Modelling salt accumulation by a bean crop grown in a closed hydroponic system in relation to water uptake

Four different NaCl concentrations in the irrigation water, 0.8, 3, 6 and 9 mol m⁻³, were applied as experimental treatments to beans (Phaseolus vulgaris L.) grown in completely closed hydroponic systems in a greenhouse. Initially, the Na and Cl concentrations increased rapidly in the root zone, as indicated by the values measured in the drainage water, and this resulted in corresponding increases in the Na/water and Cl/water uptake ratios. However, as these ratios approached equilibrium with the NaCl/water ratios in the irrigation water, the Na and Cl concentrations in the root zone converged to maximal levels, which depended on the treatment. The highest Na and Cl concentrations in the root zone and the corresponding NaCl concentrations in each treatment were used to establish relationships between the external NaCl concentration and the Na/water or Cl/water uptake ratios, which proved to be exponential for Na but linear for Cl. These relationships were then used in a previously established model [Savvas, D., Kotsiras, A., Meletiou, G., Margariti, S., Tsirogiannis, I., 2005a. Modeling the relationship between water uptake by cucumber and NaCl accumulation in a closed hydroponic system. HortScience 40, 802–807] to enable the prediction of the Na and Cl concentrations in the root zone in relation to the cumulative water uptake. The curves predicted by the model followed a convex pattern, with an initially rapid increase in Na and Cl concentrations in the root zone followed by a gradual levelling out as the cumulative water consumption rose. The measured Na and Cl concentrations in the drainage water were more accurately predicted at the higher NaCl concentrations in the irrigation water, although those predicted at 0.8 mol m⁻³ of NaCl were considered acceptable for use in commercial practice. Bean showed a high efficiency of Na exclusion from the upper leaves, while Cl was readily translocated to the young leaves as the external Cl concentration rose. Plant growth decreased with increasing salinity in a way similar to that reported for beans constantly exposed to comparable salinity levels.     

Potential hazard characteristics of Tilia, Betula, and Acer trees removed in the Helsinki City Area during 2001–2003

In order to study decay, and to improve the management and protection of old urban trees, a total of 256 felled urban trees were examined during 2001–2003: 95 Tilia spp., 74 Betula spp., and 87 Acer spp. Most of the trees (73%) were located in the main parks and along the main streets in the downtown area of Helsinki City, Finland. The mean age of the trees was over 60 years, and the majority (64%) were old park trees. Poor condition and increasing risk of failure were the main reasons for felling in 82% of the cases. Thirty three percent of these trees were degenerated or dead, but the amenity value of 14% of the risk trees was still high. The latter were old, big trees which posed a potential hazard, but had a vital and balanced crown.Some characteristic profiles for potential failure were identified for each of the tree species studied: Ganoderma lipsiense in the butts and hollows in the stems of Tilia spp., weak fork formations together with Rigidoporus populinus on Acer spp., and degeneration together with decay in the stem on Betula spp.Decay fungi most commonly identified were R. populinus, G. lipsiense, Inonotus obliquus and Piptoporus betulinus. In addition, Kretzschmaria deusta was very common in three of the parks, and on every one of the tree species investigated.     

Isolation of arbuscular mycorrhizal fungi and Azotobacter chroococcum from local litchi orchards and evaluation of their activity in the air-layers system

