Ozone distribution in central Italy and its effect on crop productivity

The focus of the present study was to assess the ozone levels in a typical area of the Mediterranean basin, viz. Tuscany (central Italy). Eighty-thousand hourly mean ozone concentrations were recorded by 10 automatic analysers in the districts of Florence, Pisa, Lucca and Prato, from May to September 1995 to 1997. The highest daily mean concentrations were reached in Florence, with a maximum hourly average of 197 ppb. In Lucca and Pisa, the peaks were close to 100 ppb. Data from Prato were much lower. Long-term critical levels for vegetation, as set by United Nations Economic Commission for Europe (UNECE), were constantly exceeded in Florence and Pisa, occasionally in Lucca, never in Prato. The results were used to fit exposure/yield response relationships proposed by UNECE and US National Crop Loss Assessment Network for some important crops. The estimated yield losses varied in Florence from 8% for corn and alfalfa to 27% for soybean, in Pisa from 5% for corn to 24% for soybean, in Lucca from 3% for corn to 17% for soybean. A preliminary economic estimate for corn, wheat, barley, soybean, tomato and alfalfa, calculated annual damage to be 4.6 M Euro in Florence, 0.5 M Euro in Lucca and 3 M Euro in Pisa. The picture must be regarded as only partial, as exposure/yield response relationships for important Italian crops (such as grapevine and vegetables) are not available.     

铅盐生产企业对周边生态环境的影响

通过连续多年的系统监测和分析,研究了小型铅盐生产企业对周边大气、水、土壤、河流底质和农作物等生态环境的影响.研究发现,生产车间和距其100 m以外的居民区大气中铅尘分别超标548倍和4倍;500 m以外的农田土壤中铅超标1.26倍;雨水排放口附近河道水质中铅超标1.08倍;雨水排放口附近及下游800 m处的河道底质中铅分别超标1.99倍和1.33倍;500 m以外种植的小麦籽粒中铅超标16.5倍.环境污染的程度与距污染源的空间距离呈负相关.在此,还对小型重金属生产企业的环境监测和防止污染的转移提出了建议.     

生物资源的多目标最佳可持续利用

在最优化控制理论的基础上,提出了生物资源的多目标最佳可持续利用的理论和方法。该理论在确定生物资源的收获量时,不但考虑到相应的经济效益和生物的种群恢复能力,同时也考虑了收获对环境和社会效益以及生物群落的影响。包括反映环境、生物、经济和社会效益在内的诸因素作为最优化的目标。为了保证理论上的最佳收获量能被应用到一个具体的生物系统,还提出了制定满意可持续收获策略的思想和方法。作为实例,本文讨论了关于凤眼莲的多目标最佳可持续利用和满意可持续收获策略。     

PIXGRO: A model for simulating the ecosystem CO2 exchange and growth of spring barley

A model, PIXGRO, developed by coupling a canopy flux sub-model (PROXEL_NEE; PROcess-based piXEL Net Ecosystem CO₂ Exchange) to a vegetation structure submodel (CGRO), for simulating both net ecosystem CO₂ exchange (NEE) and growth of spring barley is described. PIXGRO is an extension of the stand-level CO₂ and H₂O-flux model PROXEL_NEE, that simulates the NEE on a process basis, but goes further to include the dry matter production, partitioning, and crop development for spring barley. Dry matter partitioned to the leaf was converted to leaf area index (LAI) using relationships for the specific leaf area (SLA). The canopy flux component, PROXEL_NEE was calibrated using information from the literature on C3 plants and was tested using CO₂ flux data from an eddy-covariance (EC) method in Finland with long-term observations. The growth component (CGRO) was calibrated using data from the literature on spring barley as well as data from the Finland site. It was then validated against field data from two sites in Germany and partly via the use of MODIS remotely sensed LAI from the Finland site.Both the diurnal and the seasonal patterns of gross CO₂ uptake were very well simulated (R² = 0.92). A slight seasonal bias may be attributed to leaf ageing. Crop growth was also well simulated; simulated dry matter agreed with field observed data from Germany (R² = 0.90). For LAI, the agreement between the simulated and observed was good (R² = 0.80), giving an indication that functions describing the conversion of fixed CO₂ to dry matter and the subsequent partitioning leaf dry matter and LAI simulation were robust and provided reliable estimates.The MODIS LAI at a resolution of 1000 m agreed poorly (R² = 0.45) with the PIXGRO simulated LAI and the observed LAI at the Finland site in 2001. We attributed this to the coarse resolution of the image and/or the small size of the barley field (about 17 ha or 0.25 km²) at the Finland site. By deriving a regression relation between the observed LAI and NDVI from a higher resolution MODIS (500 m resolution), the MODIS-recalculated LAI agreed better with the PIXGRO-simulated LAI (R² = 0.86).PIXGRO provides a prototype model bridging the disciplines of plant physiology, crop modeling and remote sensing, for use in a spatial context in evaluating carbon balances and plant growth at stand level, landscape, regional, and with some care, continental scales. Since almost 50% of the European land surface is covered by crops, such a model is needed for the dynamic estimation of LAI and NEE of croplands.     

