Determining spatial and temporal variability in quantity and quality of vegetation for estimating the predictable sustainable stocking rate in the semi-arid savanna

This study assessed the importance of spatial and temporal variation in plant quality and quantity for determining sustainable stocking rates in game, commercial and communal ranches in semi-arid savanna of the Northern Cape Province, South Africa, in wet and dry seasons over a two-year period. We focussed on variation in plant biomass, phosphorus (P), crude protein (CP) concentrations and dry matter digestibility as parameters most likely to affect sustainable stocking rates. Habitat type had greater effects on plant quality, plant biomass and species composition than management type. The commercially-managed area had the highest tree density in the rocky habitat and lower plant quality than other management types. All of these features indicate that land degradation is occurring on commercial ranches in spite of rotational grazing and lower stocking density than on communal ranches. We recommend that commercial ranchers should introduce a greater variety of stock and/or game to reduce selective grazing of certain plant species. Quality measures (CP and P) gave more conservative predictions of stocking density than biomass. In this region of the Northern Cape, seasonally-inundated pan habitats are particularly valuable in spite of low-standing crop because they have the highest year-round quality. Contrastingly, ranchers should only lightly stock open savanna habitats, in spite of high standing biomass, because they have low vegetation quality and may be particularly susceptible to degradation and invasion by poisonous and unpalatable plants.     

桑树硬枝无土催根扦插试验

将 4个桑树品种的一年生枝条冷藏 2 0d后 ,用ABT生根粉和吲哚乙酸溶液处理插条 ,在蚕种催青室自动控制温补湿条件下无土催根。虽然不同桑树品种用不同药剂处理后 ,发根率和发根数存在显著差异 ,但各品种都能达到80 %以上的发根率和 2 5条左右的发根数。待新根刚突破皮层时移栽苗床 ,基本都可成活     

茶树种植密度与排列方式对个体与群体结构的通径分析

本文用通径分析方法对茶树不同种植密度与茶树骨架形成、分枝结构、蓬面结构三大要素进行对应分析,结果表明:1)随密度上升主干粗度、一、二级分枝粗度下降;2)分枝角度随密度上升而变小;3)随密度上升,小桩数随之增加,其它因子与之呈负相关。由于密度上升后,群体结构的光合面积增大,碳水化合物积累增多,而产量上升。选用合理密度与排列组合时,可用回归方程计算。     

四川盆西北脐橙生态适应性和主要栽培技术初探

本文研究了脐橙在四川盆西北地区的生态适应性、苗木质量性状、栽植密度和丰产栽培技术。结果表明,采用壮苗和密植是提高早期产量和经济效益的有效途径。     

玉米密度与产量及产量构成因素关系的研究

通过研究玉米密度与产量以及产量构成因素的关系。结果表明 :密度对玉米秃尖长的影响最大 ,对玉米株高的影响也很大 ,其次是千粒重、行粒数 ,对穗长的影响不显著。密度是影响玉米产量的关键因素 ,攀西地区及其类似地区的玉米高产密度不宜超过 876 0 8株 /hm2 ,最佳经济生产密度为 80 0 0 0～ 85 0 0 0株 /hm2 。     

紫杉木材解剖构造及其材性分析

运用对比分析的方法对紫杉（ＴａｘｕｓｃｕｓｐｉｄａｔａＳｉｅｂ．）木材的解剖特征、管胞的大小、长宽比等进行了较详细地测定与分析;对紫杉木材的气干密度、干缩系数、化学成分进行了测定。结果表明：紫杉木材射线管胞内壁锯齿状加厚明显,交叉场纹孔多为窗格状,偶见松型,管胞的长宽比平均值约为５０,气干密度平均值约为５９８ｋｇ／ｍ３,差异干缩约为１８;１％ＮａｏＨ抽出物较落叶松高,其它化学指标比落叶松低。     

群体密度对亚种间杂交稻Ⅱ优162产量形成的影响

通过设置９～３６株／ｍ２１０个水平的栽插密度试验,探讨了群体密度对亚种间杂交稻Ⅱ优１６２生长发育与产量形成的影响,结果表明：有效穗数随着栽插密度的增大而增多,穗粒数则相反,产量（Ｙ）与栽插密度（Ｘ）满足Ｙ＝Ｘ３３０６＋５９８６×１０－６×Ｘ１．２２３７２６方程,产量在密度１２～３０株／ｍ２范围内差异不显著,说明亚种间杂交稻Ⅱ优１６２自我调节能力很强;单株分蘖数和成穗率随着群体增大而降低,达到最高苗的时期和有效分蘖终止期随栽插密度增大而提早;抽穗后干物质积累量和ＲＧＲ随密度增大而降低。     

成都平原稻田持续高产高效种植制度的定位研究

本文通过六年定位试验，从生产能力、经济效益及对土壤理化性状的影响几方面进行分析，探讨不同种植制度的产量水平、经济效益和稳产性。综合分析结果看出：成都平原稻田麦稻晚秋，油、稻晚秋轮作方式有利于改善土壤理化性状，提高土壤肥力，实现持续高产高效，是本区较优良的持续高产高效种植制度；在目前一年二熟制为主的情况下，应大力开发利用晚秋资源，提高稻田综合效益；增种一季晚秋作物有利于后茬小麦增产，对减轻小麦连作障碍有显著作用，油菜、小麦连作都会导致土壤理化性状恶化、作物产量降低。     

颗粒茶新工艺技术研究——Ⅰ .影响颗粒的主要因素

以春季末茶和夏秋季茶鲜叶为原料加工的颗粒茶色泽深绿油润,滋味醇和爽口,清香明显,汤色黄绿明亮。末茶的比例和锤切原料的含水量,是影响颗粒茶成粒率和颗粒紧结度的主要因素。随着末茶比例或含水量地增加,颗粒茶成粒率及颗粒紧结度均呈单峰曲线变化。试验研究结果表明:茶鲜叶∶末茶为8∶2、锤切原料含水量为71%时,其颗粒的成粒率和紧结度最高,感官品质最好,加工时间较短。     

Nitrogen and phosphorus concentration in faeces: an indicator of range quality as a practical adjunct to existing range evaluation methods

Vegetation monitoring, currently complemented by climatic data in particular rainfall areas, does not always supply sufficient information to provide reliable guidelines for appropriate stocking densities on ranch or reserve scale. This paper considers how the nutrient status of animals may be used to improve the setting of management guidelines by reflecting how wild herbivores perform under differing environmental and management conditions. Faecal nitrogen concentrations of between 13 and 16 g kg^?1 are above a threshold level that indicates a dietary deficiency which may precipitate nutritional stress in animals (such as happened during the 1991/1992 drought). Faecal phosphorous concentrations of between 1.9 and 2.0 g kg^?1 over a long period of time would indicate a deficiency that may lead to low reproductive rates. Faecal analysis could therefore be used to assess whether applied stocking densities will allow grazers, and probably mixed feeders such as impala too, to select for a diet of sufficient quality for maintenance.