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Table of Content
Volume 29 Issue 6
30 September 2005

Research Articles
VARIATIONS OF FINE ROOT DIAMETER WITH ROOT ORDER IN MANCHURIAN ASH AND DAHURIAN LARCH PLANTATIONS
WANG Xiang-Rong, WANG Zheng-Quan, HAN You-Zhi, GU Jia-Cun, GUO Da-Li, MEI Li
Chin J Plan Ecolo. 2005, 29 (6):  871-877.  doi:10.17521/cjpe.2005.0123
Abstract ( 2548 )   PDF (543KB) ( 893 )
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ESTIMATION OF ABOVE_ AND BELOW_GROUND BIOMASS OF DOMINANT DESERT PLANT SPECIES IN AN OASIS_ DESERT ECOTONE OF MINQIN, CHINA
WEI Xiao-Ping, ZHAO Chang-Ming, WANG Gen-Xuan, CHEN Bao-Ming, CHENG Dong-Liang
Chin J Plan Ecolo. 2005, 29 (6):  878-883.  doi:10.17521/cjpe.2005.0116
Abstract ( 3181 )   PDF (370KB) ( 936 )
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Most desert soil management decisions are based on quantitative measu rements of the biomass of the dominant plant species. The biomass of the dominant plant species in a typical oasis_desert ecotone (ODE) of Minqin was measured in 82 plots (10 m×10 m). The results showed that the distribution and total cover was approximately 16.12%. Above and belowground biomass of five dominant desert species (Nitraria tangutorum, Calligonuum mongolicum, Haloxylon ammoden dron, Agriophyllum squarrosum and Halogeton arachnoideu) was measured by excavation. Linear regressions were used to analyze the relationships among all the biomass components for each plant (fresh and dry weight of aboveand below_ground biomass) and the basal diameter, total height and canopy cover. Best fit models were constructed for each species using 80% of the data. Our results showed that basal diameter (excluding N. tangutorum) and canopy cover were the best predictors of biomass for all five desert plant species. A validation test using the other 20 % of the data not used for estimating the regression equations indicated that these equations made accurate predictions of desert plant species biomass.

LITTERFALL OF TROPICAL RAIN FORESTS AT DIFFERENT ALTITUDES，XISHUANGBANNA, SOUTHWEST CHINA
ZHENG Zheng, LI You-Rong, LIU Hong-Mao, FENG Zhi-Li, GAN Jian-Min, KONG Wei-Jing
Chin J Plan Ecolo. 2005, 29 (6):  884-893.  doi:10.17521/cjpe.2005.0126
Abstract ( 3441 )   PDF (780KB) ( 975 )
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To assess the effects of the Indo monsoon on litterfall dynamics and changes of litterfall along altitudinal gradients in the tropical rain forests of southwestern China, eight plots were chosen along three elevational gradients of 600, 1 100 and 1 600 m in Xishuangbanna, China. We examined the relationship between litterfall dynamics and climate, and their changes with increasing altitude. On three gradients, average annual temperature was 22.1, 20.1 and 16.6 ℃ respectively, with a mean lapse rate of -0.005 3 ℃ m-1. With increasing altitude , annual average rainfall increased (1 532, 1 659 and 2 011 mm, respective ly), while in the dry season they were similar (282-295 mm); evaporation changed slightly (1 369, 1 374 and 1 330 mm, respectively); annual average relati ve humidity decreased (86%, 81% and 84%, respectively) and was much more pronounced in the late dry season; and soil water content increased significantly. Litterfall production of tropical seasonal rain forest (1 072 to 1 285 g•m-2•a-1) was higher than in the tropical montane rain forest (718 to 1 014 g •m-2•a-1). Both litterfall production and CV of annual litterf all processes had a signifi cant and negative linear relationship with altitude. Litterfall production had a significant and positive linear relationship with temperature and was inversely related to rainfall. Peak litterfall during the dry season was influenced by re lative air humidity and soil water content. Peak litterfall occurred earlier in the dry season at altitudes of 1 100 to 1 720 m due to decreasing humidity with altitude whereas at higher sites (1 820 m), increasing soil moisture levels delayed the litterfall peak. Our results suggested that 1) litterfall production of the tropical seasonal rain forest coincided with those of moist tropical rain forests in Southeast Asia; 2) water stress in the dry season changed with altitude and determined the timing of peak litterfall; and 3) with increasing altitude, there was a transition from seasonality to stability in annual litterfall process.

ALTITUDINAL PATTERNS OF SEED PLANTS ON DAWEI MOUNTAIN, YUNNAN PROVINCE, CHINA
WANG Juan, MA Qin-Yan, DU Fan, YANG Yu-Ming
Chin J Plan Ecolo. 2005, 29 (6):  894-900.  doi:10.17521/cjpe.2005.0117
Abstract ( 3008 )   PDF (761KB) ( 731 )
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Altitudinal gradients incorporate multiple resource gradients which vary continuously in different fashions. Studies of mountain floristic patterns along altitudinal radients has revealed regular patterns of the flora along envir onmental gradients, changing trends in biodiversity along altitudinal gradients as well as a better understanding of biological fitness. To explore the floristic compositional characteristics and the ecological significance of floristic patterns along altitudinal gradients in the China National Natural Reserve of Dawei Mountain in southeast Yunnan, the flora was uantified along two transects, one on the southwest slope and the other on the northeast slope of the reserve, including a vertical vegetation transect. Further investigations were conducted on the flora of Dawei Mountain which have ever been accounted for in the literature , such as Flora of Yunnan, The Seed Plant in Yunnan and so on. The structural characteristics of the flora and the altitudinal distribution patterns of its floristic components were analyzed. Systematic cluster analysis was applied to the data to determine how composition changed with changes in altitude and climate. The conclusions can be summarized as follows: 1) There was a strong boundary that ifferentiated tropical floristic elements from evergreen broad_leaved forests at an altitude of approximately 1 500 m; 2) Cluster analysis showed that humid rain forests occurred below 700 m a.s.l, mountain rain forests were between 700 m and 1 500 m, monsoon evergreen broad_leaved forests were between 1 300 m and 1 800 m, and the mountain mossy evergreen broad_leaved forest occurred above 1 800 m a.s.l. Non_representative mountain mossy dwarf forests (above 2 100 m) in the area are distributed on windward slopes and barren land on the mountain slopes.

