我国大城市地区农业生产率比较

大城市地区农业生产水平高于全国平均水平 ,但是不同城市农业增长的源泉是不相同。通过对我国大城市地区农业生产率进行比较 ,区分各地农业增长的来源与差异 ,以便采取相应的措施。     

提高种植土 pH 值、电导率方法

南方雨水多导致土壤偏酸和电导率低,原生土一般不可直接用作园林种植土。如何提高土壤的 pH 值与电导率,成为南方园林绿化工作者的重要课题。广州市生态景观林带项目——广河高速凤凰山隧道绿化工程采用增施无机肥的方法来改良种植土,是改良南方酸性种植土电导率低的有益尝试。     

福建柏人工林生物量的研究

福建柏 (ＦｏｋｉｅｎｉａｈｏｄｇｉｎｓｉｉＨｅｎｒｙｅｔＴｈｏｍａｓ)为我国二类重点保护树种 ,其树形优美 ,主干通直 ,适应性强 ,木材性质优良 ,是我国南方值得推广的树种。由于人为破坏 ,福建柏天然纯林被毁殆尽 (张炳荣 ,1 982 )。自 50、60年代 ,福建省开始营造福建柏人工林 ,不少已进入中成龄阶段 ,成为重要的森林资源。但对其进行的研究还很少。 1 997年我们对安溪半林国有林场福建柏人工林的生物量及其结构进行了研究 ,以期对福建柏人工林的研究提供基础资料 ,也为了解福建柏人工林的生产力 ,以对其进行合理经营提供科学依据。1…     

Influence of plantation site and wastewater sludge fertilization on the performance and foliar nutrient status of two willow species grown under SRIC in southern Quebec (Canada)

Salix discolor Mühl. (Sd) and Salix viminalis L. (Sv) were planted under short-rotation intensive culture (SRIC) on three unirrigated abandoned farmland sites with different drainage conditions, one well-drained (S₁) and the other two poorly-drained (S₂, S₃). One dose of dried and granulated sludge equivalent to 150 (T₁) kg of “available” N ha⁻¹ was applied to some plots in the spring of the second season while others were left unfertilized (T₀). The aims of the experiment were (i) to investigate plant response (growth and productivity) to plantation site conditions and sludge application; (ii) study nutrient status by foliar analysis. Over three seasons, growth in height and aboveground biomass were greater for S. viminalis than for S. discolor on all sites. S. viminalis planted on poorly-drained site 2 had the highest biomass yield (45.28 t ha⁻¹). Both species showed best height and diameter growth on poorly-drained sites. For both species, best performances were obtained on wastewater sludge fertilized plots. Comparative foliar analysis suggested that unfertilized sandy soil (S₁) and low foliar nitrogen concentration and content were limiting factors in the performance of the two species. Soil nitrate concentration increased as a result of sludge application. Heavy metal accumulation from sludge does not represent a risk to the environment. It was concluded that S. viminalis had the best productivity on clay sites, and that a moderate dose of dried and pelleted sludge (150 kg of “available” N ha⁻¹) may be a good fertilizer during the establishment of willows in SRIC, and may reduce nitrate leaching.     

冷地型鸭茅不同品种生产性能的研究

对日本引入的 1 2个冷地型禾草品种 (其中 9个鸭茅品种 ,3个参考品种 )的生产性能进行了研究 ,其结果表明 ,9个鸭茅品种都能适应当地的环境条件 ,且生产发育良好。 4月初返青 ,5月下旬抽穗 ,除干草王Ⅱ之外 ,返青后 6周左右即可进行第一次刈割。其干物质产量由高到低依次为 :干草王、秋绿、Potomac、早生绿、先进、夏绿、风绿、北斗和干草王Ⅱ。三年的干物质产量为 1 4 895～ 2 0 5 1 4kg/hm2 ,干草王Ⅱ的干物质产量显著低于其它品种(P <0 0 5 )。再生草产量占总产量的 6 2 2 5 %～ 72 80 %。     

油桐无性系生产力判别评级与预测研究

根据选自福建、浙江等５个油桐主产省（区）７６个油桐优良单株无性系在金华试验点的生长表现，按照其中已测定含油率、产果量和其它性状的６５个油桐无性系样本，建立了生产力评级的Ｆｉｓｈｅｒ判别模型，该模型对分属Ⅰ、Ⅱ、Ⅲ、Ⅳ４个产油量水平的各无性系的回判正判率分别达到了１００％、１００％、８２％、１００％。进而应用该模型预测了未进行气干果含油率测定的其它１１个无性的生产力等级。据此，从７６个无性系中筛选出４４、４８、５４、５６号４个高产优良无性系。     

新型稻谷型饲粮配方养猪研究报告

采用不同饲粮配方单因子试验设计，以４０头长大乐三元杂种猪为素材，在相同条件下，系统对猪的肥育、屠宰性能以及经济效益进行了研究。结果表明，在早稻谷与玉米价比合理前提下，用稻谷型饲粮养猪在技术、生产水平及饲料效率上都是可行的。同时，筛选出二种高产、优质、高效低耗的新型稻谷型饲粮配方Ⅲ、Ⅳ，可供养猪生产中推广应用。本文为合理利用当地饲料资源，促进早稻转化，推动低成本养猪提供了科学依据。     

Why is the productivity of Douglas-fir higher in New Zealand than in its native range in the Pacific Northwest,USA?

