长期施肥下农田土壤-有机质-微生物的碳氮磷化学计量学特征

探讨外源养分的输入对土壤系统内碳、氮、磷化学计量特征的影响,对于深刻认识农田土壤有机碳(C)和养分循环及其相互作用过程具有重要意义。以26年的农田长期定位施肥试验为平台,分析长期不同施肥条件下土壤、有机态及微生物生物量碳、氮、磷含量及其化学计量学特征,并根据内稳性模型y=c x~(1/H)计算其化学计量内稳性指数H。结果表明:与长期撂荒处理(CK_0)相比,种植作物条件下26年化肥配施有机肥处理(MNPK和1.5MNPK)显著降低微生物生物量氮含量,但显著提高了微生物生物量磷的含量。相对于撂荒处理,即使长期配施化肥磷处理(NP、PK、NPK),其土壤有机磷降低显著。对于C∶N比而言,化肥配施有机物料处理(秸秆或有机肥)的土壤C∶N比、有机质C∶N及微生物生物量C∶N比均显著低于化肥处理(N、NP、PK和NPK)。对于C∶P比而言,相对于撂荒处理,26年施用磷肥(化肥磷或有机磷)显著降低了土壤C∶P比和微生物生物量C∶P比,而CK和偏施化肥处理(N、NP和PK)显著降低了土壤有机质C∶P比。对于土壤N∶P比而言,撂荒处理土壤N∶P比显著高于其他处理,而撂荒处理土壤有机质N∶P比显著高于CK和化肥处理,表明不施肥或化肥条件下作物种植加剧了土壤有机质中氮素的消耗。微生物生物量C∶N、C∶P、N∶P比的内稳性指数H分别为0.24、0.75、0.64,不具有内稳性特征。微生物生物量C∶N、C∶P、N∶P比分别与土壤C∶N、C∶P、N∶P比呈显著正相关关系,但与土壤有机质碳氮磷化学计量比之间无显著相关性。表明土壤碳、氮、磷元素的改变会直接导致微生物生物量碳、氮、磷化学计量比的改变,但微生物生物量碳氮磷化学计量比对土壤有机质碳氮磷化学计量比无显著影响,土壤有机质的碳氮磷计量比可能更多是受到作物和施肥等养分管理措施的影响。     

喀斯特区不同退化程度植被群落植物-凋落物-土壤-微生物生态化学计量特征

为摸清喀斯特植被退化对群落各组分C、N、P生态化学计量特征及内稳态特征的影响，为喀斯特退化生态系统植被恢复与重建提供科学依据，以桂西北喀斯特地区5种退化程度植被群落为研究对象，测定了不同退化程度植被群落植物叶片、凋落物、土壤和微生物生物量的C、N、P含量，分析其化学计量比特征、相互关系及植物内稳性特征。结果表明：(1)随着退化程度加剧，叶片C、N、P含量、N∶P和凋落物N∶P、微生物量C显著下降，而叶片C∶N、C∶P则显著增加，且植物叶片N∶P<14;随退化程度加剧，凋落物N、P含量、土壤C、N、P含量、微生物量N、P呈先略有增后显著降低的趋势，且不同退化程度群落土壤N∶P和微生物量C∶N无显著差异。(2)叶片N、P含量与土壤N、P含量，叶片C∶P与土壤C∶N、C∶P、N∶P,叶片N∶P与凋落物N、N∶P,叶片C、N、P含量与微生物量C呈显著或极显著正相关关系；叶片C∶N与土壤C、N,叶片C∶P与土壤N、P,叶片N∶P与土壤P呈显著或极显著负相关关系。(3)喀斯特地区植物叶片N、P元素的内稳性指数(H)平均值分别为2.74和2.31,属于弱稳态型，叶片N∶P的H值为5.14,为稳...     

