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Transforming plantation monocultures into sustainable, mixed-species forests that contain native species is an important goal in South China. The establishment of native species in Eucalyptus plantations is generally considered difficult, however, because of the potential allelopathic effects of Eucalyptus . In this study, a field trial with completely randomized block was conducted to determine the degree to which Eucalyptus litter and Eucalyptus roots limit the establishment of native trees in Eucalyptus plantations. Growth of seedlings of four native tree species ( Schima superba , Michelia macclurei , Cinnamomum burmannii , Cinnamomum camphora ) that were tested was inhibited by Eucalyptus roots. Seedling emergence was less sensitive than subsequent seedling growth to inhibition by Eucalyptus roots. In contrast, litter enhanced the emergence and growth of seedlings of most of the tested species ( Castanopsis chinensis , Elaeocarpus sylvestris , S. superba , Liquidambar formosana , C. burmannii , and C. camphora ), suggesting that retaining litter on the forest floor may promote the establishment and growth of native tree species in Eucalyptus plantations. We propose the following strategies for establishing native tree species in Eucalyptus plantations: (1) direct sowing of the native tree species C. chinensis , Castanea henryi , Erythrophleum fordii , and C. camphora ; (2) transplanting of E. sylvestris , S. superba , and Tsoongiodendron odorum , which had low germination rates but high seedling establishment rates; and (3) the exclusion of Eucalyptus roots via inter-row trenching to enhance the establishment of S. superba , L. formosana , C. burmannii , and C. camphora . [ABSTRACT FROM AUTHOR]

Highlights: [•] Understory removal suppressed the ratio of fungal to bacterial biomass. [•] N fertilization did not significantly affect the soil microbial community. [•] Understory vegetations are important component in forest ecosystems. [•] Understory vegetations should not be removed from eucalyptus plantations. [ABSTRACT FROM AUTHOR]

Abstract: Dicranopteris is a common fern distributed throughout tropical and subtropical regions of the world. It often forms a mat-like understory, especially in open areas. A forest floor dominated by Dicranopteris plays an important role in ecosystem dynamics, but is often overlooked in ecological research. We conducted an experiment by removing overstory or understory Dicranopteris to compare their effects on soil microclimate, litter decomposition, soil decomposer food web and ecosystem nutrient cycling. Results of our field study showed that removal of a Dicranopteris-dominated understory leads to increased soil temperature and reduced soil moisture, subsequently, altering the components of the soil food web (microbial community, nematode and microarthropod densities) and reducing ecosystem processes of litter decomposition. When present, Dicranopteris forms a dense understory layer in subtropical and tropical regions, which is favorable for sustaining soil microclimates and acts as the major driver of soil biota and ecological processes in intensive forest ecosystems. [Copyright &y& Elsevier]

• Microorganisms and enzymes are more sensitive to litter addition than litter removal. • Microbial biomass exhibits positive responses to both litter addition and removal. • Most enzymatic activities generally exhibit negative responses to litter removal. • Enzymatic stoichiometry depended on soil depth but not on litter manipulation. • Internal associations among microbial and enzymatic variables vary with soil depth. Litter manipulation alters soil microbial community biomass and extracellular enzymatic activities due to the alteration of carbon and nutrient inputs. However, it is unclear whether adding or removing litter more significantly effects these characteristics and how they interact with depth and associated soil properties in subtropical Chinese fir (Cunninghamia lanceolata) forests. Soils were collected along 60 cm soil profiles in a Chinese fir plantation that was treated for 6.5 years with litter removal, litter addition, or no treatment (controls) using a completely randomized block experiment. Soil abiotic properties, the biomass of predominant microbial communities, and the activities of five hydrolytic enzymes were measured in 0–10 cm, 10–20 cm, 20–40 cm, and 40–60 cm soil layers. Litter addition generally resulted in positive effects on soil abiotic factors, microbial communities, and enzymatic activities, respectively, while litter removal tended to result in neutral, positive, and negative effects on these properties. Soil nutrients, microbial functional groups, and various enzymatic activities were generally more sensitive to litter addition than litter removal. In contrast, enzymatic stoichiometry depended more on soil depth than litter manipulation. Soil nutrients, microbial biomass, and enzymatic activities, in addition to their internal associations, decreased with increasing profile depths. Soil microbial communities and enzymatic activities exhibited asynchronous responses to litter manipulation with increasing profile depth. Our findings highlight the mechanistic interactions among soil abiotic properties, microbial community characteristics, and enzymatic properties that vary with soil depth. [ABSTRACT FROM AUTHOR]

