Please wait a minute...
Table of Content
    Volume 29 Issue 1
    30 January 2005
      
    Research Articles
    KRANZ ANATOMY AND C4 PHOTOSYNTHETIC CHARACTERISTICS OF TWO DESERT PLANTS, HALOXYLON AMMODENDRON AND CALLIGONUM MONGOLICUM
    SU Pei-Xi, AN Li-Zhe, MA Rui-Jun, LIU Xin-Min
    Chin J Plan Ecolo. 2005, 29 (1):  1-7.  doi:10.17521/cjpe.2005.0001
    Abstract ( 3854 )   PDF (717KB) ( 1164 )   Save
    Related Articles | Metrics

    The desert plants, Haloxylon ammodendron and Calligonum mongolicum, grow under extreme arid conditions that are associated with high temperatures and intensive radiation. Their true leaves are highly reduced and the young annual shoots become photosynthetic organs. In order to provide a theoretical basis of reference for restoring natural ecosystems of desert regions and maintaining the stability of protective ecosystems that surround oases, the cross sectional anatomical structure, stable carbon isotope ratio (δ13C) and photosynthetic characteristics of the assimilating shoots of these two species were studied. The study area lies in the northern part of the Hexi Corridor Region in Gansu Province at the southern edge of the Badain Jaran Desert. During the growing season (late May to early October in 2001), we collected assimilating shoots and prepared samples for analysis. For light microscopy, samples of assimilating shoots of H. ammodendron and C. mongolicum were cut in late July and fixed in FAA (alcohol∶formalin∶glacial acetic acid; 90∶5∶5). Transverse sections of assimilating shoots of the two desert plants were observed and photographed using a Nikon 1 671 CHR microscope. The stable carbon isotope ratios (δ13C) of assimilating shoots of the two plants were analysed using a MAT-252 mass spectrometer in the State Key Gas Geo-chemical Laboratory of the Lanzhou Institute of Geology, Chinese Academy of Sciences, and compared with other desert plants and the C4 crop, Zea mays. The response of the net photosynthetic rate (Pn) of the in vivo assimilating shoots of the two plants to different photon flux density (PFD) and CO2 concentration (Ca) were measured using a LI-6400 portable photosynthesis system (LI-COR, Nebraska, USA). The assimilating shoots were cut after measurements of Pn and their areas measured with the LI-3100 Area Meter. The difference in δ13C and Δ of leaves or assimilating shoots of different plants and the difference in δ13C values of the same plant determined in different growth periods were analyzed by single factor variance analysis. If there was a significant difference, various levels of multiple comparison tests were made using Duncan's new multiple range test. The results are summarized below. 1) Assimilating shoots of H. ammodendron and C. mongolicum have a layer of hypodermal cells and two layers of chlorenchyma on the stem periphery, i.e. an outer layer of palisade cells and an inner layer of bundle sheath cells. The central portion of the shoot is occupied by water storage tissue with the main vascular bundles located in the center. Central bundles are thus separated from Kranz-type cells by layers of water storage cells. There are some small peripheral bundles that have contact with bundle sheath cells. Mesophyll and bundle sheath cells contain chloroplasts. The chloroplast of bundle sheath cells contains starch grain, but the chloroplast of mesophyll cells does not contain starch grain. For H. ammodendron, some crystal-containing cells existed in mesophyll and water storage tissue. For C. mongolicum, many mucilage cells existed in the mesophyll and water storage tissues. These results demonstrate that these two species have Kranz anatomy. 2) The δ13C values of H. ammodendron and C. mongolicum were -14.3‰ and -14.8‰, respectively, whereas the corresponding values of Caragana korshinskii, Nitraria sphaerocarpa, Hedysarum scoparium and Reaumuria soongorica were -25.8‰, -25.8‰, -26.4‰ and -28.1‰, respectively. The δ13C values of the desert plants H. ammodendron and C. mongolicum were similar and were not significantly different from the δ13C value of maize. Under different growth periods and under high and low water conditions, the δ13C values of these two species varied between -14‰ to -16‰. However, the desert plants C. korshinskii, N. sphaerocarpa, H. scoparium and R. soongorica, and oasis shelterbelt arborous species, such as Elaeagnus angustifolia, Populus gansuensis, and the oasis species, Populus euphratica, all had similar δ13C value which varied between -25 ‰--30‰. The stable carbon isotope discrimination of H. ammodendron and C. mongolicum was 5‰-6‰ which was similar to the C4 crop maize, while those of the other plants mentioned above were 16‰-22‰. 3) The CO2 compensation point (CCP) of H. ammodemdron and C. mongolicum was 2 and 4 μmol•mol-1, respectively, and that of C. korshinskii was 91 μmol•mol-1. 4) The light saturation point (LSP) of H. ammodemdron and C. mongolicum was 1 660 and 1 756 μmol•m-2•s-1, respectively, C. korshinskii was 1 267 μmol•m-2•s-1. 5) The apparent quantum yield of H. ammodemdron and C. mongolicum was 0.044 and 0.057 mol CO2•mol-1 photons and C. korshinskii was 0.02 mol CO2•mol-1 photons.

    PHOTOSYNTHETIC CHARACTERISTICS AND CHLOROPHYLL FLUORESCENCE IN LEAVES OF COTTON PLANTS GROWN IN FULL LIGHT AND 40% SUNLIGHT
    YANG Xing-Hong, ZOU Qi, ZHAO Shi-Jie
    Chin J Plan Ecolo. 2005, 29 (1):  8-15.  doi:10.17521/cjpe.2005.0002
    Abstract ( 2450 )   PDF (743KB) ( 1525 )   Save
    Related Articles | Metrics
    Depending on the amount of light available during growth, plants possess the ability to react to the amount of available light during growth using two distinct growth-responses: the strong-light growth-response as found at high light quanta and the weak-light growth-response, which is seen in shade leaves and plants growing under low-light. This ability of plants and chloroplasts to adapt to light is a fundamental growth-response, which is associated with specific changes in the morphology, physiology, biochemistry and structure of leaves and chloroplants. In wheat-cotton intercropping systems, cotton seedlings are shaded by wheat plants for about 40-45 days and then exposed to direct sunlight and high ambient temperatures and low humidity immediately after wheat plants are harvested. The growth of cotton plants declines for about 20 days following this high light exposure and then gradually acclimate, but the squaring and inflorescence period are delayed. In this study, the effects of shading (40% of natural light intensity) on photosynthesis and chlorofluorescence characteristics of cotton leaves were examined using chlorophyll fluorescence and gas exchange techniques. Compared with cotton seedlings grown in full sunlight, a lower photosynthetic rate, lower PSⅡ activity and lower efficiency of primary energy conversion as well as lower electron transport rate were found in plants grown under shaded conditions (40% sunlight). Light saturation point (LSP), light compensation point (LCP), CO2 saturation point (CSP) and CO2 compensation point (Γ) also were higher in leaves grown in full sunlight than under 40% sunlight. Upon sudden exposure from low to high photon flux density (PFD), the net photosynthetic rate (Pn), stomatal conductance (Gs), actual PSII efficiency (ΦPSⅡ) and non-photochemical quenching (NPQ) of full light leaves increased to maximal levels in a short period, whereas it took a much longer time for those of shaded leaves to reach maximal levels. The shaded cotton leaves were more susceptible to photoinhibition due to low CO2 assimilation and protective mechanisms, such as xanthophylls cycle-dependent dissipation of excessive energy.
    RESPONSE OF PHOTOSYNTHETIC RATE AND STOMATAL CONDUCTANCE OF RICE TO LIGHT INTENSITY AND CO2 CONCENTRATION IN NORTHERN CHINA
    WANG Jian-Lin, YU Gui-Rui, WANG Bo-Lun, QI Hua, XU Zheng-Jin
    Chin J Plan Ecolo. 2005, 29 (1):  16-25.  doi:10.17521/cjpe.2005.0003
    Abstract ( 2883 )   PDF (764KB) ( 1078 )   Save
    Related Articles | Metrics

