土地利用变化与土壤养分的变化——以河北省遵化县为例

土地利用变化可以引起土壤养分的变化,以河北省遵化县为例,研究该县1980年到1999年土地利用变化及土壤养分的变化,结果表明,近20a来,旱地、草地、水田面积大幅度减少,林地和村镇用地大幅度增加,旱地转换为林地,土壤有机质提高了21％,全氮提高了10％,碱解氮提高了65％,速效磷提高了17％,速效钾提高了17％。旱地转换为草地,土壤有机质提高38％,全氮提高了37％,碱解氮提高了71％,速效磷提高了2％,速效钾提高了28％。退耕还林还草不仅改变了土地棉覆被,而且提高了土壤养分。     

Reproductive yield of individuals competing for light in a dense stand of an annual, Xanthium canadense

In a dense stand, individuals compete with each other for resources, especially for light. Light availability decreases with increasing depth in the canopy, thus light competition becoming stronger with time in the vegetative phase. In the reproductive phase, on the other hand, leaves start senescing, and the light environment, particularly of smaller individuals, will be improved. To study the effect of change in light climate on reproduction of individuals, we established an experimental stand of an annual, Xanthium canadense, and assessed temporal changes in whole plant photosynthesis through the reproductive phase with particular reference to light availability of individuals. At flowering, 83% of individuals were still alive, but only 27% survived to set seeds. Most of the individuals that died in the reproductive phase were smaller than those that produced seeds. Individuals that died at the early stage of the reproductive phase had a lower leaf to stem mass ratio, suggesting that the fate of individuals was determined partly by the pattern of biomass allocation in this period. At the early stage of the reproductive phase, leaf area index (LAI) of the stand was high and larger individuals had higher whole plant photosynthesis than smaller individuals. Although light availability at later stages was improved with reduction in LAI, whole plant photosynthesis was very low in all individuals due to a lower light use efficiency, which was caused by a decrease in photosynthetic N use efficiency. We conclude that light competition was still strong at the early stage of the reproductive phase and that later improvement of light availability did not ameliorate the photosynthesis of smaller individuals.     

Soil water status influences plant nitrogen use: a case study

We studied differences in nitrogen use efficiency (NUE) among six species [Calamagrostis epigejos (L.) Roth., Carex duriuscula C.A. Mey., Phragmites communis (L.) Trin., Salix gordejevii Y.L. Chang, Salix cheilophila Schneid., and Typha minima Funk.] growing in two contrasting habitat types, i.e., a riverine wetland with high water supply and a riparian zone with low water supply. The two sites were different in soil water supply, but not in nitrogen supply. Here, NUE was defined as the total net primary production per unit nitrogen absorbed. There was no significant difference in NUE between the species growing in the riverine wetland (Carex duriuscula, P. communis, S. cheilophila, T. minima) and the species growing in the river bank (Carex duriuscula, Calamagrostis epigejos, P. communis, S. gordejevii). We further analyzed NUE as the product of the nitrogen productivity (A, the rate of dry matter production per unit of nitrogen in the plant) and the mean residence time of nitrogen (MRT, the period of time a unit of nitrogen is present in the plant). The species growing in the riverine wetland had larger A but lower MRT than the species growing in the river bank. There was an inverse relationship between A and MRT. Consequently, NUE was similar among species and habitats. These results suggested that environmental factors, such as soil water supply, can influence N use by plants.     

Carrying capacity for species richness as a context for conservation: a case study of North American breeding birds

Aim To demonstrate that the concept of carrying capacity for species richness (S_K) is highly relevant to the conservation of biodiversity, and to estimate the spatial pattern of S_K for native landbirds as a basis for conservation planning. Location North America. Methods We evaluated the leading hypotheses on biophysical factors affecting species richness for Breeding Bird Survey routes from areas with little influence of human activities. We then derived a best model based on information theory, and used this model to extrapolate S_K across North America based on the biophysical predictor variables. The predictor variables included the latest and probably most accurate satellite and simulation‐model derived products. Results The best model of S_K included mean annual and inter‐annual variation in gross primary productivity and potential evapotranspiration. This model explained 70% of the variation in landbird species richness. Geographically, predicted S_K was lowest at higher latitudes and in the arid west, intermediate in the Rocky Mountains and highest in the eastern USA and the Great Lakes region of the USA and Canada. Main conclusions Areas that are high in S_K but low in human density are high priorities for protection, and areas high in S_K and high in human density are high priorities for restoration. Human density was positively related to S_K, indicating that humans select environments similar to those with high bird species richness. Federal lands were disproportionately located in areas of low predicted S_K.     

