Why do evergreen trees dominate the Australian seasonal tropics?

2005 ◽  
Vol 53 (5) ◽  
pp. 379 ◽  
Author(s):  
D. M. J. S. Bowman ◽  
L. D. Prior
Keyword(s):  
Fire Disturbance ◽  
Deciduous Tree ◽  
Deciduous Species ◽  
Evergreen Species ◽  
Seasonally Dry ◽  
Physiological Cost ◽  
Air Temperatures ◽  
Rainfall Seasonality ◽  
Wide Range ◽  
Extreme Variability

The northern Australian woody vegetation is predominantly evergreen despite an intensely seasonal climate and a diversity of deciduous species in the regional flora. From a global climatic perspective the dominance of evergreen rather than deciduous trees in the Australian savannas is apparently anomalous when compared with other savannas of the world. However, this pattern is not unexpected in light of existing theory that emphasises photosynthetic return relative to cost of investment between deciduous and evergreen species. (a) Climatically, monsoonal Australia is more extreme in terms of rainfall seasonality and variability and high air temperatures than most other parts of the seasonally dry tropics. Existing theory predicts that extreme variability and high temperatures favour evergreen trees that can maximise the period during which leaves assimilate CO2. (b) Soil infertility is known to favour evergreens, given the physiological cost of leaf construction, and the northern Australian vegetation grows mainly on deeply weathered and infertile Tertiary regoliths. (c) These regoliths also provide stores of ground water that evergreens are able to exploit during seasonal drought, thereby maintaining near constant transpiration throughout the year. (d) Fire disturbance appears to be an important secondary factor in explaining the dominance of evergreens in the monsoon tropics, based on the fact that most deciduous tree species of the region are restricted to small fire-protected sites. (e) Evolutionary history cannot explain the predominance of evergreens, given the existence of a wide range of deciduous species, including deciduous eucalypts, in the regional tree flora.

How drought and deciduousness shape xylem plasticity in three Costa Rican woody plant species

IAWA Journal ◽  
2014 ◽  
Vol 35 (4) ◽  
pp. 337-355 ◽  
Author(s):  
Alexander Scholz ◽  
Anke Stein ◽  
Brendan Choat ◽  
Steven Jansen
Keyword(s):  
Cloud Forest ◽  
Vessel Diameter ◽  
Dry Forest ◽  
Deciduous Tree ◽  
Deciduous Species ◽  
Evergreen Species ◽  
Seasonally Dry ◽  
Tropical Cloud Forest ◽  
Tabebuia Rosea ◽  
Seasonally Dry Forest

This paper explores the phenotypic plasticity of xylem in tropical trees in order to test the hypothesis that different leaf phenological patterns influence levels of xylem plasticity. Wood anatomy was studied in the wet-deciduous species Cordia alliodora (Ruiz & Pav.) Oken, the dry-deciduous species Tabebuia rosea (Bertol.) DC., and the evergreen species Ocotea veraguensis (Meisn.) Mez., collected from seasonally dry forest and tropical cloud forest in Costa Rica. Xylem plasticity and trait conservatism were examined by analysing the coefficient of variation (CV) and the relative distance plasticity index (RDPI) of xylem anatomical traits. The two deciduous species exhibited wider vessels, lower wood density, and higher Huber values than the evergreen species. Furthermore, intervessel connectivity was highest for the two deciduous species in seasonally dry forest compared to cloud forest, whereas the opposite was found for the evergreen species. Overall highest trait variability was found for all plants at the seasonally dry site. The evergreen species O. veraguensis had the highest plasticity values compared to the deciduous species. Highest plasticity was found for vessel composition index (vessel area/vessel number), whilestrongest trait conservatism was found for vessel diameter. In conclusion, our data indicate that evergreen O. veraguensis does not show less xylem plasticity than the two deciduous tree species studied.

scholarly journals Subtropical–Tropical Urban Tree Water Relations and Drought Stress Response Strategies

