Mediating effect of stream geometry on the relationship between urban land use and biological index

Numerous studies have stated that land use in urbanized areas can adversely affect water quality of streams. Previous studies reported that edges may play important roles in controlling flow rate of material in two systems. In this study, we examined the mediating effects of streamline geometry on the relationships between urban land use and the index of biological integrity (IBI) of the Nakdong River in Korea. Two mediation models with streamline geometry, including the partial mediation effect model and the full mediation effect model, were estimated to explore the mediating effect of streamline geometry. To measure streamline geometry, we calculated the fractal dimension of a streamline within a 1 km buffer from the sampling sites. The proportion of urban land use within a 5 km buffer of the sampling sites was also computed by GIS. We used biological assessment data from the National Aquatic Ecological Monitoring Program in Korea to delineate the IBI at the sampling sites. The results showed that urban land use significantly degraded stream morphology and IBI in the Nakdong River. It was also observed that streamline geometry mediated the influence of urban land use on the IBI. The results of structural equation modeling analysis for the two mediation models with the fractal dimension and IBI suggested that only two paths were significant in the partial mediation model, whereas all paths were significant in the estimated full mediation model.     

Influence of Habitat and Land Use on the Assemblages of Ephemeroptera,Plecoptera, and Trichoptera in Neotropical Streams

Insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are often used to assess the conditions of aquatic environments, but few studies have examined the differences in these communities between riffles and pools. Our objective was to test whether riffles shelter greater richness and abundance of EPT, as well as to assess the sensitivity of these insects for detecting impacts from different land uses in streams in southeastern Brazil. Samples were collected in the dry season of 2012 with a Surber sampler in riffles and pools of nine streams (forest, pasture, and urban areas). Principal component analysis distinguished the streams according to different land uses as a function of percentage of plant cover and water oxygenation level and showed partial distinction between riffles and pools as a function of current speed and percentage of ultrafine sand. Detrended correspondence analysis indicated the distinction in EPT composition between riffles and pools, except in urban streams. The results of this study confirm the expected differences in the EPT fauna structure between riffles and pools, especially in forest and pasture environments. The individual metrics of riffle and pool assemblages showed significantly different responses to land use. Therefore, we suggest individual sampling of riffles and pools, since the metrics of these assemblages’ insects can differ between these habitats and influence the results of assessments in low-order streams.     

湖南省生态环境质量研究

以生物丰度指数、植被覆盖指数、水网密度指数、土地退化指数、污染负荷指数为评价因子,运用生态环境质量指数(EQI)的评价体系,对湖南省生态环境进行了分析与评价.结果表明,湖南省生态环境质量在全国范围内属于优的区域,全省104个县级以上区域中,有37个市、县评价为优,占全省的35.58%,67个县生态环境质量评价等级为良,占全省的64.42%.指出了湖南省生态环境存在的主要问题.     

Prioritizing locations for the riparian establishment based on spatiotemporal change of riparian forest area at a watershed scale

A majority of streams in Korea have been channelized and their adjacent flood plains have been converted for anthropogenic land use, especially in urbanized areas. Fortunately, recent elevated public recognition to the stream ecosystem has led to governmental efforts to conserve riparian areas. In this study, a simple method to prioritize locations for riparian establishment was developed at a watershed scale based on spatiotemporal change of riparian forest area. The developed method was applied for the Ansung and Sapkyo watersheds, which were under consideration for the stream riparian area establishment by the Korean Ministry of Environment. Two riparian forest indices, Riparian Forest Index (RFI) and Riparian Forest Change Index (RFCI) were developed to represent spatial and temporal change of watershed riparian forest, respectively. LANSAT satellite images with a 30 m × 30 m resolution were used to estimate the two riparian forest indices. A precautionary approach, which intends to preserve the existing riparian forests as much as possible, was applied by ranking sub-watersheds based on the two riparian forest indices to prioritize locations for the riparian establishment at a sub-watershed level. The results showed that overall urban land cover in riparian areas increased while forests and cropland decreased over the past 25 years. More importantly, riparian forest removal occurred more rapidly in the riparian area, which is one of the most important niches for riparian ecosystems, as compared to the entire watershed. Most riparian forests appeared to be located upstream of the watersheds, and thus it is important to develop management measures to preserve existing riparian forests from human activities. The developed approach could be a useful tool that can assist policy makers to prioritize locations for the riparian area establishment. However, this method has limitations of only considering riparian forest area and therefore, other aspects such as stream morphology as well as ecology needs to be incorporated into riparian area determination process as they become available in the future. In addition, considering that substantial portions of riparian areas have already been disturbed, the restoration aspect of the impaired riparian also needs to be investigated further.     