Suitability of Zostera marina populations for transplantation to the Wadden Sea as determined by a mesocosm shading experiment

As part of eelgrass re-establishment efforts in the Wadden Sea, five northwest European eelgrass (Zostera marina L.) populations were studied in a mesocosm filled with Wadden Sea water over a 2-year period. The original habitats of these populations varied with regard to salinity, tidal regime, latitude, substrate type and water nutrient content. The reproductive strategies ranged from semi-annual to perennial. Experimental parameters studied were: planting density (64 and 121 plants m⁻²) and irradiance corresponding to 75%, 89%, 95% and 98% light reduction at the bottom. Three out of five Z. marina populations were successfully transplanted. Planting density, although initially positively correlated, had no effect on final transplantation success. The populations maintained their original reproductive strategy. The reproductive strategy of the donor population did not show a clear correlation with transplantation success. The maximum light reduction tolerated at the bottom was 75%–89%. The populations did not differ in shading tolerance. Assuming a light attenuation coefficient in the Wadden Sea of k=2.0 m⁻¹, this corresponds to a maximum transplantation depth of between 0.45 m and 0.85 m below mean sea level. The differences in transplantation success, and the conservative reproductive strategy of different Z. marina populations, indicate genetic differences and/or low phenotypic plasticity. Moreover, this implies that the characteristics of a donor population must be carefully considered prior to transplantation.     

Developing a disturbance index for five East African forests using GIS to analyse historical forest use as an important driver of current land use/cover

A means of deriving a disturbance index reflecting forest use history is demonstrated here to establish a disturbance gradient and enable comparison of different forest areas within and across individual forests. Detailed reference is made to Kakamega Forest in western Kenya for which a long‐term time series has been established, although the study is spread to four further forests in Kenya and Uganda. A wide variety of sources are drawn upon for spatially resolved data that are integrated in a geographic information system. Three indices are derived: for commercial disturbance, local disturbance, and forest cover change. Results show a wide range of disturbance values (from low to heavy) for the research sites within Kakamega Forest, while results for Budongo and Mabira Forest sites show low and moderate levels, respectively. Correlations of low disturbance levels with nature or national reserves appear to be marked, while a correlation of disturbance with differing management authority is also suggested with Kenya Wildlife Service achieving the lowest disturbance levels. Results from the index are reviewed against other means of estimating disturbance with the conclusion that disturbance evaluations should be both spatially resolved and long‐term in nature.     

基于遥感影像的城市土地利用生态环境效应研究——以城市热环境和植被指数为例

城市化过程中,农村的土壤、水面以及植被等土地覆被类型逐渐减少,取而代之的是由沥青、水泥以及金属等组成的不透水表面,这个过程导致地表水分蒸腾减少、径流加速、显热的存储和传输增加以及水质降低等一系列生态环境效应,其中最明显的两个特征就是土地覆被的植被减少、城市热岛的出现.而城市土地利用类型及其空间结构的生态环境效应同时又是城市生态学中的关键问题,其研究对优化城市功能分区和城市规划管理以及城市可持续发展等都具有重要意义.以上海市为例,采用Landsat7的ETM＋为基本数据源,首先定量反演了每个像元内的陆地表面温度（LST）和植被指数（NDVI）,然后利用GIS中的空间分析功能,将由于城市土地覆被所形成的生态环境效应综合到土地利用的图斑中来,按照这个思路对城市土地利用的生态环境效应进行研究.分析LST、NDVI在不同土地利用类型之间的差异以及二者之间的定量关系,并引入多样性指数（SHDI）,讨论了不同土地利用的空间组合下,LST和NDVI的空间差异及相互关系.研究结果显示：LST和NDVI具有明显的相关性,LST大的区域对应NDVI一般都较小,反之亦然;中心城市LST表现出热岛效应,而NDVI则为低谷效应.通过Tamhance T2 post-hoc多重比较发现,LST以及NDVI在两两土地利用类型之间的差异不同.从土地利用斑块和类型两种尺度水平上建立了LST和NDVI的定量关系,二者具有明显负相关的线性关系,但在不同土地利用类型上二者关系并不同.其中工业仓储、交通用地与公园绿地、农业用地差异最为显著.它们和SHDI之间的关系揭示,LST与土地利用多样性具有正相关关系,而NDVI则与SHDI呈负相关关系,SHDI越大的地区,LST越大,而NDVI越小.由此,可以将LST、NDVI和SHDI作为三个基本指标,来定量评价城市土地利用类型、结构对生态环境的影响,以此作为城市功能分区中生态环境影响评价的参考.也为高性价比的中等分辨率遥感数据与GIS空间分析方法结合在城市规划中的应用提供了一种新的思路.     

