沙地樟子松人工林叶凋落物的分解与养分释放

凋落物的分解和养分释放是森林生态系统养分循环的关键过程，但樟子松人工固沙林叶凋落物的分解和养分释放机理仍不清楚。文中以辽宁省章古台地区的樟子松叶凋落物为研究对象，选择标准地收集叶凋落物，采用原位分解法研究樟子松叶凋落物的分解和养分释放。结果表明：樟子松叶凋落物的年失重率为27.48%,分解常数为0.209,凋落物分解50%的时间为3.32年，分解95%的时间为14.33年。在一年分解过程中，凋落物碳(C)、纤维素和木质素含量减少，氮(N)、磷(P)含量增加；分解前60d,失重率主要受纤维素、木质素含量调控，随后主要受C含量、C/N和C/P调控。经过360d的分解，养分释放率表现为C>纤维素>木质素，N、P表现为净累积。分解过程中C释放主要受失重率、剩余凋落物P含量、纤维素和木质素含量的调控；N累积主要受剩余凋落物C含量、初期基质N含量和P素累积的调控；P累积主要受初期基质N、P含量的调控。建议在沙地樟子松人工林抚育管理时，适当添加N、P肥，促进沙地樟子松生态系统的养分循环。     

裸露与沙埋对极端干旱区凋落物分解和养分释放的影响

为了评估沙漠公路防护林林带裸露与沙埋处理下的凋落物分解和养分动态特征,以梭梭（Haloxylon ammodendron）和乔木状沙拐枣（Calligonum arborescens）同化枝、多枝柽柳（Tamarix ramosissima）叶凋落物为研究对象,用凋落物分解袋法进行分解试验。结果表明：（1）3种凋落物的质量损失在2种处理下均存在显著差异,沙埋处理下凋落物质量损失大于裸露处理,至分解试验结束,裸露处理下梭梭、乔木状沙拐枣和多枝柽柳的失重率分别为7%、6.8%、18.1%;沙埋处理下梭梭、乔木状沙拐枣和多枝柽柳的失重率分别为23.7%、9.7%、21.9%;(2)分解过程中,2种处理下凋落物C、N、P含量变化不太一致,梭梭与乔木状沙拐枣同化枝的N与P含量均呈净富集状态,而C含量则呈现净释放状态;多枝柽柳叶的N和P含量分别呈净富集、净释放状态,C含量为富集-释放状态;（3）分解速率k值与相关因素分析表明,凋落物初始N、P、C:N与C:P含量对分解速率影响显著（P<0.01）。这些结果说明,在极端干旱区,沙埋对凋落物的分解过程有显著的积极影响。     

不同坡向雪岭云杉天然更新影响因素分析

为了解不同坡向环境因子对雪岭云杉林天然更新的影响，在天山北坡中段同一海拔雪岭云杉林的阴坡、半阴坡、半阳坡、阳坡设置系列样方开展调查，构建不同坡向环境因子-更新指数结构方程模型，根据各坡向环境特征分析云杉幼苗存活现状与环境因素间的关系。结果表明：（1）半阴坡和半阳坡更适宜幼苗的存活和生长，二者更新指数(0.065、0.057)显著高于阴坡和阳坡；（2）凋落物对雪岭云杉更新有双重作用，凋落物未分解层过厚不利于更新，丰富的有机质可促进土壤形成高氮环境，有利于林下幼苗更新；（3）不同坡向环境因子对更新指数的作用强度依次为：全氮含量（0.60）>成年树密度（0.46）>凋落物半分解层（0.37）>全钾含量（0.24）>有机质含量（0.23）>全磷含量（-0.16）>速效磷含量（-0.32）>凋落物未分解层厚度（-0.34）。综合来看，该区域的雪岭云杉幼苗在郁闭度大小为0.6左右，凋落物厚度为2.5 cm左右，土壤全氮、全钾含量较高的半阴坡、半阳坡更新较好。     

模拟氮沉降对天山云杉凋落叶分解及其养分释放的影响

采用野外模拟试验,通过设计4种氮处理〔CK(对照,不施氮)、LN(低氮,5 kg·hm~(-2)·a~(-1))、MN(中氮,10kg·hm~(-2)·a~(-1))、HN(高氮,15 kg·hm~(-2)·a~(-1))〕,研究了氮沉降对天山云杉凋落叶分解及养分释放的影响。结果表明:1分解24个月后CK凋落叶干重残留率分别是LN、MN和HN的1.04倍、1.16倍和1.23倍,且4种处理间差异显著(P0.05)。CK条件下凋落叶分解50%为4.58 a,分别比LN、MN和HN多0.46 a、0.75 a和1.35 a;相应地分解95%需要的时间分别多2.01 a、3.24 a和5.87 a,说明施氮对天山云杉凋落叶的分解起到了促进作用,且促进作用随着氮沉降量的增加而加大。2从凋落叶月分解速率看,表现为HNMNLNCK,且随着分解时间的延长,4种处理间的差异逐渐缩小。3氮沉降促进了天山云杉凋落叶中木质素和纤维素的分解,同时促进了C元素的释放,增加了N元素的累积,降低了C/N值。     

