Agrobacterium tumefaciens-mediated transformation has been widely adopted for plant genetic engineering and the study of gene function(Krenek et al.,2015).This method is prevalent in the genetic transformation of herb...Agrobacterium tumefaciens-mediated transformation has been widely adopted for plant genetic engineering and the study of gene function(Krenek et al.,2015).This method is prevalent in the genetic transformation of herbaceous plants,with notable applications in species such as Arabidopsis(Yin et al.,2024),soybean(Zhang et al.,2024),rice(Zhang et al.,2020),and Chinese cabbage(Li et al.,2021).However,its application in fruit trees is limited.This is primarily due to their long growth cycles and lack of rapid,efficient,and stable transgenic systems,which severely hinders foundational research involving plant genetic transformation(Mei et al.,2024).Furthermore,for subtropical fruit trees,the presence of recalcitrant seeds adds an extra layer of difficulty to genetic transformation(Umarani et al.,2015),as most methods rely on seed germination as a basis for transformation.展开更多
Water level is the overriding control on carbon cycles in peatlands,which are important for global carbon cycles and ecosystem services.To date,our knowledge of the pattern of water level fluctuations in peatlands and...Water level is the overriding control on carbon cycles in peatlands,which are important for global carbon cycles and ecosystem services.To date,our knowledge of the pattern of water level fluctuations in peatlands and the influence of precipitation and air temperature on them in the subtropical remains poor.In this study,we conducted continuous high-resolution monitoring of water levels from 2014 to 2021 in the Dajiuhu peatland,a typically subtropical peatland in central China.Monitoring results showed that the water level had strong annual(370 days) and seasonal(130 days) oscillations in the Dajiuhu peatland.The annual oscillation is associated with both precipitation and temperature,while the seasonal oscillation is mainly controlled by precipitation.In addition,the depth of peat surface to the water table(DWT) has weak but significant correlations with precipitation and temperature on the daily and weekly scales(r = 0.1–0.21,p<0.01).Once replacing DWT with water table fluctuation cumulation,the correlation coefficients increase apparently(r = 0.47–0.69,p<0.01),especially on the monthly scale.These findings highlight a more important role of the fluctuation than the mean position of water level and have the potential to improve the interpretation of water-level related paleoenvironmental proxies and the understanding of the relationship between water level and biogeochemical processes.展开更多
There are many short-lived animals,but those displaying a lifecycle with more than one generation per year(multivoltine lifecycle)are rare amongterrestrial vertebrates.The multivoltine lifecycle requires rapid growth ...There are many short-lived animals,but those displaying a lifecycle with more than one generation per year(multivoltine lifecycle)are rare amongterrestrial vertebrates.The multivoltine lifecycle requires rapid growth and maturation and a long active season.Thus,small lizards in humidtropical or subtropical areas are candidates for multivoltine lifecycles.To test this prediction,we conducted a capture-mark-recapture study of asubtropical grass lizard,Takydromus toyamai,endemic to Miyako Islands,Japan.Juveniles grew very quickly,averaging 0.3 mm/day in the warmseason,and attained sexual maturity at 2.5 months post-hatching.The breeding season was very long,and hatchlings emerged from May toNovember.The prolonged breeding season and rapid growth to maturity allowed some individuals to produce a second generation in their frstyear.Estimates of hatching date from growth rates indicated that many females that hatched in May-June became gravid 76-120 days afterhatching and 122-165 days after oviposition of the eggs from which they hatched.Analyses of juvenile survivorship and month of hatching suggest that nearly half of breeding adults were members of multivoltine generations,although the 2 generations were not discrete.The species isshort-lived,with only 16% of individuals surviving beyond 12 months,and few individuals reproduced in a second year.We refer to this conditionas a“semi-multivoltine lifecycle.”Individuals that hatch late in the season defer reproduction until the following year and become founders ofthe next season’s cohort.This putative advantage of late-hatching individuals may have driven the evolution of this lifecycle.展开更多
Patterns and drivers of species–genetic diversity correlations(SGDCs)have been broadly examined across taxa and ecosystems and greatly deepen our understanding of how biodiversity is maintained.However,few studies ha...Patterns and drivers of species–genetic diversity correlations(SGDCs)have been broadly examined across taxa and ecosystems and greatly deepen our understanding of how biodiversity is maintained.However,few studies have examined the role of canopy structural heterogeneity,which is a defining feature of forests,in shaping SGDCs.Here,we determine what factors contribute toα-andβ-species–genetic diversity correlations(i.e.,α-andβ-SGDCs)in a Chinese subtropical forest.For this purpose,we used neutral molecular markers to assess genetic variation in almost all adult individuals of the dominant tree species,Lithocarpus xylocarpus,across plots in the Ailaoshan National Natural Reserve.We also quantified microhabitat variation by quantifying canopy structure heterogeneity with airborne laser scanning on 201-ha subtropical forest plots.We found that speciesα-diversity was negatively correlated with geneticα-diversity.Canopy structural heterogeneity was positively correlated with speciesα-diversity but negatively correlated with geneticα-diversity.These contrasting effects contributed to the formation of a negativeα-SGDC.Further,we found that canopy structural heterogeneity increases speciesα-diversity and decreases geneticα-diversity by reducing the population size of target species.Speciesβ-diversity,in contrast,was positively correlated with geneticβ-diversity.Differences in canopy structural heterogeneity between plots had non-linear parallel effects on the two levels ofβ-diversity,while geographic distance had a relatively weak effect onβ-SGDC.Our study indicates that canopy structural heterogeneity simultaneously affects plot-level community species diversity and population genetic diversity,and species and genetic turnover across plots,thus drivingα-andβ-SGDCs.展开更多
Arid West Asia(AWA)is a critical hub of the Silk Road and one of the primary dust source regions in the Northern Hemisphere.Dust storms in AWA emitting substantial dust particles into the atmosphere,significantly infl...Arid West Asia(AWA)is a critical hub of the Silk Road and one of the primary dust source regions in the Northern Hemisphere.Dust storms in AWA emitting substantial dust particles into the atmosphere,significantly influencing air quality,climate change and marine productivity.However,the variability of dust storm activity in this region during the Holocene,particularly its links to vegetation and hydroclimatic changes,remains debated,hindering our understanding of the interconnected dynamics between climate change and surface environments.This study reconstructs dust storm variations in AWA over the past 9000 years using geochemical analyses(trace elements,Sr-Nd isotopes)from a well-dated,high-resolution sediment core from the Almalou Peatland,located on the western Iranian Plateau.Our results reveal a decline in dust storm frequency from the early to mid-Holocene,a minimum occurrence during the mid-Holocene,and a significant increase in the late Holocene.Provenance analysis indicates that the primary dust sources were the arid regions of Mesopotamia,located upwind of the study area.A comparison with proxy records and paleoclimate models suggests an inverse relationship between dust storm activity and regional hydroclimatic and vegetation changes,along with a positive correlation with wind speeds.The concentration of dust storms during the wetter month of May highlights wind speed as a more critical driving factor.Moreover,given the dominant influence of the subtropical high on hydroclimatic conditions and wind speeds in AWA,we propose that this system is the key regulator of regional dust storm dynamics.Our findings provide new insights into the drivers of dust storm activity in AWA and hold implications for developing targeted dust storm management strategies.展开更多
