黄土丘陵区植被恢复中不同粒级土壤团聚体有机碳分布特征

对黄土丘陵区土壤有机碳在不同粒级团聚体中的分布特征及其对植被恢复的响应进行了研究。结果表明:(1)黄土丘陵区不同植被覆盖条件下,土壤有机碳的分布具有一定的表聚性,0~20 cm土层中有机碳的含量均高于20~40 cm中有机碳的含量,不同植被群落下有机碳的含量大小为:大针茅群落>长芒草群落>铁杆蒿群落>百里香群落;(2)同一深度土壤各粒级团聚体中有机碳的分布特征是:0.5~0.25 mm与1~0.5 mm两个粒级中有机碳的含量最高,>1 mm的团聚体中有机碳的含量有随粒级增大而减小的趋势;(3)恢复年限对不同粒级土壤团聚体中有机碳的含量影响很大,有机碳的含量随恢复年限的增加总体呈上升趋势。黄土高原沟壑区土壤有机碳的积累与土壤团聚体的粒级和植被恢复的类型、年限等有明显的关系。

黄土高原中部丘陵区生态农业结构模式及阶段目标

分析了黄土丘陵区农业生产现状和存在的主要问题 ,指出广种薄收习惯是导致土地利用不合理 ,植被遭到破坏 ,进而水土流失加剧和生态环境恶化 ,农业生产力降低的根源。该地区生态农业建设的核心是改变广种薄收习惯 ,治理水土流失 ,不断调整优化土地利用和产业结构。依据土地资源状况提出目前阶段 1 2 34的土地利用结构模式。认为在占总土地面积 2 0 %的基本农田和果园 ,只要实行集约化经营就可实现较高的经济效益 ,70 %的土地应为林草地。根据生态农业的基本原则和当前生产水平提出生态农业建设三个阶段的不同指标和适宜治理度 ,当前该地区主导产业的发展应以资源—结构—质量型模式为主

天山北麓中段土壤侵蚀影响因素及特征分析

通过对天山北麓中段土地类型、河流径流和植被覆盖等土壤侵蚀影响因素的空间分布特征分析认为 :1天山北麓中段主要侵蚀类型为风蚀、水蚀、冻融侵蚀及人为加速侵蚀 ;2侵蚀产沙类型以及产沙强度在空间上具有明显的垂直变化规律 :沙漠以风力侵蚀、高山和亚高山以冻融侵蚀为强烈侵蚀类型 ,普遍存在微度水力侵蚀 ,局部表现为中度甚至强度 ;3水蚀类型有冰川融雪径流侵蚀和降雨径流侵蚀两种方式。天山北麓中段河流产沙时间上主要在每年的 5月初至 8月末 ,且冰川雪水径流产沙要比雨水径流产沙量大 ,空间上则主要位于海拔 80 0～ 1 50 0 m的由第三纪、第四纪地层和黄土堆积所组成的中、低山丘陵地

黄土高原森林植被水土保持机理研究

土壤侵蚀是造成环境退化的一个主要因素。长期以来因不合理的利用自然资源 ,日积月累的结果使得植被生存的环境受到极大的破坏 ,导致植被衰退 ,引发了严重的水土流失 ;水土流失的不断加剧 ,破坏了土地的生产力 ,土壤肥力降低 ,土壤蓄水能力减弱 ,植被生存的环境进一步恶化 ,如此以往使生态环境陷入恶性循环状态。黄土高原严重的水土流失与该区植被覆被率低有密切的关系。据“七五”统计 ,主要水土流失区现有森林面积约 2 5× 1 0 6ｈｍ2 ,其中人工林占 40 %左右 ,有林地森林覆盖率仅为 9 3% ,而且能发挥水土保持功能的森林覆被率仅为 7 0 % ,这些覆被率高的地区 ,地处六盘山、乔山、黄龙山等地 ,该区域人口密度较低 ,人为活动轻微 ,水土流失小 ;在黄土高原水土流失严重的地区 ,森林覆被率更低 ,仅 5 9% ,即使发挥水土保持功能 ,在宏观范围内仍然难以体现出保持水土的效益 (中共陕西省委研究室等 ,1 999;吴钦孝等 ,1 998)。森林植被有强大的水土保持功能 ,体现在下列几个方面 :植被冠层及地被物的截留作用 ,使大气降水的损失量较大 ,减小了产生径流的净雨量 ;地被物层对汇流的延长作用 ...

