Wood is the product of cambial activity in trees, and the seasonal activity style of cambium directly influences wood biomass production, structures and properties. The seasonal changes in the ultrastructure of the va...Wood is the product of cambial activity in trees, and the seasonal activity style of cambium directly influences wood biomass production, structures and properties. The seasonal changes in the ultrastructure of the vascular cambium activity of Populus tonientosa Carr. planted in Beijing area were examined in shoot tissues collected during 15 months by means of transmission electron microscopy. Before xylem mother cells reactivated completely, the dividing fusiform cells in cambium and new phloem cells had appeared at the same time. The initiation of cambial activity may be related to the bud sprouting and the young leaf growth in shoots. More details about the ultrastructural changes of cambial cells at the onset of cambial activity have been gained. When the large vacuole in active cambial cells divided into smaller ones during the dormant phase, proteinaceous material that disappeared in active cambial cells refilled many of these small vactioles. In addition, lipid droplets and starch granules had the same cycles as proteinaceous material. The plasmalemma invaginations of fusiform cells were observed not only in active phase but also in dormancy. The endomembrane system consisting of nuclear membrane, endoplasmic reticulum (ER), dictyosomes and their secretory vesicles, changed in form and distribution at different phases during a cycle and performed important roles at the onset of active cambium and during the wall formation process of secondary xylem cells. The tangential walls remained relatively thin throughout the year but the radial walls thickened markedly when the cambium was dormant. During the transition from dormancy to activity, a partial autolysis occurred in the radial walls of the cambial cells, especially at the cell wall junctions. A notable feature of the cells at the onset of cambial activity was the thinning of the radial walls.展开更多
In the light of the national policy of fallow, this study was conducted to determine how the different water management and lime application would affect soil physical and chemical properties, rice yield and cadmium ...In the light of the national policy of fallow, this study was conducted to determine how the different water management and lime application would affect soil physical and chemical properties, rice yield and cadmium (Cd) content of rice in fallow season. The results showed that, compared with the arid fallow, the waterlogging fallow decreased the soil pH value whereas signifcantly increased the soil organic matter content and the cation exchange quantity, and reduced the soil effective cadmium content and the rice cadmium content whereas could increase the rice yield to a certain extent. In the fooded fallow or the dry fallow, the application of lime mainly depended on the alkali conditioning of lime and the antagonistic effect of Ca2+, which could signifcantly reduce the cadmium content of rice, and its effect would increase linearly with the increase of lime dosage, whereas had no significant effect on soil organic matter content and cation exchange quantity. In order to establish a linear equation of lime dosage and related indexes under the condition of waterlogging fallow or dry fallow, calculations showed that each application of lime at 1 000 kg/hm2 or kg/hmss2 could improve soil pH value by 0.238 2 or 0.246 5units respectively, and reduce the effective Cd content to 0.007 5 mg/kg both in the arid fallow and the waterlogging fallow conditions. The lime theoretic application rate for the lowest Cd content of late rice in the arid fallow was 5 120 kg/hm2, and the minimum limit of the Cd content in rice was 0.124 2 mg/kg; and the lime theoretic application rate for the highest yield of late rice in the submerged water fallow was 4 636 kg/hm2, the minimum theoretic Cd content in rice is 0.100 7 mg/kg, and it could reduce the Cd content in rice under the condition of submerged fallow and decrease the dosage of lime.展开更多
In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model...In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model was used to study the seasonal variations of vertical profiles of chlorophyll-a(Chl-a) in the SCS. Three parameters(i.e., SCM layer(SCML) depth, thickness, and intensity) were defined to characterize the vertical distribution of Chl-a in SCML and were obtained by fitting the vertical profile of Chl-a in the subsurface layer using a Gaussian function. The seasonal variations of SCMs are reproduced reasonably well compared to the observations. The annual averages of SCML depth, thickness, and intensity are 75 ± 10 m, 31 ± 6.7 m, and 0.37 ± 0.11 mg m-3, respectively. A thick, close to surface SCML together with a higher intensity occurs during the northeastern monsoon. Both the SCML thickness and intensity are sensitive to the changes of surface wind speed in winter and summer, but the surface wind speed exerts a minor influence on the SCML depth; for example, double strengthening of the southwestern monsoon in summer can lead to the thickening of SCML by 46%, the intensity decreasing by 30%, and the shoaling by 6%. This is because part of nutrients are pumped from the upper nutricline to the surface mixed layer by strong vertical mixing. Increasing initial nutrient concentrations by two times will increase the intensity of SCML by over 80% in winter and spring. The sensitivity analysis indicates that light attenuation is critical to the three parameters of SCM. Decreasing background light attenuation by 20% extends the euphotic zone, makes SCML deeper(~20%) and thicker(12% – 41%), and increases the intensity by over 16%. Overall, the depth of SCML is mainly controlled by light attenuation, and the SCML thickness and intensity are closely associated with wind and initial nitrate concentration in the SCS.展开更多