COMPARISON OF FRACTAL CHARACTERISTICS OF SPECIES RICHNESS PATTERNS BETWEEN DIFFERENT PLANT TAXONOMIC GROUPS ALONG AN ALTITUDINAL GRADIENT
REN Hai-Bao, ZHANG Lin-Yan, MA Ke-Ping
Chin J Plan Ecolo. 2005, 29 (6):  901-909.  doi:10.17521/cjpe.2005.0118
Abstract ( 2988 )   PDF (647KB) ( 1131 )
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SIMULATION OF SOIL WATER DYNAMICS IN A CARAGANA INTERMEDIA WOODLAND IN HUANGFUCHUAN WATERSHED: RELATIONSHIPS AMONG SLOPE, ASPECT, PLANT DENSITY AND SOIL WATER CONTENT
JIA Hai-Kun, LIU Ying-Hui, XU Xia, WANG Kun, GAO Qiong
Chin J Plan Ecolo. 2005, 29 (6):  910-917.  doi:10.17521/cjpe.2005.0122
Abstract ( 2915 )   PDF (741KB) ( 1059 )
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With an increase in vegetation coverage, there can be a decrease in soil water content due to uptake and evapotranspiration by the vegetation. At high planting densities, poor growth and even mortality has occurred due to the decrease in soil water content. Hence, a better understanding of the relationship between soil water content and the density of plants is important for designing effective restoration projects. To study these relationships, we developed a soil water dynamic simulation model of a Caragana intermediawoodland under different slope gradients and slope aspect in the Huangfuchuan watershed conditions based on previous studies and field experiments. The model took into account soil characteristics, precipitation infiltration, vegetation transpiration, and soil evaporation. Daily changes in soil water content, transpiration, and evaporation of Caragana intermedia woodlands with different vegetation coverage, slope gradient , and slope aspect was simulated from 1971 to 2000. Through model simulations, we determined the functional relationships among soil water content, plant coverage and slope as well as the optimal plant density on flat slopes. With further simulations, we determined the effects of slope gradient and slope aspect on soil water content. When slope gradient was less than 10 degrees, the optimal planting density was sensitive to slope gradient. In the range of 10 and 30 degrees, planting density was not sensitive to slope gradient. Therefore, when reconstructing vegetation, it is important to consider planting densities on the hillsides with slope gradients less than 10 degrees.

A PRELIMINARY STUDY ON THE RE_INITIALIZATION/RE_PARAMETERIZATION OF A CROP MODEL BASED ON REMOTE SENSING DATA
MA Yu-Ping, WANG Shi-Li, ZHANG Li, HOU Ying-Yu
Chin J Plan Ecolo. 2005, 29 (6):  918-926.  doi:10.17521/cjpe.2005.0127
Abstract ( 2662 )   PDF (735KB) ( 1029 )
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Crop growth simulation models have extensive application in crop growth monitoring, yield forecasting and utilization of enviromental resources. However, problems arise when scaling crop simulation models from the field to regional scales, especially in acquiring initial conditions and parameters for the model. Fortunately, satellite remote sensing has the potential to improve some of the model parameterization for monitoring crop growth at regional scales. Thus, there is interest in developing an approach and methodology for incorporating remotely_sensed information with crop growth simulation models.  In this paper, the crop model WOFOST (World food study) was adapted for simulating growth of winter wheat by using field experimental data from North China, and the radiative transfer model SAIL_PROSPECT was adapted by adjusting the sensitivity of its parameters. The two models were then coupled using LAI to simulate the vegetation indices SAVI. Finally, WOFOST was re_initialed by minimizing differences between SAVI s simulated by coupling the model and SAVIm synthesized from MODIS remote sensed data using an optimization software program (FSEOPT). The results were validated by using field experimental data (including leaf area index , dry weight of leaves, stems and storage organs) in Zhengzhou, Henan Province, Tai'an, Shandong Province, and Gucheng, Hebei Province, and some MODIS data during the growing season of winter wheat from 2001 to 2003. The main results in this study were as follows: (1) Differences between the simulated mature date, after re_initializing the emergence date using remote sensing data and simulated values, with the actual ermergence date was within 2 days, and simulated LAI and gross above_ground dry matter weight were 3-8 percent of actual values; (2) By re_initializing biomass weight in the turn_green stage, rela tive errors of the simulated LAI and gross above_ground dry matter weight were within 16% at key development stages, and simulated LAI and storage organ weight were closer to measured values during the entire growing period; (3) Appropriate remote sensing data during the period from the turn_green stage to earing stage was more critical for improving crop modeling when biomass in the turn_green stage was adjusted.  We presented a novel method for validating and adjusting crop models to regional scales. Optimization of the crop simulation model by dynamical adjustment of the initial variables and parameters based on remote sensing data produced highly satisfactory results. This research provides a basis for optimizing crop models by using remotely sensed data at regional scales. However, errors in the simulation results due to uncertainty of remote sensing data and SAIL_PROSPECT paramete rs still exist and further study is needed. 

