Long-term dynamics of leaf and root decomposition and nitrogen release in a grey alder (Alnus incana (L.) Moench) and silver birch (Betula pendula Roth.) stands

The decomposition of the leaf litter, fine roots (d?<?2?mm) and coarser roots (2?≤?d?<?5?mm) of grey alder and silver birch, as well as of α-cellulose sheets using the litterbag method was studied in two experimental stands on Podzoluvisol soils in Southern Estonia. For both tree species, the coarser roots decomposed faster than the fine roots, (p?<?.05), tree species did not affect the decomposition rate of the roots (p?>?.5). The nitrogen (N) input to soil from aboveground litter was multiple times higher than the N flux from roots. The remaining relative ash-free mass of the leaves of grey alder and silver birch after three and a half years was similar. After 11 years the remaining relative ash-free mass of the fine and coarser roots of grey alder still accounted for around 10% of the initial value. For silver birch the remaining value was around 20% after 9 years. The litterbag method to underestimates in fertile soils the decomposition of organic matter and thus did not reflect the actual dynamics of decomposition.     

Three SNPs within exons of INHA and ACVR2B genes are significantly associated with litter size in Dazu black goats

The aim of this study was to analyse the association between single-nucleotide polymorphisms within INHA and ACVR2B and litter size in Dazu black goats. In total, twenty-two SNPs were genotyped in 190 individuals by SNaPshot and resequencing. The results showed that three SNPs (SNP_1, SNP_12 and SNP_13 in this study) were detected to have significant additive genetic effect on the recorded goat litter size (p < .05). The SNP_1 (NC_030809.1), a non-synonymous substitution of G for T at chr2-g. 28314990 in the exon 2 of INHA gene (NM_001285606.1), resulted in homozygote 2 (HOM2) contributed 0.25 and heterozygote (HET) contributed 0.12 larger litter than homozygote 1 (HOM1). Meanwhile, SNP_12 (Chr22-g. 11721225 A > T) and SNP_13 (Chr22-g. 11721227 A > C) (NC_030829.1) simultaneously mutated at the first and third position of a triplet AAA (lysine, K) in the exon 4 of ACVR2B gene (XM_018066623.1) had estimated genetic effects of HOM1 (0.00) and HOM2 (0.03) larger than HET (−0.12). In conclusion, one SNPs (chr2-g. 28314990 T > G) within the exon 2 of INHA and two SNPs (Chr22-g. 11721225 A > T and Chr22-g. 11721227 A > C) i n the exon 4 of ACVR2B gene were highly recommended as candidate markers of litter size in Dazu black goats. A large-scale association study to assess the impact of these variants on litter size is still necessary.     

药材植物淋出物对油松枯落物分解和土壤酶活性的影响

【目的】研究油松(Pinus tabuliformis)林下9种药材植物淋出物对油松枯落物分解和土壤酶活性的影响,为选择适宜油松林下种植的药材植物及适宜的林药复合模式提供依据。【方法】以秦岭山区广泛分布的典型油松林及林下9种常见药材植物蒲公英(Taraxacum mongolicum)、地丁(Corydalis bungeana)、薄荷(Mentha haplocalyx)、鱼腥草(Houttuynia cordata)、细辛(Asarum sieboldii)、荆芥(Nepeta cataria)、金银花(Lonicera japonica)、绞股蓝(Gynostemma pentaphyllum)和夏枯草(Prunella vulgaris)为研究对象,通过药材植物茎叶淋出物(以水浸提液模拟)喷浇油松枯落物进行分解试验,研究药材植物茎叶淋出物对油松枯落物分解速率、养分(C、N、P、Cu、Zn和Mn)释放和土壤酶活性的影响。【结果】蒲公英、地丁、薄荷、鱼腥草、金银花和荆芥的茎叶淋出物均显著抑制了油松枯落物的分解及总体养分释放(除金银花茎叶淋出物对N释放、荆芥茎叶淋出物对N和P的释放影响不显著外)。蒲公英、地丁、薄荷、鱼腥草和金银花茎叶淋出物均显著降低了土壤多酚氧化酶的活性,金银花茎叶淋出物降低了土壤中羧甲基纤维素酶活性,荆芥茎叶淋出物均显著降低了土壤中羧甲基纤维素酶和β-葡萄糖苷酶的活性。【结论】细辛、绞股蓝和夏枯草可与油松进行林药复合种植,其余6种药材植物应避免在油松林下种植或降低种植密度。     

