A world-wide study of high altitude treeline temperatures

Aim At a coarse scale, the treelines of the world's mountains seem to follow a common isotherm, but the evidence for this has been indirect so far. Here we aim at underpinning this with facts. Location We present the results of a data‐logging campaign at 46 treeline sites between 68° N and 42° S. Methods We measured root‐zone temperatures with an hourly resolution over 1–3 years per site between 1996 and 2003. Results Disregarding taxon‐, landuse‐ or fire‐driven tree limits, high altitude climatic treelines are associated with a seasonal mean ground temperature of 6.7 °C (±0.8 SD; 2.2 K amplitude of means for different climatic zones), a surprisingly narrow range. Temperatures are higher (7–8 °C) in the temperate and Mediterranean zone treelines, and are lower in equatorial treelines (5–6 °C) and in the subarctic and boreal zone (6–7 °C). While air temperatures are higher than soil temperatures in warm periods, and are lower than soil temperatures in cold periods, daily means of air and soil temperature are almost the same at 6–7 °C, a physics driven coincidence with the global mean temperature at treeline. The length of the growing season, thermal extremes or thermal sums have no predictive value for treeline altitude on a global scale. Some Mediterranean (Fagus spp.) and temperate South Hemisphere treelines (Nothofagus spp.) and the native treeline in Hawaii (Metrosideros) are located at substantially higher isotherms and represent genus‐specific boundaries rather than boundaries of the life‐form tree. In seasonal climates, ground temperatures in winter (absolute minima) reflect local snow pack and seem uncritical. Main conclusions The data support the hypothesis of a common thermal threshold for forest growth at high elevation, but also reflect a moderate region and substantial taxonomic influence.     

Relationship between temperature and cauliflower (<Emphasis Type="Italic">Brassica oleracea</Emphasis> L. <Emphasis Type="Italic">var. botrytis</Emphasis>) growth and development after curd initiation

Two experiments were conducted to assess the response of cauliflower (Brassica oleracea L. var. botrytis) cv. “Nautilus” F1 hybrid to different constant temperatures after curd initiation by keeping the plants in six different temperature-controlled glasshouse compartments with heating set point temperatures of 6, 10, 14, 18, 22, and 26 °C (±4 °C) at the School of Plant Sciences, The University of Reading, UK during winter 1998–1999 and summer 1999. Many of the growth parameters increased with increasing mean growing temperature up to an optimum temperature and then declined with further increases in temperature. Therefore, cauliflower’s growth and development after curd initiation could be resolved into linear or curvilinear function of effective temperatures calculated with optimum temperatures between 19 and 23 °C. It is suggested that future warmer climates will be beneficial for winter cauliflower production rather than summer cauliflower production.     

The influence of various temperature regimes on the abundance dynamics and thermal tolerance of cladoceran Ceriodaphnia quadrangula (O.F. Müller, 1785)

Experimental studies on the abundance dynamics and thermal tolerance of cladoceran Ceriodaphnia quadrangula (O.F. Müller, 1785) as they depend on the value and action pattern of a thermal factor, as well as field observations and mathematical calculations were carried out. Based upon the results of these studies, the values of the temperature zone of normal vital functions (17.0–25.0°C) and of the zones of temperature “static” optimum (21.4–25.0°C) were determined for C. quadrangula. It was shown using experimental populations of C. quadrangula as an example that it is necessary not only to keep the range of the factor optimal values within the tolerance scale (i.e., the static optimum) but also to maintain the optimal parameters of dynamic factor changes (or “dynamic optimum”) in order to form optimal conditions for their growth and development. For C. quadrangula this dynamic temperature optimum is 24.0 ± 1.1°C, with non-periodical (graded) warming to 24.7–25.3°C over five to eight days.     

Upper limits of temperature for growth inChlorella (Chlorophyceae)

The upper limit of temperature for growth is a species-specific character in the genusChlorella. The limits of 14Chlorella species range from 26–30°C (C. saccharophila) to 38–42°C (C. sorokiniana), withC. fusca var.vacuolata (34°C) andC. kessleri (34–36°C) assuming an intermediate position. Thus, there is no wide gap in the temperature limits between the normal (“low-temperature”) species ofChlorella and the “high-temperature” species,C. sorokiniana.     

