Seasonal changes in camera-based indices from an open canopy black spruce forest in Alaska,and comparison with indices from a closed canopy evergreen coniferous forest in Japan

Evaluation of the carbon, water, and energy balances in evergreen coniferous forests requires accurate in situ and satellite data regarding their spatio-temporal dynamics. Daily digital camera images can be used to determine the relationships among phenology, gross primary productivity (GPP), and meteorological parameters, and to ground-truth satellite observations. In this study, we examine the relationship between seasonal variations in camera-based canopy surface indices and eddy-covariance-based GPP derived from field studies in an Alaskan open canopy black spruce forest and in a Japanese closed canopy cedar forest. The ratio of the green digital number to the total digital number, hue, and GPP showed a bell-shaped seasonal profile at both sites. Canopy surface images for the black spruce forest and cedar forest mainly detected seasonal changes in vegetation on the floor of the forest and in the tree canopy, respectively. In contrast, the seasonal cycles of the ratios of the red and blue digital numbers to the total digital numbers differed between the two sites, possibly due to differences in forest structure and leaf color. These results suggest that forest structural characteristics, such as canopy openness and seasonal forest-floor changes, should be considered during continuous observations of phenology in evergreen coniferous forests.     

How green was my valley: forest canopy density in relation to topography and anthropogenic effects in Manipur valley,India

Forest canopy density (FCD) is a major factor in the evaluation of forest status and is an important indicator of possible management interventions. The study uses the FCD model with Landsat TM and Landsat 8 OLI images to assess canopy density in India’s Manipur valley and surrounding hills. Normalized difference built-up index (NDBI) was used to extract built-up areas and population density was retrieved from LandScan data, while elevation and slope were obtained from ASTER DEMs (30 m). Four types of canopy density were delineated with crown cover above 71%, 41–70%, 11–40%, below 10% and areas with no canopy cover, that is 0%. A sharp decline in forest area occurred during 1989–2016 at a rate of loss of 2.9 % year-1 with an average rate of deforestation of 3051 ha year-1. Dense forests exhibited remarkable degradation, especially towards the central valley. The variation in the topographical (elevation and slope) gradient resulted in significant differences in the canopy density over the study area barring some hill slopes. Population pressure and various developmental activities in recent decades led to forest degradation in this fragile yet rich Eastern Himalaya biodiversity hotspot.     

Relationships between Normalized Difference Vegetation Index (NDVI) and carbon fluxes of biologic soil crusts assessed by ground measurements

The aim of this research was to study the relationships between the biological soil crusts (BSC), spectral reflectance and photosynthetic activity. Twenty field campaigns, each lasting several days, were conducted during the 2002–2003 rainy season at sand dune and loess environments in the north-western Negev desert of Israel. Simultaneous measurements of CO₂ net exchange and spectral reflectance were carried out for several types of BSC. The Normalized Difference Vegetation Index (NDVI) was derived from the BSC reflectance and correlated with their CO₂ exchange data. The relationship between NDVI and CO₂ exchange is discussed in detail with respect to environmental factors, such as soil water content, air temperature, and light intensity. Fairly good correlations were found in the rainy season. The NDVI was useful in indicating the potential magnitude and capacity of the BSC assimilation activity. Furthermore, the index corresponded well with different rates of photosynthetic activity of the different types of microphytes. The results demonstrate that spectral reflectances of the BSC can be related to photosynthetic activities and posseses the potential to assess the amount of carbon sequestration by these microphytes on an areal scale using satellite images.     

地基微波辐射仪监测的张掖大气水汽含量与雨强的关系

地基微波遥感具有反演大气水汽的能力,其具有的高时间分辨率,为分析降水过程的水汽含量变化提供了新的手段。用2005年6～7月的微波反演的水汽含量,分析了张掖降水过程的大气水汽含量变化情况。结果表明:张掖甘州降水发生的前提是大气水汽含量需达到某一阈值(夏季为27 mm),而且雨强与大气水汽含量在时间上呈同步分布,这种分布结构与中国东部季风气候区的情况存在差异,后者雨强的峰值滞后于大气水汽含量几小时。     

Spatial and temporal rockfall activity in a forest stand in the Swiss Prealps—A dendrogeomorphological case study

