Interactions between Carbon Sequestration and Shade Tree Diversity in a Smallholder Coffee Cooperative in El Salvador

Agroforestry systems have substantial potential to conserve native biodiversity and provide ecosystem services. In particular, agroforestry systems have the potential to conserve native tree diversity and sequester carbon for climate change mitigation. However, little research has been conducted on the temporal stability of species diversity and aboveground carbon stocks in these systems or the relation between species diversity and aboveground carbon sequestration. We measured changes in shade‐tree diversity and shade‐tree carbon stocks in 14 plots of a 35‐ha coffee cooperative over 9 years and analyzed relations between species diversity and carbon sequestration. Carbon sequestration was positively correlated with initial species richness of shade trees. Species diversity of shade trees did not change significantly over the study period, but carbon stocks increased due to tree growth. Our results show a potential for carbon sequestration and long‐term biodiversity conservation in smallholder coffee agroforestry systems and illustrate the opportunity for synergies between biodiversity conservation and climate change mitigation. Interacciones entre el Secuestro de Carbono y la Diversidad de Árboles de Sombra en una Cooperativa de Café de Pequeños Agricultores en El Salvador     

Understanding Interaction Effects of Climate Change and Fire Management on Bird Distributions through Combined Process and Habitat Models

Abstract: Avian conservation efforts must account for changes in vegetation composition and structure associated with climate change. We modeled vegetation change and the probability of occurrence of birds to project changes in winter bird distributions associated with climate change and fire management in the northern Chihuahuan Desert (southwestern U.S.A.). We simulated vegetation change in a process‐based model (Landscape and Fire Simulator) in which anticipated climate change was associated with doubling of current atmospheric carbon dioxide over the next 50 years. We estimated the relative probability of bird occurrence on the basis of statistical models derived from field observations of birds and data on vegetation type, topography, and roads. We selected 3 focal species, Scaled Quail (Callipepla squamata), Loggerhead Shrike (Lanius ludovicianus), and Rock Wren (Salpinctes obsoletus), that had a range of probabilities of occurrence for our study area. Our simulations projected increases in relative probability of bird occurrence in shrubland and decreases in grassland and Yucca spp. and ocotillo (Fouquieria splendens) vegetation. Generally, the relative probability of occurrence of all 3 species was highest in shrubland because leaf‐area index values were lower in shrubland. This high probability of occurrence likely is related to the species’ use of open vegetation for foraging. Fire suppression had little effect on projected vegetation composition because as climate changed there was less fuel and burned area. Our results show that if future water limits on plant type are considered, models that incorporate spatial data may suggest how and where different species of birds may respond to vegetation changes.     

河流CO2与CH4排放研究进展

河流作为连接海-陆两大碳库的主要通道,其水-气界面二氧化碳(CO_2)与甲烷(CH_4)排放构成全球碳循环的重要环节,对全球气候变暖的贡献不容小觑.明确河流水体CO_2与CH_4产排过程、时空特征以及控制因素是认识河流生态学功能以及其对变化环境响应的重要内容.基于当前河流CO_2与CH_4排放研究进展,构建河流碳排放动力学概念框架(内源代谢、陆源输入),并从全球尺度、区域尺度、流域尺度综述了河流碳排放时空变异性特征以及存在的研究不足.在理解碳排放动力学概念框架和时空变异特征的基础上,构建了河流CO_2与CH_4动力学控制因子分层框架(内部因子:有机质、温度、营养盐;外部因子:水文、地貌、人类活动),深入探讨了河流碳排放的关键影响因素.最后,根据当前研究中存在的不足,提出河流碳排放应将纳入区域陆地碳平衡过程,今后研究重点应包括流域尺度上河流CO_2与CH_4内源产生与陆源输入相对贡献的量化研究、不同界面CO_2与CH_4产生与排放过程研究、高时空分辨率的监测数据的补充以及变化环境与人类活动干扰下河流碳排放的响应过程等,为理解河流生态学过程及生态系统功能提供基础,同时为我国进一步深入开展相关研究提供借鉴.     

南京江北核心区气候环境宜居性评价

气候环境条件是影响宜居的一个重要因素。运用多层次评价模型,从气象灾害、大气环境、人体健康及生态气象等4个层面筛选出20项指标,构建区域气候环境宜居性的评价体系,基于层次分析法(AHP)确定各指标的权重,并以南京江北核心区为例,对其宜居水平进行评价。结果表明:在青奥生态建设期间(2011—2014年),研究区的宜居水平整体呈上升趋势,属于宜居范畴,接近非常宜居的标准。这反映青奥会期间的环境整治与灾害防治工作初见成效,对江北核心区的宜居性起正效应作用。     

外源Ca2+对SBR启动期活性污泥胞外多聚物的动态影响

利用无机物如Ca~(2+),加快活性污泥反应器启动,强化活性污泥絮体性能和结构稳定性,受到越来越多的重视.采用序批式反应器,研究进水中添加Ca~(2+)对反应器启动期活性污泥沉降性能和胞外多聚物的影响.结果表明运行至28 d,与进水中不添加Ca~(2+)的反应器(对照反应器)相比,进水中添加150 mg·L~(-1)外源Ca~(2+)的反应器中活性污泥MLSS和MLVSS值分别高出了89.6%和75.6%,SVI值则降低了47.9%;活性污泥胞外多聚物总量增加了76.4%,多糖增加了28.8%,蛋白质减少了31.6%,添加150 mg·L~(-1)外源Ca~(2+)的反应器中污泥胞外多聚物中多糖/蛋白质值为68.8,对照反应器的活性污泥胞外多聚物多糖/蛋白质值仅为36.6.三维荧光光谱和红外光谱分析表明外源Ca~(2+)导致活性污泥胞外多聚物组分发生了变化.实验结果为进水中添加外源Ca~(2+)改善活性污泥沉降性能提供了基础数据.     