广西大青山杉木人工林碳氮磷生态化学计量特征

为研究杉木人工林生态系统植物、凋落物和土壤碳(C)、氮(N)、磷(P)生态化学计量特征的差异和相互关系,以广西大青山杉木密度试验林为研究对象,测定了5种初植密度下杉木人工林针叶、草本、凋落物和土壤的C、N、P含量及其比值。结果表明:针叶的C、N、P含量最高,凋落物次之,土壤最低。C∶N、C∶P表现为凋落物针叶草本土壤,N∶P表现为凋落物草本针叶土壤。其中针叶的N∶P均值为16.69,凋落物C∶N显著高于N发生释放的C∶N的临界值(30)。杉木人工林针叶和草本N、C∶N呈显著负相关关系,针叶和土壤的C∶N、N∶P,草本和凋落物P含量、C∶P均呈显著正相关关系,体现了杉木生态系统内的C、N、P在针叶、草本、凋落物和土壤之间相互转化和循环。南亚热带杉木人工林植物生长受P限制,凋落物分解慢,土壤有机质的矿化作用慢,养分循环能力低,因此在人工林抚育管理中,应保护林下植被,适当施肥,提高土壤肥力,维持杉木林长期生产力。     

京东板栗主产区土壤氮磷钾的空间变异

采用经典统计学和地统计学相结合的方法,对京东板栗主产区迁西县土壤氮、磷、钾的空间变异进行了分析.结果表明：迁西县土壤全量氮、磷、钾和速效氮、钾的含量普遍较低,但表层土壤速效磷含量较高;氮、磷、钾的空间分布均表现为中等变异,且以磷的变异最大.表层土壤全氮和碱解氮的分布符合高斯模型,其空间变异主要由结构性因素决定;全钾和速效钾的分布分别符合球状模型和高斯模型,前者空间变异受结构性因素和随机性因素的共同影响,空间相关性为中等;后者主要受结构性因素的影响,空间相关性强烈.氮、钾在全县范围内的空间分布特征相似,高值区均出现在县域南部和西北部,而中部和东北部的含量较低.全磷的高值区主要分布在该县北部,速效磷高值区则分布在县区南部.氮、钾全量和有效态含量之间存在极显著正相关关系,但全磷和速效磷含量的相关性不显著.     

Effects of desertification on the C:N:P stoichiometry of soil,microbes, and extracellular enzymes in a desert grassland

为探讨荒漠草地沙漠化对“土壤-微生物-胞外酶”系统生态化学计量的影响机理, 该研究采用空间序列代替时间演替的方法, 研究了宁夏盐池荒漠草地沙漠化过程中土壤、土壤微生物及土壤胞外酶碳(C)、氮(N)、磷(P)生态化学计量的变异特征。结果表明: (1)随着荒漠草地沙漠化的不断加剧, 土壤C、N、P含量和土壤C:P、N:P均呈降低趋势, 而土壤C:N逐渐增加。(2)荒漠草地沙漠化过程中, 土壤微生物生物量C (MBC):微生物生物量P (MBP)、微生物生物量N (MBN):MBP和土壤β-葡萄糖苷酶(BG):N-乙酰氨基葡萄糖苷酶(NAG)逐渐降低, 而土壤BG:磷酸酶(AP)和NAG:AP基本表现为增加趋势。(3)随着荒漠草地沙漠化程度的加剧, 土壤微生物C利用效率CUE_C:N和CUE_C:P与土壤微生物N利用效率NUE_N:C和土壤微生物P利用效率PUE_P:C的变化趋势相反。(4)荒漠草地土壤、土壤微生物生物量和土壤胞外酶C:N化学计量(C:N, MBC:MBN, BG:NAG)与土壤、土壤微生物生物量和土壤胞外酶N:P化学计量(N:P, MBN:MBP, NAG:AP)显著负相关, 而土壤和胞外酶C:N化学计量(C:N, BG:NAG)与土壤和胞外酶C:P化学计量(C:P, BG:AP)显著正相关。土壤N:P与土壤MBN:MBP显著正相关, 而与土壤NAG:AP显著负相关。分析表明, 荒漠草地沙漠化过程中土壤微生物生物量及胞外酶活性随着土壤养分的变化而发生变化; 微生物-胞外酶C:N:P生态化学计量与土壤养分存在协变关系, 为理解荒漠草地土壤-微生物系统C、N、P循环机制提供理论依据。     