Xanthophyll-cycle pigments and photosynthetic capacity in tropical forest species: a comparative field study on canopy,gap and understory plants

Xanthophyll-cycle pigments and photosynthetic capacity (PS_max) were analyzed in 25 species from different light environments (canopy, gap, understory) within a Panamanian tropical forest. (1) Sun-exposed leaves of canopy tree species showed the highest photosynthetic capacities and largest xanthophyll-cycle pools (violaxanthin, antheraxanthin, zeaxanthin) of about 87 mmol mol^-1 chlorophyll with only small amounts of -carotene [about 7 mmol mol^-1 chlorophyll = 8% of total (+) carotene pool]. Under high natural photon flux densities (PFDs) canopy leaves rapidly converted up to 96% of the xanthophyll-cycle pool into zeaxanthin. The back reaction to violaxanthin occurred much faster in low light than in complete darkness. At the end of the night, zeaxanthin still accounted for, on average, 14% of the total xanthophyll-cycle pigments. (2) Leaves of gap plants had intermediate values of PS_max and a 43% lower total carotenoid content than canopy leaves. The average size of the xanthophyll-cycle pool was 35 mmol mol^-1 chlorophyll, and -carotene accounted for up to 66% of the total (+) carotene pool. Under high light conditions gap plants converted, on average, 86% of the xanthophyll-cycle pigments into zeaxanthin. The back reaction, following a decrease in ambient PFD, was slower than the forward reaction. At the end of the night, zeaxanthin accounted for, on average, 7% of the xanthophyll-cycle pigments in gap plants. (3) Understory plants showed the lowest values of PS_max and the smallest xanthophyll-cycle pool of about 22 mmol mol^-1 chlorophyll. -Carotene accounted for up to 70% of total carotene. The conversion of xanthophyll-cycle pigments into zeaxanthin was negligible during short sunflecks of 1–2 min duration and PFDs up to about 400 mol m^-2 s^-1. At predawn, leaves of understory plants rarely contained any detectable zeaxanthin. Aechmea magdalenae, an understory CAM plant, showed exceptionally high rates of PS_max per unit leaf area compared to sympatric C₃ understory species.     

城市土地利用变化对生态系统服务的影响——以淮北市为例

城市是一类以人类活动为中心的社会-经济-自然复合生态系统.城市的快速蔓延及强烈的人类活动显著地改变了城市的土地利用结构,进而严重影响了城市生态系统服务及人居环境.通过遥感、GIS技术及生态系统服务价值评估等方法,对淮北市1987年、2000年和2007年3个时期20a间的土地利用结构及生态系统服务价值的演变进行定量评价.研究结果表明:1987-2007年间淮北市生态用地空间结构和面积发生剧烈变化,生态用地占城市面积的比例由91.45％降低至71.86％.1987-2000年,农田面积大幅度下降,而林地和水体都呈不同程度的增加趋势,建设用地面积增长迅速.2000-2007年,农田面积有所增加,林地和水体面积却明显下降,建设用地总面积虽然没有明显变化,但其聚集度显著增加.20年间,城市生态服务功能的价值呈现先增加后减少的趋势,在2000年达31.32亿元.2000-2007年,以废物处理和水源涵养功能退化最为严重.可见,城市土地利用结构的变化与生态服务功能密切相关,此结果可为淮北市景观格局优化及土地合理调控和管理提供一定的科学依据.     

