不同遮荫程度对假俭草光合特性和抗氧化能力的影响

试验以50%和70%遮荫下生长的假俭草为材料,研究了不同遮荫程度对假俭草光合特性和抗氧化能力的影响。结果表明：与全光照相比,2种遮荫处理,尤其50%遮荫,显著地提高了叶绿素a和叶绿素b含量,而叶片净光合速率及光饱和点发生了降低,相比而言,丙二醛含量和叶绿素a/b比值没有发生显著变化。另外,随着遮荫强度的加大,超氧化物歧化酶活性不断降低,电解质外渗率不断增加,而脯氨酸的积累则显著减少、说明遮荫下植株的抗氧化能力降低。     

燕麦散黑穗病菌冬孢子萌发条件研究

为明确燕麦散黑穗病菌(Ustilago avenae)冬孢子在自然生境中的萌发条件,研究了疏亲水界面、不同温度、湿度、光照时间、pH、碳源和氮源对冬孢子萌发的影响。结果表明,亲水界面促进冬孢子萌发,在水琼脂培养基上萌发率最高;冬孢子萌发的最适温度为20~25℃,温度过高或过低均抑制其萌发。冬孢子对湿度要求较高,RH≥90%时才可萌发,且萌发率较低。光照对冬孢子萌发的影响不明显,酸性条件有利于冬孢子萌发,最适pH为4~7,葡萄糖和蛋白胨可促进冬孢子萌发。     

垂穗披碱草种子萌发的耐盐性研究

以来自高寒草地不同海拔的3份野生垂穗披碱草种子为材料,采用培养皿纸上发芽法研究了0％、0．4％、0．6％、0．8％、1．0％和1．2％不同盐浓度对种子萌发的影响,以探讨3份垂穗披碱草种子萌发的耐盐能力。结果表明,低盐环境促进了种子的萌发;随着盐胁迫的增强,种子的发芽率、发芽指数与对照相比均显著下降。当盐浓度达到1．0％时,发芽势均等于0。通过对3份种质材料在盐胁迫下的相对发芽率、相对发芽势、发芽指数等指标的综合评价表明：材料的耐盐性为G3〉G2〉G1。海拔与耐盐指标的相关性分析表明,种子的相对发芽率与海拔成正相关,种子的相对发芽势、发芽指数与海拔成负相关,但相关性均不显著。     

甘南高寒草甸草原不同海拔土壤理化性质分析

对甘肃夏河高寒草甸不同海拔梯度的土壤理化性质分异规律进行了研究,以期探究土壤理化性质与海拔之间的关系。结果表明:除0~10cm土层电导率外,其余各土层土壤理化指标均与海拔呈显著相关(P0.05),其中,含水量、有机质含量均随海拔升高而升高,且随土壤深度增加而降低;pH随海拔升高呈先降低后升高的势态;0~10cm表层土壤全氮含量随海拔升高显著增加(P0.05),10~30cm土层全氮含量随海拔的升高先缓慢下降后平缓上升。因此,对于该区域草甸生态系统的管理与利用,不但考虑植被类型及状况,也需关注不同海拔梯度的草地土壤理化特性。     

Ovarian follicular dynamics and hormones throughout the estrous cycle in Thai native (Bos indicus) heifers

Relatively few studies have been reported regarding the reproductive physiology of female Thai native cattle. Therefore, the objective of the present study was to evaluate the follicular dynamics and concentrations of follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) during the estrous cycle in Thai native heifers (TNH) and to compare obtained results with those of European and Indian cattle breeds previously reported. For the detection of estrus, ovaries of all 20 heifers were examined twice daily (12 h intervals) by ultrasonography for three consecutive estrous cycles. From data of 60 estrous cycles (n = 60 estrous cycles from 20 heifers), it was found that 14 (70%) and 6 heifers (30%) had two (42 estrous cycles collected from 14 heifers) and three follicular waves (18 estrous cycles collected from 6 heifers), respectively. The days when estrus was detected, interovulatory intervals, life‐spans of corpus lutea (CL), and days for growing and regression of CLs were shorter in the two follicular waves than those in the three follicular waves (P < 0.05). In both two and thre follicular waves, larger maximum diameters and higher growth rates of the dominant follicle (DF) in an ovulatory wave were observed than those of the preceding waves without ovulation (P < 0.05). There was a progressive increase in follicular size and FSH and E2 production during follicular growth in each follicular wave. In addition, the FSH and E2 peak concentrations during the ovulatory wave were higher than those of the anovulation waves (P < 0.05). Moreover, although the ovarian follicular dynamic patterns in Thai native heifers were similar to those previously reported for European and Indian cattle breeds, the diameter of the largest preovulatory follicle (OF), subordinate follicles (SF) and CLs were smaller than those in European and Indian cattle breeds. In conclusion, when compared with European and some breeds of Indian cattle, the length of interovulatory intervals was shorter, and the sizes of dominant SF and CLs were smaller in Thai native heifers.     

