庙岛群岛典型植物群落物种、功能、结构多样性及其对环境因子的响应

海岛植被在全球生物多样性研究中起重要作用,研究海岛植被多样性对于理解海陆相互作用下植物群落的多样性维持机制有重要意义.本研究以庙岛群岛的麻栎群落、刺槐群落、黑松群落、荆条群落4种典型植物群落为对象,采用物种多样性指数、功能多样性指数和结构多样性指数,在群落尺度上探讨了海岛典型植物群落物种、功能、结构多样性间的关系及其对环境因子的响应.结果表明: 黑松群落的物种丰富度与Rao指数高于刺槐群落与麻栎群落,而结构多样性却较低;荆条灌丛的物种、结构多样性均低于森林群落,而功能多样性高于部分森林群落.物种丰富度与Rao指数以及树高多样性间呈显著正相关,与功能均匀度呈显著负相关.结构多样性主要由坡度决定且与坡度呈负相关;功能均匀度与坡度呈正相关,而功能异质性、功能离散度和物种多样性则更多地受土壤理化性质的影响,与土壤容重及土壤总碳呈正相关,与土壤含水率呈负相关.总体而言,庙岛群岛的植物群落多样性格局既有与大陆植被相似的特征,但也有其海岛特殊性.     

中国森林土壤碳储量与土壤碳过程研究进展

森林是陆地生态系统的主体,是陆地上最大的碳储库和碳吸收汇。国内外研究表明,土壤亚系统在调节森林生态系统碳循环和减缓全球气候变化中起着重要作用。但是,由于森林类型的多样性、结构的复杂性以及森林对干扰和变化环境响应的时空动态变化,至今对森林土壤碳储量和变率的科学估算,以及土壤关键碳过程及其稳定性维持机制的认识还十分有限。综述了近十几年来我国森林土壤碳储量和土壤碳过程的研究工作,主要包括不同森林类型土壤碳储量、土壤碳化学稳定性、土壤呼吸及其组分、土壤呼吸影响机制、气候变化与土地利用对土壤碳过程的影响等;评述了土壤碳过程相关科学问题的研究进展,讨论了尚未解决的主要问题,并分析了未来土壤碳研究的发展趋势,以期为促进我国森林土壤碳循环研究,科学评价森林土壤碳固持潜力及其稳定性维持机制和有效实施森林生态系统管理提供科学参考。     

陆地生态系统碳密度格局研究概述

 准确了解陆地生态系统中碳密度的时空格局及其影响因子和作用机制,对于估算和预测不同类型生态系统中的植被和土壤的碳存储能力、判定碳汇、制定缓解全球变化的合理政策措施,具有重要意义。该文综述了现有研究中发现的世界陆地生态系统碳密度空间分布的地带性规律及中国陆地生态系统碳密度格局的独特特点。在全球尺度上,植被碳密度分布与植物生物量格局基本一致,除北方森林外其余大部分随纬度升高而减小;土壤碳密度则随纬度升高而增大。陆地生态系统中北方森林和热带森林的总体碳密度最高,不同的是,前者的碳主要集中在土壤中,而后者则集中在植被中。但在区域尺度上,由于气候、地形及人类活动影响,这种规律性可能会发生变化甚至不起作用。水热条件、土壤养分、生物多样性、气候和大气CO2浓度的变化以及土地利用与覆盖变化等是碳密度空间格局形成和发生变化的驱动因子。在某一特定区域,它们通过直接或间接提高植被净初级生产力,抑制呼吸和分解作用来增加陆地生态系统碳密度。综合分析特定时空条件下各因子对碳存储量的影响是解释碳密度分布现状,预测碳密度格局变化的关键,但目前的研究对各项驱动因子的作用机制、影响强度及多个因子间的相互作用仍不是很清楚,需要加强该方面的研究力度。碳密度研究中的数据获取、机理分析和过程模拟等方面仍存在很大的不确定性,因此有必要建立规范统一的碳密度测量估算系统和更为精准有效的估算模型,进行多尺度、多精度水平的综合研究。     

