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Litter input triggers the secretion of soil extracellular enzymes and facilitates the release of carbon (C), nitrogen (N), and phosphorus (P) from decomposing litter. However, how soil extracellular enzyme activities were controlled by litter input with various substrates is not fully understood. We examined the activities and stoichiometry of five enzymes including β-1,4-glucosidase, β-D-cellobiosidase, β-1,4- N -acetyl-glucosaminidase, leucine aminopeptidase and acidic phosphatase (AP) with and without litter input in 10-year-old Castanopsis carlesii and Cunninghamia lanceolata plantations monthly during April to August, in October, and in December 2021 by using an in situ microcosm experiment. The results showed that: 1) There was no significant effect of short-term litter input on soil enzyme activity, stoichiometry, and vector properties in C. carlesii plantation. In contrast, short-term litter input significantly increased the AP activity by 1.7% in May and decreased the enzymatic C/N ratio by 3.8% in August, and decreased enzymatic C/P and N/P ratios by 11.7% and 10.3%, respectively, in October in C. lanceolata plantation. Meanwhile, litter input increased the soil enzymatic vector angle to 53.8° in October in C. lanceolata plantations, suggesting a significant P limitation for soil microorganisms. 2) Results from partial least squares regression analyses showed that soil dissolved organic matter and microbial biomass C and N were the primary factors in explaining the responses of soil enzymatic activity to short-term litter input in both plantations. Overall, input of low-quality (high C/N) litter stimulates the secretion of soil extracellular enzymes and accelerates litter decomposition. There is a P limitation for soil microorganisms in the study area.

Forest headwater streams are the monumental cement for relating habitats of the terrene and water. Nutri-ent dynamics of non-woody debris in stream can directly and indirectly regulate the cycle and transport of forest nutrients, for example, Ca and Mg. In the rainy season (from March to August) of 2021, we monitored the dyna-mics of Ca and Mg storage of non-woody debris in a typical headwater stream in a subtropical forest. The results showed that total Ca and Mg storage of non-woody debris per unit area of stream ranged from 178.1 to 890.5 mg·m -2 and 13.8 to 61.6 mg·m -2 during the rainy season, respectively. The Ca and Mg storages of non-woody debris per unit area of stream during the rainy season displayed a pattern of first increase and then decrease, and overall a decrease pattern. The storage varied significantly among different sites, with higher values in stream source than others. The total Ca and Mg storage of non-woody debris positively correlated with precipitation, but negatively with stream water alkalinity, temperature, and dissolved oxygen. The variation of riparian forest type ( e.g. , Castano-psis carlesii forests or mixed coniferous forests) and with or without tributaries did not affect the storage of Ca and Mg in stream non-woody debris. During the rainy season, total Ca and Mg storage of non-woody debris in the headwater stream from forest generally decreased over time, which was mainly controlled by the characteristics of rainfall and stream.

To assess the dynamics and spectral characteristics of dissolved organic matter of twig litter in continuous increase stage, peak stage, and continuous decrease stage of twig litter production in different types of Castanopsis carlesii forest in middle subtropical China, a field experiment was conducted in C. carlesii natural forest, secondary forest and plantation. The results showed that litter production stage and forest type significantly affected the content and spectral characteristics of dissolved organic matter of twig litter were . Compared with the secondary forest and plantation, natural forest had higher dissolved organic carbon (DOC) content and lower special ultraviolet-visible absorption values at 254, 260 and 280 nm (SUVA 254 , SUVA 260 , SUVA 280 ) at the continuous decrease stage of twig litter production, indicating high twig litter quality of natural forest and high cycling efficiency with dissolved organic matter in the natural forest at this stage. In contrast, the higher contents of total nitrogen (TN), total phosphorus (TP), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and lower DOC:TDP and TDN:TDP ratios of twig litter in the plantation were observed at the peak stage of twig litter production, while no differences were detected in dissolved organic matter contents and spectral values in the secondary forest among the stages. In addition, the DOC, TDN, TDP of twig litter were negatively correlated with temperature and precipitation in the natural forests and secondary forests, but TDN and TDP of twig litter were positively correlated with temperature and precipitation in the plantations. These results suggested that the higher nutrient content at the peak stage of twig litter production in the C. carlesii plantation might lead to more efficient material cycling and that there would be a higher efficiency of material cycling for twig litter dissolved organic matter in C. carlesii natural forest at reduction stage of twig litter production.

To understand the nutrient use strategies of 11 tree species in a subtropical common-garden, we measured the specific leaf area, nitrogen (N) and phosphorus (P) resorption and stoichiometric characteristics of leaves in August 2019. The results showed that the specific leaf area, N and P concentrations in mature and senescent leaves of evergreen broadleaved ( Lindera communis , Cinnamomum camphora , Schima superba , Castanopsis carlesii , Michelia macclurei and Elaeocarpus decipiens ) and coniferous species ( Cunninghamia lanceolata and Pinus massoniana ) were lower than those of deciduous broadleaved species ( Liquidambar formosana , Sapindus mukorossi and Liriodendron chinense ). In contrast, C:N and C:P in mature leaves of evergreen broadleaved and coniferous species were significantly higher than those of deciduous broadleaved species. Except for C. carlesii , the N:P of all the species were lower than 14. Compared with other tree species, N and P resorption efficiencies of S. mukorossi were higher than 50% based on both mass and leaf area. Although P resorption efficiency of P. massoniana , C. lanceolata and C. camphora were higher than 50%, N and P resorption efficiency of M. macclurei were the lowest with only 15%-30%. In addition, specific leaf area of mature leaves was significantly positively correlated with N and P concentrations, but negatively correlated with C:N and C:P. In the common-garden, evergreen broadleaved species such as C. carlesii and L. communis , and coniferous species such as P. massoniana might belong to the slow investment species with lower specific leaf area, N and P concentrations, displaying relatively efficient in N and P resorption and utilization in comparison with other species. In contrast, deciduous broadleaved species such as S. mukoraiensis might be the fast investment species with low N and P use efficiency. Interestingly, tree species being restricted by N availability did not exhibit higher N resorption efficiency in the common-garden. Similarly, C. carlesii , the only P-restricted species here, did not exhibit higher P resorption efficiency. Our results provided scientific support for afforestation practice in the mid-subtropics.

