Baseline assessment for environmental services payments from satellite imagery: a case study from Costa Rica and Mexico

In this study we evaluate the accuracy of four global and regional forest cover assessments (MODIS, IGBP, GLC2000, PROARCA) as tools for baseline estimation. We conduct this research at the national scale for Costa Rica and for two tropical dry forest study sites in Costa Rica (Santa Rosa) and Mexico (Chamela-Cuixmala). We found that at the national level, the total forest cover accuracy of the four land cover maps was inflated due to an overestimation of forest in areas with an evergreen canopy. However, the four maps greatly underestimated the extent of the deciduous forest (dry forest); an ecosystem that faces high deforestation pressure and poses complications to the mapping of its extent from remotely sensed data. For the tropical dry forest sites, all maps have low forest cover accuracies (mean for Santa Rosa: 27%; mean for Chamela-Cuixmala: 56%). This has implications for policy implementation.     

Estimating Forest Ecosystem Evapotranspiration at Multiple Temporal Scales With a Dimension Analysis Approach1

Abstract:  It is critical that evapotranspiration (ET) be quantified accurately so that scientists can evaluate the effects of land management and global change on water availability, streamflow, nutrient and sediment loading, and ecosystem productivity in watersheds. The objective of this study was to derive a new semi‐empirical ET modeled using a dimension analysis method that could be used to estimate forest ET effectively at multiple temporal scales. The model developed describes ET as a function of water availability for evaporation and transpiration, potential ET demand, air humidity, and land surface characteristics. The model was tested with long‐term hydrometeorological data from five research sites with distinct forest hydrology in the United States and China. Averaged simulation error for daily ET was within 0.5 mm/day. The annual ET at each of the five study sites were within 7% of measured values. Results suggest that the model can accurately capture the temporal dynamics of ET in forest ecosystems at daily, monthly, and annual scales. The model is climate‐driven and is sensitive to topography and vegetation characteristics and thus has potential to be used to examine the compounding hydrologic responses to land cover and climate changes at multiple temporal scales.     

Watershed Evapotranspiration Increased due to Changes in Vegetation Composition and Structure Under a Subtropical Climate1

Abstract: Natural forests in southern China have been severely logged due to high human demand for timber, food, and fuels during the past century, but are recovering in the past decade. The objective of this study was to investigate how vegetation cover changes in composition and structure affected the water budgets of a 9.6‐km² Dakeng watershed located in a humid subtropical mountainous region in southern China. We analyzed 27 years (i.e., 1967‐1993) of streamflow and climate data and associated vegetation cover change in the watershed. Land use/land cover census and Normalized Difference of Vegetation Index (NDVI) data derived from remote sensing were used to construct historic land cover change patterns. We found that over the period of record, annual streamflow (Q) and runoff/precipitation ratio did not change significantly, nor did the climatic variables, including air temperature, Hamon’s potential evapotranspiration (ET), pan evaporation, sunshine hours, and radiation. However, annual ET estimated as the differences between P and Q showed a statistically significant increasing trend. Overall, the NDVI of the watershed had a significant increasing trend in the peak spring growing season. This study concluded that watershed ecosystem ET increased as the vegetation cover shifted from low stock forests to shrub and grasslands that had higher ET rates. A conceptual model was developed for the study watershed to describe the vegetation cover‐streamflow relationships during a 50‐year time frame. This paper highlighted the importance of eco‐physiologically based studies in understanding transitory, nonstationary effects of deforestation or forestation on watershed water balances.     

农林废弃物在去除废水重金属中的环境友好利用

评述了近年来国内外利用廉价农林废弃物去除废水重金属的研究进展.重点论述了化学改性处理的农林废弃物对重金属离子的吸附性能,并详细比较了改性前后及各种改性方法的吸附效率.改性处理明显提高了农林废弃物的吸附性能,一些改性的农林废弃物吸附剂对某些重金属离子具有良好的吸附性能,显示出广阔的应用前景.但在今后的研究中还应强化改性农林废弃物吸附剂表面结构表征、吸附作用机理和动力学的研究,开发新型高效的改性再生方法,并对废水处理成本进行详细评估.     

