Vegetation and biocrust play crucial roles in dune stability and mobility, and their interaction can lead to bistability, temporal oscillations, and hysteresis. We studied a two-dimensional (2D) mathematical model of vegetation and biogenic crust cover dynamics on sand dunes. Under a certain parameter range, the space-independent version of the model exhibited the bi-stability of an oscillatory state and a steady state, and we studied the 2D dynamics of the model under these parameters. The patterns developed by the 2D model showed a high degree of spatial heterogeneity and complexity depending on the initial conditions and on the state type across the front. The results suggest that spatial heterogeneity and complexity can evolve from the intrinsic dynamics between vegetation and biocrust, even without natural geodiversity and spatiotemporal climate fluctuations. In the real world, these two types of intrinsic and extrinsic heterogeneity processes interact such that it is difficult to distinguish between them.
Rainfall pulses can significantly drive the evolution of the structure and function of semiarid ecosystems, and understanding the mechanisms that underlie the response of semiarid plants to rainfall is the key to understanding the responses of semi-arid ecosystems to global climatic change. We measured sap flow in the branches and stems of shrubs (Caragana korshinskii Kom. and Hippophae rhamnoides Linn.) using sap flow gauges, and studied the response of sap flow density to rainfall pulses using the ''threshold-delay'' model in the Chinese Loess Plateau. The results showed that the sap flow began about 1 h earlier, and increased twofold after rainfall, compared to its pre-rainfall value. The sap flow increased significantly with increasing rainfall classes, then gradually decreased. The response of sap flow was different among rainfall, species, position (branch and stem) during the pulse period, and the interactive effects also differed significantly (P < 0.0001). The response pattern followed the threshold-delay model, with lower rainfall thresholds of 5.2, 5.5 mm and 0.7, 0.8 mm of stem and branch for C. korshinskii and H. rhamnoides, demonstrating the importance of small rainfall events for plant growth and survival in semi-arid regions.
Symmetrical temperature difference also known as the sap flow index (SFI) forms the basis of the Heat Field Deformation sap flow measurement and is simultaneously collected whilst measuring the sap flow. SFI can also be measured by any sap flow method applying internal continuous heating through the additional installation of an axial differential thermocouple equidistantly around a heater. In earlier research on apple trees SFI was found to be an informative parameter for tree physiological studies, namely for assessing the contribution of stem water storage to daily transpiration. The studies presented in this work are based on the comparative monitoring of SFI and diameter in stems of different species (Pseudotsuga menziesii, Picea omorika, Pinus sylvestris) and tree sizes. The ability of SFI to follow the patterns of daily stem water storage use was empirically confirmed by our data. Additionally, as the HFD multipointsensors can measure sap flow at several stem sapwood depths, their use allowed to analyze the use of stored water in different xylem layers through SFI records. Radial and circumferential monitoring of SFI on large cork oak trees provided insight into the relative magnitude and timing of the contribution of water stored in different sapwood layers or stem sectors to transpiration.
The influence of the size soil aggregates derived from loess, expressed by mean weight diameter of aggregates which build soil samples, on the saturated hydraulic conductivity was presented. It has been found that size of aggregates influenced the amount of large pores in soil samples. The relationship between the saturated hydraulic conductivity and the amount of large pores can be described by function: Ks = 0.356. Exp (6.852 PL). and Príspevok obsahuje výsledky výskumu vplyvu velkosti agregátov pôdy, z ktorých sú vytvorené vzorky pôdy, na hydraulickú vodivost vodou nasýtených vzoriek pôdy. Z výsledkov vyplýva, že velkost agregátov pôdy ovplyvnuje množstvo velkých pórov vo vzorkách pôdy. Závislost medzi hodnotami nasýtenej hydraulickej vodivosti pôdy a množstvom velkých pórov - udaným v percentách objemu všetkých pórov - môže byt vyjadrená exponenciálnou funkciou.
