The unimodal latitudinal pattern of K,Ca and Mg concentration and its potential drivers in forest foliage in eastern China

Potassium(K),calcium(Ca),and magnesium(Mg)are essential elements with important physiological functions in plants.Previous studies showed that leaf K,Ca,and Mg concentrations generally increase with increasing latitudes.However,recent meta-analyses suggested the possibility of a unimodal pattern in the concentrations of these elements along latitudinal gradients.The authenticity of this unimodal latitudinal pattern,however,requires validation through large-scale field experimental data,and exploration of the underlying mechanisms if the pattern is confirmed.Here,we collected leaves of common species of woody plants from 19 montane forests in the north-south transect of eastern China,including 322 species from 160 genera,67 families;and then determined leaf K,Ca,and Mg concentrations to explore their latitudinal patterns and driving mechanisms.Our results support unimodal latitudinal patterns for all three elements in woody plants across eastern China,with peak values at latitude 36.5±1.0°N.The shift of plant-functional-type compositions from evergreen broadleaves to deciduous broadleaves and to conifers along this latitudinal span was the key factor contributing to these patterns.Climatic factors,mainly temperature,and to a lesser extent solar radiation and precipitation,were the main environmental drivers.These factors,by altering the composition of plant communities and regulating plant physiological activities,influence the latitudinal patterns of plant nutrient concentrations.Our findings also suggest that high leaf K,Ca,and Mg concentrations may represent an adaptive strategy for plants to withstand water stress,which might be used to predict plant nutrient responses to climate changes at large scales,and broaden the understanding of biogeochemical cycling of K,Ca,and Mg.

不同发展情景下青海省土地利用布局及生物多样性变化模拟

人类活动导致土地利用格局的剧烈变迁是全球生物多样性丧失的重要原因之一。为满足青海省生物多样性保护和社会经济发展对土地利用的需求,本研究依据土地利用类型/干扰强度与生物多样性的关系,制定了基线、美丽青海、智慧青海、和谐青海4种情景的设计方案,并基于GeoSOS-FLUS模型和FLUS-Biodiversity模型分别模拟至2030年、2050年时,4种情景下青海省土地利用布局及其原生群落平均物种多度(Mean Species Abundance,MSA)的空间格局演变。结果表明,青海省大部分土地利用类型在现有格局的基础上均发生较大变化。其中,基线情景(按原有发展趋势)中湿地、森林、草地的面积均有所下降,导致生物多样性恢复速度缓慢。基于自然保护和经济发展的不同权衡,美丽青海、智慧青海、和谐青海3种情景则对未来土地利用布局的优化效果较好,大量中、高强度利用的草地恢复为湿地、原生林及低强度利用的草地,部分常规农田转换为优质农田,建设用地面积减少,生物多样性因而得以较大提高。未来各情景下的青海省MSA值都能实现目标值,生物多样性完整性相对于2020年都有所增加。

Family-level leaf nitrogen and phosphorus stoichiometry of global terrestrial plants

Leaf nitrogen(N) and phosphorus(P) concentrations are critical for photosynthesis, growth, reproduction and other ecological processes of plants. Previous studies on large-scale biogeographic patterns of leaf N and P stoichiometric relationships were mostly conducted using data pooled across taxa, while family/genus-level analyses are rarely reported. Here, we examined global patterns of family-specific leaf N and P stoichiometry using a global data set of 12,716 paired leaf N and P records which includes 204 families, 1,305 genera, and 3,420 species. After determining the minimum size of samples(i.e., 35 records), we analyzed leaf N and P concentrations, N:P ratios and N^P scaling relationships of plants for 62 families with 11,440 records. The numeric values of leaf N and P stoichiometry varied significantly across families and showed diverse trends along gradients of mean annual temperature(MAT) and mean annual precipitation(MAP). The leaf N and P concentrations and N:P ratios of 62 families ranged from 6.11 to 30.30 mg g–1, 0.27 to 2.17 mg g–1, and 10.20 to 35.40, respectively. Approximately 1/3–1/2 of the families(22–35 of 62) showed a decrease in leaf N and P concentrations and N:P ratios with increasing MAT or MAP, while the remainder either did not show a significant trend or presented the opposite pattern. Family-specific leaf N^P scaling exponents did not converge to a certain empirical value, with a range of 0.307–0.991 for 54 out of 62 families which indicated a significant N^P scaling relationship. Our results for the first time revealed large variation in the family-level leaf N and P stoichiometry of global terrestrial plants and that the stoichiometric relationships for at least one-third of the families were not consistent with the global trends reported previously. The numeric values of the family-specific leaf N and P stoichiometry documented in the current study provide critical synthetic parameters for biogeographic modeling and for further studies on the physiological and ecological mechanisms underlying the nutrient use strategies of plants from different phylogenetic taxa.