Soil samples were collected from rhizosphere of litchi-growing areas of North-Western Himalayan Region (NWHR) of India, for finding qualitative and quantitative differences in arbuscular mycorrhizal (AM) fungi and Azotobacter chroococcum. These samples were taken from plants being grown in different cultivation types namely, weed control with weedicides or tillage; orchard floor either clear or with cover crops; intercropping with cereals and legumes. Qualitative and quantitative differences were noticed with different cultivation types and a marked reduction in the AM fungi was observed in orchards where chemicals were used for weed control and intensive farming system was used on the orchard floor. AM fungi were generally abundant in the soils with range pH 5.5–6.6. Among different AM fungi retrieved from the soils, Glomus spp. was most dominant. Fifteen AM fungal species were isolated, identified and characterized and along with their ability to colonize the roots. In the soil samples, a marked variation in viable bacterial count of A. chroococcum was also noticed due to varied physico-chemical characteristics of the orchard soils. The changes in AM fungal species composition can be attributed to changes in soil chemical properties resulting from cultural practices such as ploughing, application of chemical fertilizers and weedicides. An experiment was also conducted to study the comparative efficacy of four dominant and frequently occurring indigenous AM species namely, Glomus fasciculatum (Thaxter sensu Gerdemann), G. magnicaulis (Hall), G. mosseae (Nicol. & Gerd.), Gigaspora heterogamma (Nicol. & Gerd.) and two A. chroococcum strains viz., AZ₁ and AZ₂ singly and in dual combination to evaluate their effect in air-layers system. Dual inoculation of G. fasciculatum and AZ₁ increased total root length of air-layered shoots by 81.39% over uninoculated control. These studies indicated that indigenously isolated AM fungal species and A. chroococcum strains can be used for air-layering for better adaptation under specific agro-climatic and ecological zone conditions.     

Effects of NH4:NO3:urea ratio on cut roses yield, leaf nutrients content and proton efflux by roots in closed hydroponic system

The effects of the NH₄:NO₃ ratio in replenishment solution on Rosa L. flower yield and the impact of NH₄ substitution by urea on plant performance and on solution EC and pH have not been studied previously in closed (no leaching) hydroponic systems. A greenhouse experiment with six NH₄:NO₃:urea ratios (0:100:0, 12:88:0, 25:75:0, 50:50:0, 100:0:0 and 0:50:50) and two harvest cycles (winter and spring) was carried out to investigate these relationships. In winter, total and >40 cm cut flower yields were maximal in treatment 25:75:0. At lower NH₄ percentages (12.5:87.5:0 and 0:100:0), growth container solution pH varied between 7.8 and 8.5, reducing P, Ca and Mn concentration in leaves and increasing dry matter allocated to them. At higher NH₄ percentages, Ca uptake was inhibited, solution pH reached 3, and %P in leaves increased. Consequently, reducing sugars concentration in leaves increased and sucrose and starch concentrations decreased. A stepwise regression analysis indicated that the optimal NH₄:NO₃ ratio in feed solution is 40:60, with resulting solution pH of 5.9 in the growth container. In spring the maximum yield was obtained in treatment 0:50:50 and it exceeded the winter yield despite a higher solution EC (4.3 dS m⁻¹ vs. 3.5 dS m⁻¹ at harvest). The beneficial effect of urea (0:50:50 vs. 50:50:0) stemmed from the relatively lower NH₄ concentration in solution, that alleviated the NH₄–Ca uptake competition, and higher pH. The slope of the straight line relating [H⁺ efflux rate] to [NH₄⁺ uptake rate] in treatments 25:75:0, 50:50:0 and 100:0:0 was 0.44 mol H⁺/mol NH₄. In all other treatments the proton efflux was negligible.     

Effects of NaCl application to hydroponic nutrient solution on fruit characteristics of tomato (Lycopersicon esculentum Mill.)

NaCl was applied to nutrient solution (5 dS m⁻¹ versus 1.4 dS m⁻¹ in the control) of hydroponically-grown tomato and its effects on taste grading and chemical composition of fruit were investigated. Taste panels indicated NaCl treatment increased sweetness, acidity, umami (i.e. the taste of deliciousness) and overall preference. Hexose concentration of the fruit grown on NaCl treated plants significantly increased; and at the same time, chloric ion, organic and amino acids in general had higher concentrations in NaCl treated plants than the control. Our results showed that (1) consumer grading of the tomato fruit was influenced not only by sugar content but also by the organic and amino acids; (2) increased concentration of soluble solids in the fruit of NaCl treated plants was not the result of simple overall condensation due to the reduction of water transport. The relation of diversified consumer preference, fruit chemical composition, and appropriate evaluation of tomato fruit are also discussed.     