土地利用变化对生态系统服务功能的影响——以密云水库流域为例

生态系统服务功能与人类福利息息相关,土地利用变化是生态系统服务功能退化的主要驱动力之一,以人地关系紧张,生态系统服务功能变化剧烈的密云水库流域为对象,分析流域1990-2009年土地利用的变化,采用空间显式的生态系统服务功能评估软件InVEST中的“产水量”、“土壤保持”、“水质净化”模型,研究流域土地利用变化对生态系统服务功能的影响.结果表明1990-2009年密云水库流域土地利用变化剧烈,农田、草地和水体的面积分别减少了30％、48％、61％,林地、建筑用地和裸地的面积增加,增幅分别为30％、230％、282％.随着土地利用变化,生态系统服务功能相应产生着显著变化,研究期内,土壤保持功能和固碳服务分别增加46％和19％,但水资源供给服务和水质净化功能分别减少了3％和25％.农田面积的减少和森林的扩张改善了土壤保持服务,森林面积的增加同时也改善了固碳服务,但会削弱水资源供给服务,建筑用地的扩张会大幅度削弱水质净化功能,为维持和改善流域整体的生态系统服务功能,应加强对森林和建筑用地的控制.其研究为密云水库流域土地利用科学管理决策提供参考.     

城市土地利用的生态服务功效评价方法——以常州市为例

生态服务功能的产出是生态服务功效,分为正功效和负功效.快速城市化进程严重影响了土地的生态服务功能,导致城市人居生态环境的日益恶化,自然生态系统服务负功效逐渐增加.常州是我国东部沿海快速城市化的典型代表,城市化占用生态用地由此产生了一系列生态环境问题.在GIS和RS技术的支持下,采用网格分析法和复合生态评价的方法,建立了复合生态服务功效的空间评价指标体系,从正负生态功效两方面评价了当前土地利用的复合生态功效.结果表明当前常州市的土地复合生态服务功效64.5％为正功效,35.5％的土地生态服务为负功效.按照当前的城市发展思路,新的土地利用规划将进一步导致自然生态服务正功效的衰退.该研究为城市土地利用规划管理提供了科学思路与决策依据.     

Habitat models and their transfer for single and multi species groups: a case study of carabids in an alluvial forest

Environmental factors influencing the occurrence of single species and multi species groups of carabids in alluvial forest al the River Elbe were determined with habitat suitability models. Two representative species for different ecotypes present in the investigated community. Agonum livens and Pterostichus oblongopunctatus. were defined by means of a discriminant analysis. The two species differed greatly in their microhabitat distribution, Agonum livens was chosen as target species for a multi species group of wetland species that inhabited the fringes of temporary waters in the forest. In contrast, P. oblongopunctatus should represent species of deciduous forests. Using stepwise multiple logistic regression statistically significant habitat suitability models were estimated, reliably predicting the species" occurrence, A subsequent evaluation by cross-validations and receiver operating characteristic (ROC) curves indicated a high discriminatory power. A transfer of the model onto different data sets in time was applied to validate the model. Alternatively, a multi species habitat model, taking into account weighted occurrence data of the wetland species group, was estimated. In order to show that the chosen target species truly holds an umbrella effect upon the represented multi species group, we used ROC curves to indicate the transferability of the target species' habitat model for the multi species group and vice versa.     

Abundance, distribution and life histories of grassland plants: a comparative study of 81 species

1 This study examines the abundance and distribution of grassland plant species in particular relation to features affecting colonization. Seed production (inversely related to seed size) and recruitment success (positively related) affect colonization ability, suggesting that seed size can be used as a key trait.
2 Data on seed size, dispersal mode, life form, geographical range size and abundance were gathered for 81 grassland plant species in a field study area in Sweden. Seed production and plant size were estimated for 69 of these species. Analyses were performed both across species, with species treated as independent data points, and for 43 'phylogenetically independent contrasts'.
3 The cross-species analyses suggested that local abundance was related to life forms but not dispersal or plant size. Perennials were generally most abundant, as were clonal species. If abundance reflects colonization we predicted that species with intermediately sized seeds (or intermediate seed production) would be most abundant, and this was supported by the phylogenetic contrast but not by cross-species analyses. In the former analysis, a high abundance of species was significantly associated with a small seed size deviation (and seed number deviation) from the median values of these traits in the community.
4 Local abundance, seed production and seed size deviation from the community median value were positively related to geographical range size in the cross-species analysis, but no relationships were seen in the phylogenetic contrast analysis.
5 We conclude that colonization processes do have a significant influence on abundance patterns in grasslands. Seed size is a key trait for colonizing ability, and the effects of the trade-off of seed size vs. seed number must be considered. No single mechanism can be identified that influences both abundance and geographical distribution range.     

