祁连山冷龙岭南坡移地植物叶片的碳氮特征

在祁连山冷龙岭南麓坡地进行不同海拔高度土壤(0～40(30)cm土层)和植被的整体双向移地实验,以探讨气候变化对主要物种和群落碳、氮特征的影响。结果表明,3 200 m的麻花艽移地至高海拔时,叶片碳、氮含量分别呈现出先增加后减少和一直增加的趋势,而碳/氮值下降明显。3 400 m的兰石草、珠芽蓼、垂穗披碱草、金露梅和鹅绒委陵菜5种植物大部分叶片碳、氮素含量及碳/氮呈现出随海拔增高而下降的趋势。3 600 m的矮嵩草、雪白委陵菜和重齿风毛菊3种植物叶片碳、氮含量及碳/氮在各海拔之间变化不明显。3 800 m的矮嵩草和矮火绒草的叶片碳、氮含量随海拔高度增加而增加,碳/氮下降。整个群落来讲碳含量随海拔升高而降低,氮含量和碳/氮比变化较小。研究发现,各群落和物种对移地的响应方式因物种组成、原生状态不同而存在差异;温度条件(以海拔升降模拟温度降升)对植被群落及主要植物叶片碳、氮含量和碳/氮比有一定影响,尤其是当高海拔稀疏植被移地到低海拔时,其叶片碳、氮和碳氮比与原生状况的植被群落及主要植物种相对变化较大。

典型草原不同围封年限植被-土壤系统碳氮贮量的变化

以内蒙古太仆寺旗典型草原为研究对象,研究不同围封年限下的天然草地植物和土壤有机碳、全氮贮量的变化。结果表明:与自由放牧草地相比,重度退化草地采取生长季围封恢复措施后,群落植物和土壤环境在围封8、11、14、21、25年后均得到了明显的改善,地上植物和地下根系生物量及其碳氮贮量、土壤碳氮贮量明显增加,土壤容重降低。自由放牧地和围封8、11、14、21年植物-土壤系统碳贮量分别为7 357.93、7 988.27、8 413.18、12 878.82、8 934.66 g.m-2,氮贮量分别为427.78、494.28、575.49、707.35、615.09 g.m-2。草地围封至14年植物和土壤各项理化性质达到最大值,使得植物-土壤系统的碳氮贮量分别是自由放牧地的1.75和1.65倍,说明植被与土壤间达到了良性循环的状态,退化草地正向演替。随着围封年限的继续增加,其各项指标出现下降趋势。由此可知,季节性围封措施在一定时间内可使退化草地的土壤-植物系统的碳氮贮量增加,草地在一定程度上得到恢复,但适宜的恢复时间和合理利用问题有待进一步讨论。

人为干扰对藏北高寒草原群落生物量及其碳氮磷含量特征的影响

退牧还草工程是国家为改善草原生态环境和促进牧区经济持续发展而实行的一项战略性工程,禁牧和休牧措施是其主要措施。以藏北高寒草原申扎区域的退牧还草工程为研究对象,分别选取禁牧围栏样地、休牧围栏样地和围栏外的一块自由放牧样地,比较分析这三种人为干扰下的放牧样地的生物量及其碳氮磷含量的特征。结果表明:休牧样地地上和地下生物量分别为35.69 g/m2和237.11 g/m2,均显著高于禁牧样地(22.48 g/m2和151.22 g/m2)和自由放牧样地(25.27g/m2和96.37 g/m2)。植物中碳氮磷含量,地上部分禁牧样地含碳量最高,植物氮、磷含量自由放牧样地最高;地下部分碳、氮含量差异不明显,P含量自由放牧最高。说明植物生物量大小与植物体内碳氮磷元素含量大小无相关关系。对于禁牧样地,在长期围栏封育的同时,应适当的添加P元素或N、P元素;而休牧样地,在短期围栏封育时,可添加适当的N元素。

羌塘高原高寒草地植物地上地下碳氮生态化学计量特征及其影响因素

研究高寒草地的植物生态化学计量特征对认识极端气候背景下的草地生态系统功能与服务具有重要的意义. 选择羌塘高原高寒草地作为研究区，分析东西走向60个样点植物地上、地下部分的碳（C）、氮（N）含量与C：N的分布特征，及其各自的主要驱动因素. 结果表明：高寒草地植物地上部分C、N含量（38.22%、1.82%）均高于地下部分（31.11%、1.15%），但C：N（22.08）却小于地下部分（28.88），且地上部分C含量、C：N与地下部分存在显著性差异（P 〈 0.05）. 干燥指数与植物地上部分C含量（R^2 = 0.072，P 〈 0.05）以及C：N（R^2 = 0.15，P 〈 0.005）呈负相关关系，却与植物地下部分C：N（R^2 = 0.53，P 〈 0.001）呈正相关关系；此外，年均降水量（R^2 = 0.13，P 〈 0.005）与地上部分C含量呈负相关关系，总生物量（R^2 = 0.13，P 〈 0.01）及植被总盖度（R^2 = 0.12， P 〈 0.01）与地下部分C含量呈正相关关系；海拔与地上部分C：N亦呈正相关关系（R 2= 0.15，P 〈 0.005），而年均温却与地下部分C：N呈负相关关系（R^2 = 0.31，P 〈 0.001）. 可见，水热条件是影响羌塘高原植物地上、地下C含量以及C：N差异的主要因素，而干燥指数可以作为较好的度量指标. （图7 表1 参46）

