Global Meta-Analysis Integrated with Machine Learning Assesses Context-Dependent Microplastic Effects on Soil Microbial Biomass Carbon and Nitrogen.

小兴安岭6种森林类型土壤微生物量的季节变化特征

Soil microbial biomass and metabolic quotient across a gradient of the duration of annually cyclic drainage of hillslope riparian zone in the three gorges reservoir area

Soil microbial biomass is an important indicator to measure the dynamic changes of soil carbon pool. It is of great significance to understand the dynamics of soil microbial biomass in plantation for rational management and cultivation of plantation. In order to explore the temporal dynamics and influencing factors of soil microbial biomass of Keteleeria fortunei var. cyclolepis at different stand ages, the plantation of different ages (young forest, 5 years; middle-aged forest, 22 years; mature forest, 40 years) at the Guangxi Daguishan forest station of China were studied to examine the seasonal variation of their microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) by chloroform fumigation extraction method. It was found that among the forests of different age, MBC and MBN differed significantly in the 0–10 cm soil layer, and MBN differed significantly in the 10–20 cm soil layer, but there was no significant difference in MBC for the 10–20 cm soil layer or in either MBC or MBN for the 20–40 cm soil layer. With increasing maturity of the forest, MBC gradually decreased in the 0–10 cm soil layer and increased firstly and then decreased in the 10–20 cm and 20–40 cm soil layers, and MBN increased firstly and then decreased in all three soil layers. As the soil depth increased, both MBC and MBN gradually decreased for all three forests. The MBC and MBN basically had the same seasonal variation in all three soil layers of all three forests, i.e., high in the summer and low in the winter. Correlation analysis showed that MBC was significantly positively correlated with soil organic matter, total nitrogen, and soil moisture, whereas MBN was significantly positively correlated with soil total nitrogen. It showed that soil moisture content was the main factor determining the variation of soil microbial biomass by Redundancy analysis. The results showed that the soil properties changed continuously as the young forest grew into the middle-aged forest, which increased soil microbial biomass and enriched the soil nutrients. However, the soil microbial biomass declined as the middle-age forest continued to grow, and the soil nutrients were reduced in the mature forest.

In this study,seasonal variation characteristics of surface soil microbial biomass carbon(MBC)and soil microbial biomass nitrogen(MBN)of an artificial vegetation area located in Shapotou for different time periods were studied using the chloroform fumigation method,and the results were compared with those of near-natural vegetation areas and mobile dunes.Results showed that the MBC and MBN levels in the 0–5 cm soil layer were higher in autumn than in summer and spring.As the prolongation of vegetation restoration raised the MBC and MBN levels in summer and autumn,no clear variation was found in spring.However,the MBC and MBN in 5–20 cm had no obvious seasonal variation.During summer and autumn,the variation trend of MBC and MBN in the vertical direction was shown to be0–5>5–10>10–20 cm in the vegetation area,while for mobile dunes,the MBC and MBN levels increased as the depth increased.The natural vegetation area was shown to possess the highest MBC and MBN levels,and yet mobile dunes have the lowest MBC and MBN levels.MBC and MBN levels in artificial sand-binding vegetation increased with the prolongation of vegetation restoration,indicating that the succession of sand-binding vegetation will result in the accumulation of soil carbon and nitrogen,as well as the restoration of soil fertility.

黄土高原不同乔木林土壤微生物量碳氮和溶解性碳氮的特征

Soil microbial biomass is the main driving force in the decomposition of organic materials and is frequently used as an early indicator of changes in soil properties resulting from soil management and environment stresses in agricultural ecosystems This study was designed to assess the effects of organic and inorganic inputs on soil microbial biomass carbon and nitrogen overtime at Kabete, Kenya. Tithonia diversifolia, Cassia spectabilis, Calliandra calothyrsus were applied as organic resources, and Urea as inorganic source. Soil was sampled at 0–10 cm depth before incorporating the inputs and every two months thereafter and at harvesting in a maize-cropping season. Soil microbial biomass carbon and nitrogen was determined by Fumigation Extraction method (FE) while carbon evolution was measured by Fumigation Incubation (FI) method. The results indicated a general increase in soil microbial biomass carbon and nitrogen in the season with the control recording lower values than all the treatments. Microbial biomass carbon, nitrogen and carbon dioxide evolution was affected by both quality of the inputs added and the time of plant growth. Tithonia recorded relatively higher values of microbial biomass carbon, nitrogen and carbon evolution than all the other treatments. A significant difference was recorded between the control and the organically treated soils at the of the season for the microbial biomass nitrogen and carbon dioxide evolution. Both the microbial biomass C and N showed a significance difference (P $⩽0.05) in the different months of the season

