SOIL-MOISTURE EFFECTS OF CONVERSION OF SAGEBRUSH COVER TO BUNCHGRASS COVER1

Precipitation, soil moisture, runoff, and vegetation were measured on two, 5- to 10-acre, big sagebrush (Artemisia tridentata) watersheds and two, equally small, beardless bluebunch wheatgrass (Agrophron inerme) watersheds that were converted from big sagebrush in 1967. The watersheds are located near Wolcott, Colorado, at an elevation of 7,200 feet, and are mantled with 2 to 3 feet of silty clay soils. Annual precipitation was about 13.5 inches; about 9 inches occurred as rain or snow from April through October and about 4.5 inches accumulated as a snowpack from November through March. Evapotranspiration was about 2 inches greater in 1968 and 1 inch greater in 1969 from the sagebrush watersheds than from the grass watersheds. With a mature stand of grass in 1970 and 1971 the differences in evapotranspiration were within the range of differences measured during the 3-year calibration period when all four watersheds were sagebrush. Water use was similar in the top 1 foot of soil but slightly more water was used by the grass in the 1- to 2-foot zone and more water being used by the sagebrush below 2 feet. Soil-water potential data indicated that only the big sagebrush used a small amount of water from the fractured shale at depths below 40 inches. Sagebrush used more water in August and September than the grass.     

Integrating Environmental Characteristics and Fisheries Management in Northern Finland River Impoundments

/ Three large rivers in northern Finland, the Kemijoki, Iijoki, and Oulujoki rivers, were dammed for hydropower generation in the 1940s-1960s. Due to differences in environmental conditions, these impoundments require detailed study to produce guidelines for fisheries management.Water quality, hydrology, vegetation, and geomorphology data of 16 impoundments were gathered. Shoreline land-use data were derived from maps, and fish assemblage data were collected by exploratory fishing and from the annual fishery statistics. The relations among environmental variables were studied, and a classification of the impoundments was developed by hierarchical cluster analysis. Consequently, three impoundment groups with different environmental characteristics were formed. Significant differences among impoundment groups were also detected in fish yield. We conclude that the variation in environmental conditions, together with differences in fish communities in the impoundments were important enough to justify the claim that impoundments of different types require different management strategies. KEY WORDS: Impoundments; River regulation; Fish assemblage; Water quality; Aquatic vegetation; Finland     

Upper Yellow River air concentrations of organochlorine pesticides estimated from tree bark, and their relationship with socioeconomic indices

Organochlorine pesticide(OCP) concentrations in tree bark from the upper Yellow River region were determined. Total OCP concentrations ranged from 2.7 to 82 ng/g dw, with a mean of 20 ng/g dw. Concentrations of total(Σ) DDTs(0.49–37 ng/g dw), HCHs(0.55–4.5 ng/g dw), and HCB(0.1–1.0 ng/g dw) were much higher than the other OCPs and accounted for 89% of the ΣOCP concentrations. p,p′-DDT was the dominant member of the DDT pesticide group and-HCH was the dominant HCH isomer. The p,p′-DDT/p,p′-DDE and-HCH/-HCH ratios suggested that there were recent DDT and-HCH releases. OCP concentrations in the air were estimated from the tree bark, and the estimated median ΣDDTs, ΣHCHs, and HCB concentrations in the air were 0.09, 0.14, and 0.024 pg/m3, respectively. The relationship between total OCP concentrations and socioeconomic and natural environment indices were assessed using multiple linear regression analysis, and a regression equation including all these factors was obtained. Population density and tertiary industry were the two dominant factors that appeared to affect OCP concentrations in the upper Yellow River region.     

