Overstorey tree density and understorey regrowth effects on plant composition,stand structure and floristic richness in grazed temperate woodlands in eastern Australia

As natural woodlands decline in both extent and quality worldwide, there is an increasing recognition of the biodiversity conservation value of production landscapes. In low-input, low-productivity grazing systems in Australia, the modification of natural woodlands through overstorey tree and woody regrowth removal are vegetation management options used by landholders to increase native grass production for livestock grazing; however, there is little empirical evidence to indicate at what tree densities biodiversity attributes are compromised. We examined the effects of overstorey tree density and understorey regowth on the floristic composition, stand structure and species richness of eucalypt woodlands in a grazing landscape in the Traprock region of southern Queensland, Australia. We sampled 47 sites stratified according to vegetation type (Eucalyptus crebra/Eucalyptus dealbata woodland; Eucalyptus melliodora/Eucalyptus microcarpa grassy woodland), density of mature trees (<6 trees/ha; 6–20 trees/ha; >20 trees/ha), and presence/absence of regrowth. Distinct patterns in composition were detected using indicator species analysis and non-metric multidimensional scaling, with low density areas compositionally indistinguishable, although distinct from other land management units. Within vegetation type, medium tree density woodlands were compositionally similar to high density and reference woodlands. Species richness ranged from 18 to 67 species per 500 m² across all sites. No differences in total or native species richness were detected across management units; however, some differences in exotic species richness were detected. Differences in grass cover existed between low and high density management units, yet no difference in grass cover was evident between low and medium density management units. Our results suggest that medium tree densities may provide biodiversity benefits concordant with more natural areas, yet not adversely impact on pasture production. Retaining trees in grazing landscapes provides significant landscape heterogeneity and important refuges for species that may be largely excluded from open grassland habitats. Maintaining a medium density of overstorey trees in grazed paddocks can provide both production and biodiversity benefits.     

Identification of biomes affected by marginal expansion of agricultural land use induced by increased crop consumption

In a previous study, the global agricultural expansion caused by wheat consumption in four different countries was modelled with the aim of establishing land use life cycle inventories. The previous study estimated the areas affected by expansion (in terms of square meters) but did not explain how to characterise these areas. The present study ascribes so-called biomes (natural potential vegetation) to the areas affected by agricultural expansion in order to provide a basis for assessing the environmental impacts from land use in the life cycle impact assessment (LCIA). The methodology builds on agricultural statistics and maps of global agricultural areas and the global distribution of biomes. The application of the method is illustrated with four examples. The results indicate that agricultural expansion on land suited for crop cultivation (cultivable land) typically affects forest biomes or potential grassland/steppe, whereas expansion on land suited for grazing but not for crop cultivation (grazable land) typically occurs on potential shrubland or a few other biomes depending on the region. Some uncertainty applies to the results but it is concluded that it is feasible to identify biomes affected by agricultural expansion and that the biomes can therefore be used as a starting point for land use LCIA.     

Trends in fire patterns in a southern African savanna under alternative land use practices

Climate, topography, vegetation and land use interact to influence fire regimes. Variable fire regimes may promote landscape heterogeneity, diversification in vegetation pattern and biotic diversity. The objective was to compare effects of alternative land use practices on landscape heterogeneity. Patch characteristics of fire scars were measured from 21 annual burn maps produced from 1972 to 2001 Landsat imagery. Trends in fire patterns under alternative land use practices were compared across a 250,000 ha savanna in southern Africa partitioned into three land use zones. Zone 1, Madikwe Game Reserve (MGR), has had mostly prescribed fires since 1993. Zone 2, cattle farms near MGR in South Africa (SAF), has experienced occasional fires. Zone 3, communal grazing lands in neighboring Botswana (BOT), has had the fewest fires. Cattle ranching was the predominant land use throughout the study area until 1992, when land use switched to conservation and eco-tourism in MGR. Sixteen landscape metrics were applied to this data set to uncover trends in the patch characteristics of the fire scars. A principal components analysis (PCA) reduced the dimensionality of the results so trends in the 10 most important size, shape, and proximity metrics could be better interpreted. The PCA results showed that more burning over time in MGR, and to a lesser extent in SAF, increased patch size, size variability, shape complexity and proximity, while fire exclusion in BOT produced no change or decreasing trends. We tested for significant differences in these metrics between the three land use zones and between two periods, 1972–1992 and 1993–2001. Most patch characteristics in MGR and SAF differed significantly from those in BOT, especially during the latter period, while between MGR and SAF they did not. Patch area, shape complexity and core area increased significantly between periods in MGR, while patch size, size variability and core area increased significantly between periods in SAF. In BOT, no patch characteristics changed significantly between periods. Within the time span analyzed for the study area, we conclude that increased fire occurrence promoted landscape heterogeneity while fire exclusion did not.     

