农林复合系统固碳潜力研究进展

农林复合系统是解决当前资源枯竭、农林用地紧张和实现环境保护的一种可持续土壤管理模式。自《京都议定书》签订以来, 农林复合系统因其较高的固碳潜力引起了科学家的广泛关注。深入理解农林复合系统的固碳过程及其对气候变化、环境条件的改变和管理措施的响应, 是准确地预测农林复合系统在全球变化情景下固碳潜力的关键。该文综述了农林复合系统的概念和分类, 探讨了农林复合系统相比单一系统的固碳潜力及固碳机理, 分析了农林复合系统固碳潜力的测定方法和当前面临的挑战, 综述了气候因子、环境条件和人为管理措施对农林复合系统固碳潜力的影响。我国农林复合系统的固碳潜力相比全球其他区域还处于较低水平, 为提高我国农林复合系统的固碳潜力, 未来需要加强以下四个方面的工作: 扩大农林复合系统的分布面积、加强农林复合系统的合理配置和管理、选择适宜的物种组合和优化系统的群体结构。     

小兴安岭7种典型林型林分生物量碳密度与固碳能力

森林生物碳储量作为森林生态系统碳库的重要组成部分, 在全球碳循环中发挥着重要作用。以小兴安岭7种典型林型为研究对象, 通过外业样地调查与室内实验分析相结合的方法, 从林分尺度对林分生物量与碳密度进行计量, 分析了林分生物碳储量的空间分配格局, 并对林分年固碳能力与碳汇潜力进行了探讨。结果表明: 小兴安岭不同林型从幼龄林到成熟林的乔木层碳密度增长速率为: 蒙古栎(Quercus mongolica)林>兴安落叶松(Larix gmelinii)林>云冷杉(Picea-Abies)林>樟子松(Pinus sylvestris var. mongolica)林>山杨(Populus davidiana)林>红松(Pinus koraiensis)林>白桦(Betula platyphylla)林。7种典型林型不同龄组(幼龄林、中龄林、近熟林和成熟林)林分生物量碳密度分别为: 红松林31.4、74.7、118.4和130.2 t·hm^-2; 兴安落叶松林28.9、44.3、74.2和113.3 t·hm^-2; 樟子松林22.8、52.0、71.1和92.6 t·hm^-2; 云冷杉林23.1、44.1、77.6和130.3 t·hm^-2; 白桦林18.8、35.3、66.6和88.5 t·hm^-2; 蒙古栎林25.0、20.0、47.5和68.9 t·hm^-2; 山杨林19.8、28.7、43.7和76.6 t·hm^-2。红松林、兴安落叶松林、樟子松林和蒙古栎林在幼龄林时林分年固碳量较高, 其他林型在成熟林时林分年固碳量较高。7种典型林型不同龄组的林分生物量碳密度均随林龄增长而增加, 但不同林型的碳汇功能存在差异, 同一林型不同林龄的生物量碳密度增幅差异也较大。林分年固碳量在0.4-2.8 t·hm^-2之间, 碳汇能力较强、碳汇潜力较大。尤其是小兴安岭目前林分质量较差, 幼龄林和中龄林所占的比重较大, 具有较大的碳汇潜力。研究结果可为森林经营管理及碳汇功能评价提供参考。     

Sequestration of nematocysts by divergent cnidarian predators: mechanism,function, and evolution

