Seasonal Dynamics of Terrestrial Net Primary Production in Response to Climate Changes in China

Study on seasonal responses of terrestrial net primary production (NPP) to climate changes is to help understand feedback between climate systems and terrestrial ecosystems and mechanisms of increased NPP in the northern middle and high latitudes. In this study, time series dataset of normalized difference vegetation index (NDVI) and corresponding ground-based information on vegetation, climate, soil, and solar radiation, together with an ecological process model, were used to explore the seasonal trends of terrestrial NPP and their geographical differences in China from 1982 to 1999. As the results,. seasonal total NPP in China showed a significant increase for all four seasons (spring, summer, autumn and winter) during the past 18 years. The spring NPP indicated the largest increase rate, while the summer NPP was with the largest increase in magnitude. The response of NPP to climate changes varied with different vegetation types. The increased NPP was primarily led by an advanced growing season for broadleaf evergreen forest, needle-leaf evergreen forest, and needle-leaf deciduous forest, whilst that was mainly due to enhanced vegetation activity (amplitude of growth cycle) during growing season for broadleaf deciduous forest, broadleaf and needle-leaf mixed forest, broadleaf trees with groundcover, perennial grasslands, broadleaf shrubs with grasslands, tundra, desert, and cultivation. The regions with the largest increase in spring NPP appeared mainly in eastern China, while the areas with the largest increase in summer NPP occurred in most parts of Northwestern China, Qinghai-Xizang Plateau, Mts. Xiaoxinganling-Changbaishan, Sanjiang Plain, Songliao Plain, Sichuan Basin, Leizhou Peninsula, part of the middle and lower Yangtze River, and southeastern mountainous areas of China. In autumn, the largest NPP increase appeared in Yunnan Plateau-Eastern Xizang and the areas around Hulun Lake. Such different ways of the NPP responses depended on regional climate attributes and their changes.

Responses of Vegetation and Primary Production in North-South Transect of Eastern China to Global Change Under Land Use Constraint

A regional model of vegetation dynamics was revised to include land use as a constraint to vegetation dynamics and primary production processes. The model was applied to a forest transect in eastern China (NSTEC, North-South transect of eastern China) to investigate the responses of the transect to possible future climatic change. The simulation result indicated that land use has profound effects on vegetation transition and primary production. In particular, land use reduced competition among vegetation classes and tended to result in less evergreen broadleaf forests but more shrubs and grasses in the transect area. The simulation runs with land use constraint also gave much more realistic estimation about net primary productivity as well as responses of the productivity to future climatic change along the transect. The simulations for future climate scenarios projected by general circulation models (GCM) with doubled atmospheric CO2 concentration predicted that deciduous broadleaf forests would increase, but conifer forests, shrubs and grasses would decrease. The overall effects of doubling CO2 and climatic changes on NSTEC were to produce an increased net primary productivity (NPP) at equilibrium for all seven GCM scenarios. The predicted range of NPP variation in the north is much larger than that in the south.

Influence of mesoscale eddies on primary production in the South China Sea during spring inter-monsoon period

Mesoscale eddies have been suggested to have an impact on biological carbon fixation in the South China Sea （SCS）. However, their overall contribution to primary production during the spring inter-monsoon pe riod is still unknown. Based on large-scale biological and environmental in situ observations and synchro nous remote sensing data, the distribution patterns of phytoplankton biomass and the primary production, and the role of mesoscale eddies in regulating primary production in different eddy-controlled waters were investigated. The results suggested that the surface chlorophyll a concentrations and water column inte grated primary production （IPP） are significantly higher in cyclonic eddies and lower in the anticyclonic eddies as compared to that in non-eddy waters. Although eddies could affect various environmental factors, such as nutrients, temperature and light availability, nutrient supply is suggested to be the most important one through which mesoscale eddies regulated the distribution patterns of phytoplankton biomass and pri mary production. The estimated IPP in cyclonic and anticyclonic eddies are about 29.5% higher and 16.6% lower than the total average in the whole study area, respectively, indicating that the promotion effect of mesoscale cold eddies on the primary production was much stronger than the inhibition effect of the warm eddies per unit area. Overall, mesoscale eddies are crucial physical processes that affect the biological car bon fixation and the distribution pattern of primary production in the SCS open sea, especially during the spring inter-monsoon period.