Rockfall is a major threat to settlements and transportation routes in large parts of the Alps. While protective forest stands in many locations undoubtedly reduce rockfall risk, little is known about the exact frequency and spatial distribution of rockfall activity in a given place or about how these parameters can be assessed. Therefore, the objective of the present study was to reconstruct rockfall events with dendrogeomorphological methods and to analyse the spatial and temporal rockfall activity in a subalpine forest stand. The study site is located in the transit zone of frequently passing, rather small rockfall fragments (mean diameter of 10 to 20 cm). In all, 33 stem discs from previously felled Picea abies trees found at the foot of Schwarzenberg in Diemtigtal (Swiss Prealps) were sampled, and a total number of 301 rockfall events were dated to between A.D. 1724 and 2002.Results showed that the spatial distribution of rockfall changed slightly with time, and that rockfall activity increased considerably over the last century. In contrast, rockfall magnitude presumably remained on a comparable level. The seasonal occurrence of rockfall showed a clear peak during the dormant season of trees, most probably in early spring. Furthermore, on a 10-year moving average basis, rockfall rates were positively correlated with mean annual as well as summer and winter temperatures. This means that higher temperatures resulted in increased rockfall activity. On the other hand, no correlation with annual or seasonal precipitation totals was revealed. Overall, this study provides an appropriate method for the detailed assessment of spatial and temporal variations in rockfall activity in a given place.     

Three-dimensional modelling of soil organic carbon density and carbon sequestration potential estimation in a dryland farming region of China

Soil organic carbon density(SOCD) and soil organic carbon sequestration potential(SOCP) play an important role in carbon cycle and mitigation of greenhouse gas emissions. However, the majority of studies focused on a two-dimensional scale, especially lacking of field measured data. We employed the interpolation method with gradient plane nodal function(GPNF) and Shepard(SPD) across a range of parameters to simulate SOCD with a 40 cm soil layer depth in a dryland farming region(DFR) of China. The SOCP was estimated using a carbon saturation model. Results demonstrated the GPNF method was proved to be more effective in simulating the spatial distribution of SOCD at the vertical magnification multiple and search point values of 3.0×10~6 and 25, respectively. The soil organic carbon storage(SOCS) of 40 cm and 20 cm soil layers were estimated as 22.28×10~(11) kg and 13.12×10~(11) kg simulated by GPNF method in DFR. The SOCP was estimated as 0.95×10~(11) kg considered as a carbon sink at the 20–40 cm soil layer. Furthermore, the SOCP was estimated as –2.49×10~(11) kg considered as a carbon source at the 0–20 cm soil layer. This research has important values for the scientific use of soil resources and the mitigation of greenhouse gas emissions.     

Tiller recruitment and mortality in the dryland bunchgrass Eragrostis curvula as affected by defoliation intensity

A greenhouse experiment was conducted to investigate the effects of moderate (14 cm) vs. severe (7 cm) defoliation on tiller recruitment and mortality within the interior and on the perimeter of weeping lovegrass (Eragrostis curvula) tussocks. Tiller number per marked shoot within the interior was significantly greater in plants defoliated at 14-cm stubble height than at 7-cm stubble height (2·37 vs. 0·43, p<0·05) 28 weeks after defoliation; likewise, tiller number per marked shoot was also greater on the perimeter of tussocks in the higher stubble than the lower stubble defoliation treatment (5·10 vs. 2·03, p<0·05). Tiller natality increased significantly 4 weeks after defoliation except for tillers cut to 7-cm stubble height within the interior of tussocks where tiller natality reached a peak at 4·5 weeks after defoliation. During the later stages of canopy development, tiller numbers per marked shoot gradually declined as tiller mortality increased. Tillers began senescing 13 weeks after defoliation, and the senescence rate was 52% greater in the 7-cm stubble height treatment than in the 14-cm stubble height treatment (2·33 vs. 1·53, p<0·0001). Within the interior of tussocks, number of the marked tillers more than doubled under the 14-cm stubble height treatment, whereas the plants lost 57% of the monitored tillers under the 7-cm stubble height treatment. We concluded that the central dieback process in weeping lovegrass is accelerated by severe defoliation.     

Influence of environmental, root, and stand parameters on soil surface CO2 efflux in a Populus euphratica of desert forest in extreme arid region

Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007.Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber.The mean soil CO2 efflux in the stand was 2.71 μmol/(m2·s) during the growing season and 1.38 μmol/(m2·s) in the nongrowing season.The seasonal maximum (end of May through early June) andminimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s),respectively.The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent),with theminimum appearing around 05:00 and the maximum around 15:00.Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213).When all variables were considered simultaneously,only soil temperature (R2=0.378),soil moisture (R2=0.147),and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux.Stand volumes were not correlated with soil CO2 efflux on our sites.     

The relationship between seismic velocity and density in the continental crust — a useful constraint?

