太行山南麓山区不同植被恢复类型土壤理化和细根结构特征

在干旱半干旱地区,由于水分匮乏、土壤贫瘠等因素,将形成一定的裸地斑块,而这些斑块极易造成水土流失、滑坡等灾害,而具有不同植被覆盖的林地则能有效的保持水土。为完善干旱半干旱地区不同植被恢复类型下土壤理化和细根特征,选择太行山南麓山区具有代表性的裸露地、草地、荆条地、侧柏地、栓皮地和刺槐地等植被恢复类型,比较了各植被恢复类型下的土壤养分、粒径及细根状况等差异。研究表明:1)相对于裸露地,有植被覆盖的植被恢复类型拥有良好的土壤及细根状况。2)在不同植被类型中,刺槐林的有效氮转化速率较高;侧柏林有较高的细根参数;草地能够提高土壤中可吸收的磷组分。3)林地类型和土层均对土壤中含水率、黏粒、细根生物量和比根长产生极显著影响(P0.001)。4)各植被类型的对于土壤斑块的利用能力不同;不同植被类型中土壤及细根状况变化量具有一定的相似性,研究为生态恢复中植被类型的合理布局提供了新思路。     

Palm Community Structure and Land Cover Changes in the San Juan Biological Corridor, Costa Rica

Biological corridors connect forest fragments, minimize the isolation of remaining habitats, and reduce the negative impact of fragmentation. Important studies in a corridor include documentation of land cover and the relationships between the plant community and land cover changes. In this study, density, species richness, and species diversity of palms of different life stages and growth forms were documented in forty 10 × 10 m census plots in the San Juan Biological Corridor (SJBC), Costa Rica. Changes in the percent cover of agricultural, partially forested, and forested lands from 1979 to 2001 were quantified based on existing land classifications. Associations between these palm community characteristics and the reduction in forest cover in 200-m and 1000-m annuli surrounding the census plots were investigated. These palm community characteristics were spatially interpolated to examine their distributions in SJBC. The community characteristics of palms of all growth forms varied among census plots. Forested lands in SJBC decreased from 88 percent to 26 percent during 1979–2001, while the percentage cover of agricultural and partially forested lands increased. The annual deforestation rate was 0.8 percent from 1979 to 1992, 4.3 percent from 1992 to 1997, and 7.5 percent from 1997 to 2001. Overall, palm community characteristics of small-canopy palms, dwarf palms, and cotyledonous seedlings had lower values with a lower percentage forest cover. The spatially interpolated palm community characteristics were consistently greatest within or adjacent to protected areas. This study demonstrates the complexity of the landscape and the effect of loss of adjacent forests on the palm community.     

Forest expansion or fragmentation? Discriminating forest fragments from natural forest patches through patch structure and spatial context metrics

In forest–grassland mosaics, patches can result from two processes: forest expansion over grassy ecosystems and forest fragmentation. We tested the hypothesis that patches produced by these processes differed in structure and spatial context in a forest–grassland mosaic in the southern Brazilian highlands. We compared a present‐day land cover map with a past vegetation map to identify natural forest patches and forest fragments. Patches were described according to structure (size, core area and shape metrics) and spatial context (distance from roads and urban areas, edge contrast). Principal component analyses were used to examine gradients of patch types, and differences were tested by analysis of variance with randomization test. We found 878 natural patches and 214 fragments. Natural forest patches, riparian forest patches and forest fragments differed in structure and spatial context. In comparison to natural forest patches, fragments tend to be larger, with larger core areas, and more irregular and complex in shape. Fragments are situated in a different spatial context, tending to be closer to roads and urban areas and to present higher edge contrast. Riparian natural forest patches are similar to natural forest patches, except for shape. The smaller area and regular shape of natural patches probably result from the mechanisms involved in nucleus formation in the grassland matrix and from current grassland management. Natural patches are less exposed to some anthropogenic stresses, since most of them remain in a native grassland matrix context. Our results show that inferring process from pattern is not trivial, because different processes – forest expansion and forest fragmentation – may lead to either distinct or similar patterns of patch shape and spatial context. Studying patch structure and spatial context may then provide further insight into understanding changes in vegetation pattern at landscape scale, and in disentangling the effects of concurrent processes.     

