Table of Content
Volume 28 Issue 4
12 April 2004

Research Articles
TENTATIVE CLASSIFICATION SCHEME OF EVERGREEN BROAD-LEAVED FORESTS OF CHINA
SONG Yong-Chang
Chin J Plan Ecolo. 2004, 28 (4):  435-448.  doi:10.17521/cjpe.2004.0061
Abstract ( 2093 )   PDF (479KB) ( 1342 )
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Vegetation classification is a highly complex and very contentious issue in the vegetation science. Up to now, there is no common classification system that is accepted by all vegetation scientists. The evergreen broad-leaved forests (EBLFs) is only next in complexity to tropical rain forests. Human activities have altered these forests tremendously, and there are many transitional communities which make their classification even more challenging. The classification of EBLFs of China has undergone many changes over the years. In the 1950s, we learned from the Russian school; in the 1960s, the concept of “importance value" and methods from the Wisconsin school were introduced into the study of EBLFs; additionally, the theory and method of the Braun-Blanquet school were used in th e study on the Cyclobalanopsis glaucoides forest. In the 1980s the authors of “Vegetation of China" (1980) published a principle system of vegetation classification for China which emphasized the use of “diagnostic species" in classifying the “formation" and “association" levels of vegetation in the south region. However, owing to limited resources, this principle was never adopted. Based on the previous classification schemes a new classification system including “association", “formation", “formation group", “vegetation subtype" and “vegetation type" was formalized in this paper. The high-rank units of classification are based on eco-physiognomy, while the median and lower units are based on species composition. At the same time, the role of dominant species and diagnostic species was considered. According to above guiding principles, the EBLFs of China were divided into 3 vegetation types, 8 vegetation subtypes, 14 formation groups and 53 formations. Each classification type occupied a specific geographical region and specific environmental conditions.
TWENTY YEARS OF LITTER FALL DYNAMICS IN SUBTROPICAL EVERGREEN BROAD-LEAVED FORESTS AT THE DINGHUSHAN FOREST ECOSYSTEM RESEARCH STATION
GUAN Li-Li, ZHOU Guo-Yi, ZHANG De-Qiang, LIU Ju-Xiu, ZHANG Qian-Mei
Chin J Plan Ecolo. 2004, 28 (4):  449-456.  doi:10.17521/cjpe.2004.0062
Abstract ( 2194 )   PDF (316KB) ( 1004 )
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In this paper, we summarize 20 years of observations and measurements on the production, composition, and seasonal dynamics of litter and leaf litter production of dominant species in the southern subtropical evergreen broad-leaved forests at the Dinghushan Forest Ecosystem Research Station. Annual litter production ranged from 6.39 t·hm-2 to 11.04 t·hm-2 with an average of 8.45 t·hm-2. The variation in the annual litter fall was remarkable. Total litter production decreased over the past 20 years reflecting changes in the compositional characteristics and successional stages of the forest. There were two litter fall peaks each year: one at the beginning of the rainy season (April and May) and the other at the end of the rainy season (August and September). The different components of litter production showed a consistent annual temporal sequence in the following order: leaves; flowers and other mixed-materials; branches. The mean annual leaf litter production of Castanopsis chinensis, Schima superba, Cryptocarya chinensis and Cryptocarya concinna was 1.86, 0.50, 0.26 and 0.40 t·hm-2, respectively, which accounted for about 70% of the total leaf litter production. Leaf litter production of the dominant species greatly influenced the dynamics of total litter production, and, to some degree, the dynamics of litter production reflected changes in the forest biomass and community composition over the past 20 years.

LEAF LITTER DECOMPOSITION OF COMMEN TREES IN TIANTONGWANG
WANG Xi-Hua, HUANG Jian-Jun, YAN En-Rong
Chin J Plan Ecolo. 2004, 28 (4):  457-467.  doi:10.17521/cjpe.2004.0063
Abstract ( 2438 )   PDF (473KB) ( 1134 )
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Leaf litter decomposition is a critical pathway of nutrient cycling in forests, and the spatial and temporal dynamics of leaf litter decomposition as well as the factors affecting decomposition, such as litter quality and climate, have been studied intensively. More recently, the possible consequences of global environmental change on litter decomposition have received considerable attention. However, little research on the factors influencing litter decomposition has been conducted in the broad-leaved evergreen forests of Eastern China. Therefore, we studied leaf litter decomposition and nutrient release dynamics of selected plant species in the subtropical broad-leaved evergreen forests at Tiantong in Zhejiang Province by using a litter bag method. Results showed that litter mass and N and P concentrations in the decomposing leaf litter changed greatly with time. N and P concentrations increased in the initial decomposition stages for many species. Nutrient release or accumulation from the decomposing leaf litter was not correlated with the initial nutrient content of the leaf litter. Yearly decay rates of leaf litter were significantly correlated with the initial leaf litter nitrogen content but not with phosphorus content, and species with high nitrogen contents exhibited relatively faster decomposition rates. In addition, leaf area had little effect on decomposition, but there was a strong positive correlation between yearly decomposition rates and specific leaf area. Based on decomposition models, yearly decay rate ranged from 0.558 in Litsea elongata to 6.280 in L. cubeba. For most selected plant species, 95% decomposition rates ranged from 1-4 years, with an average of 2.45 years. Leaf litter composed of mixed species had a significant effect on decomposition patterns by inhibiting decomposition rates initially but accelerating rates during later stages. Dry weight loss of leaf litter increased with an increase of the number of species in the leaf litter mixture. Also, decomposition was accelerated by an increase in plant functional groups in the litter, but this effect gradually decreased as decomposition proceeded. The characteristics of species mix were the most important factor influencing decomposition. Overall, leaf litter decomposition is related to the initial quality of leaf litter, which includes structure and nutrient content of leaf litter, and the species composition of the mixed leaf litter.
