The spatial distribution and population dynamics of Quercus liaotungensis Koidz., Fraxinus rhynchophylla Hance and Acer mono Maxim. were studied in three warm temperate deciduous forests in Dongling Mountain, Beijing....The spatial distribution and population dynamics of Quercus liaotungensis Koidz., Fraxinus rhynchophylla Hance and Acer mono Maxim. were studied in three warm temperate deciduous forests in Dongling Mountain, Beijing. Clumped distributions appeared in most seedlings (≤0.4 m), short saplings (0.4-1 m) and tall saplings (1-2 m). Random distributions appeared in adults of Q. liaotungensis in Plot 1, F. rhynchophylla in Plot 3. The LSD method was used to discern the differences of different aged population. The class distribution of Q. liaotungensis was nearly a reverse-J shape for Plot 1 and Plot 3, suggesting that the population regenerates continuously. The age-structures of F. rhynchophylla and A. mono in Plot 1 and the test results indicated that they would increase continuously. In Plot 2, the class distribution and the test results showed that all populations would not regenerate continuously.展开更多
Peperites are special kinds of volcaniclastic materials generated by mingling of magma and unconsolidated sediments. They directly demonstrate the contemporaneity of volcanism and sedimentation, and hence they can be ...Peperites are special kinds of volcaniclastic materials generated by mingling of magma and unconsolidated sediments. They directly demonstrate the contemporaneity of volcanism and sedimentation, and hence they can be used to constrain the local paleoenvironments during volcanic eruptions. We identified peperites in the lower sequence of the northwest outcrops（Inggan-Kalpin area） of Permian Tarim large igneous province（TLIP）, Northwest China. In Inggan, blocky peperites were observed at the base of lava flows generated in the second eruption phase. This kind of peperites is generated by quenching of magma in a brittle fragmentation mechanism. While in Kalpin, both the second and the fourth eruption phases preserved peperites in the base of lava flows. Not only blocky but also fluidal peperites can be observed in Kalpin. The fluidal peperites were generated in vapor films, which insulated the magmas from cold sediments and avoided direct thermal shock, and therefore kept the fluidal forms of magma. All of these peperites are hosted by submarine carbonates. In lava sequences generated in the same eruption phases but located in Kaipaizileike, ~15 km east to Inggan, terrestrial flood basalts developed while peperites are absent, implying a paleoenvironmental transition between Kaipaizileike and Inggan-Kalpin area. Gathering information from observed peperites, TLIP lava flows, and the Lower Permian sedimentary strata, we precisely constrained the spatial distribution and temporal evolution of sedimentary facies of the early stage of TLIP. As a result, two marine transgressions were identified. The first transgression occurred contemporaneous with the second eruption phase. The transition from submarine to subaerial is located between Kaipaizileike and Inggan. The second transgression occurred contemporaneous with the forth eruption phase, and the transition from submarine to subaerial occurred between Inggan and Kalpin.展开更多
文摘The spatial distribution and population dynamics of Quercus liaotungensis Koidz., Fraxinus rhynchophylla Hance and Acer mono Maxim. were studied in three warm temperate deciduous forests in Dongling Mountain, Beijing. Clumped distributions appeared in most seedlings (≤0.4 m), short saplings (0.4-1 m) and tall saplings (1-2 m). Random distributions appeared in adults of Q. liaotungensis in Plot 1, F. rhynchophylla in Plot 3. The LSD method was used to discern the differences of different aged population. The class distribution of Q. liaotungensis was nearly a reverse-J shape for Plot 1 and Plot 3, suggesting that the population regenerates continuously. The age-structures of F. rhynchophylla and A. mono in Plot 1 and the test results indicated that they would increase continuously. In Plot 2, the class distribution and the test results showed that all populations would not regenerate continuously.
基金supported by the National Natural Science Foundation of China(Grant No.41272239)the State Science and Technology Major Project(Grant No.2011ZX05009-001)
文摘Peperites are special kinds of volcaniclastic materials generated by mingling of magma and unconsolidated sediments. They directly demonstrate the contemporaneity of volcanism and sedimentation, and hence they can be used to constrain the local paleoenvironments during volcanic eruptions. We identified peperites in the lower sequence of the northwest outcrops（Inggan-Kalpin area） of Permian Tarim large igneous province（TLIP）, Northwest China. In Inggan, blocky peperites were observed at the base of lava flows generated in the second eruption phase. This kind of peperites is generated by quenching of magma in a brittle fragmentation mechanism. While in Kalpin, both the second and the fourth eruption phases preserved peperites in the base of lava flows. Not only blocky but also fluidal peperites can be observed in Kalpin. The fluidal peperites were generated in vapor films, which insulated the magmas from cold sediments and avoided direct thermal shock, and therefore kept the fluidal forms of magma. All of these peperites are hosted by submarine carbonates. In lava sequences generated in the same eruption phases but located in Kaipaizileike, ~15 km east to Inggan, terrestrial flood basalts developed while peperites are absent, implying a paleoenvironmental transition between Kaipaizileike and Inggan-Kalpin area. Gathering information from observed peperites, TLIP lava flows, and the Lower Permian sedimentary strata, we precisely constrained the spatial distribution and temporal evolution of sedimentary facies of the early stage of TLIP. As a result, two marine transgressions were identified. The first transgression occurred contemporaneous with the second eruption phase. The transition from submarine to subaerial is located between Kaipaizileike and Inggan. The second transgression occurred contemporaneous with the forth eruption phase, and the transition from submarine to subaerial occurred between Inggan and Kalpin.