Patterns of bryophyte diversity and rarity at a regional scale

Information on bryophyte diversity and rarity were combined withinformation on soil conditions and land use for Walloon Brabant (centralBelgium, 1091 km²) in order to investigate whichlandscape features sustain the most rare and diverse species assemblages.Presence–absence of 325 bryophyte species was recorded in 87 grid-squaresof 4 × 4 km. Species diversity was significantly correlatedwith forest cover (r = 0.71, P <0.001), sandy soils (r = 0.61, P <0.001), loamy soils, (r = –0.68,P < 0.001), and agricultural fields(r = –0.49, P < 0.001). Themost diverse grid-squares possessed up to 182 species and were characterized byat least 10% forest cover and the presence of unique micro-habitats.Grid-squares with forest cover reaching at least 10% but lacking uniquemicro-habitats contained between 90 and 130 species. Below 10% forest cover,diversity ranged between 55 and 110 species per grid-square. However, even theleast diverse cultivated areas included a significant amount of the regionallyrare species. A number of the latter are characteristic in other areas forspecific primary habitats lacking in Walloon Brabant but display an unexpectedability to disperse throughout hostile areas and colonize secondary habitats.The tendency of such species to occur in man-made habitats decreased our abilityto predict species richness and rarity from landscape features and soilconditions.     

庙岛群岛南五岛生态系统净初级生产力空间分布及其影响因子

净初级生产力(NPP)估算对于海岛碳源/汇研究具有重要意义。以庙岛群岛南五岛为例,结合CASA模型和区域特征构建NPP估算模型,借助RS和GIS技术进行NPP估算,进而分析南五岛NPP空间分布特征及其影响因子。结果表明:南五岛NPP总量为11043.52 t C/a,平均密度为340.19 g C m~(-2)a~(-1),处于全国平均水平,高于同纬度的西部地区,低于东部沿海大陆地区;夏季NPP总量占全年的80%左右,春季和秋季分别占11%和7%,冬季仅占1.3%;不同海岛的NPP平均密度由大到小依次为大黑山岛、北长山岛、庙岛、南长山岛和小黑山岛,各岛NPP平均密度与建设用地比例呈明显负相关;不同地表覆盖类型的NPP平均密度由大到小依次为阔叶林、针叶林、农田、草地、建设用地和裸地,林地具有较高的NPP值,说明南五岛的人工林建设具有重要生态作用;NDVI和地表覆盖类型是NPP最主要的影响参数,地形参数通过影响NDVI和地表覆盖类型间接作用于NPP结果;NPP与土壤p H、有效磷、全磷、全钾呈显著负相关,与全氮、总碳、总有机碳呈显著正相关,与含水量、速效钾和含盐量之间相关关系不明显。     