THE EFFECTS OF SPATIAL HETEROGENEITY OF UNDERSTOREY LIGHT
You-Zhi, WANG Zheng-Quan, GU Jia-Cun
Chin J Plan Ecolo. 2004, 28 (4):  468-475.  doi:10.17521/cjpe.2004.0064
Abstract ( 2424 )   PDF (328KB) ( 1074 )
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Understory light availability is a major environmental factor affecting the growth and survival of many forest species. The spatial heterogeneity of light availability most likely influences forest regeneration dynamics and determines stand-level spatial patterns of seedling regeneration. However, the implications of heterogeneity in understory light availability on regeneration patterns have not been carefully investigated. We examined spatial patterns of understory light availability and Manchurian ash (Fraxinus mandshurica) seedlings within two experimental plots in secondary hardwood forests at the Silviculture Research Station of Northeast Forestry University, northeastern China (127°30′-127°34′E，45°21′-45°25′N). Our objectives were to compare spatial patterns of understory light with seedling distribution patterns to determine whether patterns of seedling regeneration were linked to spatial patterns of understory light availability. Understory light availability was measured at 297 sample points in a regular grid-based spatial sample design. The minimum interval distance between measurements was 0.5 m and the maximum interval distance was 30 m. Light levels were measured at a height of 70 cm using an LAI-2000 Plant Canopy Analyzer at each point. Seedlings were counted at 193 sown grid subplots (20 cm×20 cm) in each plot (30 m×30 m) during the growing season. Semivariograms from geostatistical analysis methods were used to quantify the spatial variations of understory light availability and seedling distributions. We also examined the statistical relationships between light availability and seedling regeneration at different spatial scales. The results demonstrated that there was significant spatial patterning of both understory light availability and seedling regeneration. The transmittance of light to the ground within stands was 40.2%-52.3% after the growing season and only 4.2%-4.6% during the growing season. According to theoretical model parameters, understory light availability was significantly spatially autocorrelated over scales at 10.9-12.4 m, and spatially structured variance accounted for 62.5%-78.2%. Seedling density in each subplot differed significantly among microsites with significantly higher numbers of seedlings in high-light microsites than in low-light microsites. Seedling regeneration showed strong spatial patterning. Patterns of seedling regeneration were strongly linked to spatial heterogeneity of light availability. In stands with more spatially heterogeneous light availability patterns had more complex patterns of seedling distribution patterns and were spatially autocorrelated at smaller scales (2.12-6.97 m). In stands with lower complexity of light spatial distribution patterns, the patterns of seedling regeneration were relatively simple. Regeneration patterns were significantly spatially autocorrelated (>83%) at slightly larger scales (30 m) with little random variation (<17%). Our results confirmed that the spatial heterogeneity of understory light availability is a critical factor influencing the performance of seedling regeneration of Manchurian ash.
POPULATION CHARACTERISTICS OF YEW (TAXUS CUSPIDATA) IN THE MULING YEW NATURE RESERVE, HEILONGJIANG PROVINCE
ZHOU Zhi-Qiang, LIU Tong, YUAN Ji-Lian
Chin J Plan Ecolo. 2004, 28 (4):  476-482.  doi:10.17521/cjpe.2004.0065
Abstract ( 2179 )   PDF (272KB) ( 1094 )
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Based on a field investigation that consisted of 74 sample zones across a total sample area of 436.872 hm2, we describe the population characteristics of yew (Taxus cuspidata), and the relationship between its distribution and site factors. There were a total of 179 631 individual yew plants in the 34 544 hm2 nature reserve, a very large population. The population distribution was correlated to elevation, slope position, aspect and slope gradient. Altitudes between 700 and 800 m had the greatest number of plants and thus the preferred habitat for natural yew populations. More individuals were found on shady slopes than sunny slopes, and more individuals at the upper and mid-slope positions than at the toe of the slope. There were more yew individuals located on slopes with a slope gradient <15° and numbers decreased substantially with increasing slope gradient.