Animals have evolved diverse mechanisms to protect themselves from predators. Although such defenses are typically generated endogenously, some species have evolved the ability to acquire defenses by sequestering defensive chemicals or structures from other species. Chemical sequestration is widespread among animals, but the ability to sequester entire structures, such as organelles, appears to be rare. Here, we review information on the sequestration of functional nematocysts, the stinging organelles produced by Cnidaria, by divergent predators. Nematocyst sequestration has evolved multiple times, having been documented in Ctenophora, Acoelomorpha, Platyhelminthes, and Mollusca. For each of these phyla, we review the phylogenetic distribution, mechanisms, and possible functions of nematocyst sequestration. We estimate that nematocyst sequestration has evolved 9–17 times across these four phyla. Although data on the mechanism of sequestration remain limited, similarities across several groups are evident. For example, in multiple groups, nematocysts are transported within cells from the gut to peripheral tissues, and certain types of nematocysts are selectively sequestered over others, suggesting convergent evolution in some aspects of the sequestration process across phyla. Similarly, although the function of nematocyst sequestration has not been well documented, several studies do suggest that the nematocysts sequestered by these groups are effective for defense. We highlight several traits that are common to Ctenophora, Acoelomorpha, Platyhelminthes, and Mollusca and suggest hypotheses for how these traits could have played a role in the evolution of nematocyst sequestration. Finally, we propose a generalized working model for the steps that may lead to the evolution of nematocyst sequestration and discuss important areas for future research.     

Responses of Gmelina arborea, a tropical deciduous tree species, to elevated atmospheric CO2: Growth, biomass productivity and carbon sequestration efficacy

The photosynthetic response of trees to rising CO₂ concentrations largely depends on source-sink relations, in addition to differences in responsiveness by species, genotype, and functional group. Previous studies on elevated CO₂ responses in trees have either doubled the gas concentration (>700 μmol mol⁻¹) or used single large addition of CO₂ (500-600 μmol mol⁻¹). In this study, Gmelina arborea, a fast growing tropical deciduous tree species, was selected to determine the photosynthetic efficiency, growth response and overall source-sink relations under near elevated atmospheric CO₂ concentration (460 μmol mol⁻¹). Net photosynthetic rate of Gmelina was ∼30% higher in plants grown in elevated CO₂ compared with ambient CO₂-grown plants. The elevated CO₂ concentration also had significant effect on photochemical and biochemical capacities evidenced by changes in F_V/F_M, ABS/CSm, ET₀/CSm and RuBPcase activity. The study also revealed that elevated CO₂ conditions significantly increased absolute growth rate, above ground biomass and carbon sequestration potential in Gmelina which sequestered ∼2100 g tree⁻¹ carbon after 120 days of treatment when compared to ambient CO₂-grown plants. Our data indicate that young Gmelina could accumulate significant biomass and escape acclimatory down-regulation of photosynthesis due to high source-sink capacity even with an increase of 100 μmol mol⁻¹ CO₂.     

秸秆还田对水稻固碳特性及产量形成的影响

以中浙优1号为材料、秸秆不还田为对照,在大田试验条件下研究了不同秸秆还田量（4000、6000、8000 kg·hm^-2）对水稻群体干物质积累、运转、植株固碳及产量形成的影响. 结果表明： 与对照相比,秸秆还田处理的水稻群体干物质积累总量平均增加63.03 g·m^-2,以6000 kg·hm^-2处理的干物质积累量最高,比对照增加154.40 g·m^-2;在水稻各生育阶段中,秸秆还田处理对分蘖盛期—齐穗期干物质积累的影响最为明显,干物质积累量比对照平均增加71.25 g·m^-2;与对照相比,秸秆还田处理的茎叶干物质输出率和表观转变率分别平均增加4.2%和3.7%,均以6000 kg·hm^-2处理最高,分别为12.8%和11.1%.秸秆还田处理的群体植株固碳量比对照平均增加55.38 g·m^-2,以6000 kg·hm^-2处理的增幅最大,为17.8%;从固碳量在各器官中的分配来看,秸秆还田有利于生育前期茎叶固碳量的积累和生育后期固碳量向穗部的分配.秸秆还田处理的水稻产量比对照平均增加794.59 kg·hm^-2,增幅9.5%,其中6000和4000 kg·hm^-2处理的产量均显著提高,而8000 kg·hm^-2处理的产量增加不显著;从产量构成因素来看,秸秆还田处理单位面积有效穗数的增加是增产的主要原因,平均增加8.4穗·m^-2.     