印江槽谷型喀斯特地区植被碳储量及固碳潜力研究

以印江槽谷型喀斯特石漠化地区11种植被类型(人工纯林、人工混交林、天然纯林、天然混交林、疏林、竹林、经果林、灌木林、石山地、宜林地、草地)为研究对象,分析了植被碳储量的空间分布格局,并对区域植被固碳速率、碳储量进行了估算,并预测了理论最大固碳潜力。结果表明:印江研究区植被碳储量空间分布为,乔木层(25.06 t/hm²) > 灌木层(3.51 t/hm²) > 草本层(1.10 t/hm²),其平均固碳速率为10.63 t/(hm²·a),植被碳储量为172.23×10³ t,植被理论最大固碳潜力为94.02 t/hm²。研究结果对于评价和估计印江槽谷型喀斯特石漠化地区森林的碳汇功能,以及提高碳储量有重要意义。     

生态恢复背景下喀斯特地区植被覆盖的时空变化——以黔中地区为例

为了揭示退耕还林(草)、封山育林和石漠化综合治理等生态恢复工程驱动下喀斯特地区的植被覆盖度的时空变化情况,以黔中为研究区,利用2000年、2005年和2010年三期的MODIS影像数据,通过NDVI像元二分模型法,对研究区植被覆盖进行了动态变化评估。结果表明:2000年到2010年,极高植被覆盖度面积持续增长,高植被覆盖度面积持续减少,极低植被覆盖度、低植被覆盖度和中等植被覆盖度面积先增后减,植被覆盖总体呈现转好趋势;此外,植被覆盖景观斑块数减小,平均斑块面积增大,香农多样性指数减小,表明这一时期内植被覆盖景观的破碎化程度逐渐降低,生态恢复工程取得良好实效。     

基于MODIS EVI的重庆植被覆盖变化的地形效应

基于2000—2015年的MODIS EVI数据,采用趋势分析结合地形差异修正,分析了重庆市植被覆盖变化在高程、坡度和坡向上的空间分布差异。结果表明:1)近16 a来,重庆植被以低覆盖度和中覆盖度为主,低覆盖度呈下降趋势,劣覆盖度、中覆盖度和高覆盖度呈上升趋势;2)研究区植被显著减少趋势占3.84%,基本不变占81.12%,显著增加占15.04%,植被变化总体上呈恢复趋势;3)在地势低(400 m)、坡度小(6°)的区域,植被覆盖度低,但变化趋势显著;在400~1 200 m、6°~15°的区域,植被变化趋势分布出现由优势到非优势或由非优势到优势的转折;4)在地势高(1 200 m)、坡度大(15°)的区域,植被覆盖度高,变化趋势较弱,但是在高程大于1 500 m、坡度大于25°的区域也存在植被减少的现象;5)不同坡向上,除了在平地区域植被变化趋势较显著外,其余坡向差异不明显。     

矿区不同植被复垦模式对土壤细菌群落结构的影响

以安太堡露天煤矿复垦区为研究对象,用PCR-DGGE技术分析不同复垦植被(榆树、落叶松、杏树、云杉和刺槐)及复垦年限(15年和20年)对土壤细菌的影响.土壤细菌多样性分析结果表明:复垦20年组,榆树最高,杏树最低,其余3个植被无显著差异;复垦15年组,云杉显著高于刺槐;刺槐随复垦年限延长,其土壤细菌多样性显著增高,而云杉却反之.相似性系数分析、聚类分析和PCA均显示,相同复垦年限的土样细菌群落结构相似性高.相关性分析表明细菌多样性指数和土壤pH显著正相关.优势和差异条带测序鉴定出Nitrospira、Sphingomonas、Arthrobacter、Brachybacterium、Rhizobium以及Mesorhizobium等或参与氮循环、或降解多环芳烃及杂环有机物的细菌属.本研究说明榆树和云杉有利于土壤细菌多样性的恢复;复垦区土壤的优势菌群多为有利于污染土壤的生态修复和肥力恢复的功能细菌属.     