Integration of invasion ecology theories into the analysis of designed plant communities: a case study in Southern Germany

Theories regarding the establishment and persistence of self-naturalising alien species can help in interpreting these processes in designed plant communities with their combination of exotic species and native plant communities. Thus, they may provide a theoretical basis for this kind of landscape design. A case study investigated the influence of plant community conditions (invasibility), species-specific traits (invasiveness), and gap diameter size on the establishment of selected North American prairie forbs in Central European horticultural meadows. Experimental sites were located in Freising, Bavaria. Introduced forbs included Aster laevis, Aster novae-angliae, Aster x salignus, and Aster x versicolor. Establishment success was measured as survival rate and total aboveground dry biomass. Invasibility of the investigated horticultural meadows was strongly related to resource availability, as most influences of plant community traits could ultimately be attributed to this factor. Leaf area and specific leaf area above canopy height of the resident meadow species appear to be the traits that best explained differences in establishment success of the Asters. Gap size influenced species performance mainly on the less productive site, again due to higher availability of resources in the larger gaps. These results are consistent with findings of studies on self-naturalising alien species. By applying this interdisciplinary approach, valuable insights in the functioning of designed plant communities could be gained. Horticultural meadows can be one important tool in designing the highly dynamic urban landscape. In choosing suitable sites, resource availability should be strongly considered.     

Use of a cyclic high-pressure sodium lamp to inhibit flowering of chrysanthemum and velvet sage

Photoperiod is commonly controlled in the commercial production of ornamental crops to induce or prevent flowering. Flower induction in short-day (SD) plants can be prevented or delayed when the natural daylength is short by providing low-intensity lighting during the dark period. A stationary high-pressure sodium (HPS) lamp with an oscillating aluminum parabolic reflector (cyclic HPS) has been developed to provide intermittent lighting to greenhouse crops. We determined the efficacy of a cyclic HPS lamp at preventing flowering in SD plants garden chrysanthemum [Chrysanthemum × grandiflorum (Ramat.) Kitam.] ‘Bianca’, pot chrysanthemum ‘Auburn’, and velvet sage (Salvia leucantha L.) relative to traditional night interruption (NI) lighting strategies. Plants were grown in a glass-glazed greenhouse at a mean daily temperature of 19.5–20.7 °C with natural SD photoperiods. NI lighting was delivered during the middle of the night (2230–0230 h) from a 600 W cyclic HPS lamp mounted at one gable end of the greenhouse or from incandescent (INC) lamps that were illuminated for the entire 4 h (CONT INC) or for 6 min every 30 min for 4 h. Plants under cyclic HPS were grown at lateral distances of 1, 4, 7, 10, or 13 m from under the lamp. Control plants were grown under an uninterrupted 15 h skotoperiod. As the distance from the cyclic HPS lamp increased from 1 to 13 m, the maximum irradiance measured during the NI decreased from 25.4 to 0.3 μmol m⁻² s⁻¹ and time to visible inflorescence (VI) and the number of nodes at VI decreased. All species had a VI within 54 d, but ≤10% of plants flowered when grown at a lateral distance of 1 or 4 m from the cyclic HPS lamp or under CONT INC. Plants grown without NI had a VI 2 to 15 d earlier and flowered 7 to 24 d earlier than plants grown at 10 or 13 m from the cyclic HPS. All garden chrysanthemums flowered under cyclic INC, whereas velvet sage and pot chrysanthemum had 15% and 35% flowering, respectively. These results indicate that a cyclic HPS lamp can be used effectively to delay flower induction and prevent flowering in these species when NI is delivered at ≥2.4 μmol m⁻² s⁻¹.     

The use of a geographic information system to analyze long-term landscape alteration by beaver

A Geographic Information System (GIS) was used to analyze how beaver (Castor canadensis) have altered the hydrology and vegetation of Voyageurs National Park, Minnesota over a 46-year period. Maps of beaver ponds prepared from 1940, 1948, 1961, 1972, 1981, and 1986 aerial photographs were analyzed with a rasterbased based GIS to determine impoundment hydrology and vegetation distributions for each map date. Overlay and classification techniques were used to quantify hydrologic and vegetation changes between map dates. The GIS was superior to manual methods for some analyses (e.g., area measurement), and indispensible for others (e.g., transition analysis). Total area impounded increased from 1% to 13% of the landscape between 1940 and 1986, as the beaver population increased from near extirpation to a density of 1 colony/km². Most of the impoundment area increase occurred during the first two decades, when 77% of cumulative impoundment area was flooded. Once impounded ≥60% of the area maintained the same water depth or vegetation during any decade. GIS procedures were combined with field data to show that available nitrogen stocks nearly tripled between 1940 and 1986 as a result of beaver impoundment.     

