枯落物输入改变对森林生态系统土壤理化性质的影响

枯落物输入改变是影响森林生态系统土壤理化性质的一个重要因素,探究其对土壤理化性质的影响对了解和保护森林生态系统的稳定性至关重要。为探究森林生态系统土壤理化性质对枯落物输入改变的响应,对国内外已发表的研究论文中筛选出712组有效数据通过Meta分析,从枯落物输入改变、气候、海拔、林分类型、处理年限等因素揭示枯落物输入对土壤理化性质的影响程度。研究结果表明：枯落物添加使土壤pH降低2.22%;土壤含水量、有机碳、全氮、铵态氮分别提高3.99%、15.9%、9.82%和16.52%;枯落物去除使土壤含水量、pH、有机碳、全氮、C/N、铵态氮分别降低8.16%、4.02%、6.47%、5.09%、10.55%和8.86%。枯落物输入改变对土壤理化性质的影响还受到气候、海拔、林分类型、处理年限等因素的调控。在枯落物输入改变条件下,气候、海拔、林分类型、处理年限等因素对土壤含水量、有机碳、全氮、铵态氮均有显著的促进作用;海拔对土壤pH产生了显著的促进作用,而林分类型对土壤pH产生了抑制作用。同时得出枯落物输入改变条件下,年均温是土壤pH的主要调控因子,年均降水量是土壤含水量的主要调控因子;海拔是土...     

Life stage and taxonomy the most important factors determining vertebrate stoichiometry: A meta‐analysis

Whole‐body elemental composition is a key trait for determining how organisms influence their ecosystems. Using mass‐balance, ecological stoichiometry predicts that animals with higher concentrations of element X will selectively retain more X and will recycle less X in their waste than animals with lower X concentrations. These animals will also store high quantities of X during their lives and after their deaths (prior to full decomposition). Vertebrates may uniquely impact nutrient cycling because they store high quantities of phosphorus (P) in their bones. However, vertebrates have diverse body forms and invest variably in bone. Current analyses of vertebrate elemental content predominately evaluate fishes, typically neglecting other vertebrates and leaving much of the diversity unexplored. We performed a systematic review and identified 179 measurements of whole‐body percent phosphorus (%P), percent nitrogen (%N), and N to P ratio (N:P) from 129 unique species of non‐fish vertebrates (amphibians: 39 species; reptiles: 19 species; birds: 27 species; mammals: 46 species). We found that %P (mean: 1.94%; SD [standard deviation] = 0.77) and N:P (mean: 12.52) varied with taxonomy and life stage, while %N (mean: 10.51%; SD = 3.25) varied primarily with taxonomy. Habitat, diet, and size had small and inconsistent effects in different groups. Our study highlights two research gaps. Life stage, which is frequently neglected in stoichiometric studies, is an important factor determining vertebrate %P. Furthermore, amphibians dominate our dataset, while other vertebrate taxa are poorly represented in the current literature. Further research into these neglected vertebrate taxa is essential.     

Effects of soil phosphorus availability,temperature and moisture on soil respiration in Eucalyptus pauciflora forest

Rates of soil respiration (CO₂ efflux) were measured for a year in a mature Eucalyptus pauciflora forest in unfertilized and phosphorus-fertilized plots. Soil CO₂ efflux showed a distinct seasonal trend, and average daily rates ranged from 124 to 574 mg CO₂ m^–2 hr^–1. Temperature and moisture are the main variables that cause variation in soil CO₂ efflux; hence their effects were investigated over a year so as to then differentiate the treatment effect of phosphorus (P) nutrition.Soil temperature had the greatest effect on CO₂ efflux and exhibited a highly significant logarithmic relationship (r² = 0.81). Periods of low soil and litter moisture occurred during summer when temperatures were greater than 10 °C, and this resulted in depression of soil CO₂ efflux. During winter, when temperatures were less than 10 °C, soil and litter moisture were consistently high and thus their variation had little effect on soil CO₂ efflux. A multiple regression model including soil temperature, and soil and litter moisture accounted for 97% of the variance in rates of CO₂ efflux, and thus can be used to predict soil CO₂ efflux at this site with high accuracy. Total annual efflux of carbon from soil was estimated to be 7.11 t C ha^–1 yr^–1. The model was used to predict changes in this annual flux if temperature and moisture conditions were altered. The extent to which coefficients of the model differ among sites and forest types requires testing.Increased soil P availability resulted in a large increase in stem growth of trees but a reduction in the rate of soil CO₂ efflux by approximately 8%. This reduction is suggested to be due to lower root activity resulting from reduced allocation of assimilate belowground. Root activity changed when P was added to microsites within plots, and via the whole tree root system at the plot level. These relationships of belowground carbon fluxes with temperature, moisture and nutrient availability provide essential information for understanding and predicting potential changes in forest ecosystems in response to land use management or climate change.     