Exploring the formation and changes in tree microclimates can help improve the quality of urban green spaces.Temperature is an important indicator of microcli-mate,and tree temperature categories can be divided into a...Exploring the formation and changes in tree microclimates can help improve the quality of urban green spaces.Temperature is an important indicator of microcli-mate,and tree temperature categories can be divided into ambient temperature and tree surface temperature(T_(ts)),from which the mean radiation temperature(T_(mrt))and thermal comfort values are derived.In this study,the summer micro-climate of Ficus altissima in southern subtropical China was determined,focusing on soil(T_(s)),air(T_(a)),globe(T_(g)),and T_(ts).T_(mrt)and four commonly used thermal comfort indicators,i.e.,predicted mean vote(PMV),physiologically equivalent temperature(PET),standard effective temperature(SET^(*)),and universal thermal climate index(UTCI),were also cal-culated.The results showed that:(1)T_(mrt)can be used to explain both the cooling effect and to predict thermal com-fort in the shade;(2)the PET indicator is more advantageous for analyzing thermal comfort in the microclimate of Ficus altissima;(3)T_(s)is not a suitable important indicator for pre-dicting ambient temperatures and thermal comfort;and(4)the site-specific sampling method of the crowns or trunks can be used to accurately explain changes in the whole-plant thermal environment and thermal comfort,respectively.展开更多
The increase in frequency and intensity of Extreme High-temperature Events(EHEs)over Central-Eastern China(CEC)in recent decades has severely impacted social development and livelihoods.Using observation and reanalysi...The increase in frequency and intensity of Extreme High-temperature Events(EHEs)over Central-Eastern China(CEC)in recent decades has severely impacted social development and livelihoods.Using observation and reanalysis datasets,this study explores the effect of the East Asian subtropical westerly jet stream(EAJ)on the CEC EHEs for the summers spanning 1979–2020.Considering its general relative location to the right side of the upper-level jet stream exit region,CEC would theoretically suffer more EHEs with a stronger and northwardly-shifted EAJ in summer due to the likelihood of abnormal subsidence induced by the EAJ.However,such an EAJ–EHE connection has been unstable over the past four decades but has displayed an evident interdecadal change.Before the late 1990s,the interannual variation of the EAJ was manifested mainly by its meridional displacement in the northeastern part of East Asia;thus,the atmospheric responses were essentially located to the east of CEC,exerting less of an influence on the CEC EHEs.However,since the late 1990s,the EAJ variation has featured an intensity change in its center over the northwest portion of the CEC,which has resulted in a westward shift in atmospheric responses to cover the CEC region.Therefore,the EAJ could potentially affect the summer CEC EHEs during 2000–21.Our findings offer support for an in-depth understanding of the formation mechanisms of extreme weather/climate events of this nature and thus provide a scientific reference for seasonal climate predictions.展开更多
The present study employs statistical analysis to investigate the relationship between the geopotential height anomalies induced by tropical cyclones(TCs)and the meridional movement of the western Pacific subtropical ...The present study employs statistical analysis to investigate the relationship between the geopotential height anomalies induced by tropical cyclones(TCs)and the meridional movement of the western Pacific subtropical high(WPSH),as well as the mechanisms through which TCs can induce such geopotential height anomalies.Results show that TCs can cause the WPSH to move northward,and the meridional motion of the WPSH ridgeline is related with the geopotential height anomalies,which is better indicated by the relative geopotential height anomalies.In the process of TCs causing the WPSH to move northward,the TCs cause abnormal horizonal warm(cold)advection and abnormal ascending(descending)motion in the region south(north)of 40°N.Since the influence of the abnormal vertical motion is weaker,the abnormal temperature tendency eventually shows a more consistent phase distribution with the abnormal horizonal temperature advection,which is favorable for the temperature to abnormally increase near 40°N.Such an abnormal increase in temperature causes the geopotential height to abnormally increase under the static equilibrium constraint,which further changes the location of the centroid of the WPSH geopotential height,and hence the location of the WPSH ridgeline changes as well.展开更多
Structure, species composition, and soil properties of a subtropical evergreen broad-leaved forest in Okinawa, Japan, were examined by establishment of plots at thirty sites. The forest was characterized by a relative...Structure, species composition, and soil properties of a subtropical evergreen broad-leaved forest in Okinawa, Japan, were examined by establishment of plots at thirty sites. The forest was characterized by a relatively low canopy and a large number of small-diameter trees. Mean canopy height for this forest was 10 m and stands contained an average of 5400 stems-ha^-1 （ -〉 3.0 cm DBH）; 64% of those stems were smaller than 10 cm DBH. The total basal area was 54.4 m^2-ha^-1, of which Castanopsis sieboldii contributed 48%. The forest showed high species diversity of trees. 80 tree species （≥ 3.0 cm DBH） from 31 families was identified in the thirty sampling plots. C. sieboldii and Schima wallichii were the dominant and subdominant species in terms of importance value. The mean tree species diversity indices for the plots were, 3.36 for Diversity index （H＇）, 0.71 for Equitability index （J＇） and 4.72 for Species richness index （S＇）, all of which strongly declined with the increase of importance value of the dominant, C. sieboldii. Measures of soil nutrients indicated low fertility, extreme heterogeneity and possible A1 toxicity. Regression analysis showed that stem density and the dominant tree height were significantly correlated with soil pH. There was a significant positive relationship between species diversity index and soil exchangeable K^＋, Ca^2＋, and Ca^2＋/Al^3- ratio （all p values 〈0.001） and a negative relationship with N, C and P. The results suggest that soil property is a major factor influencing forest composition and structure within the subtropical forest in Okinawa.展开更多
[Objective] The aim was to make full use of light-heat resources to expand the potato planting area on the base of ensuring the production of main grain crops and the limited arable land. [Methods] Through catch crops...[Objective] The aim was to make full use of light-heat resources to expand the potato planting area on the base of ensuring the production of main grain crops and the limited arable land. [Methods] Through catch crops, multiple cropping and intercropping, new multiple planting patterns of potato with efficiency are constructed, for the purpose of increasing yield and benefit of potato. [Result] In irrigated plain and hill area, three new planting patterns such as autumn potato/rope-rice,winter potato-rice-autumn potato, and autumn（winter） potato-rice were constructed.In dry land of plain and hill area, three new planting patterns such as spring（winter）potato/maize/sweet potato, spring（winter） potato/maize-autumn potato, and wheat ＋ winter potato/maize/sweet potato were constructed. In plateau mountainous area, spring potato/maize was constructed. [Conclusion] With use of new planting patterns, the cropping index of new patterns was 200%-300%, while the accumulated temperature utilization was 68.9%-93.4%, light energy utilization was 0.98%-1.59% and straw utilization was 50%-100%. To compared with traditional planting patterns, the yield increased by 2.6%-93%, and benefit increased by 15.8%-284.3%. Furthermore,multiple planting patterns of potato have become main planting patterns in increasing yield and income in Sichuan.展开更多