Global patterns in above-ground net primary production and precipitation-use efficiency in grasslands

The above-ground net primary production(ANPP) and the precipitation-use efficiency(PUE) regulate the carbon and water cycles in grassland ecosystems, but the relationships among the ANPP, PUE and precipitation are still controversial. We selected 717 grassland sites with ANPP and mean annual precipitation(MAP) data from 40 publications to characterize the relationships ANPP–MAP and PUE–MAP across different grassland types. The MAP and ANPP showed large variations across all grassland types, ranging from 69 to 2335 mm and 4.3 to 1706 g m^(-2), respectively. The global maximum PUE ranged from 0.19 to 1.49 g m^(-2) mm^(-1) with a unimodal pattern. Analysis using the sigmoid function explained the ANPP–MAP relationship best at the global scale. The gradient of the ANPP–MAP graph was small for arid and semi-arid sites(MAP <400 mm). This study improves our understanding of the relationship between ANPP and MAP across dry grassland ecosystems. It provides new perspectives on the prediction and modeling of variations in the ANPP for different grassland types along precipitation gradients.

Response of Growing Season Gross Primary Production to El Nino in Different Phases of the Pacific Decadal Oscillation over Eastern China Based on Bayesian Model Averaging

Gross primary production(GPP) plays a crucial part in the carbon cycle of terrestrial ecosystems.A set of validated monthly GPP data from 1957 to 2010 in 0.5°× 0.5° grids of China was weighted from the Multi-scale Terrestrial Model Intercomparison Project using Bayesian model averaging(BMA).The spatial anomalies of detrended BMA GPP during the growing seasons of typical El Nino years indicated that GPP response to El Nino varies with Pacific Decadal Oscillation(PDO) phases: when the PDO was in the cool phase,it was likely that GPP was greater in northern China(32°–38°N,111°–122°E) and less in the Yangtze River valley(28°–32°N,111°–122°E);in contrast,when PDO was in the warm phase,the GPP anomalies were usually reversed in these two regions.The consistent spatiotemporal pattern and high partial correlation revealed that rainfall dominated this phenomenon.The previously published findings on how El Nino during different phases of PDO affecting rainfall in eastern China make the statistical relationship between GPP and El Nino in this study theoretically credible.This paper not only introduces an effective way to use BMA in grids that have mixed plant function types,but also makes it possible to evaluate the carbon cycle in eastern China based on the prediction of El Nino and PDO.

A preliminary study on the response of marine primary production to monsoon variations in the South China Sea Basic characteristics

Seasonal, interannual and interdecadal variations of monsoon over the South China Sea （SCS） directly influence the ocean circulation and the mass transport process, etc. , especially the changes of horizontal circulation pattern and upwelling area. These changes directly influence the nutrient transport and the photosynthesis of phytoplankton, which induce the change of the marine ecosystem in the SCS, including the change of marine primary production in this sea area. On the basis of climatic data for long-time series and primary production estimated by remote sensing, the multi-time scale variations of monsoon, seasonal and interannual variations of primary production, and the response of primary production to monsoon variations were analyzed. Furthermore, the spatio-temporal variations of primary production in different sea areas of the SCS and their relations to the monsoon variations were given. The results showed that the strong southwesterly prevailed over the SCS in summer whereas the vigorous northeasterly in winter. The seasonal primary production in the entire sea area of the SCS also produced a strong peak in winter and a suhpeak in summer. And the seasonal primary production distributions displayed different characteristics in every typical sea area. The variations of the annual and summer averaged primary production in the entire sea area of the SCS showed almost the same rising trend as the intensity of the summer monsoon. Especially for 1998, the summer monsoon reached almost the minimum in the past 54 a when the primary production was also found much lower than any other year （ 1999--2005 ）. The responses of annual primary production to monsoon variation were displayed to different extent in different sea areas of the SCS ; especially it was better in the deep sea basin. Such research activities could be very important for revealing the response of marine ecosystem to the monsoon variations in the SCS.

