菌肥与有机无机肥配施对石灰性土壤不同形态氮素的影响

利用不同施肥处理对山西省晋中市石灰性土壤几种不同形态氮素含量的变化及其相关性进行研究。结果表明:每个施肥处理施入等量的氮(N)、磷(P2O5),土壤的铵态氮、硝态氮及微生物氮含量都在逐年增加,其中有机肥+化肥+菌肥处理对提高土壤铵态氮作用明显;单施有机肥处理对提高土壤硝态氮效果显著,与有机肥+化肥+菌肥、有机肥+化肥处理效果差异性不显著;有机肥+化肥+菌肥处理对土壤微生物氮效果最明显,有机肥+化肥效果次之,两处理差异显著。土壤铵态氮和硝态氮含量呈显著正相关;微生物氮与铵态氮、硝态氮含量相关性都不好;菌肥与有机无机肥配施后,菌肥对于提高土壤微生物氮最显著(10.09%),铵态氮次之(6.24%),硝态氮不明显(2.05%),因此虽然添加了菌肥,但是没有完全改变"有机肥+化肥+菌肥"仍然是"有机肥+化肥处理"的本质属性。     

氮素和水分对贝加尔针茅草原土壤酶活性和微生物量碳氮的影响

在内蒙古贝加尔针茅草原,分别设对照(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30g·m-2(N300)(不包括大气沉降的氮量)8个氮素(NH4NO3)梯度和模拟夏季增加降水100 mm的水分添加交互试验,研究氮素和水分添加对草原土壤养分、酶活性及微生物量碳氮的影响。结果表明:氮素和水分添加对草原土壤理化性质和生物学特性有显著影响。随施氮量的增加土壤总有机碳、全氮、硝态氮、铵态氮含量呈增加的趋势,相反,土壤pH值呈降低的趋势。土壤脲酶和过氧化氢酶的活性随施氮量的增加而升高,多酚氧化酶则随施氮量的增加呈下降的趋势。氮素和水分添加对草原土壤微生物量碳氮含量有显著影响,高氮处理(N150、N200和N300)显著降低了微生物碳含量,微生物氮含量随施氮量的增加呈上升趋势。水分添加能够减缓氮素添加对微生物的抑制作用,提高微生物量碳、微生物量氮含量。草原土壤养分、土壤酶活性及土壤微生物量碳氮含量间关系密切,过氧化氢酶与全氮、总有机碳、硝态氮呈显著正相关,多酚氧化酶与铵态氮、硝态氮、全氮呈显著负相关。微生物量氮含量与土壤全氮、铵态氮、硝态氮含量以及过氧化氢酶和磷酸酶活性呈显著正相关,与多酚氧化酶呈负相关;微生物量碳与过氧化氢酶呈负相关,与多酚氧化酶活性呈正相关。     

黄土丘陵区不同植被恢复措施对土壤养分和微生物量C、N、P的影响

以黄土丘陵典型地区-宁夏固原不同植被恢复措施:撂荒地、人工草地、天然草地和灌木林地(柠条)为研究对象,分析了不同植被类型下土壤微生物量碳、氮、磷的变化.研究结果表明:不同植被类型条件下,土壤微生物量有显著差异,微生物量碳和微生物量磷含量均表现为撂荒地<人工草地<天然草地<灌木林地,微生物量氮以人工草地略低,撂荒地和柠条林地较大.土壤微生物量碳、氮、磷与土地利用方式关系密切.柠条林对土壤微生物生物量有明显的促进作用.     

