基于有效积温的中国水稻生长模型的构建

有效积温是指作物生长至某一生育阶段所需要积累的有效温度,是反映气象条件对作物生长影响的主要指标,研究有效积温对作物生长过程的影响对提高农业生产效率具有重要意义。该文以有效积温作为气象因子,收集中国气象数据网中的气象数据和已发表的学术论文中的水稻生长数据,建立了描述水稻生长过程的叶面积指数和干物质积累量的普适Logistic模型,并研究了水稻最大叶面积指数与最大干物质积累量、收获指数(作物经济产量与生物产量的比值)及降水量之间的关系。结果表明:有效积温为1000℃左右时,水稻叶面积指数最大,且此时干物质增长速率最大;水稻最大叶面积指数与最大干物质积累量之间表现为线性关系;最大叶面积指数和收获指数、降水量之间为二次抛物线关系,当降水量为670.5 mm时,最大叶面积指数为7.93,对应的水稻收获指数达到最大值0.50。该研究对于构建其他作物的生长模型具有一定的参考意义。     

Root architecture of sorghum genotypes differing in root angles under different water regimes

Plant root architecture offers the potential for increasing soil water accessibility, particularly under water-limited conditions. The objectives of this study were to evaluate the root architecture in two genotypes of sorghum (Sorghum bicolor (L.) Moench) differing in root angles and to assess the influence of different deficit irrigation regimes on root architecture. The response of two sorghum genotypes, ‘Early Hegari-Sart’ (EH; steep root angle) and ‘Bk7’ (shallow root angle) to four irrigation treatments was investigated in two replicated outdoor studies using large pots. The results indicated that EH possessed steeper brace and crown root angles, fewer brace roots, greater root biomass, and root length density than Bk7 at deeper soil depths (i.e., 15–30 and 30–45 cm) compared with a shallower depth (i.e., 0–15 cm). Across the soil profile, EH had greater root length density and length of roots of small diameter (<1 mm) than Bk7. Accordingly, EH showed more rapid soil-water capture than Bk7. Different levels of irrigation input greatly affected root architecture. Severe deficit irrigation (25% of full crop transpiration throughout the season) increased the angle and number of crown roots, root biomass, and root length density compared with 75 and 100% of full crop transpiration treatments. Consequently, root system architecture can be effectively manipulated through both genotypic selection and irrigation management to ensure optimal performance under different levels of soil available water.     

Variations of SOC and MBC observed in an incubated brown loam soil managed under different tillage systems for 12 years

To assess changes in organic carbon pools, an incubation experiment was conducted under different temperatures and field moisture capacity (FMC) on a brown loam soil from three tillage practices used for 12 years: no‐till (NT), subsoiling (ST) and conventional tillage (CT). Total microbial respiration was measured for incubated soil with and without the input of straw. Results indicated that soil organic carbon (SOC) and microbial biomass carbon (MBC) under ST, NT and CT was higher in soil with straw input than that without, while the microbial quotient (MQ or MBC: SOC) and metabolic quotient (qCO₂) content under CT followed the opposite trend. Lower temperature, lower moisture and with straw input contributed to the increases in SOC concentration, especially under NT and ST systems. The SOC concentrations under ST, with temperatures of 30 and 35°C after incubation at 55% FMC, were greater than those under CT by 28.4% and 30.6%, respectively. The increase in MBC was highest at 35°C for 55%, 65% and 75% FMC; in soil under ST, MBC was greater than that under CT by 199.3%, 50.7% and 23.8%, respectively. At 30°C, the lower qCO₂ was obtained in soil incubated under NT and ST. The highest MQ among three tillage practices was measured under ST at 55% FMC, NT at 65% FMC and CT at 75% FMC with straw input. These data indicate the benefits of enhancing the MQ; the low FMC was beneficial to ST treatment. Under higher temperature and drought stress conditions, the adaptive capacity of ST and NT is better than that of CT.     

Interactions between crop biomass and development of foliar diseases in winter wheat and the potential to graduate the fungicide dose according to crop biomass

Foliar pathogens such as Zymoseptoria tritici and Puccinia striiformis causing septoria leaf blotch and yellow rust respectively can cause serious yield reduction in winter wheat production, and control of the diseases often requires several fungicide applications during the growing season. Control is typically carried out using a constant fungicide dose in the entire field although there may be large differences in crop development and biomass across the field. The objective of the study reported in this paper was to test whether the fungicide dose response curve controlling septoria leaf blotch and other foliar diseases in winter wheat was dependent on crop development and biomass level. If such a biomass dependent dose response was found it was further the purpose to evaluate the potential to optimize fungicide inputs in winter wheat crops applying a site-specific crop density dependent fungicide dose. The study was carried out investigating fungicide dose response controlling foliar diseases in winter wheat at three biomass densities obtained growing the crop at three nitrogen levels and using variable seed rates. Further the field experiments included three fungicide dose rates at each biomass level, an untreated control, and 75%, 50% and 33% of the recommended fungicide dose rate and the experiments were replicated for three years. Crop biomass had a significant influence on occurrence of septoria and yellow rust with greater disease severity at increasing crop biomass. In two of three years, the interaction of crop biomass and fungicide dose rate had a significant influence on disease severity indicating a biomass-dependent dose response. The interaction occurred in the two years with high yield potential in combination with severe disease attack. If the variation in crop density and biomass level obtained in the study is representative of the variation found cultivating winter wheat in heterogeneous fields, then there seems to be scope for optimizing fungicide input against foliar diseases site-specific adapting the dose according to crop density/biomass.     

