Reversed animal-plant interactions: the evolution of insectivorous and ant-fed plants

Insectivorous plants and ant-fed plants represent the two ways in which plants have evolved to utilize directly nutrients derived from animals. This paper addresses the limitations under which selection acts to favour the evolution of one or the other of these nutrient-gathering tactics. Both tactics have evolved independently at least six times under similar ecological conditions, indicating that the evolutionary solutions to ecological problems are limited by the historical make-up of communities and are, to some extent, predictable. Both insectivorous and ant-fed plants evolve in environments with very low levels of availability of nutrients in the substrate; the primary use of the animal-food is probably nitrogen; the vast majority of species are perennial, and most species are tropical or subtropical, although some insectivorous genera are primarily temperate.
Although these two nutrient-gathering tactics evolve in response to similar ecological problems, whether plants evolve an insectivorous habit or the ant-fed habit depends on the growth forms of the plants and the habitats in which they grow. Most insectivorous plants evolve as herbs in wet, sterile soils or in sterile aquatic habitats; ant-fed plants evolve as epiphytes on trees in open-canopied habitats. These kinds of animal-plant interactions are relatively rare because the environments in which they are favoured by selection are uncommon.     

Production of submerged aquatic plant communities of Doodhadhari lake Raipur, (M.P. India)

The biomass of submerged aquatic plant communities was studied periodically during two annual growth periods. Najas minor contributed 78% to the total standing biomass. Ceratophyllum demersum, Hydrilla, Nelumbo nucifera, Trapa bispinosa and Potamogeton crispus contributed towards the rest of the biomass. The production was 0.64 g./m.²/day for the growing seasons of one year.     

盐性条件下植物内生真菌多样性及其生态学功能研究

<正>据统计,盐化土壤在地球上所占比例超过7%,我国盐渍土面积约9 900万hm2,土壤盐渍化对农业生产的影响已成为一个全球性的问题。盐生植物是盐渍化土壤中的天然植物类群,可显著降低土壤盐分,改善盐碱土壤肥力及土壤微生物种群结构。内生真菌生活在植物体内,可促进其宿主生长,增强宿主的抗干旱和抗病虫害能力。长期生活于盐渍化土壤中的盐生植物具有耐盐碱、耐旱等特性,其体内也因积累大量的Na+和Cl-成为一个高盐的微环境。有研究表明,内生真菌在盐胁迫条件下能促进盐生植物的生     

分水后黑河干流中游地区景观动态变化及驱动力

综合利用GIS、RS技术和景观生态学方法,分析了黑河干流中游地区1985～2005年,尤其是黑河干流水量统一调度实施后(即2000年以后)的景观动态变化及驱动机制.结果表明:(1)研究区景观发生了较大变化,1985～2000年,耕地、林地、城乡工矿居民用地逐渐增加,而草地、水域、未利用土地不断减少;2000～2005年耕地、城乡工矿居民用地逐渐增加,而草地、林地、水域、未利用土地不断减少.(2)在类型水平上,分水后,耕地和城乡工矿居民用地呈连片趋势发展,破碎度降低,形状更为规则,空间连接性增强;林地、草地、水域和未利用土地破碎度增加,分布更为分散,连通性和优势度降低.(3)在景观水平上,分水后,研究区景观多样性水平提高,异质性在增加,破碎化程度越来越大,景观中斑块空间连接性下降,优势度在减少,斑块类型在景观中趋于均匀分布,土地利用向着多样化和均匀化方向发展.(4)研究区景观变化的驱动力主要包括人口增长、经济社会发展,2000年以后,可利用水量的约束直接影响着研究区的景观变化.     

Rhizosphere soil bacterial communities and nitrogen cycling affected by deciduous and evergreen tree species

Deciduous and evergreen trees differ in their responses to drought and nitrogen (N) demand. Whether or not these functional types affect the role of the bacterial community in the N cycle during drought remains uncertain. Two deciduous tree species (Alnus cremastogyne, an N₂‐fixing species, and Liquidambar formosana) and two evergreen trees (Cunninghamia lanceolata and Pinus massoniana) were used to assess factors in controlling rhizosphere soil bacterial community and N cycling functions. Photosynthetic rates and biomass production of plants, 16S rRNA sequencing and N‐cycling‐related genes of rhizosphere soil were measured. The relative abundance of the phyla Actinobacteria and Firmicutes was higher, and that of Proteobacteria, Acidobacteria, and Gemmatimondaetes was lower in rhizosphere soil of deciduous trees than that of evergreen. Beta‐diversity of bacterial community also significantly differed between the two types of trees. Deciduous trees showed significantly higher net photosynthetic rates and biomass production than evergreen species both at well water condition and short‐term drought. Root biomass was the most important factor in driving soil bacterial community and N‐cycling functions than total biomass and aboveground biomass. Furthermore, 44 bacteria genera with a decreasing response and 46 taxa showed an increased response along the root biomass gradient. Regarding N‐cycle‐related functional genes, copy numbers of ammonia‐oxidizing bacteria (AOB) and autotrophic ammonia‐oxidizing archaea (AOA), N₂ fixation gene (nifH), and denitrification genes (nirK, nirS) were significantly higher in the soil of deciduous trees than in that of the evergreen. Structural equation models explained 50.2%, 47.6%, 48.6%, 49.4%, and 37.3% of the variability in copy numbers of nifH, AOB, AOA, nirK, and nirS, respectively, and revealed that root biomass had significant positive effects on copy numbers of all N‐cycle functional genes. In conclusion, root biomass played key roles in affecting bacterial community structure and soil N cycling. Our findings have important implications for our understanding of plants control over bacterial community and N‐cycling function in artificial forest ecosystems.     

