【作者】 贾燕锋；

【导师】 焦菊英；

【作者基本信息】 中国科学院研究生院（教育部水土保持与生态环境研究中心） ， 土壤学， 2011， 博士

【摘要】 黄土丘陵沟壑区土壤侵蚀严重,一直是我国水土流失治理的重点,而植被是控制侵蚀过程的关键。黄土丘陵沟壑区的植被恢复必然受其特殊环境的影响。在这样的环境下,不同立地条件下植被恢复的现状如何,植被恢复到一定程度土壤侵蚀的现状如何,都没有明确的答案。为此,本研究以黄土丘陵沟壑区纸坊沟和大南沟两个典型小流域不同立地环境下的自然恢复植被为研究对象,通过野外调查明确立地-自然恢复植被类型-演替阶段的对应关系,在此基础上,调查分析群落特征、演替程度、稳定性与健康状况,估算不同演替阶段植被类型下的土壤侵蚀量,并对自然植被、土壤侵蚀情况的发展趋势进行初步预测,得出以下主要结论:1)根据中国植被分类系统,纸坊沟和大南沟两个典型小流域中均包括草原植被型、灌丛植被型和森林植被型3种植被型。草原植被型群系均为自然恢复植被,陕北黄土丘陵沟壑区退耕地植被恢复演替过程中的主要植被类型在两个流域中均有出现且占有一定的比例;演替前期的猪毛蒿、阿尔泰狗娃花、二裂委陵菜、草木樨状黄芪、长芒草等群系主要分布于沟缘线以上的梁峁坡,后期的白羊草群系、茭蒿群系和铁杆蒿群系则主要分布于沟缘线以下的沟坡上,其中白羊草均分布于南向坡面上。灌丛植被型和森林植被型主要为人工植被,其中纸坊沟小流域中的自然恢复灌丛狼牙刺主要分布于南向沟坡上,栒子分布于1100^-1200 m海拔较低的沟坡下部。2)M. Godron稳定性测度表明大南沟小流域和纸坊沟小流域所有的自然恢复植被均处于不稳定状态,这与这些群落尚处于演替过程中有关。进一步通过样地重复调查,对处于不同演替阶段植物群落5-7年的演替情况进行对比,分析处于不同演替阶段植被类型的稳定性发现,演替早期的猪毛蒿群落为演替速度最快但稳定性最差的群落类型;长芒草、达乌里胡枝子群落演替速度较猪毛蒿群落慢,稳定性较猪毛蒿群落略好;演替后期的白羊草、铁杆蒿、茭蒿的群落类型基本没有发生变化,物种组成变化不大,表现出较好的稳定性;灌丛在群落类型和物种组成上的变化更小,表现出相当的稳定性。可见,演替早期群落发展快,稳定性差,而后期演替速率变小,群落相对稳定。物种多样性的变化及同一样地两次调查间的Bray Curits指数也表现出相似的趋势。3)采用CVOR指数模型对处于不同演替阶段植被类型的健康状况进行评价,发现自然恢复植被在以栒子群落作为参照系统的评价体系中多处于不健康或警戒状态,在以丁香-铁杆蒿群落为参照系统的评价体系下多处于警戒状态或亚健康状态;在两种参照系统下,灌丛的健康状况均较草原植被型好,而且在不同的群系间表现出越是演替后期的群丛,其健康状况越好,说明研究区的植被恢复过程是系统健康良性发展的过程。4)根据实测资料得到草原型植物群系的平均土壤可蚀性K值为0.043 t·ha·h(ha^-1·MJ^-1·mm^-1),灌丛的平均土壤可蚀性K值为0.038 t·ha·h(ha^-1·MJ^-1·mm^-1)。采用RULSE中关于C值的估算方法得到农田的C值为0.242,草原植被型C值的平均值为0.197,猪毛蒿群系、草木樨状黄芪群系和硬质早熟禾群系的C值约为0.22,演替中后期群落的C值均小于0.2,其中长芒草、达乌里胡枝子群系的C值为0.196,白羊草群系的C值为0.168,茭蒿群系和铁杆蒿群系的C值分别为0.175和0.179,灌丛中狼牙刺群系C值的估计值为0.048,栒子群系C值的估计值为0.086。5)运用中国土壤流失方程（CLSE）估算得到的不同植被类型下的土壤侵蚀量的估计值均比实际观测值大,总体上侵蚀量的估计值约为实测值的2^-10倍。主要是因为CLSE中关于坡度因子的算法是基于5.14^-28.8°的坡度归纳的,而纸坊沟和大南沟中坡度大于28.8°的面积分别占流域总面积的46.3%和51.9%,而且坡度是影响侵蚀强度的关键因素,从而导致CLSE在黄土丘陵沟壑区小流域土壤侵蚀估算中尚有一定的局限性。6)中国坡面水蚀预报模型（PMWEH）的估算结果较CLSE的估计值更接近实测值,侵蚀量的估计值约为实测值平均值的1-4.5倍。考虑结皮因素,对K值进行修正后,PMWEH估算的侵蚀量约为实测值平均值的1-4倍,与实测值最大值基本相当。与CLSE相比,PMWEH更适用于对黄土丘陵沟壑区小流域土壤侵蚀量进行估算。7)采用修正后的土壤可蚀性因子K值,运用PMWEH估算研究小流域地形条件下不同植被类型下的土壤侵蚀量,其中猪毛蒿群系的平均侵蚀模数为5863 t·(km^-2·a^-1),草木樨状黄芪群系的平均侵蚀模数为7383 t(·km^-2·a^-1),硬质早熟禾群系的平均侵蚀模数为4483 t(·km^-2·a^-1),长芒草、达乌里胡枝子群系的平均侵蚀模数为5352 t(·km^-2·a^-1),白羊草群系的平均侵蚀模数为5094 t·(km^-2·a^-1),茭蒿群系的平均侵蚀模数为5559 t(·km^-2·a^-1),铁杆蒿群系的平均侵蚀模数为5245 t·(km^-2·a^-1);人工灌丛多属于轻度或中度侵蚀,自然恢复灌丛狼牙刺的平均侵蚀模数为1242 t(·km^-2·a^-1),栒子群系的平均侵蚀腏·701 t(·km^-2·a^-1)。自然恢复植被在减蚀能力方面表现为灌丛>演替后期群落>演替前期群落。8)根据样地调查资料确定不同植被的演替概率矩阵,预测对未来不同时段自然恢复的发展趋势,在无其他因素（如人类活动）影响的情况下,到50年以后（即2060年）,纸坊沟小流域和大南沟小流域中的自然恢复植被90%将演替至灌丛阶段,届时纸坊沟和大南沟小流域的平均土壤侵蚀模数将降至1094 t·(km^-2·a^-1)和1157 t·(km^-2·a^-1)。更多还原

【Abstract】 In the hilly-gullied Loess Plateau, soil loss control was taken much attention because it’s serious soil erosion; and vegetation is the most efficient method to control soil erosion. However, vegetation restoration must be effected by the bad environment conditions. And the main propose of our study was to check the status of natural restoration vegetation in different sites, and the extent of soil erosion under different vegetation types. To do this, two typical watersheds, Zhifanggou and Danangou, were selected as study sites. We examined the correspondence between sites– natural vegetation– succession stage, analyzed