降水量及N添加对宁夏荒漠草原土壤C∶N∶P生态化学计量特征和植被群落组成的影响

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朱湾湾, 王攀, 樊瑾, 牛玉斌, 余海龙, 黄菊莹. 降水量及N添加对宁夏荒漠草原土壤C：N：P生态化学计量特征和植被群落组成的影响. 草业学报, 2019,28(9): 33-44
ZHU Wan-wan, WANG Pan, FAN Jin, NIU Yu-bin, YU Hai-long, HUANG Ju-ying. Effects of precipitation and N addition on soil C∶N∶P ecological stoichiometry and plant community composition in a desert steppe of Ningxia, northwestern China. Acta Prataculturae Sinica,2019,28(9): 33-44 复制到剪切板

Doi:10.11686/cyxb2019232
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降水量及N添加对宁夏荒漠草原土壤C∶N∶P生态化学计量特征和植被群落组成的影响

朱湾湾¹, 王攀¹, 樊瑾¹, 牛玉斌¹, 余海龙¹, 黄菊莹^2,^*

1.宁夏大学资源环境学院,宁夏银川 750021

2.宁夏大学环境工程研究院,宁夏银川 750021

*通信作者: E-mail: juyinghuang@163.com

作者简介:朱湾湾(1996-), 女, 河南洛阳人, 在读硕士。E-mail: 2350384309@qq.com

收稿日期: 2019-04-09

基金项目:宁夏高等学校科学研究项目(NGY2017003)和国家自然科学基金项目(31760144和31360111)资助

摘要

为了解降水格局改变和大气氮(N)沉降增加背景下土壤碳(C)∶N∶磷(P)平衡关系的改变是否会影响到荒漠草原植被群落组成, 基于2017年在宁夏荒漠草原设立的降水量(降水量减少50%、降水量减少30%、自然降水量、降水量增加30%和降水量增加50%)、N添加(0和5 g·m^-2·yr^-1)及其交互作用的野外试验, 初步分析了土壤C∶N∶P生态化学计量特征和植物群落组成的变化趋势以及二者的关系。结果表明, 增加降水量降低了土壤有机C、全N和N∶P。N添加及其与降水量的交互作用对土壤C∶N∶P生态化学计量特征的影响较小; 适量增加降水量刺激了多数植物生长, 提高了群落多样性。过量增加降水量导致猪毛蒿种群生物量急增, 且N添加对降水量效应有促进作用, 从而降低了群落多样性; 土壤含水量、全N、有机C和N∶P与种群生物量关系较为密切, 土壤含水量、有机C、C∶P和C∶N与多样性指数存在较强的相关关系。以上结果意味着降水量会通过调控土壤水分有效性, 改变土壤与植物之间N和P的满足程度, 从而对植物生长策略和群落多样性产生影响; 短期N添加对土壤养分有效性影响较小。因此, 还需通过长期的原位试验, 对N添加及其与降水量交互作用下土壤C∶N∶P计量平衡与植物群落组成的关系进行深入探讨。

关键词: 干旱半干旱区; 降水格局改变; 大气N沉降增加; 植物群落多样性; 土壤C∶N∶P

Effects of precipitation and N addition on soil C∶N∶P ecological stoichiometry and plant community composition in a desert steppe of Ningxia, northwestern China

ZHU Wan-wan¹, WANG Pan¹, FAN Jin¹, NIU Yu-bin¹, YU Hai-long¹, HUANG Ju-ying^2,^*

1.College of Resources and Environment, Ningxia University, Yinchuan 750021, China

2.Institute of Environmental Engineering, Ningxia University, Yinchuan 750021, China

*Corresponding author: E-mail: juyinghuang@163.com

Abstract

Change in precipitation pattern and increase in atmospheric nitrogen (N) deposition are two important consequences of global change. Soil carbon (C)∶N∶phosphorus (P) ecological stoichiometry could reflect soil organic C level and N and P supply and thus would be closely related to plant growth. Previous studies have reported that both of the changes in precipitation and N deposition may lead to the decoupling of soil C∶N∶P ecological stoichiometry. In order to better understand whether the changes in soil C∶N∶P ecological stoichiometry could affect plant community composition under changing precipitation regimes and increasing atmospheric N deposition, we conducted a field experiment in a desert steppe of Ningxia, northwestern China, involving five precipitation treatments (50% reduction in precipitation, 30% reduction in precipitation, natural precipitation, 30% increase in precipitation, and 50% increase in precipitation) and two N addition treatments (0 and 5 g·m^-2·yr^-1) in 2017, and primarily explored the changes in both soil C∶N∶P ecological stoichiometry and plant community composition and their relationships in August, 2018. It was found that increased precipitation led to decreases in soil organic C, total N, and N∶P, whereas N addition and its interaction with precipitation had little influences on soil C∶N∶P ecological stoichiometry; a moderate increase in precipitation stimulated the growth of most plants and thus increased community diversity. An excessive increase in precipitation resulted in a sharp increase of Artemisia scoparia biomass, combined with the positive effects of N addition, resulting in a reduction of community diversity. To a certain extent, soil water content, total N, organic C, and N∶P were closely related to plant population biomass, while soil water content, organic C, C∶P, and C∶N had closer relationships with diversity indices. Taken together, the results above indicate that precipitation could change N and P relationships between soil supply and plant demand through regulating soil water availability, thus changing plant growth strategy and community diversity; short-term N addition had little effect on soil nutrient availability, consequently, a long-term in situ experiment is needed to further explore mechanisms influencing soil C∶N∶P stoichiometric balance effects on plant community composition under N addition and the interaction between these effects and precipitation change.

Keyword: arid and semi-arid regions; changing precipitation regimes; increasing atmospheric N deposition; plant community diversity; soil C∶N∶P

文章图片

降水格局改变和大气氮(N)沉降增加是全球变化的两个重要方面。据报道, 全球总降水量在过去一个世纪有增加趋势, 但在干旱与半干旱地区减少, 干旱和洪涝等极端降水事件的频率呈明显增加趋势^[1]。如与1961-1980年相比, 1981-2010年间我国西北地区降水量总体上呈增加趋势, 但其东部区(如宁夏和陕西部分区域)年降水量呈降低趋势^[2]。另一方面, 化石燃料以及化肥的过度使用等导致N沉降量较工业革命前明显增加。近年来随着大气污染物控制措施的实施, N沉降速率在发达国家有所下降, 但在发展中国家仍呈上升趋势^[3]。就我国而言, 虽然南方等地区N沉降速率有所减缓, 但西北地区N沉降速率加快^[4]。降水量和N沉降调控着土壤水分和N有效性, 影响着植物资源利用策略, 从而会直接影响到植被群落结构^{[5, 6]}。植物群落组成是反映生态系统稳定性的重要指标, 因此有必要针对西北地区敏感生态系统开展二者相关效应的研究, 尤其是受降水和N限制的草原生态系统。

草原生态系统功能的正常发挥对维持区域性及全球生态平衡起着极为重要的作用^[7]。降水量和N有效性是草原生态系统植物生长的主要限制因子, 且降水量在介导N沉降效应方面发挥着重要作用^[8], 因此已有国内学者研究了二者交互作用对草原生态系统植物群落多样性的影响, 如针对青海高寒草原、内蒙古草甸草原、内蒙古典型草原的研究^{[9, 10, 11]}。荒漠草原是干旱半干旱区的主要草原生态系统, 具有植物群落结构简单、生态系统稳定性差等特点; 区域干旱少雨且N沉降临界负荷低^[12], 因此对降水格局改变和N沉降增加较为敏感。宁夏荒漠草原地处毛乌素沙地南缘, 是区域重要的生态屏障, 然而目前针对宁夏荒漠草原的相关研究还比较缺乏。在宁夏荒漠草原开展模拟降水量改变和N沉降增加下植物生物量和群落多样性变化特点的研究, 可为充分认识全球变化背景下干旱半干旱区退化生态系统的反应与适应提供基础数据。

生态化学计量学是研究生态系统多元素平衡关系的一门新兴学科。土壤C∶ N∶ P化学计量比是反映土壤内部3种元素循环的主要指标, 综合了生态系统功能的变异性, 因此有助于确定生态系统过程对全球变化的响应^[13]。一般而言, 土壤元素关系具有一定的内稳性, 对于维持生态系统稳定性具有重要意义。然而, 近年来降水格局改变和N沉降增加导致土壤C∶ N∶ P平衡关系趋于解耦^{[14, 15]}。土壤C∶ N∶ P化学计量比可以较好地反映土壤有机C水平和养分供给状况^{[16, 17]}, 而二者又直接影响着植物的生长发育, 因此趋于解耦的元素平衡关系可能会直接作用于植物群落组成。目前, 国内已有研究分析了自然生境下干旱半干旱区土壤C∶ N∶ P生态化学计量特征与植物群落组成的关系^{[18, 19]}, 尚未见降水量和N添加下针对宁夏荒漠草原的相关报道。为明确降水格局改变和N沉降增加背景下土壤C∶ N∶ P平衡关系的改变是否会影响到荒漠草原植被群落组成, 本研究设置了野外模拟试验, 从土壤元素平衡特征角度初步探讨了二者及其交互作用下宁夏荒漠草原植被群落组成的影响因素, 研究结果可为深入理解全球变化对区域退化生态系统植物群落结构的影响机制提供新思路。

