[Leaf economics spectrum among different plant functional types in Beijing Botanical Garden, China.] / 北京植物园不同功能型植物叶经济谱.

We measured leaf photosynthetic and chlorophyll fluorescence parameters as well as leaf area, dry biomass, and nitrogen content of different plant functional types (PFTs) at the Beijing Botanical Garden, and analyzed the leaf economics spectrum (LES) among different PFTs. The results showed that the plants with the life form of grasses, those with an annual type of life history, and with a C4 photosynthetic pathway might provide a quick return on investment for the species located at one end of the LES. Similarly, the plants with a life form of trees and shrubs, with a perennial type of life history, and with a C3 photosynthetic pathway might provide a slower return on investment for the species located at the other end of the LES. This indicated that plants with different PFTs might have diverse strategies that allowed them to adapt to the environment through a trade-off among leaf traits. The results showed that the LES existed among different PFTs. Remarkable diffe-rences were observed in most of the leaf traits among different PFTs. The various life forms analyzed here were ranked in the order of grasses > vines > shrubs > trees based on specific leaf area (SLA), mass-based nitrogen concentration (Nmass), mass-based photosynthetic capacity (Amass), and photosynthetic nitrogen use efficiency (PNUE). Among the different life histories, SLA, Nmass, Amass, and PNUE in annual species were significantly higher than those in perennial species. In addition, Amass, PNUE, and the quantum yield of PS2 electron transport (ΦPS2) were higher in C4 species than in C3 species. Nmass, Amass, and SLA were significantly positively correlated with each other. SLA was significantly negatively correlated with the photochemical efficiency of PS2 in the light (Fv'/Fm'), whereas it was significantly positively correlated with PNUE.

[Impact of fire on carbon dynamics of Larix gmelinii forest in Daxing'an Mountains of North-East China: a simulation with CENTURY model].

Fire is one of the important natural disturbances to forest ecosystem, giving strong impact on the ecosystem carbon dynamics. By using CENTURY model, this paper simulated the responses of the carbon budget of Larix gmelinii forest in Huzhong area of Daxing' an Mountains to different intensities of fire. The results indicated that after the fires happened, the soil total carbon pool of the forest had a slight increase in the first few years and then recovered gradually, while the stand biomass carbon pool increased after an initial decrease, with the recovery rate of carbon pool of the stand fine components being faster than that of the coarse components. The fluctuation of the carbon pools increased with the increase of fire intensity. After the fires, both the net primary productivity (NPP) of forest vegetation and the soil heterotrophic respiration increased after an initial decrease, but the recovery rate of the NPP was faster than that of soil heterotrophic respiration, resulting in the alternation of the stand functioned as a carbon source or sink. After light fire, the forest still functioned as a weak carbon sink, and quickly recovered as a carbon sink to the level before the fire happened. After other intensities fire, the forest functioned as a carbon source within 9-12 years, and then turned back to a carbon sink again. It was suggested that lower intensity forest fire could promote the regeneration of L. gmelinii forest, reduce the combustibles, and have no strong impact on the stand carbon budget, while higher intensity forest fire would lead to the serious loss of soil- and tree carbon sequestration, retard the recovery of the forest, and thereby, the forest would be a carbon source in a longer term.

[Effects of irrigation amount and nitrogen fertilization rate on wheat yield and soil nitrate content].

A field experiment was conducted to study the effects of irrigation amount and nitrogen fertilization rate on wheat yield and soil nitrate content. With the increase of irrigation amount, the soil nitrate content in 0-200 cm layer at the same nitrogen fertilization rates had a trend of decrease -increase-decrease. Under irrigation, the soil nitrate content was significantly lower in 0-80 cm layer while significantly higher in 80-200 cm layer, compared with the control. As the irrigation amount increased, the translocation of soil nitrate nitrogen to deeper layers accelerated dramatically, with the content decreased in 0-80 cm layer, increased in 120-200 cm layer, and peaked in 120-140 cm layer. When the nitrogen fertilization rate increased from 210 kg x hm(-2) to 300 kg x hm(-2) the soil nitrate content at the same irrigation amounts increased significantly through anthesis, filling, and maturity stages. With the increase of irrigation amount, the grain yield decreased after an initial increase, being the highest when the irrigation amount in whole growth period was 60 mm. The grain yield, grain protein content, and grain protein yield all increased significantly with increasing nitrogen fertilization rate. Under the conditions of the present experiment, the treatment with nitrogen fertilization rate 210 kg N x hm(-2) and irrigation amount 60 mm (split into two times) had the highest grain yield, grain protein content, grain protein yield, and harvest index but the least NO3(-)-N leaching, being the more available irrigation and nitrogen fertilization mode for wheat production in the study area.

