• Energy Research

We evaluated the long-term pattern of leaf area index (LAI) dynamics and radiation use efficiency (RUE) in short rotation poplar in uncoppice (single stem) and coppice (multi-stem) plantations, and compared them to annual field crops (AFCs) as an alternative for bioenergy production while being more sensitive to weather fluctuation and climate change. The aim of this study was to evaluate the potential of LAI and RUE as indicators for bioenergy production and indicators of response to changing environmental conditions. For this study, we selected poplar clone J-105 (Populus nigra L. × P. maximowiczii A. Henry) and AFCs such as barley (Hordeum vulgare L.), wheat (Triticum aestivum L.), maize (Zea mays L.), and oilseed rape (Brassica napus L.), and compared their aboveground dry mass (AGDM) production in relation to their LAI development and RUE. The results of the study showed the long-term maximum LAI (LAImax) to be 9.5 in coppice poplar when compared to AFCs, where LAImax did not exceed the value 6. The RUE varied between 1.02 and 1.48 g MJ−1 in short rotation poplar and between 0.72 and 2.06 g MJ−1 in AFCs. We found both LAI and RUE contributed to AGDM production in short rotation poplar and RUE only contributed in AFCs. The study confirms that RUE may be considered an AGDM predictor of short rotation poplar and AFCs. This may be utilized for empirical estimates of yields and also contribute to improve the models of short rotation poplar and AFCs for the precise prediction of biomass accumulation in different environmental conditions.

ABSTRACTUnder elevated atmospheric CO2 concentrations, soil carbon (C) inputs are typically enhanced, suggesting larger soil C sequestration potential. However, soil C losses also increase and progressive nitrogen (N) limitation to plant growth may reduce the CO2 effect on soil C inputs with time. We compiled a data set from 131 manipulation experiments, and used meta‐analysis to test the hypotheses that: (1) elevated atmospheric CO2 stimulates soil C inputs more than C losses, resulting in increasing soil C stocks; and (2) that these responses are modulated by N. Our results confirm that elevated CO2 induces a C allocation shift towards below‐ground biomass compartments. However, the increased soil C inputs were offset by increased heterotrophic respiration (Rh), such that soil C content was not affected by elevated CO2. Soil N concentration strongly interacted with CO2 fumigation: the effect of elevated CO2 on fine root biomass and –production and on microbial activity increased with increasing soil N concentration, while the effect on soil C content decreased with increasing soil N concentration. These results suggest that both plant growth and microbial activity responses to elevated CO2 are modulated by N availability, and that it is essential to account for soil N concentration in C cycling analyses.

Radiation use efficiency values estimation based on the biomass increment (one approach) and on NPP from eddy covariance (two approaches) estimation of NPP brings the values of 0.13, 0.40, and 0.47 g (C) MJ −1 , respectively. The productivity of terrestrial ecosystems is primarily reliant on the absorption of solar radiation energy and its conversion into biomass. Monteith (1977) first introduced the concept of radiation use efficiency (RUE), which expresses the effectiveness of a plant stand to use solar radiation for the formation of new biomass and to maintain existing biomass. The presented paper uses a long-term, decadal, time series of biomass data, which is based on forest inventory data and an allometric relation, and on the application of eddy covariance (EC) estimation of Net Primary Production (NPP). These approaches provide different values of light use efficiency (LUE). LUE is based on direct carbon exchange estimation, LUE i , which denotes instantaneous efficiency based on the relationship between the daily sum of incident global radiation (GR i ) and NPP and LUES, calculated as the ratio between the sum of NPP and the sum of GR i per growing season. RUE is based on direct yearly biomass increment expressed in carbon units (carbon = 0.5 × biomass) divided by the sum of GR i per year. The obtained values amount to 0.13, 0.40, and 0.47 g(C) MJ−1 for RUE, LUES, and LUE i , respectively. The higher value of LUE i reflects a direct relation with the efficiency of photosynthetic carbon pumping. In contrast, the RUE value, based on biomass inventories, is the result of woody mass formation that is caused by several mutually related physiological processes and “wastages” of radiation utilization.

