Performance evaluation of CLM5.0 in simulating liquid soil water in high mountainous area,Northwest China

The model performance in simulating soil water content(SWC) is crucial for successfully modeling earth’s system,especially in high mountainous areas.In this study,the performance of Community Land Model 5.0(CLM5.0) in simulating liquid SWC was evaluated against observations from nine in-situ sites in the upper reach of the Heihe River Watershed(HRW),Northwest China.The CLM5.0 shows reliable performance in the study area with correlation coefficients(R) ranging between 0.79–0.93,root mean standard errors(RMSE)ranging between 0.044–0.097 m^(3)/m^(3),and the mean bias(BIAS) ranging between-0.084–0.061 m^(3)/m^(3).The slightly worse performance of CLM5.0 than CLM4.5 on alpine meadow and grassland is mainly caused by the revised canopy interception parameterization.The CLM5.0 overestimates interception and underestimates evapotranspiration(ET) on both alpine meadow and grassland during the growth period.The systematical overestimations at all the grassland sites indicate that the underestimation of ET is much larger than the overestimation of interception on grassland during growth period,while the errors of simulated interception and ET are partially canceled out on alpine meadow.Moreover,the underestimation of ET is more responsible for the overestimation of SWC than the overestimation of interception in the high mountainous area.It is necessary to estimate reasonable empirical parameter α(proportion of leaf water collection area) in interception parameterization scheme and further improve the dry surface layerbased soil evaporation resistance parameterization introduced in CLM5.0 in future researches.The performance of CLM5.0 is better under completely frozen stage than thawing stage and freezing stage,because of low variations of liquid SWC caused by extremely low hydraulic conductivity of soils.The underestimation of liquid SWC under frozen state is caused by underestimation of soil temperature,which leads to more ice mass and less liquid water in total water content.

Effects of Land Management Practices on Soil Water in Southwestern Mountainous Area, China

The effects of selected land management practices （cross-sloping tillage, ridge culture, organic manure, and straw mulch） on soil water conservation in a southwestern mountainous area, China, were studied during November 2002 to November 2004. The experimental field is divided into three parts based on soil layer depths, 0-60 cm （part Ⅰ）, 0-40 cm （part Ⅱ）, and 0- 20 cm （part Ⅲ）, and they all had the same slope azimuth （SE）, slope （10°）, and slope type （linear）. The experimental plots were subjected to the following treatments： cross-sloping tillage （CST）; cross-sloping tillage with organic manure （CST/ OM）; cross-sloping tillage with straw mulch （CST/SM）; contour ridge culture （CRC）; contour ridge culture with organic manure （CRC/OM）; and contour ridge culture with straw mulch （CRC/SM）, to identify the effects of management practices on soil water. Water contents were determined for soil samples collected, using a 2.2 cm diameter manual probe. Soil water was monitored once every five days from Nov. 20, 2002 to Nov. 20, 2004. The results indicated that, in the study stages, an integration of rainfall, evaporative losses, and crop transcription controlled the basic tendencies of profile （mean） soil water, while land management practices, to a certain extent, only modified its amount, distribution, and routing. Moreover, these modifications also mainly focused on the first 20 cm depth of topsoil layer. When each management practice was compared with control treatment, season changes of profile （mean） soil water were pronounced, while interannual changes among them were not significant. More comparisons indicated that, in the study stages, contour ridge culture had better effects than cross-sloping tillage. And under the same tillage, the combination of organic manure could achieve more than straw mulch. These management practices should be recommended considering the effectiveness of soil and water management techniques in the southwestern mountainous area, China.

Characteristics of rock fragments in different forest stony soil and its relationship with macropore characteristics in mountain area, northern China