Initial treatment choices to achieve sustained response in major depression: a systematic review and network meta‐analysis

Major depression is often a relapsing disorder. It is therefore important to start its treatment with therapies that maximize the chance of not only getting the patients well but also keeping them well. We examined the associations between initial treatments and sustained response by conducting a network meta‐analysis of randomized controlled trials (RCTs) in which adult patients with major depression were randomized to acute treatment with a psychotherapy (PSY), a protocolized antidepressant pharmacotherapy (PHA), their combination (COM), standard treatment in primary or secondary care (STD), or pill placebo, and were then followed up through a maintenance phase. By design, acute phase treatment could be continued into the maintenance phase, switched to another treatment or followed by discretionary treatment. We included 81 RCTs, with 13,722 participants. Sustained response was defined as responding to the acute treatment and subsequently having no depressive relapse through the maintenance phase (mean duration: 42.2±16.2 weeks, range 24‐104 weeks). We extracted the data reported at the time point closest to 12 months. COM resulted in more sustained response than PHA, both when these treatments were continued into the maintenance phase (OR=2.52, 95% CI: 1.66‐3.85) and when they were followed by discretionary treatment (OR=1.80, 95% CI: 1.21‐2.67). The same applied to COM in comparison with STD (OR=2.90, 95% CI: 1.68‐5.01 when COM was continued into the maintenance phase; OR=1.97, 95% CI: 1.51‐2.58 when COM was followed by discretionary treatment). PSY also kept the patients well more often than PHA, both when these treatments were continued into the maintenance phase (OR=1.53, 95% CI: 1.00‐2.35) and when they were followed by discretionary treatment (OR=1.66, 95% CI: 1.13‐2.44). The same applied to PSY compared with STD (OR=1.76, 95% CI: 0.97‐3.21 when PSY was continued into the maintenance phase; OR=1.83, 95% CI: 1.20‐2.78 when PSY was followed by discretionary treatment). Given the average sustained response rate of 29% on STD, the advantages of PSY or COM over PHA or STD translated into risk differences ranging from 12 to 16 percentage points. We conclude that PSY and COM have more enduring effects than PHA. Clinical guidelines on the initial treatment choice for depression may need to be updated accordingly.     

Drought has negative consequences on aphid fitness and plant vigor: Insights from a meta‐analysis

1. Aphids are abundant in natural and managed vegetation, supporting a diverse community of organisms and causing damage to agricultural crops. Due to a changing climate, periods of drought are anticipated to increase, and the potential consequences of this for aphid–plant interactions are unclear.
2. Using a meta‐analysis and synthesis approach, we aimed to advance understanding of how increased drought incidence will affect this ecologically and economically important insect group and to characterize any potential underlying mechanisms. We used qualitative and quantitative synthesis techniques to determine whether drought stress has a negative, positive, or null effect on aphid fitness and examined these effects in relation to (a) aphid biology, (b) geographical region, and (c) host plant biology.
3. Across all studies, aphid fitness is typically reduced under drought. Subgroup analysis detected no difference in relation to aphid biology, geographical region, or the aphid–plant combination, indicating the negative effect of drought on aphids is potentially universal. Furthermore, drought stress had a negative impact on plant vigor and increased plant concentrations of defensive chemicals, suggesting the observed response of aphids is associated with reduced plant vigor and increased chemical defense in drought‐stressed plants.
4. We propose a conceptual model to predict drought effects on aphid fitness in relation to plant vigor and defense to stimulate further research.