Woodland conservation in privately-owned cultural landscapes: the English experience

This paper reviews the development of approaches to the conservation of woodland on private lands in England since 1949. In England, the majority of woodland sites important for nature conservation are small, isolated amongst open habitats, with a long history of management. Conservation of wildlife has since 1949 had a strong focus on private lands. Two approaches to protection have been adopted. Firstly about 80,000 ha of English woods are within statutorily protected sites; the degree of protection for these has increased through successive legislation in 1949, 1981 and 2001. Secondly, since 1985 wildlife protection has been achieved on private lands outside the protected sites through general statutory forestry policies. There has also been an increasing trend for active promotion of voluntary nature conservation through forestry incentives and grants, and the setting of targets as part of the government’s biodiversity action plan. The variety of ways in which woodland may be protected (to differing degrees) in England has enabled effective protection to be achieved over a greater area of woodland than would have been possible through nature reserves alone. These approaches may be relevant in other countries where woodland occurs as part of a cultural landscape.     

典型流域土地利用/覆被变化及其景观生态效应——以浙江省西苕溪流域为例

土地利用/覆被变化的环境效应是相关领域今后研究的重点。论文利用1985、1995和2000年的TM数据及调查资料,研究西苕溪流域的土地利用/覆被变化及其景观生态效应。结果表明:流域内农田不断减少,居民及工矿用地持续扩大,林地前期减少、后期缓慢增加;林地和农田是流域内的主要景观类型,空间集中性及斑块碎化、形状规则化、景观同化是景观结构和景观异质性变化的主要表现;土地利用/覆被变化产生了生境质量下降、边缘效应增强、土地退化和生态系统成分单调等景观生态效应;恢复与建设西苕溪流域的景观生态系统需对景观尺度上的土地利用方式进行必要的调整。     

Strategy for conservation of wild bees in an agricultural landscape

Investigations carried out by the author for 15 years on the Wielkopolsko-Kujawska Lowland (Western Poland) showed that wild bees (Apoidea) are today under strong human pressure. About 260 bee species were found in the area of 20 000 km². A similar number of species was recorded in this area by investigators half a century ago, which indicates that the survival of the fauna seems to be the result of some compensating factors reducing the effects of intensive agricultural management. The main factor among these is the mosaic structure of the landscape, consisting of meadows and residues of natural and semi-natural plant communities as a fauna refuge system and crop fields as an additional nutritive system. It was found that in a normally functioning agricultural landscape, the share of farmland should not exceed three-quarters of the total surface. The remaining part of the landscape should be made up of refuge habitats for Apoidea. Within such a system, qualitative and quantitative changes of the bee fauna can occur on a microregional scale and are usually of temporary character. On a regional scale they are not perceivable and probably not so important. Hence, instead of changes in fauna, one should rather speak about quantitative oscillations inside a given region. The second factor decreasing the negative effects of management is the introduction of extensive areas of some nutritive plants, e.g. rape.     

Delayed colonisation of arable fields by spring breeding ground beetles (Coleoptera: Carabidae) in landscapes with a high availability of hibernation sites

The colonisation of winter barley fields by spring breeding carabids and its temporal modulation by the amount of potential hibernation sites was studied. Species richness of carabids was lower in landscapes with high length of boundaries and a high amount of non-cropped open habitats during early stages of the beetles’ colonisation of arable fields. Species number of beetles with high dispersal potential responded to this landscape features at coarse spatial scales whereas beetles with low dispersal potential responded to intermediate scales. However, the negative impact of potential hibernation sites on colonisation diminished in later sampling phases. The patterns observed may be explained by both overwintering in arable soils in less complex landscapes and delayed colonisation in more complex landscapes. The seasonal patterns of landscape control suggest a need to account for temporal dynamics in interactions between species or functional groups and landscape properties. A high temporal resolution is needed in studies that focus on ecosystem function and services in agricultural landscapes, as direction of effect (positive/negative) of management on animal communities may change across spatial scales and within short time periods.     