To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0-10 cm and 10-20 cm dept...To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0-10 cm and 10-20 cm depths were collected during the growing season of carrot. Indices were used to compare and assess the response of soil free-living nernatode communities to agricultural management. Eighteen nematode families and 20 genera were observed during the growing period, with Cephalobus, Rhabditidae, Aphelenchus, Tylenchus, and Dorylaimus being the dominant genera/families. During the planting, mid-season and post-harvest periods the total number of nematodes at both depths was significantly lower (P < 0.01) in the carrot treatment than in the control plots, while during the harvest period at both depths total nematodes and bacterivores were significantly higher in the treatment plots (P < 0.01). The values of the maturity index (MI) at both depths were found to be significantly lower in the treatment plots than in the control plots during the pre-planting period (P < 0.05). Overall, WI, MI and PPI were found to be more sensitive indicators than other ecological indices for assessing the response of nematode communities to agricultural management in a Mediterranean agroecosystem展开更多
Hendra virus,a novel member of the family Paramyxovirus that has emerged from bats in Australia,causes fatal disease in livestock and humans. Eleven spillover events have been identified since the first description of...Hendra virus,a novel member of the family Paramyxovirus that has emerged from bats in Australia,causes fatal disease in livestock and humans. Eleven spillover events have been identified since the first description of the virus in 1994,resulting in a total of 37 equine cases and six human cases. All human cases have been attributed to exposure to infected horses;there is no evidence of bat-to-human or human-to-human transmission. Low infectivity and a high case fatality rate are features of Hendra virus infection in both horses and humans. The temporal pattern of spillover events suggests seasonal factors(plausibly be environmental,biological or ecological) as the proximate triggers for spillover. Minimisation of the future occurrence and impact of Hendra virus infections requires an understanding of the ecology of flying foxes,of virus infection dynamics in flying foxes,and of the factors that promote spillover. Management strategies seek to minimize the opportunity for effective contact between bats and horses,and limit potential horse-to-horse and horse-to-human transmission. Incomplete knowledge of the ecology of the virus,of the proximate factors associated with spillover,and the inherent difficulties of effectively managing wild populations,preclude a management approach targeted at bats.展开更多
This paper addresses the impact of climate change on the water cycle and resource changes in the Eastern Monsoon Region of China (EMRC). It also represents a summary of the achievements made by the National Key Basi...This paper addresses the impact of climate change on the water cycle and resource changes in the Eastern Monsoon Region of China (EMRC). It also represents a summary of the achievements made by the National Key Basic Research and Development Program (2010CB428400), where the major research focuses are detection and attribution, extreme floods and droughts, and adaptation of water resources management. Preliminary conclusions can be summarized into four points: 1) Water cycling and water resource changes in the EMRC are rather complicated as the region is impacted by natural changes relating to the strong monsoon influence and also by climate change impacts caused by CO2 emissions due to anthropogenic forcing; 2) the rate of natural variability contributing to the influence on precipitation accounts for about 70%, and the rate from anthropogenic forcing accounts for 30% on average in the EMRC. However, with future scenarios of increasing CO2 emissions, the contribution rate from anthropogenic forcing will increase and water resources management will experience greater issues related to the climate change impact; 3) Extreme floods and droughts in the EMRC will be an increasing trend, based on IPCC-AR5 scenarios; 4) Along with rising temperatures of 1 ~C in North China, the agricultural water consumption will increase to about 4% of total water consumption. Therefore, climate change is making a significant impact and will be a risk to the EMRC, which covers almost all of the eight major river basins, such as the Yangtze River, Yellow River, Huaihe River, Haihe River, and Pearl River, and to the South-to-North Water Diversion Project (middle line). To ensure water security, it is urgently necessary to take adaptive countermeasures and reduce the vulnerability of water resources and associated risks.展开更多
Understanding streamflow changes in terms of trends and periodicities and relevant causes is the first step into scientific management of water resources in a changing environment. In this study, monthly streamflow va...Understanding streamflow changes in terms of trends and periodicities and relevant causes is the first step into scientific management of water resources in a changing environment. In this study, monthly streamflow variations were analyzed using Modified Mann-Kendall(MM-K) trend test and Continuous Wavelet Transform(CWT) methods at 9 hydrological stations in the Huaihe River Basin. It was found that: 1) streamflow mainly occurs during May to September, accounting for 70.4% of the annual total streamflowamount with Cv values between 0.16–0.85 and extremum ratio values between 1.70–23.90; 2) decreased streamflow can be observed in the Huaihe River Basin and significant decreased streamflow can be detected during April and May, which should be the results of precipitation change and increased irrigation demand; 3) significant periods of 2–4 yr were detected during the 1960 s, the 1980 s and the 2000 s. Different periods were found at stations concentrated within certain regions implying periods of streamflow were caused by different influencing factors for specific regions; 4) Pacific Decadal Oscillation(PDO) has the most significant impacts on monthly streamflow mainly during June. Besides, Southern Oscillation Index(SOI), North Atlantic Oscillation(NAO) and the Ni?o3.4 Sea Surface Temperature(Ni?o3.4) have impacts on monthly streamflow with three months lags, and was less significant in time lag of six months. Identification of critical climatic factors having impacts on streamflow changes can help to predict monthly streamflow changes using climatic factors as explanatory variables. These findings were well corroborated by results concerning impacts of El Nino-Southern Oscillation(ENSO) regimes on precipitation events across the Huaihe River Basin. The results of this study can provide theoretical background for basin-scale management of water resources and agricultural irrigation.展开更多