     

苔藓和凋落物对祁连山青海云杉林土壤呼吸的影响

于2012—2014年生长季在青海云杉林下开展了地表覆盖物(苔藓和凋落物)对林下土壤呼吸速率影响的研究。采用LI8100土壤碳通量自动测量系统对苔藓覆盖、凋落物覆盖和裸土(去除地表覆盖物)的土壤呼吸进行观测,对比分析林下3种覆盖处理下的土壤呼吸差异。结果表明:苔藓覆盖土壤、凋落物覆盖土壤和裸土土壤的呼吸速率年均值分别为(3.88±0.26)μmol m~(-2)s~(-1),(3.31±0.19)μmol m~(-2)s~(-1),(2.28±0.31)μmol m~(-2)s~(-1),三者之间具有极显著差异,3组处理的地表相对湿度、土壤含水量、土壤温度和地表温度间均没有显著差异,但苔藓组和凋落物组的土壤温度分别比裸土组高8.13%和10.24%;3组处理的土壤呼吸速率均与温度呈显著指数相关性(0.53≤R~2≤0.91),且与土壤温度的相关性更高;苔藓覆盖、凋落物覆盖土壤呼吸的温度敏感性(Q_(10))分别为5.47,3.67,均高于裸土土壤呼吸的Q_(10)(2.23);裸土土壤呼吸与土壤含水量(VWC)呈高斯函数关系,VWC=34%是临界值,苔藓覆盖、凋落物覆盖土壤的呼吸速率与土壤含水量均呈线性负相关关系;苔藓和凋落物对裸土土壤呼吸的月均贡献率分别为29.33%和24.06%,可见,苔藓和凋落物在青海云杉林生态系统呼吸中起重要作用。     

Effects of SGLT2 inhibitors on haematocrit and haemoglobin levels and the associated cardiorenal benefits in T2DM patients: A meta‐analysis

To explore the effect and magnitude of effect of sodium‐glucose cotransporter‐2 (SGLT2) inhibitors on haematocrit and haemoglobin and the related cardiorenal benefits in patients with type 2 diabetes mellitus (T2DM), PubMed, Web of Science, CENTRAL and EMBASE were searched to identify eligible trials. Weighted mean differences (WMDs) with 95% confidence intervals (CIs) were calculated using a random‐effects model. Seventy‐eight studies were included in the meta‐analysis. SGLT2 inhibitors significantly increased haematocrit and haemoglobin levels compared with control (total WMD 2.27% [95% CI 2.08, 2.47] and 6.20 g/L [95% CI 5.68, 6.73], respectively). Except for dapagliflozin (p = 0.000), no notable dose‐dependent relationship was revealed for other SGLT2 inhibitors. The effect could be sustained or even slightly increased with long‐term therapy (coef. =0.009, 95% CI [0.005, 0.013], p = 0.000). In subgroup analyses, haematocrit elevation increased with higher body mass index (BMI). A greater haematocrit elevation could be observed in white patients or when compared with active controls. In conclusion, SGLT2 inhibitors increased haematocrit and haemoglobin levels in T2DM patients. Changes in haematocrit and haemoglobin seem to be surrogate markers of improvement in renal metabolic stress, and important mediators involved in cardiorenal protection.     

Globally,plant‐soil feedbacks are weak predictors of plant abundance

Plant‐soil feedbacks (PSFs) have been shown to strongly affect plant performance under controlled conditions, and PSFs are thought to have far reaching consequences for plant population dynamics and the structuring of plant communities. However, thus far the relationship between PSF and plant species abundance in the field is not consistent. Here, we synthesize PSF experiments from tropical forests to semiarid grasslands, and test for a positive relationship between plant abundance in the field and PSFs estimated from controlled bioassays. We meta‐analyzed results from 22 PSF experiments and found an overall positive correlation (0.12 ≤ r¯ ≤ 0.32) between plant abundance in the field and PSFs across plant functional types (herbaceous and woody plants) but also variation by plant functional type. Thus, our analysis provides quantitative support that plant abundance has a general albeit weak positive relationship with PSFs across ecosystems. Overall, our results suggest that harmful soil biota tend to accumulate around and disproportionately impact species that are rare. However, data for the herbaceous species, which are most common in the literature, had no significant abundance‐PSFs relationship. Therefore, we conclude that further work is needed within and across biomes, succession stages and plant types, both under controlled and field conditions, while separating PSF effects from other drivers (e.g., herbivory, competition, disturbance) of plant abundance to tease apart the role of soil biota in causing patterns of plant rarity versus commonness.     

