现阶段我国乡村旅游产品的供需特征及开发   总被引：61，自引：2，他引：59  

潘秋玲 《地域研究与开发》1999,18(2):60-62

乡村旅游是中国“９８华夏城乡旅游”的发展主题之一。文章分析了我国乡村旅游产生的背景因素,总结了现阶段我国乡村旅游产品的供给和需求特征,并提出了乡村旅游开发中面临的主要问题及建议。  相似文献   

黄土高原水土流失地区粮食生产潜力与发展途径   总被引：1，自引：0，他引：1  

彭珂珊 《云南地理环境研究》1999,11(2):24-31

农业是国民经济的基础, 粮食是基础的基础。黄土高原地区是中华民族文化的发祥地,也是我国历史上早期农牧业生产区和政治中心,粮食是该区人民赖以生存的最基本产业。探索其发展规律, 分析其障碍因素, 寻求其发展潜力, 采取 “一靠政策, 二靠科技, 三靠投入, 四靠保护, 五靠工作”的战略措施, 对同类地区的粮食发展具有重要意义。  相似文献   

Sonoran Desert productivity and the effect of trap size on litterfall estimates in dryland vegetation     

Alberto Búrquez  Angelina Martínez-Yrízar  Silvia Núez 《Journal of Arid Environments》1999,43(4):459

We describe the temporal and spatial litterfall and test the accuracy of different litter collection devices in a Sonoran Desert community. Two low-lying PVC litter trap designs were tested and compared against a standard IBP trap. The test traps collected significantly more plant litter than the IBP traps, which failed to capture most of the litter of ephemerals and low shrubs. The largest differences between the traps appeared after the pulses of growth of ephemeral plants. Data collection for a period of almost 2 years showed an annual total litterfall of 3·43 Mg ha⁻¹for the test traps and 2·77 Mg ha⁻¹for the IBP traps. These values are well above the average for deserts and fit better into the lower range of tropical dry forests. The test PVC traps are inexpensive, economical in collecting and sorting effort, and less prone to vandalism. Also, they can be laid in higher numbers than IBP traps, thus providing a better representation of the highly heterogeneous desert environment.  相似文献   

Characteristics of coastal phytoplankton near Cape Tastubec (northern Aral Sea), September 1993     

M.I. Orlova  O.M. Rusakova 《International Journal of Salt Lake Research》1999,8(1):7-18

The species composition, population density, biomass and main functional characteristics of the phytoplankton community near Cape Tastubec, northern Aral Sea in September 1993 were investigated. The characteristics investigated were daily primary production, decomposition, and photosynthetic intensity. The data indicate that certain changes in the structure and function of the phytoplankton have recently taken place.  相似文献   

水库浮游细菌生产和呼吸过程代谢内外源有机碳研究     

韩一萱  李彪  荀凡  高培鑫  毛振镀  陶晔  邢鹏 《湖泊科学》2022,34(1):162-173

全球气候变化和人类活动的加剧影响水生生态系统中溶解性有机碳(DOC)的种类和浓度.浮游细菌生产和呼吸过程对碳源变化的响应,可能影响水体乃至区域的碳循环特征.本研究选取了南京市11座中小型水库,利用碳稳定同位素技术和双端元混合模型定量分析浮游细菌在生产和呼吸代谢过程中对内外碳源的利用.依据DOC中内外碳源的比例,将11座...  相似文献   

海洋初级生产过程中原核生物和真核生物的作用   总被引：1，自引：1，他引：1  

焦念志  王荣  李超伦  吉鹏 《海洋与湖沼》1994,25(6):612-618

于１９９２年８月－１９９３年５月，运用生物抑制剂方法和＾１４Ｃ，＾１５Ｎ同位素示踪方法研究胶州湾表层水中小于２００μｍ的浮游生物群落中原核生物和真核生物对初级生产力的贡献，以及在硝态氮（ＮＯ３＾－－Ｎ）、氨态氮（ＮＨ４＾＋－Ｎ）和氨基酸氮（ＡＡ－Ｎ）吸收中的作用。结果表明，原核生物在总初级生产力中占有相当比重（１６．３８％－４１．００％），ＮＯ３＾－－Ｎ主要由真核生物所吸收（６４．８６％－８７．２  相似文献   

