Abandoned Land Research Articles

Soil moisture and soil organic carbon coupled effects in apple orchards on the Loess Plateau, China

A large number of economic forests, especially apple orchards (AOs) in the Loess Plateau region of China, have been planted to develop the local economy and increase the income of farmers. The two main constraints preventing AOs on the Loess Plateau from developing sustainably and producing a high and steady yield are soil moisture content (SMC) and soil organic carbon (SOC). Nevertheless, little is currently known about the contributions of roots to these changes in the soil profile and the temporal modes of the SMC-SOC coupled effects. In our research, we analyzed the dynamic changes in SMC and SOC in AOs of various years in northern Shaanxi Province, as well as the coupled relationship between the two, and attempted to describe the function of roots in these changes. Research have shown: (1) As the age of the AOs increased, the SMC continued to decline throughout the 0–500 cm profile, especially at depths of 100–500 cm. SMC depletion mainly occurred in AOs aged 20 years (30.02%/year) and 30 years (31.18%/year). (2) Compared with abandoned land (AL), all the AOs except for the 6-year-old AO showed a carbon sequestration effect, and the carbon sequestration effect increased with age. The carbon sequestration rate of the 12-year-old AO was the highest and then decreased with age. Both surface and deeper soils showed better carbon sequestration, with a large amount of SOC being sequestered in deeper soil layers (> 100 cm). (3) The coupled effects of SMC and SOC varied with age and depth. The SMC in the deeper layers was significantly negatively correlated with SOC. Root dry weight density (RDWD) was significantly negatively correlated with SMC and significantly positively correlated with SOC. Path analysis suggested that SMC directly affects SOC at different soil depths, and regulates SOC by affecting RDWD, but these effects are significantly different at different depths. Therefore, we propose that management of AO should focus on the moisture deficit and carbon sequestration capabilities of deeper soils to ensure the sustainability of water use in AOs and the stability of agricultural carbon sequestration on the Loess Plateau.

Core microbiota drive multi-functionality of the soil microbiome in the Cinnamomum camphora coppice planting

BackgroundCinnamomum camphora (L.) Presl (C. camphora) is an evergreen broad-leaved tree cultivated in subtropical China. The use of C. camphora as clonal cuttings for coppice management has become popular recently. However, little is known about the relationship between soil core microbiota and ecosystem multi-functionality under tree planting. Particularly, the effects of soil core microbiota on maintaining ecosystem multi-functionality under C. camphora coppice planting remained unclear.Materials and methodsIn this study, we collected soil samples from three points (i.e., the abandoned land, the root zone, and the transition zone) in the C. camphora coppice planting to investigate whether core microbiota influences ecosystem multi-functions.ResultsThe result showed a significant difference in soil core microbiota community between the abandoned land (AL), root zone (RZ), and transition zone (TZ), and soil ecosystem multi-functionality of core microbiota in RZ had increased significantly (by 230.8%) compared to the AL. Soil core microbiota played a more significant influence on ecosystem multi-functionality than the non-core microbiota. Moreover, the co-occurrence network demonstrated that the soil ecosystem network consisted of five major ecological clusters. Soil core microbiota within cluster 1 were significantly higher than in cluster 4, and there is also a higher Copiotrophs/Oligotrophs ratio in cluster 1. Our results corroborated that soil core microbiota is crucial for maintaining ecosystem multi-functionality. Especially, the core taxa within the clusters of networks under tree planting, with the same ecological preferences, had a significant contribution to ecosystem multi-functionality.ConclusionOverall, our results provide further insight into the linkage between core taxa and ecosystem multi-functionality. This enables us to predict how ecosystem functions respond to the environmental changes in areas under the C. camphora coppice planting. Thus, conserving the soil microbiota, especially the core taxa, is essential to maintaining the multiple ecosystem functions under the C. camphora coppice planting.

