MULTISCALE INFLUENCES ON PHYSICAL AND CHEMICAL STREAM CONDITIONS ACROSS BLUE RIDGE LANDSCAPES1

ABSTRACT: Streams integrate biogeochemical processes operating at broad to local spatial scales and long term to short term time scales. Humans have extensively altered those processes in North America, with serious consequences for aquatic ecosystems. We collected data on Upper Tennessee River tributaries in North Carolina to: (1) compare landuse and landscape geomorphology with respect to their ability to explain variation in water quality, sedimentation measures, and large woody debris; (2) determine if landscape change over time contributed significantly to explaining present stream conditions; and (3) assess the importance of spatial scale in examining landuse influences on streams. Stream variables were related to both landuse and landscape geomorphology. Forest cover accounted for the most variation in nearly all models, supporting predictions of nutrient enrichment, thermal pollution, and sedimentation caused by landscape disturbance. Legacy effects from past catchment disturbance were apparent in sedimentation measures. Nitrogen and phosphorus concentrations, as well as stream temperature, were lower where riparian buffers had reforested. Models of stream physicochemistry fit better when predictors were catchment wide rather than more localized (i.e., within 2 km of a site). Cumulative impacts to streams due to changes in landuse must be managed from a watershed perspective with quantitative models that integrate across scales.     

Effect of temperature and moisture on soil organic carbon mineralization of predominantly permafrost peatland in the Great Hing’an Mountains, Northeastern China

Boreal peatlands represent a large global carbon pool.The relationships between carbon mineralization,soil temperature and moisture in the permafrost peatlands of the Great Hing'an Mountains,China,were examined.The CO2 emissions were measured during laboratory incubations of samples from four sites under different temperatures(5,10,15,and 20°C) and moisture contents(0%,30%,60%,100% water holding capacity(WHC) and completely water saturated).Total carbon mineralization ranged from 15.51 to 112.92 mg C under the treatments for all sites.Carbon mineralization rates decreased with soil depth,increased with temperature,and reached the highest at 60% WHC at the same temperature.The calculated temperature coefficient(Q10) values ranged from 1.84 to 2.51 with the soil depths and moisture.However,the values were not significantly affected by soil moisture and depth for all sites due to the different peat properties(P 0.05).We found that the carbon mineralization could be successfully predicted as a two-compartment function with temperature and moisture(R2 0.96) and total carbon mineralization was significantly affected by temperature and moisture(P 0.05).Thus,temperature and moisture would play important roles in carbon mineralization of permafrost peatlands in the Great Hing'an Mountains,indicating that the permafrost peatlands would be sensitive to the environment change,and the permafrost peatlands would be potentially mineralized under future climate change.     

天山山地河流水体中微量重金属的分布特征及形态分析

为了解绿洲经济迅速发展背景下天山山地河流水体中重金属分布特征及形态特征,对乌鲁木齐-阿克苏、巴里坤-伊吾、昭苏-特克斯等3个区段河流干支流重金属Zn、Cu、Pb、Cr、As、Hg、Cd的分布、来源、污染状况及存在形态进行了分析.结果表明:1天山山地各取样河流的p H值大部分在8.0左右,为偏碱性的环境;各取样点水体的氧化还原反应电位值在150~200 m V之间,为弱氧化的环境.水质评价表明,3个采样区段河流中7种重金属的含量均低于国家Ⅰ类水质标准及WHO饮用水健康的建议标准.2多元统计分析表明,7种重金属可以归为3个主成分,其中PC1(Hg、Zn和Pb)主要受人为污染因素的影响;PC 2(Cr和As)主要受自然地质背景的影响;PC 3(Cd和Cu)同时受人为和自然因素的共同影响.3污染评价表明,天山山地河流中7种重金属的单因子污染指数值和综合污染指数值均小于1,属于安全等级,清洁水平.4形态分析表明,重金属Pb、Cd和Hg在天山中部的乌鲁木齐-阿克苏区段干支流,重金属As和Cu在天山东部的巴里坤-伊吾区段和天山西部的昭苏-特克斯区段干支流中溶解态的含量均大于50%,生物毒性较大.总体上,3个采样区段河流干支流重金属的总量及溶解态含量均较低,未造成污染.但在天山山地中部的乌鲁木齐-阿克苏区段,河流干支流中重金属Pb、Cd和Hg的总量及溶解态含量较高.应加强对该区域人类活动的合理规划以及河流水质监测,防止因人为污染而导致河流水体中重金属的含量过高,危害生态环境.     

