Carbon storage and vertical distribution in three shrubland communities in Gurbantünggüt Desert, Uygur Autonomous Region of Xinjiang, Northwest China

This study was carried out in the Gurbantünggüt Desert,Uygur Autonomous Region of Xinjiang,Northwest China in August,2009.To quantify the storage,contribution and vertical distribution patterns of plant biomass carbon (PBC)and soil organic carbon(SOC)in the study area,we investigated the carbon concentrations and its vertical distribution in three different desert shrubland communities dominated by Reaumuria soongorica,Haloxylon ammodendron+R.soongorica and Tamarix ramosissima+R.soongorica,respectively.We analyzed vertical distribution of root biomass carbon and soil carbon contents by excavating soil profiles for each dominated community.The results show that SOC is considerably the larger carbon pool in the soil layers of 1.0-3.0 m(the mean value of three shrubland communities is 38.46%)and 3.0-5.0 m(the mean value is 40.24%).In contrast,70.74%of belowground biomass carbon storage in 0-1.0 m layer,and its content decrease with increasing soil depth.The Haloxylon ammodendron+R. soongorica shrubland community has the highest belowground biomass carbon among three selected communities. This study highlights the importance of SOC stored in deep soil layers(lower than 3.0 m from the surface)in arid shrubland communities in the global carbon balance.In addition,it provides the data support for revealing deep soil solid carbon potential,and offers scientific basis for the further research in the carbon cycle of terrestrial ecosystem.     

Carbon sequestration in forest vegetation of Beijing at sublot level

Based on forest inventory data (FID) at sublot level,we estimated the carbon sequestration in forest vegetation of Beijing,China in 2009.In this study,the carbon sequestration in forest vegetation at sublot level was calculated based on net biomass production (ΔB) which was estimated with biomass of each sublot and function relationships between ΔB and biomass.The biomass of forested land was calculated with biomass expansion factors (BEFs) method,while those of shrub land and other forest land types were estimated with biomass,coverage and height of referred shrubs and shrub coverage and height of each sublot.As one of special forested land types,the biomass of economic tree land was calculated with biomass per tree and tree number.The variation of carbon sequestration in forest vegetation with altitude,species and stand age was also investigated in this study.The results indicate that the carbon sequestration in forest vegetation in Beijing is 4.12 × 106 tC/yr,with the average rate of 3.94 tC/(ha·yr).About 56.91% of the total carbon sequestration in forest vegetation is supported by the forest in the plain with an altitude of < 60 m and the low mountainous areas with an altitude from 400 m to 800 m.The carbon sequestration rate in forest vegetation is the highest in the plain area with an altitude of < 60 m and decreased significantly in the transitional area from the low plain to the low mountainous area with an altitude ranging from 200 m to 400 m due to intensive human disturbance.The carbon sequestration of Populus spp.forest and Quercus spp.forest are relatively higher than those of other plant species,accounting for 25.33% of the total.The carbon sequestration in vegetation by the forest of < 40 years amounts to 45.38% of the total.The carbon sequestration rate in forest vegetation peaks at the stand age of 30–40 years.Therefore,it would be crucial for enhancing the capability of carbon sequestration in forest vegetation to protect the forest in Beijing,to limit human disturbance in the transitional area from the plain to the low mountain area,and to foster the newly established open forest.     

DISTRIBUTION AND POPULATION DYNAMICS OF PARACALANUS PARVUS,PRACALANUS CRASSIROSTRIS,AND ACARTIA BIFILOSA（COPEPODA,CALANOIDA）IN THE BOHAI SEA

Paracalanus parvus,Paracalanus crassirostris,and Acartia bifilosa are dominant and widely distributed in the Bohai Sea,and comprise an important part of zooplankton in terms of biomass as well as production rate.In order to understand their seasonal distribution and population dynamics,their stage-specific abundance in different months of the year were analyzed based on the never analyzed yet samples collected in 1959.The three species showed clear and remarkable seasonal variation in abundance,which maximized in spring and summer,when they formed high biomass patches or concentrations in the nearshore area.For Paracalanus parvus,two peaks were observed in the annual circle,one in June and the other in September,For Paracalanus crassirostris,one peak occurred in summer and a small one in December.The seasonal pattern of Acartia bifilosa was different in different regions.In Bohai Bay it had a two-peak pattern,with the first large peak occurring in May and the second one in October.In Laizhou Bay,a winter peak in December and January could be observed besides the spring one.The number of generations during the reproductive season for the three species was estimated based on the annual cycle in abundance and ambient temperature.     

