on the season. DM digestibility of forage selected by goats ranges between 44% and 65%. Annual crude protein (CP) in forages selected by goats varies from 80 to 160 g CP kg–1 DM. Overall, pregnant and lactating goats manage to ingest food that contains higher amounts of CP and lower amounts of cell wall than non-pregnant, non-lactating goats. Goats not adapted to severe shortage of forage select a diet that does not match their nutritional requirements and fetal losses occur. Goat kids select higher quality diets than do mature goats (94.5 vs 88.5 g CP kg–1 DM). Granadina goats eat ~20% more shrubs, including 3-fold more Larrea tridentata (DC) Cav., than Nubian goats. Goats with severely eroded incisors avoid grasses, focusing on tender-leaved shrubs. During the rainy season, bucks select mainly shrubs (78% of the diet) and avoid grasses (1.7% of the diet), whereas does rely heavily on forbs (about one-third of their diet). Alternating use of grazing grounds increases shrub ingestion by 25%. No evidence exists indicating that food choice by goats in this arid environment is biased towards forages with lower secondary compounds. It is concluded that the flexible, broad-scale and opportunistic feeding behaviour of goats make them an effective animal to sustainably exploit the forage resources of the Chihuahuan Desert.

scholarly journals Simulated Links between Deforestation and Extreme Cold Events in South America

2012 ◽  
Vol 25 (11) ◽  
pp. 3851-3866 ◽  
Author(s):  
David Medvigy ◽  
Robert L. Walko ◽  
Roni Avissar
Keyword(s):  
South America ◽  
Extreme Events ◽  
Limited Area ◽  
Natural Ecosystems ◽  
Cold Event ◽  
Variable Resolution ◽  
Local Agriculture ◽  
Average Annual Temperature ◽  
Cold Events ◽  
Extreme Cold

Many modeling studies have indicated that deforestation will increase the average annual temperature in the Amazon. However, few studies have investigated the potential for deforestation to change the frequency and intensity of extreme events. This problem is addressed here using a variable-resolution GCM. The characteristic length scale (CLS) of the model’s grid mesh over South America is 25 km, comparable to that used by limited-area models. For computational efficiency, the CLS increases to 200 km over the rest of the world. It is found that deforestation induces large changes in the frequency of wintertime extreme cold events. Large increases in cold event frequency and intensity occur in the western Amazon and, surprisingly, in parts of southern South America, far from the actual deforested area. One possible mechanism for these remote effects involves changes in the position of the subtropical jet, caused by temperature changes in the Amazon. Increased understanding of these potential changes in extreme events will be important for local agriculture, natural ecosystems, and the human population.

scholarly journals Assessing vegetation structure and ANPP dynamics in a grassland-shrubland Chihuahuan ecotone using NDVI-rainfall relationships

2015 ◽  
Vol 12 (1) ◽  
pp. 51-92 ◽  
Author(s):  
M. Moreno-de las Heras ◽  
R. Diaz-Sierra ◽  
L. Turnbull ◽  
J. Wainwright
Keyword(s):  
Primary Production ◽  
Vegetation Change ◽  
Chihuahuan Desert ◽  
Plant Biomass ◽  
Net Primary Production ◽  
Larrea Tridentata ◽  
Shrub Encroachment ◽  
Grass Species ◽  
Natural Habitats ◽  
Herbaceous Vegetation

