Abstract:The combination of niche theories and plant ecophysiology may show a link between macroscopic ecology and microscopic physiology. The experiment simulated three rainfall treatments representing the minimum, average and maximum annual precipitation found in the Shapotou area. The net photosynthesis rate (P_n) of four dominant desert shrubs (Reaumuria soongorica maximum, Salsola passerina Bge., Artemisia ordosica Krasch. and Caragana korshinskii Komar.) that grow in the arid zone in Northwest China was measured, together with the available environmental resources, photosynthetically active radiation (PAR), air temperature (CT) and volumetric soil moisture (SW). Based on these data and means derived from the Levins niche breadth index, this study calculated the photosynthesis – PAR niche breadth (PB_i), the photosynthesis – CT niche breadth (TB_i) and the photosynthesis – SW niche breadth (WBi) of the four shrubs. The results showed that PAR was not a directly limiting factor on growth and survival of the four shrubs and the values for PB_i were consistent either with the PAR response ranges (R. soongorica and S. passerina) or with the values for P_n (A. ordosica and C. korshinskii), although the values for PB_i between the four desert shrubs varied. In accordance with the calculated TB_i values, the CT tolerance ranges for photosynthesis also varied among the four desert shrubs. The lowest SWs that stopped photosynthesis varied amongst the four shrubs, and the lower the SW was: the wider the response range and the higher the WBi value. The photosynthetic niche breadth and the photosynthetic response ranges of the four shrubs were in agreement with their ecological breadth and geographic distributions. Thus, some micro-mechanisms can be explained using these relationships such as floral evolution, succession and the varietal development processes of the plant communities of R. soongorica – S. passerine and A. ordosica Krasch. – C. korshinskii Komar. It is also possible to account for the physiological changes that occur in each plant by calculating the photosynthetic niche breadth. These results show that this research methodology can be extended to niche theory and promote the practicality of plant physiological ecology as well as provide new ideas for the study of plant ecology.

Abstract:Intrusive agriculture development, searching for higher profitability, has inflicted permanent damage to agroecosystems. Rapid deterioration of structure and functional properties in agroecosystems has intensified the need for research on agroecosystem health and agroecosystem management. This paper describes the concept of agroecosystem health which plays an important conceptual role in evaluating agroecosystem and agricultural research. Firstly, the development of agroecosystem health research is reviewed, and agroecosystem health from various dimensions is provided. Then, the methods and general criterias of agroecosystem health assessment are outlined, and a model for evaluating agroecosystem health is established. Finally, pathways of agroecosystem management from a holistic dimension are proposed to promote agroecosystem health and provide a scientific basis for making science-based policy decisions and formulating new plans in agricultural development.

Abstract:The monthly and ontogenetic variations in diet of hairtail Trichiurus margarites Li (1992) [20] (Perciformes, Trichiuridae) were examined in the Beibu Gulf of the South China Sea from October 2008 to September 2009. Stomachs of 666 hairtail ranging in size from 121 mm to 561 mm pre-anal length (PL) were sampled monthly from commercial fish catches. Fish were the primary prey, with Decapterus maruadsi (Perciformes, Carangidae) averaging 23% by number, 34% by weight, and 49% by Index of Relative Importance (IRI). Other important prey in the diet included the small benthic fish, Bregmaceros rarisquamosus and Bregmaceros nectabanus (Gadiformes, Bregmaceroridae) and the decapod shrimp, Acetes chinensis, with IRI percentages of 8%, 4%, and 3%, respectively. Low rates of cannibalism and predation on 30 additional species of prey were observed. Trophic diversity (Brillouin Index, H_z) was moderate throughout the year. Mean feeding intensity (Repletion Index, RI) varied considerably by month and increased with the gonad maturity stages of hairtail; conversely, the proportion of empty stomachs decreased with maturity stages, from 60.9% empty at Stage I to 41.6% empty at Stage VI. Prey weight and numbers differed significantly among the 14 PL size classes and increased with body size. Cluster analysis of prey IRI values also indicated differences in the feeding habits of hairtail by size class. Understanding the monthly and ontogenetic changes in hairtail diet may assist in the development and improvement of marine ecosystem modeling for the Beibu Gulf, South China Sea.

