A statistical dynamics model of the marine ecosystem and its application in Jiaozhou Bay

Models of marine ecosystem dynamics play an important role in revealing the evolution mechanisms of marine ecosystems and in forecasting their future changes. Most traditional ecological dynamics models are established based on basic physical and biological laws, and have obvious dynamic characteristics and ecological significance. However, they are not flexible enough for the variability of environment conditions and ecological processes found in offshore marine areas, where it is often difficult to obtain parameters for the model, and the precision of the model is often low. In this paper, a new modeling method is introduced, which aims to establish an evolution model of marine ecosystems by coupling statistics with differential dynamics. Firstly, we outline the basic concept and method of inverse modeling of marine ecosystems. Then we set up a statistical dynamics model of marine ecosystems evolution according to annual ecological observation data from Jiaozhou Bay. This was done under the forcing conditions of sea surface temperature and surface irradiance and considering the state variables of phytoplankton, zooplankton and nutrients. This model is dynamic, makes the best of field observation data, and the average predicted precision can reach 90% or higher. A simpler model can be easily obtained through eliminating the terms with smaller contributions according to the weight coefficients of model differential items. The method proposed in this paper avoids the difficulties of obtaining and optimizing parameters, which exist in traditional research, and it provides a new path for research of marine ecological dynamics.

Effects of grazing and climate change on sandy grassland ecosystems in Inner Mongolia

To understand the effects of grazing activities and climate change on sandy grassland ecosystems in northem China, a livestock field grazing and enclosure experiment was conducted from 1992 to 2006 in Horqin Sand Land, Inner Mongolia. The results showed that sustained heavy grazing resulted in serious degradation of the vegetation; moderate grazing can maintain vegetation stabilization; and light grazing can promote rapid restoration of degraded vegetation. The livestock productivity was the highest in the moderate grazing grassland, and sustained heavy grazing resulted in rapid decrease of the livestock productivity. Heavy grazing can cause a retrogressive succession of grassland vegetation, whereas moderate and light grazing may promote progressive succession of plant species. The effects of changing climate on succession processes were not significant in the short term; a warm-humid climate is favorable to restoration of degraded vegetation, whereas a sustained warm-drought climate may result in degradation of grassland vegetation. Heavy livestock grazing should be stopped for the sustainable use of grassland; the proper grazing intensity for sandy grassland is two to three sheep or sheep equivalents per hectare in Inner Mongolia.

Discussion of skill improvement in marine ecosystem dynamic models based on parameter optimization and skill assessment

Marine ecosystem dynamic models(MEDMs) are important tools for the simulation and prediction of marine ecosystems. This article summarizes the methods and strategies used for the improvement and assessment of MEDM skill, and it attempts to establish a technical framework to inspire further ideas concerning MEDM skill improvement. The skill of MEDMs can be improved by parameter optimization(PO), which is an important step in model calibration. An effi cient approach to solve the problem of PO constrained by MEDMs is the global treatment of both sensitivity analysis and PO. Model validation is an essential step following PO, which validates the effi ciency of model calibration by analyzing and estimating the goodness-of-fi t of the optimized model. Additionally, by focusing on the degree of impact of various factors on model skill, model uncertainty analysis can supply model users with a quantitative assessment of model confi dence. Research on MEDMs is ongoing; however, improvement in model skill still lacks global treatments and its assessment is not integrated. Thus, the predictive performance of MEDMs is not strong and model uncertainties lack quantitative descriptions, limiting their application. Therefore, a large number of case studies concerning model skill should be performed to promote the development of a scientifi c and normative technical framework for the improvement of MEDM skill.

