Coniferous afforestation increases soil carbon in maritime sand dunes

Afforestation of grasslands can increase C sequestration and provide additional economic and environmental benefits. Pine plantations, however, have often been found to deplete soil organic C and trigger detrimental effects on soils. We examined soil characteristics under a 45-year-old Pinus radiata stand and under adjacent grassland on maritime dunes in temperate Argentina. Soil under the pine plantation had greater soil organic C (+93%), total N (+55%) and available P (+100%) concentrations than under grassland. Carbon was stored under the pinestand at an estimated mean accretion rate of 0.64 Mg ha^?1 y^?1. At 0- to 25-cm depth, soil C amounted to 61 Mg ha^?1 under pine and 27 Mg ha^?1 under grassland. Soil C accumulated more on dune slopes (35 Mg ha^?1 y^?1) than on ridges(29 Mg ha^?1 y^?1) and bottoms (12 Mg ha^?1 y^?1). Compared with the grassland, soil acidity, cation-exchange capacity, base losses (K > Ca = Mg) and C/N ratio increased under pine. Spatial heterogeneity in soil characteristics was greater under pine than under grassland. Such variability was non-systematic and did not support the ‘single-tree influence circle’ concept. Afforestation increased C in soil, forest floor and tree biomass in dunes with ustic climate regime.     

Soil microbial communities and activities in sand dunes of subtropical coastal forests

To understand the soil microbial activities and community structures in different forests in a sand-dune ecosystem, we conducted a study of 2 topographic conditions, upland and lowland, under a Casuarina forest. As well, in the lowland site, we compared forest soil microbial properties under 3 coastal forests (Casuarina, Hibiscus and mixed stand). The soil microbial biomass did not significantly differ between the upland and lowland Casuarina forest sites. At the lowland site, the soil microbial biomass was higher in the Hibiscus than Casuarina forest soil. Cellulase, xylanase, phosphatase and urease activities did not show a consistent trend by topography or vegetation. Analysis of phospholipid fatty acids (PLFAs) of bacteria and actinomycetes revealed a significant difference in microbial community structure by both topography and vegetation. PLFA content was higher at upland than lowland sites in the Casuarina forest. At the lowland site, the level of PLFAs was higher in Hibiscus than Casuarina forest soil. In addition, we examined the ratios 16:1ω7t/16:1ω7c and, cy17:0/16:1ω7c as indicators of physiological stress; the soil in the Casuarina forest had the highest values, which suggests that the microbial community in the Casuarina forest soil is under physiological stress or starvation conditions. Comparison of soil microbial properties suggest that planting Hibiscus may help to enrich soil fertility and increase microbial activities in coastal sand-dune Casuarina forest.     

An environmental approach to the restoration of badly eroded sand dunes

On a coastline where the natural beach/dune system is essentially stable, the ability of the sand dunes to recover from degradation caused by human activities is seriously impaired, even when conventional remedial techniques are employed. This paper presents a short report on an experimental regrading scheme which has shown that the initial smoothing of the foredune profile by bulldozer is beneficial to ecological recovery. It is felt that this method is the only practical alternative in such areas, and that ecologists, planners and conservationists should not be reluctant to employ engineering techniques if environmental conditions warrant their use.     

Composition of bacterial communities in sand dunes of subtropical coastal forests

Biology and Fertility of Soils - Coastal sand dunes are a hostile environment for forests. Little is known about the composition and diversity of the bacterial community in forest soils established...     

