Biomass and carbon budgeting of sustainable agroforestry systems as ecosystem service in Indian Himalayas

Adoption of agroforestry is paramount as a climate change mitigation and adaptation strategy. The assessment of plant biomass is crucial for understanding the vulnerability of biological systems to climate change. In the present study, agroforestry systems viz., agrisilviculture (AS), agrihorticulture (AH), agrihortisilviculture (AHS) and agrisilvihorticulture (ASH) were investigated for biomass production and carbon stock in vegetation as well as in soil in the Indian central Himalaya along the elevation i.e. E₁ (<1100 m), E₂ (1100–1400 m), E₃ (1400–1700 m), E₄ (1700–2000 m) and E₅ (>2000 m). Mean aboveground and belowground biomass were 73.9% and 26.1%, respectively, of total biomass (64.4 t ha^?1) in agroforestry systems. Fodder and/or timber trees accounted for 31% (in AHS) to 74% (in AS) of total biomass, while fruit trees accounted for 18% (in ASH) to 73% (in AH) of total biomass. The contribution of agriculture crops to total biomass fluctuated between 19% (in ASH) and 26% (in AH). Total vegetation biomass, soil carbon and total carbon density in agroforestry systems increased significantly along the elevation, with maximum biomass at elevation E₅ (32.0 t ha^?1, 64.7 t C ha^?1 and 96.7 t C ha^?1). Total biomass of vegetation among agroforestry systems differed significantly. Soil carbon stock was highest in AHS (59.5 t C ha^?1) and total carbon density (vegetation + soil) was highest in ASH (93.0 t C ha^?1). Thus, in Indian Himalayas, vegetation biomass, carbon stock, soil and total carbon (vegetation + soil) stock increased along the elevation.

Abbrviations: AG: aboveground; BG: belowground; WD: wood density; VOB: volume over bark; BEF: biomass expansion factor; AS: agrisilviculture; AH: agrihorticulture; ASH: agrisilvihorticulture; AHS: agrihortisilviculture; E: elevation; C: carbon; CO₂: carbon-di-oxide; IPCC: Intergovernmental Panel on Climate Change; DBH: diameter at breast height; AGBD: aboveground biomass density; BGBD: belowground biomass density; GSVD: growing stock volume density     

Efficient Delineation of Nested Depression Hierarchy in Digital Elevation Models for Hydrological Analysis Using Level‐Set Method

In terrain analysis and hydrological modeling, surface depressions (or sinks) in a digital elevation model (DEM) are commonly treated as artifacts and thus filled and removed to create a depressionless DEM. Various algorithms have been developed to identify and fill depressions in DEMs during the past decades. However, few studies have attempted to delineate and quantify the nested hierarchy of actual depressions, which can provide crucial information for characterizing surface hydrologic connectivity and simulating the fill‐merge‐spill hydrological process. In this paper, we present an innovative and efficient algorithm for delineating and quantifying nested depressions in DEMs using the level‐set method based on graph theory. The proposed level‐set method emulates water level decreasing from the spill point along the depression boundary to the lowest point at the bottom of a depression. By tracing the dynamic topological changes (i.e., depression splitting/merging) within a compound depression, the level‐set method can construct topological graphs and derive geometric properties of the nested depressions. The experimental results of two fine‐resolution Light Detection and Ranging‐derived DEMs show that the raster‐based level‐set algorithm is much more efficient (~150 times faster) than the vector‐based contour tree method. The proposed level‐set algorithm has great potential for being applied to large‐scale ecohydrological analysis and watershed modeling.     

不同海拔对干热河谷土壤微生物量及活性的影响

以四川宁南县金沙江下游的河谷地带为研究区域,选择不同海拔下的土壤为研究对象,研究不同海拔下土壤微生物量及其活性的变异特征.结果表明,在干热河谷区,海拔对微生物量、基础呼吸强度、诱导呼吸强度(SIR)影响显著,且随着海拔高度的升高,上述指标呈显著线性增加.在海拔705~1005m处随着干热风影响的减少,微生物量及其活性逐渐增加,其后随着海拔的继续升高,干热风影响降低,微生物量及其活性总体趋于稳定.海拔1005~1400m可以作为是干热风影响的过渡区.微生物量、基础呼吸强度、SIR具有明显的干湿季变化且变化规律相似,其中干季微生物量及其活性显著低于湿季.干季代谢商(qCO2)随海拔先降低后升高并趋于稳定,湿季没有显著差异.干季和湿季土壤微生物量与理化属性具有较强的相关性,可以作为评价土壤肥力的指标.上述研究结果表明,在金沙江干热河谷区,干热风是影响土壤微生物量及其活性的主要因子之一,从生态恢复角度出发,应该尽可能的减少干热风和水分对土壤和植被的胁迫作用,促进该区域生态的可持续性发展.     