Effect of soil microbial community structure on the chemical compositions of different soil organic matter fractions in land uses of the Pearl River Estuary

Understanding the interactions between the dynamics of soil organic matter (SOM) and soil microbial communities is important for predicting the stability and fate of estuarine SOM following anthropogenic disturbance. However, current knowledge on the influence of microbial communities on the chemical compositions of different SOM fractions in estuarine land uses still remains incomplete. In this study, we used high-throughput sequencing, Fourier transform infrared spectroscopy, UV–Vis absorption, and fluorescence spectroscopy to investigate soil microbial communities and characterize the chemical compositions of bulk SOM and water-extractable organic matter (WEOM) across different land uses (artificial forests (AF), farmland (FL), natural wetland (NW), construction land (CL), and abandoned land (AL)) in the Pearl River Estuary. The results showed that the bulk SOM in FL and AL exhibited comparable or higher levels of aromatic functional groups (aromatic CH and aromatic CC) compared to other land uses. The HIX and SUV254 indexes further confirmed that AF and FL had more aromatic and hydrophobic WEOM. Apart from FL, where anthropogenic humus constituted the largest proportion, the WEOM fraction predominantly consist of three components in the following order across all land uses, ordered as anthropogenic humus < microbial humus < protein humus. The chemical compositions of the different SOM fractions showed a stronger correlation with the dominant bacterial phylum composition, especially for the WEOM fraction, compared to the fungal composition. Meanwhile, our findings demonstrate that bacterial diversity showed a stronger relationship with the chemical composition of WEOM compared to abundance. Overall, this study sheds light on the impact of land use on the quantity and quality of SOM fractions, underscoring the varying influence of microorganisms on the chemical compositions of different SOM fractions within estuarine environments.

Afforested and abandoned land ecosystems exhibit distinct soil microbial biomass stoichiometric homeostasis over chronosequence

AbstractRevegetation influences microbial biomass stoichiometry by altering the substrate conditions, yet the differences in microbial stoichiometry homeostasis and the underlying drivers under different revegetation approaches remain unexplored. Here, we selected sites across three age classes of Robinia pseudoacacia plantation (RP) and abandoned land (AL), and quantified the microbial stoichiometric characteristics during farmland‐initiated restoration. Plant community composition, leaf and soil nutrients, and microbial community composition and diversity were also measured. We found that revegetation of former farmland under both restoration types resulted in non‐isometric changes in soil carbon (C), nitrogen (N), and phosphorus (P) contents, that is, decoupling of soil C and N from P. However, AL and RP succession exhibited homeostatic and plastic microbial biomass stoichiometry, respectively, in response to altered substrate stoichiometry. These differences were associated with adjustments in the above‐ and belowground biomes. Specifically, the synergistic increase of Compositae and Actinobacteria in the late AL succession allowed the ecosystem to reduce P demand and maintain microbial stoichiometric homeostasis. In contrast, higher leaf C and N input during RP succession may have resulted excessive microbial storage of elements, which in turn leads to stoichiometric convergence between microbial biomass and soil resources. In addition, RP succession caused changes in microbial community structure, mainly the continuous increase of Proteobacteria (copiotrophs, r‐strategists), which also potentially increased the requirement for resources to maintain homeostasis and ensure the rapid growth. These findings demonstrate that AL has a comparatively greater efficacy in maintaining microbial stoichiometric homeostasis during long‐term revegetation. Our study also highlights the importance of appropriately managing existing RP plantations to alleviate the pressure of P deficiency and sustainably maintain this fragile ecosystem.

Effects of Land-Use Types on Topsoil Physicochemical Properties in a Tropical Coastal Ecologically Fragile Zone of South China

Understanding the effects of land use on soil structure and nutrients is important for soil and water conservation in an ecologically fragile zone. This study was carried out to examine the variability of physicochemical properties in three different land use types: abandoned land (AL), eucalyptus plantation (EP), and road lawn (RL) sites at soil depths of 0–10 and 10–20 cm in the Leizhou Peninsula, a tropical coastal ecologically fragile zone of South China. Soil physicochemical property patterns exhibited extremely significant differences among the three land uses (p &lt; 0.001) at both soil depths. Soil nutrients, natural water content, and total porosity, from high to low, in the different land use types were RL, AL, and EP, while the bulk density, from high to low, was EP, AL, and RL. Soil total nitrogen, total phosphorus, total potassium, available potassium, exchangeable calcium, exchangeable magnesium, and natural water content exhibited significant differences (p &lt; 0.05) among the three land use types at soil depths of 0–10 and 10–20 cm, while no significant changes were detected regarding soil organic carbon, available phosphorus, and total porosity. The correlation between physical and chemical properties at the 10–20 cm depth (R = 0.97, p &lt; 0.001) was closer and more significant than that at the 0–10 cm depth (R = 0.95, p &lt; 0.01). Overuse of land (EP) without a rest in the ecologically fragile zone leads to soil erosion and compaction. Compared with natural restoration (abandoned land), artificial restoration (road lawn) can improve soil nutrient and water status more quickly, but cannot modify the soil organic carbon and porosity in the short term.