2013 ◽  
Vol 39 (3) ◽  
Author(s):  
Roger Kjelgren ◽  
Daryl Joyce ◽  
David Doley
Keyword(s):  
Tree Species ◽  
Urban Trees ◽  
Dry Forest ◽  
Deciduous Tree ◽  
Tropical Species ◽  
Forest Species ◽  
Deciduous Species ◽  
Evergreen Species ◽  
Urban Tree ◽  
Tropical Cities

Understanding native habitats of species successful as subtropical and tropical urban trees yield insights into how to minimize urban tree water deficit stress experienced during monsoonal dry periods. Equatorial and montane wet forest species rarely subject to drought are generally absent in subtropical and tropical cities with pronounced monsoonal dry seasons. Species native to monsoonal dry forests appear to have wide environmental tolerances, and are successful as urban trees in many tropical cities. Monsoonal dry forest species have a tendency to be deep rooted to avoid drought, with leaf habits falling along an avoidance to tolerance spectrum. Dry deciduous species, typically found on more fertile soils, maximize growth during the monsoonal wet season with high photosynthesis and transpiration rates, then defoliate to avoid stress during the dry season. Evergreen tree species, typically found on less fertile soils, have a higher carbon investment in leaves that photosynthesize and transpire less year-round than do dry deciduous species. Dry deciduous tree species are more common urban trees than dry evergreen species explicitly due to more ornamental floral displays, but also implicitly due to their ability to adjust timing and duration of defoliation in response to drought. An empirical study of three tropical species exhibiting a range of leaf habits showed isohydric behavior that moderates transpiration and conserves soil water during drying. However, dry evergreen species may be less adaptable to tropical urban conditions of pronounced drought, intense heat, and limited rooting volumes than dry deciduous species with malleable leaf habit.

Leaf nitrogen dynamics with particular reference to retranslocation in evergreen and deciduous tree species of Kumaun Himalaya

1993 ◽  
Vol 23 (3) ◽  
pp. 349-357 ◽  
Author(s):  
G.C.S. Negi ◽  
S.P. Singh
Keyword(s):  
Leaf Growth ◽  
Leaf Nitrogen ◽  
Deciduous Tree ◽  
Leaf Life Span ◽  
Deciduous Species ◽  
Evergreen Species ◽  
Mature Leaves ◽  
N Concentration ◽  
Leaf Formation ◽  
N Status

The concentration and mass of nitrogen (N) were followed seasonally in leaves of 26 trees species of Central Himalaya: 11 evergreen species with about 1-year leaf life-span and 15 deciduous species. Like the deciduous species, the leaves of these evergreen species start senescing and losing mass in the year of formation. Species with higher N status retranslocated a larger proportion of leaf N prior to leaf abscission than the species with less favourable N status. The percentage of N mass in the leaf that was retranslocated during senescence ranged from 32.7 to 75.3%, but none of the species with N concentration less than 2.5% in mature leaves retranslocated more than 60% of N. Compared with evergreen species, on average the deciduous species showed higher N concentration in mature leaves (3.2 vs. 2.5%), higher proportion of leaf mass loss during senescence (31.6 vs. 26.2%), and greater proportion of retranslocated N mass from leaves (57.1 vs. 51.8%). With regard to the N-use efficiency the two groups of species were not clearly different. The dependence of deciduous species on retranslocated N mass for leaf growth during the dry period of the premonsoon season was greater than that of the evergreen species, which showed partial dependence on the soil N pool for new leaf formation.

Vulnerability of sweet cherry cultivars to continuous periods of spring frosts in Plovdiv, Bulgaria

2020 ◽  
Vol 12 (4) ◽  
pp. 348-352
Author(s):  
S. Malchev ◽  
S. Savchovska
Keyword(s):  
Sweet Cherry ◽  
Weather Conditions ◽  
Frost Damage ◽  
Cold Weather ◽  
Bud Burst ◽  
Intermediate Group ◽  
Air Temperatures ◽  
Wide Range ◽  
Group Form ◽  
Sweet Cherry Cultivars