Phytoplankton community changes indicated by biomarker from sediment in Prydz Bay, Antarctica

Biomarkers including brassicasterol, dinosterol and alkenone in sediments are used as indicators to reconstruct changes to the phytoplankton community in surface and sub-aerial sediments of Prydz Bay, Antarctica. The results indicate that the bio- marker records in surface and core sediment samples changed with time and space. The total content of phytoplankton biomarkers ranges from 391.0--1 470.6 ng.g-l. The phytoplankton biomass has increased in Prydz Bay over the past 100 years. This variation may be mainly related with climate change in the region. The total biomarker contents in surface sediments from 5 stations in Prydz Bay are in the range of 215.8--1 294.3 ng.g4. The phytoplankton biomass in Prydz Bay is higher than that outside of the bay. This is similar to the distributions of chlorophyll a, organic carbon and biogenic silica in surface waters determined through in situ investigation. Such consistency indicates a coupling between the bottom of the ocean and biogeochemical processes in the upper water.     

Spatial distribution and dynamics of carbon storage in natural Larix gmelinii forest in Daxing'anling mountains of Inner Mongolia,northeastern China

In order to clarify the geographic distribution and change of natural Larix gmelinii forest in carbon storage in Daxing'anling mountains(Great Khingan Range) in North China's Inner Mongolia, an area-irrelevant conversion equation of biomass from timber volume in the form of B = 0.6966 V was developed by using survey data. Based on the equation, the carbon storage was estimated at 190.172 Tg, and the average carbon density was 41.659 Mg/hm~2(area 4.565 × 10~6 hm~2). Carbon stored in standing trees was predominantly distributed in mid-age and mature forests and mainly stocked in the northern part of the study area. Assuming the carbon density of intact area as the maximum value, the potential carbon storage in the entire study area would be 263.674 Tg, approximately 1.4 times of the actual level. Over the period of 1995 to 2010, the carbon storage and carbon densityincreased by 3.260 Tg and 0.224 Mg/hm~2, respectively, indicating a weak carbon sink. Comparing with China's national average level, the carbon density in this area is not as high as expected. Forest quality in terms of carbon capacity is expected to be enhanced by appropriate management schemes under the in-implementation program of forest protection.     

Forest carbon storage and tree carbon pool dynamics under natural forest protection program in northeastern China

The Natural Forest Protection(NFP) program is one of the Six Key Forestry Projects which were adopted by the Chinese Government since the 1980s to address important natural issues in China. It advanced to protecting and restoring the structures and functions of the natural forests through sustainable forest management. However, the role of forest carbon storage and tree carbon pool dynamics since the adoption of the NFP remains unknown. To address this knowledge gap, this study calculated forest carbon storage(tree, understory, forest floor and soil) in the forest region of northeastern(NE) China based on National Forest Inventory databases and field investigated databases. For tree biomass, this study utilized an improved method for biomass estimation that converts timber volume to total forest biomass; while for understory, forest floor and soil carbon storage, this study utilized forest type-specific mean carbon densities multiplied by their areas in the region. Results showed that the tree carbon pool under the NFP in NE China functioned as a carbon sink from 1998 to 2008, with an increase of 6.3 Tg C/yr, which was mainly sequestrated by natural forests(5.1 Tg C/yr). At the same time, plantations also acted as a carbon sink, reflecting an increase of 1.2 Tg C/yr. In 2008, total carbon storage in forests covered by the NFP in NE China was 4603.8 Tg C, of which 4393.3 Tg C was stored in natural forests and 210.5 Tg C in planted forests. Soil was the largest carbon storage component, contributing 69.5%–77.8% of total carbon storage; followed by tree and forest floor, accounting for 16.3%–23.0% and 5.0%–6.5% of total carbon storage, respectively. Understory carbon pool ranged from 1.9 to 42.7 Tg C, accounting for only 0.9% of total carbon storage.     

