Stand and within-stand factors influencing Golden-winged Warbler use of regenerating stands in the central Appalachian Mountains

The Golden-winged Warbler (Vermivora chrysoptera) is currently being considered for protected status under the U.S. Endangered Species Act. The creation of breeding habitat in the Appalachian Mountains is considered a conservation priority for this songbird, which is dependent on extensively forested landscapes with adequate availability of young forest. We modeled abundance of Golden-winged Warbler males in regenerating harvested forest stands that were 0-17 years postharvest at both mid-Appalachian and northeast Pennsylvania regional scales using stand and within-stand characteristics of 222 regenerating stands, 2010-2011. Variables that were most influential at the mid-Appalachian scale were different than those in the northeast region. Across the mid-Appalachian ecoregion, the proportion of young forest cover, i.e., shrub/scrub cover, within 1 km of regenerating stands best explained abundance of Golden-winged Warblers. Golden-winged Warbler response was best explained by a concave quadratic relationship in which abundance was highest with 5-15% land in young forest cover. We also found evidence that the amount of herbaceous cover, i.e., the amount of grasses and forbs, within a regenerating stand positively influenced abundance of Golden-winged Warblers. In northeastern Pennsylvania, where young forest cover is found in high proportions, the distance to the nearest regenerating stand best explained variation in abundance of Golden-winged Warblers. Abundance of Golden-winged Warblers was <1 male per survey when another regenerating stand was >1500 m away. When modeling within-stand features in the northeast region, many of the models were closely ranked, indicating that multiple variables likely explained Golden-winged Warbler response to within-stand conditions. Based on our findings, we have proposed several management guidelines for land managers interested in creating breeding habitat for Golden-winged Warblers using commercial timber operations. For example, we recommend when managing for Golden-winged Warblers in the central Appalachian Mountains that managers should strive for 15% young forest in a heavily forested landscape (>70% forest cover) and cluster stands within 1-2 km of other young forest habitats.

Seasonal pattern of regional carbon balance in the central Rocky Mountains from surface and airborne measurements

[1] High-elevation forests represent a large fraction of potential carbon uptake in North America, but this uptake is not well constrained by observations. Additionally, forests in the Rocky Mountains have recently been severely damaged by drought, fire, and insect outbreaks, which have been quantified at local scales but not assessed in terms of carbon uptake at regional scales. The Airborne Carbon in the Mountains Experiment was carried out in 2007 partly to assess carbon uptake in western U.S. mountain ecosystems. The magnitude and seasonal change of carbon uptake were quantified by (1) paired upwind-downwind airborne CO2 observations applied in a boundary layer budget, (2) a spatially explicit ecosystem model constrained using remote sensing and flux tower observations, and (3) a downscaled global tracer transport inversion. Top-down approaches had mean carbon uptake equivalent to flux tower observations at a subalpine forest, while the ecosystem model showed less. The techniques disagreed on temporal evolution. Regional carbon uptake was greatest in the early summer immediately following snowmelt and tended to lessen as the region experienced dry summer conditions. This reduction was more pronounced in the airborne budget and inversion than in flux tower or upscaling, possibly related to lower snow water availability in forests sampled by the aircraft, which were lower in elevation than the tower site. Changes in vegetative greenness associated with insect outbreaks were detected using satellite reflectance observations, but impacts on regional carbon cycling were unclear, highlighting the need to better quantify this emerging disturbance effect on montane forest carbon cycling.

New manual of botany of the central Rocky Mountains (vascular plants)

Mode of access: Internet.

Recent glacier retreat in the Caucasus Mountains, Russia, and associated increase in supraglacial debris cover and supra-/proglacial lake development

This paper reports changes in supraglacial debris cover and supra-/proglacial lake development associated with recent glacier retreat (1985-2000) in the central Caucasus Mountains, Russia. Satellite imagery (Landsat TM and ETM+) was used to map the surface area and supraglacial debris cover on six neighbouring glaciers in the Adylsu valley through a process of manual digitizing on a false-colour composite of bands 5, 4, 3 (red, green, blue). The distribution and surface area of supraglacial and proglacial lakes was digitized for a larger area, which extended to the whole Landsat scene. We also compare our satellite interpretations to field observations in the Adylsu valley. Supraglacial debris cover ranges from < 5% to > 25% on individual glaciers, but glacier retreat between 1985 and 2000 resulted in a 3-6% increase in the proportion of each glacier covered by debris. The only exception to this trend was a very small glacier where debris cover did not change significantly and remote mapping proved more difficult. The increase in debris cover is characterized by a progressive upglacier migration, which we suggest is being driven by focused ablation (and therefore glacier thinning) at the up-glacier limit of the debris cover, resulting in the progressive exposure of englacial debris. Glacier retreat has also been accompanied by an increase in the number of proglacial and supraglacial lakes in our study area, from 16 in 1985 to 24 in 2000, representing a 57% increase in their cumulative surface area. These lakes appear to be impounded by relatively recently lateral and terminal moraines and by debris deposits on the surface of the glacier. The changes in glacier surface characteristics reported here are likely to exert a profound influence on glacier mass balance and their future response to climate change. They may also increase the likelihood of glacier-related hazards (lake outbursts, debris slides), and future monitoring is recommended.