Dynamics of C,N, P and S in grassland soils: a model

We have developed a model to simulate the dynamics of C, N, P, and S in cultivated and uncultivated grassland soils. The model uses a monthly time step and can simulate the dynamics of soil organic matter over long time periods (100 to 10,000 years). It was used to simulate the impact of cultivation (100 years) on soil organic matter dynamics, nutrient mineralization, and plant production and to simulate soil formation during a 10,000 year run. The model was validated by comparing the simulated impact of cultivation on soil organic matter C, N, P, and S dynamics with observed data from sites in the northern Great Plains. The model correctly predicted that N and P are the primary limiting nutrients for plant production and simulated the response of the system to inorganic N, P, and S fertilizer. Simulation results indicate that controlling the C:P and C:S ratios of soil organic matter fractions as functions of the labile P and S levels respectively, allows the model to correctly simulate the observed changes in C:P and C:S ratios in the soil and to simulate the impact of varying the labile P and S levels on soil P and S net mineralization rates.     

Determination of the soil organic carbon, nitrogen, available phosphorus and the combined aboveground plant materials in the semi-arid Mbulu District, Tanzania

Soil of the semi-arid Mbulu District is part of the tropical soils, covered with sparse trees, shrubs or grasses in which domestic grazing animals have prevented the wide spread of vegetation cover. The study aimed at determining soil organic carbon (OC), total nitrogen (N), available phosphorus (P) and the combined aboveground plant materials. Six study sites were established in which soil samples were collected at the depths of 0–5, 6–10 and 11–20 cm. Soil samples were analysed for OC, N and P as well as the levels of N and P in the combined aboveground materials of Panicum coloratum and Hyparrhenia filipendula . The percentage concentrations of OC, N and P were high in the top soil than in the deeper soil horizons. However, analysis of variance showed significant differences of OC in some sites whereas no difference for N and P between soil depth classes. OC was highly related with N and P along soil depth classes. It was concluded that the availability of N and P was because of the decomposition of organic matter in the soil. Soil N and P were highly related with the same in the combined aboveground plant materials. It was concluded that the increased concentration of N and P in the soil resulted into availability of the same in P. coloratum and H. filipendula. There was a very high variation in N and P among sites with different levels of intensity of grazing. It was concluded that grazing animals contributes to the redistribution of soil elements in the rangelands because they graze upon plant parts but the excreta are dropped away from the grazed spot.     

中国南亚热带不同造林模式碳汇林土壤碳、氮、磷的积累及化学计量特征

碳汇林的固碳效益十分显著,是实现“碳中和”的主要碳增汇途径之一,在研究南亚热带地区不同造林模式碳汇林土壤碳汇的同时,研究碳汇林土壤氮、磷储量及土壤碳、氮、磷的生态化学计量特征,能够为不同造林模式碳汇林的土壤碳、氮、磷储量的评估提供科学依据。采取单因素随机区组设计,选择立地条件基本一致的研究区和4种造林模式(新造林、封山育林、补植套种、更新改造)的碳汇林,分析了不同造林模式土壤有机碳(SOC)、全氮(TN)、全磷(TP)的含量、储量、生态化学计量比,以及微生物生物量碳(MBC)的变化特征。结果表明,不同造林模式碳汇林的土壤理化性质,碳氮磷储量、化学计量比及微生物生物量碳含量差异显著,且土壤碳氮磷储量随土壤深度增加而减少,表现出明显的垂直变化特征。4种造林模式下碳氮比(C/N)介于11.11—17.86,碳磷比(C/P)介于17.00—242.59,氮磷比(N/P)介于1.18—15.99之间,在0—60 cm土层上均以更新改造模式林最低,封山育林模式下C/P和N/P均显著高于其他造林模式。土壤SOC与TN、N/P呈极显著正相关关系,土壤TN与C/P呈极显著正相关关系。综合来看,封山育林模...     