Abstract:Most golf course green have been constructed with pure sand or sand-based rootzone mixes. As we know, high sand content provides rapid drainage despite sand’s inefficiency in retaining moisture. However, drainage capability and water retention are both essential elements to the golf course green, and the addition of peat could increase the soil moisture retention, therefore, the research on the drainage capability and water retention of the sandy golf green has become more and more important these years. In this study, extreme vertex design was applied which is one of the mixture experiment designs widely used in mixture experiments, the study investigated the effects of the thirteen different rootzone soil mixtures using middle-coarse, fine sand, very fine sand plus silt and clay as well as peat as the materials under three kinds of golf green profile (1-layer profile, 2-layer profile, 3-layer profile) conditions on the water retention of green rootzone. Through the qualitative, quantitative and optimization analysis of water retention capability of the sandy golf green, evidence a basis for choice of green profiles and rootzone matrix could be provided. And the significantly correlative regression model was established between the moisture retention and components of rootzone soil mixture. In addition, the order of factor contribution ratio, effect of single and double factor and optimization of the model were analyzed in detail. The results were as follows: both green profile and soil mixture, which had interaction of each other, had significant effects on soil moisture retention. Additional attributes include high porosity and greater water holding capacity than sand, and the higher content of peat, fine sand plus silt and clay, the better water retention. The mixtures had much higher water content in 1-layer profile than that in the other two profiles. There was significantly higher water content in 2-layer profile for pure sand mixtures (A–E) and low peat mixture (F) than that in 3-layer profile, while there was no higher water content for other 7 high peat mixtures (G–M) (>5%) in 2-layer than that in 3-layer profiles. The significance of key factors in rootzone soil mixture on moisture retention were: very fine sand plus silt and clay > peat > middle-coarse > fine sand. According to the moisture retention 15–25% specification of USGA (United States Golf Association), the optimal soil mixture in 1-layer profile was: middle-coarse 71.4–73.5%; fine sand 17.8–21.5%; very fine sand plus silt and clay 6.8–8.4%; peat 0–1%. The optimal soil mixture in 2-layer profile was: middle-coarse 65.0–73.4%; fine sand 17.8–20.5%; very fine sand plus silt and clay 7.5–8.9%; peat 0.2–6.3%. The optimal soil mixture in 3-layer profile was: middle-coarse 62.3– 73.9%; fine sand 17.7–21.4%; very fine sand plus silt and clay 7.3–10.7%; peat 0–6.3%. These optimal recipes took through the limitation of previous research, which were practically important to golf green soil selection and profile design. Thus, both proportion and interaction should be considered when we choose the soil mixture.

Abstract:It is assumed that terpenoids in biomass-derived fuels have important influences on forest fires due to their enormous flammability. The fires consuming terpenoid-rich fuels always burn violently and spread fast. But the mechanism how terpenoids influence occurrence and propagation of fires are little known. Some terpenoids are volatile organic compounds (VOC) as they are released from vegetation and litter in natural environment. Hence, they contribute to the characteristic composition of the ambient air. Many studies have reported terpenoid emissions in natural environment from different perspective. Nevertheless there are only a few studies concerning terpenoid emissions from heated fuels. The present study explored the differences in terpenoid emissions from needles of Pinus sylvestris var. mongolica under natural and heated conditions. Terpenoids were sampled on Tenax-TA and analyzed using Thermal Desorption– Gas Chromatography–Mass Spectrometry (TD–GC–MS). The results showed that the emission rate of terpenoid from P. sylvestris in natural environment was low (0.167 lg g^-1 h^-1 DW). However, terpenoid emissions dramatically increased at the temperature of 200 °C, with a major component, a-pinene. Within 15 min, the emission of terpenoids emitted by heated needles was up to 16.314 lg g^-1 DW for total and 10.321 lg g^-1 DW for a-pinene. These considerable emissions of terpenoids from heated needles will have great influences on occurrence and propagation of forest fires.