东北虎豹国家公园东部有蹄类栖息地的灌草层食物资源的量与质

东北虎和东北豹主要捕食马鹿、梅花鹿、狍及野猪等大中型有蹄类动物,而这些有蹄类的生存依赖森林灌草层的植食性食物资源,形成了东北亚温带森林生态系统完整的啃食食物链(grazing food chain)主体。本研究通过对建设中的东北虎豹国家公园东部地区有蹄类栖息地的灌草层植物进行本底调查,获得有蹄类动物的食物资源基线数据。2015年及2016年的生长季,在东北虎豹国家公园东部,随机选择141个样地嵌套496条样线,1 948个样方,对不同森林结构(郁闭林及开阔生境,开阔生境包括林窗、林缘和河岸带)的灌草层植物生物量、食物类别组成(嫩枝叶、禾莎草、杂类草和蕨类)及碳、氮含量进行调查分析。研究结果显示:灌草层生物量在开阔生境显著高于郁闭林下(94.91 g/m^2 vs.30.15 g/m^2),达到3.15倍。三种开阔生境下的灌草层食物资源类别组成差异显著,在林窗内以嫩枝叶占优势,在林缘以杂类草占优势,在河岸带以蕨类占优势。灌草层中杂类草和嫩枝叶平均氮含量高,杂类草碳含量低、C/N低;四类植物热值均超17 kJ/g,其中嫩枝叶最高。嫩枝叶、杂类草占优势的高生物量(生物量大于40 g/m^2)斑块占郁闭林下的16%、占开阔生境的50%左右,可能是精食者(browser)的取食热点区域。建议在未来国家公园建设中,在合适地段保留一定的开阔生境,为梅花鹿等食草动物补充高质量的灌草层食物资源斑块,促进有蹄类动物种群发展,并以此为基础恢复虎豹种群。

Soil C and N Pools in Chinese Fir and Evergreen Broadleaf Forests and their Changes with Slash Burning in Mid-Subtropical China

Soil organic carbon （C） and total nitrogen （N） pools of a Chinese fir （Cunninghamia lanceolata （Lamb.） Hook.） （CF） forest, and an evergreen broadleaf （EB） forest located in mid-subtropical, southeastern China, were compared before clearcutting, with the effect of slash burning on organic C and total N in the top 10 cm of soil before and after burning also being evaluated. Prior to clearcutting CF forest had significantly lower （P 〈0.05） organic C and total N in the soil （0-100 cm） compared to EB forest with approximately 60% of the C and N at the two forest sites stored at the 0 to 40 cm soil. In post-burn samples of the 0-10 cm depth at 5 days, 1 year, and 5 years for CF and EB forests, significantly lower levels （P 〈0.05） of organic C and total N than those in the pre-burn samples were observed. Compared to the pre-burn levels, at post-burn year 5, surface soil organic C storage was only 85% in CF forest and 72% in EB forest, while total N storage was 77% for CF forest and 73% for EB forest. Slash burning caused marked long-term changes in surface soil C and N in the two forest types.

Effect of Land Use Pattern on Mineralization of Residual C and N from Plant Materials Decomposing Under Field Conditions

Four kinds of plant materials (astragalus, azolla, rice straw and water hyacinth) were allowed to decompose for 10 years in two soils with different mineralogical characteristics in fields under upland and submerged conditions. Greater amounts of C and N from azolla were retained in soils throughout the 10-year experimental period compared to those from the other plant materials. The residual C Of all the plant materials in the two soils under upland conditions mineralized st rates corresponding to half-lives between 4.4-6.6 years,while the corresponding figures for thine under submerged conditions were between 6.5-13.1 years. Minerallization of residual organic N followed the same pattern as residual C. Compared to residual C, however, the mineralization rates of residual organic N in most cases were significantly lower and the percentages of added N regained in sons were higher. More N from plat materials was retained in the yellow-brown soil than in the red soil, but no consistent differences in the amounts of C from plant materials and in the mineralization rates of both residual C and residual organic N between the two soils could be found.

