Disturbance to a foraging seabird by sea-based tourism: Implications for reserve management in marine protected areas

The provision of recreational opportunities is one of the important human goals of marine protected areas. However, as levels of recreational use increase, human disturbance is likely to cause significant detrimental effects upon wildlife. Here we evaluate the best managing options to mitigate the impact of sea-based tourism on the foraging activity of an endangered population of European shags, Phalacrocorax aristotelis, in a coastal marine protected area (Cíes islands, north-western Iberia). Boat disturbance elicited a characteristic avoidance behavior that resulted in a substantial reduction in foraging activity as levels of boat use increased. Moreover, boats excluded shags from the best feeding areas, resulting in higher densities of foragers in areas of little boat traffic. We used a behavioral model to explore the effects of managing strategies aimed at reducing the impact of boats on the foraging activity of shags. Our model suggested that in low boat disturbance scenarios limiting the number of boats using the reserve would be a better management option than habitat protection (i.e. the establishment of set-aside areas free of boat traffic). On the contrary, when boat disturbance levels are high the protection of habitat is recommendable, even if spatial variation in habitat quality is unknown or poorly assessed. Our study stresses the point that management strategies to minimize disturbance to foraging seabirds may depend on the spatial overlap between sea-based recreational activities and foraging seabirds and the spatial variation in marine habitat quality for seabirds.     

Effects of wood char and activated carbon on the hydrolysis of cellobiose by β-glucosidase from Aspergillus niger

Biochar amendments to soils have been suggested as a strategy to sequester carbon and therefore mitigate global climate change. The enrichment of soils with charred materials also increases their fertility. This fertilising effect of biochar may be caused by various mechanisms; an acceleration of nutrient cycling has been suggested as one such mechanism. The rate-limiting step in nutrient cycling is thought to be the extracellular enzymatic attack on biological macromolecules. In this study, therefore, the effects of chestnut wood char (specific surface area 2.0 m² g⁻¹) and of activated carbon (specific surface area approximately 900 m² g⁻¹) on an extracellular enzymatic reaction involved in the degradation of cellulose (i.e., hydrolysis of cellobiose by β-glucosidase from Aspergillus niger) were investigated. Cellobiose was not adsorbed by chestnut wood char, whereas activated carbon absorbed more than 97% of it. Both charred materials adsorbed more than 99% of β-glucosidase. For chestnut wood char, adsorption of the enzyme caused a decrease of approximately 30% in the reaction rate, whereas for activated carbon, the nearly complete absorption of both substrate and enzyme entirely inhibited the reaction. These results show that β-glucosidase from A. niger retains most of its activity when adsorbed to chestnut wood char and that the reaction it catalyses in nature is only slightly affected by this charred material. On the other hand, a material characterised by a high specific surface area and high porosity, such as activated carbon, can make even a highly soluble substrate unavailable for soil enzymes and therefore completely inhibit the reaction. Thus, charred materials may affect nutrient cycling mainly by regulating the availability of substrates: the degradation of highly soluble substrates may be accelerated by materials with low specific surface area, which maintain an active and protected enzyme pool, whereas materials with high specific surface and high porosity may slow down the degradation by making substrates unavailable.     

不同土壤管理方式下幼龄柑橘根区土壤酶活性动态变化

以盆栽2年生纽荷尔脐橙为试材,研究了清耕、自然生草和间种绿肥条件下幼龄柑橘生长期内根区土壤酶活性的动态变化。结果表明,间种绿肥和生草能显著提高柑橘根际土壤脲酶和蛋白酶活性,但2种酶的峰值出现时间不同,脲酶的峰值出现在绿肥成熟期和压青后,而蛋白酶峰值出现在压青前,压青引起蛋白酶活性降低。生草和间种绿肥的柑橘根际土壤过氧化氢酶略高于对照,但3处理间无明显差异;压青会引起过氧化氢酶活性降低,随着绿肥压青后腐解,过氧化氢酶又开始回升。因此,柑橘园内间种绿肥要适时压青。     