Changes in agricultural land use can explain population decline in a ladybeetle species in the Czech Republic: evidence from a process-based spatially explicit model

Changes in land use affect species interactions and population dynamics by modifying the spatial template of trophic interaction and the availability of resources in time and space. We developed a process-based spatially explicit model for evaluating the effects of land use on species viability by modelling foraging performance and energy sequestration in a stage structured, three-trophic population model. The model is parameterized with realistic parameters for a ladybeetle–aphid–host plant interaction, and is run in four realistic landscapes in the Czech Republic. We analysed whether changes in crop selection and fertilizer input could explain the dramatic and unexplained decline in abundance of the ladybeetle Coccinella septempunctata in the Czech Republic from 1978 to 2005. The results indicate that a major reduction in fertilizer input after the transition to a market economy, resulting in lower aphid population densities in cereal crops and negatively affecting energy sequestration, survival and reproduction of ladybeetles, provides a sufficient explanation for the observed population decline. Simulations further indicated that the population viability of C. septempunctata is highly dependent on availability of aphid prey in crops, in particular cereal, which serves as their major reproduction habitat. The results demonstrate how the abundance of naturally occurring predators, which are instrumental for biological pest control, depends upon the spatial resource template that are provided at the landscape scale.     

Wounding of melon fruits as a model system to study rind netting

The rind of muskmelon (Cucumis melo L. var. reticulatus) fruits contains a network of suberized periderm tissue, referred as the ‘net’, which originates in response to cracking of the fruit surface during its enlargement. Shallow cuts were made on the surface of melons to mimic naturally occurring cracking and induce net-like periderm development. Histological analysis of wounded fruits of the climacteric netted variety Krimka, and of two smooth melon varieties: the climacteric Momordica and the non-climacteric Tamdew, indicated that smooth melon varieties can undergo netting when their rind is fissured. Furthermore, the results implied that the climacteric character is not essential for net-tissue development, even though most netted varieties are climacteric. The involvement of ethylene in net-like periderm development was studied by analyzing the expression pattern of the ethylene-biosynthesis genes 1-aminocyclopropane-1-carboxylate synthase 1 and 1-aminocyclopropane-1-carboxylate oxidase 1 following wounding and during periderm development, and by applying the ethylene-generating chemical, Ethrel, as a lanolin paste, on the fresh cuts. Results suggested ethylene involvement in periderm initiation, but continuous exposure may interfere with further tissue development and organization. General implications of the current study on periderm development are further discussed.     

A SCAR marker linked to the N gene for resistance to root knot nematodes (Meloidogyne spp.) in pepper (Capsicum annuum L.)

The root-knot nematodes (Meloidogyne spp.) are important nematode pests and cause serious diseases in pepper in the world. No molecular markers linked to the nematodes resistance N gene have been reported. In this paper, ‘Carolina Wonder’ (Capsicum annuum L.), a sweet pepper line resistant to root-knot nematode with N gene, ‘20080-5-29’ (C. annuum L.), an inbred line susceptible to root-knot nematode with good horticultural characteristics, and their F₂ progeny with 320 individuals were used as materials. Evaluation of resistance and susceptibility of parental lines, F₁ and F₂ progeny inoculated with root-knot nematodes (Meloidogyne incognita) were carried out. ‘Bulked segregant analysis’ method was used to search for polymorphic markers from 512 pairs of AFLP primers. Based on the assessment of resistance and susceptibility and polymorphism of the AFLP marker in F₂ population, the genetic linkage distance between the AFLP marker and the N gene was estimated. One AFLP marker E39/M41-339 was obtained and transferred to a SCAR marker amplifying a 315 bp DNA fragment linked to the N resistant allele and a 331 bp fragment linked to the N⁺ susceptible allele. The distance between the molecular marker and the nematodes resistance N gene is 6.3 cM. This research delivered a valuable tool for the marker assisted selection of nematodes resistance in pepper.     