Heliorestis daurensis, gen. nov. sp. nov., an alkaliphilic rod-to-coiled-shaped phototrophic heliobacterium from a Siberian soda lake

A novel alkaliphilic heliobacterium was isolated from microbial mats of a low-salt alkaline Siberian soda lake. Cells of the new organism were tightly coiled when grown in coculture with a rod-shaped bacterium, but grew as short filaments when finally obtained in pure culture. The new phototroph, designated strain BT-H1, produced bacteriochlorophyll g and a neurosporene-like pigment, and lacked internal photosynthetic membranes. Similar to other heliobacteria, strain BT-H1 grew photoheterotrophically on a limited range of organic compounds including acetate and pyruvate. Sulfide was oxidized to elemental sulfur and polysulfides under photoheterotrophic conditions; however, photoautotrophic growth was not observed. Cultures of strain BT-H1 were alkaliphilic, growing optimally at pH 9, and unlike other heliobacteria, they grew optimally at a temperature of 25 °C rather than at 40 °C or above. Analysis of the 16S rRNA gene sequence of the new organism showed that it groups within the heliobacterial clade. However, its branching order was phylogenetically basal to all previously investigated species of heliobacteria. The G+C content of the DNA of strain BT-H1 (44.9 mol%) was also quite distinct from that of other heliobacteria. This unique assemblage of properties implicates strain BT-H1 as a new genus and species of the heliobacteria, Heliorestis daurensis, named for its unusual morphology (“restis” is Latin for “rope”) and for the Daur Steppe in Russia in which these soda lakes are located. Received: 15 March 1999 / Accepted: 25 June 1999     

A study of the macro-environment at BenCat in southern Vietnam

Based on the meteorological data over a period of 4 years (1980–3), the macro-environment of BenCat Farm situated in the southern part of Vietnam (27 m above mean sea-level, 11° N and 106° E) was categorized as a “monsoon tropical climate”, due to heavy rainfall (annual mean 2028.96 mm) and about 32% wet days (annual mean 116.52 days) together with high air temperature (annual mean daily temperature 28.58, max. 32.33 and min 24.85° C). April was the hottest (monthly mean >35°C) and January the coldest month (monthly mean <22° C) of the year. The maximum number of wet days were during September and October (mean 18 days.month), whereas the minimum number of wet days were during January and February (mean <1 day/month). The months of December and January at Ben-Cat buffalo farm were categorized as the “comfortable (moderate-Dry) period” as the mean daily temperature was <27° C, while the remaining 10 months of the Calender year (February–November) were categorized as the “hot period” (mean daily temperature >27° C). On the basis of rainfall and the number of wet days, the hot period was further subdivided into a “hot-dry period” (February–April, mean of 1.67 wet days/month and mean rainfall 19.43 mm/month) and a “hot-humid period” (May–November, mean of 15.57 wet days/month and mean rainfall 276.28 mm/month).     

Final thermal preference in parthenogenetic females of Daphnia magna straus (Crustacea: Cladocera) acclimated to various temperatures

The final thermal preference FTP) range in parthenogenetic females of cladoceran Daphnia magna was assessed by “acute” and “chronic” methods. The first method included 4-month acclimation to different temperatures in the range of 14.2 ± 0.7 to 27.1 ± 0.3°C; the “chronic” method was characterized by long-term acclimation to +20°C. Two ranges of FTP were found for D. magna, 13.3–15.4°C and 20.2–26.2°C. The thermal preference of daphnids and the temperature of acclimation were correspondingly linearly. The range of FTP was independent of the season. The searching activity of D. magna rose in April, when the FTP range increased, and the FTP was less pronounced.     

