Species richness,diversity and density of understory vegetation along disturbance gradients in the Himalayan conifer forest     

Kesang WANGCHUK  András DARABANT  Prem Bahadur RAI  Maria WURZINGER  Werner ZOLLITSCH  Georg GRATZER 《山地科学学报》2014,11(5):1182-1191

We investigated whether species richness, diversity and density of understory herbaceous plants differed along logging(gap) and grazing(primarily by cattle) disturbance gradients, and sought to identify drivers of richness, diversity and density of understory vegetation of logged sites. A factorial experiment was conducted in the mixed conifer forest of Gidakom in Western Bhutan. Levels of the logging treatment included small(0.15 – 0.24 ha), medium(0.25 – 0.35 ha) and large(0.36 – 1.31 ha) gaps. The grazing treatment included grazed(primarily by cattle) and ungrazed(where herbivores were excluded by a fence) plots nested within each gap. Data were collected from 12 gaps(4 replicates at each level of logging) using the point intercept method. Shannon Weaver Diversity and Margalef's indices were used to estimate species diversity and describe species richness, respectively. Soil samples were analyzed for pH and nutrients. The interaction effect of logging and grazing was significant(p≤0.001) only on species diversity. Relative to ungrazed areas, species diversity was significantly higher(0.01≤p≤0.05) in medium grazed gaps. Under grazed conditions, soil P was negatively correlated with gap size and species diversity. While species diversity was positivelycorrelated(0.01≤p≤0.05) with soil N in grazed plots species richness was positively correlated(0.001≤p≤0.01) with soil N in ungrazed plots. Relative density of Yushania microphylla and Carex nubigena were higher under ungrazed conditions. Our study suggests that the combined effect of cattle grazing and logging results in higher species diversity of understory vegetation in medium and grazed gaps in mixed conifer forests of Bhutan,whereas increase or decrease in relative density of major species is determined primarily by the independent effects of grazing and logging. From management perspective, forest managers must refrain from creating large gaps to avoid loss of nutrients(mainly P and N), which may eventually affect tree regeneration. Managers intending to maintain understory vegetation diversity must consider the combined effects of grazing and logging, ensuring low to moderate grazing pressure.  相似文献   

A new physically based stochastic event catalog for hail in Europe     

H. J. Punge  K. M. Bedka  M. Kunz  A. Werner 《Natural Hazards》2014,73(3):1625-1645

Hailstorms represent one of the major sources of damage and insurance loss to residential, commercial, and agricultural assets in several parts of Central Europe. However, there is little knowledge of hail risk across Europe beyond local historical damage reports due to the relative rarity of severe hail events and the lack of uniform detection methods. Here we present a new stochastic catalog of hailstorms for Europe. It is based on satellite observations of overshooting cloud tops (OT) that indicate very strong convective updrafts and hail reports from the European Severe Weather Database (ESWD). Historic hail events are defined based on OT detections from satellite infrared brightness temperatures between 2004 and 2011 for the warm seasons (April–September). The satellite-based historical event properties are complemented by hailstone observations from ESWD to stochastically simulate more than 1 million individual events with an event footprint resolution of 10 km. The final hail event catalog presented in this paper is the first one with a spatial event distribution that is based on a single homogeneous observation source over Europe. Areas of high hail probability or hail risk are found over Central and Southern Europe, including mountainous regions such as the Alps or the Pyrenees. Another region of relatively high hail risk is present over central Eastern Europe.  相似文献   

A Close Look at Satloc's Real-Time WADGPS System     

Michael L. Whitehead  Gary Penno  Walter J. Feller  Ivan C. Messinger  Willy I. Bertiger  Ronald J. Muellerschoen  Byron A. Iljima  Greg Piesinger 《GPS Solutions》1998,2(2):46-63

  相似文献   

Mutual Potential of Homogeneous Polyhedra   总被引：2，自引：0，他引：2  

Robert A. Werner  Daniel J. Scheeres 《Celestial Mechanics and Dynamical Astronomy》2005,91(3-4):337-349

The mutual gravitational potential between a pair of homogeneous polyhedra is expressed using an infinite series. The nested volume integrals are evaluated analytically and result in simple tensor expressions containing no special functions. However, complexity increases as O(6 ⁿ ), where n is the term degree. An alternate formulation due to Liebenthal is also presented.  相似文献   

Coeval Lower Miocene subsidence of the Eisenstadt Basin and relative updoming of its Austroalpine frame: implications from high-resolution geophysics at the Oslip section (Northern Burgenland,Austria)     

Hermann Häusler  Jürgen Scheibz  Werner Chwatal  Franz Kohlbeck 《International Journal of Earth Sciences》2015,104(2):475-493

  相似文献   

The myth of the brackish Sarmatian Sea     

Werner E. Piller  Mathias Harzhauser 《地学学报》2005,17(5):450-455

The biota of the 1.5 Ma period of the Middle Miocene Sarmatian of the Central Paratethys lack stenohaline components. This was the reason to interpret the Sarmatian stage as transitional between the marine Badenian and the lacustrine Pannonian stages. However, our new data indicate that brackish water conditions could not have prevailed. Sarmatian foraminifera, molluscs, serpulids, bryozoans, dasycladacean and corallinacean algae as well as diatoms clearly indicate normal marine conditions for the entire Sarmatian. During the Lower Sarmatian, however, a sea-level lowstand forced the development of many marginal marine environments. During the Late Sarmatian a highly productive carbonate factory of oolite shoals, mass-occurrences of thick-shelled molluscs and larger foraminifera, as well as marine cements clearly point to normal marine to hypersaline conditions. This trend is not restricted to the western margin of the Pannonian Basin System but can be observed in the entire Central and even Eastern Paratethys.  相似文献   

Evidence for a new MeV source observed by the COMPTEL experiment aboard CGRO     

Shu Zhang  Werner Collmar 《Astrophysics and Space Science》2007,309(1-4):23-27

We report first evidence for a new unidentified and variable MeV source, located near the galactic plane at (l,b)∼(284.5°, 2.5°). The source, GRO J1036-55, is found at a significance level of ∼5.6σ by COMPTEL in its 3–10 MeV band. The energy spectrum indicates a spectral maximum at 3–4.3 MeV with a steep slope at higher energies. Since the COMPTEL 3–4.3 MeV data contain contamination by an instrumental background line, we performed several consistency checks, which all are consistent with an astrophysical nature of this emission feature.  相似文献   

Comments on “Climatology: The Challenge for the Eighties” Revisited     

Werner H. Terjung 《The Professional geographer》1982,34(1):100-101

  相似文献   

Die Galaktische BeschleunigungK(z) Und Das Lokale System     

Werner Lohmann 《Astrophysics and Space Science》1971,11(3):407-411

The galactic accelerationK(z) calculated by Perry (1969) is explained by the influence of a local galactic mass concentration.

---

---

Mitteilungen Serie A, Nr. 46.  相似文献   

On the equilibrium of an exact charge neutral magnetopause     

Werner Alpers 《Astrophysics and Space Science》1971,11(3):471-474

The way is discussed by which microinstabilities of an exact charge neutral magnetopause could lead to a trapped particle flow, the absence of which causes the non-existence of an equilibrium magnetospheric boundary layer in the Parker-Lerche model. Furthermore, it is argued that instead of the non-equilibrium effect of Parker and Lerche, microinstabilities of an exact charge neutral magnetopause might be the underlying physical process of an Axford and Hines' type viscous interaction.  相似文献