Abstract:Coccolithophorids are one of the dominant groups of marine phytoplankton. They are found in large numbers throughout the surface euphotic zone of the ocean, and are able to form large-scale blooms that persist for long periods of time. Coccolithophorid cells are covered by species-specific calcium carbonate crystals of various structures. In the process of calcification in coccolithophorids, Ca²⁺ is absorbed into cells from the culture medium, and a coccolith unit is formed inside the cell. Then, the coccolith unit extrudes to the cell surface where it is constructed into crystal layers. The formation of these crystals is regulated by cellular metabolism under different environmental conditions. The carbon biogeochemical cycle in the coccolithophorids involves both photosynthetic and calcification processes, which not only play an important role in population dynamics, but also in the global carbon cycle and climate change. However, one important question remains, namely, whether the relationship between photosynthesis and calcification is species-dependent. Previous studies have yielded controversial results, even in the same species. In this paper, we selected Pleurochrysis carterae, a coccolithophore species that frequently blooms in coastal areas, to study the relationship between calcification and photosynthesis. First, we studied population growth in a batch culture over several days. For batch cultures, P. carterae was inoculated into a 10 L bioreactor at an initial cell density of approximately 5 × 10⁴ cells mL^-1. The culture conditions were optimal for cell growth. Dissolved oxygen (DO) was detected during all the culture period, and the rate of photosynthetic oxygen evolution was calculated according the DO changes during the 12-h illumination period. Algal samples (10 mL) were collected during the population growth phases. The calcium carbonate content on the cell surface was determined each day by chemical titration. Next, we studied the relationship between photosynthesis and calcification at the cellular level by observing patterns of recalcification during a 12-h period. In this study, non-calcified cells were obtained by decalcifying calcified cells collected during the exponential growth period in MES-NaOH buffer solution (pH 5.5). The non-calcified cells were inoculated into culture media containing different concentrations of Ca²⁺ (0, 5, 20, 40, 50, or 100 mg L^-1). The rate of recalcification was determined by microscopic analyses in which the number of recalcified cells per 100 cells was counted at 0, 3, 6, 9, and 12 h of culture. Ca²⁺ absorbed into the cell was detected by measuring the fluorescence intensity of Fluo-3/AM labeled Ca²⁺. The rate of photosynthetic oxygen evolution in the non-calcified cell cultures was detected by measuring the changes in dissolved oxygen during the 12-h illumination period. The results showed that during the population growth period, the rate of photosynthetic oxygen evolution was inversely related to the calcium carbonate content per cell. When the amount of calcium carbonate on the cell surface increased, the relative photosynthetic ability (the rate of photosynthetic oxygen evolution) decreased, and vice versa. Both recalcification rates and photosynthetic oxygen evolution were affected by the extracellular calcium concentration. Non-calcified cells showed different recalcification abilities at different extracellular Ca²⁺ concentrations. The recalcification rate of non-calcified cells was positively correlated with the extracellular calcium concentration when [Ca²⁺] in the medium ranged from 0 to 100 mg L^-1. However, photosynthetic oxygen evolution was suppressed at higher cell calcification rates, especially when extracellular [Ca²⁺] was 50–100 mg L^-1. Our analyses of the population growth process and the cell recalcification process confirmed that photosynthesis is inversely related to calcification in P. carterae.