放牧对内蒙古典型草原枯落物积累及分解的影响

文中依托中国农业科学院草原研究所锡林浩特试验基地的放牧控制试验平台,测定了大针茅+羊草草原不同放牧强度下枯落物量及厚度,采用分解袋法测定了不同放牧小区内的枯落物残留率和分解速率,研究了短期放牧时间内,放牧强度对大针茅+羊草草原枯落物分解的影响。研究结果表明:1)不同放牧强度下枯落物现存量存在极显著差异(p <0. 01),且随放牧强度的增加而减少,极重度放牧下枯落物现存量比CK减少了95. 49%;2)不同放牧强度下枯落物厚度存在显著差异(p <0. 05),且随放牧强度的增加而减少,比CK减少了25. 93%~93. 22%;3)分解第一年,枯落物质量损失率最大,为45. 75%~53. 1%,尤其是分解的前90天(6~8月),水热条件较好,有利于土壤微生物的生长和繁殖,对枯落物的分解具有促进作用,枯落物质量损失率达到20%左右。分解第二年枯落物分解变慢,质量损失率为12. 55%~20. 8%。4)放牧不同程度的加快了枯落物的分解,轻度和中度放牧强度下分解速率最快,其次为重度和极重度放牧,围封对照区枯落物分解最慢,说明适度放牧更有利于枯落物分解。     

干热河谷罗望子人工林凋落物分解及养分释放

通过长期野外监测和分析,研究了金沙江干热河谷罗望子人工林凋落物分解和养分释放动态,结果表明:经过420d分解期,林地A和林地B的凋落物残留率为42.57%和29.22%,半衰期为0.87a和0.75a,周转期为4.81a和3.61a;养分迁移方式,K元素是淋溶-富集-释放;N、Ca、Mg、Cu元素是富集-释放,Fe元素是富集,P元素在林地A和林地B中迁移方式略有差异;养分释放特征,P、Ca、Mg元素表现为净释放,七种元素释放率大小,林地A和林地B均为:Ca﹥K﹥P﹥Mg﹥N﹥Cu﹥Fe;P、K、Ca、Mg元素易分解和循环,返回林地时间较短,易被林木吸收。罗望子林凋落物的分解总体特征符合亚热带气候的地带性特点,受气温和降雨量影响较小。     

典型荒漠植物凋落物分解及养分动态研究

采用分解网袋法,对古尔班通古特沙漠南缘粗柄独尾草(Eremurus inderiensis)、尖喙牻牛儿苗(Erodium oxyrrhynchum)和沙漠绢蒿(Seriphidium santolinum)3种荒漠植物叶、茎和根的分解、养分释放特性进行了研究。结果表明：叶片、茎、根系的质量损失过程均符合指数衰减模型。经过364 d的分解,粗柄独尾草叶、粗柄独尾草根、尖喙牻牛儿苗叶、尖喙牻牛儿苗茎、尖喙牻牛儿苗根、沙漠绢蒿茎、沙漠绢蒿根的失重率分别为41.96%、81.94%、42.18%、29.32%、47.02%、20.66%和20.71%;3种植物根、茎、叶的分解速率存在显著差异,分解速率依次为：粗柄独尾草根>叶;尖喙牻牛儿苗根>叶>茎;沙漠绢蒿根>茎。在整个分解过程中,N和P含量总的趋势表现为释放,叶、根凋落物质量损失与初始N、P含量显著负相关,非生物因素对其分解有重要影响。     

放牧强度对小针茅草原枯落物分解的影响

文中依托内蒙古苏尼特右旗中国农业科学院荒漠草原试验示范基地的放牧控制试验平台,研究了不同放牧强度下小针茅草原枯落物的残留率、分解速率和质量损失率的动态变化,并探讨了分解速率与水热因子的关系。研究结果表明:1)经过一个生长季的分解,放牧不同程度地加速了枯落物的分解。中度放牧小区群落枯落物的分解速率最高,为1.225×10~(-3)g·d~(-1),比对照区高35.28%。2)随着分解时间的延长,不同放牧强度下小针茅群落枯落物的质量累积损失率呈增加的趋势。3)枯落物分解的质量损失量在不同的季节其增加的快慢有差异,在分解的5~7月,枯落物月质量损失量迅速增加,8月份以后枯落物月质量损失量开始降低。不同放牧强度下枯落物质量损失量大小依次为:MG>EG>HG>LG>CK。说明适度放牧有利于枯落物的分解。4)7月份枯落物的分解速率最快,其次为8月份,7、8月份水热条件较好,有利于土壤微生物的生长和繁殖,对枯落物的分解具有促进作用。     