WATER RELATIONS AND ACTIVITY OF CELL DEFENSE ENZYMES TO WATER STRESS IN SEEDLING LEAVES OF DIFFERENT PROVENANCES OF QUERCUS VARIABILIS
ZHANG Wen-Hui, DUAN Bao-Li, ZHOU Jian-Yun, LIU Xiang-Jun
Chin J Plan Ecolo. 2004, 28 (4):  483-490.  doi:10.17521/cjpe.2004.0066
Abstract ( 2081 )   PDF (426KB) ( 1112 )
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Quercus variabilis is an important economic tree because it not only provides timber and firewood for local farmers, but also is used to produce cork, tannin extract, and edible fungi for commercial use. It is distributed in 22 provinces in China from sub-tropical to temperate regions and at altitudes that range from 50 to 2 000 m. It also plays an important role in the conservation of water and soil. However, little is known about the physiological tolerance mechanisms of drought stress. In order to discriminate among the drought-tolerant characteristics of different Q. variabilis provenances, we conducted a drought stress experiment using potted 3-year old seedlings of four provenances from different regions. Changes in superoxide dismutas activity (SOD), catalase activity (CAT), malondial dehyde content (MDA), electrolyte leakage rate, osmotic potential at saturation (ψπsat), osmotic potential at turgor loss point (Wπtlp), water saturation deficit at turgor loss point (WSDtlp), and modulus of elasticity (εmax) of leaves were measured and analysed as soil drought conditions developed. Under similar conditions of soil drought stress, provenance 4 (from Huanglong Mt. in the loess plateau) and provenance 3 (from the north slope of Qinling Mt.) revealed more antioxidant ability than provenance 2 (from Funiu Mt.) and provenance 1 (from the north slope of Bashan Mt.). During the development of soil drought stress, the MDA content and electrolyte leakage rate were enhanced to different extents in the four provenances; the greatest change was provenance 1 and the lowest change in provenance 4. The activities of SOD and CAT increased at the beginning of stress conditions but decreased at the end of the drought stress period. All provenances had the ability to maintain turgor and osmotic adjustment throughout the experiment but distinct differences among provenances were apparent: provenance 4 and provenance 3 had greater turgor maintenance and osmotic adjustment while provenance 1 performed the worst. Using Fuzzy synthetic evaluation of the parameters of water relations and the activities of two cell defense enzymes to water stress in leaves, the level of drought-tolerance among the four provenances decreased in the following order: provenance 4> provenance 3> provenance 2> provenance 1. Among the four provenances, provenance 4 was significantly different from the provenance 2 and provenance 1 (p<0.05). Differences in the drought tolerant characteristics of the four provinces resulted from long-term evolution and adaptation to their particular environmental conditions and are most likely genetically controlled. Therefore, these characteristics should be used for selecting and identifying drought tolerant provenances for use in forest management and restoration of Q. variabilis in arid regions.

SPATIAL DISTRIBUTION OF GRASSLAND BIOMASS IN CHINA
PIAO Shi-Long, FANG Jing-Yun, HE Jin-Sheng, XIAO Yu
Chin J Plan Ecolo. 2004, 28 (4):  491-498.  doi:10.17521/cjpe.2004.0067
Abstract ( 3106 )   PDF (274KB) ( 2294 )
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Estimating carbon storage in terrestrial ecosystems has been a central focus of research over the past two decades because of its importance to terrestrial carbon cycles and ecosystem processes. As one of the most widespread ecosystem types, China’s grasslands play an important role in global change research. The grasslands in China, which are distributed primarily throughout the temperate regions and on the Tibetan Plateau, were classified into 17 community types. In the present study, a statistical model was established to estimate grassland biomass and its geographical distribution in China based on a grassland inventory data set and remote sensing data (Normalized Difference Vegetation Index) using GIS and RS techniques. We found that there was a significant correlation between aboveground biomass density and the maximum annual NDVI when expressed as a power function (R2=0.71, p<0.001). The aboveground biomass was estimated to be 146.16 TgC (1Tg=1012 g) and belowground biomass was estimated as 898.60 TgC (6.15 times of the above biomass) for a total biomass of 1 044.76 TgC. This value accounts for about 2.1%-3.7% of the world’s grassland biomass. The grassland biomass is distributed primarily in the arid and semiarid regions of Northern China and the Qinghai-Xizang Plateau. The average biomass density of China’s grasslands was 315.24 gC·m-2, smaller than the world average. The aboveground biomass density decreases from southeastern China toward the northwest corresponding with changes in precipitation and temperature. Furthermore, aboveground biomass density reached the lowest levels at 1 350 m elevation and peak levels at 3 750 m above sea level which most likely is related to China’s three-step topographical background. The ratio of total biomass of grassland to forest biomass in China is 1/4, much higher than that of the world, suggesting a greater contribution of grasslands to China’s carbon pool.

