Estimating dyad association probability under imperfect and heterogeneous detection

In animal behaviour studies, association indices estimate the proportion of time two individuals (i.e. a dyad) spend in association. In terms of dyads, all association indices can be interpreted as estimators of the probability that a dyad is associated. However, traditional indices rely on the assumptions that the probability to detect a particular individual (p) is either approximately one and/or homogeneous between associated and not associated individuals. Based on marked individuals we develop a likelihood based model to estimate the probability a dyad is associated (ψ) accounting for p < 1 and possibly varying between associated and not associated individuals. The proposed likelihood based model allows for both individual and dyadic missing observations. In addition, the model can easily be extended to incorporate covariate information for modeling p and ψ. A simulation study showed that the likelihood based model approach yield reasonably unbiased estimates, even for low and heterogeneous individual detection probabilities, while, in contrast, traditional indices showed moderate to strong biases. The application of the proposed approach is illustrated using a real data set collected from a population of Commerson's dolphin (Cephalorhynchus commersonii) in Patagonia Argentina. Finally, we discuss possible extensions of the proposed model and its applicability in animal behaviour and ecological studies.     

Integrating soil carbon cycling with that of nitrogen and phosphorus in the watershed model SWAT: Theory and model testing

In this paper we describe and test a sub-model that integrates the cycling of carbon (C), nitrogen (N) and phosphorus (P) in the Soil Water Assessment Tool (SWAT) watershed model. The core of the sub-model is a multi-layer, one-pool soil organic carbon (S_C) algorithm, in which the decomposition rate of S_C and input rate to S_C (through decomposition and humification of residues) depend on the current size of S_C. The organic N and P fluxes are coupled to that of C and depend on the available mineral N and P, and the C:N and N:P ratios of the decomposing pools. Tillage explicitly affects the soil organic matter turnover rate through tool-specific coefficients. Unlike most models, the turnover of soil organic matter does not follow first order kinetics. Each soil layer has a specific maximum capacity to accumulate C or C saturation (S_x) that depends on texture and controls the turnover rate. It is shown in an analytical solution that S_x is a parameter with major influence in the model C dynamics. Testing with a 65-yr data set from the dryland wheat growing region in Oregon shows that the model adequately simulates the S_C dynamics in the topsoil (top 0.3 m) for three different treatments. Three key model parameters, the optimal decomposition and humification rates and a factor controlling the effect of soil moisture and temperature on the decomposition rate, showed low uncertainty as determined by generalized likelihood uncertainty estimation. Nonetheless, the parameter set that provided accurate simulations in the topsoil tended to overestimate S_C in the subsoil, suggesting that a mechanism that expresses at depth might not be represented in the current sub-model structure. The explicit integration of C, N, and P fluxes allows for a more cohesive simulation of nutrient cycling in the SWAT model. The sub-model has to be tested in forestland and rangeland in addition to agricultural land, and in diverse soils with extreme properties such high or low pH, an organic horizon, or volcanic soils.     

Ecosystems emerging. 5: Constraints

Ecosystem constraints are both ontic and epistemic. They limit activity, and as problems to be solved they drive organization, which is our hypothesis:

The driver of organization is constraint.

Solutions proliferate further constraints in an unending spiral of problem (constraint) generation and solution. As constraints proliferate, behavior narrows, and species diversify to compensate (paradox of constraint). Resource enrichment reduces constraints, releases behavior, and reduction of challenges decreases diversity (paradox of enrichment)—high diversity is expressed in low-resource environments and low diversity in high-resource environments. A three-part model of constraints is formulated for non-living systems, and also for goal-directed, problem-solving biota. Mode 1: dynamical means behavior is co-determined by internal states and external inputs. Mode 2: cybernetic employs negative feedback to keep dynamics within goal-oriented operating limits. Mode 3: model-making entails ability to represent (model) physical reality and respond to both phenomenal (modeled) and physical inputs; this property distinguishes living from nonliving systems. Principal sections of the paper elaborate dynamical constraints (three classes), boundary constraints (expressed in edge effects and trophic dynamics), physical constraints (space, time, temperature), chemical constraints (environment fitness, ecological stoichiometry, chemical evolution, limiting factors), coding constraints (environmental vs. genetic coding), network and pathway constraints (connectivity), and natural selection constraints (fitting to the biosphere). Consideration of how the world would look without constraints suggests how fundamental these are in ecosystem emergence, and how the next property in this series, differentiation, would be unmotivated without them. We conclude that constraints as a category are under-studied in ecology, poorly understood in ecological phenomenology, and (our hypothesis) comprise a ubiquitous organizing force in nature.     

