柳杉人工林生物量及生产力研究

对广西六万林场31年生柳杉人工林的生物量和生产力进行研究,并建立柳杉不同器官的生物量模型。结果表明:不同径阶单株平均木生物量随着径阶的增大而增大,且不同径阶间生物量差异显著;所拟合的各器官生物量的回归估测模型的决定系数R2值均在0.983以上,达0.01显著水平;不同器官生物量大小依次为:树干>枝条>根蔸>树叶>枯枝>粗根>细根>中根;林分乔木层总生物量达到了239.03 t.hm-2,其中树干的生物量达到了120.24 t.hm-2,占全株的50.30%;林分的年净生产力达7.89 t.hm-2.a-1。     

Factors influencing the variability of Mg, Ca and K in waters of a mangrove creek in Bragança, North Brazil

Sodium, potassium, magnesium, calcium and physicochemical parameters were monitored for one year in a mangrove tidal creek near Bragança, North Brazil, to determine their tidally induced and seasonal variations and the main parameters controlling the concentration of these cations. On a daily basis, cation concentrations showed a strong tidal rhythm due to the mixing of estuarine and mangrove waters. Mean concentrations were highest at the end of the dry season (December 1996) and lowest (April 1997) towards the end of the rainy season. Average values over one year were: Na+ = 329± 118mM, K+ = 6.9±2.5mM, Mg++=37 ±14 mM and Ca++= 6.9±2.4mM. Dissolved oxygen concentration was higher during the dry season due to enhanced aquatic primary production, with a maximum daily average value of 8.5mg/L in July 1996, and a minimum value of 4mg/L in June 1997. Cation concentrations were transformed relating them to the respective average values in standard seawater at salinity 35. Although cation concentrations and salinity tightly correlated, this standardization showed that the concentrations of K+, Ca++ and Mg++ did not depend solely on salinity and reflected the seasonal variation in aquatic primary production. It also allowed the discrimination of their sources (marine, riverine and groundwater). Thermodynamic equilibrium calculations indicate that phytoplankton may be regulating the concentration of these cations in the water column indirectly by inducing precipitation through pH increase and directly through metabolic uptake.     

Managing natural resources of watersheds in the semi-arid tropics for improved soil and water quality: A review

Soil, water and production systems constitute the most important natural resources of a watershed in the rainfed agro-ecosystem; and for sustainability of the production systems they need to be in harmony with the environment. To learn from the past research, a review is made of literature on the impact of natural resource management practices on soil and water quality in the semi-arid tropical regions of India. The results from long-term on station field experiments show that an integrated use of soil and water conservation practices with balanced plant nutrition can not only sustain increased productivity but also maintain soil quality at the watershed or catchment level. Natural resource management practices that conserve soil and water also help to maintain surface and groundwater quality. The changes in soil and water quality, as impacted by natural resource management practices, need to be monitored and assessed on a continuing basis as the outcome of such research offers valuable opportunity for the implementation of corrective management practices, as and when needed.     

显脉金花茶无菌体系建立及增殖培养研究

以显脉金花茶幼嫩带芽茎段作为外植体,开展外植体灭菌、启动培养及增殖培育试验,结果表明:3月采集的外植体最易灭菌,其最佳灭菌方案为先用75%酒精浸泡20 s后用0.1%升汞浸泡9 min;最佳启动培养基配方为WPM+6-BA 7 mg.L-1+NAA 0.25 mg.L-1;最佳增殖培养基配方为:改良WPM(NO3-∶NH4+=2∶1)+6-BA 5 mg.L-1+NAA 0.05 mg.L-1。     

桤木生物量及根系分布规律

采用全部、分层挖取法,研究洞庭湖区9年生桤木人工林的生物量及根系分布规律。结果表明：桤木单株生物量为44.39ks／株,各器官生物量大小排序为树干〉树根〉树枝〉树皮〉树叶;林分总生物量为96.06/hm^2;林分净生产力为10.67/（hm^2·年）。桤木根系发达,根深60～80cm;根系中以根桩和粗根的生物量所占的比例最大,两者之和占根系总生物量的84.27％。在垂直分布上,根系主要分布在0～40cm的土层中,其生物量占根系总生物量的84.51％。在水平分布上,根系主要分布在离树桩0～50cm的范围内,其生物量占根系总生物量的84.49％;特别是粗根,其生物量占根系总生物量的29.47％;茵根的生物量占根系总生物量的0.39％,主要分布在离树桩50～100cm的范围内,该区域根系的生物量占茵根总生物量的70.97％。     