控释肥残膜对小麦各生育期土壤微生物和酶活性的影响

为了探明控释肥树脂残膜对土壤环境可能造成的影响,采用小麦池栽试验研究了控释肥树脂残膜对土壤有关微生物数量和酶活性的影响。结果表明,控释肥树脂残膜使土壤细菌和放线菌数量分别相对增加了19.01%～62.87%和17.03%～132.39%,土壤脲酶、转化酶、中性磷酸酶活性分别提高了17.39%～85.71%、31.77%～158.40%、35.14%～189.47%,但对过氧化氢酶活性无明显影响。施肥处理（施肥不施残膜和施肥施残膜处理）显著增加了土壤转化酶和中性磷酸酶活性;但对土壤细菌和放线菌数量、过氧化氢酶和脲酶活性没有显著影响。控释肥树脂残膜施用量在90～360g/m2 范围内,对土壤细菌和放线菌数量以及有关土壤酶活性没有产生不良影响。     

小麦–玉米轮作体系长期施肥对塿土微生物量碳、氮及酶活性的影响

以20年塿土小麦玉米轮作体系长期肥料定位试验为平台,探讨不同施肥模式下土壤化学肥力要素、微生物量碳氮及酶活性的响应。试验包括不施肥（CK）、单施氮肥（N）、氮磷（NP）、磷钾（PK）、氮磷钾（NPK）、NPK+秸秆（SNPK）以及不同量有机肥+NPK（M1NPK、M2NPK）等8种施肥模式。结果表明,与CK相比,长期施用NP提高土壤有机碳含量达34.0%、全氮34.0%、全磷58.5%、速效磷608.9%、微生物量碳23.3%、微生物量氮54.0%、蔗糖酶53.9%、脲酶132.6%、碱性磷酸酶29.9%以及脱氢酶40.9%。长期施用NPK与NP效果相似,钾素效果甚微。作物秸秆还田配合氮磷钾化肥与氮磷钾相比没有明显影响土壤有机碳、氮和磷水平,但是显著提高微生物量碳的含量（29.5%）、碱性磷酸酶（23.0%）和脱氢酶（26.9%）的活性。有机肥配合氮磷钾与其它施肥处理相比,显著提升土壤化学肥力要素、微生物量碳氮和酶活性,特别是引起了磷素的大量富集（速效磷含量大于150 mg/kg）。因此,塿土不施有机物情况下,氮磷配合可以提高土壤化学和生物肥力,作物秸秆还田配合氮磷钾化肥的培肥效果优于氮磷钾化肥配合,而合理的有机无机肥配合是塿土提升化学肥力和保证生物健康的最佳施肥模式。     

旅游干扰对武夷山风景区土壤质量的影响

为探讨旅游干扰对武夷山风景区土壤质量综合影响的程度,2008年以5个核心景点区土壤为研究对象,采用土壤质量综合指数进行评价,结果表明:(1)景点土壤容重比对照点平均增加了43.0%,而土壤的非毛管孔隙度、毛管孔隙度、总孔隙度、最大持水量、最小持水量及毛管持水量平均下降了31.4%、27.2%、28.7%、26.6%、26.9%及30.8%;(2)旅游干扰使一些景点的pH下降,另一些景点的pH增大,景点土壤有机质、全N、水解N及全P平均下降的比率较大,分别为46.05%、49.74%、56.71%及42.75%,全K、速效K和有效P则表现为增大或减少不定的变化趋势;(3)不同景点土壤质量综合指数表现为:大红袍(0.601)>水帘洞(0.382)>大王峰(0.327)>一线天(0.264)>天游峰(0.238).旅游干扰对武夷山风景区土壤质量已产生了严重的影响,据此提出了旅游可持续发展的几点建议.     

Characterization of humus-protease complexes extracted from soil

Pyrophosphate (140 mM, pH 7.1) extracts of two arable soils and one pasture soil were ultrafiltrated separating the extracted material into three fractions: A_I with nominal molecular weight (nmw) > 100 kD, A_II with nmw between 10 kD and 100 kD and R with nmw < 10 kD. Protease activity was determined in the fractions by using three different substrates: N-benzoyl-l-argininamide (BAA), specific for trypsin; N-benzyloxy-carbonyl-l-phenylalanyl l-leucine (ZPL), specific for carboxypeptidases; and casein, essentially a non-specific substrate. The derivative fractions were also analysed for their amino acid N and humic (HA) and fulvic (FA) acid contents. The organic matter of extracts and derivative fractions obtained from the pasture soil was analysed by isoelectric focusing (IEF) and that of fractions analysed by pyrolysis gas chromatography (Py-GC). Activities of the extract were monitored for their thermal stability and those of the extract and derivative fractions for their optimal pH.Due to the mechanical disintegrating action of sodium pyrophosphate over the humic substances during the fractionation process the amount of total organic C and FA in the fractions was ranked as R > A_II > A_I. The lowest amino acid N/organic C was found in the R fraction, whereas A_II fraction was rich in humic acids, carbohydrates and amino acid N and A_I fraction showed the lowest carbohydrate content. At least 70% of the total BAA- and ZPL-hydrolysing activity was associated to particles with nmw higher than 10 kD and at least 30% of these activities were present in particles with nmw higher 100 kD. Casein-hydrolysing activity was quite evenly distributed among the three fractions (A_I, A_II and R). The extracted protease-organic complexes were resistant to thermal denaturation and some of them showed optimal activity at pH values higher than 10 as a result of the polyanionic characteristics of the humic material surrounding enzyme molecules and of the presence of alkaline protease. Comparison of data obtained in Py-GC analyses and in protease activity suggests that BAA-hydrolysing activity was associated to a highly condensed humic matter and ZPL-hydrolysing activity to less resistant humic substances, while at least some of the extracted casein-hydrolysing activity was present as glyco-proteins not associated to humus. BAA-hydrolysing activity was probably inhibited by fresh organic matter of carbohydrate origin whereas lignin derived organic matter probably inhibited ZPL- and casein-hydrolysing activity.     

