兰州大学机构库 >生命科学学院
青藏高原高寒草甸不同放牧强度与施肥处理条件下土壤氮素矿化季节动态
Alternative TitleThe Seasonal Dynamics of the Soil Nitrogen Mineralization Under the Different Grazing Intensity and Fertilizing Treat- ment in the Apline Meadow of Qing Hai-Tibetan Plateau
杨玉民
Subtype硕士
Thesis Advisor杜国祯
2007-05-27
Degree Grantor兰州大学
Place of Conferral兰州
Degree Name理学硕士
Degree Discipline生态学
Keyword青藏高原 Qinghai-tibetan plateau 高寒草甸 alpine meadow 放牧强度 grazing intensity 施肥处理 fertilizationtreatment 氮素矿化 nitrogen mineralization 有效养分 effective nutrients 地上生物量 overground biomass
Abstract

为了探索青藏高原高寒草甸牧区草地退化原因及恢复措施,评价不同放牧强度与不同施肥梯度对土壤氮素矿化的影响,我们于2005年4月-2005年10月在青藏高原东部高寒草甸牧区进行了两个实验:不同放牧强度对土壤氮素矿化的影响实验、不同施肥梯度对土壤氮素矿化的影响实验。

1.不同放牧强度对土壤氮素矿化的影响实验:放牧实验的三个样地设置于青藏高原典型高寒草甸由重到轻的放牧退化梯度上。其中:居民点:距宿营点(牧民定居点)0.5km,代表重度退化草甸,用Ⅰ组表示;围栏外:距宿营点(牧民定居点)1.5km,代表中度退化草甸,用Ⅱ组表示;围栏内:距宿营点(牧民定居点)1.5km,代表轻度退化草甸,用Ⅲ组表示。在每个放牧退化梯度上(居民点、围栏外、围栏内),均设置面积20m×50m的样带。在长50m的主样带上每隔10m设置1个子样带(每条主样带上共3个子样带)。在子样带上进行地上植物量、根生物量及土壤取样及PVC埋管。每次埋管之后的40天为野外原位培养时间(相邻2次埋管的时间间隔)。40天培养期满后,进行样品采集。植物样本用1.5m 2样方框取样,根生物量样本以及土壤样本用普通管型土钻取样(15cm深,100cm 3/钻)。将每3土钻(或每3个经过野外培养后的PVC管内土壤)混匀合成1个土壤样品,对氮磷钾及生物量进行测定分析。2.不同施肥梯度对土壤氮素矿化的影响实验:尿素施肥实验的三个样地设置于青藏高原典型高寒草甸的半阳坡、滩地、半阴坡的三个围栏内。其中:半阳坡:代表中氮施肥处理组(50g/m 2,相当于23.2 gN/m 2),用Ⅳ组表示;滩地:代表低氮施肥处理组(25g/m 2,相当于11.6 gN/m 2),用Ⅴ组表示;半阴坡:代表对照处理组(0g/m 2,相当于0gN/m 2),用Ⅵ组表示。在三个围栏内分别对土壤做尿素(CO(NH 2)2)施肥与对照处理。在每个围栏内分别设置东西走向30m×50m的样带(东西长50米,南北宽30米)。在样带内各设两个长50米,宽10米的主样带;两个主样带间距10米,距离样带边沿各10米。每个主样带上埋6只PVC管;在两个主样带与样带边沿的两个10m×50m的范围内进行植物、根生物量样本以及土壤样本的取样,取样方法同实验(1)。

试验结果表明:1.在放牧强度对氮矿化的影响实验中:随着放牧强度加强,土壤全氮、硝态氮含量明显升高,氨态氮则相反。在不同放牧强度下,0-15cm土壤全氮、硝态氮的储量变化明显:Ⅰ组>Ⅱ组>Ⅲ组(P<0.05);同时,土壤全氮含量季节动态明显,峰值出现在7月,最低值出现在4月;净氮矿化率的峰值出现在中牧-轻牧的水平上,中牧区净氮矿化率明显高于重牧区和轻牧区(P<0.05)。0-15cm土壤净氮矿化率五月份各组间差异不显著(P>0.05),7、8、10月份重牧区(Ⅰ组)、中牧区(Ⅱ组)、轻牧区(Ⅲ组)各组之间差异显著(P<0.05);随着放牧强度的加强,地上生物量在每个月份内明显下降。Ⅲ组>Ⅱ组>Ⅰ组(P<0.01),峰值都出现在8月;根生物量4、5、7月份表现为Ⅲ组>Ⅱ组>Ⅰ组;8月份:Ⅱ组>Ⅲ组>Ⅰ组;10月份:Ⅰ组>Ⅱ组>Ⅲ组(P<0.05)。2.在施肥梯度对氮矿化的影响实验中:施肥处理对土壤氮素矿化有明显的激发效应,产生激发效应的主要原因有两个:施肥刺激了MIT平衡体系、施肥刺激了根际微生物的活性。在激发效应的影响下,全氮、铵态氮、硝态氮的含量:CO(NH 2)2施肥处理明显比对照处理高,中氮处理明显比低氮处理高:Ⅳ组>Ⅴ组>Ⅵ组(P<0.05);净铵化率与净氮矿化率:施肥处理明显比对照处理高,中氮处理明显比低氮处理高:Ⅳ组>Ⅴ组>Ⅵ组(P<0.05);净硝化率恰好相反:施肥处理明显比对照处理低,中氮处理明显比低氮处理低,Ⅳ组<Ⅴ组<Ⅵ组(P<0.05);随着施肥量的增加,地上生物量与根生物量明显增加(P<0.05)。Ⅳ组(中氮处理)>Ⅴ组(低氮处理),Ⅴ组(低氮处理)>组Ⅵ(对照处理)。地上植物量与根生物量的峰值分别出现在8月和10月。

Other Abstract

For the aim of assessing the influence of the different grazing intensity andfertilization grads on the soil nitrogen mineralization and for the sake of seeking afterthe causation of degradation and the measures of comeback of the pasture in theAlpine Meadow of Qinghai-Tibetan Plateau.In the dry season ranging from Aprilto October of 2005,using the closed-top and interred-tube incubation method, twoexperiments were conducted:the experiments on the impact of the different grazingintensity and fertilization grads on the soil nitrogen mineralization.