Land cover dynamics of different topographic conditions in Beijing, China

Topographic conditions play an important role in controlling land cover dynamic processes. In this study, remotely sensed data and the geographic information system were applied to analyze the changes in land cover along topographic gradients from 1978 to 2001 in Beijing, a rapidly urbanized mega city in China. The study was based on five periods of land cover maps derived from remotely sensed data: Landsat MSS for 1978, Landsat TM for 1984, 1992, 1996 and 2001, and the digital elevation model (DEM) derived from 1:250,000 topographic map. The whole area was divided into ten land cover types: conifer forest, broadleaf forest, mixed forest, shrub, brushwood, meadow, farmland, built-up, water body and bare land. The results are summarized as follows. (1) Shrub, forest, farmland and builtup consist of the main land cover types of the Beijing area. The most significant land cover change from 1978 to 2001 was the decrease of the farmland and expansion of the builtup area. Farmland decreased from 6354 to 3813 km2 in the 23 years, while the built-up area increased from 421 to 2642 km2. Meanwhile, the coverage of forest increased from 17.2% to 24.7% of the total area. The conversion matrix analysis indicated that the transformation of farmland to the built-up area was the most significant process and afforestation was the primary cause of the replacement of shrub to forest. (2) Topographic conditions are of great importance to the distribution of land cover types and the process of land cover changes. Elevation has an intensive impact on the distribution of land cover types. The area below 100 m mostly consists of farmland and built-up areas, while the area above 100 m is mainly covered by shrub and forest. Shrub has the maximum frequency in areas between 100 and 1000 m, while forest has dominance in areas above 800 m. According to the analysis of land cover changes in different ranges of elevation, the greatest change below 100 m was the process of urbanization. The process of the main land cover change occurred above 100 m was the transformation from shrub to forest. This result was consistent with the vertical change of natural vegetation distribution in Beijing. (3) Slope has a great influence on the distribution of land cover. Farmland and built-up areas are mostly distributed in flat areas, while shrub and forest occupy steeper areas compared with other land cover types. Forest frequency increased with the increasing slope. Land cover changes differed from the slope gradients. In the plain area, the land cover change occurred as the result of urbanization. With the increasing of the slope gradient, afforestation, which converts shrub to forest, was the process of the primary land cover change. __________ Translated from Journal of Plant Ecology, 2006, 30(2): 239–251 [译自: 植物生态学报]     

Distribution and effects of tree leaf litter on vegetation composition and biomass in a forest-grassland ecotone

Aims After abandonment of grasslands, secondary succession leads to the invasion by woody species. This process begins with the accumulation of tree litter in the forest–grassland ecotone. Our objectives were to determine the relationships between litter amounts and vegetation composition and cover along natural forest–grassland ecotones and to experimentally study the initial effects of tree litter accumulation on grassland vegetation and on microsite conditions.Methods We established 11 transects varying from 12 to 15 m in length in different forest–grassland ecotones in the Lahn-Dill highlands, Germany, and measured the mass and cover of tree litter and the cover and composition of vegetation at five sequential positions along each transect by using 1 m 2 plots with five replications. In a field experiment, we established plots subjected to different litter amounts (0, 200 and 600g m ?2) and evaluated changes in grassland vegetation, soil temperature and soil nutrient availability below the litter layer.Important findings Tree litter amounts decrease from 650 to 65g m ?2 across the forest–grassland ecotone. Vegetation changed from shrubs and annual species (adapted to more stressful conditions) in the forests edge to grasses, rosettes and hemirosette species (with higher competitive abilities) in the grassland. These anthropogenic forest–grassland ecotones showed abrupt edges, and the two adjacent ecosystems were characterized by different species pools and functional groups. In the field experiment, the presence of a litter layer reduced vegetation biomass and cover; the species richness was only reduced in the treatment with high litter (600g m ?2). Additionally, adding litter on top of vegetation also reduced thermal amplitude and the number of frost days, while increasing the availability of some nutrients, such as nitrogen and aluminium, the latter being an indicator of soil acidification. Adding a tree litter layer of 600g m ?2 in grassland areas had strong effects on the composition and diversity of grassland vegetation by reducing the cover of several key grassland species. In, or near, forest edges, litter accumulation rapidly changes established vegetation, microsite conditions and soil nutrients.     