LAND COVER CLASSIFICATION OF REMOTELY SENSED IMAGERY USING A METHOD BASED ON TOPOGRAPHICAL RESTRICTIVE FEATURES: A CASE STUDY OF THE JINHE WATERSHED
HONG Jun, GE Jian-Ping, CAI Ti-Jiu, NIE Yi-Huang
Chin J Plan Ecolo. 2005, 29 (6):  927-933.  doi:10.17521/cjpe.2005.0121
Abstract ( 2237 )   PDF (589KB) ( 735 )
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Based on non_supervised classification methods, multi_temporal images, such as NOAA_AVHRR, SPOT_VEGETATION and MODIS series data, have been used to map regional, continental or global land cover patterns. Because of limitations of the classification method and spatial resolution of images, traditional non_supervised classification often results in many errors in the transition zones in which the spatial distribution of vegetation show segmental patterns. This problem can decrease the integral accuracy of the classification to a certain extent.  In this paper, a new method, the topographical restrictive features, is presented to classify remotely sensed images using the Jinhe watershed in the Loess plateau as a case study. First, 25 relatively independent classes were obtained using the non_supervised classification method with multi_temporal NDVI data derived from the first two bands of MODIS data. Every cell with 500 m spatial resolution of the classification determined by the non_supervised method was divided into 25 homogenous cells with 100 m spatial resolution. Then, topographical features were defined. Information about aspect, slope, elevation, river net structure, and vegetation regional characteristics, derived from 1∶250 000 geographical spatial data, ETM+ image and yield data, were used to construct topographical restrictive features. Finally, the classification of every sub_cell was tested using the restrictive features and some cells were reclassified while maintaining their original classification. After the secondary classification, all cells were labeled by land cover type according to the land cover classification system, which was defined previously on the base of the IGBP land cover classification system and UMD system.  Using this new method, the accuracy of the land cover classification increased from 71.88%, in traditional non_supervised classification method, to 84.09%. Inparticular, the accuracy of cropland and urban type classification improved. The method of cell sub_division avoids the shortcomings of traditional classification methods owing to the coarse resolution of the image processing, and makes it more highly probable that land cover types are homogenous within cells. The introduction of topographical restrictive features decreases uncertainty of traditional fuzzy classification and provides more precise distinctive features to classify the fuzzy zone, and thus improves the accuracy of classification.

LAND COVER CLASSIFICATION IN CHINA BASED ON THE NDVI_TSFEATURE SPACE
YU Feng, LI Xiao-Bing, WANG Hong, YU Hong-Jing, CHEN Yun-Hao
Chin J Plan Ecolo. 2005, 29 (6):  934-944.  doi:10.17521/cjpe.2005.0115
Abstract ( 2181 )   PDF (780KB) ( 987 )
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Mapping and quantifying land use and land cover changes are important for evaluating recent changes in the regional and global environment and for simulating future changes under different climate change and human land use scenarios. The normalized difference vegetation index (NDVI) and surface temperature (Ts) are two important parameters used to describe the characteristics of land cover. The NDVI_Ts feature space combines these two parameters into one variable. By and large, Ts/NDVI is synchronized to the growing season of vegetation so it can approximate the different phases and status of vegetation growth. Compared to NDVIand Ts, NDVI_Tscontains more land cover information and should be more suitable for characterizing the distribution of vegetation or land cover. The aim of this paper was to discuss the feasibility of using the NDVI_Ts feature space to better characterize the current distribution and changes in vegeta tion and land cover in China. We used several classification methods, including Principal Component Analysis (PCA), unsupervised classification and post_classification sustained based on digital elevation models (DEM). The results indicated that Ts/NDVI was highly sensitive and could discriminate different vegetation cover categories in China at large_scales. The accuracy of vegetation classificat ion based on Ts/NDVI was 72.0%, a 3.3% improvement in accuracy as comp ared to NDVI images, using unsupervised classification, and the Kappa value increased 0.020 2. Moreover, because of the simplexity of remote sensing information, the classification based on seasonal Ts/NDVIdata could not avoid completely the mixed cl assification phenomena. It was necessary to add other information, reflecting vegetation characteristic and its environment to implement post_classification, such as DEM. When the inversing accuracy of Tsimproved, Ts/NDVIdata can precisely describe the status of vegetation or land cover in China and improve monitoring of land use changes. This technique has great research potential and practical value.

