The overlooked carbon loss due to decayed wood in urban trees

Decayed wood is a common issue in urban trees that deteriorates tree vitality over time, yet its effect on biomass yield therefore stored carbon has been overlooked. We mapped the occurrence and calculated the extent of decayed wood in standing Ulmus procera, Platanus × acerifolia and Corymbia maculata trees. The main stem of 43 trees was measured every metre from the ground to the top by two skilled arborists. All trees were micro-drilled in two to four axes at three points along the stem (0.3 m, 1.3 m, 2.3 m), and at the tree’s live crown. A total of 300 drilling profiles were assessed for decay. Simple linear regression analysis tested the correlation of decayed wood (cm²) against a vitality index and stem DBH. Decay was more frequent and extensive in U. procera, than P. acerifolia and least in C. maculata. Decay was found to be distributed in three different ways in the three different genera. For U. procera, decay did appear to be distributed as a column from the base to the live crown; whereas, decay was distributed as a cone-shape in P. acerifolia and was less likely to be located beyond 2.3 m. In C. maculata decay was distributed as pockets of variable shape and size. The vitality index showed a weak but not significant correlation with the proportion of decayed wood for P. acerifolia and C. maculata but not for U. procera. However, in U. procera, a strong and significant relationship was found between DBH and stem volume loss (R² = 0.8006, P = 0.0046, n = 15). The actual volume loss ranged from 0.17 to 0.75 m³, equivalent to 5%–25% of the stem volume. The carbon loss due to decayed wood for all species ranged between 69–110 kg per tree. Based on model’s calculation, the stem volume of U. procera trees with DBH ≥ 40 cm needs to be discounted by a factor of 13% due to decayed wood regardless of the vitality index. Decayed wood reduces significantly the tree’s standing volume and needs to be considered to better assess the carbon storage potential of urban forests.     

Influence of nickel-contaminated soils on fenugreek (Trigonella corniculata L.) growth and mineral composition

Leafy vegetables accumulate higher amount of heavy metals like nickel (Ni) due to their more leafy vegetative growth. Therefore, a screenhouse experiment was conducted using an alkaline sandy loam soil equilibrated with graded levels of Ni (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250 and 300 mg kg⁻¹ soil) to assess the Ni accumulation pattern and its influence on growth and micronutrient distribution in fenugreek plants. Green as well as the dry matter yields of fenugreek increased slightly up to 20 g Ni kg⁻¹ soil but decreased significantly with the application ≥40 mg Ni kg⁻¹ soil. Crops showed characteristic toxicity symptoms of interveinal chlorosis in pots receiving ≥40 mg Ni kg⁻¹ soil. While the total content of Ni in the plant tissues increased consistently with increasing rates of applied Ni, the roots accumulated much higher amount of this element compared to the shoot. The content of Fe in plants showed an increase whereas that of Cu and Zn experienced a decrease with the rise in the applied Ni.     

The influence of NaCl salinity on growth,yield and fruit quality of strawberry cvs. ‘Elsanta’ and ‘Korona’

In a 2-year field study, strawberry cvs. ‘Elsanta’ and ‘Korona’ were exposed to three different levels of NaCl salinity supplied as aqueous solutions characterised by electrical conductivities of 0.3 dS/m, 2.6 dS/m, and 5.1 dS/m. Salinity in the rhizosphere reduced plant growth by up to 44% in ‘Korona’ and 90% in ‘Elsanta’. A rather distinct cultivar difference represented the reduction in leaf area per plant of 85% in the second year of experiment in ‘Elsanta’ compared to 29% in ‘Korona’. Strawberry can be regarded as a Na⁺ excluder, because Na⁺ content of both strawberry cultivars remained below 3 mg g⁻¹ dry mass at all salinity levels. Cl⁻ content increased considerably, up to 70 mg g⁻¹ dry mass in ‘Korona’ and 80 mg g⁻¹ dry mass in ‘Elsanta’ plants. ‘Korona’ retained most of its Cl⁻ in roots and crowns, whereas in ‘Elsanta’ the maximum was detected in petioles. ‘Korona’ was able to accumulate up to 33% higher Cl⁻ content in the roots than ‘Elsanta’. Macronutrient deficiency due to NaCl salinity was not observed and in comparison to ‘Elsanta’, higher Cl⁻ content in roots of ‘Korona’ did not coincide with an impairment of macronutrient uptake. Salinity stress reduced fruit yield by up to 27% in ‘Korona’ and 64% in ‘Elsanta’. Fruit quality, characterised as taste, aroma, and texture by a consumer-type panel, decreased by more than 24% in ‘Elsanta’, but in ‘Korona’ differences were insignificant. Total soluble solids (Brix) and the ratio Brix/TA (TA, titratable acid) decreased significantly by about 20% in ‘Korona’ and 35% in ‘Elsanta’. To summarise, the ability of ‘Korona’ to retain Cl⁻ in the root system more effectively than ‘Elsanta’ resulted not only in a 41% lower leaf Cl⁻ content at the highest salinity level and a better growth under NaCl stress, but also in a relatively higher fruit yield and fruit quality.     