基于土地利用的喀斯特地区生态系统服务功能价值评估——以贵州省为例

为探讨喀斯特地区生态系统服务功能价值特征,对贵州省生态系统服务功能价值进行评估,结果表明生态系统服务功能价值在2005、2010、2020年分别为1 610.43亿、2 357.86亿、4 328.89亿元.贵州省各类生态系统服务功能单价顺序为湿地>水体>森林>草地>农田>荒漠,其中湿地生态系统是荒漠生态系统服务功能价值的149.31倍.2005～2020年贵州省生态服务功能价值结构和土地利用结构以森林生态系统占绝对优势,各类型生态系统服务功能价值顺序为森林>农田>草地>水体>荒漠>湿地,各类型生态系统面积大小顺序为森林>农田>荒漠>草地>水体>湿地.2005、2010、2020年贵州省单位面积生态系统服务功能价值分别为9 142、13 385、24 573元/hm2.根据至2020年的土地利用规划,贵州省生态系统服务功能将持续增加.     

基于主成分分析的云南省生态脆弱性评价

人口资源环境矛盾造成了脆弱生态环境问题突出。以典型生态脆弱区云南省为研究区,根据导致该省生态环境脆弱的自然-结果表现因素,构建科学客观地评价指标体系,运用主成分分析法进行生态脆弱性分析评价。以生态脆弱度大小为依据,对云南省16个地（州）、市生态脆弱性进行了分区,划分为极强度、强度、中度、轻度脆弱区4个区。评价结果显示,极强度、强度、中度、轻度生态脆弱区分别占全省面积的5.84%、27.84%、43.08%、23.24%。为生态脆弱性评价提供了一个可行的方法,同时应用生态脆弱性分区结果可为后续的生态环境恢复重建工作、制定综合治理策略及区域可持续发展规划提供依据。     

MODIS植被叶面积指数对贵州高原山地气象条件的响应

用EOS/MODIS卫星遥感分辨率为1 km的贵州2001—2008年每8 d合成植被叶面积指数（LAI）,分析了LAI的时间变化规律和年、季空间分布特征;还用贵州69个气象站的日观测数据,分别与各气象点所对应的3×3个像元LAI平均值进行气象要素（温度、降水、日照时数和水汽压）与LAI的相关分析。结果表明：该地区LAI年变化为0.3~3.0,多年平均LAI的空间分布是东南部最高（4.0）,西部和西南部最低（1.0）。显著影响LAI变化的气象因子按相关系数的大小排列是：温度、水汽压、日照时数和降水（均通过了99.9%信度检验）。水汽压对LAI产生影响的原因可能与高原喀斯特地区土壤层较薄有关。在考虑云贵高原植被年际间变化对气候变化的响应时可以把这些要素作为重要的影响因子。     

基于景观指数聚类的粤北典型区景观生态区划

通过选取不同层次的景观指数,对粤北典型区域的景观生态子区进行分区研究,探讨了景观指数在景观生态区划方面的应用,为景观生态区划提供了一种新的思路和方法。采用2009年广东省南雄市DOM数字正射影像为数据源,应用ENVI 4.3和ARCGIS 9.3对遥感影像进行解译和分类,把研究区景观类型分为耕地、林地、疏林地、城镇建设用地、水体、未利用地6大类;根据镇级行政界线把研究区分为18个景观生态子区;选取不同层次的景观指数,应用Fragstats 3.3计算研究区的景观指数;以经过筛选后的景观指数为变量因子,18个景观生态子区为聚类对象,在SPSS 17.0中选择Q型聚类欧式距离平方法进行聚类分析,在聚类图谱中选择水平距离7.5为标准线,对景观子区进行分类,把18个景观生态子区分为4个区域。聚类结果显示,各分区内子区的景观结构特征高度一致。把景观指数应用到景观生态区划,通过聚类分析,分区结果能够较好的反映景观生态结构的显著特征与空间分异状况。     

