Species richness and stand stability in conifer forests of the Sierra Nevada

Theoretical and empirical studies have long suggested that stability and complexity are intimately related, but evidence from long-lived systems at large scales is lacking. Stability can either be driven by complex species interactions, or it can be driven by the presence/absence and abundance of a species best able to perform a specific ecosystem function. We use 64 years of stand productivity measures in forest systems composed of four dominant conifer tree species to contrast the effect of species richness and abundance on three stability measures. To perform this contrast, we measured the annual growth increments of > 900 trees in mixed and pure forest stands to test three hypotheses: increased species richness will (1) decrease stand variance, (2) increase stand resistance to drought events, and (3) increase stand resilience to drought events. In each case, the alternate hypothesis was that species richness had no effect, but that species composition and abundance within a stand drove variance, resistance, and resilience. In pure stands, the four species demonstrated significant differences in productivity, and in their resistance and resilience to drought events. The two pine species were the most drought resistant and resilient, whereas mountain hemlock was the least resistant and resilient, and red fir was intermediate. For community measures we found a moderately significant (P = 0.08) increase in the community coefficient of variation and a significant (P = 0.03) increase in resilience with increased species richness, but no significant relationship between species richness and community resistance, though the variance in community resistance to drought decreased with species richness. Community resistance to drought was significantly (P = 0.001) correlated to the relative abundance of lodgepole pine, the most resistant species. We propose that resistance is driven by competition for a single limiting resource, with negative diversity effects. In contrast resilience measures the capacity of communities to partition resources in the absence of a single limiting resource, demonstrating positive diversity effects.     

Predicting breeding habitat for amphibians: a spatiotemporal analysis across Yellowstone National Park

The ability to predict amphibian breeding across landscapes is important for informing land management decisions and helping biologists better understand and remediate factors contributing to declines in amphibian populations. We built geospatial models of likely breeding habitats for each of four amphibian species that breed in Yellowstone National Park (YNP). We used field data collected in 2000-2002 from 497 sites among 16 basins and predictor variables from geospatial models produced from remotely sensed data (e.g., digital elevation model, complex topographic index, landform data, wetland probability, and vegetative cover). Except for 31 sites in one basin that were surveyed in both 2000 and 2002, all sites were surveyed once. We used polytomous regression to build statistical models for each species of amphibian from (1) field survey site data only, (2) field data combined with data from geospatial models, and (3) data from geospatial models only. Based on measures of receiver operating characteristic (ROC) scores, models of the second type best explained likely breeding habitat because they contained the most information (ROC values ranged from 0.70 to 0.88). However, models of the third type could be applied to the entire YNP landscape and produced maps that could be verified with reserve field data. Accuracy rates for models built for single years were highly variable, ranging from 0.30 to 0.78. Accuracy rates for models built with data combined from multiple years were higher and less variable, ranging from 0.60 to 0.80. Combining results from the geospatial multiyear models yielded maps of "core" breeding areas (areas with high probability values for all three years) surrounded by areas that scored high for only one or two years, providing an estimate of variability among years. Such information can highlight landscape options for amphibian conservation. For example, our models identify alternative areas that could be protected for each species, including 6828-10 764 ha for tiger salamanders, 971-3017 ha for western toads, 4732-16 696 ha for boreal chorus frogs, and 4940-19 690 ha for Columbia spotted frogs.     

青藏高原东北边缘桦木林木本植物种间联结

青藏高原东北边缘地区位于我国东部季风区、西北干旱区与青藏高原高寒区的交汇地带,该区既兼具3大自然区的特点,又具有边缘地带气候波动不稳定性和自然生态环境的脆弱性,是全球变化重点监测的地区之一。研究青藏高原东北边缘亚高山桦木林的种间联结,不仅有助于更深刻地认识该地区桦木群落的结构、功能和演替,对于维持该地区群落稳定性以及生态恢复具有重要意义。本文选取青藏高原东北边缘桦木林中20个优势种,采用方差比率法(VR)检验多物种间的联结性,2×2列联表分析共同出现百分率(JI)、点相关系数(Ф)、Dice指数(DI)来表示种间联结程度,用重要值的Pearson相关和Spearman秩相关来检验相伴出现的机率等方法分析其种间关联性。结果表明:群落总体联结VR值为1.094,说明20个种群间表现出净正关联,其统计量W值为10.94说明20个种群之间在总体上的正关联不显著;大多数种对的JI值、DI值在0.4以下,说明种对之间联结程度不显著,Φ值大部分处于[-0.2, 0.2]值域内,说明种对之间的正或负的联结性较弱;而Spearman秩相关所测得的正负关联比要大于Pearson相关所测得的,且Spearman秩相关要优于Pearson相关。从以上结果可以看出,青藏高原东北边缘三种桦树天然次生林处于不稳定的状态,即演替的中期阶段,其逐渐会被地带性植被所取代。     