Removal of invasive plant species is the first step to restoring the invaded ecosystems. The soil microbial biomass and extracellular enzyme activities were measured in Moso bamboo (Phyllostachys edulis) pure forest (completely invasion), invasive P. edulis removal forest (secondary succession 5 years after clear cutting), and the evergreen broadleaved forest (no invasion) in Tianmu Mountain. The results showed that compared with P. edulis pure forest, invasive P. edulis removal significantly increased the contents of soil organic carbon (SOC), nitrate nitrogen, available phosphorus and potassium, as well as microbial biomass carbon (MBC) and microbial biomass phosphorus (MBP), while significantly decreased microbial biomass nitrogen (MBN). The activities of α-glucosidase (AG), β-glucosidase (BG), leucine aminopeptidase (LAP) and phenol oxidase (POX) in the forest with removal of invasive P. edulis were significantly higher than those in P. edulis pure forest, while invasive P. edulis removal did not change the activities of cellodisaccharide hydrolase (CBH), β-N-acetyl-glucosaminopeptidase (NAG), acid phosphatase (ACP) and peroxidase (PER). Furthermore, the activities of AG, BG and LAP were positively correlated with SOC and MBC, while the increase in POX activity was positively correlated with soil nitrate content. In addition, MBC, MBN and MBP, and activities of AG, BG, NAG, LAP and ACP in P. edulis removal forest forest were significantly higher than those in evergreen broadleaved forests. Taken together, the removal of invasive P. edulis could increase soil nutrient contents, microbial biomass and extracellular enzyme activities, thus could be considered as an effective way to restore the invaded forests. Our results provide important theoretical basis for controlling P. edulis invasion in subtropical forests.

Soil microbial functional diversity and biomass as affected by different thinning intensities in a Chinese fir plantation

Effects of transforming multiple ecosystem types to tree plantations on soil microbial biomass carbon, nitrogen, phosphorus and their ratios in China

Vegetation restoration is a critical strategy for addressing ecosystem degradation globally. However, understanding the specific impacts of land-use changes, particularly the conversion of farmland to forestland and grassland, on soil nutrients and microbial biomass in the Loess Plateau remains limited and requires further evaluation. Therefore, this study was conducted to explore how these conversions affect soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and microbial biomass components under various land-use patterns. We studied the SOC, TN, TP, soil microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) content and their ratios under six land-use patterns (Farmland (FL), Abandoned cropland (ACL), Natural grassland (NG), Alfalfa grassland (Medicago sativa L. (MS)), Spruce forestland (Picea asperata Mast. (PA)) and Cypress forestland (Platycladus orientalis (L.) Franco (PO))). The conversion of FL to grassland and forestland significantly increased C:N and C:P by 9.82~64.12%, 10.57~126.05%, and 51.44~113.40%, 22.10~116.09%, respectively. The conversion of FL to ACL reduced the C:N and C:P by 5.34~13.57% and 1.51~7.55%, respectively. The conversion of FL to NG can increase soil N:P. The conversion of FL to grassland and forestland increased soil MBC, MBN, and MBP by −31.54~84.48%, −48.39~1533.93%, −46.55~173.85%, and −34.96~17.13%, 68.72~432.14%, −38.39~318.46%, respectively. However, the MBC, MBN, and MBP contents in the soil converted from FL to ACL varied from −28.21~11.95%, 11.17~531.25%, and −82.64~70.77%, respectively. Soil SOC, TN, TP, available potassium (AK), pH, and soil bulk density (BD) are the main factors causing microbial biomass differences. These results indicate that converting farmland into forestland and grassland can improve soil nutrient structure and increase soil microbial biomass and carbon accumulation. The results of this study provide theoretical support for the scientific management of regional land.