Soils play a critical role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecos...Soils play a critical role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecosystem in terms of water and nutrient uptake. In this study the effects of thinning and litter fall removal on fine root production and soil organic carbon content were examined in 20-year-old Masson pine (Pinus resinosa) plantations in Huitong, Hunan Province of China in the growing seasons of 2004 and 2005. The results showed that fine root production was significantly lower in the thinning plots than in the control plots, with a decrease of 58% and 14% in 2004 and 2005 growing seasons, respectively. Litter fall removal significantly increased fine root production by 14% in 2004. Soil temperature (Tsoil) and soil moisture (Msoil) were higher in the thinning plots than those in the controls. Litter fall removal had significant effects on Tsoil and Msoil. Soil organic carbon content was higher in the thinning plots but was lower in the plots with litter fall removal compared with that in the controls. Our results also indicated that annual production of fine roots resulted in small carbon accumulation in the upper layers of the soil, and removal of tree by thinning resulted in a significant increase of carbon storage in Masson pine plantations.展开更多
The results of the three-year researches which had the purpose to establish an optimum depth of seeding at sowing and rational norm of seeding of red beetroot seeds at under-winter sowing in conditions of mid-loamy ty...The results of the three-year researches which had the purpose to establish an optimum depth of seeding at sowing and rational norm of seeding of red beetroot seeds at under-winter sowing in conditions of mid-loamy typical grey soils of the central climatic zone of Uzbekistan are stated in article. The researches were spent at statement of field experiences in quadruple frequency with the area of a registration allotment 10 M^-1. Crops were carried out in the first decade of December against mulching surfaces of ridges by humus and without mulching. Crops were carried out on ridges in width of 70 sm tape-two-lined with distance between tapes of 50 sm, between lines-20 sm and distance between plants in a line of 12-13 sm, at density of standing of 228-230 thousand plants/hectares. Experiences were spent with zoned in Uzbekistan multi-seedling grade of a red beetroot "Bordo 237". Experiences were accompanied by phenological supervision, biometric accounts, the account of field germination of seeds, density of standing of plants and definition of size and quality of a crop. Results of researches were exposed to the statistical analysis by a dispersive method. It has been revealed that at under-winter sowing of a red beetroot the effective way providing acceleration of shoots occurrence, formations of high-grade density of standing and increase of productivity of root crops is mulching the surfaces of ridges by humus. It is defined that optimum depth of seeding at sowing both at application of mulching and without it is the depth of seeding 4 sm. It is established that the most rational norm of seeding of the seeds, providing high-grade density of standing, is at cultivation with application of mulching 8 kg/ha, and at cultivation without mulching 8-10 kg/ha. Application of mulching the surfaces of ridges by humus, depths of seeding of 4 sm and norms of seeding of seeds of 8-10 kg/ha in conditions of under-winter sowing in comparison with cultivation without mulching and depth of seeding 2 sm and norms of seeding of 6 kg/ha provides an acceleration of receipt of fresh production of a red beetroot for 12-14 days and considerably raises root crops productivity. Application of agro receptions improved by us is the important reserve of acceleration of receipt of red beetroot early production and increase of its manufacture.展开更多
The production of some seedless table grapes under tropical conditions presents low bud fertility on the main canes and low yield, which leads to the need of pruning in the lateral shoots. The objective of this study ...The production of some seedless table grapes under tropical conditions presents low bud fertility on the main canes and low yield, which leads to the need of pruning in the lateral shoots. The objective of this study was to evaluate the influence of the canopy management for the formation of lateral shoots associated with dellsity of canes on the yield and quality of grapes "Sugraone" in the Sao Francisco Valley. The experiment was carried out over two growing seasons (2011-2012) in a commercial vineyard of Sugraone in Petrolina, Pernambuco state, Brazil. The treatments consisted of two canopy managements (shoot topping associated to elimination of lateral shoots and shoot topping and formation of lateral shoots) combined with two to three densities of canes after pruning (1.8, 2.8 and 3.8 canes/m^2). The formation of "lateral shoots" increased yield and number of clusters per plant during two consecutive growing seasons, besides using 2.8 varas/m^2 resulted in highest yields only in 2011 growing season. The variables mass bunch, mass berry, soluble solids (SS), soluble sugar, titxatable acidity (TA) and pulp firmness were not affected by treatments, while the attributes related to color, as like brightness and hue angle of the skin, and total extractable polyphenols content were influenced by canopy management, especially in the 2012 growing season. Shoot topping to induce formation of laterals shoots associated with density of 2.8 canes/m2 increased the yield of seedless grapes cultivar Sugraone grown in the Sao Francisco Valley, not significantly affecting the quality of the grape.展开更多