[Effects of irrigation on the water soluble carbohydrate contents in different wheat cultivars stem and sheath and the grain yield].

Taking two wheat (Triticum aestivum L.) cultivars Jimai 20 and Taishan 22 as test objects, this paper studied the effects of different irrigation treatments on the water soluble carbohydrate contents in penult stem internode and sheath and the grain yield. Four irrigation treatments were installed, i. e. , no irrigation (W0), irrigation at overwintering and jointing stages (W1), irrigation at overwintering, jointing and anthesis stages (W2), and irrigation at overwintering, jointing, anthesis and filling stages (W3). In treatment W0, the contents of total soluble sugar and of fructan with the degree of polymerization (DP) > or = 4 and = 3 in the penult stem internode and sheath of the two cultivars at early filling stage and the fructose content at later filling stage were the highest, indicating that the accumulation and degradation of water soluble carbohydrate in the penult stem internode and sheath were promoted under no irrigation, which in turn increased the 1000-grain weight. In treatment W1, the contents of fructan with DP > or = 4 and DP = 3 in the penult stem internode and sheath of Jimai 20 at early filling stage, the total soluble sugar and fructose contents at middle and later filling stages, and the grain yield were the highest. In treatment W2, Taishan 22 had the highest contents of fructan with DP > or = 4 and DP=3 in the penult stem internode and sheath at early filling stage, lower fructose content at higher filling stage than in treatment W1, and the highest grain yield. Comparing with Jimai 20, Taishan 22 had higher contents of total soluble sugar and of fructan with DP > or = 4 in the penult stem internode and sheath at early filling stage and higher content of fructose at later filling stage, and lower grain yield in treatments W0 and W1 but higher grain yield in treatments W2 and W3. In this study, treatments W1 and W2 promoted the accumulation and degradation of water soluble carbohydrate in the penult stem internode and sheath of Jimai 20 and Taishan 22, and gained the highest grain yields of the two cultivars, respectively, being most appropriate irrigation treatments for Jimai 20 and Taishan 22, respectively.

[Effects of supplemental irrigation based on measuring soil water content on wheat photosynthetic characteristics and dry matter accumulation and allocation].

Taking high-yielding winter wheat cultivar Jimai 22 as test material, a field experiment was conducted to study the effects of supplemental irrigation based on measuring soil water content on the wheat photosynthetic characteristics and dry matter accumulation and allocation. Six treatments were installed, i. e., W1 (soil relative water content was 65% at jointing stage and was 70% at anthesis), DW1 (soil relative water content was 65% 10 d after jointing and was 70% at anthesis), W2 (soil relative water content was 75% at jointing and was 70% at anthesis), DW2 (soil relative water content was 75% 10 d after jointing and was 70% at anthesis), W3 (soil relative water content was 80% at jointing stage and was 70% at anthesis), and DW3 (soil relative water content was 80% 10 d after jointing and was 70% at anthesis). In treatments W2 and DW2, the flag leaf photosynthetic rate (P(n)) and phi(PS II) at late filling stage were higher than those in treatments W3 and DW3, respectively, the dry matter accumulation amount at anthesis and maturity stage and the allocation of accumulated dry matter at pre-anthesis to grain were significantly higher than those in treatments W1 and DW1, and the water use efficiency (WUE) and irrigation production efficiency (IPE) were significantly higher than those in W3 and DW3. Under the same irrigation levels, the flag leaf P(n), and phi(PS II) at late filling stage were higher in treatments DW2 and DW3 than in W2 and W3, respectively, and the dry matter accumulation amount at anthesis and its allocation to grain were lower whereas the dry matter accumulation amount after anthesis, the grain yield, WUE, and IPE were higher in DW2 and DW3 than in W2 and W3. Under our experimental condition, DW2 could be the optimal irrigation pattern of high-yielding with high WUE.