    The response of photosynthetic rate and stomatal conductance of rice (Oryza sativa var. Japonica) to changes in light intensity and CO2 concentrations was studied using a Li-6400 in Northern China. In general, photosynthetic rates increased with light intensity and CO2 concentrations and could be expressed by a Michaelis-Menten function. Apparent quantum yield increased with CO2 concentrations but decreased slightly when CO2 concentrations exceeded 800 mol•mol-1. Similarly, apparent carboxylation efficiency increased with light intensity but decreased slightly when light intensity exceeded 1 600 mol•m-2•s-1. The response of stomatal conductance to light intensity can also be expressed by a Michaelis-Menten function, whereas the response to CO2 concentrations can be expressed by a hyperbola. If the combined effects of light intensity and CO2 concentrations are considered, the photosynthetic rate can be estimated by a Michaelis-Menten equation with a maximum photosynthetic rate of 71.74 mol•m-2•s-1. Apparent quantum yield was 0.056 0 mol CO2•mol-1 photons and carboxylation rate was 0.1031 mol•m-2•s-1/mol•mol-1. The response of stomatal conductance (Gsw) to light intensity can be expressed by a Michaelis-Menten function too, but the response to CO2 concentrations (Cs) can be simulated by the equation: Gsw=Gmax,c/(1+Cs/Cs0) where Gmax,c is maximum stomatal conductance of stomatal response to CO2 under a defined light intensity and Cs0 is a constant, because the stomatal conductance decreases with increases in CO2 concentrations, stomatal conductance can be estimated by Gsw=Gmax(PFD/PFDc)/[(1+PFD/PFDc)(1+Cs/Cs0)]+Gct in response to the combined effects of CO2 concentration and light intensity (I). The potential maximum stomatal conductance, Gmax, can reach 0.670 9 mol•m-2•s-1 under saturated light levels and CO2 near 0 mol•mol-1. Ball-Berry model and its revised form can still be used to express the coupled relationship of stomatal conductance and photosynthesis. The simulation precision will be improved if saturation vapor pressure deficit, Ds, at the leaf surface was used in the Ball-Berry model instead of relative humidity.

    LEAF TRANSPIRATION AND STOMATAL STRUCTURE OF YOUNG GRAPE PLANTS GROWN IN A LOW LIGHT ENVIRONMENT
    ZHAN Ji-Cheng, HUANG Wei-Dong, WANG Xiu-Qin, WANG Li-Jun
    Chin J Plan Ecolo. 2005, 29 (1):  26-31.  doi:10.17521/cjpe.2005.0004
    Abstract ( 2434 )   PDF (612KB) ( 1235 )   Save
    Related Articles | Metrics

    Plant adaptation to its growing environment is reflected in physiological responses, such as stomatal conductance, photosynthetic rate, transpiration rates, and water use efficiency. We studied the influence of low light levels on leaf transpiration rate and stomal structure of young `Jingyu' grape plants, Vitis vinefera L. cv. Jingyu, grown for 30 days under different light intensities (65% shading and 85% shading). The transpiration rate, stomatal conductance, and water use efficiency were measured using a portable photosynthesis system, and the stomata were observed using a scanning electron microscope. The results showed that the leaf water potential of young grape plants grown under a low light environment was higher but water use efficiency was lower as compared to the controls. Transpiration rate and stomatal conductance responded slowly to varied light intensities, whereas the young grape plants grown under natural light environment were more sensitive to changing light intensities. For the young grape plants grown under low light environment, the horizontal axes of their stomata were broaden and the difference between “larger” and “smaller” stomata was reduced. The stomata protruded out of the epidermal wall and even distorted the cuticle of the epidermal surface. Our results showed that young grape plants were able to adapt to a low light environment, and their leaf transpiration characteristics were correlated with stomatal structure.

    EFFECTS OF WATER SUPPLY AND SAND BURIAL ON SEED GERMINATION AND SEEDLING EMERGENCE OF FOUR DOMINANT PSAMMOPHYTES IN THE ORDOS PLATEAU
    NIE Chun-Lei, ZHENG Yuan-Run
    Chin J Plan Ecolo. 2005, 29 (1):  32-41.  doi:10.17521/cjpe.2005.0005
    Abstract ( 2376 )   PDF (700KB) ( 798 )   Save
    Related Articles | Metrics

