[Research progress on air pollutant distribution in urban street canyons]. / åŸŽå¸‚è¡—è°·å¤§æ°”æ±¡æŸ“ç‰©åˆ†å¸ƒç ”ç©¶è¿›å±•.

Urban street canyon is one of the most important characteristics and spatial forms of cities. It is one of the most frequently used public spaces in cities, with the most serious automobile exhaust pollution and the largest population density. The unreasonable space configuration and internal composition might decrease self-purification of urban ventilation but increase local air pollutant concentration. Here, we reviewed the impacts of street canyon morphology, street trees, vehicle flow and meteorological factors on the distribution of air pollutants in street canyons. We scrutinized the relevant methods of numerical simulation, wind tunnel experiments, and field monitoring on the distribution and diffusion of air pollutants in street canyons. We recommended that future research should concentrate on the impacts of various parameters on the distribution and diffusion of air pollutants based on the field monitoring data. Meanwhile, further research should develop optimization strategies for street canyon design which is conducive to the dispersion of air pollutants, and put forward scientific support and optimization scheme for the controlling of air pollutants from the perspective of urban planning and pattern optimization.

Tropospheric ozone and cadmium do not have interactive effects on growth, photosynthesis and mineral nutrients of Catalpa ovata seedlings in the urban areas of Northeast China.

Heavy metal contamination and tropospheric ozone (O3) pollution often co-occur in heavy industrial urban areas, adversely affecting urban plant health. Little is known about the characteristics of growth, physiological metabolism, bioaccumulation of cadmium (Cd) and mineral nutrients in urban trees under the combination of soil Cd contamination and elevated O3 exposure. In this study, one-year-old street tree Catalpa ovata G. Don seedlings were exposed to Cd contaminated soil (0, 100, 500 mg/kg soil) with 40 µg/m3 O3 (ambient air) and 120 µg/m3 O3 (elevated O3 exposure) for 4 weeks. The results revealed that 500 mg/kg soil Cd addition alone decreased net photosynthetic rate, stomatal conductance, peroxidase activity and increased abscisic acid content and oxidative injury in the leaves of C. ovata. Furthermore, Cd soil contamination decreased leaf, stem, root and total biomass and affected Cd, Mg, Fe, and Zn contents in leaves (P < 0.01), but it did not affect Mg, Fe and Zn contents in roots. O3 exposure did not affect growth, net photosynthetic rate, Cd accumulation and mineral nutrient contents of C. ovata. No interactive effect between Cd and O3 was found on growth, oxidative injury, photosynthetic rate, and the contents of Cd, Mg, Fe and Zn in plant tissues (P > 0.05). Our findings suggest that C. ovata is an appropriate tree species for urban greening and afforestation in heavy industrial urban areas with high O3 pollution in Northeast China. To ensure successful afforestation in heavy industrial areas, the long-term and large scale studies are needed to advance our understanding of the combined effects from extreme climate conditions and multi-pollutant exposure on the metabolism of mature urban trees.

[The latest progress in ecosystem service flow research methods.] / ç”Ÿæ€ç³»ç»ŸæœåŠ¡æµç ”ç©¶æ–¹æ³•æœ€æ–°è¿›å±•.

Ecosystem service flow is the key point and difficulty of ecosystem services research, which is now at the initial stage and show a developing trend of quantity and spatialization. However, the term "ecosystem service flow" is ambiguous. In this paper, we presented two descriptions about the term, and two corresponding theories and methods: the transmission of a service from ecosystems to people and distributed ecosystem model, and the flow of benefits accruing to people as generated by stocks of ecosystem structure and grey/black box theory. Then the latest researches related to the two descriptions were listed, and their merit and demerit were summarized. Finally, we pointed out several directions for future research in ecosystem service flow. Especially, the use of newest space technology and information technology (such as big data) and comprehensive understanding of ecosystem services (such as taking urban ecosystem services flow and abiotic flow into account) should be stressed in the future research.

[Effects of increased O3 concentration on growth, subcellular structure and reactive oxygen metabolism of turf-type Festuca arundinace]. / è‡­æ°§æµ“åº¦å‡é«˜å¯¹åªç”¨é«˜ç¾ŠèŒ ç”Ÿé•¿ã€äºšç»†èƒžç»“æž„åŠæ´»æ€§æ°§ä»£è°¢çš„å½±å“.