天山北坡城市群PM2.5浓度时空分布特征及影响因素分析

针对天山北坡城市群开展PM_2.5浓度时空分布特征和影响因素分析,对区域经济建设和环境保护具有积极的意义.通过地理加权回归（GWR）模型,利用MCD19A2气溶胶产品结合气象因子,反演得到天山北坡城市群2015~2021年3~11月的PM_2.5浓度时空分布,继而实现变化趋势和影响因素分析.结果如下：①研究区PM_2.5浓度高值主要分布在天山北麓和古尔班通古特沙漠之间的绿洲城市群地带,呈现“四周低,中间高”和“西低东高”的空间分布特征,2015~2021年研究区的ρ（PM_2.5）年均值为16.98 μg·m^-3,高值主要聚集在乌鲁木齐市市区部分,并向昌吉市和阜康市延伸递减;ρ（PM_2.5）月均值分布规律与年均一致,但存在季节差异,表现为：秋季（20.32 μg·m^-3）>春季（18.25 μg·m^-3）>夏季（12.47 μg·m^-3）,春季和冬季聚集现象会更明显;②研究区PM_2.5浓度年均值在2015~2021年呈现下降趋势,3~10月均值同样表现为下降趋势,仅11月表现为略有升高;从PM_2.5浓度变化趋势空间分布分析,下降集中在主要城市市区部分,尤其是乌鲁木齐市市区部分及其周边地区减少幅度最大,变化最为剧烈;③研究区气温、气压与PM_2.5浓度呈现正相关效应,而相对湿度,风速,大气边界层高度,降水量与PM_2.5浓度呈现负相关效应;各因子影响程度从高向低排列为：大气边界层高度>相对湿度>气压>气温>风速>降水量.     

Predicting tree distributions in an East African biodiversity hotspot: model selection, data bias and envelope uncertainty

The Eastern Arc Mountains (EAMs) of Tanzania and Kenya support some of the most ancient tropical rainforest on Earth. The forests are a global priority for biodiversity conservation and provide vital resources to the Tanzanian population. Here, we make a first attempt to predict the spatial distribution of 40 EAM tree species, using generalised additive models, plot data and environmental predictor maps at sub 1 km resolution. The results of three modelling experiments are presented, investigating predictions obtained by (1) two different procedures for the stepwise selection of predictors, (2) down-weighting absence data, and (3) incorporating an autocovariate term to describe fine-scale spatial aggregation. In response to recent concerns regarding the extrapolation of model predictions beyond the restricted environmental range of training data, we also demonstrate a novel graphical tool for quantifying envelope uncertainty in restricted range niche-based models (envelope uncertainty maps). We find that even for species with very few documented occurrences useful estimates of distribution can be achieved. Initiating selection with a null model is found to be useful for explanatory purposes, while beginning with a full predictor set can over-fit the data. We show that a simple multimodel average of these two best-model predictions yields a superior compromise between generality and precision (parsimony). Down-weighting absences shifts the balance of errors in favour of higher sensitivity, reducing the number of serious mistakes (i.e., falsely predicted absences); however, response functions are more complex, exacerbating uncertainty in larger models. Spatial autocovariates help describe fine-scale patterns of occurrence and significantly improve explained deviance, though if important environmental constraints are omitted then model stability and explanatory power can be compromised. We conclude that the best modelling practice is contingent both on the intentions of the analyst (explanation or prediction) and on the quality of distribution data; generalised additive models have potential to provide valuable information for conservation in the EAMs, but methods must be carefully considered, particularly if occurrence data are scarce. Full results and details of all species models are supplied in an online Appendix.     

Response of a Group of Sichuan Snub-Nosed Monkeys to Commercial Logging in the Qinling Mountains, China

Abstract:  Habitat destruction is one of the greatest threats to primates worldwide. To understand the impact of forest logging on the habitat use of primates in temperate mixed forest, we compared the range, habitat used, population size, and diet of a troop (ERT) of Sichuan snub-nosed monkeys ( Rhinopithecus roxellana ) in the Qinling Mountains before (1989), during (1997), and after (2002–2003) commercial logging. Logging significantly changed the composition of the forest and the food supply for the troop. Some areas were heavily logged and formed patches in the forest that lacked canopy cover. The troop moved 7 km away from their original range when logging took place and returned to their original range after logging stopped, but they avoided heavily logged areas that lacked canopy cover. Their movement indicated some degree of site fidelity in this species. Diet and home range changed after logging, but the population size remained stable, which suggests that this species has some ability to adapt to habitat changes. Our results may reflect a natural flexibility in primates to adapt to the changing food resources in temperate areas with marked seasonal variations in food availability and distribution. This flexibility may have contributed to their higher degree of resilience to habitat alterations caused by human activities compared with tropical forest primates that have a more specialized diet. Our findings provide important baseline information that will help decision makers in their efforts to conserve primates, especially in temperate regions, and to sustainably manage primate habitat.     