石羊河下游退耕地土壤微生物变化及土壤酶活性

Mining causes severe damage to soil ecosystems. Vegetation restoration in abandoned mine areas is an inevitable requirement for sustainable development. Soil microbes, as the most active component of soil organic matter, play a crucial role in the transformation of carbon, nitrogen, phosphorus, and other elements. They are often used as indicators to assess the extent of vegetation restoration in ecologically fragile areas. However, the impacts of vegetation restoration on soil microbial community structure in mining areas at the global scale remains largely unknown. Based on 310 paired observations from 44 papers, we employed the meta-analysis approach to examine the influence of vegetation restoration on soil microbial abundance and biomass in mining area. The results indicated that vegetation restoration significantly promotes soil microbial biomass in mining areas. In comparison to bare soil, vegetation restoration leads to a significant 95.1% increase in soil microbial biomass carbon and a 87.8% increase in soil microbial biomass nitrogen. The abundance of soil bacteria, fungi, and actinomycetes are significantly increased by 1005.4%, 472.4%, and 177.7%, respectively. Among various vegetation restoration types, the exclusive plan-ting of trees exhibits the most pronounced promotion effect on soil microbial biomass and population, which results in a significant increase of 540.3% in soil fungi and 104.5% in actinomycetes, along with a respective enhancement of 110.3% and 106.4% in microbial biomass carbon and nitrogen. Model selection results revealed that soil satura-ted water content and vegetation restoration history contribute most significantly to the abundance of soil bacteria and fungi. Soil available nitrogen has the most significant impact on the abundance of actinomycetes and microbial biomass carbon, while soil available phosphorus emerges as a crucial factor affecting microbial biomass nitrogen. This research could contribute to understanding the relationship between vegetation restoration and the structure of soil microbial communities in mining areas, and providing scientific support for determining appropriate vegetation restoration types in mining areas.

Exploring the differential responses of rhizosphere soil phosphorus contents associated with nitrogen-fixing and non-nitrogen-fixing plants to different soil nitrogen levels in subtropical karst forests can provide valuable insights into the effects of nitrogen-fixing plants on soil nutrient cycling. Such knowledge will serve as a scientific reference for the extensive planting of nitrogen-fixing plants in vegetation restoration efforts in karst regions. Taking karst forests with varying soil nitrogen levels in Jianshui County, Yunnan Province as test objects, we collected soil samples from the rhizosphere of three types of dominant nitrogen-fixing and non-nitrogen-fixing plants with the same age and analyzed the total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (IP), available phosphorus (AP), and other soil physicochemical properties. Soil microbial biomass and enzyme activities were measured to assess the influence of nitrogen-fixing plants on rhizosphere soil phosphorus contents under different soil nitrogen levels, as well as the main driving factors. Results showed that the contents of TP, OP and AP in the rhizosphere soil of nitrogen-fixing plants significantly increased by 16.0%, 66.5% and 139.5% under a low soil nitrogen level with the available nitrogen of 15.62 mg·kg-1, and significantly increased by 13.5%, 25.7% and 15.7% under higher soil nitrogen level with the available nitrogen of 37.15 mg·kg-1, respectively. There was no significant difference in IP content between nitrogen-fixing and non-nitrogen-fixing plants under the two soil nitrogen levels. Compared with low soil nitrogen level, the contents of TP and IP in the rhizosphere soil of nitrogen-fixing plants under high soil nitrogen level significantly decreased by 21.3% and 31.7%, and those of non-nitrogen-fixing plants significantly decreased by 19.6% and 39.1%. The AP content in the rhizosphere soil of nitrogen-fixing and non-nitrogen-fixing plants significantly increased by 32.8% and 174.8%, respectively, with no notable change in OP content. Under low nitrogen conditions, nitrogen-fixing plants significantly increased microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP), and alkaline phosphatase (ALP) activity in the rhizosphere soil. Under high nitrogen condition, nitrogen-fixing plants significantly increased MBP and ALP activity, but had no significant effect on MBC and MBN. As soil nitrogen level increased, soil MBC, MBN, MBP, and nitrogen cycle-related enzyme activities in the rhizosphere soil of nitrogen-fixing plants decreased significantly, while ALP activity increased. In contrast, in the rhizosphere soil of non-nitrogen-fixing plants, MBN and ALP activity significantly increased, while nitrogen cycle-related enzyme activities significantly decreased. Mantel analysis indicated that under low nitrogen level, rhizosphere soil phosphorus contents were primarily regulated by a combination of soil physicochemical properties, microbial biomass, and enzyme activity, while they were mainly regulated by soil physicochemical properties under high nitrogen level. In conclusion, compared to non-nitrogen-fixing plants, nitrogen-fixing plants in subtropical karst forests can significantly increased soil TP, OP, and AP contents and this effect is largely regulated by soil nitrogen level. Therefore, introducing nitrogen-fixing plants into low-nitrogen subtropical karst areas at the beginning of vegetation restoration may alleviate phosphorus limitation, improve soil nutrient status, and facilitate vegetation restoration in these regions.

林窗尺度对侧柏人工林土壤微生物生物量碳氮的短期影响

峡谷型喀斯特不同生态系统的土壤微生物数量及生物量特征