1 材料与方法

1.1 研究区概况

试验样地位于宁夏回族自治区盐池县柳杨堡乡杨寨子村围栏草地内。该区位于毛乌素沙地西南边缘, 是黄土高原向鄂尔多斯台地的过渡地带。地理位置为37.80° N, 107.45° E, 海拔为1367 m。具有典型的温带大陆性气候特征: 年均降水量为289.4 mm; 年均蒸发量为2131.8 mm; 年均气温为7.7 ℃, 1月平均气温为-8.9 ℃, 7月平均气温为22.5 ℃。主要的土壤类型为灰钙土, 土壤质地多为沙壤土。该试验样地植物群落结构简单, 植被组成以一年生和多年生草本为主, 如猪毛蒿(Artemisia scoparia)、猪毛菜(Salsola collina)、牛枝子(Lespedeza potaninii)、草木樨状黄芪(Astragalus melilotoides)、针茅(Stipa capillata)、白草(Pennisetum centrasiaticum)、糙隐子草(Cleistogenes squarrosa)、阿尔泰狗娃花(Heteropappus altaicus)、苦豆子(Sophora alopecuroides)和地梢瓜(Cynanchum thesiodes)等。

1.2 研究方法

1.2.1 试验设计 2017年9月, 在围栏草地内选择地势平坦、植被均匀有代表性的地段作为降水量和N添加处理的试验样地。降水增减量以近几十年来我国西北地区西部降水量增加而东部减少的趋势为主要依据, 同时参考了国内同类研究方法^[11]。N肥施用量以2011-2013年设立的N添加原位试验的观察结果为主要依据^[20], 同时参考了区域大气N沉降水平^[4]。试验采用随机区组的裂区设计, 主区为降水量处理, 副区为N添加处理。降水量处理依次为: 降水量减少50% (W₁)、降水量减少30% (W₂)、自然降水量(对照, W₃)、降水量增加30% (W₄)和降水量增加50% (W₅)。降水量减少处理使用自制的减雨架实现(全年遮雨)。减雨架上端离地约1.8 m, 用5 cm宽的瓦面状透明聚氯乙烯(polyvinyl chloride, PVC)板搭建分别相当于50%和30%样方面积的遮雨面, 并均匀放置于减雨架上方。降水量增加处理利用流量控制的人工喷灌装置实现。试验期间采用雨量计收集降水量, 统计月降水量和年降水量。由于试验地超过80%的降水量集中在生长季(5-10月), 考虑到野外试验的可操作性, 因此将全年需要补给的降水量分8次于5-8月每月上旬和中旬喷于小区内。N添加处理设置2个水平: 0 g N· m^-2· yr^-1 (N₀)和5 g N· m^-2· yr^-1 (N₅), 所施N肥为硝酸铵(NH₄NO₃, 含纯N 34%)。施用时, 将每个小区每次需要施加的NH₄NO₃溶解于少量水中, 于2018年5-8月每月月初均匀喷施到小区内。对照小区喷洒相同量的水, 以避免因水分施用量不同造成的试验误差。试验共计30个小区, 每个处理3次重复。小区面积为8 m× 8 m, 各小区之间设置1.5 m的缓冲带。

1.2.2 样品收集与测定于2018年8月下旬, 在每小区内随机选取3个1 m× 1 m的样方进行植被群落调查。调查指标包括物种名称、物种数、物种高度和物种个体数。调查结束后, 用剪刀齐平地面剪下样方内所有植物地上部分, 按牛枝子、草木樨状黄芪、针茅、猪毛蒿、白草、糙隐子草、阿尔泰狗娃花以及其他物种归类, 并分开装入纸袋带回实验室, 将归类好的植物样品在65 ℃恒温箱烘干(48 h)、称重。群落生物量为所有物种地上生物量之和。植物群落多样性用以下几个指标表征:

重要值(P_i)=(相对生物量+相对高度+相对密度)/3

Shannon-Wiener多样性指数(H')= $- \overset{i = 1}{\sum_{S}}$ P_i lnP_i

Simpson优势度指数(D)= $- \overset{i = 1}{\sum_{S}} {D_{i}}^{2}$

Patrick丰富度指数(R)=S

Pielou均匀度指数(E)=H'/lnS

式中: P_i为种i的重要值; D_i为种i的相对密度; S为群落中物种数。

同期, 采用直径为5 cm的土钻收集0~20 cm土壤, 每个小区取3钻, 混匀过2 mm筛后分为3部分: 一部分直接用于含水量和pH的测定; 一部分4 ℃保存, 用于N ${H_{4}}^{+}$ -N、N ${O_{3}}^{-}$ -N和速效P的测定; 最后一部分自然风干后用于有机C、全N和全P的测定。其中, 采用烘干称重法、酸度计法、重铬酸钾容量法-外加热法、凯氏定N法、钼锑抗比色法和0.5 mol· L^-1 NaHCO₃法测定土壤含水量、pH、有机C、全N、全P和速效P; 采用连续流动分析仪(Auto Analyzer 3, SEAL Analytical GmbH, Hanau, Germany)测定N ${H_{4}}^{+}$ -N和N ${O_{3}}^{-}$ -N^[21]。

1.3 数据分析

采用SigmaPlot 12.5绘图, 数据均为平均值+标准误差(n=3)。用SPSS 24.0进行方差分析: 采用单因素方差分析(One-way ANOVA)中最小显著性差异法(LSD), 进行不同处理间植物生物量、群落多样性以及土壤C∶ N∶ P生态化学计量特征等指标的多重比较; 采用裂区设计方差分析和Duncan检验比较降水量处理、N添加处理以及二者的交互作用对各指标的影响。采用Canoco 5.0进行植物指标与土壤指标对应关系的冗余分析(redundancy analysis, RDA)。

2 结果与分析

2.1 降水量和N添加对土壤C∶ N∶ P生态化学计量特征的影响

裂区设计方差分析结果显示(表1), 降水量对全N及N∶ P具有显著影响, N添加对全N、全P、C∶ P以及N∶ P有显著影响, 二者仅对土壤C∶ N以及C∶ P有显著的交互作用(P< 0.05)。

表1 降水量、N添加及其交互作用对土壤C∶ N∶ P生态化学计量特征的影响 Table 1 Effects of precipitation, N addition, and their interaction on soil C∶ N∶ P ecological stoichiometry

降水量和N添加改变了土壤C∶ N∶ P生态化学计量特征(图1): 0 g· m^-2· yr^-1的N添加下, 降水量对全P、C∶ N和C∶ P无显著的影响, 减少和增加降水量降低了有机C、全N和N∶ P; 5 g· m^-2· yr^-1的N添加下, 降水量对C∶ N无显著的影响, 增加降水量提高了全P, 一定程度上减少和增加降水量降低了有机C、全N、C∶ P和N∶ P; 相同降水量处理间, N添加对土壤C∶ N∶ P生态化学计量特征影响较小, 仅在降水量减少30%处理下提高了有机C、全N、C∶ N、C∶ P和N∶ P, 降低了全P。

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图1 不同N添加处理下降水量对土壤C∶ N∶ P生态化学计量特征的影响
大写字母表示0 g· m^-2· yr^-1的N添加下, 降水量处理间土壤各指标的差异显著性, 字母不同表示差异显著(P< 0.05)。小写字母表示5 g· m^-2· yr^-1的N添加下, 降水量处理间土壤各指标的差异显著性, 字母不同表示差异显著(P< 0.05)。* 表示相同降水量处理间, N添加对土壤各指标有显著影响(P< 0.05)。下同。Fig.1 Effects of precipitation on soil C∶ N∶ P ecological stoichiometry under different N addition
he capital letters indicate significant differences between soil indices within precipitation treatments under 0 g· m^-2· yr^-1 of N addition (P< 0.05). The lowercase letters indicate significant differences between soil indices within precipitation treatments under 5 g· m^-2· yr^-1 of N addition (P< 0.05). * indicates that N addition has significant effects on soil indices under the same precipitation treatments (P< 0.05). The same below.