Fruits are more sensitive to salinity than leaves and stems in pepper plants (Capsicum annuum L.)

The effects of NaCl stress on plant growth, gas-exchange, activity of superoxide dismutase (SOD), rate of lipid peroxidation, and accumulation of Na⁺ ion and sugar were investigated in leaves and fruits of pepper plants (Capsicum annuum L.). Especially, the gene expression of l-galactono-1,4-lactone dehydrogenase (GalLDH), which is the last enzyme of ascorbic acid (AsA) biosynthesis, and the relationships between AsA level and Na⁺ concentration in plant tissue were investigated with increasing salinity. Plants were treated with three treatments: the control (0 mM NaCl) and two salinity levels (50 and 100 mM NaCl) for 21 days under greenhouse conditions. Plant growth was markedly restricted due to the reduction of photosynthetic rate and the increase of Na⁺ accumulation in leaves with the increasing intensity of NaCl stress. Salinity had more effect on fruit growth comparing to leaf growth, suggesting that fruits could be more sensitive to salinity than leaves. In comparison with the control, salt stress significantly increased lipid peroxidation (as measured as malondialdehyde content) but decreased SOD activity in both fruits and leaves although the effect was larger in fruits; and the rate of the decrease in SOD activity was greater than that of the increase in lipid peroxidation. The AsA concentration transiently increased first 7 days but it slightly decreased from the initial level in the end of treatment day 21. The change in GalLDH gene expression was similar to AsA concentration. The accumulation of Na⁺, the reduction of AsA level at severe salinity stress were greater in fruits than in leaves; and AsA level had a negative relationship with Na⁺ concentration in both leaves and fruits. These results suggest that the difference in salt sensitivity between fruits and leaves in pepper plants can be related to the difference in inhibition of AsA synthesis, which in turn is probably due to the toxicity of extreme accumulation of Na⁺.     

Responses of non-primed or primed seeds of ‘Marketmore 76’ cucumber (Cucumis sativus L.) slurry coated with Trichoderma species to planting in growth media infested with Pythium aphanidermatum

Aqueous slurries of commercial preparations of Trichoderma harzianum Rifai strain KRL-AG2 G41 (Th), T. virens Strain G-41 (Tv), or their combination (ThTv, at half rates each of the single application rate) were applied to ‘Marktetmore 76’ cucumber seeds (Cucumis sativus L.) that were non-primed or primed for 3 days at 25 °C either osmotically (−2.5 MPa from 0.337 molal Ca(NO₃)₂) or osmomatrically (−1.0 MPa from 0.135 molal Ca(NO₃)₂ plus −1.5 MPa from 50% water in exfoliated grade 5 vermiculite). Slurries were applied to seeds (1 mg per seed) either before or after priming. Seeds were sown in soilless, peat-based media with or without inoculation with Pythium aphanidermatum (Pa). Protection against damping-off caused by high pressures of Pa (16% emergence in non-coated, non-primed seeds) was increased by slurry coating Th on non-primed (76.4% emergence) or on osmotically primed seeds, with coating either before or after priming having no effect on efficacy (average 62.6% emergence). Slurry coating Th on osmomatrically primed seeds failed to increase final emergence percentage (FEP). Colony forming units per three seeds (CFU, all 10³) was 2.8 for non-primed seeds, and 3.2 and 2.6, respectively, when osmotically and osmomatrically primed seeds were coated after priming. In a second study with lower disease pressure (58.1 FEP from non-coated, non-primed seeds), slurry coating of non-primed or osmotically primed seeds with Th, Tv or ThTv reduced percentage damping-off and increased FEP. The combination coating eliminated damping-off only in non-primed seeds, and tended to reduce percentage damping-off in osmotically or osmomatrically primed seeds compared to coating with Th or Tv alone. In a third study using only non-primed seeds, slurry coatings with mefenoxam fungicide, Th, Tv, or ThTv decreased total damping-off to 2.6%, 7.4%, 2.0%, and 0%, respectively, from the 30.1% occurring in non-coated seeds. Th, Tv or ThTv applied to growth media at the same rate as the seed coating (1 mg per seed) were generally as effective as the seed coatings, and only the ThTv growth medium application eliminated damping-off. A fourth experiment revealed that Th, Tv or ThTv remained viable on non-primed seeds for up to 4 weeks (the longest storage duration) at 21 or 4 °C, but 21 °C storage resulted in faster seed germination by week 3 and higher CFU per three seeds by week 4. In summary, coating of non-primed seeds with Th, Tv or ThTv was more effective than coating primed seeds in reducing percentage damping-off. While priming treatments generally led to faster seedling emergence and greater seedling shoot fresh weight than was achieved with non-primed seeds, only for non-primed seeds was damping-off eliminated by the ThTv seed coating or growth medium application.     