To evaluate the applicability of the Standardized Precipitation-Evapotranspiration Index (SPEI) and the self-calibrated Palmer Drought Severity Index (scPDSI) to paleoclimate reconstructions in the east Asian summ...To evaluate the applicability of the Standardized Precipitation-Evapotranspiration Index (SPEI) and the self-calibrated Palmer Drought Severity Index (scPDSI) to paleoclimate reconstructions in the east Asian summer monsoon region, we used a 194-year tree-ring width chronology from Guancen Mountain, Shanxi Province, China, to investigate its correlation with SPEI and scPDSI, respectively. The results indicated scPDSI as a robust drought index that could be reconstructed from tree-ring width on Guancen Mountain other hydroclimate-related Significant correlations with series illustrated that our reconstruction captured common variations of hydroclimate in the surrounding areas. Additionally, our reconstruction showed significant correlation with nearby grid points of the Monsoon Asia Drought Atlas (MADA). However, while unprecedented drying trend existed during the past several decades in MADA, it was not represented in our reconstruction or in instrumental scPDSI/Dai-PDSI. This may imply that MADA overestimated drought severity during the past several decades in our study area; this overestimation was probably caused by an insufficient spatiotemporal distribution of the tree-ring network used by MADA. Therefore, more drought reconstructions based on individual sampling sites in eastern Asia are necessary to gain a thorough understanding of the Asian Monsoon climate variability.展开更多
Uncertainty analysis and risk analysis are two important areas of modern water resource management,in which accurate variance estimation is required.The traditional runoff model is established under the assumption tha...Uncertainty analysis and risk analysis are two important areas of modern water resource management,in which accurate variance estimation is required.The traditional runoff model is established under the assumption that the variance is a constant or it changes with the seasons.However,hydrological processes in the real world are often heteroscedastic,which can be tested by McLeod-Li test and Engle Lagrange multiplier test.In such cases,the GARCH model of hydrological processes is established in this article.First,the seasonal factors in the sequence are removed.Second,the traditional ARMA model is established.Then,the GARCH model is used to correct the residual.At last,the daily runoff data in 1949-2001 of Yichang Hydrological Station is taken to be an example.The result shows that compared to the traditional ARMA model,the GARCH model has the ability to predict more accurate confidence intervals under the same confidence level.展开更多
Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems. A field soil survey was conducted to compare microbial biomass carbon (Cmin) and soil fauna communities ...Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems. A field soil survey was conducted to compare microbial biomass carbon (Cmin) and soil fauna communities in the two main grassland management systems in subalpine regions of Yunnan Province, China: perennial grazing currently practiced due to increasing herd sizes and traditional seasonal grazing. A three-year exclosure experiment was then conducted to further compare the effects of different grazing practices, including treatments of no mowing, perennial grazing (NM + G), mowing followed by seasonal grazing (M + G), mowing and no grazing (M + NG), and no mowing or grazing (NM + NG). The comparative survey result revealed that Cmin and total density of soil fauna were significantly lower at a perennially grazed site than at a seasonally grazed site. The experiment results showed that in comparison to non-grazing treatments (M + NG and NM + NG), grazing (NM + G and M + G) reduced total fauna density (by 150 individuals m-2) and the number of taxonomic groups present (by 0.32 taxa m-2). Mowing decreased Cmin (by 0.31 mg g-l). Furthermore, the NM + G treatment (perennial grazing) had the lowest density of Collembola (16.24 individuals m-2), one of the two most common taxonomic groups, although other taxonomic groups responded differently to the treatments. Treatment effects on soil fauna were consistent with those on above-ground grasses, in which C:N ratios were greatly reduced by grazing, with this effect being the greatest for the NM + G treatment. In contrast, different grazing treatments had little effect on C:N ratio of soil. Furthermore, the traditional grazing method (mowing followed by seasonal grazing) may have less severe effects on some taxonomic groups than perennial grazing. Therefore, an appropriate management should aim to protect soil fauna and microbes in this area from over-grazing and against further degradation.展开更多
文摘Wood is the product of cambial activity in trees, and the seasonal activity style of cambium directly influences wood biomass production, structures and properties. The seasonal changes in the ultrastructure of the vascular cambium activity of Populus tonientosa Carr. planted in Beijing area were examined in shoot tissues collected during 15 months by means of transmission electron microscopy. Before xylem mother cells reactivated completely, the dividing fusiform cells in cambium and new phloem cells had appeared at the same time. The initiation of cambial activity may be related to the bud sprouting and the young leaf growth in shoots. More details about the ultrastructural changes of cambial cells at the onset of cambial activity have been gained. When the large vacuole in active cambial cells divided into smaller ones during the dormant phase, proteinaceous material that disappeared in active cambial cells refilled many of these small vactioles. In addition, lipid droplets and starch granules had the same cycles as proteinaceous material. The plasmalemma invaginations of fusiform cells were observed not only in active phase but also in dormancy. The endomembrane system consisting of nuclear membrane, endoplasmic reticulum (ER), dictyosomes and their secretory vesicles, changed in form and distribution at different phases during a cycle and performed important roles at the onset of active cambium and during the wall formation process of secondary xylem cells. The tangential walls remained relatively thin throughout the year but the radial walls thickened markedly when the cambium was dormant. During the transition from dormancy to activity, a partial autolysis occurred in the radial walls of the cambial cells, especially at the cell wall junctions. A notable feature of the cells at the onset of cambial activity was the thinning of the radial walls.