河南典型草地碳氮库构成对植物多样性的响应

以河南4种典型草地类型(暖性草丛、暖性灌草丛、热性草丛与热性灌草丛)为研究对象,基于野外调查与室内测定,结合RDA冗余分析方法,分析了植物多样性与生态系统碳氮库构成之间的关系。结果表明:河南草地植物物种多样性整体上呈现出灌草丛类草地大于草丛类草地;河南草地具有符合地域特征的植物功能群类型,C3植物比例均远大于C4植物,杂类草占64%～73%,有性兼无性繁殖方式的植物类型多达49%～56%;而生活型组成较为复杂,暖性草地以多年生草本和灌木为主,热性草地以一或两年生草本以及多年生草本为主; RDA分析结果显示,暖性草丛、暖性灌草丛植被氮密度与Shannon和Pielou指数呈正相关,植被碳密度、土壤氮密度与Shannon和Pielou指数呈负相关;热性草丛植被碳氮密度与物种丰富度指数呈正相关,土壤氮密度与Shannon和Pielou指数呈正相关,植被氮密度与Shannon和Pielou指数呈负相关;热性灌草丛土壤碳氮密度与Shannon指数呈正相关,植被碳氮密度与物种丰富度和Shannon指数呈负相关,即物种多样性及不同草地类型植被的组成共同作用影响植被和土壤碳氮密度。总之,河南草地生态系统碳氮库构成是植物物种丰富程度和分布均匀程度综合作用的结果。     

中国东部10个海岛植被近自然度评价

植被近自然度评价是森林近自然恢复的重要理论基础。海岛因特殊的生物地理环境,其植被结构和功能有别于陆地植被,当前还未有从植物生理生态角度,联合植物功能性状的海岛植被近自然度评价指标体系。基于中国东部10个典型海岛的74个植物群落,以植被信息、土壤属性和多样性特征（物种和功能多样性）构建海岛植被近自然度评价指标体系。利用敏感性分析筛选出13个反映海岛植被近自然度的中、高敏感性指标,基于筛选指标用层次分析法初次构建了中国东部海岛植被近自然度评价指标体系,并计算典型海岛的植被近自然度综合指数和划定植被近自然度等级。结果显示：海岛植被近自然度综合评价指标的权重：植被信息 > 多样性特征 > 土壤属性,其中植物自然构成系数、土壤含水量、Shannon-Wiener指数、Rao二次熵指数的权重较大;典型海岛的植被近自然度综合指数在0.345-0.611间,其中大金山岛的植被近自然度最高,属半天然林,北长山岛最低,为近人工林,其他海岛为远天然林;中亚热带的海岛植被近自然度较高,暖温带和南亚热带的海岛植被近自然度较低。本研究基于陆地植被近自然度评价指标,联合植物功能多样性对我国东部海岛植被近自然度进行综合评价,为海岛植被的生态状况提供定量依据,以及为海岛植被保护与管理和近自然恢复提供理论支撑。     

湖南省杉木人工林生态系统碳储量分配格局及固碳潜力

人工林生态系统碳储量的空间分配格局对全球陆地碳循环有重要的影响,但湖南省杉木人工林生态系统碳储量的分配格局并不清楚。本研究在湖南省样地野外调查的基础上,结合第八次全国森林资源清查的结果,计算出湖南省杉木人工林生态系统的碳储量空间分布格局。结果表明:杉木人工林生态系统碳密度随着林龄增加而增加,幼龄林、中龄林和成熟林分别为125.70、138.57、193.72 Mg·hm~(-2);其中,幼龄林、中龄林和成熟林的植被生物量碳密度分别为18.72、38.86、62.48 Mg·hm~(-2);土壤碳密度随着林分发育先降低后增加,幼龄林为105.49 Mg·hm~(-2)、中龄林为97.23 Mg·hm~(-2)、成熟林126.7 Mg·hm~(-2);湖南省杉木人工林生态系统碳储量为307.48 Tg,其中幼龄林为90.57 Tg,中龄林为91.87 Tg,成熟林为125.31 Tg;湖南省杉木人工林生态系统的固碳潜力为85.56 Tg,其中,植被固碳潜力为47.19 Tg,土壤的固碳潜力为34.82 Tg。确定杉木人工林固碳潜力有助于量化人工林对碳汇的贡献及其制定实现潜力的森林经营管理措施。     

