Conservation in Brazil's Chocolate Forest: The Unlikely Persistence of the Traditional Cocoa Agroecosystem

/ In southern Bahia, Brazil, the traditional cocoa agroecosystem with a dense shade canopy of native trees is now recognized as a secondary conservation route for highly endangered Atlantic Rainforest species. This "chocolate forest" of the densely shaded farms persists despite a massive 20-year Brazilian government modernization program in which shade was seen as a chief impediment to raising cocoa production. The objective of this study was to determine how this traditional agroecosystem endured. Although dense shade limits cocoa yield, it provides several agroecological benefits: control of insect pests and weeds, microclimate stability, and soil fertility maintenance. A keycomponent of modernization efforts was a shade-tree removal program designed to maximize cocoa production by using low shade and fertilizer while substituting agrochemicals for many beneficial roles of the overhead trees. This research found that many farmers rejected, or only partially accepted, the shade reduction process although it promised much higher cocoa yield and profit. Farmers employing a wide range of shading were interviewed, and it was found that decisions to remove or maintain the shade trees were linked to both agroecological and risk-minimization factors. Farmers' perceptions of the agroecological functions of the shade trees and individual willingness to entertain the economic risk associated with substituting agrochemicals for these were important. A less-profitable, but lower-risk approach of occasional fertilizer and agrochemical use with the traditional shade intact was a rational and widespread choice. Policies designed to maintain the traditional agroecosystem through the current economic crisis should heed the multiple functions of the overhead trees. KEY WORDS: Conservation; Brazil; Atlantic Rainforest; Cocoa; Agroecology; Risk; Agroforestry     

华北平原不同农田管理措施对于土壤碳库的影响

华北平原是我国重要的粮食生产基地,土壤碳氮水平直接作用于区域的土壤肥力和粮食生产.通过长期定位实验,研究了包括自然恢复(F)、清茬翻耕(N)、秸秆还田免耕(S)和秸秆还田翻耕(TS)这4个处理下土壤有机碳(SOC)、无机碳(SIC)、全碳(TS)、全氮(TN)含量和储量以及13C和15N分布状况.结果表明,与F相比,在0~20 cm土层,N、S和TS的土壤有机碳储量分别降低21.6%、12.3%和3.4%,土壤无机碳储量变化不显著.在20~40 cm土层,土壤有机碳储量变化不显著,而3个农田耕作处理的土壤无机碳储量较F分别增加4.1%(N)、7.3%(S)和5.0%(TS),无机碳增加主要是次生碳酸盐的贡献,农田土壤PIC增加了97%~261%.与自然恢复地相比,农田土壤表层δ15N、δ13CSIC、δ13CSOC偏高且δ13CSOC达显著差异,20~40 cm土层δ15N、δ13CSIC偏低而δ13CSOC偏高.该地区农田土壤中原生碳酸盐以分解作用为主,土壤-作物系统通过增加CO_2含量促进次生碳酸盐的形成,秸秆还田是恢复农田耕作引起土壤碳库储存下降的有效措施.对于华北平原,今后应加强关于秸秆还田和耕作措施对土壤有机碳和无机碳影响的综合研究,对于表层以下层次土壤的碳转化和变化规律需要更多的长期观测.     

华北干旱缺水的现状与成因探索

我国华北地区人均水资源占有量很少，近几年，河北、北京、山东、山西、陕西、河南等地相继出现严重干早，导致河道时有断流，水资源供需矛盾十分突出，人畜饮水困难，城市供水不足，工厂被迫停工，生态环境遭到破坏等一系列不良后果，水资源有进一步减少的趋势。本文对华北干早缺水的成因进行了探索，认为长江流域江河湖泊水资源的减少是引起华北干早的重要因素，为了恢复长江中下游水资源环境提出几点对策与建议。     

华北山区温度推算模式和应用

利用华北山区气象站观测的温度与其所在纬度、经度和高度，分山区建立宏观地面气温场方程。采用１：２０万地形图，以１０＇经、纬度为步长，判读其高度值，代入已建立好的方程中，经地形项订正，推算华北山区年、月平均温度、年较差和ΣＴ＇≥１０℃，其精度达极显著水平。计算结果使我们对华北山区热量资源有了新的认识，最后求算华北山区的主要水果最优品质种植上限高度。     

Distribution of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in surface water and sediments from Baiyangdian Lake in North China

Persistent organochlorine compounds, including hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethanes (DDTs) and polychlorinated biphenyls (PCBs) were analyzed in surface water and sediments from Baiyangdian Lake, North China. Total concentrations of HCHs, DDTs and PCBs in surface water were in the range of 3.13-10.60, 4.05-20.59 and 19.46-131.62 ng/L, respectively, and total concentrations of HCHs, DDTs and PCBs in sediments were 1.75-5.70, 0.91-6.48 and 5.96-29.61 ng/g dry weight, respectively. Among the groups of HCHs (sum of α-HCH, β-HCH, γ-HCH and δ-HCH) and DDTs (sum of DDT, DDD and DDE), the predominance of β-HCH, DDE and DDD in water and sediment samples was clearly observed. This observation suggested that β-HCH was resistant to biodegradation and the DDTs had been transformed to its metabolites, DDE and DDD. For PCBs, penta-, hexa- and hepta-chlorinated congeners were the most abundant compounds in the both phases. Furthermore, the partitioning of chlorinated compounds between sediment and water was investigated to understand their transport and fates in aquatic ecosystems. The results indicated that average logs of organic carbon-normalized sediment-water partition coefficients (logK_oc') for OCPs varied between 3.20 and 5.53, and for PCBs, logK_oc' values ranged from 3.19 to 5.57. The observed logK_oc' was lower than their equilibrium logK_oc predicted from linear model, which may be attributed to the solubility enhancement effect of colloidal matter in water phase and the disequilibrium between sediment and water.     