HSPF水文水质模型应用研究综述

HSPF(Hydrological Simulation Program-Fortran)模型采用FORTRAN语言编写,以Stanford水文模型为基础,能够综合模拟径流、土壤流失、污染物传输、河道水力等过程,并大量应用于气候变化与土地利用变化的流域水环境效应情景模拟.该模型是半分布式水文水质模型的优秀代表,在国外得到广泛的应用.HSPF模型包括PERLND、IMPLND与RCHRES等3个主要模块,分别实现对透水地段、不透水地段与地表水体的水文水质模拟.总体来看,HSPF模型在国外水文、水质过程模拟,以及涉及气候变化和土地利用影响的情景分析中发挥重要作用,但是国内该模型的应用非常有限.HSPF模型存在的主要问题包括:①模型中某些方案和算法还有改进和完善的空间;②模型对数据输入要求较高,模拟的精度受到空间和属性等数据的限制;③模型只限于均匀混合的河流、水库和一维水体模拟,对于复杂流域或水体的模拟研究,需要与其它模型整合以解决更加综合的问题.目前,针对发展与完善HSPF模型的研究仍在继续,包括模型平台开发、模型功能扩展、模型校正方法研究、参数敏感性研究等方面.随着我国基础数据的积累及共享程度的提高,HSPF模型在我国的应用也将更加广泛.     

河套灌区土壤水和地下水动态变化及水平衡研究

为探究田间土壤水及地下水在不同作物种植区、不同灌期等情况下的动态变化规律与水平衡特征,以春小麦、玉米、向日葵为典型作物,在河套灌区选取4块2亩的试验田,于2009年4-11月采集田间土壤及地下水样品进行研究.结果表明,不同作物地块间土壤含水率的变化差别主要集中在5-9月的作物生长期.夏灌灌水量不足,土壤含水率呈下降趋势,田间土壤水分变化属于“蒸腾蒸发消耗型”;秋浇期内水量充足,各地块各土层含水率均明显增加,田间土壤水分呈“入渗补给型”.各地块地下水埋深月均变化趋势基本一致,由于优先流的存在,地下水对灌溉降水响应快.本文定量研究了区域土壤水和地下水的变化规律,揭示了灌区水平衡要素间的相互转换关系,可为灌区科学合理的水资源管理提供理论依据.     

深水型水库藻类功能组时空演替及生境变化的影响

藻类功能分组是近年来生态学藻类研究的重要理论和方法.为了探明西安某深水型水源水库藻类功能组时空演替及生境变化的影响,于2011年8月起开展实验研究.研究采用现场在线监测和实验室分析相结合的方法.结果表明,水库藻类可分为10个功能组类别:B、D、P、X1、X3、F、G、J、LM、MP.其中,功能组B、P、F、X1、MP、D、J在水库中较为常见,X3、G、LM出现几率较低,功能组B、D、P、X1、X3的藻类数量占优.通过分析环境因子的变化对功能组时空演替的影响,发现水温为最主要的影响因子.水库藻类生长策略为:春季R/CR策略藻种→春末夏初CR/C策略藻种→夏末秋初C/CR/R/CS/S策略藻种→秋末及冬季CR/R策略藻种.此研究可为深水型水库安全取水提供理论支持.     

Investigation of low-molecular weight organic acids and their spatiotemporal variation characteristics in Hongfeng Lake, China

The identities and concentrations of low-molecular-weight organic acids (LMWOAs) were determined by ion chromatography throughout a 20-m water column in Hongfeng Lake, China. The spatiotemporal variations of LMWOAs and their contributions to dissolved organic matter (DOM) in a research period of 24 hr were also investigated. The results demonstrated that five LMWOAs (lactic, acetic, pyruvic, sorbic, oxalic acid) were detected, and their total concentration and proportion in DOC were 6.55 μmol/L and 7.47%. Their average levels were 2.50, 0.65, 2.35, 0.96 and 0.09 μmol/L, respectively. LMWOAs were higher during daytime (10:00-18:00 on Jun 13, 2008) than nighttime (21:00-6:00 the next morning), in particular 4.99 μmol/L high in the epilimnion ( 1 m water depth), reflecting the fact that direct import from terrigenous sources and photochemical production from humic materials were dominant during LMWOAs’ origin and accumulation. The same factors caused LMWOAs to be 0.63 μmol/L in the epilimnion higher than in the hypolimnion. The rapid decrease of total organic acid (TOA) up until 18:00 mainly resulted from bio-uptake and mineralization in the hypolimnion (>1 m water depth). Pyruvic acid increased with time in the epilimnion and decreased in the hypolimnion, largely related to the two contrary processes of continuous degradation and synthesis of macromolecular organic matter during life materials’ cycle mediated by organisms. Simultaneously, plankton behavior and thermal stratification played a pivotal role in LMWOAs’ behavior in the water column, causing decreasing and increasing profiles. The distribution of LMWOAs represents an interesting resource for biogeochemical research of DOM in aquatic ecosystems.     

昆明市主城区三种温室气体的月份和干、湿季的小时变化规律及原因分析

研究了昆明市主城区3种温室气体浓度的最新变化情况,采用2009年、2010年和2011年的月份和小时平均浓度数据,结合昆明市气候特点,对3种温室气体浓度的月份和干、湿季的小时变化规律及原因进行了分析。