不同肥料对土壤养分三要素平衡与累积的影响

本文探讨不同肥料、施肥结构、施肥方法对土壤养分三要素平衡与累积的影响。结果表明,不同形态单位氮素投入对土壤氮素盈余影响为猪粪> 化肥> 稻草,对土壤全氮提高的影响为稻草> 化肥> 猪粪;不同形态单位磷素投入对土壤磷素盈余的影响为猪粪> 化肥> 稻草,对土壤全磷提高的影响为化肥> 猪粪> 稻草;不同形态单位钾素投入对土壤钾素盈余影响为化肥> 猪粪> 稻草,对缓解土壤钾素下降的影响为猪粪> 稻草> 化肥。     

Salinity effects on germination,growth, and seed production of the halophyte Cakile maritima

The growth ofEucalyptus regnans seedlings in forest soil is enhanced when it has been air-dried. In undried forest soil seedlings grow poorly and develop purple coloration in the foliage, indicating P deficiency. This paper reports the results of pot experiments designed to investigate the relationship between growth and P acquisition, ectomycorrhizal infection and age of seedlings grown in air-dried and undried soil. The effect on seedling growth of their inoculation with air-dried or undried soil or with ectomycorrhizal roots from plants growing in air-dried or undried soil was also investigated. Ectomycorrhizal root tips were detected in 3-week-oldE. regnans seedlings in both air-dried and undried soil, and from then on the frequency of ectomycorrhizal root tips increased rapidly. In air-dried soil, seedlings were fully ectomycorrhizal at 9 weeks, and the occurrence of maximum ectomycorrhizal infection coincided with enhanced P acquisition and the initiation of rapid seedling growth. In undried forest soil, seedling growth remained poor, even though the seedlings had well-developed ectomycorrhizae and the incidence of ectomycorrhizal root tips was the same as in air-dried soil. The dominant ectomycorrhizae in airdried soil were associated with an ascomycete fungus, whereas in undried, undisturbed soil they were commonly associated with basidiomycete fungi. Inoculation of sterile soil/sand mix with washed ectomycorrhizal roots from air-dried soil increased the P acquisition and growth of the seedlings significantly compared with controls, whereas ectomycorrhizal inocula from undried soil had no effect on seedling growth, although both inocula resulted in a similar incidence of ectomycorrhizal root tips. Similarly, addition of a small amount of air-dried soil into sterile soil/sand mix resulted in a significantly greater increase in the P content and dry weight of the seedlings, compared with the control, than addition of undried soil. In both treatments, the incidence of ectomycorrhial root tips was similar. As (i) the differentiation in seedling growth between air-dried and undried soil occurred after seedlings became ectomycorrhizal, (ii) the dominant ectomycorrhizae in air-dried soil were different from those in undried soil, and (iii) inocula from air-dried soil, but not from undried soil, stimulated seedling growth in sterile soil/sand mix, it is concluded that development of particular ectomycorrhizae may be involved in seedling growth stimulation and enhanced P acquisition associated with air drying of forest soil.     

水分对敦煌阳关湿地芦苇叶片与土壤C、N、P生态化学计量特征的影响

土壤水分是影响干旱区植物养分吸收和利用策略的关键因子之一。研究不同水分梯度叶片与土壤生态化学计量特征,有助于揭示植物对环境变化的响应特征及生态适应性。通过野外调查与实验分析,对敦煌阳关不同水分梯度芦苇叶片与土壤碳(C)、氮(N)、磷(P)生态化学计量特征及其关系进行了研究。结果表明:(1)随土壤含水率升高,叶片C、N、P含量降低,叶片C/N、C/P、N/P升高。(2)随土壤含水率升高,土壤有机碳(OC)、总氮(TN)、总磷(TP)含量及土壤N/P升高,土壤C/N降低,土壤C/P先升后降。(3)低水分梯度叶片N、C/N与土壤N、C/N显著负相关(P0.05),叶片C、P、C/P、N/P与土壤C、P、C/P、N/P无显著相关性(P0.05);高、中水分梯度叶片C、N、P与土壤C、N、P化学计量特征相关性均不显著(P0.05)。低水分梯度叶片受干旱胁迫和土壤养分制约,且能够保持较高的叶养分含量,体现了干旱区湿地植物异质生境下独特的养分调节机制。     

Interaction of phosphorus and molybdenum and the availability of zinc,copper, manganese,molybdenum and phosphorus in waterlogged rice soil