The precipitation climate of Central Asia: intercomparison of observational and numerical data sources in a remote semiarid region

In this study, we systematically compare a wide range of observational and numerical precipitation datasets for Central Asia. Data considered include two re-analyses, three datasets based on direct observations, and the output of a regional climate model simulation driven by a global re-analysis. These are validated and intercompared with respect to their ability to represent the Central Asian precipitation climate. In each of the datasets, we consider the mean spatial distribution and the seasonal cycle of precipitation, the amplitude of interannual variability, the representation of individual yearly anomalies, the precipitation sensitivity (i.e. the response to wet and dry conditions), and the temporal homogeneity of precipitation. Additionally, we carried out part of these analyses for datasets available in real time. The mutual agreement between the observations is used as an indication of how far these data can be used for validating precipitation data from other sources. In particular, we show that the observations usually agree qualitatively on anomalies in individual years while it is not always possible to use them for the quantitative validation of the amplitude of interannual variability. The regional climate model is capable of improving the spatial distribution of precipitation. At the same time, it strongly underestimates summer precipitation and its variability, while interannual variations are well represented during the other seasons, in particular in the Central Asian mountains during winter and spring

Late Glacial and Holocene vegetational changes on the Ulagan high-mountain plateau, Altai Mountains, southern Siberia

Three well-dated pollen diagrams from 1985 m, 2050 m, and at the tree line at 2150 m asl show the vegetational succession in the central Altai Mountains since 16 cal ka BP. Pioneer vegetation after deglaciation was recorded first at the lowest site. Subsequently, dense dry steppe vegetation developed coincident with the change from silt to organic sediments at the two lower sites, but silt lasted longer at the highest site, indicating the persistence of bare ground there. Forests of Pinus sibirica, Pinus sylvestris, Picea obovata, Larix sibirica, Abies sibirica, and Betula pendula started to develop about 12 cal ka BP with the change to a warmer and wetter climate at the beginning of the Holocene. Results indicate that the timberline did not rise above the highest site. Mesophilous dark-coniferous forests were fully developed by 9.5 cal ka BP. The role of Abies and Picea decreased by about 7.5 cal ka BP suggesting cooler climate, after which the forests changed little until today. The vegetational development in this portion of the central Altai Mountains is compatible with that described in neighbouring areas of the Altai, southern Siberia, Mongolia, and Kazakhstan.

U-Pb (zircon) geochronologic analyses for rocks of the Transantarctic Mountains (Table 4.3-1)

The Byrd Glacier discontinuity us a major boundary crossing the Ross Orogen, with crystalline rocks to the north and primarily sedimentary rocks to the south. Most models for the tectonic development of the Ross Orogen in the central Transantarctic Mountains consits of two-dimensional transects across the belt, but do not adress the major longitudinal contrast at Byrd Glacier. This paper presents a tectonic model centering on the Byrd Glacier discontinuity. Rifting in the Neoproterozoic producede a crustal promontory in the craton margin to the north of Byrd Glacier. Oblique convergence of the terrane (Beardmore microcontinent) during the latest Neroproterozoic and Early Cambrian was accompanied by subduction along the craton margin of East Antarctica. New data presented herein in the support of this hypothesis are U-Pb dates of 545.7 ± 6.8 Ma and 531.0 ± 7.5 Ma on plutonic rocks from the Britannia Range, subduction stepped out, and Byrd Glacier. After docking of the terrane, subduction stepped out, and Byrd Group was deposited during the Atdabanian-Botomian across the inner margin of the terrane. Beginning in the upper Botomian, reactivation of the sutured boundaries of the terrane resulted in an outpouring of clastic sediment and folding and faulting of the Byrd Group.

中部天山林线动态对气候变化的响应研究

中部天山高山林线构成一个对气候变化及其变化程度的理想而敏感的代表性指标，低温、干旱和水分胁迫等都可能限制森林的分布和影响林线的形成。本文通过沿海拔梯度定位调查高山林线样地天山云杉种群的更新情况，利用树木年轮气候学和生态学方法，研究了林线天山云杉种群的时间动态和空间动态及其与气候变化的关系，并取得了一些初步结果。 利用不同年龄的树木年轮序列建立了三个不同年龄的树木年轮宽度年表，幼龄(<100年)，中龄(100-200年)和老龄(>200年) 树木都与当年生长季前期1-3月份的温度显著正相关，和当年1月份和7月份的降水显著正相关。但不同年龄的天山云杉对气候变化的响应结果不同，幼龄(<100年)天山云杉对气候变化的响应程度随年龄的增加而增加，但变化趋势不明显；中龄树木(100-200年)对气候变化的响应随年龄的增加而降低；老龄(>200年)天山云杉受年龄的影响不大。 有关古气候变化的相关研究中，都是尽可能采取年代长的树木年轮样本建立年代较长的年表，并利用最近几十年的气候资料与最近几十年的树木生长的相关关系来重建古气候变化情况。本文的研究结果表明，将不同年龄天山云杉的树木年轮宽度序列放在一起所建成的多年龄复合年表包含有更多的气候信息，显示出当地天山云杉种群对气候变化反应的共性。研究结果表明在建树木年轮的宽度年表时，选用一定数量的不同年龄的树木年轮宽度序列可增强年表对气候变化的响应关系。 利用不同年龄的天山云杉样本建成的复合年龄的树木年轮宽度年表对冬季的最低温度的响应关系，重建了中部天山高山林线地区过去300年来的冬季最低温度。重建的冬季最低温度的有几个明显的暖期和冷期，20世纪50年代以来冬季低温则表现出显著增高的变化趋势。 中部天山高山林线天山云杉种群的胸径和年龄结构以都呈倒-J型分布，说明天山云杉种群更新良好，处于稳定发展时期。随着全球变暖和温度的升高，20世纪以来中部天山高山林线天山云杉的种群更新数量较多，天山云杉的密度有所增加，但林线位置并没有显著的上升，不同年代内更新的树木所到达的海拔高度也不一样。中部天山高山林线天山云杉种群发生的时间动态主要和冬季最低温度正相关，而不同时间内更新的天山云杉种群空间动态形成原因比较复杂，主要和冬季低温负相关。