添加尿素和秸秆对三熟制水旱轮作土壤各形态氮素的影响

添加不同外源氮对土壤中不同形态氮素的转化具有十分重要的影响。选取长期耕作土壤,设置对照、添加尿素N 150 kg/hm~2(U150)、添加秸秆(相当于添加N 38 kg/hm~2,Straw)、添加尿素N 150 kg/hm~2+秸秆(相当于添加N188 kg/hm~2,U150+Straw)和添加尿素N 188 kg/hm~2(U188)5个处理进行室内培养试验,研究了添加不同外源氮对土壤铵态氮、硝态氮、可溶性有机氮、微生物生物量氮含量的影响。结果表明,土壤铵态氮随着培养时间的延长表现为先增后减的趋势,添加尿素的两个处理其土壤铵态氮较Straw、U150+Straw处理能够更快地达到峰值;而土壤硝态氮则表现为逐步增加的趋势。添加尿素处理能够显著提高土壤矿质氮的含量,在添加等量氮素的条件下,U188处理矿质氮含量在培养期间始终高于U150+Straw处理;此外,U150+Straw处理矿质氮含量在培养前期均低于U150处理,至培养30天后其含量略高于U150处理。与对照相比,培养结束时添加不同外源氮素处理的土壤矿质氮含量能够提高169.61%~496.75%。对于微生物生物量氮和可溶性有机氮而言,添加不同外源氮素分别在培养10天和30天达到峰值,此后逐渐降低。不同处理而言,添加秸秆+尿素、添加秸秆处理的微生物生物量氮和可溶性有机氮含量在培养前期明显高于仅添加尿素的两个处理,说明添加有机物料氮源主要有益于提高土壤有机态的氮素含量。     

多糖微生物菌液对油菜吸收养分和土壤氮磷淋失的影响

为探究富含多糖微生物菌液和化肥混合使用对植物吸收养分和控制土壤氮磷淋失的影响,采用油菜盆栽试验方法,把一定体积微生物菌液和不同量化肥进行混合灌溉油菜,油菜收获后,测定油菜和上下两层土壤的理化性质。结果表明,T5 处理(50 mL 微生物菌液,1.2 g 尿素和0.72 g 磷酸二氢钠混合加入到4.5 kg 土壤中)油菜生物量最大,油菜对氮、磷、钾具有较高同化吸收能力;随着化肥用量的增加,上层土壤有效磷含量增加缓慢,下层土壤有效磷含量与对照没有显著性差异,磷的垂直淋失风险较小;当化肥用量低于T5 处理用量时,上层土壤铵态氮含量高于对照,而土壤硝态氮含量低于对照,下层土壤铵态氮和硝态氮含量与对照没有显著性差异,说明氮淋失量较小;化肥用量高于T5 处理用量时,与对照相比,上层土壤硝态氮和铵态氮含量显著增加,下层硝态氮增加不显著,但是土壤铵态氮显著增加,提高了氮垂直淋失风险。加入微生物菌液可以活化土壤中的钾元素,有利于油菜对钾的吸收。研究表明,微生物菌液与适量化肥混合使用,有助于化肥减量和油菜不减产,不但对土壤氮、磷淋失具有一定抑制作用,还可促进油菜对土壤中钾的吸收。     

宁夏黄土丘陵区植被恢复对土壤养分和微生物生物量的影响

本研究以宁夏固原天然草地、农地、撂荒地和不同年限的柠条林地为研究对象,分析了不同植被类型下土壤养分和土壤微生物生物量碳、氮、磷的变化。研究结果表明:土壤养分除速效磷和全氮外,其他指标均为农地最低,撂荒地次之,并且随植被恢复年限的增加而增加;不同植被类型条件下,土壤微生物生物量有显著差异,微生物量碳含量表现为撂荒地农地天然草地3年柠条林地13年柠条林地23年柠条林地,微生物量氮以天然草地最低,农地、撂荒地和不同年限柠条林地较大,不同植被类型土壤微生物量磷差异显著,在5~20cm土层和20~40cm土壤中表现尤为突出。土壤微生物量碳、氮、磷与植被类型和植被恢复年限关系密切。柠条林对土壤微生物生物量有明显促进作用,并且随着植被恢复年限的增加改良效果越显著。     

