Short-term effects of sheep excrement on carbon dioxide, nitrous oxide and methane fluxes in typical grassland of Inner Mongolia

Excrement patches of grazing animals play an important role in greenhouse gas (GHG) fluxes due to the high nitrogen (N) and available carbon (C) deposited in small areas, but little information is available for the effect of excrement in the Inner Mongolian grassland (43 26 degrees N, 116 degrees 40'E). To elucidate the effect of grazing sheep urine, fresh dung and compost on fluxes of methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O), a short-term field study (65 days) was carried out in the typical grassland of Inner Mongolia with the optimised closed chamber/GC technique. Compared with the control, cumulative net CH4 consumption decreased 36, 31, and 18% from urine, fresh dung, and compost plots, respectively; net CO2-C output increased by 6.5, 1.5, and 1.2% from urine, fresh dung, and compost treated soil, respectively; about three times as much N2O-N was emitted from urine and the fresh dung treatments during 65 days. Nitrous oxide emission was positively correlated with CO, emission (R = 0.691, P < 0.01) and water-filled pore space (R = 0.698, P < 0.01). The percentages of N2O-N loss of applied-N were 0.44 and 1.05% for urine and fresh dung, respectively. Our results suggest that in autumn in the degraded grassland of Inner Mongolia, the effect of sheep excrement may be ignored when evaluating the total GHG emissions.

Distribution and species diversity of plant communities along transect on the Northeastern Tibetan plateau

The distribution and species diversity of plant communities along a 600 km transect through the northeastern Tibetan Plateau (32 degrees 42'-35 degrees 07' N, 101 degrees 02'-97 degrees 38' E) with altitudes from 3255 to 4460 m are described. The transect started from the Youyi Bridge of Banma through Dari, Maqin and Maduo to Zaling Lake. The data from 47 plots along the transect are summarized and analyzed. The mean annual temperature, the mean annual rainfall and the length of growing season decreases from 2.6 to -4.5 degrees C, from 767.2 to 240.1 mm, from 210 to 140 days, respectively, along the transect from the southeastern Banma to northwestern Zaling Lake. The number of vascular plant species recorded in 47 plots is 242 including 2 tree, 34 shrub, 206 herb species. Main vegetation types on the transect from southeast to northwest are: Sabina convallium forest, Picea likiangensis forest, Pyracantha fortuneana + Spiraea alpina shrub, Hippophae neurocarpu shrub, Sibiraea angustata + Polygonum viviparum shrub, Stellera chamaejasme herb meadow, Potentilla fruticosa + Salix obscura + Carex sp. Shrub, Kobresia capillifolia meadow, P. froticosa + Kobresia humilis shrub, Caragana jubata + S. obscura shrub, Kobresia tibetica meadow, Kobresia pygmaea meadow, K. pygmaea + Stipa purpurea steppe meadow, Stipa purpurea steppe. Plant richness and diversity index all showed a decreasing trend with increasing of elevation along transect from southeast to northwest. Detailed information on altitudinal ranges and distribution of the alpine vegetation, vascular flora and environments over the alpine zone at northeastern Tibetan Plateau provides baseline records relevant to future assessment of probable effects of global climate changes.

Modeling trophic positions of the alpine meadow ecosystem combining stable carbon and nitrogen isotope ratios

