Tree biomass was investigated in an age-sequence of secondary lacebark pine (Pinus bungeana) forests to understand biomass partitioning patterns during stand development. Mean biomass of each tree component increased steadily as stands aged. Average growth rates and ratios of tree biomass to stand age increased with age. The ratio of below-to above-ground biomass remained relatively constant independent of stand age. Compared to DBH-H allometric equations, the DBH-only equations performed slightly better and are more efficient to apply. These new equations for lacebark pine are an important supplement to China' s national tree biomass equations. These equations and the findings on biomass partitioning patterns during stand development are applicable for the accurate estimation of ecosystem carbon accounting and will contribute to the sustainable management of lacebark pine forests.Keywords: age-sequence, biomass allocation, Pinus bungeana RÉSUMÉ La biomasse des arbres a été étudiée selon une séquence chronologique dans le cas d'une forêt secondaire de pin Napoléon (Pinus bungeana) afin de comprendre les schémas de répartition de la biomasse au cours du développement du peuplement. La biomasse moyenne de chacun des arbres a augmenté de façon constante à mesure du vieillissement du peuplement. Le taux moyen de croissance et le ratio de la biomasse des arbres par rapport à l'âge du peuplement ont augmenté au cours des ans. Le ratio de la biomasse dans le sol par rapport à celle au-dessus du sol est demeuré de façon constante relativement indépendant de l'âge du peuplement. Suite à des comparaisons des équations allométriques dhp-h, les équations portant uniquement sur le dhp ont donné des résultats légèrement plus intéressants et sont plus efficaces. Ces nouvelles équations pour le pin Napoléon représentent une contribution significative aux équations nationales décrivant la biomasse tirée des arbres en Chine. Ces équations et ces résultats sur les schémas de répartition de la biomasse au cours du développement du peuplement peuvent être utilisés pour effectuer une estimation précise de la comptabilisation du carbone des écosystèmes et contribueront à l'aménagement durable des forêts de pin Napoléon.Mots clés : séquence chronologique, répartition de la biomasse, Pinus bungeana
Tree planting has been proposed by Beijing's municipal government as a measure to alleviate airborne fine particulate matter (PM) in the city as trees have large surface areas to filter pollution out of the air. To maximize this eco-efficiency, a series of active measures have been taken by the city's forestry sector. These strategies are elaborated here to provide a valuable reference for other megacities facing similar challenges.Keywords: PM 2.5 , air pollution, forestry strategies RéSuméLa plantation d'arbres a été proposée par le gouvernement municipal de Pékin en tant que mesure de réduction de la quantité de particules fines (PM) en suspension dans l'air de la ville compte tenu que les arbres offrent une importante surface foliaire pouvant filtrer cette forme de pollution de l'air. Afin de maximiser l' efficacité écologique de cette approche, une série de mesures ont été entreprises par le secteur forestier de la ville. Ces stratégies sont décrites ci-après afin de servir de références aux autres mégalopoles confrontées à de semblables défis.Mots clés : PM 2.5 , pollution de l'air, stratégies forestières 1 College of Forestry, Beijing Forestry University, Beijing, China 2 Beijing Forestry Carbon Administration, Beijing, China 3 The school of Nature Conservation, Beijing Forestry University, Beijing, China *corresponding author: e-mail liujl66@hotmail.com even approaching 1000 μg/m 3 (Sun et al. 2014). In recent years, the Government has taken a series of measures to combat this pollution. For example, 35 environmental monitoring stations have been built in Beijing and the 24 hours of data is published at http://zx.bjmemc.com.cn; industrial and energy infrastructures are being adjusted, with some heavily polluting enterprises eliminated; new vehicles are required to meet Euro V emission standards, and diesel buses are being converted to natural gas (He et al. 2001, Li and Ding 2012). These positive measures may be insufficient, however, in the face of significant economic, political and social limitations. Therefore, in addition to reducing emissions, other measures to remove airborne particles will be necessary. Reducing air pollutants by increasing urban vegetation could prove to be an effective long-term solution for the improvement of air quality (Litschke and Kuttler 2008). Effectiveness of Tree Cover in Reducing Airborne PollutionTrees may mitigate the damaging effects of airborne particles through removal and subsequent lowering of concentrations (Beckett et al. 2000, Litschke and Kuttler 2008, Prajapati 2012, Schaubroeck et al. 2014). Farmer (1993 reported that trees are biological filters for airborne particles due to their large leaf surfaces relative to ground covered. According to Cavanagh et al. (2009), trees currently remove around 300 t of air pollutants annually from Christchurch, New Zealand and around 4% of primary PM 10 (particles with a diameter smaller than 10 μm) in the West Midlands in the United Kingdom. Yang et al. (2005) Deposition is a combination of processes removing ...
This paper surveys invasive plant species in Songshan National Nature Reserve and analyzes their characteristics and distribution. Canonical Correspondence Analysis (CCA) illustrates relationships between environmental and human factors and species distribution. Eight species of invasive plants are distributed throughout the experimental area. Aspect, longitude and human activities influence distribution. Three measures are proposed for better management of the Reserve: reinforce research on invasive species, strengthen public awareness of alien species introductions, and establish laws and regulations to control unwanted introductions.
As one of the most commonly ordered imaging tests, the computed tomography (CT) scan comes with inevitable radiation exposure that increases cancer risk to patients. However, CT image quality is directly related to radiation dose, and thus it is desirable to obtain high-quality CT images with as little dose as possible. CT image denoising tries to obtain high-dose-like high-quality CT images (domain Y ) from low dose low-quality CT images (domain X ), which can be treated as an image-to-image translation task where the goal is to learn the transform between a source domain X (noisy images) and a target domain Y (clean images). Recently, the cycle-consistent adversarial denoising network (CCADN) has achieved state-of-the-art results by enforcing cycle-consistent loss without the need of paired training data, since the paired data is hard to collect due to patients’ interests and cardiac motion. However, out of concerns on patients’ privacy and data security, protocols typically require clinics to perform medical image processing tasks including CT image denoising locally (i.e., edge denoising). Therefore, the network models need to achieve high performance under various computation resource constraints including memory and performance. Our detailed analysis of CCADN raises a number of interesting questions that point to potential ways to further improve its performance using the same or even fewer computation resources. For example, if the noise is large leading to a significant difference between domain X and domain Y , can we bridge X and Y with a intermediate domain Z such that both the denoising process between X and Z and that between Z and Y are easier to learn? As such intermediate domains lead to multiple cycles, how do we best enforce cycle- consistency? Driven by these questions, we propose a multi-cycle-consistent adversarial network (MCCAN) that builds intermediate domains and enforces both local and global cycle-consistency for edge denoising of CT images. The global cycle-consistency couples all generators together to model the whole denoising process, whereas the local cycle-consistency imposes effective supervision on the process between adjacent domains. Experiments show that both local and global cycle-consistency are important for the success of MCCAN, which outperforms CCADN in terms of denoising quality with slightly less computation resource consumption.
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