2.2 降水量和N添加对植物群落组成的影响

裂区设计方差分析结果表明(表2和表3), 降水量对牛枝子、草木樨状黄芪、猪毛蒿、白草以及群落生物量有显著影响, N添加对猪毛蒿、白草、糙隐子草以及群落生物量有显著影响, 二者交互作用仅对针茅、猪毛蒿和白草种群生物量有显著影响; 降水量对4个多样性指数有显著影响, N添加对Pielou均匀度指数有极显著影响。

表2 降水量、N添加及其交互作用对植物种群生物量的影响 Table 2 Effects of precipitation, N addition, and their interaction on plant population biomass

表3 降水量、N添加及其交互作用对植物群落生物量以及多样性指数的影响 Table 3 Effects of precipitation, N addition, and their interaction on plant community biomass and diversity indices

降水量和N添加改变了植物生物量, 且其影响程度具有明显的物种差异性(图2和图3); 0 g· m^-2· yr^-1的N添加下, 随降水量增加牛枝子和猪毛蒿种群生物量以及群落生物量呈增加趋势, 草木樨状黄芪、糙隐子草、白草、阿尔泰狗娃花以及其他物种种群生物量呈先增加后降低的趋势, 针茅种群生物量无明显的变化规律; 5 g· m^-2· yr^-1的N添加下, 草木樨状黄芪和猪毛蒿种群生物量以及群落生物量呈增加趋势, 牛枝子、针茅、糙隐子草、白草、阿尔泰狗娃花以及其他物种种群生物量呈先增加后降低的趋势; 相同降水量处理间, N添加对群落生物量无显著影响, 但对种群生物量有所影响, 如降水量减少50%处理下N添加显著提高了草木樨状黄芪种群生物量, 降水量减少30%处理下N添加显著提高了白草种群生物量, 降水量增加50%处理下N添加显著降低了牛枝子和针茅种群生物量, 显著提高了猪毛蒿种群生物量。

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	图2 不同N添加处理下降水量对植物群落生物量的影响Fig.2 Effects of precipitation on plant community biomass under different N addition

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	图3 不同N添加处理下降水量对植物种群生物量的影响Fig.3 Effects of precipitation on plant population biomass under different N addition

降水量和N添加改变了植物群落多样性(图4): 0 g· m^-2· yr^-1的N添加下, 随降水量增加Patrick丰富度指数和Shannon-Wiener多样性指数均呈先增加后降低的趋势, Pielou均匀度指数呈逐渐降低的趋势, Simpson优势度指数无显著的变化规律; 5 g· m^-2· yr^-1的N添加下, 随降水量增加Simpson优势度指数逐渐升高, 其他3个指数则呈先增加后降低的趋势; 相同降水量处理间, N添加对4个多样性指数的影响较小。

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	图4 不同N添加处理下降水量对植物群落多样性的影响Fig.4 Effects of precipitation on plant community diversity under different N addition

2.3 土壤C∶ N∶ P生态化学计量特征及其他因子与植物群落组成的关系

在土壤因子与植物种群生物量的RDA结果中(图5), 两个典范轴累计方差解释率为75.07%。二者的对应关系存在物种差异性, 如牛枝子种群生物量与含水量、有机C、N∶ P、C∶ P以及C∶ N正相关, 与pH、N ${H_{4}}^{+}$ -N和N ${O_{3}}^{-}$ -N负相关; 草木樨状黄芪种群生物量与含水量、全N、有机C、N∶ P、C∶ P、有效P、全P以及C∶ N正相关, 与pH负相关; 猪毛蒿种群生物量与含水量、全N、有机C、N∶ P、C∶ P、有效P和C∶ N正相关, 与pH、N ${H_{4}}^{+}$ -N和N ${O_{3}}^{-}$ -N负相关。

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	图5 降水量和N添加下土壤因子与植物种群生物量的RDA分析Fig.5 RDA of soil factors and plant population biomass under precipitation and N addition

土壤因子与植物群落多样性指数的RDA结果显示(图6), 两个典范轴累计方差解释率为92.26%: Patrick丰富度指数与含水量、有机C、C∶ N、全N、pH和有效P正相关; Shannon-Wiener多样性指数与含水量、有机C、C∶ P、C∶ N、N∶ P、全N、pH和有效P正相关; Pielou均匀度指数与N ${O_{3}}^{-}$ -N、C∶ P、N∶ P和N ${H_{4}}^{+}$ -N正相关, 与含水量负相关; Simpson优势度指数与含水量和全P正相关, 与其他指标呈不同程度的负相关关系。

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	图6 降水量和N添加下土壤因子与植物群落多样性的RDA分析Fig.6 RDA of soil factors and plant community diversity under precipitation and N addition

3 讨论

3.1 土壤C∶ N∶ P生态化学计量特征对降水量和N添加的响应

降水量和N沉降调控着土壤有机质分解和养分迁移转化等过程, 从而会对土壤C∶ N∶ P生态化学计量关系产生影响, 且其影响程度与降水量、N沉降量、土壤水分以及N素饱和程度有关。本研究中, 降水量减少30%条件下N添加提高了土壤有机C和全N、降低了全P, 导致C∶ P和N∶ P升高, 表明土壤P受限性增强, 与以往研究结果相似^[22]。依据利比希最小因子定理, 5 g· m^-2· yr^-1N添加有助于缓解中度水分胁迫引起的生长限制, 从而刺激了植物对P的摄取, 导致土壤全P含量降低^[23]; 无N添加下, 增加30%和50%降水量降低了土壤全N和N∶ P, 可能是水分增多引起植物和微生物N消耗增加^[24]以及土壤中N淋溶损失增强^[25]等方面综合作用的结果, 且这种影响在过量增加降水量条件下尤为明显。5 g· m^-2· yr^-1的N添加缓解了植物N消耗以及土壤N淋溶损失引起的N含量降低(图1), 同时提高了土壤全P, 从而降低了C∶ P和N∶ P, 与周纪东等^[26]对内蒙古温带典型草原研究结果相似。土壤中P的来源主要为成土母质、植物地上凋落物以及地下部分P输入。由于本研究仅为短期试验结果, 因此还需要通过长期的观测深入揭示降水量及N添加交互作用对土壤P状况的影响机制。

Lp、Am、Sc、As、Pc、Cs和Ha分别代表牛枝子、草木樨状黄芪、针茅、猪毛蒿、白草、糙隐子草和阿尔泰狗娃花; SWC、SOC、TN、TP、C∶ N、C∶ P、N∶ P、AP、pH、N ${H_{4}}^{+}$ -N和N ${O_{3}}^{-}$ -N分别代表土壤含水量、土壤有机C、全N、全P、C∶ N、C∶ P、N∶ P、速效P、pH值、铵态氮和硝态氮。Lp, Am, Sc, As, Pc, Cs and Ha represent L. potaninill, A. melilotoides, S. capillata, A. scoparia, P. centrasiaticum, C. squarrosa and H. altaicus, respectively. SWC, SOC, TN, TP, C∶ N, C∶ P, N∶ P, AP, N ${H_{4}}^{+}$ -N and N ${O_{3}}^{-}$ -N represent soil water content, soil organic C, total N, total P, C∶ N, C∶ P, N∶ P, available P, pH value, ammonium nitrogen and nitrate nitrogen, respectively.

3.2 植物群落组成对降水量和N添加的响应

降水量和N有效性是荒漠草原植物生长的主要限制因子。适量增加降水量以及提高N有效性通过影响土壤水分和养分有效性, 间接调节着植物生长和群落组成^{[27, 28]}。由于不同植物对水分和N素的利用能力不同, 使得植物群落发生相应的变化^{[20, 29]}。本研究中, 自然生长状况下(N₀), 增加降水量提高了牛枝子、草木樨状黄芪、针茅、猪毛蒿以及白草种群生物量, 但过量增加降水量(降水量增加50%)显著抑制了其他物种生长。这表明降水量增加缓解了水分限制, 因此促进了多数植物生长、提高了群落多样性, 与以往研究结果相似^{[5, 30]}; 过量增加降水量时, 牛枝子和猪毛蒿等凭借其较强的生存能力开始大量繁殖, 与其他物种产生资源竞争关系^[31], 导致这些物种地上生物量积累降低。相同降水量条件下, N添加提高了草木樨状黄芪、糙隐子草、猪毛蒿和白草种群生物量, 表明少量N添加缓解了土壤N限制, 因此促进了多数植物生物量积累, 与潘庆民等^[32]和LeBaue 等^[33]针对荒漠草原的研究结果相似。以往研究发现N添加促进了植物群落优势种生长, 导致优胜劣汰现象的出现, 从而降低了植物群落多样性^{[10, 34, 35]}。本研究中, N添加对群落多样性影响较小, 意味着短期N添加较难改变荒漠草原植被群落组成。

