Effects of altitude on plant-species diversity and productivity in an alpine meadow, Qinghai-Tibetan plateau

During the growing seasons of 2002 and 2003, biomass productivity and diversity were examined along an altitudinal transect on the south-western slope of Beishan Mountain, Maqin County (33 degrees 43'-35 degrees 16'N, 98 degrees 48'-100 degrees 55'E), Qinghai-Tibetan Plateau. Six altitudes were selected, between 3840 and 4435 m. Soil organic matter, soil available N and P and environmental factors significantly affected plant-species diversity and productivity of the alpine meadows. Aboveground biomass declined significantly with increasing altitude (P < 0.05) and it was positively and linearly related to late summer soil-surface temperature. Belowground biomass (0 - 10-cm depth) was significantly greater at the lowest and highest altitudes than at intermediate locations, associated with water and nutrient availabilities. At each site, the maximum belowground biomass values occurred at the beginning and the end of the growing seasons (P < 0.05). Soil organic matter content, and available N and P were negatively and closely related to plant diversity (species richness, Shannon-Wiener diversity index, and Pielou evenness index).

CO2 fluxes of alpine shrubland ecosystem on the north-eastern Tibetan plateau

We measured ecosystem CO2 fluxes for an alpine shrubland on the north-eastern Tibetan Plateau, Qinghai, China. The study is to understand (1) the seasonal variation of CO2 flux and (2) how environmental factors affect the seasonality of CO2 exchange in the alpine ecosystem. Daytime ecosystem respiration was extrapolated from the relationship between temperature and nighttime CO2 fluxes under high turbulent conditions.Seasonal patterns of gross ecosystem production, ecosystem respiration and net ecosystem CO2 exchange followed highly the seasonal change of aboveground biomass in the alpine shrubland. The net ecosystem CO2 exchange was mainly controlled by the variation of photosynthetic photon flux density, while the ecosystem respiration was closely correlated to the soil temperature at 5-cm depth. Integrated values of gross ecosystem production, ecosystem respiration and net ecosystem CO2 exchange for the period from November 1, 2002 to October 31 2003 were estimated to be 1418, 1155 and 222 g CO2 m(-2) yr(-1), respectively.

Temperature and biomass influences on interannual changes in CO2 exchange in an alpine meadow on the Qinghai-Tibetan Plateau

Three years of eddy covariance measurements were used to characterize the seasonal and interannual variability of the CO2 fluxes above an alpine meadow (3250 m a.s.l.) on the Qinghai-Tibetan Plateau, China. This alpine meadow was a weak sink for atmospheric CO2, with a net ecosystem production (NEP) of 78.5, 91.7, and 192.5 g C m(-2) yr(-1) in 2002, 2003, and 2004, respectively. The prominent, high NEP in 2004 resulted from the combination of high gross primary production (GPP) and low ecosystem respiration (R-e) during the growing season. The period of net absorption of CO2 in 2004, 179 days, was 10 days longer than that in 2002 and 5 days longer than that in 2003. Moreover, the date on which the mean air temperature first exceeded 5.0 degrees C was 10 days earlier in 2004 (DOY110) than in 2002 or 2003. This date agrees well with that on which the green aboveground biomass (Green AGB) started to increase. The relationship between light-use efficiency and Green AGB was similar among the three years. In 2002, however, earlier senescence possibly caused low autumn GPP, and thus the annual NEP, to be lower. The low summertime R-e in 2004 was apparently caused by lower soil temperatures and the relatively lower temperature dependence of R-e in comparison with the other years. These results suggest that (1) the Qinghai-Tibetan Plateau plays a potentially significant role in global carbon sequestration, because alpine meadow covers about one-third of this vast plateau, and (2) the annual NEP in the alpine meadow was comprehensively controlled by the temperature environment, including its effect on biomass growth.

Carbon dioxide dynamics and controls in a deep-water wetland on the Qinghai-Tibetan Plateau