RESEARCH ON THE COMPLICATED DYNAMICAL BEHAVIORS OF NONLINEAR ECOSYSTEMS(Ⅱ)

This paper is a further study of reference [1]. In this paper, we mainly discuss the complicated dynamical behaviors resulting from a simple one-dimensional model of nonlinear ecosystems: fixed point motion, periodic motion and chaotic motion etc., and briefly discuss the universality of the complicated dynamical behaviors, which can be described by the first and the second M. Feigenbaun. constants. At last, we discuss the 'one-side lowering phenomenon' due to near unstabilization when the nonlinear ecosystem approaches bifurcation points from unbifurcation side. It is of important theoretical and practical meanings both in the development and utilization of ecological resources ar.d in the design and management of artifilial ecosystems.

Development and Application of a Marine Ecosystem Dynamic Model

A nutrient-phytoplankton-zooplankton-detritus （NPZD） type of marine ecosystem model was developed in this study,and was further coupled to a three-dimensional primitive-equation ocean circulation model with a river discharge model and a solar radiation model to reproduce the dynamics of the low nutrition level in the Bohai Sea （BS）.The simulation results were validated by observations and it was shown that the seasonal variation in the phytoplankton biomass could be characterized by the double-peak structure,corresponding to the spring and summer blooms,respectively.It was also found that both nitrogen and phosphate declined to the lowest level after the onset of the summer bloom,since the large amounts of nutrients were exhausted by phytoplankton for photosynthesis,and the concentrations of nutrients could resume in winter after a series of the biogeochemical-physical processes.By calculating the nitrogen/phosphorus （N/P） ratio,it is easy to see that the phytoplankton dynamics is nitrogen-limited as a whole in BS,though the phosphorus limitation may occur in the Yellow River （YR） Estuary where the input of riverine nitrogen is much more than that of phosphate.

Numerical study on spatially varying control parameters of a marine ecosystem dynamical model with adjoint method

Based on the simulation of a marine ecosystem dynamical model in the Bohai Sea, the Yellow Sea and the East China Sea, chlorophyll data are assimilated to study the spatially varying control parameters （CPs） by using the adjoint method. In this study, the CPs at some grid points are selected as the independent CPs, while the CPs at other grid points can be obtained through linear interpolation with the independent CPs. The independent CPs are uniformly selected from each 30′ × 30′area, and we confirm that the optimal influence radius is 1.2° by a twin experiment. In the following experiments, when only the maximum growth rate of phytoplankton （Vm） is estimated by two given types of spatially varying CPs, the mean relative errors of Vm are 1.22% and 0.94% while the decrease rates of the mean error of chlorophyll in the surface are 94.6% and 95.8%, respectively. When the other four CPs are estimated respectively, the results are also satisfactory, which indicates that the adjoint method has a strong ability of optimizing the prescribed CP with spatial variations. However, when all these five most important CPs are estimated simultaneously, the collocation of the changing trend of each parameter influences the estimation results remarkably. Only when the collocation of the changing trend of each parameter is consistent with the ecological mechanisms which influence the growth of the phytoplankton in marine ecosystem, could the five most important CPs be estimated more accurately.

Population Dynamics of Croton blanchetianus Baill.in a Caatinga Area in the Brazilian Semi-Arid

The vegetation of the Caatinga, present in the dry areas of the Brazilian Semi-arid region has been little studied, when it relates to population dynamics of their species. The objective of this study was to evaluate the mortality and recruitment rates of a Croton blanchetianus Baill. population in a two-year interval (January/2013 to January/2015), in area of caatinga in the semi-arid Paraiba. Monitoring of structural changes in the vegetation was carried out in 96 10 × 10 m contiguous plots. The phytosociological survey conducted in January 2013 sampled 1078 individuals of C. blanchetianus, occurring in the 96 plots studied. The years of 2012 and 2013 had rainfall below the annual average. Take into consideration the evaluation period;there was a high mortality rate (M = 47.33% year-1) and a low recruitment rate (R = 0.18% year-1) for the population of C. blanchetianus. The real gain (RG) of the population was significantly negative (-93.91% year-1) since the number of dead individuals was much higher than the recruited ones in the population. The highest height class, composed of individuals of 4.1 to 5.0 m height, was the most tolerant to water scarcity, resulting in 53.85% of surviving individuals. Therefore, the results demonstrated that periodic droughts compromise the recruitment, development, survival, and establishment of individuals in natural systems in the Brazilian semi-arid region.