RELATIONSHIPS BETWEEN CLIMATE CHANGE AND VEGETATION IN BEIJING USING REMOTE SENSED DATA AND PHENOLOGICAL DATA
ZHANG Xue-Xia, GE Quan-Sheng, ZHENG Jing-Yun
Chin J Plan Ecolo. 2004, 28 (4):  499-506.  doi:10.17521/cjpe.2004.0068
Abstract ( 2659 )   PDF (311KB) ( 1009 )
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Vegetation is the most active component of natural ecosystems and is highly responsive to many factors such as atmospheric conditions, water availability, and soil factors; thus, vegetation is a sensitive indicator of environmental change in terrestrial ecosystems. With growing concerns on global change and global warming, more and more scholars are focusing their research on understanding how plants respond to environmental change. Based on climate data collected from 1951 to 2000, NOAA/AVHRR NDVI data from 1982 to 2000 and flowering phenophase data for Prunus davidiana collected from 1951 to 2000 in Beijing, relationships between climatic factors and vegetation at different time scales were investigated. The purpose of the study was to assess the impacts of climate change on vegetation and feedbacks between land cover changes and climate to better understand the effects of global change. Time lag cross-correlation analyses were used to examine time lags in climatic factors and NDVI, and P． davidiana flowering phenophase. Our statistical analyses indicated that at different temporal scales different relationships between climate factors and growing conditions of plants were found. On an annual scale, there were no differences between actual temperature or effective temperature and actual precipitation or effective precipitation and their relationship to vegetation. Relationships between effective temperature, effective precipitation and vegetation were the highest when examined at the scale of a month. The highest correlation between NDVI and temperature occurred when the time lag was zero. At the scale of a year, the influencing threshold was about one year while at the scale of a month it was about one month. Land surface temperature in Beijing had a statistically more meaningful relationship with NDVI and the flowering phenophase than with precipitation. At the scale of a year, the influencing threshold between climate factors and plant phenophase was two years, whereas at the scale of a month, the influencing threshold between actual temperature and plant phenophase was about one month.
RESPONSE OF LEYMUS CHINENSIS GRASSLAND VEGETATION IN INNER MONGOLIA TO TEMPERATURE CHANGE
WANG Yu-Hui, ZHOU Guang-Sheng
Chin J Plan Ecolo. 2004, 28 (4):  507-514.  doi:10.17521/cjpe.2004.0069
Abstract ( 2477 )   PDF (322KB) ( 800 )
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Global temperatures are increasing, and, in particular, global minimum temperatures are increasing faster than maximum temperatures. Because temperature is a key factor hat controls the growth and distribution of vegetation, and there is no a priori reason to assume that ecosystems will respond similarly to changes in minimum and maximum temperatures, it is very important to explore the ecological consequences of global warming on terrestrial communities. The Leymus chinensis grassland is a dominant ecosystem of Inner Mongolia, and this region is very vulnerable to global climate change. We analyzed a long term climate and vegetation data base (1981-1994) for Inner Mongolia to examine the characteristics and the ecological consequences of temperature changes on Leymus chinensis grasslands. The results showed that temperatures increased and minimum temperatures, especially winter minimum temperatures, increased faster than maximum and average temperatures. There were no significant relationships between winter minimum temperatures and diversity indices (Simpson index and Shannon-wiener index), species saturation, and aboveground net primary productivity (ANPP) at the community scale. At the species level, the importance value and ANPP of most species had no significant relationship with winter minimum temperatures, except for Agropyron michnoi, Heteropappus altaicus and Carex duriuscula, all of which showed significant negative relationships. Because these are important species in this grassland community, the results suggest that the structure and function of the L. chinensis grassland community could be altered if winter minimum temperatures continue to increase. Thus, the identification of key elements of temperature change is very important for understanding and predicting the impacts of global warming to L. chinensis grassland communities.
VARIATIONS IN FOLIAR CARBON ISOTOPE COMPOSITION AND ADAPTIVE STRATEGIES OF CAREX KORSHINSKYI ALONG A SOIL MOISTURE GRADIENT
CHEN Shi-Ping, BAI Yong-Fei, HAN Xing-Guo, AN Ji-Lin, GUO Fu-Cun
Chin J Plan Ecolo. 2004, 28 (4):  515-522.  doi:10.17521/cjpe.2004.0070
Abstract ( 2079 )   PDF (382KB) ( 1158 )
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The carbon isotope composition (δ13C value) of plants is a useful index for assessing intrinsic water use efficiency (WUE) and can also provide information on long term WUE, because the δ13C value integrates photosynthetic activity throughout the entire life span of the leaf tissue. Water is the limiting environmental factor for growth and reproduction of steppe plants in the Xilin River Basin, Inner Mongolia. Carex korshinskyi, a perennial forb, is widely distributed throughout the Xilin River Basin and shows strong adaptive characteristics enabling it to survive in habitats with widely varying nutrient and water conditions. In this study, six plant communities were selected which differed in floristic composition and soil water status but had similar climatic conditions, such as temperature and precipitation. Foliar δ13C values, leaf water content (LWC) and population characteristics (including height, density and aboveground biomass) of C. korshinskyi were measured in each of the six communities. Our objectives were to study the variations in foliar δ13C values, LWC and population characteristics of C. korshinskyi along a soil water gradient to better understand the adaptive strategies of C. korshinskyi to water stress. Results showed that: 1) There were significant variations in foliar δ13C values of C. korshinskyi in different habitats (changing range 1.8‰). The foliar δ13C values of different C. korshinskyi populations tended to increase with decreasing soil water content (SWC). A significant negative correlation was found between foliar δ13C values and SWC in different soil layers, indicating that C. korshinskyi populations could change WUE in response to water availability. 2) A significantly negative correlation was found between foliar δ13C values and LWC of C. korshinskyi. Only small variations in LWC were found among the six different C. korshinskyi populations indicating that the WUE of C. korshinskyi was sensitive to changes in leaf water status. 3) There were significant differences in height, density, aboveground biomass and frequency of occurrence among C. korshinskyi communities along the soil water gradient. The C. korshinskyi populations with higher δ13C values had higher occurrences in the plant community and contributed more to total aboveground biomass and community productivity. Our results suggest that C. korshinskyi can adjust its water use pattern (such as enhancing WUE) to adapt to habitats with different soil water availability increasing its competitive ability across a wide range of habitats.