Aboveground biomass and net primary production of semi-evergreen tropical forest of Manipur,north-eastern India

The aboveground biomass dynamics and net primary productivity were investigated to assess the productive potential of Dipterocarpus forest in Manipur, Northeast India.Two forest stands(stand I and II) were earmarked randomly in the study site for the evaluation of biomass in the different girth classes of tree species by harvest method.The total biomass was 22.50 t·ha-1 and 18.27 t·ha-1 in forest stand I and II respectively.Annual aboveground net primary production varied from 8.86 to 10.43 t·ha-1 respectively in two forest stands(stand I and II).In the present study, the values of production efficiency and the biomass accumulation ratio indicate that the forest is at succession stage with high productive potential.

Linkages between the biomass of Scomber japonicus and net primary production in the southern East China Sea

Fish biomass is a critical component of fishery stock assessment and management and it is often estimated from ocean primary production（OPP）. However, the relationship between the biomass of a fish stock and OPP is always complicated due to a variety of trophic controls in the ecosystem. In this paper, we examine the quantitative relationship between the biomass of chub mackerel（Scomber japonicus） and net primary production（NPP） in the southern East China Sea（SECS）, using catch and effort data from the Chinese mainland large light-purse seine fishery logbook and NPP derived from remote sensing. We further discuss the mechanisms of trophic control in regulating this relationship. The results show a significant non-linear relationship exists between standardized CPUE（Catch-Per-Unit-Effort） and NPP（P〈0.05）. This relationship can be described by a convex parabolic curve, where the biomass of chub mackerel increases with NPP to a maximum and then decreases when the NPP exceeds this point. The results imply that the ecosystem in the SECS is subject to complex trophic controls. We speculate that the change in abundance of key species at intermediate trophic levels and/or interspecific competition might contribute to this complex relationship.

Size structure of biomass and primary production of phytoplankton：environmental impact analysis in the Dongsha natural gas hydrate zone, northern South China Sea

The size-fractionated biomass and primary production of phytoplankton, and the influence of environmental factors on it were studied in the Dongsha natural gas hydrate zone of the northern South China Sea in May 2013.Low nutrient, low chlorophyll a（Chl a） and primary productivity characteristics were found in these waters. The phenomena of subsurface Chl a maximum layers（SCMLs） and primary production maximum layers（SPMLs）were observed in the Dongsha waters. There were significant differences in the size-fractionated biomass and primary production that showed picophytoplankton〉nanophytoplankton〉microphytoplankton in terms of biomass and degree of contribution to production. Vertical biomass distribution indicated there were considerable differences among different phytoplankton within the euphotic zone（Zeu） in spring. For example,microphytoplankton was distributed evenly in the euphotic layer and nanophytoplankton was mainly distributed in the subsurface or in the middle of the euphotic layer, while picophytoplankton was mainly distributed in the middle or bottom of the euphotic layer. Smaller cell size and larger relative surface area allow picophytoplankton to benefit from nutrient competition and to hold a dominant position in the tropical oligotrophic waters of low latitudes. There was a positive correlation between size-fractionated biomass and temperature with pH and a negative correlation between size-fractionated biomass and silicate with phosphate. There was a positive correlation between size-fractionated primary production and temperature and a negative correlation between size-fractionated biomass and salinity with phosphate. Phosphate was an important factor influencing the size structure of phytoplankton. Meanwhile, irradiation and the euphotic layer were more important in regulating the vertical distribution of size-fractionated phytoplankton in the Dongsha natural gas hydrate zone.

Distribution characteristics of size-fractionated chlorophyll a, primary production and new production in the Laizhou Bay, July 1997

The distributions of chlorophyll a concentration, primary production and new productionwere observed in the Laizhou Bay of the Bohai Sea in both spring and neap tides during July 1997. The results showed that there were marked features of spatial zonation in the surveyed area, due to the differences between the geographic environment and the hydrological conditions. Chlorophyll a, primary production and new production were all higher in spring tides than that in neap tides in the Laizhou Bay. The highest values of these parameters were encountered in the central regions of the bay. At most stations, chlorophyll a concentrations at the bottom were higher than that at the surface. The results of size-fractionated chlorophyll a and primary production showed that contributions of nanocombining pi-coplankton ( <20 μm) to total chlorophyll a and primary production were dominant in phytoplankton community biomass and production of the Laizhou Bay. The environmental factors, primary production and new production in the Laizhou Bay are compared with other sea areas.