Rock fragments have major effect on soil macropores and water movement. However, the characteristics of rock fragments and their relationship with macropore characteristics remain elusive in forest stony soils in northern mountainous area of China. The objectives of this study are to(1) use Industrial Computed Tomography(CT) scanning to quantitatively analyze rock fragment characteristics in intact soil columns in different forest lands and(2) identify the relationship between characteristics of rock fragments and that of the macropores. Intact soil columns that were 100 mm in diameter and 300 mm long were randomly taken from six local forest stony soils in Wuzuolou Forest Station in Miyun, Beijing. Industrial CT was used to scan all soil column samples, and then the scanned images were utilized to obtain the three-dimensional(3 D) images of rock fragments and macropore structures. Next, theparameters of the rock fragments and macropore structure were measured, including the volume, diameter, surface area, and number of rock fragments, as well as the volume, diameter, surface area, length, angle, tortuosity and number of macropores. The results showed that no significant difference was found in soil rock fragments content in the 10-30 cm layer between mixed forest and pure forest, but in the 0-10 cm soil layer, the rock fragments in mixed forest were significantly less than in pure forest. The number density of macropores has significant negative correlation with the number of rock fragments in the 0-10 cm soil layer, whereas this correlation is not significant in 10-20 cm and 20-30 cm soil layers. The volume density of macropore was not correlated with the volume density of rock fragments, and there is no correlation between the density of macropore surface area and the density of rock fragment surface area. Industrial CT scanning combined with image processing technology canprovide a better way to explore 3 D distribution of rock fragments in soil. The content of rock fragments in soil is mainly determined by parent rocks. The surface soil(0-10 cm) of forest contains fewer rock fragments and more macropores, which may be caused by bioturbation, root systems, gravitational settling and faunal undermining.

Fractal features and infiltration characteristics of the soil from different land uses in a small watershed in a rocky,mountainous area in Shandong Province

We studied infiltration and fractal mechanisms on sloping farmlands in a small watershed in Shandong Province in the rocky mountain areas of northern China.We studied soil fraction and soil water retention curves,and developed a soil infiltration model to analyze its quantitative relationship with soil particle size and pore dimensions under four types of land use,including sloping farmland,abandoned land,natural forest,and forest plantation(Malus pumila,Crataegus pinnatifida).Soil stability infiltration rate ranked as sloping farmland>abandoned land>natural forest>forest plantation.The sequence of soil particle size and pore dimension ranked as natural forest>forest plantation>abandoned land>sloping farmland.There were significant positive correlations between soil particle size and pore dimension,and both were positively correlated with the percent volume of silt and clay.They were negatively correlated with soil infiltration rate.The Horton model and the power function model were more suitable for simulating soil infiltration and the infiltration rate.We concluded that the soil in this area displayed typical fragments of rocky mountainous regions due to the loss of silt and clay caused by cultivation on sloping farmland.The uniformity and fractal dimensions of soil particle sizes and pore distribution decreased,thereby enhancing soil infiltration capacity and decreasing soil water retention capacity.

Depth Distribution Pattern of Soil Organic Carbon in Forest from Taowan Basin of Funiu Mountain Area

[Objectives]By testing applicability of SOC depth distribution model in geographical and climatic conditions of Funiu Mountain area,SOC depth distribution model in the region was established and applied. The constructed model was used to estimate SOC mass density in other regions,thereby obtaining SOC abundance distribution chart at different depths.[Methods]165 soil sampling sites were selected from Quercus variabilis forest,Pinus tabulaeformis forest,mixed forest,and shrub forest in Taowan basin of Funiu Mountain area,to determine SOC content at different depths,study SOC depth distribution pattern of forest in Taowan basin of Funiu Mountain area,and assess SOC reserve at different depths.[Results]Average SOC density of Q. variabilis forest,P. tabulaeformis forest,mixed forest,and shrub forest at the depth of 0-20 cm was 7. 92,8. 42,8. 14 and 9. 67 kg/m^2,and there was significant difference in SOC density between shrub forest and Q. variabilis forest,P. tabulaeformis forest,mixed forest( P < 0. 05),and SOC density of four kinds of vegetation all abruptly declined with soil depth increased. At the depth of 0-20 cm,correlation between SOC density and vegetation type,canopy density,clay content and sand content was significant,and the correlation with altitude was insignificant. When carbon density at the depth of 0-100 cm was used to describe regional SOC reserve,the estimated value was lower. The established space model could predict SOC density of forest.[Conclusions]The estimation of deep-layer SOC by the established model needed further consideration,and estimation method for special areas needed to be further demonstrated.

