三峡库区端坊溪小流域的森林水文效益

 三峡库区的森林水文作用,对于长江三峡水利枢纽工程的安全运行和效益发挥具有重要意义,对于改善和维持三峡库区的生态环境具有重要作用。根据1992— 2000年实测降雨、径流等观测资料,分析了三峡库区端坊溪小流域森林的林冠截留作用、林地枯落物的水文作用及森林覆盖率与土壤容重、土壤孔隙和小流域径流的关系。结果表明:三峡库区端坊溪小流域不同树种枝条基部直径与枝叶质量呈线性正相关,不同树种枝叶容水量与枝叶质量呈线性正相关,不同森林类型在场降雨中,林冠截留量为0.38～8.78mm,截留率为10.27%～49.48%,林冠截留量与降雨量呈幂函数关系;随着森林覆盖率的增加,林地的土壤容重减少,总孔隙度增加;主要森林类型中,针阔混交林林地枯落物的饱和持水量最大,端坊溪小流域枯落物层截留量可达到降水量的2.8%～6.3%;小流域径流量与同期降水量呈线性正相关。端坊溪小流域森林覆盖率每增加1%,小流域汛期径流深减少6.95mm。     

榆林市黄河沿岸土石山区枣树育苗技术

结合黄河沿岸土石山区干旱缺水,土壤贫瘠特点和育苗地缺乏的实际,总结了该区域比较适应的归圃育苗和根孽育苗两种育苗技术,主要包括苗圃地选择、育苗方法、苗木等级分类及起苗、包装、调运等关键技术。     

县市级尺度土地利用与土地覆盖变化初步研究——以江苏昆山市为例

在分析县市级尺度土地利用与土地覆盖变化(LUCC)研究的重要性的基础上，以江苏省昆山市为例，根据其1994—2000年土地利用详查及变更资料，从土地利用现状入手，分析其土地利用的现状特征。并采用土地利用程度、土地利用变化和景观学的空间格局的相关指数等具体指标，对昆山市的土地利用现状及其变化进行了定量分析。最后根据分析结果给出了相关的结论。     

Small isolated aspen stands enrich bird communities in southwestern ponderosa pine forests

Small aspen stands are disappearing from the landscape in the Southwest, so it is important to understand their contribution to the avian community. We sampled birds in 53 small, isolated aspen stands and 53 paired plots within the ponderosa pine forest in northern Arizona, during the 1996 and 1997 breeding seasons. Bird species richness and abundance were higher in aspen than in pine. However, bird species richness and abundance did not vary with size of the aspen patch or isolation index. In addition, direct ordination of species distributions with habitat factors suggested no distinct avian communities. This suggests that aspen stands do not harbor separate populations, but rather are locations where the regional avifauna reaches high local density and richness and may be crucial to birds in years of resource scarcity. Thus it is important for avian conservation to maintain many aspen stands across the landscape, encompassing a diversity of vegetation structure and composition.     

辽宁省东部山区六县农村能源生态建设情况的调查

该文以大量数据，说明辽宁省东部山区清原等6县生态环境及农村能源生态建设情况，提出加强东部山区农村能源生态建设的建议。东部山区森林资源生态价值和经济价值巨大，是辽宁省绿色天然屏障。清原等6县森林资源在全省占有重要份额，但农户生活耗柴对森林资源造成极为严重的破坏，导致水土流失，生态环境恶化。 进一步加强农村能源生态建设，已经成为保护森林资源的重大举措，成为东部山区实施可持续发展战略的重要内容。建议从认识、法制、科研、培训、投入、体系建设等方面入手，加大农村能源生态建设力度。     

Soil phosphorus dynamics in cropping systems managed according to conventional and biological agricultural methods

