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1.
采用根系生物量梯度上土壤呼吸变化趋势线外推法对锡林河流域一个羊草 (Leymuschinensis (Trin .)Tzvel.)群落中根系呼吸占土壤总呼吸的比例进行了估计 ,对生物量各组分 (地上、地下部分 )之间以及它们与土壤呼吸间的相关性进行了分析。结果表明 :在测定年度 (1998年 )整个生长季的不同月份 ,该群落中根系呼吸量占土壤呼吸总量的比例在 14 %~ 39%之间 ,平均为 2 7% ;地上总生物量及根系生物量与土壤呼吸间的相关性较差 ,但地上活生物量与土壤呼吸间存在着显著的乘幂关系。上述结果与国外同类研究结果相比 ,具有很好的一致性。  相似文献
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温带草地主要优势植物不同器官间功能性状的关联   总被引:7,自引:2,他引:5       下载免费PDF全文
 理解植物各器官间功能性状的关联, 有助于确定控制功能性状的内在机制以及性状间的比例关系。基于内蒙古温带草地19个地点、42种优势草本植物的野外观测, 分析了叶片、茎、生殖器官、细根和粗根间功能性状(N、P含量、N:P、比叶面积、比根长以及叶片和细根的组织密度)的关联。主要结果如下: 在种群和物种水平上, 各器官的N和P含量都显著正相关, 比叶面积与叶片N、P含量和组织密度在种群水平上显著负相关, 而在物种水平上没有显著的相关关系; 而比根长仅在种群水平上与细根的组织密度显著负相关。N、P含量以及N:P在各器官之间一致呈显著正相关, 而比叶面积和比根长没有显著的相关关系。叶片和细根的组织密度在种群水平上显著负相关, 而在物种水平上没有显著的相关关系。非禾草比禾草相应器官(除茎外)的N、P含量高, 但二者茎的N、P含量没有显著的差异; 豆科植物比非豆科植物相应器官的N含量高, 而P含量没有显著的差异。  相似文献
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Carbon balance along the Northeast China Transect (NECT-IGBP)   总被引:6,自引:0,他引:6       下载免费PDF全文
The Northeast China Transect (NECT) along a precipitation gradient was used to cal-culate the carbon balance of different vegetation types, land-use practices and temporal scales. NECT consists of mixed coniferous-broadleaved forest ecosystems, meadow steppe ecosystemsand typical steppe ecosystems. Analyses of the C budget were carried out with field measurement based on dark enclosed chamber techniques and alkali absorption methods, and the application of the CENTURY model. Results indicated that: (1) soil CO_2 flux had a strong diurnal and seasonal variation influenced by grassland type and land-use practices. However, the seasonal variation on soil CO_2 fluxes did not show obvious changes between non-grazing and grazing Leymus chinensis dominated grasslands. (2) Hourly soil CO_2 fluxes mainly depended on temperature, while dailyCO_2 fluxes were affected both by temperature and moisture. (3) NPP of the three typical ecosys-tems showed linear relationships with inter-annual precipitation, but total soil carbon of those eco-systems did not. NPP and total soil carbon values decreased westward with decreasing precipita-tion. (4) Model simulation of NPP and total soil carbon showed that mean annual precipitation was the major limiting factor for ecosystem productivity along NECT. (5) Mean annual carbon budget is the largest for the mixed coniferous- broadleaved forest ecosystem (503.2 gC m~(-2)a~(-1)), followed bythe meadow steppe ecosystem (227.1 gC m~(-2)a~(-1)), and the lowest being the typical steppe eco-system (175.8 gC m~(-2)a~(-1)). This study shows that concurrent field measurements of terrestrial ecosystems including the soil and plant systems with surface layer measurements along the wa-ter-driven IGBP-NECT are valuable in understanding the mechanisms driving the carbon cycle in different vegetation types under different land-use practices. Future transect research should be emphasized.  相似文献
4.