Arsenic as a factor affecting virus infection in tomato plants: changes in plant growth,peroxidase activity and chloroplast pigments

The influence of arsenic and Cucumber mosaic virus (CMV), applied separately and simultaneously on young tomato plants was studied. The plants were cultivated in containers under glasshouse conditions. Four main variants were arranged. The first one was without additional As pollution of soil, named as a control, and the other three variants, with As added at 25, 50 and 100 mg kg⁻¹ to dry soil respectively. Half of the plants in each experimental container were inoculated with CMV and the rest uninoculated. A clear response in plant behavior under the conditions of biotic and abiotic stress was estimated. Both arsenic and virus infection had a negative effect on tomato plants by limiting the growth of their roots and above growth parts. The changes in roots were more significant than of stems. Virus infection was a stronger stress factor than arsenic applied at levels of 25 and 50 mg kg⁻¹. The effect of each stress factor applied separately was enhanced in cases of their simultaneous application. The strongest negative effect was manifested in the infected plants, treated with excess arsenic of 100 mg kg⁻¹. It was established that the infection, caused by CMV in tomatoes, was affected by the presence of arsenic in the soil and concentration of the latter. Doses of 25 and 50 mg kg⁻¹ were favorable for infection development, while the dose of 100 mg kg⁻¹ was an inhibitor.Virus infection induced stronger specific peroxidase activity (SPOA) than As treatment. The combination of both stress factors reduced the positive peroxidase response caused by virus infection. Arsenic at rate 50 and 100 mg kg⁻¹, virus infection and the combination of both stress factors at 25 mg kg⁻¹ reduced chlorophyll a, chlorophyll b and carotenoid content The virus infection in cases of the higher arsenic doses reduced the As effect. There was an interaction between the two effects of biotic and abiotic stress. When arsenic and virus infection were applied simultaneously, they caused modification of the effect of each stress on the plants, when applied separately.     

Microtuberization of Andean potato species (Solanum spp.) as affected by salinity

The effects of NaCl stress on in vitro tuberization of potato species were studied. Three species of potato (Solanum tuberosum L., S. curtilobum Juz. and Bukasov, and S. juzepczuckii Bukasov) differing in frost resistance were subjected to 0, 25, 50, 75, and 100 mmol l⁻¹ NaCl. Stolon growth and microtuberization were evaluated. The in vitro induced microtubers were characterized with respect to their carbohydrate composition by measuring reducing, non-reducing, total soluble sugars and starch contents. Tuberization and stolon growth, expressed by stolon height or fresh mass, were significantly affected by salinity. The highest saline level (100 mmol l⁻¹ NaCl) completely inhibited tuber development in all species, but not stolon growth. Stolon growth for sensitive species (S. tuberosum) had a significant decrease, whereas both frost tolerant species (S. juzepczuckii and S. curtilobum) tended to increase stolon length with increasing saline levels. Salinity differentially influenced sugar accumulation among potato genotypes. The starch levels in both, S. curtilobum and S. juzepczuckii, remained constant under all salt levels, whereas starch increased in S. tuberosum microtubers.     

Establishment and plant regeneration of somatic embryogenic cell suspension cultures of the Zingiber officinale Rosc.