研究表明, 降水在调控N添加促进植物生长等方面发挥着重要的介导作用^{[8, 10]}。因此在受降水和N有效性共同限制的荒漠草原, 降水量和N添加交互作用可能对多数植物生长具有正效应。本研究中, 与0 g· m^-2· yr^-1N添加水平相比较, 5 g· m^-2· yr^-1N添加下随降水量增加针茅、白草和猪毛蒿种群生物量均有不同程度的提高, 且降水量和N添加具有显著的交互作用, 表明增加降水量可以促进N肥效应的释放, 从而刺激了3个植物种的生长。相比之下, 二者对其他物种种群生物量以及3个群落多样性指数无显著的交互作用(表2和表3), 与针对青海高寒草原^[9]、内蒙古典型草原^[36]以及新疆荒漠草原^[37]的研究结果相似。其可能原因一方面在于, 相同降水量条件下N添加对牛枝子、针茅和阿尔泰狗娃花等物种生长表现出负效应, 降水量正效应与N添加负效应的相互抵消可能使得二者交互作用不明显。另一方面, 有研究发现降水量与N添加的交互作用具有一定的时滞性^[38], 因此短期降水量对N添加效应的促进作用未达到显著水平。

3.3 土壤C∶ N∶ P生态化学计量特征及其他因子与植物群落组成的关系

表层土壤C∶ N∶ P化学计量比反映了土壤有机C水平和养分供给状况^{[13, 16, 17]}, 因此, 一定程度上可以指示植物生长养分受限程度。随后的研究进一步证实, 土壤元素动态及其化学计量关系与植物群落组成密切相关。例如针对高寒草甸退化草地的研究发现, 土壤有机C、全N以及全P与植物群落生物量和多样性存在不同程度的正相关关系^{[39, 40]}。针对科尔沁沙地不同退化程度沙化草地的研究亦发现, 土壤全N和全P与植物群落多样性正相关, 且N∶ P能很好地反映养分平衡对多样性的影响作用^[18]。此外, 杨祥祥等^[19]发现沙地植物群落多样性随土壤C∶ N和N∶ P增加而增加。本研究中, 土壤含水量、全N、有机C和N∶ P与植物种群生物量存在较强的正相关关系, 含水量、有机C、C∶ P和C∶ N则与Patrick丰富度指数和Shannon-Wiener多样性指数关系较为密切(图5和图6), 证实土壤元素及其平衡关系影响着植被群落组成, 但短期降水量和N添加下含水量是植物群落组成发生改变的主要驱动因子, 与以往研究结果类似^[41]。此外, pH与牛枝子、猪毛蒿等植物种群生物量负相关, 与群落多样性指数关系较弱。这意味着pH在调控植物生长方面扮演中重要角色^{[42, 43]}, 但由于试验处理时间较短, 且研究区土壤呈弱碱性, 因此总体上对群落多样性影响较小。

4 结论

本研究发现, 增加降水量降低了土壤有机C、全N和N∶ P, N添加及其与降水量的交互作用对土壤C∶ N∶ P生态化学计量特征的影响较弱; 适量增加降水量刺激了多数植物生物量积累、提高了群落多样性。过量增加降水量导致猪毛蒿种群生物量急增, 且N添加对降水量效应有促进作用, 从而降低了群落多样性; 土壤含水量、全N、有机C和N∶ P与种群生物量存在较强的正相关关系, 土壤含水量、有机C、C∶ P和C∶ N与群落多样性存在较强的正相关关系。综合而言, 降水量提高了土壤水分有效性, 促进了土壤N和P的迁移和转化, 调节了土壤元素化学计量平衡关系, 从而刺激了多数植物生长、提高了群落多样性。由于本试验处理时间较短, N添加效应尚不明显。因此, 有必要通过长期的原位观测, 深入探讨N添加及其与降水量交互作用下土壤C∶ N∶ P平衡特征对荒漠草原植物群落组成的调控机制。

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[32]	Pan Q M, Bai Y F, Han X G, et al. *Effects of nitrogen additions on a Leymus chinensis* population typical steppe of Inner Mongolia*. Acta Phytoecologica Sinica, 2005, 29(2): 311-317. 潘庆民, 白永飞, 韩兴国, 等. 氮素对内蒙古典型草原羊草种群的影响*. 植物生态学报, 2005, 29(2): 311-317. [本文引用:1]
[33]	LeBauer D S, Treseder K K. Nitrogen limitation of net primary productivity in terrestrial ecosystems is globally distributed. Ecology, 2008, 89(2): 371-379. [本文引用:1]
[34]	Tang Z S, Deng L, An H, et al. The effect of nitrogen addition on community structure and productivity in grassland s: A meta-analysis. Ecological Engineering, 2017, 99: 31-38. [本文引用:1]
[35]	Yang Q, Wang W, Zeng H. Effects of nitrogen addition on plant community diversity and biomass of degraded grassland in Inner Mongolia. Chinese Journal of Plant Ecology, 2018, 42(4): 430-441. 杨倩, 王娓, 曾辉. 氮添加对内蒙古退化草地植物群落多样性和生物量的影响. 植物生态学报, 2018, 42(4): 430-441. [本文引用:1]
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[37]	Zhao X F, Xu H L, Zhang P, et al. Effects of nutrient and water additions on plant community structure and species diversity in desert grassland s. Chinese Journal of Plant Ecology, 2014, 38(2): 167-177. 赵新风, 徐海量, 张鹏, 等. 养分与水分添加对荒漠草地植物群落结构和物种多样性的影响. 植物生态学报, 2014, 38(2): 167-177. [本文引用:1]
[38]	Bai C L, *Alata, Chen H J, et al. Effects of addition of nitrogen and water on plant community characteristics of Stipa breviflora* desert steppe*. Chinese Journal of Grassland* , 2013, 35(2): 69-75. 白春利, 阿拉塔, 陈海军, 等. 氮素和水分添加对短花针茅荒漠草原植物群落特征的影响. 中国草地学报, 2013, 35(2): 69-75. [本文引用:1]
[39]	Zhao J X, Qu G P, Duo Ji D Z, et al. Relationship between species diversity and soil factors of alpine grassland s in north Tibet. Journal of Arid Land Resources and Environment, 2011, 25(6): 105-108. 赵景学, 曲广鹏, 多吉顿珠, 等. 藏北高寒植被群落物种多样性与土壤环境因子的关系. 干旱区资源与环境, 2011, 25(6): 105-108. [本文引用:1]
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[41]	Wang Z T, Yang L, Li G, et al. *Effects of alfalfa ( Medicago sativa* L. ) degradation on herbage distribution and diversity in the semi-arid Loess Plateau*. Acta Ecologica Sinica, 2019, 39(10). doi: 105846/stxb201805181099. 王子婷, 杨磊, 李广, 等. 半干旱黄土区苜蓿退化对坡面草本植物分布及多样性的影响*. 生态学报, 2019, 39(10). doi: 10.5846/stxb201805181099. [本文引用:1]
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2013

0.0

... 据报道, 全球总降水量在过去一个世纪有增加趋势, 但在干旱与半干旱地区减少, 干旱和洪涝等极端降水事件的频率呈明显增加趋势^[1] ...

2015

0.0

. 2015, 35(5):1359-1370 DOI:10.5846/stxb201305101013

Climate characteristics of precipitation and extreme drought events in Northwest China

中国西北地区降水量及极端干旱气候变化特征

Huang X Y , Li Y H , Feng J Y

黄小燕, 李耀辉, 冯建英

Based on the daily data observed at 111 meteorological stations in Northwest China from 1960 to 2011, the potential evaporation was calculated using the FAO Penman-Monteith model, and then the humid index was derived, as well as the extreme drought frequency. The temporal and spatial variations of the precipitation and extreme drought frequency were discussed in this paper. The results indicated that the precipitation in Northwest China has increased by 0.17 mm per year in the last 52 years. According to the spatial variation of precipitation, the study area could be divided into three subregions including obvious increasing, light increasing and decreasing. The mean extreme drought frequency was 3.8 months per year during 1960-2011, at a decreasing rate of 0.011 months per year. The variation of the extreme drought frequency also showed a spatial diversity and could be divided into three subregions including obvious decreasing, light decreasing and increasing. The extreme drought frequency showed a negative correlation with precipitation and average temperature, and a positive correlation with rainless days.

采用1960-2011年西北地区111个观测站逐日气象资料,利用FAO Penman-Monteith模型,计算出各气象站的潜在蒸散量,由此计算出各站的湿润指数,并对其进行标准化,统计极端干旱发生频率。对西北全区和不同自然区的降水量及极端干旱发生频率的时空变化特征进行了探讨分析。结果表明:近52年来西北全区年降水量变化倾向率表现出微弱的上升趋势,平均每年上升0.17 mm。由该区年降水量变化的空间差异,可将研究区划分为3个部分:明显增加区、轻度增加区、减少区。西北全区极端干旱发生频率的平均值为3.8 月/a,气候变化倾向率总体上表现出明显的下降趋势,平均每年下降0.011 月。根据西北地区极端干旱发生频率变化的空间差异,也可将研究区划分为3个部分:明显减少区、轻度减少区、增加区。极端干旱发生频率与降水量和平均气温表现为显著的负相关性,与无雨总日数呈现出显著的正相关性。

... 如与1961-1980年相比, 1981-2010年间我国西北地区降水量总体上呈增加趋势, 但其东部区(如宁夏和陕西部分区域)年降水量呈降低趋势^[2] ...