广东省下庄和南雄铀矿区周围大气环境氡浓度调查

对广东省下庄和南雄两个铀矿区的大气氡环境地球化学进行了研究．矿区废渣和坑道口释放出来的氡气对周围大气形成了氡污染,特别是在矿区周围1～2km范围内的污染严重．但是空气中的氡污染随着离矿区的距离增大而迅速减弱．矿区周围居民室内氡的浓度高,是广东省室内氡浓度平均值的7～8倍左右．在进行调查的29个居室中,有9个（31％）居室内氡浓度超过美国环境保护局制定的0.15Bq/L室内氡浓度的上限值．居室中氡浓度的升高,除了受矿区释放出来的氡污染外,还因为本地区属高本底辐射区,房基下的土壤、岩石和建筑材料中的铀、镭等放射性元素的含量高,其放射性衰变产生的氡释放出来进入室内．     

Strong ozone production at a rural site in theNorth China Plain: Mixed effects of urban plumesand biogenic emissions

Regional ozone (O₃) pollution has drawn increasing attention in China over the recent decade, but the contributions from urban pollution and biogenic emissions have not been clearly elucidated. To better understand the formation of the regional O₃ problem in the North China Plain (NCP), intensive field measurements of O₃ and related parameters were conducted at a rural site downwind of Ji'nan, the capital city of Shandong province, in the summer of 2013. Markedly severe O₃ pollution was recorded, with the O₃ mixing ratios exceeding the Chinese national ambient air quality standard on 28?days (a frequency of 78%) and with a maximum hourly value of 198 ppbv. Extensive regional transport of well-processed urban plumes to the site was identified. An observation-constrained chemical box model was deployed to evaluate in situ photochemical O₃ production on two episodes. The results show that the in situ formation accounted for approximately 46% of the observed O₃ accumulation, while the remainder (~ 54%) was contributed by regional transport of the O₃-laden urban plumes. The in situ ozone production was in a mixed controlled regime that reducing either NOx or VOCs would lead to a reduction of ozone formation. Biogenic VOCs played an important role in the local ozone formation. This study demonstrates the significant mixed effects of both anthropogenic pollution from urban zones and biogenic emission in rural areas on the regional O₃ pollution in the NCP region, and may have general applicability in facilitating the understanding of the formation of secondary pollution over China.     

Effects of vegetation type on soil microbial community structure and catabolic diversity assessed by polyphasic methods in North China

Soil microbes play a major role in ecological processes and are closely associated with the aboveground plant community.In order to understand the effects of vegetation type on the characteristics of soil microbial communities,the soil microbial communities were assessed by plate counts,phospholipid fatty acid (PLFA) and Biolog microplate techniques in five plant communities,i.e.,soybean field (SF),artificial turf (AT),artificial shrub (AS),natural shrub (NS),and maize field (MF) in Jinan,Shandong Province,North China.The results showed that plant diversity had little discernible effect on microbial biomass but a positive impact on the evenness of utilized substrates in Biolog microplate.Legumes could significantly enhance the number of cultural microorganisms,microbial biomass,and community catabolic diversity.Except for SF dominated by legumes,the biomass of fungi and the catabolic diversity of microbial community were higher in less disturbed soil beneath NS than in frequently disturbed soils beneath the other vegetation types.These results confirmed that high number of plant species,legumes,and natural vegetation types tend to support soil microbial communities with higher function.The present study also found a significant correlation between the number of cultured bacteria and catabolic diversity of the bacterial community.Different research methods led to varied results in this study.The combination of several approaches is recommended for accurately describing the characteristics of microbial communities in many respects.     

华北平原不同生产模式设施蔬菜生命周期环境影响评价

全面系统地评价不同生产模式下设施蔬菜生产过程的环境效应,可为降低蔬菜生产过程中的负面环境影响提供理论指导.本文以华北平原河北省曲周县4 a春茬设施茄子生产为例,采用田间实测结合生命周期评价的方法,分析和比较了该地区常规、综合和有机生产模式下设施茄子的生产过程及其对环境的影响.结果表明,3种模式的水体毒性、富营养化和土壤毒性危害潜势对环境影响的贡献较大,分别占82.05%~84.02%、10.29%~12.32%和2.62%~3.48%,且主要发生在农作子系统中,均主要是由氮磷流失、农药残留及有机肥所携带的重金属所致.综合模式的环境影响综合指数最低,为0.596,分别比常规和有机模式降低了30.3%和6.7%,该模式显著降低了设施蔬菜农作子系统的污染物排放,为最佳生产模式.因此,优化田间管理措施(如施用生物农药、优质有机肥和提高氮磷利用效率)可较好地控制蔬菜生产生命周期负面环境影响及提高该地区设施蔬菜生产的环境可持续能力.     

中国华北区域城市间污染物输送研究

通过对华北地区城市间大气污染监测资料分析发现,城市之间存在着大气污染的相互影响和输送问题,大气污染是一个区域性的环境问题。治理和改善北京地区的大气环境,需要考虑周边地区影响,并实施综合性的污染控制和治理对策。使用二维欧拉统计模式,以SO2,SO42-,PM₁₀为模拟对象,模拟其远距离输送和沉降过程。对2002年的区域空气污染状况进行了模拟,模拟区域包括了所要研究的北京市、天津市、河北省等地区。利用实测资料对模式计算结果的检验显示,二者的相关系数平均为0 55。对资料的综合分析表明,北京大气环境中20%的PM₁₀及23%左右的SO2都是来自北京周边地区。