High-frequency monitoring of hydrological and biogeochemical fluxes in forested catchments of southern Chile     

Cristián Frêne  Juan J. Armesto  Freddy Véliz  Fernando D. Alfaro  Kathleen C. Weathers 《水文研究》2021,35(5):e14175

The variability of rainfall-dependent streamflow at catchment scale modulates many ecosystem processes in wet temperate forests. Runoff in small mountain catchments is characterized by a quick response to rainfall pulses which affects biogeochemical fluxes to all downstream systems. In wet-temperate climates, water erosion is the most important natural factor driving downstream soil and nutrient losses from upland ecosystems. Most hydrochemical studies have focused on water flux measurements at hourly scales, along with weekly or monthly samples for water chemistry. Here, we assessed how water and element flows from broad-leaved, evergreen forested catchments in southwestern South America, are influenced by different successional stages, quantifying runoff, sediment transport and nutrient fluxes during hourly rainfall events of different intensities. Hydrograph comparisons among different successional stages indicated that forested catchments differed in their responses to high intensity rainfall, with greater runoff in areas covered by secondary forests (SF), compared to old-growth forest cover (OG) and dense scrub vegetation (CH). Further, throughfall water was greatly nutrient enriched for all forest types. Suspended sediment loads varied between successional stages. SF catchments exported 455 kg of sediments per ha, followed by OG with 91 kg/ha and CH with 14 kg/ha, corresponding to 11 rainfall events measured from December 2013 to April 2014. Total nitrogen (TN) and phosphorus (TP) concentrations in stream water also varied with rainfall intensity. In seven rainfall events sampled during the study period, CH catchments exported less nutrients (46 kg/ha TN and 7 kg/ha TP) than SF catchments (718 kg/ha TN and 107 kg/ha TP), while OG catchments exported intermediate sediment loads (201 kg/ha TN and 23 kg/ha TP). Further, we found significant effects of successional stage attributes (vegetation structure and soil physical properties) and catchment morphometry on runoff and sediment concentrations, and greater nutrients retention in OG and CH catchments. We conclude that in these southern hemisphere, broad-leaved evergreen temperate forests, hydrological processes are driven by multiple interacting phenomena, including climate, vegetation, soils, topography, and disturbance history.  相似文献   

The possible response of life zones in China under global climate change   总被引：5，自引：0，他引：5  

Xiongwen Chen  Xin-Shi Zhang  Bai-Lian Li 《Global and Planetary Change》2003,38(3-4):327-337

The response of natural vegetation to climate change is of global concern. In this research, an aggregated Holdridge Life Zone System was used to study the possible response of life zones in China under doubled atmospheric CO₂ concentration with the input climatic parameters at 0.5×0.5° resolution of longitude and latitude from NCAR regional climate model 2 (RegCM2) coupled with the CSIRO global climate model. The results indicate that the latitudinal distribution of life zones would become irregular because of the complicated climate change. In particular, new life zones, such as subtropical desert (SD), tropical desert (TDE) and tropical thorn woodland (TTW), would appear. Subtropical evergreen broadleaved forest (SEBF), tropical rainforest and monsoon forest (TRF), SD, TDE and TTW zones would appear in the northeastern China. Cool-temperate mixed coniferous and broadleaved forest (CMC) and warm-temperate deciduous broadleaved forest (WDBF) zones would appear at latitudes 25–35°N. The temperate desert (TD) in the western China would become Tibetan high-cold plateau (THP), SEBF, WDBF and temperate steppe (TS), and a large part of THP would be replaced by TRF, TDE, SEBF, TS and TTW. The relative area (distribution area/total terrestrial area) of CMC, TRF, TDE and TTW zone would increase about 3%, 21%, 3% and 6%, respectively. However, the relative area of SEBF, TS, TD and THP would decrease about 5%, 3%, 19% and 4%, respectively. In all, the relative area of forests (CCF, CMC, WDBF, SEBF, TRF) would increase about 15%, but the relative area of desert (TD, SD, TDE, and TTW) and THP would decrease about 9% and 4%, respectively. Therefore, responses of different life zones in China to climate change would be dramatic, and nationwide corridors should be considered for the conservation of migrating species under climate change.  相似文献   

A transdisciplinary analysis of water problems in the mountainous karst areas of Morocco     