Comprendre les relations entre le climat et l'échange de carbone par les écosystèmes terrestres est essentiel pour prédire les niveaux futurs de dioxyde de carbone atmosphérique en raison des effets d'accélération potentiels des rétroactions positives du cycle climat-carbone. Cependant, les relations directement observées entre le climat et l'échange de CO2 terrestre avec l'atmosphère à travers les biomes et les continents font défaut. Nous présentons ici des données décrivant les relations entre l'échange net de carbone par les écosystèmes (NEE) et les facteurs climatiques tels que mesurés à l'aide de la méthode de covariance de Foucault sur 125 sites uniques dans divers écosystèmes sur six continents avec un total de 559 années de site. Nous trouvons que le NEE observé aux sites de covariance tourbillonnaire est (1) une fonction forte de la température annuelle moyenne aux latitudes moyennes et élevées, (2) une fonction forte de la sécheresse aux latitudes moyennes et basses, et (3) une fonction à la fois de la température et de la sécheresse autour de la ceinture moyenne-latitudinale (45°N). La sensibilité du NEE à la température annuelle moyenne se décompose à ~ 16 °C (une valeur seuil de la température annuelle moyenne), au-delà de laquelle aucune augmentation supplémentaire de l'absorption de CO2 avec la température n'a été observée et la sécheresse influence les règles de dépassement de l'influence de la température. Comprender las relaciones entre el clima y el intercambio de carbono por parte de los ecosistemas terrestres es fundamental para predecir los niveles futuros de dióxido de carbono en la atmósfera debido a los posibles efectos aceleradores de las retroalimentaciones positivas del ciclo clima-carbono. Sin embargo, faltan relaciones directamente observadas entre el clima y el intercambio terrestre de CO2 con la atmósfera a través de biomas y continentes. Aquí presentamos datos que describen las relaciones entre el intercambio neto de carbono (NEE) del ecosistema y los factores climáticos medidos utilizando el método de covarianza de remolinos en 125 sitios únicos en varios ecosistemas de seis continentes con un total de 559 años-sitio. Encontramos que la NEE observada en los sitios de covarianza de remolinos es (1) una fuerte función de la temperatura media anual en latitudes medias y altas, (2) una fuerte función de sequedad en latitudes medias y bajas, y (3) una función tanto de la temperatura como de la sequedad alrededor del cinturón latitudinal medio (45°N). La sensibilidad de NEE a la temperatura media anual se rompe a ~ 16 °C (un valor umbral de la temperatura media anual), por encima del cual no se observó ningún aumento adicional de la absorción de CO2 con la temperatura y la influencia de la sequedad anula la influencia de la temperatura. Understanding the relationships between climate and carbon exchange by terrestrial ecosystems is critical to predict future levels of atmospheric carbon dioxide because of the potential accelerating effects of positive climate–carbon cycle feedbacks. However, directly observed relationships between climate and terrestrial CO2 exchange with the atmosphere across biomes and continents are lacking. Here we present data describing the relationships between net ecosystem exchange of carbon (NEE) and climate factors as measured using the eddy covariance method at 125 unique sites in various ecosystems over six continents with a total of 559 site-years. We find that NEE observed at eddy covariance sites is (1) a strong function of mean annual temperature at mid- and high-latitudes, (2) a strong function of dryness at mid- and low-latitudes, and (3) a function of both temperature and dryness around the mid-latitudinal belt (45°N). The sensitivity of NEE to mean annual temperature breaks down at ~ 16 °C (a threshold value of mean annual temperature), above which no further increase of CO2 uptake with temperature was observed and dryness influence overrules temperature influence. يعد فهم العلاقات بين المناخ وتبادل الكربون بواسطة النظم الإيكولوجية الأرضية أمرًا بالغ الأهمية للتنبؤ بالمستويات المستقبلية لثاني أكسيد الكربون في الغلاف الجوي بسبب التأثيرات المتسارعة المحتملة للتغذية المرتدة الإيجابية لدورة المناخ والكربون. ومع ذلك، لا توجد علاقات ملحوظة مباشرة بين المناخ والتبادل الأرضي لثاني أكسيد الكربون مع الغلاف الجوي عبر المناطق الحيوية والقارات. نقدم هنا بيانات تصف العلاقات بين صافي تبادل النظام البيئي للكربون (NEE) والعوامل المناخية كما تم قياسها باستخدام طريقة التباين الدوامي في 125 موقعًا فريدًا في أنظمة بيئية مختلفة عبر ست قارات بإجمالي 559 سنة موقع. نجد أن NEE التي لوحظت في مواقع التباين الدوامي هي (1) وظيفة قوية لمتوسط درجة الحرارة السنوية عند خطوط العرض المتوسطة والعالية، (2) وظيفة قوية للجفاف عند خطوط العرض المتوسطة والمنخفضة، و (3) وظيفة لكل من درجة الحرارة والجفاف حول حزام العرض المتوسط (45درجةشمالاً). تنهار حساسية NEE لمتوسط درجة الحرارة السنوية عند حوالي 16 درجة مئوية (قيمة عتبة لمتوسط درجة الحرارة السنوية)، والتي لم يلاحظ فوقها أي زيادة أخرى في امتصاص ثاني أكسيد الكربون مع درجة الحرارة ويتجاوز تأثير الجفاف تأثير درجة الحرارة.

