Adaptation of leaf anatomical characteristics of eleven understory species to different environments in coniferous plantations

人工林内两种主要生境（林窗和林内）的光照条件存在着显著差异，而这种差异也是影响人工林林下植物叶片形态和结构的重要环境因子。对川西米亚罗林区60a人工云杉林2种不同生境（林窗和林内）的11种植物比叶重、叶片解剖结构及气孔特征等进行了比较研究，结果显示：林窗生境中11种供试植物比叶重（LMA）均显著大于林内生境；多数阔叶物种叶片厚度（LT）、栅栏组织厚度（PT）、栅栏组织厚度／海绵组织厚度（PT／ST）、栅栏细胞层数在林窗生境中更大或更多，但叶表皮细胞厚度（UET、LET）、海绵组织厚度（ST）在两种生境中无显著差异；林窗生境中生长的各物种栅栏细胞均为长形且长度大于林内生长的相同物种；不同物种气孔密度（SD）对两种生境有一致的响应趋势，但显著程度有异，除三褶脉紫菀外10种植物的气孔长径（SL）受两种生境影响不大，这与气孔特性受多种环境因素制约，且各种因素对气孔作用效应和作用方面不同有关。结合各物种喜光特性综合分析后认为同一群落的林下植物对光生境具有一定程度的趋同适应性；从可塑性方面分析发现叶片光合组织的可塑性大于非光合组织，且各物种叶片平均可塑性与喜光特性基本吻合

Comparative study of amorphous and crystalline Zr-based alloys in response to nanosecond pulse laser ablation

In this work, we comprehensively investigate the response of amorphous and crystalline Zr-based alloys under nanosecond pulse laser ablation. The in situ multiphysics processes and ablation morphologies of the two alloy targets are explored and compared. The results indicate that the dynamics of laser-induced plasma and shock waves obey the idea blast wave theory and are insensitive to the topological structures of targets. Both targets experience significant superheating and culminate in explosive boiling. This ablation process leads to the formation of a hierarchical structure in the resultant ablation crater: microdents covered by widespread nanovoids. The amorphous target shows shallower microdents and smaller nanovoids than their crystalline counterparts because the former has a smaller heat-affected zone and experiences a higher degree of superheating. The hierarchical structure can adjust the surface wettability of targets from initial hydrophilic to hydrophobic, showing an increase of the contact angle approximately 119% for amorphous alloy compared with the crystal approximately 64%. This work demonstrates that amorphous alloys have a better performance against nanosecond pulse laser ablation and provides a feasible and one-step method of wettability modification for either amorphous or crystalline alloys

WARMING EFFECTS ON GROWTH AND PHYSIOLOGY OF SEEDLINGS OF BETULA ALBO-SINENSIS AND ABIES FAXONIANA UNDER TWO CONTRASTING LIGHT CONDITIONS IN SUBALPINE CONIFEROUS FOREST OF WESTERN SICHUAN, CHINA

川西亚高山针叶林是青藏高原东部高寒林区的重要组成部分，也是研究全球变化对森林生态系统影响的重要森林类型。开展亚高山针叶林不同树种对气候变暖响应差异的研究，可为预测未来气候变暖背景下亚高山针叶林植被组成和森林动态提供科学依据。我们以川西亚高山针叶林两种主要树种红桦（Betula albo-sinensis）和岷江冷杉（Abies faxoniana）为研究材料，采用开顶式增温法（Open-top chamber,OTC）模拟气候变暖，研究了增温对全光条件和林下低光环境中（约为全光的10％）生长的红桦和岷江冷杉幼苗生长和生理的影响。在人工林环境下，OTC使增温框内平均气温和地表温度分别升高了0．51和0．33℃；而在林外空地处，OTC使二者分别升高了0．69和0．41℃。研究结果显示，增温总体上促进了两种幼苗的生长和生理过程，并促使幼苗将更多的生物量投入到其同化部位叶，使幼苗的根冠比（R/S）显著降低。增温通过增加叶片的光合色素含量和表观量子效率等光合参数，促进了幼苗的光合过程和生长。然而，增温对两种幼苗生长和生理的影响效果与植物种类及其所处的光环境有关。增温仅在林外全光条件下显著影响红桦幼苗的生长和生理过程。岷江冷杉幼苗对增温的响应与红桦相反，即增温仅在林下低光环境下对岷江冷杉幼苗的生长和生理过程有明显促进作用。这种响应差异可能赋予这两种植物在未来气候变暖背景下面对外界环境变化时具有不同的适应能力和竞争优势，从而对亚高山针叶林生态系统物种组成和森林动态产生潜在影响

Nanoparticles produced by nanosecond pulse laser ablation of a metallic glass in water