Association between IGF‐1 levels ranges and all‐cause mortality: A meta‐analysis

The association between IGF‐1 levels and mortality in humans is complex with low levels being associated with both low and high mortality. The present meta‐analysis investigates this complex relationship between IGF‐1 and all‐cause mortality in prospective cohort studies. A systematic literature search was conducted in PubMed/MEDLINE, Scopus, and Cochrane Library up to September 2019. Published studies were eligible for the meta‐analysis if they had a prospective cohort design, a hazard ratio (HR) and 95% confidence interval (CI) for two or more categories of IGF‐1 and were conducted among adults. A random‐effects model with a restricted maximum likelihood heterogeneity variance estimator was used to find combined HRs for all‐cause mortality. Nineteen studies involving 30,876 participants were included. Meta‐analysis of the 19 eligible studies showed that with respect to the low IGF‐1 category, higher IGF‐1 was not associated with increased risk of all‐cause mortality (HR = 0.84, 95% CI = 0.68–1.05). Dose–response analysis revealed a U‐shaped relation between IGF‐1 and mortality HR. Pooled results comparing low vs. middle IGF‐1 showed a significant increase of all‐cause mortality (HR = 1.33, 95% CI = 1.14–1.57), as well as comparing high vs. middle IGF‐1 categories (HR = 1.23, 95% CI = 1.06–1.44). Finally, we provide data on the association between IGF‐1 levels and the intake of proteins, carbohydrates, certain vitamins/minerals, and specific foods. Both high and low levels of IGF‐1 increase mortality risk, with a specific 120–160 ng/ml range being associated with the lowest mortality. These findings can explain the apparent controversy related to the association between IGF‐1 levels and mortality.     

Cryo‐EM structure of the CENP‐A nucleosome in complex with phosphorylated CENP‐C

The CENP‐A nucleosome is a key structure for kinetochore assembly. Once the CENP‐A nucleosome is established in the centromere, additional proteins recognize the CENP‐A nucleosome to form a kinetochore. CENP‐C and CENP‐N are CENP‐A binding proteins. We previously demonstrated that vertebrate CENP‐C binding to the CENP‐A nucleosome is regulated by CDK1‐mediated CENP‐C phosphorylation. However, it is still unknown how the phosphorylation of CENP‐C regulates its binding to CENP‐A. It is also not completely understood how and whether CENP‐C and CENP‐N act together on the CENP‐A nucleosome. Here, using cryo‐electron microscopy (cryo‐EM) in combination with biochemical approaches, we reveal a stable CENP‐A nucleosome‐binding mode of CENP‐C through unique regions. The chicken CENP‐C structure bound to the CENP‐A nucleosome is stabilized by an intramolecular link through the phosphorylated CENP‐C residue. The stable CENP‐A‐CENP‐C complex excludes CENP‐N from the CENP‐A nucleosome. These findings provide mechanistic insights into the dynamic kinetochore assembly regulated by CDK1‐mediated CENP‐C phosphorylation.     

凋落物输入对三江平原弃耕农田土壤基础呼吸和活性碳组分的影响

土壤有机碳的积累主要由土壤有机质的输入与输出间的净平衡决定的,植被的恢复和凋落物质的大量输入是土壤恢复的先决条件,凋落物的输入在土壤恢复过程中起着至关重要的作用.通过对不同类型凋落物输入到三江平原弃耕农田后土壤的基础呼吸、溶解有机碳(DOC)和土壤微生物量碳(MBC)的研究表明:相同种类凋落物输入后,输入到土壤总有机碳(TOC)背景值低的凋落物被微生物降解的速率大于TOC背景值高的土壤,TOC较低的土壤能够加快微生物对输入凋落物的分解,不利于有机质的积累;不同类型凋落物的输入使土壤基础呼吸、DOC和MBC等活性组分的生成和降解产生差异,改变了凋落物的降解速率,在三江平原研究的4种主要植被类型中,人工林凋落物最容易降解,小叶章、大豆的降解能力次之,玉米是最难降解的凋落物.     