The effects of spatial variability of land use on stream water quality in a costal watershed

Researchers generally accept that land use types within a watershed closely relate with the water quality characteristics of streams. Despite numerous studies investigating the relationships between water quality and land use, there are increasing concerns about the geographical variation and lack of spatial integration in previous studies. We investigated the relationships between land use and water quality characteristics including biological oxygen demand (BOD₅), total nitrogen (TN), total phosphorus (TP), and Escherichia coli in the Wha-Ong estuarine reservoir watershed in Korea, which has spatially integrated land uses. Residential and paddy areas appear to be positively and negatively correlated, respectively, with degraded water quality. The spatial variations of these relationships were also examined using zonal analysis. Some results contrasted with those of previous studies that were conducted mostly in developed Western countries and may reflect the different land use intensities and agricultural practices in Korea. Relationships across zones, distinguished by distances from streams, were inconsistent and erratic, suggesting that the relationships between remote land uses and water quality may be affected more significantly by sub-basin characteristics than by the land use itself. The geographical differences and spatial variations found in this study indicate that caution must be taken in generalizing the relationship between land use and water quality.     

The world's richest tadpole communities show functional redundancy and low functional diversity: ecological data on Madagascar's stream-dwelling amphibian larvae

Background  

Functional diversity illustrates the range of ecological functions in a community. It allows revealing the appearance of functional redundancy in communities and processes of community assembly. Functional redundancy illustrates the overlap in ecological functions of community members which may be an indicator of community resilience. We evaluated patterns of species richness, functional diversity and functional redundancy on tadpole communities in rainforest streams in Madagascar. This habitat harbours the world's most species-rich stream tadpole communities which are due to their occurrence in primary habitat of particular interest for functional diversity studies.     

Application of biotic indices in assessing the ecological quality status of Bahrekan estuary (Persian Gulf)

The aim of present study was to examine the macro invertebrates as an assessment tool for characterization of the state of Bahrekan estuary in Persian Gulf, by using different biotic indices. An investigation on benthos was carried out during autumn 2008 to summer 2009 in the Bahrekan estuary (Persian Gulf). In order to identify and assess the benthic community structure, seasonal sampling was done from 21 stations with three replicates using van veen grab (./285 m2). The ecological indices, such as (AMBI, BI and Bentix), Shannon-Wiener index (H'), species richness (S) were applied to the available benthic species data, and evaluated comparatively. The grain size of sediments and total organic matter as essential factors in distribution and population diversity of macrobenthos communities were also analysed. According to the results, 17 groups of macrobenthos were identified. Out of 111 genus/species identified in this study, Gastropoda was the dominate group (79.8%), followed by Bivalvia (5.5%). Pyrgohydrobia sp. belonged to gastropoda was dominant in all of seasons. The results showed that all of the stations are characterized as muddy bottom and Bahrekan estuary are classified in slightly to moderate pollution status.     

Evaluation of land use change and groundwater use impact on stream drying phenomena using a grid-based continuous hydrologic model

The effect of land use change on drying streams was evaluated using a grid-based continuous hydrological model (PGA-CC). For a drying stream-progressed watershed (398.8 km²), the model was calibrated and validated using 7 years (2005–2011) of streamflow data at the watershed outlet with an average Nash–Sutcliffe model efficiency of 0.71. Based on the model simulation results for 36 years (1976 to 2011), both land use change and climate change decreased the 10-day minimum flow by 0.16 m³/s and increased the day counts below the annual average by 40.6 days/year. These changes resulted from the 8.7 % increase in urban area, 1.43-fold increase in groundwater use, and 1.1 °C temperature increase during the 36-year period. From the distributed results of the model, we identified the drying stream location and progression. The spring and winter seasons were relatively strongly affected, and drying streams were identified in more urbanized areas with greater groundwater use.     

海南省生态盈亏及其空间结构研究

以生态足迹计算方法和泰尔指数等区域差距计算方法为模型工具,对海南的生态盈亏及其空间结构进行了系统研究。结果表明：海南省总量生态盈亏(ED)为2 357 083 hm2。在各项生态生产性土地中,盈亏较高的是总量水域、总量林地和总量耕地生态盈亏,较低的是总量草地、总量建设用地和总量化石能源用地生态盈亏。在18个市县中,总量耕地生态盈亏最高的市县是海口市,最低的是临高县。海南省人均生态盈亏为0.267 983 hm2。其中,人均水域、林地和耕地生态盈亏较高,人均草地、建设用地和化石能源用地生态盈亏较低。在18个     

海南省土地资源综合承载力研究

在分析海南省土地资源主要功能的基础上，构建评价指标体系，对海南省土地资源承载力进行了计算。结果表明：2007～2012年间海南省土地资源承载力呈现上升趋势，其中土地生态承载力、土地生产承载力占海南省土地资源承载力的30%以上，是海南省土地资源开发利用的主要方向。     