Temperature dependent UV-Vis spectral changes in hydrogen-and deuterium-bonded photosynthetic reaction centers of Rhodobacter sphaeroides

The UV-Vis absorption spectra of detergent-isolated hydrogen-and deuterium-bonded reaction centers (RCs) from Rhodobacter sphaeroides PUC 705Ba were examined as a function of temperature between 20 and 55 °C. The enthalpy and entropy of denaturation for the specimens was determined, revealing that their process of thermal denaturation is significantly different. Deuterium-bonded RCs are most stable at 37 °C, rather than at room temperature, and undergo a “cold denaturation” as the temperature is lowered to room temperature. At room temperature the addition of 1,3,5-heptanetriol brought the deuterium-bonded RC back to its more stable configuration. Hence the hydrogen bonding interactions in the RC do influence its conformation and this is reflected in the microenvironment of its associated pigments.     

Lesions in thighs from hunted Brown Hares (<Emphasis Type="Italic">Lepus europaeus</Emphasis>) and microflora under vacuum-packaging storage

In two surveys, thighs of a total of 137 hunted hares were tested for the presence of intramuscular shots and femur fractures, which were detected in 42.7% and 29.2% of 274 thighs, respectively. Femur fractures were significantly associated with the presence of intramuscular shots. In the second survey (46 hares), 92 thighs were grouped into three categories, “A” (no fractures, no intramuscular shot), “B” (one intramuscular shot), and “C” (multiple shots and hematoma), with 49.0%, 33.6%, and 17.4%, respectively. Category “C” was found unfit for human consumption. During 7-day storage of vacuum-packed “A” and “B” thighs, total aerobic counts increased from initially 3.3 ± 0.3 (mean ± SD) and 4.1 ± 0.6 log cfu/g by ca. 2 log units when stored at 3–4°C, whereas the increase was clearly <1 log unit at 0°C. In comparison to temperature, differences between “A” and “B” category were less pronounced. Similar dynamics were observed for Enterobacteriaceae. In all categories, muscle pH values (mean = 5.83) were similar. It is concluded that storage at temperatures of ca. 4°C, although in compliance with EU legislation, does not afford keeping microbial contaminants in check, and thus will not preserve microbiological quality of vacuum-packed hare meat.     

Evidence of threshold temperatures for xylogenesis in conifers at high altitudes

Temperature is the most important factor affecting growth at high altitudes. As trees use much of the allocated carbon gained from photosynthesis to produce branches and stems, information on the timing and dynamics of secondary wood growth is crucial to assessing temperature thresholds for xylogenesis. We have carried out histological analyses to determine cambial activity and xylem cell differentiation in conifers growing at the treeline on the eastern Alps in two sites during 2002–2004 with the aim of linking the growth process with temperature and, consequently, of defining thresholds for xylogenesis. Cambial activity occurred from May to July–August and cell differentiation from May–June to September–October. The earliest start of radial enlargement was observed in stone pine in mid-May, while Norway spruce was the last species to begin tracheid differentiation. The duration of wood formation varied from 90 to 137 days, depending on year and site, with no difference between species. Longer durations were observed in trees on the south-facing site because of the earlier onset and later ending of cell production and differentiation. The threshold temperatures at which xylogenesis had a 0.5 probability of being active were calculated by logistic regressions. Xylogenesis was active when the mean daily air temperature was 5.6–8.5°C and mean stem temperature was 7.2–9°C. The similar thresholds among all trees suggested the existence of thermal limits in wood formation that correspond with temperatures of 6–8°C that are supposed to limit growth at the treeline. Different soil temperature thresholds between sites indicated that soil temperature may not be the main factor limiting xylogenesis. This study represents the first attempt to define a threshold through comparative assessment of xylem growth and tissue temperatures in stem meristems at high altitudes.     

