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Table of Content
    Volume 36 Issue 5
    01 May 2012

    The physiognomy of Carex muliensis swamp in June on the Riganqiao broad valley, Zoigê Plateau. The plants on the hummock were C. meyeriana and on hollow C. muliensis. Han et al. studied the impact of anthropogenic drainage on the interspecific relationship of plants and plant species diversity of the swamp vegetation in the area (Pages 411–419 of this issue). (Photographed by HAN Da-Yong)

      
    Research Articles
    Effects of phenological change on ecosystem productivity of temperate deciduous broadleaved forests in North America
    ZHAO Jing-Jing and LIU Liang-Yun
    Chin J Plan Ecolo. 2012, 36 (5):  363-371.  doi:10.3724/SP.J.1258.2012.00363
    Abstract ( 1437 )   PDF (501KB) ( 1734 )   Save
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    Aims Results of effects of phenological change on terrestrial ecosystem carbon budgets almost always lack comparability because of differences in data sources and time and spatial scales. Our objective was to determine how phenological change effects ecosystem productivity by analyzing annual  phenological change of two deciduous broad-leaved forests in North America based on four-class carbon flux data.
    Methods We designed a relative threshold method to extract the phenological parameters, including start of growing season (SOS), end of growing season (EOS) and growing season length (GSL) from four-class carbon flux data. The phenological parameters were linked to ecosystem productivity of North American deciduous broad-leaved forests (DBF) at Harvard Forest and the University of Michigan Biological Station.
    Important findings Prolonged GSL influences annual gross primary productivity (GPP), but not net ecosystem productivity (NEP) due to disturbance of  ecosystem respiration (RE). Advanced SOS has the most significant influence on the first half year’s GPP, with a correlation coefficient of 0.76 at Harvard Forest and 0.93 at the University of Michigan. Delayed EOS has little influence on annual GPP and NEP. Although increases of GPP and RE were observed with advanced SOS or delayed EOS, the relationship between phenology and NEP remains complicated due to the uncertainty of RE.

    Relationship between climatic factors and geographical distribution of spruce forests in China
    LI He, ZHANG Wei-Kang, and WANG Guo-Hong
    Chin J Plan Ecolo. 2012, 36 (5):  372-381.  doi:10.3724/SP.J.1258.2012.00372
    Abstract ( 1505 )   PDF (799KB) ( 1531 )   Save
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    Aims Our objective was to examine the relationship between climatic factors and geographical distribution of spruce forests in China.
    Methods We sampled 613 points within the geographical range of Chinese spruce forests, of which 235 points were at the upper altitudinal limit and 228 at the lower altitudinal limit. The elevation for each point was determined using Google Earth while climatic data were from the Chinese meteorological interpolation database. Linear regression, comparison of coefficient of variation (CV) and principal component analysis (PCA) were conducted for data analysis.
    Important findings Within the distribution range of Chinese spruce forests, mean values of mean annual air temperature (MAT), mean air temperature of the coldest month (MTCM), mean air temperature of the warmest month (MTWM), growing degree days on a 5 ℃ basis (GDD5) and on a 0 ℃ basis (GDD0), mean annual precipitation (MAP), soil moisture (SM) and aridity index (α) are 3.38 ℃, –9.75 ℃, 14.78 ℃, 1 227.83 ℃·d, 2 271.19 ℃·d, 712.23 mm, 80.02% and 0.50, respectively. Both the upper and lower limits of altitude were significantly correlated with each of the climatic factors. In terms of CV, MAT and MTCM are significantly higher than the other six climatic factors; however, no significant differences were detected among those six. In addition, GDD5 and GDD0 have higher loading on the first principal component, yet MAP and SM have higher loading on the second and third principal component. Major conclusions are that GDD0 and GDD5 are likely the key factors that influence the distribution of Chinese spruce forest, followed by MAP and SM.