湖北省油菜主产区杂草群落的数量分析

采用七级目测法定量调查了湖北省油菜主产区28个样点的杂草发生情况,应用主成分分析法对杂草群落进行了数量分析。结果表明,28个样点可以分为4个聚类群,即江汉平原鄂北旱茬油菜田、鄂东南旱茬油菜田、江汉平原稻茬油菜田和鄂东南稻茬油菜田。轮作制度与地理因素决定了湖北省油菜主产区杂草群落的分布。根据综合草害指数和发生频率明确了各聚类群相应的优势杂草,并就该地区油菜田杂草发生的特点提出了治理策略。     

农村土地利用视角下的环境友好乡村建设研究

农村土地利用存在多种问题，土地利用规划随意性大、农村土地产权不清、耕种地块分散、农地质量下降、休闲农业缺乏规范等问题共同制约环境友好乡村建设与发展。加强土地规划、明确农村土地产权、促进农业适度规模经营，推行环境友好型生产生活模式、建立农业生态补偿机制、培育新常态下的乡村休闲产业等举措将有利于推动环境友好乡村建设及发展。研究表明，环境友好型土地利用模式有助于推进两型农业生产体系的建设，是环境友好乡村建设的必要推动因素和解决“三农”问题的重要途径之一。     

Limited impacts of extensive human land use on dominance,specialization, and biotic homogenization in boreal plant communities

Background

Niche theory predicts that human disturbance should influence the assembly of communities, favouring functionally homogeneous communities dominated by few but widespread generalists. The decline and loss of specialists leaves communities with species that are functionally more similar. Evenness of species occupancy declines, such that species become either widespread of rare. These patterns have often been observed, but it is unclear if they are a general result of human disturbance or specific to communities that are rich in species, in complex, spatially heterogeneous environments where the problem has often been investigated. We therefore tested whether human disturbance impacts dominance/evenness of species occupancy in communities, specialism/generalism of species, and functional biotic homogenization in the spatially relatively homogeneous, species poor boreal forest region of Alberta, Canada. We investigated 371 boreal vascular plant communities varying 0 – 100% in proportion of human land use.

Results

Rank species occupancy curves revealed high species dominance regardless of disturbance: within any disturbance class a few species occupied nearly every site and most species were found in a low proportion of sites. However, species were more widespread and displayed more even occupancy in intermediately disturbed communities than among communities of either low or high disturbance. We defined specialists and generalists based on turnover in co-occupants and thereby assessed impacts of human disturbance on specialization of species and community homogenization. Generalists were not disproportionately found at higher disturbance sites, and did not occupy more sites. Communities with greater human disturbance were not more functionally homogeneous; they did not harbor communities with more generalists.

Conclusions

We unexpectedly did not observe strong linkages between species specialism/generalism and disturbance, nor between community homogenization and disturbance. These results contrast previous findings in more species rich, complex or spatially heterogeneous systems and ecological models. We suggest that broad occupancy-based intercommunity patterns are insensitive to human land use extent in boreal vascular plants, perhaps because of ubiquity of generalists, low species richness, and history of natural disturbance. The poor sensitivity of these metrics to disturbance presents challenges for monitoring and managing impacts to biodiversity in this region.     

2000～2014年闽东海岸带土地利用动态变化

海岸带地区因其特殊的海陆生态系统环境而成为土地利用/覆被变化(LUCC)研究的热点区域.本文以位于海峡西岸经济区东北翼的闽东海岸带作为研究对象,利用2000、2009和2014年3期Landsat TM/OLI影像作为数据源,对该区2000～2014年的土地利用动态变化特征进行分析.结果表明:研究区土地利用类型以林草地和耕地为主,其中林草地面积迅速扩增,研究期间共增加了1 047.24 km2,相比之下,耕地面积显著减少,近14a间共减少了959.45 km2;在人类活动影响下,水产养殖的动态变化最为剧烈,稳定性最差,而由于政府加强对建筑用地的集约利用,使其成为近14 a研究区最为稳定的土地利用类型,面积基本保持不变;闽东海岸带土地利用的集约化程度远超全国平均水平,土地利用程度综合指数达255.19,但2000～2009年间,研究区土地利用仍处于调整期,2009～2014年,随着经济的快速发展及前期的调整,土地利用效率有所提高,其变化量和变化率分别为4.86和0.019,土地利用步入发展期.本研究对闽东及其他地区的土地集约化利用及生态环境可持续具有指导意义.     