COMPARISON BETWEEN STANDARDIZED PRECIPITATION INDEX AND Z-INDEX IN CHINA
YUAN Wen-Ping, ZHOU Guang-Sheng
Chin J Plan Ecolo. 2004, 28 (4):  523-529.  doi:10.17521/cjpe.2004.0071
Abstract ( 2851 )   PDF (307KB) ( 2251 )
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Droughts are the world’s costliest natural disasters, causing an estimated $6-$8 billion in global damages annually and affecting more people than any other form of natural disaster. Given the consequences and pervasiveness of droughts, it is important to assess the specialized indices that are used to assess drought severity. The standardized precipitation index (SPI) has several characteristics that are an improvement over previous indices, including its simplicity and temporal flexibility that allow it to examine both short term and long term drought conditions. Computation of the SPI involves fitting a gamma probability density function to a given time series of monthly precipitation totals for a weather station. The resulting parameters are then used to find the probability of a particular precipitation event over a given time scale. This probability is then converted to the standard normal random variable SPI index value. In this article, 1-month SPI are calculated and compared with the Z-index, the most widely used index in China. The results demonstrated that 1-month SPI calculated for 7 observational stations are greatly consistent with Zindex, but that the SPI rarely relates to distributing on precipitation, avoiding some of the irregularities associated with the Z-index. Thus, the SPI is superior to the Z-index in its application. We also investigated drought and flood events from 1951-1995 for Beijing in greater detail. By using the 24-month SPI (SPI24), three well-defined drought and flood events were identified from the data series. In general, the same drought and flood events were observed using the 12-month SPI (SPI12) as the SPI24, although there were some interruptions where the SPI12 values approached zero or became negative for short periods. For 3-month periods (SPI3), the SPI values frequently fell above and below zero. These results highlight the SPI characteristics at different time scales. As the time scale increases from 1 to 24 months, the SPI responds more slowly to short-term precipitation variation, and the cycles of positive (wet conditions) and negative (drought) SPI values become more visible. The possibility of calculating the SPI for different time scales enhances its analysis capacity, since it allows the estimation of different antecedent conditions in the soils. Whereas the shortest scales (1 to 3 months) quantifies superficial soil water, which bears a direct significance for agriculture, the longest accumulation scales (12 to 24 months) indicate the state of subsoil moisture as well as other surface and subsurface water resources. The joint consideration of different SPI scales in the analysis contributed to a satisfactory explanation of risk conditions before each flood event reported. These results indicate that the SPI is an effective index for assessing drought conditions at different time scales and should be adopted for use in China.
