Five provinces located in the five main rice-growing regions in China were selected as study areas, which were Jiangsu, Heilongjiang, Sichuan, Guangdong and Hunan province respectively in the middle and lower reaches of the Yangtze River, northern, southwest, southern and central rice districts. Carbon footprints of rice production in these five provinces were calculated through the life cycle assessment method using governmental statistical data, industrial standards and relevant technical data separately. Material and energy consumptions were estimated, key stages of energy consumptions and carbon emissions were identified as well. Moreover, improving measurements had been suggested correspondingly. The results indicated that: the energy consumptions of rice production in these five provinces ranked as following (high to low): Guangdong, Heilongjiang, Hunan, Sichuan and Jiangsu. The carbon footprints of rice production were 2504.20 kg carbon dioxide equation per ton rice (kgCO -eq./t) (Guangdong province), 2326.47 kgCO -eq./t (Hunan province), 1889.97 kgCO -eq./t (Heilongjiang province), 1538.90 kgCO -eq./t (Sichuan province) and 1344.92 kgCO -eq./t (Jiangsu province) respectively. Reducing the quantities of urea and using the intermittent irrigation method could decrease energy consumption as well as carbon footprint.
L. (Chenopodianceae) is an annual halophytic species. Experiments were carried out in laboratory to determine the effects of temperature, perianths and various types of salinity on seed germination and germination recovery. Seeds were germinated at 6 levels of temperature with perianths, plus perianths and removed perianths in complete darkness for 9 days. The germination responses of the seeds without perianths at 25 °C were determined over a wide range of NaCl, NaHCO or NaCl–NaHCO mixed stress for 13 days. Perianths seriously affected germination as a barrier for seed germination and the optimal temperature was at 25 °C. Highest germination percentage was obtained under control and seed germination was progressively inhibited with the increase of salinity concentration. The negative effect of NaHCO at the same concentration on germination was stronger than that of NaCl and NaCl–NaHCO mixed. When substrate salinity was removed, seeds exposed to a high NaCl concentration (400–800 mM), NaHCO (50–200 mM) and NaCl–NaHCO mixed (100–400 mM) germinated well. Final germination of seeds was significantly affected by types of salt at the low salinity (⩽200 mM) and with increased salinity it was influenced mainly by salinity concentration for various proportion of salt–alkali mixed stress.
Seeds of both and have high germination level and germination speed, and form a transient seed bank in nature. The impacts of storage period and condition on germination level and speed were assessed in the two species. Storage for three months significantly increased both germination level and speed of seeds stored under the different conditions, compared to that of fresh seeds. In both species, nine months storage did not affect germination percentage in cold storage seeds, but completely inhibited it in field seeds. Storage for longer time in room and warm temperatures resulted in significant reduction or complete inhibition in the germination of the two species, so this was more pronounced in . Storage significantly increased germinate rate index of seeds stored in all conditions till 17 months in and till 12 months in . In both species, fridge storage had little effects on final germination and germination speed of seeds incubated at the different temperatures, compared to fresh seeds. However, room temperature and warm storages significantly reduced final germination and germination speed at the different temperatures, so the reduction was more pronounced at 35 °C, especially in .
Some kinds of agricultural castoffs such as sawdust (SD) and the powder of coconut coir (PCC) were used as growing media to substitute peat moss for the New Guinea Impatiens. It showed that all the substitute media should fit for the growth of the root system without disturbing the spatial development of the root. The growths of the plants in substitute media are all exceeded that in PM or only below the contrast indistinctly. The comprehensive indexes of plants in PCC and SD are 0.76 and 0.98, and the comprehensive indexes of plants in PSS and PPH are all higher than that in PM. It means that those four kinds of substitutes can be used to take the place of the peat moss totally as soilless growing media. In the period of 50–100 s, the differences of the Ultra-Weak Photon Intensity of the leaves among all the treatments are different significantly, and the trend is similar to that of the root. The photosynthesis of the New Guinea Impatiens is very different to the data of morphology evaluation indexes. There is no noticeable effect of the growing medium itself on the elements contents of the plant. The determinant may be the nutrients solution. There is no significant difference of the contents of chlorophyll in the plant that was planted in the substitute media between the PM. Under almost the same growth conditions, the Hoagland nutrients solution can make a steady and balanced supply of nutrients for the plant which cannot be evidently disturbed by the type of media. The substitute media have lower performance of preserving moisture and fertility, under normal cultivating conditions, the plants developed well, but in order to keep the plant in good condition, the substitute media depends more on extraneous nutrients from nutrients solution than PM.