    The Ordos Plateau of North China has experienced serious desertification. Hedysarum leave, Caragana korshinskii, Artemisia sphaerocephala and A. ordosica are four dominant psammophyte species that inhabit the Mu-Us Sandland, Ordos Plateau that are used in aerial seeding, a primary method for vegetation restoration in deserts and sand lands, in the Ordos Plateau, Seedling emergence is closely related to sand burial depth and water content of the soil but survival is low. In this paper, seed germination and seedling emergence characteristics of the four species in response to different levels of water availability and burial depth were studied and compared to determine the optimal time for aerial seeding to enhance seedling emergence and improve vegetation restoration efforts. The experiment was conducted in a non-heated greenhouse at the Ordos Sandland and Grassland Ecological Station of the Chinese Academy of Sciences in the summer of 2003. All seeds used in the experiment were collected from their natural habitat near the ecological station. The seed mass (mean±SE) varied among species: H. leave, (11.70±0.9) mg; C. korshinskii, (34.15±2.2) mg; A. sphaerocephala, (0.67±0.12) mg; A. ordosica, (0.22±0.09) mg. Seed germination, tested under the same environmental conditions, also varied among species: H. leave, (65.6±4.8)%; C. korshinskii, (52±4.7)%; A. sphaerocephala, (94.4±1.6)%; A. ordosica, 95.2%±0.8%. Each species was grown at seven sand burial depths (0, 0.5, 1, 1.5, 2, 3, 5 cm) under three water supply regimes (123, 185, 246 ml). The different water treatments corresponded to mean monthly precipitation levels of 50, 75, and 100 mm during growing season (from June to September). The average monthly precipitation in June in this area was about 50 mm. There were 21 treatments for each species with 5 replicates of each treatment. Each replicate consisted of 25 seeds planted in a plastic pot 5.6 cm in diameter and 11 cm in height with a drainage hole at the bottom of pot. Seedling emergence was checked and recorded everyday and water was added every three days. The experiment was terminated after 30 days when the seedling emergence became almost steady. The number of seedlings that did not emerge was quantified. As the main purpose of this study was on seedling emergence, dormant and decomposed seeds were counted as non-germinated. For each species, sand burial depth, water supply regime, and their interactions all had significant effects on the percentage and the rate of seedling emergence. All seeds lying on the soil surface did not germinate. The optimal burial depth for H. leave, C. korshinskii, A. sphaerocephala and A. ordosica was 0.5, 1, 0.5, and 0.5 cm, respectively. As the sand burial depth increased, the percentage and rate of seedling emergence decreased and the emergence time was delayed, but the percentage of seedlings that did not emerge was not affected. Seeds of A. sphaerocephala and A. ordosica could not emerge from burial depths greater than 1.5 cm, but seeds of H. leave and C. korshinskii were able to emerge from depths of 2-3 cm. This difference may be because of the greater mean seed mass of H. leave and C. korshinskii. The tolerance to sand burial depth was in the following order: H. leave> C. korshinskii > A. ordosica> A. sphaerocephala. The optimal water supply for all four species was 123 ml, which was close to the mean monthly precipitation of June (50 mm), the time when most seedling emergence occurs in the Ordos Plateau. As the amount of water increased, the percentage and rate of seedling emergence decreased and the emergence time delayed, but the percentage of seedlings that did not emerge was not affected. The maximum percentage (mean±SE) of seedling emergence of these four species was H. leave, 56.80%±1.96%, C. korshinskii, 39.20%±5.12%; A. sphaerocephala, 62.4%±4.12%; and A. ordosica, 77.6%±9.85%. Too much water and too deep of burial reduced the percentage of seedlings that emerged. This reflected the adaptation of the plants to the local climate and environment. In the Ordos Plateau, aerial seeding is often conducted during early June. Based on our results, weather conditions are not suitable for seedling establishment during this time because wind speeds are low, and the seeds are not buried by the sand. Our results indicate that this may reduce the percentage of seedlings that emerge as all four species require sand burial. During middle and late May, the winds are stronger and the seeds have a greater chance of being buried at their optimal depth. Even though there is no precipitation or the seeds might be buried too deep, they can survive in the soil and emerge later under more favorable conditions. Therefore, it is suggested that the time of aerial seeding be advanced from early June to mid to late May in order to enhance the emergence of the seedlings.

    A COMPARATIVE STUDY ON HEAT AND DROUGHT TOLERANCE BETWEEN SALIX GORDEJEVII AND SALIX BABYLONICA
    YANG Jia-Ding, ZHAO Ha-Lin, ZHANG Tong-Hui
    Chin J Plan Ecolo. 2005, 29 (1):  42-47.  doi:10.17521/cjpe.2005.0006
    Abstract ( 2097 )   PDF (621KB) ( 894 )   Save
    Related Articles | Metrics
    Salix gordejevii (SG), a useful dune-fixing plant, is a pioneer bush that establishes primarily on the margins of moving sand dunes in Horqin Sand Land and Hunshandak Sand Land, Inner Mongolia, China. In this study, the heat and drought tolerance of SG were examined and compared to S. babylonica (SB). Leaves removed from the two species were subjected to six temperature treatments (25, 30, 35, 40, 45, 50 ℃) for 60 minutes and six drought treatments (0, -0.25, -0.5, -0.75, -1.0, -1.25 MPa) for 24 hours. The relative water content, membrane permeability and maximal quantum efficiency of photosystem II (PSII) were assayed. Leaves of SG maintained more water during both temperature and drought treatments. Temperature treatments below 45 ℃ had no effect on the membrane permeability of either of the two species, but treatments above 45 ℃ induced much higher electrolyte leakage in SG than in SB. Each drought treatment caused an increase in membrane permeability in both SG and SB but was greater in SB in all drought treatments. Temperatures below 35 ℃ did not influence maximal quantum efficiency of PSⅡ (measured as Fv/Fm) in either of the two species, whereas treatments above 40 ℃ caused Fv/Fm to decrease in both species but was significantly lower in SG. Drought treatments resulted in a decline in Fv/Fm in both species but declines were significantly higher in SG when the osmotic potential was lower than -0.75 MPa. These results suggest that SG has a higher capacity for drought tolerance and a lower capacity for heat tolerance compared to SB. The different stress tolerance between SG and SB was due mainly to different sensitivities of electron transport through PSII to heat and drought.
    EFFECT OF WATER CONTROL ON ACTIVITIES OF NITROGEN ASSIMILATION ENZYMES AND GRAIN QUALITY IN WINTER WHEAT
    MA Xin-Ming, LI Lin, ZHAO Peng, XIONG Shu-Ping, GUO Fei
    Chin J Plan Ecolo. 2005, 29 (1):  48-53.  doi:10.17521/cjpe.2005.0007
    Abstract ( 2298 )   PDF (559KB) ( 890 )   Save
    Related Articles | Metrics

    In order to understand the effects of soil water availability on nitrogen assimilation enzyme activity and grain quality in winter wheat cultivar, pot experiments were carried out at the Henan Agricultural University Research Station during 2001-2003. Soil containing 9.8 g•kg-1 organic matter, 0.986 g•kg-1 total N, 25.43 mg•kg-1 olsen-P and 259 mg•kg-1 NH4OAc-K were used for the experiments. 18 kg of sieved soil was placed in each 30 cm × 40 cm pot. ‘Yumai 34’, a strong gluten cultivar, was used in the experiments. Three water treatments were used: soil water content of 60% field capacity (FC), 40% FC and 80% FC. All pots were under a rain-shelter, and water levels were controlled from elongation stage to harvest. Water content was measured by weight every two days. Before sowing, 3.5 g N, 3.3 g K2O and 2.9 g P2O5 were applied to each pot and a further 1.6 g N was applied to each pot during the elongation stage. Seven plants from each pot were selected when plants had five leaves. The experiment was arranged in a completely randomized design with ten replications per treatment, and all pots were managed in the same way. The results indicated that nitrate reductase (NR) activity in the flag leaf declined after anthesis in a decreasing order of 60%FC >40%FC >80%FC. Glutamine synthetase (GS) activity in both the flag leaf and grain all declined from the beginning of anthesis to 15 days after anthesis and then increased with the order among the three water treatments as follows: 80%FC>60%FC>40%FC. A similar pattern was found for glutamate synthase (GOGAT) as for GS. The highest grain yield and the best nutritional quality occurred in the 60%FC treatment whereas the 80%FC treatment had the lowest quality and 40%FC had the lowest grain yield. Grain protein content was positively correlated to NR and GS activity in flag leaves and GOGAT activity in the grain, and was negatively correlated to GOGAT activity in the flag leaves for all water treatments. In the 40%FC and 80%FC treatments, there was a significant correlation between grain protein content and GS activity in flag leaves. In the 60%FC treatment, there were significant correlations between grain protein content and NR activity in flag leaves and GS activity in grain, and grain protein was closely correlated to GS activity in flag leaves.