模拟氮沉降凋落物管理对樟树人工林土壤呼吸的影响

以湖南省植物园樟树人工林为对象,研究了模拟氮沉降下,不同凋落物处理对土壤呼吸的影响。设置4个施氮水平,分别为CK(0 kg N hm~(-2)a~(-1))、LN(50 kg N hm~(-2)a~(-1))、NM(150 kg N hm~(-2)a~(-1))以及HN(300 kg N hm~(-2)a~(-1));凋落物处理分别为去除凋落物、添加凋落物以及凋落物对照组。经过为期2年的观测研究,结果表明:(1)模拟氮沉降不同凋落物处理下,土壤温度呈现显著的季节性变化,但不存在显著差异;土壤湿度呈现显著的波动性变化,施氮及凋落物管理对土壤温度无影响。土壤湿度仅受凋落物管理的影响。在不同施氮水平下,去除凋落物的土壤湿度与加倍凋落物的土壤湿度均存在显著差异性。(2)模拟氮沉降不同凋落物处理下,土壤呼吸均呈现显著的季节性变化,最大值出现在6—8月;最小值出现在1月,且在生长季期间(4—8月),不同处理下土壤呼吸存在显著差异。(3)施氮对土壤呼吸表现为抑制作用,添加凋落物对土壤呼吸起促进作用,去除凋落物对土壤呼吸起抑制作用。(4)在凋落物对照组中,LN、MN、HN较CK相比,土壤呼吸速率年均值分别降低了35.4%、30.6%、36.8%,且各施氮水平与CK存在显著差异(P0.05);添加凋落物处理下,LN、MN、HN处理较CK相比,土壤呼吸速率年均值土壤呼吸分别降低了23.2%、15.8%、14.7%。去除凋落物处理下,LN、MN、HN较CK相比,土壤呼吸速率年均值分别降低了3.5%、0.5%、-11.6%。且添加或去除凋落物均能削弱施氮对土壤呼吸的抑制作用,且这种作用随着施氮水平的增加而增大。(5)土壤呼吸与5 cm处土壤温度存在显著相关性(P0.05),土壤温度可解释土壤呼吸变异的47.76%—72.61%;与土壤湿度呈现正相关,但未达到显著相关水平(P0.05)。     

Permafrost response to temperature rise in carbon and nutrient cycling: Effects from habitat‐specific conditions and factors of warming

Permafrost is experiencing climate warming at a rate that is two times faster than the rest of the Earth''s surface. However, it is still lack of a quantitative basis for predicting the functional stability of permafrost ecosystems in carbon (C) and nutrient cycling. We compiled the data of 708 observations from 89 air‐warming experiments in the Northern Hemisphere and characterized the general effects of temperature increase on permafrost C exchange and balance, biomass production, microbial biomass, soil nutrients, and vegetation N dynamics through a meta‐analysis. Also, an investigation was made on how responses might change with habitat‐specific (e.g., plant functional groups and soil moisture status) conditions and warming variables (e.g., warming phases, levels, and timing). The net ecosystem C exchange (NEE) was found to be downregulated by warming as a result of a stronger sensitivity to warming in respiration (15.6%) than in photosynthesis (6.2%). Vegetation usually responded to warming by investing more C to the belowground, as belowground biomass increased much more (30.1%) than aboveground biomass (2.9%). Warming had a minor effect on microbial biomass. Warming increased soil ammonium and nitrate concentrations. What''s more, a synthesis of 70 observations from 11 herbs and 9 shrubs revealed a 2.5% decline of N in green leaves. Compared with herbs, shrubs had a stronger response to respiration and had a decline in green leaf N to a greater extent. Not only in dry condition did green leaf N decline with warming but also in wet conditions. Warming in nongrowing seasons would negatively affect soil water, C uptake, and biomass production during growing seasons. Permafrost C loss and vegetation N decline may increase with warming levels and timing. Overall, these findings suggest that besides a positive C cycling–climate feedback, there will be a negative feedback between permafrost nutrient cycling and climate warming.     

帽儿山3种森林生态系统土壤动物与土壤呼吸及其相互关系研究

土壤呼吸是森林生态系统碳循环的关键过程,土壤动物可通过自身代谢及影响微生物活动调控土壤呼吸,因此研究土壤动物与土壤呼吸的相互关系对进一步揭示生态系统碳循环的规律和机理具有重要意义。通过野外定点,以帽儿山3种森林生态系统的土壤呼吸及土壤动物为研究对象,探讨不同森林生态系统的土壤呼吸、土壤动物个体密度和生物量的时间变化规律及二者相互关系。结果表明:(1)3种森林生态系统土壤总呼吸速率与土壤异养呼吸速率均呈现先增强后减弱的时间动态变化(P<0.05),且不同森林生态系统土壤异养呼吸速率差异显著(P<0.05),表现为硬阔叶林最高,红松人工林最低;(2)3种森林生态系统土壤动物生物量也具有显著的时间动态变化(P<0.05),均在9月份达到最大,且不同森林生态系统土壤动物个体密度显著不同(P<0.05),蒙古栎林土壤动物个体密度显著小于红松人工林与硬阔叶林;(3)通过回归分析可得,土壤动物数量及生物量的增加抑制了土壤呼吸速率,尤其在生长季初期、末期。研究表明土壤动物可通过抑制微生物生命活动和降低根系呼吸从而对土壤总呼吸及异养呼吸产生负反馈作用,三者是不可分割的整体,与土壤温度、水分等环境因子共同调控着土壤呼吸。     