(1).In the grazing intensity experiment,three sampling plots,witch with the area of 20m×50m,werechosen and located in three habitats with marked differences of grazing intensity.Residenter locus,plots outside the enclosure and inside the enclosure.they representedheavy-grazing,medial-grazing and light-grazing respectively,and we marked them with groupⅠ,groupⅡand groupⅢ.in every sampling plot, we setup three branchessampling plots with 10 meters spacing.and then intered PVC tubes,after 40 days, incubation,we took out the PVC tubes and synchronously collected the overgroundbiomass and root biomass.then took the samplings of the soil,plant and roots tolaboratory to analysed the contents of nitrogen,phosphorus and kalium,afterword,netmineralization rate,net ammonification tate and net nitrification rate were calculatedrespectively.(2)In the fertilization treatments experiment,three habitats with dirrerentwater-heat conditions were selected.There were bottomland(BOT)、sunnyslope(SUS)and shade slope(SHS)represently.and respectively represented medial-fertilization,treatment(groupⅣ,50g urea/m 2)and the low-fertilization treatment(groupⅤ,25g urea/m 2),control experiment(groupⅥ,0g urea/m 2),witch were equal to23.2g N/m 2,11.6g N/m 2,0g N/m 2 respectively.in every sampling plot,we setup threebranches sampling plots with 10 meters spacing.and then intered PVC tubes,after 40days, incubation, we took out the PVC tubes and synchronously collected the overground biomass and root biomass.then took the samplings of the soil,plant androot to laboratory to analyse the contents of nitrogen,phosphorus and kalium, afterword, net mineralization rate,net ammonification tate and net nitrification ratewere calculated respectively.

Our results showed that:(1)In the grazing intensity experiment, along with theenhance of the intensity of grazing,both the total N and theNO 3--N of the soilascended significantly,that is:groupⅠ>groupⅡ>groupⅢ(p<0.05);but thecontents of NH 4+-N(ammonium)just appeared an opposite trend:group<Ⅰgroup<Ⅱ<groupⅢ(p<0.05);the peak value of the total nitrogenoccued in July and the minimum appeared in April;the peak value of net nitrogenmineralization rate showed up at the level of medium grazing–light grazing,the netnitrogen mineralization rate in the groupⅡwas significantly higher than that in thegroupⅠand groupⅢ(p<0.05);to the net mineralization rate of the soil in May in uplayer of 0-15cm,there were no significant differences among thegroups(p>0.05),howere in July,August and September, the differences among thegroups ofⅠ,Ⅱ,Ⅲwere so significant (p<0.05);and that along with the enhance ofthe grazing intensity,in every month,the biomass aboveground declined markedly:groupⅢ>groupⅡ>groupⅠ(p<0.01),all the peak value appeared in August;thebiomass of root in April,May and July showed:groupⅢ>groupⅡ>groupⅠ;August:groupⅡ>groupⅢ>groupⅠ; October: groupⅠ>groupⅡ>groupⅢ(p<0.05).(2)In the fertilization treatments experiment,there was obviously kindling effectof fertilization treatments on nitrogen mineralization of soil. and two main reasonsexisted,one wsa that fertilization stimulated the banlance system of MIT and the otherwas that fertilization stimulated the activities of the microbes round thr roots of theplants.for the contents of the total nitrogen,ammonium nitrogenand nitrition nitrogen in the soil:therewas coincident trend of changing:groupⅣ(medium N treatment)>groupⅤ(low N treatment)>groupⅥ(control expreiment)(p<0.05);.for the netammonitrification rate and net nitrogen mineralization rate:groupⅣ(medium Ntreatment) >groupⅤ(low N treatment)>groupⅥ(control expreiment)(p<0.05);whereas,for the net nitrification,there was obviously an opsite resultcompared with the results of the both before:groupⅣ(medium N treatment)<groupⅤ(low N treatment)<groupⅥ(control expreiment)(p<0.05);along withthe increase of the quantity of fertilization, the weight of the biomass-abovegroundand roots augmented distinctly:groupⅣ(medium N treatment)>groupⅤ(low Ntreatment)>groupⅥ(control expreiment)(p<0.05);The peak value of the weight ofboth aboveground-biomass and roots appeared in August and October represently.

Subject Area植物生态学
MOST Discipline Catalogue理学 - 生态学
URL查看原文
Language中文
Other Code262010_042020138
Document Type学位论文
Identifierhttps://ir.lzu.edu.cn/handle/262010/533319
Collection生命科学学院
Affiliation
兰州大学生命科学学院
Recommended Citation
GB/T 7714
杨玉民. 青藏高原高寒草甸不同放牧强度与施肥处理条件下土壤氮素矿化季节动态[D]. 兰州. 兰州大学,2007.
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