文摘In the light of the national policy of fallow, this study was conducted to determine how the different water management and lime application would affect soil physical and chemical properties, rice yield and cadmium (Cd) content of rice in fallow season. The results showed that, compared with the arid fallow, the waterlogging fallow decreased the soil pH value whereas signifcantly increased the soil organic matter content and the cation exchange quantity, and reduced the soil effective cadmium content and the rice cadmium content whereas could increase the rice yield to a certain extent. In the fooded fallow or the dry fallow, the application of lime mainly depended on the alkali conditioning of lime and the antagonistic effect of Ca2+, which could signifcantly reduce the cadmium content of rice, and its effect would increase linearly with the increase of lime dosage, whereas had no significant effect on soil organic matter content and cation exchange quantity. In order to establish a linear equation of lime dosage and related indexes under the condition of waterlogging fallow or dry fallow, calculations showed that each application of lime at 1 000 kg/hm2 or kg/hmss2 could improve soil pH value by 0.238 2 or 0.246 5units respectively, and reduce the effective Cd content to 0.007 5 mg/kg both in the arid fallow and the waterlogging fallow conditions. The lime theoretic application rate for the lowest Cd content of late rice in the arid fallow was 5 120 kg/hm2, and the minimum limit of the Cd content in rice was 0.124 2 mg/kg; and the lime theoretic application rate for the highest yield of late rice in the submerged water fallow was 4 636 kg/hm2, the minimum theoretic Cd content in rice is 0.100 7 mg/kg, and it could reduce the Cd content in rice under the condition of submerged fallow and decrease the dosage of lime.
基金supported by the National Natural Science Foundation of China (Nos. 41106007, 41210008)the China Postdoctoral Science Foundation (No. 2013M 541958)the International Cooperation Project of China (No. 2010DFA91350)
文摘In the South China Sea(SCS), the subsurface chlorophyll maximum(SCM) is frequently observed while the mechanisms of SCM occurrence have not been well understood. In this study, a 1-D physical-biochemical coupled model was used to study the seasonal variations of vertical profiles of chlorophyll-a(Chl-a) in the SCS. Three parameters(i.e., SCM layer(SCML) depth, thickness, and intensity) were defined to characterize the vertical distribution of Chl-a in SCML and were obtained by fitting the vertical profile of Chl-a in the subsurface layer using a Gaussian function. The seasonal variations of SCMs are reproduced reasonably well compared to the observations. The annual averages of SCML depth, thickness, and intensity are 75 ± 10 m, 31 ± 6.7 m, and 0.37 ± 0.11 mg m-3, respectively. A thick, close to surface SCML together with a higher intensity occurs during the northeastern monsoon. Both the SCML thickness and intensity are sensitive to the changes of surface wind speed in winter and summer, but the surface wind speed exerts a minor influence on the SCML depth; for example, double strengthening of the southwestern monsoon in summer can lead to the thickening of SCML by 46%, the intensity decreasing by 30%, and the shoaling by 6%. This is because part of nutrients are pumped from the upper nutricline to the surface mixed layer by strong vertical mixing. Increasing initial nutrient concentrations by two times will increase the intensity of SCML by over 80% in winter and spring. The sensitivity analysis indicates that light attenuation is critical to the three parameters of SCM. Decreasing background light attenuation by 20% extends the euphotic zone, makes SCML deeper(~20%) and thicker(12% – 41%), and increases the intensity by over 16%. Overall, the depth of SCML is mainly controlled by light attenuation, and the SCML thickness and intensity are closely associated with wind and initial nitrate concentration in the SCS.