青葙的自毒作用及对其他植物的化感作用

【目的】研究青葙Celosia argentea L.的自毒作用及对其他植物的化感作用,从化感作用的角度探讨其作为常见田间杂草并与入侵植物三叶鬼针草Bidens pilosa L.共存的适应机制。【方法】采用室内生测方法,测定了青葙新鲜叶片水浸提液对青葙、三叶鬼针草、油菜Brassica campestris L.和萝卜Raphanus sativus L.4种植物种子萌发和幼苗生长的影响;采用室内盆栽试验,测定了青葙鲜叶水提取液浇灌和鲜叶覆盖对青葙生长的影响,以及青葙和三叶鬼针草凋落物覆盖的相互化感作用。【结果】青葙鲜叶水浸提液对4种受体植物种子萌发和幼苗生长均有不同程度的抑制作用,且随着提取液质量浓度的增加,抑制作用增强。无论是浇灌青葙水浸提液还是添加青葙叶片覆盖的处理都可以降低盆栽青葙的生物量,其中,质量浓度为0.250 0 g·mL~(-1)提取液浇灌盆栽的青葙,其生物量比对照降低了37.5%。将三叶鬼针草和青葙的凋落物覆盖盆栽的青葙和三叶鬼针草,40 d后均显著抑制了青葙生物量;与对照相比,单独覆盖青葙凋落物使盆栽三叶鬼针草的地上部质量和总生物量分别降低了23.0%和22.2%。【结论】青葙既有自毒作用,又对油菜和萝卜有较强的化感作用,应控制田间青葙的大量生长,同时栽培青葙时应避免连作;青葙和三叶鬼针草具有相互的化感抑制作用,青葙通过化感作用实现与三叶鬼针草的共存。     

Interacting effects of yak dung deposition and litter quality on litter mass loss and nitrogen dynamics in Tibetan alpine grassland

The effects of grazing‐induced dung deposition on plant growth and soil attributes are well established, but little is known about dung effects on litter decomposition. Here, we tested effects of yak dung on litter decomposition and nutrient content in a Tibetan alpine meadow. We incubated litter of four common alpine meadow species using litter bags in the field. Two low‐quality species (Kobresia capillifolia and Elymus nutans) with low nitrogen (N), high C/N and Lignin/N, and two high‐quality species, (Saussurea nigrescens and Thermopsis lanceolata) were incubated in monoculture with and without dung addition. Mass loss of leaf litter, fibre fraction (cellulose, hemi‐cellulose and lignin), N and phosphorus (P) were measured after 6, 12 and 18 months of incubation in the field. Dung addition significantly increased decomposition constants for low‐quality litter species, but not for high‐quality litter species. Dung addition promoted cellulose and hemi‐cellulose loss, but lignin loss was not affected by dung addition, except after 12 months for high‐quality litter species. Dung reduced N immobilization after 6 months and did not affect subsequent release in low‐quality litter species, and promoted N release after 6 and 12 months in high‐quality litter species. Regardless of litter quality, dung increased P release after 6 and 12 months. Our results suggest grazing‐induced dung deposition may accelerate C and nutrient turnover, primarily through increasing the mass loss of low‐quality litter, P release from litter and N release from high‐quality litter. The mechanisms underlying the effects of dung deposition need to be clarified in future studies.     

草坪草屑的加工与利用

我国每年修剪草坪产生大量的草坪草屑,对草坪草屑的加工利用,可以对我国能源、饲料、肥料及蛋白资源的短缺起到一定的缓解作用,因此如何对草坪草屑进行合理利用已成为一项重要的研究课题。本文综述了草坪草屑能源化、饲料化、肥料化和深加工4种利用方式,详细介绍了草坪草屑在发酵生产能源、饲喂家畜、堆肥还坪以及加工叶蛋白等方面的研究进展,指出禾本科草坪草屑和豆科草坪草屑应采用不同的处理方式,对各加工方式的投入和产出也应进行进一步的量化核算,同时总结并展望了草坪草屑利用方式的发展前景。     

