Factors driving natural regeneration beneath a planted urban forest

Cities around the world are investing in urban forest plantings as a form of green infrastructure. The aim is that these plantations will develop into naturally-regenerating native forest stands. However, woody plant recruitment is often cited as the most limiting factor to creating self-sustaining urban forests. As such, there is interest in site treatments that promote recruitment of native woody species and simultaneously suppress woody non-native recruitment. We tested how three, common site treatments—compost, nurse shrubs, and tree species composition (six-species vs. two-species)—affected woody plant recruitment in 54 experimental plots beneath a large-scale tree planting within a high-traffic urban park. We identified naturally regenerating seedling and sapling species and measured their abundance six-years after the site was planted. This enabled us to examine initial recruitment dynamics (i.e. seedlings) and gain a better understanding of seedling success as they transition to the midstory (i.e. saplings). Seedling and sapling recruitment (native and total) was greater in areas with higher canopy cover. The combination of the nurse shrub treatment with compost and species composition (six-species) treatments increased seedling recruitment by 47% and 156%, respectively; however, the nurse shrub treatment by itself decreased seedling recruitment by 5% and native seedling recruitment by 35%. The compost treatment alone had no effect on the total number of recruits but resulted in 76% more non-native seedlings. The sizes of these treatment effects were strongly dependent on whether the forest plantings were in open areas, versus areas with existing tree canopy, the latter condition facilitating recruitment. Our findings therefore suggest that combinations of site treatments, paired with broad canopy tree species, may be most effective for promoting regeneration of native species resulting in more self-sustaining urban forests.     

脲酶抑制剂NBPT对鸡粪好氧堆肥的保氮效果

利用堆肥反应器, 以鸡粪和蘑菇渣为原料进行好氧堆肥, 在堆肥中添加不同浓度的脲酶抑制剂NBPT, 研究其对堆肥氮素转化的影响及保氮效果。结果表明: 添加不同浓度的脲酶抑制剂NBPT对堆肥进程中温度无显著影响, 在堆肥的高温阶段可有效控制堆料pH的升高, 在堆肥高温前期的0~10 d可有效降低堆肥的脲酶活性, 在堆肥中后期10~25 d明显提高全氮含量。堆肥25 d后, 添加0.04 mL·kg^-1、0.08 mL·kg^-1、0.16 mL·kg^-1脲酶抑制剂NBPT分别比CK减少氮素损失6.61%、4.89%和13.51%。堆肥过程中, 堆料铵态氮含量呈升-降-升-降的双峰趋势, 且大部分时间CK处理的铵态氮含量高于添加脲酶抑制剂NBPT处理, 且CK处理铵态氮的两次升高速度均高于添加脲酶抑制剂NBPT处理。在堆肥的升温和高温期硝态氮含量不稳定, 但堆肥结束时, 各添加脲酶抑制剂NBPT处理的硝态氮含量显著高于CK处理。本试验结果表明, 在堆肥过程中添加脲酶抑制剂NBPT可延缓鸡粪中的尿素态氮向铵态氮的转化, 增加堆肥成品中的硝态氮含量。在畜禽粪好氧堆肥中加入脲酶抑制NBPT可起到一定的保氮作用。     

双孢蘑菇培养料贴堆再发酵技术

前发酵采用并排贴近式小堆群,以增加好气发酵比重,省工省时;后发酵根据二次发酵后培养料偏生、偏干或氨味3种情况,区别进行再发酵,以提高发酵品质。     

粉煤灰和猪粪好氧混合堆肥过程中养分转化研究

以猪粪为堆肥原材料,以玉米秸秆粉为调理剂,并添加干质量分数为0、2.5％、5.0％、7.5％和10％的粉煤灰进行90 d好氧堆肥,研究不同用量粉煤灰对猪粪堆肥过程中养分转化的影响。结果表明：添加粉煤灰能提高堆体的pH值,但在后期对电导率（EC）的增加有一定的抑制;碳氮比随着堆肥时间的延长而降低,而总氮（TN）则相反;当粉煤灰质量分数达10%时,在60d后堆体TN明显降低;添加粉煤灰对NH+4-N无明显影响,而所有添加粉煤灰均会抑制堆肥中NO3-N 的生成,且与粉煤灰用量呈正相关;添加粉煤灰对总磷（TP）和总钾（TK）的影响不大,但会抑制雪里蕻根部的生长。结合发芽率试验结果可以认为,90 d的试验中所添加的粉煤灰对猪粪堆肥的腐熟没有影响。     

Influence of compost and lime on population structure and element concentrations of forest soil invertebrates