Stable carbon and nitrogen isotope ratios of single tissues or whole bodies were analyzed to establish trophic positions of main consumers living at the alpine meadow ecosystem in the Tibetan Plateau. The results demonstrated that delta C-13 and delta N-15 values of vertebrates showed great variations and ranged from -26.83 to -22.51 parts per thousand and from 2.33 to 8.44 parts per thousand, respectively. Plateau pika, root vole, plateau hare, infants of rodents and hatchlings of passerine bird species had the lowest delta C-13 and delta N-15 values. delta C-13 and delta N-15 values of omnivorous and insectivorous birds and amphibians showed intermediate. Carnivorous species, steppe polecat and Upland buzzard, and omnivorous Robin accentor and White wagtail possessed extremely higher VC and delta N-15 values. Omnivorous birds captured in earlier year had significantly less negative delta C-13 and greater delta N-15 values than those captured later. Based on steady angular enrichment between trophic levels, an "alpha and vector model" combing delta C-13 and delta N-15 values was introduced to reveal trophic positions, the results indicated that Tibetan sheep, Tibetan yak, plateau pika, root vole, plateau hare, infants of small rodents showed the lowest trophic positions (TP 1.81-2.38). While omnivorous and insectivorous birds, their hatchlings and amphibians showed intermediate trophic positions (TP 2.06-2.89), carnivorous species steppe polecat and Upland buzzard, migrant birds possessed extremely higher trophic positions (TP 2.89-3.05). The isotopic investigation of organisms and the introduced "alpha and vector model" successfully demonstrated the same trophic positions and diet prediction of consumers as nitrogen enrichment model at the alpine meadow ecosystem. Besides of this information, the "alpha and vector model" can also be incorporated into multiple isotope signatures to infer trophic relationships. This angular enrichment model has the potential to address basic ecological questions, such as trophic structure, trophic dynamics, and energy flow in other terrestrial ecosystems of properly handled. (C) 2005 Elsevier B.V. All rights reserved.

Phylogeography of the Qinghai-Tibetan Plateau endemic Juniperus przewalskii (Cupressaceae) inferred from chloroplast DNA sequence variation

The vegetation of the northeast Qinghai-Tibetan Plateau is dominated by alpine meadow and desert-steppe with sparse forests scattered within it. To obtain a better understanding of the phylogeography of one constituent species of the forests in this region, we examined chloroplast trnT-trnF and trnS-trnG sequence variation within Juniperus przewalskii, a key endemic tree species. Sequence data were obtained from 392 trees in 20 populations covering the entire distribution range of the species. Six cpDNA haplotypes were identified. Significant population subdivision was detected (G(ST) = 0.772, N-ST = 0.834), suggesting low levels of recurrent gene flow among populations and significant phylogeographic structure (N-ST > G(ST), P < 0.05). Eight of the nine disjunct populations surveyed on the high-elevation northeast plateau were fixed for a single haplotype (A), while the remaining, more westerly population, contained the same haplotype at high frequency together with two low frequency haplotypes (C and F). In contrast, most populations that occurred at lower altitudes at the plateau edge were fixed or nearly fixed for one of two haplotypes, A or E. However, two plateau edge populations had haplotype compositions different from the rest. In one, four haplotypes (A, B, D and E) were present at approximately equivalent frequencies, which might reflect a larger refugium in the area of this population during the last glacial period. Phylogenetic analysis indicated that the most widely distributed haplotype A is not ancestral to other haplotypes. The contrasting phylogeographic structures of the haplotype-rich plateau edge area and the almost haplotype-uniform plateau platform region indicate that the plateau platform was recolonized by J. przewalskii during the most recent postglacial period. This is supported by the findings of a nested clade analysis, which inferred that postglacial range expansion from the plateau edge followed by recent fragmentation is largely responsible for the present-day spatial distribution of cpDNA haplotypes within the species.

Molecular systematics of pikas (genus Ochotona) inferred from mitochondrial DNA sequences

The phylogenetic relationships among worldwide species of genus Ochotona were investigated by sequencing mitochondrial cytochrome b and ND4 genes. Parsimony and neighbor-joining analyses of the sequence data yielded congruent results that strongly indicated three major clusters: the shrub-steppe group, the northern group, and the mountain group. The subgeneric classification of Ochotona species needs to be revised because each of the two subgenera in the present classification contains species from the mountain group. To solve this taxonomic problem so that each taxon is monophyletic, i.e., represents a natural clade, Ochotona could be divided into three subgenera, one for the shrub-steppe species, a second for the northern species, and a third for the mountain species. The inferred tree suggests that the differentiation of this genus in the Palearctic Region was closely related to the gradual uplifting of the Tibet (Qinghai-Xizang) Plateau, as hypothesized previously, and that vicariance might have played a major role in the differentiation of this genus on the Plateau, On the other hand, the North American species, O. princeps, is most likely a dispersal event, which might have happened during the Pliocene through the opening of the Bering Strait. The phylogenetic relationships within the shrub-steppe group are worth noting in that instead of a monophyletic shrub-dwelling group, shrub dwellers and steppe dwellers are intermingled with each other. Moreover, the sequence divergence within the sister tars of one steppe? dweller and one shrub dweller is very low. These findings support the hypothesis that pikes have entered the steppe environment several times and that morphological similarities within steppe dwellers were due to convergent evolution. (C) 2000 Academic Press.