Filterability of oil sands tailings

In Canadian oil sands mining operations, bitumen is extracted from oil sands using the hot water extraction process, which produces tremendous amounts of tailings. Currently, these tailings are disposed of in large ponds, in which coarse particles settle out relatively quickly and fine particles remain suspended in water and settle very slowly. After years of settling, the fine particles form a stable suspension in water known as mature fine tailings (MFTs). Long-term storage of the MFT is costly and poses a major environmental liability.Oil sands companies are now actively investigating different approaches to replace or reduce the use of oil sands tailings ponds. Filtration of the tailings to produce “dry tailings” for stacking is now being investigated as an alternative by a number of companies. Fast water drainage is a critical step for the filtration process. In this paper, we use simple laboratory-scale filtration tests to evaluate the filterability of the oil sands tailings and to generate a parameter that can be used in filtration scale-up. It was found that the filterability of the original coarse oil sands tailings was relatively low. However, after the fines are flocculated with the coarse particles to form uniform flocs the filterability was improved by several orders of magnitude. The results demonstrate that filtration of the flocculated coarse tailings to produce the “dry” stackable tailings may be viable.     

pH、温度和水土比对酸性土壤溶液中铝离子形态分布的影响

溶液中Al3 、Al-F和有机络合态铝（Al-OM的浓度随pH降低而增加,Al3 在总单核铝中所占比例随pH的降低而增加,而Al-F络合物呈相反的变化趋势.土壤中铝的溶解度与土壤中铝氧化物的结晶形态有关,处于较高纬度地区的土壤,由于铝氧化物的结晶形态较差,在相同pH下,其铝的溶解度较大.土壤溶液中有机络合态铝的浓度随温度升高而增加,在pH不变的情况下,土壤中无机铝的溶解量随温度降低而增加.随水土比增加,土壤溶液中Al3 、Al-F络合物和Al-OM浓度减小,但按每kg土计算的铝溶解量随水土比的增加而增加.     

对地观测技术在重大自然灾害监测与评估中的应用实例分析

对地观测技术可提供大范围、多时相、高分辨率的海量数据,用于自然灾害的监测与评估有其极大的优越性。本文叙述了对地观测技术在洪涝灾害、沙尘天气、森林火灾的监测与评估和地震形变场研究中的应用,并指出对地观测技术是建立数字减灾系统不可或缺的强大信息源。     

杨树刺槐混交林沙地土壤的水分—物理性质

研究了刺槐与杨树混交林后沙地土壤水分－物理性质变化的状况,结果表明,刺槐与杨树混交后,土壤水分－物理性质得到了改善,表现在土壤最大持水量增加,毛管持水量、田间持水量得以提高,土壤有效持水量也有了较大幅度的提高,刺槐与杨树混交后土壤总孔隙度、非毛管孔隙度、毛管孔隙度得到提高,并由此而改善了混交林土壤的渗透性能,表4参7     

杉木观光木混交林群落的能量生态

对杉木观光木混交林群落能量的研究结果表明：混交林中观光木地上部分灰分含量以皮最高,而杉则以叶最高,两者GCV（干重热值）和AFCV（去灰分热值）均以叶为最高;观光木、杉木地下各部分的灰分含量均随径级的减小而增加,GCV均以粗根最高,细根最低;观光木的平均灰分含量高于杉木,但GCV和AFCV均低于杉木;从乔木层、灌木层到草本层,灰分含量依次增加,GCV和AFCV则依次降低,混交林群落的能量现存量公占群落的很小一部分,而其能量年净增量、归还量和净固定量却占有一定比重,混交林群落的太阳能转化率为1.57%,而纯林为1.44%,表明杉观混交林是一种能量生产力较高和维持地力能力较强的杉阔混交类型。同时,混交林的能量累积比大于纯林,能量流动速率则低于纯林;乔木层的能量累积比高于林下植被,能量流动速率则低于林下植被,从能量的角度看,构建合理的群落结构必须选择高能量累积比的乔木层树种,同时须促进能量流动速率快的林下植被的发育以维持和提高地力。     

秸秆腐解剂在秸秆还田中的效果研究初报

在大田、微区和盆栽条件下,研究了秸秆腐解剂对小麦、水稻生长及产量的影响,同时研究了秸秆腐解剂对小麦、水稻秸秆腐解速率及对土壤肥力的影响。结果表明,稻、麦秸秆还田时施用秸秆腐解剂对提高稻、麦产量具有明显的增产效果,增产的原因是穗数和粒数增加;稻、麦秸秆还田量不同时,还田量大且配施秸秆腐解剂的效果较还田量小好;麦秸秆还田方式不同时,麦秸以栽稻前耕翻还田且配施秸秆腐解剂的效果较好,上水沤制的效果较差;秸秆腐解剂能促进稻、麦秸秆较快腐解,减轻和防止多量秸秆还田给作物生长带来不利影响,并可稳定和提高土壤养分含量。