中国北方自然生态系统土壤有机碳含量及其影响因素

土壤有机碳是陆地生态系统碳库中最活跃的组分,其较小幅度的变动,可导致大气中CO_2浓度的剧烈变化,从而影响全球气候变化。本研究以中国北方荒漠、草地、灌丛和森林生态系统为研究对象,结合气候、土壤和植被群落特征等因素,探究区域尺度下表层土壤有机碳含量及影响因素。结果表明:研究区内各生态系统间土壤有机碳含量差异显著,其中森林土壤有机碳含量最高,其次为灌丛和草地,荒漠土壤有机碳含量最低;土壤有机碳含量与年平均温度、土壤pH和砂粒含量呈显著负相关,与年平均降水量、黏粒含量、粉粒含量、NDVI指数和植物物种丰富度呈显著正相关,与植物物种多样性呈正相关趋势但未达到显著水平;在区域尺度下,土壤有机碳含量主要受到气候因子、土壤因子和植被因子共同作用的影响。     

The response of ecosystem carbon and nitrogen pools to experimental warming in grasslands: a meta-analysis

草地生态系统碳氮库对增温响应的整合分析 陆地生态系统碳氮耦合过程有可能改变全球碳循环对气候变化的敏感性。然而,碳氮的交互作用对陆地生态系统碳固存的贡献仍不明确。本研究采用Meta分析的方法量化了野外增温条件下草地碳氮储量的变化,并且进一步评估了3个主要的碳氮耦合过程(生态系统氮总量的变化,氮在植被和土壤之间的重新分配,植被与土壤碳氮比的变化)对草地碳固存的相对贡献。增温使得土壤、凋落物 和植被的碳氮比增加,并导致约2%的氮从土壤转移到植被和凋落物中。增温提高了植被和凋落物的碳储量(111.2 g m⁻²),而降低了土壤的碳储量(30.0 g m⁻²),由此可见,增温提高了整个草地生态系统的碳储量。碳氮比的变化是温度升高条件下草地碳储量增加的主要贡献者,氮的重新分配次之。相反,氮总量的减少则降低了生态系统的碳储量。这些结果表明,温度升高对草地生态系统碳氮储量的变化及其耦合过程具有显著的影响,建议生态模型考虑碳氮循环的交互作用,以便更准确地预测未来陆地碳储量的变化。     

贵州月亮山不同演替阶段亮叶水青冈林碳储量及其分配格局

林龄对森林生态系统碳储量及其在不同碳组分(植被、木质残体、凋落物和土壤)中的分配有着重要影响。亚热带森林在陆地生态系统碳循环中起着重要作用, 水青冈属(Fagus)植物是我国亚热带广泛分布的重要树种, 而有关水青冈林碳储量随林龄变化的研究在我国鲜有报道。该研究选取贵州月亮山3个演替阶段(林龄分别为33年、82年和208年)的亮叶水青冈(Fagus lucida)林为研究对象, 对其生态系统全组分的碳储量及其分配格局进行了调查与估算。研究发现, 随林龄增加, 亮叶水青冈林生态系统碳储量显著增加, 33年、82年和208年林分别为(186.9 ± 46.0)、(265.8 ± 82.3)和(515.1 ± 176.4) Mg·hm ^-2, 且生态系统碳储量的增加主要由植被碳储量(占比由32%增长至79%)贡献。凋落物与木质残体碳储量随林龄增加亦呈增加趋势, 但二者占生态系统碳储量的比例很小(<1%)。而不同林龄土壤碳储量无显著差异, 其占比由33年林的67%降至208年林的20%。这些结果验证了林龄对森林生态系统各组分碳储量及其分配的重要影响, 同时指出干扰和土地利用历史等对森林植物残体和土壤碳积累的重要作用。     