基金Project partly supported by the Fred and Barbara Kort Sino-Israel Postdoctoral Fellowship
文摘To determine the effect of agricultural management on the dynamics and functional diversity of soil nematode communities in a carrot field at Kibbutz Ramat Hakovesh, Israel, soil samples from 0-10 cm and 10-20 cm depths were collected during the growing season of carrot. Indices were used to compare and assess the response of soil free-living nernatode communities to agricultural management. Eighteen nematode families and 20 genera were observed during the growing period, with Cephalobus, Rhabditidae, Aphelenchus, Tylenchus, and Dorylaimus being the dominant genera/families. During the planting, mid-season and post-harvest periods the total number of nematodes at both depths was significantly lower (P < 0.01) in the carrot treatment than in the control plots, while during the harvest period at both depths total nematodes and bacterivores were significantly higher in the treatment plots (P < 0.01). The values of the maturity index (MI) at both depths were found to be significantly lower in the treatment plots than in the control plots during the pre-planting period (P < 0.05). Overall, WI, MI and PPI were found to be more sensitive indicators than other ecological indices for assessing the response of nematode communities to agricultural management in a Mediterranean agroecosystem
文摘Hendra virus,a novel member of the family Paramyxovirus that has emerged from bats in Australia,causes fatal disease in livestock and humans. Eleven spillover events have been identified since the first description of the virus in 1994,resulting in a total of 37 equine cases and six human cases. All human cases have been attributed to exposure to infected horses;there is no evidence of bat-to-human or human-to-human transmission. Low infectivity and a high case fatality rate are features of Hendra virus infection in both horses and humans. The temporal pattern of spillover events suggests seasonal factors(plausibly be environmental,biological or ecological) as the proximate triggers for spillover. Minimisation of the future occurrence and impact of Hendra virus infections requires an understanding of the ecology of flying foxes,of virus infection dynamics in flying foxes,and of the factors that promote spillover. Management strategies seek to minimize the opportunity for effective contact between bats and horses,and limit potential horse-to-horse and horse-to-human transmission. Incomplete knowledge of the ecology of the virus,of the proximate factors associated with spillover,and the inherent difficulties of effectively managing wild populations,preclude a management approach targeted at bats.
基金Acknowledgment This study was supported by the National Key Basic Research Development Program Project (2010CB428400) and the Natural Science Foundation of China (51279140).
文摘This paper addresses the impact of climate change on the water cycle and resource changes in the Eastern Monsoon Region of China (EMRC). It also represents a summary of the achievements made by the National Key Basic Research and Development Program (2010CB428400), where the major research focuses are detection and attribution, extreme floods and droughts, and adaptation of water resources management. Preliminary conclusions can be summarized into four points: 1) Water cycling and water resource changes in the EMRC are rather complicated as the region is impacted by natural changes relating to the strong monsoon influence and also by climate change impacts caused by CO2 emissions due to anthropogenic forcing; 2) the rate of natural variability contributing to the influence on precipitation accounts for about 70%, and the rate from anthropogenic forcing accounts for 30% on average in the EMRC. However, with future scenarios of increasing CO2 emissions, the contribution rate from anthropogenic forcing will increase and water resources management will experience greater issues related to the climate change impact; 3) Extreme floods and droughts in the EMRC will be an increasing trend, based on IPCC-AR5 scenarios; 4) Along with rising temperatures of 1 ~C in North China, the agricultural water consumption will increase to about 4% of total water consumption. Therefore, climate change is making a significant impact and will be a risk to the EMRC, which covers almost all of the eight major river basins, such as the Yangtze River, Yellow River, Huaihe River, Haihe River, and Pearl River, and to the South-to-North Water Diversion Project (middle line). To ensure water security, it is urgently necessary to take adaptive countermeasures and reduce the vulnerability of water resources and associated risks.
基金Under the auspices of National Science Foundation of China(No.41601023,41771536)National Science Foundation for Distinguished Young Scholars of China(No.51425903)+2 种基金State Key Laboratory of Earth Surface Processes and Resource Ecology(No.2017-KF-04)Creative Research Groups of National Natural Science Foundation of China(No.41621061)Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(China Institute of Water Resources and Hydropower Research)(No.IWHR-SKL-201720)
文摘Understanding streamflow changes in terms of trends and periodicities and relevant causes is the first step into scientific management of water resources in a changing environment. In this study, monthly streamflow variations were analyzed using Modified Mann-Kendall(MM-K) trend test and Continuous Wavelet Transform(CWT) methods at 9 hydrological stations in the Huaihe River Basin. It was found that: 1) streamflow mainly occurs during May to September, accounting for 70.4% of the annual total streamflowamount with Cv values between 0.16–0.85 and extremum ratio values between 1.70–23.90; 2) decreased streamflow can be observed in the Huaihe River Basin and significant decreased streamflow can be detected during April and May, which should be the results of precipitation change and increased irrigation demand; 3) significant periods of 2–4 yr were detected during the 1960 s, the 1980 s and the 2000 s. Different periods were found at stations concentrated within certain regions implying periods of streamflow were caused by different influencing factors for specific regions; 4) Pacific Decadal Oscillation(PDO) has the most significant impacts on monthly streamflow mainly during June. Besides, Southern Oscillation Index(SOI), North Atlantic Oscillation(NAO) and the Ni?o3.4 Sea Surface Temperature(Ni?o3.4) have impacts on monthly streamflow with three months lags, and was less significant in time lag of six months. Identification of critical climatic factors having impacts on streamflow changes can help to predict monthly streamflow changes using climatic factors as explanatory variables. These findings were well corroborated by results concerning impacts of El Nino-Southern Oscillation(ENSO) regimes on precipitation events across the Huaihe River Basin. The results of this study can provide theoretical background for basin-scale management of water resources and agricultural irrigation.