Ecological immunology in a fluctuating environment: an integrative analysis of tree swallow nestling immune defense

Evolutionary ecologists have long been interested by the link between different immune defenses and fitness. Given the importance of a proper immune defense for survival, it is important to understand how its numerous components are affected by environmental heterogeneity. Previous studies targeting this question have rarely considered more than two immune markers. In this study, we measured seven immune markers (response to phytohemagglutinin (PHA), hemolysis capacity, hemagglutination capacity, plasma bactericidal capacity, percentage of lymphocytes, percentage of heterophils, and percentage of eosinophils) in tree swallow (Tachycineta bicolor) nestlings raised in two types of agro‐ecosystems of contrasted quality and over 2 years. First, we assessed the effect of environmental heterogeneity (spatial and temporal) on the strength and direction of correlations between immune measures. Second, we investigated the effect of an immune score integrating information from several immune markers on individual performance (including growth, mass at fledging and parasite burden). Both a multivariate and a pair‐wise approach showed variation in relationships between immune measures across years and habitats. We also found a weak association between the integrated score of nestling immune function and individual performance, but only under certain environmental conditions. We conclude that the ecological context can strongly affect the interpretation of immune defenses in the wild. Given that spatiotemporal variations are likely to affect individual immune defenses, great caution should be used when generalizing conclusions to other study systems.     

Rates of Disturbance vary by data resolution: implications for conservation schedules using the Alberta Boreal Forest as a case study

Investigations of biophysical changes on earth caused by anthropogenic disturbance provide governments with tools to generate sustainable development policy. Canada currently experiences one of the fastest rates of boreal forest disturbance in the world. Plans to conserve the 330 000 km² boreal forest in the province of Alberta exist but conservation targets and schedules must be aligned with rates of forest disturbance. We explore how disturbance rate, and the accuracy with which we detect it, may affect conservation success. We performed a change detection analysis from 1992 to 2008 using Landsat and SPOT satellite image data processing. Canada's recovery strategy for boreal caribou (Rangifer tarandus caribou) states that ≤35% of a caribou range can be either burned or within 500 m of a man‐made feature for caribou to recover. Our analyses show that by 2008 78% of the boreal forest was disturbed and that, if the current rate continues, 100% would be disturbed by 2028. Alberta plans to set aside 22% for conservation in a region encompassing oil sands development to balance economic, environmental, and traditional indigenous land‐use goals. Contrary to the federal caribou recovery strategy, provincial conservation plans do not consider wildfire a disturbance. Based on analyses used in the provincial plan, we apply a 250 m buffer around anthropogenic footprints. Landsat image analysis indicates that the yearly addition of disturbance is 714 km² (0.8%). The higher resolution SPOT images show fine‐scale disturbance indicating that actual disturbance was 1.28 times greater than detected by Landsat. If the SPOT image based disturbance rates continue, the 22% threshold may be exceeded within the next decade, up to 20 years earlier than indicated by Landsat‐based analysis. Our results show that policies for sustainable development will likely fail if governments do not develop time frames that are grounded by accurate calculations of disturbance rates.     

Soil organic carbon changes as influenced by agricultural land use and management: a case study in Yanhuai Basin, Beijing, China

The effects of agricultural land use and management practices on soil organic carbon (SOC) are of great concern. In this study, SOC changes were investigated in sandy loam soils (Ustochrepts, USDA Soil Taxonomy) under orchard, vegetable, corn (Zea maize L.), and soybean (Glycine max L.) cultivation in northern China. The corn fields were further classified into three categories based on their inputs, i.e. high-input, mid-input, and low-input corn fields. In April 2005, a total of 197 soil samples were collected from 42 soil sites within 100 cm soil depth in Yanhuai Basin, Beijing, China. SOC contents were determined using rapid dichromate oxidation, and ANOVA statistical analysis was used to test the significances between land use and management practices at p<0.05. The results showed that: (1) the effects of land use and management practices on SOC primarily occurred within the topsoil (0–25 cm), and the SOC contents sharply decreased with the increase in soil depth. (2) SOC content and density values of orchard, vegetable, and high-input corn fields were higher than those of soybean, mid- and low-input corn fields.