全 文 ：第 16 卷 第 1 期
Vol. 16 No . 1
草地学报
ACTA AGRESTIA SINICA
2008 年 1 月
Jan. 2008
博士论文摘要
环县典型草原放牧家畜践踏的模拟研究
博士生 :林慧龙导师:任继周
(兰州大学草地农业科技学院, 甘肃草原生态研究所, 兰州 730020)
践踏是放牧家畜对草地的三大影响因素之一, 也是导致
草原全面退化的主要原因。但是由于技术和方法的限制, 相
关报道较少,极大地削弱了对草地农业生态系统的主体- 草
畜界面生态动力机制的整体认识。基于此 ,在我国干旱半干
旱的黄土高原典型草原区 兰州大学环县草畜生产系统野
外实验点,通过滩羊夏季轮牧试验践踏强度的跟群观测、践
踏同质性试验、模拟降水与试验践踏双因子试验进行了为期
2 年的系列研究。主要结果如下 :
1. 提出践踏强度是在特定的放牧方式(自由放牧或轮
牧)下, 单一种或组合种畜群单位时间内(指一个放牧季 )对
单位草地面积所施加的践踏重力或践踏面积,它应有三种表
示方法:重力表示法、面积表示法、频率表示法。首次提出了
践踏单位和践踏当量概念,以明确践踏强度计算标准和折算
标准,有助于践踏强度表示方法的规范。
2. 通过不同放牧强度下轮牧试验的跟群观测, 获得了家
畜践踏强度依放牧强度的幂函数式增大的定量结论, 揭示了
放牧强度与践踏强度的关系, 为调控践踏提供了实践途径,
为制定科学的放牧制度提供新的理论与实践基础。
3.研制了模拟践踏器,通过对试验践踏样区与传统的滩
羊夏季轮牧样区土壤和植被的 6 项指标对比研究表明,模拟
践踏与滩羊践踏具有同质性,为本研究提供了将践踏与采食
和排泄的影响区分开来的试验手段,使研究更加精确。
4. 以 0~ 10 cm 地下生物量为目标函数,以践踏强度、牧
草生长期降水量为决策变量的践踏、降水耦合模型, 以地下
生物量最大化为准则, 进行解析和寻优分析, 确定出环县典
型草原适宜的放牧强度是 3. 84- 5. 09 羊单位/ hm2。
5. 对模拟降水与试验践踏的双因子野外控制试验的 48
个试验处理组合的 5 项土壤化学指标进行分析, 结果表明土
壤化学性状对模拟降水更为敏感。践踏强度与模拟降水量交
互效应对碱解氮( mg/ kg )、全磷( % )、有机质 ( % )影响显著,
说明践踏和模拟降水均是引起土壤化学性质变化的驱动因素。
6. 对不同试验组合样区表土 ( 0~ 15 cm )质地的机械组
成,利用分形模型计算土壤粒径分形维数, 结果表明: 分维数
指标对践踏强度呈负相关,即践踏强度越大土壤的分维数值
越小。但分形维数递减幅度与模拟降水处理水平相关, 在模
拟降水处理水平依次为干旱、自然降水、平水、丰水时, 粒径分
形维数递减幅度依次为 4. 33%、2. 61%、1. 34%和 1. 23%。降
水与践踏的匹配关系,对形成确定的分形维数具有决定性作
用,其回归模型是: F = 2. 427+ 2. 0982 10- 4 W - 1. 3333
10
- 4
T。土壤侵蚀过程在土壤颗粒分形维数上亦可表现为
分形维数降低,因此 ,土壤分形维数测算对土壤侵蚀程度评
估具有一定指示意义。
7. 以牧草生长期单位面积累计践踏量和模拟降水量为
自变量的土壤可蚀性 K 值的 ANN ( A rt ificial Neural Net-
w orks)关系模型具有较好的拟合结果和预测能力, 说明直接
从输入到草地生态系统的外侵蚀营力着手,跨越系统内土壤
可蚀性变化的内在的复杂的隐含过程建立的输出端- 土壤
可蚀性 K 值与土壤侵蚀外营力的 ANN 关系模型, 是准确确
定土壤可蚀性 K 值的一次成功尝试。
8. 模拟降水和试验践踏通过各种不同的组合方式改变
土壤抗蚀力,从而起到对草地土壤侵蚀的增减作用。在牧草
生长期,中、高强度践踏对土壤的扰动, 加剧了干旱状况下土
壤风蚀的风险,降水具有双向调节作用, 但其对土壤侵蚀的
限制作用小于践踏对侵蚀的增加。构建以试验期土壤侵蚀模
数为因变量,以践踏、模拟降水累计量为自变量的机理模型,
可为黄土高原放牧地土壤侵蚀产沙量提供计算方法。据此,
以土壤侵蚀最小化为目标,对于不同的牧草生育期降水量解
析得到的最适放牧强度,对正确确定载畜量是一次新尝试。
关键词: 践踏; 践踏单位; 践踏当量; 践踏强度; 试验践踏 ; 模型
中图分类号: S812 文献标识码: A 文章编号: 1007-0435( 2008) 01-0097-03
完成时间: 2007年 5月
收稿日期: 2007-12-24; 修回日期: 2008-01-09
基金项目: 国家自然科学基金( 30771529)、国家科技支撑计划( 2006BAD16B01)和教育部博士点基金( 20030730008)
作者简介: 林慧龙( 1965-) ,男,汉族,副教授,博士,主要从事草地农业生态学的研究和教学, E-mail: linh uilong@ lzu . ude. cn
导师简介: 任继周( 1924-) ,男,教授,中国工程院院士,研究方向为草业科学, E-mail: Renjiz@ lzu. edu. cn
草地学报 第 16卷
Quantitative Studies of the Effects of Trampling on Typical Steppe
of Huanxian in Eastern Gansu, China
Candidate: LIN Hu-i long Adv isor: REN J-i zhou
( College of Pastoral Agricu lture Science an d T echnology, Lanzhou U niver sity, Gansu Gras sland E cological
Research Inst itute, Lanzhou 730020, China)
Trampling is one o f the three impact act ivities ( t rampl ing, defoliat ion, and excret ion) performed by a
grazing animal on gr assland and also the major reason for range degradat ion. L it t le is known about the re-