Summary Laboratory incubation experiments were conducted with low-land rice soil to study the effect of applying three different levels of molybdenum (0, 2.5 and 5.0 ppm) and phosphorus (0, 100 and 200 ppm), in all possible combinations, on the changes in available Mo, P, Mn, Zn and Cu in soil. The results showed that application of Mo at both the levels increased the content of extractable Mo and P but decreased those of Cu and Mo in soil whereas application of Mo at higher level only increased the content of extractable Zn in soil. Application of P at both the levels decreased the content of extractable Mo, Mn and Cu but increased that of P whereas it showed an inconsistent effect on the extractable Zn content in soil. The P × Mo interaction effect was found to be beneficial for the content of P, Mo and Zn only. During the initial period of incubation all elements except Cu recorded an increase but with the progress of incubation period the content of all the elements except Mn gradually declined.     

Effects of root-knot nematodes on cucumber leaf N and P contents, soil pH, and soil enzyme activities

A pot experiment was conducted to study the effects of inoculation with root-knot nematodes on the cucumber leaf N and P contents, and the rhizospheric and non-rhizospheric soil pH and enzyme activities. The rhizospheric soil pH didn't have a significant decrease until the inoculation rate reached 6000 eggs per plant. With the increase of inoculation rate, the leaf N and P contents, rhizospheric soil peroxidase activity, and rhizospheric and non-rhizospheric soil polyphenol oxidase activity all decreased gradually, rhizospheric soil catalase activity was in adverse, non-rhizospheric soil pH decreased after an initial increase, and non-rhizospheric soil catalase activity had no regular change. After inoculation, rhizospheric soil urease activity decreased significantly, but rhizospheric and non-rhizospheric soil phosphatase activity and non-rhizospheric soil peroxidase activity only had a significant decrease under high inoculation rate. In most cases, there existed significant correlations between rhizospheric soil pH, enzyme activities, and leaf N and P contents; and in some cases, there existed significant correlations between non-rhizospheric soil pH, enzyme activities, and leaf N and P contents.     

沙化草地土壤碳氮磷化学计量特征及其对植被生产力和多样性的影响

沙化草地土壤碳(C)、氮(N)、磷(P)化学计量特征及其对植被生产力与多样性的影响对于认识草地沙漠化过程中土壤与植被的互馈关系,以及沙漠化发展的生态学机理具有重要的意义。通过对科尔沁沙地75个沙化样地的野外调查,研究了科尔沁沙地不同程度沙化草地的表层土壤C、N、P化学计量特征及其与生产力和多样性的相关关系。结果表明:1)科尔沁沙地沙化草地表层土壤具有较低的有机C、全N、全P含量及C∶N、N∶P和C∶P,平均值分别为1.39 mg/g、0.117 mg/g、0.079 mg/g和7.50、2.22、16.91;草地沙漠化过程中,土壤有机C、全N、全P含量显著降低的同时,C∶N、N∶P和C∶P亦显著降低,表明土壤有机C、全N、全P在沙漠化过程中的损失是不同步的;2)科尔沁沙地沙化草地表层土壤有机C、全N、全P元素间均呈显著正相关,具有一定的耦合关系,且土壤有机C和全P间的耦合关系不随沙漠化的发展而发生改变;3)草地沙化过程中,土壤养分的损失限制着草地生产力,而土壤N∶P较全N、全P含量更能反映土壤养分对生产力的限制作用;4)沙化草地土壤全N含量与物种丰富度间具有显著正相关关系,而土壤全P含量与其无显著相关性;多样性指数与全N、全P含量间均具有显著正相关关系;相对于土壤全N、全P含量,N∶P能更好地反映养分平衡对物种多样性的影响作用。     

The influence of time,soil characteristics,and land‐use history on soil phosphorus legacies: a global meta‐analysis