Estimation of relative contribution of “mobile phycobilisome” and “energy spillover” in the light–dark induced state transition in Spirulina platensis

Previously, it was clarified that phycobilisome (PBS) mobility and energy spillover were both involved in light-to-dark induced state transitions of intact Spirulina platensis cells. In this work, by taking advantage of the characteristic fluorescence spectra of photosystem I (PSI) trimers and monomers as indicators, the relative contributions for the “mobile PBS” and “energy spillover” are quantitatively estimated by separating the fluorescence contribution of PBS mobility from that of PSI oligomeric change. Above the phase transition temperature (T _PT) of the membrane lipids, the relative proportion of the contributions is invariable with 65% of “mobile PBS” and 35% of “energy spillover”. Below T _PT, the proportion for the “mobile PBS” becomes larger under lowering temperature even reaching 95% with 5% “energy spillover” at 0°C. It is known that lower temperature leads to a further light state due to a more reduced or oxidized PQ pool. Based on the current result, it can be deduced that disequilibrium of the redox state of the PQ pool will trigger PBS movement instead of change in the PSI oligomeric state.     

Heat resistance of allograft tissue

Lyophilized allograft musculoskeletal tissue is generally intended to be stored at “ambient” or “room” temperature, and usually is kept in climate controlled indoor storage areas. However, there is a question of what temperature extremes tissue may see, especially during transportation, in that these extremes may exceed even the limits of “ambient” conditions. Temperatures may become quite hot, but only for a few hours and only during daytime. Damage from high temperatures, if it occurs, is expected to be evident by damage to the collagen component of bone, soft tissue, and demineralized bone, as well as to the growth factors contained in demineralized bone. If damage is significant, then temperature monitoring requirements for lyophilized allograft tissue might be necessary. To answer this question, a literature review was carried out to look at the short-term temperature resistance of collagen and demineralized bone. Both collagen and the growth factors in demineralized bone show remarkable short term tolerance to elevated temperatures in the dry state, and it was concluded that temperature excursions of 50°C or less, lasting for a few days or less, would not cause any significant deterioration. This means that temperature monitoring also should not be required.     

Demography of the cycad Ceratozamia mirandae (Zamiaceae) under disturbed and undisturbed conditions in a biosphere reserve of Mexico

The cycad Ceratozamia mirandae is endemic to Chiapas, Mexico. Demographic studies were made in two of its populations in the Sepultura Biosphere Reserve under different conservation conditions; in the nucleus zone “Tres Picos” (conserved) and buffer zone “La Sombra” (disturbed and under management). Spatial distribution of C. mirandae was aggregated, showed a clumped local distribution on shallow soils on steep slopes and male and female cones appear to be synchronous in both populations. The population structure was of type I (Bongers) for both sites. Individuals between the sites showed differences in growth pattern. The oldest plants (80–90 cm tall) were estimated to be about 490 years at “La Sombra”. The finite growth rate () in the buffer zone population showed a tendency for decrease whilst in the nucleus zone this estimate remained stable. The highest elasticity values lied in the transition of the first three classes of the “La Sombra” population, in “Tres Picos” this corresponded to adult plants between 20 and 30 cm tall. Given the above, it is proposed that in the nucleus zone, reproductive adults should be of highest conservation priority, whereas in the buffer zone seedling reintroduction should be carried out regularly until the population increases. We recommend an IUCN Red List category of Vulnerable (VU C, 2a), largely due to difficult-to-control destructive annual forest fires that occur in this Reserve.     

Characterization of the thermal tolerances of forest ants of New England

Characterization of thermal tolerances of ants, which are both abundant and important in most terrestrial ecosystems, is needed since thermal constraints can inform how a species may respond to local climatic change. Here we identified the thermal tolerances of 16 common ant species of the Northeastern United States and determined relationships between body size, desiccation, and thermal tolerance among species. We hypothesized that maximum heat tolerances of these species would differ and be related to body size and capacity to resist desiccation. We identified four distinct groups of species belonging to one of three subfamilies, Dolichoderinae, Formicinae, or Myrmicinae, with different maximum thermal tolerances. Group “a” had a mean thermal tolerance of approximately 43°C (±1°C), group “b” had a mean thermal tolerance of 40°C (±1°C), group “c” had a mean thermal tolerance of 38°C (±0°C), and group “d” had a mean thermal tolerance of 36°C (±0°C). Groups “a” and “d” consisted of a single species (in the subfamilies Myrmicinae and Formicinae, respectively), while groups “b” and “c” were a mix of species in the subfamilies Myrmicinae, Formicinae, and Dolichoderinae. In the subfamily Formicinae, thermal tolerance increased with body size and critical water content, a metric of desiccation tolerance. In contrast, in the subfamily Myrmicinae, higher thermal tolerance was correlated with intermediate body size and lower critical water content. These findings suggest that the two dominant subfamilies in Northeastern deciduous forests have different relationships between body size, capacity to tolerate desiccation, and thermal tolerances across species. This variation in thermal tolerance suggests that climatic change may impact species differently.     

