Spatial Variation in Lesser Prairie-Chicken Demography: A Sensitivity Analysis of Population Dynamics and Management Alternatives

ABSTRACT The lesser prairie-chicken (Tympanuchus pallidicinctus) is currently considered a candidate for protection under the Endangered Species Act. To identify potential limiting factors for lesser prairie-chicken populations, we developed an age-based matrix model of lesser prairie-chicken population dynamics to compare the relative importance of components of reproduction and survival, and determine if various management alternatives stabilize or increase rates of population change. We based our analyses on an intensive 6-year population study from which demographic rates were estimated for each age class in Kansas. We used deterministic models and elasticity values to identify parameters predicted to have the greatest effect on the rate of population change (λ) at 2 study sites. Last, we used life-stage simulation analysis to simulate various management alternatives. Lambda was <1 for both populations (site 1: λ = 0.54, site 2: λ = 0.74). However, we found differences in sensitivity to nest success and chick survival between populations. The results of the simulated management scenarios complemented the lower-level elasticity analysis and indicated the relative importance of female survival during the breeding season compared with winter. If management practices are only capable of targeting a single demographic rate, changes to either nest success or chick survival had the greatest impact on λ at site 1 and 2, respectively. Management that simultaneously manipulated both nest success and chick survival was predicted to have a greater effect on λ than changes in survival of adult females. In practice, our demographic analyses indicate that effective management should be based on habitat conservation measures to increase components of fecundity.     

Frost and forest stand effects on the population dynamics of Asplenium scolopendrium

Our objective was to analyze which factors are critical for the dynamics of terrestrial Asplenium scolopendrium populations at the northern edge of its distribution. Therefore, a long-term study (1978–1999) on the performance and demography of this fern species has been carried out in three different forest stands (Picea sitchensis with Fagus sylvatica, P. sitchensis with thinning, and Fraxinus excelsior) in the Netherlands. We used the recorded demographic data to parameterize 37 transition matrices. The number of frost days in severe winters correlated closely with frond damage and resulted in increased mortality and retrogression. Landslip on the trench banks and intraspecific competition were also found to increase mortality. In the F. excelsior plot, plants grew faster and bigger, produced more fronds and formed a more closed fern cover than in the P. sitchensis stands, likely due to higher light levels. Life-table response experiments revealed that reproduction contributed greatly to the differences in projected population growth rates: reproduction was importantly higher in the F. excelsior and in the thinned P. sitchensis plots than in the P. sitchensis–F. sylvatica plot. These differences can be attributed to an initial difference in light climate and to the accumulation of F. sylvatica litter which reduced recruitment. Recruitment occurred on bare soil but also in open moss carpets. We expect that the fern Asplenium scolopendrium will profit at its northern distribution edge when severe winters will occur less frequently, which is one of the expectations for global climate change.     

Pair-wise analyses of the effects of demographic processes, vital rates, and life stages on the spatiotemporal variation in the population dynamics of the riparian tree Aesculus turbinata Blume

Population growth rates (λ) of the riparian tree Aesculus turbinata varied from 0.9988 to 1.0524 spatiotemporally. We conducted a series of pair-wise demographic and matrix analyses, including randomization tests, three types of life table response experiments (LTREs), analysis of variance and χ² tests, to test which life stages had the greatest effect on this variation in λ. Randomization tests detected significant variations in λ between plots affected or not by typhoons in three habitats and between periods with high and low recruitment in one habitat. Mixed-level LTREs identified that the demographic processes and life stages that had the strongest effect on the actual variation in λ were: (1) progressions of small and intermediate juveniles and (2) founding process from seeds to 1-year-old seedlings. These juvenile stages had medium sensitivities and variances that explained high upper-level LTRE contributions. Lower-level LTREs showed that the vital rates contributing the most were the growth rates of these juvenile stages. These findings demonstrate that progression from one stage to the next, growth rates of 1-year-old seedlings, and stunted aging juveniles are the most important stages in the population dynamics of this long-lived primary tree species. Transition matrix elements with high elasticities had little effect on the variation in λ, indicating that high-elasticity vital rates do not necessarily drive variation in population growth. As compared with the results of randomization tests, significant differences in vital rates examined using ANOVA or χ² tests showed that typhoon disturbance had the greatest effect on the demographic parameters of individual trees.     