Ocean-atmosphere Teleconnections Play a Key Role in the Interannual Variability of Seasonal Gross Primary Production in China

Since the 1950s,the terrestrial carbon uptake has been characterized by interannual variations,which are mainly determined by interannual variations in gross primary production(GPP).Using an ensemble of seven-member TRENDY(Trends in Net Land-Atmosphere Carbon Exchanges)simulations during 1951-2010,the relationships of the interannual variability of seasonal GPP in China with the sea surface temperature(SST)and atmospheric circulations were investigated.The GPP signals that mostly relate to the climate forcing in terms of Residual Principal Component analysis(hereafter,R-PC)were identified by separating out the significant impact from the linear trend and the GPP memory.Results showed that the seasonal GPP over China associated with the first R-PC1(the second R-PC2)during spring to autumn show a monopole(dipole or tripole)spatial structure,with a clear seasonal evolution for their maximum centers from springtime to summertime.The dominant two GPP R-PC are significantly related to Sea Surface Temperature(SST)variability in the eastern tropical Pacific Ocean and the North Pacific Ocean during spring to autumn,implying influences from the El Niño-Southern Oscillation(ENSO)and the Pacific Decadal Oscillation(PDO).The identified SST and circulation factors explain 13%,23%and 19%of the total variance for seasonal GPP in spring,summer and autumn,respectively.A clearer understanding of the relationships of China’s GPP with ocean-atmosphere teleconnections over the Pacific and Atlantic Ocean should provide scientific support for achieving carbon neutrality targets.

Aboveground biomass and net primary production of semi-evergreen tropical forest of Manipur, north-eastern India

The aboveground biomass dynamics and net primary productivity were investigated to assess the productive potential of Diptero- carpus forest in Manipur, Northeast India. Two forest stands （stand Ⅰ and Ⅱ） were earmarked randomly in the study site for the evaluation of biomass in the different girth classes of tree species by harvest method. The total biomass was 22.50 t.ha^-1 and 18.27 t.ha^-1 in forest stand I and II respectively. Annual aboveground net primary production varied from 8.86 to 10.43 t.ha^-1 respectively in two forest stands （stand Ⅰ and Ⅱ）. In the present study, the values of production efficiency and the biomass accumulation ratio indicate that the forest is at succession stage with high productive potential.

Chlorophyll a and primary production in the northeastern Pacific Ocean

The primary production and chlorophyll a concentration of picoplankton （0.2 - 2 μm） , nanoplankton （2 - 20μm） and micro- plankton （20 -200 μm） are described in the northeastern Pacific Ocean near the Hawaii Islands during the six survey cruises from 1996 to 2003：DY85-4, DY95-7, DY95-8, DY95-10, DY105-11 and DY105-12.14. The primary production of carbon was in range from 76.8 to 191.9 mg/（m^2 · d） with an average of 116.1 mg/（ m^2 · d） in the east region, and from 73.1 to 222.5 mg/（ m^2 · d） with an average of 127.1 mg/（ m^2 · d） in the west region, similar to the other oligotrophic regions of the Pacific Ocean investigated. The chlorophyll a concentration was about 0.1 mg/m^3 from the surface to the 50 m depth, about 0.2 -0.4 mg/m^3from 50 to 100 m, and gradually decreased below the 100 m depth. The picoplankton accounted for more than 70% of the total chlorophyll a in the upper layer （ surface to 125 m）, but it decreased to less than 50% in depth below 125 m. The nanoplankton and microplankton combined only accounted for less than 30% of the total chlorophyll a in the upper layer, but showed a more even vertical distribution.