Abstract To study how the understory vegetation influences the catalytic properties of extracellular hydrolases, we established a paired treatment experiment, with understory vegetation and litter removed from one treatment (understory removal, UR) and litter removed and the understory vegetation left intact in the other (control, CK), in a subtropical Chinese fir (Cunninghamia lanceolata) plantation. We used fluorescent substrates to determine the maximum velocity (V max), the affinity of hydrolases to the substrates (K m), and the catalytic efficiency (V max /K m) of three extracellular hydrolases (β-1,4-glucosidase (βG), β-1,4-N-acetylglucosaminidase (NAG) and acid phosphatase (AP)). We found that the V max values for βG and NAG were 23.0% and 16.8% lower, respectively, in the UR treatment than in the CK treatment, and that the V max for AP was similar in both treatments. The K m and V max /K m for all the three hydrolases remained steady after the understory vegetation was removed. The soil C and N contents and the bacterial and fungal biomass were generally positively correlated with the V max values. Thus, understory vegetation had more influence on the activities (V max) than on the substrate affinities of extracellular hydrolases (K m). Microbes tended to concentrate on maintaining the catalytic efficiency when the SOC contents were between 15.8 and 20.3 g kg−1 when the understory vegetation was removed from a subtropical Chinese fir forest, and the catalytic efficiency could decrease under extremely low soil C contents. We suggest that understory vegetation should be maintained to sustain the potential microbial activity in subtropical Chinese fir forests. Highlights • The V max of βG and NAG, but not AP, decreased when understory vegetation was removed. • The K m and V max / K m values did not change when understory vegetation was removed. • Soil C and N and microbial biomass were mainly positively related to the V max. • Understory vegetation should be maintained to sustain potential microbial activity. [ABSTRACT FROM AUTHOR]

Edible mushroom cultivation is an important industry in intensively managed forest understories. However, proper disposal of spent mushroom substrate (SMS) presents a challenge to its sustainable development. Biochar derived from SMS could be used to improve soil quality while providing a solution for SMS disposal. But SMS biochar pyrolyzed at different temperatures may alter carbon dioxide (CO 2) and nitrous oxide (N 2 O) emissions associated with global warming, especially under the context of nitrogen (N) addition and warming. We conducted a factorial incubation study to examine greenhouse gas emissions and N transformations in moso bamboo forest soil amended with SMS-biochar (control vs. pyrolyzed at 300, 450 or 600 °C) in different N-addition (0 or 100 mg N kg-1 soil) and temperature (20, 25 or 30 °C) treatments. Pyrolysis temperature affected pH, C and N of SMS-biochars. N-transformations depended on the interaction of pyrolysis temperature, N-addition, and incubation temperature but were generally lower with 450 °C biochar addition. Soil N 2 O emissions increased with N-addition and they were more sensitive to incubation temperatures without biochar. Soil CO 2 emissions increased with incubation temperature or biochar pyrolyzed at lower temperatures. Pyrolysis temperature might have regulated the effects of SMS-derived biochar on N 2 O emissions via changes in dissolved C, N, pH and associated changes in soil microbial community compositions. Because of the importance of sustainable development of this understory industry, amending soils with biochar produced at higher temperatures may be the best strategy for both the disposal of SMS and the mitigation of greenhouse gas emissions. Image 1 • PH of spent mushroom substrate (SMS) biochar increased with pyrolysis temperature. • SMS-biochar reduced the temperature sensitivity of soil N 2 O emission rates. • Lower pyrolysis temperature SMS-biochar increased CO 2 emissions. • Spent mushroom substrate biochar pyrolyzed at 450 °C decreased nitrification rate. [ABSTRACT FROM AUTHOR]