西北荒漠草原针毛收获蚁的筑巢行为

针毛收获蚁Messoraciculatus(F .Smith)是我国北方特别是西北荒漠草原的优势种蚂蚁 ,亦是重要的种子收获性蚁类 ,收获、贮藏和取食 1 0余种荒漠植物种子。自然巢穴深 80cm～ 1 3 7cm ,单一巢口 ,沿主隧道不同深度有水平延伸的各层巢室 ,巢室向四周的延伸范围随巢深减小 ,层间距拉大。自然巢穴的空间结构与社群越冬与种子的深层贮藏有着密切的关系。饲养社群筑巢行为由蚁后主导 ,起始营巢位点数与蚁后头数有关 ,每一蚁后带领 5 0～ 70头工蚁 ,营巢时程 0 5～ 0 67d 60工蚁 蚁后 ,蚁巢有多个巢口。自然与饲养社群的巢穴结构差异很大 ,但两者单一蚁后与工蚁所占的有效巢穴空间是基本一致的 ,自然社群 1 81 3 7cm3 蚁后 ,2 99cm3 工蚁 ,饲养社群 1 5 6 2 6cm3 蚁后 ,2 60cm3 工蚁     

针毛收获蚁社群密度与分布及社群各品级在自然穴巢中的季节迁移行为

针毛收获蚁Messoraciculatus(F .Smith)是我国北方特别是西北荒漠草原的优势种蚂蚁 ,亦是重要的种子收获性蚁类 ,收获、贮藏和取食 1 0余种荒漠植物种子。本文以沙坡头自然保护区红卫固定沙丘地段为样地 ,对该蚁的社群密度与分布及社群各品级在自然穴巢中的季节迁移行为作了研究。最近邻体法测定表明 ,社群在新生生境中起初随机定居 ,随社群密度的不断定居 ,空间分布型逐渐向均匀六边形过渡 ;社群密度为成熟社群 34 .98巢 hm2 ,发展中社群 2 6 .99巢 hm2 ,新建社群 4 4.98巢 hm2 ,种群密度 2 .6 8工蚁 m2 。社群结构的季节动态总蚁量和幼蚁为双峰型 ,蚁后和雄蚁为单峰型。室内人工蚁巢饲养表明 ,社群结构约 1月后趋于稳定 ,蚁量 5 0～ 70头 ,单蚁后以 4个品级混合越冬。自然社群的挖掘表明 ,各品级在蚁巢中的季节迁移行为明显呈现上迁、前层持续活动、下迁和深层越冬四期。此外 ,讨论了该蚁对荒漠草原环境的适应性。     

宁夏荒漠草原针毛收获蚁对植物种子的觅食作用

针毛收获蚁Messor aciculatus (F．Smith)是西北荒漠地区典型的食种子蚂蚁种类之一。以宁夏中卫县沙坡头自然保护区红卫固定沙丘地段为主要研究基地。由田间系统调查和室内饲养得出：针毛收获蚁可取食的植物种子达30余种以上。在红卫固定沙丘草地针毛收获蚁的自然种群收获的植物种子主要有6种：狗尾草Setaria viridis、猪毛菜Salsola collina、雾冰藜Bassia dasyphylla、地锦Euphobia humifuse、刺沙蓬Salsola ruthenica、叉枝鸦葱Scorzonera divaricata。被收获的种子大小主要在1．20～2．50mm之间．或有棱角、扁平、易于衔夹的种子。在蚁巢中种子以种类和形态的不同被分类、分层保存于不同深处的巢室．总贮量随工蚁和蚁后数量的增加而增加。在自然条件下,收获的种子种类及数量与穴巢附近环境中的植物种类及分布有关。蚂蚁对种子的收集贮藏在一定程度上可影响种子的萌发力．特别是对一些1年生质量较轻的种子影响力较大。蚂蚁觅食对土壤中种子库种子密度的影响因植物种类的不同而异．其中对1年生草本植物影响较大．间接的影响到植物群落的组成和空间分布的变化。     