2014

0.0

... 近年来随着大气污染物控制措施的实施, N沉降速率在发达国家有所下降, 但在发展中国家仍呈上升趋势^[3] ...

2016

0.0

. 2016, 36(12):3591-3600 DOI:10.5846/stxb201409211868

Modeling the temporal-spatial patterns of atmospheric nitrogen deposition in China during 1961-2010

1961-2010年中国区域氮沉降时空格局模拟研究

Gu F X , Huang M , Zhang Y D

顾峰雪, 黄玫, 张远东

Anthropogenic activities have altered the global nitrogen cycle, which has led to increases of nitrogen input into ecosystems through N deposition. China has become the third largest N deposition region. Excess N input can have negative impacts on ecosystem health via processes such as soil acidification, losses of biodiversity, and changes in the carbon cycle. Meanwhile, nitrogen input is an important factor linked to terrestrial carbon sinks. Specifically, such input is connected with a number of biogeochemical cycles that can influence the carbon cycle and its spatial pattern. Because of these wide-ranging effects, atmospheric N deposition rates have attracted much concern, and several studies have attempted to reveal the spatial and temporal patterns of N deposition with the purpose of evaluating N deposition effects on the carbon cycle of terrestrial ecosystems. We have established a new mathematical model that can be used to estimate regional N deposition over long time periods based on data related to precipitation, energy consumption, and fertilizer use. Comparisons between simulations and observations showed that the model can simulate the spatial and temporal variations of N deposition reasonably well. Then, we estimated the N deposition in China during 1961-2010 based on this model. The results were as follows. (1) During 1961-2010, the average total nitrogen deposition in China was 0.81 g N m -2 a -1 , and the deposition values increased from 0.31 g N m -2 a -1 in the 1961-1970 to 1.71 g N m -2 a -1 in the 2001-2010; the total N deposition increased from 2.85 Tg N/a to 15.68 Tg N/a. (2) The NH x -N deposition rate was about 4 times that of NO y -N, and NH x -N was the main deposition type. The wet deposition rate was 3.63 times that of the dry deposition during 1961-2010; thus, wet deposition represents a main pathway for N input into ecosystems in the region. (3) In terms of spatial distribution patterns, the N deposition decreased from southeastern to northwestern China. The north, central, and cropland areas of the northeast had the largest overall N deposition rates and the largest increases in the N deposition rates over time.

由于人类活动的干扰,近年来,通过沉降和施肥形式进入陆地生态系统的氮素持续增加,众多研究表明,中国已经成为继欧洲和北美之后的第三大氮沉降区。氮与陆地生态系统生物地球化学循环的一系列过程都相互联系,碳循环及其格局也受到氮的影响,因此大气氮沉降的变化受到广泛关注,探明区域大气氮沉降的时空格局对评估氮沉降对陆地生态系统碳循环的影响具有重要意义。构建了一个基于降水、能源消费和施肥数据的氮沉降时空格局模拟方法,通过与观测数据的比较说明该模拟方法能够较好地模拟氮沉降的时空变化,在此基础上,利用该方法模拟了1961-2010年中国区域氮沉降的时空格局。结果表明:(1)1961-2010年中国区域年平均氮沉降速率为0.81 g N m -2 a -1 ,由20世纪60年代的0.31 g N m -2 a -1 增加到21世纪初的1.71 g N m -2 a -1 ,年增长率为0.04 g N m -2 a -1 。总氮沉降量由20世纪60年代的2.85 TgN/a增加至15.68 TgN/a。(2)NH x -N的沉降速率大约是NO y -N的4倍,是主要的氮沉降形式。1961-2010年我国湿沉降平均速率为0.63 g N m -2 a -1 ,是干沉降速率(0.17 g N m -2 a -1 )的3.63倍,是氮素进入陆地生态系统的重要途径。(3)在空间上,我国的大气氮沉降速率呈现出由东南向西北梯度递减的格局,华北、华中和东北的农田是氮沉降速率最大的区域,同时也是氮沉降速率增长最快的区域。

... 就我国而言, 虽然南方等地区N沉降速率有所减缓, 但西北地区N沉降速率加快^[4] ...

... N肥施用量以2011-2013年设立的N添加原位试验的观察结果为主要依据^[20], 同时参考了区域大气N沉降水平^[4] ...

2010

0.0

... 降水量和N沉降调控着土壤水分和N有效性, 影响着植物资源利用策略, 从而会直接影响到植被群落结构^[5,6] ...

... 这表明降水量增加缓解了水分限制, 因此促进了多数植物生长、提高了群落多样性, 与以往研究结果相似^[5,30] ...

2016

0.0

. 2016, 24(2):192-200

Responses of plant biomass and net primary production to nitrogen fertilization and increased precipitation in re-grassed croplands in Duolun County of Inner Mongolia, China. Chinese Journal of

水氮添加对内蒙古多伦县退耕还草地生物量、生产力及其分配的影响

Zhang J F , Xu Y Q

张金凤, 徐雨晴

Biomass and NPP (net primary productivity) are the primary data which describe the structure and function of ecosystems. The allocations of biomass and NPP are related to nutrient, water use efficiencies and the ability to resist erosion of ecosystems. Excessive farming has intensified wind-erosion desertification in northern China, which has not only affected local economic development and ecological conditions, but also posed threat to the ecological state of the inland areas. Re-grassing abandoned croplands has been a common measure to prevent wind-erosion-caused desertification in the agro-pastoral ecotone of northern China. Grassland vegetation is very sensitive to nitrogen and water in arid and semiarid areas, but is unclear whether and how nitrogen (N) fertilization and increased precipitation affect the restoration of vegetation in re-grassed croplands. The responses of biomass and NPP to N fertilization [N10: 10 g(N).m -2 .a -1 ] and irrigation ( irrigation amount was 180 mm to simulate 50% increase in precipitation ) were investigated in a re-grassed abandoned cropland in Duolun County of Inner Mongolia, China. The results showed that fertilization increased the aboveground biomass of re-grassed croplands by nearly 100% while irrigation increased aboveground biomass by only 17%–37%. Either fertilization or irrigation had no significant effect on belowground biomass in re-grassed croplands ( P > 0.05) while irrigation enhanced belowground NPP (BNPP) by 35%–90%. Fertilization reduced root-to-shoot ratio (R︰S) and ratio of BNPP to aboveground NPP (ANPP) in re-grassed cropland but increased precipitation had no significant effect on the two indicators ( P > 0.05). The dominant species (Agropyron mongolicum and Artemisia scoparia) had significant positive responses to fertilization, respectively with 130% and 70% increase in biomass in the second year. However, fertilization had no significant effect on biomass of forbs ( P > 0.05). Asymmetric competition for fertilizer among plant species increased the proportion of perennial grass and decreased the proportion of forbs in vegetation community of re-grassed cropland. In contrast, forbs were very sensitive to irrigation, with 128% increase in biomass in the second year of treatments. Increased precipitation enhanced the proportion of forbs in the community by 13%. A. mongolicum and A. scoparia biomass was not affected by increased summer precipitation. Belowground biomass, BNPP, total NPP (TNPP) and R︰S ratio of treated or untreated re-grassed croplands were much lower than those of fenced grassland. The results indicated that fertilization significantly increased aboveground biomass and changed the proportions of biomass and NPP in re-grassed farmlands. The results also suggested that increased precipitation hastened vegetation restoration in abandoned croplands. This strongly depended on functional types of dominant species due to the distinct sensitivity of plant species to increased precipitation.

以内蒙古多伦县退耕还草地为研究对象, 调查了施肥[N10:10 g(N)m -2 a -1 ]和加水(180 mma -1 )对其植被生物量、生产力和分配方式的影响, 并与围封草地作比较。结果发现: 1)施肥使退耕还草地地上生物量增加近1倍; 加水使退耕还草地地上生物量提高17%~37%, 但未达到统计显著性; 2)无论施肥还是加水都没有显著影响退耕还草地地下生物量, 加水使其地下净初级生产力(BNPP)提高35%~90%; 3)施肥降低了退耕还草地根冠比和地下、地上净初级生产力比(BNPP/ANPP), 而降水增加对两个指标无显著影响; 4)施肥使退耕还草地禾草类植物比例增加, 生物量均匀度降低; 加水处理后, 退耕还草地的杂类草生物量提高128%, 而优势种猪毛蒿( Artemisia scoparia )和蒙古冰草( Agropyron mongolicum )的地上生物量对加水处理不敏感; 5)水肥处理后, 退耕还草地总生产力、根冠比和生物量远小于围封草地。表明水氮添加对退耕还草地生物量的影响主要在地上部分, 且与物种组成有关。

... 降水量和N沉降调控着土壤水分和N有效性, 影响着植物资源利用策略, 从而会直接影响到植被群落结构^[5,6] ...