Impacts of warming on root biomass allocation in alpine steppe on the north Tibetan Plateau

Biomass is an important component of global carbon cycling and is vulnerable to climate change. Previous studies have mainly focused on the responses of aboveground biomass and phenology to warming, while studies of root architecture and of root biomass allocation between coarse and fine roots have been scarcely reported in grassland ecosystems. We conducted an open-top-chamber warming experiment to investigate the effect of potential warming on root biomass and root allocation in alpine steppe on the north Tibetan Plateau. The results showed that Stipa purpurea had significantly higher total root length, root surface area and tips than Carex moocroftii. However,there were no differences in total root volume, mean diameter and forks for the two species. Warming significantly increased total root biomass(27.60%), root biomass at 0–10 cm depth(27.84%) and coarse root biomass(diameter 0.20 mm, 57.68%) in the growing season(August). However, warming had no significant influence on root biomass in the non-growing season(April). Root biomass showed clear seasonalvariations: total root biomass, root biomass at 0–10 cm depth and coarse root biomass significantly increased in the growing season. The increase in total root biomass was due to the enhancement of root biomass at 0–10 cm depth, to which the increase of coarse root biomass made a great contribution. This research is of significance for understanding biomass allocation, carbon cycling and biological adaptability in alpine grassland ecosystems under future climate change.     

Biomass carbon storage and its sequestration potential of afforestation under natural forest protection program in China

Based on the data from China′s Seventh Forest Inventory for the period of 2004–2008, area and stand volume of different types and age-classes of plantation were used to establish the relationship between biomass density and age of planted forests in different regions of the country. Combined with the plantation area in the first-stage of the Natural Forest Protection(NFP) program(1998–2010), this study calculated the biomass carbon storage of the afforestation in the first-stage of the program. On this basis, the carbon sequestration potential of these forests was estimated for the second stage of the program(2011–2020). Biomass carbon storage of plantation established in the first stage of the program was 33.67 Tg C, which was majority accounted by protection forests(30.26 Tg C). There was a significant difference among carbon storage in different regions, which depended on the relationship of biomass carbon density, forest age and plantation area. Under the natural growth, the carbon storage was forecasted to increase annually from 2011 to 2020, reaching 96.03 Tg C at the end of the second-stage of the program in 2020. The annual growth of the carbon storage was forecasted to be 6.24 Tg C/yr, which suggested that NFP program has a significant potential for enhancing carbon sequestration in plantation forests under its domain.     

River flow control on the phytoplankton dynamics of Chesapeake Bay

Recent observations support an emerging paradigm that climate variability dominates nutrient enrichment in costal eco-systems, which can explain seasonal and inter-annual variability of phytoplankton community composition, biomass (Chl-a), and primary production (PP). In this paper, we combined observation and modeling to investigate the regulation of phytoplankton dynamics in Chesapeake Bay. The year we chose is 1996 that has high river runoff and is usually called a ’wet year’. A 3-D physical-biogeochemical model based on ROMS was developed to simulate the seasonal cycle and the regional distributions of phytoplankton biomass and primary production in Chesapeake Bay. Based on the model results, NO3 presents a strong contrast to the river nitrate load during spring and the highest concentration in the bay reaches around 80 mmol Nm-3 . Compared with the normal year, phytoplankton bloom in spring of 1996 appears in lower latitudes with a higher concentration. Quantitative comparison between the modeled and observed seasonal averaged dissolved inorganic nitrogen concentrations shows that the model produces reliable results. The correlation coefficient r2 for all quantities exceeds 0.95, and the skill parameter for the four seasons is all above 0.95.     

A Model Study on Dynamical Processes of Phytoplankton inLaizhou Bay

A three-dimensional ecosystem model, using a PIC （Particle-In-Cell） method, is developed to reproduce the annual cycleand seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN （dissolved inorganicnitrogen）, phosphate, DON （dissolved organic nitrogen）, DOP （dissolved organic phosphorus）, COD （chemical oxygen demand）,chlorophyll-a （Chl-a）, detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the ob-served temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at highlevel in winter and at low level in summer. Double-peak structure of the phytoplankton （PPT） biomass exists in Laizhou Bay, corre-sponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limita-tion, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitationexist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are themain pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the YellowRiver discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River ex-cluded.     

Ecological studies ofGracilaria asiatica andGracilaria lemaneiformis in Zhanshan Bay,Qingdao

Natural populations ofG. asiatica Zhang & Xia andG. lemaneiformis (Bory) Weber van Bosse were studied during 1984 and 1986 in Zhanshan Bay, Qingdao (36°4'N, 120° 21'E). Rapid growth (length, weight) of these plants occurred between mid-May and late June (water temperatures, 15–20°C). The major epiphyte ofG. asiatica wasEnteromorpha linza, whilePunctaria latifolia was the major epiphyte ofG. lemaneiformis. Epiphytism declined throughout early summer, and epiphytes were rare after mid-July (1984); they did not reappear in late summer, although macrophyte growth declined abruptly after early July. Populations ofG. asiatica varied during late spring-early summer between adjacent sandy and rocky portions of the intertidal zone; plants at the sandy site were larger and epiphyte-free. Amphipod densities were low on both species ofGracilaria, but the most abundant species wereAmpithoe lacertosa, Caprella equilibra, C. krøyeri, C. scauraandPontogeneia rostrata. Additional information on general community structure is provided for theG. asiatica zone.     