菹草腐烂分解过程中污染物的动态释放

采用分解袋法,对典型沉水植物菹草进行了连续100天的室外腐烂分解试验,分析了菹草干物质的损失及营养元素释放的动态变化规律。结果表明:在100天的分解实验中,菹草干物质量急剧减少,且表现为前期损失快,后期损失减缓的趋势,第100天时,菹草干物质质量损失了92.51%,残留率为7.49%。采用Olson指数模型菹草枯落物干物质的动态变化,计算其分解速率常数(k)为0.028g/d,分解50%干物质所需时间为24.47天,分解95%干物质量所需时间为105.57d,年残留率为0,表明菹草枯落物在一年内能彻底分解。植物枯落物中氮磷含量随着分解时间的延长而呈波动变动,但氮磷营养元素的损失与干重的损失速率并不同步。分解初期氮含量上升,随后呈下降-上升的变化趋势,而磷含量总体呈现波动下降趋势。试验结束后,氮、磷元素分别释放了9.14%、32.02%。此外,菹草枯落物氮、磷元素积累指数(NAI)平均值分别为46.10和32.23,表明菹草在腐烂分解过程中,氮磷元素均以净释放为主。     

长期轮作对旱地黑垆土纤维素分解菌数量及分解强度的影响

采用最大或然数法(MPN法)和埋片法研究了黄土高原旱地粮草长周期(苜蓿→苜蓿→苜蓿→苜蓿→马铃薯→小麦→小麦→小麦)和粮草短周期(红豆草→小麦→小麦+红豆草)轮作制度及茬口年限对黑垆土纤维素分解菌数量和分解强度的影响。结果表明:轮作制度及茬口年限对黑垆土纤维素分解菌数量的影响程度大于分解强度。纤维素分解菌数量呈现显著性差异变化,分别在粮草长周期轮作中第1年苜蓿茬和粮草短周期轮作中第2年小麦茬达到最高值,在粮草长周期轮作中马铃薯茬和粮草短周期轮作中第1年小麦茬达到最低值;纤维素分解强度在同一轮作制度中各茬口差异不显著,但换茬可提高分解强度;随着苜蓿和小麦种植年限延长,纤维素分解菌数量和分解强度均大致呈现降低趋势。红豆草茬纤维素分解菌数量低于苜蓿茬,但粮草短周期轮作更有利于提高黑垆土纤维素分解强度。     

围栏封育对新疆山地退化草原植物群落特征的影响

围栏封育作为一种有效的退化草原管理措施,近年来在我国退化草原恢复中得到极为广泛的应用。以新疆巴里坤县退化温性荒漠草原为研究对象,通过连续4 a围栏封育样地和自由放牧样地的植被调查资料,对比分析围栏封育样地和自由放牧样地的植被群落组成和地上生物量的动态特征。结果表明:(1)通过围栏封育措施,退化草原的物种多样性和群落生态优势度与自由放牧样地相比略有提高,群落均匀度略有降低,但通过t检验,差异均未达到显著水平(P0.05)。(2)随着封育措施的实施,总体上草原群落优势种为沙生针茅和伊犁绢蒿,反映出西部内陆半干旱地区温性荒漠草原特有的特征;自由放牧样地,沙生针茅和伊犁绢蒿在群落中的优势地位发生变化。(3)围栏封育措施提高了植物群落的平均高度、地上生物量。随着围封时间的延长,群落地上生物量增加,且显著高于自由放牧区,然而4 a围栏封育并不能使温性荒漠草原产草量达到最高水平,也不能使植物群落的多样性指标与自由放牧样地形成显著差异。     

土地资源结构与农林牧合理用地布局的探讨——以甘肃省河西走廊为例

本文以土地资源结构理论为依据,论述了甘肃省河西走廊地区的农业分区,土地资源质量数量结构、农林牧合理用地构成及区域开发的整体布局。     

Litter decomposition and C and N dynamics as affected by N additions in a semi-arid temperate steppe,Inner Mongolia of China