DISSOLVED ORGANIC CARBON CONCENTRATIONS IN SOIL UNDER DIFFERENT LAND USES IN THE LIUPAN MOUNTAIN FOREST ZONE
WU Jian-Guo, XU De-Ying
Chin J Plan Ecolo. 2005, 29 (6):  945-953.  doi:10.17521/cjpe.2005.0133
Abstract ( 2625 )   PDF (746KB) ( 797 )
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Dissolved organic carbon is an important component of the carbon balance of terrestrial ecosystems and source of energy, carbon, and nutrient transfer from terrestrial to aquatic ecosystems. Land use changes caused by human activities have had major impacts on terrestrial ecosystem carbon cycles, including impacts of soil DOC dynamics. Hence, it is important to understand the impacts of land use changes on DOC for assessing the impacts of land use change on the carbon cycle. Over the last several centuries, extensive areas of native vegetation in the Liupan Mountain Forest Zone have been replaced by croplands or rangelands, whereas in recent decades former arable lands and rangelands have been afforested. However, the impacts of these land_use changes on the terrestrial ecosystem carbon cycle are unclear, especially on the soil DOC dynamics. In order to assess the impacts of land_use changes on soil DOC dynamics, we measured the concentrations of DOC in precipitation, subsurface water, soil leachate, detrital leachate solutions, throughfall, and water percolating through the soil in plots with the same elevation, exposure, and soil types but with different vegetation types. A natural secondary forest dominated by Querces liaotungensis, Populus davidiana, or brushwood, a cropland and rangeland derived from destruction of the natural secondary forests, and a 13, 18 and 25 year old larch plantation, Larix pricipis_rupprechtii, afforested on former croplands or rangelands were studied. Our results showed that concentrations of DOC in precipitation and subsurface water from May to October was 0.80 -1.60 mg•L－1 and 2.43-7.66 mg•L－1, respectively. From September to October, the concentration of DOC in throughfall was 1.78-15.20 mg•L－1 which was higher under natural forests or plantations than in croplands or rangelands and positively correlated with annual production of aboveground detritus (p=0.05). The concentration of DOC in detrital leachate solutions, derived from detritus submerged in water for 24 h, was 12.30-64.79 mg•L－1 and its fraction was not more than 1%. The concentration of detrital DOC was 400% and 153% higher under natural forests than cropland and rangeland, respectively, and 194% and 50% higher under plantation than cropland and rangeland, respectively. Its fraction was 79% and 98% higher in the cropland and rangeland than the natural forest, respectively, and 180% and 210% higher in the cropland and rangeland than the plantation, respectively. The concentration of DOC in detrital leachate was positively correlated with aboveground detrital carbon storage of leaf, branch, humus and litter (p=0.05, n=184). The concentration of DOC in soil solutions in the 0-20 cm deep soil layer was 7.88-88.44 mg•L－1 and its fraction was not more than 1%. The concentration of soil solution DOC was higher under the natural secondary forest or the plantation than cropland or rangeland, and its fraction was lower under natural forest than cropland or rangeland but higher under the plantation than natural secondary forests. The difference of the soil solution DOC concentration or fraction between the natural secondary forest or plantation and rangeland or cropland was greater at 0-10 cm soil depth than 10-20 cm soil layer. The change of this DOC concentration with soil depth was greater under the natural secondary forest or plantation than cropland or rangeland. The concentration of this DOC was positively correlated with detrital carbon storage and soil water content (p=0.05), and soil water content was the main factor that influenced the concentration of DOC in soil solutions. The concentration of DOC in soil percolation water was 5.76-58.84 mg•L－1 which was higher under the natural forest or plantation than cropland or rangeland. The difference in this DOC concentration between the natural secondary forest or plantation and rangeland or cropland was greater in the 0-10 cm than 10-40 cm soil layer. The change of this DOC concentration with soil depth was greater under the natural secondary forest or plantation than cropland or rangeland. These differences were ascribed to the differences in vegetation and soil properties that resulted from changes in land use and their consequent impacts on hydrological processes. The results of this study indicate that changes in land use have large impacts on terrestrial DOC concentrations.

SIZE_DEPENDENT REPRODUCTIVE OUTPUT AND LIFE_HISTORY STRATEGIES IN FOUR EPHEMERAL SPECIES OF TRIGONELLA
YAO Hong, TAN Dun-Yan
Chin J Plan Ecolo. 2005, 29 (6):  954-960.  doi:10.17521/cjpe.2005.0124
Abstract ( 2673 )   PDF (610KB) ( 820 )
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Phenological characteristics and patterns of biomass allocation were studied in four ephemeral species of Trigonella (T. cancellata, T. arcuata, T. monantha and T. orthoceras) from the Zhungaer desert. The results showed that germination strategies were diverse among species. Seed germination occurred in the spring, summer and autumn in all four species, but was most prevalent in the spring and autumn. The germination time of seeds was very closely related to environmental factors, such as temperature and precipitation. There were no obvious interspecific differences in germination time. Plant growth was quick and the life cycle short in all four species. The fruits maturate before the arrival of t he arid summer season. All four species are monocarpic, and their life_history s trategy can be described as that of escaping aridity. The reproductive yield of plants germinated in the spring and autumn was maximized by an instantaneous switch from vegetative growth to reproductive growth after a short period of vegetative growth. The four species allocate a high proportion of carbon to reproductive output and was 62.3%, 51.9%, 54.3% and 58.3% for the four species, and the absolute measures of reproductive output were size_dependent. The reproductive output increased with plant size, with the r_value 0.989, 0.935, 0.720 and 0.924 in all the four species (p<0.001). There were significant differences in the size (p<0.01) and the reproductive output (p<0.05, p<0.01) among plants that germinated in different seasons. The plants that germinated in the spring were smaller and their reproductive output lower than those hat germinated in the autumn, but the difference in the proportion of reproductive allocation was not significant (p>0.05). These results indicate that differences in reproductive output can be explained by size differences in plants from different germination times. Fin ally, we discussed the life_history strategies of the four ephemeral species and analyzed their differences based on individual size, survival ability and repro ductive output of plants germinated during different season, and their adaptation strategies to the arid environment of the Zhungaer desert.