Water inputs across a tropical montane landscape in Veracruz,Mexico: synergistic effects of land cover,rain and fog seasonality,and interannual precipitation variability

Land‐cover change can alter the spatiotemporal distribution of water inputs to mountain ecosystems, an important control on land‐surface and land‐atmosphere hydrologic fluxes. In eastern Mexico, we examined the influence of three widespread land‐cover types, montane cloud forest, coffee agroforestry, and cleared areas, on total and net water inputs to soil. Stand structural characteristics, as well as rain, fog, stemflow, and throughfall (water that falls through the canopy) water fluxes were measured across 11 sites during wet and dry seasons from 2005 to 2008. Land‐cover type had a significant effect on annual and seasonal net throughfall (NTF <0=canopy water retention plus canopy evaporation; NTF >0=fog water deposition). Forest canopies retained and/or lost to evaporation (i.e. NTF<0) five‐ to 11‐fold more water than coffee agroforests. Moreover, stemflow was fourfold higher under coffee shade than forest trees. Precipitation seasonality and phenological patterns determined the magnitude of these land‐cover differences, as well as their implications for the hydrologic cycle. Significant negative relationships were found between NTF and tree leaf area index (R²=0.38, P<0.002), NTF and stand basal area (R²=0.664, P<0.002), and stemflow and epiphyte loading (R²=0.414, P<0.001). These findings indicate that leaf and epiphyte surface area reductions associated with forest conversion decrease canopy water retention/evaporation, thereby increasing throughfall and stemflow inputs to soil. Interannual precipitation variability also altered patterns of water redistribution across this landscape. Storms and hurricanes resulted in little difference in forest‐coffee wet season NTF, while El Niño Southern Oscillation was associated with a twofold increase in dry season rain and fog throughfall water deposition. In montane headwater regions, changes in water delivery to canopies and soils may affect infiltration, runoff, and evapotranspiration, with implications for provisioning (e.g. water supply) and regulating (e.g. flood mitigation) ecosystem services.     

Land‐use History Affects the Distribution of the Saprophytic Orchid Wullschlaegelia calcarata in Puerto Rico's Tabonuco Forest1

Human activities such as logging and agriculture can severely damage forest ecosystems by changing forest structure, ecosystem function, and biodiversity. These changes may have long‐lasting consequences, which influence forest recovery. We investigated the effect of past human disturbance on the current distribution of an understory, achlorophyllous orchid, Wullschlaegelia calcarata in Puerto Rico's tropical rain forest after 70 yr of recovery. Our study site was the 16‐ha Luquillo Forest Dynamics Plot located in the Luquillo Experimental Forest, which has four areas with differing intensity of land use that have been distinguished from variation in canopy cover seen in aerial photographs taken in 1936. We recorded orchids in six 10‐m‐wide, 500‐m‐long transects across four different areas of land‐use history. We found that the orchid was not present in an area of the plot which had <20 percent canopy cover in 1936, and was most abundant in the area with >80 percent canopy cover, which had been minimally impacted by human activity. Tree species composition varied among land‐use history areas, and our observations suggested that this variation might be influencing the local distribution of W. calcarata. We also measured leaf litter biomass and identified the leaves of litter in areas with and without the orchid. Litter with a high proportion of Buchenavia tetraphylla leaves had more orchids. Even though human disturbance ceased in 1932, land‐use history in the Luquillo Forest still casts a shadow over the distribution of W. calcarata.     

滇南喀斯特断陷盆地土地利用方式对土壤有机碳及其活性组分的影响

土地利用方式是影响土壤有机碳库的重要因素,为探究喀斯特断陷盆地土壤有机碳库对土地利用方式及环境因素的响应,以滇南喀斯特地区5种典型土地利用方式(耕地、草地、灌丛、人工林、天然林)为研究对象,分析不同土地利用方式土壤有机碳(SOC)及活性有机碳(LOC)组分,即可溶性有机碳(DOC)、易氧化性有机碳(EOC)及微生物量碳(MBC)的含量、储量及分配比例在土壤垂直剖面(0-60 cm)的变化特征。结果表明：5种土地利用方式的SOC含量随土层深度的增加逐渐降低,其储量依次为灌丛(191.77 t/hm²)、草地(166.86 t/hm²)、耕地(142.47 t/hm²)、人工林(134.31 t/hm²)和天然林(102.62 t/hm²);EOC和MBC的平均含量及储量均以草地及灌丛最高、人工林及天然林次之,二者在土壤垂直剖面上与SOC含量的变化特征一致,但EOC和MBC含量在土层间的下降幅度大于SOC;土地利用方式和土层深度对DOC无显著影响(P>0.05);活性有机碳的分配比例受土地利用方式及土层深度的显著影响(P<0.01),其中人工林的EOC/SOC和MBC/SOC显著低于草地、灌丛及天然林。通径分析指出SOC和EOC主要受C/P比、全磷、砂粒和交换性钙的影响,砂粒和C/P比是影响MBC的主要因子。研究阐明在喀斯特断陷盆地地区EOC和MBC对土地利用方式的响应比SOC更敏感。另外,今后在土壤碳库的研究中应更多关注土壤磷和物理结构对其的影响。     