Methyl jasmonate plays a role in fruit ripening of ‘Pajaro’ strawberry through stimulation of ethylene biosynthesis

The role of methyl jasmonate (MJ) in strawberry (Fragaria × ananassa Duch. cv Pajaro) fruit ripening was investigated by monitoring its endogenous concentrations in fruit at various stages of development and the effects of exogenously applied MJ at these stages on ethylene biosynthesis. The concentration of endogenous trans-MJ was significantly higher in the white fruit (31.7–162.2 ng g⁻¹) and decreased sharply in half and fully ripe fruit. Higher concentrations of endogenous trans-MJ at the white stage of strawberry fruit development followed by a decline during fruit ripening indicate that MJ may play an important role in modulating fruit ripening. Significantly increased ethylene production was measured in the fruit when MJ was applied at white, half ripe and at fully ripe stage. The application of MJ (50 μM) resulted in significantly highest ethylene production and increased activities of 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and ACC oxidase as compared to all other treatments. The effect of exogenously applied MJ on ethylene production, ACC synthase and ACC oxidase activities was dependent on concentration of MJ applied and on fruit developmental stage. In conclusion, MJ in strawberry modulates fruit ripening, as its concentration is higher in white fruit and is declined with the progression of ripening and exogenous application of MJ increases ethylene production, activities of ACC oxidase and ACC synthase depending upon the concentration of MJ applied and fruit developmental stage.     

Spatial spread of an alien tree species in a heterogeneous forest landscape: a spatially realistic simulation model

The effect of environmental heterogeneity on spatial spread of invasive species has received little attention in the literature. Altering landscape heterogeneity may be a suitable strategy to control invaders in man-made landscapes. We use a population-based, spatially realistic matrix model to explore mechanisms underlying the observed invasion patterns of an alien tree species, Prunus serotina Ehrh., in a heterogeneous managed forest. By altering several parameters in the simulation, we test for various hypotheses regarding the role of several mechanisms on invasion dynamics, including spatial heterogeneity, seed dispersers, site of first introduction, large-scale natural disturbances, and forest management. We observe that landscape heterogeneity makes the invasion highly directional resulting from two mechanisms: (1) irregular jumps, which occur rarely via long-distance dispersers and create new founder populations in distant suitable areas, and (2) regular, continuous diffusion toward adjacent cells via short- and mid-distance vectors. At the landscape scale, spatial heterogeneity increases the invasion speed but decreases the final invasion extent. Hence, natural disturbances (such as severe storms) appear to facilitate invasion spread, while forest management can have contrasting effects such as decreasing invasibility at the stand scale by increasing the proportion of light interception at the canopy level. The site of initial introduction influences the invasion process but without altering the final outcome. Our model represents the real landscape and incorporates the range of dispersal modes, making it a powerful tool to explore the interactions between environmental heterogeneity and invasion dynamics, as well as for managing plant invaders. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Street tree survival rates: Meta-analysis of previous studies and application to a field survey in Philadelphia, PA, USA