黄土高原中部60万年来黄土—古土壤序列有机碳同位素研究

Vegetation is very sensitive to climate change. Carbon isotopes in paleosol have been widely used to contruct the propotion of plants using C3 and C4 photosynthetic pathways. δ13C of Loess organic matter were analyzed on the loess- paleosols samples from Jingchuan sections and Luochuan S4—S5 sequence. This paper presents a long carbon isotope time series, covering the last 600kyr. δ13C record of Loess organic matter in Jingchuan is correlated with marine oxygen isotope records. Basing on former research work, this paper discusses temperature, rainfall and P CO2 effect on δ13Corg value. In the interglacial periods, carbon isotope is more sensitive than other proxies and indicates several climate fluctuations. The main conclusions are as follows: 1. Obtained δ13C composition from paleosols and loess sediments in Jingchuan range of -20.0‰ to -24.6‰, the maximum biomass of C4 is 35%, indicating a C3 and C4 mixed steppe with C3 dominated. C4 plant is not always expansion during paleosols periods. The minimum values of Jingchuan section appeared in S4 soil, and the vegetation was almost pure C3 plant at that time. δ13Corg value in S5-2 is also lower than loess in S5, reaching the minimum valus of S5 soil. 2. PCO2 variation has little impact on δ13Corg value in interglacial periods for the last 600kyr. The correlation between δ13Corg value curve and magnetic susceptibility curve as proxy of summer monsoon in general, means summer monsoon drive C4 plant expansion during glacial and interglacial. 3. The lowerδ13Corg values in S4 and S5-2 appear at Jingchuan and Luochuan, suggest origin from woodland or C3 grassland. Whatever vegetation it is, indicate strengthened East Asian summer monsoon and increase of precipitation. C4 plant percentage is lower in S5-1 and S1 which have stronger summer monsoon, than S0 and S2. And it also indicates increase of precipitation.δ13Corg values has not always non-linearity correlation with summer monsoon. 4. The maximum entroy spectral analysis of δ13C values of the last 600kyr indicates there is 21 kyr cycles in Loess sequence. It means that summer monsoon in the Chinese Loess Plateau also has the precession cycles like its origin low latitude.

中国黄土高原洛川剖面 630 kyr 以来的孢粉记录

It is known that global climate changed from the early Tertiary “Green House” to the Quaternary “Ice House” of cyclic glacial-interglacial climatic changes. Since the middle Pleistocene, the climate cycles changed from 40 kyr to 100 kyr, and the amplitudes of climatic fluctuations increased significantly. Therefore, it is important to study the climate changes since the middle Pleistocene. The loess-paleosol sequence in China is considered as one of the most continuous continental records of the last 2.58 Ma. Paleoclimatic and environmental changes have been widely extracted through various climatic parameters. However, the history of paleovegetation on the Loess Plateau still remains unclear. Did an extensive broadleaf forest ever exist on the Loess Plateau? Pollen preserved in the loess and paleosol provides a direct record for vegetation and paleoenvironmental change on the Plateau. However, because it is difficult to extract sufficient pollen grains from loess, the pollen record since the middle Pleistocene especially in the central part of the Chinese Loess Plateau has not been well studied. So we preliminarily focus on the palynological records of the loess-paleosol sequence spanning the last 630 kyr at Luochuan and aim to understand the evolution of vegetation and climate change on the Chinese Loess Plateau. The main results and conclusions are as follows: 1. The palynological results show that the grassland has been a dominant vegetation in the Luochuan area since 630 kyr, even during the intervals of relatively warm and wet climatic conditions. 2. The pollen concentration of Luochuan section sharply decreases from the bottom of S1 to downward depth. This decrease can be attributed to depositional environment rather than climate change. In loess, not only oxidation, but also the PH of deposits and bacteria or fungi have been able to degrade sporopollenin. 3. The paleoclimatic condition during S4 stage, characterized with warmer condition during the early stage, was warmer and wetter than that during S5 in Luochuan area. Paleoclimate was warmer and wetter during the early stage of S5 and became colder and drier later. The special pedogenic features of S5-I can be attributed to a prolonged pedogenic duration rather than a warm-wet climate. 4. Evidence from pollen assemblage suggests that the Holocene vegetation has been affected by human impacts, especially after the Yangshao Culture. 5. The present steppe environment on the loess plateau is mainly due to natural conditions. Temperature, seasonal precipitation and soil structure are three important factors which control the vegetation type. 6. The vegetation on the loess plateau is characterized with zonal or azonal distribution. So local conditions should be taken into account when recover natural vegetation. Finally, the restoration and reconstruction of ecosystem on the loess plateau area should be focused on planting grassland rather than forests.