The dimension, water content and germination of the seeds from 90 woody species in the lower subtropical forest were analyzed in this study. Out of 90 species, germination analysis was performed in 45 species (in whic...The dimension, water content and germination of the seeds from 90 woody species in the lower subtropical forest were analyzed in this study. Out of 90 species, germination analysis was performed in 45 species (in which there were enough germinating individuals), and the effect of storage of seed and fruit on germination of seed was studied in 41 species (in which there were enough seeds and germinating individuals). Most of the species began to germinate within 60 d. Hypogeal species had longer dormancy than epigeal species. Dormancy of fleshy seeds and seeds in pulpy fruit was also longer than that of dry seeds. There were no significant differences in length of dormancy (LD, days from sowing to germination) between fleshy seeds ripening in summer and those ripening in winter and spring, and between big seeds and small seeds. Seeds in pulpy fruit or fleshy seeds had more germination than the dry seeds ( P <0.05), however, percentage germination was not significantly correlated with water content of fresh seeds. Water loss in the seeds could obviously affect percentage germination, especially during the early three days when the seeds were laid open in air in the laboratory. When water content of the seeds decreased to about 20% (fresh weight basis), percentage germination became very low, this happened when the seeds were laid open in air for 10-14 d. Percentage germination decreased with the length of storing in refrigerator ((4±1) ℃), but it was not markedly affected for one month's storage, with a decrease by 8.3% in comparison with the fresh seeds, and it was greatly affected by storing for more than three months, with values decreasing by 37%, 63%, and 81% for three months', six months' and 12 months' storage respectively. Difference in percentage germination as well as in LD was not significant for most lots after different storing periods between big seeds and small seeds, between fruit storage and seed storage, and between seeds in pulpy fruits or fleshy seeds and dry seeds.展开更多
By using the monthly mean grid data of NCAR/NCEP reanalysis at 500 hPa geopotential height from 1958 to 1997,the relationship between the Northeast cold vortex and the western Pacific subtropical high was analyzed.The...By using the monthly mean grid data of NCAR/NCEP reanalysis at 500 hPa geopotential height from 1958 to 1997,the relationship between the Northeast cold vortex and the western Pacific subtropical high was analyzed.The influence of the sea surface temperature(SST) and outgoing longwave radiation(OLR) on the Northeast cold vortex and subtropical high was studied.As was shown in the results,in summer,there was a positive correlation between the Northeast cold vortex and the subtropical high,and an anti-phase relationship existed between the threshold characteristic line of GMS-SST=28 ℃ and the height index of the Northeast cold vortex and the subtropical high.With the gradual northward moving of the threshold characteristic line,the subtropical high was weakening,and the Northeast cold vortex was increasing and strengthening.展开更多
The monthly observed average precipitation data of 160 meteorological stations in China from 1960 to 2007,had been reorganized by the China Meteorological Administration.By employing that precipitation data,NCEP/NCAR ...The monthly observed average precipitation data of 160 meteorological stations in China from 1960 to 2007,had been reorganized by the China Meteorological Administration.By employing that precipitation data,NCEP/NCAR reanalysis data and the index of intensity of western Pacific subtropical high,the seasonal variations of subtropical high and precipitation in eastern China during the past decades are discussed.The relationships between them also are discussed by correlation and composite analyses.The results show that the intensity of subtropical high,which has significantly strengthened in the recent 50 years,especially in spring,autumn and winter,has notable impact on the simultaneous rainfall in the eastern region of China for all seasons,especially in winter.展开更多
Based on observational daily data of 730 meteorological stations in China, the south edge of the subtropical winter monsoon is defined according to relevant criterion and its variation characteristics are analyzed. Re...Based on observational daily data of 730 meteorological stations in China, the south edge of the subtropical winter monsoon is defined according to relevant criterion and its variation characteristics are analyzed. Results show that this south edge has obvious inter-annual variation characteristics and shows a northward moving tendency as a whole, but since the 21 st century it has moved southwards and date of the south edge entering winter becomes earlier. Wind fields of the anomalously northward south edge of the subtropical winter monsoon in East Asia has an obvious southerly wind component which prevents cold air from moving southward. The index of this south edge and winter temperature has a positive correlation. Climate warming might be the main reason for the northward movement of the south edge of the subtropical winter monsoon.展开更多
Using the relative vorticity averaged over a certain area, a new index for measuring the longitudinal position of the subtropical high (SH) in the western Pacific is proposed to avoid the increasing trend of heights i...Using the relative vorticity averaged over a certain area, a new index for measuring the longitudinal position of the subtropical high (SH) in the western Pacific is proposed to avoid the increasing trend of heights in the previous indices based on geopotential height. The years of extreme westward and eastward extension of SH using the new index are in good agreement with those defined by height index. There exists a distinct difference in large-scale circulation between the eastward and westward extension of SH under the new definition, which includes not only the circulation in the middle latitudes but also the flow in the lower latitudes. It seems that when the SH extends far to the east (west), the summer monsoon in the South China Sea is stronger (weaker) and established earlier (later). In addition, there exists a good relationship between the longitudinal position of SH and the summer rainfall in China. A remarkable negative correlation area appears in the Changjiang River valley, indicating that when the SH extends westward (eastward), the precipitation in that region increases (decreases). A positive correlation region is found in South China, showing the decrease of rainfall when the SH extends westward. On the other hand, the rainfall is heavier when the SH retreats eastward. However, the anomalous longitudinal position of SH is not significantly related to the precipitation in North China. The calculation of correlation coefficients between the index of longitudinal position of SH and surface temperature in China shows that a large area of positive values, higher than 0.6 in the center, covers the whole of North China, even extending eastward to the Korean Peninsula and Japan Islands when using NCEP/NCAR reanalysis data to do the correlation calculation. This means that when the longitudinal position of the SH withdraws eastward in summer, the temperature over North China is higher. On the other hand, when it moves westward, the temperature there is lower. This could explain the phenomenon of the seriously high temperatures over North China during recent summers, because the longitudinal position of SH in recent summers was located far away from the Asian continent. Another region with large negative correlation coefficients is found in South China.展开更多
Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical c...Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical circulations including the Asian monsoon as well as the convective activity are studied. In order to study the physical process of the air-sea interaction related to STH anomaly, the correlation of STH with SST at various sea areas, lagged and simultaneous, has been calculated. Comparing the difference of OLR, wind fields, vertical circulations and SST anomalies in the strong and weak STH, we investigate the characteristics of global circulations and the SST distributions related to the anomalous STH at the western Pacific both in winter and summer. Much attention has been paid to the study of the air-sea interaction and the relationship between the East Asian monsoon and the STH in the western Pacific. A special vertical circulation, related to the STH anomalies is found, which connects the monsoon current to the west and the vertical flow influenced by the SST anomaly in the tropical eastern Pacific.展开更多
A field-scale experiment arranged in a complete randomized block design with three N addition treatments including a control (no addition of N), a low N (5 g m-2 year-1), and a medium N (10 g m-2 year-1) was performed...A field-scale experiment arranged in a complete randomized block design with three N addition treatments including a control (no addition of N), a low N (5 g m-2 year-1), and a medium N (10 g m-2 year-1) was performed in each of the three typical forests, a pine (Pinus massoniana Lamb.) forest (PF), a pine-broadleaf mixed forest (MF) and a mature monsoon evergreen broadleaf forest (MEBF), of the Dinghushan Biosphere Reserve in subtropical China to study the response of soil fauna community to additions of N. Higher NH4+ and NO3- concentrations and a lower soil pH occurred in the medium N treatment of MEBF, whereas the NO3- concentration was the lowest in PF after the additions of N. The response of the density, group abundance and diversity index of soil fauna to addition of N varied with the forest type, and all these variables decreased with increasing N under MEBF but the trend was opposite under PF. The N treatments had no significant effects on these variables under MF. Compared with the control plots, the medium N treatment had significant negative effect on soil fauna under MEBF. The group abundance of soil fauna increased significantly with additions of higher N rates under PF. These results suggested that the response of soil fauna to N deposition varied with the forest type and N deposition rate, and soil N status is one of the important factors affecting the response of soil fauna to N deposition.展开更多
To better understand the effect of forest succession on carbon sequestration, we investigated carbon stock and allocation of evergreen broadleaf forest, a major zonal forest in subtropical China. We sought to quantify...To better understand the effect of forest succession on carbon sequestration, we investigated carbon stock and allocation of evergreen broadleaf forest, a major zonal forest in subtropical China. We sought to quantify the carbon sequestration potential. We sampled four forest types, shrub （SR）, pine （Pinus massoniana） forest （PF）, pin~ and broadleaf mixed forest （Mr） and evergreen broadleaf forest （BF）. A regression equation was constructed using tree height and diameter at breast height （DBH） and elements of total tree biomass. The equation was subse- quently utilized to estimate tree carbon storage. The carbon storage of understory, litter, and soil was also estimated.展开更多
Using the NCEP/NCAR reanalysis data, the China rainfall data of the China Meteorological Administration, and the sea surface temperature (SST) data of NOAA from 1951-2000, the features of the anomalous longitudinal po...Using the NCEP/NCAR reanalysis data, the China rainfall data of the China Meteorological Administration, and the sea surface temperature (SST) data of NOAA from 1951-2000, the features of the anomalous longitudinal position of the subtropical high in the western Pacific (SHWP) in the pre-rainy season in South China and associated circulation and precipitation are studied. Furthermore, the relationship between SHWP and SST and the eastern Asian winter monsoon is also investigated. Associated with the anomalous longitudinal position of SHWP in the pre-rainy season in South China, the flow patterns in both the middle and lower latitudes are different. The circulation anomalies greatly influence the precipitation in the pre-rainy season in South China. When the SHWP is in a west position (WP), the South China quasi-stationary front is stronger with more abundant precipitation there. However, when the SHWP is in an east position (EP), a weaker front appears with a shortage of precipitation there. There exists a good relationship between the longitudinal position of SHWP and SST in the tropical region. A negative correlation can be found both in the central and eastern tropical Pacific and the Indian Ocean. This means that the higher (lower) SST there corresponds to a west (east) position of SHWP. This close relationship can be found even in the preceding autumn and winter. A positive correlation appears in the western and northern Pacific and large correlation coefficient values also occur in the preceding autumn and winter. A stronger eastern Asian winter monsoon will give rise to cooler SSTs in the Kuroshio and the South China Sea regions and it corresponds to negative SST anomaly (SSTA) in the central and eastern Pacific and positive SSTA in the western Pacific in winter and the following spring. The whole tropical SSTA pattern, that is, positive (negative) SSTA in the central and eastern Pacific and negative (positive) SSTA in the western Pacific, is favorable to the WP (EP) of SHWP.展开更多
Agriculture is still the biggest contributor of non-point source (NPS) pollution to water bodies andrunoff discharges of nutrients and other chemicals are one of the most important pathways. This studywas conducted du...Agriculture is still the biggest contributor of non-point source (NPS) pollution to water bodies andrunoff discharges of nutrients and other chemicals are one of the most important pathways. This studywas conducted during 1998～1999 in a typical watershed with complex agriculture and forestry systems aswell as dotted farmer villages, in a transitional region between the mid- and northern subtropical zones ofChina. Continuous sampling of stream water was performed regularly at a weekly frequency, with additionalsampling after all major rainfall events. The discharges of N and P nutrients and suspended materials weremeasured and the total and area-averaged annual discharges of all components were calculated. The resultsshowed an uneven seasonal distribution of nutrient discharges with summer storms contributing most tothe total fluxes. This study demonstrated a high dependence of runoff volume on rainfall but the overallrunoff coefficients were dependent on land use type and watershed size. The area-averaged annual dischargesvaried greatly among the sub-watersheds with different sizes and land use structures. This is the first studyestimating the area-averaged annual discharges of N and P in the hilly areas of subtropical China, which were1.5 g m-2 a-1 and 0.1 g m-2 a-1, respectively, providing important reference values for the assessment ofregional agricultural non-point source pollution.展开更多
基金funded by the Key-Area Research and Development Program of Guangdong Province(Grant No.2022B0202070002)the Guangxi Science and Technology Major Program(Grant No.GuikeAA23023007-2)+1 种基金the Guangdong Province Modern Agricultural Industry Technology System Innovation Team Construction Project(2024CXTD19)Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515010303)。
文摘Agrobacterium tumefaciens-mediated transformation has been widely adopted for plant genetic engineering and the study of gene function(Krenek et al.,2015).This method is prevalent in the genetic transformation of herbaceous plants,with notable applications in species such as Arabidopsis(Yin et al.,2024),soybean(Zhang et al.,2024),rice(Zhang et al.,2020),and Chinese cabbage(Li et al.,2021).However,its application in fruit trees is limited.This is primarily due to their long growth cycles and lack of rapid,efficient,and stable transgenic systems,which severely hinders foundational research involving plant genetic transformation(Mei et al.,2024).Furthermore,for subtropical fruit trees,the presence of recalcitrant seeds adds an extra layer of difficulty to genetic transformation(Umarani et al.,2015),as most methods rely on seed germination as a basis for transformation.