湖泊光学研究进展及其展望   总被引：11，自引：4，他引：7  

张运林 《湖泊科学》2011,23(4):483-497

从湖泊光学研究理论框架、研究方法、水体生物光学特性、有色可溶性有机物(CDOM)生物地球化学循环、光与浮游植物相互关系、沉积物再悬浮光学效应、湖泊水色遥感等几个方面全面回顾了湖泊光学研究进展.湖泊光学研究理论框架主要包括各光学组份吸收、散射、漫射衰减及辐射传输方程;近年来,逐步发展了野外时空格局调查、水动力水华过程连续...  相似文献   

Chlorophyll a and primary production in the northeastern Pacific Ocean     

CHEN Xingqun  LIN Rongcheng 《海洋学报(英文版)》2008,27(1):77-84

The primary production and chlorophyll a concentration of picoplankton （0.2 - 2 μm） , nanoplankton （2 - 20μm） and micro- plankton （20 -200 μm） are described in the northeastern Pacific Ocean near the Hawaii Islands during the six survey cruises from 1996 to 2003：DY85-4, DY95-7, DY95-8, DY95-10, DY105-11 and DY105-12.14. The primary production of carbon was in range from 76.8 to 191.9 mg/（m^2 · d） with an average of 116.1 mg/（ m^2 · d） in the east region, and from 73.1 to 222.5 mg/（ m^2 · d） with an average of 127.1 mg/（ m^2 · d） in the west region, similar to the other oligotrophic regions of the Pacific Ocean investigated. The chlorophyll a concentration was about 0.1 mg/m^3 from the surface to the 50 m depth, about 0.2 -0.4 mg/m^3from 50 to 100 m, and gradually decreased below the 100 m depth. The picoplankton accounted for more than 70% of the total chlorophyll a in the upper layer （ surface to 125 m）, but it decreased to less than 50% in depth below 125 m. The nanoplankton and microplankton combined only accounted for less than 30% of the total chlorophyll a in the upper layer, but showed a more even vertical distribution.  相似文献   

Growth and production of Pisidium amnicum in the freshwater tidal area of the River Minho estuary     

Ronaldo Sousa  Antnio J.A. Nogueira  Carlos Antunes  Lúcia Guilhermino 《Estuarine, Coastal and Shelf Science》2008,79(3):467-474

  相似文献   

Primary production and implications for metabolic balance in Hawaiian lee eddies     

Patricia M. McAndrew  Robert R. Bidigare  David M. Karl 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(10-13):1300

Recent discrepancies between geochemical and biological approaches for determining whether ocean ecosystems are net heterotrophic or net autotrophic have led to uncertainty in the net metabolic state of open ocean ecosystems. Geochemical approaches indicate that the oceans are net positive autotrophic, but direct observations based on short-term incubation techniques suggest that the ocean is in a state of net heterotrophy. One hypothesis for the apparent discrepancy is that net autotrophic production occurs in aperiodic “bursts,” which are superimposed on a more constant background state of net heterotrophy. Mixing events, which introduce new nutrients to the surface ocean, provide one mechanism for fueling such aperiodic bursts of net production. In conjunction with the Eddy Flux (E-Flux) program in the lee of the Hawaiian Islands during winter 2004–2005, we examined the relationship between photosynthesis and irradiance (P vs. E) in surface waters inside and outside of two cold-core, cyclonic eddies, and conducted five incubation experiments to examine the metabolic response of mixed-layer plankton communities to nutrient-rich deep-sea water additions. Our results showed that in the mixed layer, maximum rates of light-saturated photosynthesis, derived from photosynthesis–irradiance experiments were not significantly different inside vs. outside the eddies (p=0.35 and 0.44 for E-Flux I and E-Flux III, respectively). Addition of nutrients to mixed-layer water showed that (1) gross primary production (GPP) became decoupled from a more constant rate of respiration and (2) net system metabolism shifted from approximate balance, or slight net heterotrophy, to a demonstrably net autotrophic system. From these results, we determined that the threshold GPP for net autotrophic production for the mixed layer of the study region was 1.65 mmol O₂ m⁻³ d⁻¹, which is consistent with previous estimates for the oligotrophic open ocean.  相似文献