Douglas-fir (Pseudotusga menziesii (Mirb.) Franco), a native to the Pacific Coast Range in North America, is recognized as a tree that is long-lived and can grow rapidly to standing volumes that approach the highest recorded for temperate conifers. Managed plantations in western Oregon register maximum periodic annual increments (PAI) at ages between 20 and 40 years of ∼30 m³ ha⁻¹ year⁻¹. The same seed source, when planted in New Zealand and elsewhere in the Southern Hemisphere, may attain a PAI of ∼50 m³ ha⁻¹ year⁻¹. Is this higher productivity mainly related to climate or to isolation from native pests? To evaluate the role of climate, we obtained meteorological data from plantation sites in New Zealand and Oregon, from which we established relationships between mean monthly temperature extremes and solar irradiance, air humidity deficits, and frost frequency. Using these empirical relationships, long-term weather records were converted to the meteorological variables required to drive a process-based forest growth model, 3-PG, for sites approaching the most productive in New Zealand and in Oregon. Annual precipitation is similar in both areas, but sites in Oregon receive only 10% during the growing season, resulting in humidity deficits 30% larger than those recorded in New Zealand. According to sensitivity analyses and direct measurements, the more productive Douglas-fir forests in Oregon avoid the limiting effects of summer drought by obtaining water from the subsoil and fractured bedrock. If such forests were under a reduced evaporative demand similar to that in New Zealand, we show that they would exhibit comparable productivity.     

Herb-layer diversity in deciduous forests: Raised by tree richness or beaten by beech?

Where natural production capacity permits, modern silvicultural management in Central Europe frequently aims at the development of mixed broadleaved stands, instead of pure European beech (Fagus sylvatica) stands. It is crucial to study the effects of these tree-layer diversity variations on herb-layer vegetation, since herb-layer vegetation contributes significantly to ecosystem functioning in forests. In Hainich National Park (Thuringia, Germany), we conducted observational research in deciduous stands to investigate whether herb-layer diversity was related to canopy-layer diversity, and to ascertain possible causal mechanisms. We found that herb-layer vegetation of deciduous forest stands rich in canopy species appeared to be more diverse than herb-layer vegetation of beech-dominated stands. We surmise that herbaceous understorey diversity was indirectly influenced by canopy tree species through the medium of the altered environmental factors soil pH and litter layer thickness. Apparently, lower beech proportion had a more profound effect than the number of secondary tree species. There were no correlations between herb-layer diversity and light transmissibility of the canopy layer, indicating that the light factor was not crucial for herb-layer diversity. At least for the Hainich research sites, our results indicated that small-scale light and soil heterogeneity is insignificant for herb-layer diversity. We found several herb-layer species whose occurrence was particularly correlated with tree-layer diversity and environmental factors. Remarkably, all species positively correlated with soil pH were important for the phytosociological classification of the research sites. Beech-dominated research sites showed high tree-layer volumes, whereas research sites with high tree-layer diversity tended to feature lower tree-layer volumes. These findings could be the result of differing former silvicultural systems and varying soil clay contents affecting tree species composition. In contrast, herb-layer biomass was positively correlated with tree-layer diversity. Herb-layer productivity might be promoted in more diverse research sites by increased nutrient supply and base saturation. It is also possible that greater beech proportion interfered with herb-layer productivity. However, herb-layer biomass was also positively correlated with herb-layer diversity. Hence, our study hints that positive diversity-functioning relationships might occur in the herb-layer of the deciduous forest under investigation.     

我国人工林生产力问题的研究（Ⅰ）—影响我国人工林生产力的自然因素评价

以桉树、杉木、马尾松、落叶松及樟子松等为对象 ,利用样地调查资料 ,结合已有研究成果 ,对造成我国人工林生产力低下的多种自然因素 ,进行了系统地分析研究。结果表明 ,按人工林现实分布格局及立地质量水平 ,全国人工林气候—立地生产潜力 (材积 )平均为 8 6m3 hm2 ·a ;现有人工林由于大面积幼龄林的存在 ,所带来的生产力总体水平下降的幅度为 31%～ 35 %。