东北黑土区不同耕作方式土壤养分与酶活性的时空变化

通过田间试验研究了东北黑土区玉米不同耕作方式的土壤养分与酶活性的时空变化规律.结果表明,整个生育期不同处理在各个土层均有较高的碱解氮含量,而在播种前常规耕作高于宽窄行,玉米生长中期则是宽窄行高于常规耕作,收获后各处理含量水平基本一致.有效磷不同处理均表现出养分表聚现象,且宽窄行在各个生育期的不同土层内均高于常规耕作.速效钾含量随着土层的加深降低不十分明显,处理间没有表现出明显的差异,体现了钾素养分移动性大的特点.玉米生长关键期的全量氮、磷、钾变化幅度不大,处理问含量水平一致;有机质含量在2%～3%之间;pH值不同处理均随着土层的加深逐渐升高的趋势,说明不同的耕作措施都有促进土壤表层酸化的现象.不同耕作方式土壤酶活性在整个生育期变化趋势相同,无明显差异.     

FACE对三系杂交籼稻汕优63根系活性影响的研究

2005、2006年利用我国惟一的农田开放式空气CO2浓度增高（FACE）研究平台,设计施N量为125kg·hm^-2（LN）、250kg·hm^-2（NN）处理,研究大气CO2浓度比对照高200umol·mol^-1的FACE处理对三系杂交籼稻汕优63根系活性的影响。结果表明：（1）FACE处理使汕优63不同生育时期单位干质量根系的总吸收面积、活跃吸收面积、α-萘胺氧化量等根系活性指标均极显著小于对照。由于FACE处理促进汕优63根系发生量的大幅度增加,因此分蘖期、拔节期其单穴根系活性与对照多无明显差异,到抽穗期FACE处理单穴根系活性显著大于对照;（2）拔节期、抽穗期汕优63每穴的不定根数、不定根总长度、根系体积、根干质量与单位干质量根系活性的关系密切,根量越大单位于质量根系活性越低;（3）不同生育时期汕优63植株含氮率与单位干质量的根系活性多呈正相关,植株碳氮比与单位干质量的根系活性多呈负相关;（4）FACE处理汕优63根系生长量大、植株含氮率低、碳氮比高等可能是造成其单位干质量根系活性低于对照的重要原因。     

再生水灌溉对土壤性能和土壤微生物的影响研究

土壤性能和土壤微生物是再生水灌溉对环境安全效应评价的重要指标。通过模拟试验,以北京高碑店污水处理厂生产的再生水浇灌大豆为例,分析了收获期土壤理化特性及微生物类群变化。结果表明,再生水灌溉能够在一定程度上提高土壤肥力,表现为有机质和有效磷显著增加;土壤重金属铅、镉含量相对清水和土壤本底无明显增加,但土壤溶液电导值（EC）增加显著,在一定程度上造成盐度累积。在土壤微生物方面,再生水灌溉使土壤细菌数量相对清水灌溉处理增加;二级再生水和三级再生水灌溉处理间的放线菌数量差异显著,且明显高于清水对照;再生水灌溉对真菌数量影响不大。再生水灌溉使大豆根际土壤脲酶活性增加,碱性磷酸酶活性最高。土壤微生物数量、酶活性与土壤养分含量之间呈显著相关关系,可作为评价土壤肥力和土壤环境质量的指标。