砷对蔬菜生长的影响和临界值的研究

本文研究了紫色土添加砷对蔬菜生长的影响与临界值,并采用灰色系统的关联度分析方法,使它们与土壤性度联系起来,结果表明:三种紫色土砷的临界值一般为:红紫泥> 灰棕紫泥>红棕紫泥.     

Effects of landforms on the erosion rate in a small watershed by the Cs tracing method

It's very important to analyze and evaluate quantitatively the effects of landforms on soil erosion for the prevention and treatment of soil loss in a small watershed. The objective of this study was to evaluate the effects of landform factors on erosion rate by the ¹³⁷Cs tracing method in a small watershed in the Purple Hilly Area of China. The erosion rates under different slope lengths, slope gradients and slope aspects were estimated in Xiangshuitan watershed in the Purple Hilly Area in Sichuan Basin by the ¹³⁷Cs tracing method. The results showed that the erosion rate decreased exponentially with downslope distance, and it increased with increasing slope gradient during the scope of 5°-16°. The slope aspect had great impact on the erosion rate, and the hillside on the sunny slope had larger erosion rate than that on the shady slope, particularly for the farmland.     

Migration and control of purple loosestrife (Lythrum salicaria L.) along highway corridors

The east-west density gradient and the pattern and mode of migration of the wetland exotic, purple loosestrife (Lythrum salicaria L.), were assessed in a survey of populations along the New York State Thruway from Albany to Buffalo to determine if the highway corridor contributed to the spread of this species. During the peak flowering season of late July to early August, individual colonies of purple loosestrife were identified and categorized into three size classes in parallel belt transects consisting of the median strip and highway rights-of-way on the north and south sides of the road. Data were also collected on the presence of colonies adjacent to the corridor and on highway drainage patterns. Although a distinct east-west density gradient existed in the corridor, it corresponded to the gradient on adjacent lands and was greatly influenced by a major infestation at Montezuma National Wildlife Refuge. The disturbed highway corridor served as a migration route for purple loosestrife, but topographic features dictated that this migration was a short-distance rather than long-distance process. Ditch and culvert drainage patterns increased the ability of purple loosestrife to migrate to new wetland sites. Management strategies proposed to reduce the spread of this wetland threat include minimizing disturbance, pulling by hand, spraying with glyphosate, disking, and mowing.Contribution 719 of the National Fisheries Research Center-Great Lakes, US Fish and Wildlife Service, 1451 Green Road, Ann Arbor, Michigan 48105, USA.     

Mg2+ improves biomass production from soybean wastewater using purple non-sulfur bacteria

Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria (PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg²⁺ under the light-anaerobic condition. Results showed that with the optimal Mg²⁺ dosage of 10 mg/L, biomass production was improved by 70% to 3630 mg/L, and biomass yield also was improved by 60%. Chemical Oxygen Demand (COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72 hr. The mechanism analysis indicated that Mg²⁺ could promote the content of bacteriochlorophyll in photosynthesis because Mg²⁺ is the bacteriochlorophyll active center, and thus improved adenosine triphosphate (ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials (biomass yield) and COD removal, leading to more biomass production. With 10 mg/L Mg²⁺, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively.     

落叶中DOM和NDOM对紫色土中Cu迁移的影响

以黄葛榕落叶中可溶性有机质(DOM)和不可溶性有机质(NDOM)为研究对象,分析用DOM、NDOM和DOM+NDOM改良碱性(Al-P)、中性(Ne-P)和酸性紫色土(Ac-P)后,土中Cu的形态变化。结果表明：随着老化时间的增加,各改良紫色土中离子交换态Cu含量均明显降低,碳酸盐结合态Cu含量基本保持不变,铁锰氧化物结合态和有机结合态Cu含量均逐渐增加。老化后,供试改良紫色土中Cu表现为有机结合态≈铁锰氧化物结合态＞碳酸盐结合态＞离子交换态的趋势,Cu迁移能力整体降低,降低幅度为44.22%~68.99%。     

三峡库区紫色土生态优化评价体系的探讨

本文计对三峡库区紫色丘陵地区的土壤生态环境状况，提出了优化评价的总目标、评价指标体系和评价程序，探讨了单项指数评价方法的数学模型与基准参数，在此基础上，应用了层次分析与模糊数学的原理和方法，对紫色土生态优化进行综合评价，旨在为库区及库周生态与环境建设及经济综合开发提供依据。     

Condition-dependent control of paternity by female purple martins: implications for coloniality