sult of t rampling- induced feedback among the soil environment , g rass, and their interrelationship. In add-i
t ion, more information is needed about the effects of animal t rampling on the managed g razing ecosy stems.
In typical steppe of loess plateau reg ions, w her e the management object ive is to maintain the g rassland eco-
system structure and funct ion, the impacts of g razing t rampling could be a serious problem. The object of
the study w as to separately evaluate the ef fect o f t rampling on the typical steppe in Huanxian County,
eastern Gansu Pr ovince, China. A series of f ield experiments w ere conducted fo r tw o years including the
tailing- up observ at ion of trampling intensity of T an-sheep in summer ro tat ional grazing t rail, t rampling
homogeneity t rial, tw o- facto r t rail o f simulated precipitat ion and experimental tr ampling. T he results are
as follow s.
1. Trampling intensity ( T I) w as proposed by this paper as the tr ampling area o r tr ampling pressure
created by a single or mult iple gr azing liv esto ck per hectar e during a unit time under free or rotat ional gr az-
ing. It had three expression methods: t rampling pressure method, trampling area method, t rampling f re-
quency method. The t rampling unit and Trampling Equivalent U nit ( TEU ) w ere put forw ard for the f ir st
time in order to def ine the calculation and conversion standard of T I.
2. By tailing-up obser vation of the f locks on typical steppe of H uanxian County in Eastern Gansu
Province, China, the regression analy sis shows that liv estock t rampling intensity w as increased by the
pow er funct ion of g razing intensity . T his fully demonst rated that the t rampling effects played a key ro le in
the w holesomeness maintenance of grassland and the adjustment and control of the t rampling effects of
grazing livestock should be an impor tant aspect of g razing management.
3. Trampler w as manufactured to im itate the mechanical character ist ics o f T an-sheep trampling. By
the simulat ion homogeneity experiment , w e compared the experimental t rampling area and tradit ional T an-
sheep ro tat ional gr azing area in summer season. Stat ist ical analyses ( t test ) indicated that there w ere no
significant differ ences betw een the simulated area created by the tr ampler and the t radit ional r otat ional
grazing ar ea in the height of leaf layer, vegetat iv e species number, soil w ater content of top layer ( 0-
15cm) , soil porosity , bulk density , and soil compact ion. T his homogeneity provided the foundat ion fo r
more accurate resear ch in animal t rampling effects out of defoliat ion and excret ion in the future.