    Seasonal dynamics in soil microbial biomass carbon and nitrogen and microbial quantity in a forest-alpine tundra ecotone, Eastern Qinghai-Tibetan Plateau, China
    LIU Yang, ZHANG Jian, YAN Bang-Guo, HUANG Xu, XU Zhen-Feng, and WU Fu-Zhong
    Chin J Plan Ecolo. 2012, 36 (5):  382-392.  doi:10.3724/SP.J.1258.2012.00382
    Abstract ( 1533 )   PDF (617KB) ( 1947 )   Save
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    Aims The forest-alpine tundra ecotone is one of the most conspicuous climate-driven ecological boundaries. However, dynamics of soil microbial biomass and quantity during different stages of the growing season in the ecotone remain unclear. Our objective was to understand the temporal and spatial variations of microbial biomass and quantity to explore the main drivers in the ecotone.
    Methods We collected soil samples in a forest-alpine tundra ecotone (dark-conifer forest, timberline, treeline, dense shrub, sparse shrub and alpine meadow) during early, mid and late growing season (EGS, MGS and LGS). The number and species composition of soil microorganisms were determined by means of the plate count method. Soil microbial biomass carbon (MBC) and nitrogen (MBN) were measured by the chloroform fumigation leaching method.
    Important findings Vegetation and seasonality significantly influence MBC, MBN and microbial community structure. Microbial biomass distribution among vegetation types was different in the three stages of the growing season. MBC above treeline was higher than below during EGS and MGS. The MBC of dark-conifer forest, timberline and treeline during LGS was significantly increased, and MBC differences among different vegetation types decreased. There were significant differences in measured soil microbial quantity between above- and below-treeline vegetation types; bacteria of dense shrub were highest among vegetation types. The amount of cultivated microorganisms was LGS>EGS>MGS. The ratio of MBC to MBN was the highest and the quantity of fungi increased largely late in the growing season. Statistical analysis showed that there were significant correlations between MBN and bacteria, fungi and actinomyces quantity, while only MBC and fungi quantity were significantly correlated (p < 0.05). Litter input and snow cover late in the growing season were external factors of microbial seasonal variation. Soil microbes and alpine plants competing for nitrogen may be internal factors. Plant nitrogen absorption early in the growing season and microorganisms’ nitrogen fixation late in the growing season enhanced the alpine ecosystem’s nitrogen fixation and utilization. Climate warming may extend the growing season of alpine plants, increasing the alpine soil microbial biomass, and accelerate the decomposition of soil organic matter, which may change soil carbon sequestration rates in the alpine ecosystem.

    A panbiogeographical explanation of the disjunct distribution of Fagus (Fagaceae) in the northern temperate zone
    WANG Li-Na, JIANG Xiao-Long, LEI Yun, and ZHANG Ming-Li
    Chin J Plan Ecolo. 2012, 36 (5):  393-402.  doi:10.3724/SP.J.1258.2012.00393
    Abstract ( 1177 )   PDF (537KB) ( 1186 )   Save
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    Aims Fagus L. has a disjunct distribution in the northern temperate zone, and there is a rich collection of Tertiary fossils from East Asia, Europe and North America. A panbiogeographical analysis of Fagus was undertaken to analyze the distribution pattern and evolution of the genus.
    Methods Distribution data of 581 records of 10 species were obtained from herbaria and monographs. Track analysis of panbiogeography and software MartiTrack were used for data analysis.
    Important findings Results indicated that there was no generalized track linking the distributions among China, Japan, Europe and North America or even between China and Japan, two adjacent areas in East Asia. Two regional generalized tracks were only found within China and Japan. These facts imply that the Fagus distribution cannot be explained by dispersal. Dispersal probably only occurred in limited and/or local regions and not as dispersal across the northern temperate zone in the Tertiary. The disjunction most likely resulted from (1) geological historical events such as Tethys westward movement, Qinghai-Tibet Plateau uplift, and Asian monsoon action, (2) climate change since the Tertiary, especially climate fluctuation during Quaternary glaciation, and (3) Fagus biological characteristics with regard to humid and temperate climate and annual rainfall.