Characteristics of Soil Seed Banks of Typical Plant Communities in Hilly Area of Funiu Mountain

[Objectives]The purpose was to investigate the characteristics of soil seed bank of typical plant communities in hilly area of Funiu Mountain.[Methods]The seed density,number of species and species composition of the soil seed bank of typical plant communities such as Themeda japonica,Imperata cylindrica,Vitex negundo,Quercus acutissima,Robinia pseudoacacia,Platycladus orientalis and Populus canadensis in the surface,top 0-5 and top 5-10 cm soil were studied.[Results]The seed reserves of plant communities at different succession stages were(220.00±95.39)–(2650.00±1064.52)seeds/m2.A total of 48 species were counted in the seed bank,belonging to 45 genera in 22 families.Total 27 species were identified in the above-ground vegetation,belonging to 25 genera in 14 families.In the shallow soil where the seeds gathered,the seed densities of Imperata cylindrica and Themeda japonica were relatively low.The reserves of plant communities with different naturalness degrees were(403.33±64.29)-(2110.00±356.79)seeds/m2.A total of 67 species were counted in the seed bank,belonging to 64 genera in 37 families.A total of 45 species were identified in the above-ground vegetation,belonging to 43 genera in 28 families.In the soil layers of 0-5 and 5-10 cm,the seed density of natural secondary Q.acutissima was higher than those of planted P.canadensis,P.orientalis and R.pseudoacacia.In each soil layer,the species number of natural secondary Q.acutissima forest was slightly smaller than those of planted P.canadensis,P.orientalis and R.pseudoacacia forests.[Conclusions]The seeds in the soil seed bank may not completely come from existing above-ground vegetation.Manual assistance is required for vegetation restoration or reconstruction relying on soil seed bank,to ensure the direction of community succession.

A comparison of measured ^(137)Cs and excess ^(210)Pb levels in the cultivated brown and cinnamon soils of the Yimeng Mountain area

This contribution analyzes the similarities and differences between the measured activities of 137Cs and excess 210Pb(210Pbex) in the cultivated brown and cinnamon soils of the Yimeng Mountain area, discusses the influence of soil texture on the measurement of 210Pbex, and presents differences between the two types of soils. Fields A and B were selected to represent the fields that contain cultivated brown and cinnamon soils, respectively. From either study field, one site of sectioned core and six bulk cores were collected to measure 137Cs levels, 210Pbex levels, and the particle-size composition of soil samples. Three undisturbed soil samples were collected to measure capillary and aeration porosities. The 137Cs inventories for the two study fields are very similar. The 137Cs is a man-made radionuclide, which means that its measured levels for soils are unaffected by soil texture. In contrast, levels of the naturally occurring 210Pbex of soils from Field A were lower than those of Field B by about 50%. In contrast to aquatic sediments, levels of 210Pbex in terrestrial surface soils are affected by the emanation of 222Rn from the soils. It can be assumed that the coarser the soils, the greater the emanation of 222Rn; in addition, the lower the measured 210Pbex, the greater the underestimate of this value. The cultivated brown soils in Field A are coarser than the cultivated cinnamon soils in Field B. As a result, 222Rn in Field A will diffuse more easily into the atmosphere than that in Field B. As a consequence, the measured 210Pbex in soils from Field A is much lower than the actual value, whereas the value measured for Field B is much closer to the actual value.

Trade-off analyses between food provision and soil conservation service of Grain for Green Program in Mountainous Area

The Grain for Green Program and soil and water conservation engineering initiatives are crucial for controlling erosion in steep-slope agriculture.However,it is still unclear how these two management methods should be carried out in respect to the situation in mountainous areas.Therefore,taking a typical mountainous area in southwest China as an example,we simulated six scenarios in order to compare the food provisioning service(FPS)and soil conservation service of the Grain for Green Program(converting to grassland)and Construction Measures(converting to sloping terrace)under different slopes.Results showed that when farmland with a>25°slope was converted into grassland,the amount of soil erosion(M)decreased by 21.0%,while FPS decreased by only 0.7%.However,when farmland with a>25°slope was converted into sloping terrace,M decreased by 31.3%while FPS increased by 18.7%.With the increases of farmland slope ranges in the Construction Measures scenario,M gradually decreased and FPS gradually increased.Particularly when farmland>15°was converted into sloping terrace,M decreased by 63.9%and FPS increased by 52.7%.Furthermore,the trade-offs of Construction Measures are lower than that of Grain for Green on different slope ranges.Therefore,we conclude that Construction Measures are a more suitable method in mountainous areas than the Grain for Green,and we suggest that further research be conducted to consider the ecological risks of construction engineering measures.