The effects of conventional and biological farming systems on soil P dynamics were studied by measuring some microbiological parameters after 13 years of different cropping systems. The treatments included control, biodynamic, bio-organic, and conventional plots and a mineral fertilizer treatment. The farming systems differed mainly in the form and quantity of nutrients applied and in the plant protection strategies. The results of a sequential fractionation procedure showed that irrespective of the form of P applied, neither 0.5 M NaHCO _inf3 ^sup- nor 0.1 M NaOH-extractable organic P, but only the inorganic fractions, were affected. The residual organic P, not extracted by NaHCO₃ or NaOH was increased in the biodynamic and bio-organic plots. The soil microbial biomass (ATP content) and the activity of acid phosphatase were also higher in both biologically managed systems. These results were attributed to the higher quantity of organic C and organic P applied in these systems, but also to the absence of or severe reduction in chemical plant protection. The relationship between acid soil phosphatase and residual organic P was interpreted as an indication that this fraction might be involved in short-term transformations. The measurement of the intensity, quantity, and capacity factors of available soil P using the ³²P isotopic exchange kinetic method showed that P could not be the factor limiting crop yield in the biological farming systems. The kinetic parameters describing the ability of P ions to leave the soil solid phase, deduced from isotopic exchange, were significantly higher for the biodynamic treatment than for all other treatments. This result, showing a modification of chemical bonds between P ions and the soil matrix, was explained by the higher Ca and organic matter contents in this system.     

Sensitivity to information upscaling of agro-ecological assessments: Application to soil organic carbon management

Upscaling of agro-ecological indicators applied in regional analyses is sensitive to scale issues of the input data. This study develops a methodology to quantify this sensitivity for an indicator of soil organic carbon (SOC) dynamics at the farming system level. A reference case consists of seven fully described farms in northern Italy. Both upscaling in complexity by substituting measured input with estimated input and upscaling in space by extending the methods to farms not included in the reference case are addressed. The indicator increased with 3-107% at four farms after substituting measured management input with that estimated by an expert, whereas it remained unchanged or decreased at the other three farms. Taking the modal value from a cluster of pedological input did not lead to additional uncertainty in most cases, and only slightly increased it in others. We evaluated spatial upscaling by including 733 farms divided in 18 clusters that were described with less information as compared to the reference farms. Within each cluster, we observed relevant variability of the indicator (coefficients of variation of 12-43%), as a consequence of the heterogeneity of farms comprised in each cluster. In each cluster we calculated the indicator for one virtual farm, defined by using modal values for basic farm inputs. In this case the indicator was highly correlated (R² = 0.98) with the average of the values obtained using measured basic farm inputs. We conclude that upscaling in complexity and space introduces uncertainty in the values of the indicator compared to the reference case. The extent of such differences depends on the variability of the systems under analysis and on indicator sensitivity.     

湖南永州地区钙质页岩土壤动物群落多样性研究

通过对永州不同生境设立5个样区进行取样调查，共获得土壤动物2024头，隶属于5门、10纲、31目、111科、共152种。其中垫刃目、弹尾目、蜱螨目属于优势类群；矛线目、膜翅目等14个目属于常见类群，构成了永州土壤动物的主体。不同生境中土壤动物的种类和个体数量都有一定的差异，苗由和杉树林远远大于其它3个生境。土壤动物的垂直分层也比较明显，种类和个体数量随着土壤层次的加深而减少，具有明显的表聚性。对各生境的密度一类群指数DG、丰富度指数D、多样性指数H、优势度指效c、均匀性指数E和相似性系数进行分析，结果表明，植被类型、土壤有机质含量是影响土壤动物群落结构的主要生态因子。     

邵东县水田种植制度优化模型的研究

本文应用线性规划原理,建立了湖南中部丘陵地区邵东县水田种植制度优化模型。优化过程中,以净产值(不包括利息和税金)为目标函数,对总面积、主要作物播种面积、适宜用地、冬闲田等进行了约束。优化结果净产值可增加17801900元,增长了14.4%。     

高寒牧区大牧场生产系统的能量流研究

为了研究高寒牧区经济生态复合系统的能量结构与功能,作者对青海门源种马场和其中一个家庭牧场1987～1988年生产情况进行了详细调查,以系统的观点分析了大牧场及其家庭牧场生产系统的能量结构与转化效率。计算出青海门源地区大牧场生产系统的能量转化效率为:太阳辐射能→牧草地上部分0.037％,牧草地上部分→畜群51.10％,畜群→家庭牧场2.15％,家庭牧场→大牧场61.61％,大牧场→系统外13.88％。全系统的能量转化效率(太阳能→系统外)为:3.5×10~(-7)。