黄土高塬沟壑区不同坡位和植被下的土壤硝态氮特征研究

地形和植被会改变水分在土壤中的运移,进而影响土壤中硝态氮(NO_3~--N)的分布,并可能导致对水体污染的差异.在黄土高塬沟壑区黑河流域选取3个样点,采集刺槐林和草地在不同坡位(上、中和下坡位)的6 m深土样,分析了坡位和植被对NO_3~--N迁移的影响,并初步评估了其对地表水及地下水污染的潜在风险.不同坡位及植被条件下,土壤中硝态氮均没有出现累积,在表层土壤达到最大值后逐渐减小.2种植被下NO_3~--N达到稳定时的深度约为200 cm,稳定浓度均为下坡位上坡位中坡位,但在同一坡位的稳定浓度均有草地高于刺槐林的特点,说明坡位及植被覆盖类型均会影响NO_3~--N在土壤中的分布.整个流域地表水NO-3含量枯水期及汛期分别为(6.90±2.10)mg·L~(-1)和(5.84±2.86)mg·L~(-1),而坡地表层土壤(0~20 cm)中可移动态NO_3~-为(29.55±6.59)mg·L~(-1),明显大于地表水中的浓度,很有可能随径流流失造成地表水氮素污染.地下水枯水期和汛期的NO_3~-含量分别为(24.61±23.72)mg·L~(-1)和(15.70±10.78)mg·L~(-1),而坡地深层土壤(200 cm)中NO-3为(0.78±0.16)mg·L~(-1),由于浓度较低,对地下水造成污染的可能性较小.     

黄土高原不同植被类型下土壤细菌群落特征研究

研究黄土高原不同植被类型对土壤细菌微生物多样性的影响,对发挥土壤潜在肥力、了解土壤健康状况,实现植被的管理与可持续利用有着重要的意义.本文选取黄土高原4种草原植被与4种乔木林植被的表层土壤(0~5 cm)为研究对象,利用第二代高通量测序技术454 Hi Seq对其进行16S r DNA V1~V3可变区的高通量测序,分析土壤细菌的Alpha多样性、物种组成和丰度,并研究土壤性质对细菌群落结构的影响.结果表明,所测土壤样品中共检测到细菌的36个门,84个纲,187个目,优势菌门为变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)、绿弯菌(Chloroflexi)、浮霉菌门(Planctomycetes),主要的优势菌纲为放线杆菌纲(Actinobacteria)、α-变形菌纲(α-Proteobacteria)、酸杆菌纲(Acidobacteria)、β-变形菌纲(β-Proteobacteria)、浮霉菌纲(Planctomycetacia).草原植被土壤分布更多的是Actinobacteria,森林植被土壤分布更多的是Proteobacteria.Proteobacteria与土壤有机质、全氮、全磷呈显著的相关性,其相对丰富度主要受土壤碳氮磷含量的限制.Actinobacteria的生长主要受土壤pH、水分和土壤有机质的影响.通过RDA分析发现,影响黄土高原土壤细菌分布的主要土壤因子是土壤水分,这些结果丰富了黄土高原土壤微生物多样性的理论知识,而且可为黄土高原植被恢复模式的选择提供理论依据.     

科尔沁沙地退化植被恢复过程中土壤有机碳和全氮的空间异质性

采用地统计学分析方法研究了沙地退化植被恢复过程中(封育0 a的流动沙丘、封育11 a的流动沙丘和封育20 a的流动沙丘)土壤有机碳和全氮的空间异质性,探讨了它们与植被恢复演替和地形特征变化的关系.结果表明,随着流动沙丘的固定和封育年限的增加,植被盖度、丰富度、物种多样性、土壤有机碳和全氮含量(0~20 cm)逐渐增加.在流动沙丘植被恢复过程中,土壤有机碳和全氮的结构方差与基台值的比值C/(C0+C)均大于65%,反映出它们具有明显的空间自相关性;土壤有机碳和全氮含量的空间自相关范围分别为58.39 m和91.00 m(封育0 a)、28.59 m和23.61 m(封育11 a)和63.31 m和61.05 m(封育20 a).由半方差函数及其参数和空间分布格局图分析表明,其空间异质性在所研究的尺度上表现出先增大(封育0~11 a)后减小(封育11~20 a)的变化特点.沙丘植被恢复过程中植被盖度、丰富度、物种多样性与土壤有机碳和全氮均有极显著的正相关关系(p<0.01).分析表明沙丘植被变化和地形特征影响着土壤有机碳和全氮在沙丘上的空间分布,沙丘植被恢复演替过程极大地影响了土壤有机碳和全氮的积累及其空间异质性...