Proposed causal links between extra-pair copulation (EPC) and colony formation in socially monogamous birds hinge on the question of which sex controls fertilizations. We examined in colonial purple martins Progne subis (1) whether EPCs were forced or accepted by females, and (2) the degree to which apparently receptive females were able to obtain EPCs against their mates’ paternity defenses. Paternity analyses of multilocus DNA fingerprinting confirmed previous findings of a marked relationship between age class and extra-pair fertilizations (EPFs), with young males losing paternity of 43% (n = 53) of their putative offspring compared to 4% (n = 85) by old males. All assignable extra-pair offspring were sired by old males, with one male obtaining most EPFs each year. Contrary to the hypothesis that EPCs are forced, EPF frequency within age class did not increase with seasonal increases in the number of males per fertile female. Whereas the male control hypothesis predicted that the male age class that mate-guarded more would be cuckolded less, the reverse was true: young males guarded significantly more intensely. The male age class difference in cuckoldry could not be explained by the possibility that young and inexperienced females (which are usually paired to young males) were more vulnerable to forced copulation because EPFs were unrelated to female age. These findings suggest that females (1) pair with old males and avoid EPCs, or (2) pursue a mixed mating strategy of pairing with young males and accepting EPCs from old males. The receptivity to EPCs by females paired to young males put them in conflict with their mates. Two factors determined the paternity achieved by young males: (1) the relative size of the male to the female, with young males achieving much higher paternity when they were larger than their mates, and (2) the intensity of mate-guarding. Both variables together explained 77% of the variance in paternity and are each aspects of male-female conflict. Given female receptivity to EPCs, mate-guarding can be viewed as male interference with female mating strategies. We conclude that EPCs are rarely or never forced, but the opportunity for females paired to young males to obtain EPCs is relative to the ability of their mates to prevent them from encountering other males. Evidence of mixed mating strategies by females, combined with other features of the martin mating system, is consistent with the female-driven “hidden lek hypothesis” of colony formation which predicts that males are drawn to colonies when females seek extra-pair copulations. Received: 23 March 1995/Accepted after revision: 14 January 1996     

Mg2+ improves biomass production from soybean wastewater using purple non-sulfur bacteria

Soybean wastewater was used to generate biomass resource by use of purple non-sulfur bacteria(PNSB). This study investigated the enhancement of PNSB cell accumulation in wastewater by Mg2+under the light-anaerobic condition. Results showed that with the optimal Mg2+dosage of 10 mg/L, biomass production was improved by 70% to 3630 mg/L,and biomass yield also was improved by 60%. Chemical Oxygen Demand(COD) removal reached above 86% and hydraulic retention time was shortened from 96 to 72 hr. The mechanism analysis indicated that Mg2+could promote the content of bacteriochlorophyll in photosynthesis because Mg2+is the bacteriochlorophyll active center, and thus improved adenosine triphosphate(ATP) production. An increase of ATP production enhanced the conversion of organic matter in wastewater into PNSB cell materials(biomass yield) and COD removal, leading to more biomass production. With 10 mg/L Mg2+, bacteriochlorophyll content and ATP production were improved by 60% and 33% respectively.     

衡阳紫色土丘陵坡地土壤酶活性对植被恢复的响应

以典型的衡阳紫色土丘陵坡地植被不同恢复阶段为研究对象。采用空间代替时间序列的方法,选用立地条件基本相似的裸荒地、草本群落、灌木群落和乔木群落4种类型表示恢复的4个阶段,通过调查取样和实验分析,探索不同恢复条件下0-10、10-20、20-40 cm土层酶活性的分布特征,以及土壤酶活性对植被恢复的响应。结果表明：1）随着恢复的进行,脲酶、蔗糖酶与碱性磷酸酶活性显著增加（P＜0.05）,过氧化氢酶活性显著减小（P＜0.05）。2）随着土层的加深,脲酶、蔗糖酶与碱性磷酸酶活性显著减小（P＜0.05）,过氧化氢酶活性显著增加（P＜0.05）。3）脲酶、蔗糖酶与碱性磷酸酶之间呈极显著正相关（P＜0.01）,且均与土壤含水量、物理性黏粒、土壤有机碳、全氮、全磷、碱解氮、速效钾、阳离子交换量呈极显著正相关（P＜0.01）,与容重及pH值呈显著或极显著负相关（P＜0.05或P＜0.01）。4）过氧化氢酶与脲酶呈极显著负相关（P＜0.01）,与蔗糖酶与碱性磷酸酶相关性不显著（P＞0.05）,与土壤有机碳、全氮、碱解氮、速效钾及阳离子交换量呈显著或极显著负相关（P＜0.05或P＜0.01）,与 pH 值呈显著正相关（P＜0.05）。5）土壤脲酶、蔗糖酶与碱性磷酸酶可敏感地反映植被过程中土壤质量的变化,植被恢复可改善表层与深层土壤的生物学性质。     

入侵植物凋落物浸提液对紫色土吸附金霉素的影响

用3种入侵植物的地上(O)和地下(U)凋落物浸提液(Le)对紫色土进行修饰,采用批处理法研究各Le修饰土样对金霉素(CTC)的等温吸附特征,分析pH值、离子强度和温度对CTC吸附的影响。结果表明：各Le修饰紫色土对CTC的吸附等温线最适用于Freundlich模型描述;当pH值为2,离子强度为0.1 mol/L和试验温度40 ℃时,一年蓬(Conyzaannumus)Le修饰紫色土对CTC的吸附效果最佳,最大吸附量为1.68 mmol/kg~7.94 mmol/kg;当Le修饰比例为100%时,OLe和ULe修饰紫色土对CTC的吸附量均达到最大,且OLe修饰紫色土对CTC的吸附效果相比ULe更佳。