Impact of land use change on soil respiration and methane sink in tropical uplands, Southwestern China

Land use conversion could modulate soil CO2 emissions and the balance between CH4 oxidation and production via changing soil physical, chemical and biological properties. Large areas of natural forests have been converted to rubber plantations in Southeast Asia, but its impact on soil CO2 and CH4 fluxes has not been sufficiently understood. This study was conducted in Xishuangbanna, Southwestern China, aiming to quantify the impact of this land use change on soil CO2 and CH4 fluxes and to clarify mechanisms responsible for the differences between natural forests and rubber plantations. Dynamics of soil respiration rates in two land uses were compared, and a mixed effect model was used in studying the interference of soil moisture on estimating temperature sensitivity (Q10) of soil respiration (Chapter 2). The land use change impact on the ability of soils to function as CH4 sink was firstly assessed with surface CH4 fluxes measured by static chambers, and then assessed with gas concentration profiles determined from soil probes. Confounded controlling factors and land use effects were disentangled, and the pathway of interactions between CH4 processes and mineral nitrogen was identified (Chapter 3). The concentration gradient method and one-dimensional diffusion-oxidation model were applied to quantify the vertical distribution of CH4 uptake in soil profiles, and to separate the relative control by gas diffusivity and by methanotrophic oxidation on CH4 uptake (Chapter 4). Distinct different temporal patterns of soil respiration were observed on sites during most of the rainy season: forest maintained a high soil respiration rate, while soil respiration in rubber plantations became suppressed (by up to 69%). Forest soils thus emitted the highest amount of CO2 with an annual cumulative flux of 8.48 ± 0.71 Mg C ha-1 yr-1, compared to 6.75 ± 0.79, 5.98 ± 0.42 and 5.09 ± 0.47 Mg C ha-1 yr-1 for 22-year-old rubber, rubber-tea intercropping, and 9-year-old rubber, respectively. Adding a quadratic soil moisture term into the regression model accounted for interference of moisture effect on the effect by soil temperature, therefore, improved temperature sensitivity assessments when high soil moisture suppressed soil respiration under rubber plantations. The static chamber method showed that soils under natural forest were stronger CH4 sinks than soils under rubber plantations, with annual CH4 fluxes of -2.41 ± 0.28 kg C ha-1 yr-1 and -1.01 ± 0.23 kg C ha-1 yr-1, respectively. Water-filled pore space was the main factor explaining the differences between natural forests and rubber plantations. Although soils under rubber plantations were more clayey than soils under natural forest, this was proved not to be the decisive factor driving higher soil moisture and lower CH4 uptake in the former soils. Concentration gradients method showed that CH4 consumption in 0-5 cm soil was significantly higher in natural forests than in rubber plantations, with a mean CH4 flux of -23.8 ± 1.0 and -14.4 ± 1.0 ug C m-2 h-1 for forest and rubber plantations, respectively. The atmospheric CH4 oxidized by top 10 cm soil accounted for 93% and 99% of total consumption for forest and rubber plantations, respectively. CH4 diffusivity at four sampled depths were significantly lower in rubber plantation than in forest. This reduced CH4 diffusivity, caused by altered soil water regime, predominately explained the weakened CH4 sink in converted rubber plantations. Estimated isotopic fractionation factor for carbon due to CH4 oxidation was 1.0292 ± 0.0015 (n=12). Modeling 13CH4 distribution in soil profiles using a diffusion-oxidation model explained the observations in the dry season, but suggested CH4 production in subsoil in the rainy season. In summary, converting natural forests into rubber plantations tended to reduce soil CO2 emissions, but this conversion substantially weakened CH4 uptake by tropical upland soils. The altered soil water regime and conditions of soil aeration under converted rubber plantations appear to have a pronounced impact on processes of gaseous carbon fluxes from soils. The clarified mechanisms in this study could improve the regional budget of greenhouse gases emissions in response to land use change and climate change.Landnutzungsänderungen können CO2 Emissionen, sowie das Gleichgewicht zwischen der Oxidation und Produktion von CH4 beeinflussen, indem sie physikalische, chemische und biologische Bodeneigenschaften verändern. Trotz der Umwandlung großer Flächen der