Taking ambient environmental O3(40 nmol·mol-1) as control, the study was conducted to assess the impact of elevated O3(80 and 160 nmol·mol-1) on the growth, subcellular structure and reactive oxygen metabolism of turf-type Festuca arundinace in open top-chambers (OTCs). The results showed that under 14-day fumigation, the height and leaf width of F. arundinace decreased significantly, and the total biomass decreased by 43.7%, and some fully expanded leaves yellowed under 80 nmol·mol-1 O3. Some visible injury symptoms, brown spots and necrosis appeared in the leaves, the total biomass decreased by 46.2%, and plasma membrane became loose from the cell wall and convoluted, chloroplast and mitochondria were damaged under 160 nmol·mol-1 O3. The rate of superoxide anion (O2-·) production, hydrogen peroxide (H2O2) content, malonaldehyde (MDA) content and the activities of antioxidant enzymes were higher under the increasing O3 concentrations (80 and 160 nmol·mol-1) compared with control. Total phenolics and the antioxidant capacity increased at first and then decreased with the rise of O3 concentration. It indicated that O3 has already affected F. arundinace growth and antioxidative metabolism before visible injury symptom appeared. F. arundinace had an adaptive response to elevated O3, but it could not protect itself from excessive O3 or long-term O3 exposure.

[Effects of elevated O3 on leaf litter decomposition and nutrient release of Quercus mongolica in city].

The leaf litters of 10-year-old Quercus mongolica were put in nylon bags and exposed to elevated 03 level (120 nmol . mol-1) with the control of 40 nmol . mol-1 in open top chambers (OTCs) for 150 days to test the effect of high O3 on the litter decomposition. The results showed that no significant difference was observed in residual mass between elevated O3 treatment and the control. Elevated 03 inhibited the release of C and K during the decomposition, the residual rate of K under elevated O3 treatment (23.9%) was significantly higher than that of the control (17.1%) after 150-day decomposition. Compared with the control, N mineralization and lignin degradation in elevated O3 treatment were inhibited during early period of decomposition (0-60 d), but were promoted in later period (90-150 d). The changes of lignin/N showed no significant difference between elevated O3 treatment and the control during the decomposition. Elevated O3 generally promoted the release of P in leaf litter of Q. mongolica during the decomposition. C/P ratio was higher under elevated 03 than that under control. Significant positive correlation was shown between residual dry mass of leaf litters and the residual rate of C, N, K, C/N ratio during decomposition. Elevated 03 might play an important role in the nutrient cycle of forest ecosystem in high-O3 pollution area.

[Metabolism and interaction of C and N in the arbuscular mycorrhizal symbiosis].

The arbuscular mycorrhiza (AM) is the symbiont formed by the host plant and the arbuscular mycorrhizal fungi (AMF). The transfer and metabolism of C and N in the symbiosis plays an important role in keeping nutrient balance and resource reallocation between the host plant and the fungi. The carbohydrates produced by plant photosynthesis are transferred to the fungi, where they are metabolized as materials and energy used for fungal spore germination, mycelium growth and uptake of nitrogen and other nutrients. At the same time, N is transferred and reallocated from the fungi to the host plant, where the final released ammonium is used for plant growth. Accordingly, we reviewed the current progress in C and N transfer and metabolism in the AM symbiosis, and the crosstalk between them as well as some key issues to elucidate the mechanism of the interaction between C and N transport in the symbiosis, so as to provide the theory foundation for the application of AM in sustainable agriculture and ecosystem.

[Effects of soil PAHs pollution on plant ecophysiology].

Polycyclic aromatic hydrocarbons (PAHs) are the ubiquitous organic persistent pollutants in natural environments (especially in soil), giving serious potential risks to the eco-environment, plants, and human beings. At present, the remediation of PAHs-polluted soil is one of the hot topics in the research fields of soil and environment. Phytoremediation is one of the environmental restoration techniques with most potentiality. This paper reviewed the newest progress in the researches of the effects of soil PAHs pollution and its combined stress with other pollutants on the plant growth, morphological structure, photosynthesis, and antioxidant system, and prospected the important fields and hotspots of related researches in the future.

Differences in the arbuscular mycorrhizal fungi-improved rice resistance to low temperature at two N levels: aspects of N and C metabolism on the plant side.

We performed an experiment to determine how N and C metabolism is involved in the low-temperature tolerance of mycorrhizal rice (Oryza sativa) at different N levels and examined the possible signaling molecules involved in the stress response of mycorrhizal rice. Pot cultures were performed, and mycorrhizal rice growth was evaluated based on treatments at two temperatures (15 °C and 25 °C) and two N levels (20 mg pot(-1) and 50 mg pot(-1)). The arbuscular mycorrhizal fungi (AMF) colonization of rice resulted in different responses of the plants to low and high N levels. The mycorrhizal rice with the low N supplementation had more positive feedback from the symbiotic AMF, as indicated by accelerated N and C metabolism of rice possibly involving jasmonic acid (JA) and the up-regulation of enzyme activities for N and C metabolism. Furthermore, the response of the mycorrhizal rice plants to low temperature was associated with P uptake and nitric oxide (NO).

