土壤保肥—供肥机理及其调节Ⅲ.棕壤型菜园土的N素保持与供应

对辽宁省北部、中部及南部棕壤型菜园土１５ 对肥、瘦地Ｎ 素保持与供应性能的研究表明,绝大多数肥地及其各粒级微团聚体的全Ｎ 量、ＮＨ＋４ 吸附与解吸量均大于瘦地及其各相应粒级微团聚体的,而ＮＨ＋４ 解吸率则相反．除了大粒级微团聚体外,肥、瘦地及其小粒级微团聚体全Ｎ 储量与ＮＨ＋４ 吸附与解吸性能均有显著差异．肥、瘦地微团聚体的ＮＨ＋４ 吸附与解吸量均随粒径的增大而降低,解吸率则随之升高．ＮＨ＋４ 吸附与营养物质或酶活性等大多没有显著的线性相关关系;肥地及各粒级微团聚体ＮＨ＋４ 解吸与土壤有机质及其结合形态、全Ｎ 含量、脲酶与磷酸酶活性等呈显著线性正相关,瘦地及其各相应粒级微团聚体的与营养物质含量和酶活性均无显著线性相关关系．     

黄土高原长期培肥土壤团聚体中养分和酶的分布

土壤养分和生物酶是衡量土壤肥力的指标,土壤团聚体性质则决定了土壤物理结构的好坏,探讨不同培肥措施下土壤养分和生物酶在团聚体中的分布,对合理培肥和改善土壤性状具有重要的实际意义。对连续25a的长期有机培肥定位试验地进行测定,结果表明：培肥增加了大级别土壤团聚体、特征微团聚体的数量,显著地改善了土壤结构。培肥土壤团聚体平均重量直径、特征微团聚体C／F0.01较无肥对照土壤有显著增加。长期培肥增强了土壤化学、生物性质的“微域”变异性。相同培肥措施下土壤主要养分含量和酶活性均随土壤团聚体直径的增大而减小。除厩肥处理土壤碱性磷酸酶和蔗糖酶外,其它各培肥土壤的养分含量和酶活性均在〈0．01mm级别特征微团聚体中含量高、活性大。相同级别团聚体和特征微团聚体中,养分含量和酶活性在不同培肥土壤间基本表现出施厩肥处理〉施秸秆处理〉施化肥处理〉对照的规律性。将团聚体的含量和养分含量或酶活性在团聚体中的丰度结合考虑,发现〉5mm级别团聚体中养分含量或酶活性对土壤的贡献率最大。结果充分地显示着土壤性质在不同空间尺度下、不同管理措施下变异的复杂性和多样性。     

土壤保肥-供肥机理及其调节Ⅲ.棕壤型菜园土的N素保持与供应

对辽宁省北部、中部及南部棕壤型菜园土15对肥、瘦地N素保持与供应性能的研究表明,绝大多数肥地及其各粒级微团聚体的全N量、NH₄⁺吸附与解吸量均大于瘦地及其各相应粒级微团聚体的,而NH₄⁺解吸率则相反。除了大粒级微团聚体外,肥、瘦地及其小粒级微团聚体全N储量与NH₄⁺吸附与解吸性能均有显着差异。肥、瘦地微团聚体的NH₄⁺吸附与解吸量均随粒径的增大而降低,解吸率则随之升高。NH₄⁺吸附与营养物质或酶活性等大多没有显着的线性相关关系;肥地及各粒级微团聚体NH₄⁺解吸与土壤有机质及其结合形态、全N含量、脲酶与磷酸酶活性等呈显着线性正相关,瘦地及其各相应粒级微团聚体的与营养物质含量和酶活性均无显着线性相关关系。     

土壤保肥-供肥机理及其调节Ⅱ.棕壤型菜园土的腐殖质结合形态及其肥力学意义

采自辽宁省不同地区的１５对棕壤型菜园土肥、瘦地及其各粒级微团聚体的有机质储量和腐殖质结合形态的研究表明,肥地及其各粒级微团聚体的有机质和各结合形态腐殖质的含量与松结态腐殖质占有机质总量的比例均比瘦地及其各相应粒级微团聚体的高,稳结态腐殖质的比例较小,紧结态腐殖质的比例肥瘦地大体相当．无论肥地或瘦地,小粒级微团聚体的有机质和各结合形态腐殖质的含量及松、稳结态腐殖质占有机质总量的比例均较大粒级的高,而紧结态腐殖质则相反,表明大、小粒级微团聚体具有不同的肥力学意义     