Somatic embryogenic cell suspension cultures of four ginger cultivars were established. Somatic embryogenic calli were induced from ginger shoot tips on MS agar medium supplemented with 1.0 mg l⁻¹ 2,4-D and 0.2 mg l⁻¹ Kn, which contained only half concentration of NH₄NO₃. Rapid-growing and well-dispersed suspension cultures were established by subculturing this kind of callus in the same liquid MSN medium. The suspension cultures (about 1–2 mm in diameter) were placed on the MSN agar medium for callus proliferation. Thereafter embryogenic callus (1.5 cm²) was transferred to solid media (MS + 0.2 mg l⁻¹ 2,4-D + 5.0 mg l⁻¹ BA + 3% sucrose + 0.7% agar). Somatic embryos produced shoots and roots, and shoots developed into complete plantlets on solid MS medium supplemented with 3.0 mg l⁻¹ BA and 0.1 mg l⁻¹ NAA. The relationship between the DW of suspension cultures and pH changes in medium is also discussed. The suspension cultures still kept their vitalities after subculture for 8 months.     

Effect of phytohormones on in vitro shoot multiplication and rooting of lime Citrus aurantifolia (Christm.) Swing

Multiple shoots were produced from node explants of lime (Citrus aurantifolia (Christm.) Swing) on MS medium supplemented with 6-benzylaminopurine (BAP), 6-furfurylaminopurine (kinetin) and α-naphthaleneacetic acid (NAA). The highest number of shoots, nine shoots per node, were produced on a medium containing 2 mg l⁻¹ BAP (8.8 μM), 1 mg l⁻¹ kinetin (4.6 μM) and 1 mg l⁻¹ NAA (5.4 μM). Depending on the concentration of BAP and kinetin, NAA either inhibited, stimulated or did not affect shoot multiplication, which also depended on the cytokinin level. Maximum shoot length was obtained from treatments containing 0.5 mg l⁻¹ BAP (2.2 μM) combined with 1 mg l⁻¹ kinetin (4.6 μM) and 0.5 mg l⁻¹ NAA (2.7 μM). The largest leaves of resultant shoots were produced on a medium containing 0.5 mg l⁻¹ each of kinetin (2.3 μM) and NAA (2.7 μM). Transferring in vitro shoots to rooting media containing indole-3-butyric acid (IBA) and NAA produced complete plantlets. The highest rooting percentage was obtained on a medium containing either 1 mg l⁻¹ NAA (5.4 μM) alone or 0.5 mg l⁻¹ NAA (2.7 μM) combined with 2 mg l⁻¹ IBA (9.6 μM), whereas the highest number of roots were produced on a treatment containing both 2 mg l⁻¹ NAA (10.8 μM) and 2 mg l⁻¹ IBA (9.6 μM). Roots elongated most on treatments containing 0.5 mg l⁻¹ of either NAA (2.7 μM) or IBA (2.4 μM). Shoot growth associated with the rooting phase was the highest in response to 2 mg l⁻¹ IBA (9.6 μM) or 0.5 mg l⁻¹ NAA (2.7 μM). Plantlets that survived acclimatization, 82%, exhibited normal growth in soil under greenhouse conditions.     

Rose productivity and physiological responses to different substrates for soil-less culture

Cultivation of roses in various soil-less media was studied with the aim to identify the optimum soil condition for rose production. Madelon roses grafted on rootstock of Rosa indica var. major were transplanted to polyethylene bags containing zeolite and perlite (at ratios of 25z:75p, 50z:50p, 75z:25p and 100z:0p, v/v) in a climate-controlled greenhouse. Net photosynthesis (A_net), stomatal conductance (g_s) and water use efficiency (WUE) of roses were followed for 5 months. Flower production and quality were recorded in three flowering flushes during a 5-month period. Analysis of variance of repeated measurements showed that even though the overall A_net did not differ among treatments (average 18.7 μmol m⁻² s⁻¹), trends in A_net seasonality for roses in 25z:75p substrate differed significantly from those in 50z:50p, 75z:25p or 100z:0p. Stomatal conductance did not show any significant seasonality or trends in response to substrate mixtures, averaging 0.89 mol m⁻² s⁻¹. Water use efficiency was significantly lower for roses in 25z:75p than in 100z:0p mixtures (1.8 ± 0.15 and 2.0 ± 0.13 μmol m⁻² s⁻¹ CO₂/mmol m⁻² s⁻¹ H₂O, respectively). Cumulative production of rose plants did not differ among substrate mixtures. Productivity significantly differed among flower stem classes. Stem class I (>70 cm) and class V (≤30 cm) exhibited the least production, contributing to only 7.6 and 3.7% of the total production, respectively. The highest productivity was observed in classes III (51–60 cm) and IV (31–50 cm), contributing to the bulk of productivity (68.4%). Class II contributed a 20.3% of the production. Results showed that zeolite and perlite acted as inert materials. Zeolite did not exert any positive effect on productivity, in contrast to what has been reported in literature recently. Use of perlite resulted in a little improvement in photosynthesis, however this improvement was not reflected by a significant increase in production.     