    Effect of change of plant community composition along degradation gradients on water conditions in an alpine swamp wetland on the Qinghai-Tibetan Plateau of China
    LI Hong-Lin, XU Dang-Hui, and DU Guo-Zhen
    Chin J Plan Ecolo. 2012, 36 (5):  403-410.  doi:10.3724/SP.J.1258.2012.00403
    Abstract ( 1417 )   PDF (444KB) ( 1592 )   Save
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    Aims Wetlands degradation has drawn increased concern recently. Many researchers have reported the changes of plant communities and the relevant degradation mechanism of wetlands. However, few studies have explored the effects of plant community change on the water conditions of swamp meadow. Our objective was to investigate how change of alpine swamp meadow along degradation gradients affects its water conditions.
    Methods The study was conducted at the Research Station of Alpine Meadow and Wetland Ecosystems of Lanzhou University (Maqu Branch Station) (33°39′ N, 101°53′ E). We examined 47 species (15 families) selected from a degradation gradient of alpine swamp meadow. Net photosynthesis rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) were measured simultaneously with a portable gas exchange system LI-6400 (Li-COR, Lincoln, NE, USA). Measurements were performed from 9:00 am to 12:00 am on clear days in mid-July and mid-August, using photosynthetically active radiation (PAR) = 1 800 μmol·m–2·s–1 and flow = 750 μmol·s–1. The value of water use efficiency (WUE) was determined by Pn/Tr. We also investigated the cover of different functional groups (grasses, sedges, legumes and other forbs) at different degradation levels.
    Important findings The photosynthetic physiology traits were different among species and functional groups (p < 0.01). The sequence of Pn values of functional groups was grasses > sedges > legumes and other forbs, and WUE was sedges > grasses > legumes and other forbs. Species composition of the plant community had been changed due to the degradation of the swamp meadow. The abundance of forbs increased with degradation. WUE was lower for forbs than other functional groups, which implied that more soil water is transpired, exacerbating the drought condition of degraded meadows. Successful restoration requires protection and replenishment of the typical native species.

    Changes of plant species diversity and interspecific correlation in a degraded swamp community along drainage gradients on the Zoigê Plateau of China
    HAN Da-Yong, YANG Yong-Xing, and YANG Yang
    Chin J Plan Ecolo. 2012, 36 (5):  411-419.  doi:10.3724/SP.J.1258.2012.00411
    Abstract ( 1310 )   PDF (533KB) ( 1349 )   Save
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    Aims Plant species diversity and interspecific correlation are central topics in phytocoenology and biodiversity science. Our objective is to study the dynamics and interrelationships of plant species diversity and interspecific correlation in a Zoigê Plateau swamp community at different stages of degradation caused by anthropogenic drainage.
    Methods Spearman’s rank correlation and regression analysis were employed to analyze plant species diversity and interspecific correlation as well as their relationship.
    Important findings Along drainage gradients from relatively pristine swamp to extremely degraded swamp, different plant species had restricted ecological distributions. The total number of species, species richness per quadrat, Shannon-Wiener index and Whittaker index all increased monotonically, and the intensity of interspecific correlation increased in general. The proportion of species pairs with positive correlation increased gradually with increasing level of degradation. The proportion of species pairs with negative correlation showed an opposite trend. Shannon-Wiener index showed significant linear correlation with the proportion of species pairs with positive or negative correlation (p < 0.05), but Whittaker index showed no significant correlation (p > 0.05). The positive interspecific correlation and plant species diversity of the swamp community were promoted by habitat heterogeneity caused by anthropogenic drainage.