CHARACTERISTICS OF THE LEAF EPIDERMIS OF CARAGANAPLANTS ON THE ORDOS PLATEAU AND THEIR ECOLOGICAL ADAPTATIONS
YANG Jiu-Yan, YANG Jie, YANG Ming-Bo, LIANG Na, KONG Wei-Xue
Chin J Plan Ecolo. 2005, 29 (6):  961-967.  doi:10.17521/cjpe.2005.0119
Abstract ( 2986 )   PDF (528KB) ( 945 )
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Characteristics of the leaf epidermis of 8 species in the genus Caragana, wh ich grow from the east to the west on the Ordos Plateau, were studied by observation through a light microscope (LM) and a scanning electron microscope (SEM). The study showed that the leaf epidermal cells were usually irregular or polygonal shaped, and the type of stomatal apparatus was mainly anomocytic. The stomatal density and the stomatal index of the xero_mesophytic C． purdomiiwere higher than these of the seven other xerophilous species (C. opulens, C. i ntermedia, C. korshinskii, C. roborovskyi, C. stenophylla, C. tibeticaand C . brachypoda). Comparisons within species showed that C. intermedia, C. sten ophylla, and C. tibeticahad higher stomatal density when growing in heavier drought areas， whereas C. korshinskiihad lower stomatal density; C. s tenophyllaand C. tibeticahad a higher stomatal index whereas C. intermediaand C. korshinskiihad a lower stomatal index. The leaf epidermis of C. intermedia, C. korshinskii, C. tibeticaand C. roborovsky had a dense trichome, which was an adaptive characteristic caused by the droughty environment. The leaf epidermis of xerophytic species had a higher plasticity than that of mesophytic species. The plasticity index of C . stenophyllaand C. tibetica, which are the dominant species in semi_deserts, was the highest among the 8 species. Observation using SEM revealed that there were two types of stomas: stomas located below the epidermal cells and stomas located on the same level with epidermal cells. It also revealed that there was cuticle and wax on the leaf epidermis, and that the trichome on the leaf epidermis was a single cell hair.

AXIAL AND RADIAL CHANGES IN XYLEM ANATOMICAL CHARACTERISTICS IN SIX EVERGREEN BROADLEAVED TREE SPECIES IN AILAO MOUNTAIN, YUNNAN
FAN Ze-Xin, CAO Kun-Fang, ZOU Shou-Qing
Chin J Plan Ecolo. 2005, 29 (6):  968-975.  doi:10.17521/cjpe.2005.0129
Abstract ( 2464 )   PDF (850KB) ( 801 )
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The model of West, Brown and Enquist shows that total hydraulic resistance in trees can be independent of path length provided that vascular conduits taper upward sufficiently. This model contradicts the hydraulic limitation hypothesis on tree height growth. To test the validity of this model, we investigated axial and radial changes in xylem anatomical characteristics of six evergreen broadleaved tree species in a subtropical forest in Yunnan. The six species studied included Castanopsis wattii, Lithocarpus chintungensis, L. xylocarpus, Cyclobalanopsis stewardiana, Schima noronhae, and Hartia sinensis. The first four species are from the Fagaceae and the other two species are from Theaceae. Fourteen trees (15-25 m) were sampled from the six species. Sapwood cores were taken from each tree at intervals of 1 m along the trunk to study the axial variation in xylem anatomy. Stem cross sections were collected at three heights from the four Fagaceae species to characterize radial variation. Transve rse sections of 50-80 μm thickness were made using a sliding microtome. Our analysis of transverse microscopic sections showed that the conduit lumen diameters increased from the top to the base of the crown in all trees and to the base of the bole in four trees. Conduit lumen diameter was approximately constant from the crown base to the tree base in the remaining trees. Vessel density increased with height, especially within the crown. The lumen/total sapwood area ratio was constant along the trunk in four of the twelve trees and decreased from the base of the crown to its top in most of the remaining trees. The theoretical specific hydraulic conductivity decreased substantially from the base of the crown to its top and was constant below the crown base in most trees. Conduit lumen diameters increased linearly for the first 20 - 40 years of cambial age and then stabilized in most of the eight trees of Fagaceae. There was no difference in conduit lumen diameter produced by the same aged cambium at different aboveground heights. Our results suggested that axial and radial trends in conduit lumen diameter of the six evergreen broadleaved species were consistent with partial buffering of hydraulic resistance from path length effects. The uniform size of conduit lumens below the crown base contradicted the critical assumption of constant conduit taper along the trunk in the model of WBE.

DIURNAL CHANGES OF PHOTOSYNTHETIC CHARACTERISTICS AND CHLOROPHYLL FLUORESCENCE IN CANOPY LEAVES OF FOUR DIPTOCARP SPECIES UNDER EX_SITU CONSERVATION
MENG Ling-Zeng, ZHANG Jiao-Lin, CAO Kun-Fang, XU Zai-Fu 
Chin J Plan Ecolo. 2005, 29 (6):  976-984.  doi:10.17521/cjpe.2005.0130
Abstract ( 2654 )   PDF (808KB) ( 1234 )
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Dipterocarps dominate the canopy of tropical rainforest of Southeast Asia. They are not only the world's main source of hardwood timber, but their canopy leaves are main organs for global carbon sequestration. Due to anthropogenic activities, many species of dipterocarps are threatened. Because of this situation, ex_situ conservation efforts were employed to conserve the genetic resources of several dipterocarps.  In this study, four dipterocarp species, Dipterocarpus retusus, Hopea hain anensis, Parashorea chinensis(emergent tree species in the rainforest) and Vatica xishuangbannaensis, were selected as study species that had been transplanted in 1981 to an ex_situdipterocarp conservation forest in Xishuangbanna Tropical Botanical Garden. We measured the diurnal changes in photosynthetic rates, parameters of chlorophyll fluorescence, and morphological traits of their canopy leaves at 15-21 m height during the rainy season of 2004. The results indicated that the maximum photosynthetic rates (Pmax) per unit leaf area (7.5～18.1μmol•m－2•s－1) and mass (89.08 to 150 .82 nmol•g-1 DW•s-1), dark respiration rates (Rd), light saturation point (LSP), light compensation point (LCP) and leaf morphological traits differed significantly among species. Photosynthesis in the four species was depressed at midday. The results revealed that stomatal closure induced by high leaf_to_air vapor pressure deficit (LAVPD) led to photosynt hetic depression at midday. Quantum yields of photosystem II (φSⅡ) in four dipterocarp species decreased significantly at midday, indicating that photoinhibition occurred. However, their PSⅡ values recovered to the early morning value by sunset, indicating that photoinhibition was reversible. The nonphotochemical quenching rate (NPQ) increased significantly in D. retusus, H. hainanensis and V. xishuangbannaensis， indicating that NPQwas used mainly to dissipate excess light energy a bsorbed by PSⅡ. At midday, the electron transport rate (ETR) in P. chinensis was maintained at high levels, while its photosynthetic rate decreased, suggesting that a large proportion of electrons were allocated to photorespiration. Thus photorespiration was the main mechanism protecting the photosynthetic apparatuses of P. chinensisduring the midday photosynthesis depression. Other parameters , such as leaf area, size and density of stomata, and total chlorophyll content, also were measured at the same time. There was a general ranking of Pmax in the following order from highest to lowest: D. retusus, P. chinensis, H. hainanensi, V.xishuangbannaensis.Based on the diurnal changes in chlorophyll fluorescence, both leaf stomatal limitations and non_stomatal effects played an important role to prevent photodamage during the midday depression of photosynthesis brought by the high irradiances, high air temperature, low humidity, and so on. The high midday leaf water potential of the four species showed that water limitations had no influence on photosynthetic rates.