[Nitrogen metabolism and translocation in arbuscular mycorrhizal symbiote and its ecological implications].

Arbuscular mycorrhizal fungi (AMF) can form mutually beneficial relations with more than 80% of vascular plants, and the existence of the symbiote is of significance in promoting the growth and stress tolerance of host plants. AMF can obtain the photosynthate carbohydrates from host plants, and in the meantime, effectively promote the nitrogen (N) uptake by host plants via the absorption of various N sources by mycorrhiza mycelia, resulting in the N exchange at population or community level, the improvement of host plants nutrition and metabolism, and the strengthening of the stress tolerance of host plants. However, there are still in debates in which ways the symbiote absorbs and transfers N and what the mechanisms the N metabolism and translocation from AMF to host plants. This paper reviewed the mechanisms of N metabolism and translocation in the symbiote and the effects of carbon and phosphorous on the N metabolism and translocation. The roles of AMF in the N allocation in host plants and the related ecological significance at community and ecosystem levels were briefly elucidated, and some issues to be further studied on the N metabolism in the symbiote were addressed.

[Effects of elevated ozone on Pinus armandii growth: a simulation study with open-top chamber].

By using open-top chamber (OTC) and the techniques of dendrochronology, this paper studied the growth of Pinus armandii under elevated ozone, and explored the evolution dynamics and adaptation mechanisms of typical forest ecosystems to ozone enrichment. Elevated ozone inhibited the stem growth of P. armandii significantly, with the annual growth of the stem length and diameter reduced by 35.0% and 12.9%, respectively. The annual growth of tree-ring width and the annual ring cells number decreased by 11.5% and 54.1%, respectively, but no significant change was observed in the diameter of tracheid. At regional scale, the fluctuation of ozone concentration showed significant correlation with the variation of local vegetation growth (NDVI).

[Litterfall amount and its dynamics in urban forest of Shenyang, Northeast China].

Twenty sampling sites were set in the urban forest of Shenyang to continuously observe the amount of forest litterfall and its dynamics in 2005-2007. During the three years, the leaf litters collected in twenty 1 m2 litterfall traps were of 30 tree species, which accounted for 15.5% of the entire tree species in Shenyang, but the individual number and leaf area of the populations accounted for 63.8% and 69.9%, respectively. A significant positive correlation was observed between the leaf litterfall amount and the leaf area of the corresponding tree species, and there was a great difference in the beginning time of the leaf fall between different tree species. The species with earlier beginning time of leaf fall finished their leaf fall earlier, and thus, there was a significant positive correlation between the beginning time of leaf fall and the ending time and duration of leaf fall. The average annual litter production was 4229.0 kg x hm(-2), among which, leaf litterfall was 3397.36 kg x hm(-2), branch litterfall was 463.89 kg x hm(-2), and fruit- and flower litterfall was 367.73 kg x hm(-2), accounting for 80.3%, 11.0%, and 8.7% of the total production, respectively. The seasonal dynamics of the litterfalls showed a single peak, with the maximum appeared in October and accounted for about 50.0% of the total. The large amount of the litterfalls could supply nutrients and energy for urban forest.

[Temporal changes of shoal reclamation in Jinzhou Bay sea area based on remote sensing analysis].

By using Landsat and high resolution ALOS images, and based on the comparison of the precision of sea area extracted from various water indices, a modified index MNDWI was adopted to study the shoal reclamation in Jinzhou Bay sea area in 1988, 1995, and 2006. In the period 1988-2006, the reclaimed area in Jinzhou Bay sea area reached 23.63 km2, among which, 12.38 km2, 5.48 km2, 3.47 km2, 1.37 km2, and 0.93 km2 were used for development zone, industry, port construction, seawater aquaculture, and beach bathing, respectively. The large acreage shoal reclamation reflected the urgent demand of land for coastal urban construction and economic development along the Jinzhou Bay, while at the meantime, brought about greater impacts on the local eco-environment, which needed to be further monitored and assessed.

[Responses of Pinus sylvestris var. mongolica radial growth to climate warming in Great Xing' an Mountins: a case study in Mangui].