荒漠草原典型植物群落枯落物生态水文功能

在退化荒漠草原生态系统恢复过程中,枯落物是联系植被和土壤物质循环与能量流动的重要中间环节,且发挥着重要的生态水文功能。通过调查荒漠草原5种典型植物群落（蒙古冰草群落、甘草群落、赖草群落、杂类草群落和沙蒿群落）枯落物蓄积量、持水性能、对降雨的截留和对土壤水分蒸发的抑制作用,分析了荒漠草原不同植被类型枯落物的生态水文功能。结果表明：枯落物蓄积量和最大持水量均为蒙古冰草群落〉甘草群落〉赖草群落〉杂类草群落〉沙蒿群落;5种群落枯落物层对降雨的截留量在3.36～5.27 mm,截留率在3.40%～6.82%,枯落物对降雨的截留量与降雨量呈正相关,而降雨量与截留率呈负相关,且枯落物对降雨的截留具有显著的季节变化规律。在不同枯落物覆盖下,枯落物对土壤的抑制效应也存在显著差异,0.5~2 cm覆盖厚度比不盖枯落物土壤水分蒸发减少了19.25%～76.82%,枯落物层减少土壤水分蒸发效应随枯落物层厚度增大而增加。枯落物的蓄积与覆盖对土壤水分的运移和蓄存产生明显的生物学作用,已经成为荒漠草原最重要的生态过程之一。     

基于氮磷指数的小流域氮磷流失风险评价

识别区域氮磷流失综合风险分布状况并对氮磷流失进行综合调控是控制非点源污染的有效措施。但传统的研究往往局限于氮或磷流失风险的单独评估和调控,以密云水库沿湖集约化农区东庄小流域为例,应用氮指数、磷指数及氮磷综合指数法,对区域氮磷流失风险进行综合评价。结果表明：流域氮、磷流失风险总体上较小,80%以上的区域均处于氮、磷流失的无风险或低风险区,但氮、磷流失的空间分布存在较大差异。其中氮流失的高度风险区集中在山地中土壤侵蚀指数较大的果园;而磷流失的高风险区域主要分布在河流沿岸的农业用地。氮磷综合风险指数显示,93.1%的区域处于无风险和低风险区,中度以上风险区占总面积的6.9%,主要集中在流域中部有着较高的肥料施用、地势陡峭且处在河流沿岸的农业用地或山地中。单独考虑氮指数或磷指数都难以反映区域氮磷流失的综合风险状况,容易忽略磷指数高氮指数低、氮指数高和磷指数低以及氮、磷风险在中等的区域。因此,在氮、磷流失风险评估基础上,进行氮磷流失风险的综合评价,可为氮磷流失的综合调控提供指导。     

喀斯特地区长期草地利用制度对群落稳定性的影响

草地利用方式和混播组合对群落特性的长期影响不同。利用方式对白三叶(Trifolium repens)盖度没有显著影响,而混播组合与利用方式的交互作用影响显著。白三叶在宿营处理和刈割为主利用下的与鸭茅(Dactylis glomerata)混播中的比例最低,而在刈割利用和宿营处理的多年生黑麦草(Lolium perenne)组合中的盖度最高。混播组合对禾本科组分盖度影响不显著,但利用方式和交互作用有显著的作用,长期放牧绵羊的混播草地多年生黑麦草很少。混播组合对杂草密度、盖度和多样性指数的影响不明显,而利用方式和交互作用显著地影响杂草盖度和多样性指数。放牧草地中的杂草密度高于刈割草地的,其中放牧利用的白三叶/多年生黑麦草草地最高。放牧牛的草地杂草密度较少,而放牧绵羊的草地杂草较多。白三叶、禾本科牧草以及杂草的密度都显著地受混播组合、利用方式及其交互作用的影响,说明密度是一个敏感的指标。