EFFECTS OF NACL STRESS ON ACTIVE OXYGEN METABOLISM AND MEMBRANE STABILITY IN PISTACIA VERASEEDLINGS
YUAN Lin, KARIM Ali, ZHANG Li-Quan
Chin J Plan Ecolo. 2005, 29 (6):  985-991.  doi:10.17521/cjpe.2005.0131
Abstract ( 2613 )   PDF (720KB) ( 1258 )
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Pistachio (Pistacia vera) is one of the most important dried fruit trees in the world and is mainly cultivated in Xinjiang, China. However, soil salinization is one of the main limiting factors for its promising potential of development. In this experiment, the effects of NaCl stress on physiological and biochemical characteristics were investigated in seedlings of two cultivars of Pistacia vera, Changguo' and Kerman'. Seedlings were grown in pots and treated with four NaCl concentrations: 50, 150, 250 and 500 mmol•L-1. The membrane permeability , malondialdehyde content (MDA), superoxide dismutase (SOD) activity, catalase ( CAT) activity and peroxidase (POD) activity in the leaves of these two cultivars were measured and compared after 5, 10 and 20 days of NaCl treatments.  The experimental results showed that the membrane permeability and MDA content in both cultivars increased considerably with the increasing NaCl stress, which aggravated the degree of membrane lipid peroxidation and injured the membrane stability. The membrane permeability and MDA content in the Changguo' cultivar increased more quickly than the Kerman' cultivar and thus experienced greater damage at higher NaCl concentrations. The activities of SOD, CAT and POD had similar trends for both cultivars, first increasing with NaCl concentrations up to 250 mmol •L-1and then decreasing at the highest NaCl stress of 500 mmol•L-1. The coordinated changes of activities among the antioxidant enzymes of SOD, POD and CAT could scavenge active oxygen and maintain a balance of active oxygen accumulation in cells to protect membrane structure. The results also showed that the damage by NaCl stress to the membrane structure and function for both cultivars were mitigated considerably 20 days after the treatments were initiated. There were significant correlations among the membrane permeability, MDA content and the activity of SOD in both cultivars, which implied that the membrane permeability in the plant cells had a close relation with MDA content and oxygen free radical content, as well as the activity of antioxidant enzymes. Together, these results in dicated that the Kerman' cultivar has higher antioxidant levels and greater salt_tolerance than the Changguo' cultivar of Pistachio.

DIFFERENCES OF Pb ACCUMULATION AMONG PLANT TISSUES OF 25 ZEA MAYS VARIETIES
DAI Quan-Lin, YUAN Jian-Gang, FANG Wei, YANG Zhong-Yi
Chin J Plan Ecolo. 2005, 29 (6):  992-999.  doi:10.17521/cjpe.2005.0134
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Pollutions of agricultural land by heavy metals impose a more and more serious risk to environmental and human health in recent years. Heavy metal pollutants may enter the human food chain through agricultural products and groundwater from the polluted soils. Progress has been made on phytoremediation, a safe and inexpensive approach to remove contaminants from soil and water using plants, in the past decade. However, in most cases, agricultural land in China can not afford to grow phytoremediator plants instead of growing crops to be economically sustainable. Therefore, new and effective methods to decrease the risk of heavy metal pollution in crops and to clean the contaminated soils are urgently needed. If we can find crop germplasms (including species and varieties) which sequester heavy metals in their edible parts, such as fruits of vegetables or grain of cereals, at low enough level for safe consumption, then we can grow these selected species or varieties in the lands contaminated or potentially contaminated by heavy metals. If we can find crop germplasms sequester low concentrations of heavy metals in their edible parts and high content of the metals in their ine dible parts, then we can use these selected species or varieties for soil remediation. In this study, the feasibility of the method is assessed by analyzing Pb contents in edible and inedible parts of 25 varieties of Zea mays grown under Pb contaminated soils. The soil concentrations of Pb were 595.55 mg•kg-1 in the high Pb_stress group and 195.55 mg•kg-1 in the control group.  The results showed that the Pb concentrations in different tissues were in the order of root>shoot≌leaf >grain. Compared with the control, the Pb concentration s in root, shoot and leaf were greatly increased under the highly Pb_ stressed c ondition, while the increments of Pb concentration in grain were relatively lower. Under the high Pb_stress, the grain Pb concentrations of 12 varieties exceede d the National Sanitation Standard of China (NSSC) and were inedible. This indic ates that there is a high Pb pollution risk for Zea mays grown on Pb polluted sites. Although 22 of the 25 tested varieties had harvest loss under the highly stressed condition, ranging from 0.86%-38.7% of the grain biomass acquired at the control, the average harvest loss of all tested varieties was only 12.6%, which is usually imperceptible in normal farming practices. Therefore the risk of Pb pollution in Zea mays products can not be promptly notified and prevented based on the outcome of the harvest. However, we did find 13 varieties of 25 tested varieties had grain Pb concentration lower than the NSSC. It is, therefore, possible to reduce the pollution risk if these favorable varieties are used for Zea mays production in Pb polluted or potentially polluted agricultural lands.  Pb concentrations in vegetative tissues (root, stem and leaf) were significantly correlated with each other, while Pb concentrations of each vegetative tissues were not significantly correlated with that of grain. Among the 25 tested varieties, some varieties had Pb concentrations in grain lower than (No.1-3 and No.6) or slightly above (No.4) the NSSC level, while their Pb concentrations in the vegetative tissues were among the highest. When excluding these varieties, correla tions between the Pb concentrations of grain and those of vegetative tissues of the rest of the tested varieties became highly significant. In addition, variety No.1 had the lowest harvest loss under high Pb_stress, and the highest Pb seque stration in vegetative tissues (51.69 mg•plant-1, 12 times as much as in the control). The similar features were also observed in varieties No.2, No.3 and No.6 , which sequestered 36-42 mg•Pb plant-1 under high Pb_stress. We recommen d these varieties of Zea mays to be used for bioremediation of Pb contaminated soil and crop production at the same time.