Efficacy and safety of combination PD‐1/PD‐L1 checkpoint inhibitors for malignant solid tumours: A systematic review

Treatment of multiple malignant solid tumours with programmed death (PD)‐1/PD ligand (PD‐L) 1 inhibitors has been reported. However, the efficacy and immune adverse effects of combination therapies are controversial. This meta‐analysis was performed with PubMed, Web of Science, Medline, EMBASE and Cochrane Library from their inception until January 2020. Random‐effect model was adopted because of relatively high heterogeneity. We also calculated hazard ratio (HR) of progression‐free survival (PFS), overall survival (OS) and risk ratio (RR) of adverse events (AEs), the incidence of grade 3‐5 AEs by tumour subgroup, therapeutic schedules and therapy lines. Nineteen articles were selected using the search strategy for meta‐analysis. Combined PD‐1/PD‐L1 inhibitors prolonged OS and PFS (HR 0.72, P < 0.001) and (HR 0.66, P < 0.001). In addition, incidence of all‐grade and grade 3‐5 AEs was not significant in the two subgroup analyses (HR 1.01, P = 0.31) and (HR 1.10, P = 0.07), respectively. Our meta‐analysis indicated that combination therapy with PD‐1/PD‐L1 inhibitors had greater clinical benefits and adverse events were not increased significantly.     

Psychotherapies for depression: a network meta‐analysis covering efficacy,acceptability and long‐term outcomes of all main treatment types

The effects of psychotherapies for depression have been examined in several hundreds of randomized trials, but no recent network meta‐analysis (NMA) has integrated the results of these studies. We conducted an NMA of trials comparing cognitive behavioural, interpersonal, psychodynamic, problem‐solving, behavioural activation, life‐review and “third wave” therapies and non‐directive supportive counseling with each other and with care‐as‐usual, waiting list and pill placebo control conditions. Response (50% reduction in symptoms) was the primary outcome, but we also assessed remission, standardized mean difference, and acceptability (all‐cause dropout rate). Random‐effects pairwise and network meta‐analyses were conducted on 331 randomized trials with 34,285 patients. All therapies were more efficacious than care‐as‐usual and waiting list control conditions, and all therapies – except non‐directive supportive counseling and psychodynamic therapy – were more efficacious than pill placebo. Standardized mean differences compared with care‐as‐usual ranged from –0.81 for life‐review therapy to –0.32 for non‐directive supportive counseling. Individual psychotherapies did not differ significantly from each other, with the only exception of non‐directive supportive counseling, which was less efficacious than all other therapies. The results were similar when only studies with low risk of bias were included. Most therapies still had significant effects at 12‐month follow‐up compared to care‐as‐usual, and problem‐solving therapy was found to have a somewhat higher long‐term efficacy than some other therapies. No consistent differences in acceptability were found. Our conclusion is that the most important types of psychotherapy are efficacious and acceptable in the acute treatment of adult depression, with few significant differences between them. Patient preference and availability of each treatment type may play a larger role in the choice between types of psychotherapy, although it is possible that a more detailed characterization of patients with a diagnosis of depression may lead to a more precise matching between individual patients and individual psychotherapies.     

马尾松林土壤呼吸组分对不同营林措施的响应

针对不同营林措施(对照、除灌、采伐1(15%)、采伐2(70%)后的三峡库区马尾松飞播林,采用LI-8100对其土壤呼吸组分的呼吸速率和土壤温度、湿度进行为期1年的连续观测分析表明,不同营林措施对土壤呼吸组分的影响不同。1)观测期内,各营林措施下凋落物层呼吸速率差异并不显著,对照、除灌、采伐1、采伐2的根呼吸速率均值分别为:1.00、0.83、0.86、1.11μmolCO_2m~(-2)s~(-1);采伐处理下矿质土壤呼吸显著高于对照和除灌(P0.05);2)与对照相比,营林措施并未显著改变凋落物呼吸对于土壤总呼吸的贡献率(18.78%-23.70%),但降低了根呼吸的贡献率,其中以采伐1最为显著(P0.05);除灌的矿质土壤呼吸贡献率(37.00%)与对照(38.32%)相近,而采伐1(45.63%)和采伐2(43.07%)均显著增加了矿质土壤呼吸的贡献率,矿质土壤呼吸的变化是造成采伐措施下土壤呼吸变化的主要土壤呼吸组分;3)营林后仅采伐2措施下土壤温湿度显著高于对照,土壤温湿度双因子模型较单因子模型能更好的解释土壤呼吸组分变化,但仅能解释其部分变化(4.6%-59.3%),仍需对营林后其他相关因子进行深入的综合研究。     

