Land-use diversity can better predict urban spontaneous plant richness than impervious surface coverage at finer spatial scales.

Urban spontaneous plants, that are not intentionally propagated by humans and do not belong to the remnants of the natural habitats, not only occur in green spaces but are also distributed in diverse microhabitats in impervious surface areas. Impervious surface coverage is commonly used in studies on spontaneous plant diversity patterns in human-dominated landscapes; however, the role of habitat diversity (i.e., land-use diversity) has been overlooked. Here, we surveyed spontaneous plant composition and land uses (12 types) in 321 0.25 ha sampling sites on the Chongming District islands, Shanghai, to determine the role of land-use diversity in explaining species richness. We examined the linear relationships between species richness and land-use diversity, and quantified the importance of impervious surface coverage and land-use diversity using the random forest (RF) method. All these analyses were conducted for spatial scales from 0.25 to 5 ha in 0.25 ha increments. We found an overall positive relationship between species richness and land-use diversity, and the RF model predicted approximately 50% of the species richness variation at the smallest spatial scale. However, the positive relationship weakened with spatial scale increase, and a rapid decline in explanatory power occurred for all predictor variables in the RF model. Besides impervious surface coverage, both the vegetated and non-vegetated land-use diversity contributed substantially to the prediction of species richness at finer spatial scales. The findings clarify how land-use diversity, both in green spaces and impervious surface areas, affect urban spontaneous plant richness and should be considered in urban biodiversity conservation strategies at the neighborhood scale.

Trends of the contributions of biophysical (climate) and socioeconomic elements to regional heat islands.

The development of urban accumulations in recent decades has led to the transformation of urban heat islands (UHI) into regional heat islands (RHI). The contributions of the biophysical, climate, and socioeconomic factors to RHI in urban agglomeration remain poorly understood. Here Yangtze River Delta urban agglomeration (YRDUA) in eastern China has been selected as a case area to explore the influences trends, of the influencing factors to RHI by using MODIS data from 2003 to 2017. Results showed that, in summer, the area fraction of daytime RHI in YRDUA has increased from 21.74 to 31.03% in 2003 and 2017, respectively. As compared to 2003, the annual nighttime RHI area in 2017 has increased from 7510 to 20,097 km2. The dominant factors of surface RHI intensity (SRHII) showed seasonal variation. Enhanced vegetation index (EVI) (interpretation of 33.27%) was the dominant factor of daytime SRHII in spring. The most important factor was normalized difference build-up density (NDBI) (37.28% and 26.83%, respectively) in summer and autumn. In winter, precipitation (26.16%) was the most influential. At night, Modified Normalized Difference Water Index (MNDWI) had a dominant effect on SRHII in spring (54.12%), autumn (52.62%), and winter (24.19%). The dominant factor of nighttime SRHII in summer was EVI (42%). Moreover, water bodies harm RHI during the day while having a positive effect at night. These findings can provide a theoretical basis for regional environment improvement and regional sustainable development.

Experimental study on thermal structure inside flame front with a melting layer for downward flame spread of XPS foam.

Thermal structure inside flame front during downward flame spread was experimentally measured for XPS foam with thicknesses of 1.6, 2.4, 3.4, and 4.4 cm. The temperature distribution and temperature gradient in the condensed phase, as well as the shape of the molten liquid, were obtained by 2-D heat transfer equations and experimental measurement. The results show that both the temperature and its temperature gradient decrease from the sample surface to the inside of the condensed phase, which results in the inclination of the melting interface. The molten layer is the thinnest near the sample surface and thicker inside the condensed phase. The adhering of the molten liquid to the wall greatly increases the thickness of the molten layer near the back wall, and the higher the thickness, the more molten material adheres to the wall. Finally, there is a relatively flat solid-liquid interface near the sample surface and a large inclined solid-liquid interface near the back of the sample, especially for the thicker samples of 3.4cm and 4.4cm. It is indicated that the distribution of the molten layer in the direction perpendicular to the plane of the XPS sheet is a significant factor for dripping and collapsing.

Enhanced effects of biotic interactions on predicting multispecies spatial distribution of submerged macrophytes after eutrophication.

Water eutrophication creates unfavorable environmental conditions for submerged macrophytes. In these situations, biotic interactions may be particularly important for explaining and predicting the submerged macrophytes occurrence. Here, we evaluate the roles of biotic interactions in predicting spatial occurrence of submerged macrophytes in 1959 and 2009 for Dianshan Lake in eastern China, which became eutrophic since the 1980s. For the four common species occurred in 1959 and 2009, null species distribution models based on abiotic variables and full models based on both abiotic and biotic variables were developed using generalized linear model (GLM) and boosted regression trees (BRT) to determine whether the biotic variables improved the model performance. Hierarchical Bayesian-based joint species distribution models capable of detecting paired biotic interactions were established for each species in both periods to evaluate the changes in the biotic interactions. In most of the GLM and BRT models, the full models showed better performance than the null models in predicting the species presence/absence, and the relative importance of the biotic variables in the full models increased from less than 50% in 1959 to more than 50% in 2009 for each species. Moreover, co-occurrence correlation of each paired species interaction was higher in 2009 than that in 1959. The findings suggest biotic interactions that tend to be positive play more important roles in the spatial distribution of multispecies assemblages of macrophytes and should be included in prediction models to improve prediction accuracy when forecasting macrophytes' distribution under eutrophication stress.