EFFECTS OF IRRIGATION WITH DILUTED SEAWATER ON ‘OLEIC SUNFLOWER G101’ GROWN IN SALINIZED SOILS, LAIZHOU, CHINA
TANG Qi-Zhi, LIU Zhao-Pu, LIU Ling, ZHENG Qing-Song, CHEN Ming-Da
Chin J Plan Ecolo. 2005, 29 (6):  1000-1006.  doi:10.17521/cjpe.2005.0125
Abstract ( 2539 )   PDF (609KB) ( 970 )
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Nearly half the irrigated fields in the world are becoming saline and alkaline. Soil salinization is becoming a serious problem in China, especially in the seashore plain of north China where there is a highly developed industrial and agricultural economy and a huge population. With the high speed of industrial development and rapidly increasing population, groundwater overuse is leading to an influx of seawater and further expediting salinization of freshwater resources and soil. Lack of freshwater is a main factor restricting social and economic development in the seashore plain of north China.  Irrigation of crops with diluted seawater has been proposed as a way to conserve freshwater supplies. This experiment was conducted to study the characteristics and effects of irrigation with diluted seawater on a salt tolerant economic pla nt and provide recommendations for saline water irrigation in these drought/semi _drought seashore areas. Oleic sunflower G101' (Helianthus annuus), a salt_ tolerant economic plant, was irrigated with different proportions of diluted seawater in the Laizhou, Shandong Province, where seawater intrusion is a very serious problem. The effects of irrigation with diluted seawater on various growth indices, the accumulation and distribution of ions in the plant, and total yields of G101' planted under local rainfall conditions were investigated during two growing seasons, 2002 (drought year) and 2003 (wet year). The sunflower was irrigated twice during the growing season, one at early bud and the other at early florescence. The results showed that 1) In both the drought year (2002) and the wet year (2003), a 40% seawater irrigation solution was a safe dilution ensuring economic yields for the 100 day growth period of G101'. During the drought year, G101' see d yields decreased significantly when irrigated with 40% seawater or greater, while there were no differences in seed yields in the wet year when irrigated with 40% or 60% seawater . Thus, irrigation with a 40% seawater solution was economically feasible. 2) During the drought year, most growth indices of oleic sunflowers when treated with 20% seawater were not significantly different with that irrigated with freshwater (p=0.95), except for stem thickness and disc fresh weight during early florescence. However, in the wet year, all measured growth indices were not significantly different from the freshwater treatment when treated with up to 40% seawater (p=0.95). 3) When irrigated with 0－40% seawater, Ca2+ and Mg2+ homeostasis was maintained in the leaves and root K+ selective ion transport to the disc was strong. Accumulation of Na+ was mainly in the root and stem, while Na+ concentrations in the leaves and disc were lower. Chloride content was the greatest in the stem as compared to other parts of the oleic sunflowers.

ECOLOGICAL STOICHIOMETRY: A SCIENCE TO EXPLORE THE COMPLEXITY OF LIVING SYSTEMS
ZENG De-Hui, CHEN Guang-Sheng
Chin J Plan Ecolo. 2005, 29 (6):  1007-1019.  doi:10.17521/cjpe.2005.0120
Abstract ( 3607 )   PDF (966KB) ( 2119 )
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The biological sciences developed very fast during the 20th century and have become increasingly sophisticated and predictive. Along with this trend, areas of research also have become increasingly specialized and fragmented. However, this fragmentation and specialization risks overlooking the most inherent biological characteristics of living organisms. One can ask if the living organism son the earth have unified and essential characteristics that can connect the disparate disciplines and levels of biological study from molecular structure of genes to ecosystem dynamics. By exploring this question, a new science, ecological stoichiometry, has been developed over the past two decades. Ecological stoichiometry is a study of the mass balance of multiple chemical elements in living systems; it analyzes the constraints and consequences of these mass balances during ecological interactions. All biological entities on the earth have a specific elemental composition and specific elemental requirements, which influence their interactions with other organisms and their abiotic environment in predictable ways. Ecological stoichiometry has been incorporated successfully into many levels of biology from molecular, cellular, organismal and population to ecosystem and globe. At present, the principles of ecological stoichiometry have been broadly applied to research on population dynamics, trophic dynamics, microbial nutrition, host_pathogen interactions, symbiosis, comparative ecosystem analysis, and consumer_driven nutrient cycling. This paper reviews the concepts, research history, principles, and applications of ecological stoichiometry and points out future research hotspots in this dynamic field of study with an aim to promote this discipline of research in China.