2009

0.0

... 草原生态系统功能的正常发挥对维持区域性及全球生态平衡起着极为重要的作用^[7] ...

2012

0.0

... 降水量和N有效性是草原生态系统植物生长的主要限制因子, 且降水量在介导N沉降效应方面发挥着重要作用^[8], 因此已有国内学者研究了二者交互作用对草原生态系统植物群落多样性的影响, 如针对青海高寒草原、内蒙古草甸草原、内蒙古典型草原的研究^[9,10,11] ...

... 研究表明, 降水在调控N添加促进植物生长等方面发挥着重要的介导作用^[8,10] ...

2016

0.0

... 相比之下, 二者对其他物种种群生物量以及3个群落多样性指数无显著的交互作用(表2和表3), 与针对青海高寒草原^[9]、内蒙古典型草原^[36]以及新疆荒漠草原^[37]的研究结果相似 ...

2015

0.0

. 2015, 35(19):6460-6469 DOI:10.5846/stxb201403180471

Effects of nitrogen and water addition on plant species diversity and biomass of common species in the Stipa baicalensis Steppe, Inner Mongolia, China

氮素和水分添加对贝加尔针茅草原植物多样性及生物量的影响

Li W J , Liu H M , Zhao J N

李文娇, 刘红梅, 赵建宁

Increases in atmospheric nitrogen deposition and changes in precipitation patterns are important phenomena related to changes in the global environment. These changes have created a series of increasingly serious ecological problems affecting the structure and function of grassland ecosystems. Therefore, grasslands have become a focus of ecological research in China and around the world in recent years. High nitrogen deposition can acidify grassland soils and lead to nutritional imbalances, decreases in biodiversity and productivity, and grassland degradation, all of which are serious threats to the function of grassland ecosystems. Precipitation can increase the efficiency of nitrogen fertilizer used by plants, and climate warming is accompanied by changes in precipitation. Studies of the interactive effects of nitrogen deposition and variation in rainfall on natural grassland ecosystems can help to increase our understanding of the responses of such ecosystems to changes in the global climate. In China, the Stipa baicalensis steppe, a type of meadow steppe, is mainly distributed in the forest steppe zone of the Songliao Plain and the east Inner Mongolian Plateau. In Inner Mongolia, farmers mainly use S. baicalensis steppe as natural pasture;therefore, it has an important role in livestock production. The aim of this study was to evaluate the responses of grassland plant community species diversity and the aboveground biomass of several common plant species to nitrogen deposition and irrigation.We set up a factorial experiment to test the interactive effects of eight nitrogen treatments and water addition in S. baicalensis steppe in Inner Mongolia in June 2010. This involved nitrogen (NH 4 NO 3 ) application levels of 0 (the control treatment, CK), 15, 30, 50, 100, 150, 200, 300 kg N hm -2 a -1 (referred to as N0, N15, N30, N50, N100, N150, N200, N300, respectively) and simulated 100 mm summer rainfall. In mid-August 2013, we established 96 1 m×1 m sample plots. The vegetation was harvested from each plot and the biomass of each species was measured to determine the effects of nitrogen and water addition on species diversity and the aboveground biomass of several common plants. Nitrogen and water application reduced plant species diversity in the steppe community, and there was a significant interaction effect between nitrogen and moisture. When water was added, increasing nitrogen application levels resulted in decreases in plant species richness, Shannon-Wiener index, and Pielou evenness index. When water was not added, increasing nitrogen application levels resulted in changes in species richness, Shannon-Wiener index, and Pielou evenness index that showed a "single-peak", but overall downward trend. Plant species differed in their responses to nitrogen and water addition. With increasing nitrogen application levels, the aboveground biomass of Leymus chinensis increased significantly, reaching a maximum at N300;the aboveground biomass of S. baicalensis , Achnatherum sibiricum , Cleistogenes squarrosa , Carex duriuscula, and Artemisia frigida first increased and then decreased, showing a "single-peak" trend;and the aboveground biomass of Potentilla acaulis , Thermopsis lanceolata , Melilotoides ruthenica , and Filifolium sibiricum decreased gradually. There was a significant interaction effect between water and nitrogen application level on the biomass of S. baicalensis , A. sibiricum, and M. ruthenica . We concluded that the changes in plant species diversity and aboveground biomass were related to nutrient application levels, water availability, their own characteristics, and interspecific and intraspecific competition.

为了解草原植物群落物种多样性和植物地上生物量对氮沉降增加和降水变化的响应,在内蒙古贝加尔针茅( Stipa baicalensis )草原,分别设置对照(N0)、1.5 g/m 2 (N15)、3.0 g/m 2 (N30)、5.0 g/m 2 (N50)、10.0 g/m 2 (N100)、15.0 g/m 2 (N150)、20.0 g/m 2 (N200)和30.0 g/m 2 (N300)(不包括大气沉降的氮量)8个氮素(NH 4 NO 3 )添加梯度和模拟夏季增加降水100mm的水分添加交互试验,研究氮素和水分添加对草原群落植物物种多样性和几种常见植物地上生物量的影响。结果表明:(1)氮素和水分的添加降低了草原群落植物物种多样性,且氮素和水分有显著的互作效应。在水分添加的条件下,随着施氮水平的增加,群落植物物种多样性减小;在无水分添加的条件下,随着施氮水平的增加,群落植物物种多样性呈先增加后减小的"单峰"变化趋势。(2)不同植物对氮素和水分添加的响应不同,随着施氮水平的增加,羊草地上生物量显著增加;贝加尔针茅、羽茅、糙隐子草、寸草苔和冷蒿先增加后减少,呈单峰曲线;星毛委陵菜、牧马豆、扁蓄豆和线叶菊地上生物量则逐渐减少。而且氮素和水分对贝加尔针茅、羽茅、扁蓄豆地上生物量有显著的交互作用。

... 以往研究发现N添加促进了植物群落优势种生长, 导致优胜劣汰现象的出现, 从而降低了植物群落多样性^[10,34,35] ...

... 研究表明, 降水在调控N添加促进植物生长等方面发挥着重要的介导作用^[8,10] ...

2018

0.0

... 降水增减量以近几十年来我国西北地区西部降水量增加而东部减少的趋势为主要依据, 同时参考了国内同类研究方法^[11] ...

2002

0.0

... 区域干旱少雨且N沉降临界负荷低^[12], 因此对降水格局改变和N沉降增加较为敏感 ...

2008

0.0

. 2008, 28(8):3937-3947

Ecological stoichiometry characteristics of ecosystem carbon, nitrogen and phosphorus elements

生态系统碳氮磷元素的生态化学计量学特征

Wang S Q , Yu G R

王绍强, 于贵瑞

Ecosystem element balance has been a main focus of global change ecology and biogeochemical cycle research. This paper first introduces progresses in ecological stoichiometry and carbon, nitrogen and phosphorus cycles. Then application of C∶N∶P stoichiometry in nutrient limitation, biogeochemical cycle, forest succession and degraded land is reviewed, especially in the fields of distribution characteristics, indication role, effect on carbon sequestration and human activity influence on soil C∶N∶P ratio. We also discuss future research directions in ecological stoichiometry. The development of ecological stoichiometry theory and research method can help us better understand nutrient controlling factors of plant-litter-soil interaction. It is more important to reveal interaction among carbon, nitrogen and phosphorus in order to provide insight and theoretial foundation for alleviation of greenhouse effects.

生态系统元素平衡是当前全球变化生态学和生物地球化学循环的研究热点和焦点。在系统介绍生态化学计量学与碳氮磷元素循环研究进展的基础上，重点从土壤C∶N∶P化学计量比的分布特征、指示作用、对碳固定的影响，以及人类活动对C∶N∶P比的影响等方面探讨了C∶N∶P比在养分限制、生物地球化学循环、森林演替与退化等领域中的应用等问题，并展望了生态系统碳氮磷平衡的元素化学计量学未来研究的发展方向。通过对生态化学计量学理论和方法的研究，可以深入认识植物-凋落物-土壤相互作用的养分调控因素，对于揭示碳氮磷元素之间的相互作用及平衡制约关系，为减缓温室效应提供新思路和理论依据，具有重要的现实意义。

... P化学计量比是反映土壤内部3种元素循环的主要指标, 综合了生态系统功能的变异性, 因此有助于确定生态系统过程对全球变化的响应^[13] ...

... P化学计量比反映了土壤有机C水平和养分供给状况^[13,16,17], 因此, 一定程度上可以指示植物生长养分受限程度 ...

2013

0.0

... P平衡关系趋于解耦^[14,15] ...

2014

0.0

... P平衡关系趋于解耦^[14,15] ...

2010

0.0

... P化学计量比可以较好地反映土壤有机C水平和养分供给状况^[16,17], 而二者又直接影响着植物的生长发育, 因此趋于解耦的元素平衡关系可能会直接作用于植物群落组成 ...