Assessment of seismic ground motion amplification and liquefaction at a volcanic area characterized by residual soils

A seismic hazard was assessed related to site effects at Abbadia San Salvatore, central Italy, on the Mt. Amiata slopes, an ancient volcanic area characterized by residual soils(thick layers of loose to dense sands originated from weathering of the trachydacitic lavas). The seismic ground amplification and soil liquefaction related to these layers were recognized as the major seismic hazards for the area.Geological, geophysical, and geotechnical surveys were carried out on the volcanic rocks. The Horizontal-to-Vertical Spectral Ratio(HVSR) analysis of 252 noise measurements and 29 shear-wave velocity models of the subsoil allowed a seismic microzonation of the studied area, distinguished by thick weathered volcanic sands and shear-wave impedance contrast with respect to the seismic bedrock(volcanic bedrock). The differentiation of classified zones allowed recognition of areas characterized by residual(almost undisturbed) soils from those with soils probably affected by flowing water. The analysis of hazards revealed that peak acceleration by seismic amplification of ground motion exceeded the value set by the national rules(0.175 g) in a restricted area of the zone characterized by the most perturbed soils(Zone D);the potential occurrence of soil liquefaction was also greater in this zone. Finally, the study showed potential high hazards due to site effects of the volcanic mountainous area characterized by residual soils as opposed to an alluvial plain formed by volcanic debris where these effects have generally been more recognized.

Soil Erosion and Its Basic Characteristics at Karst Rocky-desertified Land Consolidation Area: A Case Study at Muzhe Village of Xichou County in Southeast Yunnan, China

Xichou County of Wenshan Zhuang and Miao Autonomous Prefecture in southeast Yunnan is one of the karst mountainous areas in southwest China showing typical rock desertification. During this study, we set up three soil erosion contrast test spots at Muzhe Village, Benggu Township, Xichou County, which was the birthplace of the Xichou rock-desertified land consolidation mode. The three spots included the terrace land spot (already consolidated land), sloping land spot (unconsolidated sloping land under rock desertification), and standard runoff spot (bare land spot). In 2007, a whole-year complete observation was conducted during the rainy season and "rainfall-erosion" data were obtained for 32 times. Our analysis showed that during the entire observation period, the number of the rainfalls that led to soil erosion accounted for 34.04% of the number of all rainfalls and the amount of the rainfalls that led to soil erosion accounted for 84.17% of the total amount of all rainfalls. The average erosive rainfall standard in the three test spots was 11.0 mm, slightly higher than the 10 mm standard that has been adopted all over China, but lower than the 12.7 mm standard of the US and the 13.0 mm standard of Japan. According to single-factor analysis, the soil loss in the sloping land spot (L2) and that in the bare land spot (L3) are correlated to certain extent to many other factors, including the single precipitation (P), rainfall intensity during the maximum ten minutes (I10), rainfall intensity during the maximum 20 minutes (I20), rainfall intensity during the maximum 30 minutes (I30), rainfall intensity during the maximum 40 minutes (I40), and rainfall intensity during the maximum 60 minutes (I60). Among these factors, they are of the highest relativity with I60. According to double-factor analysis, both L2 and L3 are of good relativity with P and I60. According to multi-factor analysis, L2 and L3 are also of good relativity with seven rainfall indexes, namely, P, Ia (average rainfall intensity), I10, I20, I30, I40, and I60, with their related coefficient R reaching 0.906 and 0.914, respectively. The annual soil losses in the three test spots are widely different: 1030.70 t/km2·a in the terrace land spot, which indicates a low-level erosion; 12913.22 t/km2·a in the sloping land spot (unconsolidated spot), some 12.5 times than that in the terrace land spot, which indicates an ultra-high-level erosion; and 19511.67 t/km2·a in the bare land spot, some 18.9 times than that in terrace land spot, indicating an acute erosion. These figures fully show that the Xichou rock-desertified land consolidation mode plays a significant role in soil conservation.