不同施氮水平下土壤的生化性质对干湿交替的响应

以中国科学院封丘农业生态试验站水氮耦合长期试验地为研究平台,采集五个施氮水平(施氮0、150、190、230、270 kg hm-2)下表层0 ～ 20 cm土壤并测定其土壤肥力参数(土壤pH、全氮、全磷、全钾、碱解氮、速效磷、速效钾、有机碳).结果表明:施氮降低了土壤pH、速效磷、全钾,增加了全氮、碱解氮、有机碳,除有机碳随施氮水平的增加而增加外,其他肥力参数并未随施氮水平的增加而发生规律性变化.土壤经过0、3、6、10次干湿交替,培养60 d后测定其生物和化学性质(土壤铵态氮、硝态氮、溶解性有机碳、脲酶活性、脱氢酶活性、微生物生物量碳、土壤基本呼吸).双因素方差分析显示干湿交替次数对铵态氮、硝态氮、无机氮、溶解性有机碳、脱氢酶活性、微生物生物量碳和土壤基本呼吸均有极显著作用,而干湿交替次数和施氮水平对除脱氢酶活性以外的其他土壤性质均无交互作用.五个施氮水平下土壤硝态氮、无机氮、溶解性有机碳、脲酶活性、脱氢酶活性和微生物生物量碳均随干湿交替次数增加而增加,土壤基本呼吸随干湿交替次数增加而降低.高施氮水平(施氮超过190 kg hm-2)下土壤性质的变异系数更小并能更好地发生聚类.研究表明当土壤遭遇干湿交替时,高施氮水平下土壤更能维持其生化性质的稳定.     

封育对蒿类荒漠草地土壤氮素含量及其组分特征的影响

为探讨蒿类荒漠草地土壤氮素含量及其组分特征,采用成对试验设计,研究封育对天山北坡不同区域蒿类荒漠草地土壤全氮、碱解氮、硝态氮和铵态氮含量的影响。结果表明:(1)封育后蒿类荒漠草地0—50 cm土层土壤氮密度(0.59~0.79 kg/m²)、土壤全氮含量(0.81~1.50 g/kg)、土壤碱解氮含量(19.44~67.49 mg/kg)变化不显著(p＞0.05)。(2)封育对蒿类荒漠草地土壤硝态氮含量(6.41~21.26 mg/kg)、铵态氮含量(0.26~2.53 mg/kg)的影响因区域差异而有所不同。封育后巩留、呼图壁样地0—50 cm土层硝态氮含量依次显著降低24.61%,47.25%(p＜0.01),而奇台样地则显著增加20.95%(p＜0.05);封育后玛纳斯样地0—50 cm土层铵态氮含量显著增加27.98%(p＜0.05),而巩留、博乐、呼图壁样地则降低不显著(p＞0.05)。(3)蒿类荒漠草地土壤硝态氮、铵态氮含量依次占全氮量的0.27%~3.01%,0.02%~0.42%,且随土壤全氮的增加,有机氮占比增加,而无机氮、硝态氮和铵态氮占比降低。(4)相关分析表明,土壤全氮、碱解氮、硝态氮、铵态氮与有机碳、全磷呈正相关,与土壤容重、pH、电导率呈负相关,铵态氮与土壤含水量呈正相关,与速效磷呈负相关。偏冗余分析表明,土壤理化因子对土壤氮素影响的主要因子为土壤有机碳和土壤含水量,解释率依次为32.60%,17.90%。研究结果为揭示封育过程中蒿类荒漠草地土壤恢复及养分管理提供科学数据支撑。     