Seasonal Dynamics of Soil Enzymatic Activity under Different Land-Use Types in Rocky Mountainous Region of North China

To reveal the effects of different land-use types on soil enzyme activities, soil samples were collected from 0–10, 10–20 and 20–30 cm soil layers to compare and analyze soil β-glucosidase (BG), urease (URE), protease (PROT) and catalase (CAT) activities in farmland (FL), abandoned land (AL) and three plantation forests: Platycladus orientalis (L.) Franco (PO), Robinia pseudoacacia L. (RP) and Quercus variabilis Bl. (QV) in the rocky mountainous region of North China. The results showed that the soil enzyme activities varied significantly under different land-use types, and the interannual mean values of FL and PO were remarkably higher than those of other land uses in the 0–30 cm soil layer, in which the soil BG and URE activities of FL were 22% and 12% higher than those of AL, and 428% and 179% higher than those of QV, respectively; the soil PROT and CAT activities of PO were 66% and 23% higher than those of AL, and 479% and 113% higher than those of QV, respectively. Soil BG, URE and PROT activities were all higher in June and lower in December, while soil CAT activity was slightly lower in June. The soil enzymatic activities all showed a notable decrease with the depth of the soil layer. Soil BG, URE, PROT and CAT activities were remarkably (p &lt; 0.01) or significantly (p &lt; 0.05) positively correlated with available nitrogen, available phosphorus, available potassium, dissolved organic carbon (DOC), NO3−-N, soil organic carbon, water content, clay and silt volume fraction, and significantly negatively correlated with sand volume fraction. Soil DOC and pH were important factors influencing soil enzymatic activity, implying that changes in soil enzymatic activity under different land-use types may be the result of a combination of temperature, moisture and plant type. In conclusion, PO plantations are conducive to improving the physicochemical and biological properties of soil and enhance soil fertility, which is a reasonable land-use method to achieve sustainable development in the rocky mountainous region of North China.

New insights into carbon mineralization in tropical paddy soil under land use conversion: Coupled roles of soil microbial community, metabolism, and dissolved organic matter chemodiversity

Although the impact of land conversion on carbon mineralization in paddy soils has received increasing attention, the coupled roles of soil microdiversity and chemodiversity in these processes are largely unknown. To address this issue, the land use conversion from paddy fields (PF) to vegetable fields (VF), rice-vegetable rotation (RV), and abandoned land (AL), were investigated in this study. The relationships between soil mineralization characteristics and microbial community, metabolism physiology and dissolved organic matter (DOM) chemodiversity were analyzed. After the conversion, soil mineralization enhanced in AL and RV, which were 217.49% and 183.02% of that in PF. In contrast, no significant change was observed in VF, although the anaerobic environment was transformed into an aerobic one and the fungal richness/ diversity increased in the soil. This was because soil mineralization was directly regulated by DOM quantity and microbial metabolism of labile carbon, and indirectly by DOM chemodiversity and microbial community. Specifically, the largest mineralization in AL was attributed to the strongest microbial metabolism of labile carbon, as AL had the largest DOC contents, hydrophilic substances (e.g., carboxyl, carbohydrate, and amino), and abundant eutrophic taxa (e.g., Actinobacteria and Proteobacteria). In contrast, no significant change in VF was mainly related to more condensed aromatics and oligotrophic microbes, and fewer DOC in soil, resulting in the dominance of microbial metabolism of soil recalcitrant carbon. The recalcitrant carbon metabolism also prevailed in RV. However, RV showed moderate soil mineralization due to having the proper DOM with high bioavailability. Collectively, the results provide molecular insights into the impact of land conversion on soil mineralization from a micro-chemodiversity perspective, which highlights the importance of nutrient supply and microbial metabolism strategy.