土壤保肥—供肥机理及其调节Ⅱ,棕壤型菜园土的腐殖质结合形态及 …

采自辽宁省不同地区的１５对棕壤型菜园土肥、瘦地及其各粒级微团聚体的有机质储量和腐殖质结合形态的研究表明,肥地及其各粒级微团聚 的有机质和各结合形态腐殖质的含量与松态腐殖质占有机质总理的比例比瘦地及其各相应粒级微团聚体的高、稳结态腐殖质的比例较小,紧结态腐殖质的比例肥瘦地大体相当,无论肥地或瘦地,闰级微团聚体的有机质和各结合形态腐殖质的含量及松、稳结态腐殖质占有机质总量的比例均较大粒级的高,而紧结态     

东北黑土成土母质培肥过程中土壤肥力变化特征

利用已设置14年的黑土成土母质(表层以下2.0～3.0 m深)培肥定位试验,研究不同农艺措施培肥后土壤肥力指标的变化特征,结合小麦盆栽耗竭试验评估土壤供肥能力,综合评价不同农艺措施对黑土母质培肥的效应。与初始母质相比,黑土母质培肥14年后,土壤总有机碳、全氮、团聚结构稳定性和其他养分含量均不同程度提高,土壤肥力水平的高低直接影响盆栽试验中土壤对小麦的供肥能力。主成分分析发现,母质经过14年的培肥,碳投入量较大的农田秸秆还田处理和苜蓿培肥处理与表层(0～20 cm)黑土更接近,其次是农田有机肥和自然草地培肥处理,农田单施化肥和不施肥处理培肥效果最差。14年连续的外源碳输入通过改善土壤团聚结构和进入土壤的碳分解转化,影响土壤的物理和生物化学性质,促进母质土壤肥力发育。农田秸秆还田、施用有机肥和种植苜蓿对黑土母质肥力提升效果最好,是保证黑土肥力和土壤培肥的有效措施,研究结果可为东北黑土区退化土壤培肥提供理论依据和指导。     

土壤保肥—供肥机理及其调节Ⅰ.棕壤型菜园土的P素保持与供应

对辽宁省北部、中部及南部的棕壤型菜园土１５对肥、瘦地的保Ｐ供Ｐ性能的测定表明,在绝大多数供试土样中,肥地及其各粒级微团聚体的全Ｐ量、Ｐ解吸量及Ｐ解吸率均大于瘦地及其各相应粒级微团聚体的,Ｐ吸附量则相反．不论肥地或瘦地,＜１０μｍ微团聚体均比＞１０μｍ微团聚体具有更大的Ｐ吸附能力．供试菜园土的＜１０μｍ微团聚体亦具有较大的供Ｐ潜势,其Ｐ解吸率比其他农用土壤相同粒级微团聚体的大１个数量级．     

土壤保肥-供肥机理及其调节 Ⅰ.棕壤型菜园土的P素保持与供应

对辽宁省北部、中部及南部的棕壤型菜园土15对肥、瘦地的保P-供P性能的测定表明,在绝大多数供试土样中,肥地及其各粒级微团聚体的全P量、P解吸量及P解吸率均大于瘦地及其各相应粒级微团聚体的,P吸附量则相反。不论肥地或瘦地,<10μm微团聚体均比>10μm微团聚体具有更大的P吸附能力。供试菜园土的<10μm微团聚体亦具有较大的供P潜势,其P解吸率比其他农用土壤相同粒级微团聚体的大1个数量级。     

九龙江流域杉木混交林土壤结构的分形研究

运用分形理论对九龙江流域4种类型杉木混交林土壤粒径的分形维数与土壤水稳性团聚体、团聚体含量及结构体破坏率关系进行研究,比较分析了不同类型杉木混交林土壤结构的分形维数,建立了土壤结构分形维数与土壤理化性质的回归模型.研究结果表明,杉木混交林土壤分形维数与土壤水稳性团聚体、团聚体含量、结构体破坏率及土壤理化性质呈显著回归关系,分形维数与0.25mm土壤颗粒含量线性负相关,与结构体破坏率呈线性正相关.杉木米老排混交林土壤团粒结构的分形维数最小,土壤结构、稳定性及肥力状况最好,而杉木巨尾按混交林土壤自我培肥能力最差.分形理论在林地土壤肥力研究上的应用为林地评价提供了新方法.     