Comparison in copper accumulation and physiological responses of Gracilaria lemaneiformis and G. lichenoides (Rhodophyceae)

Heavy metal pollution has become a worldwide problem in aquaculture. We studied copper (Cu2+ ) accumulation and physiological responses of two red algae Gracilaria lemaneiformis and Gracilaria lichenoides from China under Cu2+ exposure of 0-500 μg/L in concentration. Compared with G. lemaneiformis, G. lichenoides was more capable in accumulating Cu2+ , specifically, more Cu2+ on extracellular side (cell wall) than on intracellular side (cytoplasm) and in cell organelles (especially chloroplast, cell nucleus, mitochondria, and ribosome). In addition, G. lichenoides contained more insoluble polysaccharide in cell wall, which might promote the extracellular Cu2+ -binding as an efficient barrier against metal toxicity. Conversely, G. lemaneiformis was more vulnerable than G. lichenoides to Cu 2+ toxin for decreases in growth, pigment (chlorophyll a, chlorophyll b, phycobiliprotein, and β-carotene) content, and photosynthetic activity. Moreover, more serious oxidative damages in G. lemaneiformis than in G. lichenoides, in accumulation of reactive oxidative species and malondialdehyde, and in electrolyte leakage, because of lower antioxidant enzyme (superoxide dismutase and glutathione reductase) activities. Therefore, G. lichenoides was less susceptible to Cu2+ stress than G. lemaneiformis.     

Inhibition of photosynthesis in the microalga Chaetoceros curvisetus （Bacillariophyta） by macroalga Gracilaria lemaneiformis （Rhodophyta）

We investigated the effects of dried macroalga Gracilaria lemaneiform （Rhodophyta） on photosynthesis of the bloom-forming microalga Chaetoceros curvisetus. C. curvisetus was cultured with different amounts of dried G. lemaneiformis under controlled laboratory conditions. We measured the photosynthetic oxygen evolution rate and established the chlorophyll a fluorescence transient （OJIP） curve coupled with its specific parameters. We observed concentration-dependent and time-dependent relationships between dried G. lemaneiformis and inhibition of photosynthesis in C. curvisetus. Co-culture with dried G. lemaneiformis also resulted in a decrease in the light-saturated maximum photosynthetic oxygen evolution rate （P~ax） in C. curvisetus, and a decrease in the OJIP curve along with its specific parameters; the maximum photochemical efficiency of PSII （FJFm）, the amount of active PSII reaction centers per excited cross section at t=0 and t=--tFM （RC/CS0 and RC/CSm, respectively）, the absorption flux per excited cross section at t=0 （ABS/ CS0）, and the efficiency with which a trapped exciton moves an electron into the electron transport chain （~u0）. The dark respiration rate （Rd） increased in C. curvisetus co-cultured with dried G. lemaneiformis. The JIP-test and the oxygen evolution results indicated that dried G. lemaneiJbrmis decreased the number of active reaction centers, blocked the electron transport chain, and damaged the oxygen-evolving complex of C. curvisetus. This result indicated that dried fragments of G. lemaneiformis could effectively inhibit photosynthesis of C. curvisetus, and thus, could serve as a functional product to control and mitigate C. curvisetus blooms.     

A comparison of different Gracilariopsis lemaneiformis (Rhodophyta) parts in biochemical characteristics,protoplast formation and regeneration

Gracilariopsis lemaneiformis is a commercially exploited alga. Its filaceous thallus can be divided into three parts, holdfast, middle segment and tip. The growth and branch forming trend and agar content of these three parts were analyzed, respectively, in this study. The results showed that the tip had the highest growth rate and branched most, although it was the last part with branch forming ability. The holdfast formed branches earliest but slowly. Holdfast had the highest agar content. We also assessed the difference in protoplast formation and regeneration among three parts. The middle segment displayed the shortest enzymolysis time and the highest protoplast yield; whereas the tip had the strongest vitality of protoplasts formation. Juvenile plants were only obtained from the protoplasts generated from the tip. These results suggested that the differentiation and function of G. lemaneiformis was different.     