小麦-玉米轮作体系下氮肥对长期不同施肥处理土壤氮含量及作物吸收的影响

以长期不同施肥处理土壤为对象,研究了不同施肥土壤中施用氮肥后土壤氮素含量、微生物固持及释放和作物吸收及利用特性。结果表明,施用氮肥显著增加长期不施肥土壤(NF)矿质氮含量,对长期施用化肥土壤(NPK)和有机无机配施土壤(MNPK)矿质态氮含量无显著影响;施用氮肥对NF中土壤微生物生物量氮(SMBN)含量无显著影响,使拔节期NPK和MNPK中SMBN含量分别增加了4.3倍和0.8倍。从小麦拔节期到开花期,NPK和MNPK中土壤微生物生物量氮含量分别显著降低51%和56%。小麦收获时NPK和MNPK土壤氮肥的利用率分别为36%和45%;而NF土壤所施入的氮素几乎未被小麦吸收利用,但在玉米季有34%被吸收。小麦收获时,NF土壤施入的氮肥有50%以上淋溶至土壤30 cm以下土层,施氮也显著提高了NPK土壤30～50 cm土层硝态氮含量,但施用氮肥对MNPK土壤0～100 cm剖面硝态氮含量无显著影响。说明长期有机无机配施增强了土壤氮素的缓冲能力,协调了土壤氮素固持与作物吸氮间的关系,为提高氮素利用率,减少氮素对环境影响的有效手段。     

不同培肥处理对采煤塌陷区复垦土壤氮素形态的影响

采煤塌陷造成了严重的耕地破坏,复垦是恢复塌陷土壤肥力的重要措施。目前人们对复垦土壤氮素形态变化的机理认识较为有限。该试验以采煤塌陷区复垦1a土壤为研究对象,研究其在有机肥(M)、无机肥(NP)、有机+无机肥(NP+M)、有机+无机肥+菌肥(NP+M+B)等培肥方式下土壤铵态氮、硝态氮、微生物氮等不同氮素形态含量的变化,探究复垦土壤上氮素转化机理,加快土壤熟化速度。结果表明:不同培肥处理与对照相比,M处理土壤有机质、微生物量氮最为明显,增幅分别为53.85%,54.9%;NP+M+B、NP+M、M处理均明显提高了土壤全氮、全磷含量,但各处理间差异不显著;NP+M+B处理的土壤速效磷增幅最大(48.13%);不同培肥处理间土壤pH值差异不明显。NP+M+B处理提高土壤铵态氮含量效果最为明显(68.06%),NP+M+B与NP+M处理均可明显提高土壤硝态氮含量,增幅分别是24.13%和36.94%。NP+M+B处理明显提高了土壤氨化细菌数量且与NP+M处理差异显著,2个处理的硝化细菌数量则差异不显著。NP+M+B与NP+M处理脲酶活性高于其余处理,但二者差异不显著。氨化细菌数量与铵态氮含量相关性极显著。     

Temporal changes in fertility and microbial properties of soil in forest-converted oil palm plantations in Okomu forest reserve,Nigeria

Evidence of the impacts of land-use change on soil biological activities, a determinant of nutrient cycling in soil, will provide a better understanding of soil health and productivity. The study investigates temporal changes in soil chemical and microbial properties in a forest converted to oil palm plantation. Soil samples from four locations: native forest and Elaeis guineensis plantations of 2-, 13- and 14-year were collected. Total carbon C and N were significantly higher (p < 0.05) in the native forest (NF) followed by 14- and 13-year E. guineensis plantations respectively. Microbial biomass carbon (MBC) and nitrogen (MBN) in NF were significantly higher (p < 0.05) than in the E. guineensis plantations. There were no significant differences in the microbial biomass phosphorus (MBP) among the E. guineensis plantation of all ages. The qCO₂ in the 13- and 14-year E. guineensis plantations was higher than in NF and 2-year E. guineensis plantation. There was a positive correlation between MBC, MBN, MBP and pH, P, TC, and TN. These results indicated that conversion of native forest to E. guineensis plantation affected soil nutrient and microbial properties. And there could be a return to healthy soil condition as age of E. guineensis plantation increased.     

Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

Background, Aims, and Scope  An improved understanding of important soil carbon (C) and nutrient pools as well as microbial activities in forest ecosystems is required for developing effective forest management regimes underpinning forest productivity and sustainability. Forest types and management practices can have significant impacts on soil C and nutrient pools as well as biological properties in forest ecosystems. Soil C and nutrient pools were assessed for adjacent natural forest (NF), first rotation (1R) (50-year-old), and second rotation (2R) (1-year-old) hoop pine (Araucaria cunninghamii Ait. ex D. Don) plantations in southeast Queensland of subtropical Australia. Materials and Methods  Five transects spaced 3 m apart with 9 sampling points along each transect were selected (9.6 m × 12.0 m each site), with 45 soil cores (7.5 cm in diameter) collected and separated into 0–10 and 10–20 cm depths. These soils were analysed for total C, total nitrogen (N), C (δ¹³C) and N (δ¹⁵N) isotope composition. The 0–10 cm soils were analysed for pH, CEC, exchangeable cations, total P and total K, and assayed for microbial biomass C and N, respiration, metabolic quotient, potential mineralizable N (PMN), gross N mineralization (M) and immobilization (I). Results  Total C and N in 0–10 cm soils were higher under NF and 1R plantation than under 2R plantation, while they were highest in 10–20 cm soils under NF, followed by the 1R and then 2R plantation. δ¹³C was lower under NF than under the plantations, while δ¹⁵N was higher under NF than under the plantations. Total P was the highest under NF, followed by the 1R and then 2R plantation, while total K was higher under the 2R plantation. No significant differences were detected for pH, CEC, exchangeable cations, microbial C and N, respiration and metabolic quotient among the 3 sites. PMN and M were higher under NF, while I was the highest under the 2R plantation, followed by the NF and then 1R plantation. Discussion  Soil total C and N in 0–10 cm depth were significantly lower under 2R hoop pine plantation than those under NF and 1R hoop pine plantation. There were significant reductions in soil total C and N from NF to 1R and from 1R to 2R hoop pine plantations in 10–20 cm depth. This highlights potential N deficiency in the 2R hoop pine plantations, and application of N fertilizers may be required to improve the productivity of 2R hoop pine plantations. There were no significant differences in other soil chemical and physical properties in 0–10 cm depth among the 3 sites under NF, 1R and 2R hoop pine plantations, except for soil total P and K. Soil microbial biomass C, CO₂ respiration and metabolic quotient did not differ among the 3 sites assessed, perhaps mainly due to these biological variables being too sensitive to variations in soil chemical and physical properties and thereby being associated with a larger variability in the soil biological properties. However, soil potential mineralizable N, gross N mineralization and immobilization were rather sensitive to the conversion of NF to hoop pine plantation and forest management practices. Conclusions  Total C and N in the top 20 cm soil were highest under NF, followed by 1R and then 2R hoop pine plantations, indicating that N deficiency may become a growth-limiting factor in the 2R hoop pine plantations and subsequent rotations of hoop pine plantation. The sample size for soil δ¹³C seems to be much smaller than those for soil total C and N as well as δ¹⁵N. The significant reductions in soil total P from NF to 1R and then from 1R to 2R hoop pine plantations highlight that P deficiency might become another growth-limiting factor in the second and subsequent rotations of hoop pine plantations. Soil microbial properties may be associated with large spatial variations due to these biological properties being too sensitive to the variations in soil chemical and physical properties in these forest ecosystems. Recommendations and Perspectives  Soil potential mineralizable N, gross N mineralization and immobilization were useful indices of soil N availability in response to forest types and management practices. The sampling size for soil δ¹³C was much smaller than the other soil chemical and biological properties due to the different patterns of spatial variation in these soil properties.     