Evaluating the Evolution of Soil Erosion under Catchment Farmland Abandonment Using Lakeshore Sediment

Discriminating the potential sources contributing to lacustrine sediment is helpful for decision-making for catchment soils and lake management strategies within lake-catchment systems. Using a sediment fingerprinting approach from the multivariate mixing model, the spatiotemporal sources of geology and land use were identified in a small agricultural catchment in southwest China. Results showed that sediment accumulation rates (SARs) were estimated to range from 0.002 to 0.065 g cm−2 a−1 (mean 0.015 ± 0.016 g cm−2 a−1), which has a positive correlation with instrumental Indian Summer Monsoon (ISM) precipitation. Time-integrated sources were divided into four zones in combination with the changes in SARs, which were qualitatively and quantitively interpreted by particle size, and precipitation, and historical land use polies over the past ~160 years. Spatially, Quaternary granite (QG) in geology and channel bank (CB) in land use were the dominant contributors to the lakeshore sediment, respectively. Two relatively higher contributions of abandoned land (AL) to lakeshore sediment were found during the periods of 1930s–1950s and post-1990s, which originated from the dual impacts of topographical factors of slope gradient and elevation, and socioeconomic factors of the gap of farmer’s expenditure to income. The results illustrate that restricting the farmland to be abandoned would be useful for reducing the soil erosion within the lake-catchment system.

Molecular linkages between chemodiversity and MCPA complexation behavior of dissolved organic matter in paddy soil: Effects of land conversion

Complexation of dissolved organic matter (DOM) plays a crucial role in regulating the fate and risk of agrochemicals. Here, taking a toxic herbicide MCPA (4-chloro-2- methylphenoxyacetic acid) as the target, the effect of land conversion on complexation behavior of DOM to agrochemicals was investigated in paddy soil. Furthermore, the mechanisms were explored in a new perspective of DOM chemodiversity. Soil DOMs were selected from four long-term cropping systems, including paddy field (PF), vegetable field (VF), rice-vegetable rotation (RV) and abandoned land (AL). The results showed that the DOMs in PF and AL were rich in hydrophilic substances (e.g., carbohydrates or protein-like molecules) with low aromaticity. However, after converting PF to VF and RV, abundant aromatic macromolecules and aliphatic alkanes were observed in DOM. Due to those changes in DOM chemodiversity, the binding site and capability of DOM were highest in VF and RV, and were positively correlated with DOM aromaticity, MW, humus and polar groups (e.g., amino). This was because the complexation of “DOM-MCPA” was static binding via ligand exchange and H-bonding among polar groups and hydrophobic interaction among aromatic skeletons. The EEM-PARAFAC confirmed that microbial humic-like substances dominated the complexation of DOM rather than terrestrial humic-like and tryptophan-like matters. The 2D-COS analysis further revealed that the complexation of DOM preferentially occurred in amino, polysaccharide C–O and aliphatic C–H for PF and AL, but in aromatic C=C, amide C=N for RV and VF. In summary, these findings provide molecular insight into the effect of land conversion on DOM complexation activity, which highlight the importance of DOM chemodiversity. These results will contribute to the risk assessments of agrochemicals in paddy soil.

Land Use Affects Soil Water Balance and Soil Desiccation within the Soil Profile: Evidence from the Western Loess Plateau Case

This study evaluated the properties of soil water dynamics and desiccation to a depth of 500 cm and tested the idea that land use affects soil drying in deep profiles. Four land use types were chosen: farmland, artificial forest and grassland, and abandoned land. Soil water content was most outstanding under long-term wheat fields, but average soil water content under artificial vegetation of Caragana korshinskii Kom. and alfalfa dropped to 6–8% within the 160–500 cm soil profile, very near to the 7.0% wilting point. Long-term continuous maize cultivation in a fully mulched ridge–furrow system significantly depleted soil water and resulted in a dried soil layer with a thickness of 240 cm. Short-term or long-term land abandonment enhanced soil reservoir and reduced soil water storage deficit degree compared to long-term maize and artificial vegetation. Soil water storage in the 160–500 cm soil profile was depleted by 240 and 464 mm under long-term maize and Caragana korshinskii Kom., respectively, by 267, 319, 381, and 463 mm under 5-, 10-, 20-, and 30-year alfalfa, and by −58, 278, 234, and 93 mm under 5-, 10-, 20-, and 30-year abandonment land, respectively, compared to long-term wheat. Based on the analysis of long-term experimental results, this study shows that the phenomenon of soil drying caused by long-term intensive maize production cannot be ignored in semi-arid areas and that natural re-vegetation under long-term abandonment, rather than artificial vegetation, may be the best type of vegetation reconstruction for this region based on soil water balances.

