Effects on soil quality of biochar and straw amendment in conjunction with chemical fertilizers

The objective of this study was to evaluate the effects on chemical and microbiological properties of paddy soil of short-term biochar,straw,and chemical fertilizers compared with chemical fertilization alone.Five soil fertilization treatments were evaluated：regular chemical fertilizers（RF）,straw＋regular chemical fertilizers（SRF）,straw biochar＋regular chemical fertilizers（SCRF）,bamboo biochar（BC）＋regular chemical fertilizers（BCRF）,and straw biochar＋70%regular chemical fertilizers（SC＋70%RF）.Their effects were investigated after approximately 1.5 years.The soil p H and cation exchange capacity（CEC）were significantly higher in biochar-treated soils.The soil phosphorous（P）and potassium（K）contents increased with biochar application.The soil Colwell P content was significantly increased with the addition of straw biochar in the treatments of SCRF and SC＋70%RF.The oxygen（O）：carbon（C）ratio doubled in BC picked from the soil.This indicated that BC underwent a significant oxidation process in the soil.The denaturing gradient gel electrophoresis（DGGE）fingerprints of microbial communities differed among the treatments.Soils with added biochar had higher Shannon diversity and species richness indices than soils without biochars.The results suggest that biochar can improve soil fertility.

不同经营措施对毛竹林土壤理化性质、酶活性和有机碳矿化特征的影响

毛竹林是我国特有的具有显著固碳潜力的森林类型。笔者以不同经营类型(无经营M_(0)、粗放经营M_(1)和集约经营M_(2))毛竹林和对照天然次生林(CK)土壤为研究对象,通过室内模拟培养试验,探讨各经营类型毛竹林土壤理化性质、酶活性及有机碳矿化特征的差异。结果表明:降低毛竹林的经营强度后,土壤养分元素含量得到增加。无经营和粗放经营显著增加了毛竹林土壤的总有机碳、全氮、全磷和可溶性氮的含量,提高了土壤含水率并降低了土壤容重。与对照相比,无经营和粗放经营毛竹林土壤的β-葡萄糖苷酶、多酚氧化酶和过氧化物酶在0~20 cm和20~40 cm土层中均显著提高,土壤酸性磷酸酶活性则显著降低。各土壤潜在矿化有机碳量介于154~844 mg·kg^(-1),占土壤有机碳总量的0.82%~2.44%。相比对照,无经营显著增加了0~20 cm和20~40 cm土层中有机碳的潜在活性碳库以及累积碳矿化量,粗放经营次之。集约经营导致土壤碳矿化率显著高于其它经营土壤。总的来说,随着经营强度的增加,林下土壤呈现出理化性质和酶活性逐渐降低,有机碳矿化率逐渐增加的变化规律。因此,减少人为干扰降低经营强度有利于增加毛竹林土壤肥力,促进有机碳的周转。

Comparison of Soil Nitrogen Availability Indices under Two Temperate Forest Types

To evaluate the validity of different indices in estimating soil readily mineralizable N, soil microbial biomass （Nmic）, soil active N （SAN）, soluble organic N （SON）, net N mineralization rate （NNR） and gross N mineralization rate （GNR） in mineral soils （0-10 cm） from six forest stands located in central Germany were determined and compared with two sampling times： April and November. Additionally, soil density fractionation was conducted for incubated soils （with addition of ^15NH4-N and glucose, 40 days） to observe the sink of added ^15N in different soil fractions. The study showed that Nmic and NNR in most stands differed significantly （P 〈 0.05） between the two sampling times, but not GNR, SAN and SON. In November, no close relationships were found between GNR and other N indices, or between Nrnic, SON, and SAN and forest type. However, in April, GNR was significantly correlated （P 〈 0.05） with Nmic, SAN, and NNR along with Nmlc under beech being significantly higher （P 〈 0.05） than under conifers. Furthermore, density fractionation revealed that the light fraction （LF, 0.063-2 mm, 〉 1.7 gcm^-3） was not correlated with the other N indices. In contrast, results from the incubation study proved that more 15N was incorporated into the heavy fraction （HF 〈 0.063 ram, 〉 1.7 g cm^-3） than into LF, indicaing that more labile N existed in HF than in LF. These findings suggested that attention should be paid to the differences existing in N status between agricultural and forest soils.

经营措施对毛竹林土壤不同组分有机碳、氮及化学结构的影响

以次生常绿阔叶林为对照,选择立地条件相近的无经营、粗放经营和集约经营3种类型毛竹林为研究对象,应用密度-粒径联合分组以及化学、生物分析和傅里叶变换红外光谱(FTIR)方法,探讨经营措施对毛竹林土壤不同组分有机碳、氮含量,分配比例及结构特征的影响。结果表明:与对照相比,无经营和粗放经营毛竹林显著提高了土壤总有机碳(TOC)、全氮(TN)、游离态颗粒有机碳、氮、可溶性有机碳(DOC)、氮(DON)和矿物结合态有机碳、氮的含量。无经营毛竹林虽然显著增大了游离态颗粒有机碳、氮的分配比例,但其与黏土矿物结合的有机碳依然是土壤有机碳的最大贮存库(67.6%)。集约经营导致竹林土壤有机碳、全氮的贮量及各组分有机碳、氮含量下降,但明显增大了DOC/TOC、微生物生物量氮与全氮比值以及微生物生物量碳和土壤有机碳的比值(微生物商)。经营措施对土壤有机碳的化学结构也具有显著影响。与对照相比,无经营和粗放经营毛竹林土壤有机碳中酚醇-OH、脂肪族-CH、芳香族C=C和羰基C=O吸收峰相对强度增强,土壤疏水性显著增加。土壤有机碳的脂肪碳、芳香碳和疏水性与土壤碳氮总量呈显著正相关,与微生物商呈显著负相关。在人为干扰减少的情况下,毛竹林凋落物、根系等有机质残体输入量的增多引起土壤难分解化合物的相对积累,使有机碳化学稳定性明显增强。同时,土壤黏土矿物质对土壤有机碳起到了很好的保护作用,通过矿物-有机碳复合使土壤碳储存稳定性更高,进而有利于土壤碳的长期保存。