张家界武陵源风景区自然景观价值评估

自然景观提供给人们观赏、娱乐和休闲的效用和价值,长期以来,人们对自然景观的价值忽略并低估,导致在开发利用自然资源过程中出现资源浪费和生态破坏的问题.如果赋予自然景观合适的经济价值,能为其开发利用提供决策支持.为评价张家界武陵源风景区的景观价值,构建了相应的指标体系.自然景观价值乃使用价值与非使用价值之和,并对这两种价值分别运用旅行费用法和条件价值法进行评估.结果表明:2011年武陵源风景区的自然景观价值为89.01亿元,其中使用价值为79.30亿元,非使用价值为9.71亿元.分析表明,武陵源风景区的自然景观价值要远高于以往的研究及近年的旅游收入,建议景区当局全面认识其景观价值,在旅游人次不断攀升的形势下,全力保护该地生态环境,探究武陵源风景区的可持续发展道路.     

北京东灵山区景观类型空间邻接与分布规律

景观由斑块实间镶嵌而成。如何从错综复杂的斑块镶嵌中发现景观类型的空间分布规律,是景观格局研究中亟待解决的问题。通过对北京东灵山地区景观类型空间邻接关系的研究,借鉴群落生态学方法对其空间分布规律进行了探讨。结果表明,各个景观类型的空间邻接特征明显差异,可依紧密邻接的类型数目和程度分为３类;决定景观类型邻接多样性的主要因素是邻接类型的数目;采用作者提出的以景观类型空间邻接长度替代群落学数据的群落分类方     

SWAT模型对景观格局变化的敏感性分析——以丹江口库区老灌河流域为例

景观的空间配置与类型组成能够对流域的产流、产沙及非点源污染产生影响。在以往SWAT模型研究中,往往默认水文模型考虑了该影响。为分析SWAT模型对不同景观格局变化的敏感性,根据老灌河流域2000年土地利用在各子流域的组成,模拟研究区更为破碎、复杂的景观空间配置,通过设置多套试验参数,利用SWAT模型生成基于不同景观格局的模拟结果。结果表明,SWAT模型不能反映除坡度和面积变化之外的景观水平下各斑块之间因景观空间格局改变对流域产流、产沙以及非点源污染的影响;模型通过其他参数的调整,弥补了模型分析数据的不足,使实测数据与模型部分结果高度吻合。这表明,一个能够反映流域部分水文特征的SWAT模型,未必是对研究区真实情形的模拟,而是各个参数间平衡的结果。因此,在利用SWAT模型分析模拟景观变化时,不应默认模型能够模拟景观空间格局改变对流域水文过程的影响,同时研究者可以通过划分坡度带,提高模型对不同坡度土地利用的敏感性。     

城市“源-汇”热景观变化及其空间作用强度特征——以深圳西部地区为例

城市热岛作为一种整体涌现性的地球表层系统环境问题受到地理学和景观生态学的广泛关注,基于空间异质性对城市冷热岛影响方面的研究初步揭示了城市热环境的形成机制,然而城市冷热岛在空间上是否存在相互影响及相互作用强度还有待研究。以深圳市西部城市区为例,应用地表温度和景观分类数据,通过构建二维矩阵识别"源-汇"热景观,并采用"源-汇"热贡献指数和空间引力模型等方法定量分析了城市"源-汇"热景观的演变过程,"源-汇"热贡献程度的时空分异特征,以及两者在空间上的整体相互作用强度及演变特征。结果表明：（1）1988-2019年,城市热源、汇在空间上呈现由包围到反包围的变化,热源景观呈现基质化,其面积增长210.45%;热汇景观则表现为破碎化趋势,其面积减少48.07%。与之对应的热汇景观地表温度与区域的平均温度的温差逐渐增大,从1988年的0.49℃上升到2019年的1.91℃。（2）源、汇对热环境的贡献规模呈增长趋势,热源景观的贡献程度会随着热岛规模从零星状向区域化的转变过程中提升,形成温度聚集效果;而热汇景观的贡献程度会随着冷岛规模的破碎化过程中被抑制。（3）1988-2019年"源-汇"热景观的作用对基本保持稳定,但总作用强度发生了显著的变化,30年间增长了8倍。从热汇景观一对多影响热源景观转变为热源景观一对多影响热汇景观,且作用强度也越来越强。研究发现城市热"源-汇"的空间相互作用强度与"源-汇"热景观的贡献程度有密切关联,因此控制热源景观规模和维护热汇景观规模对调控城市热环境,对提升城市居民生活质量有重要意义。     

沙地景观中矢量数据栅格化方法及尺度效应

针对景观生态学研究中的数据转换(矢量数据转换为栅格数据)问题,从斑块面积、周长、数量对转换方法及尺度的响应角度进行了详尽的分析.以库布齐沙漠地区的2003年1:10万的矢量数据为例,转换尺度以10m为起点,200m为终点,10m为间隔,利用最大面积值方法(RMA)和中心属性值方法(RCC)两种转换方法分别进行栅格化,讨论了面积、周长、斑块数量对不同尺度及不同转换方法的响应,同时还讨论了运算时间对转换方法及尺度的响应.得出了"30m大小的转换尺度为最佳尺度,最大面积值方法(RMA)优于中心属性值方法(RCC)"的结论.