旅游干扰对芦芽山亚高山草甸植物生物量分配的影响

芦芽山作为华北地区亚高山草甸的典型分布区,在日益加剧的旅游压力下面临着巨大的退化风险,明晰旅游干扰背景下亚高山草甸植物生物量的分配策略、平衡当地经济发展和生态保护成为当前亟待解决的问题。本研究以芦芽山亚高山草甸为研究对象,关注不同旅游干扰强度和海拔梯度对植物群落整体和各功能群地上、地下生物量及分配策略的影响机制和关键调控因子。结果表明:芦芽山亚高山草甸的植物群落生物量与旅游干扰强度呈负相关,且生物量分配支持最优分配效应;植物地上生物量主要受到植物丰富度、旅游干扰强度、海拔、土壤容重以及土壤速效钾的调控,地下生物量和根冠比受到旅游干扰强度和土壤全磷的调控。本研究表明规范游客行为和提高土壤肥力是亚高山草甸恢复和管理的关键要素。

陆生植物生物量分配对模拟氮沉降响应的Meta分析

分析了陆生植物地上、地下各组织中生物量分配对氮沉降的响应,为研究大气氮沉降背景下陆地生态系统的碳、氮循环过程及植物生物量分配、立木收获、定向培育等相关研究和实践提供参考依据。共收集整理了国内外63篇论文的原始数据资料进行Meta分析(Meta-analysis),用以定量评估氮沉降对植物生物量分配的影响,并通过亚组分析进一步探讨了不同生态系统类型、植物种类、氮肥形式、施氮水平和持续时间对生物量分配的影响。结果表明,总体来看施氮会显著促进植物地上部分生物量分配,植物叶生物量和茎生物量在施氮条件下均显著增加;然而地下生物量所受促进作用要低于地上部分,表现为植物细根生物量和粗根生物量在氮输入下并没有显著变化;植物根冠比在氮沉降下显著降低;叶重比、茎重比和根重比在氮沉降下没有显著变化。此外,亚组分析结果表明生态系统类型和植物类型会显著影响植物总生物量和根冠比对氮沉降的响应,草本植物在氮沉降下的生物量累积明显优于木本,这说明短期氮沉降可能会增加草本的覆盖面积;施肥形式对根冠比的影响存在明显差异,相比于尿素,硝酸铵对植物根冠比的作用更显著;不同施氮水平显著影响地上生物量分配,中氮水平(本研究为60—120 kg hm-2a-1)促进作用最大,高氮水平(本研究为≥120 kg hm-2a-1)促进作用明显减弱,这与总生物量的变化一致,表明过高的氮沉降量将抑制植物生长;氮沉降处理时间长短对植物地上生物量的影响也存在显著差异,当施氮时间高于3年,氮沉降对地上生物量的促进作用几乎消失。总之,短期氮沉降会使植物分配更多生物量给地上部分,且氮沉降对草本植物生物量的累积作用明显优于木本,这些发现可为未来大气氮沉降背景下植物地上、地下部分碳存储、植物群落结构、植被动态等相关研究提供科学依据。

铅胁迫下地被竹的生长响应与铅富集、解毒策略

地被竹(Dwarf bamboos)被认为是具有土壤重金属污染修复潜力的克隆植物,但其在铅(Pb)污染环境中的适应策略与解毒机制尚未见报道。文章以6种地被竹为研究对象,对其进行3个浓度水平(0、300、1500 mg/kg)的土壤Pb胁迫处理,结果表明:1)多数地被竹种会通过“减少新竹生物量分配”和“降低地上部分生物量分配”2种生物量分配策略以适应Pb胁迫逆境;2)地被竹主要将Pb积累分布在地下鞭根系统及老秆中,6个竹种形成了3种不同的Pb富集策略,分别为:“鞭主导老秆协同”(菲黄竹、菲白竹、白纹椎谷笹和狭叶倭竹),“老秆主导鞭协同”(美丽箬竹)和“老秆主导新根协同”(铺地竹);3)在Pb 300和Pb 1500土壤Pb胁迫处理下,转运系数大于1的竹种有菲白竹(1.51,1.86)、铺地竹(1.38,1.02)和美丽箬竹(1.59,1.11),富集系数大于1的竹种只有铺地竹(1.86,1.06)。进一步以铺地竹为研究对象,采用水培方式,设计4个Pb胁迫水平(0、300、600、900 mg/L),分析其不同器官的亚细胞间隔区域化作用、Pb化学赋存形态以及植物细胞螯合作用,从生理水平到细胞水平揭示出铺地竹的器官Pb解毒策略:1)鞭根系统对Pb的滞留是铺地竹缓解Pb对地上部分伤害的解毒策略之一;2)细胞壁固持是鞭、根、秆的主导Pb解毒策略,液泡区隔化是叶的主导Pb解毒策略;3)根、鞭、秆中的Pb主要以4种低迁移能力(低毒)的化学形态赋存(FNaCl,FHAc,FHCl和FR),叶片中的Pb主要以2种高迁移能力(高毒)的化学形态赋存(FE和FW);4)根系、叶片参与Pb解毒的主要细胞螯合物质不同,前者通过PCs、后者通过GSH发挥解毒作用。综上,铺地竹具有合理的Pb耐受与解毒机制,以及较强的Pb富集能力(在300、1500 mg/kg Pb污染的20 cm浅层土壤中,一个生长季可分别回收提取238 mg/m^(2)、535 mg/m^(2)土壤Pb),具有Pb污染修复的应用潜力。

A Functional-Structural Model of Rice Seedling Coupled with Nitrogen Metabolism

With the ability of representing the association and inner-feedback between plant morphological structure and physiological functions, functional-structural plant modeling （FSPM） approach has been used in many works, trying to better understand the mechanisms of integrating plant functions and its structure, and their communication with environmental factors. To do so, an FSPM of rice seedling was developed in this study, including structural morphogenetic model, photosynthetic model and biomass partitioning module. It can thus describe the developmental course of the rice structure dynamically based on the processes of biomass producing and partitioning. Furthermore, the processes of nitrogen metabolism, which influence the N content and growth dynamics of the virtual rice, were also considered. The model was developed with L-system on a platform established with Java programming language, which took over the parsing and visualization of the L-system strings to 3D objects using Java 3D extended library. The physiological processes in the model can be modified and further improved to gradually meet the needs for modeling the whole life cycle of rice, e.g., considering the respiration, and interaction with other environmental factors like CO2, temperature, etc.. The model was developed to provide a platform to systematically study and understand how plant systems like rice seedling work. The model and the virtualization platform can be expanded to provide decision support on N fertilizer application for the rice seedling and the other crops.

Effects of competitive interactions of different life forms submersed plants on biomass allocation in shallow lakes

Plant competition has been recognized as one of the most important factors influencing the soructure and function of lake ecosystems. Competition from plants of dissimilar growth form may have profound effects on shallow lakes＇. An experiment was conducted to investigate the effects of competitive interactions of submersed plants with dis- similar growth forms on the biomass allocations. Hydrilla verticitlata and Vallisneria natans were selected and were planted in a single-species monoculture and a mixed-species pattern, Results showed that the growth of E natans was＇ significantly affected by the tt, verticillata and caused a sharp reduction of biomass, but the root：shoot ratio of E ha- tans was not affected significantly and there was a minimal increase in mixture： while for H. verticillata, the biomass and the root：shoot ratio were not significantly changed by the competitive interactions ore natans, there was minimal increase of biomass and minimal decrease of the root：shoot ratio. These results may indicate that theplant which can develop a dense mat or canopy at the water surface would be a stronger competitor relative to the plant that depends more on light availability near the sediment.