Increase in plasma total antioxidant capacity of grazing Japanese Black heifers and cows in forestland in Japan

Blood total antioxidant capacity (TAC) has become a key bio‐marker for animal health. Forest‐grazing cattle are known to forage various native plants that have high TAC. This study evaluated differences of plasma TAC between forest‐grazing (FG) and pasture‐grazing cattle (PG). Experiment 1 monitored the plasma TAC levels of 32 Japanese Black cattle. The level in PG did not change throughout the grazing period. However, that in FG, which increased from summer, was significantly higher than that in PG through fall (P < 0.05). In experiment 2, we used nine Japanese Black heifers and investigated their blood antioxidant parameters and the TAC in plants that the cattle consumed in late June and September. The plasma TAC levels in FG were significantly higher than those in PG in both periods (P < 0.05). Plasma levels of lipid peroxidation in FG tended to be lower than that in PG (P = 0.098). Furthermore, the TAC levels in various species of shrubs and trees consumed by FG were higher than those in pasture grasses. Results of this study show that plasma TAC of grazing Japanese Black cattle in forestland increase from summer through fall.     

Changes in soil organic carbon in a clay loam soil following ploughing and reseeding of permanent grassland under temperate moist climatic conditions

This study investigated changes in soil organic carbon (SOC) in a poorly drained clay loam soil under (i) permanent grassland (PG) over 7 years and (ii) after PG renovation over 2·5 years. The experimental area was divided into four blocks with four paddocks per block. Composite soil samples from each PG block were taken to 30‐cm depth on five occasions between 2004 and 2011. In June 2008, one paddock per block was renovated by ploughing and reseeding and sampled as above on the latter four occasions. Renovation decreased SOC (P < 0·05) by 32·2 t ha^?1 in the 2·5 years following ploughing; the difference developed almost entirely (86%) in the first four months. Renovation had no effect on above‐ground productivity, standing root and stubble phytomass or on dissolved organic matter leaching. Therefore, soil respiration was considered to be a single potential pathway responsible for the SOC loss from renovated grassland. Although a simple linear regression indicated a tendency for PG to accumulate SOC, there was no evidence of recovery in SOC to previous levels following renovation during the study period. These results could have implications for greenhouse gas inventories in countries where PG is an important land‐use type.     

施用等养分量有机肥和化肥对干旱胁迫下玉米生物量影响的比较

  目的  研究干旱胁迫条件下施用有机肥和与之等氮磷钾养分量化肥对玉米生物量的影响及其机制,为玉米抗旱技术措施的提出提供理论依据。  方法  通过温室盆栽模拟试验研究施肥（不施肥、施用牛粪和施用化肥）、微生物（不灭菌和灭菌）和水分（不干旱即田间持水量的70%和干旱即田间持水量的40%）三因素对苗期（45天后）玉米生长及土壤性质的影响。  结果  （1）与不施肥相比,施肥处理显著提高玉米生物量,其中地上部生物量提高了155% ~ 278%,根系提高了71% ~ 122%,总生物量提高了125% ~ 221%;在灭菌条件下,干旱后玉米生物量显著降低（30% ~ 34%）。（2）施肥后,未显著改变土壤无机氮的含量,显著提高了土壤速效磷和速效钾的含量;与正常水分处理相比,干旱仅在有机肥处理下显著降低了土壤速效钾含量,达43.8%;施肥对土壤微生物总生物量和细菌生物量均无显著影响,显著提高了真菌生物量以及真菌和细菌的比值;干旱后,土壤微生物总生物量、细菌和真菌生物量均未发生显著改变。（3）随土壤速效磷含量的增加,玉米总生物量显著增加。  结论  干旱显著降低了苗期玉米生物量,且这种干旱效应仅在灭菌土壤上出现,说明了土壤微生物能够增强植物对干旱胁迫的抗性;在干旱情况下,有机肥施用后玉米生物量显著高于化肥处理,土壤速效磷是主要的驱动因子。     