Abstract. The periods with continuous freezing air temperatures reported during the spring of 2020 (13 incidents) affected a wide range of local and introduced sweet cherry cultivars in the region of Plovdiv. They vary from -0.6°C on March 02 to -4.9°C on March 16-17. The duration of influence of the lowest temperatures is 6 and 12 hours between March 16 and 17. The inspection of fruit buds and flowers was conducted twice (on March 26 and April 08) at different phenological stages after continuous waves of cold weather conditions alternated with high temperatures. During the phenological phase ‘bud burst’ (tight cluster or BBCH 55) some of the flowers in the buds did not develop further making the damage hardly detectable. The most damaged are hybrid El.28-21 (95.00%), ‘Van’ (91.89%) and ‘Bing’ (89.41%) and from the next group ‘Lapins’ (85.98%) and ‘Rosita’ (83.33%). A larger intermediate group form ‘Kossara’ (81.67%), ‘Rozalina’ (76.00%), ‘Sunburst’ (75.00%), ‘Bigarreau Burlat’ (69.11%) and ‘Kuklenska belitza’ (66.67%). Candidate-cultivar El.17-90 ‘Asparuh’ has the lowest frost damage values of 55.00% and El.17-37 ‘Tzvetina’ with damage of 50.60%.

Effects of Air Temperature on Combustion Characteristics of LPG Diffusion Flame

2020 ◽  
Vol 1008 ◽  
pp. 128-138
Author(s):  
Ahmed M. Salman ◽  
Ibrahim A. Ibrahim ◽  
Hamada M. Gad ◽  
Tharwat M. Farag
Keyword(s):  
Air Temperature ◽  
Diffusion Flame ◽  
Nitrogen Addition ◽  
Flame Length ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Low Oxygen ◽  
Air Temperatures ◽  
Air Stream ◽  
Wide Range

In the present study, the combustion characteristics of LPG gaseous fuel diffusion flame at elevated air temperatures were experimentally investigated. An experimental test rig was manufactured to examine a wide range of operating conditions. The investigated parameters are the air temperatures of 300, 350, 400, 450, and 500 K with constant percentage of nitrogen addition in combustion air stream of 5 % to give low oxygen concentration of 18.3 % by mass at constant air swirl number, air to fuel mass ratio, and thermal load of 1.5, 30, and 23 kW, respectively. The gaseous combustion characteristics were represented as axial and radial temperatures distributions, temperatures gradient, visible flame length and species concentrations. The results indicated that as the air temperature increased, the chemical reaction rate increased and flame volume decreased, the combustion time reduced leading to a reduction in flame length. The NO concentration reaches its maximum values near the location of the maximum centerline axial temperature. Increasing the combustion air temperature by 200 K, the NO consequently O2 concentrations are increased by about % 355 and 20 % respectively, while CO2 and CO concentrations are decreased by about % 21 and 99 % respectively, at the combustor end.

scholarly journals El Niño-Southern Oscillation affects the water relations of tree species in the Yucatan Peninsula, Mexico

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jorge Palomo-Kumul ◽  
Mirna Valdez-Hernández ◽  
Gerald A. Islebe ◽  
Manuel J. Cach-Pérez ◽  
José Luis Andrade
Keyword(s):  
Water Potential ◽  
Leaf Area ◽  
Tropical Forests ◽  
Specific Leaf Area ◽  
Tree Species ◽  
Deciduous Species ◽  
Mature Trees ◽  
Seasonally Dry ◽  
Seasonally Dry Tropical Forests ◽  
Dry Tropical Forests

AbstractWe evaluated the effect of ENSO 2015/16 on the water relations of eight tree species in seasonally dry tropical forests of the Yucatan Peninsula, Mexico. The functional traits: wood density, relative water content in wood, xylem water potential and specific leaf area were recorded during the rainy season and compared in three consecutive years: 2015 (pre-ENSO conditions), 2016 (ENSO conditions) and 2017 (post-ENSO conditions). We analyzed tree size on the capacity to respond to water deficit, considering young and mature trees, and if this response is distinctive in species with different leaf patterns in seasonally dry tropical forests distributed along a precipitation gradient (700–1200 mm year−1). These traits showed a strong decrease in all species in response to water stress in 2016, mainly in the driest site. Deciduous species had lower wood density, higher predawn water potential and higher specific leaf area than evergreen species. In all cases, mature trees were more tolerant to drought. In the driest site, there was a significant reduction in water status, regardless of their leaf phenology, indicating that seasonally dry tropical forests are highly vulnerable to ENSO. Vulnerability of deciduous species is intensified in the driest areas and in the youngest trees.