宁夏典型温性天然草地固碳特征

本文研究了宁夏草甸草原、温性草原、草原化荒漠和荒漠草原4种温性典型天然草地生态系统碳储量及其构成特征。结果表明: 草甸草原、温性草原、草原化荒漠和荒漠草原植被总生物量分别为1178.91、481.22、292.80和209.09 g·m^-2。其中,地下根系生物量是构成草甸草原和温性草原植被总生物量的主体,分别占总生物量的73.1%和56.6%;地上植被生物量是构成草原化荒漠和荒漠草原植被总生物量的主体,分别占总生物量的50.3%和47.6%;枯落物生物量占比较低,分别仅为8.5%、8.0%、6.4%和16.2%。草甸草原、温性草原、草原化荒漠和荒漠草原4种天然草地生态系统碳储量分别为13.90、5.94、2.69和2.37 kg·m^-2,其中植被碳储量分别为470.26、192.23、117.17、83.36 g·m^-2,0～40 cm土层土壤有机碳储量分别为13.43、5.75、2.58和2.29 kg·m^-2,土壤有机碳储量是构成宁夏典型天然草地碳储量的主体,分别占到了生态系统碳储量的96.6%、96.8%、95.6%和96.5%。4种草地类型植被总生物量、植被碳储量、土壤有机碳储量和生态系统碳储量均表现为:草甸草原＞温性草原＞草原化荒漠＞荒漠草原。     

西藏草地生态系统植被碳贮量及其空间分布格局

在广泛收集资料的基础上,利用平均碳密度方法,估算了西藏高原草地生态系统17类草地植被的碳贮量,并分析了其空间分布格局.结果表明:(1)17类草地植被总面积为8205.194×104hm2,总碳贮量为189.367 Tg (1TgC＝1012g),平均碳密度为2307.895 kgC/hm2,不同植被类型差异较大,在395.977～20471.161kgC/hm2之间波动;(2)从草地类型分布看,高寒草原和高寒草甸是西藏分布面积最大的2类草地,分布面积占西藏草地总面积的70.210%,又是西藏草地碳贮量的主要贮库,碳贮量占西藏草地总碳贮量的79.393%;(3)在空间分布格局上,随着自藏东南向西北的延伸,草地植被总碳密度逐次降低,这一水平分布格局与西藏独特的水热分布相一致;碳密度的垂直分布规律因地区而异,但各地区均以高寒草甸或高寒荒漠的低碳密度为终点,表现出"殊途同归"的特征.     

樟树人工林生态系统碳素贮量与分布研究

对 1 8年生樟树人工林生物量、碳素含量、贮量及其空间分布进行测定。结果表明 ,樟树各器官的碳素含量为 4 2 1 2 %～ 5 5 4 2 % ,排列顺序为树叶 >树枝 >树根 >树干 >树皮。林冠上层与下层叶的碳素含量比中层叶的碳素含量低 ,但差别不大 ;下层枝条碳素含量明显比上、中层枝条高。灌木层植物的碳素含量平均为 5 1 30 % ,草本植物为 4 8 90 % ,死地被物层为4 0 89%。土壤的碳素含量为 1 2 5 % ,随土层深度的增加 ,各层次土壤碳素含量逐渐减少。樟树林生态系统总的碳贮量为 2 0 0 4 4× 1 0 3 kgC·hm-2 ,其中乔木层为 4 5 0 1× 1 0 3 kgC·hm-2 ,占整个生态系统总贮量的 2 2 4 5 % ,灌木层为 2 2 9× 1 0 3 kgC·hm-2 ,占 1 1 4 % ,草本层为 1 0 9×1 0 3 kg·C·hm-2 ,占 0 5 5 % ,死地被物层为 5 0 8× 1 0 3 kg·C·hm-2 ,占 2 5 4 % ,林地土壤 (0～ 1m)的碳贮量为 1 4 6 97× 1 0 3 kg·C·hm-2 ,占 73 32 %。樟树各器官的碳素贮量与其生物量成正比例关系 ,树干的生物量最大 ,其碳贮量也最高 ,占乔木层碳贮量的 4 0 0 6 %。樟树碳贮量的垂直分布随高度的增加而减少 ,在 8～ 1 0m区段出现明显增加的现象。樟树林年净生产力为9 5 5× 1 0 3 kg·hm-2 ·a-1 ,碳的年净固定量为 4 98×     

民勤绿洲-荒漠过渡区水量平衡规律研究

以甘肃省民勤县刘家地村外缘的绿洲 -荒漠过渡地带为定位研究区域 ,利用长期调查和水文学研究方法从生态系统的角度对绿洲 -荒漠过渡区的水量平衡特别是土壤水分和蒸散量的时空格局与动态特征进行了研究。结果显示 :1沿绿洲至流动沙丘这一过渡带 ,随着与绿洲距离的逐渐拉大 ,土壤含水量减小 ,0～ 80 cm土层的月平均土壤含水量的大小顺序为红柳沙包(5 .6 1% ) >白刺沙包 (5 .4 7% ) >流动沙丘 (5 .2 2 % ) ;土壤水分垂直变化规律是由表层到深层依次递增。 2在蒸散日进程中 ,红柳沙包和白刺沙包的蒸散率峰值到来时间比流动沙丘早 1～ 2 h,且日最大蒸散速率大小顺序为红柳沙包 (0 .2 4 mm / h) >白刺沙包 (0 .2 0 m m/ h) >流动沙丘 (0 .18mm/ h) ;影响绿洲荒漠 -过渡区蒸散的主要气象因子为日照百分率、气温、空气饱和差以及风速等 ,它们与日蒸散量的斜率关联度分别为 0 .717、0 .6 4 3、0 .6 4 9和 0 .70 5。3生态系统总的水量平衡特点是 ,水分输入主要靠降水和土壤水分的水平运动补给 ,而土壤和植被蒸发散是系统的主要输出项。     