Resorptions of 10 mineral elements in leaves of desert shrubs and their contrasting responses to aridity

Aims We aim to investigate variations in the resorption efficiencies of 10 mineral nutrients[i.e.nitrogen(N),phosphorus(P),potassium(K),magnesium(Mg),calcium(Ca),manganese(Mn),zinc(Zn),alu-minum(Al),iron(Fe)and copper(Cu)]in leaves of desert shrubs and to explore effects of aridity on resorption efficiency of these nutrients.Methods Plant samples were collected from 10 sites in northern Xinjiang Uygur Autonomous Region of China.Samples of green and senesced leaves were analysed to determine concentrations of N,P,K,Mg,Ca,Mn,Zn,Al,Fe and Cu and thus the nutrient resorption efficiency.Important Findings The mean nutrient concentrations in the desert shrubs varied,with the stoichiometric ratio Ca:N(19.3 mg g−1):K(10.5 mg g−1):Mg:P(1.01 mg g−1):Al:Fe:Mn:Zn:Cu(4.78 mg kg−1)=4038:2950:2199:1816:211:37:32:11:2:1 in green leaves;and Ca:N(12.6 mg g−1):Mg:K(7.6 mg g−1):P(0.56 mg g−1):Fe:Al:Mn:Zn:Cu(2.85 mg kg−1)=5583:3710:2943:2523:178:133:119:19:3.7:1 in senesced leaves.Resorption generally occurred for six elements(N,P,K,Cu,Mg and Mn,with average resorption efficiency 47.8%,52.0%,38.6%,41.0%,12.7%and 7.89%,respectively)during leaf senescence,while the other four nutrients tended to accumulate in senesced leaves,showing averagely negative resorption efficiencies[Ca(-3.87%),Al(−57.1%),Zn(−62.6%),Fe(−89.6%)].Aridity showed strikingly different effects on the resorption process of the 10 nutri-ents.Of the four elements with totally(N/P/K)or mostly(Cu)posi-tive observations of resorption efficiency,their resorption generally decreased with aridity,suggesting that drought stress had negative effects on the resorption efficiencies of these elements.In contrast,with at least one-third observations of resorption efficiency being negative,the other elements(Mg/Mn/Ca/Zn/Al/Fe)showed gener-ally increasing resorptive tendency with aridity,except for Zn.This research provided a systematic analysis on the large variation and contrasting responses of the resorption of multi-elements to aridity in typical desert shrubs.Our findings foster the understanding of nutrient resorption patterns of desert plants and enable us to better predict the contrastive effects of drought stress on the cycling of diverse nutrients and the consequent stoichiometric decoupling in plants of desert ecosystems.

3个小型高原湖泊水陆交错带中植物叶片pH值变异及其潜在影响因素

陆生植物叶片pH值是与植物生理功能和养分利用状况息息相关的重要植物属性,并随植物功能型和环境的变化而变化。然而,水生植物叶片pH值的变异特征及其与陆生植物间的差异性仍不清楚。在3个自然形成的小型高原湖泊的湖滨植物群落中,我们采集植物、土壤和湖水样品,检测了植物叶片pH值与碳、氮含量以及环境条件(水或土壤pH值、土壤水位状况)。从植物功能型和群落两个水平分析了湖滨植物叶pH值沿水分梯度的变化及其潜在影响因素。研究结果表明,不同类型的水生植物,以及水生、沼生和陆生环境中生长的植物的叶pH存在较大差异;浮叶植物叶片pH值(4.21±0.05)显著低于挺水植物(5.71±0.07)和沉水植物(5.82±0.06);水生草本植物叶片pH值(5.43±0.10)显著低于沼生草本植物(6.12±0.07)和陆生草本植物(5.74±0.05);陆生草本植物叶片pH值显著高于木本植物。植物功能群间叶片pH值的变异可能与叶片的结构、光利用特性和养分特性有关。群落水平的结果与植物功能型水平相一致:水生群落叶片pH值显著低于陆生群落。群落水平叶片pH值可能主要受物种组成、水分条件和环境pH值的影响。本研究首次探索了水生植物的pH值,并且在景观尺度上对比了不同功能型植物的叶片pH值,为深入探索植物pH值变异机制以及其在水生和湿地生态系统中的生态意义提供参考。

植物叶片pH值的测定及样品预处理和保存方法的比较研究

植物叶片pH值是叶片能量运转、新陈代谢、养分平衡等生理活动的重要调节因素。但目前尚缺乏一套合适的植物叶片样品的保存和测试方法,能同时满足叶片样品的长期保存和接近鲜叶片pH值测定的要求。本文通过探索植物叶样品的预处理和保存方式以及叶:水混合比例对叶片pH测定值的影响,提出一种能够长期保存植物叶片,同时对叶片pH值影响较小的测定方法,并且建立不同处理方法间的转换关系。本研究采集多种植物的叶片样品,并分别进行短期冷藏、冷冻和烘干处理保存,以刚采摘的新鲜绿色叶片作为对照,研究叶片样品不同保存方式对其pH值的影响。对烘干绿色叶片按叶片和水1:8的体积比和1:10的质量比分别进行pH值测定,对冷冻叶片:水按质量比为1:10和1:15的比例分别进行测定,分析不同加水比例对所测叶片样品pH值的影响。结果表明,短期冷藏和冷冻处理对植物叶片pH值的测量结果没有显著影响,但是烘干处理一般会使测定值偏高。因此,在长时间的野外采样工作中,通过便携式冷藏箱对植物样品进行冷冻保存,是保持叶片样品pH值稳定、即更接近新鲜叶pH测量值的较好的样品保存方式。对于长时间野外采样,冷冻预处理是植物叶样品保存的最佳选择;而冷藏预处理是短时间保存的最佳选择。不同的叶片:水比例对pH测量值存在显著影响:样品稀释比例越高,氢离子浓度越低,测量到的叶片pH值越大。因此,为了建立现有不同植物叶pH值测量方法之间的联系,本文为叶片样品的不同前处理和测量方式提供了转换关系。本研究结果将有助于植物叶片pH值的研究,从而提高对这一功能性状的认识。