黄土高原不同演替阶段草地植被细根垂直分布特征与土壤环境的关系

研究了黄土区不同演替阶段草地植被细根垂直分布特征与土壤环境的关系,结果表明不同演替阶段草地植被细根生物量、根长密度、表面积、直径和比根长均具有明显的垂直分布特征。细根生物量、根长密度和细根表面积一般随土层加深而逐渐减少,且集中分布于0~40cm土层;随着演替的进行,除20a弃耕地外,0~80 cm土层细根生物量、根长密度和细根表面积逐渐增加;除25a弃耕地外,细根直径随演替进行逐渐减小。0~100 cm土层土壤含水量随演替进行而增加,不同演替阶段深层土壤水分较表层稳定。土壤容重的变化趋势为9<4<15<20<25a弃耕地,根系对表层土壤水分和容重的影响较大,而对深层土壤水分与容重影响较少。不同演替阶段细根各参数和土壤水分、容重差异均达到显著水平。各弃耕地细根参数之间,细根参数和土壤环境因子之间存在不同程度的相关关系,土壤含水量在草本植被的不同演替阶段均是影响其细根垂直分布的关键因素。土壤容重在演替早期对草本植被根系的影响较小,随着演替进行其影响作用进一步增强。

区域水土流失植被因子的遥感提取

NDVI是区域土壤侵蚀评价的最佳植被因子。基于遥感影像TM数据提取了NDVI值并将其与土地利用信息同时集成于土壤侵蚀图的每个图斑,建立了包含多种因子的空间数据库。通过每个图斑林草地面积百分比和NDVI值的统计分析,建立了NDVI与植被盖度的线性关系。多重因子数据库和NDVI-植被盖度关系,可以为区域土壤侵蚀定量评价提供支持。

Estimation of wind erosion rates by using Cs-137 tracing technique: A case study in Tariat-Xilin Gol transect, Mongolian Plateau

Wind erosion is one of the major environmental problems in semi-arid and arid regions. Here we established the Tariat-Xilin Gol transect from northwest to southeast across the Mongolian Plateau, and selected seven sampling sites along the transect. We then estimated the soil wind erosion rates by using the Cs-137 tracing technique and examined their spatial dynamics. Our results showed that the Cs-137 inventories of sampling sites ranged from 265.63 +/- 44.91 to 1279.54 +/- 166.53 Bq.m(-2), and the wind erosion rates varied from 64.58 to 419.63 t.km(-2).a(-1) accordingly. In the Mongolia section of the transect (from Tariat to Sainshand), the wind erosion rate increased gradually with vegetation type and climatic regimes; the wind erosion process was controlled by physical factors such as annual precipitation and vegetation coverage, etc., and the impact of human activities was negligible. While in the China section of the transect (Inner Mongolia), the wind erosion rates of Xilin Hot and Zhengxiangbai Banner were thrice as much as those of Bayannur of Mongolia, although these three sites were all dominated by typical steppe. Besides the physical factors, higher population density and livestock carrying level should be responsible for the higher wind erosion rates in these two regions of Inner Mongolia.