The Research of Forest Soil Organic Carbon Accumulation in Dabie Mountain

In subtropical to warm temperate transitional zone of the Dabie Mountains hinterland forest topsoil as the research object this text,through the different levels of soil bulk density,organic carbon content of the determination of analytical studies in the area of forest surface soil organic carbon density.Because of the ecological role of small environment,the study area within the soil bulk density increased with depth,surface soil porosity,and bulk density from top to bottom in 0.8.All measuring points are the 0-10 cm surface layer soil organic carbon content are highest,content between 67.232-61.940 g/kg,this,because the forest soil organic carbon important source withers and falls in the vegetation stack and rotten.Different measuring point organic carbon along with depth change characteristic slightly different,low elevation the measuring point soil organic carbon content increases the monotonous drop along with the depth,the elevation is high,the measuring point slightly has in the 30-40 cm depth content increases.The comprehensive bulk specific gravity factor computation,the 0-40 cm soil organic carbon total content slightly has along with altitude above sea level’s rise increases,each square meter organic carbon content between 16 560.5-18 354.6 g,studies the region 0-40 cm soil organic carbon content mean value by 3 measuring points mean value achievement,then this region 0-40 cm soil organic carbon density approximately 174.3 t/hm2;Refers to the related research between the surface layer and the 0-100 cm soil layer organic carbon content relational reckoning,studies the region 0-100 cm soil organic carbon density to be possible to reach 233.9 t/hm2,it indicated that the Dabie Mountain area forest soil system has the giant organic carbon capacity.

毛竹扩张对幕阜山区森林土壤碳氮磷含量及生态化学计量特征的影响

以幕阜山区同一片毛竹林向两侧杉木林和阔叶林扩张形成的连续生态界面为研究对象,分析不同林型土壤有机碳(SOC)、全氮(TN)、全磷(TP)、硝态氮(NO_(3)^(−)−N)、铵态氮(NH_(4)^(+)−N)含量及其生态化学计量比,探讨毛竹不同扩张模式对森林土壤碳(C)、氮(N)、磷(P)的影响。结果表明:在2种扩张模式下,随土壤层次的增加,除NO_(3)^(−)−N呈不规律变化外,SOC、TN、TP、NH_(4)^(+)−N含量均呈逐渐降低趋势。在毛竹向杉木林扩张过程中,杉木林、竹杉混交林、毛竹林同一土层SOC、TN、TP含量均无显著差异;在毛竹向阔叶林扩张过程中,毛竹林0~10 cm土层SOC和TN含量较阔叶林和竹阔混交林分别降低了27.71%、30.45%和36.67%、31.11%,而在10~20 cm和20~30 cm土层则无显著差异;毛竹扩张对杉木林和阔叶林各土层TP含量无显著影响;毛竹向杉木林扩张增加了0~10 cm和20~30 cm土层NH_(4)^(+)−N含量,毛竹向阔叶林扩张增加了10~20 cm土层NH_(4)^(+)−N含量及20~30 cm土层NO_(3)^(−)−N含量;毛竹向杉木林扩张对土壤C/N、C/P、N/P无显著影响,毛竹向阔叶林扩张导致0~10 cm土层N/P明显降低、10~20 cm土层C/N显著增加。综上,毛竹向杉木林扩张对土壤SOC、TN、TP影响不显著,但提升了表层和深层土壤NH_(4)^(+)−N含量,毛竹向阔叶林扩张造成表层土壤SOC、TN含量显著降低,并导致中层土壤NH_(4)^(+)−N含量和深层土壤NO_(3)^(−)−N含量明显增加。