In this paper hydrological scenarios of changes in the long-term mean annual and the mean monthly runoff due to the climate change in the upper part of the Hron River basin were evaluated. The Hron river basin was selected as a representative mountainous basin in Central Slovakia. An empirical raster-based and a conceptual hydrological balance model were used for modelling changes in runoff with an annual and monthly time step. Both models were calibrated using data from a standard period 1951-1980, which is considered to be representative for the distribution of runoff in unchanged conditions. Four different climate change scenarios were used in the study. Two scenarios were downscaled from the outputs of the CCCM and GISS Global Circulation Models (GCMs), the others represent analogies with warmer climatic periods in the past. The runoff change scenarios developed for the upper Hron River basin for future time horizons 2010, 2030 and 2075 show the decrease in the long-term mean annual runoff and changes in the runoff distribution within the year. and V článku sú odvodené scenáre zmien dlhodobých priemerných ročných a priemerných mesačných prietokov, vyjadrujúce možný vplyv zmeny klímy na odtok v budúcnosti na povodí horného Hrona. Na modelovanie dlhodobých priemerných ročných prietokov bol použitý rastrovo-orientovaný empirický model hydrologickej bilancie, na modelovanie priemerných mesačných prietokov bol použitý koncepčný hydrologický bilančný model so sústredenými parametrami. Obidva modely boli kalibrované na údajoch z obdobia 1951-1980, ktoré sme považovali za reprezentatívne obdobie pre nezmenené podmienky hydrologického režimu. Ako scenáre zmeny klímy boli použité scenáre CCCM a GISS, regionalizované z najnovších výstupov globálnych cirkulačných modelov atmosféry, a scenáre SD a WP, vyvinuté v rámci Národného klimatického programu SR na základe analógie s teplými obdobiami v minulosti u nás. Scenáre zmeny odtoku, odvodené pre časové horizonty 2010, 2030 a 2075 ukazujú možný pokles dlhodobých priemerných ročných prietokov, ako aj zmenu priemerných mesačných prietokov na povodí horného Hrona v budúcnosti.
In this paper the seasonality of summer, winter and annual maximum discharges in mid-sized catchments of Slovakia was analysed. The seasonality measure represents an important indicator of flood processes and can be used as a pooling characteristic in regional flood frequency analysis. The seasonality characteristics such as mean date of flood occurrence (DQ) and seasonal concentration index (r) were derived in 142 Slovak catchments, with the lengths of observation 20 to 70 years. The DQ value represents the fictive centre of the occurrence of Qmax within a year and the weighted value of all dates of Qmax occurrence; the index r expresses a measure of the variability of the date of occurrence and it is based on the principles of directional statistics. The analysis of summer, winter and annual flood seasonality in the territory of Slovakia showed that a majority of the catchments show higher potential for summer floods than winter floods. Catchments with high flood risk are located mainly in the flysch region of Slovakia, the Spis Region and the Laborec Mountains, the Slovenske Rudohorie, the Slovenske stredohorie Mts. and the Fatra Region. and Predložený príspevok sa zaoberá analýzou charakteristík sezónnosti letných, zimných a ročných maximálnych prietokov na vybraných povodiach Slovenska. Charakteristiky sezónnosti sú významným ukazovateľom procesu tvorby povodní, a sú často typizačnou hodnotou pre následné regionalizačné analýzy. Do procesu vyhodnocovania sezónnosti letných, zimných a ročných maximálnych prietokov bolo vybraných 142 povodí Slovenska s radom pozorovaní do roku 2001 s dĺžkou časového radu od 20 do 70 rokov. Sezónnosť bola definovaná dvoma charakteristikami: priemerným dňom výskytu povodní (DQ) a indexom sezónnej koncentrácie r. Veličina DQ charakterizuje fiktívne ťažisko výskytov Qmax v kalendárnom roku a v jej hodnote sú vážené všetky dátumy výskytov prietokov. Index sezónnej koncentrácie maximálnych ročných prietokov (r) indikuje rozptyl dní výskytu maximálnych prietokov v priebehu roka a jeho výpočet je založený na princípoch teórie centroidných dát (directional statistics). Na základe vykonanej analýzy bolo možné začleniť povodia Slovenska z hľadiska náchylnosti na výskyt povodní v jednotlivých ročných sezónach do viacerých oblastí. Za najrizikovejšie oblasti sa javia povodia západného flyšového pásma, povodia v oblasti Spiša, Šariša, Slovenského Rudohoria, Slovenského stredohoria a FatranskoTatranskej oblasti, a to z hľadiska výskytu letných ako aj ročných maximálnych prietokov.