基金supported by the National Natural Science Foundation of China(No.U20A2094)。
文摘Water level is the overriding control on carbon cycles in peatlands,which are important for global carbon cycles and ecosystem services.To date,our knowledge of the pattern of water level fluctuations in peatlands and the influence of precipitation and air temperature on them in the subtropical remains poor.In this study,we conducted continuous high-resolution monitoring of water levels from 2014 to 2021 in the Dajiuhu peatland,a typically subtropical peatland in central China.Monitoring results showed that the water level had strong annual(370 days) and seasonal(130 days) oscillations in the Dajiuhu peatland.The annual oscillation is associated with both precipitation and temperature,while the seasonal oscillation is mainly controlled by precipitation.In addition,the depth of peat surface to the water table(DWT) has weak but significant correlations with precipitation and temperature on the daily and weekly scales(r = 0.1–0.21,p<0.01).Once replacing DWT with water table fluctuation cumulation,the correlation coefficients increase apparently(r = 0.47–0.69,p<0.01),especially on the monthly scale.These findings highlight a more important role of the fluctuation than the mean position of water level and have the potential to improve the interpretation of water-level related paleoenvironmental proxies and the understanding of the relationship between water level and biogeochemical processes.
基金supported fnancially by the Nanseishoto Project of WWFJ,Pro Natura Foundation Japan’s 31st Pro Natura Fundthe Project for Biodiversity Conservation Promotion of the Japan Ministry of the Environment.
文摘There are many short-lived animals,but those displaying a lifecycle with more than one generation per year(multivoltine lifecycle)are rare amongterrestrial vertebrates.The multivoltine lifecycle requires rapid growth and maturation and a long active season.Thus,small lizards in humidtropical or subtropical areas are candidates for multivoltine lifecycles.To test this prediction,we conducted a capture-mark-recapture study of asubtropical grass lizard,Takydromus toyamai,endemic to Miyako Islands,Japan.Juveniles grew very quickly,averaging 0.3 mm/day in the warmseason,and attained sexual maturity at 2.5 months post-hatching.The breeding season was very long,and hatchlings emerged from May toNovember.The prolonged breeding season and rapid growth to maturity allowed some individuals to produce a second generation in their frstyear.Estimates of hatching date from growth rates indicated that many females that hatched in May-June became gravid 76-120 days afterhatching and 122-165 days after oviposition of the eggs from which they hatched.Analyses of juvenile survivorship and month of hatching suggest that nearly half of breeding adults were members of multivoltine generations,although the 2 generations were not discrete.The species isshort-lived,with only 16% of individuals surviving beyond 12 months,and few individuals reproduced in a second year.We refer to this conditionas a“semi-multivoltine lifecycle.”Individuals that hatch late in the season defer reproduction until the following year and become founders ofthe next season’s cohort.This putative advantage of late-hatching individuals may have driven the evolution of this lifecycle.
基金funded by the Strategic Priority Research Program of Chinese Academy of Sciences (XDB31000000)the Joint Fund of the National Natural Science Foundation of China-Yunnan Province (U1902203)+1 种基金Major Program for Basic Research Project of Yunnan Province (202101BC070002)Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (151C53KYSB20200019)
文摘Patterns and drivers of species–genetic diversity correlations(SGDCs)have been broadly examined across taxa and ecosystems and greatly deepen our understanding of how biodiversity is maintained.However,few studies have examined the role of canopy structural heterogeneity,which is a defining feature of forests,in shaping SGDCs.Here,we determine what factors contribute toα-andβ-species–genetic diversity correlations(i.e.,α-andβ-SGDCs)in a Chinese subtropical forest.For this purpose,we used neutral molecular markers to assess genetic variation in almost all adult individuals of the dominant tree species,Lithocarpus xylocarpus,across plots in the Ailaoshan National Natural Reserve.We also quantified microhabitat variation by quantifying canopy structure heterogeneity with airborne laser scanning on 201-ha subtropical forest plots.We found that speciesα-diversity was negatively correlated with geneticα-diversity.Canopy structural heterogeneity was positively correlated with speciesα-diversity but negatively correlated with geneticα-diversity.These contrasting effects contributed to the formation of a negativeα-SGDC.Further,we found that canopy structural heterogeneity increases speciesα-diversity and decreases geneticα-diversity by reducing the population size of target species.Speciesβ-diversity,in contrast,was positively correlated with geneticβ-diversity.Differences in canopy structural heterogeneity between plots had non-linear parallel effects on the two levels ofβ-diversity,while geographic distance had a relatively weak effect onβ-SGDC.Our study indicates that canopy structural heterogeneity simultaneously affects plot-level community species diversity and population genetic diversity,and species and genetic turnover across plots,thus drivingα-andβ-SGDCs.
基金National Natural Science Foundation of China,No.42201170Young Elite Scientists Sponsorship Program by CAST,No.2022QNRC001。
文摘Arid West Asia(AWA)is a critical hub of the Silk Road and one of the primary dust source regions in the Northern Hemisphere.Dust storms in AWA emitting substantial dust particles into the atmosphere,significantly influencing air quality,climate change and marine productivity.However,the variability of dust storm activity in this region during the Holocene,particularly its links to vegetation and hydroclimatic changes,remains debated,hindering our understanding of the interconnected dynamics between climate change and surface environments.This study reconstructs dust storm variations in AWA over the past 9000 years using geochemical analyses(trace elements,Sr-Nd isotopes)from a well-dated,high-resolution sediment core from the Almalou Peatland,located on the western Iranian Plateau.Our results reveal a decline in dust storm frequency from the early to mid-Holocene,a minimum occurrence during the mid-Holocene,and a significant increase in the late Holocene.Provenance analysis indicates that the primary dust sources were the arid regions of Mesopotamia,located upwind of the study area.A comparison with proxy records and paleoclimate models suggests an inverse relationship between dust storm activity and regional hydroclimatic and vegetation changes,along with a positive correlation with wind speeds.The concentration of dust storms during the wetter month of May highlights wind speed as a more critical driving factor.Moreover,given the dominant influence of the subtropical high on hydroclimatic conditions and wind speeds in AWA,we propose that this system is the key regulator of regional dust storm dynamics.Our findings provide new insights into the drivers of dust storm activity in AWA and hold implications for developing targeted dust storm management strategies.