秸秆还田与优化施氮改善烤烟根际土壤碳氮转化及氮素吸收

针对华南沙泥田烟区氮肥过量施用导致烟叶品质下降的问题,拟通过秸秆还田与氮肥优化配施调节烤烟各生育期氮吸收、根际土壤碳氮转化及相关酶的活性。试验采用随机区组设计,设水稻秸秆还田与氮肥两因素,其中3个碳（秸秆还田）水平：C0,无秸秆还田,0 kg/hm ²;C1,中量秸秆还田,4500 kg/hm ²;C2,全部秸秆还田,9000 kg/hm ²;2个氮水平：N1,传统施氮,169.50 kg/hm ²;N2,优化施氮,105.00 kg/hm ²。结果表明,与N1相比,N2处理秸秆还田下烤烟前期烟叶和根系氮吸收和累积正常,而后期有所下降;C1、C2处理时,与现蕾期相比,成熟期时根系氮含量均降低4.2 g/kg,叶片氮含量降低3.8、3.0 g/kg;成熟期时,与N1处理相比,N2处理时C1、C2处理的土壤无机氮含量降低30.4%、20.0%,前期2个氮处理间土壤无机氮含量无差异,优化施氮下中量秸秆还田（C1N2）处理烤烟土壤NH₄ ⁺-N含量在整个生育期内较高且呈降低趋势,而硝态氮和土壤无机氮含量在成熟期最低,表明中量秸秆还田下优化施氮能够维持生育前期土壤无机氮含量,且降低成熟期土壤无机氮含量。2个秸秆还田量处理时,团棵期N2处理的土壤转化酶活性是N1处理的1.30、1.13倍;旺长期土壤转化酶活性是N1处理的1.27、1.10倍;与传统施氮相比,秸秆还田下优化施氮处理增加了整个生育期土壤脲酶、磷酸酶、过氧化氢酶活性。在中量秸秆还田（C1）处理下,与N1水平相比,现蕾期和成熟期的N2处理土壤水溶性碳含量提高11.2%和14.1%;与N1相比,N2处理的土壤微生物量氮含量呈降低趋势。综上所述,优化施氮耦合中量秸秆还田（C1N2）能够提高土壤水溶性碳含量,维持土壤氮素合理供应,稳定烤烟生育前期对氮素吸收与累积,减少生育后期烟叶氮素奢侈吸收,与烤烟吸氮规律比较吻合。     

Summer drought decreases Leymus chinensis productivity through constraining the bud,tiller and shoot production

Extreme drought events can directly decrease productivity in perennial grasslands. However, for rhizomatous perennial grasses it remains unknown how drought events influence the belowground bud bank which determines future productivity. Ninety‐day‐long drought events imposed on Leymus chinensis, a rhizomatous perennial grass, caused a 41% decrease in the aboveground biomass and a 28% decrease in belowground biomass. Aboveground biomass decreased due to decrease in both the parent and the daughter shoot biomass. The decreases in daughter shoot biomass were due to reductions in both the shoot number and each individual shoot weight. Most importantly, drought decreased the bud bank density by 56%. In addition, drought induced a bud allocation change that decreased by 41% the proportion of buds that developed into shoots and a 41% increase in the buds that developed into rhizomes. Above results were supported by our field experiment with watering treatments. Thus, a 90‐day‐long summer drought event decreases not only current productivity but also future productivity, because the drought reduces the absolute bud number. However, plasticity in plant development does partly compensate for this reduction in bud number by increasing bud development into rhizomes, which increases the relative allocation of buds into future shoots, at the cost of a decrease in current shoots.     