the degree of succession of different natural vegetation, assessed the stability and health of natural vegetation, estimated the soil loss of different vegetation types, and then predicted vegetation and soil loss in the future.And the main results are shown as follows:1) According to the Chinese vegetation classification system,there are grasslands, bush and forest in both Zhifanggou and Danangou watersheds. All the grasslands are natural, and the typical communities during the second succession of hilly-gullied Loss Plateau were easily found in the two watersheds. The formations of the early stage of succession, such as formation （For.） Artemisia scoparia, For. Heteropappus altaicus, For. Potentilla bifurca, For. Astragalus melitoloides, For. Stipa bungeana and so on, mainly distributed on the upper slope, and the formations of the late of succession, such as For. Bothriochloa ischcemum, For. Artemisia giraldil and For. Artemisia gmelinii, mainly distributed on the gully slope, and all For. B. ischcemum distributed on the south slopes. The shrub and forest in the two watershed are mainly artificial vegetation, but there are some natural Sophora viciifolia on the south gully slope in Zhifanggou, and some natural Cotoneaster multiflorus on the bottom of gully slope about 1100^-1200 m in Zhifanggou watershed.2) M. Godron test indicated that all the natural vegetation in Zhifanggou and Danangou watersheds are in an unstable state, and all they are progressing communities may account for it. Further investigation was done to check out the changes during the first and the second investigation, and to compare the stability of communities in different succession stage, and we found that the early stage For. A. scoparia developed most rapidly, but worst in stable; the middle stage For. S. bungeana, Lespedeza davurica developed slower and better in stable than For. A. scoparia; the later stage For. B. ischcemum, For. A. giraldil, For. A. gmelinii and shrubs developed more slowly, and species composition of these formations changed little, which suggests that they are more stable. In conclusion, the earlier formations developed faster, but less stable; the later formations developed slower, but more stable. And the species diversity and the Bray Curits index also showed a similar trend.3) CVOR index model was used to evaluate the health status of vegetation in the different succession stages, and found that almost natural vegetation were unhealthy or in the alert state when For. C. multiflorus was used as the reference system, and most of the natural vegetation types were in the alert state or sub-healthy state when For. Syringa pekinensis-A. gmelinii was used as the reference system. However, shrubs were healthier than grasslands under each reference system, and the formations of the later stage were healthier than formations of the early stage.4) Based on measured data, the soil erodibility values （K） were calculated and the results shown that the average K value of grasslands was 0.043 t·ha·h(ha^-1·MJ^-1·mm^-1), and the average K