Based on the theory and methodology of dendrochronology, the tree ring width chronology of Pinus sylvestris var. mongolica in Mangui of Great Xing' an Mountains was developed, and the relationships between the standardized tree ring width chronology and local climate factors (temperature and precipitation) as well as the effects of climate factors on the P. sylvestris var. mongolica radial growth were analyzed. In this region, the mean monthly temperature in April-August of current year was the main factor limiting the radial growth, and the increasing mean monthly temperature from April to August had negative effects to the radial growth. The simulation of the variations of the radial growth by the mean monthly temperature change in April-August showed that the radial growth of P. sylvestris var. mongolica would present a declining trend accompanied with the warmer and drier regional climate condition.

[Recognition of landscape characteristic scale based on two-dimension wavelet analysis].

Three wavelet bases, i. e., Haar, Daubechies, and Symlet, were chosen to analyze the validity of two-dimension wavelet analysis in recognizing the characteristic scales of the urban, peri-urban, and rural landscapes of Shenyang. Owing to the transform scale of two-dimension wavelet must be the integer power of 2, some characteristic scales cannot be accurately recognized. Therefore, the pixel resolution of images was resampled to 3, 3.5, 4, and 4.5 m to densify the scale in analysis. It was shown that two-dimension wavelet analysis worked effectively in checking characteristic scale. Haar, Daubechies, and Symle were the optimal wavelet bases to the peri-urban landscape, urban landscape, and rural landscape, respectively. Both Haar basis and Symlet basis played good roles in recognizing the fine characteristic scale of rural landscape and in detecting the boundary of peri-urban landscape. Daubechies basis and Symlet basis could be also used to detect the boundary of urban landscape and rural landscape, respectively.

[Effects of elevated CO2 and O3 on active oxygen metabolism of Quercus mongolica leaves].

By using open top chamber fumigation method, this paper studied the effects of elevated O3 (approximately 80 nmol x mol(-1)) and CO2 (approximately 700 micromol x mol(-1)), single and in combination, on the active oxygen metabolism of Quercus mongolica leaves. Elevated O3 increased the superoxide anion radical (O2 divided by) generation rate, hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents, and electrolyte leakage (EL) (P < 0.05), but decreased the superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) activities and ascorbate (AsA) content (P < 0.05); while elevated CO2 had no significant effects on the active oxygen metabolism of Q. mongolica leaves. The combination of elevated O3 and CO2 had less effects on the O2 divided by generation rate, H2O2 and MDA contents, and EL, indicating that elevated CO2 alleviated the oxidative stress of elevated O3 on Q. mongolica leaves, but increased the SOD, APX, and CAT activities and the AsA and total phenol contents, compared with elevated O3 (P < 0.05), indicating that elevated CO2 alleviated the negative effects of elevated O3 on Q. mongolica leaf antioxidant system.

[Effects of elevated CO2 or/and O3 on growth and daily changes of photosynthesis in leaves of Pinus armandi].

To study the responses of growth and daily changes of photosynthesis in leaves of Pinus armandi to elevated O3, elevated CO2 and elevated O3 + CO2 in urban area, experiment was conducted in Shenyang Arboretum located at the center of the city. Five-year-old trees grown in open-top chambers (OTC) were exposed to control, elevated O3 and elevated O3 + elevated CO2 for a growing season, and the growth (fresh weight, dry weight, leaf length, axial shoot, lateral shoot), daily changes and diurnal assimilation amounts of Pinus armandi leaves were measured. The results showed that (1) the increments of fresh weight and dry weight in 70 days were reduced 45.8% and 38.9% by elevated O3 compared to the control. After 90 days, leaf length decreased 15.3%, but there were no significant difference detected in axial shoot and lateral shoot compared to the control. Diurnal assimilation amounts were decreased in elevated O3 treatment, and after 30 days exposure, net photosynthesis rate (P(n)) of leaves was decreased significantly compared to the control. Under O3 exposure, the diurnal pattern of net photosynthetic rate curve was two peaks, and a midday depression at noon was lower than control. (2) Under elevated CO2 exposure, the increments of fresh weight and dry weight in 70 days were increased 41.7% and 22.2%, but leaf length, axial shoot and lateral shoot after 90 days were not changed compared to control. Diurnal assimilation amounts were increased after elevated CO2 exposure in total, and in 30 and 60 days, net photosynthesis rates (P(n)) of leaves were higher than that of control mostly. From diurnal variation of P(n), the diurnal pattern of net photosynthetic rate curves of Pinus armandi leaf was changed from two-peaks to one-peak curue after 90 days elevated CO2 exposure, that means the midday depression was relieved by high CO2.(3) When trees were exposed to both elevated O2 and elevated CO2, the increments of fresh weight and dry weight in 70 days were all decreased compared to the control, which indicates that season-long exposure to elevated O3 had a greater effect on Pinus armandi leaves than elevated CO2, but dry weight was significantly higher than the only elevated O3 treatment, that means the O3-induced negative effect to growth of leaves can be ameliorated by elevated CO2. There were also no effects on leaf length, axial shoot and lateral shoot after 90 days exposure. When elevated O3 and CO2 were combined, net photosynthesis rate (P(n)) of leaves was lower than that of control mostly. Diurnal assimilation amounts were significantly lower than control but higher than only elevated O3 treatment, which indicated that high CO2 can largely relieve the damage of high O3 to photosynthesis of Pinus armandi leaves. The diurnal pattern of net photosynthetic rate curves of Pinus armandi leaf were also two-peak curves.

