森林与径流关系——一致性和复杂性

@论文综述国外近一个世纪以来在配对集水区研究方面所取得的结论,从水的自然属性出发,从森林变化对径流(年径流量、洪峰与枯水径流)的影响,径流响应的干扰临界值及水文恢复各方面探讨森林变化与径流关系的一致性与复杂性。森林变化与径流关系的一致性主要表现在由较长时间尺度表达的年径流量上。绝大多数的配对集水区的试验研究表明,采伐森林就会增加年径流量,而在荒地上造林就会减少年径流量。而由较短时间尺度表达的洪峰径流与枯水流量则呈现较大的复杂性和难预估性。综述表明,对径流特别是洪峰与枯水径流的定义及分析方法的不同也是造成森林与径流关系复杂性的重要原因。森林与径流关系的复杂性要求人们在研究及应用其关系时就必须有系统观,必须考虑植被、径流与其它过程(土壤变化、气候变化等)的相互作用。论文还认为尽管配对集水区试验作为一种研究方法为研究者提供了许多可靠的结论,但由于许多研究者只把集水区看作是“黑箱”Q从而对认识森林与径流关系的复杂性有一定的局限性。未来的研究应把配对集水区的试验与其它对过程的研究技术(同位素、GIS等技术)结合起来。     

林带对交通噪声衰减的效果研究及公路防噪林带设计

采用一套试验方案 ,对 8处林带降噪效果进行测试 ,得出了林带总的衰减、愈量衰减与宽度、能见度的定量关系 ,并对衰减效果进行了频谱分析 ,为公路防噪林带的设计提供了依据。     

Variation in photosynthetic photon flux density within a tropical seasonal rain forest of Xishuangbanna, south-western China

Introduction Photosyntheticphotonfluxdensity(PPFD)withinforestcanopiesisintrinsicallyheterogeneousinspaceandtime.Becausesomespeciesaregenotypicallysuitedforspecificlightregimes,understandingtheheterogeneityofthelightregimewithinaforestcanopyisimportantfor…     

扑救森林火灾应遵守的安全规则

本文简要介绍了在林火扑救中扑火队员应遵守的安全规则。     

温带亚高山针叶林土壤碳循环微生物群落的时空动态

选取参与碳固定的二磷酸羧化/加氧酶基因（cbbM）、有机碳降解的淀粉酶基因（amylase）和纤维素酶基因（cellulase）作为分子标记,用实时定量PCR方法对温带亚高山华北落叶松（Larix gmelinii var.principis-rupprechtii）林、白杄（Picea meyeri）林、青杄（P.wilsonii）林和油松（Pinus tabulaeformis）林土壤碳循环功能微生物类群丰度的时空动态开展研究.结果显示,总碳（TC）、总氮（TN）、总硫（TS）、有机质（OM）和有机碳（TOC）、pH值、铵态氮（NH₄⁺-N）、硝态氮（NO₃^--N）、过氧化氢酶、蔗糖酶和脲酶活性在4种森林土壤中都有不同程度的差异,且有显著的季节变化特征.高海拔华北落叶松林土壤TC、TN、TS、C/N、OM和TOC含量最高,而pH值最低.土壤TC、TN、亚硝态氮（NO₂^--N）含量、蔗糖酶和脲酶活性,与碳循环微生物类群的丰度呈极显著相关.土壤NO₃^--N含量与有机碳分解和固碳微生物类群的相对丰度显著相关;土壤C/N、NO₂^--N、pH值、OM、TOC、过氧化氢酶及脲酶活性,与降解易分解碳（labile C）和难分解碳（recalcitrant C）的微生物类群的相对丰度呈极显著相关.植被类型和季节变化共同影响土壤碳循环微生物类群的丰度,而季节变化是主导因素.植被和土壤环境因子通过调控微生物群落碳代谢功能类群的结构,影响森林土壤碳源-汇的平衡.     

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.     

Analyzing the cost effectiveness of Santiago, Chile's policy of using urban forests to improve air quality

Santiago, Chile has the distinction of having among the worst urban air pollution problems in Latin America. As part of an atmospheric pollution reduction plan, the Santiago Regional Metropolitan government defined an environmental policy goal of using urban forests to remove particulate matter less than 10 microm (PM(10)) in the Gran Santiago area. We used cost effectiveness, or the process of establishing costs and selecting least cost alternatives for obtaining a defined policy goal of PM(10) removal, to analyze this policy goal. For this study, we quantified PM(10) removal by Santiago's urban forests based on socioeconomic strata and using field and real-time pollution and climate data via a dry deposition urban forest effects model. Municipal urban forest management costs were estimated using management cost surveys and Chilean Ministry of Planning and Cooperation documents. Results indicate that managing municipal urban forests (trees, shrubs, and grass whose management is under the jurisdiction of Santiago's 36 municipalities) to remove PM(10) was a cost-effective policy for abating PM(10) based on criteria set by the World Bank. In addition, we compared the cost effectiveness of managing municipal urban forests and street trees to other control policies (e.g. alternative fuels) to abate PM(10) in Santiago and determined that municipal urban forest management efficiency was similar to these other air quality improvement measures.     

Coupling a 3D patch model and a rockfall module to assess rockfall protection in mountain forests

Many forests in the Alps are acknowledged for protecting objects, such as (rail) roads, against rockfall. However, there is a lack of knowledge on efficient silvicultural strategies and interventions to maintain these forests at optimal protection level. Therefore, assessment tools are required that quantify the rockfall protection effect of forest stands over time, and thereby provide the ability to evaluate the necessity and effect of management interventions. This paper introduces such a tool that consists of a 3D rockfall module embedded in the patch based forest simulator PICUS. The latter is extended for this study with a new regeneration module. In a series of experiments the new combined simulation tool is evaluated with regard to parameter sensitivity, model intercomparison experiments with recently proposed algorithms from the literature, and the ability to respond realistically to different management regimes in rockfall protection forests. Results confirm the potential of the new tool for realistic simulation of rockfall activity in heterogeneous mountain forests, but point at the urgent need to improve the knowledge base on the interaction of understory and rockfall activity. Further work will focus on model validation against empirical rockfall data, and include reduced tree vitality due to damage from boulder collisions as well as the explicit consideration of downed dead wood.     

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.