[Effects of shading at different phases of grain-filling on wheat grain protein components contents and processing quality].

Taking three wheat cultivars Jimai 20 (strong gluten), Taishan 23 (medium gluten), and Ningmai 9 (weak gluten) as test materials, a field experiment was conducted to examine the effects of shading at different phases of grain-filling on the grain protein components contents and processing quality. Four treatments were installed, i. e., no shading (S0), shading at early grain-filling phase (from 0 day after anthesis (DAA) to 11 DAA; S1), shading at medium grain-filling phase (from 12 DAA to 23 DAA; S2), and shading at late grain-filling phase (from 24 DAA to 35 DAA; S3). No significant differences were observed in the grain albumin+globulin contents of the three cultivars among the four treatments. Shading increased the grain HMW-GS, LMW-GS, gluten, glutenin, and total protein contents of Jimai 20 and Taishan 23 significantly, and the increments were higher in treatment S2 than in other shading treatments. Treatments S2 and S3 increased the grain protein components contents of Ningmai 9 significantly. Comparing with the control, shading decreased the grain yield significantly, but increased the dough development time, dough stability time, and sedimentation volume, especially for treatment S2, which suggested that the wheat grain quality had a close relationship with the light intensity at medium phase of grain-filling. Overall, the regulation effect of shading at grain-filling stage on the wheat grain yield, grain protein components contents, and indices values of grain processing quality for the test cultivars was in the order of Jimai 20 > Taishan 23 > Ningmai 9.

[Dynamic simulation of photosynthate allocation in maize organs based on functional equilibrium hypothesis].

By using the 2004-2008 observation data of maize biomass and related environmental factors from the Jinzhou Agricultural Ecosystem Research Station of Shenyang Institute of Atmospheric Environment under China Meteorological Administration (CMA), the Friedlingstein model was validated and tested at station site and daily time scales. A model of soil available nutrient coefficient for maize field was developed, based on fertilization, soil temperature, and soil available water; and a daily time scale maize photosynthate allocation model was built, according to the functional equilibrium hypothesis. Comparing with Friedlingstein model, the daily time scale maize photosynthate allocation model could give more accurate simulation of photosynthate allocation in maize root, stem, and leaf, and provide technical support for accurate simulation of daily net primary productivity of maize agro-ecosystem.

[Effects of irrigation amount on water use characteristics and grain yield of wheat under different nitrogen application rates].

A field experiment was conducted to examine the effects of irrigation amount on the water consumption, flag leaf physiological characteristics, and grain yield of wheat under the nitrogen application rates 180 kg x hm(-2)(N180)) and 240 kg x hm(-2)(N240). Four irrigation regimes were designed, i.e., no irrigation during whole growth period (W0), irrigation with 60 mm water before sowing (W1), irrigation with 60 mm water before sowing and at jointing stage, respectively (W2), and irrigation with 60 mm water before sowing, at jointing stage, and at flowering stage, respectively (W3). In treatment W0, the water consumption amount below 100 cm soil layer was lower than that in other treatments; and in treatments W1 and W2, the water consumption amount in 100-200 cm and 0-200 cm soil layers was higher than that in treatment W3. The soil water consumption amount in 0-80 cm soil layer, the consumption percentage from flowering to maturing stage, and the total water consumption amount were all higher under N240 than under N180. At mid and late grain-filling stages, the relative water content (RWC) and water potential (psi w) of flag leaves were higher in treatments W2 and W3 than in treatments W0 and W1. The RWC and psi w at late grain-filling stage were higher in treatments N240W0 and N240 than in N180W0 and N180 W1, respectively, but had no significant differences between treatments N240W2 and N180W2, and N240W3 and N180W3. In this study, treatment N180W2 had the higher grain yield, water use efficiency (WUE), and nitrogen use efficiency, while over-irrigation increased the water consumption amount, and decreased the WUE, irrigation water use efficiency, and irrigation benefit.

[Effects of water-nitrogen interaction on soil water utilization by wheat and fructan content in wheat stem].