Summary . Plots of seismic velocity and density of rock samples show that a range of densities is possible for rocks of each seismic velocity and vice versa. although a single linear relationship is often assumed in crustal gravity calculations. Because of the scatter, whenever rocks of known seismic velocity are converted to density using this relationship, a reduction is made to the resolving power of the resulting gravity calculation. If these rocks reach thicknesses of more than a few kilometres, then the uncertainties become significant when compared with the size of commonly observed gravity anomalies. Examples are considered from the North Sea, Mississippi and Carolina Trough. It is concluded that the use of a seismic velocity measurement as the only indication of rock density does not provide a useful constraint when attempting to reproduce observed gravity variations. An appropriate model for isostatic compensation is probably the most important factor for successful predictions of crustal structure on the basis of gravity data.     

Stable carbon isotope ratios in lake and swamp sediments as a proxy for prehistoric forest clearance and crop cultivation in the Neotropics

Close correspondence between stable carbon isotope ratios ( ¹³ C), pollen, and charcoal profiles in sediment cores from Laguna Zoncho and Machita swamp, Costa Rica, shows that prehistoric forest clearance and crop cultivation can be detected in the stable carbon isotope ratios of total organic carbon ( ¹3C _TOC ). Analyses of δ 13C _TOC complement evidence from pollen, charcoal, and phytoliths and provide a proxy that is sensitive to the intensity and/or proximity to core sites of prehistoric forest clearance and agriculture in watersheds. Stable carbon isotope analyses are particularly useful in situations in which other evidence of forest clearance and agriculture is limited.     

Cartographic approach in studying the structure and dynamics of geosystems as exemplified by the middle Ob region

The structure and dynamics of geosystems in the northwestern part of Western Siberia is considered using the Kazym-Lyamin interfluve, based on the landscape-assessment map for the middle part of the Khanty-Mansi Autonomous District. The study used the landscape structural-dynamical approach and the methods of studying the spatio-temporal dynamics of taiga geosystems.     

Land use dynamics and land cover structure change in Thailand (as exemplified by mountainous Nan Province

Changes in the land use pattern and in the land cover structure for the time interval 1995–2012 in Thailand are considered by using, as an example, Nan Province located in the northern mountainous part of the country. Interpretation of satellite images and vector data that were provided by the Land Development Department (Thailand) revealed the main directions of change in the region’s land use: deforestation, expansion of areas under crops, transition from slash and burn cultivation to permanent cultivation, and intensive utilization of agrochemicals. In spite of a decrease in the deforestation rate across Thailand in general, it is shown that for the period under review the proportion of natural forests in Nan Province decreased by nearly one half. On the other hand, the agricultural lands increased for the same period by more than 50%. The highest deforestation rates were recorded during 2009–2012. It was found that the changes in the land use pattern disturbed the existing centuries-old balance of man–natural environment interaction within the framework of the traditional system of slash and burn agriculture which is well adapted to local conditions. The study revealed the chief causes for such changes: an ineffective monitoring of forests; an unclear character of the boundaries separating lands of rural communities and protected territories, and possibilities for sales of commercial products (maize, cassava, etc.) cultivated in illegal fields. It is shown that rapid changes in land cover due to deforestation and plowing of mountainous areas for cultivation of commercial crops led to an intensification of slope processes (landslides and solifluction), an increase in overland runoff, and to an enhanced hazard of heavy floods during the monsoon season. To keep track of deforestation and deal with nature management conflicts requires a continuous monitoring of the land cover dynamics.     

Nutrients as a link between ionic concentration/composition and diatom distributions in saline lakes

Diatom profiles in closed-basin lake sediments are commonly used to reconstruct climate change based on the observed correlations between salinity (ionic concentration) and modern diatom assemblages. Diatom assemblages are strongly correlated not only with salinity but also anion composition, with certain taxa characteristic of carbonate systems and others sulfate-dominated waters. Although strong correlations exist, the actual mechanisms behind these correlations are unknown. Here we briefly review the influence of salinity and ionic composition on nutrient dynamics in saline lakes and suggest that these interactions may drive shifts in diatom species composition along gradients of ionic concentration/composition. We discuss the influence of salinity and anion composition on nutrient availability, as well as on nutrient requirements and uptake by diatoms.     