THE MINERALIZATION OF SOIL ORGANIC CARBON UNDER DIFFERENT LAND USES IN THE LIUPAN MOUNTAIN FOREST ZONE
WU Jian-Guo, ZHANG Xiao-Quan, XU De-Ying
Chin J Plan Ecolo. 2004, 28 (4):  530-538.  doi:10.17521/cjpe.2004.0072
Abstract ( 2055 )   PDF (334KB) ( 1494 )
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Soil organic carbon is a large component of the global carbon cycle and the influence of land-use changes on SOC pools can significantly affect atmospheric CO2 concentrations. The response of soil carbon mineralization rates to changes in land-use type is the crux for understanding the influence of land-use changes on SOC. Over the last several centuries, extensive areas of the native vegetation of the Liupan Mountain forest zone has been converted to cropland or rangeland and, over the last several decades, some of these former croplands and rangelands have returned to forests. However, the impacts of these land-use changes on the SOC are unclear. In order to assess the impacts of land-use change on LSC, we compared the LSC concentrations in adjacent plots of natural secondary forest (i.e. dominated by Querces liaotungensis, Populus davidiana, or brushwood), cropland, rangeland, and 13, 18 and 25-year old larch (Larix principis-rupprechtii) plantations that were planted on former croplands and rangelands. To determine the rate of SOC mineralization, soils were collected from each of these land use types, incubated in the laboratory at 30 ℃ with a constant moisture of 60% field water capacity over 180 days and the amount of cumulative CO2-C released over 180 days was compared among the different land use types. It was found that the mean concentration (g CO2-C·kg-1 soil·180 d-1) of SOC mineralization in the 0-110 cm soil layer was 155% and 17% higher under the plantation than under cropland and rangeland, respectively, and was 65% lower under cropland and 23% lower under rangeland as compared to the natural secondary forest. The change in the concentration of cumulative CO2-C released by SOC mineralization with soil depth under the natural secondary forest and plantation was greater than under the cropland or rangeland. The difference in the cumulative CO2-C released by SOC mineralization between natural secondary forest and cropland or rangeland was greater in 0-40 cm depth than the 50-110 cm soil layer, but the difference between the plantation and cropland or rangeland was greater in 0-70 cm than 70-110 cm soil layer. The fraction of cumulative CO2-C mineralized as a percent of total SOC in the 0-110 cm soil layer was 12% lower under cropland than under the natural secondary forest, 29% higher under plantation than cropland, 18% and 9% higher under rangeland than natural secondary forest and plantation, respectively. There were no significant differences in the change of the fraction of cumulative CO2-C released by SOC mineralization with soil depth among the different land uses. The difference between the fraction of cumulative CO2-C released by SOC mineralization from the natural secondary forest and cropland or rangeland was greatest in the 0-40 cm soil layer, whereas this difference between plantation and cropland or rangeland was greatest in the 0-50 cm soil layer. In general, the concentration of cumulative CO2-C released by SOC mineralization was greater than the fraction among different land uses as well with changes with soil depth. These differences were attributed to differences in the inputs of SOC, stabilization, and quality of soil organic matter among different land uses. Overall, our results suggest that the rate of SOC mineralization will decline with conversion from natural forests to cropland or rangeland and will increase following afforestion of former croplands or rangelands. In addition, the distribution of cumulative CO2-C released by SOC mineralization in different soil layers will also change with the magnitude of change greater in concentration than the fraction following changes in land use.
PHOTOSYNTHESIS AND NITROGEN UTILIZATION IN LEAVES OF CINNAMOMUM BURMANNI GROWN UNDER ELEVATED ATMOSPHERIC NH3 CONCENTRATIONS AND SUPPLIED WITH DIFFERENT FORMS OF SOIL N
SUN Gu-Chou, ZHAO Ping, CAI Xi-An, ZENG Xiao-Ping, RAO Xing-Quan
Chin J Plan Ecolo. 2004, 28 (4):  539-546.  doi:10.17521/cjpe.2004.0073
Abstract ( 2194 )   PDF (357KB) ( 855 )
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We investigated the effects of different forms of soil nitrogen additions (NO－3N, NH+4N or NH4NO3N) and exposure to elevated atmospheric NH3 concentrations on photosynthesis, nitrogen utilization and nitrogen allocation in photosynthetic components in leaves of Cinnamomum burmanni. The results showed that maximum rates of carboxylation (Vcmax) and maximum rates of potential electron transport (Jmax) were achieved in plants grown with additions of NO－3N and under elevated atmospheric NH3 concentrations compared to plants growing under ambient conditions. Both Jmax and Vcmax declined in plants supplied with NH+4N or NH4NO3N and grown under elevated atmospheric NH3. Regardless of the different forms of nitrogen supply, leaf nitrogen content on an area basis (Na) significantly increased under elevated atmospheric NH3 concentrations (p<0.05). Thylakoid nitrogen (NT), Rubisco nitrogen (NR) and nitrogen associated with electron transport (NE) increased significantly in plants supplied with NO3-N and exposed to the elevated atmospheric NH3 when compared to plants grown under ambient condition (p<0.05); however, Na, NT, NR and NE all decreased in plants supplied with NH+4N or NH4NO3N. These results suggest that increased atmospheric NH3 promotes the utilization of nitrogen for the synthesis of photosynthetic components, but inhibits the partitioning of nitrogen to NT, NR, and NE in plants supplied with NH+4N or NH4NO3N. The organic nitrogen content per unit dry mass increased in plants that were supplied with NO－3N or NH4NO3N (but not NH+4N) when exposed to increased atmospheric concentrations of NH3. The soluble protein nitrogen content also increased in plants grown with NO－3N additions but not in plants grown with additions of NH+4N. The results suggest that increased atmospheric NH3 concentration enhances nitrogen absorption and utilization and promotes photosynthesis in plants supplied with NO－3N additions but inhibits photosynthesis and nitrogen in plants supplied with NH+4N or NH4NO3N.