甘肃临夏盆地龙担剖面晚新生代磁性地层与古环境

Linxia Basin, situated in the northeast belt of the Tibetan Plateau, is a late Cenozoic depression basin bounded by the Tibetan Plateau and the Chinese Loess Plateau. The Cenozoic deposition, spanning over 30Ma, in which very abundant mammal fossils were discovered, is very suitable for study of uplift processes and geo-morphological evolution of the Tibetan Plateau. The Longdan section (35°31′31.6″N，103°29′0.6″E) is famous for the middle Miocene Platybelodon fauna and the late Miocene Hipparion fauna for a long time and is also one of the earliest known places for wooly rhino, which lies on the east slope of Longdan, a small village of township Nalesi in the south of the Dongxiang Autonomous County, Linxia Hui Nationallity Autonomous Prefecture. The Longdan mammal fauna was discovered at the base of the Early Pleistocene loess deposits at Dongxiang, where the lithology is different from the typical Wucheng Loess on the Chinese Loess Plateau. The rich fossils contain many new species and the major two layers of fossils are in the loess beds. Geologically the fossiliferous area is located in the central part of the Linxia Cenozoic sedimentary basin. Tectonically the Linxia Basin is an intermountain fault basin, bordered by the Leijishan major fault in the south and the north Qinling and Qilianshan major faults in the north. The section is 51.6m thick above the gravel layer, including the 1.6m Late Pleistocene Malan Loess on the top and the other loess-paleosol sequences in the middle of the section. The base of the section is the Jishi Formation, consisting of gravel layer of 13 ~ 17m thick. In this study, 972 bulk samples were collected with an interval of 5cm and other 401 orientied samples were taken with a magnetic compass. In the laboratory, the paleomagnetism, medium grain size, susceptibility, color, micromorphology, anisotropy of magnetic susceptibility were analyzed. From the stratigraphic analysis, the Longdan section from the top 0.3m to the bottom 51.6m, containing 5 normal polarities (N1-N5) and 5 reversal polarities (R1-R5). The paleomagnetic results show N3 is the Olduvai subchron in the middle of the Matuyama chron, and then the chronology of the Longdan mammal fauna is constructed along the section. The Matuyama-Gauss boundary is 45m and N5 enters Gauss chron. The Olduvai subchron with the age of 1.77 ~ 1.95Ma is found just in the upper fossiliferous level of Longdan mammal fauna. Taking the deposit rate of the section into account, the geological age of the upper fossiliferous level of Longdan mammal fauna is estimated to be about 1.9Ma. The lower fossiliferous level is just below the Reunion subchron and its age is estimated to be 2.25Ma. In addition, anisotropy of magnetic susceptibility of the loess-paleosol and other climatic indexes were used for discussing the late Cenozoic paleoenvironmental changes at Longdan, from which the Longdan area should have been an area of predominantly steppe the same as the Longdan mammal fauna.