Sea level rise and eelgrass (Zostera marina) production: A spatially explicit relative elevation model for Padilla Bay, WA

The dynamics that govern the elevation of a coastal wetland relative to sea level are complex, involving non-linear feedbacks among opposing processes. Changes in the balance between these processes can result in significant alterations to vegetation communities that are adapted to a specific range of water levels. Given that current sedimentation rates in Padilla Bay, Washington are likely less than historical levels and that eustatic sea level rise is accelerating, the extensive Zostera marina (eelgrass) meadows in the bay may be at risk of eventual submergence. We developed a spatially explicit relative elevation model and used it to project changes in the productivity and distribution of eelgrass in Padilla Bay over the next century. The model is mechanistic and incorporates many of the processes and feedbacks that govern coastal wetland elevation change. Accretion estimates made using ²¹⁰Pb dating of sediment cores, sediment characteristics measured within cores, and eelgrass productivity and decomposition data were used to initialize and calibrate the model. Validation was performed using an elevation change rate measured with a network of surface elevation tables. Both the field data and model simulations revealed a net accretion deficit for the bay. Simulations using current rates of sea level rise indicated an overall expansion of eelgrass within Padilla Bay over the next century as it migrates from the center of the bay shoreward.     

Vulnerability assessment and adaptation to the impacts of sea level rise on the Kingdom of Bahrain

This paper assesses quantitatively the impact of sea level rise (SLR) at the global and regional scale as a result of climate change (CC) on the coastal areas of the Kingdom of Bahrain’s islands (36 Islands). The standard Intergovernmental Panel on Climate Change (IPCC) guidelines was modified as appropriate for the situation of the study area. Geographic Information Systems (GIS) coupled with Remote Sensing (RS) were used as the main techniques of collecting, analyzing, modeling simulating and disseminating information to build SLR scenarios in a geographically referenced context. Also, these tools were used to assess vulnerability and risk of the coastal area of the islands with the expectation that coastal planner and government authorities will profit from integrating these knowledge into a broad based environmental decision making. Three SLR scenarios: low, moderate and high were developed to examine the impacts from SLR on all islands. The low SLR scenario (Optimistic) assumes a 0.5-m rise above current sea level, the moderate scenario (Intermediate) assumes a one meter rise, and the high scenario (Pessimistic) assumes a 1.5 m rise in sea level. Two more SLR scenarios were assumed to perform risk analysis, a 2 and 5 meter rise above current sea level. The simulation of SLR are quite straightforward, emphasizing on the uses of both of the data that are incorporated from the satellite images and the created Digital Elevation Model (DEM) to estimate SLR scenarios that are adapted in the study. These data were used to predict consequences of the possibility of the rise in sea level at different scenarios which may alter the landuse and patterns of human communities. Results indicate that low-lying coastal areas of Bahrain islands are at risk from the effects of any SLR resulting from CC. These islands are vulnerable under different SLR Scenarios. More than 17% of the country total area may be inundated under 1.5 m SLR in 2100. The total area that might be lost under different sea level scenarios will vary from more than 77 km² if SLR reaches 0.5 m, to about 100 km² under 1.0 m SLR and may reach 124 km² under 1.5 m SLR scenario. The total inundated areas due to risk scenarios will reach 133 km², if the SLR rises to 2.0 m, and it is estimated to be more than (22%) of the main island total area. Under the second scenario, if the SLR reaches 5.0 m, the main islands will lose approximately half of its area (47%) equal to 280 km². Hawar islands group will lose about (30%) of its total area under 2.0 m SLR, which is about 15.5 km².A SLR adaptation policy framework (APF) and adaptation policy initiatives (APIs) are suggested for planners to build upon for reducing the likely effects of SLR in the Kingdom of Bahrain. The framework is composed of four steps namely, acquisition of information, planning and design, implementation and monitoring and evaluation. A general policy framework for a national response to SLR is suggested. Additionally, a range of policy adaptation options/initiatives to sustain coastal developments under the likely effects of SLR are recommended.     

DEM AGGREGATION FOR WATERSHED MODELING1

ABSTRACT: The widely available USGS 7.5‐minute Digital Elevation Model (DEM) has a cell size of approximately 30 m × 30 m. This high resolution topographic information is impractical for many applications of distributed hydrologic and water quality models. In this study, cells were aggregated into coarse‐resolution areal units, termed grids, and a method to approximate flow direction for coarse‐resolution grids from 30 m DEM cells was developed. The method considers the flow path defined from the fine‐resolution DEM in determining a grid's flow direction and makes flow directions for grids closely follow the flow pattern suggested by the DEM. The aggregation method was applied to a DEM of Goodwater Creek, a nearly flat watershed that is located in central Missouri. The drainage networks derived for different levels of cell aggregations showed that grid aggregates of the Goodwater Creek watershed provided an adequate representation of the landscape topography.     