Maize is one of the most widespread grain crops in the world; however, more than 70% of corn in China suffers some degree of drought disaster every year. Leaf area index (LAI) is an important biophysical parameter of the vegetation canopy and has important significance for crop yield estimation. Using the data of canopy spectral reflectance and leaf area index (LAI) for maize plants experiencing different levels of soil moisture from 2011 to 2012, the characteristics of the canopy reflective spectrum and its first derivative, and their relationships to leaf area index, were analyzed. Soil moisture of the control group was about 75% while that of the drought stress treatment was about 45%. In addition, LAI retrieval models for maize were established using vegetation indices (VIs) and principal component analysis (PCA) and the models were tested using independent datasets representing different soil water contents and different developmental stages of maize. The results showed that canopy spectral reflectances were in accordance with the characteristics of green plants, under both drought stress and at different developmental stages. In the visible band, canopy reflectance for both healthy and damaged vegetation had a green-wavelength peak and a red-wavelength valley; reflectance under drought stress, especially in the green peak (about 550 nm) and the red valley (about 676 nm) was higher than in the control group. In the near-infrared band, the canopy spectral reflectance decreased substantially between 780 and 1350 nm under drought stress. Moreover, the red edge of the spectrum was shifted toward blue wavelengths. The first derivative spectrum showed a double peak phenomenon at the edge of the red band at different developmental stages: the main peak appeared between 728 and 732 nm and the minor peak at about 718 nm. The double peaks become more obvious through the growth and development of the maize, with the most notable effect during the silking and milk stages, after which it gradually decreased. During maize growth, the LAI of all plants, regardless of soil moisture conditions, increased, and the largest LAI also occurred during the silking and milk stages. During those stages, the LAI of plants under different drought stress levels was significantly lower (by 20% or more) than in normal plants with sufficient water supplies. The LAI was highly significantly correlated with canopy spectral reflectance in the bands from 350 nm to 510 nm, from 571 nm to 716 nm, and from 1450 nm to 1575 nm. Also, the LAI was significantly correlated with red edge parameters and several VIs. The Perpendicular Vegetation Index (PVI) had the best correlation with LAI, with a coefficient of determination ( ) of 0.726 for the exponential correlation. Using dependent data, a LAI monitoring model for the maize canopy was constructed using PCA and VI methods. The test results showed that both the VI and PCA methods of monitoring maize LAI could provide robust estimates, with the predicted values of LAI being significantly correlated with the measured values. The model based on PVI showed higher precision under the drought stresses, with a correlation coefficient of 0.893 ( = 27), while the model based on PCA was more precise under conditions of adequate soil moisture, with a correlation coefficient of 0.877 ( = 32). Therefore, a synthesis of the models based on both VI and PCA could be more reliable for precisely predicting LAI under different levels of drought stresses in maize.