Biomass harvesting in Eucalyptus plantations in Western Australia

Australia is at an early stage of exploring the use of forest biomass to generate energy. This study evaluated the biomass yield and the productivity rates of equipment for harvesting biomass in a poor-quality eucalypt plantation. The operation consisted of a tracked feller-buncher, grapple skidder and mobile chipper. Time study methods were used to measure the harvesting operation. A multiple regression model was constructed to predict skidding productivity. Biomass production was 63.9 t ha^?1 based on the recorded load weight of eight trucks. Delays were documented and analysed. The average delay for all equipment was about 30% of working time. The study results will help guide biomass harvesting managers to estimate productivity and cost of similar operation sites.     

缺氮条件下玉米自交系叶绿素含量与光合效率的变化

在低氮胁迫条件下,对25个玉米自交系穗三叶叶绿素含量、光合速率等进行了研究。结果表明：不同玉米自交系穗三叶叶绿素含量的降低呈现相似的规律性,光合速率也出现不同程度的降低,不同自交系间降低的幅度存在较大差异。穗位叶叶绿素含量的降低可作为氮素利用效率的次级选择指标,以穗位叶叶绿素含量降低的百分率为指标,将供试材料分成4类,其中许178、辽5114等自交系叶绿素含量降低幅度较小,具有较高的氮素利用效率。     

北疆棉花生产力及生产潜力的研究

应用 FAO生态区域法等测算结果 ,北疆棉花光合皮棉生产力理论上限为每公顷 2 0 0 0 7.6kg,北疆各地平均光温皮棉生产力为 2 72 1～5 4 1 9.5 kg,最大光温皮棉生产力达 60 4 5 .0 kg。棉花增产潜力在 1 998年的基础上尚可增加 1 .63～4.2 6倍。北疆棉花光合生物量最大光能利用率为7.5 8% ,生物量光温光能利用率为 2 .0 34%～2 .1 1 0 % ,子棉光温光能利用率为 0 . 81 3%～1 .0 5 5 % ,皮棉光能利用率为 0 .2 76%～ 0 .474%。从而为北疆的棉花持续增产、棉花高产栽培技术及其理论研究提供了信息     

1961—2018年西藏高原青稞产区气候生产潜力时空变化特征

定量评估西藏高原青稞产区不同气候区气候生产潜力空间分布格局、演变特征及其影响机理,对于西藏高原青稞生长环境变化研究和产业可持续发展具有重要意义。基于西藏高原青稞产区不同气候区的7个典型气象站观测资料序列,采用Miami模型、Thornthwaite Memorial模型、气候倾向率、Mann-Kendall突变检验等方法,分析西藏高原青稞产区气候生产潜力时空分布特征及其对气候变化的响应。结果显示：1961—2018年青稞产区各站气温生产潜力(NPP_t)呈极显著增加趋势,降水生产潜力(NPP_r)呈显著增加趋势,蒸散生产潜力(NPP_e)和标准气候生产潜力(NPP_b)也均表现为波动的增加趋势。西藏高原主要青稞产区东部及沿雅江一带气候生产潜力限制因子为降水,高寒的北部地区气候生产潜力限制因子为气温或蒸散。NPP_t、NPP_r、NPP_e、NPP_b均表现为年代际增加趋势,20世纪80—90年代发生突变,且在21世纪初显著增加。1961—2018年气候的“暖湿型”变化趋势有利于当地青稞气候生产潜力的提高,青稞的生产不仅依赖于气候资源,还依赖于水资源的调配和利用。     

农业生产力呈梯次分布的实证分析——以广东农业发展的实际为例

揭示农业生产力呈梯次分布的性质是深入认识农业生产力发展规律的重要标志。选择农业生产力的构成因素及其衡量指标，确定每个构成因素及其衡量指标的权重．从而测算出农业生产力的水平值并对其作梯次划分，可以据此对农业生产力在质的规定上和量的差别上进行剖析，以揭示出一个地区农业生产力的特点及其发展方向，为有针对性地实现农业生产力的科学发展提供决策指导。