    Responses of PSII photochemistry efficiency and photosynthetic pigments of Saussurea superba to short-term UV-B-supplementation
    SHI Sheng-Bo, SHANG Yan-Xia, SHI Rui, and ZHANG Bo
    Chin J Plan Ecolo. 2012, 36 (5):  420-430.  doi:10.3724/SP.J.1258.2012.00420
    Abstract ( 1300 )   PDF (618KB) ( 1099 )   Save
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    Aims Native alpine plants that have grown and evolved on the Qinghai-Tibetan Plateau of China for a long time have developed a strong adaptation capacity for harsh environmental factors, such as low temperature, low air pressure, strong sunlight and solar UV-B radiation. The objective of this study was to determine the response of PSII photochemistry efficiency to short-term enhanced solar UV-B intensity in alpine plants. We examined whether UV-B-absorbing compounds were sufficiently efficient to protect the photosynthetic apparatus from UV-B photo-inactivation or photo-damage and evaluated the influence of UV-B radiation on photosynthetic pigments.
    Methods Field experiments were conducted during the 2008 and 2009 growing seasons in alpine Kobresia humilis meadow near Haibei Alpine Meadow Ecosystem Research Station (37°29′–37°45′ N, 101°12′–101°33′ E; alt. 3 200 m) using the native alpine plant Saussurea superba. Short-term UV-B-supplementation studies were performed over 5 days using UV-B-313 fluorescence lamps, which were filtered with a cellulose diacetate film to get increased UV-B treatment and a Mylar film as a control. Pulse-modulated in-vivo chlorophyll fluorescence was used to obtain rapid information of UV-B on photosynthetic processes. The 3-min dark-adapted maximum quantum efficiency of PSII photochemistry, F(v)/F(m), and PSII photochemistry efficiency were measured under natural sunlight. The contents of photosynthetic pigments and UV-B-absorbing compounds were analyzed based on leaf area unit.
    Important findings Although there was no significant difference, F(v)/F(m) showed a decreasing trend after short-term exposure to enhanced UV-B radiation in all measurements throughout the growing season. The reduction of the actual photochemical quantum efficiency and photochemical quenching as well as the increase of non-photochemical quenching in UV-B supplemented treatment, when compared to the control, indicated there was a decrease in PSII photochemistry efficiency and an increase in non-photochemical quenching. These phenomena indicated photo-inactivation or photo-damage of photosynthesis occurred in the PSII reaction center. The photosynthetic pigments showed a small decrease in the UV-B supplemented treatment, which may be related to the enhancement of photo-oxidation, a reduction of pigment synthesis and small variation of leaf thickness. The UV-B-absorbing compounds were not influenced by short-term enhancement of UV-B radiation when analyzed based on leaf area unit. This demonstrated that higher contents of UV-B-absorbing compounds in the epidermal layer of alpine plant S. superba were efficient for defense against UV-B radiation and stabilized for further enhancement of UV-B radiation

    Comparison of soil labile organic carbon in Chinese fir plantations and natural secondary forests in north subtropical areas of China
    LIU Rong-Jie, WU Ya-Cong, ZHANG Ying, LI Zheng-Cai, MA Shao-Jie, WANG Bin, and GERI Le-Tu
    Chin J Plan Ecolo. 2012, 36 (5):  431-437.  doi:10.3724/SP.J.1258.2012.00431
    Abstract ( 1444 )   PDF (2836KB) ( 1125 )   Save
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    Aims Our objective was to assess the effects of land use type conversion on the soil liable organic carbon pool in north subtropical areas of China.
    Methods We used reference land unit to collect soil samples in natural secondary forests and Chinese fir (Cunninghamia lanceolata) plantations and analyzed liable organic carbon in the depth of 0–60 cm.
    Important findings The contents of soil total organic carbon (TOC), easily-oxidized carbon (EOC), water-soluble organic carbon (WSOC) and light fraction organic matter (LFOM) in the soil of natural secondary forests were higher than those in Chinese fir plantations. The variations in amplitude for these four parameters were 19.0%–32.6%, 0.8%–30.3%, 3.8%–54.1% and 6.3%–38.6%, respectively. There were significant differences in the depth of 0–10 cm and 10–20 cm (p < 0.05) (WSOC was only significantly different in the depth of 0–10 cm). The ratios of WSOC and EOC to TOC content in Chinese fir plantations were higher than those in natural secondary forests. WSOC, EOC and LFOM were significantly related to TOC in the two forest stands, and the correlation
    coefficients of EOC and LFOM to TOC in natural secondary forests were higher than those in Chinese fir plantations. TOC, WSOC, EOC and LFOM were all significantly related to soil nutrients (total N, hydrolysis N and available K, Ca and Mg).