My aim in this paper is to examine Mitchell S. Green’s notion of self-expression and the role it plays in his model of illocutionary communication. The paper is organized into three parts. In Section 2, after discussing Green’s notions of illocutionary speaker meaning and self-expression, I consider the contribution that self-expression makes to the mechanisms of intentional communication; in particular, I introduce the notion of proto-illocutionary speaker meaning and argue that it is necessary to account for acts overtly showing general commitments that are not ‘marked’ as being specific to one or another illocutionary force. In Section 3, I focus on Green’s account of expressive norms and argue that their function is to stabilize rather than constitute the structure of illocutionary signaling systems; moreover, I examine critically Green’s idea according to which expressive norms enable us to indicate the force of our speech acts and suggest that they play a key role in the mechanisms for epistemic vigilance. Finally, in Section 4, I elaborate on the idea of discourse-constituted thoughts—or, in other words, thoughts that ex- ist in virtue of being expressed in making certain conversation-bound speech acts—and use it to develop a more comprehensive model of the expressive dimension of speech acts.
Presented are results of simulations of root water uptake applying a macroscopic model of water transport in Soil - Plant - Atmosphere - Continuum. As a simulation tool is used the software package GLOBAL, based on the solution of the one-dimensional Richards equation. The main objective is to examine the contribution of root extraction functions (sink terms) based on different root morphological parameters to the changes in the soil water content profiles during the vegetation period of three crops. The root extraction functions are estimated using dry mass, length and surface area density distributions of all (total) and the fine roots (< 0.5 mm) of spring barley, winter rye and maize. It was observed that the ''root mass'' extraction curves slightly deviate from the ''length'' and ''surface area'' ones, especially in the topsoil and for the crops with a longer vegetation period. Nevertheless, the resulted differences in the soil water content distributions were small. The role of ''fine roots'' distribution was also examined. Calculating the water storage, it was found that the deviations were within the error of direct measurements. The sensitivity of the models based on the Richard´s equation to the different root extraction functions was found to be low, which reflected in small differences in soil water content distributions. Hence, any of the studied root morphological parameters can be successfully applied for simulations of root uptake at macro scale. and Práca obsahuje výsledky simulácie odberu vody koreňmi rastlín makroskopickým modelom pohybu vody v systéme pôda - rastlina - atmosféra, ak boli funkcie odberu vody koreňovým systémom určené z rozdelení rôznych charakteristík koreňového systému. Použili sme simulačný model GLOBAL, založený na riešení jednorozmerného tvaru rovnice Richardsa. Cieľom práce bolo určiť funkcie odberu vody koreňovým systémom rastlín, s využitím rozdelenia rôznych charakteristík koreňového systému tej istej rastliny a ich vplyv na vlhkostné profily v pôde počas ontogenézy rastlín. Simulácia bola vykonaná pre tri porasty - jarný jačmeň, ozimnú raž a kukuricu. Funkcie odberu vody boli vypočítané z údajov o rozdelení hmotnosti suchých koreňov, ich mernej dĺžky a merného povrchu pre všetky korene a pre ''jemné'' korene (< 0,5 mm v priemere). Ukázalo sa, že funkcie odberu založené na rozdelení hmotnosti koreňov sa nevýrazne odlišovali od tých, ktoré boli vypočítané s použitím ''dĺžky'' a ''povrchu'' koreňov v orničnej vrstve pôdy a pre porasty s dlhším vegeračným obdobím. Aj rozdiely medzi funkciami odberu s využitím rozdelenia rôznych vlastností ''jemných'' a všetkých koreňov boli v medziach presnosti merania. Z toho vyplýva, že ľubovoľný z použitých rozdelení parametrov koreňov (hmotnosť, dĺžka, povrch) môže byť použitý na výpočet odberových funkcií pre simuláciu pohybu vody v systéme PRAT a následnú simuláciu makroskopickými modelmi, založenými na riešení rovnice Richardsa.