Quantifying the altered hydrologic connectivity of forest roads resulting from decommissioning and relocation

The decommissioning of roads is occurring in many forest environments with the aim of reducing the negative impacts of road runoff on water quality and aquatic habitat. Works associated with decommissioning are expensive so prior assessment of the outcomes of various options is merited. This paper presents a method of quantifying the degree to which a road is hydrologically connected to the stream network and thus the likely impacts of constructing a road of different configurations upon water quality. The method permits comparisons between different road network management options and is useful for assessing the likely result of decommissioning works. Emphasis is placed on quantifying the uncertainty of key performance measures. The procedures developed here are an extension of the probabilistic ‘volume to breakthrough’ model recently formulated by Australian water quality researchers and allow the quantification of road/stream connectivity without the need for extensive parameterization. To demonstrate its utility, the model was applied to an actual road decommissioning and replacement project in southeast Australia. Road areas and drainage outlets were surveyed in the field and flow paths to streams derived from a 1 metre resolution LiDAR based digital elevation model. The results demonstrate that the actual road decommissioning examined in this case was unlikely to reduce runoff to the stream network and that the overall impact of the works in conditions of design storms are likely to result in a net reduction in stream water quality. Copyright © 2007 John Wiley & Sons, Ltd.     

Fog interception by non‐vascular epiphytes in tropical montane cloud forests: dependencies on gauge type and meteorological conditions

Precipitation is the most fundamental input of water for terrestrial ecosystems. Most precipitation inputs are vertical, via rain, but can be horizontal, via wind‐driven rain and snow, or, in some ecosystems such as tropical montane cloud forests (TMCFs), via fog interception. Fog interception can be particularly important in ecosystems where fog is frequently present and there are seasonal periods of lower rainfall. Epiphytes in trees are a major ecological component of TMCFs and are particularly dependent on fog interception during periods of lower rainfall because they lack access to soil water. But assessing fog interception by epiphytes remains problematic because: (i) a variety of field or laboratory methods have been used, yet comparisons of interception by epiphytes versus interception by various types of fog gauge are lacking; (ii) previous studies have not accounted for potential interactions between meteorological factors. We compared fog interception by epiphytes with two kinds of commonly used fog gauges and developed relations between fog interception and meteorological variables by conducting laboratory experiments that manipulated key fog characteristics and from field measurements of fog interception by epiphytes. Fog interception measured on epiphytes was correlated with that measured from fog gauges but was more than an order of magnitude smaller than the actual measurements from fog gauges, highlighting a key measurement issue. Our laboratory measurements spanned a broad range of liquid water content (LWC) values for fog and indicate how fog interception is sensitive to an interaction between wind speed and LWC. Based on our results, considered in concert with those from other studies, we hypothesize that fog interception is constrained when LWC is low or high, and that fog interception increases with wind speed for intermediate values of LWC—a net result of deposition, impaction, and evaporation processes—until interception begins to decrease with further increases in wind speed. Copyright © 2007 John Wiley & Sons, Ltd.     

塞罕坝林场机载综合遥感试验

本文介绍了"碳循环、水循环和能量平衡遥感综合试验"中"碳循环航空试验"的小滦河流域塞罕坝森林机载综合遥感实验.阐述了森林机载遥感实验的目的、实验设计方案,观测实施过程以及数据的处理和产品生产等方面内容.实验利用中国林业科学研究院机载遥感系统CAF-LiCHy(Chinese Academy of Forestry's ...     

森林采伐对五营气候的影响

利用五营区森林未开采期1958～1967年的10a与开采后1994～2003年的10a气象资料,1971～1980年森林内（原始林）与森林外（本站）气象资料和1957～2005年五营区汤旺河年最高水位变化情况进行对比分析,得出了森林采伐对五营林区生态环境的影响。     

Regional Fluxes Of Momentum And Sensible Heat Over A Sub-Arctic Landscape During Late Winter

Based on measurements at Sodankylä Meteorological Observatory the regional (aggregated) momentum and sensible heat fluxes are estimated for two days over a site in Finnish Lapland during late winter. The forest covers 49% of the area. The study shows that the forest dominates and controls the regional fluxes of momentum and sensible heat in different ways. The regional momentum flux is found to be 10–20% smaller than the measured momentum flux over the forest, and the regional sensible heat flux is estimated to be 30–50% of the values measured over a coniferous forest.The regional momentum flux is determined in two ways, both based on blending height theory. One is a parameterised method, the other represents a numerical solution of an aggregation model. The regional sensible heat flux is determined from the theory of mixed-layer growth. At near neutral conditions the regional momentum flux can be determined independently of the regional sensible heat flux. At unstable conditions the two models become coupled.The information that is needed by the parameterised blending height method and by the mixed-layer evolution method in order to derive the regional fluxes of momentum and sensible heat can be obtained from radiosonde profiles of wind speed and temperature.     