To initially characterize the dynamics and environmental controls of CO2, ecosystem CO2 fluxes were measured for different vegetation zones in a deep-water wetland on the Qinghai-Tibetan Plateau during the growing season of 2002. Four zones of vegetation along a gradient from shallow to deep water were dominated, respectively by the emergent species Carex allivescens V. Krez., Scirpus distigmaticus L., Hippuris vulgaris L., and the submerged species Potamogeton pectinatus L. Gross primary production (GPP), ecosystem respiration (Re), and net ecosystem production (NEP) were markedly different among the vegetation zones, with lower Re and GPP in deeper water. NEP was highest in the Scirpus-dominated zone with moderate water depth, but lowest in the Potamogeton-zone that occupied approximately 75% of the total wetland area. Diurnal variation in CO2 flux was highly correlated with variation in light intensity and soil temperature. The relationship between CO2 flux and these environmental variables varied among the vegetation zones. Seasonal CO2 fluxes, including GPP, Re, and NEP, were strongly correlated with aboveground biomass, which was in turn determined by water depth. In the early growing season, temperature sensitivity (Q(10)) for Re varied from 6.0 to 8.9 depending on vegetation zone. Q(10) decreased in the late growing season. Estimated NEP for the whole deep-water wetland over the growing season was 24 g C m(-2). Our results suggest that water depth is the major environmental control of seasonal variation in CO2 flux, whereas photosynthetic photon flux density (PPFD) controls diurnal dynamics.

Effect of burrowing activity of root vole (Microtus oeconomus Pallas) on plant diversity in alpine meadow

Herbivory and burrowing activity of mammals may influence the species composition and diversity of plant communities. The effect of corridors and holes systems constructed by root vole (Microtus oeconomus Pallas) on the plant species diversity was studied in the habitat of high - mountain meadow (3250 in a.s.l in Qinghai-Tibet Plateau, China). By using grid method, these disturbances were studied on 16 plots (100 cm x 100 cm) distributed in 4 transects in studied area, in August 2000 and 2001. The disturbance intensity index, D, was calculated as the percent of the ground surface disturbed by voles in the study area. Plant species were identified and counted on the same plots. In total 46 plant species were identified - 39% of this number was considered as sensitive to the vole disturbances as their occurrence and/or abundance decreased along the disturbance intensity. Generally, a significantly negative correlation (r = - 0.911 P < 0.01) between vole aboveground disturbances and plant species diversity (H') was found. The results suggest that root vole ground disturbances, especially in the form of actively utilized holes and corridors have significantly negative influence on plant species diversity in high-mountain grassland habitat.

The effect of land management on carbon and nitrogen status in plants and soils of alpine meadows on the Tibetan plateau

Large-scale grassland rehabilitation has been carried out on the severely degraded lands of the Tibetan plateau. The grasslands created provide a useful model for evaluating the recovery of ecosystem properties. The purposes of this research were: (1) to examine the relative influence of various rehabilitation practices on carbon and nitrogen in plants and soils in early secondary succession; and (2) to evaluate the degree to which severely degraded grassland altered plant and soil properties relative to the non-disturbed native community. The results showed: (1) The aboveground tissue C and N content in the control were 105-97 g m(-2) and 3.356gm(-2), respectively. The aboveground tissue C content in the mixed seed treatment, the single seed treatment, the natural recovery treatment and the severely degraded treatment was 137 per cent, 98 per cent, 49 per cent and 38 per cent, respectively, of that in the control. The corresponding aboveground tissue N content was 109 per cent, 84 per cent, 60 per cent and 47 per cent, respectively, of that in the control. (2) Root C and N content in 0-20 cm depths of the control had an 2 2 average 1606 gm(-2) and 30-36 gm(-2) respectively. Root C and N content in the rehabilitation treatments were in the range of 26-36 per cent and 35-53 per cent, while those in the severely degraded treatment were only 17 per cent and 26 per cent of that in the control. (3) In the control the average soil C and N content at 0-20 cm was 11307 gm(-2) and 846 gm(-2), respectively. Soil C content in the uppermost 20 cm in the seeded treatments, the natural recovery treatment and the severely degraded treatment was 67 per cent, 73 per cent and 57 per cent, respectively, while soil N content in the uppermost 20cm was 72 per cent, 82 per cent and 79 per cent, respectively, of that in the control. The severely degraded land was a major C source. Restoring the severely degraded lands to perennial vegetation was an alternative approach to sequestering C in former degraded systems. N was a limiting factor in seeding grassland. It is necessary for sustainable utilization of seeding grassland to supply extra N fertilizer to the soil or to add legume species into the seed mix. Copyright (c) 2005 John Wiley & Sons, Ltd.

The potential importance of grazing to the fluxes of carbon dioxide and methane in an alpine wetland on the Qinghai-Tibetan Plateau

To assess the impact of livestock grazing on the emission of greenhouse gases from grazed wetlands, we examined biomass growth of plants, CO2 and CH4 fluxes under grazing and non-grazing conditions on the Qinghai-Tibetan Plateau wetland. After the grazing treatment for a period of about 3 months, net ecosystem CO2 uptake and aboveground biomass were significantly smaller, but ecosystem CH4 emissions were remarkably greater, under grazing conditions than under non-grazing conditions. Examination of the gas-transport system showed that the increased CH4 emissions resulted from mainly the increase of conductance in the gas-transport system of the grazed plants. The sum of global warming potential, which was estimated from the measured CO2 and CH4 fluxes, was 5.6- to 11.3-fold higher under grazing conditions than under non-grazing conditions. The results suggest that livestock grazing may increase the global warming potential of the alpine wetlands. (c) 2005 Elsevier Ltd. All rights reserved.