[Diversity and classification system of weed community in Harbin City, China].

To analyze the causes of weed community diversity and their strategies of adaption to the high heterogeneity of urban habitats, weed communities in the central urban area of Harbin, China were studied, and a classification system was established for the weed communities. There were 175 weed species, belonging to 128 genera and 38 families. The heterogeneous urban habitats and species' temporal niche differentiation resulted in the highly diversified weed communities. The high proportions of mono-species dominance and annual species dominance communities were their response to the unstable urban habitats under human disturbances with high intensities and frequencies. A four-level classification system was established in terms of plant species and habitat conditions. Within this system, the identified 1763 weed communities could be categorized into two types of life form, 5 types of dormancy form, 22 community groups, and 119 dominance communities.

Insights into the selective binding and toxic mechanism of microcystin to catalase.

Microcystin is a sort of cyclic nonribosomal peptides produced by cyanobacteria. It is cyanotoxin, which can be very toxic for plants and animals including humans. The present study evaluated the interaction of microcystin and catalase, under physiological conditions by means of fluorescence, three-dimensional (3D) fluorescence, circular dichroism (CD), Fourier Transform infrared (FT-IR) spectroscopy, and enzymatic reactionkinetic techniques. The fluorescence data showed that microcystin could bind to catalase to form a complex. The binding process was a spontaneous molecular interaction procedure, in which electrostatic interactions played a major role. Energy transfer and fluorescence studies proved the existence of a static binding process. Additionally, as shown by the three-dimensional fluorescence, CD and FT-IR results, microcystin could lead to conformational and microenvironmental changes of the protein, which may affect the physiological functions of catalase. The work provides important insights into the toxicity mechanism of microcystin in vivo.

[Magnetic response of street tree leaves to particulate pollution in Shanghai].

To reveal the magnetic response to atmospheric particulate pollution in tree leaves along urban streets, twenty-four evergreen tree leaves were collected from green belt along Jinshajiang road, Shanghai, which were subjected to magnetic and heavy metals (Zn, Cu, Pb) analyses. The result revealed that in all leaf samples chi, SIRM varied in ranges of (4-59) x 10(-8) m3 x kg(-1) and (496-6 114) x 10(-6) Am2 x kg(-1), respectively, S(-300mT) varied from 89% to 98% and chi(ARM)/chi < 4, chi(ARM)/SIRM < 30 x 10(-5) mA(-1) was found. The magnetic parameters showed that ferromagnetic/ferrimagnetic particles were the main magnetic carriers in dust-loaded tree leaves, and magnetic grains were predominantly pseudo-single domain (PSD) and multidomain (MD) in size. The significant positive correlation between heavy metals (Zn, Cu, Pb) contents and chi, SIRM, chi(ARM), suggested that magnetic parameters like SIRM could be used as a proxy for heavy metal contents. We recommend that Magnolia grandiflora, widely distributed in Shanghai, can be used for particulate pollution monitoring.

[Allelopathic interactions between invasive plant Solidago canadensis and native plant Phragmites australis].

Taking the seeds of invasive plant Solidago canadensis and native plant Phragmites australis from their mono- and co-dominant communities as allelopathic acceptors, this paper analyzed the differences in the seed germination rate and sprout length after treated with five level (12.5, 25, 50, 100, and 200 mg x mL(-1)) S. canadensis and P. australis extracts, aimed to understand the allelopathic interactions between the two species. The 1000-grain weight and seed germination rate under distilled water treatment of the two species in co-dominated community were greater than those in mono-dominant community. Low level (12.5 and 25 mg x mL(-1)) S. canadensi extracts slightly promoted the seed germination rates of S. canadensis in both mono- and co-dominant communities, but high level (50, 100, and 200 mg x mL(-1)) S. canadensi extracts had strong inhibition effect, especially for the S. canadensis in co-dominated community. No significant patterns were observed about the effects of P. australis extract on S. canadensis seed germination. The sprout length of S. canadensis seeds in both mono- and co-dominant communities decreased with increasing level of S. canadensis extract, but decreased in a fluctuation way with increasing level of P. australis extract. After treated with the extracts of P. australis or S. canadensis, the seed germination rate of P. australis in mono-dominant community was significantly greater than that in co-dominant community (P < 0.05), but there was no significant difference between these two extracts.

The biomass and aboveground net primary productivity of Schima superba-Castanopsis carlesii forests in east China.