荒漠草原与典型草原NPP、碳积累对不同降雨年份和利用方式的响应

不同草原利用方式正在影响着内蒙古的草原生态系统,而且在未来降水空间格局变化的背景下,它们共同决定了生态系统植被类型、净初级生产力(NPP)和生态系统碳积累。选取内蒙古中部两个重要的草地类型:荒漠草原和典型草原,研究不同草原利用方式(围栏禁牧、划区轮牧、割草、自由放牧)植物群落在降雨量不同的两个生长季节地上(ANPP)、地下净初级生产力(BNPP)的变化,同时也评估了植物群落的碳积累,研究结果表明:1)在降雨量亏缺年份,与围封相比,荒漠草原自由放牧区ANPP、BNPP及碳积累分别下降了57.1%、51.7%和56.0%,而典型草原自由放牧区分别下降了18.4%、25.1%和17.9%。2)在降雨量充足年份,与围封相比,荒漠草原划区轮牧区ANPP、BNPP以及碳积累分别增加了18.2%、9.8%和21.9%,而典型草原各处理下围封禁牧区ANPP仍是最高;3)两种草地类型下,降雨量对自由放牧的调控作用高于其它草地利用方式;4)荒漠草原ANPP在丰雨年是欠雨年的2倍,而典型草原仅增加了79.0%,降雨量对荒漠草原生产力的季节调控作用远高于典型草原。在未来全球气候变暖和降水格局变化的情况下,荒漠草原降雨量是影响荒漠植物群落NPP和碳积累的主导因子。     

祁连山中部四种典型生态系统土壤有机碳矿化及其影响因素

以正交试验培养土壤探讨了祁连山4种典型生态系统土壤有机碳矿化及其与温湿度的关系。结果表明:温度对土壤有机碳累积矿化量及其比例影响显著(P<0.05)。就土壤有机碳累积矿化量,35℃和25℃比5℃下高(P<0.05);土壤培养14d,10%含水量下为最低,山地森林土壤比荒漠草原和干草原高,高寒草甸比荒漠草原高(P<0.05)。就土壤有机碳矿化比例,35℃和25℃比5℃下高,35℃比15℃下高(P<0.05);荒漠草原和干草原比山地森林和高寒草甸低(P<0.05)。土壤有机碳矿化速率及其比例随培养时间延长而递减。温度和生态系统类型对土壤有机碳矿化速率及比例影响显著(P<0.05)。就土壤有机碳矿化速率,25℃和35℃比5℃下高(P<0.05);土壤培养0～4d和6～10d,10%含水量下最低,高寒草甸和山地森林比荒漠草原高(P<0.05)。就土壤有机碳矿化速率比例,25℃和35℃比5℃下高,35℃比15℃下高;山地森林和高寒草甸比荒漠草原和干草原中高(P<0.05)。一阶动态方程拟合土壤有机碳矿化动态效果较好(R2>0.95)。表明祁连山4种典型生态系统土壤有机碳分解受温度变化影响较大。     