Abstract. Climate change and the widespread alteration of natural habitats are major drivers of vegetation change in drylands. A classic case of vegetation change is the shrub-encroachment process that has been taking place over the last 150 years in the Chihuahuan Desert, where large areas of grasslands dominated by perennial grass species (black grama, Bouteloua eriopoda, and blue grama, B. gracilis) have transitioned to shrublands dominated by woody species (creosotebush, Larrea tridentata, and mesquite, Prosopis glandulosa), accompanied by accelerated water and wind erosion. Multiple mechanisms drive the shrub-encroachment process, including exogenous triggering factors such as precipitation variations and land-use change, and endogenous amplifying mechanisms brought about by soil erosion-vegetation feedbacks. In this study, simulations of plant biomass dynamics with a simple modelling framework indicate that herbaceous (grasses and forbs) and shrub vegetation in drylands have different responses to antecedent precipitation due to functional differences in plant growth and water-use patterns, and therefore shrub encroachment may be reflected in the analysis of landscape-scale vegetation–rainfall relationships. We analyze the structure and dynamics of vegetation at an 18 km2 grassland-shrubland ecotone in the northern edge of the Chihuahuan Desert (McKenzie Flats, Sevilleta National Wildlife Refuge, NM, USA) by investigating the relationship between decade-scale (2000–2013) records of medium-resolution remote sensing of vegetation greenness (MODIS NDVI) and precipitation. Spatial evaluation of NDVI-rainfall relationship at the studied ecotone indicates that herbaceous vegetation shows quick growth pulses associated with short-term (previous 2 months) precipitation, while shrubs show a slow response to medium-term (previous 5 months) precipitation. We use these relationships to (a) classify landscape types as a function of the spatial distribution of dominant vegetation, and to (b) decompose the NDVI signal into partial primary production components for herbaceous vegetation and shrubs across the study site. We further apply remote-sensed annual net primary production (ANPP) estimations and landscape type classification to explore the influence of inter-annual variations in seasonal precipitation on the production of herbaceous and shrub vegetation. Our results suggest that changes in the amount and temporal pattern of precipitation comprising reductions in monsoonal summer rainfall and/or increases in winter precipitation may enhance the shrub-encroachment process in desert grasslands of the American Southwest.

scholarly journals Seasonal Cumulative Effect of Ural Blocking Episodes on the Frequent Cold events in China during the Early Winter of 2020/21

2022 ◽  
Author(s):  
Yao Yao ◽  
Wenqi Zhang ◽  
Dehai Luo ◽  
Linhao Zhong ◽  
Lin Pei
Keyword(s):  
Sea Ice ◽  
Cumulative Effect ◽  
Cumulative Effects ◽  
The Arctic ◽  
Early Winter ◽  
Sea Ice Extent ◽  
Cold Event ◽  
Cold Events ◽  
Extreme Cold ◽  
The Impact

AbstractStarting in mid-November, China was hit by several cold events during the early winter of 2020/21. The lowest temperature observed at Beijing station on 7 January reached −19.6°C. In this paper, we show that the outbreak of the record-breaking extreme cold event can be attributed to a huge merging Ural blocking (UB) ridge over the Eurasian region. The sea-ice cover in the Kara and East Siberia Seas (KESS) in autumn was at its lowest value since 1979, which could have served as a precursor signal. Further analysis shows that several successive UB episodes occurred from 1 September 2020 to 10 January 2021. The persistent UB that occurred in late September/early October 2020 may have made an important contribution to the October historical minimum of sea ice in the KESS region. Our results also show that, after each UB episode in winter, significant upward propagation of wave activity occurred around 60°E, which resulted in weakening the stratospheric vortex. Meanwhile, each UB episode also caused a significant reduction in sea-ice extent in KESS and a significant weakening of the westerly jet in mid-high-latitude Eurasia. Results suggest that the Arctic vortex, which is supposed to enhance seasonally, became weaker and more unstable than the climatic mean under the seasonal cumulative effects of UB episodes, KESS warming, and long-lasting negative-phase North Atlantic Oscillation (NAO-). Those seasonal cumulative effects, combined with the impact of La Niña winter, led to the frequent occurrence of extreme cold events.