    Effects of doubled CO2 concentration on leaf photosynthesis, transpiration and water use efficiency of eight crop species
    WANG Jian-Lin, WEN Xue-Fa, ZHAO Feng-Hua, FANG Quan-Xiao, and YANG Xin-Min
    Chin J Plan Ecolo. 2012, 36 (5):  438-446.  doi:10.3724/SP.J.1258.2012.00438
    Abstract ( 1373 )   PDF (503KB) ( 1941 )   Save
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    Aims Our objective was to elucidate the response of crop photosynthesis, transpiration and water use efficiency to atmospheric CO2 concentration. This has great significance to predicting crop productivity and water-demand changes under increasing atmospheric CO2 concentration.
    Methods The photosynthesis rate, transpiration rate and water use efficiency of eight crops (soybean (Glycine max), sweet potato (Ipomoea batatas), peanut (Arachis hypogaea), rice (Oryza sativa), cotton (Gossypium hirsutum), corn (Zea mays), sorghum (Sorghum vulgare) and millet (Setaria italica)) were studied under natural CO2 concentration, doubled CO2 concentration and natural CO2 concentration after doubled CO2 conditions.
    Important findings Doubled CO2 concentration increased the photosynthesis rate and decreased the transpiration rate, and therefore water use efficiency was more significantly increased. The increase of water use efficiency showed greater dependence on the increase of photosynthesis rate than the decrease of transpiration rate. The variations of photosynthesis rate and water use efficiency of C3 crops were larger than those of C4 crops. The effect of photosynthesis rate of C3 crops on the water use efficiency was larger than that of C4 crops. The photosynthesis rate under natural CO2 concentration after doubled CO2 concentration was lower than that under natural CO2 concentration, but no significant difference was found for the transpiration rate. The photosynthetic capacity under natural CO2 concentration after doubled CO2 concentration was decreased mainly by the decreasing of some non-stomatal factors, including the protein content, activation levels and specific activity of the enzyme Rubisco.

    Effects of elevated CO2 concentration and N deposition on leaf element contents of major native tree species in southern subtropical China
    LI Yi-Yong, HUANG Wen-Juan, ZHAO Liang, FANG Xiong, and LIU Ju-Xiu
    Chin J Plan Ecolo. 2012, 36 (5):  447-455.  doi:10.3724/SP.J.1258.2012.00447
    Abstract ( 1265 )   PDF (477KB) ( 1259 )   Save
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    Aims The effects of elevated atmospheric CO2 concentration and N deposition on terrestrial ecosystems and plants are the focus of international ecological study. Changes of nutrient element content in plants induced by atmospheric CO2 concentration and/or N deposition directly affect the productivity of forest ecosystems; however, few studies have examined this in subtropical China. Our purpose is to study the effects of elevated CO2 and N deposition on leaf element contents of major native tree species in southern subtropical China.
    Methods Five tree species native in southern China were planted in model forest ecosystems. The species were exposed to elevated CO2 and N deposition in open top chambers in May 2005. The four treatments are: CN (elevated CO2 and high N deposition), CC (elevated CO2 and ambient N deposition), NN (high N deposition and ambient CO2) and CK (ambient CO2 and ambient N deposition). The elevated CO2 was (700 ± 20) μmol·mol–1, and the total amount of added NH4NO3-N was 100 kg N·hm–2·a–1. Leaves were harvested in January 2009, and elements in the leaves were measured.
    Important findings Compared to the control, elevated CO2 concentration significantly increased leaf-element contents in all species (p < 0.05) except for Ca content in Ormosia pinnata. High N deposition decreased K and Ca contents in the species. There was no interactive effect of high CO2 concentration and N deposition treatments on most leaf element contents. The interactive effect of high CO2 concentration and N deposition treatments only decreased leaf Ca contents in Schima superba and Syzygium hancei and leaf Mn contents in Schima superba, Syzygium hancei and Ormosia pinnata, as well as increased leaf P content in trees of Acmena acuminatissima.