不同植物灌丛沙丘表面沉积物粒度变化及其固沙能力

研究沙区不同类型植物灌丛沙丘地表沉积物环境敏感粒度组分体积百分含量变化及其影响因素有助于精确描述地表风沙运动过程,为快速比较不同植物种固沙能力和沙区植被恢复提供参考。采用激光衍射法对乌兰布和沙漠内部5种荒漠植物灌丛沙丘地表沉积物粒度差异进行测定,以粒级-标准偏差法对风沙环境敏感组分进行提取,根据敏感组分体积百分含量变化对植物固沙能力进行评价,并以多元线性回归方法拟合了敏感组分体积百分含量对植株形态指标变化的响应。结果表明:沙鞭、沙蓬、芦苇样地表层沙物质分布同裸沙丘均为单峰型,白刺和油蒿为双峰型。植被分布区沙丘表层沉积物中沙、细沙减少,极细沙和粉粒增加,沉积物颗粒分选性变差,频率曲线趋于正偏,峰度值降低。整体而言,颗粒组成由细到粗依次为:白刺油蒿芦苇沙蓬沙鞭裸沙丘。乌兰布和沙漠地表沉积物存在1.45~76和76~456μm 2个环境敏感粒度组分,中值分别为57.3和193.6μm,分别命名为细组分和粗组分,细组分对应风沙流中的悬移质,粗组分为跃移质。环境敏感组分在各植物覆盖下差异显著,细组分体积百分含量变化为:白刺油蒿沙蓬芦苇沙鞭裸沙丘,粗组分体积百分含量变化相反,植株对风动力的阻滞能力相应降低。多元线性回归显示,细组分体积百分含量与株高、冠幅、分枝数呈正相关关系,与疏透度呈负相关关系,表层沉积物中细组分体积百分含量越高的植物灌丛,影响其体积百分含量多少的因素越复杂。     

阿拉善流动沙漠区沙层CO2浓度与昼夜变化规律研究

利用红外CO2监测仪,对全球最高大的巴丹吉林诺尔图湖东大沙山、沙坡头流动沙丘和民勤流动沙丘进行了19个钻孔的CO2浓度昼夜观测。结果表明,阿拉善流动沙漠区空气中CO2浓度较1 m、2 m、3 m、4 m、5 m沙层中CO2浓度均低,表明在植物极稀少的流动沙漠区温暖季节会向空气中释放CO2,是大气CO2的来源区。沙层不仅白天向空气释放CO2,夜间也在释放CO2。在极端干旱的阿拉善流动沙漠区沙层2 m深处CO2浓度一般较1 m、3 m、4 m、5 m的大,但也有个别例外。流动沙漠区沙层CO2浓度的昼夜变化也具有明显的规律性,各个深度沙层CO2浓度从早8时至次日7时均呈现由低到高再到低的变化规律。沙层CO2浓度与昼夜温度变化呈显著正相关关系。在极端干旱的阿拉善流动沙漠区水分含量较高的沙层CO2浓度明显高,表明沙层含水量高低是决定沙层CO2浓度水平的主要因素。     

用气象数据估算固定和半固定沙地的起沙速率

Taibus County, Inner Mongolia, China, lies in a farming-pastoral ecotone, where severe wind erosion and various aeolian sand hazards are prevalent and fixed and semi-fixed sand dunes occur frequently. This study was conducted to investigate the relationships between sand transportation rate and wind speed for the fixed and semi-fixed sand dunes based on field measurements. The annual quantity of soil erosion by wind was estimated using meteorological wind data. The results indicated that the sand transportation rate in Taibus County in 2000 was 57.38 kg cm-1 year-1 for the semi-fixed dunes and 4.56 kg cm-1 year-1 for the fixed dunes. The total duration of erosive winds covered 12.5% of the time of the year, and spring posed the highest potential of sand transportation. Wind with low speed (≤17 m s-1) and high frequency plays a dominant role in sand transportation, while strong wind (≥17 m s-1) with low frequency significantly enhanced the sand transportation. Erosive wind speed, directions, and frequency were three crucial dynamic factors influencing sand hazards in the farming-pastoral ecotone. The dominant factors intensifying sand and dust storms in Taibus County might be related to the favorable wind condition in combination with the durable drought, which led to land desertification and vegetation degradation.     