Soil organic carbon content and composition of 130-year crop, pasture and forest land-use managements

Conversion of former agricultural land to grassland and forest ecosystems is a suggested option for mitigation of increased atmospheric CO₂. A Sharpsburg prairie loess soil (fine, smectitic, mesic Typic Argiudoll) provided treatments to study the impact of long‐term land use on soil organic carbon (SOC) content and composition for a 130‐year‐old cropped, pasture and forest comparison. The forest and pasture land use significantly retained more SOC, 46% and 25%, respectively, compared with cropped land use, and forest land use increased soil C content by 29% compared with the pasture. Organic C retained in the soils was a function of the soil N content (r=0.98, P<0.001) and the soil carbohydrate (CH) concentration (r=0.96, P<0.001). Statistical analyses found that soil aggregation processes increased as organic C content increased in the forest and pasture soils, but not in the cropped soil. SOC was composed of similar percentages of CHs (49%, 42% and 51%), amino acids (22%, 15% and 18%), lipids (2.3%, 2.3% and 2.9%) and unidentified C (21%, 29% and 27%), but differed for phenolic acids (PAs) (5.7%, 11.6% and 1.0%) for the pasture, forest and cropped soils, respectively. The results suggested that the majority of the surface soil C sequestered in the long‐term pasture and forest soils was identified as C of plant origin through the use of CH and PA biomarkers, although the increase in amino sugar concentration of microbial origin indicates a greater increase in microbial inputs in the three subsoils. The practice of permanent pastures and afforestation of agricultural land showed long‐term potential for potential mitigation of atmospheric CO₂.     

基于黄土高原关键带类型的土地利用与年径流产沙关系空间分异研究

区域植被恢复改变了土地利用类型,从而有效控制了水土流失,但土地利用与水土流失关系的空间分异尚未明晰。整合了黄土高原坡面径流小区试验观测研究文献59篇和1121条年径流产沙记录,以8大关键带类型作为空间分层依据,采用地理探测器分析了土地利用与年径流产沙关系的空间分异。结果显示：撂荒地的年均径流量和产沙量最高分别为35.99 mm和4208.82 g/m²,撂荒地、裸地和耕地的产流产沙能力显著高于人工草地、林地、自然草地和灌丛,灌丛和林地的年均产沙量显著低于人工和自然草地（P<0.05）;除了撂荒地的年均产沙量在山地森林关键带最高（16240.40 g/m²）外,在丘陵沟壑农林草交错关键带的撂荒地年均径流产沙显著高于丘陵农业-草地关键带,丘陵沟壑农林草交错关键带和丘陵农业-草地关键带裸地、耕地的产流产沙能力较高,人工草地和灌丛年均产沙量显著高于其他关键带类型（P<0.05）;在山地森林关键带的林地年均径流量、径流系数和产沙量最低,分别为1.56 mm、0.41%和307.36 g/m²,而自然草地在各关键带类型都有较高的年均产流量和较低的年均产沙量;坡面径流小区的局地特征（如土地利用、面积、坡度、坡长）是影响年径流产沙关键带分异的首要因素,且存在多因子互作、非线性增强的关系。这些结果表明植被恢复能有效地保持水土,但是区域植被恢复时需要选择合适的类型,黄土丘陵沟壑区应首选自然草地、灌丛和林地。研究可为黄土高原区域植被恢复的优化配置提供科学依据。     