A field experiment was conducted to study the effects of water-nitrogen interaction on the flag leaf photosynthetic rate, penult stem fructan content, fertilizer N use efficiency, and soil water use efficiency of strong gluten wheat variety 'Jimai 20'. Three N application levels (N0, 0 kg x hm(-2); N1, 180 kg x hm(-2); and N2, 240 kg x hm(-2)) and four irrigation schedules (W0, no irrigation; W1, irrigation before sowing and at jointing and flowering stages; W2, irrigation before sowing, before wintering, and at jointing and flowering stages; W3, irrigation before sowing, before wintering, and at jointing, flowering, and grain-filling stages) were designed. The irrigation amount was 60 mm each time. Among the N treatments, treatment N1 had a higher flag leaf net photosynthetic rate and penult stem fructan content, and the highest grain yield, apparent N use efficiency, agronomic N use efficiency, and water use efficiency. Treatment N2 had a higher penult stem fructan content than treatments N0 and N1. No N application and applying excessive N did not benefit the increase of grain yield, fertilizer N use efficiency, and water use efficiency. Treatment W1 promoted the fructan accumulation in penult stem and accelerated the translocation of the accumulated fructan to grain, being beneficial to the increase of grain yield. Treatment N1W1 had the highest grain yield, and higher fertilizer N use efficiency and water use efficiency. Excessive irrigation and N application increased the flag leaf net photosynthetic rate and penult stem fructan content, but decreased the fertilizer N use efficiency and water use efficiency, with no significant effects on grain yield.

[Effects of regulated deficit irrigation on water consumption characteristics and water use efficiency of winter wheat].

With the high-yielding winter wheat cultivar Jimai 22 as test material, a field experiment was conducted in Yanzhou of Shandong to examine the effects of regulated deficit irrigation on the water consumption and water use efficiency (WUE) of the cultivar. Five treatments were installed, i.e., the soil relative moisture content at sowing, jointing, and anthesis stages being 80%, 65% and 65% (W0), 80%, 70% and 70% (W1), 80%, 80% and 80% (W2), 90%, 80% and 80% (W3), and 90%, 85% and 85% (W4), respectively. Under the condition of 228 mm precipitation in growth season, the total water consumption was higher in treatments W1 and W4 than in treatments W0, W2, and W3, and no difference was observed between treatments W1 and W4. Comparing with W4, treatment W1 decreased the water storage in 0-200 cm soil layer and the water consumption by wheat from jointing to anthesis stages, but increased the water consumption from anthesis to maturity stages. The water consumption rates at the stages from jointing to anthesis and from anthesis to maturity in treatment W4 were higher. Under regulated deficit irrigation, treatment W0 had higher WUE, but the grain yield was the lowest. The WUE in other treatments increased first, and then decreased with increasing irrigation amount. Both the water consumption and the grain yield were the highest in treatments W1 and W4, and treatment W1 had higher irrigation water use efficiency and irrigation benefit than treatment W4, being the best irrigation regime of high-yielding and water-saving in our study.

[Effects of irrigation stage and amount on winter wheat fructan accumulation and translocation after anthesis and water use efficiency].

Field experiments were conducted in Tai' an and Yanzhou of Shandong Province in 2004-2005 and 2005-2006 to study the effects of irrigation stage and amount on the accumulation and translocation of fructan in winter wheat penult stem and sheath after anthesis and the water use efficiency. No irrigation in whole growth period promoted the translocation of fructan from penult stem and sheath to grain at late grain-filling stage. Irrigation with 60 mm water at jointing and anthesis stages increased the flag leaf photosynthetic rate and photo-assimilate accumulation after anthesis, and the contribution of the photo-assimilates to the grain. Irrigation with 60 mm water at jointing, anthesis, and grain-filling stages, and with 90 mm water at jointing and anthesis stages decreased the flag leaf photosynthetic rate at late grain-filling stage, increased the photo-assimilate accumulation before anthesis and the contribution of the photo-assimilates to the grain, and reduced the translocation of the photo-assimilates after anthesis to the grain. Excessive irrigation also increased the contents of fructan with the degree of polymerization (DP) > or = 4 and = 3 in penult stem and sheath at late grain-filling stage, limiting the translocation of fructan from penult stem and sheath to grain. Irrigation with 60 mm water at jointing and anthesis stages led to a higher grain yield and the highest water use efficiency, while irrigation with 60 mm water at jointing, anthesis, and grain-filling stages, and with 90 mm water at jointing and anthesis stages had little effects on the grain yield but decreased the water use efficiency.

