Agroecosystem functional assessment and its difficulties

来源 :环境科学学报 | 被引量 : 0次 | 上传用户:zhangersong
下载到本地 , 更方便阅读
声明 : 本文档内容版权归属内容提供方 , 如果您对本文有版权争议 , 可与客服联系进行内容授权或下架
论文部分内容阅读
Agroecosystem functional assessment indicators provide a necessary bridge between decision-makers and scientists. The development of acceptable indicators, however, remains a difficult task because the current knowledge and understanding of ecosystems is not sufficient to allow an objective assessment of all ecosystem functions. These difficulties were summarized from three perspectives. First, there are difficulties in individual function assessment. Of the four functions associated with agroecosystems-energy flow, materials cycling, information flow and value flow - data on material cycling and information flow remain difficult to obtain and the indicators relatively immature. Secondly, there are difficulties of integration. During the assessment process, the integration of the agroecosystem functions remains the biggest obstacle. Until now, there has been no practical or effective methodology established to resolve the problem. At present, the makeshift approach has been to weight the various indicators and then add them together. Thirdly, there is the problem of obscure concepts and concept confusion. When assessments of agroecosystems are conducted, concepts such as structure, function, benefit, and resource utilization are used extensively. To date, no logical relationship(either real or implied) has been developed between any of these concepts. Are they causes and results such that the relationship between them is linear, or are they independent from one another such that the relationship is parallel? Thus far, the essence of this question is yet to be explored.
其他文献
计划生育工作是我国的一项重要的国策,关系到社会主义现代化建设的成败。国有企业作为国家经济社会发展的重要经济实体,有必要也有责任做好计划生育工作,从而为民营企业起到模范
Over-use of fertilizer in paddy fields could lead to agro-environmental pollution. Therefore, the Paddy Fertilizer Recommendation System (PFRS) application pack
CBF1转录激活因子是一类受低温诱导的反式作用因子,能有效提高植物抗低温的能力。以抗寒性较强的长白山野生山葡萄(耐-40℃低温)为材料,通过RT-PCR方法成功地克隆低温诱导转
液压传动是一门新的学科,20世纪30年代,由于工艺制造水平提高,开始生产液压元件,并首先应用于机床。50年代初,液压技术已开始应用到各行各业,如机床、汽车、工程机械等。目前,流体传
特殊行业固定资产弃置费用计入成本成为现行会计准则的亮点之一.弃置费用会计处理模式的建立,为特殊行业的特定企业通过逐步建立支付储务,最终有足够的财力承担环境恢复义务
目的探讨增强Zeste同源2(EZH2)与年龄相关性胰岛细胞功能的关系。方法健康SD大鼠分为1、6、12及24月龄组,每组各6只。取大鼠胰腺,行免疫组化染色。Western blot检测胰岛内EZH
The operational performance of a full-scale subsurface-flow constructed wetland, which treated the mixed industrial and domestic wastewater with BOD5/COD mean r
This paper presents the detailed results and analyses on the ecological footprints and bio-capacities of the individual cities and the province as a whole for t
An aminated hypercrosslinked macroporous polymeric adsorbent was synthesized and characterized. Adsorption isotherms for 1-amino-2-naphthol-4-sulfonic acid(1, 2
In this paper a three-dimensional tidal current model has been used to examine variations of local fluid field due to establishment of a dam. By imputing ten ti