Differential impact of liana colonization on the leaf functional traits of co-occurring deciduous and evergreen trees

2021 ◽  
Author(s):  
vivek pandi ◽  
Kanda Naveen Babu
Keyword(s):  
Functional Traits ◽  
Tree Species ◽  
Dry Matter Content ◽  
Differential Impact ◽  
Deciduous Species ◽  
Evergreen Species ◽  
Leaf Functional Traits ◽  
Leaf Trait ◽  
Host Trees ◽  
Significant Difference

Abstract The present study was carried out to analyse the leaf functional traits of co-occurring evergreen and deciduous tree species in a tropical dry scrub forest. This study also intended to check whether the species with contrasting leaf habits differ in their leaf trait plasticity, responding to the canopy-infestation by lianas. A total of 12 leaf functional traits were studied for eight tree species with contrasting leaf habits (evergreen and deciduous) and liana-colonization status (Liana+ and Liana−). In the liana-free environment (L−), evergreen trees had significantly higher specific leaf mass (LMA) and leaf dry matter content (LDMC) than the deciduous species. Whereas, the deciduous trees had higher specific leaf area (SLA) and mass-based leaf nitrogen concentration (Nmass). The leaf trait-pair relationship in the present study agreed to the well-established global trait-pair relationships (SLA Vs Nmass, Lth Vs SLA, Nmass Vs Lth, Nmass Vs LDMC, LDMC Vs SLA). There was no significant difference between L+ and L− individuals in any leaf functional traits studied in the deciduous species. However, evergreen species showed marked differences in the total chlorophyll content (Chlt), chlorophyll b (Chlb), SLA, and LMA between L+ and L− individuals of the same species. Deciduous species with the acquisitive strategy can have a competitive advantage over evergreen species in the exposed environment (L−) whereas, evergreen species with shade-tolerant properties were better acclimated to the shaded environments (L+). The result revealed the patterns of convergence and divergence in some of the leaf functional traits between evergreen and deciduous species. The results also showed the differential impact of liana colonization on the host trees with contrasting leaf habits. Therefore, liana colonization can significantly impact the C-fixation strategies of the host trees by altering their light environment. Further, the magnitude of such impact may vary among species of different leaf habits. The increased proliferation of lianas in the tropical forest canopies may pose a severe threat to the whole forest carbon assimilation rates.

Architectural differences in saplings of temperate versus tropical angiosperms; consequences of the deciduous habit?

2005 ◽  
Vol 83 (11) ◽  
pp. 1391-1401 ◽  
Author(s):  
David A. King
Keyword(s):  
High Frequency ◽  
Plant Architecture ◽  
Tropical Species ◽  
Deciduous Species ◽  
Evergreen Species ◽  
Crown Shape ◽  
Temperate Deciduous ◽  
Lower Height ◽  
Filtering Effect ◽  
Overstory Trees

The architecture of saplings of temperate deciduous species of the southeastern United States was compared with that of tropical evergreen species of Central America, Borneo, and northeastern Australia. The deciduous species were more planar in the understory than were the tropical species, because of (i) more planar leaf displays within branches, (ii) a high frequency of arching, plagiotropic main stems (associated with greater plasticity in crown symmetry in relation to light), and (iii) a lower height of first branching. The deciduous species also had more planar branches than did subtropical and temperate evergreen angiosperms. This greater planarity in temperate deciduous understories may be associated with the simultaneous positioning of most leaves during a single flush in the spring. In contrast, saplings in tropical understories typically bear multiple leaf cohorts and position new leaves at the peripheries of existing leaf displays. These results and those of other studies suggest that there are adaptive links between plant architecture and phenology. Other factors, such as latitudinal variation in sun angles, may influence crown shape in overstory trees, but did not seem to be involved here, possibly because the filtering effect of the canopy results in smaller latitudinal shifts in understory illumination angles during the growing season. Thus, by favouring the deciduous habit, the cold winters and warm, humid summers of the eastern deciduous biome of North America appear to have had a notable influence on sapling architecture.