[Biomass allocation of Leymus chinensis population: a dynamic simulation study].

Based on a greenhouse simulation experiment, this paper studied the dynamics of the above- and below-ground biomass of Leymus chinensis populations with four planting densities (120, 240, 360 and 480 plants x m(-2)). The results showed that the above- and below-ground biomass of L. chinensis populations had an increasing trend with the growth, and increased with increasing planting density. However, the relative growth rates (RGRs) of the above- and below-ground biomass did not show significant difference among the L. chinensis populations. The ratio of root to shoot (RRS) of the L. chinensis populations increased with their growth, but did not show significant difference among the planting densities, implying that environmental factors were the controlling factors for RRS. There existed significant power function relationships between the above- and below-ground biomass of L. chinensis individuals and populations, but the power function indices and coefficients varied with the planting density. It was suggested that the difference of microenvironment resulted from resources competition could induce the changes of L. chinensis RRS, and the latter could be used as a reference to quantitatively study the allocation of photosynthetic products.

Combined effects of water stress and high temperature on photosynthesis, nitrogen metabolism and lipid peroxidation of a perennial grass Leymus chinensis.

Drought and high-temperature stresses have been extensively studied; however, little is known about their combined impact on plants. In the present study, we determined the photosynthetic gas exchange, chlorophyll fluorescence, nitrogen level, and lipid peroxidation of the leaves of a perennial grass (Leymus chinensis (Trin.) Tzvel.) subjected to three constant temperatures (23, 29 and 32 degrees C), and five soil-moisture levels (75-80%, 60-65%, 50-55%, 35-40% and 25-30% of field capacity, respectively). High temperature significantly decreased plant biomass, leaf green area, leaf water potential, photosynthetic rate (A), maximal efficiency of PSII photochemistry (F (v)/F (m)), actual PSII efficiency (Phi(PSII)), the activities of nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2), but markedly increased the ratio of leaf area to leaf weight (SLA), endopeptidase (EP; EC 3.4.24.11) activity, and malondialdehyde (MDA) content, especially under severe water stress conditions. The A and F (v)/F (m) were significantly and positively correlated with leaf-soluble protein content, and the activities of NR and GS. However, both photosynthesis parameters were significantly and negatively correlated with EP activity and MDA content (P < 0.05). It is suggested that high temperature, combined with severe soil drought, might reduce the function of PSII, weaken nitrogen anabolism, strengthen protein catabolism, and provoke lipid peroxidation. The results also indicate that severe water stress might exacerbate the adverse effects of high temperature, and their combination might reduce the plant productivity and distribution range of L. chinensis in the future.

Responses of chlorophyll fluorescence and nitrogen level of Leymus chinensis seedling to changes of soil moisture and temperature.

Controlled experiment of Leymus chinensis seedlings grown in the environmental growth chambers at 3 soil moisture levels and 3 temperature levels was conducted in order to improve the understanding how leaf photosynthetic parameters will respond to climatic change. The results indicated that soil drought and high temperature decreased the photochemical efficiency of photosystem (Fv/Fm), the overall photochemical quantum yield of PSII(yield), the coefficient of photochemical fluorescence quenching(qP), but increased the coefficient of non-photochemical fluorescence quenching(qN). Severe soil drought would decrease Fv/Fm and yield by 3.12% and 37.04% under 26 degrees C condition, respectively, and 6.60% and 73.33% under 32 degrees C condition, respectively, suggesting that higher temperature may enhance the negative effects of soil drought. All the soil drought treatments resulted in the decline in leaf nitrogen content. There was no significant effect of temperature on leaf nitrogen level, but higher temperature significantly reduced the root nitrogen content and the ratio of root nitrogen to leaf nitrogen, indicating the different strategies of adaptation to soil drought and temperature. It was also implied that higher temperature would enhance the effect of soil drought on leaf photosynthetic capacity, decrease the adaptability of Leymus chinensis to drought.