    THE EFFECT OF PHOSPHORUS DEFICIENCY STRESS ON ACTIVITIES OF ACID PHOSPHATASE IN DIFFERENT CLONES OF CHINESE FIR
    LIANG Xia, LIU Ai-Qin, MA Xiang-Qing, FENG Li-Zhen, CHEN You-Li
    Chin J Plan Ecolo. 2005, 29 (1):  54-59.  doi:10.17521/cjpe.2005.0008
    Abstract ( 2160 )   PDF (496KB) ( 678 )   Save
    Related Articles | Metrics

    Phosphorus (P) deficiency is one of the main factors that influences plant productivity in agricultural and forestry systems. Fertilization and soil improvement are the primary measures used to meet the P demands of crops in traditional agriculture and trees in forestry management. Recently, plants with high phosphorus use efficiency have been discovered and used to replace traditional measures for improving phosphorus use efficiency of corps. Chinese fir (Cunninghamia lanceolata), a fast-growing, evergreen conifer tree with high yield and excellent wood quality, is the most important tree species of timber plantations in subtropical China. In order to understand the P demands of Chinese fir clones, levels of acid phosphatase (APA) activity were studied in the leaves and rhizosphere soil of different potted Chinese fir clones under different levels of phosphorus additions. The potted Chinese fir clones were subjected to four P supply levels: normal P supply (16 mg•kg-1), slight P deficiency (8 mg•kg-1), medium phosphorus deficiency (4 mg•kg-1) and heavy phosphorus deficiency (0 mg•kg-1). The results showed that the activities of APA in the leaves and rhizosphere soil under the P-deficiency treatment were higher than those under normal P treatment, and there were significant differences in the levels of APA activity among the 8 Chinese fir clones. The activities of APA in the leaves and rhizosphere soil of clones 8, 24 and 37 under the P-deficiency treatment were much higher than those under normal P treatment. Compared with the APA levels in leaves, the activities of APA in the rhizosphere soil of clones 5 and 9 under the P-deficiency treatment had higher amplitudes than those under normal P treatment. The clones 3, 23 and 34 were insensitive to P stress, and there were no significant treatment effects on APA levels for these clones. Under the P-deficiency treatment, the activities of APA in the leaves and rhizosphere soil of different Chinese fir clones increased in response to the P stressed environment, and there were significant differences in the abilities of the different Chinese fir clones to adapt to low P levels. Therefore, more research is needed in order to determine whether APA level is an important index for evaluating and selecting Chinese fir clones with high phosphorus use efficiency.

    MODELING CANOPY RAINFALL INTERCEPTION IN THE UPPER WATERSHED OF THE MINJIANG RIVER
    LI Chong-Wei, LIU Shi-Rong, SUN Peng-Sen, ZHANG Yuan-Dong, GE Jian-Ping
    Chin J Plan Ecolo. 2005, 29 (1):  60-67.  doi:10.17521/cjpe.2005.0009
    Abstract ( 2266 )   PDF (846KB) ( 1002 )   Save
    Related Articles | Metrics

    The headwaters of the Minjiang River are on the eastern edge of the Tibetan plateau. Canopy rainfall interception plays an important role in the water balance at the regional-scale. Many studies on canopy rainfall interception have been carried out at the stand level but less effort has been devoted towards understanding canopy interception at large scale, neither in the Minjiang River basin nor other areas. In this study, modeling canopy rainfall interception in subalpine forests and meadows in the upper reaches of the Minjiang River was carried out by using field surveys, MODIS data, and RS,GPS and GIS technologies. LAI (leaf area index), vegetation cover and canopy capacity per unit leaf area were the main parameters used in the model. LAI was derived from the vegetation index and measured using a LAI-2000 in the forests and LAI-3000 in the sub-alpine meadows. The LAI of coniferous stands were multiplied by a correction factor because of the clumped arrangement of needles in the crown. Normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) were composed by red, near-infrared and blue reflectances from the 500 m 32-day composites available from the MODIS level 3 surface reflectance (MOD09A1). The results indicated that LAI was non-linearly correlated to NDVI and EVI. EVI was preferable to NDVI as NDVI saturates in well-vegetated areas and the degree of correlation between LAI and EVI is higher than that between LAI and NDVI. The results showed that the LAI of vegetation in the upper reaches of the Minjiang River were in the following categories: 28.57% between 0 and 2, 63.06% between 2 and 4.5, and 8.37% above 4.5. LAI was estimated using EVI, and the results showed that LAI could better reflect the spatial distribution of the vegetation. LAI in the upper watershed was lower than down river due to a large number of trees in the down river. Vegetation cover was derived from NDVI. The spatial distribution of canopy capacity per unit leaf area was modeled on the basis of a vegetation-classification map (1∶1000000). Canopy rainfall interception in the well-vegetated areas was higher than that in other areas. The model was validated using field measurements made in Wolong and Miyaluo and some additional sites in the upper watershed of the Minjang River. Empirical expressions to describe evaporation from the wet canopy were derived from additional sites and evaporation from the wet canopy was closely correlated to rainfall. Based on the empirical expressions, simulation results showed that there was a 15.4 percent error in Wolong and a 19.4 percent error in Miyaluo.

    VEGETATION COVER CHANGES OVER TIME AND ITS EFFECTS ON RESISTANCE TO WIND EROSION
    ZHAO Cai-Xia, ZHENG Da-Wei, HE Wen-Qing
    Chin J Plan Ecolo. 2005, 29 (1):  68-73.  doi:10.17521/cjpe.2005.0010
    Abstract ( 1987 )   PDF (549KB) ( 979 )   Save
    Related Articles | Metrics
    Vegetation cover characteristics have both spatial and temporal components. In the past, researchers have paid particular attention to spatial characteristics of vegetation cover in protecting soil from wind erosion, but temporal changes in vegetation have been ignored. In this study, we examined both the spatial and temporal characteristics of vegetation cover. The monthly changes of different plant cover types were studied from June, 2002 to June, 2003 in Wuchuan County of the Inner Mongolia of China using sample thread and random step distance measures combined with photography to compare and correct possible errors. Quantitative relationships for vegetation cover types, the amount of wind erosion, and a wind erosion climatic factor were determined by field investigation and theoretical analysis. Using a wind erosion formula for different plant types, the total wind erosion was calculated. The results indicated that the effectiveness of different plant types in increasing soil resistance to wind erosion were: perennial shrubs > perennial pasture > forest > annual pasture > forage crops. The dynamic annual change in total vegetation cover was inversely related to the amount of soil wind erosion. The results indicate that low vegetation cover is one of the primary causes of serious soil wind erosion in this region. Planting annual pasture and forage crops instead of perennial pasture will result in a loss of protection from wind erosion and require more land reclamation efforts in the future. Our results also suggest that the current reclamation practice of converting wind eroded landscapes to woodlands is not ecologically sound and planting shrubs or perennial pastures offers greater protection to wind erosion, especially in the more arid and semi arid regions.
    APPARENT REFLECTANCE AND ITS APPLICATIONS IN VEGETATION REMOTE SENSING
    CHI Hong-Kang, ZHOU Guang-Sheng, XU Zhen-Zhu, XIAO Chun-Wang, YUAN Wen-Ping
    Chin J Plan Ecolo. 2005, 29 (1):  74-80.  doi:10.17521/cjpe.2005.0011
    Abstract ( 2635 )   PDF (564KB) ( 1241 )   Save
    Related Articles | Metrics