scholarly journals Quantitative estimates of deciduousness in woody species from a seasonally dry tropical forest are related to leaf functional traits and the timing of leaf flush

2021 ◽  
Author(s):  
Souparna Chakrabarty ◽  
Sheetal Sharma ◽  
Shatarupa Ganguly ◽  
Asmi Jezeera ◽  
Neha Mohanbabu ◽  
...  
Keyword(s):  
Tropical Forest ◽  
Functional Traits ◽  
Woody Species ◽  
Leaf Phenology ◽  
Deciduous Species ◽  
Seasonally Dry Tropical Forest ◽  
Leaf Functional Traits ◽  
Dry Tropical Forest ◽  
Seasonally Dry ◽  
Quantitative Estimates

AbstractLeaf phenology based classification of woody species into discrete evergreen and deciduous categories is widely used in ecology, but these categories hide important variation in leaf phenological behaviour. Few studies have examined the continuous nature of deciduousness and our understanding of variation in quantitative estimates of leaf shedding behaviour and the causes and consequences of this is limited. In this study we monitored leaf phenology in 75 woody species from a seasonally dry tropical forest to quantify three quantitative measures of deciduousness, namely: maximum canopy loss, duration of deciduousness, and average canopy loss. Based on proposed drought tolerance and drought avoidance strategies of evergreen and deciduous species, respectively, we tested whether the quantitative measures of deciduousness were related to leaf functional traits. Additionally, to understand the functional consequences of variation in deciduousness we examined relationships with the timing of leaf flushing and senescing. We found wide and continuous variation in quantitative measures of deciduousness in these coexisting species. Variation in deciduousness was related to leaf function traits, and the timing of leaf flushing. Along a continuous axis ranging from evergreen to deciduous species, increasing deciduousness was associated with more acquisitive leaf functional traits, with lower leaf mass per area and leaf dry matter content, and greater leaf nitrogen content. These results indicate that the continuous nature of deciduousness is an important component of resource acquisition strategies in woody species from seasonally dry forests.

scholarly journals Susceptibility of Viburnum Species and Cultivars to Phytophthora ramorum

2010 ◽  
Vol 28 (4) ◽  
pp. 197-202 ◽  
Author(s):  
Timothy L. Widmer
Keyword(s):  
Leaf Area ◽  
Phytophthora Ramorum ◽  
Necrotic Area ◽  
Deciduous Species ◽  
Evergreen Species ◽  
Whole Plants

Abstract Phytophthora ramorum causes ramorum blight on Viburnum species, which are commonly grown as ornamentals. This study evaluated 24 different species or cultivars for susceptibility to P. ramorum. Whole plants were inoculated with an NA1 isolate of P. ramorum and placed in dew chambers at 20C (68F). After 5 days, the percentage of necrotic leaves for each plant and the percentage of necrotic area for each leaf were calculated. The percentage of necrotic leaves per plant ranged from 96.1% (V. tinus) to 7.9% (V. opulus ‘Notcutt’) and the percentage of necrotic leaf area ranged from 73.0% (V. × carlcephalum ‘Cayuga’) to 2.4% (V. trilobum ‘Wentworth’). In addition, six species or cultivars were evaluated for their susceptibility to a EU1 isolate of P. ramorum. The isolate had a significant effect on three of the six species or cultivars tested, although one isolate did not always yield the greatest necrosis. Evergreen species and cultivars had a higher percentage of necrotic leaves and higher percentage of necrotic leaf area than semi-evergreen or deciduous species and cultivars. All Viburnum species and cultivars showed some degree of susceptibility to P ramorum.

Sign in / Sign up

Export Citation Format

Share Document