[Selection of distance thresholds of urban forest landscape connectivity in Shenyang City].

By using the QuickBird remote sensing image interpretation data of urban forests in Shenyang City in 2006, and with the help of geographical information system, this paper analyzed the landscape patches of the urban forests in the area inside the third ring-road of Shenyang. Based on the habitat availability and the dispersal potential of animal and plant species, 8 distance thresholds (50, 100, 200, 400, 600, 800, 1000, and 1200 m) were selected to compute the integral index of connectivity, probability of connectivity, and important value of the landscape patches, and the computed values were used for analyzing and screening the distance thresholds of urban forest landscape connectivity in the City. The results showed that the appropriate distance thresholds of the urban forest landscape connectivity in Shenyang City in 2006 ranged from 100 to 400 m, with 200 m being most appropriate. It was suggested that the distance thresholds should be increased or decreased according to the performability of urban forest landscape connectivity and the different demands for landscape levels.

[Effects of elevated O3 concentration on anti-oxidative enzyme activities in Pinus tabulaeformis].

An open-top chamber experiment was conducted to study the effects of high concentration O3 (80 nmol x mol(-1)) on the superoxide anion radical (O2*-) generation rate, hydrogen peroxide (H2O2) content, activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR), and ascorbic acid content in Pinus tabulaeformis leaves. Under high concentration O3 exposure, the superoxide anion radical generation rate and H2O2 and malondialdehyde (MDA) contents increased, while the ascorbic acid content and the activities of SOD, APX, DHAR, MDHAR, and GR increased in early growth season but decreased then to a level lower than the control, which illustrated that the antioxidant system of P. tabulaeformis did respond in an acclimation way in the early growth season, but could not bear the damage of long-term elevated O3 exposure.

[Selection of landscape metrics for urban forest based on simulated landscapes].

Based on the existing urban forest landscape of Shenyang, four landscape pattern gradients were simulated, and one existing landscape pattern gradient in accordance with the trend of these gradients was selected. By analyzing the responses of 28 landscape metrics for landscape fragmentation and patch shape complexity to various landscape pattern gradients, preference landscape metrics were selected for describing the degree of the two landscape pattern characteristics. The results showed that patch density (PD) and mean patch area (AREA_MN) regularly responded to the change of landscape fragmentation. The increase of landscape fragmentation resulted in an increase of PD value while a decrease of AREA_MN value. Patch shape complexity of area weighted mean perimeter area ratio (PARA_AM) coincided with the gradients of landscape pattern. PARA AM value increased with increasing patch shape complexity, which precisely characterized the degree of patch shape complexity.

[Urban vegetation coverage change inside the Third-Ring Road of Shenyang City, China: a study with linear spectral unmixing technique].

Based on the Landsat TM images of 2001 and 2006, and by using linear spectral unmixing (LSU) technique, the information of urban vegetation coverage inside the Third-Ring Road of Shenyang City was extracted, and the dynamic change of the vegetation coverage in 2001-2006 was analyzed, in combining with a land use map derived from the visual interpretation of a QuickBird image of 2006. The results showed that in 2001-2006, the urban vegetation coverage in study area changed drastically. Urban greening and the cropland encroachment caused by urban sprawl coexisted, and the vegetation gain from urban greening was larger than the vegetation loss from cropland encroachment. The vegetation coverage of road, residence, public facilities, and park and square increased with varying degrees (5%-9%), while industrial land changed little. The spatial distribution of urban greening was relatively reasonable. Though the polarization of vegetation coverage between central city and suburban still existed, this polarization had been mitigated to some extent. With the increase of the distance from city center, the vegetation coverage increased in sequence of park and square (0.8% x km(-1)) < residence (1.5% x km(-1)) < industrial land (1.7% x km(-1)) < public facilities (2.4% x km(-1)) < road (2.9% x km(-1)). The polarization of vegetation coverage in public facilities and road were still serious, suggesting that more greening programs and strict conservation efforts were needed.