黄河三角洲不同退化程度人工刺槐林土壤酶活性、养分和微生物相关性研究

由人为及自然多种因素的影响造成很多地区人工林地出现衰退现象。本研究选择黄河三角洲不同退化程度的刺槐人工林,对林地土壤酶、养分和微生物及其相关性进行了研究,探讨人工刺槐林退化的原因。结果表明:随着人工刺槐林退化程度加重,土壤脲酶、多酚氧化酶和过氧化物酶活性下降;过氧化氢酶活性则先上升,重度退化林地下降。脲酶与多酚氧化酶和过氧化物酶活性显著相关,过氧化物酶与多酚氧化酶活性显著相关,其他酶之间相关性不显著。土壤养分与土壤酶的变化趋势基本一致,随着林分退化程度加重,有机质、全氮、碱解氮、速效磷含量均呈下降趋势;土壤pH、含盐量随着林分退化程度加重与土壤深度增加而上升,与土壤酶活性的变化趋势相反。土壤酶特别是脲酶活性与土壤养分显著正相关性,与土壤pH和含盐量呈显著负相关。不同退化程度的人工刺槐林地土壤细菌数量最多;真菌和放线菌与细菌变化趋势各不相同,随着退化程度的增加,细菌平均数量表现为未退化>轻度退化>中度退化>重度退化,真菌数量为轻度退化>未退化>中度退化>重度退化,放线菌数量为中度退化>轻度退化>未退化>重度退化。脲酶与细菌、真菌和放线菌数量显著相关,细菌与除过氧化氢酶外的土壤酶活性显著相关,其他酶活性与各类微生物数量相关性不显著。     

Soluble organic C and N and their relationships with soil organic C and N and microbial characteristics in moso bamboo (Phyllostachys edulis) plantations along an elevation gradient in Central Taiwan

Purpose

Moso bamboo (Phyllostachys edulis), an important economic crop, is distributed from low- to medium-elevation mountains in Taiwan. Bamboo is a fast-growing herbaceous species with an extensive rhizome structure. With the hypothesis that the characteristics of soil organic matter and microbes might change after long-term bamboo plantation, we investigated different fractions of organic C and N as well as soil microbial biomass and activities in five moso bamboo plantations along an elevation gradient in Central Taiwan.

Materials and methods

Five soil samples (top 10 cm of soil) were collected from each bamboo plantation (600, 800, 1,000, 1,200, and 1,400 m above sea level (asl)) in January 2011. Soil was processed and analyzed for soil total C and N contents, biologically available C, potentially mineralizable N, soil microbial biomass and soil respiration (CO₂). Two extraction methods (2 M KCl and hot-water extraction) were used to estimate soil soluble organic C and N (S_bOC and S_bON) and soil inorganic N (NH₄ ⁺ and NO₃ ^?) concentrations to evaluate the relationship with soil organic matter and microbe characteristics in bamboo plantations.

Results and discussion

Soil total C and N contents as well as soil microbial biomass and soil respiration (CO₂) of the bamboo plantations increased along the elevation gradient. Temperature changes along elevation contributed to such variations observed among the selected bamboo plantations. The S_bON in hot-water extracts was highest in the 1,200-m plantation, then in the 1,400-m plantation, and lowest in the low-elevation plantations (600, 800, and 1,000 m). However, S_bON in 2 M KCl extracts did not differ by elevation. The S_bON was strongly correlated with soil total N in both 2 M KCl and hot-water extracts, but only S_bON in hot-water extracts was strongly correlated with microbial biomass N and potentially mineralizable N. S_bOC was strongly correlated with soil total C content, microbial biomass C, and biologically available C in both 2 M KCl and hot-water extracts.

Conclusions

Soil total C and N, S_bOC and S_bON, and microbial biomass characteristics increased in the moso bamboo plantations with increasing elevation. No altitudinal difference in specific soil respiration (CO₂) rate suggested that the enhanced potentially mineralizable N and soil respiration (CO₂) in the high-elevation plantations were associated with increased microbial biomass rather than microbial activities.     