Growth,gas exchange,and nutrient status in pepper (Capsicum annuum L.) grown in recirculating nutrient solution as affected by salinity imposed to half of the root system

Pepper plants grown in recirculating nutrient solution were exposed to NaCl-salinity (60 mM NaCl, 8 dS m⁻¹) imposed either to the entire or to half of the root system and compared to plants supplied with a standard nutrient solution (1.9 dS m⁻¹). The saline solution was obtained by adding NaCl to the standard nutrient solution. In the split-root treatment, the root compartment not exposed to salinity was supplied with raw water (0.38 dS m⁻¹). Both the stem and the root dry weights were markedly restricted by salinity, irrespective of salinizing half or the entire root system. In the split-root treatment, the dry weight of the root compartment receiving raw water did not differ significantly from that exposed to salinity. The net photosynthesis and the leaf chlorophyll content were restricted by both salinity treatments, but the decrease was more marked when the entire root system was exposed to salinity. In contrast, the stomatal conductance and the transpiration rate were equally reduced, regardless of salinizing the entire or part of the root system. The leaf Na and Cl concentrations were raised by the NaCl-salinity, but only in one sampling date the increase was significantly higher when the entire root zone was exposed to salinity, as compared with salinization of half of the root system. Salinity reduced significantly the leaf K, Ca, and Mg uptake but not to levels that could cause nutrient deficiencies. These results indicate that pepper is susceptible to high salinity, predominantly due to reduced stomatal conductance. However, after long-term exposure to salinity the growth may be suppressed due also to inhibition of photosynthesis at chloroplast level. The adverse effects of high NaCl-salinity are hardly mitigated when only a part of the root system is salinized, which indicates that the response is governed by root exposure to high NaCl concentrations and not by inefficiency of the roots to take up water.     

Long-term remediation of compacted urban soils by physical fracturing and incorporation of compost

On the Cornell University campus a long-term study has measured the impacts of a soil remediation strategy on plant growth and soil quality using the Cornell Soil Health Test. The Scoop & Dump (S&D) process of soil remediation consists of physically fracturing compacted urban soils, incorporating large quantities (33% by volume) of compost with the use of a backhoe, and annually top dressing with mulch. This study was designed to investigate the impact of this remediation technique for the amelioration of compaction and degradation of soils in the urbanized environment.The study finds that over a 12-year period remediated soils exhibit improved (reduced) bulk density (R² = 0.50) (P < .0001) (n = 30), increased active carbon (R² = 0.61) (P < .0001) (n = 30) and increased potentially mineralizable nitrogen (R² = 0.61) (P < .0001) (n = 30). When S&D soils were compared to unamended (Unam) soils, improvements were found in aggregate stability (S&D = 72.41%, Unam = 34.90%, P < .0001, n = 30), available water holding capacity (S&D = 0.22%, Unam = 0.15%, P < .0001, n = 30), total organic matter (S&D = 8.43%, Unam = 3.23%, P < .0001, n = 30), potentially mineralizable nitrogen (S&D = 27.53 mg/kg, Unam = 3.11 mg/kg, P = 0.0005, n = 30), active carbon (S&D = 1022.47 mg/kg, Unam = 361.60 mg/kg, P < .0001, n = 30), and reduction in bulk density (S&D = 0.89 g/cm³, Unam = 1.47 g/cm³, P < .0001, n = 30). Application of the S&D process provides an alternative to using specified soils and has potential for improving long term soil quality using locally sourced materials and simple methods.     

Protocol for rapid propagation,and to overcome delayed rhizome formation in field established in vitro derived plantlets of Kaempferia galanga L.