Modeling Gross Primary Production by Integrating Satellite Data and Coordinated Flux Measurements in Arid and Semi-Arid China

Assessing large-scale patterns of gross primary production (GPP) in arid and semi-arid (ASA) areas is important for both scientific and practical purposes.Remote sensing-based models,which integrate satellite data with input from ground-based meteorological measurements and vegetation characteristics,improve spatially extended estimates of vegetation productivity with high accuracy.In this study,the authors simulated GPP in ASA areas by integrating moderate resolution imaging spectral radiometer (MODIS) data with eddy covariance and meteorological measurements at the flux tower sites using the Vegetation Photosynthesis Model (VPM),which is a remote sensing-based model for analyzing the spatial pattern of GPP in different land cover types.The field data were collected by coordinating observations at nine stations in 2008.The results indicate that in the region during the growing season GPP was highest in cropland sites,second highest in woodland sites,and lowest in grassland sites.VPM captured the temporal and spatial characteristics of GPP for different land covers in ASA areas.Further,Enhanced Vegetation Index (EVI) had a strong liner relationship with GPP in densely vegetated areas,while the Normalized Difference Vegetation Index (NDVI) had a strong liner relationship with GPP over less dense vegetation.This study demonstrates the potential of satellite-driven models for scaling-up GPP,which is a key component for studying the carbon cycle at regional and global scales.

Standing crop and primary production of benthic microalgae on tidal flats in the Sanggou and Jiaozhou Bays, China

The standing crop and primary production of benthic microalgae on tidal flats have seasonally been observed in the Sanggou and Jiaozhou Bays of the northern China coast during 1999 - 2000. The results show that the annual primary productions of benthic microalgae on tidal flats in the two bays are 2 532 and 7 542 tons carbon, which would be able to support 3.1 x 103 and 9.2 x 103 tons shellfish meat, respectively. The nature of sediment is essential for governing the biomass and primary production of benthic microalgae on tidal flats. The biomass and primary production of benthic microalgae on tidal flats with muddy sediments are higher than those with sandy sediments, which resulted from higher nutrient concentration and lower grazing pressure. That is the reason why in comparison with Xiangshan Bay the standing crop and production of benthic microalgae on tidal flats of the Sanggou and Jiaozhou Bays are low. Light was a key factor controlling vertical distribution of biomass and production of benthic microalgae on tidal flats of the two bays, resulted in appearance of maximum chlorophyll a and primary production at the surface layer and sharply decreased with depth of sediment.

Size-fractionated phytoplankton standing stock and primary production in the Bohai Sea during late spring

During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chi a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be found. Chlorophyll a concentration vertically decreased from surface to bottom in the Liaodong Gulf and the Bohai Gulf, while it increased in the Laizhou Bay, the strait and the central region of the Bohai Sea, and the highest value was encountered at the bottom. Size-fractionation results showed that nano - combining pico -plankton ( < 20 μm) predominated in phytoplankton communities of the Bohai Sea during late spring. The average contribution to total Chl a in each station ranged 76% -95 % (mean is 87 %). The contribution of net (> 20 μm), nano - (2- 20 fan) and picoplankton (< 2 μm) was 13% , 63% and 24% to total production, and 9% , 53% and 38% to total Chl a, respectively. It proved the importance of nano - and pico -plankton in phytoplankton communities in the Bohai Sea e-cosystems. In this paper the factors, such as light intensity and zooplankton grazing pressure, governing standing stock and production of phytoplankton in the Bohai Sea were also discussed.

Standing Crop and Primary Production of Benthic Microalgae on the Tidal Flats in Yueqing Bay

The standing stock and primary production of benthic microalgae on tidal flats were measured seasonally at 3 transects (Puqing, Dahengchuang and Puqi) in Yueqing Bay during 2002 2003. The results showed that the integral chlorophyll a (Chl a) concentration in tidal flat mud exhibited a seasonal variation with the order of magnitude: winter (14.0 4.2 mg m-2) > spring (13.0 6.3 mg m-2) > autumn (7.7 5.9 mg m-2) > summer (4.6 3.2 mg m-2). The primary production showed an order of magnitude: spring (270.5 224.9 mgC m-2 d-1)>winter (238.7 225.5 mgC m-2 d-1)>autumn (214.1 56.2 mgC m-2 d-1)>summer (71.6 44.6 mgC m-2 d-1). Both chlorophyll a and primary production showed maximum values in the surface layer of sediment, and decreased rapidly with increasing depth due to sun light limitation. The results of variance analysis indicated that seasonal variation and tidal flat condition affected Chl a greatly, but had no significant effect on primary production. The annual primary production of benthic microalgae on tidal flats in Yueqing Bay was estimated at 16143 tons carbon, which is sufficient to support 1.02×105 tons shellfish production. The environmental factors affecting chlorophyll and primary production on the tidal flats in Yueqing Bay were discussed. By comparing with other bays on China's coast, it was observed that Yueqing Bay is a region with high benthic microalgae standing crop and primary production, which may be related to the type of its sediment.