Landslides and Their Contribution to Land‐cover Change in the Mountains of Mexico and Central America1

Landsliding is a natural process influencing montane ecosystems, particularly in areas with elevated rainfall and seismic activity. Yet, to date, little effort has been made to quantify the contribution of this process to land‐cover change. Focusing on the mountains of Mexico and Central America (M‐CA), we estimated the contribution of landsliding to land‐cover change at two scales. At the scale of M‐CA, we classified the terrain into major landforms and entered in a GIS historical data on earthquake‐ and rainfall‐triggered landslides. At the scale of the Sierra de Las Minas of Guatemala, we investigated Landsat TM data to map rainfall‐triggered landslides. During the past 110 yr, >136,200 ha of land in the mountains of M‐CA have been affected by landslides, which translates into disturbance rates exceeding 0.317 percent/century. In Sierra de Las Minas, rainfall associated with hurricane Mitch affected 1765 ha of forest, or equivalently, landslides triggered by storms of this magnitude transformed between 0.196 (return time of 500 yr) and 1.290 (return time of 75 yr) percent of forest/century. Although landsliding results in smaller rates of land‐cover change than deforestation, we hypothesize that it has a stronger impact on ecosystems, both in qualitative and quantitative terms, given its influence on vegetation and soil. Moreover, interactions between landsliding and deforestation may be altering the expression of this complex process such that the few protected areas in the mountains of M‐CA may represent the only possibility for the conservation of this process.     

基于MODIS数据的中国三种主要土地类型变化的空间特征分析

人类活动使得土地利用和植被覆盖发生了巨大变化,直接影响着全球气候。本研究通过从2000—2013年对中国三种主要土地利用类型的NDVI变化特征进行了分析,结果表明:(1)14年来,中国三种主要土地利用类型NDVI平均值均有增强的趋势。(2)三种主要土地利用类型中除耕地中的水田,林地中的有林地和草地中的高覆盖草地增长速率不显著外,其他土地类型增长速率均显著。(3)三种土地利用类型均以改善面积大于退化面积,耕地中改善面积占总耕地的64.21%,退化的区域占18.50%;林地改善的区域占总林地的54.21%,退化的区域占20.13%;草地改善的区域占55.53%,退化的区域占18.23%。三种土地类型均有所改善且改善明显的区域主要集中在甘肃以南,陕西以北和东北部分地区。     

北京地区不同地形条件下的土地覆盖动态

利用MSS/TM影像和1∶250 000 高程数据分析了1978~2001年北京地区土地覆盖的变化。为研究人类活动对土地覆盖类型及植被变化的影响,根据植被的分布规律和人类活动影响,利用数字高程模型(DEM)将研究区遥感影像分为不同海拔段,分别建立标志进行解译。通过转移概率矩阵计算、不同地形因子影响下的土地覆盖类型分布的GIS分析,得到如下结果:1) 1978~2001年间北京市土地覆盖变化主要发生在平原和低海拔、小坡度的平缓地区,表现为农业用地向城镇用地的转变;高海拔地区主要为天然植被所覆盖,土地覆盖变化相对较小,主要是灌丛向林地的转变。2) 地形因子显著影响土地覆盖类型的分布及变化。随着海拔的升高和坡度的增大,农业用地和城镇用地减少,林地和灌丛逐渐增加。坡向对植被的分布也有较大影响。     