Single medium based efficient protocol for rapid propagation, and to overcome the delayed rhizome formation in field established in vitro derived plantlets of Kaempferia galanga L. through in vitro rhizome induction was achieved. MS medium with combination of 8.87 μM N⁶-benzyladenine (BA), and 2.46 μM indole-3-butyric acid (IBA) induced a mean of 6.2 shoots per explant. Addition of 11.7 μM silver nitrate to 8.87 μM BA and 2.46 μM IBA supplemented medium facilitated the highest number of shoots (mean of 8.3 shoots) as well as roots within 60 days. Subculture of isolated shoots on medium with the same concentration of BA, IBA and silver nitrate increased the number to a mean of 12.1 shoots. Silver nitrate enriched medium developed rhizome at the base of shoots. Increase of sucrose concentration (6–8%) in medium with BA, IBA and silver nitrate favoured the best rhizome development. Ninety five per cent of the plantlets survived in field conditions. The plantlets established in field without in vitro developed rhizome (from medium with BA and IBA) did not form rhizome even at 7 months after transplantation. Instead, they developed tuberous roots only. The plantlets with in vitro developed rhizome (on medium having BA, IBA, silver nitrate, and 6–8% sucrose), and that established from conventional way (through splitting of old rhizome) showed no difference in growth of the rhizome. The present study emphasizes the efficacy of silver nitrate and sucrose to develop rhizome in vitro, which enabled to overcome the delayed development of rhizome, and reduced yield of plantlets established in field without in vitro developed rhizome.     

Weather effect on thermal and energy performance of an extensive tropical green roof

This study investigated the weather effect on thermal performance of a retrofitted extensive green roof on a railway station in humid-subtropical Hong Kong. Absolute and relative (reduction magnitude) ambient and surface temperatures recorded for two years were compared amongst antecedent bare roof, green roof, and control bare roof. The impacts of solar radiation, relative humidity, soil moisture and wind speed were explored. The holistic green-roof effect reduced daily maximum tile surface temperature by 5.2 °C and air temperature at 10 cm height by 0.7 °C, with no significant effect at 160 cm. Green-roof passive cooling was enhanced by high solar radiation and low relative humidity typical of sunny summer days. High soil moisture supplemented by irrigation lowered air and vegetation surface temperature, and dampened diurnal temperature fluctuations. High wind speed increased evapotranspiration cooling of green roof, but concurrently cooled bare roof. Heat flux through green roof was also weather-dependent, with less heat gain and more heat loss on sunny days, but notable decline in both attributes on cloudy days. On rainy days, green roof assumed the energy conservation role with slight increase instead of reduction in cooling load. Daily cooling load was 0.9 kWh m^?2 and 0.57 kWh m^?2, respectively for sunny and cloudy summer days, with negligible effect on rainy days. The 484 m² green roof brought potential air-conditioning energy saving of 2.80 × 10⁴ kWh each summer, equivalent to electricity tariff saving of HK$2.56 × 10⁴ and upstream avoidance of CO₂ emission of 27.02 t at the power plant. The long-term environmental and energy benefits could justify the cost of green roof installation on public buildings.     

Analysis of xylem water as an indicator of current chloride uptake status in citrus trees

The potential use of stem xylem chloride (Cl⁻) analysis as an indicator for sudden variation in Cl⁻ uptake by the tree was examined. Three extraction techniques (xylem sap extracted by centrifuge, and water extraction of fresh or dry ground xylem) were linearly correlated to each other as well as to soil salinity. Chloride values in xylem sap extracted by centrifugation were about half (3–34 mM) of those found in water extraction of fresh or dry ground xylem (9–84 mM), reflecting some Cl⁻ accumulation by existing living cells. Based on dry ground xylem, xylem Cl⁻ concentration was not affected by time of day; however, when centrifuge extraction was used, daily values were highest at the beginning and end of the day, and lowest during mid-day. Additionally, Cl⁻ concentration was not affected by stem thickness (5–25 mm) using the dry ground extraction method. Rootstock affected xylem Cl⁻ content in the same way it affected leaf Cl⁻ content; xylem Cl⁻ content was highest for trees grafted on salt-sensitive rootstocks and vice versa. As opposed to leaf analysis in which Cl⁻ concentration can only increase with time, xylem Cl⁻ content always followed soil salinity variation, either increasing or decreasing. Thus, analysis of stem xylem water can be a valuable tool for detecting short-term variation in Cl⁻ uptake. This method is important in trees since leaf analysis reflects the cumulative Cl⁻ content and therefore does not always give the current transitory mineral uptake status.     