Organic Matter Dynamics in Reclaimed Lignite Mine Soils under Robinia pseudoacacia L. Plantations of Different Ages in Germany

In temperate regions, cultivation of Robinia pseudoacacia L. has recently received considerable attention because it is a fast-growing species for biomass and bioenergy production, while acting as a potential carbon (C) sink to counterbalance carbon dioxide (CO₂) emissions and an alternative to agricultural crops on marginal sites. The objective of our work was to compare total organic carbon (TOC), total nitrogen (TN), and organic C fractions in postlignite mining soils under different development stages of R. pseudoacacia. Soil samples from three different depths (0–3, 3–10 and 10–30 cm) were taken in plantations 2, 3, 4, and 14 years old (R2, R3, R4, and R14, respectively). The TOC and TN contents increased with increasing tree age in all layers (P < 0.01). In the top 30 cm, TOC and TN stocks ranged from 11.7 to 59.8 Mg C ha^?1 and from 0.30 to 2.61 Mg N ha^?1 at R2 and R14, respectively. The rate of C sequestration was calculated to be 4.0 Mg C ha^?1 year^?1. Microbial biomass C and N were strongly correlated to TOC (r² = 0.96 – 0.81; P < 0.001) and TN contents (r² = 0.92 – 0.91; P < 0.001). The light fraction C (C_LF) accounted for 15–30% and the heavy fraction C for 70% of TOC in all layers. In the 0- to 3-cm layer, C_LF increased by 0.5 g kg^?1 year^?1. The results indicate that plantations of R. pseudoacacia are an attractive alternative to increase soil C contents in reclaimed lignite mining soils. In the short term, microbial biomass C and light fraction C are sensitive and provide an appropriate measure to assess soil C changes caused by cultivation of R. pseudoacacia.     

PH对红壤微生物生物量碳和生物量磷的影响

The impact of pH changes on microbial biomass carbon (Cmic) and microbial biomass phosphorus (Pmic) were examined for 3 red soils under citrus production with different lengths of cultivation. Soil pH significantly affected Cmic and Pmic. The Cmie and Pmic changes, as a function of soil pH, appeared to follow a normal distribution with the original soil pH value at the apex and as pH increased or decreased compared to the original soil pH, Cmic and Pmic declined. Moreover, there were critical pH values at both extremes (3.0 on the acidic side and 8.0 to 8.5 on the alkaline side), beyond which most of microorganisms could never survive. The effect of pH on Cmic and Pmic was also related to the original soil pH. The higher the original soil pH was, the less Cmic or Pmic were affected by pH change. It is suggested that soil microorganisms that grow in a soil environment with a more neutral soil pH range (i.e. pH 5.5-7.5) may have a greater tolerance to pH changes than those growing in more acidic or more alkaline soil pH conditions.     

桂西北不同年龄阶段秃杉人工林的水源涵养功能

为探究秃杉人工林水源涵养功能及其变化趋势,以广西南丹县不同年龄阶段(9,17,25,37年生)秃杉人工林为研究对象,采用室内浸泡法和环刀法分别研究4种林分的林冠层、林下植被层、凋落物层和土壤层持水特性。结果表明:(1)秃杉人工林林冠层和林下植物层持水量分别为18.79～28.37,1.27～4.72 t/hm~2,其中林下植物层持水量随林龄增加而显著增大(P0.05);凋落物现存量为2.23～10.67 t/hm~2,最大持水量为5.95～34.15 t/hm~2,随林龄增加而显著增大(P0.05)。(2)不同林龄秃杉林土壤非毛管孔隙度和总孔隙度分别为5.60%～15.68%和48.27%～66.85%,其中0—20,20—40 cm土层非毛管孔隙度和总孔隙度均显著大于40—80 cm土层(P0.05),同时随林龄增加而增大;土壤层(0—80 cm)最大持水量和有效持水量分别为4 196.74～4 416.47,540.13～648.07 t/hm~2,其中0—20,20—40 cm土层最大持水量和有效持水量随林龄增加而增大。(3)9,17,25,37年生秃杉人工林林分的总持水量依次为4 222.43,4 272.55,4 355.29,4 484.32 t/hm~2,随林龄增加而增大。综上,秃杉人工林能够改善土壤结构和水分状况,增强林分水源涵养功能。     