Ecosystem carbon stock and within-system distribution in successional Fagus lucida forests in Mt. Yueliang,Guizhou, China

林龄对森林生态系统碳储量及其在不同碳组分(植被、木质残体、凋落物和土壤)中的分配有着重要影响。亚热带森林在陆地生态系统碳循环中起着重要作用, 水青冈属(Fagus)植物是我国亚热带广泛分布的重要树种, 而有关水青冈林碳储量随林龄变化的研究在我国鲜有报道。该研究选取贵州月亮山3个演替阶段(林龄分别为33年、82年和208年)的亮叶水青冈(Fagus lucida)林为研究对象, 对其生态系统全组分的碳储量及其分配格局进行了调查与估算。研究发现, 随林龄增加, 亮叶水青冈林生态系统碳储量显著增加, 33年、82年和208年林分别为(186.9 ± 46.0)、(265.8 ± 82.3)和(515.1 ± 176.4) Mg·hm ^-2, 且生态系统碳储量的增加主要由植被碳储量(占比由32%增长至79%)贡献。凋落物与木质残体碳储量随林龄增加亦呈增加趋势, 但二者占生态系统碳储量的比例很小(<1%)。而不同林龄土壤碳储量无显著差异, 其占比由33年林的67%降至208年林的20%。这些结果验证了林龄对森林生态系统各组分碳储量及其分配的重要影响, 同时指出干扰和土地利用历史等对森林植物残体和土壤碳积累的重要作用。     

千岛湖库区岛屿面积对植物分布的影响及植物物种多样性保护研究

修建大坝形成水库蓄水是造成景观破碎化的原因和形式之一.本研究选取了浙江千岛湖库区景观破碎化的典型区域小金山林场,调查了74个大小不一的岛屿,研究了面积对植物物种分布的影响,并比较了使物种多样性最大化的几种植物物种保护方案:小岛组合、中岛组合、大岛组合、大中小组合岛.调查共记录到乔木物种56种,灌木物种79种.将岛屿按照面积由大到小排序,将相对应分布的乔木、灌木绘制成植物物种分布表.结果显示:乔木中分布不受面积影响的物种有15种,受面积影响的有11种,介于两者之间的有30种;灌木物种中不受面积影响的有24种,受面积影响的有16种,介于两者之间的有39种.将乔木、灌木和总物种数分别累加,同时将相对应的岛屿面积按不同组合累加,绘制累加物种和面积关系图,发现在特定的相同累加面积下,组合岛的累加乔木、灌木、总物种数最多,小岛组合次之,大岛组合最少.因此,建立相同面积的保护区时,组合岛有利于保护更多的物种.     

Species richness promotes ecosystem carbon storage: evidence from biodiversity-ecosystem functioning experiments

Plant diversity has a strong impact on a plethora of ecosystem functions and services, especially ecosystem carbon (C) storage. However, the potential context-dependency of biodiversity effects across ecosystem types, environmental conditions and carbon pools remains largely unknown. In this study, we performed a meta-analysis by collecting data from 95 biodiversity-ecosystem functioning (BEF) studies across 60 sites to explore the effects of plant diversity on different C pools, including aboveground and belowground plant biomass, soil microbial biomass C and soil C content across different ecosystem types. The results showed that ecosystem C storage was significantly enhanced by plant diversity, with stronger effects on aboveground biomass than on soil C content. Moreover, the response magnitudes of ecosystem C storage increased with the level of species richness and experimental duration across all ecosystems. The effects of plant diversity were more pronounced in grasslands than in forests. Furthermore, the effects of plant diversity on belowground plant biomass increased with aridity index in grasslands and forests, suggesting that climate change might modulate biodiversity effects, which are stronger under wetter conditions but weaker under more arid conditions. Taken together, these results provide novel insights into the important role of plant diversity in ecosystem C storage across critical C pools, ecosystem types and environmental contexts.     