We studied for two years the seasonal changes in plant available nitrate and ammonium nitrogen (N), nitrification, N-mineralization, microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) in two forest and three cropland sites, derived from a tropical forest ecosystem of India. Results indicated that seasonal values of nitrate N, ammonium N and phosphate P ranged from 7.33–12.99, 5.1–10.22 and 4.0–7.8 μg g in forest and 4.13–9.26, 9.35–14.46 and 2.8–5.8 μg g in cropland ecosystems, respectively, with maximum values in summer and minimum in rainy seasons. Nitrification and N-mineralization values varied from 6–28 and 4–26 μg g mo in forest and 3–14 μg g mo and 4–17 μg g mo in cropland, with maximum values in rainy season and minimum in summer season. MBC, MBN MBP ranged from 393–753, 34–80 and 16–36 μg g in forests and 186–414, 21–41 and 11–22 μg g in croplands, being maximum in summer and minimum in rainy seasons. There was gradual increase in the values of inorganic N, nitrification, N-mineralization and MBC, MBN and MBP along the age of cropland. Analysis of variance indicated significant difference in the concentration of inorganic N, nitrification and N-mineralization and MBC, MBN and MBP due to sites and seasons. Cultivation caused decline in the mean annual organic C, N and P by 42%, 29% and 13%. The values of nitrate N were decreased by 23–38%, while ammonium N was increased by 39–74%. Nitrification and N-mineralization values were reduced by 39–63% and 40–60%, respectively. Microbial C, N and P were reduced by 44–54%, 41–50% and 28–44%, respectively. Nonetheless, the contribution of soil microbial biomass reflected in total N was enhanced from 4.76% in forest to 5.03% in cropland ecosystem. Enhancement of plant available ammonium-N and microbial contribution in total N are an indicator of natural conserving mechanism to check the nitrogen loss from the nutrient poor agro-ecosystem.
Wetlands provide a large pool of organic matter and nutrients, and are important for maintaining material cycle balances in terrestrial ecosystems, and also help retard climate change. Land use changes in wetlands have greatly disturbed the natural evolution of wetland ecosystems. Wetland drainage and reclamation alters the physical, chemical and biological conditions of the wetland, thus significantly disturbing the material cycles, leading to significant changes in the biogeochemical processes of carbon, nitrogen and phosphorus in the wetland. The wetlands in the Sanjiang Plain are the largest area of fresh wetlands in China. However, the area has experienced major land uses changes since the 1950s; areas of the wetland have been drained and converted to arable land. Some studies have been conducted into the effects of land use change on material cycles in the Sanjiang Plain wetlands but few reports have discussed the C/N and C/P ratios and pH values as indicators of wetland degradation due to land use changes. We selected eight land uses: humus marsh (HM), marshy meadow (MM), drained humus marsh (DHM), drained marshy meadow (DMM), tillage land (TL), abandoned land (AL), natural secondary forest (NSF) and artificial forest (AF), in the Honghe area of the Sanjiang Plain. We studied changes in the total organic carbon (TOC), total nitrogen (TN), total phosphorus (TP), C/N and C/P ratios and pH values in topsoil (0–20 cm) of these eight different land uses. The possible mechanisms underlying the changes, and the significance of the C/N and C/P ratios as indicators of soil quality were also discussed. In the natural wetland, the TOC, TN and TP concentrations in the soil were high, with values of 203.5 g/kg, 20.2 g/kg and 1.44 g/kg, respectively, in HM; and 59.2 g/kg, 5.28 g/kg and 0.83 g/kg, respectively, in MM. Drainage of the HM has led to decreases in the TOC, TN and TP concentrations of about 50%. Significant decreases were also observed in TOC, TN and TP for NSF and AF compared to HM. Drained MM led to decreases in the TOC and TN of about 45%, but had little effect on TP. Marshy meadow that had been drained for more than 10 years experienced an exponential decline in TOC, TN and TP, with decreases of more than 60% for TOC and TN, and 20% for TP. However, after being abandoned for a short time (5 years), the TOC, TN and TP concentrations in soil experienced little change because poor water conditions combined with low productivity led to a large loss of soil organic matter. Land use change in the marsh areas has led to a decrease in C/N and C/P ratios of the soil, which are positively related to TOC and TN with different land uses ( < 0.05). Marsh reclamation has led to decreasing C/N and C/P ratios in soil and increasing pH values, which are negatively related to TOC, TN and TP ( < 0.05). Changes in carbon, nitrogen and phosphorus in soil with different land uses were mainly regulated by water-heat conditions and microbial activity, while the C/N and C/P ratios were mainly regulated by substrate availability. Our results suggest that C/N and C/P ratios and the pH value could be used as indicators to evaluate the quality and nutrient status of wetland soil under different land uses.