黄河三角洲长期人工林地对土壤有机碳库的影响

[目的]探讨黄河三角洲长期人工林对盐碱土壤有机碳库的作用效果,为充分发挥其生态功能与经济效益提供科学依据与技术参考。[方法]以刺槐、白蜡、白榆和臭椿纯林以及刺槐—白蜡、刺槐—白榆和刺槐—臭椿混交林等近30a的7个长期人工林为研究对象,并分别设置标准池,采用多点混合采样法,研究土壤活性有机碳、碳库管理指数的变化规律。[结果]3个混交林地土壤的微生物量碳含量较高,并显著高于其他林地,其中刺槐—白蜡混交林较未造林荒地、刺槐、白蜡、白榆和臭椿纯林分别提高26.16%,17.62%,88.41%,47.99%和21.64%。与未造林荒地相比,长期人工林地的水溶性有机碳含量均明显升高,而在各个不同造林措施中,刺槐—白蜡混交林的水溶性有机碳含量显著高于其他措施。各人工林地较荒地均显著提高了土壤总有机碳含量,其中3种混交林模式的土壤总有机碳含量明显高于对应纯林;同时,林地土壤不同活性有机碳含量的总体变化规律为:惰活性有机碳中活性有机碳高活性有机碳,其中刺槐—白蜡混交林更利于惰性有机碳的积累。此外,各人工林地土壤碳库指数较未造林荒地明显上升,其中刺槐—白蜡混交林的碳库管理指数达最高值,与刺槐—白榆、刺槐—臭椿混交林无显著性差异,但分别较刺槐、白蜡、白榆和臭椿纯林明显高出46.51,34.88,27.55,33.38。[结论]混交林模式较纯林对林地土壤有机碳库的改善效果更显著,对土壤具有较好的培肥作用,并处于良性管理状态,有利于林木的生长发育。     

川西亚高山针叶林植物群落演替对生物学特性的影响

通过对川西亚高山针叶林人工重建过程中土壤微生物数量、酶活性及其与土壤养分性状的关系研究表明,云杉人工成熟林土壤微生物数量、酶活性明显低于云杉人工幼林地,也低于同龄的次生阔叶林地,人工云杉林随着林龄的增加土壤肥力严重退化。土壤微生物数量、酶活性与土壤有机质、全N、全P和碱解N等养分指标呈显著相关关系,土壤生物学指标能较好地反映土壤肥力状况。解决当前人工成熟云杉林土壤退化的主要措施应因地制宜地进行抚育间伐,改善林地的微生态条件,尽量避免营造针叶纯林,建议营造针阔混交林。     

黄土高原中国松人工林演替过程中的土壤微生物和酶活性

Successional and seasonal effects on soil microbial and enzymatic properties were studied in Chinese pine (Pinus tabu- laeformis) plantations in an age sequence of 3-, 7-, 13-, 21- and 28-year-old in northern Ziwuling region in the middle of Loess Plateau, China. The results indicated that plantation age and season affected soil microbial and enzymatic parameters significantly. Soil organic C, total N, microbial biomass C, microbial quotient, basal respiration, dehydrogenase, N-α-benzoyl-L-argininamide (BAA)-protease, urease and β-glucosidase increased quickly and tended to be highest at PF21 (21-year plantation), thereafter they remained nearly at a constant level, whereas the metabolic quotient (qCO 2 ) showed an initial increase and then decreased gradually. Measures of these soil properties showed significant seasonal fluctuations except for organic C and total N, which were found to be relatively stable throughout the study period, and the seasonal distributions were autumn spring summer winter for microbial biomass C, microbial quotient, dehydrogenase, and β-glucosidase; autumn summer spring winter for BAA-protease and urease; and summer autumn spring winter for basal respiration and qCO 2 . Significant season × age interaction was observed for biomass C, basal respiration, dehydrogenase and BAA-protease.