Optimising the organic components of topsoil mixtures for urban grassland

In order to optimise the organic components of topsoil mixtures for urban grassland, we conducted two pot experiments, each with seven topsoil mixtures and perennial ryegrass (Lolium perenne) as the experimental crop. The mineral base material of the topsoil mixtures was a blend of crushed bedrock (0–2 mm), sand and agricultural topsoil. The organic components comprised three types of organic waste-based products (WBP), namely sewage sludge (SS), water sludge (WS) and garden-park compost (GPC), which were added in varying ratios to a total amount of 0.3 m³ WBP m^?3. In both experiments, mineral nitrogen (N) availability was the key limiting factor for plant growth. Plant growth increased with increasing amounts of the N-rich SS, whereas WS and/or GPC alone resulted in sparse biomass production. Topsoil mixtures with 0.1 m³ m^?3 each of SS, WS, GPC or with 0.1 m³ SS m^?3 and 0.2 m³ WS m^?3 resulted in favourable growth patterns and acceptable soil chemical properties. Topsoil mixtures containing ≤0.1 m³ SS m^?3 can therefore be recommended for the establishment of urban grassland. With >0.1 m³ SS m^?3, N and phosphorus (P) were applied in excess, causing intensive plant growth and strongly increased readily available phosphorus (P-AL) content in topsoil. We therefore suggest revision of the current Norwegian regulations, which permit inclusion of 0.3 m³ SS m^?3 in topsoil mixtures for urban greening.     

Shoot induction and plant regeneration from receptacle tissues of Lilium longiflorum

An efficient system has been developed for the in vitro plant regeneration of Lilium longiflorum Thunb. by culturing receptacle sections from flower buds. The sections were cultured on one-half MS medium plus 30 g l⁻¹ sucrose, 8 g l⁻¹ agar, 5.4 μM NAA or 4.9 μM IBA plus 2.2 μM BAP. A section size of 3–4 mm was found to be optimal. After 60 days an average of 41 shoots were formed per explant. More vigorous shoots were obtained by subculturing on hormone-free medium with 20 g l⁻¹ sucrose. Rooting occurred on one-half MS medium with 1.1 μM NAA. Rooted plants were hardened-off in a greenhouse for two months, and normal flowering plants were produced.     

The impact of photoperiod and irradiance on flowering of several herbaceous ornamentals

Forty-one herbaceous species were grown under short-days (8 h photoperiod, ambient irradiance averaged 12–13.2 and 6.4–8.3 mol m⁻² day⁻¹ for Experiments I and II, respectively) with or without supplemental high-pressure sodium lighting (+50, 100, or 150 μmol m⁻² s⁻¹); or under long-days delivered using natural day lengths and irradiance with night interruption lighting (2200–0200 h at 2 μmol m⁻² s⁻¹ from incandescent lamps) or under ambient daylight plus supplemental irradiance during the day and as a day extension to 18 h (0800–0200 h) with supplemental high pressure sodium lighting (+50, 100, or 150 μmol m⁻² s⁻¹) to identify the impact of photoperiod and irradiance on flowering of each species. Days to first open flower, leaf number below first flower, and mean dry weight gain per day (MDWG) were measured when the first flower opened. Twenty-seven species were photoperiodic with examples of five photoperiodic response groups represented: obligate short-day (2), facultative short-day (5), obligate long-day (16), facultative long-day (4); 13 were day neutral (no photoperiod response in flowering). One species, Salvia sclarea L., did not flower. A facultative irradiance response was observed with 10 species; 28 species were irradiance indifferent; 2 had delayed flowering as irradiance increased. Photoperiod affected MDWG of 30 species. Increasing irradiance affected MDWG with 14 species. Photoperiod interacted with irradiance to affect MDWG of 11 species. Cobaea scandens had the greatest MDWG (0.40 g day⁻¹) while Amaranthus hybridus had the least MDWG (0.01 g day⁻¹) across photoperiod and irradiance levels.     

Influence of soil aeration on rooting and growth of the Beuys-trees in Kassel,Germany

Soil aeration is an important factor in tree growth. Oxygen must be taken from the atmosphere for root respiration, and carbon dioxide must be discharged to the atmosphere. Because the pore space of the soil could be considered the “dead end” of the free atmosphere, topsoil gas diffusivity is particularly important for soil aeration. Due to diverse land uses, several soil cover types alternate on a small scale at urban sites, competing with the natural function of soil as the living space for roots.During Documenta 7 in 1982, the artist Joseph Beuys initiated the spectacular landscape art project “7000 Oaks”. Seven thousand trees of approximately the same age were planted over the whole city of Kassel, Germany, offering best possible conditions for investigating the influence of specific site factors on root and tree development. At 8 different sites featuring 36 Beuys-oaks and 15 Beuys-planes, topsoil gas diffusivity, soil CO₂ concentration and soil respiration of different soil cover types were measured and correlated with fine root density and tree growth.Topsoil gas diffusivity and soil respiration depend on soil cover type. The lowest gas diffusivities and respiration rates were found at sealed sites, and the highest values were measured at vegetated sites such as lawn or flower beds. Soil gas diffusivity primarily controls soil respiration. Soil CO₂ concentration is not strictly linked to the coverage type and does not show a strictly directed dependence on top soil gas diffusivity and soil respiration. Tree root density and height as well as diameter at breast height (1.3 m) of the oaks were decisively shaped by the gas diffusivity of the soil cover, whereas the investigated planes were not affected by soil aeration deficiencies. The vitality of urban trees can be controlled by the design of the tree site and the choice of the species.     