Phylogeography of Pinus tabulaeformis Carr. (Pinaceae), a dominant species of coniferous forest in northern China

How coniferous trees in northern China changed their distribution ranges in response to Quaternary climatic oscillations remains largely unknown. Here we report a study of the phylogeography of Pinus tabulaeformis, an endemic and dominant species of coniferous forest in northern China. We examined sequence variation of maternally inherited, seed-dispersed mitochondrial DNA (mtDNA) (nad5 intron 1 and nad4/3-4) and paternally inherited, pollen- and seed-dispersed chloroplast DNA (cpDNA) (rpl16 and trnS-trnG) within and among 30 natural populations across the entire range of the species. Six mitotypes and five chlorotypes were recovered among 291 trees surveyed. Population divergence was high for mtDNA variation (G(ST) = 0.738, N-ST = 0.771) indicating low levels of seed-based gene flow and significant phylogeographical structure (N-ST > G(ST), P < 0.05). The spatial distribution of mitotypes suggests that five distinct population groups exist in the species: one in the west comprising seven populations, a second with a north-central distribution comprising 15 populations, a third with a southern and easterly distribution comprising five populations, a fourth comprising one central and one western population, and a fifth comprising a single population located in the north-central part of the species' range. Each group apart from the fourth group is characterized by a distinct mitotype, with other mitotypes, if present, occurring at low frequency. It is suggested, therefore, that most members of each group apart from Group 4 are derived from ancestors that occupied different isolated refugia in a previous period of range fragmentation of the species, possibly at the time of the Last Glacial Maximum. Possible locations for these refugia are suggested. A comparison of mitotype diversity between northern and southern subgroups within the north-central group of populations (Group 2) showed much greater uniformity in the northern part of the range both within and between populations. This could indicate a northward migration of the species from a southern refugium in this region during the postglacial period, although alternative explanations cannot be ruled out. Two chlorotypes were distributed across the geographical range of the species, resulting in lower levels of among-population chlorotype variation. The geographical pattern of variation for all five chlorotypes provided some indication of the species surviving past glaciations in more than one refugium, although differentiation was much less marked, presumably due to the greater dispersal of cpDNA via pollen.

冰期间冰期转换过程中陆地碳库的演化规律研究

Terrestrial carbon pool mainly consists of three parts: the active carbon pool of the vegetation，soil carbon pools and the lithosphere carbon pool of less activity. Under natural conditions，vegetation carbon pools，soil carbon exchange with atmospheric carbon pool directly，the lithosphere participate in the global carbon cycle by weathering Our research have coverd the soil organic carbon density，plant biomass (carbon density)，plant net primary productivity of past 40 ka，and the magnetic susceptibility，grain size，weathering of silicate carbon consumption of past 140 ka. This study has achieved a number of conclusions as shown below. 1 Silicate weathering CO2 consumption in the long-term fluctuations with a similar deep-sea δ18O record，demonstate that it not only can be used as one of the instructions of terrestrial carbon pool，even can be used as indicators of global environmental change; silicate weathering CO2 consumption and susceptibility shown a clear relationship between lag or lead at different times，it maybe lies on how the climate change. 2 Soil carbon pools in line with the global climate on long-term，but the relationship between soil carbon density and climate change was not obvious in short-term change，generally lags behind the changes in other climatic proxies. 3 Carbon density of vegetation and other proxy indicators of climate have good consistency. In the study period，perform the cycle of glacial and interglacial completely，but because of the ancient vegetation of accurate information is difficult to obtain，it did not reflect rapid response to climate change. 4 Cooling events is conducive to soil organic carbon accumulation but not conducive to weathering and vegetation growth. High temperature environment is not conducive to the accumulation of soil organic carbon. 5 In the deglacial time from the last glacial maximum to the Holocene，weathering carbon consumption seems earlier than vegetation and soil organic carbon in the fluctuant increase.Does it imply that the effects of silicate weathering is an important factor to the global carbon cycle and global climate change? It is worth further research.