Conversion effects of farmland to Zanthoxylum bungeanum plantations on soil organic carbon fractions in the arid valley of the upper reaches of the yangtze river, china

Farmland afforestation is an effective measure to sequester carbon (C) into soil, but the effects of different farmland conversion approaches on soil organic C (SOC) fractions in arid valley are still not clear. In this work, the concentrations of each SOC fraction in 0–100 cm soil depth, litter stock (LS) and fine root biomass (FRB) in farmland (FL), abandoned land (AL) and Zanthoxylum bungeanum plantations of different ages (with planting ages of 8, 15, 20 and 28 years, abbreviated as ZB8, ZB15, ZB20 and ZB28, respectively) were measured. The results showed that 1) the concentrations of each SOC fraction in the same soil layer increased after the farmland conversion, and these indices ranked as AL > ZB28 > ZB20 > ZB15 > ZB8 > FL, and all of them decreased with the soil depth; 2) the SOC stock, SOC sequestration and SOC sequestration rate increased by 120.1–158.9 Mg ha−1, 4.9–43.8 Mg ha−1 and 0.6–1.6 Mg ha−1 yr−1, respectively, after FL was converted to AL and Z. bungeanum plantations and ranked the same order as the SOC fractions with the land-use types; and 3) the C pool management index (CPMI), LS and FRB of different land-use types ranked as AL > Z. bungeanum plantations > FL, and LS and FRB were significantly (p < 0.05) correlated with each SOC fraction and CPMI, while CPMI was significantly (p < 0.05) correlated with each SOC fraction. This implies that the farmland conversion in arid valleys mediated by LS and FRB is helpful to improve the size and activity of soil C pools, and CPMI can be used as a useful index to estimate soil C pools in this region. In this sense, litter and roots should be emphasized in the process of farmland conversion to increase soil C sequestration.

Conversion effects of farmland to Zanthoxylum bungeanum plantations on soil organic carbon mineralization in the arid valley of the upper reaches of Yangtze River, China.

Farmland conversion to forest is considered to be one of the effective measures to mitigate climate change. However, the impact of farmland conversion to forest land or grassland on soil CO2 emission in arid areas is unclear due to the lack of comparative information on soil organic carbon (SOC) mineralization of different conversion types. The SOC mineralization in 0–100 cm soil layer in farmland (FL), abandoned land (AL) and different ages (including 8, 15, 20 and 28 years) of Zanthoxylum bungeanum plantations were measured by laboratory incubation. The size and decomposition rate of fast pool (Cf) and slow pool (Cs) in different land-use types and soil layers were estimated by double exponential model. The results showed that: 1) Farmland conversion increased the cumulative CO2-C release (Cmin) and SOC mineralization efficiency, and those indexes in AL were higher than that in Z. bungeanum plantations. The Cmin and SOC mineralization efficiency of 0–100 cm soil increased with the ages of Z. bungeanum plantation. Both Cmin and SOC mineralization efficiency decreased with the increase of soil depth; 2) Both soil Cf and Cs increased after farmland converted to Z. bungeanum plantations and AL. The Cs in the same soil layer increased with the ages of Z. bungeanum plantation, and the Cf showed a “V” type with the increased ages of Z. bungeanum plantation. The Cf and Cs decreased with the increase of soil depth in all land-use types; 3) Farmland conversion increased the decomposition rate of Cf (k1) in all soil layer by 0.008–0.143 d−1 and 0.082–0.148 d−1 in Z. bungeanum plantations and AL, respectively. The k1 was obviously higher in the 0−20 cm soil layer than that in other soil layers, while the decomposition rate of Cs (k2) was not affected by FL conversion and soil depth; and 4) The initial soil chemical properties and enzyme activity affected SOC mineralization, especially the concentrations of total organic nitrogen (TON), SOC, easily oxidizable organic carbon (EOC) and microbial biomass carbon (MBC). It indicated that the conversion of farmland to Z. bungeanum plantations and AL increases SOC mineralization, especially in deeper soils, and it increased with the ages. The conversion of farmland to Z. bungeanum plantation is the optimal measure when the potential C sequestration of plant-soil system were taken in consideration.