The biomass and productivity of Schima superba-Castanopsis carlesii forests in Tiantong, Zhejiang Province, were determined using overlapping quadrants and stem analyses. The total community biomass was (225.3+/-30.1) t hm(-2), of which the aboveground parts accounted for 72.0% and the underground parts accounted for 28.0%. About 87.2% of biomass existed in the tree layer. The resprouting biomass was small, of which over 95.0% occurred in the shrub layer. The productivity of the aboveground parts of the community was (386.8+/-98.9) g m(-2)a(-1), in which more than 96.0% was present at the tree level. The trunk's contribution to productivity was the greatest, while that of leaves was the smallest. In China, the community biomass of subtropical evergreen broadleaved forests differs significantly with the age of the forest. The community biomass of the 52-year-old S. superba-C. carlesii forests in this study was lower than the average biomass of subtropical evergreen broadleaved forests in China, and was lower than the biomass of other subtropical evergreen broadleaved forests elsewhere in the world. Moreover, its productivity was lower than the model estimate, indicating that without disturbance, this community has great developmental potential in terms of community biomass and productivity.

Temporal and spatial characteristics of the urban heat island during rapid urbanization in Shanghai, China.

Based on meteorological data from 1978 to 2007, we investigated the annual, seasonal, and fixed hourly variations of Shanghai urban heat island (UHI) in urban and suburban areas and spatial distribution of UHI. The results demonstrated a remarkable interannual increase of UHI intensity in Shanghai. The UHI was the strongest in autumn and the weakest in summer, as a consequence of the prevailing weather conditions. Similar to previous studies of other cities, the UHI in Shanghai was stronger in the nighttime than in the daytime. The SW-NE cross section followed the general cross section of the typical UHI described by Oke (1987) who defines its characteristic parts as "cliff", "plateau", and "peak". Analysis of the association of UHI and urbanization indicated that the UHI increased with the expansion of population and rapid increase of gross domestic product. The continuous increase of power consumption and area of paved road and decrease of area of cropland caused the growth of UHI intensity. Green land had a positive effect on mitigation of heat island based on an inversed U-shaped curve with UHI intensity.

Temporal variations of surface water quality in urban, suburban and rural areas during rapid urbanization in Shanghai, China.

As the economic and financial center of China, Shanghai has experienced an extensive urban expansion since the early 1980s, with an attendant cost in environmental degradation. We use an integrated pollution index to study the temporal variations of surface water quality in urban, suburban and rural areas between 1982 and 2005. Data on monitored cross-sections were collected from the Shanghai Environmental Monitoring Center. The results indicated that the spatial pattern of surface water quality was determined by the level of urbanization. Surface water qualities in urban and suburban areas were improved by strengthening the environmental policies and management, but were worsening in rural areas. The relationship between economic growth and surface water quality in Shanghai showed an inversed-U-shaped curve, which reflected a similar pattern in most developed countries. This research suggests that decision makers and city officials should be more aware of the recent pollution increases in Shanghai.

[Age structure and growth characteristic of Castanopsis fargesii population].

In this paper, the age structure and growth characteristics of Castanopsis fargesii population in a shade-tolerant broadleaved evergreen forest were studied, aimed to understand more about the regeneration patterns and dynamics of this population. The results showed that the age structure of C. fargesii population was of sporadic type, with two death peaks of a 30-year gap. This population had a good plasticity in growth to light condition. Because there were no significant differences in light condition under the canopy in vertical, the saplings came into their first suppression period when they were 5-8 years old, with a height growth rate less than 0. 1 m x a(-1) lasting for 10 years. The beginning time of the first growth suppression period was by the end of the first death peak of the population, and the ending time of the first growth suppression period was at the beginning of the second death peak of the population, demonstrating that growth characteristic was the key factor affecting the age structure of C. fargesii.

[Effect of Suining Tributary ecoremediation to all size-fractionated chlorophyll-a contents].

Through analysis of the size-fractionated chlorophyll-a contents in the remedied part, control part and non-remedied part in Suining Tributary, this paper discussed the effect of bioremediation to all size-fractionated chlorophyll-a contents. The averaged Chlorophy-a content of nano-plus pico-phytoplankton made up 85.232%, 92.402%, 95.205% of the total, respectively for the remedied, control and non-remedied part. Among these, the nano fraction alone made up 78.460%, 87.943%, 87.211%, respectively. Nano-phytoplankton contributed most to the total biomass of Chl a. Its average contribution was 84.538% to the whole tributary, whereas net-phytoplankton contribued only 9.054%. Nano- and pico-phytoplankton was most sensitive to the test eco-remedy. The remedy reduced the relative biomass of net-phytoplankton, and increased the relative biomass of Pico-enhance. The relative biomass of nano- and ultra-phytoplankton fraction was little effected.

[A review on mast seeding studies].

Mast seeding means that the plants of a population have a highly variable seed production in different years synchronously, and it is widely existed in perennial plants. The periodic variation of seed yield and synchrony of seed production among individuals are the key characteristics. Several hypotheses, including evolutionary bases and limitations of mast seeding, were reviewed in this paper. Moreover, the synchronous degree among individuals was discussed, and the temporal permanence and spatial heterogeneity were emphasized.