渭南地区末次冰期以来的蜗牛化石记录及古气候古环境研究

In this study, 172 mollusk assemblages from the Weinan loess section in the southeast of Loess Plateau, China, were identified quantitatively at relative high resolution. The results show: 1) the history and processes of paleoclimatic and paleoenvironmental changes in Weinan since the last 70 ka; 2) the characteristics of climatic changes during the period of the last glacial maximum (LGM); 3) the spatial pattern of paleoclimate variations at the south and middle parts of the Loess Plateau during the LGM period; 4) the timing of the last deglaciation and the return event of rapid climate change during the last deglaciation. The main conclusions are as follows: 1) 172 mollusk samples taken from the uppermost 9 m deposits cover the past 70 ka, which were sampled at the internals of 5 cm for S_0, 3 cm for L_(1-1) and L_(1-2), and 10 cm for L_(1-3), L_(1-4) and L_(1-5). Author analyzed quantitatively all individuals including broken pieces of snail shells, percentages of 15 species identified from 172 samples. Three main groups were determined according to the ecological requirement of each taxon. Based on the variations of three ecological groups and typical ecological species, The author intended to reconstruct the history of and processes of climate and environment since the last 70 ka in the Weinan region. The climate and environment in this region experienced the following changes: relative warm and humid stage from 67.5-20.3 cal. ka B.P., a period of forest-steppe or steppe developed; cold and arid stage from 20.3-15.5 cal. ka B.P., a dry steppe period, later wetter and colder; cold and humid period once time from 15.5 to 12.3 cal. ka B.P., a typical steppe or forest-steppe stage; cold and humid again from 12.3 cal. ka B.P. to 8.2 cal. ka B.P., a tropical steppe stage; warm and humid climate, a forest-steppe developed. 2) The climate during the period of the last glacial maximum (LGM) in Weinan was characterized by a general cold-humid condition, represented by occurrence of a number of the cool-humidiphilous mollusk species such as Gastocopta amigerella and Vallonia cf. pulchella in the section. 3) Comparison of the variations in abundance of Puncture orphana at Weinan with those at Luochuan and Changwu sections suggests that the summer monsoon intensity influenced differently at the three regions during the LGM period. The Weinan was weaker summer monsoon impact during all the period, the Luochuan was influenced occasionally, and Changwu was only a very short time affected, which indicated it might be located at the western margin of the summer monsoon influence during that period. 4) The ratio of thermo-humidiphilous mollusk group to cold-aridiphilous one shows an increase tendency at about 15 cal. ka B.P., reflecting the climate warming after the deglaciation in Weinan, which is approximately corresponding to the timing of warming period of the last deglaciation, found in the East Atlantic Ocean, the South China Sea and the Loess Plateau (indicated by the phytolith study). 5) A remarkable decrease in the number of thermo-humidiphilous and cool-humidiphilous mollusk species from 12.7 - 11.6 cal. ka B.P. indicates a cooling in climate and might be the reflection of the Younger Dryas event in Weinan. 6) Variations in the ratios of thermo-humidiphilous mollusk species to cold-aridiphilous ones reflect the climate instability in Holocene. There were four warm-humid periods (10-8.1 cal. ka B.P., 6.9-6.1 cal. ka B.P., 5.2-2.6cal. ka B.P., 1.6cal. ka B.P. to the present ) and three relative cold-arid periods (8.1-6.9 cal. ka B.P., 6.1-5.2 cal. ka B.P., 2.6-1.6 cal. ka B.P.), showing about a 1,000 year climatic oscillation.

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.