2008年春季中国南方冰雪冻害林木折损分析

An abrupt ice and snow storm disaster which occurred in the spring of 2008 severely destroyed forests over a surprisingly large portion of southern China. A transect crossing Jinggang Mountain-Jitai Basin-Yushan Mountain-Wuyi Mountain was selected as the study area. The authors integrated field data collected in two field surveys to analyze the impacts of the disturbance on forests. The following results were obtained. (1) The extent of damage to plantations along the transect decreased in the order of slash pine > masson pine > mixed plantation > Chinese fir. Slash pine is an introduced species from southern America which is characterized by fast growth, low wood quality and rich oleoresin, and showed a damage rate of 61.3% of samples, of which 70.4% cannot recover naturally. Masson pine is the native pioneer species of forests with harder wood, and 52.5% were damaged due to turpentine, of which 60.9% cannot recovery naturally. Chinese fir is a local tree species and samples showed a rate of 46% and a relative rate of 32.5%, lower than the mixed plantation. (2) From west to east along the transect, we can see that evergreen broad-leaved forest of the western transect on Jinggang Mountain showed the lightest damage extent, and a Cryptomeria plantation at an altitude of 700 m was severely destroyed while Chinese fir showed light damage below 700 m and relatively severe damage above 900 m. Masson pine and slash pine in the central transect in Jitai Basin were damaged severely due to turpentine activities, and closed natural secondary deciduous broad-leaved forest was damaged severely due to high ice and snow accumulation on intertwined shrubs. Masson pine aerial-seeding plantations below 400 m along the eastern transect in Xingguo and Ningdu counties were nearly undamaged for small tree sizes, and Chinese fir at 500-900 m altitude showed a lighter damage extent. However, masson pine which was distributed above 400 m and planted in the 1960s, was severely damaged due to turpentine.     

2008年春季中国南方冰雪冻害林木折损分析

An abrupt ice and snow storm disaster which occurred in the spring of 2008 se-verely destroyed forests over a surprisingly large portion of southern China.A transect crossing Jinggang Mountain-Jitai Basin-Yushan Mountain-Wuyi Mountain was selected as the study area.The authors integrated field data collected in two field surveys to analyze the impacts of the disturbance on forests.The following results were obtained.(1) The extent of damage to plantations along the transect decreased in the order of slash pine > masson pine > mixed plantation > Chinese fir.Slash pine is an introduced species from southern America which is characterized by fast growth,low wood quality and rich oleoresin,and showed a damage rate of 61.3% of samples,of which 70.4% cannot recover naturally.Masson pine is the native pioneer species of forests with harder wood,and 52.5% were damaged due to turpentine,of which 60.9% cannot recovery naturally.Chinese fir is a local tree species and samples showed a rate of 46% and a relative rate of 32.5%,lower than the mixed plantation.(2) From west to east along the transect,we can see that evergreen broad-leaved forest of the western transect on Jinggang Mountain showed the lightest damage extent,and a Cryp-tomeria plantation at an altitude of 700 m was severely destroyed while Chinese fir showed light damage below 700 m and relatively severe damage above 900 m.Masson pine and slash pine in the central transect in Jitai Basin were damaged severely due to turpentine ac-tivities,and closed natural secondary deciduous broad-leaved forest was damaged severely due to high ice and snow accumulation on intertwined shrubs.Masson pine aerial-seeding plantations below 400 m along the eastern transect in Xingguo and Ningdu counties were nearly undamaged for small tree sizes,and Chinese fir at 500-900 m altitude showed a lighter damage extent.However,masson pine which was distributed above 400 m and planted in the 1960s,was severely damaged due to turpentine.     

基于结构与功能安全性的景观生态安全时空变化——以人工园林大面积种植区西盟县为例

受人类活动强度干扰,大面积人工园林种植区景观结构趋于均质性,仅从景观结构方面分析很难反映景观生态安全性,需将景观功能纳入到景观生态安全研究中才能系统、客观地体现景观生态安全变化特征。以景观干扰度和景观脆弱度作为景观结构安全指数,引入生态系统服务价值作为景观功能安全指数,构建景观生态安全模型,将安全度从低到高分为Ⅰ、Ⅱ、Ⅲ级,分析2000-2010年西盟县景观生态安全时空变化特征。结果表明:1建立的景观生态安全模型能有效反映景观类型的生态安全性,大小排序为有林地橡胶林桉树林水域茶园灌木林水田草地旱地建设用地。2大面积人工园林的种植使得西盟县景观生态安全由Ⅲ级向Ⅰ和Ⅱ级发生转换,全区景观生态安全降低,但仍保持于中等水平。3西盟县景观生态安全空间差异显著,整体呈现东北、东南部高,西北、西南低的分布格局。中课乡景观生态安全性最好,而勐梭镇安全性最差。     

Relationships between morphological and sedimentological parameters in source‐to‐sink systems: a basis for predicting semi‐quantitative characteristics in subsurface systems