土地利用变化对西南喀斯特土壤团聚体组成、稳定性以及C、N、P化学计量特征的影响

土壤团聚体稳定性和养分化学计量特征对土地利用变化的响应研究,以及对当前脆弱生态环境保护与修复具有重要意义.为探明西南喀斯特山地土地利用方式变化对土壤团聚体组成、稳定性与C、 N、 P养分化学计量特征的影响规律,选取了西南喀斯特典型区域为研究区,针对7种主要土地利用方式建立了系列样地,开展了土壤团聚体组成与稳定性、团聚体C、 N、 P含量与计量比特征研究.结果表明,土地利用变化显著影响了土壤团聚体稳定性.玉米地和撂荒地的土壤团聚体稳定性相对较高,草地和裸地的团聚体稳定性相对较低,土壤团聚体稳定性总体随土层增加呈现降低趋势.不同土地利用方式土壤团聚体C、 N和P含量存在显著差异.疏林地和撂荒地土壤团聚体C和N含量较高,草地土壤团聚体C和N含量较低,裸地和撂荒地土壤团聚体P含量相对较高.土地利用变化对土壤团聚体C、 N和P计量比也存在明显影响.乔木林地、疏林地和撂荒地土壤团聚体C∶N相对较高,草地土壤团聚体C∶N最低;乔木林地和疏林地土壤团聚体C∶P较高,明显高于其他土地利用方式;乔木林地、疏林地和灌木林地土壤团聚体N∶P较高,明显高于裸地和撂荒地.喀斯特土壤团聚体组成和稳定性与土壤C、 N...     

2000-2009年芜湖市LUCC对植被碳储量的影响

LUCC是影响陆地植被碳循环的重要因子之一。采用2000、2005和2009年3期遥感影像解译及运用GIS技术提取芜湖市2000-2009年的土地利用变化数据,根据前人对植被NPP的研究成果,计算芜湖市土地利用变化对生态系统中植被碳储量的影响。结果表明:在2000-2005年,耕地大量转化为林地、草地大量转化为耕地等使其植被碳储量净增加了4.43×103～22.14×103t;2005年-2009年,林地大量的转移为耕地、建筑用地,耕地转为水域、建设用地等使其植被碳储量净减少了72.34×103～289.38×103t。研究结果显示,芜湖市植被碳储量总体呈减少趋势,且林地是影响芜湖市植被碳储量的主要因素。     

Chronosequence analysis of two enclosure management strategies in degraded rangeland of semi-arid Kenya

The establishment of enclosures has become an important measure to combat land degradation in many of the world's semi-arid rangelands. In view of the increased pressure exerted by this land reclamation strategy on the neighbouring agricultural lands, knowledge of the time required for restoring vegetation cover and soil health, and of the potential positive impact of an adapted management strategy, is highly required. This paper assesses the vegetation and soil rehabilitation in a 23-year chronosequence of two different enclosure management types. In the severely degraded, semi-arid Njemps Flats plain of the Lake Baringo Basin in Kenya communal enclosures characterised by high quality inputs and strict control, and private enclosures managed by individual farmers, were installed since the 1980s. Six communal enclosures (3–17 years since establishment) and six private enclosures (13–23 years since establishment) were selected. Vegetation cover was estimated along three 50 m transects set within each enclosure and in the adjacent open grazing area using the point-to-line transect method. Five 0.5 m² quadrats systematically placed alongside each transect were sampled for herbaceous standing biomass and topsoil physical, chemical and biological analyses. Grass cover and herbaceous biomass production proved to be the most responsive biotic parameters under both management types, whereas the recovery of the forbs was unsuccessful. Under communal management, the biomass production fully recovered up to its optimal level as recorded in the neighbouring nature reserves. Within private enclosures however, the adopted management strategies seriously restricted biomass production to a significantly lower level. Soil quality generally recovered more slowly with time. Significant improvements compared to the open rangeland were recorded in topsoil bulk density, organic C and total N stocks, and microbial biomass C and N stocks of the communal enclosures. Unlike the communal enclosures, only topsoil bulk density and the microbial biomass C stock showed a significant difference in the private enclosures. With respect to C and total N stocks, and the microbial biomass N a non-significant improving trend was recorded. The level of chemical and biological soil quality obtained under both management types is still low and draws the attention to the importance of careful monitoring of grazing and grass cutting activities under both enclosure management strategies. The chronosequences further highlight the potential of some well-managed private enclosures, whereas intrinsic soil properties such as high alkalinity, as well as changes in management, limit the rehabilitation of some other private as well as communal enclosures.     