海南岛森林生态系统碳储量及其空间分布特征

利用最新的森林资源二类调查分布数据和野外样地调查资料,采用InVEST模型和空间统计分析等方法,研究了海南岛森林生态系统碳储量及其空间分布特征。结果表明：海南岛森林生态系统总碳储量为338.15 TgC,其中地上生物、地下生物、凋落物和土壤的碳储量分别为85.12、18.73、2.90 TgC和231.40 TgC,所占比重依次为25.17%、5.54%、0.86%和68.43%。海南岛森林生态系统平均碳密度为147.66 MgC/hm²,其中地上生物、地下生物、凋落物和土壤碳密度分别为37.17、8.18、1.27 MgC/hm²和101.04 MgC/hm²。不同市县森林生态系统碳储量分布在8.55—35.40 TgC的范围内,最高的是琼中县。不同植被类型中,橡胶林的碳储量最高,占全岛森林生态系统总碳储量的27.72%;热带山地雨林的碳密度最高,达到249.64 MgC/hm²。在海拔梯度上,森林生态系统碳密度呈现先增加后减少的变化特征,在海拔600—1300 m范围内的碳密度最高,碳密度为20...     

The biodiversity‐dependent ecosystem service debt

Habitat destruction is driving biodiversity loss in remaining ecosystems, and ecosystem functioning and services often directly depend on biodiversity. Thus, biodiversity loss is likely creating an ecosystem service debt: a gradual loss of biodiversity‐dependent benefits that people obtain from remaining fragments of natural ecosystems. Here, we develop an approach for quantifying ecosystem service debts, and illustrate its use to estimate how one anthropogenic driver, habitat destruction, could indirectly diminish one ecosystem service, carbon storage, by creating an extinction debt. We estimate that c. 2–21 Pg C could be gradually emitted globally in remaining ecosystem fragments because of plant species loss caused by nearby habitat destruction. The wide range for this estimate reflects substantial uncertainties in how many plant species will be lost, how much species loss will impact ecosystem functioning and whether plant species loss will decrease soil carbon. Our exploratory analysis suggests that biodiversity‐dependent ecosystem service debts can be globally substantial, even when locally small, if they occur diffusely across vast areas of remaining ecosystems. There is substantial value in conserving not only the quantity (area), but also the quality (biodiversity) of natural ecosystems for the sustainable provision of ecosystem services.     

Determinants of floristic diversity and vegetation composition on the islands of Lake Burollos,Egypt

Abstract. A floristic and environmental survey was carried out on 22 uninhabited islands (0.1‐8.4 ha) in Lake Burollos, Egypt. A total of 58 vascular plant species was recorded. The number of habitats on each island was counted. There was a positive correlation between island area and number of habitat types. Island area was significantly positively correlated with various measures of floristic diversity, including the total number of species present, and the numbers of annual, herbaceous, and shrublet species. Perennial and shrub species numbers did not differ significantly with island area. In addition to island area, elevation and soil salinity, as well as distance to the Mediterranean Sea, all contributed significantly to variation in species composition in the terrestrial habitats. Water salinity and transparency accounted for 69% of the variation in aquatic species numbers. There was a weak effect of isolation on similarity of species composition on islands. Eight vegetation types, represented by 13 indicator species identified after TWINSPAN analysis, were distinguished by soil characteristics. Species richness was inversely correlated with clay, organic carbon and total nitrogen in the soil, but positively correlated with calcium carbonate content. From a management perspective, long‐term monitoring of threatened habitats in the lake is urgently required as a starting point to preserve biodiversity. Finally, we conclude that the present study supports the hypothesis indicating that larger areas feature higher species richness due to increased numbers of habitats.     