Greater sage-grouse winter habitat use on the eastern edge of their range

Greater sage-grouse (Centrocercus urophasianus) at the western edge of the Dakotas occur in the transition zone between sagebrush and grassland communities. These mixed sagebrush (Artemisia sp.) and grasslands differ from those habitats that comprise the central portions of the sage-grouse range; yet, no information is available on winter habitat selection within this region of their distribution. We evaluated factors influencing greater sage-grouse winter habitat use in North Dakota during 2005–2006 and 2006–2007 and in South Dakota during 2006–2007 and 2007–2008. We captured and radio-marked 97 breeding-age females and 54 breeding-age males from 2005 to 2007 and quantified habitat selection for 98 of these birds that were alive during winter. We collected habitat measurements at 340 (177 ND, 163 SD) sage-grouse use sites and 680 random (340 each at 250 m and 500 m from locations) dependent sites. Use sites differed from random sites with greater percent sagebrush cover (14.75% use vs. 7.29% random; P < 0.001), percent total vegetation cover (36.76% use vs. 32.96% random; P ≤ 0.001), and sagebrush density (2.12 plants/m² use vs. 0.94 plants/m² random; P ≤ 0.001), but lesser percent grass cover (11.76% use vs. 16.01% random; P ≤ 0.001) and litter cover (4.34% use vs. 5.55% random; P = 0.001) and lower sagebrush height (20.02 cm use vs. 21.35 cm random; P = 0.13) and grass height (21.47 cm use vs. 23.21 cm random; P = 0.15). We used conditional logistic regression to estimate winter habitat selection by sage-grouse on continuous scales. The model sagebrush cover + sagebrush height + sagebrush cover × sagebrush height ( = 0.60) was the most supported of the 13 models we considered, indicating that percent sagebrush cover strongly influenced selection. Logistic odds ratios indicated that the probability of selection by sage-grouse increased by 1.867 for every 1% increase in sagebrush cover (95% CI = 1.627–2.141) and by 1.041 for every 1 cm increase in sagebrush height (95% CI = 1.002–1.082). The interaction between percent sagebrush canopy cover and sagebrush height (β = −0.01, SE ≤ 0.01; odds ratio = 0.987 [95% CI = 0.983–0.992]) also was significant. Management could focus on avoiding additional loss of sagebrush habitat, identifying areas of critical winter habitat, and implementing management actions based on causal mechanisms (e.g., soil moisture, precipitation) that affect sagebrush community structure in this region. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

黑河中上游地区2000-2010年土地利用变化及水土保持服务功能

基于遥感影像数据,分析了黑河中上游地区2000年到2010年土地利用变化,在此基础上,从上游、中游以及整个区域的角度综合评价了该区域的水源涵养和土壤保持生态系统服务功能物质量变化。研究结果表明:1研究区60%以上为未利用地,2000—2010年,耕地、林地和未利用地面积大量增加,草地和水域面积减少。2耕地增加以荒漠和草地转入为主;林地转入表现为草地和荒漠造林,转出主要为林地荒漠化;草地转出主要去向为造林和荒漠化,而增加主要来源于冰雪覆盖地和荒漠;未利用地增加主要来源于草地的退化。3研究区土地利用程度较低,由东南向西北递减,2000—2010年,上游土地利用程度有所降低,中游大部分地区呈上升趋势。4由于上游山区林地面积的增加,植被覆盖下土壤的水源涵养量显著增加,土壤贮水量增加了0.764×108t。5土壤保持量由1.860×108t增加到1.899×108t,主要原因为草地转化为林地。在气候变化背景下,黑河流域应控制上游地区人工林面积,减少林地蒸腾量,以增加下游可用水量;适当控制中游地区耕地面积的扩张趋势,保证湿地、草地等自然生态系统生态用水量,维持流域山地-绿洲-荒漠系统的稳定,进而持续发挥生态系统土壤保持等功能。     