... P化学计量比反映了土壤有机C水平和养分供给状况^[13,16,17], 因此, 一定程度上可以指示植物生长养分受限程度 ...

2012

0.0

... P化学计量比反映了土壤有机C水平和养分供给状况^[13,16,17], 因此, 一定程度上可以指示植物生长养分受限程度 ...

2019

0.0

... P生态化学计量特征与植物群落组成的关系^[18,19], 尚未见降水量和N添加下针对宁夏荒漠草原的相关报道 ...

... P能很好地反映养分平衡对多样性的影响作用^[18] ...

2019

0.0

... P生态化学计量特征与植物群落组成的关系^[18,19], 尚未见降水量和N添加下针对宁夏荒漠草原的相关报道 ...

... 此外, 杨祥祥等^[19]发现沙地植物群落多样性随土壤C#cod#x02236 ...

2016

0.0

... N肥施用量以2011-2013年设立的N添加原位试验的观察结果为主要依据^[20], 同时参考了区域大气N沉降水平^[4] ...

... 由于不同植物对水分和N素的利用能力不同, 使得植物群落发生相应的变化^[20,29] ...

2002

0.0

... 采用连续流动分析仪(Auto Analyzer 3, SEAL Analytical GmbH, Hanau, Germany)测定N H4+-N和N O3--N^[21] ...

2013

0.0

... P升高, 表明土壤P受限性增强, 与以往研究结果相似^[22] ...

2018

0.0

... yr^-1N添加有助于缓解中度水分胁迫引起的生长限制, 从而刺激了植物对P的摄取, 导致土壤全P含量降低^[23] ...

2011

0.0

... P, 可能是水分增多引起植物和微生物N消耗增加^[24]以及土壤中N淋溶损失增强^[25]等方面综合作用的结果, 且这种影响在过量增加降水量条件下尤为明显 ...

2009

0.0

2016

0.0

. 2016, 27(8):2467-2476

Effects of the frequency and intensity of nitrogen addition on soil pH, the contents of carbon, nitrogen and phosphorus in temperate steppe in Inner Mongolia, China

施氮频率和强度对内蒙古温带草原土壤pH及碳、氮、磷含量的影响

Zhou J D , Shi R J , Zhao F

周纪东, 史荣久, 赵峰

( 1 Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China;  2 University of Chinese Academy of Sciences, Beijing 100049, China).

A four-year simulated nitrogen (N) deposition experiment involving nine N gradients and two N deposition frequencies (N was added either twice yearly or monthly) was conducted in Inner Mongolian grassland, to examine the effects of frequency and intensity of N addition on pH and the contents of carbon, nitrogen and phosphorus in soil. The results indicated that the soil pH and total phosphorus content, regardless of the N addition frequency, gradually decreased with the increase of N addition intensity. By contrast, the contents of soil available nitrogen and available phosphorus showed an increasing trend, while no significant variation in dissolved organic carbon (DOC) content was observed, and the contents of soil total carbon and total nitrogen had no change. Compared with the monthly N addition, the twiceayear N addition substantially overestimated the effects of N deposition on decreasing the soil pH and increasing the available phosphorus content, but underestimated the effects of N deposition on increasing the soil available nitrogen content, and the significant difference was found in 0-5 cm soil layer.

以内蒙古温带典型草原为研究对象，通过 9 个氮沉降梯度以及一年 12 次和一年 2 次的施氮频率比对，经过4年的氮沉降模拟，研究不同氮沉降强度和频率对不同土层土壤 pH 及碳、氮、磷含量的影响.结果表明：随着施氮强度的增加，土壤 pH 及全磷含量逐渐降低，但土壤有效氮和有效磷的含量呈增加趋势，可溶性有机碳(DOC)含量无明显变化规律，而土壤全碳、全氮含量基本保持不变.与更接近于自然氮沉降状况的一年 12 次施氮相比，一年 2 次施氮明显高估了氮沉降在降低土壤 pH和增加有效磷含量上的作用，低估了氮沉降在增加土壤有效氮含量上的作用，其中0～5 cm土层差异显著.

... P, 与周纪东等^[26]对内蒙古温带典型草原研究结果相似 ...

2008

0.0

... 适量增加降水量以及提高N有效性通过影响土壤水分和养分有效性, 间接调节着植物生长和群落组成^[27,28] ...

2008

0.0

... 适量增加降水量以及提高N有效性通过影响土壤水分和养分有效性, 间接调节着植物生长和群落组成^[27,28] ...

2012

0.0

... 由于不同植物对水分和N素的利用能力不同, 使得植物群落发生相应的变化^[20,29] ...

2012

0.0

... 这表明降水量增加缓解了水分限制, 因此促进了多数植物生长、提高了群落多样性, 与以往研究结果相似^[5,30] ...

2005

0.0

. 2005, 13(4):328-333

Studies on the vegetation succession of abandoned farmland in the loess hilly region of northern Shaanxi-succession series after being abandoned

陕北黄土丘陵区撂荒演替研究-撂荒演替序列

Du F , Shan L , Chen X Y

杜峰, 山仑, 陈小燕

Institute of Soil and Water Conservation, Chinese Academy of Science;State Key Laboratoryof Soil Erosion and Dryland Farming on the Loess Plateau;Northwest Sci-techUniversity of Agriculture and Forestry, Yangling, Shaanxi Province, 712100, China

Using system clustering to divide the secondary successive of the abandoned farmland in the loess hilly regions of northern Shaanxi province,the similarity of lengths of years and standing conditions of the abandoned farmlands were discerned.Combining the above discernment with the quantitative ordination of DCA,the abandoned farmland successive phases and series were affirmed.The successive phases are as follows: annual weeds Artemisia scoparia+other annual weeds association→annual weeds A.scoparia assocaiation→annual weeds A.scoparia Waldstet kit+perennial herbage or undershrub assocaiation→rhizoma grass Agropyron cristatum (L.)association→perennial herbage or tuft grass+annual weeds association→perennial herbage association→undershrub Lespedeza davurica association→perennial herbage + undershrub or thick tuft grass association→short rhizome and thick tuft grass association.

用系统聚类法划分陕北黄土丘陵区撂荒地的次生演替阶段,可以定量的认识不同年限、立地条件下撂荒地群落的相似性,结合DCA数量排序确定撂荒地的演替阶段或序列。其撂荒演替的各阶段分别为:一年生杂类草猪毛蒿( Artemisia scoparia )+其它杂类草群丛→一年生杂类草猪毛蒿群丛→一年生杂类草猪毛蒿+多年生草种或小灌木的共优群丛→根茎禾草冰草( Agropyron cristatum )群丛→多年生草本或丛生禾草+一年生杂类草群丛→多年生草本群丛→小灌木达乌里胡枝子( Lespedeza davurica )群丛→多年生草本+小灌木或密丛型禾草群丛→短根茎密丛型禾草白羊草( Bothriochloa ischaemum )群丛。

... 过量增加降水量时, 牛枝子和猪毛蒿等凭借其较强的生存能力开始大量繁殖, 与其他物种产生资源竞争关系^[31], 导致这些物种地上生物量积累降低 ...

2005

0.0

. 2005, 29(2):311-317

Effects of nitrogen additions on a Leymus chinensis population typical steppe of Inner Mongolia

氮素对内蒙古典型草原羊草种群的影响

Pan Q M , Bai Y F , Han X G

潘庆民, 白永飞, 韩兴国

(Inner Mongolia Grassland Ecosystem Research Station, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China)

Leymus chinensis, a rhizomatous graminoid, is a dominant species in the grasslands of northern China. The characteristics of L. chinensis populations have been well documented in many research papers. Because of overgrazing, grasslands of northern China have become degraded since the 1980s. As a result, the density and biomass of L. chinensis populations have decreased significantly. Fertilization is a common technique for management of pastures in many countries; however, it is not widely used in the grasslands of China. Nitrogen is an important driver of community succession in grassland ecosystems, but the response of L. chinensis populations to nitrogen additions in typical steppe, a semiarid area of northern China, remains unclear. We conducted a sequential nitrogen addition experiment in a lightly degraded grassland plot that was fenced in 1999. Nitrogen (NH4NO3) was applied on July 5 for two years at application rates of: 0, 1.75, 5.25, 10.5, 17.5, and 28 g N·m-2,respectively. There were 9 replicate 5 m×5 m plots of each of the six treatments with each plot spaced 1 m apart. A completely randomized design was used for this experiment. Before the experiment, soil samples were collected and dry bulk density, pH, soil nitrogen and soil carbon were analyzed. After two years of nitrogen fertilization, we measured the density, height, aboveground biomass and belowground biomass of L. chinensis in each plot. The results showed that L. chinensis population characteristics were highly responsive to nitrogen additions. With an increase in nitrogen application rates, the density, height, aboveground biomass, belowground biomass and total biomass of L. chinensis increased significantly whereas the ratio of aboveground biomass/belowground biomass decreased. The allocation of biomass among plant parts was significantly affected by nitrogen additions: the proportion of biomass allocated to rhizomes decreased remarkably with increasing nitrogen rates whereas that allocated to leaves and roots increased significantly. The relative biomass and relative density of L. chinensis also increased with increasing nitrogen additions. In summary, adding nitrogen to lightly degraded grassland not only increased the density and biomass of L. chinensis population but changed the resource partitioning among plant parts as well.