4. Taking t rampling intensity and rainfall as independent variables and max imum underg round plant
biomass as tar get, the coupling model w as opt im ized for underground plant biomass in 0- 10cm soil lay er.
The most suitable grazing intensity for the typical steppe in Huanxian County w as decided to be 3. 84-
5. 09 sheep unit / hm2 which w as conver ted by the conversion equat ion betw een trampling intensity and
grazing intensity . T he models offered a new quant itative to ol for the grazing system management .
5. Five soil chemical indices w ere analyzed by mult ivariate variance in a tw o- factor ( exper imental
tr ampling and simulated precipitation) cont rolled f ield experiment including 48 treatment combinations.
The analy sis results by mult ivariate and multiple analyses o f v ar iance indicate that soil chemical propert ies
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第 1期 林慧龙:环县典型草原放牧家畜践踏的模拟研究
ar e more sensit ive to simulated precipitation. The effects of interact ion betw een experimental t rampling
and simulated precipitation have signif icant inf luences on hydro N ( mg/ kg ) , to tal P ( % ) and organic con-
tent. T rampling and simulated precipitation factors play a ro le in facilitat ing ecosy stem state change in the
typical steppe of Huanx ian County in Eastern Gansu, China.
6. We analy zed the soil mechanical composit ion ( 0- 15 cm) of dif ferent sampling plo ts in a tw o- facto r
( exper imental t rampling and simulated precipitat ion) cont rolled field experiment . Fractal dimension of soil
part icle w ere calculated using fr actal model. T he result show s that a negat ive co rrelation w as found be-
tw een fractal dimension and trampling intensity. How ever, the decreased extent of f ractal dimension w as
related to the simulated precipitat ion level. When the precipitat ion level w as dry, natural precipitat ion,
moder ate rainfall, and abundant rainfall, the declined ex tent of f ractal dimension value was 4. 33%, 2.
61% , 1. 34% , and 1. 23% , respect iv ely . T he matching relationship betw een precipitat ion and trampling
determ ined the f ractal dimension values. Tw o-variable r eg ression pat tern w as established as fo llow s:
F= 2. 427+ 2. 0982 10- 4W - 1. 3333 10- 4 T
The soil eroding process can also be characterized by the decreased fractal dimension values. There-
fore, so il f ractal dimension measur ement could be meaning ful for the soil er osion evaluation.
7. Compared w ith tr aditional r eg ression models, the art ificial neural netw or k ( ANN) model has bet-
ter ability o f im itat ion and pr edict ion. T herefo re the soil erodibility factor K value w as calculated by ANN
model based on the independent variables of the accumulated t rampling effects per unit area and simulated
precipitat ion. T he ANN model allow ed to skip the complicated soil erodibility mechanism and establish the
relat ionship betw een the so il erodibility and its influencing factors, e. g. t rampling and rainfall. Obvious-
ly, this w as an innovative at tempt to precisely evaluate the soil er odibility.
8. Trampling by the hoof act ion of grazing animals is the most important factor cont ribut ing to soil e-
r osion. Study results f rom the differ ent combinat ions o f exper imental tr ampling and simulated precipitat ion
indicate that the moderate and heavy t rampling agg ravated the risk o f soil erosion under arid circumstances
during the g row th per iod of g rasses. Precipitat ion had tw o-side effects on soil erosion. How ever, the re-
st raint ef fects of simulated pr ecipitat ion on soil er osion w ere less than the st imulat ive effects by t rampling
on soil erosion. T he mechanism model, w hich took soil erosion modulus as dependent variable and the ex-
perimental t rampling and simulated precipitation as independent variables, w as validated by exper imental
data and could be used as an innovat ive method to evaluate the so il erosion in arid and sem-i arid grassland
regions. Taking minimum soil erosion as the target , the most suitable grazing intensity could be rat ionally
ascertained by analy zing the precipitation amount during dif ferent fo rage g row th periods.
Key words: Tr ampling; T rampling unit ; T r ampling equivalent unit; T r ampling intensity; Experimen-
tal tr ampling; M odel.
(责任编辑 才 杰 梁艳萍)
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