Factors influencing vascular plant diversity on 22 islands off the coast of eastern North America

Aim The influence of physiographic and historical factors on species richness of native and non‐native vascular plants on 22 coastal islands was examined. Location Islands off the coast of north‐eastern USA and south‐eastern Canada between 41° and 45° N latitude were studied. Island size ranges from 3 to 26,668 ha. All islands were deglaciated between 15,000 and 11,000 yr bp ; all but the four New Brunswick islands were attached to the mainland until rising sea level isolated them between 14,000 and 3800 yr bp . Methods Island species richness was determined from floras compiled or revised since 1969. Simple and multiple regression and rank correlation analysis were employed to assess the relative influence of independent variables on species richness. Potential predictors included island area, latitude, elevation, distance from the mainland, distance from the nearest larger island, number of soil types, years since isolation, years since deglaciation, and human population density. Results Native vascular plant species richness for the 22 islands in this study is influenced most strongly by island area, latitude, and distance from the nearest larger island; richness increases with island area, but decreases with latitude and distance from the nearest larger island as hypothesized. That a similar model employing distance from the mainland does not meet the critical value of P confirms the importance of the stepping‐stone effect. Habitat diversity as measured by number of soil types is also an important predictor of native plant species richness, but at least half of its influence can be attributed to island area, with which it is correlated. Two historical factors, years since deglaciation and years since isolation, also appear to be highly correlated with native species richness, but their influence cannot be separated from that of latitude for the present sample size. Non‐native vascular plant species richness is influenced primarily by island area and present‐day human population density, although human population density may be a surrogate for the cumulative effect of several centuries of anthropogenic impacts related to agriculture, hunting, fishing, whaling, tourism, and residential development. Very high densities of ground‐nesting pelagic birds may account for the high percentage of non‐native species on several small northern islands. Main conclusions Many of the principles of island biogeography that have been applied to oceanic islands apply equally to the 22 islands in this study. Native vascular plant species richness for these islands is strongly influenced by physiographic factors. Influence of two historical factors, years since deglaciation and years since isolation, cannot be assessed with the present sample size. Non‐native vascular plant species richness is influenced by island area as well as by human population density; human population density may be a surrogate for other anthropogenic impacts.     

Quantifying soil organic carbon in complex landscapes: an example of grassland undergoing encroachment of woody plants

The invasion of woody plants into grass‐dominated ecosystems has occurred worldwide during the past century with potentially significant impacts on soil organic carbon (SOC) storage, ecosystem carbon sequestration and global climate warming. To date, most studies of tree and shrub encroachment impacts on SOC have been conducted at small scales and results are equivocal. To quantify the effects of woody plant proliferation on SOC at broad spatial scales and to potentially resolve inconsistencies reported from studies conducted at fine spatial scales, information regarding spatial variability and uncertainty of SOC is essential. We used sequential indicator simulation (SIS) to quantify spatial uncertainty of SOC in a grassland undergoing shrub encroachment in the Southern Great Plains, USA. Results showed that both SOC pool size and its spatial uncertainty increased with the development of woody communities in grasslands. Higher uncertainty of SOC in new shrub‐dominated communities may be the result of their relatively recent development, their more complex above‐ and belowground architecture, stronger within‐community gradients, and a greater degree of faunal disturbance. Simulations of alternative sampling designs demonstrated the effects of spatial uncertainty on the accuracy of SOC estimates and enabled us to evaluate the efficiency of sampling strategies aimed at quantifying landscape‐scale SOC pools. An approach combining stratified random sampling with unequal point densities and transect sampling of landscape elements exhibiting strong internal gradients yielded the best estimates. Complete random sampling was less effective and required much higher sampling densities. Results provide novel insights into spatial uncertainty of SOC and its effects on estimates of carbon sequestration in terrestrial ecosystem and suggest effective protocol for the estimating of soil attributes in landscapes with complex vegetation patterns.     