微生物菌剂对连作芹菜根际土壤真菌群落多样性与结构的影响

以宁南旱区连作4年芹菜根际土壤为研究对象,采用田间定位试验结合高通量测序技术,以常规施肥(CK)为对照,研究常规施肥+枯草·哈茨复合菌剂(MF),常规施肥+枯草芽孢杆菌(BS),常规施肥+哈茨木霉菌(TH)3个处理对芹菜连作根际土壤真菌多样性及群落组成的影响。结果表明:施用枯草·哈茨复合菌显著提高了土壤有效磷、速效钾含量,增幅分别为34.29%和9.98%。施用微生物菌剂增加了土壤脲酶、蔗糖酶活性,平均增幅分别为43.16%和12.98%,并显著改变了土壤真菌的β-多样性。被孢霉属(Mortierella)、织球壳属(Plectosphaerella)、赤霉菌属(Gibberella)、链格孢属(Alternaria)、镰刀菌属(Fusarium)是各处理优势菌属,施用枯草·哈茨复合菌显著降低了赤霉菌属、链格孢属、镰刀霉属等真菌性病原菌的相对丰度,降幅分别为59.88%、51.63%、36.13%。冗余分析表明土壤蔗糖酶、脲酶、碱性磷酸酶活性、pH值和全磷是影响真菌群落结构组成的主要驱动因子。综合而言,枯草·哈茨复合菌剂的施用不仅降低了连作芹菜根际土壤镰刀菌属、链格孢属、赤霉菌属等病原菌的富集,还通过改变有效磷、速效钾等土壤理化性质,进一步重塑土壤真菌群落结构。

北京山区不同植被恢复类型土壤质量综合评价

[目的]综合评价北京山区不同植被恢复类型土壤质量,并进一步确定影响土壤质量的关键因素,为该地区植被恢复与重建提供数据支撑。[方法]以立地条件相近的侧柏纯林、油松纯林、侧柏油松混交林、侧柏针阔混交林、油松针阔混交林、落叶阔叶混交林和无林地(对照)为研究对象,测定14个土壤理化指标作为土壤质量评价的总数据集(TDS),采用主成分分析法(PCA)和Pearson相关性分析建立土壤质量最小数据集(MDS),利用线性(L)和非线性(NL)2种评分方法计算土壤质量指数(SQI)和一般线性模型(GLM)确定影响土壤质量的关键因素。[结果]植被恢复后相较于无林地,土壤容重、砂粒含量下降,而有机质、全氮、全钾、速效氮、速效钾等土壤养分含量增加。筛选出的研究区土壤质量评价MDS指标为全氮、砂粒、全钾、pH、有效含水量。4种方法(SQI-LT、SQI-NLT、SQI-LM、SQI-NLM)下,不同植被恢复类型的SQI值排序均为落叶阔叶混交林>侧柏针阔混交林>油松纯林>油松针阔混交林>侧柏油松混交林>侧柏纯林>无林地,植被恢复后土壤质量显著提升。SQI-NLM的土壤质量评价方法在北京山区具有更好的适用性。相较于无林地,其他植被恢复类型的SQI-NLM分别提高64%,48%,45%,36%,33%,27%。GLM模型解释了土壤质量指数总变异的85.24%,植被类型对土壤质量指数的解释比例最大(45.09%)。[结论]选择适宜的植被恢复类型是改善区域土壤质量的关键。未来实施植被恢复时,树种选择上优先考虑阔叶树种。造林配置方式的选择应取决于树种而定,如侧柏纯林中引入本土阔叶树种形成侧柏针阔混交林或选择油松纯林是最佳造林模式。

北京山区典型植被土壤水分对次降雨的响应

为了揭示北京山区不同植被类型土壤水分对不同强度降雨的响应过程,选取北京山区内侧柏、荆条灌丛、荒草地为研究对象,基于2022年6—10月降雨和土壤水分的连续观测数据,分析土壤水分对不同降雨事件的响应特征。结果表明:(1)观测期内研究区降雨事件主要由小雨构成,小雨事件的总降雨量占总降雨量的14.78%,小雨事件对土壤水分的响应深度可达到40—60 cm土层;中雨、大雨、暴雨事件的总降雨量占总降雨量的85.52%,中雨、大雨、暴雨事件对土壤水分的响应深度均可达到60—80 cm土层;大降雨事件对土壤水分的补给作用更明显,降雨量越大,降雨能补给的土层深度越深,土壤水分补给效果越好。(2)三种植被平均土壤水分补给速率大小依次为荒草地>侧柏>荆条灌丛,说明降雨对荒草地的补给效果最好;土层活跃程度对植被土壤水分有影响,土层越活跃,土壤水分波动越大,三种植被平均土壤水分变异系数大小依次为荒草地>荆条灌丛>侧柏,而三种植被平均土壤储水量大小则依次为侧柏>荒草地>荆条灌丛,说明侧柏的土壤水分最为稳定。(3)荒草地、荆条灌丛剖面上各层土壤水分逐渐减少,侧柏则增加,说明土壤水分剖面分布受植被类型影响;侧柏、荆条灌丛、荒草地平均最大补给速率均发生在20—40 cm土层,说明降雨对浅层土壤水分的补给最为明显,对0—40 cm土层土壤水分的补给效果要更好。研究成果进一步解释了北京山区生态系统水分运动规律,为易干旱生态脆弱地带生态环境建设提供依据。