Effects of afforestation on carbon storage in Boyang Lake Basin, China

By using field survey data from the sixth forest inventory of Jiangxi Province in 2003, the biomass and carbon storage for three studied species （Pinus massoniana, Cunninghamia lanceolata, and Pinus elliottii） were estimated in Taihe and Xingguo counties of Boyang Lake Basin, Jiangxi Province, China. The relationship between carbon density and forest age was analyzed by logistic equations. Spatio-temporal dynamics of forest biomass and carbon storage in 1985-2003 were also described. The results show that total stand area of the three forest species was 3.10 × 10^5 ha, total biomass 22.20 Tg, vegetation carbon storage 13.07 Tg C, and average carbon density 42.36 Mg C/ha in the study area in 2003. Carbon storage by forest type in descending order was： P. massoniana, C. lanceolata and P. elliottii. Carbon storage by forest age group in descending order was： middle stand, young stand, near-mature stand and mature stand. Carbon storage by plantation forests was 1.89 times higher than that by natural forests. Carbon density of the three species increased 8.58 Mg C/ha during the study period. The carbon density of Taihe County was higher in the east and west, and lower in the middle. The carbon density of Xingguo County was higher in the northeast and lower in the middle. In general, the carbon density increased with altitude and gradient. Afforestation projects contribute significantly to increasing stand area and carbon storage. Appropriate forest management may improve the carbon sequestration capacity of forest ecosystems.     

Analysis of DNA Methylation of <Emphasis Type="Italic">Gracilariopsis lemaneiformis</Emphasis> Under Temperature Stress Using the Methylation Sensitive Amplification Polymorphism (MSAP) Technique

Gracilariopsis lemaneiformis is an economically important agarophyte, which contains high quality gel and shows a high growth rate. Wild population of G. lemaneiformis displayed resident divergence, though with a low genetic diversity as was revealed by amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) analyses. In addition, different strains of G. lemaneiformis are diverse in morphology. The highly inconsistence between genetic background and physiological characteristics recommends strongly to the regulation at epigenetic level. In this study, the DNA methylation change in G. lemaneiformis among different generation branches and under different temperature stresses was assessed using methylation sensitive amplified polymorphism (MSAP) technique. It was shown that DNA methylation level among different generation branches was diverse. The full and total methylated DNA level was the lowest in the second generation branch and the highest in the third generation. The total methylation level was 61.11%, 60.88% and 64.12% at 15°C, 22°C and 26°C, respectively. Compared with the control group (22°C), the fully methylated and totally methylated ratios were increased in both experiment groups (15°C and 26°C). All of the cytosine methylation/demethylation transform (CMDT) was further analyzed. High temperature treatment could induce more CMDT than low temperature treatment did.     

A model study on dynamical processes of phytoplankton in Laizhou Bay

A three-dimensional ecosystem model, using a PIC (Particle-In-Cell) method, is developed to reproduce the annual cycle and seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN (dissolved inorganic nitrogen), phosphate, DON (dissolved organic nitrogen), DOP (dissolved organic phosphorus), COD (chemical oxygen demand), chlorophyll-a (Chl-a), detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the observed temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at high level in winter and at low level in summer. Double-peak structure of the phytoplankton (PPT) biomass exists in Laizhou Bay, corresponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limitation, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitation exist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are the main pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the Yellow River discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River excluded.     

Aboveground biomass of the alpine shrub ecosystems in Three-River Source Region of the Tibetan Plateau

Though aboveground biomass (AGB) has an important contribution to the global carbon cycle, the information about storage and climatic effects of AGB is scare in Three-River Source Region (TRSR) shrub ecosystems. This study investigated AGB storage and its climatic controls in the TRSR alpine shrub ecosystems using data collected from 23 sites on the Tibetan Plateau from 2011 to 2013. We estimated the AGB storage (both shrub layer biomass and grass layer biomass) in the alpine shrubs as 37.49 Tg, with an average density of 1447.31 g m^-2. Biomass was primarily accumulated in the shrub layer, which accounted for 92% of AGB, while the grass layer accounted for only 8%. AGB significantly increased with the mean annual temperature (P < 0.05). The effects of the mean annual precipitation on AGB were not significant. These results suggest that temperature, rather than precipitation, has significantly effects on of aboveground vegetation growth in the TRSR alpine shrub ecosystems. The actual and potential increase in AGB density was different due to global warming varies among different regions of the TRSR. We conclude that long-term monitoring of dynamic changes is necessary to improve the accuracy estimations of potential AGB carbon sequestration across the TRSR alpine shrub ecosystems.