秦岭南部地区农业气候资源的变化及其对油菜的影响

秦岭南部地区地形及气候条件复杂,作为油菜主要种植区之一,研究其农业气候资源的变化特征及其对油菜的影响,可以为该区有效利用农业气候资源、合理安排农事活动提高油菜生产提供实践参考。以1960~2014年秦岭南部33个站点的逐日气象数据和近25a各省市统计年鉴资料,通过滑动平均、线性倾向估计、灰色关联分析等方法,研究秦岭南部农业气候资源的时空变化特征及对油菜产量的影响。结果表明:(1)近55a来,秦岭南部地区油菜生长季内平均气温和≥5℃积温呈上升趋势,平均速率分别为0.2、29.3℃/10 a,冻害指数、降水量、开花期降水量和相对湿度与日照时数都呈减少趋势,平均每10 a分别减少0.3、14.8 mm、1.4 mm、0.6%、32.2 h。(2)近55a来研究区油菜生长季内平均气温与≥5℃积温的多年平均空间分布都表现为由西南向东北方向递减,冻害指数的空间变化与二者相反,表明越冬期极端最低气温值在空间上由西南向东北逐渐减小;其水资源指标多年平均空间分布由南向北递减,日照时数则由西南向东北递增。(3)1960~2014年秦岭南部油菜生长季内平均气温与≥5℃积温在空间上均呈极显著的增加趋势,研究区西部变化幅度较小,东部变化幅度较大,冻害指数的空间变化趋势与二者相同;水资源与日照时数在空间上均呈极显著的减少趋势,只有少数站点表现为极显著的增加趋势,而日照时数在研究区东部变化幅度相对较大,其余区域变化幅度相对较小。总体上,平均气温和≥5℃积温高值区的变化幅度小,低值区变化幅度大,其他指标与之相反。(4)近25a来秦岭南部油菜气候产量呈不明显的上升趋势,平均速率为3.79 kg/(a·hm~2),其空间变化幅度差异大,且大部分站点的变化趋势均不显著;由关联度得作用于各区域油菜气候产量的主要影响因子存在差异。各农业气候资源指标的变化幅度越大,对油菜单产的可能影响相对较大。     

Assessing the Potential Impacts to Riparian Ecosystems Resulting from Hemlock Mortality in Great Smoky Mountains National Park

Hemlock Woolly Adelgid (Adelges tsugae) is spreading across forests in eastern North America, causing mortality of eastern hemlock (Tsuga canadensis [L.] Carr.) and Carolina hemlock (Tsuga caroliniana Engelm.). The loss of hemlock from riparian forests in Great Smoky Mountains National Park (GSMNP) may result in significant physical, chemical, and biological alterations to stream environments. To assess the influence of riparian hemlock stands on stream conditions and estimate possible impacts from hemlock loss in GSMNP, we paired hardwood- and hemlock-dominated streams to examine differences in water temperature, nitrate concentrations, pH, discharge, and available photosynthetic light. We used a Geographic Information System (GIS) to identify stream pairs that were similar in topography, geology, land use, and disturbance history in order to isolate forest type as a variable. Differences between hemlock- and hardwood-dominated streams could not be explained by dominant forest type alone as forest type yields no consistent signal on measured conditions of headwater streams in GSMNP. The variability in the results indicate that other landscape variables, such as the influence of understory Rhododendron species, may exert more control on stream conditions than canopy composition. The results of this study suggest that the replacement of hemlock overstory with hardwood species will have minimal impact on long-term stream conditions, however disturbance during the transition is likely to have significant impacts. Management of riparian forests undergoing hemlock decline should, therefore, focus on facilitating a faster transition to hardwood-dominated stands to minimize long-term effects on water quality.     

乌蒙山山脉药用植物资源调查研究

通过野外考察、标本采集、资料查阅整理及标本鉴定,对乌蒙山山脉药用植物资源进行了调查。结果表明,乌蒙山山脉共有药用植物272科1189属3184种（含变种和亚种）,其中地衣植物8科9属13种、苔藓植物40科74属116种、蕨类植物45科108属358种、裸子植物10科22属37种、被子植物169科976属2660种。对其物种组成、生态类型、分布、优势科属、药用部位、功效等进行了统计分析,对常用中药、国家重点保护野生药材、民间习用药物进行了简要介绍,并对其开发利用提出了建议。     

Is tourism damaging ecosystems in the Andes? Current knowledge and an agenda for future research

Despite the popularity of tourism and recreation in the Andes in South America and the regions conservation value, there is limited research on the ecological impacts of these types of anthropogenic use. Using a systematic quantitative literature review method, we found 47 recreation ecology studies from the Andes, 25 of which used an experimental design. Most of these were from the Southern Andes in Argentina (13 studies) or Chile (eight studies) with only four studies from the Northern Andes. These studies documented a range of impacts on vegetation, birds and mammals; including changes in plant species richness, composition and vegetation cover and the tolerance of wildlife of visitor use. There was little research on the impacts of visitors on soils and aquatic systems and for some ecoregions in the Andes. We identify research priorities across the region that will enhance management strategies to minimise visitor impacts in Andean ecosystems.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-014-0550-7) contains supplementary material, which is available to authorized users.