文摘Exploring the formation and changes in tree microclimates can help improve the quality of urban green spaces.Temperature is an important indicator of microcli-mate,and tree temperature categories can be divided into ambient temperature and tree surface temperature(T_(ts)),from which the mean radiation temperature(T_(mrt))and thermal comfort values are derived.In this study,the summer micro-climate of Ficus altissima in southern subtropical China was determined,focusing on soil(T_(s)),air(T_(a)),globe(T_(g)),and T_(ts).T_(mrt)and four commonly used thermal comfort indicators,i.e.,predicted mean vote(PMV),physiologically equivalent temperature(PET),standard effective temperature(SET^(*)),and universal thermal climate index(UTCI),were also cal-culated.The results showed that:(1)T_(mrt)can be used to explain both the cooling effect and to predict thermal com-fort in the shade;(2)the PET indicator is more advantageous for analyzing thermal comfort in the microclimate of Ficus altissima;(3)T_(s)is not a suitable important indicator for pre-dicting ambient temperatures and thermal comfort;and(4)the site-specific sampling method of the crowns or trunks can be used to accurately explain changes in the whole-plant thermal environment and thermal comfort,respectively.
基金supported by the Natural Science Foundation of China(Grant No:42105025,42075189,42275036,and 42430610)the National Key R&D Program of China under Grant 2021YFA0718000+3 种基金the China Meteorological Administration Youth Innovation Team(CMA2023QN15)China Meteorological Administration Key Innovation Team(CMA2024ZD07)the development fund of South China Sea Institute of Oceanology of the Chinese Academy of Sciences(SCSIO202203 and SCSIO202208)the Open Research Fund of the State Key Laboratory of Tropical Oceanography(South China Sea Institute of Oceanology,Chinese Academy of Sciences)(LTO2110)。
文摘The increase in frequency and intensity of Extreme High-temperature Events(EHEs)over Central-Eastern China(CEC)in recent decades has severely impacted social development and livelihoods.Using observation and reanalysis datasets,this study explores the effect of the East Asian subtropical westerly jet stream(EAJ)on the CEC EHEs for the summers spanning 1979–2020.Considering its general relative location to the right side of the upper-level jet stream exit region,CEC would theoretically suffer more EHEs with a stronger and northwardly-shifted EAJ in summer due to the likelihood of abnormal subsidence induced by the EAJ.However,such an EAJ–EHE connection has been unstable over the past four decades but has displayed an evident interdecadal change.Before the late 1990s,the interannual variation of the EAJ was manifested mainly by its meridional displacement in the northeastern part of East Asia;thus,the atmospheric responses were essentially located to the east of CEC,exerting less of an influence on the CEC EHEs.However,since the late 1990s,the EAJ variation has featured an intensity change in its center over the northwest portion of the CEC,which has resulted in a westward shift in atmospheric responses to cover the CEC region.Therefore,the EAJ could potentially affect the summer CEC EHEs during 2000–21.Our findings offer support for an in-depth understanding of the formation mechanisms of extreme weather/climate events of this nature and thus provide a scientific reference for seasonal climate predictions.
基金sponsored by the National Natural Science Foundation of China[grant number 42305011]。
文摘The present study employs statistical analysis to investigate the relationship between the geopotential height anomalies induced by tropical cyclones(TCs)and the meridional movement of the western Pacific subtropical high(WPSH),as well as the mechanisms through which TCs can induce such geopotential height anomalies.Results show that TCs can cause the WPSH to move northward,and the meridional motion of the WPSH ridgeline is related with the geopotential height anomalies,which is better indicated by the relative geopotential height anomalies.In the process of TCs causing the WPSH to move northward,the TCs cause abnormal horizonal warm(cold)advection and abnormal ascending(descending)motion in the region south(north)of 40°N.Since the influence of the abnormal vertical motion is weaker,the abnormal temperature tendency eventually shows a more consistent phase distribution with the abnormal horizonal temperature advection,which is favorable for the temperature to abnormally increase near 40°N.Such an abnormal increase in temperature causes the geopotential height to abnormally increase under the static equilibrium constraint,which further changes the location of the centroid of the WPSH geopotential height,and hence the location of the WPSH ridgeline changes as well.
基金supported by National Natural Science Foundation of China (No.30471386)Japanese Society for Promotion of Sciences (15P03118)
文摘Structure, species composition, and soil properties of a subtropical evergreen broad-leaved forest in Okinawa, Japan, were examined by establishment of plots at thirty sites. The forest was characterized by a relatively low canopy and a large number of small-diameter trees. Mean canopy height for this forest was 10 m and stands contained an average of 5400 stems-ha^-1 （ -〉 3.0 cm DBH）; 64% of those stems were smaller than 10 cm DBH. The total basal area was 54.4 m^2-ha^-1, of which Castanopsis sieboldii contributed 48%. The forest showed high species diversity of trees. 80 tree species （≥ 3.0 cm DBH） from 31 families was identified in the thirty sampling plots. C. sieboldii and Schima wallichii were the dominant and subdominant species in terms of importance value. The mean tree species diversity indices for the plots were, 3.36 for Diversity index （H＇）, 0.71 for Equitability index （J＇） and 4.72 for Species richness index （S＇）, all of which strongly declined with the increase of importance value of the dominant, C. sieboldii. Measures of soil nutrients indicated low fertility, extreme heterogeneity and possible A1 toxicity. Regression analysis showed that stem density and the dominant tree height were significantly correlated with soil pH. There was a significant positive relationship between species diversity index and soil exchangeable K^＋, Ca^2＋, and Ca^2＋/Al^3- ratio （all p values 〈0.001） and a negative relationship with N, C and P. The results suggest that soil property is a major factor influencing forest composition and structure within the subtropical forest in Okinawa.