马尾松低产林套种木荷的林地与根际土壤养分特性的研究

马尾松低产林套种木荷的混交林林地与根际土壤养分特性研究表明，木荷根际对土壤养分的活化能力大于马尾松，这利于混交林中马尾松的生长．套种后所形成的混交林根际微区对土壤养分活化程度的提高改善了两树种的养分利用状况，这可能是低产林改造后林地土壤养分高于纯林地且林分生产力提高的主要原因之一．     

施石灰对新垦赤红壤化学性质和作物生长的影响

本文采用pH4.8、交换性酸2.8cmol kg~(-1),交换性Ca0.8cmol kg~(-1)的花岗岩赤红壤(荒丘),进行盆栽试验和田间试验,研究施生石灰对土壤化学性质及花生、甘薯生长的影响。结果表明,大田施用相当于交换酸60％的生石灰,可使土壤pH值在9个月内保持在5.8以上,但就提高花生产量来说,石灰用量以中和交换性酸30％为宜。土壤中Fe、Al的固P能力远比Ca大,即使施用高量的石灰,新形成的Fe-P、Al-P各为新形成Ca-P的2倍以上,同时亦有大量的O-P形成。各水平的石灰处理均显著改善花生的经济性状和品质,但产量的提高却以低水平石灰处理为显著。     

秸秆与氰胺化钙调控技术对温室黄瓜生长及氮素残留的影响

温室蔬菜生产中普遍存在着土壤硝态氮积累及地下水硝酸盐污染问题,合理调控氮素是减少氮素淋洗的重要措施之一。文章在京郊温室栽培条件下,以农户的习惯施肥措施为对照,在菜田夏季休闲期间施用秸秆-氰胺化钙并结合作物后期的氮素追施调控技术对秋冬茬黄瓜的生长及土壤硝态氮残留进行研究。结果表明:与当地农户的习惯施肥措施相比,采用秸秆-氰胺化钙综合调控技术显著提高黄瓜的产量,增产率达到20%;显著减少氮素追施数量,并具有最低的根层土壤无机氮(Nmin)含量;收获时该处理的土壤剖面(30～180cm)中硝态氮的积累量比农户习惯施肥降低388kg·hm-2,其中最明显的差异出现在30～90cm土层。表明采用秸秆-氰胺化钙综合调控措施通过土壤氮素形态的调控,明显减轻黄瓜生长季节期间的硝态氮淋洗的风险。     

200 years of sustainability in forestry: Lessons from history

Since the end of the 1980s the concept of sustainable development has gained general acceptance, but much uncertainty still exists on how to operationalize this concept. In forestry the concept of sustainability has been an accepted principle since the 18th century. The experiences with its application in forestry may contribute towards obtaining a better insight into the implications and operational significance of the concept of sustainability. This article describes the history of sustainability in forestry, including the various social values on which its interpretation has been based. The original principle of sustained yield has gradually been broadened to a more inclusive principle of sustainable forest management. The dynamics in social valuation of forest resources resulted in various attempts at practical operationalization of the principle. Notwithstanding 200 years of efforts to operationalize the concept of sustainability, its exact application in forestry remains troublesome. Three lessons are drawn: (1) the need to recognize the different nature of ecological limits and social dynamics, (2) the role of dynamic social values with respect to forest resources, and (3) the significance of operational experiences in trying to attain sustainability within a concrete context.     

POLLUTANT RUNOFF MODELS: SELECTION AND USE IN DECISION MAKING1

Models for pollutant runoff can be useful in water quality management planning if appropriately structured for the problem at hand. Accordingly, a “top-down” approach is proposed for the examination of extant pollutant runoff models. The approach consists of the identification of objectives and attributes that reflect the needs of planners and decision makers when these models are used for water quality management planning. Ideally, the attributes should concern the effect of model information on improved decision making and the cost of model application. Practical difficulties with the first attribute necessitates substitution of surrogate attributes reflecting model appropriateness, resolution, and uncertainty. Common pollutant runoff models, in particular export coefficients and hydrology-driven simulation models, are found to have serious weaknesses on some of the attribute scales. The “top-down” approach leads to a set of desirable pollutant runoff model attributes; alternate modeling techniques are thus examined in order to identify promising future directions for model development. The focus of this examination is phosphorus, due to its importance in the eutrophication of surface waters. Models for both sediment-attached and dissolved phosphorus are considered. Among the conclusions is the belief that the partial contributing area concept can yield an effective yet simple simulation despite the variable and complex nature of runoff.     

USING CROP YIELD AND EVAPOTRANSPIRATION RELATIONS FOR REGIONAL WATER REQUIREMENT ESTIMATION1

ABSTRACT: Values of dry biomass of corn, sugarcane, sorghum, rice, taro, millet, cotton, cowpeas, soybeans, and velvet beans as related to the evapotranspiration (ET) were studied. The linear regression model was sufficiently accurate to establish the crop dry biomass and ET relations. A water-use efficiency index (WUE), which is defined as the additional crop dry biomass per unit ET, is used in this study. The WUE were grouped into high, medium, and low categories. The WUE varied from greater than 35 kg ha^-1/mm for the high category, between 15 and 35 kg ha^-1/mm for the medium category, and less than 15 kg ha^-1/mm for the low category. Application of the established model to the Everglades Agricultural Area, Florida, showed that the regional El can be predicted from the known regional crop yields. The crop yield and ET relations could be used as a potential tool to improve water resources planning and management practices for crop production.