Effect of long-term grazing on soil organic carbon content in semiarid steppes in Inner Mongolia

To clarify the response of soil organic carbon (SOC) content to season-long grazing in the semiarid typical steppes of Inner Mongolia, we examined the aboveground biomass and SOC in both grazing (G-site) and no grazing (NG-site) sites in two typical steppes dominated by Leymus chinensis and Stipa grandis, as well as one seriously degraded L. chinensis grassland dominated by Artemisia frigida. The NG-sites had been fenced for 20 years in L. chinensis and S. grandis grasslands and for 10 years in A. frigida grassland. Above-ground biomass at G-sites was 21-35% of that at NG-sites in L. chinensis and S. grandis grasslands. The SOC, however, showed no significant difference between G-site and NG-site in both grasslands. In the NG-sites, aboveground biomass was significantly lower in A. frigida grassland than in the other two grasslands. The SOC in A. frigida grassland was about 70% of that in L. chinensis grassland. In A. frigida grassland, aboveground biomass in the G-site was 68-82% of that in the NG-site, whereas SOC was significantly lower in the G-site than in the NG-site. Grazing elevated the surface soil pH in L. chinensis and A. frigida communities. A spatial heterogeneity in SOC and pH in the topsoil was not detected the G-site within the minimal sampling distance of 10 m. The results suggested that compensatory growth may account for the relative stability of SOC in G-sites in typical steppes. The SOC was sensitive to heavy grazing and difficult to recover after a significant decline caused by overgrazing in semiarid steppes.

Methane emissions from different vegetation zones in a Qinghai-Tibetan Plateau wetland

We measured methane (CH4) emissions in the Luanhaizi wetland, a typical alpine wetland on the Qinghai-Tibetan Plateau, China, during the plant growth season (early July to mid-September) in 2002. Our aim was to quantify the spatial and temporal variation of CH4 flux and to elucidate key factors in this variation. Static chamber measurements of CH4 flux were made in four vegetation zones along a gradient of water depth. There were three emergent-plant zones (Hippuris-dominated; Scirpus-dominated; and Carex-dominated) and one submerged-plant zone (Potamogeton-dominated). The smallest CH4 flux (seasonal mean = 33.1 mg CH4 m(-2) d(-1)) was, observed in the Potamogeton-dominated zone, which occupied about 74% of the total area of the wetland. The greatest CH4 flux (seasonal mean = 214 mg CH4 m(-2) d(-1)) was observed in the Hippuris-dominated zone, in the second-deepest water area. CH4 flux from three zones (excluding the Carex-dominated zone) showed a marked diurnal change and decreased dramatically under dark conditions. Light intensity had a major influence on the temporal variation in CH4 flux, at least in three of the zones. Methane fluxes from all zones increased during the growing season with increasing aboveground biomass. CH4 flux from the Scirpus-dominated zone was significantly lower than in the other emergent-plant zones despite the large biomass, because the root and rhizome intake ports for CH4 transport in the dominant species were distributed in shallower and more oxidative soil than occupied in the other zones. Spatial and temporal variation in CH4 flux from the alpine wetland was determined by the vegetation zone. Among the dominant species in each zone, there were variations in the density and biomass of shoots, gas-transport system, and root-rhizome architecture. The CH4 flux from a typical alpine wetland on the Qinghai-Tibetan Plateau was as high as those of other boreal and alpine wetlands. (C) 2004 Elsevier Ltd. All rights reserved.