Soil organic carbon pool along different altitudinal level in the Sygera Mountains, Tibetan Plateau

Labile organic carbon（LOC） is one of the most important indicators of soil organic matter quality and dynamics elevation and plays important function in the Tibetan Plateau climate. However, it is unknown what the sources and causes of LOC contamination are. In this study, soil organic carbon（SOC）, total nitrogen（TN）, microbial biomass carbon（MBC）, microbial biomass nitrogen（MBN） and LOC were analyzed based on different soil horizons and elevations using turnover time in an experimental site（3700 m to 4300 m area） in Sygera. SOC and LOC in higher-elevation vegetation types were higher than that of in lower-elevation vegetation types. Our results presented that the soil microbial biomass carbon（SMBC） and soil microbial biomass nitrogen（SMBN）were positively correlated with SOC. The content of easily oxidized carbon（EOC）, particulate organic carbon（POC） and light fraction organic carbon（LFOC） decreased with depth increasing and the content were the lowest in the 60 cm to 100 cm depth.The total SOC, ROC and POC contents decreased with increasing soil horizons. The SOC, TN, MBC and MBN contents increased with increasing altitude in the Sygera Mountains. The MBC and MBN contents weredifferent with the changes of SOC（p＆lt;0.05）,meanwhile, both LFOC and POC were related to total SOC（p＆lt;0.05）. The physical and chemical properties of soil, including temperature, humidity, and altitude,were involved in the regulation of SOC, TN, MBC,MBN and LFOC contents in the Sygera Mountains,Tibetan Plateau.

Influence of Different Plant Materials in Combination with Chicken Manure on Soil Carbon and Nitrogen Contents and Vegetable Yield

The use of plant materials as soil amendments is an uncommon practice amongst major farming communities in Ghana, although it is necessary for soil fertility improvement. An examination of the effects of soil amendments is necessary to encourage the use of under-utilized organic resources in Ghana. Thus, a field experiment was conducted using 8 different tropical plant materials mixed with chicken manure as soil amendments for growth of tomato as a test crop. The plant materials included Leucaena leueocephala, Centrosema pubescens, Sesbania sesban, Gliricidia sepium, Mucuna pruriens, Pueraria phaseoloides, Azadirachta indiea, and Theo- broma cacao. There were two other treatments： one with equivalent amounts of chemical fertilizers and the other with no-fertilizer input （control）. Plant materials were mixed with chicken manure to obtain a uniform carbon-to-nitrogen （C：N） ratio of 5：1. Except the no-fertilizer control, all treatments received the same amount of nitrogen （N）. To clarify the decomposition pattern of the plant materials in soil, an incubation experiment was conducted using only the plant materials before the field experiment. The Glirieidia treatment released significantly more mineral N than the other plant materials in the incubation experiment. However, the tomato fruit yield was not enhanced in the Gliricidia treatment in the field experiment. The known quality parameters of the tested plant materials, such as total N, total carbon （C）, C：N ratio, and total polyphenols, had minimal effects on their mineralization dynamics. Azadirachta showed the best synergistic effect with chicken manure through significantly increasing soil microbial biomass and fruit yield of tomato. This result provides insights into the possible adoption of Azadirachta in combination with chicken manure as a soil amendment in small-scale agricultural holdings.

An Invasive Succulent Plant (Kalanchoe daigremontiana) Influences Soil Carbon and Nitrogen Mineralization in a Neotropical Semiarid Zone

It has long been recognized that plant invasions may alter carbon （C） and nitrogen （N） cycles, but the direction and magnitude of such alterations have been rarely quantified. In this study, we quantified the effects caused by the invasion of a noxious exotic plant, Kalanchoe daigrernontiana （Crassulaceae）, on C and N mineralization and enzymatic and microbial activities in the soil of a semiarid locality in Venezuela. We compared soil parameters associated with these processes （C and N mineralization time and the cumulative values, fluorescein diacetate hydrolytic activity, and activities of dehydrogenase, β-glucosidase, glucosaminidase, and urease） between invaded and adjacent non-invaded sites. In addition, correlations among these parameters and the soil physical-chemical properties were also examined to determine if a positive feedback exists between nutrient availability and K. daigremontiana invasion. Overall, our results showed that C mineralization and transformation of organic compounds to NH4^＋ were favored at sites colonized by K. daigrernontiana. With this species, we found the highest cumulative amounts of NH4^＋-N and C and the lowest mineralization time. These results could be explained by higher activities of urease and glueosaminidase in soils under the influence of K. daigremontiana. In addition, higher amounts of organic matter and moisture content in invaded soils might favor C and N mineralization. In conclusion, invasion of Neotropical semiarid zones by K. daigrernontiana may influence the chemical and biological properties of the soils covered by this species, increasing nutrient bioavailability, which, in time, can facilitate the invasion process.