Agriculturally driven changes in soil phosphorus (P) are known to have persistent effects on local ecosystem structure and function, but regional patterns of soil P recovery following cessation of agriculture are less well understood. We synthesized data from 94 published studies to assess evidence of these land‐use legacies throughout the world by comparing soil labile and total P content in abandoned agricultural areas to that of reference ecosystems or sites remaining in agriculture. Our meta‐analysis shows that soil P content was typically elevated after abandonment compared to reference levels, but reduced compared to soils that remained under agriculture. There were more pronounced differences in the legacies of past agriculture on soil P across regions than between the types of land use practiced prior to abandonment (cropland, pasture, or forage grassland). However, consistent patterns of soil P enrichment or depletion according to soil order and types of post‐agricultural vegetation suggest that these factors may mediate agricultural legacies on soil P. We also used mixed effects models to examine the role of multiple variables on soil P recovery following agriculture. Time since cessation of agriculture was highly influential on soil P legacies, with clear reductions in the degree of labile and total P enrichment relative to reference ecosystems over time. Soil characteristics (clay content and pH) were strongly related to changes in labile P compared to reference sites, but these were relatively unimportant for total P. The duration of past agricultural use and climate were weakly related to changes in total P only. Our finding of reductions in the degree of soil P alteration over time relative to reference conditions reveals the potential to mitigate these land‐use legacies in some soils. Better ability to predict dynamics of soil nutrient recovery after termination of agricultural use is essential to ecosystem management following land‐use change.     

森林类型对土壤有机质、微生物生物量及酶活性的影响

以澳大利亚南昆士兰州典型森林类型——湿地松、南洋杉和贝壳杉林为对象,开展土壤可溶性有机碳和氮(SOC和SON)、微生物生物量碳和氮(MBC和MBN),以及土壤酶活性的研究,剖析森林类型对土壤质量的影响.结果表明:不同林型土壤SOC、SON含量分别在552 ～1154 mg·kg-1和20.11～57.32mg·kg-1;MBC、MBN分别在42～149 mg·kg-1和7～35 mg·kg-1.MBC、MBN之间呈显著相关.土壤几丁质酶、酸性磷酸酶、碱性磷酸酶和β-葡萄糖苷酶的活性分别为2.96 ～7.63、16.5 ～29.6、0.79 ～ 3.42和3.71 ～9.93 μg ·g-1·h-1,亮氨酸氨肽酶活性为0.18～0.46 μg·g-1·d-1.不同林型土壤SOC含量,以及土壤几丁质酶和亮氨酸氨肽酶活性为湿地松林、南洋杉林、贝壳杉林依次降低;而SON含量为南洋杉林＞贝壳杉林＞湿地松林,且南洋杉林的SON含量显著(P＜0.05)高于湿地松林;MBC和MBN以及碱性磷酸酶活性为贝壳杉林＞湿地松林＞南洋杉林;酸性磷酸酶和β-葡萄糖苷酶活性为湿地松林＞贝壳杉林＞南洋杉林.在土壤生物代谢因子中,MBC、MBN、SON和亮氨酸氨肽酶对不同森林类型土壤影响较大.     

帽儿山5种林型土壤碳氮磷化学计量关系的垂直变化

采用土壤分层取样法测定了帽儿山地区相同气候条件、不同立地条件下林龄相近的2种人工针叶林(红松林和兴安落叶松林)和3种天然落叶阔叶林(蒙古栎林、杨桦林、硬阔叶林)的土壤碳(C)、氮(N)、磷(P)元素含量,以及土壤容重、土壤厚度等,研究土壤C、N、P含量和密度及化学计量关系的垂直变化特征.结果表明: 不同林型间土壤C、N、P含量和密度差异显著,其中硬阔叶林土壤O层和A层的C、N含量和密度均显著高于其他林型.所有林型土壤的C、N含量均随土层加深而下降;落叶阔叶林土壤P含量随土层加深而显著下降,但针叶林各土层间P含量差异不显著.不同林型间A层土壤C/N、O层土壤N/P,以及A和B层土壤C/P均存在显著差异.不同林型间土壤C-N存在显著的线性关系,且其斜率和截距在林型间差异均不显著,但土壤N-P、C-P关系只在阔叶林中存在显著相关关系.这表明不同林型间土壤C-N耦联关系有趋同现象,而土壤N-P和C-P关系随林型而变.     