新疆焉耆盆地人类活动与气候变化的效应机制

通过对新疆焉耆盆地及其周边近40a(1973—2014)的气候变化趋势检测、LUCC和生物量估算,探讨气候变化和人类活动的生态效应机制,研究区域陆地生态系统演变及其归因。分析结果表明:(1)焉耆盆地山区和平原区降水变化都有明显的突变点,并呈现增加趋势,蒸发量在山区减少,在平原区波动性减少趋势;(2)LUCC分析表明,山区裸地面积减少5.40%,冰川面积减少3.36%,高地植被面积增加8.76%;同时平原区天然绿洲面积增加1.96%,沙漠面积减少1.62%,水域面积减少1.30%,人工绿洲面积增加15.41%,湿地面积增加1.27%;(3)山区陆地生态系统对区域气候变化非常敏感,其中降水变化是决定山区地表植被生存状态和分布的重要因素;(4)人类活动的推动作用和有益气候变化的支撑是绿洲平原区生态系统好转的原因,其中人口急剧增加和社会经济快速发展,导致绿洲平原区生态系统结构及其时空分布的主要因素。焉耆盆地及其周围区域陆地生态系统的演变对气候变化和人类活动有明显的时空尺度效应,其反应程度各不相同。     

基于区域城市化LUCC的人类生态过程定量研究——以上海市区典型城市化样带为例

借鉴流域研究的范例,根据上海市1987年、1995年和2003年3期Landsat5 TM遥感影像记录的土地利用／覆被数据和有关的社会经济统计数据,运用Rs和GIS技术在上海市中心西南城市边缘建立典型城市化样带。采用生态足迹法分析该样带内人类的生态供给与需求;提出一城市化区域人类生态过程的新研究方法,得出城市化过程中区域的人类生态质量指数与波动指数,并根据模型计算出的指数值,对样带区域总体及其中城乡区域在城市化中的人类生态状况进行了动态分析,以尝试对区域城市化中人类生态过程进行定量化研究。     

干旱区绿洲土地利用/覆被及景观格局变化特征——以新疆精河县为例

从宏观上运用3S技术,利用1972年MSS、1990年Landsat TM、2001年Landsat ETM+和2005年CBERS 4个时期遥感影像数据,将GIS和景观生态学的数量分析方法相结合,运用ArcGIS以及Fragstats,分析了干旱区绿洲精河县1972～2005年间的土地利用/覆被和景观格局的变化.结果表明:(1)1972～2005年的33a中,精河县LUCC的总体变化趋势是绿洲面积有小幅度扩张,其中人工绿洲面积扩张尤为显著,天然绿洲面积减少.(2)研究区水域面积的变化受艾比湖湖面面积的变化影响较大,变化不显著,但总体上呈缓慢增长的趋势.(3)盐渍地面积的变化经历了先扩张后减小的一个过程.1990年达到最大值,但到2005年面积又有很大程度减少.沙地面积小幅度减小,其他地类的面积始终呈增加趋势.(4)景观在各个研究时段也发生显著变化.总的来说,整个研究区景观的密度持续增大,最大斑块指数先减小后增大,面积加权形状指数减小,形状趋于规则;斑块间的最邻近距离减小.表明1972年时景观中的优势斑块类型的连接性较2005年好,逐渐向具有多种要素的密集格局演变,景观更加破碎.同时不同斑块间的分离度增大,也说明景观破碎化程度加深.从香农多样性指数和香农均度指数的变化可以看出,景观的多样性增加,且均度增强.景观多样性及破碎化程度增加,也反映了土地利用越来越丰富.总之,要实现区域土地资源的可持续发展和景观生态功能的良性发挥,必须注重土地利用格局优化,维护景观生态过程与格局的连续性.     

The impact of sea‐level rise on Snowy Plovers in Florida: integrating geomorphological,habitat, and metapopulation models

Sea‐level rise (SLR) is a projected consequence of global climate change that will result in complex changes in coastal ecosystems. These changes will cause transitions among coastal habitat types, which will be compounded by human‐made barriers to the gradual inland migration of these habitat types. The effect of these changes on the future viability of coastal species will depend on the habitat requirements and population dynamics of these species. Thus, realistic assessments of the impact of SLR require linking geomorphological models with habitat and population models. In this study, we implemented a framework that allows this linkage, and demonstrated its feasibility to assess the effect of SLR on the viability of the Snowy Plover population in Florida. The results indicate that SLR will cause a decline in suitable habitat and carrying capacity for this species, and an increase in the risk of its extinction and decline. The model projected that the population size will decline faster than the area of habitat or carrying capacity, demonstrating the necessity of incorporating population dynamics in assessing the impacts of SLR on coastal species. The results were most sensitive to uncertainties in survival rate and fecundity, and suggested that future studies on this species should focus on the average and variability of these demographic rates and their dependence on population density. The effect of SLR on this species’ viability was qualitatively similar with most alternative models that used the extreme values of each uncertain parameter, indicating that the results are robust to uncertainties in the model.     