Since the water storage was initiated in 2003, the environment of Three Gorges Reservoir (TGR) has changed significantly. Algal blooms and eutrophication have been a frequent occurrence, with serious eutrophication in the tributary bays. To provide some theoretical evidence for the prevention and control of algal blooms, the goal of this study is to elucidate factors that influence algal blooms at different sections of the Xiangxi Bay (XXB). Using field data from the XXB, the responses of phytoplankton communities to their habitats were investigated from March to May, 2010. The results indicated a significant spatial and temporal heterogeneity in phytoplankton composition, cellular abundance, and habitats in the spring. Fifty-four genera representing 6 phyla were monitored. Redundancy analysis indicated that the variation in water temperature and relative water column stability (RWCS) contributed greatly to the succession of spring phytoplankton. Due to different physiological adaptabilities and mechanisms of competition among the algae species, significant succession of the community structure had been observed. The predominant species appears to have changed from those adapted to low temperatures and strong mixing (dinoflagellates and diatoms) to those adapted to high temperatures and weak mixing (green algae and cyanobacteria). The lack of silicate resulted in the succession from diatoms to green algae. Due to the influence of the Yangtze River, there is a low potential for algal blooms at lower reaches of the bay because of frequent water exchange. In contrast, the potential is high at middle and upper reaches where the water temperature increases gradually. The hierarchical status of the two sections is significantly different. Precipitation would inhibit algal blooms somewhat, and heavy rainfall would eliminate algal blooms throughout the bay. Phytoplankton are sensitive to their changing habitat in XXB. For a bloom to occur, sufficient nutrients, a lower flow velocity, and appropriate temperature and light conditions are necessary. As an artificial regulating reservoir, proper ecological regulation could not only significantly affect the dynamic conditions of the water body tributaries, but it could also change the transfer characteristics of light and heat, abolishing the algae habitats and thereby inhibiting the water bloom.
Analyzing the relationship between species and environment is always a focal question of ecological research. In recent years species distribution models (SDMs) has been widely used to predict the spatial distribution of species. SDMs are numerical tools that combine observations and species occurrence or abundance with environmental variables to predict the spatial distribution of species across landscapes, sometimes requiring extrapolation in space and time. (Taiwan red cypress, TRCs) is a coniferous species endemic to Taiwan, where it natural grows in the central mountains at moderate to high altitudes of 800–2800 m, and most stands in the range of 1500–2150 m. It is threatened by habitat loss and over-cutting for its valuable timber. To preserve TRCs species and achieve sustainable use of biological resources, we choose TRCs as a target for the study to predict its distribution in central Taiwan. The pure forests of TRCs in the study area were mainly located in Pachsienshan (P), Shouchentashan (S) and Baigou Mountain (B) in central Taiwan, and the distribution data were originally obtained by The Third Survey of Forest Resources and Land Use in Taiwan. Elevation, slope, aspect, and three vegetation indices were derived from both SPOT-5 satellite images and DEM. GIS technique was used to overlay those factors. Discriminant analysis (DA), decision tree (DT) and maximum entropy (MAXENT), three commonly used SDMs, were applied based on above-mentioned six variables to predict the suitable habitat of TRCs, and to evaluate which the best model is in terms of accuracy and efficiency. Three experiment designs (ED1, ED2 and ED3) with different combinations of samples were used for model building and validation. The 200 target samples were collected from the site P–B, B–S and P–S for model building under ED1, ED2 and ED3 respectively, while the 100 samples were collected from the site S, P and B for model validation. All experiment designs had same 1350 background samples. The results showed that the overall accuracy and kappa coefficient of DT (96%, 0.88) was higher than that of MAXENT (91%, 0.70), and their accuracies were better than that of DA (84%, 0.58). All the three models were highly efficient in implementation of model construction and evaluation, while the DT model was difficult for generating the entire predicted map of potential habitat due to its complex conditional sentence. Vegetation indices derived from SPOT-5 satellite images could not improve model accuracy because of its insufficiency of spectral resolution and spatial resolution. High spatial resolution and spectral resolution remotely sensed imagery should be used in our future research to improve model performance and reliability.