Litter decomposition is the fundamental process in nutrient cycling and soil carbon（C） sequestration in terrestrial ecosystems. The global-wide increase in nitrogen（N） inputs is expected to alter litter decomposition and,ultimately, affect ecosystem C storage and nutrient status. Temperate grassland ecosystems in China are usually N-deficient and particularly sensitive to the changes in exogenous N additions. In this paper, we conducted a 1,200-day in situ experiment in a typical semi-arid temperate steppe in Inner Mongolia to investigate the litter decomposition as well as the dynamics of litter C and N concentrations under three N addition levels（low N with 50 kg N/（hm2？a）（LN）, medium N with 100 kg N/（hm2？a）（MN）, and high N with 200 kg N/（hm2？a）（HN）） and three N addition forms（ammonium-N-based with 100 kg N/（hm2？a） as ammonium sulfate（AS）, nitrate-N-based with 100 kg N/（hm2？a） as sodium nitrate（SN）, and mixed-N-based with 100 kg N/（hm2？a） as calcium ammonium nitrate（CAN）） compared to control with no N addition（CK）. The results indicated that the litter mass remaining in all N treatments exhibited a similar decomposition pattern： fast decomposition within the initial 120 days, followed by a relatively slow decomposition in the remaining observation period（120–1,200 days）. The decomposition pattern in each treatment was fitted well in two split-phase models, namely, a single exponential decay model in phase I（〈398 days） and a linear decay function in phase II（≥398 days）. The three N addition levels exerted insignificant effects on litter decomposition in the early stages（〈398 days, phase I; P〉0.05）. However, MN and HN treatments inhibited litter mass loss after 398 and 746 days, respectively（P〈0.05）. AS and SN treatments exerted similar effects on litter mass remaining during the entire decomposition period（P〉0.05）. The effects of these two N addition forms differed greatly from those of CAN aft     

Changes in the relationship between species richness and belowground biomass among grassland types and along environmental gradients in Xinjiang,Northwest China

The association between biodiversity and belowground biomass (BGB) remains a central debate in ecology. In this study, we compared the variations in species richness (SR) and BGB as well as their interaction in the top (0-20 cm), middle (20-50 cm) and deep (50-100 cm) soil depths among 8 grassland types (lowland meadow, temperate desert, temperate desert steppe, temperate steppe desert, temperate steppe, temperate meadow steppe, mountain meadow and alpine steppe) and along environmental gradients (elevation, energy condition (annual mean temperature (AMT) and potential evapotranspiration (PET)), and mean annual precipitation (MAP)) based on a 2011-2013 survey of 379 sites in Xinjiang, Northwest China. The SR and BGB varied among the grassland types. The alpine steppe had a medium level of SR but the highest BGB in the top soil depth, whereas the lowland meadow had the lowest SR but the highest BGB in the middle and deep soil depths. The SR and BGB in the different soil depths were tightly associated with elevation, MAP and energy condition; however, the particular forms of trends in SR and BGB depended on environmental factors and soil depths. The relationship between SR and BGB was unimodal in the top soil depth, but SR was positively related with BGB in the middle soil depth. Although elevation, MAP, energy condition and SR had significant effects on BGB, the variations in BGB in the top soil depth were mostly determined by elevation, and those in the middle and deep soil depths were mainly affected by energy condition. These findings highlight the importance of environmental factors in the regulations of SR and BGB as well as their interaction in the grasslands in Xinjiang.     

Characteristics of soil organic carbon and total nitrogen under various grassland types along a transect in a mountain-basin system in Xinjiang,China

Soil organic carbon(SOC) and soil total nitrogen(STN) in arid regions are important components of global C and the N cycles, and their response to climate change will have important implications for both ecosystem processes and global climate feedbacks. Grassland ecosystems of Funyun County in the southern foot of the Altay Mountains are characterized by complex topography, suggesting large variability in the spatial distribution of SOC and STN. However, there has been little investigation of SOC and STN on grasslands in arid regions with a mountain-basin structure. Therefore, we investigated the characteristics of SOC and STN in different grassland types in a mountain-basin system at the southern foot of the Altai Mountains, north of the Junggar Basin in China, and explored their potential influencing factors and relationships with meteorological factors and soil properties. We found that the concentrations and storages of SOC and STN varied significantly with grassland type, and showed a decreasing trend along a decreasing elevation gradient in alpine meadow, mountain meadow, temperate typical steppe, temperate steppe desert, and temperate steppe desert. In addition, the SOC and STN concentrations decreased with depth, except in the temperate desert steppe. According to Pearson's correlation values and redundancy analysis, the mean annual precipitation, soil moisture content and soil available N concentration were significantly positively correlated with the SOC and STN concentrations. In contrast, the mean annual temperature, p H, and soil bulk density were significantly and negatively correlated with the SOC and STN concentrations. The mean annual precipitation and mean annual temperature were the primary factors related to the SOC and STN concentrations. The distributions of the SOC and STN concentrations were highly regulated by the elevation-induced differences in meteorological factors. Mean annual precipitation and mean annual temperature together explained 97.85% and 98.38% of the overall variations in the SOC and STN concentrations, respectively, at soil depth of 0–40 cm, with precipitation making the greatest contribution. Our results provide a basis for estimating and predicting SOC and STN concentrations in grasslands in arid regions with a mountain-basin structure.     