The effects of land use and its patterns on soil properties in a small catchment of the Loess Plateau

Due to relatively strong human activities in the hilly area of Loess Plateau,the natural vegetation has been destroyed,and landscape pattern based on agricultural land matrix was land use mosaic composing of shrub land,grassland,woolland and orchard.This pattern has an important effect on soil moisture and soil nutrients.The Danangou catchment,a typical small catchment,was selected to study the effects of land use and its patterns on soil moisture and nutrients in this paper.The results are as follows:The comparisons of soil moisture among seven land uses for wet year and dry year were performed:(1)the average of soil moisture content for whole catchment was 12.11% in wet year,while it was 9.37% in dry year;(2)soil moisture among seven land uses was significantly different in dry year,but not in wet year;(3) form wet year to dry year,the profile type of soil moisture changed from decreasing type to fluctuation-type and from fluctuant type to increasing type;(4)the increasing trend in soil moisture from the top to foot of hillslope occurred in simple land use along slope,while complicated distribution of soil moisture was observed in multiple land uses along slope.The relationships between soil nutrients and land uses and landscape positions were analysed:(1)five nutrient contents of soil organic matter(SOM),total N(TN),available N(AN),total P(TP) and available P(AP) in hilly area were lower than that in other areas.SOM content was less than 1%,TN content less than 0.07%,and TP fallow land and cropland,and higher level in soil fertility was found in crop-fruit intercropping land among croplands;(3)soil nutrient distribution and responses to landscape positions were variable depending on slope and the location of land use types.     

科尔沁沙地农牧交错区景观持续性研究

科尔沁沙地农牧交错区景观持续性的分析表明,在不同时间尺度上,景观多样性的持续性增加1.038(±0.033),而景观优势度持续性下降0.873(±0.112),说明在1958年固定沙丘地占主导地位的景观逐渐演化成流动沙丘、半固定沙丘、固定沙丘和农田相间分布、平分秋色的景观。在农牧业生产活动的影响下,景观格局的持续性在空间形状的变化上趋向复杂(景观分维数持续性为1.008),而其相邻性下降(景观修改分维数0.953)。斑块尺度上,不同时间尺度的分析显示,流动沙丘和半固定沙丘斑块面积持续性增加,而固定沙丘和农田斑块面积持续减少;从斑块格局的持续性来看,半固定沙丘地空间格局的持续性呈增加的趋势最明显,为1.038(±0.087),固定沙丘地空间格局的持续性呈减少的趋势最明显,为0.806(±0.032);40年来科尔沁沙地的农牧交错活动对斑块修改分维数的持续性影响是一致的,呈下降的趋势,说明该过程减少了景观中斑块间的相邻性。     

Land use structure optimization based on carbon storage in several regional terrestrial ecosystems across China