提高勘探成熟区地震资料精度的方法研究

With the Oil field exploration and exploitation, the problem of supervention and enhaning combination gas recovery was faced.then proposing new and higher demands to precision of seismic data. On the basis of studying exploration status,resource potential,and quality of 3D seismic data to internal representative mature Oil field, taking shengli field ken71 zone as study object, this paper takes advantage of high-density 3D seismic technique to solving the complex geologic problem in exploration and development of mature region, deep into researching the acquisition, processing of high-density 3D seismic data. This disseration study the function of routine 3D seismic, high-density 3D seismic, 3D VSP seismic,and multi-wave multi-component seismic to solving the geologic problem in exploration and development of mature region,particular introduce the advantage and shortage of high-density 3D seismic exploration, put forward the integrated study method of giving priority to high-density 3D seismic and combining other seismic data in enhancing exploration accuracy of mature region. On the basis of detailedly studying acquisition method of high-density 3D seismic and 3D VSP seismic,aming at developing physical simulation and numeical simulation to designing and optimizing observation system. Optimizing “four combination” whole acquisition method of acquisition of well with ground seimic and “three synchron”technique, realizing acquisition of combining P-wave with S-wave, acquisition of combining digit geophone with simulation geophone, acquisition of 3D VSP seismic with ground seimic, acquisition of combining interborehole seismic,implementing synchron acceptance of aboveground equipment and downhole instrument, common use and synchron acceptance of 3D VSP and ground shots, synchron acquisition of high-density P-wave and high-density multi-wave, achieve high quality magnanimity seismic data. On the basis of detailedly analysising the simulation geophone data of high-density acquisition ,adopting pertinency processing technique to protecting amplitude,studying the justice matching of S/N and resolution to improving resolution of seismic profile ,using poststack series connection migration,prestack time migration and prestack depth migration to putting up high precision imaging,gained reliable high resolution data.At the same time carrying along high accuracy exploration to high-density digit geophone data, obtaining good improve in its resolution, fidelity, break point clear degree, interbed information, formation characteristics and so on.Comparing processing results ,we may see simulation geophone high-density acquisition and high precision imaging can enhancing resolution, high-density seismic basing on digit geophone can better solve subsurface geology problem. At the same time, fine processing converted wave of synchron acquisition and 3D VSP seismic data,acquiring good result. On the basis of high-density seismic data acquisition and high-density seismic data processing, carry through high precision structure interpretation and inversion, and preliminary interpretation analysis to 3D VSP seismic data and multi-wave multi-component seismic data. High precision interpretation indicates after high resolution processing ,structural diagram obtaining from high-density seismic data better accord with true geoligy situation.

西藏高原草原化嵩草草甸生态系统呼吸及碳平衡

The soil respiration and net ecosystem productivity of Kobresia littledalei meadow ecosystem was investigated at Dangxiong grassland station, one grassland field station of Lhasa Plateau Ecosystem Research Station. Soil respiration and soil heterotrophic respiration were measured at the same time by using Li6400-09 chamber in growing season of year 2004. The response of soil respiration and its components, i.e. microbial heterotrophic respiration and root respiration to biotic and abiotic factors were addressed. We studied the daily and seasonal variation on Net Ecosystem carbon Exchange (NEE) measured by eddy covariance equipments and then the regression models between the NEE and the soil temperature. Based on the researches, we analyzed the seasonal variation in grass biomass and estimated NEE combined the Net Ecosystem Productivity with heterogeneous respiration and then assessed the whether the area is carbon source or carbon sink. 1.Above-ground biomass was accumulated since the grass growth started from May; On early September the biomass reached maximum and then decreased. The aboveground net primary production (ANPP) was 150.88 g m~" in 2004. The under-ground biomass reached maximum when the aboveground start to die back. Over 80% of the grass root distributed at the soil depth from 0 to 20cm. The underground NPP was 1235.04 g m"2.. Therefore annual NPP wasl.385X103kg ha"1, i.e.6236.6 kg C ha"1. 2. The daily variation of soil respiration showed single peak curve with maximum mostly at noon and minimum 4:00-6:00 am. Daily variations were greater in June, July and August than those in September and October. Soil respiration had strong correlation with soil temperature at 5cm depth while had weaker correlation with soil moisture, air temperature, surface soil temperature, and so on. But since early September the soil respiration had a obviously correlation with soil moisture at 5cm depth. Biomass had a obviously linearity correlation with soil respiration at 30th June, 20th August, and the daytime of 27th September except at 23lh October and at nighttime of 27th September. We established the soil respiration responding to the soil temperature and to estimate the respiration variation during monsoon season (from June through August) and dry season (May, September and October). The regression between soil respiration and 5cm soil temperature were: monsoon season (June through August), Y=0.592expfl()932\ By estimating , the soil daily respiration in monsoon season is 7.798gCO2m"2 and total soil respiration is 717.44 gCC^m" , and the value of Cho is 2.54; dry season (May, September and October), Y=0.34exp°'085\ the soil daily respiration is 3.355gCO2m~2 and total soil respiration is 308.61 gCC^m", and the value of Cho is 2.34. So the total soil respiration in the grown season (From May to October) is 1026.1 g CO2IT1"2. 3. Soil heterogeneous respiration had a strong correlation with soil temperature especially with soil temperature at 5cm depth. The variation range in soil heterogeneous respiration was widely. The regression between soil heterogeneous respiration and 5cm soil temperature is: monsoon season, Y=0.106exp ' 3x; dry season, Y=0.18exp°"0833x.By estimating total soil heterotrophic respiration in monsoon season is 219.6 gCC^m"2, and the value of Cho is 3.78; While total soil heterogeneous respiration in dry season is 286.2 gCCbm"2, and the value of Cho is 2.3. The total soil heterotrophic respiration of the year is 1379.4kg C ha"1. 4. We estimated the root respiration through the balance between soil respiration and the soil heterotrophic respiration. The contribution of root respiration to total respiration was different during different period: re-greening period 48%; growing period 69%; die-back period 48%. 5. The Ecosystem respiration was relatively strong from May to October, and of which the proportion in total was 97.4%.The total respiration of Ecosystem was 369.6 g CO2 m" .we got the model of grass respiration respond to the soil temperature at 5cm depth and then estimated the daytime grass respiration, plus the nighttime NEE and daytime soil respiration. But when we estimated the grass respiration, we found the result was negative, so the estimating value in this way was not close. 6. The estimating of carbon pool or carbon sink. The NPP minus the soil heterogeneous respiration was the NEE, and it was 4857.3kg C o ha"1, which indicated that the area was the carbon sink.