Net CO2 exchange rate of in vitro plum cultures during growth evolution at different photosynthetic photon flux density

CO₂ concentration was monitored during three 15-day subculturing cycles in vessels containing actively proliferating plum cultures of Prunus cerasifera, clone Mr.S. 2/5. The effects of two photosynthetic photon flux density regimes: 50 ± 5 μmol m⁻² s⁻¹ and 210 ± 5 μmol m⁻² s⁻¹ were compared. Three distinct phases in the CO₂ trend were distinguished during each culturing cycle of both light treatments. In the first, occurring at the beginning of the culture cycle, the amount of CO₂ emitted by the cultures during dark periods was greater than that assimilated during the light periods. In the second phase, the opposite trend was detected, while in the third, the range of CO₂ day–night fluctuations increased or remained stable according to the number of explants per vessel. The treatment with 210 ± 5 μmol m⁻² s⁻¹ did not modify the CO₂ phase trend but induced more pronounced fluctuations in day–night CO₂ concentration. Under this light treatment, cultures reached CO₂ compensation point for a period as long as 48% of the total number of light hours, while under 50 ± 5 μmol m⁻² s⁻¹, it was only 8%. The different range in CO₂ day–night fluctuations monitored throughout a subculturing cycle, appeared to be mainly induced by changes in culture growth dynamics.     

Private residential urban forest structure and carbon storage in a moderate-sized urban area in the Midwest,United States

In conjunction with urbanization and its importance as a major driver of land-use change, increased efforts have been placed on understanding urban forests and the provisioning of ecosystem services. However, very little research has been conducted on private property and little is known about the structure and function of privately owned urban forests. This research examines the structure of and carbon storage services provided by private residential urban forests in a moderate-sized Midwestern city. The primary research questions are as follows: What is the structure of private urban forests, and how does it vary across parcels? How much carbon is stored in tree and soil pools of private urban forests, and how does carbon vary across parcels? Ecological inventories were conducted on 100 residential parcels within 14 Neighborhood and Homeowners Associations of varying size and development age. Tree species richness, diversity, density, and diameter distribution were determined on a per parcel basis and for the entire tree population sampled. Further, tree and soil carbon storage were determined for each parcel. Results of this research demonstrated large variability in per-parcel tree metrics. Twelve of the parcels sampled had two or fewer trees, while eleven had greater than 50 trees. Further, tree carbon storage ranged from no carbon to 11.22 kg C m^?2. Alternatively, soil carbon storage was less variable and averaged 4.7 kg C m^?2, approximately 1.9 times higher than the average carbon stored in trees (2.5 kg C m^?2). Management efforts aimed at maintaining or enhancing carbon storage and other ecosystem services should focus on both soil protection and maximizing services in living biomass. Our results demonstrate that sustaining tree-produced ecosystem services requires maintenance of large old trees and species diversity, not only in terms of relative abundance, but also relative dominance, and in combination, species–specific size distributions.     

Micropropagation of Karonda (Carissa carandas) through shoot multiplication

Shoot tips from field grown, mature plants of Carissa carandas cv. Pant Sudarshan were cultured on Murashige and Skoog’s (MS) basal medium supplemented with benzyladenine (BA) and indolebutyric acid (IBA) during different seasons. The maximum sprouting rate was obtained with 1.5 cm long explant collected in spring season (February–March) followed by those collected in summer season (April–June). Shoot proliferation was highest on MS basal media supplemented with 3.0 mg l⁻¹ BA. Rooting of microshoots was noted to be the best in 1/2 MS plus 0.8 mg l⁻¹ IBA and 0.2 mg l⁻¹ naphthalene acetic acid (NAA). The rooted plantlets were successfully acclimatized in vermiculite:sand:soil (1:1:1) potting mixture.