Land use change is a main driver of carbon storage in terrestrial ecosystems. Based on land use data, research results related to carbon densities in vegetation and soil as well as government policies related to development in different regions of China, this paper optimized land use structure in 2020 for different regions with the goal of increasing terrestrial ecosystem carbon storage. We defined seven types of land use: (1) cultivated land, (2) garden land, (3) woodland, (4) pasture land, (5) other agricultural land, (6) urbanized land, and (7) a mixture of other land which we call mixed land which included open water, swamps, glaciers and other land as defined below. We found: (1) For most eastern regions, woodland has the highest carbon (C) densities while C densities of pasture land and cultivated land did not differ widely. Both have C densities higher than urbanized land while urbanized land has higher carbon densities than the areas placed in the mixed land type. (2) Under an optimized land use structure projected for 2020, the area of cultivated land will decrease compared with 2005 for most regions. The areas of garden land, pasture land and other agricultural land are much smaller compared with the mixed land use type, and the changes there are not obvious and their contributions to increased carbon storage are not significant. The area of woodland will increase the most obviously and it will contribute the most to increased carbon storage. The increasing urbanization of land and the decreasing trend of other land types make it difficult to change carbon storage patterns since the Chinese economy is expanding rapidly. (3) The optimized land use structure presented here will have effects on the entire country though with regional differences. Some inland regions will always have a larger potential to increase carbon storage than other areas because the potentialities in some coastal regions are limited by social and economic development.     

海平面上升和土地利用驱动下红树林生境脆弱性研究

为了探索海平面上升(SLR)和土地利用导致的红树林生境潜在变化,本文以我国红树林分布最集中的雷州半岛为研究区域,基于SLAMM模型和景观生态模型建立了红树林生境脆弱性指数,设置4个SLR-土地利用组合情景(SLR4.5-土地开发利用、SLR4.5-土地自然转换、SLR8.5-土地开发利用、SLR8.5-土地自然转换),预测2050年雷州半岛红树林的生境变化和脆弱程度,并提出应对环境变化的管理策略.结果表明,(1)SLR和土地利用双重压力的叠加将造成红树林生境的显著退化,预测生境面积将减少16.59%～25.61%,减少地点集中在铁山港、安铺港、湛江港、雷州湾和流沙湾沿岸.(2)在土地自然转换情景下,尽管仍应对着海平面上升的压力,红树林潜在生境面积可增加44.66%～67.74%,增加的区域集中在岸线往内陆方向和沿水系向内陆延伸的两岸,但新增生境面临着破碎化程度高的问题.(3)在所有情景下均呈现红树林迁出现有保护区的趋势,保护区内红树林面积由5949.8hm²下降至4732.1～5192.9hm².(4)高脆弱区主要分布在雷州湾、湛江港近岸和流...     

华北油田二连分公司蒙古林作业区生态环境质量状况研究

本文选取二连油田蒙古林作业区生态环境质量为研究对象,对该区域内的土地利用／覆盖状况、植被状况、景观类型及其破碎度进行定性、定量研究。结果表明：（1）2008年,该区域土地利用类型主要为有林地、中覆盖度草地、低覆盖度草地、工矿交通建设用地和盐碱地等;工交建设占地明显。（2）该区2008年主要植物群落类型有：克氏针茅＋羊草＋杂类草、克氏针茅＋锦鸡儿＋杂类草、羊草＋针茅＋杂类草等;受到气候变暖等原因影响,小针茅已经在本区广泛分布。（3）该区2008年主要景观类型为针茅＋锦鸡儿草原景观、针茅草原景观、羊草草原景观、林地景观、人工建设区景观和道路景观;景观破碎度较高,人为干扰较为严重。建议相关单位足够重视并采取切实可行的措施,防止本区生态环境恶化。     

典型海岛景观生态网络构建以崇明岛为例

人类活动的日益频繁使得海岛生物多样性保护压力不断增大,构建景观生态网络是缓解海岛生物多样性压力的重要途径。基于RS和GIS,运用最小阻力距离法和重力模型构建了崇明岛景观生态网络,结果显示:崇明岛景观生态网络由重要生态功能斑块和生态廊道构成;重要生态斑块共17个,面积170.6 km2,占崇明岛总面积的12%,其中东滩湿地为核心生态源地,东平国家森林公园附近区域为核心生态节点;生态廊道共25条,包括核心生态廊道17条,总长度分别为164.2 km和74.1 km,其中东滩湿地和北湖湿地之间廊道以及东风西沙周边廊道是崇明岛生态连接的关键;随着生态廊道宽度的增大,景观生态网络中最适宜景观比例相应减少,中等适宜景观和不适宜景观比例则有所增大,网络构建的难度也随之上升。     

Stable carbon isotope reconstructions of diet and paleoenvironment from the late Middle Pleistocene Snake Cave in Northeastern Thailand