“双碳”目标下山水林田湖草沙一体化保护和修复工程优先区与技术策略研究

巩固与提升生态系统碳汇能力是实现碳达峰、碳中和目标的重要途径之一。生态保护修复对生态系统固碳增汇有着重要影响。2016—2021年,财政部、自然资源部、生态环境部在我国27个省(自治区、直辖市)共支持了三批山水林田湖草生态保护修复工程试点和第一批山水林田湖草沙一体化保护和修复工程,共35个山水工程。通过分析已部署的35个山水工程布局的空间特征和碳汇效益,结合国家重点关注的生态保护修复区域、全国重要生态系统保护和修复重大工程分布、生态系统碳汇重要区域和敏感区域,探索“双碳”目标下山水工程布局优先区及生态保护修复技术策略。研究发现山水工程的碳汇效益具有空间差异性,且山水工程优先区主要依次分布在青藏高原生态屏障区、东北森林带、长江重点生态区(含川滇生态屏障)、南方丘陵山地带、黄河重点生态区(含黄土高原生态屏障)、北方防沙带等的森林、高原草地、荒漠、岩溶地区等区域。基于此,提出未来山水工程在不同区域的技术策略。在森林生态系统为主地区,不仅要提高森林覆盖度、森林质量,还应当加强生物多样性的保护和土壤碳汇能力的提升;在高原草原及冻土地区应加强草地退化和冻土监测,提高草地质量;在西北荒漠化地区加强碳...     

农田生态系统碳汇研究进展

农田生态系统碳汇包括农作物生物量碳汇和农田土壤碳汇两个方面，中国农田生态系统面积大，碳储量高，是全球生态系统碳循环的重要组成部分。厘清中国农作物生物量和土壤有机碳含量、变化率和影响因素对于解析全球碳循环和维系粮食安全具有重要意义。梳理农田生态系统碳汇相关概念的基础上，比较农田生态系统碳汇研究方法的适用性及存在问题，通过以往研究和SoilGrids250数据研究中国农田生态系统碳库时空分布，并分析农田生态系统碳汇的影响因素及固碳方法。结果表明，中国近30年来农作物生物量呈现增加趋势，农田土壤有机碳含量普遍较低且空间分布不均，0-5cm土壤有机碳含量平均值在16.7 g/kg到86.5 g/kg之间，增加农田土壤有机碳含量是未来中国农田生态系统碳汇的重要方向。肥料和有机残留管理、保护性耕作、种植模式、灌溉等管理措施是增加土壤有机碳汇的主要措施，但农田生态系统碳汇潜力估算仍存在不确定性。最后，从农田生态系统碳汇潜力估算、影响因素厘定和增汇技术研发3个方面提出未来研究方向。研究结果有助于推动农田生态系统碳汇科学研究和技术推广，为实现农田生态系统助力"碳中和"寻求重要路径。     

Predicting community structure in snakes on Eastern Nearctic islands using ecological neutral theory and phylogenetic methods

Predicting species presence and richness on islands is important for understanding the origins of communities and how likely it is that species will disperse and resist extinction. The equilibrium theory of island biogeography (ETIB) and, as a simple model of sampling abundances, the unified neutral theory of biodiversity (UNTB), predict that in situations where mainland to island migration is high, species-abundance relationships explain the presence of taxa on islands. Thus, more abundant mainland species should have a higher probability of occurring on adjacent islands. In contrast to UNTB, if certain groups have traits that permit them to disperse to islands better than other taxa, then phylogeny may be more predictive of which taxa will occur on islands. Taking surveys of 54 island snake communities in the Eastern Nearctic along with mainland communities that have abundance data for each species, we use phylogenetic assembly methods and UNTB estimates to predict island communities. Species richness is predicted by island area, whereas turnover from the mainland to island communities is random with respect to phylogeny. Community structure appears to be ecologically neutral and abundance on the mainland is the best predictor of presence on islands. With regard to young and proximate islands, where allopatric or cladogenetic speciation is not a factor, we find that simple neutral models following UNTB and ETIB predict the structure of island communities.