THE EFFECT OF DIFFERENT LEVELS OF POTASSIUM NUTRITION ON THE DIURNAL VARIATION OF PHOTOSYNTHETIC RATES OF WHEAT FLAG LEAVES
TONG Guan-He
Chin J Plan Ecolo. 2004, 28 (4):  547-553.  doi:10.17521/cjpe.2004.0074
Abstract ( 2361 )   PDF (341KB) ( 1122 )
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A study on the effects of different levels of potassium nutrition on the diurnal variation of the photosynthetic rate of flag leaves of wheat (Triticum aestivum cv. Anlong 8903) planted in the fields showed that from flowering stage to middle grain filling stage (May 1-20), the potassium content in the plants and leaves increased with increasing levels of potassium nutrition. Potassium content in the plant and leaves reached maximum levels that were 2.7 times the control at application rates of 82.5 kg potassium·hm-2, whereas at higher application rates of 330 kg·hm-2, potassium levels were lower (about 10%-30％). During the course of grain filling, the potassium content of the plants increased but that of the leaves decreased. From flowering stage to middle grain filling stage, the diurnal variation of stomatal conductance and of net photosynthetic rate revealed two maxima at about 10∶00 and 15∶00 because of the strong intensity of sunlight, high temperature and relatively low humidity. The maximum at 10∶00 is higher than that at 15∶00, with a minimum at 14∶00. However, the diurnal variation of the intercellular CO2 concentration (Ci) showed a contrasting tendency with two minima at about 12∶00 and 15∶00, and the former was lower than the latter. The maximum Ci level between the two minima was most pronounced at flowering stage but less pronounced at the middle grain filling stage. The results showed that increasing the potassium nutrition in the soil can increase stomatal conductance and net photosynthetic rates, and reduce the loss of photosynthetic CO2 fixation caused by photosynthetic midday depression by 10％-37% thereby raising the wheat output. The correlation between potassium content and intercellular CO2 concentration was not significant. The results of this study indicate that potassium additions of 165 kg K2O·hm-2 is the most economically efficient and optimal strategy for increasing net photosynthetic rates and thus wheat yields.
EFFECTS OF DIFFERENT WATER IRRIGATION SCHEMES AFTER ANTHESIS ON QUALITY OF TWO GLUTEN WINTER WHEAT VARIETIES
PENG Yu, GUO Tian-Cai, JIANG Gao-Ming, WANG Chen-Yang, LI Yong-Geng, ZHANG Xue-Lin
Chin J Plan Ecolo. 2004, 28 (4):  554-561.  doi:10.17521/cjpe.2004.0075
Abstract ( 2271 )   PDF (318KB) ( 988 )
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The effects of different irrigation schemes in both the amount of water applied (45 mm water every time with maximum total 45-315 mm water) and the timing of water applications (7-28 days) after anthesis on the quality characteristics of the strong gluten wheat (Triticum aestivum) Yumai 34' and the soft gluten wheat Luoyang 8716' were studied in Zhengzhou and Luoyang experimental sites in Henan Province during the 1999-2001 growing seasons. All natural precipitation was excluded from the controlled experiment. The experiment included eight irrigation treatments: irrigating on the 7th day, the 14th day, the 21st day, the 28th day, the 7th day plus the 14th day, the 7th day plus the 21st day after anthesis and a treatment of irrigating on the 7th, 14th, 21th and 28th days after anthesis and one treatment with no irrigation after anthesis. We summarize the main results below. 1) The content of wet gluten and sed.value increased by 12%-17% under the treatment of no irrigation and 21%-35% under a single, late water application following anthesis. In irrigation treatments that consisted of two or more applications after anthesis, increases were very small. The general tendency was that the greater the amount of water applied, the smaller the value of wet gluten and sed. value. 2) In irrigation treatments that consisted of only one application following anthesis, quality indicators such as dough development time, stability time, and valorimeter value, all increased (the increase ranged from 12%-76% in different cultivars and treatments) when irrigation was late (21-28 days after anthesis). These quality indicators all decreased when there was too much irrigation water (>90 mm) or when applied more than one time. Soften degree became large when irrigation was high (>90 mm). 3) Comparing values between the two cultivars, those of Yumai 34' were larger than those of Luoyang 8716', including quality and yield. The variation coefficients of the strong gluten wheat Yumai 34' were larger than those of weak gluten wheat Luoyang 8716' which showed that traits of Yumai 34' changed easily under changing environmental conditions. Changes in the coefficients of water absorption and wet gluten were very small and appeared to be affected mainly by genetics with little environmental effect. The correlated coefficients among sed.value, development time, stability time, and valorimeter value were positive and significant, but correlations between soften degree and other quality items were negative but not significant. 4) Irrigation treatments that consisted of one application only after anthesis tended to produce lower yields, and the later the irrigation time, the lower the yields. In contrast, when the wheat was irrigated more than once, yields tended to increase and, in general, the more water applied, the greater the yields. Generally, under irrigation levels of 180-315 mm without natural precipitation, moderate increases in yield (5 792-8 161 kg•hm-2) were gained. Cultivar Yumai 34' has a greater yield potential under water conservation strategies whereas Luoyang 8716' could realize higher yields under sufficient water supply. Considering the quality, yields and the water use efficiency, irrigating on 7th day or 14th day after anthesis was suitable for strong gluten wheat cultivars like Yuami34 to get high yield and quality. For weak gluten wheat cultivars, such as Luoyang 8716', the best irrigation strategy was at least 2 application times after anthesis to improve yields and quality.