Effect of prior disturbances on the extent and severity of wildfire in Colorado subalpine forests

Disturbances are important in creating spatial heterogeneity of vegetation patterns that in turn may affect the spread and severity of subsequent disturbances. Between 1997 and 2002 extensive areas of subalpine forests in northwestern Colorado were affected by a blowdown of trees, bark beetle outbreaks, and salvage logging. Some of these stands were also affected by severe fires in the late 19th century. During a severe drought in 2002, fires affected extensive areas of these subalpine forests. We evaluated and modeled the extent and severity of the 2002 fires in relation to these disturbances that occurred over the five years prior to the fires and in relation to late 19th century stand-replacing fires. Occurrence of disturbances prior to 2002 was reconstructed using a combination of tree-ring methods, aerial photograph interpretation, field surveys, and geographic information systems (GIS). The extent and severity of the 2002 fires were based on the normalized difference burn ratio (NDBR) derived from satellite imagery. GIS and classification trees were used to analyze the effects of prefire conditions on the 2002 fires. Previous disturbance history had a significant influence on the severity of the 2002 fires. Stands that were severely blown down (> 66% trees down) in 1997 burned more severely than other stands, and young (approximately 120 year old) postfire stands burned less severely than older stands. In contrast, prefire disturbances were poor predictors of fire extent, except that young (approximately 120 years old) postfire stands were less extensively burned than older stands. Salvage logging and bark beetle outbreaks that followed the 1997 blowdown (within the blowdown as well as in adjacent forest that was not blown down) did not appear to affect fire extent or severity. Conclusions regarding the influence of the beetle outbreaks on fire extent and severity are limited, however, by spatial and temporal limitations associated with aerial detection surveys of beetle activity. Thus, fire extent in these forests is largely independent of prefire disturbance history and vegetation conditions. In contrast, fire severity, even during extreme fire weather and in conjunction with a multiyear drought, is influenced by prefire stand conditions, including the history of previous disturbances.     

川西亚高山针叶林人工恢复过程的土壤性性质变化

研究川西岷江上游高山针叶林区不同年龄阶段的人工云杉林地凋落物及其养分贮量和土壤养分及主要理化性质的变化趋势,结果表明：（1）人工云杉林的凋落物及其氮、磷、钾贮量、以60年代抚育成熟林最高,40年代抚育成熟林大幅度下降,分别下降34．1％及49．8％,70．5％,46．7％;（2）人工云杉林地表土的有机质、全氮、全磷随林龄的增加而降低,据典型土壤剖面资料,40年代比60年代抚育林土壤分别降低72．4％,78．6％,42．2％;（3）相应于土壤有机质的变化,与60年代人工云杉成熟林相比,40年代成熟林土壤的自然含水量、总孔工、保肥力（CEC）和交换性盐某养分等均明显降低,表现出肥力退化的趋势,因此,当人工云杉林达到成熟林后,后采取诸如适当间伐等措施,以改善林地生态条件,避免土壤肥力退化,图4表6参11。     

Modelling the spatial distribution of montane and subalpine forests in the central Alps using digital elevation models