Abstract We analyzed the effect of manipulated water availability on an accumulation of nutrients and metals, their stoichiometry, and allocation to roots or leaves in a short rotation coppice (SRC) poplar plantation. The aim of this study was also to clarify how these changes are related to the effects of drought on growth parameters. This study was conducted in Domaninek, Czech Republic in an SRC poplar clone J-105 (Populus nigra L. × P. Maximowiczii H.). This plantation was established as an uncoppiced (single stem) and later on converted into multi-stem (coppice). A rain-out shelter experiment (reduced throughfall) was established in the second year of coppice and the drought stress (DS) applied for 3 years. Water availability altered the accumulation and allocation of nutrients and metals in above and belowground biomass. Reduced water availability led, in particular, to the significantly lower accumulation of potassium (K) in both leaves and roots and a higher carbon (C) to potassium (K) ratio (C:K) in leaves. The significant decline of zinc (Zn) was also found in roots under reduced throughfall. Reduced water availability led to increased accumulation of cadmium (Cd) in leaves and decreased accumulation in roots. This resulted in significantly lower root:leaf ratio for Cd content. An opposite response was found for the allocation of copper (Cu). We also demonstrated that major changes in accumulation and allocation are associated with changes in growth. The results indicated that such knowledge may contribute to understanding the role of nutrient uptake and translocation in acclimation to DS and it may help in developing phytoextraction methods on contaminated soils.

The abandonment of traditional mowing methods of mountain meadows in the Czech Republic at the end of the last century has resulted in secondary re-colonization of these areas. Altered accumulation of plant biomass resulted in a deceleration of N turnover. A mountain meadow may be regarded as a N-limited ecosystem in which plant nutrition is dependent on direct uptake of soil amino acids. The composition and distribution of ammonium ions, nitrate ions and the 16 bio-available proteinaceous amino acids were investigated in the top 7 cm of the Ah horizon of a Gleyic Luvisol in a long-term moderately mown meadow and an eleven year old, abandoned or uncut meadow. Ammonium N has a dominant role in both ecosystems. The moderately mown meadow showed accelerated N-turnover and higher net ammonization. The plant community showed a dependence on this form. Plant utilization of nitrates and amino acids appeared to be negligible. The uncut or abandoned meadow showed net ammonization from May (start of the experiment) through August, after which plant N-uptake consisted only of amino acids due to microbial immobilization. The release of bio-available nitrogen from spring until the beginning of summer in the Ah horizon was too low to explain total plant N-uptake. Glutamic acid, arginine and aspartic acids had the highest concentrations of any of the amino acids analyzed.

A growing body of scientific evidence indicates that we have entered the Anthropocene Epoch. Many assert that society has exceeded sustainable ecological planetary boundaries and that altered biogeophysical processes are no longer reversible to natural rates of ecosystem functioning. To properly and successfully address societal needs for the future, more holistic and complex methods need to be applied at various spatial and temporal scales. The increasingly interconnected nature of human and natural environments—from individuals to large megacities and entire continents and from cells through ecosystems to the biosphere as a whole (e.g., as seen in the carbon cycle)—demand new and often interdisciplinary and international approaches to address emerging global challenges. With that perspective in mind, the Czech Republic’s National Climate Program was established in 1991 with the aim to understand the impact of global environmental change on society. The National Climate Program was updated in 2017 to formulate a new Climate Protection Policy. Here, we outline the multifaceted problems that climate change poses for the Czech Republic, as well as a new scientific infrastructure and approaches directed to better understanding the effects of climate change on our ecosystems, water resources, urban environment, agriculture, human health, and general economy.