基金Supported by the "948" Grant of the National Forestry Administration of China (No.2007-4-19)the Special Grantof Chinese Forestry Public Benefits (Nos.200804030 and 2007-4-15)the Provincial Fund for Distinguished Young Scholars of Hunan, China (No.07JJ1004)
文摘Soils play a critical role in the global carbon cycle, and can be major source or sink of CO2 depending upon land use, vegetation type and soil management practices. Fine roots are important component of a forest ecosystem in terms of water and nutrient uptake. In this study the effects of thinning and litter fall removal on fine root production and soil organic carbon content were examined in 20-year-old Masson pine (Pinus resinosa) plantations in Huitong, Hunan Province of China in the growing seasons of 2004 and 2005. The results showed that fine root production was significantly lower in the thinning plots than in the control plots, with a decrease of 58% and 14% in 2004 and 2005 growing seasons, respectively. Litter fall removal significantly increased fine root production by 14% in 2004. Soil temperature (Tsoil) and soil moisture (Msoil) were higher in the thinning plots than those in the controls. Litter fall removal had significant effects on Tsoil and Msoil. Soil organic carbon content was higher in the thinning plots but was lower in the plots with litter fall removal compared with that in the controls. Our results also indicated that annual production of fine roots resulted in small carbon accumulation in the upper layers of the soil, and removal of tree by thinning resulted in a significant increase of carbon storage in Masson pine plantations.
文摘The results of the three-year researches which had the purpose to establish an optimum depth of seeding at sowing and rational norm of seeding of red beetroot seeds at under-winter sowing in conditions of mid-loamy typical grey soils of the central climatic zone of Uzbekistan are stated in article. The researches were spent at statement of field experiences in quadruple frequency with the area of a registration allotment 10 M^-1. Crops were carried out in the first decade of December against mulching surfaces of ridges by humus and without mulching. Crops were carried out on ridges in width of 70 sm tape-two-lined with distance between tapes of 50 sm, between lines-20 sm and distance between plants in a line of 12-13 sm, at density of standing of 228-230 thousand plants/hectares. Experiences were spent with zoned in Uzbekistan multi-seedling grade of a red beetroot "Bordo 237". Experiences were accompanied by phenological supervision, biometric accounts, the account of field germination of seeds, density of standing of plants and definition of size and quality of a crop. Results of researches were exposed to the statistical analysis by a dispersive method. It has been revealed that at under-winter sowing of a red beetroot the effective way providing acceleration of shoots occurrence, formations of high-grade density of standing and increase of productivity of root crops is mulching the surfaces of ridges by humus. It is defined that optimum depth of seeding at sowing both at application of mulching and without it is the depth of seeding 4 sm. It is established that the most rational norm of seeding of the seeds, providing high-grade density of standing, is at cultivation with application of mulching 8 kg/ha, and at cultivation without mulching 8-10 kg/ha. Application of mulching the surfaces of ridges by humus, depths of seeding of 4 sm and norms of seeding of seeds of 8-10 kg/ha in conditions of under-winter sowing in comparison with cultivation without mulching and depth of seeding 2 sm and norms of seeding of 6 kg/ha provides an acceleration of receipt of fresh production of a red beetroot for 12-14 days and considerably raises root crops productivity. Application of agro receptions improved by us is the important reserve of acceleration of receipt of red beetroot early production and increase of its manufacture.
文摘The production of some seedless table grapes under tropical conditions presents low bud fertility on the main canes and low yield, which leads to the need of pruning in the lateral shoots. The objective of this study was to evaluate the influence of the canopy management for the formation of lateral shoots associated with dellsity of canes on the yield and quality of grapes "Sugraone" in the Sao Francisco Valley. The experiment was carried out over two growing seasons (2011-2012) in a commercial vineyard of Sugraone in Petrolina, Pernambuco state, Brazil. The treatments consisted of two canopy managements (shoot topping associated to elimination of lateral shoots and shoot topping and formation of lateral shoots) combined with two to three densities of canes after pruning (1.8, 2.8 and 3.8 canes/m^2). The formation of "lateral shoots" increased yield and number of clusters per plant during two consecutive growing seasons, besides using 2.8 varas/m^2 resulted in highest yields only in 2011 growing season. The variables mass bunch, mass berry, soluble solids (SS), soluble sugar, titxatable acidity (TA) and pulp firmness were not affected by treatments, while the attributes related to color, as like brightness and hue angle of the skin, and total extractable polyphenols content were influenced by canopy management, especially in the 2012 growing season. Shoot topping to induce formation of laterals shoots associated with density of 2.8 canes/m2 increased the yield of seedless grapes cultivar Sugraone grown in the Sao Francisco Valley, not significantly affecting the quality of the grape.