natürlichen Wälder Südost Asiens zu Kautschukplantagen, wurde der Einfluss auf die CO2 und CH4 Flüsse des Bodens bisher unzureichend erforscht. Dazu wurde die vorliegende Studie in Xishuangbanna im Südwesten Chinas durchgeführt. Die Ziele der Arbeit waren, den Einfluss der Landnutzungsänderungen auf die CO2 und CH4 Flüsse des Bodens zu quantifizieren, sowie Unterschiede der relevanten Mechanismen zwischen naturnahen Wäldern und Kautschukplantagen zu erklären. Der Verlauf der Bodenatmungsraten der beiden Landnutzungen wurde verglichen. Durch ein Modell mit gemischten linearen Effekten wurde die Interferenz der Bodenfeuchtigkeit bei der Schätzung der Temperaturempfindlichkeit (Q10) der Bodenatmung analysiert (Kapitel 2). Der Einfluss der Landnutzungsänderungen auf die Fähigkeit des Bodens, CH4 aufzunehmen, wurde anhand von CH4 Flüssen der Bodenoberfläche, gemessen durch die statische Kammermethode, bewertet. Zudem wurden Gaskonzentrationsprofile durch Bodensensoren gemessen. Die Landnutzungseffekte wurden um die Störfaktoren bereinigt um die Wechselwirkungen zwischen CH4-Prozessen und mineralischem Stickstoff zu identifizieren (Kapitel 3). Danach wurde die Methode des Konzentrationsgradienten sowie ein eindimensionales Diffusions-Oxidationsmodel genutzt, um die vertikale Verteilung der CH4 Aufnahme in Bodenprofilen zu quantifizieren, und die relativen Einflüsse des Gasdiffusionsvermögens und der methanotrophen Oxidation bei der CH4-Aufnahme abzuschätzen (Kapitel 4). Über weite Teile der Regenzeit hinweg zeigten die zwei Standorte deutlich verschiedene zeitliche Bodenatmungsverläufe. Die Respirationsrate des Waldstandortes war konstant hoch, in den Kautschukplantagen hingegen war sie in der Regenzeit (um bis zu 69 %) reduziert. Waldböden emittierten somit das meiste CO2, mit einem jährlichen kumulativen Fluss von 8.48 ± 0.71 Mg C ha-1 a-1, verglichen mit 6.75 ± 0.79, 5.98 ± 0.42 and 5.09 ± 0.47 Mg C ha-1 a-1 beim ausgewachsenen Kautschuk, der Mischkultur aus Kautschuk und Tee sowie den jungen Kautschukplantagen, respektive. Ein zusätzlicher quadratischer Bodenfeuchtigkeitsterm im verwendeten Modell erklärte den Einfluss der Bodenfeuchte auf den Temperatureffekt und verbesserte dadurch die Analyse der Temperatursensitivität, da hohe Bodenfeuchte die Bodenrespiration in Kautschukplantagen limitierte. Laut den Ergebnissen der statischen Kammermethode, waren die Böden unter naturnahem Wald, mit CH4 Flüssen von -2.41 ± 0.28 kg C ha-1 a-1, stärkere CH4 Senken als Böden unter Kautschukplantagen, welche Flüsse von -1.01 ± 0.23 kg C ha-1 a-1 besaßen. Das wassergesättigte Porenvolumen der Böden war der Hauptfaktor welcher die Unterschiede zwischen naturnahem Wald und Kautschukplantagen erklären konnte. Obwohl die Böden unter den Kautschukplantagen höhere Tongehalte als die Waldböden vorwiesen, war dies nicht der entscheidende Faktor für höhere Bodenwassergehalte und niedrigere CH4 Aufnahmen. Die Konzentrationsgradientenmethode zeigte, dass die CH4 Aufnahme in 05 cm Bodentiefe im naturnahem Wäldern signifikant höher war als in den Kautschukplantagen. Die mittleren CH4 Flüsse lagen bei -23.8 ± 1.0 im Wald und bei 14.4 ± 1.0 ug C m-2 h-1 in den Kautschukplantagen. Das atmosphärische CH4, welches in den obersten 10 cm der Böden oxidiert wurde, machte 93% bzw. 99% der Gesamtaufnahme des Waldes und der Kautschukplantagen aus. Die Diffusität des CH4 in den Kautschukplantagen war in allen vier beprobten Bodentiefen signifikant niedriger als im Wald. Diese verminderte, durch Veränderungen des Wasserhaushalt verursachte, Diffusionsfähigkeit, war der wichtigste Erklärungsfaktor für die geringeren CH4 Aufnahmen der konvertierten Kautschukplantagen. Der geschätzte Isotopenfraktionierungsfaktor von Kohlenstoff bei der CH4 Oxidation war 1.0292 ± 0.0015 (n=12). Die Modellierung der Verteilung von 13CH4 im Bodenprofil unter Verwendung eines Diffusions-Oxidationsmodells konnte zwar die Beobachtungen in der Trockenzeit erklären, sagte für die Regenzeit jedoch eine Produktion von CH4 im Unterboden vorher. In der Tendenz verringerte eine Konvertierung von naturnahem Wald zu Kautschukplantagen die CO2 Emissionen, verringerte gleichzeitig jedoch substanziell die CH4 Aufnahme der tropischen Böden. Die resultierenden Wasser- und Lufthaushaltveränderungen der Böden von konvertierten Kautschukplantagen schienen die Prozesse der gasförmigen Kohlenstoffflüsse von Böden deutlich zu beeinflussen. Das bessere Verständnis der Mechanismen durch diese Studie könnte daher zur Verbesserung der regionalen Budgetierung von Treibhausgasemissionen infolge von Landnutzungsänderungen und des Klimawandels beitragen