Factors controlling deep-profile soil organic carbon and water storage following Robinia pseudoacacia afforestation of the Loess Plateau in China

Afforestation is a common and effective approach used for the restoration of degraded ecosystems worldwide. In China, Robinia pseudoacacia (RP) is among the main non-native tree species and has been widely planted in revegetation of the Loess Plateau. However, owing to uncertainties regarding soil water consumption and carbon sequestration, it is necessary to assess the suitability and sustainability of R. pseudoacacia in restoration. In this study, we aimed to analyse the dynamic effects of R. pseudoacacia forest on soil carbon storage (SCS) and soil water storage (SWS). Specifically, we investigated the association between soil water content (SWC) and soil organic carbon (SOC) and underlying factors in the 0–500 cm profile of a 10- to 50-year-old chronosequence. The results obtained indicated that the dynamics of SWS and SCS on this time scale could be divided into an initial reduction phase (the initial 20 years after afforestation) and subsequent recovery (20–50 years after afforestation). Compared with in the abandoned land (AL), the net accumulation of SCS in R. pseudoacacia forest was 2.51 Mg·ha−1 at 50 years after afforestation, whereas there was a 398.76 mm deficit in SWS. Additionally, the natural succession of R. pseudoacacia forest has contributed to the continuous change in stand structure (e.g. vegetation cover (VC), understory vegetation coverage (UVC), and litter biomass (LB)). These findings indicate that vegetation restoration increases carbon sequestration while causing soil water deficit. Furthermore, stand density (SD) was established to make a predominant contribution to the dynamics of SWS and SCS via its effects in altering vegetation, soil, and litter characteristics. Therefore, high-density plantation forests in the Loess Plateau area should be appropriately thinned to reduce the density of forest stands on the basis of soil erosion control and wind and sand fixation, so as to increase carbon sink with lower water consumption, thus realizing the synergistic development of soil carbon sequestration and water connotation.

Effects of land-use types on the temporal dynamics of soil active carbon and nitrogen in the rocky mountainous of North China

ABSTRACT To evaluate the effects of land-use types on the temporal dynamics of soil active carbon (C) and nitrogen (N), a field experiment was conducted from five adjacent sites, farmland (FL), abandoned land (AL), Platycladus orientalis artificial forest (PO), Robinia pseudoacacia artificial forest (RP) and Quercus variabilis artificial forest (QV) in the rocky mountainous of North China. Soil dissolved organic C and N (DOC, DON), soil microbial biomass C and N (MBC, MBN), ammonium-N (NH4 +-N) and nitrate-N (NO3 −-N) were determined during four seasons. The results showed that soil DOC, DON, MBC, MBN, NH4 +-N, and NO3 −-N contents in PO were higher than other land-use types, especially in QV. Soil DOC, DON, MBC, and MBN contents all showed a higher value in March. Both soil DOC/DON and MBC/MBN showed peak values in June. With the increase of soil depth, soil DOC, DON, MBC, and MBN contents all tended to decrease. Most of soil active C and N components had significant correlations with SOC, TN, AP, soil particle volume fraction and the activities of BG and PROT, while the main influencing factors for soil active C and N components were various. The key contributing factors to soil DOC and MBC was SOC, accounting for 62.6% and 67.9%, respectively. Soil TN was the main affecting factor of soil DON (98.4%) and MBN (75.7%). Soil NH4 +-N and NO3 −-N were, respectively, affected by volume fraction of silt particles (10.3%) and AP (15.0%). In conclusion, soil active C and N components are more likely to accumulate in the PO soil in spring, indicating tree species and temperature are the key factors driving soil active C and N turnover in this area.

Effect of Vegetation Restoration on Soil Hydrology in Karst Area of Southwest China: Inspiration from Barrel Planting Experiments

The purpose of this study was to explore the effects of different vegetation restoration types on soil hydrology characteristics in the Karst Plateau Gorge and to clarify the soil moisture (θ) use characteristics. A barrel experiment was conducted to monitor θ and the water potential (Ψ) of three vegetation types (Zanthoxylum bungeanum (ZB), Zea mays L. (ZM), and Sophora tonkinensis (ST), Abandoned land (AL)) was used as a control to explore θ use conditions of each vegetation type. A larger surface permeability led to lower moisture storage. The soil moisture storage showed the law of ZM &gt; ST &gt; AL &gt; ZB. The soil moisture storage also had obvious characteristics in dry-wet seasons. As a typical drought-tolerant crop, ZB responded more obviously to rainfall and had the highest effective replenishment amount and efficiency. Two processes were clearly involved in decreasing soil moisture, which could be divided into three stages of changes: a consumption period (CP), a moisture supplying period (SP), and a relatively stable period (RSP). CP occurred primarily in November to April, when θ was prone to water stress and required proper artificial replenishment. SP was characterized by limited rainfall replenishment in January and May, which significantly increased θ. During the rainy season, corresponding with RSP, θ fluctuated within a relatively stable range. At the end of the CP, the water shortage was more severe. In actual agricultural production, attention should be given to reasonable artificial recharge. This research aims to provide a theoretical basis for karst θ management.