The analysis of complex interactions between spatial distribution patterns of site factors and vegetation types is crucial for understanding high mountain ecosystems, especially in the view of a changing climate. Therefore, in the present study, a GIS and remote sensing-based approach is followed to produce a vegetation map for a study area in the Western Alps (Switzerland). Two major forest alliances are chosen for analysis: subalpine coniferous forest Vaccinio-Piceion/Larici-Pinetum cembrae and montane oak forest Quercion pubescenti-petraeae. As spatial information on site factors is commonly lacking in mountain areas, the use of a digital elevation model (DEM) is a potential substitute for use in vegetation analyses: it highly correlates with temperature, moisture, geomorphological processes and disturbance factors. Thus, it is important to analyse the capabilities of a DEM for indicating habitat conditions in a landscape characterised by high topodiversity and a patchwork of microclimatic habitats.For the purpose of identifying the potential of landform parameters for the indication of forest habitat structures in the present study, 24 primary and secondary landform parameters have been derived, indicating temperature and moisture distribution, exposure towards wind, snow, etc. Quantitative analyses were performed using statistical means such as contingency correlation coefficients and principal components analysis. The results formed the basis for the development of parallel-epiped-vegetation models (PED) used to simulate the spatial distribution patterns of the subalpine coniferous and the montane oak forest. It can be shown that topographic variables derived from a DEM at a spatial resolution of 25 m are very useful for indicating habitats of large forest types. Additionally potential forest sites in the cultural landscape, removed by human logging, can be reconstructed.Inaccuracies within the simulation results can partly be attributed to the insufficient parameterisation of geomorphologic activity and to poor spatial resolution of the DEM as compared to the vegetation data. Although the lack of information on the human dimension leads to some uncertainties in the interpretation of spatial patterns of vegetation, the exclusive use of topographic variables in vegetation models for the indication of forest habitats is very promising.     

氮沉降下西南亚高山针叶林生长的养分限制特征

长期氮(N)沉降及其诱导的N、磷(P)养分平衡性对森林生长与生产力的生态反馈效应已成为当前森林生态学研究的前沿与热点,但目前大多研究主要基于已有文献数据整合分析,而缺乏野外原位系统性研究与试验证据.以西南亚高山两种典型人工针叶林——云杉(Picea asperata)林和华山松(Pinus armandii)林为对象,...     

Classification of floristic composition of mangrove forests using hyperspectral data: case study of Bhitarkanika National Park, India

The aim of the present work is to unveil the potential of some of the unexplored remote sensing techniques for mangrove studies. The paper deals with the classification of an Earth Observing–1 Hyperion image of the mangrove area of Bhitarkanika National Park, Odisha, India into mangrove floristic composition classes. Out of 196 calibrated bands of the image, 56 were found to be highly uncorrelated and contained maximum information; therefore, these 56 bands were used for classification. Amongst the three full–pixel classifiers tested in the investigation, Support Vector Machine produced the best results in terms of training pixel accuracy with overall precision of 96.85 %, in comparison to about 70–72.0 % for the other two classifiers. A total of five mangrove classes were obtained – pure or dominant class of Heritiera fomes, mixed class of H. fomes, mixed Excoecaria agallocha with Avicennia officinalis, mixed class of fringing Sonneratia apetala and class comprising of mangrove associates with salt resistant grasses. Post–classification field data also established the same. Pure or dominant classes of H. fomes occupied more than 50 % of the total mangrove vegetation in the forest blocks of the National Park. Spectral profile matching of image pixels with that of in–situ collected canopy reflectance profile revealed good match for H. fomes (pure or dominant stands). Red–edge index, which was a preferred criterion for matching was notably correlated in case of H. fomes and E. agallocha. The outcomes indicated the efficacy of hyperspectral canopy reflectance library for such kind of work. It is hoped that the methodology presented in this paper will prove to be useful and may be followed for producing mangrove floristic maps at finer levels.     

川西亚高山暗针叶林恢复初期土壤酶活性研究

研究以川西亚高山暗针叶林恢复过程中初级阶段的鲜类阔叶林（MBLF）、鲜类针阔混交林（MCBLF）和箭竹阔叶林（BBLF）土壤为研究对象,针对不同森林类型采用多点分层[0-10 cm（A层）、10-20 cm（B层）、20-30 cm（C层）和30-40 cm（D层）]采样、测定混合样的方式,研究了不同森林类型不同土层土壤的pH值、有机碳、全氮、全磷含量及脲酶、酸性磷酸酶、淀粉酶、过氧化氢酶、蛋白酶和蔗糖酶活性。研究结果表明,MBLF、MCBLF、BBLF不同土层土壤pH值均低于5.0,有机碳、全氮、全磷含量呈下降趋势,且有机碳、全氮与A层土壤差异显著（P〈0.05）。MBLF和BBLF随土层深度的增加脲酶活性较A层呈显著下降趋势（P〈0.05）,而MCBLF土壤脲酶活性以B、C层活性最高,分别为A层的1.22和1.08倍。蔗糖酶和酸性磷酸酶活性呈现先升后降的趋势,均以MCBLF活性最高;在林型MCBLF和BBLF中,随着土层深度的增加,蛋白酶和淀粉酶活性较A层显著降低（P〈0.05）,而MBLF、MCBLF、BBLF过氧化氢酶活性则一直呈显著下降趋势（P〈0.05）,D层过氧化氢酶活性分别为A层的60.21%、73.37%和46.84%。     