Study of monthly variations in primary production and their relationships with environmental factors in the Daya Bay based on a general additive model

In this study, the horizontal and vertical distribution of primary production(PP) and its monthly variations were described based on field data collected from the Daya Bay in January–December of 2016. The relationships between PP and environmental factors were analyzed using a general additive model(GAM). Significant seasonal differences were observed in the horizontal distribution of PP, while vertical distribution showed a relatively consistent unimodal pattern. The monthly average PP(calculated by carbon) ranged from 48.03 to 390.56 mg/(m~2·h),with an annual average of 182.77 mg/(m~2·h). The highest PP was observed in May and the lowest in November.Additionally, the overall trend in PP was spring>summer>winter>autumn, and spring PP was approximately three times that of autumn PP. GAM analysis revealed that temperature, bottom salinity, phytoplankton, and photosynthetically active radiation(PAR) had no significant relationships with PP, while longitude, depth, surface salinity, chlorophyll a(Chl a) and transparency were significantly correlated with PP. Overall, the results presented herein indicate that monsoonal changes and terrestrial and offshore water systems have crucial effects on environmental factors that are associated with PP changes.

Primary Production and the Hydrochemical Parameters of the Salt Lakes in the North-Western Part of the Crimea(Russia)

1 Introduction It is known that more than 300 lakes and lagoons are present in the Crimean Peninsula,which are divided depending on position to 7 groups:Perekop,Tarkhankut,Evpatoriyskaya,Khersonesskaya,lake on the mountainpastures,Kerch and Genicheskaya.Almost the all lakes,with the exception of the small freshwater lakes,which situated on mountain pastures of the Main ridge of

Specific oceanographic characteristics and phytoplankton responses influencing the primary production around the Ulleung Basin area in spring

The East Sea(Sea of Japan)is a marginal,semi-closed sea in the northwestern Pacific.The Ulleung Basin area,which is located near the subpolar front of the East Sea,is known to have high primary production and good fisheries in spring season.After episodic wind-driven events during the spring of 2017,horizontal and vertical profiles of physical chemical biological factors were investigated at 29 stations located in the Ulleung Basin area.In addition,growth responses of phytoplankton communities to nutrient additions were evaluated by bioassay experiments to understand the fluctuation of phytoplankton biomass.Because of strong northwestern wind,phytoplankton biomass was scattered and upwelling phenomenon might be suppressed in this season.The phytoplankton abundances in the coastal stations were significantly higher than offshore and island stations.In contrast,the nutrient and chlorophyll a(Chl a)concentrations and the phytoplankton biomass were quite low in all locations.Bacillariophyceae was dominated group(>75.1%for coastal,40.0%for offshore and 43.6%for island stations).In the algal bioassays,the phytoplankton production was stimulated by N availability.The in vivo Chl a values in the+N and+NP treatments were significantly higher than the values in the control and the+P treatments.Based on the field survey,the higher nutrients in coastal waters affected the growth of diatom assemblages,however,little prosperity of phytoplankton was observed in the offshore waters despite the injection of sufficient nutrients in bioassay experiments.The growth of phytoplankton depended on the initial cell density.All of results indicated that a dominant northwestern wind led to a limited nutrients condition at euphotic layers,and the low level of biomass supply from the coasts resulted in low primary production.Both supplying nutrients and introducing phytoplankton through the currents are critical to maintain the high productivity in the Ulleung Basin area of the East Sea.