Adaptive latitudinal variation of the duration and thermal requirements for development in the ground beetle Amara communis (Panz.) (Coleoptera, Carabidae)

The data are obtained on development time at six constant temperatures (12, 14, 16, 18, 20, 22°C) and thermal requirements for preimaginal development in a ground beetle Amara communis from Arkhangelsk (64°34′N) and St. Petersburg (59°53′N). The larval and pupal development times were found to be significantly shorter in the Arkhangelsk than in the St. Petersburg population under all temperatures. As a result, total preimaginal development appeared to be shorter by 6.2–6.6% in the Arkhangelsk population. The regression lines of the larval, pupal and total (egg-to-adult) development rate on temperature for the Arkhangelsk population run above and steeper than the respective lines for the St. Petersburg population. Both populations share the similar values of the thermal thresholds (7.2–8.2°C). This explains faster preimaginal development in the northern population under all temperatures above the threshold. Thus, the slope of the regression lines increases, i.e., the sum of degree-days decreases, whereas the thermal threshold for development exhibited no distinctive changes from south to north in this species. Adults from Arkhangelsk reared in the experiments appeared heavier on the average in comparison with those from St. Petersburg, especially at 18–22°C. Temperature did not significantly affect adult weight, except the fact that the beetles were slightly heavier at 20 and 22°C. Consequently, the well-known “temperature-size rule” is violated in this species. Relative growth rate in larvae of A. communis increased considerably with temperature rise from 14 to 22°C. It was significantly higher in the beetles from Arkhangelsk at 18–22°C. There were no differences in larval growth rate between the two populations at 14 and 16°C.     

Effects of salinity and temperature on Deschampsia antarctica

Deschampsia antarctica is one of two species of vascular plants native to Antarctica. Populations of D. antarctica have become established on recently exposed glacial forelands on the Antarctic Peninsula and these plants may rely upon nutrient inputs from hauled out mammals, seabirds and sea spray. However, not much is known about the ability of these plants to tolerate salinity stress. We examined the effects of salinity and temperature on growth, reproduction, chlorophyll fluorescence and water relations of D. antarctica. In addition, we analysed concentrations of free proline in leaves and roots as previous studies have found large increases in the concentration of this amino acid in response to environmental stress. The growth chamber experiment was a 3 × 3 (temperature × salinity) complete factorial. Plants were grown at three temperature regimes: 7°/7°C, 12°/7°C, and 20°/7°C day/night and three salinity levels: <0.02 decismen per metre (dS m⁻¹; “low salinity”), 2.5 dS m⁻¹ (“medium salinity”), and 5.0 dS m⁻¹ (“high salinity”) for 66 days. Warmer temperatures improved leaf and tiller production as well as leaf and root length, which is consistent with previous findings on this species. Salinity reduced final root length by 6 and 13% in the medium and high-salinity treatments, respectively. Plants growing in medium and high-salinity treatments had xylem pressures that were more negative and higher free-proline concentrations, suggesting that proline may act as an osmoregulant in D. antarctica.     