In this paper, we perform a single nanosecond pulse laser ablation of a Zr-based metallic glass (Vitreloy 1) target in water. The violent ejection of high-temperature ablation matter is observed from the target by means of explosive boiling, which is accompanied by a formation of cavitation bubble. These ablation products entered the water include a rich variety of nanoparticles that can be classified into three different types: full amorphous, amorphous-crystalline composite, and polycrystalline. The amorphous nanoparticles have relatively smaller sizes and a uniform elemental distribution. The latter two types of nanoparticles exhibit a unique core-shell feature with an obvious compositional segregation. It is proposed that the diversity of the nanoparticles closely depends on the different pathways that they enter the water: directly before the bubble formation or via the bubble, in which the cooling rate and the glass-forming ability of ablation products are two competing factors

增温对川西亚高山针叶林内不同光环境下红桦和岷江冷杉幼苗生长和生理的影响

川西亚高山针叶林是青藏高原东部高寒林区的重要组成部分,也是研究全球变化对森林生态系统影响的重要森林类型。开展亚高山针叶林不同树种对气候变暖响应差异的研究,可为预测未来气候变暖背景下亚高山针叶林植被组成和森林动态提供科学依据。我们以川西亚高山针叶林两种主要树种——红桦(Betula albo-sinensis)和岷江冷杉(Abies faxoniana)为研究材料,采用开顶式增温法(Open-top chamber,OTC)模拟气候变暖,研究了增温对全光条件和林下低光环境中(约为全光的10%)生长的红桦和

激光驱动的微弹道冲击

微颗粒对材料的高速冲击与诸多重要应用领域密切相关,比如航天器的微陨石撞击、雾霾颗粒对发动机叶片的冲击、冷喷涂技术等.激光驱动颗粒冲击实验(Laser-Induced Particle Impact Test, LIPIT)于2010年被提出,是一种新型动态加载技术,能够对不同维度的多种材料进行微弹道冲击.相较于其他的微弹道技术, LIPIT独特的优势在于能够对单个微颗粒进行有效操控,进而实现各类材料(尤其是低维材料)的单颗粒微弹道高速冲击.本文回顾了LIPIT的发展历程,介绍了其系统构成及工作原理,对基于LIPIT技术的不同维度靶材的微弹道冲击研究进行了评述,主要内容包括:基于弹道动力学分析的能量耗散评估、微弹道冲击下的能量耗散机制、微弹道冲击导致的动力学现象及其相关的物理规律(包括反弹幂律、附着机制).最后对发展现状和值得进一步研究的问题进行了简要总结

The rebound law of micro-particle on amorphous alloys under high impact velocities

Compared to their crystalline counterparts, amorphous alloys due to disordered structures are expected to have higher elasticity of deformation. However, in this work, we use the micro-ballistic impact technique to show a smaller dynamic redound of micro-particles on a Zr-based amorphous alloy than that on its corresponding polycrystalline target. We find that the two alloys follow the same rebound law of micro-particle under low impact velocities, but with increasing impact velocity the amorphous alloy exhibits a faster decrease in rebound velocity of micro-particle. This lower rebound results from the easier activations of shear banding in glassy structures, thus contributing to more significant energy dissipation during the micro-particle impact. Further analyses imply that the amorphous alloys and their crystalline counterparts are more favorable in shock wave and projectile protection, respectively. This work is useful in the understanding of the dynamic elasticity and shock energy dissipation of amorphous alloys under micro-particle impacts

纳秒脉冲激光烧蚀非晶合金的研究进展

非晶合金是一类原子排列处于长程无序状态的新型结构材料,具有一系列优异的力学和物理性能,从而有望应用于国防、空天等关键领域.在这些领域的应用中,非晶合金易受到强激光或空间等离子体的作用而失效.同时,非晶合金在高能激光辐照下的结构响应本身也极具科学意义.因此,近年来这方面的研究得到了越来越多的关注.论文将重点关注纳秒脉冲激光对非晶合金在大气和水环境下的烧蚀,针对熔化、流体动力学失稳、爆炸沸腾、气泡动力学等烧蚀过程中的几种典型现象,简要介绍相关的实验和理论研究进展.最后,对未来值得进一步研究的方向进行了概述

Root exudates and soil microbes in three Picea asperata plantations with different stand ages

采用野外原位收集方法,对川西米亚罗林区不同林龄(9、13、31年)的粗枝云杉人工林根系分泌物和土壤微生物进行了研究.结果表明:不同林龄粗枝云杉人工林根系的单位质量、长度、面积及根尖分泌速率存在显著差异,表现为9年生云杉林的分泌速率显著大于13年生和31年生云杉林.13年生云杉林的根系活力显著小于9年生和31年生云杉林.不同林龄粗枝云杉人工林的根际土、非根际土微生物量碳(MBC)和氮(MBN)存在显著差异,根际土表现为31年生>13年生>9年生,非根际土为13年生>31年生>9年生.随林龄的增加,粗枝云杉的根际土细菌、真菌、放线菌磷脂脂肪酸含量及总量呈现出高-低-高的变化趋势,而非根际土细菌、真菌磷脂脂肪酸含量、总量及真菌/细菌呈低-高-低的趋势.粗枝云杉根系对土壤MBC、MBN及功能群磷脂脂肪酸含量具有正根际效应