Soil macrofaunal response to sand dune conversion from mobile dunes to fixed dunes in Horqin sandy land,northern China

The response of macrofauna to dune conversion from mobile dunes to fixed dunes was investigated in Horqin sandy land, northern China. Macrofaunal communities were compared in four major stages: mobile dunes (MD), semi-mobile dunes (SMD), semi-fixed dunes (SFD) and fixed dunes (FD). Macrofauna were collected by hand in the field and identified in the lab on the basis of features observed under a magnifying glass. They were then classified into morphotypes at the order and family level. Environmental parameters indicated a significant alteration of the soil environment in the conversion process. A clear increasing trend in abundance, richness, and diversity of the macrofaunal community could be established from mobile dunes to fixed dunes. Data for the different taxa suggested specific responses to dune conversion. Specific groups in the initial stage were predators (Labiduridae and Myrmeleontidae larvae, presumably feeding on Noctuidae and other small flying insects), which in the intermediate stages were replaced by saprophagous taxa (Diptera larvae, feeding on many decaying roots buried in semi-mobile and semi-fixed dunes), and burrowing Tenebrionidae (adults, then larvae) with herbivorous Hemiptera in later fixation stages with higher plant density and cover. Overall, the conversion process, particularly the fixed dunes, provided more suitable habitats with greater soil organic matter and plant cover supporting macrofaunal communities with higher diversity, which further enhanced the stabilization process, benefiting the restoration of soil and vegetation in this semiarid sandy area.     

Invasive Acacia longifolia induce changes in the microbial catabolic diversity of sand dunes

Acacia longifolia is one of the main plant species invading Portuguese dune ecosystems. Areas invaded by this exotic tree have reduced plant diversity and altered soil microbial processes and nutrient pools, but the impacts on microbial functional diversity in the soil have been little explored. Soil samples were collected in areas invaded by A. longifolia for more than 20 years, in areas invaded after 1995 and in non-invaded areas. Respiration responses to 20 different substrates were analysed, in order to assess the catabolic response profile (CRP) as a measure of microbial functional diversity. Five substrate groups were tested: amino acids, carbohydrates, carboxylic acids, plant litters, and plant polymers. CRP clearly discriminated between the three different areas. Respiratory responses to the individual substrates α-ketoglutaric acid, oxalic acid, starch, citric acid, and xylose and to the groups of amino acids and plant polymers were similar in both invaded areas and different in the non-invaded. The responses to tartaric acid, gallic acid, fumaric acid, Cistus litter, and Acacia litter were the same in long- and non-invaded areas, but different from recently invaded areas. The duration of invasion, carbon (C) content, nitrogen (N) content, C/N ratio, pH, and litter quantity explained 39.6% of the variance of catabolic responses. It is concluded that invasion by A. longifolia has substantial effects on the catabolic diversity of the soil microbial communities. These effects may have wider implications for nutrient cycling and ecosystem-level processes and for the invasibility of the system.     

矿山边坡生态建设的植被特征与群落动态变化

为了解边坡生态防护工程植被建植的生长变化规律,依托实际工程,以植生基质喷射技术（Planting Material Spraying,简称PMS绿化工程技术）体系作为矿山边坡复绿的应用背景,对3个不同坡向、坡度的边坡在人工植被建植后5年内主要群落特征（物种、盖度和高度等）进行跟踪调查.结果表明：1）边坡人工植被建植1周年内,数量特征总体上表现为组成简单、垂直结构不明显.刺槐、胡枝子、狗牙根、紫花苜蓿和高羊茅长势优于其他物种.2）植被建设5年后,建设效果良好,多样性和丰富度得到提高,优势度下降,均匀度趋于稳定,形成有较强固土护坡效果的多年生草本＋胡枝子＋刺槐的植被群落,乔灌草植株根系发运良好,且豆科植物在群落中占据着主要的优势.3）植被越冬越夏期间,部分高羊茅出现倒伏现象,少量刺槐出现叶片萎缩,波斯菊相较于其他植物死亡植株较多,但大部分植物对于极端天气抵抗力较好,并初步形成有较强固土护坡效果和较好景观效果的植物群落.     

The decline of the sand lizard, Lacerta agilis L. Population on the sand dunes of the Merseyside coast,England

The population of the sand lizard Lacerta agilis in northwest England has declined sharply since 1930. The reasons for this decline are considered.Between Southport and the River Alt, approximately 50% of the sand dune habitat has been destroyed and a further 12% modified since 1801. Habitat losses resulting from building developments help to explain the sand lizard decline. The species has also disappeared from areas still supporting dune habitat. Here a combination of factors appear responsible, the effects of which are not uniform throughout the dune system.It is concluded that, in conjunction with a trend of less favourable climate over the last 15 years, habitat destruction, fragmentation and change of quality have brought about a catastrophic decline in the sand lizard population within the last 20 years. It is predicted that this population will become extinct before 2000 unless present trends are halted and adequate conservation measures taken.     

