30 research outputs found
Effects of changes in micro-weather conditions on structural features, total protein and carbohydrate content in leaves of the Atlantic rain forest tree golden trumpet (Tabebuia chrysotricha)
Temporal and spatiotemporal autocorrelation of daily concentrations of Alnus, Betula, and Corylus pollen in Poland
Stochastic flowering phenology in Dactylis Glomerata populations described by Markov chain modelling
Understanding the relationship between flowering patterns and pollen dispersal is important in climate change modelling, pollen forecasting, forestry and agriculture. Enhanced understanding of this connection can be gained through detailed spatial and temporal flowering observations on a population level, combined with modelling simulating the dynamics. Species with large distribution ranges, long flowering seasons, high pollen production and naturally large populations can be used to illustrate these dynamics. Revealing and simulating species-specific demographic and stochastic elements in the flowering process will likely be important in determining when pollen release is likely to happen in flowering plants. Spatial and temporal dynamics of eight populations of Dactylis glomerata were collected over the course of two years to determine high-resolution demographic elements. Stochastic elements were accounted for using Markov Chain approaches in order to evaluate tiller-specific contribution to overall population dynamics. Tiller-specific developmental dynamics were evaluated using three different RV matrix correlation coefficients. We found that the demographic patterns in population development were the same for all populations with key phenological events differing only by a few days over the course of the seasons. Many tillers transitioned very quickly from non-flowering to full flowering, a process that can be replicated with Markov Chain modelling. Our novel approach demonstrates the identification and quantification of stochastic elements in the flowering process of D. glomerata, an element likely to be found in many flowering plants. The stochastic modelling approach can be used to develop detailed pollen release models for Dactylis, other grass species and probably other flowering plants
The mass distribution of coarse particulate organic matter exported from an Alpine headwater stream
Coarse particulate organic matter (CPOM) particles span sizes from 1 mm,
with a dry mass less than 1 mg, to large logs and entire trees, which can
have a dry mass of several hundred kilograms. Pieces of different size and
mass play different roles in stream environments, from being the prime
source of energy in stream ecosystems to macroscopically determining channel
morphology and local hydraulics. We show that a single scaling exponent can
describe the mass distribution of CPOM heavier than 0.1 g transported in the
Erlenbach, a steep mountain stream in the Swiss pre-Alps. This exponent takes
an average value of −1.8, is independent of discharge and valid for particle
masses spanning almost seven orders of magnitude. Similarly, the mass
distribution of in-stream large woody debris (LWD) in several Swiss streams
can be described by power law scaling distributions, with exponents varying
between −1.8 and −2.0, if all in-stream LWD is considered, and between −1.3
and −1.8 for material locked in log jams. We found similar values for
in-stream and transported material in the literature. We had expected that
scaling exponents are determined by stream type, vegetation, climate,
substrate properties, and the connectivity between channels and hillslopes.
However, none of the descriptor variables tested here, including drainage
area, channel bed slope and the percentage of forested area, show a strong
control on exponent value. Together with a rating curve of CPOM transport
rates with discharge, the scaling exponents can be used in the design of
measuring strategies and in natural hazard mitigation