Thailand’s geographical location in the tropics and almost complete, relatively uninterrupted forest cover makes it valuable for paleodiet and paleoclimate research. We present the first dietary and environmental reconstructions in Northeastern Thailand, using stable isotope abundances in mammalian tooth enamel from the late Middle Pleistocene locality, Tham Wiman Nakin (Snake Cave), which reflect a much higher (over 70%) than modern (13%) occurrence of C4 plants. Bovids and cervids appear to have had almost entirely a C4 plant diet. Carnivores consumed a mixture of C3 (suids) and C4 (bovids, cervids) consumers. Rhinoceroses and orangutan appear to have maintained their preference through time for forested or open C3 environment, respectively. ¹³C/¹²C from bone bioapatite, horn and hair of modern Southeast Asian mammals almost exclusively demonstrate C3 vegetation dominance. C4 consumption is rare in analysed modern species and it could be related to anthropogenic influences such as ingestion of domestic crops or livestock. Interesting implications emerge in the C4 vegetation distribution in southern Eurasian ecosystems, indicating that Southeast Asia, south of the Tibet, could be part of the global C4 vegetation spread, which occurred around 7 Ma. However, the C4 percentage in ecosystems varied geographically. Despite modern reversal towards C3 habitats due to factors such as increasing CO₂, we think that anthropological influences may be responsible for habitat and dietary changes in extant species. Bovids demonstrate the most significant shift in diet and habitat through time, from C4-dominated open habitats to C3-dominated habitats indicative of dense forest understory.     

三亚城市景观变化的监测研究

区域生态环境变化的动态监测是自然资源合理利用和区域环境保护中急需解决的问题。本项研究采用了遥感技术,对三亚城市景观中不同景观组分的优势度值和边界形状等空间结构指标,对林木覆盖率和生物量等景观稳定状况指标进行了监测,同时配合了典型采样和勘测等地面工作,提高监测数据的可信度。在此基础上建立了区域生态环境变化监测体系和Sanya－Landscape信息系统,对三亚城市生态环境变化趋势进行了评价,准确地反映了该区域生态环境的现状和特征,为三亚城市生态环境的规划和管理提供了科学依据。结果证明,本研究采用的指标及指标的采集方法是区域生态环境动态监测的有效手段。     

景观生态学在农业园区规划环评中的应用

根据西南一农业园区规划前后土地利用变化的结果,借助地理信息系统技术,运用景观生态学基本理论分析了农业园区规划前后景观格局变化,主要结果为:规划后区域优势景观类型仍为耕地,但各类生境斑块的生态系统能力有所下降,农村居民点的集中建设有利于景观破碎化程度减轻,但路网的建设又加重了景观破碎化。在农业园区的规划中,须考虑林地和自然保留地这两类土地类型的合理分布,特别是现有生态系统较好的斑块,对评价区生物多样性的保持具有重大意义。     

输气管道建设项目景观及生态系统影响评价—以广东省天然气管网一期工程为例

广东省天然气一期总长约466．5km,其中干线长度约369．1km,支干线长约97．4km。项目建设区域包括广州、佛山、肇庆、惠州、韶关、清远和东莞6市。天然气管道建设因其工程特性、施工方式,不可避免对土地利用类型、土壤、植被、动物、农业等方面带来影响,其表征为景观生态的直接影响,由此带来生态系统结构和功能的改变。以广东省天然气一期为例,采用遥感解译和GIS分析技术进行生态影响评价。通过地貌、植被、土地利用现状和现代地理过程等要素的组合,结合景观破碎度、多样性、优势度等指标,定量评价管道建设造成的景观生态影响。选取植被、土壤亮度、湿度、热度等指数,确立各指数权重分后,建立生态评价模型,对生态系统质量进行综合评价,分析管道建设可能造成的生态系统影响。评价区内景观生态类型可分为水域、旱地、水田、林地、草地、建设用地6种,各占6．5％、9．9％、51．2％、25．2％、2．8％和4．3％,破碎度为0．298,均匀度0．743,优势度0．594;生态环境质量可分为良好、中等、较差3类,各占39．8％、26．0％和34．2％。