长白山地区土壤水蚀时空演变特征及驱动因素分析

探讨长白山地区受极端降水、地形复杂、植被破坏等因素影响造成的土壤侵蚀状况,可以研判该地区水土流失情况,为当地水土生态保护提供科学参考。利用修正的通用土壤流失方程(RUSLE)、趋势及相关分析法,定量分析长白山地区土壤水蚀的空间格局及时空分布特征,并探究土壤水蚀与气候、植被覆盖度及地形驱动因子的关系。结果表明:2000-2020年长白山地区土壤水蚀模数均值总体呈“西南高,东北低”的空间格局。相较于其他地类,草地、未利用地、林地更易发生土壤水蚀。近21 a来,土壤水蚀模数平均以0.0255 t/(hm^(2)·a)的速度上升,土壤水蚀模数表现为上升趋势的地区占研究区总面积的68.3%,侵蚀等级总体以微度和轻度为主,且轻度侵蚀比例也呈增加趋势,表明该地区土壤侵蚀状况趋于好转,未来吉林市中北部和延边州部分地区的水土流失风险较高。土壤水蚀与降水、海拔高度及坡度具有较为显著的正相关关系,而与气温、植被覆盖度的相关性以负相关为主。海拔大于1000 m或坡度大于20°的草地、林地区域是水土防治的重点地形区。

皖南山区不同类型森林土壤阳离子交换性能差异

为了解皖南山区不同类型森林土壤阳离子交换性能差异,为该区合理营林提供参考,选取皖南山区6种不同类型森林土壤(杉木林、马尾松林、栓皮栎林、外松林、天然阔叶林和杉木-栓皮栎混交林)为研究对象,比较森林土壤阳离子交换性能的差异。结果表明:(1)研究区土壤呈强酸性,土壤有机质含量为33.84~91.50 g·kg^(-1),总氮含量为0.94~3.37 g·kg^(-1),碱解氮含量为131.58~203.62 mg·kg^(-1),总磷含量为0.22~0.77 g·kg^(-1),有效磷含量为0.17~0.32 mg·kg^(-1);土壤主要缺乏速效磷养分。(2)阳离子交换量在8.09~12.57 cmol·kg^(-1)之间,排序为:天然阔叶林>外松林>马尾松林>混交林>杉木林>栓皮栎林,不同森林土壤间阳离子交换量的差异主要由其土壤有机质的差异引起。(3)交换性盐基总量在1.74~2.72 cmol·kg^(-1)g之间,排序为:马尾松林>外松林>杉木林>栓皮栎林>混交林>天然阔叶林,Ca^(2+)和Mg^(2+)是主要的盐基离子,是成土过程中Ca、Mg优先固持形成的。(4)盐基饱和度在13.97%~28.98%之间,排序为:马尾松林>杉木林>栓皮栎林>外松林>混交林>天然阔叶林,该差异是由淋溶作用和树木对盐基离子的吸收共同作用形成的差异。综上,研究区土壤保肥和缓冲性能较低且供肥能力较差,尤其是土壤速效磷供应能力差。其中松林的供肥保肥能力及缓冲性能明显优于其他树种森林,混交林的速效养分含量更高,故可通过营造松类混交林以及施肥来提高森林土壤供肥保肥能力和缓冲性能。