Natural and Managed Grasslands Productivity during Multiyear in Ex-Arable Lands (in the Context of Climate Change)

Ex-arable land-use change is a global issue with significant implications for climate change and impact for phytocenosis productivity and soil quality. In temperate humid grassland, we examined the impact of climate variability and changes of soil properties on 23 years of grass productivity after conversion of ex-arable soil to abandoned land (AL), unfertilized, and fertilized managed grassland (MGunfert and MGfert, respectively). This study aimed to investigate the changes between phytocenosis dry matter (DM) yield and rainfall amount in May–June and changes of organic carbon (Corg) stocks in soil. It was found that from 1995 to 2019, rainfall in May–June tended to decrease. The more resistant to rainfall variation were plants recovered in AL. The average DM yield of MGfert was 3.0 times higher compared to that in the AL. The DM yields of AL and MG were also influenced by the long-term change of soil properties. Our results showed that Corg sequestration in AL was faster (0.455 Mg ha−1 year−1) than that in MGfert (0.321 Mg ha−1 year−1). These studies will be important in Arenosol for selecting the method for transforming low-productivity arable land into MG.

Response of Ecoenzymatic Stoichiometry to Soil Physicochemical Properties after Afforestation on Loess Hilly Region

Afforestation has significantly affected interactions between soil nutrients and microbial enzymes. To understand the detailed variations in extracellular enzyme activity and their link with soil nutrient availability after returning farmland (FL) to forest, soil samples were collected from FL and three afforested lands, Robinia pseudoacacia L. forest (RP), Caragana korshinskii Kom. forest (CK), and abandoned land (AL) in the Loess Hilly Region of northern China. The soil enzymes: β-glucosidase (BG), N-acetylglucosaminidase (NAG), alkaline phosphatase (AP), and leucine aminopeptidase (LAP); their stoichiometric ratios; and soil properties such as soil organic carbon, total nitrogen (TN), total phosphorus (TP), dissolved organic carbon, dissolved organic nitrogen, available phosphorus, soil moisture content (SMC), soil bulk density, and pH were measured. The BG activity showed similar trends as AP activity during afforestation, reaching the highest level in CK and showing a value 205% higher than that in FL. The NAG and LAP activities were not altered by afforestation; only the (NAG + LAP) : AP ratio decreased significantly by 44 to 60%. The BG : AP and (NAG + LAP) : AP ratios were strongly correlated with pH. Compared with other soil physicochemical properties, the soil moisture content greatly affected soil enzyme activity. The most relevant nutrients for the enzymes and stoichiometry were TN and TN : TP. Thus, our results suggest that soil enzyme activity and its stoichiometry are sensitive to changes in soil physical and chemical properties and total soil nutrients content, particularly pH, SMC, TN, and TN : TP.

CONTROLING THE ABANDONED LAND IN SUMBARANG VILLAGE, JATINEGARA SUB-DISTRICT, TEGAL REGENCY

This research is aimed to know and to analyze the cause of Abandoned land in Sumbarang village Jatinegara sub-district Tegal regency, the effort which has been done by land office of Tegal regency toward the Abandoned land, and the obstacle which is faced by the tegal regency’s land office in controling the Abandoned land. The type of thus research is an empirical law which placed in Sumbarang village, Jatinegara sub-district Tegal regency. The source of the data consist of primary, an interview, and secondary data are law materials which can support the resarch’s accuracy which is analyzed by using qualitative technique. The approach method which is uses is juridical sociology. The results of this research find that the factors of the Abandoned land in Sumbarang village are: (1) the wide of the land is not comparable with the worker, the wide land is ±24,1700 ha which is only worked by 40 peoples which makes the land is not used all. (2) the right land is lended to PG. Pangkah, so the farm is changing function. (3) plant hama attack, many of orange plants which is cultivated by CVPD virus which cause stagnancy of the farming bussiness activity. The efforts which is done by the land office of Tegal regency toward the Abandoned land are (1) directing the right holder to use their land. (2) monitoring towards the land right, (3) evaluating the land right (4) controling based on Government Regulation Number 11 of 2010 jo. Regulation of the Head of the National Land Agency Number 4 of 2010 which is about controlling and using Abandoned land. The steps are: a. Inventaritation, b. Identification and researching, c. Warning, d. Determining Abandoned land in controling the Abandoned land. The Tegal office land faces some obstacles they are (1) the right holder lives is unknown, so, it causes difficulty in giving the warn. (2) the right holder is not cooperative. There is no coordination and coorperation betwen the right holder and land Office.