C. de Jong  S. Cappy  M. Finckh  D. Funk 《Engineering Geology》2008,99(3-4):228

Water management and engineering in the karstic High Atlas of Morocco are difficult tasks under the prevailing geological, hydrogeological, geomorphological, vegetational and climatic conditions. It is important to be able to understand and predict the characteristics and availability of water for future water planning in the region under changing climatic and agricultural conditions. An interdisciplinary analysis of problems and adequate hydrological modelling tools developed by geologists, hydrologists and biologists are necessary. The karst areas of the High Atlas Mountains are characterised by impermeable triassic basalt underlying substantial subsurface reservoirs with high potential discharge rates. The karst groundwater aquifers are extensive but largely unknown in dimension, probably with a hierarchical network of groundwater flow paths. It is estimated that approximately 70% of the surface water is directly lost to groundwater. Steep landslide- and debris flow prone slopes exist next to coarse-grained, highly porous river beds. Infrequent, high intensity rainfall or snowmelt causes a particularly high flood risk to these karst areas. In addition, agriculture and land use changes have degraded the karst areas. The most important driving forces for degradation include permanent overgrazing even during droughts and the use of firewood by a continually growing population. Large scale degradation of vegetation has occurred in the oro-mediterranean (mountainous Mediterranean) zone, between 2600 and 3400 m which coincides with the most important zone for karstic groundwater creation. The combination of high amounts of groundwater flow and rapid surface flow due to sparse vegetation has increased the problems of flood flow.  相似文献   

大鹏澳水域秋季浮游植物优势种的演替及其与春季的比较     

韦桂峰  王肇鼎  练健生 《热带海洋学报》2004,23(5):10-16

根据2002年11月在亚大湾大鹏澳进行的连续30d(每日采样一次)观测资料，运用主成分分析和多元回归分析相结合方法，分析大鹏澳非养殖区中各浮游植物优势种之间的关系及影响其生长与演替的主要理化因子．建立秋季浮游植物优势种演替模型，并与春季的大鹏澳现场调查建立的浮游植物优势种演替模型进行比较，分析生境变化(降雨)对浮游植物优势种演替过程的影响。结果表明，春，秋季浮游植物优势种发生不同的演替过程。春季浮游植物对资源的竞争较为激烈，大量降雨引起海水中营养盐浓度升高，促进并维持中肋骨条藻(Skeletonema costatum)高密度生长，待营养盐被大量消耗后，中肋骨条藻数量下降，减轻了对柔弱菱形藻(Nitzschia delicatissima)的生长压力而使其成为优势种；而秋季水温较低，浮游植物细胞数量较春季大为减少，中肋骨条藻和柔弱菱形藻对资源的竞争较为缓和，使外界环境变化成为影响优势种变化的主要原因；降雨期间虽然营养盐增加，但环境变化使浮游植物的生长受到限制，雨后柔弱菱形藻数量不能恢复，水体中高营养盐浓度促使中肋骨条藻出现生长峰值。  相似文献   

Facies reconstruction from resistivity-at-the-bit images recorded in a submarine felsic volcanic succession     

Juliane Arnold  Anne Bartetzko  Holger Paulick  Gerardo Iturrino 《Marine Geophysical Researches》2007,28(4):331-341

  相似文献   

Development of fouling communities on vertical structures in the Baltic Sea   总被引：6，自引：2，他引：6  

Susanne Qvarfordt  Hans Kautsky  Torleif Malm 《Estuarine, Coastal and Shelf Science》2006,67(4):618-628

The pillars of the bridge connecting the Island of Öland with the Swedish mainland were rebuilt between 1990 and 2000. The renovation produced pristine vertical concrete substrates, which became submerged in known years and seasons. The fouling communities on the pillars were examined in 2001 to determine whether the community structure could be explained in terms of either orderly successional development or of seasonal variation in the settlement of benthic organisms. As well, the communities on the pillars were compared to communities on the vertical surfaces of boulders in the area. The results indicated that an annual species composition is the final stage in the succession on the observed, vertical constructions. The few perennial species add to the variation between pillars as they increase in biomass (Polysiphonia fucoides) or become out-competed (Balanus improvisus). Also, observed seasonal differences in the biomass of these perennial species indicated that the time of year free space becomes available might be an important determinant of the future structure of the community. Comparison between the pillar and boulder communities showed that the artificial structures were not surrogates for the natural hard substrate: pillar communities differed in that they lacked most perennial algal species and had a high biomass of B. improvisus.  相似文献   

Colonization, succession, and nutrition of macrobenthic assemblages in a restored wetland at Tijuana Estuary, California     

Serena M. Moseman  Lisa A. Levin  Carolyn Currin  Charlotte Forder   《Estuarine, Coastal and Shelf Science》2004,60(4):755-770