经颅多普勒超声对脑血管状态与人格特征相关性研究

目的:研究脑血管状态与人格特征的相关性。方法:人格特征应用A型行为类型量表、艾森克人格问卷(EPQ)对60名20-35岁青年人群进行问卷调查,并划分出不同类型;脑血管状态应用经颅多普勒超声(TCD)的诊断技术测查60人的大脑中动脉(MCV)的血流速度来判断脑血管的紧张程度。结果:脑血管紧张组:A型人格为19人占59.3%,对照组:A型人格为3人占10.7%,以A型人格占优势(x2=22.85,P0.01)。脑血管紧张组(36.2±5.8)A型行为问卷平均得分高于对照组(20.3±2.4))(t=6.81,P0.01)。脑血管紧张组P分、N分、L分与正常对照组比较,差异无统计学意义(均P0.05);脑血管紧张组E分(内外向)高于对照组,差异有统计学意义(P0.05)。四种性格类型相比,外向情绪不稳定型的脑血管紧张组13(40.6%)与对照组4(14.3%)相比所占比例较高(x2=21.91,P0.05)。结论:A型人格,外向不稳定的人格特征与脑血流速度增快有关,可能是脑血管紧张的诱发因素之一。     

Roving females and patient males: a new perspective on the mating strategies of chimpanzees

Mating strategies are sets of decisions aimed at maximizing reproductive success. For male animals, the fundamental problem that these strategies address is attaining mating access to females in a manner that maximizes their chances of achieving paternity. For chimpanzees (Pan troglodytes), despite substantial interest in mating strategies, very little attention has been paid to the most fundamental problem that mating strategies need to solve: finding mates. Only a single model, Dunbar's general model of male mating strategies, exists to explain mate‐searching behaviour in chimpanzees. Under this model, males in most populations are regarded as pursuing a ‘roving’ strategy: searching for and sequestering fertile females who are essentially passive with respect to mate searching. The roving mating strategy is an assumption deeply embedded in the way chimpanzee behaviour is considered; it is implicit in the conventional model for chimpanzee social structure, which posits that male ranging functions both to monitor female reproductive state and to ward these females from other groups of males through collective territoriality: essentially, ranging as mating effort. This perspective is, however, increasingly at odds with observations of chimpanzee behaviour. Herein, I review the logic and evidence for the roving‐male mating strategy and propose a novel alternative, a theoretical framework in which roving is a strategy pursued by female chimpanzees in order to engage successfully in promiscuous mating. Males, unable to thwart this female strategy, instead maximise the number of reproductive opportunities encountered by focusing their behaviour on countering threats to health, fertility and reproductive career. Their prolonged grooming bouts are seen, in consequence, as functioning to mitigate the negative impacts of socially induced physiological stress. In this new framework, the roving‐male strategy becomes, at best, a ‘best of a bad job’ alternative for low‐ranking males when faced with high levels of competition for mating access. Male chimpanzees do not search for mates, but for one another, for food, and, at times, for rivals in other communities. To the extent that female promiscuity functions to counter infanticide risk, mate searching by female chimpanzees—and any associated costs—can be seen as an unavoidable consequence of male sexual coercion. This novel framework is a better fit to the available data than is the conventional account. This review highlights the desperate need for additional work in an area of chimpanzee biology that has been somewhat neglected, perhaps in part because assumptions of roving males have remained unquestioned for too long. It also highlights the need, across taxa, to revisit and revise theory, and to test old assumptions, when faced with contrary data.     

Do grasslands act as a perpetual sink for carbon?

It is increasingly commonly suggested that grasslands are a perpetual sink for carbon, and that just maintaining grasslands will yield a net carbon sink. I examine the evidence for this from repeated soil surveys, long term grassland experiments and simple mass balance calculations. I conclude that it is untenable that grasslands act as a perpetual carbon sink, and the most likely explanation for observed grassland carbon sinks over short periods is legacy effects of land use and land management prior to the beginning of flux measurement periods. Simply having grassland does not result is a carbon sink, but judicious management or previously poorly managed grasslands can increase the sink capacity. Given that grasslands are a large store of carbon, and that it is easier and faster for soils to lose carbon that it is for them to gain carbon, it is an important management target to maintain these stocks.