基于山地-绿洲-荒漠系统的生态系统服务正负价值测算——以新疆玛纳斯河流域为例

基于不同生态单元分析生态系统服务正负价值有助于全面客观地了解生态系统服务的异质性。选择典型山地-绿洲-荒漠系统(Mountain-Oasis-Desert System,MODS)下的玛纳斯河流域作为研究区,以1990年、1995年、2000年、2005年、2010年及2015年Landsat系列遥感影像为数据源,采用修正后的生态系统服务价值系数对不同生态单元下的生态系统服务正负价值进行估算。结果表明:(1)1990—2015年玛纳斯河流域土地利用/覆被变化较为显著,耕地、水域及建设用地面积呈现增加趋势,林地、草地及未利用地面积呈减少趋势,其中耕地和未利用地面积变化最为剧烈,建设用地增幅最大,林地减幅最大。(2)研究时段内,研究区正向价值远高于负向价值,且净价值小幅度增加。正向价值在经历"增加-减少-减少-增加-增加"的变化过程后呈现增加趋势,并呈现山地区>绿洲区>荒漠区的特征;各负向价值均表现为不同程度的增大趋势,其中温室气体排放、化肥流失及水资源消耗是流域内最为突出的负向生态系统服务,三者价值之和占比在不同时间段上均达90%以上;净价值由研究初期的8947.89×10<...     

南疆生态脆弱区土地利用变化及其生态影响评价--以新疆阿克苏市为例

在城市化速度加快的背景下,研究LUCC对生态脆弱区的生态环境影响过程,对了解区域生态环境变化具有重要意义。利用南疆生态脆弱区———阿克苏市1995、2000和2003年的TM遥感影像,采用景观生态学的空间格局指数对城乡土地利用动态变化特征进行了研究,参照Costanza等对全球不同生态系统类型服务功能价值测算结果的比例关系,分析了阿克苏市城乡土地利用类型的生态价值,定量综合评价了阿克苏市城乡区域LUCC的生态影响。结果表明,阿克苏市域景观总体构成表现为景观破碎度较高,斑块数目较多;农业用地中有近半数不稳定,水土条件差致使农用地和未利用地相互转换。研究时段内市域土地利用变化带来了较好的生态影响,土地利用生态效益持续提高,并表现出了较大空间差异。     

Long‐term terrestrial carbon dynamics in the Midwestern United States during 1850–2015: Roles of land use and cover change and agricultural management

To meet the increasing food and biofuel demand, the Midwestern United States has become one of the most intensively human‐disturbed hotspots, characterized by widespread cropland expansion and various management practices. However, the role of human activities in the carbon (C) cycling across managed landscape remains far from certain. In this study, based on state‐ and national census, field experiments, and model simulation, we comprehensively examined long‐term carbon storage change in response to land use and cover change (LUCC) and agricultural management in the Midwest from 1850 to 2015. We also quantified estimation uncertainties related to key parameter values. Model estimation showed LUCC led to a reduction of 1.35 Pg (with a range of 1.3–1.4 Pg) in vegetation C pool of the Midwest, yet agricultural management barely affected vegetation C change. In comparison, LUCC reduced SOC by 4.5 Pg (3.1 to 6.2 Pg), while agricultural management practices increased SOC stock by 0.9 Pg. Moreover, we found 45% of the study area was characterized by continuously decreasing SOC caused by LUCC, and SOC in 13% and 31% of the area was fully and partially recovered, respectively, since 1850. Agricultural management was estimated to increase the area of full recovery and partial recovery by 8.5% and 1.1%. Our results imply that LUCC plays an essential role in regional C balance, and more importantly, sustainable land management can be beneficial for strengthening C sequestration of the agroecosystems in the Midwestern US, which may serve as an important contributor to C sinks in the US.     

Variation in life-cycle between three rare and endangered floodplain violets in two regions: implications for population viability and conservation

We studied the demography of Viola elatior, V. pumila, and V. stagnina, three rare and endangered Central European floodplain species, to (i) analyse variation in life-cycles among congeners and between regions (Dyje-Morava floodplains, Czech Republic; Upper Rhine, Germany), (ii) to define sensitive stages in the life-cycles, and (iii) to identify possible threats for population viability and species conservation. Matrix models were based on the fate of marked individuals from a total of 27 populations over two years. We analysed population growth rate (λ), stage distribution, net reproductive rate (R ₀), generation time, age at first reproduction, and elasticity and calculated a life table response experiment (LTRE). Most populations were declining and λ did not differ between species or regions during the observed interval. Despite higher probabilities for survival and flowering in the Dyje populations, R ₀ was higher in the Rhine populations. Also other demographic traits showed consistent differences between regions and/or species. Complex life-cycles and large variation in λ precluded unequivocal identification of sensitive stages or vital rates for conservation. Variation between regions may be a consequence of differences in habitat quality. Our results suggest that deterministic processes such as reduced management, succession, habitat destruction, and lack of disturbance through reduced or eliminated flooding present the strongest threat for the viability and persistence of populations of the three floodplain violets as compared with stochastic processes. However, the persistent seed bank of the species may buffer populations against environmental variation and represents a reservoir for recovery after resumption of suitable land-use management.