Since the beginning of the 21st century, the global warming trend is an increasing cause for concern. Frequent extreme weather events occur under the conditions of global change. Exploring the relationship between climate change and drought disasters using climate change performance characteristics has become a prime research problem. It is increasingly important to study the temporal and spatial distribution of aridity and drought causes in the southwest region. We collected meteorological data from 16 meteorological stations from 1956 to 2010 in Yunnan Province of Southwest China, and used a composite index (CI) of meteorological drought to analyze temporal and spatial characteristics of droughts in the province. Based on daily CI values of each station during the 50 years, drought processes there were confirmed individually. Occurrence frequencies, scopes and severities of meteorological droughts were computed and analyzed to reveal their temporal and spatial occurrence patterns in different parts of the province. The results are as follows: (1) Temperature in the province, showing the well-being of the turn, has an obvious 4-year principal cycle. Temperature gradually rose after 1980. Fluctuation of precipitation was relatively stable, with a cycle of about 2 years. (2) On the spatial scale, drought occurred over wide areas in the province. Its overall distribution showed a gradual increase from northwest to southeast. Drought days were the most numerous in the southeast, and fewer in the southwest. (3) Examining seasonal variation, the occurrence of spring droughts was high. The multi-year average of drought frequency exceeded 70%. The frequency of summer and autumn drought was less, and that of winter drought was highest. (4) The causes of drought are complex, comprising the combined effects of atmospheric circulation, geography, and human factors. There was a strong negative correlation between the interannual variation of drought days and precipitation anomaly values. With warming temperatures, the chances for regional drought significantly increased, but the interaction mechanism remains unexplained and should be explored in the future. The climate in Yunnan Province has typical characteristics. The temperature and extreme weather of recent years has certainly changed in response to global climate change, and has caused regional disasters. The aforementioned mechanism represents the next research direction.
The impact of land-cover types on soil erosion and runoff, as well as on physico-chemical soil properties, was monitored. The study area, an agroforestry landscape was located in Sierra Nevada Mountains in south-eastern Spain. Eight land-cover types were investigated: farmland planted with olive, almond, and cereals; forest with and ; shrubland; grassland; and abandoned farmland. The erosion plots replicated twice were located on hillslopes, where erosion and runoff were measured after 22 storm events. Forest dominated by stands exhibited significantly the lowest amounts of erosion and runoff, contrasting with abandoned farmland. Olive had higher erosion than did almond, cereals, or grasslands, but with the highest runoff rate under almond groves. The erosion and runoff response to shrubland showed an intermediate situation between forest and farmland–grassland uses. Under forest and shrubland, better soil properties were determined, especially higher organic C and total N, and lower soil-bulk density. Erosion was highly dependent on runoff, bulk density, soil organic C, and the degree of soil surface covered. Thus, the alteration in land cover is essential to an understanding of productivity of soil undergoing erosion, as sustainable planning can mitigate soil-degradation processes in the overall agroforestry landscape.