植物残体对青藏高原高寒草甸土壤、微生物和胞外酶C∶N∶P化学计量特征的影响

植物残体是引起土壤、微生物和胞外酶C∶N∶P改变的关键因素,但是其作用机理尚不明确。本研究以青藏高原东缘高寒草甸为对象,通过测定土壤、微生物生物量和胞外酶活性等指标,探究移除地上植物或根系及植物残体添加对土壤、微生物和胞外酶C∶N∶P的影响。结果表明: 与无人为扰动草甸相比,移除地上植物显著降低了土壤C∶N(变幅为-23.7%,下同)、C∶P(-14.7%)、微生物生物生物量C∶P、N∶P,显著提高了微生物生物量C∶N、胞外酶C∶N∶P。与移除地上植物相比,移除地上植物和根系显著降低了土壤C∶N(-11.6%)、C∶P(-24.0%)、N∶P(-23.3%)和微生物生物量C∶N,显著提高了微生物生物量N∶P和胞外酶N∶P;移除地上植物后添加植物残体显著提高了微生物生物量C∶N、C∶P和胞外酶C∶N,显著降低了胞外酶N∶P。与移除地上植物和根系相比,移除地上植物和根系后添加植物残体显著降低了土壤C∶N(-16.4%)、微生物生物量C∶P、N∶P和胞外酶N∶P,显著提高了胞外酶C∶N。综上可知,去除植物显著影响土壤、微生物和胞外酶的C∶N∶P,微生物生物量和胞外酶C∶N∶P对植物残体的响应更为敏感。有无根系是添加植物残体时土壤、微生物和胞外酶的生态化学计量稳定性强弱的关键所在。添加植物残体的措施适用于植物根系尚且完好的草甸,有利于高寒草甸土壤碳固存,对没有根系的草甸土壤可能不适用,会增加土壤CO₂排放。     

贵州月亮山5种森林类型土壤生态化学计量特征研究

为了解贵州省月亮山森林土壤的化学计量特征,分层采集5种森林类型的土壤,测定C、N、P含量并分析化学计量特征。结果表明,5种森林类型0~20 cm土壤中变异最大的是P,20~100 cm土壤中变异最大的是C,最小的是N。5种森林类型0~10 cm土壤的C、N含量远高于中国陆地0~10 cm土壤的平均含量,而P含量远低于其平均含量。硬阔和软阔自然林土壤C、N、P含量存在明显差异,C含量为硬阔自然林软阔自然林,N和P含量基本呈现为软阔自然林硬阔自然林。不同森林类型土壤的C∶N为硬阔自然林软阔自然林,针阔混交林杉木和马尾松纯林。硬阔和软阔自然林、针阔混交林的C∶P、N∶P均随土层深度的增加而下降,而杉木和马尾松纯林的C∶P、N∶P随土层深度增加呈先下降后升高再下降的趋势,且均在30~50 cm处出现累积峰。相关分析表明0~100 cm土壤的C、N、P含量呈极显著正相关关系,土壤C含量、N含量与C∶N、C∶P、N∶P均呈极显著的正相关关系,P含量与C∶N呈极显著正相关关系(P0.001)。因此,贵州月亮山5种森林类型和不同土层的C、N、P含量及其化学计量特征存在显著差异。     

鼎湖山3种演替阶段森林土壤C、N、P现状及动态

为探讨森林演替过程中土壤C、N、P的变化,通过测定鼎湖山3种演替阶段的森林土壤有机碳(SOC)、总氮(TN)、总磷(TP)含量,对他们的化学计量进行分析。结果表明,鼎湖山3种森林土壤SOC和TN随演替阶段而增加,演替中后期表层土壤(0~20 cm)与演替初期的差异达到显著水平(P0.05),在土壤剖面上的分布都呈现显著的表层富集现象,且表层土壤与其他土层均有显著差异(P0.05)。土壤TP含量随演替阶段没有呈现出有规律的变化,不同演替阶段间也没有显著差异,但不同演替阶段土壤TP在土壤剖面上的分布表现不同,演替前期土壤TP含量随着土层深度增加而增加,演替后期土壤TP随土层深度的增加而降低,而演替中期土壤TP含量在各土层间没有显著差异。土壤C∶N不受土层深度和演替进程的影响,而土壤C∶P和N∶P均表现为随演替阶段而增加,随土层加深而降低。这些揭示了森林土壤SOC、TN和TP含量随演替进展及其在土壤剖面上的分布取决于土壤C、N、P的来源方式。