热察绥地区过去300年土地利用覆被变化

The historical land use and land cover changes is one of the key issues in LUCC research. However, the achievement of China in this field doesn't match her position in the world yet. And the reliability of the quantitive records in Chinese historical literature, the basic data for historical land use research, has been doubted. This research focuses on Re-Cha-Sui, a typical area for the farming-pastoral region in the north of China, to make a detailed case study in this field. Based on a deep mining and calibration on the data from massive historical documents and land-use surveys, the author gives a detailed analysis on the administrative region evolution, historical population dynamics, reclamation policy, and the land statistic system. According to textual researches, parallel validation and physical geographical analysis, a unified land use series for recent 300 years, which founded on the results of modern land-use surveys, is constructed. And the thematic maps on the cultivation index for different counties in several temporal sections are plotted. Based on the endeavor above, the dynamic of forest and steppe is reconstructed as well. The temporal-spatial patterns of land use/land cover changes in the area is analyzed. And the influence of different driving forces are discussed. The main conclusions of the research are as followed: 1. The quantitive records in literatures on Re-Cha-Sui area are reflection of real amounts of croplands. It is practical to reconstruct a result comparable with the modern land-use surveys, based of a deep mining and considerate validation on historical documents. The unexceptional negative attitude towards the numerical records in historical documents is unnecessary. 2. In recent 300 years, 3 climax of reclamation appeared in Re-Cha-Sui area and altered the pure pastoral area into a farming-pastoral region. The interval were respectively the early time till mid time of the Qing dynasty, the end of the Qing dynasty till early time of the Republic of China(ROC), and the time after A.D. 1949. After the first expansion, the area of cropland in this region reached 2.0 million ha. Among them, Guisui area, which was most densely cultivated, had a cultivation index over 30%, which is similar with modern situation. The second expansion covered broader area, and the amount of cropland reached 3.5 million ha. The increase of farming area after 1949 is due to the recultivation of abandoned farmland. The current area of cropland in this region is 5.6 million ha. In the southern area where the land was reclaimed early, the amount on of the cropland has some fluctuation in 300 years. While in the new reclaimed area in the north, the area of cropland has kept the trend of increasing. 3. Due to the different natural conditions, most forests in Re-Cha-Sui area distribute in the mountain area of North Hebei province, and the upland of West Liaoning province, especially the former, which has a forest coverage near 70%. However, most of these forests were destroyed before the end of the Qing dynasty. In 1949, the natural forest near Chengde was nearly cleared up. They were partly renewed after 1949 due to plantation. 4. In the steppe zone such as northern Rehe, Suiyuan and Chahar, the area of steppe has a negative correlation with that of cropland. With the expansion of cropland, the percentage of steppe has shrunk from over 80% to 53%. In the mountain area of North Hebei province, steppe expanded with the shrinkage of forest, though cropland was expanding. The percentage once reached 60%, and then fell with the renew of forest. However, in the upland of West Liaoning province, the steppe shrink slowly from original 50% to current 26%, with the expansion of cropland. 5. The land use and land cover change in Re-Cha-Sui area in recent 300 years is driven by various factors, including human dimensions such as population, policy of the government, disorder of the society, cultural tradition, and natural factors such as climate change and natural disasters. Among them, pressure from surplus population is the basic driving force.