A spatially explicit empirical model of structural development processes in natural forests based on climate and topography

Stand structure develops with stand age. Old-growth forests with well-developed stand structure support many species. However, development rates of stand structure likely vary with climate and topography. We modeled structural development of 4 key stand variables and a composite old-growth index as functions of climatic and topographic covariates. We used a hierarchical Bayesian method for analysis of extensive snap-shot National Forest Inventory (NFI) data in Japan (n = 9244) to account for differences in stand age. Development rates of structural variables and the old-growth index exhibited curvilinear responses to environmental covariates. Flat sites were characterized by high rates of structural development. Approximately 150 years were generally required to attain high values (approximately 0.8) of the old-growth index. However, the predicted age to achieve specific values varied depending on environmental conditions. Spatial predictions highlighted regional variation in potential structural development rates. For example, sometimes there were differences of >100 years among sites, even in the same catchment, in attainment of a medium index value (0.5) after timber harvesting. The NFI data suggested that natural forests, especially old natural forests (>150 years), remain generally on unproductive ridges, steep slopes, or areas with low temperature and deep snow, where many structural variables show slow development rates. We suggest that maintenance and restoration of old natural forests on flat sites should be prioritized for conservation due to the likely rapid development of stand structure, although remaining natural forests on low-productivity sites are still important and should be protected.     

旋流塔板叶片仰角对湿钙法烟气脱硫过程的影响

实验研究了旋流塔板叶片仰角对钙基湿法烟气脱硫工艺的影响。结果表明 ,一般情况下 ,叶片仰角增大 ,脱硫率有所下降 ,塔的运行稳定性有所下降 ,结垢有所增加。因此 ,在将麻石水膜除尘器改造成旋流板塔脱硫除尘系统的过程中 ,增大叶片仰角的同时一定要考虑脱硫率的下降问题。     

隆回县高海拔山区高效生态经济型退耕还林造林模式研究

通过对六种植物配置方式及三种开发模式的对比试验分析，试验出了一种融水土保持效益与经济效益于一体的高效生态经济型造林模式，并探讨了灰毡毛忍冬产量与海拔高度的关系．结果表明：在自然条件恶劣的小沙江高海拔山区，采用金银花(品种为灰毡毛忍冬) 三木药材或其它草本药材，运用景观生态学原理进行设计开发，可获得很好的经济效益与社会效益，并能保持山区的可持续发展．同时还试验出了主栽树种灰毡毛忍冬在海拔1000～1400m之间时经济效益最好．     

PREP-PAC: a nutrient replenishment product designed for smallholders in western Kenya

Continuous cropping in the absence of external nutrient inputs to soils has led to the expression of poorly productive patches in farmers’ fields of western Kenya. Farmers attempting to correct these conditions are often confused by the spatial and symptomatic irregularity of affected plants and, until recently, no soil management product was commercially available that is specifically formulated to restore soil fertility to these patches. PREP-PAC consists of 2.0 kg of Minjingu rock phosphate (RP), 200 g of urea, seeds of various symbiotic nitrogen-fixing food legumes, rhizobial inoculant, gum arabic seed adhesive, lime for seed pelleting, and instructions for the use of these materials. It is intended for addition to 25 m² and produced at a cost of $ 0.56 per unit. The general principle is to apply slowly available RP sufficient for several cropping seasons with readily available nitrogenous fertilizer and to intercrop farmer’s maize (Zea mays) with a legume that provides residual fixed-nitrogen and organic inputs to the soil. This approach was tested in on-farm experiments conducted in collaboration with several grassroots rural development organizations. An experiment examined interactions between PREP-PAC components in a maize–soybean (Glycine max) intercrop in nutrient-depleted soils with sandy and clayey surface horizons. The treatments included ±RP, ±urea, and ±inoculants arranged as a 2³ factorial with four replicates at each location. Total value of the intercrops ranged between $ 0.83 in the unamended plots and $ 2.44 in plots treated with PREP-PAC. Significant positive effects were observed with the addition of RP (P<0.001), urea (P=0.04), and inoculant (P=0.01) and in interactions between RP and urea (P=0.02) or inoculant (P=0.07). The return ratio to PREP-PAC investment was 2.6 in the sandy soil and 3.7 in the clay. PREP-PACs were tested on-farm in 52 symptomatic patches containing maize–bean intercrops with and without an improved variety of climbing Phaseolus vulgaris cv. Flora. Unamended patches (25 m²=0.0025 ha) produced 1.6 kg maize and 0.08 kg bean. With addition of PREP-PAC containing Flora, yields increased to 4.1 kg maize and 1.1 kg bean (P<0.001 for both crops). Improvement in bean yield during the first cropping season nearly offset PREP-PAC’s investment costs. PREP-PAC is a strategic approach because all of its ingredients, except for urea, originate from East Africa, and are relatively inexpensive; the product is intended for distribution through existing retail and development networks.