流域尺度土地利用与土壤类型空间分布的相关性研究

随着人类活动日益加强,土地利用变化及其驱动力研究已经成为国际地理学界研究的热点。但目前更多的工作侧重于研究人为因子,如人口增长、政策变化等因子对土地利用变化的影响,其实土地利用在宏观尺度上的变化一定程度上取决于自然环境背景,因此研究土地利用变化的自然环境背景特征对于进一步探讨土地利用变化的自然驱动力具有重要意义。土壤类型的空间分布在一定程度将影响土地利用的空间分布格局和变化过程。本文利用遥感、地理信息系统,通过选取景观格局指标,以于桥水库流域为例,研究了土地利用与土壤类型空间分布之间的相互关系。结果表明：(1)受人类活动干扰较弱的土地利用类型,如有林地、稀疏林地、灌木林地、其他林地和草地,主要分布在淋溶褐土、褐土性土以及棕壤地区;而与人类活动密切的土地利用类型,如山区旱耕地、丘陵区水田、丘陵区旱耕地和平原区旱耕地主要分布在淋溶褐土、褐土性土和潮土地区;(2)同类地区土地利用的多样性指数要比土壤的低。并且土地利用和土壤类型多样性均表现出明显的地形梯度效应,从中低山区、低山丘陵区、丘陵平原区到山间盆地区,土壤多样性指数从小到大有规律地变化。而土地利用类型多样性变化较为复杂,反映出人类活动对土地利用格局的影响较强,而对土壤类型的影响相对较小;(3)随着平均斑块面积的增加,流域多样性指数将呈下降趋势。土地利用多样性指数与流域总面积之间的相关性较差,但土壤多样性指数与流域总面积表现出的相关性较好;(4)土地利用类型与土壤类型之间,平均斑块面积上没有明显的相关关系,但在多样性指数之间存在着较好的相关性。土壤类型丰富多样的地区,土地利用的多样性指数也相对较高。     

黄土丘陵区植被类型与土壤微生物区系及生物量的关系

以陕西延安黄土丘陵区5种不同植被类型(人工刺槐林、天然侧柏林、天然辽东栎林、灌丛和裸地)为研究对象,分析了土壤微生物生物量碳、氮含量、细菌和真菌的丰度变化规律及其与土壤基本化学性质的关系。结果表明:(1)4种植被类型的土壤质量较之裸地都有不同程度的改善,总体趋势:天然林地人工林地裸地;(2)土壤微生物生物量碳、氮的总体趋势:天然林地最高,人工林次之,裸地最低,且与土壤有机碳(SOC)、全氮(TN)和速效磷(AP)极显著正相关(P0.01);(3)裸地土壤的细菌丰度最低,人工刺槐林真菌含量显著低于天然辽东栎林。细菌丰度与土壤营养状况呈显著正相关(P0.05),而真菌与土壤营养无明显相关性,只与土壤pH负相关。说明在该研究区域,植被类型与土壤质量对微生物资源都具有不同程度的作用。     

Soil quality regime in relation to land cover and slope position across a highly modified slope landscape

Vegetation and land-use mosaics of shrub land, grassland, farmland and reforested land are characteristic for residential areas of the Wolong nature reserve in Sichuan province, southwest China. The patterns represent a stage in long-term human disturbance and natural secondary succession since deforestation. The aim of this paper was to elucidate the soil-land cover types, soil-slope position relationships on a typical disturbed slope in the humid mountainous region. Soils were taken from four typical land cover types (shrub land, grassland, farmland and reforested land) under four slope positions (upper slope, middle slope, lower slope, foot slope) to study the distribution of soil nutrients and moisture on the transect scales of the slope. To elucidate the influence of land-use and slope position on soil quality, two integrated quantitative indexes were developed to compare soil quality under different land-use types (QI) and under different slope positions (PI). The results showed shrub land had the highest QI value, while the QI of reforested land and farmland had lower values. Foot slopes and upper slopes had higher soil quality levels compared to middle slopes and lower slopes. The results indicated that on the slope scale shrub land had high soil quality levels. The results also suggested that in the area of China where the climate favors secondary succession, leave nature as it is is a better choice than the policy change farmland to forest land.