黄土高原不同土壤质地农田土壤碳、氮、磷及团聚体分布特征

结合野外观测和室内分析,研究了黄土高原不同土壤质地农田土壤碳、氮、磷含量及其生态计量学特征,以及土壤团聚体分布状况,以揭示土壤质地对区域农田土壤肥力的影响,以及土壤团聚体对肥力的调控作用.结果表明: 黄土高原农田土壤大团聚体含量、主要养分含量及其生态计量比值均随土壤质地由细变粗(壤质黏土→黏壤土→砂质壤土)逐渐降低;土壤pH值和微团聚体含量则呈现出相反的变化趋势. 随土壤黏粒含量增加,大团聚体含量、有机碳、全氮和全磷含量,以及C/P和N/P显著增加,土壤pH和微团聚体含量显著降低. 土壤有机碳、全氮和全磷含量,以及C/P和N/P随大团聚体含量的增加显著增加.表明区域尺度上农田土壤肥力状况取决于土壤质地,并受土壤大团聚体的调节.     

烟草根际微生物研究

利用选择性培养基,对土壤肥力肥沃、中等、贫瘠的烟区根际细菌、真菌和放线菌进行了分离和测数。根据菌体形态及培养特征、生理生化指标及16S rDNA部分序列分析等,对根际自生固氮菌、磷细菌、钾细菌进行了鉴定和分类。主要结果为：土壤肥沃的烟区根际细菌的数量最多,土壤贫瘠的烟区数量最少;土壤贫瘠烟区根际真菌的数量较多,中等和肥沃烟区的较少;根际故线菌的数量随土壤肥力的降低而依次减小。从不同肥力烟区分离的根际自生固氮菌、磷细菌、钾细菌以革兰氏阴性杆菌为主,分别属于10个属。土壤的肥沃程度对根际3类细菌的种类和数量都有影响,总体上看,土壤肥沃和中等的条件下,细菌类群的多样性和丰富度较大,而贫瘠土壤细菌类群的优势度较大。     

Removal of vertebrate-dispersed fruits in vegetation on fertile and infertile soils

Summary The hypothesis that more plant species with vertebrate-dispersed fruits occur on fertile soils because there is a greater probability of fruit removal from the parent plant was tested at 16 sites around Sydney, Australia. Removal rates from artificial fruit spikes were two and a half times greater on fertile than infertile soil sites, although this was not quite statistically significant. High variability in removal rate between sites was evident irrespective of fertility. Most removal occurred during the day indicating that birds were important consumers, rather than nocturnal mammals. Bird abundance and diversity did not differ between soil types. More frugivorous species were found in plant communities growing on fertile soil. Two models could explain the patterns observed. Firstly, plants with vertebrate-dispersed fruits could be favoured on fertile soils because of a high abundance of frugivorous birds accomplishing seed dispersal. Alternatively, plants with vertebrate-dispersed fruits could be favoured on fertile soil sites for some other reason and frugivorous birds could be attracted to these areas of abundant food. The correlation between soil fertility and the percentage of vertebrate-dispersed fruits was stronger than the correlation between soil fertility and removal rates and suggests that the second model is more likely to be true. Frugivorous birds are unlikely to be responsible for the high percentage of species with vertebrate-dispersed fruits in fertile soil environments.     

长期施肥对红壤水稻土磷脂脂肪酸特性和酶活性的影响

对中国科学院红壤生态实验站长期定位试验中不同施肥处理红壤水稻土磷脂脂肪酸(PLFA)特性及酶活性进行了分析.结果表明:不同施肥处理的土壤酶活性、养分、微生物生物量及微生物群落多样性差异较大;施肥处理增加了PLFA的种类和微生物量;施肥土壤的真菌PLFA量大于不施肥土壤,细菌PLFA量小于不施肥土壤,说明真菌较细菌更能适应养分贫瘠的条件.NPK平衡施肥和施有机肥处理的PLFA总量均高于施无机氮肥和未施肥处理,两者分别比未施肥处理高222%和79%,表明NPK平衡施肥和施有机肥更有利于作物生长.施肥还可增加土壤酶活性,其中,土壤脲酶和磷酸酶活性可以作为衡量土壤肥力水平的指标.     