不同生态系统土壤氨基酸氮的组成及含量

采集于内蒙古白音锡牧场、陕西澄城、杨凌、宜川和太白山等地不同生态系统的 1 2个土样 ,用 6 mol/ L HCl水解 ,经 H型酸性阴离子交换树脂柱纯化后 ,用 Beckman 1 2 1 MB型氨基酸分析仪测定了 1 7种常见氨基酸。测定结果表明 ,不同生态系统土壤酸解氨基酸含量有很大差异 ,表现为草甸土壤 (氨基酸含量为 2 2 83.9μg N/ g) >森林土壤 ( 1 733.6μg N/g) >草原土壤 ( 85 6 .3μg N/ g) >农田土壤 (平均为 2 4 8.5± 37.8μg N/ g) ,并且氨基酸氮与土壤全氮有极显著的正相关关系 ( p<0 .0 1 ) ;在氨基酸中以中性氨基酸所占比例最大 ,平均为 5 3.99% ,其次为碱性和酸性氨基酸 ,分别为 2 4 .94 %和2 0 .5 9% ,含硫氨基酸最少 ,仅为 0 .4 8% .游离氨基酸以草甸土壤最高 ,为 1 4 .5 8μg N/ g,其它土壤在 1 .1 4～ 8.6 7μg N/ g之间 ,大部分在 2～ 3μg N/ g。游离氨基酸不仅数量低 ,而且种类也比酸解氨基酸少。不管是酸解氨基酸 ,还是游离氨基酸 ,在 0～ 2 0 cm土层的含量均大于 2 0～ 4 0 cm土层 ,从不同土壤样品的平均结果看 ,对酸解氨基酸 ,0～ 2 0 cm土层为96 0 .9μg N/ g,2 0～ 4 0 cm土层为 5 2 8.9μg N/ g ;对游离氨基酸氮 ,0～ 2 0 cm土层 6 .2 8μg N / g,2 0～ 4 0 cm土层 2 .2 2μgN/ g。施用氮     

Harvester ant seed removal in an invaded sagebrush ecosystem: Implications for restoration

A better understanding of seed movement in plant community dynamics is needed, especially in light of disturbance‐driven changes and investments into restoring degraded plant communities. A primary agent of change within the sagebrush‐steppe is wildfire and invasion by non‐native forbs and grasses, primarily cheatgrass (Bromus tectorum). Our objectives were to quantify seed removal and evaluate ecological factors influencing seed removal within degraded sagebrush‐steppe by granivorous Owyhee harvester ants (Pogonomyrmex salinus Olsen). In 2014, we sampled 76 harvester ant nests across 11 plots spanning a gradient of cheatgrass invasion (40%–91% cover) in southwestern Idaho, United States. We presented seeds from four plant species commonly used in postfire restoration at 1.5 and 3.0 m from each nest to quantify seed removal. We evaluated seed selection for presented species, monthly removal, and whether biotic and abiotic factors (e.g., distance to nearest nest, temperature) influenced seed removal. Our top model indicated seed removal was positively correlated with nest height, an indicator of colony size. Distance to seeds and cheatgrass canopy cover reduced seed removal, likely due to increased search and handling time. Harvester ants were selective, removing Indian ricegrass (Achnatherum hymenoides) more than any other species presented. We suspect this was due to ease of seed handling and low weight variability. Nest density influenced monthly seed removal, as we estimated monthly removal of 1,890 seeds for 0.25 ha plots with 1 nest and 29,850 seeds for plots with 15 nests. Applying monthly seed removal to historical restoration treatments across the western United States showed harvester ants can greatly reduce seed availability at degraded sagebrush sites; for instance, fourwing saltbush (Atriplex canescens) seeds could be removed in <2 months. Collectively, these results shed light on seed removal by harvester ants and emphasize their potential influence on postfire restoration within invaded sagebrush communities.     

Diet of two sympatric Pheidole spp. ants in the central Monte desert: implications for seed–granivore interactions

Ants of the genus Pheidole are important seed consumers in several desert ecosystems. In South American deserts, although several Pheidole spp. have been characterized as seed harvesters, studies on their diet and ecological role are still missing. Pheidole spininodis (Mayr) and Pheidole bergi (Mayr) are capable of removing seeds in the central Monte desert. The aim of this study was to quantify and compare the diet of these species and to interpret the results in the context of seed–granivore interactions. Diet was estimated during mid-summer by collecting items brought back to the nest by foragers in ten colonies per species. While P. spininodis was mainly granivorous, P. bergi was mainly insectivorous. However, they both collected ~40% of other types of items. Among seeds, the diet of P. spininodis included mostly grass seeds, whereas the diet of P. bergi was mainly made up of shrub and tree seeds, usually retrieved cooperatively. This behavior allowed P. bergi to carry larger seeds, resulting in diet partitioning in terms of seed size. However, diet of P. spininodis is very similar to that of three sympatric Pogonomyrmex species. Thus, specialized harvester ants remove large quantities of grass seeds in the central Monte desert during the summer, potentially affecting their abundance in the soil seed bank. P. bergi directs its feeding pressure to shrub and tree seeds, and although seeds constitute ~10% of its diet, its high colony density and high activity levels, added to the lower proportion of large seeds in the soil seed bank, indicate that their importance as seed consumers cannot be ruled out.     