A conceptual framework and an empirical test of complementarity and facilitation with respect to phosphorous uptake by plant species mixtures

Plant species have different traits for mobilizing sparingly soluble phosphorus (P) resources, which could potentially lead to overyielding in P uptake by plant species mixtures compared to monocultures due to higher P uptake as a result of resource (P) partitioning and facilitation. However, there is circumstantial evidence at best for overyielding as a result of these mechanisms. Overyielding (the outcome) is easily confused with underlying mechanisms because of unclear definitions. We aimed to define a conceptual framework to separate outcome from underlying mechanisms and test it for facilitation and complementarity with respect to P acquisition by three plant species combinations grown on four soils. Our conceptual framework describes both mechanisms of complementarity and facilitation and outcomes (overyielding of mixtures or no overyielding) depending on the competitive ability of the species to uptake the mobilized P. Millet/chickpea mixtures were grown in pots on two calcareous soils mixed with calcium-bound P (CaP) and phytate P (PhyP). Cabbage/faba bean mixtures were grown on both acid and neutral soils mixed with P-coated iron (hydr)oxide (FeP) and PhyP. Wheat/maize mixtures were grown on all four soils. Rhizosphere carboxylate concentration and acid phosphatase activity (mechanisms) as well as plant P uptake and biomass (outcome) were determined for monocultures rhizosphere and species mixtures. Facilitation of P uptake occurred in millet/chickpea mixtures on one calcareous soil. We found no indications for P acquisition from different P sources, neither in millet/chickpea, nor in cabbage/faba bean mixtures. Cabbage and faba bean on the neutral soil differed in rhizosphere acid phosphatase activity and carboxylate concentration, but showed no overyielding. Wheat and maize, with similar root exudates, showed overyielding (the observed P uptake being 22% higher than the expected P uptake) on one calcareous soil. We concluded that although differences in plant physiological traits (root exudates) provide necessary conditions for complementarity and facilitation with respect to P uptake from different P sources, they do not necessarily result in increased P uptake by species mixtures, because of the relative competitive ability of the mixed species.     

东祁连山高寒草甸土壤酶活性及其化学计量特征对海拔和坡向的响应

研究高寒草甸微尺度海拔和坡向下土壤酶活性及其化学计量特征的变化对于探讨草地生态系统养分循环过程具有重要的生态学意义。以东祁连山高寒草甸为研究对象,分析了7个海拔（2 800,3 000,3 200,3 400,3 600,3 800,4 000 m）和2个坡向（阴坡、阳坡）高寒草甸的土壤酶活性、化学计量特征变化规律及其与土壤理化因子之间的关系。结果表明：海拔和坡向的交互效应对土壤亮氨酸氨基肽酶（LAP）、β-葡萄糖苷酶（BG）、多酚氧化酶（PPO）和过氧化物酶（POD）酶活性、lnBG/ln （NAG+LAP）、lnBG/lnAP和ln （NAG+LAP）/lnAP有显著影响;LAP、AP、BG、POD、lnBG/ln （NAG+LAP）、lnBG/ln （NAG+LAP）随海拔的升高呈先升高后降低,β—1,4—乙酰基氨基葡萄糖苷酶（NAG）和PPO随海拔升高而降低;同一海拔,阳坡土壤AP、BG、POD、PPO酶活性低于阴坡,阳坡土壤NAG酶活性高于阴坡,海拔3 800 m以下阳坡LAP酶活性低于阴坡,除海拔3 000 m和4 000 m外的其他海拔阳坡的土壤lnBG/ln （NAG+LAP）高于阴坡,海拔3 000~3 400 m的土壤lnBG/lnAP和海拔3 000~3 600 m的土壤ln （NAG+LAP）/lnAP在阳坡低于阴坡。相关分析发现,土壤酶活性及其化学计量特征不同程度受土壤C、N、P资源及土壤水分条件等的调控,土壤含水量和有机碳是影响土壤酶活性的主要因子。综上,土壤酶活性及其化学计量特征在微尺度海拔和坡向上具有差异性,且受土壤C、N、P资源及土壤水分条件的综合影响,以土壤含水量和有机碳尤为突出。