Joint Transceiver Optimization for Two-Way MIMO Relay Systems with MSE Constraints

Transceiver design for two-way multiple-input multiple-output (MIMO) relay systems has attracted much research interest recently. However, there is little research on the impact of quality-of-service (QoS) constraints on two-way MIMO relay systems, which greatly affects the user experience. In this letter, we propose a transceiver design for two-way MIMO relay systems which minimizes the total network transmission power subjecting to QoS constraints expressed as upper-bounds on the mean-squared error (MSE) of the signal waveform estimation at both destinations. An iterative algorithm is developed to optimize the source, relay, and receive matrices. Simulation results demonstrate the fast convergence of the proposed algorithm

Effects of the merger history on the merger rate density of primordial black hole binaries

We develop a formalism to calculate the merger rate density of primordial black hole binaries with a general mass function, by taking into account the merger history of primordial black holes. We apply the formalism to three specific mass functions, monochromatic, power-law and log-normal cases. In the former case, the merger rate density is dominated by the single-merger events, while in the latter two cases, the contribution of the multiple-merger events on the merger rate density can not be ignored. The effects of the merger history on the merger rate density depend on the mass function.Comment: 9 pages, 7 figures; V2, references added, discussion added, title changed. v3, a new subsection adde

An Analysis of Business Strategies and Managements Which Cause Company's Success or Challenges in the International Market: A Case Study in IKEA Company

There is a general agreement among researchers that the IKEA company which established in 1943 in Sweden has become one of the most famous international furniture retailer and opened massive stores all around the world. On account of that, many successful unique strategies and creative managements made by some famous companies which explored and studied by the researchers appear. However, there is some evidence to show that some successful companies such as IKEA may still have failures or face challenges during the steps of decision or the operation such as entering the USA market and quality issues about products, which need some effective actions to overcome and avoid them. This paper seeks to explore the operation of famous companies with the case study of IKEA company which create success or problems in the international level, and 3 main perspectives from the company are discussed: the company’s strategies, the organization’s managements and the international markets in the strategic management; and in the case, it also talk about company’s unique innovation, the success and the challenge. According with this, it argues, in general, that these useful business strategies and managements such as IKEA’s success has played an important role in the advancement of the company, it also suggests that some problems and challenges could not be avoided and still need to learn a lesson. It is recommended that further comprehensive studies should be conducted with the relation of the other business area of the company as well as to cover the topic from more various aspects and research fields

Effect of ley inclusion in crop rotations on soil carbon stocks in a life cycle perspective

Carbon sequestration in agricultural soils has been proposed as an important climate change mitigation strategy. Carbon stocks in soils can be increased by different cropland management options, one of which is greater inclusion of perennial crops in crop rotations. This study compared the climate impact in a life cycle perspective of continuous ley-dominated rotations and continuous cereal rotations at two different sites (loam, clay) in Sweden. Effects of these systems on carbon content in topsoil and subsoil over 35 years were assessed based on data from two ongoing longterm field trials. The continuous cereal rotations led to a decrease in soil organic carbon stocks at both sites, resulting in an increase in overall climate impact of 8-19%. The ley-dominated rotationsincreased soil organic carbon stocks at both sites over time, contributing to a decrease in overall climate impact of 7% (clay) and 18% (loam). The high soil carbon accumulation in the ley rotation at the site with loamy soil, where soil carbon stocks increased in both topsoil and subsoil, waspossibly due to more roots entering the subsoil than at the site with clay soil

Gravitational and electromagnetic radiation from binary black holes with electric and magnetic charges: Elliptical orbits on a cone

Extending the electromagnetic and gravitational radiations from binary black holes with electric and magnetic charges in circular orbits in Phys. Rev. D {\bf 102}, 103520 (2020), we calculate the total emission rates of energy and angular momentum due to gravitational and electromagnetic radiations from dyonic binary black holes in precessing elliptical orbits. It is shown that the emission rates of energy and angular momentum due to gravitational and electromagnetic radiations have the same dependence on the conic angle for different orbits. Moreover, we obtain the evolutions of orbits and find that a circular orbit remains circular while an elliptic orbit becomes quasi-circular due to electromagnetic and gravitational radiations. Using the evolution of orbits, we derive the waveform models for dyonic binary black hole inspirals and show the amplitudes of the gravitational waves for dyonic binary black hole inspirals differ from those for Schwarzschild binary black hole inspirals, which can be used to test electric and magnetic charges of black holes.Comment: 10 pages, 2 figures, a new section adde