Low street tree survival rates and the resulting short lifespans are frequently discussed but inadequately quantified in urban forestry literature. This study addresses street tree survival rates with a meta-analysis of previous literature and a case study assessment of street trees in Philadelphia, USA 2–10 years after planting. Reported survivorship rates from 16 previous studies were compiled. Estimated annual survival rates for individual past studies were mostly above 91.0%. To estimate the annual street tree survival rate across multiple studies, a subset of previous studies was pooled for regression analysis of ln transformed cumulative survivorship vs. time since planting. Lifespan metrics were estimated using the annual survival rates determined from regression analysis. Based on the meta-analysis, we estimated that street tree annual survival rates ranged from 94.9 to 96.5%, and street tree population half-life ranged from 13 to 20 years. Estimated mean life expectancy ranged from 19 to 28 years, which is considerably longer than the 7- or 13-year street tree average lifespan reported in previous studies. Estimated annual survival rates and lifespan metrics were similar in the Philadelphia case study. Urban forest researchers are encouraged to use demographic concepts and analyses in the study of tree survival and mortality, and to monitor tree survival at repeated time intervals every few years.     

Developing and testing a landscape habitat suitability model for the American marten (<Emphasis Type="Italic">Martes americana</Emphasis>) in the Cascades mountains of California

We used field surveys and Geographic Information System data to identify landscape-scale habitat associations of American martens (Martes americana) and to develop a model to predict their occurrence in northeastern California. Systematic surveys using primarily enclosed track plates, with 10-km spacing, were conducted across a 27,700 km² area of largely forested, mountain terrain. Martens were detected at 20/184 (10.8%) of the sample units, aggregated in three distinct regions. We investigated habitat selection at multiple scales using circular assessment areas of 3, 20, and 80 km². The model for the largest assessment area best fit the data and included the following predictors: amount of reproductive habitat, number of habitat patches and land ownership category. These results support the hypothesis that martens select habitat based upon broad scale landscape conditions and that these conditions vary with ownership. We tested the model using an independent set of data, collected primarily during the winter. Poor fit of the test data in some locations raised concerns that our model, which was developed using data collected during the snow-free season, may not predict winter distribution well. We are investigating possible causes for the seasonal variation and until they can be incorporated our model represents a conservative view of marten habitat suitability based on summer occupancy. During the summer months, which is the reproductive season, martens are predicted to occur largely in relatively undisturbed landscapes where high-elevation, late-successional forests are common. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Measurement system of whole-canopy carbon dioxide exchange rates in grafted cucumber transplants in which scions were exposed to different water regimes using a semi-open multi-chamber

A continuous CO₂ measurement system was developed to monitor the CO₂ exchange rate of the whole canopy of grafted transplants using semi-open multiple chambers. Air heating or cooling and humidification inside a healing box were under control, if needed. To test the system, the gas exchange rate of the cucumber (Cucumis sativus L.) transplants grafted onto pumpkin (Cucurbita maxima cv. ‘New-Shintozwa’) was analysed. During the healing and acclimatisation of the grafted cucumber plants, the air temperature in the box remained constant at night but ranged above 1 °C of a set value under high humidity in daytime. The relative humidity was kept within the set point during the daytime, and it nearly reached 100% at night when not controlled. The cucumber seedlings were exposed to different water stresses before grafting, and the water potentials of each treatment were −0.579 (non-stressed), −0.814 (mildly water-stressed), and −0.870 MPa (strongly water-stressed) on grafting. At the water-stressed scions, leaf expansion was inhibited by 30.9–53.3% compared with the non-stressed scions. Therefore, the gas exchange rates of the strongly water-stressed scions based on the leaf area were decreased to 72.7% compared with the non-stressed scions. After grafting, the apparent photosynthesis of the transplants of all treatments was negative, with higher respiration in the strongly water-stressed scions during the initial period of healing. However, they turned to positive values and exceeded those of the non-stressed scions from three days after grafting. This result provides critical information that the water column is physiologically connected between the stock and scion within two days after grafting. As a result of water stress, the leaf area and dry weight of the transplants in the strongly water-stressed scions were inhibited by 67.5% and 83% compared with the non-stressed scions at the end of acclimatisation. In contrast, the relative growth rate and graft-take of the strongly water-stressed transplants were slightly increased, which suggests that the water stress prior to grafting alleviated the water demand of the scion. This system may provide useful information for diagnosis at the early stage by monitoring the whole canopy's photosynthesis over a long term.