A Model Evaluation of Biological Effects on Seasonal Variation of Air–Sea CO2 Flux in the Yellow and East China Seas

Based on a coupled physical-biogeochemical model of the Yellow and East China Seas (YECS), the influence of biological activity on the seasonal variation of the air–sea CO₂ flux is evaluated. The solution of a sensitivity experiment that excludes biological activity is compared with that of a reference experiment that includes the full processes. The comparison reveals that biological activity results in a much stronger seasonal variation of surface dissolved inorganic carbon (DIC) and, hence, the ratio of total alkalinity to DIC in the northern parts of the YECS. The increased ratio resulting from biological DIC consumption contributes to the undersaturated partial pressure of CO₂ at the sea surface with respect to the atmosphere, causing the central Yellow Sea in summer and autumn to shift from being a CO₂ source to a sink; this same shift also occurs over the Changjiang Bank in summer. In the southern YECS, the biological effect is relatively weak. The comparison further reveals that low water temperature, instead of biological activity, is the dominant factor causing the YECS to become a carbon sink in spring. The biological effect on the variation of DIC (both at the surface and in the water column) differs greatly among the three representative regions of the YECS because of differences in primary production and hydrodynamic conditions. Particle-tracking simulations quantify the regional difference in horizontal advection. In the northern region, weaker horizontal advection causes the longer residence time of low DIC water induced by biological consumption. Over the entire YECS, biological activity contributes to about one-third of the total annual absorption of atmospheric CO₂.     

耦合Rothermel模型与粒子系统的林火蔓延模拟方法北大核心CSCD

科学准确地模拟分析森林火灾蔓延动态对防灾减灾救灾工作具有重要意义。现有的林火蔓延模拟方法在林火蔓延计算和可视化表达上,耦合程度低且难以将动态物理模型计算结果实时可视化表达。针对这一问题,本文在综合考虑国内外各种火灾蔓延模型优缺点的基础上,选取应用广泛的Rothermel模型作为物理模型。通过惠更斯理论优化了火灾演进范围边界点割裂的不足,采取着火点密度阈值控制种子点数量与模拟可视化效率的平衡;利用布尔运算提高多着火点蔓延范围计算效率,将火灾模型与Open Scene Graph的粒子系统进行紧密耦合,完成火灾演进可视化表达。本文方法实现了对森林火灾蔓延的精确计算和实时、逼真模拟,为灾害应急部门提供信息化支撑。     

NDSI与NDFSI结合的山区林地积雪制图方法

积雪是冰冻圈的重要组成部分,因其在可见光波段的高反射率、低导热率的特性以及大面积的覆盖,成为全球辐射平衡的重要决定因子。在中纬度的干旱和半干旱山区,季节性的冰雪融水是春季河川径流的主要补给水源,山区积雪分布的变化对融雪期河流径流量的波动具有重要影响。当前的积雪产品在下垫面为山区林地时会低估积雪面积,从而影响了山区水文过程模拟的精度。本文基于Landsat OLI影像,采用归一化差值积雪指数NDSI和归一化差值林地积雪指数NDFSI相结合的方法,对春季融雪期的阿尔泰山区泰加林地进行积雪识别,并采用海拔高度、温度、以及对应的高分数据对提取结果进行了定量分析。结果表明,采用NDSI进行积雪识别时,山区林地的积雪会被大量漏分;对林地像元采用NDFSI阈值法可以区分林地中是否有积雪分布。NDSI和NDFSI相结合的积雪识别方法操作简单,不需要提供森林分布图等辅助数据,可以有效提高山区林地复杂环境下积雪制图的精度。     

两种机器学习方法在重庆夏季旱涝预测中的应用

利用1961—2010年重庆34个气象观测站夏季降水资料及国家气候中心130项环流指数,采用机器学习的决策树和随机森林方法建立重庆夏季旱涝预测模型,通过2011—2018年预测效果检验发现,夏季同期环流指数决策树模型和前冬海温指数决策树模型预测的8 a降水异常趋势均正确,比考虑单一指数的PC评分分别提高37.5%和12.5%。此外,用随机森林模型预测重庆2014—2018年的夏季降水,5 a平均PS、CC和PC评分分别是84.6、0.27和67.1,相比于业务发布预报质量均有明显提高,且随机森林的预测质量较为稳定。     

Effects of an Urban Park and Residential Area on the Atmospheric CO2 Concentration and Flux in Seoul, Korea

The CO₂ concentrations and fluxes over an urban forest site (Namsan) and an urban residential region (Boramae) in Seoul, Korea, during the non-growing season (2–4 March 2011), the growing season (10–12 June 2011), and the late-growing season (22–24 September 2011) were analyzed. The CO₂ concentrations of two sites showed nearly the same diurnal variation, with a maximum value occurring during the night and a minimum value occurring during daytime, as well as the same seasonal variation, with a maximum value during the non-growing season (early spring) and a minimum value during the growing season (summer). The CO₂ flux over the urban forest did not show any typical diurnal variation during the non-growing season, but did show diurnal variation with a small positive value during the night and a large negative value during daytime in the growing and late-growing seasons due to photosynthesis in the urban forest. The CO₂ flux over the urban residential region showed a positive daily mean value for all periods, with large values during the non-growing season and small values during the growing season, and it also showed diurnal variation with two maxima at 0600–1000 LST and 1800–2400 LST, and two minima at 0300-0600 LST and 1100-1500 LST, and was strongly correlated with the use of liquefied natural gas for cooking and heating by surrounding houses.