Relacje między zgrupowaniami ameb skorupkowych, roślinnością i parametrami siedliskowymi torfowisk minerotroficznych Wielkopolski

Wydział Biologii: Instytut Biologii Środowiska/Zakład Hydrobiologii

Biodiversity change in the Irish uplands - the effects of grazing management

As a prominent form of land use across much of upland Europe, extensive livestock grazing may hold the key to the sustainable management of these landscapes. Recent agricultural policy reform, however, has resulted in a decline in upland sheep numbers, prompting concern for the biodiversity value of these areas. This study quantifies the effects of varying levels of grazing management on plant, ground beetle and breeding bird diversity and assemblage in the uplands and lowlands of hill sheep farms in County Kerry, Ireland. Farms represent a continuum of light to heavy grazing, measured using a series of field indicators across several habitats, such as the internationally important blanket bog, home to the ground beetle, Carabus clatratus. Linear mixed effects modelling and non-metric multidimensional scaling are employed to disentangle the most influential management and environmental factors. Grazing state may be determined by the presence of Molinia caerulea or Nardus stricta, and variables such as % traditional ewes, % vegetation litter and % scrub prove valuable indicators of diversity. Measures of ecosystem functioning, e.g. plant biomass (nutrient cycling) and % vegetation cover (erosion rates) are influenced by plant diversity, which is influenced by grazing management. Levels of the ecosystem service, soil organic carbon, vary with ground beetle abundance and diversity, potentially influencing carbon sequestration and thereby climate change. The majority of species from all three taxa are found in the lowlands, with the exception of birds such as meadow pipit and skylark. The scale of measurement should be determined by the size and mobility of the species in question. The challenge is to manage these high nature value landscapes using agri-environment schemes which enhance biodiversity by maintaining structural heterogeneity across a range of scales, altitudes and habitats whilst integrating the decisions of people living and working in these marginal areas.

Interactions spatiales et auto-organisation des végétations semi-arides

Les recherches récapitulées dans cette thèse de doctorat ont porté sur les causes de l’organisation spatiale des végétations périodiques. Ces structures paysagères aux motifs réguliers, tachetés, tigrés ou labyrinthiques, d’échelle décamétrique à hectométrique, couvrant des étendues considérables sur au moins trois continents, constituent un cas d’école dans l’étude des processus endogènes présidant à l’hétérogénéité du couvert végétal. Ces structures prennent place sur un substrat homogène, mis à part la rétroaction du couvert lui-même, et sont marquées par des écotones abrupts et la persistance d’une proportion considérable de sol nu. Plusieurs modèles ont mis en avant l’existence possible d’un phénomène d’auto-organisation du couvert, qui verrait une structure d’ensemble émerger des interactions locales entre individus. Ces modèles se basent sur le jeu simultané de la consommation de la ressource (compétition) et de l’amélioration de l’un ou l’autre des éléments du bilan de la même ressource par le couvert (facilitation). La condition à l’existence d’une structure d’ensemble spatialement périodique et stable réside dans une différence entre la portée de la compétition (plus grande) et celle de la facilitation. L’apparition de ces structures est modulée par le taux de croissance biologique, qui est le reflet des contraintes extérieures telles que l’aridité, le pâturage ou la coupe de bois. Le modus operandi des interactions spatiales supposées entre individus reste largement à préciser.

Nos recherches ont été menées au sud-ouest de la République du Niger, à l’intérieur et dans les environs du parc Régional du W. Trois axes ont été explorés :(i) Une étude de la dépendance spatiale entre la structure de la végétation (biovolumes cartographiés) et les paramètres du milieu abiotique (relief, sol), sur base d’analyses spectrales et cross-spectrales par transformée de Fourier (1D et 2D). (ii) Une étude diachronique (1956, 1975 et 1996) à large échelle (3000 km²) de l’influence de l’aridité et des pressions d’origine anthropique sur l’auto-organisation des végétations périodiques, basée sur la caractérisation de la structure spatiale des paysages sur photos aériennes via la transformée de Fourier en 2D. (iii) Trois études portant sur les interactions spatiales entre individus :En premier lieu, via l’excavation des systèmes racinaires (air pulsé) ;Ensuite, par un suivi spatio-temporel du bilan hydrique du sol (blocs de gypse) ;Enfin, via le marquage de la ressource par du deutérium.