To clarify how dung patches from grazing yaks affect soil and pasture in the alpine meadow of Qinghai-Tibetan Plateau, yak dung was collected, mixed and redistributed in a cold grazing season. The soil physical and chemical properties and forage growth were then monitored under the yak dung patch, and 10 cm and 50 cm from the edge of yak dung patches. The result has shown that yak dung significantly improved soil moisture, total organic matter, and soil available N and P under or close to the dung patches. The forage production at 10 cm from the dung patch (303 g/m ) was significantly higher than that at 50 cm from the dung patch (control) (284 g/m ) in the second year, while the production was similar to the control in the first and the third year. The process of yak dung decomposition was slow and yak dung remains were observed 3 years after the drop. The dung patches also formed a strong ‘shell’, very difficult for plant underneath to penetrate and grow. Therefore, almost all plants under yak dung patches died, leading to decline in forage yield in the first, second, and the third year. In practice in the Qinghai-Tibetan Plateau regions, yak dung is often collected as fuel by the local farmers. Removing yak dung from alpine meadow may on one hand lead to losses in soil nutrients, but on the other hand reduces some of the negative effects, e.g. the reduction of forage yield under yak dung patches.
Plant growth, biomass allocation, root distribution and plant nutrient content were investigated in the submerged macrophyte growing in heterogeneous sediments. Three experimental sediments heterogeneous in nutrient content and phosphorus release capacity were used: sandy loam with low nutrient content (A), clay with intermediate nutrient content (B), and clay with high nutrient content (C). Biomass accumulation was significantly affected by the sediment type, and was highest in clay C (1.23 mg per plant dry weight) but lowest in sandy loam (0.69 mg per plant dry weight). The root:shoot ratios in treatments A, B and C were 0.30, 0.14 and 0.09, respectively. . allocated more biomass to roots in sandy loam compared with the other sediments. The average root numbers in sediments A, B and C were 16, 19 and 20, respectively, and the total root lengths in sediments A, B and C were 238.84, 200.36 and 187.21 cm, respectively. Almost 90% of the root biomass was distributed in the 0–15 cm depth in sediments B and C, compared with 64.53% in sediment A. The rank order of plant nitrogen and phosphorus concentrations in the sediment types was C > B > A. These results indicate that both sediment structure and nutrient availability influence the growth and distribution of the root system of . .
Establishing nature conservation reserves is an effective and widely accepted practice to protect biodiversity. In order to promote the effectiveness and efficiency of the reserve, spatial attributes of the reserve should be considered. Connectedness (contiguity) is one of these important spatial attributes. Currently in the biological literature there are only a few formal/exact optimization approaches to endogenously designing a connected nature reserve. This article adds a new approach by adapting a spatial unit allocation model to the reserve design problem. Using concepts from network flow theory, the model defines a sink site from which no flow directs out and ensures contiguity by specifying the outflow and inflow relationship of the potential sites. Computational performance of the model is tested using hypothetical problems with various sizes including up to 400 potential sites. Results show that the time needed to solve the problem to optimality increases exponentially both as number of potential sites increases and as species distribution gets more sparse. An empirical application involving 80 potential sites and 15 bird species in part of Fox River watershed, Illinois USA is presented. Factors influencing an IP model’s computational performance and potential extensions of the model were discussed.
Interspecific niche differentiation has attracted much more attention than intraspecific niche differentiation. If the intraspecific competition of invasive species is greater than the interspecific competition, it should reduce the invasive abilities of invasive species. Thus, it is important to understand how invasive species avoid or reduce the intraspecific competition. in southern China is more competitive than many trees. After it invades a community, it can displace other trees. In the current study, we tested whether the different aged bamboo plants (aged two to eight in two-yr increments) exhibited spatial segregation (spatial niche differentiation). The study was performed in the Ecological Station of Dagang Mountain (114°30′∼114°45′E, 27°30′∼27°50′N), about 200 km east from Nanchang City, Jiangxi province, China. We recorded the planar coordinates of all the plants with diameter at breast height (DBH) ⩾3 cm. We used the conditional probability (type-specific probability) surface to show the spatial niche differentiation. We also compared the DBH of four aged groups of bamboo plants. We used the Shapiro–Wilk test to test the normality of DBHs of each age group. If DBHs did not follow the Normal distribution, we used the Weibull function to fit these data. Then we used the Kolmogorov–Smirnov test to test whether any two aged groups of DBHs came from the same population. At the end, we used the generalized additive models (GAMs) and a local regression model (LOESS) to explore whether there is a correlation between DBHs and the corresponding planar coordinates. We found that there was significant spatial segregation in four aged groups based on the statistical test. Bamboo plants may reduce their intraspecific competition by spatial niche differentiation. We found that the DBHs approximated the Weibull distribution, and there were very weak relationships between the DBHs and the spatial locations. We concluded that different aged bamboo plants exhibited spatial segregation and may reduce their intraspecific competition by spatial niche differentiation.