Blowout dynamics on Lake Huron sand dunes: analysis of digital multispectral data from colour air photos

We adapted a digital image analysis procedure to extract multispectral data from sequential colour air photos of a Lake Huron sand dune system and then classify land cover into water, sand, and vegetation. We isolated portions containing individual blowouts from georeferenced land cover maps of the dune system in 1973 and 1998 and overlaid the sequential images using geographic information systems (GIS). This allowed us to quantify changes in blowouts over the 25-year period. Net change in land cover (m²) within each blowout was expressed as the difference between retrogression (bare areas created by erosion or burial of existing vegetation) and colonization (vegetation patches created by plant establishment on bare areas). The analysis procedure produced maps with an overall accuracy of ≥90% for land cover classification within blowouts. The individual blowouts fell along a continuum of activity, varying from significant retrogression (+748 m²) to significant colonization (−1148 m²). Overall, sand movement in all sampled blowouts produced 3991 m² (17.9% of the blowout area in 1998) of bare sand patches that replaced formerly existing patches of vegetation. Colonization of bare areas over the 25-year period was 4127 m² or 18.5% of the 1998 blowout area. Retrogression and colonization are natural cooccurring processes in coastal dune systems, and the technique described here represents a new tool for the study of temporal and spatial vegetation dynamics in blowouts.     

Spatial pattern and heterogeneity of soil properties in sand dunes under grazing and restoration in Horqin Sandy Land, Northern China

Applying a combination of classical and geostatistical methods, we identified soil properties and their spatial variation in a 5-year grazed sand dune (GSD5) and a 20-year recovered sand dune (RSD20) in Horqin Sandy Land, northern China. The paper assesses the effect of grazing, topography and vegetation restoration on spatial heterogeneity of soil properties. The results showed that soil organic carbon, total nitrogen, very fine sand (0.1–0.05 mm) content and their coefficients of variation were lower in GSD5 than in RSD20, while soil water contents (0–20 cm and 20–40 cm depths) were higher in GSD5 than in RSD20. Geostatistical analysis revealed that the spatial structured variance accounted for the largest proportion of total sample variance in soil properties at the measured scale under grazing and restoration. The spatial autocorrelation ranges were 66.30 m for soil organic carbon and 50.80 m for total nitrogen in GSD5 less than those in RSD20 (70.00 m and 76.10 m, respectively), while the spatial autocorrelation ranges of soil particle size fractions and soil water contents in RSD20 were less than those in GSD5. Kriging-interpolated maps also showed that the heterogeneity of soil organic carbon and total nitrogen and their degree of patch fragmentation were higher in GSD5 than in RSD20. These results suggested that continuous grazing resulted in an increase in spatial variability of soil nutrient and a decrease in spatial variability of soil particle size fractions and soil water content. Soil organic carbon and total nitrogen of sand dunes are associated closely with soil particle size fractions, relative height of sampling site and vegetation cover. Spatial patterns of soil properties are most strongly related to grazing, topography and plant-induced heterogeneity in sand dune ecosystems prone to wind erosion.     

A study of the effects of trampling on the vegetation of Lake Huron sand dunes at Pinery Provincial Park

Plots in established heath-grassland vegetation and pure stands of Calamovilfa longifolia (Hook) Scribn. on Lake Huron sand dunes were subjected to tramppling treatments at various intensities during 1977 and 1978 and were monitored for one year following treatment. Both heath-grassland and Calamovilfa plots given 50 walking passages showed complete recovery within one year after treatment. Heavier treatments (200 walking passages) on Calamovilfa caused a significant reduction in cover one year later. Heavily trampled heath-grassland plots, although visually similar to their controls, had a continued loss of lichen cover over one year. Several species including Arctostaphylos uva-ursi (L.) Spreng., Andropogon scoparius Michx., some Carex species, Liatris cylindracea Michx. and Rosa blanda Ait. initiated new growth in the fall following heavy trampling treatment, but only shoots of Arctostaphylos survived the winter.     