    Remote sensing of vegetation is developing into a highly quantitative science. However, some concepts and terms related to quantitative remote sensing are confusing for novices of this field. The goal of this paper is to clarify fuzzy concepts and promiscuous terms and to introduce methods about data processing of remote sensing information. First, concepts about radiometric correction, radiometric calibration, atmospheric correction and the differences and relationships between them were discussed. In optical remote sensing, radiometric correction includes radiometric calibration and atmospheric correction. The aim of radiometric calibration is to eliminate the errors in the sensors of the satellite, and the aim of atmospheric correction is to eliminate the effects of atmospheric interference on satellite data. In general, the first step is radiometric calibration and then atmospheric correction. Apparent reflectance is one of the results of radiometric calibration and is a very important physical variable in processing remote sensing data. The definition of apparent reflectance can be indicated with a formula. The calculation of apparent reflectance was explained step-by-step using examples with Landsat-5 and Landsat-7 satellite images. A case study was presented in order to show the importance of apparent reflectance in the calculation of NDVI (Normalized difference vegetation index). Finally, its applications in vegetation remote sensing were listed and discussed.

    DEFINING PLANT FUNCTIONAL TYPES IN CHINA FOR GLOBAL CHANGE STUDIES
    WENG En-Sheng, ZHOU Guang-Sheng
    Chin J Plan Ecolo. 2005, 29 (1):  81-97.  doi:10.17521/cjpe.2005.0012
    Abstract ( 2583 )   PDF (1226KB) ( 866 )   Save
    Related Articles | Metrics
    Plant functional types (PFTs) bridge the gap between plant physiology and ecosystem processes, providing a powerful tool for studies on global change, vegetation dynamics and vegetation-atmosphere processes. In this paper, a two-stepped hierarchical PFT classification system was proposed based on six key plant attributes. Three of six key attributes were related to plant canopy structure, including permanence of aboveground live biomass (woody vs. herbaceous), leaf longevity (evergreen vs. deciduous) and leaf structure (broad-leaved vs. needle-leaved). The other three attributes were related to plant physiological characteristics, including photosynthetic pathway (i.e. C3 vs. C4 grasses), drought resistance and temperature tolerance (e.g. warm evergreen, cool conifer). In the first step of the analysis, five basic plant types were derived based on canopy attributes. In the second step, these five basic plant types were sub-divided into 29 types according to their photosynthetic pathways, drought resistance and temperature tolerance. We tested this PFT classification system by simulating the distribution of vegetation in China. A sub-set of 18 plant types was selected from the 29 PFTs that were characteristic of the vegetation in China, especially in relation to the water balance and energy budget as affected by the monsoon climate and the Tibetan Plateau. This set of PFTs contained 7 trees, 6 shrubs and 5 grasses. Two types of bare ground were added for the simulation. Six climatic variables were selected to be used as the distributional constraint of each PFT, which included absolute minimum temperature (Tmin), mean temperature of the warmest month (Tw), growing-day degrees (GDDs), annual range of monthly mean temperature (DTY), moisture index (annual precipitation-annual potential evapo-transpiration, MI), annual precipitation (P). The values of these climatic variables were determined based on the geographical distribution of each plant functional type. Using BIOME1, the distribution of the PFTs across China was then modeled. The simulated map of China's vegetation was in close agreement with the actual vegetation map, indicating that this set of PFTs was capable of simulating the geographical distribution of vegetation in China. This study provides a basis for future studies on climate-vegetation interactions and for developing regional dynamic vegetation models and regional climate models for China.
    SPECIES-CLIMATE RELATIONSHIPS OF 10 DESERT PLANT SPECIES AND THEIR ESTIMATED POTENTIAL DISTRIBUTION RANGE IN THE ARID LANDS OF NORTHWESTERN CHINA
    JIANG Xia, NI Jian
    Chin J Plan Ecolo. 2005, 29 (1):  98-107.  doi:10.17521/cjpe.2005.0013
    Abstract ( 2670 )   PDF (926KB) ( 897 )   Save
    Related Articles | Metrics
    We choose the arid land of northwestern China as our study area because of its extensive area, specific geographical location, dry climate, varied topography, vulnerable ecosystems and long-term human disturbance, as well as the existence of current conflicts between economic development and environmental protection. Based on the literature, we choose ten desert species with clear and relatively accurate geographical distribution ranges to model their distributions: Anabasis brevifolia, Atraphaxis frutescens, Calligonum mongolicum, Ephedra przewalskii, Gymnocarpos przewalskii, Haloxylon ammodendron, Haloxylon persicum, Kalidium cuspidatum, Salsola laricifolia, and Sympegma regelii. The quantitative relationship between each species distribution range and climatic factors was analyzed. The central and maximum potential distribution ranges of the 10 species were estimated and compared to their actual geographical distributions. Results showed that the mean value, standard deviation, maximum and minimum Holdridge's annual biotemperature, annual precipitation and potential evapotranspiration ratio of the 10 desert species reflected typical characteristics of desert climates and were in good agreement. The calculated central distribution ranges were in good agreement with a species'actual distribution range, but there were differences among a species's maximum potential distribution and actual distribution due to three major factors: 1) The uncertainties associated with a species current distribution and lack of accurate climate data restricted the accuracy of the species-climate relationships and human impacts have altered the actual distributions of these desert species; 2) The maximum potential distribution area was estimated using the maximum and minimum climate values of species, which is less accurate than the potential central distribution range estimated by the mean climate and standard deviation; and, 3) The estimated potential range was calculated based on species-climate relationships only. Other environmental factors, such as soil, geology and topography, which also influence species distributions, were not considered.
    SEED RAIN AND SOIL SEED BANKS OF PICEA ASPERATA IN SUBALPINE SPRUCE FORESTS, WESTERN SICHUAN, CHINA
    YIN Hua-Jun, LIU Qing
    Chin J Plan Ecolo. 2005, 29 (1):  108-115.  doi:10.17521/cjpe.2005.0014
    Abstract ( 2473 )   PDF (722KB) ( 1026 )   Save
    Related Articles | Metrics
    Subalpine coniferous forests dominate most parts of the forested areas in western Sichuan, including the upper reaches of the Yangtze River. Since the 1940s, natural coniferous forests have been cleared, and Picea asperata is an important species used for reforestation. Up to now, a total of ca. 13 000 hm2 of plantations have been planted with this species in this region. Hence, studies on seed source, dynamics of the soil seed bank and seedling survival of Picea asperata populations are of significance for the management and conservation of coniferous forest ecosystem. The seed rain and soil seed bank of spruce plantations that were 20, 30, and 60 years old and a 150 years old natural spruce forest in the Miyaluo subalpine coniferous forest in western Sichuan, China were studied using seed traps, sieving and counting seeds in the soil, conducting seed germination experiments, and measuring seedling density in the three plantations and the forest. The area is located on a high mountain valley in the transitional zone between the Qinghai-Tibet plateau and the Sichuan basin. The results showed that seed rain lasted from early October to the end of January. The intensity of seed rain of the different aged plantations increased in the following order; 20 years old plantation ((66.73±5.71) seeds•m-2) < natural spruce forest ((579.99±28.93) seeds•m-2) < 30 years old plantation ((973.45±63.12) seeds•m-2) < 60 years old plantation ((1 088.16±52.34) seeds•m-2). The timing of the seed rain and the peak fall differed among sites and was correlated with the age of the plantation age. The soil seed bank of the 30 years old, and 60 years old plantations and natural spruce forest at two sampling periods was (507.2±40.32) and (267.6±25.14), (1 065.6±88.06) and (872.8±77.12), (472.8±20.82) and (185.5±22.48) seeds•m-2, respectively. The vertical distribution of seeds in the soil bank showed that about 66% of the total seeds were distributed in the litter layer, 24% in the 0-2 cm layer and 10% at 2-5 cm depth. By August 21, 2003, all of the spruce seeds had lost viability in the soil, and the number and proportion of decayed seeds and vacant seeds greatly increased. Seed decay from soil pathogens and seed-predation by animals were the most important factors affecting soil seed bank dynamics. The proportion of seeds removed from the soil seed bank via germination was quite low. The spruce soil seed bank belongs to the type Ⅱ as defined by Thompson and Grime, namely, the soil seed bank only existed in winter and germinated in spring. There were significant differences in the seedling density in the 30 years old plantation ((28.57±6.39) seedlings•m-2) 60 years old plantation ((39.42±16.21) seedlings•m-2) and natural spruce forest ((10.75±2.37) seedlings•m-2). Seedling mortality was high due to poor habitat quality. The recruitment potential increased with plantation stand age, but the recruitment potential of spruce plantations were higher than that of natural spruce forests when seed rain, soil seed bank and seedling number were considered together. In Miyaluo spruce woodlands in western Sichuan, China, despite high seed production, the number of spruce seedlings recruited from the seed to seedling stage was relatively few.
    EFFECTS OF PARENT RAMET SIZE ON CLONAL GROWTH IN NEOSINOCALAMUS AFFINIS
    WANG Qiong, SU Zhi-Xian, LEI Ning-Fei, ZHANG Yun-Chun
    Chin J Plan Ecolo. 2005, 29 (1):  116-121.  doi:10.17521/cjpe.2005.0015
    Abstract ( 2157 )   PDF (582KB) ( 1029 )   Save
    Related Articles | Metrics