Modes of colonization, the successional trajectory, and trophic recovery of a macrofaunal community were analyzed over 19 months in the Friendship marsh, a 20-acre restored wetland in Tijuana Estuary, California. Traditional techniques for quantifying macrofaunal communities were combined with emerging stable isotopic approaches for evaluation of trophic recovery, making comparisons with a nearby natural Spartina foliosa habitat. Life history-based predictions successfully identified major colonization modes, although most taxa employed a variety of tactics for colonizing the restored marsh. The presence of S. foliosa did not seem to affect macrofaunal colonization or succession at the scale of this study. However, soil organic matter content in the restored marsh was positively correlated with insect densities, and high initial salinities may have limited the success of early colonists. Total macrofaunal densities recovered to natural marsh levels after 14 months and diversity, measured as species richness and the Shannon index (H′), was comparable to the natural marsh by 19 months. Some compositional disparities between the natural and created communities persisted after 19 months, including lower percentages of surface-feeding polychaetes (Polydora spp.) and higher percentages of dipteran insects and turbellarians in the Friendship marsh. As surficial structural similarity of infaunal communities between the Friendship and natural habitat was achieved, isotopic analyses revealed a simultaneous trajectory towards recovery of trophic structure. Enriched δ¹³C signatures of benthic microalgae and infauna, observed in the restored marsh shortly after establishment compared to natural Spartina habitat, recovered after 19 months. However, the depletion in δ¹⁵N signatures of macrofauna in the Friendship marsh indicated consumption of microalgae, particularly nitrogen-fixing cyanobacteria, while macroalgae and Spartina made a larger contribution to macrofaunal diets in the natural habitat. Future successional studies must continue to develop and employ novel combinations of techniques for evaluating structural and functional recovery of disturbed and created habitats.  相似文献   

Modelling phytoplankton succession on the Bering Sea shelf: role of climate influences and trophic interactions in generating Emiliania huxleyi blooms 1997–2000     

Agostino Merico  Toby Tyrrell  Evelyn J. Lessard  Temel Oguz  Phyllis J. Stabeno  Stephan I. Zeeman  Terry E. Whitledge 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1929

Several years of continuous physical and biological anomalies have been affecting the Bering Sea shelf ecosystem starting from 1997. Such anomalies reached their peak in a striking visual phenomenon: the first appearance in the area of bright waters caused by massive blooms of the coccolithophore Emiliania huxleyi (E. huxleyi). This study is intended to provide an insight into the mechanisms of phytoplankton succession in the south-eastern part of the shelf during such years and addresses the causes of E. huxleyi success by means of a 2-layer ecosystem model, field data and satellite-derived information. A number of potential hypotheses are delineated based on observations conducted in the area and on previous knowledge of E. huxleyi general ecology. Some of these hypotheses are then considered as causative factors and explored with the model. The unusual climatic conditions of 1997 resulted most notably in a particularly shallow mixed layer depth and high sea surface temperature (about 4 °C above climatological mean). Despite the fact that the model could not reproduce for E. huxleyi a clear non-bloom to bloom transition (pre- vs. post-1997), several tests suggest that this species was favoured by the shallow mixed layer depth in conjunction with a lack of photoinhibition. A top-down control by microzooplankton selectively grazing phytoplankton other than E. huxleyi appears to be responsible for the long persistence of the blooms. Interestingly, observations reveal that the high N:P ratio hypothesis, regarded as crucial in the formation of blooms of this species in previous studies, does not hold on the Bering Sea shelf.  相似文献   

胶州湾女姑山水域夏季赤潮高发期浮游植物群落结构特征   总被引：7，自引：0，他引：7  

张利永  刘东艳  孙军  邹景忠 《中国海洋大学学报(自然科学版)》2004,34(6):997-1002

根据 1998年 5～ 8月夏季赤潮高发期间 ,胶州湾女姑山水域浮游植物群落结构的种群组成特征和演替变化对赤潮的发生和种群变动特点进行初步研究。结果表明 ,夏季女姑山水域的浮游植物主要由硅、甲藻组成 ,硅藻在细胞和物种丰度上都占优势。浮游植物优势种在调查期间出现明显的演替现象 ,水温的升高和营养条件的变化是引起物种演替的主要原因。浮游植物细胞丰度在夏季呈明显的增长趋势 ,从 5月份 6.3× 10 5个cell/m3 增至 8月份的 6.7× 10 6个cell/m3 ;其中 ,由于赤潮的爆发 ,细胞丰度的最高峰出现在 7月份 ,为 1.5× 10 7个 /m3 。在赤潮爆发期间 ,赤潮原因种高齿状藻和中肋骨条藻发生了明显的演替现象 ,不同细胞大小的优势种和营养条件的变化是发生物种演替的主要原因。叶绿素a的浓度和细胞丰度的变化共同反映了赤潮发生的全部过程。  相似文献   

组织培养板在获取微藻种质中的应用   总被引：3，自引：0，他引：3  

周成旭  严小军 《海洋技术学报》2006,25(4):54-57

报道一种基于选择演替和及时显微跟踪的原理获取一次野外水样中多种微藻的方法。利用组织培养板方便的显微观测条件和适宜容积提供微藻存活的空间,在不同培养条件下,进行微藻群落演替、及时显微跟踪检测和优势种分离,可以使野外水样初期低生物量种类优势化,以利于纯系种质的获得。并通过不同演替条件获得其中出现的未鉴定或初期样品中未检出的种质,提供进一步研究的基础。该方法在获取微藻种质和种质库建设上不失为一可行技术手段。论文以一次野外采集海水样品在不同营养条件下的主要优势种类演替跟踪检测、低生物量种质优势化过程和纯系种质分离为例,说明该方法在获取微藻种质中的应用。  相似文献