Study on high-temperature-resistant and high-yield <Emphasis Type="Italic">Laminaria</Emphasis> variety “Rongfu”

Hybridization of gametophytes, continuous self-crossing and targeted selection were utilized to breed a new Laminaria variety. After five-generation selection breeding, the new variety “Rongfu” was obtained. Its male parent “Yuanza No.10” was the high-yield cultivation variety, and its female parent was variety “Fujian” which could tolerate relatively high seawater temperature. “Yuanza No.10” and “Fujian” were different but complement in their morphological characteristics and biological habits. Variety “Rongfu” was bred through their hybridization which exhibited high-yield potential and high seawater temperature tolerance. The results of traits evaluation in consecutive years showed that “Rongfu” attained higher yields by 24–27% compared to the control (widely used commercial variety) and also contained considerable amounts of iodine, mannitol, and algin. When seawater temperature was 18–21°C, the blade growth of “Rongfu” was maintained and tissue loss by abrasion was significantly lower than the control. Since the adoption of variety “Rongfu” in 2001, its cultivation areas have been extended to Shandong, Fujian and Guangdong province and have reached 14,133 ha currently, i.e., almost one-tenth of the total cultivation areas of Laminaria in China. The results of Random Amplified Polymorphic DNA analysis showed that the relationship between “Rongfu” and other cultivation varieties in China was very close.     

Thermal comfort in naturally ventilated and air-conditioned buildings in humid subtropical climate zone in China

A thermal comfort field study has been carried out in five cities in the humid subtropical climate zone in China. The survey was performed in naturally ventilated and air-conditioned buildings during the summer season in 2006. There were 229 occupants from 111 buildings who participated in this study and 229 questionnaire responses were collected. Thermal acceptability assessment reveals that the indoor environment in naturally ventilated buildings could not meet the 80% acceptability criteria prescribed by ASHRAE Standard 55, and people tended to feel more comfortable in air-conditioned buildings with the air-conditioned occupants voting with higher acceptability (89%) than the naturally ventilated occupants (58%). The neutral temperatures in naturally ventilated and air-conditioned buildings were 28.3°C and 27.7°C, respectively. The range of accepted temperature in naturally ventilated buildings (25.0∼31.6°C) was wider than that in air-conditioned buildings (25.1∼30.3°C), which suggests that occupants in naturally ventilated buildings seemed to be more tolerant of higher temperatures. Preferred temperatures were 27.9°C and 27.3°C in naturally ventilated and air-conditioned buildings, respectively, both of which were 0.4°C cooler than neutral temperatures. This result suggests that people of hot climates may use words like “slightly cool” to describe their preferred thermal state. The relationship between draught sensation and indoor air velocity at different temperature ranges indicates that indoor air velocity had a significant influence over the occupants’ comfort sensation, and air velocities required by occupants increased with the increasing of operative temperatures. Thus, an effective way of natural ventilation which can create the preferred higher air movement is called for. Finally, the indoor set-point temperature of 26°C or even higher in air-conditioned buildings was confirmed as making people comfortable, which supports the regulation in China that in public and office buildings the set-point temperature of air-conditioning system should not be lower than 26°C.     

A Common Parched Future? Research and Management of Australian Arid-zone Floodplain Wetlands

Wetlands in arid and semi-arid areas face intensifying pressure for their water resources yet harbour unique biota and ecological processes that rely on the “boom and bust” regime of alternating flood and drought. Recent research in Australia has revealed that models of ecosystem processes derived from northern temperate zone wetlands are often inapplicable to arid zone wetlands, confounding efforts to manage or protect these threatened habitats. We review four case studies from inland Australia that demonstrate different degrees of successful management, aiming to draw out lessons learned that will improve our sustainable use of these delicate systems. Inappropriate extrapolation across scales that ignores the inherent spatial and temporal variability of arid-zone wetlands, “reactive” rather than “collaborative” research and management, and a reluctance to adopt functional indicators to complement state variables are several common themes. We are optimistic that managers and researchers are collaborating to tackle these issues but warn that a parched future faces some wetlands where jurisdictional boundaries hamper their effective management or entrenched beliefs and community distrust of managers threaten ecologically sustainable resource use. In arid areas where water is so precious, environmental allocations are costly and their long-term effects are difficult to identify against a backdrop of high inherent variability. Preservation of this variability is the key to successful management of these “boom and bust” systems but diametrically opposes the desire for regulated, reliable water supplies for human use. Social and institutional acceptance and change now appear to be greater barriers than limited ecological understanding to effective management of many “parched wetlands” in Australia.