 植物的叶片与细根分别作为植物体地上和地下部分重要的营养器官, 很多功能性状在二者之间存在着一定的关联性。研究这种关联有助于理解植物各性状之间的相互作用、植物生长过程中对资源的利用和分配, 以及建立细根性状的估算模型。该研究对内蒙古锡林河流域65种植物叶片与细根的氮(N)含量、磷(P)含量、N:P以及比叶面积(SLA)和比根长(SRL)进行了比较研究, 结果表明: 在种间尺度上, 叶片与细根间的N、P和N:P存在显著的相关性, 而SLA与SRL之间相关性较弱; 在种内尺度上, 叶片和细根的N、P及SLA与SRL, 在不同的物种中呈现出不同的趋势。此外, 叶片与细根性状的关联, 在不同的植物功能群之间存在差异。例如, 双子叶植物叶片与细根间的N含量显著相关, P含量不相关; 而单子叶植物二者之间的P含量显著相关, N含量无关联。该研究的主要结论是, 在相对一致的生境中, 植物叶片与细根性状的关联主要发生在不同物种之间, 在种内尺度上这种关联不明显, 这可能与植物功能性状在种内存在较小的变异幅度有关。  相似文献
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Ecosystem carbon stocks and their changes in China’s grasslands   总被引:2,自引:0,他引:2       下载免费PDF全文
The knowledge of carbon (C) stock and its dynamics is crucial for understanding the role of grassland ecosystems in China’s terrestrial C cycle. To date, a comprehensive assessment on C balance in China’s grasslands is still lacking. By reviewing published literature, this study aims to evaluate ecosystem C stocks (both vegetation biomass and soil organic C) and their changes in China’s grasslands. Our results are summarized as follows: (1) biomass C density (C stock per area) of China’s grasslands differed greatly among previous studies, ranging from 215.8 to 348.1 g C m−2 with an average of 300.2 g C m−2. Likewise, soil C density also varied greatly between 8.5 and 15.1 kg C m−2. In total, ecosystem C stock in China’s grasslands was estimated at 29.1 Pg C. (2) Both the magnitude and direction of ecosystem C changes in China’s grasslands differed greatly among previous studies. According to recent reports, neither biomass nor soil C stock in China’s grasslands showed a significant change during the past 20 years, indicating that grassland ecosystems are C neutral. (3) Spatial patterns and temporal dynamics of grassland biomass were closely correlated with precipitation, while changes in soil C stocks exhibited close associations with soil moisture and soil texture. Human activities, such as livestock grazing and fencing could also affect ecosystem C dynamics in China’s grasslands.  相似文献
9.
Biodiversity is thought to be essential for ecosystem stability, function and long-term sustainability. Since nitrogen is the limiting nutrient for plant growth in many terrestrial ecosystems, reactive nitrogen has the potential to reduce the diversity of terrestrial vegetation and associated biota through favouring species adapted to quickly exploiting available nutrients. Although the potential has long been recognised, only recently has enough evidence come together to show beyond reasonable doubt that these changes are already occurring. Linked together, experimental, regional/e.rnpirical, and time-series research provide a powerful argument that enhanced deposition of reactive nitrogen across Great Britain, and potentially the rest of Europe, has resulted in a significant and ongoing decline in grassland species richness and diversity.  相似文献
10.
Orthopteroid assemblages (orders Orthoptera and Mantodea) were compared along moisture gradient at five sites of the Slovak Karst in southern Slovakia. A total of 40 species were recorded by sweep-net sampling. The occurence of each identified species varied with soil moisture and other factors. Sites with similar moisture conditions tend to have similar assemblages. No species occurred simultaneously at the wettest and driest sites. There were two principal and five subordinate assemblages within the moisture gradient. Assemblages were related to the two commonest habitat types demarcated by the presence of different indicator species. Total orthopteroid species richness and number of grasshopper (Acridoidea) species increased linearly with falling soil moisture and Ellenbergs’s indicator value for moisture. The author died on February 24, 2006  相似文献
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