    Clonal growth plays an important role in the population dynamics of Neosinocalamus affinis. In order to better understand the ecological adaptability of Neosinocalamus affinis at the individual level, we investigated the relationships between ramet size, rhizome size and shoot production. We measured the size of the parent ramet in terms of both basal diameter and biomass,the effects of parent ramet size on new shoot production, and new shoot and rhizome size of Neosinocalamus affinis. The experiment ran from June to November, 2000. We measured parent ramet size, new shoot size, new shoot number, rhizome size, mortality of new shoots, and the number of new shoots emerging and surviving at 9 plots in Xishan, Nanchong, Sichuan province. The data were analyzed by one-way ANOVA, independent-sample t-test and linear regression. The following results were obtained: 1) The basal diameter of the primary and secondary parent ramet, but and average biomass of two-year-old and three-year-old parent ramets were positively correlated to basal diameter of surviving new shoots. But the effects of the primary parent ramet on surviving new shoots were more than the secondary parent ramet on, indicating that the basal diameter of surviving new shoots was size-dependent. 2) There were no effects of parent ramet size on the number of surviving, dead and emerging new shoots and the clonal population dynamics were probably affected by the number of parent ramets. 3) The basal diameter of the parent ramet producing new shoots was larger than that of parent ramet not producing new shoots, suggesting that new shoot production was determined by a critical threshold size. Contrary to earlier conclusions, there was no significant differences in the basal diameter of the parent ramet producing one new shoot and the parent ramet producing more than two new shoots. The best basal diameter of the parent ramet was 6.1 cm. 4) The length and diameter of rhizomes were positively correlated to basal diameter of the primary parent ramet and the average biomass of two year-old and three year-old parent ramets. Primary parent ramets affected shoot size through rhizome size because the rhizome stored critical resources. Our results showed that clonal growth in Neosinocalamus affinis was related to parent ramet size at the individual level indicating that shoot survival was most likely enhanced due to the higher availability of resources for investment into new shoots.

    GEOGRAPHIC DISTRIBUTION AND GENETIC DIFFERENTIATION OF ARTEMISIA SPHAEROCEPHALA
    WANG Tie-Juan, YANG Chi, MA Jing, QIAO Shu-Jun, YIN Jun
    Chin J Plan Ecolo. 2005, 29 (1):  122-127.  doi:10.17521/cjpe.2005.0016
    Abstract ( 1947 )   PDF (563KB) ( 986 )   Save
    Related Articles | Metrics

    Artemisia sphaerocephala is an extreme xerophytic subshrub and sand dominant species of northwest China. It has important sand binding properties and grows on drifting dunes, semi-drifting dunes and sometimes on fixed dunes in the steppe zone and desert zone. The current distribution range of A. sphaerocephala was investigated. The results show that it is distributed in central and western Inner Mongolia, northwestern Shanxi, northern Shaanxi, northern Ningxia, northern Qinghai, eastern Xinjiang, and Gansu in China and in southern Mongolia and is a Gobi- Mongolia distribution species. A new natural distribution site of A. sphaerocephala was discovered on the Otindag Sandy Land in central Inner Mongolia. The areal map of A. sphaerocephala has been drawn according to the specimens collected in different provinces and based on the literatures. Five populations of A. sphaerocephala were collected from main areas of their distribution and one population was collected from the new distribution site. The six populations were analyzed using random amplified polymorphic DNA (RAPD) markers. A total of 255 loci were obtained from 15 random primers, among which 232 loci were polymorphic. At the species level, the percentage of polymorphic loci was 91%. It showed that genetic polymorphism of A. sphaerocephala was high. The sequence of the percentage of polymorphic loci of the six populations was: Shapotou (SHPT) 83.4% >Yulin (YL) 75.3% >Azuoqi (AZQ) 74.1% >Wuhai fixed dune (WH2) 72.4%>Xilinhot (XLHT) 68.8%>Wuhai drifting dune (WH1) 66.7%. This sequence was slightly different from Shannon's diversity index. The latter was: SHPT>YL>AZQ>XLHT>WUH2>WUH1. The sequence of Nei's gene diversity was the same as the sequence for Shannon's diversity index. The genetic differentiation among populations (Gst) was 0.234 8 indicating that there was genetic differentiation among populations, but 76.52% of this variation existed within the populations. According to the results of cluster analysis based on Nei's genetic distances, correlations existed between genetic distances and geographical distances. However, for the Xilinhot population of Otindag Sandy Land and Yulin population of Mu Us Sandy Land, the geographical distances were far and genetic distances were close, indicating that there was a close connection between the populations on these two sandy lands of grassland regions. It is highly likely that A. sphaerocephala of Otindag Sandy Land came from Mu Us Sandy Land.