放牧绵羊排泄物在荒漠草原土壤内的养分降解

试验研究了放牧绵羊粪便在内蒙古短花针茅草原土壤内的降解。结果显示:羊粪干物质的降解率为0.74mg.g-1.day-1,有机物质、C和N含量在一年的试验期间分别降解了25.0%、35.5%和16.6%;各成分间的降解有显著的相关性,其降解符合回归曲线方程为y=y0+a(1-e-bx);夏季是羊粪分解的主要时期。     

新疆博尔塔拉蒙古自治州草原蝗虫多样性及群落结构特征

2015―2018年,利用百网和“Z”形取样法系统调查了博尔塔拉蒙古自治州草原七个草地类型的蝗虫群落多样性,明确其蝗虫的群落结构特征和多样性组成。经过调查分类鉴定,确定博州草原蝗虫有 65种,隶属于5科30属,优势种为黑腿星翅蝗、黑条小车蝗和小米纹蝗。在博州,黑条小车蝗垂直海拔分布的范围最广（257～2382 m）,亚洲飞蝗和绿纹蝗垂直海拔的分布范围最为狭窄,仅为187～195 m;小翅曲背蝗和西伯利亚蝗多分布于高海拔地区（2000～2200 m）,红斑翅蝗则多分布于低海拔区域（750～1200 m）。温性荒漠的特有种为简蚍蝗、红翅瘤蝗和红斑翅蝗,低地草甸的特有种为亚洲飞蝗、小垫尖翅蝗和绿纹蝗。蝗虫群落的Shannon-Wiener多样性指数在温性荒漠、温性草原化荒漠和温性荒漠草原要显著高于低地草甸;Pielou均匀度指数和Simpson优势度指数在七个草地类型间无显著性差异。温性荒漠草原和温性草原的蝗虫群落最为相似,两者Jaccard相似系数为0.56。     

Effects of climate change on phenology and primary productivity in the desert steppe of Inner Mongolia

 Variations in temperature and precipitation affect local ecosystems. Considerable spatial and temporal heterogeneity exists in arid ecosystems such as desert steppes. We analyzed the spatiotemporal dynamics of climate and vegetation phenology in the desert steppe of Inner Mongolia, China, using meteorological data from 11 stations (1961–2010) and phenology data from 6 ecological stations (2004–2012). We also estimated the gross primary production for the period of 1982–2009 and found that the annual mean temperature increased at a rate of 0.47ºC/decade during 1961–2010, with the last 10 years being consistently warmer than the 50-year mean. The most significant warming occurred in winters. Annual precipitation slightly decreased during the 50-year period, with summer precipitation experiencing the highest drop in the last 10 years, and spring precipitation, a rise. Spatially, annual precipitation increased significantly in the northeast and eastern central area of the region next to the typical steppe. From 2004 to 2012, vegetation green-up and senescence date advanced in the area, shortening the growing season. Consequently, the primary productivity of the desert steppe decreased along precipitation gradient from southeast to northwest. Temporally, productivity increased during the period of 1982–1999 and significantly decreased after 2000. Overall, the last decade witnessed the most dramatic climatic changes that were likely to negatively affect the desert steppe ecosystem. The decreased primary productivity, in particular, decreases ecosystem resilience and impairs the livelihood of local farmers and herdsmen.     

鄂尔多斯高原西部阿拉巴斯山地区第三纪残遗植物避难所的自然保护问题

阿拉巴斯山地区为干旱区第三纪残遗植物的避难所,是内蒙古地区植物特有现象最明显的地区。共有维管植物251种。地带性植被为草原化荒漠,主要群落类型为四合木荒漠、半日花荒漠、绵刺荒漠、沙冬青荒漠等荒漠群系。以戈壁种和东阿拉善种为主的荒漠成分构成了本地区植物区系的主体。古老残遗种及特有种在植物区系和植被组成中均起主导作用。但是这块宝地目前面临严重破坏,应该尽快成立阿拉巴斯第三纪残遗植物保护区。