A three-dimensional coupled physical-biological model study in the spring of 1993 in the Bohai Sea of China

A three-dimensional （3-D） coupled physical and biological model was used to investigate the physical processes and their influence on the ecosystem dynamics of the Bohai Sea of China. The physical processes include M2 tide, time - varying wind forcing and river discharge. Wind records from 1 to 31 May in 1993 were selected to force the model. The biological model is based on a simple, nitrate and phosphate limited, lower trophic food web system. The simulated results showed that variation of residual currents forced by M2 tide, fiver discharge and time-varying wind had great impact on the distribution of phytoplankton biomass in the Laizhou Bay. High phytoplankton biomass appeared in the upwelling region. Numerical experiments based on the barotropic model and baroclinic model with no wind and water discharge were also conducted. Differences in the results by the baroclinic model and the barotropic model were significant： more patches appeared in the baroclinic model comparing with the barotropic model. And in the baroclinic model, the subsurface maximum phytoplankton biomass patches formed in the stratified water.

Numerical experiments of HAB inducement in Qingdao adjacent coastal area

A three-dimension ecological dynamic model was established to numerically study the relationship of HAB and environmental conditions.The numerical experiments showed that the growth of diatom,the dominant HAB specie,was mainly restricted by phosphate and silicate.If the concentrations of phosphate and silicate reach 17-25 μg/L and 300-375 μg/L respectively,the water is in a state of eutrophication.When phosphate and silicate up to 26-32 μg/L and 350-500 μg/L respectively,HAB could be induced.The major regions of HAB occurrence are Jiaozhou Bay mouth,coastal bays,and coastal area from Maidao to Shilaoren.To avoid HAB occurrence,concentration of phosphate and silicate should not exceed 17-20 μg/L and 300 μg/L as a whole.Reasonable control of pollutant discharge is a key point to prevent water eutrophication and HAB occurrence.

Improved Model for Semideciduous Seasonal ForestProduction of Leaves and Deciduousness

The climate,mainly the water availability and temperature,drives the renewal of biomass inseasonal forest ecosystem,and the greenness and leaf area of its canopy are responsive climate variations.This study verified models to explain the phenomenon of leaf production and deciduousness by time,with LAI（Leaf Area Index）,NDVI（Normalized Difference VegetationIndex）and climate variables,on period 2011-2016. The data were obtained in satellite images and in plots installed at forestmonitoring sites,visited monthly.The analysis incorporated the water balance.Three equations were compared,two alreadypublished and the equation that was adjusted in this work.The model was improved and validated with new variables and data.It is possible to estimate the fall and renew of leaves biomass in semideciduous forests with reasonable precision.

Vegetation biomass dynamics in a desert ecosystem in NW China

Subject Code:D01With the support by the National Natural Science Foundation of China,a collaborative study by Prof.Wang Xinping(王新平)from the Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences and the research group led by Prof.Ignacio Rodriguez-Iturbe from

Environment-ecosystem dynamic processes of Spartina alterniflora salt-marshes along the eastern China coastlines