    LEAF EXPANSION OF THE DOMINANT WOODY SPECIES OF THREE DECIDUOUS OAK FORESTS IN NANJING, EAST CHINA
    ZHU Xu-Bin, LIU Ya-Mei, SUN Shu-Cun
    Chin J Plan Ecolo. 2005, 29 (1):  128-136.  doi:10.17521/cjpe.2005.0017
    Abstract ( 2099 )   PDF (735KB) ( 994 )   Save
    Related Articles | Metrics
    Leaf expansion in plants is a process determined by both genetic and environmental factors and is considered to reflect life history strategies at the population level and to be a mechanism for maintaining species diversity at the community level. The evolution of leaf phenology has been suggested to maximize plant carbon gain and minimize leaf losses due to the herbivory. In temperate broad-leaved forests, because low light levels often limit the photosynthetic capacity of understory woody species, understory species are expected to leaf out earlier in the spring than canopy species so as to obtain long leaf life span and positive carbon balance. Leaf traits, including leaf length, area, and leaf dry mass per unit area (LMA), together with leaf phenology, including timing of leaf emergence, duration of emergence, expansion, and leaf expansion rate, were investigated from the beginning of March to early June of 2001 and 2002, for the dominant shrub and tree species in three deciduous broad-leaved oak forests in the Nanjing area, East China. The leaf traits and leaf phenological parameters were compared among canopy and understory species, and the relationship between leaf traits and leaf phenology was examined by correlation and regression analyses. The canopy species were characterized by larger leaf areas and higher LMA than the understory species. The understory species leafed out earlier, but not significantly earlier, than the canopy species. This is in contrast to the hypothesis, possibly because individuals experienced different environmental conditions due to habitat heterogeneity that affected leaf phenology. Leaf expansion rate of canopy species was greater than that of shrub species: the larger the final leaf area of the species, the greater the expansion rate. This is assumed to be a strategy for large-leaved canopy species to decrease defoliator damage during leaf expansion. Small-leaved species were found to leaf out earlier than species with large leaves. This suggests a possible approach for small-leaved species to avoid leaf loss since herbivory pressure is often low in early spring. Inter-specific correlation analysis indicated that species with high LMA leafed out earlier than their counterparts. This is consistent with results of previous studies on leaf life span, including mathematic models and empirical investigations, in which species with high LMA were found to need more time to gain positive carbon balance. In general, dynamics of leaf emergence and expansion of the woody species in the study forests indicate that the timing of leaf emergence is of significance for a species' carbon gain, survival and reproduction.
    COMPARATIVE STUDY OF TWO KINDS OF AMOMUM VILLOSUM CULTIVATION MODELS IN XISHUANGBANNA
    FENG Zhi-Li, GAN Jian-Min, ZHENG Zheng, FENG Yu-Long
    Chin J Plan Ecolo. 2005, 29 (1):  137-143.  doi:10.17521/cjpe.2005.0018
    Abstract ( 2243 )   PDF (669KB) ( 1008 )   Save
    Related Articles | Metrics

    Amomum villosum is a perennial herb that occurs in the understory of tropical and subtropical forests and is an important medicinal plant. A. villosum, native to Guangdong Province, was introduced intentionally to Xishuangbanna, Yunnan in 1963 and was planted under tropical rainforests. Farmers often thin out some of the canopy trees (5%-85%) when they grow this plant for commercial purposes in these primary forests, resulting in a loss of biodiversity in these forests. A. villosum fruit yield is low and varies greatly among fields and years due to the crude cultivation method. The area of primary rainforest is much smaller than secondary forests in Xishuangbanna. The influence of A. villosum cultivation on rainforest biodiversity, biomass, and net productivity was significant, but the influence on secondary forests was negligible. To improve A. villosum yield and to protect rainforest biodiversity, we explored the possibility of cultivating A. villosum in secondary forests. Plant density, biomass, biomass allocation, and fruit yield were measured in A. villosum cultivated in tropical wet seasonal rainforests and secondary forests in Xishuangbanna. The density and biomass of vigorous plants were 72.60% and 85.29% of the total plants in the secondary forest and 71.27% and 86.69% in the rainforest and was significantly higher than those of other plant types. The density of shoots, seedlings, and senescent plants were not significantly different within the same forest types, but the biomass of senescent plants was significantly higher than that of shoots and seedlings. The sum of shoots and seedlings in secondary forest and rainforest were 1.45 and 2.18 times of senescent plants, respectively, indicating that A. villosum populations could be maintained. In the rainforest, many A. villosum seedlings were old and most of them grew poorly and could not develop into normal, healthy and vigorous plants. It is worthwhile to note that the A. villosum yield was very low, stem biomass ratio was very high (above 0.58), and fruit biomass ratio was extremely low (about 0.01). This suggests that increasing the yield potential of A. villosum could be achieved by improving biomass partitioning between the fruit and stem. In one of the experimental plots in the secondary forest, soil water conditions were improved by a rivulet, and fruit yield production was 211.149 0 kg•hm-2, much higher than that of other fields. Apparently, A. villosum cannot tolerate dry conditions and moderate dry periods might influence A. villosum yield. These yields were related to its low root biomass ratio and shallow root system. Leaf area index, biomass of both vigorous plants and other plants were significantly and positively correlated with fruit yield in A. villosum. Fruit yield and leaf area index were 105.034 5 kg•hm-2 and 2.908 2 in the secondary forest, and 60.931 9 kg•hm-2 and 2.560 0 in the rainforest, respectively. The density and biomass of the same plant types were not significantly different between the secondary forest and the rainforest. These results suggest that A. villosum can be cultivated in secondary forests.