北方土石山区坡面水土流失特征研究

[目的]揭示北方土石山区坡面水土流失规律,为山区土壤侵蚀防治和生态建设提供科学依据。[方法]利用1988—1991年坡面径流小区观测数据,运用统计和相关分析等方法,对不同下垫面条件下坡面水土流失特征进行了分析,并探讨了坡面径流深度、土壤侵蚀模数、土壤入渗率与有效降雨量、平均降雨强度、降雨历时、降雨等级的关系。[结果](1)在5°08′~24°08′坡度范围内,坡面径流深度随坡度增加逐渐减小,土壤侵蚀模数和土壤入渗率随坡度增加逐渐增大;(2)在2.18~33.19 m坡长范围内,坡面径流深度随坡长增加逐渐减小,土壤侵蚀模数和土壤入渗率随坡长增加呈现先增后减的变化趋势,存在临界坡长;(3)随着植被覆盖度增加,坡面径流深度、土壤侵蚀模数迅速减小,土壤入渗率逐渐增加;裸地的坡面径流深度和土壤侵蚀模数显著高于30%植被覆盖度坡面,但植被覆盖度由30%增加到60%,90%时,坡面水土流失过程的影响差异并不明显,说明在水土流失治理中存在临界植被覆盖度;(4)坡面径流深度、土壤侵蚀模数主要受到有效降雨量和平均降雨强度影响,且均呈显著正相关;而土壤入渗率主要受到平均降雨强度和降雨历时影响,与平均降雨强度呈显著正相关,与降雨历时呈显著负相关;随降雨等级的增加,坡面径流深度和土壤侵蚀模数呈增加趋势而土壤入渗率呈先增加后减少的趋势。[结论]下垫面条件和降雨因素对北方土石山区坡面水土流失过程产生了重要影响。未来应结合室内试验和模型模拟,进一步加强该区域不同自然因素和人类活动对坡面水土流失过程和影响机制的研究。

基于RUSLE模型的武陵山区土壤侵蚀研究

基于降水、土壤属性、数字高程模型(DEM)、归一化差值植被指数(NDVI)和土地利用等数据,采用修正后的通用土壤流失方程(RUSLE)模型计算了武陵山区的多年平均土壤侵蚀模数,探讨了武陵山区土壤侵蚀的空间分布特征.结果表明:(1)2001—2020年武陵山区约71.59%的区域受到土壤侵蚀的威胁,中度及中度以上土壤侵蚀占比30.55%;(2)坡度是影响土壤侵蚀强度分布的主要因素,中度及中度以上的土壤侵蚀主要分布在大于15°的坡度上;(3)同一坡度级下,林地土壤侵蚀强度最低;(4)重庆武陵山区多年平均土壤侵蚀模数最高,其次分别是湖北武陵山区和贵州武陵山区,湖南武陵山区多年平均土壤侵蚀模数最低;(5)重庆市武隆区,湖北省巴东县、五峰土家族自治县、秭归县、长阳土家族自治县,贵州省江口县和湖南省古丈县是多年平均土壤侵蚀模数较高的县(区);(6)武陵山区土壤侵蚀的空间分布具有正的空间自相关性,高高集聚主要分布在湖北武陵山区,低低集聚主要分布在湖南武陵山区.研究结果对于武陵山区水土资源优化管理和地质灾害分区防治具有一定的指导意义.

火烧迹地恢复后不同稳定机制土壤有机碳库特征研究

以大兴安岭重度火烧迹地经过不同方式恢复的林分土壤为研究对象,采用物理-化学联合分组方法,研究未保护、物理保护、化学保护、生物化学保护、物理-化学保护和物理-生物化学保护有机碳组分含量特征及其与土壤总有机碳含量间的关系。结果表明,1)人工恢复的林分土壤总有机碳、未保护有机碳、物理保护有机碳、物理-化学保护有机碳、物理-生物化学保护有机碳和生物化学保护有机碳含量均显著高于自然恢复。化学保护有机碳含量在不同恢复方式下变化不显著。除化学保护有机碳和物理-化学保护有机碳外,其余各保护态有机碳均表现为上层土壤含量显著高于下层(P<0.05)。2)2种恢复方式下的土壤有机碳组分均以未保护有机碳占比最高,物理-化学保护有机碳占比最低。与天然恢复相比,人工恢复下的土壤物理保护有机碳含量占比显著提高2.80%~3.19%(P<0.05)。3)回归分析表明,除物理-化学保护有机碳和化学保护有机碳组分外,其余各保护态有机碳组分与总有机碳含量之间均呈极显著的正相关关系(P<0.001)。大兴安岭重度火烧迹地经过32 a的人工恢复,更利于土壤总有机碳积累,土壤未保护有机碳的积累更多。研究结果为该区域重度火烧迹地植被恢复提供科学依据。