植物叶片养分重吸收效率的质量损失校正

养分重吸收是植物保持养分的关键机制,但以往多数研究未考虑叶片衰老过程中的质量损失,低估了植物的叶片养分重吸收效率(NuRE);或只能基于文献中植物功能群水平的平均质量损失,校正所研究的不同物种的叶片NuRE,从而影响了该参数的精确性。本研究通过采集中国北方地区35种常见木本植物的绿色叶片和凋落叶片样本,测量绿色叶片和凋落叶片的质量,计算了叶片衰老过程中的质量损失,并给出了这些物种凋落叶片的质量损失校正系数(MLCF)。总体而言,植物凋落叶片的质量比成熟绿色叶片平均损失17%,物种水平质量损失变化范围为1.3%–36.8%,功能群水平为11.7%–19.6%。相应地,这35种木本植物的凋落叶片的MLCF值平均为0.832,变化范围为0.632–0.987。与校正前相比,用MLCF校正后的NuRE总体上显著增加。例如,校正后氮和磷的平均NuRE皆增高约9%,即比其校正前(低估)更接近真实值;当植物NuRE较低时,这种校正作用(改善)表现得尤为明显。本研究基于物种水平的野外实测数据,报道了中国北方部分常见木本植物的MLCF参考值,研究结果将有助于更准确地计算此类植物的养分重吸收效率,提升本地区植物-土壤系统中养分流通评估的精准度。

高寒草地土壤掩埋对凋落物分解速率的影响大于氮素富集

由于高寒草地退化、鼠害严重、大风频繁等原因,凋落物被频繁掩埋在土壤中。但凋落物的位置变化和氮富集对高寒草原凋落物分解速率和养分动态影响的认识尚不清楚。为了研究凋落物位置变化(地表、掩埋10 cm和悬空60 cm)和氮富集对高寒草原优势植物凋落物分解的影响,本研究依托2009年在新疆天山巴音布鲁克高寒草原设置的长期模拟氮沉降研究平台,以对照和氮富集处理样方的优势植物羊茅(Festuca ovina)和赖草(Leymus tianschanicus)凋落物为试验材料,测定分解过程中凋落物质量损失和碳氮磷含量的变化特征。研究结果表明,掩埋凋落物分解速率显著快于地表凋落物,悬空处理凋落物分解速率慢于地表凋落物。氮富集显著影响凋落物质量,进而影响凋落物分解。而凋落物质量残留在对照与氮富集土壤掩埋之间无显著差异。这些结果表明,氮富集通过凋落物质量而不是通过土壤环境因素,影响短期凋落物分解。不同处理的所有试验凋落物均有碳和磷的释放现象。对照处理的凋落物,凋落物氮以累积为主,而氮富集处理的凋落物,凋落物氮以释放为主。这表明凋落物分解可能受到氮元素限制,氮富集改变了凋落物分解调控的氮循环过程。本研究提供了直接证据,掩埋处理的凋落物有更快的质量损失和碳元素释放,土壤掩埋是旱地凋落物分解速率比模型预测的快的一个候选解释。

Density-induced social stress alters oxytocin and vasopressin activities in the brain of a small rodent species

It is known that social stress could alter oxytocin(OT)and arginine-vasopressin(AVP)expression in specific regions of brains which regulate the aggressive behavior of small rodents,but the effects of density-induced social stress are still unknown.Brandt’s voles(Lasiopodomys brandtii)are small herbivores in the grassland of China,but the underlying neurological mechanism of population regulation is still unknown.We tested the effects of housing density of Brandt’s voles on OT/AVP system with physical contact(allowing aggression)and without physical contact(not allowing aggression)under laboratory conditions.Then,we tested the effects of paired-aggression(no density effect)of Brandt’s voles on OT/AVP system under laboratory conditions.We hypothesized that high density would increase aggression among animals which would then increase AVP but reduce OT in brains of animals.Our results showed that high housing density induced more aggressive behavior.We found high-densityinduced social stress(with or without physical contact)and direct aggression significantly increased expression of mRNA and protein of AVP and its receptor,but decreased expression of mRNA and protein of OT and its receptor in specific brain regions of voles.The results suggest that density-dependent change of OT/AVP systems may play a significant role in the population regulation of small rodents by altering density-dependent aggressive behavior.