Gongga Mountain is a unique mountain in western China which has not only modern low-latitude glaciers, but also an integrated vertical vegetation distribution from subtropical forests to tundra. Our study aimed to understand the soil fertility status of subalpine and alpine ecosystems in this region through measuring the soil available nitrogen (SAN), dissolved organic carbon (DOC) and soil microbial biomass (SMB) along the eastern slope of Gongga Mountain. We found that the SAN, DOC and SMB varied along the altitudinal gradient, and decreased from the soil surface to subsurface, probably due to the different return plant residue, decomposition rate, as well as temperature and moisture in different elevations. The range of −N content was from 1.7 mg kg to 134.2 mg kg ; + −N was from 2.6 mg kg to 202.0 mg kg ; DOC was from 30.6 mg kg to 610.2 mg kg ; soil microbial biomass carbon (SMBC) was from 41.4 mg kg to 2538.5 mg kg ; and soil microbial biomass nitrogen (SMBN) was from 0.6 mg kg to 410.7 mg kg . SAN, DOC and SMB were all significantly related to each other, indicating that all these three indexes are dependent on soil organic matter. At last, the ratio of SMBC to SMBN ranged from 2.4 to 65.3, mostly less than 6.0, which meant the bacteria dominated the soil microbial community in our study sites.
The impact of conservation tillage practices on soil carbon has been of great interest in recent years. Conservation tillage might have the potential to enhance soil carbon accumulation and alter the depth distribution of soil carbon compared to conventional tillage based systems. Changes in the soil organic carbon (SOC) as influenced by tillage, are more noticeable under long-term rather than short-term tillage practices. The objective of this study was to determine the impacts of long-term tillage on SOC and dissolved organic carbon (DOC) status after 19 years of four tillage treatments in a Hydragric Anthrosol. In this experiment four tillage systems included conventional tillage with rotation of rice and winter fallow system (CTF), conventional tillage with rotation of rice and rape system (CTR), no-till and ridge culture with rotation of rice and rape system (NT) and tillage and ridge culture with rotation of rice and rape system (TR). Soils were sampled in the spring of 2009 and sectioned into 0–10, 10–20, 20–30, 30–40, 40–50 and 50–60 cm depth, respectively. Tillage effect on SOC was observed, and SOC concentrations were much larger under NT than the other three tillage methods in all soil depths from 0 to 60 cm. The mean SOC concentration at 0–60 cm soil depth followed the sequence: NT (22.74 g kg ) > CTF (14.57 g kg ) > TR (13.10 g kg ) > CTR (11.92 g kg ). SOC concentrations under NT were significantly higher than TR and CTR ( 0.05). In conclusion, NT increased SOC concentration and storage compared to conventional tillage operation but not for DOC.