Summary We tested the effects of two organic fertilizers (composts) and lime on the soil fauna of a spruce stand. One compost was obtained from chopped wood and the other from household garbage. At the time of distribution the pH of the control plots averaged 3.2, the garbage compost had a pH of 7.5, and the wood compost of 6.2. During the experimental period the pH of the compost layers decreased. The pH of the former litter layer beneath the composts showed a steep increase after 5 months, but beneath the treatment with wood compost this effect did no persist. Liming increased the pH only slightly in the litter layer. The two types of compost, the litter layer, and lumbricids (Lumbricus rubellus) were analyzed for concentrations of essential and potentially toxic elements. The element burden was highest in the garbage compost with 7- to 11-fold concentrations of Zn, Cd, Pb, Mg, and Cu compared to the needle litter. K, Ba, and Ca were 4 times more concentrated. L. rubellus showed an increased Cu concentration after extraction from the highly contaminated sites of garbage compost. Despite the differences in Pb contamination in the needle litter and in the two compost types, all investigated individuals of L. rubellus contained similar concentrations of Pb. In contrast to Pb, Cd accumulated in this lumbricid. Seasonal fluctuations of microarthropods, their total abundance, and differences in the colonization of the compost layers were observed. Collembola abundance was significantly increased in the garbage compost plots in July 91. There were generally more Prostigmata in the control and limed plots than in the compost plots. Oribatid numbers fell under all treatments compared to the controls. Mesostigmata were identified to species level and 33 species were found in the experimental areas. Certain species, such as Arctoseius cetratus and Uropoda minima, were only found in the treated sites.     

The effect of urban refuse compost and different tractors tyres on soil physical properties, soil erosion and maize yield

Application of urban refuse compost to agricultural soil could help to solve municipalities' problems related to the increasing production of waste only if soil property improvement and environmental conservation can be demonstrated. The use of low-pressure tractor tyres is another proposal in modern agriculture for reducing soil compaction. This study thus aimed to detect the effects of both compost and low-pressure tractor tyres on soil loss, runoff, aggregate stability, bulk density, penetrometer resistance and maize (Zea mays L.) yield. A 3-year field experiment was carried out on a hilly (15% slope) clay loam soil in central Italy. Twelve plots (200 m² each) were monitored with tipping-pot devices for runoff and soil erosion measurement. Treatments were: compost addition (64 Mg ha⁻¹), mineral fertilisation, use of low-pressure tyres, use of traditional tyres, with three replicates, in a fully randomised block design. Compost was applied once at the beginning of the experiment. Runoff reduction due to compost ranged between 7 and 399 m³ ha⁻¹ during seasons, while soil erosion was reduced between 0.2 and 2.4 Mg ha⁻¹. Mean weight diameter (MWD) of stable aggregates, measured on wheel tracks, increased by 2.19 mm, then progressively decreased. Compost significantly increased bulk density by 0.08 Mg m⁻³ due to its inert fraction content. This effect was less evident in the second and third year, probably due to harrowing. Maize yields were slightly, but significantly, reduced in composted plots by 1.72 Mg ha⁻¹ in the third year. Low-pressure tyres significantly reduced soil loss in the third year by 1 Mg ha⁻¹. Furthermore, they did not significantly influence runoff volumes and soil structural stability. Low-pressure tyres or compost addition were singly able to prevent an increase in penetrometer resistance due to agricultural machinery traffic. Low-pressure tyres increased the maize yield during the 3 years and the difference (0.4 Mg ha⁻¹) became significant in the third year. In conclusion, results show the positive lasting effect of compost in ameliorating soil physical properties and reducing runoff and soil erosion. Low-pressure tyres appear justifiable both for the observed increase of grain production and reduction of soil compaction. This latter effect is, nevertheless, masked by compost addition which is also able to reduce penetrometer resistance. Further research is required to explain the causes of the slight inhibition of grain yield observed when compost was compared with mineral fertilisation.     

Soil fumigation and compost amendment alter soil microbial community composition but do not improve tree growth or yield in an apple replant site