基金Supported by Special Fund of Sichuan Financial Genetic Engineering(2011QNJJ-019)Science and Technology Support Program of Sichuan Province(2011NZ0068)"12th Five-Year Plan" Breeding Project of Crops and Livestock of Sichuan Province(2011NZ0098-15)~~
文摘[Objective] The aim was to make full use of light-heat resources to expand the potato planting area on the base of ensuring the production of main grain crops and the limited arable land. [Methods] Through catch crops, multiple cropping and intercropping, new multiple planting patterns of potato with efficiency are constructed, for the purpose of increasing yield and benefit of potato. [Result] In irrigated plain and hill area, three new planting patterns such as autumn potato/rope-rice,winter potato-rice-autumn potato, and autumn（winter） potato-rice were constructed.In dry land of plain and hill area, three new planting patterns such as spring（winter）potato/maize/sweet potato, spring（winter） potato/maize-autumn potato, and wheat ＋ winter potato/maize/sweet potato were constructed. In plateau mountainous area, spring potato/maize was constructed. [Conclusion] With use of new planting patterns, the cropping index of new patterns was 200%-300%, while the accumulated temperature utilization was 68.9%-93.4%, light energy utilization was 0.98%-1.59% and straw utilization was 50%-100%. To compared with traditional planting patterns, the yield increased by 2.6%-93%, and benefit increased by 15.8%-284.3%. Furthermore,multiple planting patterns of potato have become main planting patterns in increasing yield and income in Sichuan.
文摘The dimension, water content and germination of the seeds from 90 woody species in the lower subtropical forest were analyzed in this study. Out of 90 species, germination analysis was performed in 45 species (in which there were enough germinating individuals), and the effect of storage of seed and fruit on germination of seed was studied in 41 species (in which there were enough seeds and germinating individuals). Most of the species began to germinate within 60 d. Hypogeal species had longer dormancy than epigeal species. Dormancy of fleshy seeds and seeds in pulpy fruit was also longer than that of dry seeds. There were no significant differences in length of dormancy (LD, days from sowing to germination) between fleshy seeds ripening in summer and those ripening in winter and spring, and between big seeds and small seeds. Seeds in pulpy fruit or fleshy seeds had more germination than the dry seeds ( P <0.05), however, percentage germination was not significantly correlated with water content of fresh seeds. Water loss in the seeds could obviously affect percentage germination, especially during the early three days when the seeds were laid open in air in the laboratory. When water content of the seeds decreased to about 20% (fresh weight basis), percentage germination became very low, this happened when the seeds were laid open in air for 10-14 d. Percentage germination decreased with the length of storing in refrigerator ((4±1) ℃), but it was not markedly affected for one month's storage, with a decrease by 8.3% in comparison with the fresh seeds, and it was greatly affected by storing for more than three months, with values decreasing by 37%, 63%, and 81% for three months', six months' and 12 months' storage respectively. Difference in percentage germination as well as in LD was not significant for most lots after different storing periods between big seeds and small seeds, between fruit storage and seed storage, and between seeds in pulpy fruits or fleshy seeds and dry seeds.
文摘By using the monthly mean grid data of NCAR/NCEP reanalysis at 500 hPa geopotential height from 1958 to 1997,the relationship between the Northeast cold vortex and the western Pacific subtropical high was analyzed.The influence of the sea surface temperature(SST) and outgoing longwave radiation(OLR) on the Northeast cold vortex and subtropical high was studied.As was shown in the results,in summer,there was a positive correlation between the Northeast cold vortex and the subtropical high,and an anti-phase relationship existed between the threshold characteristic line of GMS-SST=28 ℃ and the height index of the Northeast cold vortex and the subtropical high.With the gradual northward moving of the threshold characteristic line,the subtropical high was weakening,and the Northeast cold vortex was increasing and strengthening.
基金Supported by Projects Funded by Scientific Research Special Fund for Public Welfare Industry (GYHY20076029)
文摘The monthly observed average precipitation data of 160 meteorological stations in China from 1960 to 2007,had been reorganized by the China Meteorological Administration.By employing that precipitation data,NCEP/NCAR reanalysis data and the index of intensity of western Pacific subtropical high,the seasonal variations of subtropical high and precipitation in eastern China during the past decades are discussed.The relationships between them also are discussed by correlation and composite analyses.The results show that the intensity of subtropical high,which has significantly strengthened in the recent 50 years,especially in spring,autumn and winter,has notable impact on the simultaneous rainfall in the eastern region of China for all seasons,especially in winter.
基金supported by "Definition of the south edge of the subtropical winter monsoon in East Asian and its variation characteristics" of The High School Specialized Research Fund for The Doctoral Program Funding Issue in 2011 (20113228110003)
文摘Based on observational daily data of 730 meteorological stations in China, the south edge of the subtropical winter monsoon is defined according to relevant criterion and its variation characteristics are analyzed. Results show that this south edge has obvious inter-annual variation characteristics and shows a northward moving tendency as a whole, but since the 21 st century it has moved southwards and date of the south edge entering winter becomes earlier. Wind fields of the anomalously northward south edge of the subtropical winter monsoon in East Asia has an obvious southerly wind component which prevents cold air from moving southward. The index of this south edge and winter temperature has a positive correlation. Climate warming might be the main reason for the northward movement of the south edge of the subtropical winter monsoon.
基金supported by the Innovation Key Prograrn of the Chinese Academy of Sciences ZKCX2-SW-210the National Natural Science Foundation of China under Grant Nol40135020,and 40233033.
文摘Using the relative vorticity averaged over a certain area, a new index for measuring the longitudinal position of the subtropical high (SH) in the western Pacific is proposed to avoid the increasing trend of heights in the previous indices based on geopotential height. The years of extreme westward and eastward extension of SH using the new index are in good agreement with those defined by height index. There exists a distinct difference in large-scale circulation between the eastward and westward extension of SH under the new definition, which includes not only the circulation in the middle latitudes but also the flow in the lower latitudes. It seems that when the SH extends far to the east (west), the summer monsoon in the South China Sea is stronger (weaker) and established earlier (later). In addition, there exists a good relationship between the longitudinal position of SH and the summer rainfall in China. A remarkable negative correlation area appears in the Changjiang River valley, indicating that when the SH extends westward (eastward), the precipitation in that region increases (decreases). A positive correlation region is found in South China, showing the decrease of rainfall when the SH extends westward. On the other hand, the rainfall is heavier when the SH retreats eastward. However, the anomalous longitudinal position of SH is not significantly related to the precipitation in North China. The calculation of correlation coefficients between the index of longitudinal position of SH and surface temperature in China shows that a large area of positive values, higher than 0.6 in the center, covers the whole of North China, even extending eastward to the Korean Peninsula and Japan Islands when using NCEP/NCAR reanalysis data to do the correlation calculation. This means that when the longitudinal position of the SH withdraws eastward in summer, the temperature over North China is higher. On the other hand, when it moves westward, the temperature there is lower. This could explain the phenomenon of the seriously high temperatures over North China during recent summers, because the longitudinal position of SH in recent summers was located far away from the Asian continent. Another region with large negative correlation coefficients is found in South China.