Vegetation and sand characteristics influencing nesting activity of Caretta caretta on Sekania beach

Despite its relatively small length (650 m), Sekania beach on Zakynthos island (Ionian sea) is the single most important Caretta caretta L. nesting beach in the Mediterranean Sea. The aim of this work was to tackle the possible relationships of sand and vegetation characteristics with the nesting activity of sea turtle C. caretta. The vegetation structure and distribution along the sandy beach was studied with the use of line transect method. Grouping of plant species was revealed through an ordination method. Plant groups were distinguished and mapped. Sand texture, pH, and organic matter were measured on the transects. Nesting activity was also mapped on the beach and hatching success was recorded. It was concluded that where sand salinity is high enough to prevent vegetation development, wet sand is located at a threshold depth for excavating an egg chamber. It seems that well-sorted sand grains favor nesting activity on the beach. The increase of fine sand - from east to west - is proportional with the reduction of nesting density. The data collected for this study are organized in a GIS database, which could be the basis for the establishment of an integrated monitoring system for Sekania beach.     

Organic matter status and the size,activity and metabolic diversity of the soil microflora as indicators of the success of rehabilitation of mined sand dunes

The effectiveness of the rehabilitation of mined sand dunes on the northern coast of KwaZulu–Natal, South Africa, was assessed based on measurements of the total and labile organic matter content and the size, activity and metabolic diversity of the soil microflora. Soil was sampled (0–10 cm) after 0, 5, 10, 20 and 25 years of rehabilitation and compared with soil under undisturbed native forest and under long-term commercial pine forest. Following topsoil removal, stockpiling and respreading on reformed dunes, there was a massive loss of organic C such that, at time zero, organic C content was only 24% of that present under native forest. Soil organic C content increased progressively during rehabilitation until, after 25 years, it represented 93% of that present under native forest. The pattern of change in light-fraction C, KMnO₄-extractable C, water-soluble C, microbial biomass C, basal respiration and arginine ammonification rate was broadly similar to that for organic C, but the extent of the initial loss and the magnitude of the subsequent increase differed. Microbial biomass C, water-soluble C and KMnO₄-extractable C, expressed as a percentage of organic C, declined during rehabilitation as humic substances progressively accumulated. Principal component (PC) analysis of catabolic response profiles to 36 substrates revealed that the catabolic diversity of microbial communities differed greatly between native forest, commercial pine forest, 0 years and 10 years of rehabilitation. On the PC1 axis, values for soils under native forest and after 25 years rehabilitation were similar, but there was still separation on the PC2 axis. The main factor explaining variation in response profiles on the PC1 axis was organic C content; and the greatest catabolic diversity occurred in soils under native forest and after 25 years of rehabilitation.     

Evaluation of experimental plot design for a sloping and eroding site

Abstract

Sloping and eroding soils are often avoided by many agronomists when selecting a site for long term crop or soils research due to concerns about the impact of soil variability on experimental results. The extent of soil loss and erosion phase was determined by comparisons of soil properties at the cultivated site with a forest site having similar soil, slope and landscape characteristics. The cultivated site was dominated by the moderately eroded phase of the Grantsburg soil with approximately 7.5 cm of soil (38% of upper 20 cm of original soil) eroded during the previous 80 years. Prior to the establishment of the tillage treatments of no‐tillage (NT); chisel‐plow (CP); and moldboard plow (MP), a number of selected soil property parameters were examined to measure the inherent soil conditions that existed within the experimental area, and to test the precision of the experimental design. An experimental design was selected which fit within the field boundaries, landscape position, soil and slope constraints. The experimental design was a Youden Type III, and Incomplete Latin Square, that allowed for randomization of treatments to the plots by both row (block) and column (replication) to control random variability in the two directions. Overall, the experimental design selected to control random variability that existed within the experimental area was effective. This was evidenced by the lack of significant differences among most of the tillage treatment locations with respect to the background data collected.