内蒙古草地植被群落生物量的梯度特征研究

Relationship between biology and environment is always the theme of ecology. Transect is becoming one of the important methods in studies on relationship between global change and terrestrial ecosystems, especially for analysis of its driving factors. Inner Mongolia Grassland is the most important in China Grassland Transect brought forward by Yu GR. In this study, changes in grassland community biomass along gradients of weather conditions in Inner Mongolia was researched by the method of transect. Methods of regression about biomass were also compared. The transect was set from Eerguna county to Alashan county (38° 07' 35" ~50° 12' 20" N, 101° 55' 25" -120° 20' 46" E) in Inner Mongolia, China. The sample sites were mainly chosen along the gradient of grassland type, meadow steppe-* typical steppe-*desert steppe-*steppification desert-^desert. The study was carried out when grassland community biomass got the peak in August or September, 2003 and 2004. And data of 49 sample sites was gotten, which included biomass, mean annual temperature, annual precipitation, accumulated temperature above zero, annual hours of sunshine and other statistical and descriptive data. The aboveground biomass was harvested, and the belowground biomass was obtained by coring (30 cm deep). Then all the biomass samples were dried within (80 + 5) °C in oven and weighted. The conclusion is as follows: 1) From the northeast to the southwest in Inner Mongolia, along the gradient of grassland type, meadow steppe-*typical steppe-*desert steppe-*steppification desert-* desert, the cover degree of vegetation community reduces. 2) By unitary regression analysis, biomass is negatively correlated with mean annual temperature, s^CTC accumulated temperature, ^10°C accumulated temperature and annual hours of sunshine, among which mean annual temperature is crucial, and positively with mean annual precipitation and mean annual relative humidity, and the correlation coefficient between biomass and mean annual relative humidity is higher. Altitude doesn't act on it evidently. Result of multiple regression analysis indicates that as the primary restrictive factor, precipitation affects biomass through complicated way on large scale, and its impaction is certainly important. Along the gradient of grassland type, total biomass reduces. The proportion of aboveground biomass to total biomass reduces and then increases after desert steppe. The trend of below ground biomass's proportion to total biomass is adverse to that of aboveground biomass. 3) Precipitation is not always the only driving factor along the transect for below-/aboveground biomass ratio of different vegetation type composed by different species, and distribution of temperature and precipitation is more important, which is much different among climatic regions, so that the trend of below-/aboveground biomass ratio along the grassland transect may change much through the circumscription of semiarid region and arid region. 4) Among reproductive allocation of aboveground biomass, only the proportion of stem in total biomass notably correlates to the given parameters. Stem/leaf biomass ratio decreases when longitude and latitude increase, caloric variables decrease, and variables about water increase from desert to meadow steppe. The change trends are good modeled by logarithm or binomial equations. 5) 0'-10 cm belowground biomass highly correlates to environmental parameters, whose proportion to total biomass changes most distinctly and increases along the gradient from the west to the east. The deeper belowground biomass responses to the environmental change on the adverse trend but not so sensitively as the surface layer. Because the change value of 0~10 cm belowground biomass is always more than that of below 10 cm along the gradient, the deference between them is balanced by aboveground biomass's change by the resource allocation equilibrium hypothesis.