中国北方典型生态区表土孢粉组合特征及其与现代植被和气候的关系

Surface pollen assemblages and their relationhips with the modern vegetation and climate provide a foundation for investigating palaeo-environment conditions by fossil pollen analysis. A promising trend of palynology is to link pollen data more closely with ecology. In this study, I summarized the characteristics of surface pollen assemblages and their quantitative relation with the vegetation and climate of the typical ecological regions in northern China, based on surface pollen analysis of 205 sites and investigating of modern vegetation and climate. The primary conclusions are as follows:The differences in surface pollen assemblages for different vegetation regions are obvious. In the forest communities, the arboreal pollen percentages are more than 30%, herbs less than 50% and shrubs less than 10%; total pollen concentrations are more than 106 grains/g. In the steppe communities, arboreal pollen percentages are generally less than 5%; herb pollen percentages are more than 90%, and Artemisia and Chenopodiaceae are dominant in the pollen assemblages; total pollen concentrations range from 103 to 106 grains/g. In the desert communities, arboreal pollen percentages are less than 5%. Although Chenopodiaceae and Artemisia still dominate the pollen assemblages, Ephedra, Tamaricaceae and Nitraria are also significant important in the pollen assemblages; total pollen concentrations are mostly less than 104grains/g. In the sub-alpine or high and cold meadow communities, arboreal pollen percentages are less than 30%. and Cyperaceae is one of the most significant-taxa in the pollen assemblages. In the shrub communities, the pollen assemblages are consistent with the zonal vegetation; shrub pollen percentages are mostly less than 20%, except for Artemisia and Hippophae rhamnoides communities.There are obvious trends for the pollen percentage ratios of Artemisia to Chenopodiaceae (A/C), Pinus to Artemisia (P/A) and arbor to non-arbor (AP/NAP) in the different ecological regions. In the temperate deciduous broad-leaved forest region, the P/A ratios are generally higher than 0.1, the A/C ratios higher than 2 and the AP/NAP ratios higher than 0.3. In the temperate steppe regions, the P/A ratios are generally less than 0.1, the A/C ratios higher than 1 and the AP/NAP ratios less than 0.1. In the temperate desert regions, the P/A ratios are generally less than 0.1, the A/C ratios less than 1, and the AP/NAP ratios less than 0.1.The study on the representation and indication of pollen to vegetation shows that Pinus, Artemisia, Betula, Chenopodiaceae, Ephedra, Selaginella sinensis etc. are over-representative in the pollen assemblages and can only indicate the regional vegetation. Some pollen types, such as Quercus, Carpinus, Picea, Abies, Elaeagus, Larix, Salix, Pterocelis, Juglans, Ulmus, Gleditsia, Cotinus, Oleaceae, Spiraea, Corylus, Ostryopsis, Vites, Tetraena, Caragana, Tamaricaceae, Zygophyllum, Nitraria, Cyperaceae, Sanguisorba etc. are under-representative in the pollen assemblages, and can indicate the plant communities well. Populus, Rosaceae, Saxifranaceae, Gramineae, Leguminosae, Compositae, Caprifoliaceae etc. can not be used as significant indicators to the plants.The study on the relation of pollen percentages with plant covers shows that Pinus pollen percentages are more than 30% where pine trees exist in the surrounding region. The Picea+Abies pollen percentages are higher than 20% where the Picea+Abies trees are dominant in the communities, but less than 5% where the parent plants are sparse or absent. Larix pollen percentages vary from 5% to 20% where the Larix trees are dominant in the communities, but less than 5% where the parent plants are sparse or absent. Betula pollen percentages are higher than 40% where the Betula trees are dominant in the communities" but less than 5% where the parent plants are sparse or absent. Quercus pollen percentages are higher than 10% where the Quercus trees are dominant in the communities, but less than 1% where the parent plants sparse or absent. Carpinus pollen percentages vary from 5% to 15% where the Carpinus trees are dominant in the communities, but less than 1% where the parent plants are sparse or absent. Populus pollen percentages are about 0-5% at pure Populus communities, but cannot be recorded easily where the Populus plants mixed with other trees in the communities. Juglans pollen accounts for 25% to 35% in the forest of Juglans mandshurica, but less than 1% where the parent plants are sparse or absent. Pterocelis pollen percentages are less than 15% where the Pterocelis trees are dominant in the communities, but cannot be recorded easily where the parent plants are sparse or absent. Ulmus pollen percentages are more than 8% at Ulmus communities, but less than 1% where the Ulmus plants mixed with other trees in the communities. Vitex pollen percentages increase along with increasing of parent plant covers, but the maximum values are less than 10 %. Caragana pollen percentages are less than 20 % where the Caragana plant are dominant in the communities, and cannot be recorded easily where the parent plants are sparse or absent. Spiraea pollen percentages are less than 16 % where the Spiraea plant are dominant in the communities, and cannot be recorded easily where the parent plants are sparse or absent.The study on the relation of surface pollen assemblages with the modern climate shows that, in the axis 1 of DCA, surface samples scores have significant correlation with the average annual precipitations, and the highest determination coefficient (R2) is 0.8 for the fitting result of the third degree polynomial functions. In the axis 2 of DCA, the samples scores have significant correlation with the average annual temperatures, average July temperatures and average January temperatures, and the determination coefficient falls in 0.13-0.29 for the fitting result of the third degree polynomial functions with the highest determination coefficient for the average July temperature.The sensitivity of the different pollen taxa to climate change shows that some pollen taxa such as Pinus, Quercus, Carpinus, Juglans, Spiraea, Oleaceae, Gramineae, Tamariaceae and Ephedra are only sensitive to the change in precipitation.