为了研究氮素对内蒙古典型草原植物种群的影响，在中国科学院内蒙古草原生态系统定位研究站，实施了长期的氮素添加试验。就两年来不同梯度氮素处理对羊草(Leymus chinensis)种群的影响进行了分析。结果表明，氮素对羊草种群具有显著的调节效应，随着氮素梯度的增加，羊草种群密度、种群高度、地上生物量、地下生物量、总生物量均显著增加，羊草种群地下生物量／地上生物量比值逐渐降低。氮素对羊草种群构件的生物量分配有显著影响，随着氮素梯度的增加，羊草种群生物量向根茎的分配比例显著降低，向叶片和根系的分配比例显著提高。羊草种群的相对密度和相对生物量也随着氮素梯度的增加而显著提高。

... 相同降水量条件下, N添加提高了草木樨状黄芪、糙隐子草、猪毛蒿和白草种群生物量, 表明少量N添加缓解了土壤N限制, 因此促进了多数植物生物量积累, 与潘庆民等^[32]和LeBaue 等^[33]针对荒漠草原的研究结果相似 ...

2008

0.0

2017

0.0

... 以往研究发现N添加促进了植物群落优势种生长, 导致优胜劣汰现象的出现, 从而降低了植物群落多样性^[10,34,35] ...

2018

0.0

... 以往研究发现N添加促进了植物群落优势种生长, 导致优胜劣汰现象的出现, 从而降低了植物群落多样性^[10,34,35] ...

2012

0.0

2014

0.0

. 2014, 38(2):167-177 DOI:10.3724/SP.J.1258.2014.00015

Effects of nutrient and water additions on plant community structure and species diversity in desert grasslands

养分与水分添加对荒漠草地植物群落结构和物种多样性的影响

Zhao X F , Xu H L , Zhang P

赵新风, 徐海量, 张鹏

1 Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Ürümqi 830011, China; 2 Water Balancing Test Station of Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Aral, Xinjiang 843300, China; 3 School of Geographical Science and Tourism, Xinjiang Normal University, Ürümqi 830054, China; 4 College of Grassland and Environment Sciences, Xinjiang Agricultural University, Ürümqi 830052, China

Aims Better understanding the response of community structure and species diversity to nutrient and water enrichment is critical for desert grassland in arid areas. Nitrogen, phosphorus and potassium are the three elements necessary for plant production, and water promotes plant absorption of nutrients. Our objective was to analyze the effects of nutrient and water addition on community structure and species diversity in typical desert grassland in northwestern China. Methods Field experiments were conducted in Gubantunggut Desert grassland from 2009 to 2012. Nutrient and water additions were done on May 15, 2009–2011, and vegetation investigation was conducted on May 25, 2009–2012. The responses of community structure and species diversity of plants to nutrient, rainfall and snow additions were studied. Important findings After the nutrient and water additions, the number of species decreased by 35.3%, the number of species in Poaceae family increased and species in Cruciferae family decreased. In 2009 and 2010, none of the three treatments (nutrient addition, water addition and the coupling effect of nutrient and water) significantly influenced species richness, Simpson index, Shannon-Wiener index or Pielou evenness index. In 2012, nutrient addition had a significant effect on species richness ( p

为进一步了解养分添加和水分添加对干旱区草地植物多样性的影响, 2009–2011年5月15日, 对准噶尔盆地荒漠草地进行养分和水分添加, 2009–2012年5月25日进行植被调查, 研究群落结构与植物多样性对养分N、P、K与水分(雨、雪)添加的响应, 得出以下结果: (1)添加肥、水后, 荒漠草地植物群落结构发生了变化, 物种数由肥、水添加前的17种减少到添加后的11种, 减少了35.3%, 禾草类植物数目增加, 十字花科植物数量下降; (2)通过裂区试验方差分析, 2009年和2010年, 养分主效应对物种丰富度、Simpson指数、Shannon-Wiener指数、Pielou均匀度指数的影响不显著, 水分主效应和肥水交互作用对以上4个植物多样性指数的影响也不显著; (3) 2012年, 养分主效应对物种丰富度影响显著( p p

2013

0.0

... 另一方面, 有研究发现降水量与N添加的交互作用具有一定的时滞性^[38], 因此短期降水量对N添加效应的促进作用未达到显著水平 ...

2011

0.0

... 例如针对高寒草甸退化草地的研究发现, 土壤有机C、全N以及全P与植物群落生物量和多样性存在不同程度的正相关关系^[39,40] ...

2014

0.0

. 2014, 36(5):1298-1305 DOI:10.7522/j.issn.1000-0240.2014.0155

Species diversity and biomass in relation to soil properties of alpine meadows in the eastern Tibetan Plateau in different degradation stages

青藏高原东缘高寒草甸退化过程中植物群落多样性、生产力与土壤特性的关系

Luo Y Y , Meng Q T , Zhang J H

罗亚勇, 孟庆涛, 张静辉

1. Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China; 2. Research Institute of Ecology Environment of Inner Mongolia Coal Mine, Hohhot 010020, China

To clarify the changes of species diversity and biomass in relation to soil properties of alpine meadows in different degradation stages, mild degraded meadow, moderate degraded meadow, severe degraded meadow and serious sandy meadow were chosen to measure species diversity, biomass and soil properties. The changes of vegetation and soil properties, followed by degraded process of alpine meadow, show the following trends: 1) vegetation diversity and biomass decrease gradually; 2) contents of soil moisture, soil clay, silt, soil organic carbon, total nitrogen (N), total phosphorous (P), available N and available potassium (K) decrease consistently, while content of soil sand and total K as well as pH value increase consistently. The correlation between species diversity or biomass and soil factors such as soil moisture, soil clay, silt, soil organic carbon, total N, total N, available N, available P and available K is significant positive, while the correlation between species diversity or biomass and soil factors such as content of soil sand and total K as well as pH value is significant negative. Therefore, changes of species diversity and biomass are governed by soil texture, soil nutrients, soil water content, pH and electrical conductivity.

为了阐明高寒草甸退化过程中植物群落物种多样性、生产力与土壤特性的关系, 在青藏高原东缘的玛曲县沿着高寒草甸退化梯度选取了轻度退化草甸、中度退化草甸、重度退化草甸和沙化草甸, 测定了高寒草甸退化过程中植物群落物种多样性、生产力与土壤理化性状. 结果表明: 从轻度退化到中度、重度和沙化草甸, 植被地下生物量分别降低了36%、48%和91%, 总生物量分别降低了34%、47%和91%, 土壤有机碳分别下降了18%、81%和97%, 全N分别下降了25%、82%和95%, 全P含量分别下降了14%、33%和41%. 随着高寒草甸的退化, 植被群落的生物多样性和地上生物量呈先稳定后降低的趋势, 土壤砂粒含量、pH值和全K含量呈增加趋势, 黏粉粒呈降低趋势, 速效N、速效P和速效K呈先增加后降低的趋势. 相关分析表明, 群落物种多样性和生产力与土壤有机碳、全N、全P、速效N、速效P、速效K、黏粒含量、粉粒含量、水分含量均呈显著正相关( P P <0.05). 因此, 高寒草甸退化过程中, 土壤质地、养分和水分等的复杂变化及其相互关系共同决定着高寒草甸群落物种多样性和生产力的变化. 同时, 植被生产力和土壤碳、氮的降低产生明显的正反馈效应, 导致在重度退化阶段和沙化阶段, 植被生产力和土壤碳氮的急剧下降.

... 例如针对高寒草甸退化草地的研究发现, 土壤有机C、全N以及全P与植物群落生物量和多样性存在不同程度的正相关关系^[39,40] ...

2019

0.0

... N则与Patrick丰富度指数和Shannon-Wiener多样性指数关系较为密切(图5和图6), 证实土壤元素及其平衡关系影响着植被群落组成, 但短期降水量和N添加下含水量是植物群落组成发生改变的主要驱动因子, 与以往研究结果类似^[41] ...

2019

0.0

... 这意味着pH在调控植物生长方面扮演中重要角色^[42,43], 但由于试验处理时间较短, 且研究区土壤呈弱碱性, 因此总体上对群落多样性影响较小 ...

2019

0.0

... 这意味着pH在调控植物生长方面扮演中重要角色^[42,43], 但由于试验处理时间较短, 且研究区土壤呈弱碱性, 因此总体上对群落多样性影响较小 ...