PERSPECTIVES ON SMALL_SCALE SPATIAL STRUCTURE OF PLANT SPECIES IN PLANT COMMUNITIES
LIU Zhen-Guo, LI Zhen-Qing
Chin J Plan Ecolo. 2005, 29 (6):  1020-1028.  doi:10.17521/cjpe.2005.0135
Abstract ( 2564 )   PDF (757KB) ( 955 )
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Small_scale spatial structure of plant species is important in plant e cology as it affects the dynamics of plant populations, communities and ecosyste m processes. Plants interact primarily with their immediate neighbors, and the v iew of the community as seen by an individual plant can be quite different from processes averaged over large spatial scales. Many processes influence the forma tion and dynamics of small_scale spatial structures of plant species, and local spatial structure in turn has an effect on the vital processes of plant growth, birth and death. This paper summarizes developments in this area of research bas ed on the extensive literature on small_scale spatial structure of plant species to help direct further research efforts. Firstly, this paper introduces six fac tors that lead to the formation of small_scale spatial structure of plant specie s, including 1) habitat spatial heterogeneity, 2) dispersal of propagules, 3) in teractions between plants, 4) effects of the biological environment (animals and microbes), 5) effects of exoteric disturbances, and 6) the integrated effects o f many factors. The significance and effects of small_scale spatial structure on studies of biological diversity, plant population genetics and restoration ecol ogy are then examined. Finally, several questions were raised and a list of sugg ested areas of future research on this topic were presented that included: 1) In f ormation on small_scale spatial structure should be integrated into vegetation d ynamics at large scales; 2) Either biologically or ecologically, the research ab out small_scale spatial structure of vegetation should focus on plants, make cer tain the adequate scale and adopt correct spatial statistical methods; 3) The pr actical implications of small_scale spatial structure for degraded ecosystems sh ould be highly taken into account; 4) Integration of whole community characteris tics should begin with local patterns on small scales; and 5) Small_scale spatia l structure should be combined with traditional mean_field theory in order to de eply explore plant community dynamics.

PROGRESS AND PROSPECTS IN RESEARCH OF AN EXOTIC INVASIVE SPECIES, EUPATORIUM ADENOPHORUM
LU Ping, SANG Wei-Guo, MA Ke-Ping
Chin J Plan Ecolo. 2005, 29 (6):  1029-1037.  doi:10.17521/cjpe.2005.0128
Abstract ( 6801 )   PDF (897KB) ( 1580 )
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INFLUENCE OF METHANOL ELUATES FRACTIONATED FROM MACADAMIA INTEGRIFOLIAROOTS ON SPORE GERMINATION AND HYPHAL GROWTH OF AM FUNGI
LIU Jian-Fu, YANG Dao-Mao, OUYANG Ming-An, WANG Li-Na, ZHANG Yong, ZENG Ming
Chin J Plan Ecolo. 2005, 29 (6):  1038-1042.  doi:10.17521/cjpe.2005.0132
Abstract ( 3030 )   PDF (490KB) ( 845 )
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Macadamia integrifoliaoriginated from Australia where it grows in the rainforests of the eastern coastal areas of the Northern Rivers district of New South Wales and South_East Queensland. The Macadamiatree belongs to Proteaceae. The Macadamiawas in fact the only native Australian plant ever developed to a commercial food crop. Arbuscular mycorrhizal fungi (AMF) form symbiotic associations with the roots of approximately 90% of terrestrial plant species. These fungi are an important component of ecosystems, and the diversity of the AMF could largely influence plant biodiversity, ecosystem variability and productivity.  We examined the role of M. integrifolia root exudates in stimulating the germination and growth of AMF. In September 2003, 100 g of M. integrifolia roots were sampled, dried and crushed. The roots were then extracted for two hours in a 70% methanol solution, stirred in 80 ℃ water and filtered. The extract was diluted to 20%, 40%, 60%, 80% and 100% with methanol. The AMF cultures were sterilized, and the spores of Gornas mosseae and Gigaspora margarita were inoculated and cultured at 25 ℃ in the dark for 20 days. The number of spores that germinated was counted and the length of the mycelium measured. When the concentration of the extract was diluted by 60% methanol, spore germination of Gornas mosseae and Gigaspora margarita reached maximum levels of 81.7% and 76.0%, respectively. At higher extract dilution levels, spore germination decreased, and at 100% dilution, spore germination was lower than 65%. The mycelium reached maximum lengths when the extract was diluted by 60%. The length of Gornas mosseaewas 31.2 mm and Gigaspora margarita was 28.0 mm. Mycelium growth declined when the extract dilution increased, especially at 100% dilution. At lower dilutions of 20%, the growth of Gornas mosseae appeared to be stimulated but no effect on Gigas poramargarita growth was observed. At the zero percent dilution, the promotion of mycelium growth was not observed. The concentration of flavones in the extract was the greatest in the 60% methanol dilution (19.26%) but was lower at lower dilutions and only 2.56% in the zero percent dilution. Flavone concentrations also decreased at higher dilutions and the content of flavones was lower than 80% at 100% dilution. There were significant positive correlations (correlation coefficient > 0.95) between the concentration of flavones in the extract and spore germination and mycelium growth of AMF.

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