Allelopathic potential of sunflower ( L.) fresh plant tissues aqueous extraction in bioassay, rhizosphere soil in pot experiment and phytotoxicity of decomposed sunflower plant biomass in bioassay against , , and was investigated. In bioassay aqueous extracts of fresh sunflower plant tissue inhibited the germination, seedling growth (shoot and root) and dry matter accumulation of test plant species. In pot study sunflower rhizosphere soil inhibited growth attributes (plant height, population, number of branches) and yield attributes (grain yield, biomass yield) of selected crops and weeds. Phytotoxicity of decomposed sunflower biomass showed inhibitory effect on selected plant species. The fresh plant tissues was greatest inhibitory to test plants and followed by that of the decomposed biomass extracts in all bioassays. Significant reductions in the root and shoot growth were observed as the extract concentration was increased. The concentrations of extract fraction of fresh sunflower was determined, since nine compounds i.e. ferulic, p-coumaric, syringic, chlorogenic acid, isochlorogenic acid, neochlorogenic acid, vanillic acid, p-hydroxybenzoic acid, caffeoylquinic acid, found to be main growth inhibitors in sunflower plant tissue. These results suggested that sunflower plants may possess allelopathic potential, and the plant tissues may be potentially useful for weed management.
The endolithic environment is a ubiquitous microbial habitat for microorganisms, such as lichens, Cyanobacteria and fungi, and it provides mineral nutrients and growth surfaces. In extremely environments, such as hot and cold desert, endolithic communities are often the main form of life. More recently, endolithic microbial communities have been observed inhabiting a variety of rock types ranging from hard granite to porous rocks such as basalt, dolomite, limestone, sandstone and granites. Regardless of geographic location and rock type, each of these habitats is characterized by a subsurface microclimate that prevents endolithic microorganisms growth. Photosynthesis-based endolithic microbial communities commonly inhabit the outer millimeters to centimeters of rocks exposed to the surface. The ability to fix carbon dioxide and in some cases atmospheric dinitrogen, gives the Cyanobacteria a clear competitive advantage over heterotrophic bacteria, so it is been called the main primary producer. Light quality and intensity appear to be the main determinant of the maximum depth to which growth occurs in endolithic phototrophic communities. Valleys of Fantastic Rocks in Bole is close to Alashankou Port of Xinjiang which belongs to extreme continental climate. In order to investigate the structure, composition and diversity of endolithic bacterial community in exposed granitic porphyry in the Valleys of Fantastic Rocks, environmental DNA was directly extracted from granite rock, the 16S rRNA genes were amplified from the total DNA by PCR with bacterial-specific primers, and an endolithic bacterial clone library was constructed. Positive clones were randomly selected from the library and identified by Restriction Fragment Length Polymorphism (RFLP). The unique rRNA types clones were sequenced, analysised and then constructed phylogenetic tree. In total, 129 positive clones were screened and grouped into 46 operational taxonomic unites (OTUs). The clone coverage value was 89.15%, indicating that most of the estimated endolithic bacterial diversity was sampled. BLAST analysis indicated that 46 OTUs were divided into seven phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Cyanobacteria, Planctomycetes, Proteobacteria) and five unknown groups. Cyanobacteria (43%), especially the Gp I, form the functional basis for an endolithic bacteria community which contain a wide spectrum species of chemotrophic bacteria (33%) with mainly Actinobacteria, α-Proteobacteria, Acidobacteria. Additionally, most clones that derived from the endolithic bacteria clone library showed high similarity to the sequence deposited in GenBank database with 97%–99%. Besides, 35% of the clones showed less than 97% of sequence similarity, of which 12% sequences were affiliated to genus The results suggested that endolithic bacteria in Valleys of Fantastic Rocks in Xinjiang were highly diverse in species richness, and maybe have a diversity of potential novel species and lineages.
Many studies concerning wetland loss have been conducted in the last two decades. However, tidal freshwater marsh’s research topics, mirroring hot points, vary in scientific community and change over time. A bibliometrical analysis method is demonstrated in this paper to describe tidal freshwater marsh research and changes in the research over time. For example, habitat restoration, soil composition, plantation pattern and coastal wetland have drawn increasing attention since 2005. The bibliographic methods described in this paper involved the use of 54 case studies to find critical paths regarding how tidal freshwater wetland loss has been induced by different causes. From case studies, it has been concluded that urbanization is the most important cause of tidal freshwater marsh loss. Critical paths of tidal freshwater marsh loss driving forces have been also demonstrated in this paper.