改变凋落物输入对川西亚高山天然次生林土壤呼吸的影响

2019年5月-10月,采用LI-8100A土壤碳通量自动测量分析仪对川西米亚罗林区20世纪60年代采伐后经自然更新恢复形成的岷江冷杉（Abies faxoniana）次生针叶林（针叶林）、红桦（Betula albo-sinensis）+青榨槭（Acer davidii）+岷江冷杉次生针阔混交林（针阔混交林）和青榨槭+红桦+陕甘花楸（Sorbus koehneana Schneid）次生阔叶林（阔叶林）的土壤呼吸及土壤温湿度因子（对照、去除凋落物和加倍凋落物）进行观测。结果显示：去除和加倍凋落物对土壤温湿度的影响不显著,且3种林型之间的土壤呼吸速率差异不显著。与对照相比,去除凋落物使针叶林、针阔混交林、阔叶林的土壤呼吸速率分别降低了17.65%、21.01%和19.83%（P<0.05）;加倍凋落物则分别增加6.76%、7.28%、8.16%（P>0.05）。3种林分土壤呼吸速率均与土壤温度极显著指数相关,与土壤湿度不相关。对照Q₁₀值变幅为2.01-3.29,去除凋落物降低了3种林型的Q₁₀值;加倍凋落物分别提高了针叶林和降低了针阔混交林和阔叶林的Q₁₀值。土壤呼吸速率仅表现在天然次生林对照处理中受到土壤pH、有机质、可溶性有机氮和草本Pielou均匀度指数的显著影响。研究结果表明,天然次生阔叶林和针阔混交林凋落物对土壤呼吸的贡献及Q₁₀值高于天然次生针叶林,说明在未来CO₂浓度及温度升高背景下,地表凋落物增加并未引起天然次生林土壤呼吸速率成倍增加,更有利于该区域天然次生林尤其是针叶林的土壤碳吸存。     

Belowground community responses to fire: meta‐analysis reveals contrasting responses of soil microorganisms and mesofauna

Global fire regimes are shifting due to climate and land use changes. Understanding the responses of belowground communities to fire is key to predicting changes in the ecosystem processes they regulate. We conducted a comprehensive meta‐analysis of 1634 observations from 131 empirical studies to investigate the effect of fire on soil microorganisms and mesofauna. Fire had a strong negative effect on soil biota biomass, abundance, richness, evenness, and diversity. Fire reduced microorganism biomass and abundance by up to 96%. Bacteria were more resistant to fire than fungi. Fire reduced nematode abundance by 88% but had no significant effect on soil arthropods. Fire reduced richness, evenness and diversity of soil microorganisms and mesofauna by up to 99%. We found little evidence of temporal trends towards recovery within 10 years post‐disturbance suggesting little resilience of the soil community to fire. Interactions between biome, fire type, and depth explained few of these negative trends. Future research at the intersection of fire ecology and soil biology should aim to integrate soil community structure with the ecosystem processes they mediate under changing global fire regimes.     

A UV‐C LED‐based unit for continuous decontamination of the sheath fluid in a flow‐cytometric cell sorter

Aseptic cell sorting is challenging, especially when a flow‐cytometric cell sorter is not operated in a sterile environment. The sheath fluid system of a cell sorter may be contaminated with germs such as bacteria, yeasts, viruses, or fungi. Thus, a regular chemical cleaning procedure is required to prepare a sorter for aseptic cell sorting by flushing the fluidic system. However, this procedure is time consuming, and most importantly, the researcher can never be sure that the cleaning process was successful. Here we present a method in which the sheath fluid of a cell sorter was decontaminated by irradiation with UV‐C light using a flow‐through principle. Using this principle, we were able to achieve a 5 log reduction of bacteria in the sheath fluid.