阿拉善干旱荒漠区不同植被类型土壤种子库研究

[1]兰州大学草地农业科技学院,兰州730020 [2]甘肃草原生态研究所,兰州730020 [3]内蒙古阿拉善盟草原站,巴彦浩特750360     

The effects of harvester ant (Messor ebeninus Forel) nests on vegetation and soil properties in a desert dwarf shrub community in north-eastern Arabia

In desert ecosystems, harvester ants have been shown to be important granivores and seed dispersers. Because many desert plants exist as seeds in the ground for long periods, harvester ants may greatly influence plant population dynamics. In this study, we examine the effects of harvester ant nests on vegetation and soil properties in a desert ecosystem dominated by the dwarf shrub Rhanterium epapposum in Kuwait, north-eastern Arabia. Soil properties were greatly modified in the circular refuse zone around the nests of the harvester ants, with elevated levels of nutrients (except nitrogen) and organic matter. Plant species richness and productivity were also significantly enhanced in the refuse zone. The vast majority of species inhabiting this zone were desert annuals, but there is no evidence to suggest that the species involved have any distinct association with ant nests. Harvester ants therefore contribute substantially to small-scale spatial heterogeneity in this aridland plant community. It is also suggested that the significance of ant nests in providing favourable sites for plant growth is enhanced in drier years, when many species in off-nest sites may die prematurely due to drought. Furthermore, because ants occasionally abandon their nests and create new colonies, the addition of nutrient-rich patches to the landscape over time could represent an important mechanism for maintaining fertility of desert soils, possibly with long-term implications for plant biodiversity. Harvester ants can therefore be regarded as a key ecosystem engineer in this relatively undisturbed desert ecosystem of Kuwait.     

古尔班通古特沙漠植物种子大小变异的空间格局

在古尔班通古特沙漠70个固定样地中采集了87种植物种子,通过测量种子百粒重,分析了种子大小在不同分类群中的变异规律,并调查了样地中不同类型种子总数目的空间格局。结果发现:1)古尔班通古特沙漠植物种子大小可分为:A(0.1—1 mg)、B(1—10 mg)、C(10—100 mg)、D(100—1000 mg)、E(1000—5000 mg)5种类型。拥有不同类型物种数量差异较大,其中D型种子物种最多,含41种占总物种数目的 47.1%,其次C型种子30种占总物种数目的 34.5%,E型种子占总物种数的13.8%,B型种子总物种数的3.5%,A型种子占总物种数的1.1%。沙漠植物中中等种子大小物种占多数,与以色列特拉维夫以北的Poleg自然保护区地中海沿岸沙漠地区相似。由于本地属、种为地中海区、西亚至中亚分布,所以认为本沙漠种子大小主要受系统演化影响。2)科间种子大小存在极显著差异,百粒重最大科是蓼科(29315 mg)、最小的是列当科(0.3 mg)。藜科,菊科,紫草科的属间种子大小差异显著。3)生活型间种子大小差异显著,种子大小从大到小排序为:灌木类短命植物多年生草本短命植物半灌木1年生草本。4)种子大小与物种相对分布频度相关性不显著,但将相对分布频度小于1.4%的环境特化物种去除后,种子大小与物种相对分布频度呈指数型极显著负相关。5)B型、C型、D型三类种子在样地中的总数目随海拔、经度和降水的增加而极显著增加,随纬度的增加而极显著降低,E型种子则与之相反。表明古尔班通古特沙漠未来随着降水的增加,B型、C型、D型种子的植物优势性逐渐增加,而E型种子的灌木类等物种优势性逐渐减少,注意加以保护。     

The effects of the red imported fire ant on seed fate in the longleaf pine ecosystem

The natural patterns of myrmecochory are disrupted by the dominance of red imported fire ants (Solenopsis invicta) in the southeastern United States. This leads to questions about the role of fire ants as seed dispersers. We examined the fate of ant-dispersed seed in the longleaf pine ecosystem. First, we determined removal rates for a suite of common ground cover species. Then, we verified the final location of removed seeds by using a wax cast to examine nest contents, and locating dyed seeds deposited in trash piles on the ground surface. Finally, we determined if the germination rate of seeds deposited by fire ants was affected by ant dispersion. Fire ants were most attracted to elaiosome-bearing seed and collected nonelaiosome-bearing seed at a much lower rate. No seeds were found in the contents of wax castings of fire ant nest chambers, suggesting that seed is not stored within the nest. Of the dyed seeds that we presented to fire ants, 30–40 % were recollected in surface trash piles in the mound vicinity within 1 week following removal. Undiscovered seeds were considered destroyed or buried in foraging tunnels. A small percentage of the deposited seeds were able to germinate, but there was no difference in the percent germination between seeds manipulated by fire ants and the control. Low germination was likely due to a high percentage of immature seeds used in the study. Our findings support a growing body of evidence that fire ants facilitate the movement of seeds in the longleaf pine ecosystem.