Abstract:Plateau pika (Ochotona curzoniae) is a key component of alpine meadow ecosystem in the Qinghai- Tibetan Plateau, and the increase of its number leads plant components of alpine meadow ecosystem to adaptively response. A field survey was carried out to determine the response of alpine meadow community to population densities of plateau pika by using available burrow density to replace the population density of plateau pika. This study showed that the height of alpine meadow communities gradually increased, and the cover of alpine meadow communities firstly decreased, and then increased as the available burrow density increased. With the increase of available burrow density, the richness index of alpine meadow communities firstly decreased and then increased, and the evenness index of alpine meadow communities firstly increased and then decreased, however, the diversity index of alpine meadow communities firstly increased, and then decreased, finally increased. In the increasing process of available burrow density, the total plant biomass and the unpalatable plant biomass firstly decreased and then increased, and the palatable plant biomass firstly increased and then decreased, indicating that the palatable plant biomass was the highest and the unpalatable plant biomass was the lowest at 14 available burrow per 625 m². In the economic groups of plant biomass, the weed biomass was the highest and the legume biomass was the lowest at any available burrow densities, and the grass biomass and the sedge biomass were related to available burrow densities, indicating that the sedge biomass were bigger than the grass biomass at 3 available burrow per 625 m², inverse at 54 available burrow per 625 m², similar between 3 and 34 available burrow per 625 m². Accompanying by the increase of available burrow densities, the legume biomass and the sedge biomass significantly decreased (P < 0.05) and the legume became disappearance at 54 available burrow per 625 m²; the grass biomass firstly increased and then decreased, peaking at 14 available burrow per 625 m². The weed biomass firstly decreased and then increased, and was the lowest at 14 available burrow per 625 m². This study suggested that the responses of alpine meadow communities to population density of plateau pika at 14 available burrows per 625 m² were more sensitive than that at other available burrow per 625 m² from plant species diversity, biomass, height, cover and economic group.

Abstract:Amaranthus retroflexus L. and Chenopodium glaucum L. are two widely distributed destructive weeds. Their strong adaptability and massive seed production make them the hardest weeds to deal with. This present study intended to investigate the effect of leachate from Eupatorium adenophorum on the growth of these weeds and explore the potential to develop an environmental friendly strategy to use the leachate to control the weeds.
Seeds of A. retroflexus L. and C. glaucum L. were soaked in solutions containing 0%, 0.6%, 1.25%, 2.5%, and 5% leachate from E. adenophorum leaves. A. retroflexus and C. glaucum seedlings grown in pots were sprayed with leachate solutions in the same concentration range. The effects of these leachate solutions on membrane permeability and germination of seeds, and growth and physiological characteristics of the seedlings were investigated. The highest concentration of leachate (5%) caused significant damage to the cell membrane of seeds of both weed species, whereas lower concentrations (0.6%) promoted repair of the membrane system, as reflected by higher and lower than control in relative conductivity (RC), respectively. Different concentrations of leachate showed distinct allelopathic inhibitory effects on the two weed species; lower concentrations showed weak inhibitory or even positive effects, whereas higher concentrations showed stronger inhibitory effects. Higher concentrations of leachate (2.5% and 5%) delayed germination and significantly decreased the emergence rate of the seeds, survival rate, and dry matter accumulation of the seedlings. When treated by 5% leachate, the emergence date of A. retroflexus was delayed by 3.6 d, emergence rate of the seeds and survival rate was 69.1% and 70.6% of the control, respectively, seedling dry matter was 48.6% less than the control; In the case of C. glaucum, the emergence date was delayed by 2.7 d, emergence rate of the seeds and survival rate was 45.1% and 58.6% of the control, respectively, seedling dry matter was 44.7% less than the control. There were significant interactions among the different concentrations of leachate and the length of treatment period with respect to activities of antioxidant enzymes, malondialdehyde (MDA) contents, and chlorophyll contents. Seedlings treated with 0.6%, 1.25%, or 2.5% leachate solution for 24–72 h showed increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities. When seedlings were treated with leachate solutions for 96 h, antioxidant enzyme activities and chlorophyll content decreased in A. retroflexus, but only CAT activity decreased in C. glaucum. When seedlings of the two weed species were treated with 5% leachate solution, CAT activity and chlorophyll content decreased and MDA content gradually increased with longer treatment times (from 24 to 96 h). The two weed species showed different allelopathic responses to E. adenophorum; A. retroflexus was more sensitive than C. glaucum.
Based on the investigation, it could be speculated that the delayed germination and low germination rate of the weeds after treatment by leachate could be due to the fact that leachate damaged the membrane system of the seeds. By delaying germination, lowering the germination rate of the weeds and inhibiting seedling growth, leachate from E. adenophorum could provide an effective way of controlling the weeds.