Responses of soil nosZ-type denitrifying microbial communities to the various land-use types of the Loess Plateau, China

Microbial denitrification is an important part of the soil nitrogen cycling process and is the main way that naturally-fixed nitrogen returns to the atmosphere. Research to date has mainly focused on the effects of temperature, pH and carbon sources on denitrification, with the effects of different vegetation types thought to be relatively small. This study investigated the soil denitrification process in the Loess hilly region of China. Four typical land-use types were selected: farmland (FL), abandoned land (AL), Caragana korshinskii (CK), and Robinia pseudoacacia (RP). The functional gene nosZ, which regulates nitrous oxide reductase (N2OR), was selected as the target primer. High-throughput sequencing was carried out and the composition of soil properties was determined. The physicochemical properties of soil, including nitrate nitrogen and organic carbon levels, were studied to explore soil microbial compositions and species diversities and their main influences. Compared with FL, the content of ammonium nitrogen (AN) in AL, CK, and RP soils was 28.5%, 29.7% and 28.8% higher, respectively, while nitrate nitrogen was 1.39-, 1.96-, and 1.55-fold higher, respectively. The Shannon index showed that the microbial diversity of the nosZ gene in RP was greater than that in FL. Nonmetric multidimensional scaling analysis showed that the FL distribution was much different from those of AL, CK, and RP; meanwhile, the AL, CK, and RP distributions tended to overlap, which indicates that there were only small differences in species compositions. Redundancy analysis showed that AN is a key environmental factor affecting the nosZ type microorganisms composition in different taxonomic levels, and the contribution rates can reach 74.3% (p = 0.006), 73.2% (p = 0.004), and 62.6% (p = 0.008), respectively (from phylum to order). This study revealed the α- and β -diversities of nosZ type microorganisms and the key environmental influences on the composition of microorganisms with the land-use change. It provides a reference for further study on the heterogeneity of nitrogen output processes in different land use types.

Growing seasonal characteristics of soil and plants control the temporal patterns of bacterial communities following afforestation

Soil microbial communities are closely associated with aboveground plant communities and soil properties. This study explored the dynamics of soil bacterial communities during the plant growing season and their interaction with soil carbon and nitrogen, physicochemical properties, plant biomass and diversity following afforestation. The study investigated afforested lands containing Robinia pseudoacacia L (RP) and Caragana korshinskii Kom (CK), as well as abandoned land (AL) and farmland (FL) in the Loess Hilly Region of northern China. After establishment on former FL for 40 years, the Richness and Shannon's index, above-ground herbaceous biomass (AGB) and below-ground biomass (BGB) in RP and CK increased by 0.5, 0.1, 1.2 and 1.7 times, respectively, compared with AL. Additionally, the soil organic carbon (SOC), total nitrogen (TN), dissolved organic carbon/nitrogen (DOC/N) and microbial biomass carbon/nitrogen (MBC/N) increased by 1.7, 1.9, 0.8 and 2.5 times, respectively, while the soil bacterial abundance and alpha diversity (Shannon index) increased by 4.7% and 2.0% compared with FL. During the growing season, the soil carbon and nitrogen content was higher in August or October than in April or June. Particularly, the AGB, DOC and MBC showed a temporal pattern of normal distribution that was 36.7%, 48.2% and 74.9% higher in August than the rest of the study period. The BGB also increased by 123.5% in October compared with June in all study areas. The soil bacterial abundance in afforested lands was also higher in October, and beta bacterial diversity (Principal coordinates analysis plots: PCoA) was greater in June and August than in April and October. The dominant bacterial taxa, Proteobacteria and Bacteroidetes, were significantly higher in afforested lands than in FL, and Proteobacteria increased from April to October, while Actinobacteria and Acidobacteria peaked in June or August. These seasonal changes in the soil bacterial community were significantly correlated with carbon and nitrogen levels of soil and plant biomass, especially with DOC and BGB. Additionally, soil variables explained 41.2% of the total variation in bacterial-dominant phyla, while plant biomass only explained 20.2% of it, which indicates that soil properties are more important controlling factors of the bacterial community than plant biomass. In conclusion, soil variables change seasonally, which drives the composition and diversity of the soil bacterial community to exhibit a temporal pattern over the growing season after return of AL to forest.