Spartina alterniflora is ecologically important in its original habitat; however, it has caused controversy since it was introduction into China(now it has been spreading rapidly on the Jiangsu, Shanghai, Zhejiang and Fujian coasts). The purpose of the present contribution is, on the basis of an analysis and synthesis of existing data sets, to evaluate the environmental-ecological effects of S. alterniflora, and to identify the relevant scientific problems that require further research in the future. Investigations have shown that, by reducing the near-bed shear stress associated with tidal currents, S. alterniflora can enhance the settling flux of suspended sediment and deposition rate on the tidal flats over the region. Further, field survey and analysis indicate that the S. alterniflora salt-marsh has a high primary production and provides a new type of habitat for the native benthic fauna. Some macro-, meio- and micro-fauna that used to live in the native salt-marshes have adapted to the S. alterniflora salt-marsh, forming a new ecosystem. Under the influences of a number of background factors, such as latitude variations and the coastal type, the environmental-ecological changes induced by Spartine have regional differentiations. To the north of Hangzhou Bay, with a high position of the pre-Holocene stratum base, a large width of the tidal flats, and a gentle bed slope, only a small part of the intertidal zone is occupied by the S. alterniflora salt-marsh. Here, the S. alterniflora salt-marshes mainly play a positive role in coastal protection and ecosystem functioning. In contrary, to the South of Hangzhou Bay, The pre-Holocene deposits are situated in relatively deeo waters, and the width of the tidal flats formed within coastal embayments is relatively narrow. As such, the expansion of S. alterniflora has squeezed the living space of other intertidal organisms, thus has a negative ecological effect. Therefore, the regional differentiation of the Spartina effects should be sufficiently considered in coastal development and management. Furthermore, in order to predict the future evolution of the S. alterniflora wetlands over the region, in addition to in situ monitoring and measurements, an ecosystem dynamic model should be established, taking into account the coupling of the rerrestrial and marine environmental-ecological processes.

Combining European Earth Observation products with Dynamic Global Vegetation Models for estimating Essential Biodiversity Variables

Global,fast and accessible monitoring of biodiversity is one of the main pillars of the efforts undertaken in order to revert it loss.The Group on Earth Observations Biodiversity Observation Network(GEO-BON)provided an expert-based definition of the biological properties that should be monitored,the Essential Biodiversity Variables(EBVs).Initiatives to provide indicators for EBVs rely on global,freely available remote sensing(RS)products in combination with empirical models and field data,and are invaluable for decision making.In this study,we provide alternatives for the expansion and improvement of the EBV indicators,by suggesting current and future data from the European Space Agencýs COPERNICUS and explore the potential of RS-integrated Dynamic Global Vegetation Models(DGVMs)for the estimation of EBVs.Our review found that mainly due to the inclusion of the Sentinel constellation,Copernicus products have similar or superior potential for EBV indicator estimation in relation to their NASA counterparts.DGVMs simulate the ecosystem level EBVs(ecosystem function and structure),and when integrated with remote sensing data have great potential to not only offer improved estimation of current states but to provide projection of ecosystem impacts.We suggest that focus on producing EBV relevant outputs should be a priority within the research community,to support biodiversity preservation efforts.

Recent patterns of terrestrial net primary production in Africa influenced by multiple environmental changes

Terrestrial net primary production(NPP)is of fundamental importance to food security and ecosystem sustainability.However,little is known about how terrestrial NPP in African ecosystems has responded to recent changes in climate and other environmental factors.Here,we used an integrated ecosystem model(the dynamic land ecosystem model;DLEM)to simulate the dynamic variations in terrestrial NPP of African ecosystems driven by climate and other environmental factors during 1980-2009.We estimate a terrestrial NPP of 10.22(minimum-maximum range of 8.9-11.3)Pg C/yr during the study period.Our results show that precipitation variability had a significant effect on terrestrial NPP,explaining 74%of interannual variations in NPP.Over the 30-yr period,African ecosystems experienced an increase in NPP of 0.03 Pg C/yr,resulting from the combined effects of climate variability,elevated atmospheric CO_(2)concentration,and nitrogen deposition.Our further analyses show that there is a difference in NPP of 1.6 Pg C/yr between wet and dry years,indicating that interannual climatic variations play an important role in determining the magnitude of terrestrial NPP.Central Africa,dominated by tropical forests,was the most productive region and accounted for 50%of the carbon sequestered as NPP in Africa.Our results indicate that warmer and wetter climatic conditions,together with elevated atmospheric CO_(2)concentration and nitrogen deposition,have resulted in a significant increase in African terrestrial NPP during 1980-2009,with the largest contribution from tropical forests.