Nous avons ainsi pu établir que les végétations périodiques constituent bien un mode d’auto-organisation pouvant survenir sur substrat homogène et modulé par les contraintes climatiques et anthropiques. Un ajustement rapide entre l’organisation des végétations périodiques et le climat a pu être montrée en zone protégée. La superficie et l’organisation des végétations périodiques y ont tour à tour progressé et régressé en fonction d’épisodes secs ou humides. Par contre, en dehors de l’aire protégée, la possibilité d’une restauration du couvert semble fortement liée au taux d’exploitation des ressources végétales. Ces résultats ont d’importantes implications quant à la compréhension des interactions entre climat et écosystèmes et à l’évaluation de leurs capacités de charge. La caractérisation de la structure spatiale des végétations arides, notamment par la transformée de Fourier d’images HR, devrait être généralisée comme outil de monitoring de l’état de ces écosystèmes. Nos études portant sur les modes d’interactions spatiales ont permis de confirmer l’existence d’une facilitation à courte portée du couvert végétal sur la ressource. Cependant, cette facilitation ne semble pas s’exercer sur le terme du bilan hydrique traditionnellement avancé, à savoir l’infiltration, mais plutôt sur le taux d’évaporation (deux fois moindre à l’ombre des canopées). Ce mécanisme exclut l’existence de transferts diffusifs souterrains entre sols nu et fourrés. Des transferts inverses semblent d’ailleurs montrés par le marquage isotopique. L’étude du bilan hydrique et la cartographie du micro-relief, ainsi que la profondeur fortement réduite de la zone d’exploitation racinaire, jettent de sérieux doutes quant au rôle communément admis des transferts d’eau par ruissellement/diffusion de surface en tant que processus clé dans la compétition à distance entre les plantes. L’alternative réside dans l’existence d’une compétition racinaire de portée supérieure aux canopées. Cette hypothèse trouve une confirmation tant par les rhizosphères excavées, superficielles et étendues, que dans le marquage isotopique, montrant des contaminations d’arbustes situés à plus de 15 m de la zone d’apport. De même, l’étude du bilan hydrique met en évidence les influences simultanées et contradictoires (facilitation/compétition) des ligneux sur l’évapotranspiration.

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This PhD thesis gathers results of a research dealing with the causes of the spatial organisation of periodic vegetations. These landscape structures, featuring regular spotted, labyrinthine or banded patterns of decametric to hectometric scale, and extending over considerable areas on at least three continents, constitute a perfect study case to approach endogenous processes leading to vegetation heterogeneities. These patterns occur over homogeneous substratum, except for vegetation’s own feedbacks, and are marked by sharp ecotones and the persistence of a considerable amount of bare soil. A number of models suggested a possible case of self-organized patterning, in which the general structure would emerge from local interactions between individuals. Those models rest on the interplay of competitive and facilitative effects, relating to soil water consumption and to soil water budget enhancement by vegetation. A general necessary condition for pattern formation to occur is that negative interactions (competition) have a larger range than positive interactions (facilitation). Moreover, all models agree with the idea that patterning occurs when vegetation growth decreases, for instance as a result of reduced water availability, domestic grazing or wood cutting, therefore viewing patterns as a self-organised response to environmental constraints. However the modus operandi of the spatial interactions between individual plants remains largely to be specified.

We carried out a field research in South-West Niger, within and around the W Regional Park. Three research lines were explored: (i) The study of the spatial dependency between the vegetation pattern (mapped biovolumes) and the factors of the abiotic environment (soil, relief), on the basis of spectral and cross-spectral analyses with Fourier transform (1D and 2D). (ii) A broad scale diachronic study (1956, 1975, 1996) of the influence of aridity and human induced pressures on the vegetation self-patterning, based on the characterisation of patterns on high resolution remote sensing data via 2D Fourier transform. (iii) Three different approaches of the spatial interactions between individuals: via root systems excavation with pulsed air; via the monitoring in space and time of the soil water budget (gypsum blocks method); and via water resource labelling with deuterated water.