油菜生长过程对核桃凋落叶化感作用的响应

为研究农作物白菜型油菜生长过程对核桃凋落叶化感作用的生理响应，采用盆栽试验，通过设置空白对照CK（不添加凋落叶）和3个凋落叶添加剂量水平:L₆₀（60 g·盆^-1）、L₁₂₀（120 g·盆^-1）和L₁₈₀（180 g·盆^-1），测定盆栽油菜生长中后期的营养生长、生殖生长及生理响应相关指标。结果表明:1）核桃凋落叶分解对油菜中期营养生长（地径、株高）有显著抑制，在后期得到明显减弱，可仍对后期油菜生殖生长（开花性状、结实性状和产量）产生抑制影响；但这种抑制效应不会影响油菜结实种子的萌发。2）油菜生长中期（100 d），随核桃凋落叶剂量增大，油菜叶片中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）活性逐步增强，过氧化物酶（POD）活性无显著变化；丙二醛（MDA）含量仅在L₁₈₀处理下显著>CK（P＜0.05），可溶性糖（SS）含量逐步增加，而可溶性蛋白（SP）含量呈逐步下降；到油菜生长后期（140 d）时，各处理下油菜POD、CAT的活性和SS、SP的含量均逐步下降，MDA含量均显著P<0.05）。3）各核桃凋落叶处理对油菜叶片各类叶绿素均有明显抑制作用,随凋落叶添加量增加，油菜叶片净光合速率（P_n）、气孔导度（G_s）和胞间CO₂浓度（C_i）呈先降后增的趋势。综上所述，核桃凋落叶经土壤分解对油菜中后期生长造成强烈的化感胁迫，其主要通过对油菜的细胞膜造成过氧化伤害，使叶绿素合成受到抑制，光合作用受到影响，进而妨碍其生长及产量品质的形成。     

Seasonal Losses of Surface Litter in Northern Great Plains Mixed-Grass Prairies

Surface litter protects rangeland soils against wind and water erosion and provides food and nesting materials for wildlife and insects. However, the ability of grassland systems to provide these services depends on the little studied topic of seasonal surface litter decomposition. Seasonal and annual surface litter decomposition rates were determined between 2014 and 2015 in central and western South Dakota at three mixed-grass prairie locations. Residue bags containing surface litter were placed in the field in late fall (1 November) of 2014 and removed after the winter (1 April), spring (1 July), and summer + fall seasons (1 November) of 2015. The litter was analyzed for total C, total N, acid detergent fiber (ADF), and acid detergent lignin (ADL). Average winter temperatures ranged from −5^oC to −15^oC, while summer temperatures ranged from 10^oC to 35^oC. Litter decomposition was lowest during the winter (0.57−0.86 g [kg × day]⁻¹) and greatest during the summer + fall (2.12−2.69 g [kg × day]⁻¹). Over the entire season, 40.8−62% of the surface litter decomposed. Winter litter decomposition was positively correlated with air temperature (r = 0.62, P < 0.01) and snow depth (r = 0.61, P < 0.01), and negatively correlated with C/N ratio (r = −0.65, P < 0.01), ADF (r = −0.35, P < 0.05), and ADL (r = −0.25, P < 0.05) concentrations. These findings indicate that winter decomposition cannot be ignored and that winter surface litter decomposition increases with snow depth.     

Soil Fertility Improvement by Litter Decomposition and Inoculation with the Fungus Mortierella sp. in Avocado Plantations of Colombia

Litter decomposition is a major process in nutrient recycling, despite that few studies have considered this in soil fertility management. The aim of this study was to evaluate the effect of litter decomposition and its inoculation with the fungus Mortierella sp. on soil fertility parameters in Andisols cultivated with avocado cv. Hass. Litterbags containing avocado leaves either uninoculated or inoculated were distributed around the trees. As control litter was not allowed to accumulate on the soil surface. Eighteen months later soil samples were collected just below uninoculated and inoculated litterbags and control sites. Soil pH, potassium, calcium, phosphorus, magnesium, and boron significantly increased with litter and in some sites the increase was higher with inoculation. By contrast, soil aluminum, iron, and manganese were significantly lower in the presence of litter (uninoculated and inoculated), whereas zinc was significantly higher when litter was present.