Apple replant disease (ARD) is a disease complex that reduces survival, growth and yield of replanted trees, and is often encountered in establishing new orchards on old sites. Methyl bromide (MB) has been the fumigant used most widely to control ARD, but alternatives to MB and cultural methods of control are needed. In this experiment, we evaluated the response of soil microbial communities and tree growth and yield to three pre-plant soil treatments (compost amendment, soil treatment with a broad-spectrum fumigant, and untreated controls), and use of five clonal rootstock genotypes (M.7, M.26, CG.6210, G.30 and G.16), in an apple replant site in Ithaca, New York. Polymerase chain reaction (PCR)—denaturing gradient gel electrophoresis (DGGE) analysis was used to assess changes in the community composition of bacteria and fungi in the bulk soil 8, 10, 18 and 22 months after trees were replanted. PCR-DGGE was also used to compare the community composition of bacteria, fungi and pseudomonads in untreated rhizosphere soil of the five rootstock genotypes 31 months after planting. Tree caliper and extension growth were measured annually in November from 2002 to 2004. Apple yield data were recorded in 2004, the first fruiting year after planting. Trees on CG.6210 rootstocks had the most growth and highest yield, while trees on M.26 rootstocks had the least growth and lowest yield. Tree growth and yield were not affected by pre-plant soil treatment except for lateral extension growth, which was longer in trees growing in compost-treated soil in 2003 as compared to those in the fumigation treatment. Bulk soil bacterial PCR-DGGE fingerprints differed strongly among the different soil treatments 1 year after their application, with the fingerprints derived from each pre-plant soil treatment clustering separately in a hierarchical cluster analysis. However, the differences in bacterial communities between the soil treatments diminished during the second year after planting. Soil fungal communities converged more rapidly than bacterial communities, with no discernable pattern related to pre-plant soil treatments 10 months after replanting. Changes in bulk soil bacterial and fungal communities in response to soil treatments had no obvious correlation with tree performance. On the other hand, rootstock genotypes modified their rhizosphere environments which differed significantly in their bacterial, pseudomonad, fungal and oomycete communities. Cluster analysis of PCR-DGGE fingerprints of fungal and pseudomonad rhizosphere community DNA revealed two distinct clusters. For both analyses, soil sampled from the rhizosphere of the two higher yielding rootstock genotypes clustered together, while the lower yielding rootstock genotypes also clustered together. These results suggest that the fungal and pseudomonad communities that have developed in the rhizosphere of the different rootstock genotypes may be one factor influencing tree growth and yield at this apple replant site.     

微生物发酵菌剂对猪粪堆肥腐熟的影响

研究了添加微生物发酵菌剂对猪粪堆肥腐熟的影响。结果表明,添加微生物发酵菌剂堆肥温度第6d达到50℃,50℃以上持续时间达7d,符合粪便无害化卫生标准要求,C/N第20d下降为19.7∶1,第25d NH4+-N含量减少至72.6mg/kg,水溶性碳降低至4.7g/kg,种子发芽指数达到81.4%,上述指标均达到腐熟要求;对照堆肥温度第12d达到50℃,50℃以上持续时间为3.5d,第25d C/N为22.8∶1,NH4+-N含量为973.4mg/kg,水溶性碳含量为12.8g/kg,种子发芽指数为47.5%,均未达到腐熟要求;此外,添加菌剂处理堆肥物理性状明显改善,臭味明显减少。说明接种微生物发酵菌剂能明显加速堆肥的腐熟进程。     

微生物制剂促进鸡粪堆肥腐熟和臭味控制的研究

鸡粪中添加微生物制剂ＥＭ，堆制２０ｄ堆肥腐熟，较传统堆制法腐熟进程明显加快，堆制９ｄ后堆肥散发出酿酒的芳香。ＮＨ４＋－Ｎ含量下降４１．９４％～５６．７４％，除臭效果显著。ＥＭ能显著提高堆肥中有机质和氮素的保留率，减少氮的气态损失。ＥＭ的除臭功能与其促进堆肥中大分子有机物转化为小分子芳香有机物和ＮＨ４＋－Ｎ向其他形态氮的转化有关。     

茶树菇菌糠复合红泥土基质对西瓜育苗的影响

研究不同茶树菇菌糠复合基质对西瓜穴盘育苗的影响,旨在筛选出适用于西瓜育苗的基质配方。试验分别用3~5 mm、<3 mm 2 种粒径的茶树菇菌糠,按照不同比例与红泥土复合并进行西瓜穴盘育苗试验,研究不同基质下西瓜苗的各项指标差异。结果表明：随着复合基质中茶树菇菌糠体积比例的增加,西瓜苗的成苗率、干物质积累、壮苗指数等指标总体呈现上升趋势;而当基质中菌糠体积比例超过70%时,西瓜苗各指标有所下降;复合基质中菌糠比例为70%时较为适宜于西瓜穴盘育苗,且小粒径菌糠较大粒径复合基质更有利于西瓜苗的生长。茶树菇菌糠复合红泥土基质可用于西瓜穴盘育苗,建议使用小粒径(<3 mm)茶树菇菌糠:红泥土=7:3的配方进行西瓜育苗。