国家公园建设背景下的白洋淀生态保护现状与发展研究

《河北雄安新区总体规划(2018—2035年)》明确了白洋淀远景规划建设国家公园,推进白洋淀流域整体保护系统修复和综合治理,构建"淀水林田草"综合治理示范区.结合国家公园设立规范,从生态系统代表性等9个方面对白洋淀现状进行评估和分析.生态系统代表性、生物物种代表性、自然景观独特性、生态系统完整性、自然资源资产产权和全民...     

国家公园效果评价体系研究

建立国家公园是保护生物多样性和促进地方发展的重要途径之一,开展国家公园效果评价是了解国家公园功能发挥的有效途径。通过查阅大量文献及德尔菲法（Delphi）,确定了与国家公园效果相关的28个评价指标,同时以功能为主导,将评价指标归纳为5个功能指标群：保护功能指标群（7个评价指标）、科研功能指标群（6个评价指标）、游憩功能指标群（7个评价指标）、教育功能指标群（4个评价指标）和经济发展功能指标群（4个评价指标）,通过对评价指标的赋分（5分制原则）和计算权重,从而达到国家公园效果评价的量化,实现对国家公园建设效果的评价。     

大贵寺国家森林公园野生青檀居群的遗传多样性

利用ISSR分子标记技术对湖北省大贵寺国家森林公园野生青檀（Pteroceltis tatarinowii Maxim．）居群进行遗传多样性分析。用11条ISSR引物对6个青檀居群64个样品进行扩增,扩增片段长度在200bp至3000bp之间,检测到179个位点,其中多态位点165个,多态位点百分率（P）为92．14％。青檀在物种水平上的Nei基因多样性指数（胁）和Shannon信息指数∽分别为0．273和0．423,在居群水平上分别为0．225和0．343,显示出青檀有着较高的遗传多样性。居群间的遗传分化系数（Gsr）为0．192,表明青檀居群间存在着较大的遗传分化;UPGMA聚类分析表明遗传距离与海拔差距有一定的相关性,相邻海拔的青檀居群间遗传距离较近。不同海拔导致的异质生境可能是影响青檀居群遗传分化的主要原因。     

西樵山国家森林公园有害植物现状分析

结合西樵山国家森林公园管理公司提供的植被及道路图,运用面上调查和点调查相结合的方法对西樵山国家森林公园的有害植物进行了系统和全面的调查,对西樵山国家森林公园的有害植物危害现状进行了分析.调查结果显示,西樵山国家森林公同有害植物共有25种,录属19科25属,包括本地种20种,外来种5种,达到严重危害的有19种.本地植物成灾面积达56万m2,外来植物成灾面积14万m2,本地植物与外来植物的成灾比例是4:1.针对主要的15种有害植物,对其分布、危害面积与危害特点进行了逐一分析与描述.根据西樵山国家森林公园有害植物的危害现状的分析,本地植物的危害程度和范围都比外来植物大得多,并分析了西樵山国家森林公园有害植物的发展趋势.     

Heavy metal content of moss from Kampinos National Park in Poland

The results are presented of studies on the content of Zn, Pb, Cu, Ni and Cd inPleurozium schreberi moss within the spatial system of Kampinos National Park (KPN) adjacent to the Warsaw urban agglomeration. Over a large area (64.3–78.3%) of the Park, mosses contain the following amounts of metals in mg kg^–1 dw: 80–120 of Zn, 60–80 of Pb, 10–15 of Cu, 4–8 of Ni and 0.6–0.9 of Cd. All trace metals were found to accumulate in elevated amounts in moss in the south-eastern portion of the Park bordering the urban area, and it is this part of the Park that should be considered as most polluted by heavy metals.