    Changes of photosynthetic pigment and photosynthetic enzyme activity in stems of Phyllostachys pubescens during rapid growth stage after shooting
    WANG Xing-Xing, LIU Lin, ZHANG Jie, WANG Yu-Kui, WEN Guo-Sheng, GAO Rong-Fu, GAO Yan, and ZHANG Ru-Min
    Chin J Plan Ecolo. 2012, 36 (5):  456-462.  doi:10.3724/SP.J.1258.2012.00456
    Abstract ( 1254 )   PDF (468KB) ( 1502 )   Save
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    Aims Our objective was to reveal photosynthetic characters in Phyllostachys pubescens stems. We determined the distribution of chloroplasts and detected changes of pigment content and photosynthetic enzyme activity in the stems during their rapid growth stage.
    Methods We detected the pigment content and photosynthetic enzyme activity by the colorimetric method and observed the distribution of chloroplasts using a laser scanning confocal microscope.
    Important findings Chloroplasts were mainly distributed in the ground tissues under the epidermis and in cells around the vascular bundle, similar to Kranz anatomy in C4 plants. The content of chlorophyll a, chlorophyll b and carotenoid was significantly (p < 0.01) increased with the growth of the stems of P. pubescens. The activities of ribulose-1, 5-bisphosphate carboxylase change/add oxygen enzymes (Rubisco), phosphoenolpyruvate carboxylase (PEPC) and nicotinamide-adenine dinucleotide phosphate-malic enzyme (NADP-ME) in the stems reached the highest level after 10 days, and they declined gradually with the growth of the stems. After 30 days, the activities decreased by 88.55% (p < 0.01), 77.46% (p < 0.01) and 72.50% (p < 0.01), respectively, compared with after 10 days. The ratio of PEPC/Rubisco increased gradually and reached 12.83 after 30 days, which was markedly higher than that in C3 plants. These results indicated that there was C4 photosynthetic pathway in the stems, and the pathway may play an important role in the efficient photosynthesis and rapid growth of P. pubescens.

    Parameterization of water response functions in leaf stomatal conductance model for winter wheat
    YUAN Guo-Fu, ZHUANG Wei, and LUO Yi
    Chin J Plan Ecolo. 2012, 36 (5):  463-470.  doi:10.3724/SP.J.1258.2012.00463
    Abstract ( 1423 )   PDF (408KB) ( 1335 )   Save
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    Aims Water response functions in leaf stomatal conductance models are used to simulate the effects of water stress on stomatal conductance. Especially under a water-limited environment, the water response function is a critical method for modeling gas exchange between plant and air. Winter wheat (Triticum aestivum) is an important crop grown under water-limited environment in North China. Our objective is to determine the responses of stomatal conductance of winter wheat to vapor humidity, soil water content and leaf water potential and to determine the appropriate water response functions for winter wheat in North China based on field experiments.
    Methods Field experiments were carried out at Yucheng Comprehensive Station. Eight water treatment plots were set up to produce different degrees of water stress on winter wheat. Leaf gas exchange and stomatal conductance were measured, along with other environmental and water factors. We analyzed relationships between leaf stomatal conductance and air vapor humidity, soil water content and leaf water potential.
    Important findings Leaf stomatal conductance of winter wheat decreased with increasing air vapor pressure deficit (VPD). About 1 kPa in VPD is a valuable threshold value for winter wheat. When VPD is <1 kPa, leaf stomatal conductance decreases rapidly with increasing VPD. But when VPD is >1 kPa, leaf stomatal conductance decreases slightly even with a large VPD increase. A hyperbolic function can simulate the response of stomatal conductance of winter wheat to VPD. Midday leaf stomatal conductance linearly increases when soil water content increases, but the maximum threshold is about 25% of mean soil water volumetric contents, above which leaf stomatal conductance fluctuates in high conductance and does not show a simple increasing trend. A similar relationship between midday leaf stomatal conductance and soil water content occurs between midday leaf water potential and midday leaf stomatal conductance, where the maximum threshold in midday leaf water potential is about –1 MPa when the leaf stomatal conductance becomes relatively stable. We obtained the vapor humidity response function for winter wheat in hyperbolic and power exponent forms based on our field experimental data by data-fitting methods. We also obtained the soil water content response function and leaf water potential response function in simple linear form. These water response functions are useful for the application on modelling surface processes for winter wheat, especially in North China.


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