CONSERVATION BIOLOGY BASED ON THE SPATIAL ANALYSIS
JIANG Hong, MA Ke-Ping, ZHANG Yan-Li, ZHU Chun-Quan, James R. STRITTHOLT
Chin J Plan Ecolo. 2004, 28 (4):  562-578.  doi:10.17521/cjpe.2004.0076
Abstract ( 2730 )   PDF (2694KB) ( 1244 )
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The use of spatial analysis in conservation biology as a research tool has grown tremendously over the past decade and a half. Although conservation biologists and ecologists have recognized the potential of spatial information for informing conservation biology and policy for a long time, such as for studying changes and trends in populations and habitats, it has been only recently that spatial analysis has been incorporated into most conservation biology studies. Since the 1990s, conservation biology has developed quickly by the application of spatial analysis technologies. In this paper, we review the history, methodologies and applications of this tool, and the potential for growth and other applications by using some projects and works in which the authors were involved as examples. First, we discussed the use of spatially explicit data on biodiversity and its distribution, and the significance of using spatially explicit methods in conservation biology was summarized. We presented patterns of biodiversity at the global scale and country level, and discussed plant diversity centers and vascular plant family diversity as monitored by the World Conservation Monitor Center (WCMC). We also discussed the spatial distribution of four groups (plant, birds, fishes and molluscs) of endangered species in the United States. Mapping the spatial distribution of biodiversity is a useful comparative tool for analyzing the patterns, magnitude and extent of biodiversity, changes in spatial distributions at different temporal scales, understanding the relationships between populations and habitats, and for conservation by spatial overlap analysis as in GAP analysis. Second, we reviewed various conservation projects including Global Forest Watch of World Resource Institute, National GAP Analysis of United States, Roadless Area of Forest Service-USA, and Nature Audit of Canada. Also, some examples from the literature were used, such as a comparative study of plant diversity richness between East Asia and North America and the spatial analysis of biological invasions. The spatial analysis of patterns of biodiversity and habitats were discussed in the third part of this paper. During the last two decades, pattern-oriented ecology and conservation biology has made a lot progress, especially spatial pattern analyses, spatial statistics originating from geo-statistics, geographic information systems, spatially explicit model-based growth of individuals (grid), population theory based on patch analysis (e.g., metapopulations and source-sink models), and so on. The application of spatial pattern analysis in conservation biology was summarized by examining two conservation projects: the forest fragmentation analysis of the USA and late seral forests spatial pattern analysis in the Pacific Northwest, USA. We also presented the theory of “Matrix conservation” by Lindenmayer and Franklin, “Conserving Forest Biodiversity, A Comprehensive Multiscaled Approach”(2002). We agree with the authors of this new initiative that extends conservation efforts beyond nature reserves to integrated conservation strategies that balance conservation and development at landscape or regional scales. Lastly, models that are used widely in conservation biology, the spatially explicit model, process-based spatial model, agent-based spatial adaptation model (SWAM) and Dynamics Global Vegetation Model (DGVM), were discussed.This new branch of conservation, spatial conservation biology, has matured as a new discipline that contains a lot of spatial and information technology and may make more contributions to the global biodiversity conservation.

ECO-PHYSIOLOGICAL CHARACTERISTICS OF SEED GERMINATION OF LARIX CHINENSIS, A TIMBERLINE TREE
ZHANG Ling
Chin J Plan Ecolo. 2004, 28 (4):  579-583.  doi:10.17521/cjpe.2004.0077
Abstract ( 2492 )   PDF (239KB) ( 1061 )
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Larix chinensis is a timberline tree species on Mt. Taibai in the Qinling mountains. To better understand climatic and physiological processes that control timberline formation, the eco-physiological characteristics of L. chinensis seeds were investigated in the laboratory by exposing seeds to different treatments of illumination and temperature. The major results are summarized below. An alternating photoperiod of 12 h light∶12 h dark increased phytohormone levels of ABA and GA in imbibed seeds during germination. Under conditions of constant temperatures of 25 ℃ or 12 ℃, constant illumination had a positive affect on phytohormone levels of IAA in imbibed seeds. Under alternating temperatures of 25 ℃ for 12 h and 12 ℃ for 12 h, alternating illumination did not affect phytohormone contents of IAA. Changes in phytohormone levels of CTK showed an opposite response as IAA. Constant temperatures had a positive effect on phytohormone contents in imbibed seeds. Temperature was crucial for seed germination, and the rate of seed germination at a constant temperature of 25 ℃ was greater than at a constant temperature of 12 ℃. Alternating illumination (12 h light∶12 h dark) also had a strong, positive effect on seed germination. Otherwise the results showed that endogenous phytohormone levels were important for seed germination. The results indicated that temperature affected the germination rate and success of L. chinensis seeds, which is crucial for regeneration of L. chinensis, while illumination impacts were weak. Further studies are needed to better understand the underlying mechanisms of how temperature affects timberline formation on Mt. Taibai, Qinling mountains.
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