The study of source‐to‐sink systems relates long‐term variations in sediment flux to morphogenic evolution of erosional–depositional systems. These variations are caused by an intricate combination of autogenic and allogenic forcing mechanisms that operate on multiple time scales – from individual transport events to large‐scale filling of basins. In order to achieve a better understanding of how these mechanisms influence morphological characteristics on different scales, 29 submodern source‐to‐sink systems have been investigated. The study is based on measurements of morphological parameters from catchments, shelves and slopes derived from a ∼1 km global digital elevation model dataset, in combination with data on basin floor fans, sediment supply, water discharge and deposition rates derived from published literature. By comparing various morphological and sedimentological parameters within and between individual systems, a number of relationships governing system evolution and behaviour are identified. The results suggest that the amount of low‐gradient floodplain area and river channel gradient are good indicators for catchment storage potential. Catchment area and river channel length is also related to shelf area and shelf width, respectively. Similarly to the floodplain area, these parameters are important for long‐term storage of sediment on the shelf platform. Additionally, the basin floor fan area is correlative to the long‐term deposition rate and the slope length. The slope length thus proves to be a useful parameter linking proximal and distal segments in source‐to‐sink systems. The relationships observed in this study provide insight into segment scale development of source‐to‐sink systems, and an understanding of these relationships in modern systems may result in improved knowledge on internal and external development of source‐to‐sink systems over geological time scales. They also allow for the development of a set of semi‐quantitative guidelines that can be used to predict similar relationships in other systems where data from individual system segments are missing or lacking.     

Analyzing land-cover change and corresponding impacts on carbon budget in a fast developing sub-tropical region by integrating MODIS and Landsat TM/ETM+ images

Land-cover change has significant impacts on regional carbon dynamics. Understanding the carbon consequences of land-cover change is necessary for decision makers to address the issues of carbon reduction and climate change mitigation. Optical remote sensing images have been widely used for detecting regional land-cover change. However, it is difficult to acquire desirable images for regions that are frequently affected by cloudy and rainy weather. In this study, we proposed an approach to deal with this problem by integrating moderate-resolution imaging spectroradiometer (MODIS) and Landsat images based on the mixed-label analysis (MLA) model. We tested this model in Guangdong Province, a fast developing sub-tropical region in China, to derive the provincial land-cover data for the analysis of land-cover change between 2000 and 2009 and its impacts on regional carbon dynamics. Results show that forest land decreased by 3.03%, while built-up area rapidly expanded by 73.01% from 2000 to 2009. The regional vegetation carbon sink declined by 2.6%, whereas the regional carbon emissions increased by more than 100% due to the fast urbanization and economic development. The regional vegetation carbon sink can only offset 4.1% of total carbon emissions in 2009, far below the national level (about 7.0–7.7%) at the same period. Future efforts to improve the regional carbon budget should focus more on the control of land development and the advance of energy efficiency.     

ESSAY PAPER The interaction between geological structure and global tectonics in multistoreyed landscape development: a denudation chronology of the South Indian shield

This study constitutes a comprehensive attempt to interpret the multistoreyed benchland scenery of the South Indian shield. In South India, two rifted margins (and now competing base levels), a low-elevation margin facing the Bay of Bengal, in existence since ≈130  Ma, and a younger (65  Ma) high-elevation margin facing the Arabian Sea, together with a high-standing backbone of extremely resistant granulitic rocks known as charnockites, have influenced the long-term erosional response to rock uplift and to the eustatic shift of shorelines in a complex way.
Several tiers of flat-lying, denudational topographic surfaces, which are indifferent to stratification, schistosity or foliation and highlighted by a characteristic weathering mantle, are identified and the conditions of their genesis discussed. General definitions and assumptions concerning the evolution of planation surfaces are presented. A major key issue is the nature of crustal uplift in cratonic regions: its relation to global tectonics, its role in the redistribution in time and space of available relief and in the deformation of pre-existing planation surfaces, and its bearing on denudational signals which may be recorded both by isotopic measurement techniques and offshore sedimentary sequences. The proposed denudation chronology considers all these aspects, and the analysis sets out to establish a thread of geodynamic events that can account for the observed morphology. Drainage, weathering and crustal uplift patterns, geological structures and chronostratigraphic data are examined in relation to their possible connections with the migration of drainage divides and surface lowering patterns. The high number of degrees of freedom involved when considering the long-term interplay between gravity-driven and radiation-driven denudation systems is one of the many problems facing this analysis, and is extensively addressed in the discussion.