基金supported by the National Natural Science Foundation of China(41201046,40890051),KZZDEW-04-01the State Key Laboratory of Loess and Quaternary Geology(SKLLQG),and the West Doctoral Foundation of Chinese Academy of Sciences.This is a SISTRR contribution(No.29)
文摘To evaluate the applicability of the Standardized Precipitation-Evapotranspiration Index (SPEI) and the self-calibrated Palmer Drought Severity Index (scPDSI) to paleoclimate reconstructions in the east Asian summer monsoon region, we used a 194-year tree-ring width chronology from Guancen Mountain, Shanxi Province, China, to investigate its correlation with SPEI and scPDSI, respectively. The results indicated scPDSI as a robust drought index that could be reconstructed from tree-ring width on Guancen Mountain other hydroclimate-related Significant correlations with series illustrated that our reconstruction captured common variations of hydroclimate in the surrounding areas. Additionally, our reconstruction showed significant correlation with nearby grid points of the Monsoon Asia Drought Atlas (MADA). However, while unprecedented drying trend existed during the past several decades in MADA, it was not represented in our reconstruction or in instrumental scPDSI/Dai-PDSI. This may imply that MADA overestimated drought severity during the past several decades in our study area; this overestimation was probably caused by an insufficient spatiotemporal distribution of the tree-ring network used by MADA. Therefore, more drought reconstructions based on individual sampling sites in eastern Asia are necessary to gain a thorough understanding of the Asian Monsoon climate variability.
基金supported by the National Hi-Tech Research and Development Program of China ("863" Project) (Grant No. 2012BAB02B04)
文摘Uncertainty analysis and risk analysis are two important areas of modern water resource management,in which accurate variance estimation is required.The traditional runoff model is established under the assumption that the variance is a constant or it changes with the seasons.However,hydrological processes in the real world are often heteroscedastic,which can be tested by McLeod-Li test and Engle Lagrange multiplier test.In such cases,the GARCH model of hydrological processes is established in this article.First,the seasonal factors in the sequence are removed.Second,the traditional ARMA model is established.Then,the GARCH model is used to correct the residual.At last,the daily runoff data in 1949-2001 of Yichang Hydrological Station is taken to be an example.The result shows that compared to the traditional ARMA model,the GARCH model has the ability to predict more accurate confidence intervals under the same confidence level.
基金supported by the Biogeochemistry Laboratory of Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, the National Natural Science Foundation of China (Nos. 40671103 and 41271278)the Innovative Program of Chinese Academy of Sciences- “The Effects of Different Land Use on Biodiversity in Northwest of Yunnan, China” (No. KSCX2-SW-123-5)
文摘Grazing and over-grazing may drive changes in the diversity and functioning of below-ground meadow ecosystems. A field soil survey was conducted to compare microbial biomass carbon (Cmin) and soil fauna communities in the two main grassland management systems in subalpine regions of Yunnan Province, China: perennial grazing currently practiced due to increasing herd sizes and traditional seasonal grazing. A three-year exclosure experiment was then conducted to further compare the effects of different grazing practices, including treatments of no mowing, perennial grazing (NM + G), mowing followed by seasonal grazing (M + G), mowing and no grazing (M + NG), and no mowing or grazing (NM + NG). The comparative survey result revealed that Cmin and total density of soil fauna were significantly lower at a perennially grazed site than at a seasonally grazed site. The experiment results showed that in comparison to non-grazing treatments (M + NG and NM + NG), grazing (NM + G and M + G) reduced total fauna density (by 150 individuals m-2) and the number of taxonomic groups present (by 0.32 taxa m-2). Mowing decreased Cmin (by 0.31 mg g-l). Furthermore, the NM + G treatment (perennial grazing) had the lowest density of Collembola (16.24 individuals m-2), one of the two most common taxonomic groups, although other taxonomic groups responded differently to the treatments. Treatment effects on soil fauna were consistent with those on above-ground grasses, in which C:N ratios were greatly reduced by grazing, with this effect being the greatest for the NM + G treatment. In contrast, different grazing treatments had little effect on C:N ratio of soil. Furthermore, the traditional grazing method (mowing followed by seasonal grazing) may have less severe effects on some taxonomic groups than perennial grazing. Therefore, an appropriate management should aim to protect soil fauna and microbes in this area from over-grazing and against further degradation.