Influence of soil type,crop and air drying on residual carbohydrate content and aggregate stability after treatment with periodate and tetraborate

Summary The relationship between the water stability of microaggregates and the residual carbohydrate content of soil was examined in 15 soils from 7 soil series under various cultivations. The carbohydrate was progressively removed by increasing the time of treatment with 0.02M periodate and 0.1M tetraborate. The resulting decrease in reducing sugar content was significantly correlated with an increased disruption of microaggregates (>45 m) as determined by a turbidimetric method. The most effective treatment removed about 80% of the soil carbohydrate and caused an increase of about 75% in the fraction of microaggregates (<45 m) compared to untreated soil.15–20 percent of the soil carbohydrate was resistant to oxidation by periodate, even after prolonged reaction times and contained a higher relative proportion of glucose, arabinose, and xylose than the oxidised material. Sugars typical of microbial sources, mannose, galactose, rhamnose and fucose, were therefore preferentially oxidised by the periodate treatment.The grassland soils generally had higher carbohydrate contents than the arable soils and initially had a greater degree of aggregation. However, periodate oxidation affected each soil in its own characteristic manner. A significant inverse linear relationship between the degree of disruption and the residual sugar content was found with 13 of the 15 soils. Over the range measured aggregate stability was therefore related to the presence of carbohydrate predominantly from microbial sources.     

Spatial patterns of herbivory by gall-forming insects: a test of the soil fertility hypothesis in a Mexican tropical dry forest

It has been proposed that fertile soils reduce the incidence of gall-forming insect (GFI) species in plant communities. This is known as the soil fertility hypothesis. The main objective of this study was to analyze the spatial distribution of GFI species under different habitats in a tropical dry forest at the Chamela-Cuixmala Biosphere Reserve, Mexico. Eight habitats which differ in soil type, topography, nutrient availability and vegetation were chosen. We found that 38 GFI species specialize on their host plant species. GFI species richness was negatively correlated with phosphorous and nitrogen availability. Using phosphorous as an indicator of soil fertility, we found low frequency and density of GFI on fertile soils. Our study indicates that soil fertility is one of the factors that negatively affects the patterns of spatial distribution of species richness, incidence and abundance of GFI at the community level in two different ways: i) indirectly affecting GFI species richness in plants adapted to infertile soils and ii) directly affecting GFI responses to plant traits of hosts found in a fertility gradient.     

Plant functional assembly is mediated by rainfall and soil conditions in a seasonally dry tropical forest

Understanding how species assembly is influenced by the interplay of climate, local environmental conditions and human-caused disturbances remains a central question in ecology and conservation. Here, we assess how plant species abundance is determined by combinations of functional traits (ecological strategies) and interacting gradients of rainfall, soil conditions (fertility and field capacity) and chronic anthropogenic disturbance in a Caatinga dry tropical forest, Brazil. We tested for trait–environment relationships using multivariate methods (RLQ) accounting for groups of species sharing similar responses to gradients and similar expression of multiple traits (i.e. response groups). Overall, species’ abundances changed predictably in response to rainfall and soil fertility, and were mediated by functional traits, i.e. species with particular trait combinations tended to respond similarly to multifactorial conditions. Briefly, three ecological strategies emerged: species with low wood density and soft (i.e. lower dry matter content), thick leaves converged into a trait syndrome characterizing a drought-avoidance strategy through water storage. They were particularly abundant under extremely low precipitation and relatively high soil field capacity. Under conditions of increasing rainfall and decreasing soil field capacity, species with high wood density were favored, consistent with a drought-tolerance strategy. However, these species fell into two groups relative to leaf-investment: more conservative leaves (low SLA) on relatively fertile soils vs. thinner and softer (i.e. high SLA) leaves on unfertile soils. In seasonally dry tropical forests, low SLA on relatively fertile soils may represent a water conservation strategy. Unexpectedly, no ecological strategy emerged in response to disturbance. The patterns we uncovered help to understand the interplay between precipitation, soil fertility and anthropogenic disturbance in plant species filtering in seasonally dry tropical forests. Moreover, our results underline that impacts of future climate change will depend on how rainfall patterns covary with finer-scale environmental factors such as soil fertility and field capacity.