    A GIS, LANDSCAPE PATTERN AND NETWORK ANALYSIS BASED PLANNING OF ECOLOGICAL NETWORKS FOR XIAMEN ISLAND
    WANG Hai-Zhen, ZHANG Li-Quan
    Chin J Plan Ecolo. 2005, 29 (1):  144-152.  doi:10.17521/cjpe.2005.0019
    Abstract ( 2252 )   PDF (997KB) ( 1444 )   Save
    Related Articles | Metrics
    Urbanization is arguably the most dramatic form of land transformation with profound impacts on the natural environment, biological diversity and human life. Human activities have inevitably altered the structure, function, and dynamics of ecological systems, such as fragmentation of natural elements in the urban landscape. Therefore, it has become increasingly important for large-scale ecological research and applications (e.g., urban landscape planning, land use planning, and biodiversity conservation) to consider the ecological consequences of these dramatic land transformations. It is a major task for urban landscape planners to construct effective and harmonious urban greenbelt networks and maintain a sustainable urban development environment. Based on a land use map created from a Landsat-TM satellite image from the year 2000, a map of a greenbelt system from 2002 and a map of a planned greenbelt system, we used landscape spatial pattern analysis and a series of landscape pattern metrics on a GIS platform to assess the present situation and the planned greenbelt system for Xiamen Island. Based on these analyses, a number of new planning scenarios were designed by using network analysis methods for optimizing the ecological network of Xiamen Island. Some indices that reflected corridor characteristics, such as corridor length and corridor density, were also calculated for every planning scenario. Using network indices such as α、β、γ indices, cost ratio and corridor metrics, an optimal planning scenario E was selected among those planning scenarios of ecological networks. The optimal planning scenario E was then overlaid on the existing plans for a greenbelt system on a GIS platform. A series of landscape metrics were then calculated to assess the improvement of the optimal planning scenario E on the ecological network of the existing greenbelt system plans for Xiamen Island. Our results showed that the greenbelt system plan for Xiamen Island was an improvement as indicated by a decrease in patch density and increase in edge density, mean patch fractal dimension on the patch level, landscape diversity, landscape evenness, and landscape connectivity. Compared to the existing greenbelt system plan, the optimal planning scenario E would improve the network connectivity and network circuitry considerably. The optimal planning scenario E greenbelt system could improve the degree of landscape fragmentation, increase the shape complexity of greenbelt patches and increase the landscape connectivity greatly. Our results indicated that the methods used were able to integrate landscape pattern metrics with network analyses and quantitatively assess the present situation and the rationality of planning for urban greenbelt systems. Also we demonstrated that these methods could be used to optimize planning scenarios for urban ecological networks to make them more aligned with the principles of conformity, harmony, circulation, safety, diversity and sustainability.
    PHOSPHORUS CYCLING IN TERRESTRIAL ECOSYSTEMS AND ITS CONTROLLING FACTORS
    ZHAO Qiong, ZENG De-Hui
    Chin J Plan Ecolo. 2005, 29 (1):  153-163.  doi:10.17521/cjpe.2005.0020
    Abstract ( 2093 )   PDF (882KB) ( 1351 )   Save
    Related Articles | Metrics
    Phosphorus (P) is a key element of all life and the limiting nutrient in many ecosystems of the world. P biogeochemistry partly controls ecosystem structure and function. Over the past couple of decades, the importance of P biogeochemistry in controlling terrestrial ecosystem processes has received increasing attention. Advances in P cycling in terrestrial ecosystems were reviewed in this paper. Characteristics of P cycling in ecosystem were attributed to factors such as the source of P, the chemical form, traits in soils and the complexity of its controlling factors. P in terrestrial ecosystems is derived mainly from weathering of apatite, and biological and chemical processes, such as microbial absorption, precipitation and adsorption by Fe and Al oxides and CaCO3, easily immobilize P in soil. Transformations of P between different chemical forms in the ecosystem, especially in the soil, and its controlling factors were discussed in detail. P cycling in terrestrial ecosystems is mainly intra-ecosystem cycling which is controlled mainly by the genotype of plant and soil properties, especially pH and ion concentration. The relative importance of different controlling factors differs among ecosystems and across temporal and spatial scales. Also, methods for studying P cycling in terrestrial ecosystems were reviewed. Pot experiments, fertilization trials and sequential extraction procedures were commonly used to test for the bioavailability of different forms of soil P; however, in situ field experiments that used resin bags, litter bags, new isotope tracer methods using 32P and 33P, and NMR spectroscopy to study P dynamics and the chemical structure of soil P were more useful for understanding P cycling and plant availability. Additionally, the significance of P cycling in arid regions was analyzed. P cycling in arid regions, where vegetation is sparse and soil is infertile, are very different from humid regions, and ecosystems there are more easily limited by P. Finally, the trends and hotspots of P cycling in terrestrial ecosystems are summarized for different temporal and spatial scales, different study areas and contents.
    EXPERIMENTAL STUDIES ON NATURAL REGENERATION AND ARTIFICIAL CULTURES OF MOSS CRUSTS ON FIXED DUNES IN THE TENGGER DESERT
    TIAN Gui-Quan, BAI Xue-Liang, XU Jie, WANG Xian-Dao
    Chin J Plan Ecolo. 2005, 29 (1):  164-169.  doi:10.17521/cjpe.2005.0021
    Abstract ( 2239 )   PDF (544KB) ( 1299 )   Save
    Related Articles | Metrics

    Soil microbiotic crusts cover extensive portions of the arid and semiarid regions of the world. Moss is one of the major components of the crusts. The reproduction and establishment of the mosses are crucial to the formation of moss crusts. Although many laboratory experiments have indicated that mosses can reproduce through spores, gemmae and fragmentation, the process of the dispersal and reproduction in natural conditions is not well understood in moss crusts. Bryum argenteum is the dominant species of moss crusts in the Shapotou region (37°27′ N, 104°57′ E) of the Tengger Desert. To examine characteristics of natural reproduction and establishment, 10 quadrats (10 cm×10 cm) were established on different positions of fixed dunes and the moss crust removed. These 10 quadrats were observed for three consecutive years and the species establishment and their coverage measured. In the third year, 2 quadrats (1 m×1 m) were established in a crust-absent area, and two different experiments were conducted, one on broadcast planting and the other on offshoots. The reproductive process was observed under the microscope, and the morphological indicators of new individuals measured. The results were compared with results from indoor experiments using the same methods. Our results showed that 70% of the quadrats (i.e., 7 of the 10 quadrats) recovered within 3-4 years. The quick recovery was most likely due to dispersal and reproduction of leaf and stem fragments of B. argenteum. Results from the artificial reproduction experiment showed that new plants occupied the uncovered space of the quadrats within one month. There were two main forms of reproduction: 1) stems continually branched and produced young plants; 2) young plants and the fragments of the stems and leaves repeatedly and extensively reproduced protonema which developed into a large number of new plants. The reproductive characteristics were identical between the two experiments although the protonema in the field was more robust and had more branches than the ones indoors. This research reveals the reproductive mechanism of the establishment of mosses in natural conditions in this region, and provides experimental evidence for the formation of moss crusts on fixed dunes.

    RECLASSIFICTION OF MONSOON TROPICAL FORESTS IN SOUTHERN YUNNAN, SW CHINA
    ZHU Hua
    Chin J Plan Ecolo. 2005, 29 (1):  170-174.  doi:10.17521/cjpe.2005.0022
    Abstract ( 1863 )   PDF (427KB) ( 978 )   Save
    Related Articles | Metrics
    Southern Yunnan is located biogeographically at a transitional zone between tropical Southeast (SE) Asia and subtropical East Asia, and though far north of the Equator and at a relatively high altitude, has a rich and diverse tropical flora. The terminology used to describe the different tropical forest types in the region are confusing because the classification schemes used come from different disciplines. Using the classification scheme of tropical plant formations by Schimper (1903) and Richards (1996), which is based primarily on climatic factors, we discuss a new classification scheme of the tropical forests in southern Yunnan. Horizontal vegetation types in southern Yunnan are represented by tropical seasonal rain forests and monsoon forests. The tropical seasonal rain forest is a tropical Asian rain forest at altitudinal and latitudinal limits, while the monsoon forest is considered to be a transitional vegetation type between tropical rain forests and savannas based on their physiognomy and distribution. The monsoon forest is largely leafless during the dry season. The forests that occur on the middle and upper limestone slopes in southern Yunnan, which was called a monsoon forest in some Chinese botanical references, is reclassified as a seasonal moist forest. These forests are not equivalent to classical monsoon forests in their physiognomy, despite of the fact that it is affected by seasonal dryness and contains a high percentage of deciduous trees. The floristic composition also is different from monsoon evergreen broad-leaved forests in the region. This limestone forest, which abuts the seasonal rain forest on lower slopes and in the limestone valleys, is an altitudinal vegetation type on limestone bedrock in southern Yunnan.

  • WeChat Service: zwstxbfw

  • WeChat Public:zwstxb