We could establish that periodic vegetations are indeed the result of a self-organisation process, occurring in homogeneous substratum conditions and modulated by climate and human constraints. A rapid adjustment between vegetation patterning and climate could be observed in protected zones. The area and patterning of the periodic vegetations successively progressed and regressed, following drier or wetter climate conditions. On the other hand, outside protected areas, the restoration ability of vegetation appeared to depend on the degree of vegetation resource exploitation. These results have important implications regarding the study of vegetation-climate interactions and the evaluation of ecosystems’ carrying capacities. Spatial pattern characterisation in arid vegetations using Fourier transform of HR remote sensing data should be generalised for the monitoring of those ecosystems. Our studies dealing with spatial interaction mechanisms confirmed the existence of a short range facilitation of the cover on water resource. However, this facilitation does not seem to act through the commonly accepted infiltration component, but rather on the evaporative rate (twice less within thickets). This mechanism excludes underground diffusive transfers between bare ground and vegetation. Inverse transfers were even shown by deuterium labelling. Water budget study and micro-elevation mapping, along with consistent soil shallowness, together cast serious doubts on the traditional mechanism of run-off/diffusion of surface water as a key process of the long range competition between plants. An alternative explanation lies in long range root competition. This hypothesis find support as well in the excavated root systems, shallow and wide, as in isotopic labelling, showing contaminations of shrubs located up to 15 m of the irrigated area. Water budget study also evidenced simultaneous contradictory effects (facilitation/competition) of shrubs on evapotranspiration.

Comments On The Pseudo-Microfossil Linotolypen

Hollow, black reticulate ‘microfossils’ of unknown affinity found in Ordovician to late Cretaceous sediments from North America, Europe and Australia were given the name Linotolypa by Eisenack in 1962. In 1978, he recognised that they were pseudo-microfossils consisting of asphalt, and noted that their structure resembled that of soap bubbles formed in agitated suspensions. These objects are well known as a component of the particles caught from the air by pollen and spore traps at the present day. They are correctly termed ‘cenospheres’ and are formed from coal and possibly pitch and fuel oil by incomplete combustion. If their presence were to be confirmed in Palaeozoic sediments, this would provide important new evidence for the occurrence of fire in the geological record and of the history of levels of O2 in the atmosphere.

Flora y vegetación briofítica de la Sierra del Relumbrar (SO de Albacete, España)

Heras-Ibáñez. J. de las, J., Ros. R. M.~ & Guerra, J. Bryophyiic flora and vegetation of ¡he Sierra del Relumbrar (SW of A/bace¡e, Spainj Lazaroa 11: 149-175 (1989). A brophytic and phytosociologic study of the Sierra del Relumbrar (SW of Albacete, Spain) is made. The caíalogue presenís 136 taxa (23 liverworts and 133 mosses). It includes 34 new [br Albacete province and 19 [br he SE ol? Spain. Bryophytic conirnunities are analysed. Sorne of ihem can be assignated to previously known associations in the Iberian Peninsula and a new one is described.

New wild Brassica oleracea L. germplasm at its western distribution limit in the Iberian Peninsula

An exploration and collection mission for wild Brassica oleracea populations was carried out in spring and summer of 2013. The aim of this collection was to expand the number of accessions of wild Brassica oleracea available for basic and applied research in plant breeding. In this paper we report a new accession of wild Brassica oleracea in an unexplored coastal area of Galicia, NW Iberian Peninsula. Details of population ecology and vegetation, soil, climate and geographic data were recorded for this population. The “Endangered” threat category for the region is proposed, and actions for in situ and ex situ conservation are proposed. Seeds will be added to the germplasm collections of University of Santiago de Compostela and Misión Biológica de Galicia (CSIC) for further research on diverse aspects of the dynamics and ecophysiology of the population along with characterization and evaluation of useful traits.