Analysis of urbanization characteristics causing farmland loss in a rapid growth area using GIS and RS

This study aims to analyze the spatial characteristics of urbanization in a rapid growth area. Remote sensing (RS) and geographic information system (GIS) techniques were used to classify land uses in 1986 and 1996, the most rapid growth period. The two land-use maps were classified with accuracies of 90% and 86% in verification areas for 1986 and 1996, respectively, by a supervised maximum likelihood method. Urbanization in the greenbelt within the study area was restricted, while outside the greenbelt it occurred rapidly. Fifty seven percent of the total increase in built-up area in the study area was concentrated in a 10-km GIS-defined buffer zone adjacent to the greenbelt. The priority for new residential development was put on areas with slopes of less than 15 degrees and potential farmland in the areas surrounding Seoul. In the priority area, farmland loss was very significant. These results show that although the environmental protection of ecologically valuable land was well enforced by the greenbelt from urbanization, farmland was not conserved in comparison to new residential development in the rapid growth area.     

师法热带雨林自然群落，构建城市森林景观：以海口城市道路绿地为例

在城市园林景观设计中模拟地带性森林植被,使城市景观生态系统以及群落外貌近自然化,不仅可以提高城市园林的生态效益,降低养护管理费用,还可以打造具有地方特色的园林景观.本文在调查海口市城市道路绿地景观植物群落结构与组成的基础上,以景观生态学为指导原则,对如何营造兼具景观功能与生态效益的热带园林植物群落进行了探讨.认为海口市园林群落配置应以热带雨林自然群落的结构和演替为依据,以乡土树种为主、引种为辅,增加城市景观植物的多样性;力争做到“师法自然、高于自然”,构建我国南方特色的热带滨海城市森林景观.     

Comparisons of radiation use efficiency of mono-/inter-cropping systems with different row orientations

Intercropping may be helpful to solve future food problem in developing countries. The aim of this study was to compare production efficiency in intercropping with sole cropping in terms of radiant energy use. For analysing crop radiation capture and utilisation, three indices are often used: the fraction of radiation intercepted (F), radiation use efficiency (RUE) and harvest index (HI). Using those indices, maize–bean intercropping was evaluated and compared with maize and bean sole cropping systems. The findings were as follows: the intercrop F was higher than the sole crop F, the sole maize RUE was higher than the others, and there was no difference in HI among cropping systems. From those results, the intercropping may be equivalent to maize sole cropping in the overall efficiency of radiation interception and use. Therefore, when it is considered that both maize and beans would be planted in a given area of land, intercropping has more efficient radiation harvests than sole cropping. No effect of row orientation was found on F, RUE and HI.     

Transition of Ethiopian highland forests to agriculture-dominated landscapes shifts the soil microbial community composition

Background

Land use changes and related land management practices significantly alter soil physicochemical properties; however, their effects on the soil microbial community structure are still unclear. In this study, we used automated ribosomal intergenic spacer analysis to determine the fungal and bacterial community composition in soils from different land use areas in the Ethiopian highlands. Soil samples were collected from five areas with different land uses, natural forest, eucalyptus plantation, exclosure, grassland and cropland, which had all historically been natural forest.

Results

Our results showed a significant shift in the soil bacterial and fungal community composition in response to land use change. We also identified soil physicochemical factors corresponding to the changes in bacterial and fungal communities. Although most soil attributes, including soil organic carbon, total soil nitrogen, labile P, soil pH and soil aggregate stability, were related to the change in bacterial community composition, the total soil nitrogen and soil organic carbon had the strongest relationships. The change in fungal community composition was correlated with soil nutrients, organic carbon, soil nitrogen and particularly the labile P concentration.

Conclusions

The fungal community composition was likely affected by the alteration of vegetation cover in response to land use change, whereas the bacterial communities were mainly sensitive to changes in soil attributes. The study highlights the higher sensitivity of fungal communities than bacterial communities to land use changes.

     

夏玉米叶片生理特性与生态因子间关系的研究

通过对防雨棚下测坑中种植的夏玉米设置不同的土壤水分控制下限,研究了不同的土壤水分状况及气象因子对夏玉米叶片生理特性的影响。结果表明,各生理指标受生态因子的影响有着明显的日变化特征,不同处理气孔导度(Gs)峰值出现的时间早于光合速率(Pn)和蒸腾速率(Tr),高水分下Tr峰值出现的时间滞后于Pn,随着土壤水分胁迫程度的增加,Gs、Tr、Pn的峰值有提前出现的趋势;不同土壤水分条件下细胞液浓度(CSC)的峰值及叶水势(LWP)的低谷均在14:00左右出现。土壤水分与Tr、Pn、Gs、LWP呈极显著正相关,而与CSC呈极显著负相关。此外,气象因素对夏玉米生理指标的影响程度会随着土壤水分状况而发生变化,生理指标与生态因子的逐步回归结果表明,土壤水分和光合有效辐射是影响夏玉米生理指标最主要的生态因子。