Effect of an extreme cold event on the metabolism of planktonic microbes in the northernmost basin of the Mediterranean Sea

2019 ◽  
Vol 225 ◽  
pp. 106252 ◽  
Author(s):  
Vincenzo Manna ◽  
Cinzia Fabbro ◽  
Federica Cerino ◽  
Matteo Bazzaro ◽  
Paola Del Negro ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Cold Event ◽  
Extreme Cold ◽  
The Mediterranean

A 16,000 14C yr B.P. packrat midden series from the USA–Mexico Borderlands

2003 ◽  
Vol 60 (3) ◽  
pp. 319-329 ◽  
Author(s):  
Camille A. Holmgren ◽  
M. Cristina Peñalba ◽  
Kate Aasen Rylander ◽  
Julio L Betancourt
Keyword(s):  
Late Holocene ◽  
Chihuahuan Desert ◽  
Summer Precipitation ◽  
Late Glacial ◽  
Larrea Tridentata ◽  
Desert Grassland ◽  
Time Intervals ◽  
The Usa ◽  
Juniperus Scopulorum ◽  
Desert Scrub

AbstractA new packrat midden chronology from Playas Valley, southwestern New Mexico, is the first installment of an ongoing effort to reconstruct paleovegetation and paleoclimate in the U.S.A.–Mexico Borderlands. Playas Valley and neighboring basins supported pluvial lakes during full and/or late glacial times. Plant macrofossil and pollen assemblages from nine middens in the Playas Valley allow comparisons of two time intervals: 16,000–10,000 and 4000–0 14C yr B.P. Vegetation along pluvial lake margins consisted of open pinyon–juniper communities dominated by Pinus edulis, Juniperus scopulorum, Juniperus cf. coahuilensis, and a rich understory of C4 annuals and grasses. This summer-flowering understory is also characteristic of modern desert grassland in the Borderlands and indicates at least moderate summer precipitation. P. edulis and J. scopulorum disappeared or were rare in the midden record by 10,670 14C yr B.P. The late Holocene is marked by the arrival of Chihuahuan desert scrub elements and few departures as the vegetation gradually became modern in character. Larrea tridentata appears as late as 2190 14C yr B.P. based on macrofossils, but may have been present as early as 4095 14C yr B.P. based on pollen. Fouquieria splendens, one of the dominant desert species present at the site today, makes its first appearance only in the last millennium. The midden pollen assemblages are difficult to interpret; they lack modern analogs in surface pollen assemblages from stock tanks at different elevations in the Borderlands.

scholarly journals Lizard community structure across a grassland – creosote bush ecotone in the Chihuahuan Desert

2003 ◽  
Vol 81 (11) ◽  
pp. 1829-1838 ◽  
Author(s):  
Sean B Menke
Keyword(s):  
Chihuahuan Desert ◽  
Function Analysis ◽  
Larrea Tridentata ◽  
Desert Grassland ◽  
Creosote Bush ◽  
Lizard Species ◽  
Common Lizard ◽  
Risk Of Predation ◽  
Increased Risk ◽  
Species Specific

I investigated the distribution and abundance of lizard species (Aspidoscelis inornatus, Aspidoscelis tesselatus, Aspidoscelis tigris, Aspidoscelis uniparens, Cophosaurus texanus, Crotaphytus collaris, Eumeces obsoletus, Gambelia wislizenii, Holbrookia maculata, Phrynosoma cornutum, Sceloporus magister, and Uta stansburiana) across a desert grassland – creosote bush (Larrea tridentata) ecotone in Dona Ana County, New Mexico. The ecotonal area in the Jornada del Muerto basin has increased dramatically in the past 150 years because of the rapid spread of creosote bush. I asked four related questions: how large and where is the ecotone based on vegetative structure, and do lizard abundance and diversity change across the ecotone? Vegetation data were analyzed using discriminate function analysis to determine the extent of the ecotone. Changes in lizard abundance across the ecotone were analyzed by analysis of variance. During two summers, 677 individual lizards of 9 genera and 12 species were captured. Lizard abundance increased with increasing distance from the ecotone and was similar in grassland and creosote bush habitat. Grasslands had higher species richness than both the creosote bush and ecotone habitats. Grassland sites had greater habitat heterogeneity than did creosote bush sites. No ecotone specialist species were detected, and all common lizard species could be found in each habitat. Three potential explanations for decreased abundance in the ecotone are presented: (1) increased risk of predation, (2) decreased prey abundance, and (3) lack of species-specific microhabitat requisites.

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