文摘Using the data of 500 hPa geopotential height from 1951 to 1995, SST roughly in the same period and OLR data from 1974 to 1994, the relation between the anomalies of subtropical high (STH for short) and the tropical circulations including the Asian monsoon as well as the convective activity are studied. In order to study the physical process of the air-sea interaction related to STH anomaly, the correlation of STH with SST at various sea areas, lagged and simultaneous, has been calculated. Comparing the difference of OLR, wind fields, vertical circulations and SST anomalies in the strong and weak STH, we investigate the characteristics of global circulations and the SST distributions related to the anomalous STH at the western Pacific both in winter and summer. Much attention has been paid to the study of the air-sea interaction and the relationship between the East Asian monsoon and the STH in the western Pacific. A special vertical circulation, related to the STH anomalies is found, which connects the monsoon current to the west and the vertical flow influenced by the SST anomaly in the tropical eastern Pacific.
基金Project supported by the National Natural Science Foundation of China (NO. 30270283)the "100-Talent" Project of the Chinese Academy of Sciences (CAS)the Director Foundation of South China Institute of Botany, CASthe Innovation Priority Project of CAS (No. KSCX2-SW-120).
文摘A field-scale experiment arranged in a complete randomized block design with three N addition treatments including a control (no addition of N), a low N (5 g m-2 year-1), and a medium N (10 g m-2 year-1) was performed in each of the three typical forests, a pine (Pinus massoniana Lamb.) forest (PF), a pine-broadleaf mixed forest (MF) and a mature monsoon evergreen broadleaf forest (MEBF), of the Dinghushan Biosphere Reserve in subtropical China to study the response of soil fauna community to additions of N. Higher NH4+ and NO3- concentrations and a lower soil pH occurred in the medium N treatment of MEBF, whereas the NO3- concentration was the lowest in PF after the additions of N. The response of the density, group abundance and diversity index of soil fauna to addition of N varied with the forest type, and all these variables decreased with increasing N under MEBF but the trend was opposite under PF. The N treatments had no significant effects on these variables under MF. Compared with the control plots, the medium N treatment had significant negative effect on soil fauna under MEBF. The group abundance of soil fauna increased significantly with additions of higher N rates under PF. These results suggested that the response of soil fauna to N deposition varied with the forest type and N deposition rate, and soil N status is one of the important factors affecting the response of soil fauna to N deposition.
基金supported by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(XDA05050205)"International Science&Technology Cooperation Program of China(2012DFB30030)""Youth Innovation Fund of Hunan Academy of forestry"and the CFERN&GENE Award Funds for Ecological Papers
文摘To better understand the effect of forest succession on carbon sequestration, we investigated carbon stock and allocation of evergreen broadleaf forest, a major zonal forest in subtropical China. We sought to quantify the carbon sequestration potential. We sampled four forest types, shrub （SR）, pine （Pinus massoniana） forest （PF）, pin~ and broadleaf mixed forest （Mr） and evergreen broadleaf forest （BF）. A regression equation was constructed using tree height and diameter at breast height （DBH） and elements of total tree biomass. The equation was subse- quently utilized to estimate tree carbon storage. The carbon storage of understory, litter, and soil was also estimated.
基金This work was supported by the National Key Basic Research and Development Project of China 2004CB18300the Key Knowledge Innovation Project of Chinese Academy of Sciences(Grand No.KZCX3-SW-226)the National Natural Science Foundation of China under Grant Nos.40135020 and 40325015.
文摘Using the NCEP/NCAR reanalysis data, the China rainfall data of the China Meteorological Administration, and the sea surface temperature (SST) data of NOAA from 1951-2000, the features of the anomalous longitudinal position of the subtropical high in the western Pacific (SHWP) in the pre-rainy season in South China and associated circulation and precipitation are studied. Furthermore, the relationship between SHWP and SST and the eastern Asian winter monsoon is also investigated. Associated with the anomalous longitudinal position of SHWP in the pre-rainy season in South China, the flow patterns in both the middle and lower latitudes are different. The circulation anomalies greatly influence the precipitation in the pre-rainy season in South China. When the SHWP is in a west position (WP), the South China quasi-stationary front is stronger with more abundant precipitation there. However, when the SHWP is in an east position (EP), a weaker front appears with a shortage of precipitation there. There exists a good relationship between the longitudinal position of SHWP and SST in the tropical region. A negative correlation can be found both in the central and eastern tropical Pacific and the Indian Ocean. This means that the higher (lower) SST there corresponds to a west (east) position of SHWP. This close relationship can be found even in the preceding autumn and winter. A positive correlation appears in the western and northern Pacific and large correlation coefficient values also occur in the preceding autumn and winter. A stronger eastern Asian winter monsoon will give rise to cooler SSTs in the Kuroshio and the South China Sea regions and it corresponds to negative SST anomaly (SSTA) in the central and eastern Pacific and positive SSTA in the western Pacific in winter and the following spring. The whole tropical SSTA pattern, that is, positive (negative) SSTA in the central and eastern Pacific and negative (positive) SSTA in the western Pacific, is favorable to the WP (EP) of SHWP.
基金Project supported by the International Foundation of Science(No.C/2661-1)the National Key Basic Research Support Foundation of China(No.G1999011809).
文摘Agriculture is still the biggest contributor of non-point source (NPS) pollution to water bodies andrunoff discharges of nutrients and other chemicals are one of the most important pathways. This studywas conducted during 1998～1999 in a typical watershed with complex agriculture and forestry systems aswell as dotted farmer villages, in a transitional region between the mid- and northern subtropical zones ofChina. Continuous sampling of stream water was performed regularly at a weekly frequency, with additionalsampling after all major rainfall events. The discharges of N and P nutrients and suspended materials weremeasured and the total and area-averaged annual discharges of all components were calculated. The resultsshowed an uneven seasonal distribution of nutrient discharges with summer storms contributing most tothe total fluxes. This study demonstrated a high dependence of runoff volume on rainfall but the overallrunoff coefficients were dependent on land use type and watershed size. The area-averaged annual dischargesvaried greatly among the sub-watersheds with different sizes and land use structures. This is the first studyestimating the area-averaged annual discharges of N and P in the hilly areas of subtropical China, which were1.5 g m-2 a-1 and 0.1 g m-2 a-1, respectively, providing important reference values for the assessment ofregional agricultural non-point source pollution.