value of shrub was 0.038 t·ha·h(ha^-1·MJ^-1·mm^-1). According to algorithm of RULSE, the cover and management factor （C） was calculated, and the results show that the C value of croplands was 0.242, the average C value of grasslands was 0.197, the C value of For. A. scoparia, For. Artemisia gmelinii and For. Poa sphondylodes was approximately 0.22, the C value of later stage formations were less than 0.2, the C value of For. S. bungeana, L. davurica, For. B. ischcemum, For. A. giraldil and For. A. gmelinii were 0.196, 0.168, 0.175 and 0.179, respectively. And the C value of the For. S. viciifolia was 0.048, the C value of For. C. multiflorus was 0.086.5) The soil erosion of different vegetation types estimated by Chinese Soil Loss Equation （CLSE） were much higher than observed, the estimated values were about 2^-10 times of the observation values. The main reason why the estimate value was much higher was that the algorithm for S factor in CLSE was drown from slope of 5.14^-28.8°, but 46.3% slope in Zhifanggou and 51.9% slope in Danangou had a gradient greater than 28.8°. In addition, the slope is a key factor of erosion intensity. As a result, CLSE was limited to estimate soil loss of watershed in the hilly-gullied Loess Plateau at some extent.6) The soil erosion of different vegetation types estimated by Prediction Model of Water Erosion on Hillslopes （PMWEH） were more close to the measured value, the estimated values were about 1-4.5 times of the observation values. If the soil bio-crust was considered, the soil loss of different vegetation types estimated by PMWEH were about 1-4 times of the average observation values, and were about equal to the maximum observation values. Compared with CLSE, PMWEH was more suitable to estimate soil loss of watershed in hilly-gullied Loess Plateau.7) After K values revised, the soil losses of different vegetation types in the study sites were estimated. And the results shown, the average erosion modulus of For. A. scoparia, For. A. gmelinii, For. P. sphondylodes and For. S. bungeana, L. davurica were 5863 t·(km^-2·a^-1), 7383 t·(km^-2·a^-1), 4483 t·(km^-2·a^-1) and 5352 t·(km^-2·a^-1), respectively, and the average erosion modulus of For. B. ischcemum, For. A. giraldil and For. A. gmelinii were 5094 t·(km^-2·a^-1), 5559 t·(km^-2·a^-1) and 5245 t·(km^-2·a^-1). The soil loss erosion intensity of artificial shrubs were moderate erosion, and the average erosion modulus of For. S. viciifolia was 1242 t·(km^-2·a^-1), average erosion modulus of For. C. multiflorus was 701 t·(km^-2·a^-1). Compared with the late-successional communities and early-successional communities, shrubs were more capable of reducing soil loss.8) According to survey data, the probalility matix of different vegetation types during secondary succession was determined, and the vegetation types in the future were predicted. In 2060, 90% natural vegetation in the watershed would be shrubs, and the soil loss of Zhifanggou watershend and Danangou watershend would down to 1094 t·(km^-2·a^-1)and 1157 t·(km^-2·a^-1), respectively.更多还原