高州油茶人工林碳储量分布特征

【目的】探明高州油茶Camellia gauchowensi人工林碳储量及分布特征,并估算评价其固碳效应。【方法】根据样地植株径级分布特征,选取不同径级样株各2～3株,取树叶、树干、树枝、树根、果实、花芽各器官测定生物量和碳含量,并建立各器官生物量模型;在标准地内按"S"形选取8个样点,沿土壤剖面分层采集0～20、20～40、40～60和60～100 cm土层的土壤样品,测定土壤容重与碳含量,计算碳储量。【结果】高州油茶中龄林植株各器官生物量分配比例依次为树干树根树叶树枝果实花芽,各器官生物量均随地径的增大而增大。试验林分总生物量为26.902 t·hm~(-2),树体平均碳质量分数为483.45 g·kg-1。同径级各器官的碳含量不同,其中,果实平均碳含量最高。林地100 cm深土层中,土壤碳含量随着土层深度的增加呈明显递减规律,其中,0～20 cm土层碳含量最高,碳质量分数为26.550 g·kg-1。高州油茶林地总碳储量为144.538 t·hm~(-2),其中,树体碳储量为12.857 t·hm~(-2),占总碳储量的8.90%;林地土壤碳储量为131.681 t·hm~(-2),占总碳储量的91.10%。根据中国生物多样性国情报告编写组数据,碳价格为260.90元·t-1,则本试验高州油茶林的碳汇经济效益约为3.8万元·hm~(-2)。【结论】高州油茶林分碳储量高于广东省经济林平均碳储量,林地土壤碳储量高于广东省平均土壤碳储量,林分总碳储量高于珠三角森林生态系统碳储量,具有较高的生态效益。高州油茶不仅有较好的生产效益,而且具有十分广阔的固碳前景。     

甘蓝型油菜耐低温生长生理生化响应机制

为提高甘蓝型油菜耐寒育种过程中的筛选效率，研究甘蓝型油菜耐低温机理，以8个不同抗寒性的甘蓝型油菜为材料，对低温条件下各材料的生物量、叶绿素、脯氨酸和相对电导率进行测定，发现在室外平均气温2.75℃时，抗性材料的生物量、叶绿素和脯氨酸的累积量都显著高于敏感材料，相对电导率没有显著差异；当平均气温7.52℃回升至12.39℃，抗性材料和敏感材料生物量的累积量无显著差异；在恒定低温10℃/4℃处理下抗性材料和敏感材料在处理前3周生物量均持续累积，但从第4周开始敏感材料新叶出现白斑，生物量减少，抗性材料老叶出现白斑，生物量维持不变。结果表明，耐低温材料在低温条件下叶绿素含量受到的影响较小，脯氨酸的积累量持续上升，具有较强的快速适应能力，在低温下具有显著的持续生长优势。     

广西巨尾桉2年生人工幼林生物量及生产力研究

在对广西沙塘林场巨尾桉2年生人工林调查基础上，按标准木法测定巨尾桉人工幼林生物量，建立其估算模型，计算出巨尾桉人工林分的生物量和生产力，分析各器官生物量分配规律及林分生产力水平。结果表明，2年生巨尾桉人工林年生物量为16.57 t/hm^2，其中，干、根、叶、枝、皮各器官生物量所占比例依次为46.67％、16.85％、14.62％、12.16％、9.62％。应用建立的估算模型估测巨尾桉人工幼林生物量，其相关程度达显著水平。     

保水剂和微生物菌肥配施对旱作燕麦土壤微生物生物量碳、氮含量及酶活性的影响

为探讨保水剂和微生物菌肥配施后旱作燕麦土壤微生物生物量碳、氮含量及酶活性的影响,在内蒙古黄土高原旱作农田设置不施用保水剂和微生物菌肥(CK)、保水剂和微生物菌肥配施(A)、单施微生物菌肥(B)和单施保水剂(C)4个处理,分析燕麦全生育期内0—10,10—20,20—40 cm土壤微生物生物量碳、氮含量及酶活性时空动态变化和产量变化。结果表明:(1)全生育期,土壤微生物量碳含量呈"双峰"曲线变化,峰值均出现在孕穗期和灌浆期;氮含量呈先降低后升高再降低趋势,苗期含量最高;过氧化氢酶、蔗糖酶、脲酶活性均呈"单峰"曲线变化,过氧化氢酶、土壤蔗糖酶峰值在孕穗期,土壤脲酶则在抽穗期。(2)除CK外,土壤微生物量碳、氮含量及过氧化氢酶、蔗糖酶和脲酶活性表现为0—10 cm10—20 cm20—40 cm,其中配施(A)对0—10,10—20 cm影响均显著(p0.05),单施(B、C)仅对10—20 cm土层影响显著(p0.05)。(3)10—20 cm土层,配施(A)与其他3个处理间差异均显著(p0.05),提高微生物量碳含量4.82%～40.28%、微生物生物量氮含量8.44%～68.66%、过氧化氢酶活性13.32%～60.16%、蔗糖酶活性10.45%～39.14%、脲酶活性12.40%～55.62%。(4)配施(A)能同时显著(p0.05)提高燕麦籽粒产量和生物产量,提高幅度分别为8.40%～20.12%和10.80%～25.09%。因此,保水剂和微生物菌肥配施在黄土高原旱作区具有较好改善土壤微生物活性效果,提高旱作燕麦产量。