Regional ecological quality is largely affected by human activities, which restricts the sustainable development of regional economy. Taking the China-Laos railway economic belt as an example, we investigated the effects of human activities on ecological quality. The remote sensing images of 1999, 2009 and 2019 were selected to calculate remote sensing ecological index (RSEI). Spatial autocorrelation statistics and local G statistics were used to explore the spatial-temporal variations of ecological quality in the study area. Combined with the population density in the same period, a geographically weighted regression model was constructed to quantitatively analyze the ecological effects of different human activity intensities in the study area. The results showed that the ecological quality in the study area presented a trend of increasing firstly and then decreasing later from 1999 to 2019, and that the mean value of RSEI varied from 0.645 (1999) to 0.738 (2009) and then decreasing to 0.721 in 2019. Specially, the ecological quality fluctuated more apparently in the midlands. The results of fitting population density and ecological quality based on geographical weighted regression model (GWR) were significantly better than that of least square method. R 2 of different periods based on GWR was higher than 0.7 and the fitting effect was stable. The fitting degree of GWR in 2019 was the best ( R 2 was 0.785), and R 2 in 1999 and 2009 were 0.726 and 0.754, respectively. The ecological quality along the China-Laos railway south area (such as Vientiane) was more sensitive to human activities, with most of these places belonged to moderately sensitive regions. For the highly, moderately and lowly ecological sensitive regions, every 10, 100, 1000-fold increases in population density would lead to a decrease of 0.2, 0.4 and 0.6 to the mean value of RSEI in turn. The development of economic belt would increase population density. During the planning and layout of economic belt, human activities should be controlled to avoid the deterioration of ecological quality in the potential and current sensitive regions.

In two growing seasons of wheat (2015-2017), we conducted a field trial with Taishan 28 in Tai'an Academy of Agricultural Science Feicheng experimental base, Tai'an City, Shandong Province. There were four irrigation levels of 150 (A 1 ), 300 (A 2 ), 450 (A 3 ), and 600 (A 4 ) m 3 ·hm -2 , and four nitrogen application levels of 90 (B 1 ), 135 (B 2 ), 180 (B 3 ), and 225 (B 4 ) kg·hm -2 . We examined the effects of the combination effects of irrigation and nitrogen on dry matter accumulation and transport, nitrogen accumulation and transport, water consumption and utilization, photosynthetic characteristics, wheat grain yield and yield components of wheat. The results showed that dry matter accumulation, nitrogen accumulation, vegetative organs production, storage and the transportation volume to grains of the dry matter and nitrogen, and dry matter and nitrogen accumulation of grain in the mature stage of wheat all reached the maximum in A 3 B 3 treatment, which were significantly different from other treatments. Under all the nitrogen treatments, soil water consumption in the 60-200 cm soil layer was A 3 >A 4 >A 2 >A 1 . Water use efficiency and nitrogen use efficiency in A 3 B 3 treatment were higher than that under A 3 B 4 , A 4 B 3 and A 4 B 4 . The net photosynthetic rate, stomatal conductance and transpiration rate of flag leaves from 7 to 28 days after flowe-ring were all significantly higher in A 3 B 3 treatment, which was conducive to the photosynthetic synthesis of carbohydrates in wheat. The interaction effect of water and nitrogen addition significantly affected grain yield and yield components. Wheat yield was the highest in A 3 B 3 treatment which reached at 9400 kg·hm -2 . In conclusion, the treatment with irrigation of 450 m 3 ·hm -2 and nitrogen of 180 kg·hm -2 could significantly improve dry matter and nitrogen accumulation, and promote transportation volume of the dry matter and nitrogen to grain. Compared with the high water and nitrogen treatment, it could effectively increase water use efficiency and nitrogen use efficiency, enhance photosynthetic capacity of flag leaf, produce more carbohydrate, and increase grain yield.

Landscape pattern and its vulnerability have direct impacts on ecological environment in the basin. In order to protect the ecological security in Nansihu Lake basin, we analyzed the changes of landscape pattern based on seven sets of land use data (1980-2015), with landscape adaptability index (LAI) and landscape sensitivity index (LSI) being used to build the landscape vulnerability index (LVI). The spatial distribution and changes of LVI were analyzed. Results showed that the percentage of arable land areas decreased by 4.6% and construction land areas increased by 39.7% from 1980 to 2015. Other land use types showed fluctuating changes. The areas of forest land, grassland, and unused land decreased while water area increased. The arable land was the dominant land use type from 1980 to 2015 in this area. The degree of fragmentation of arable land and water area in the basin increased, whereas other land use types decreased. The fragmentation of whole basin decreased, but connectivity among landscape types enhanced. The irregularity and complexity of landscape pattern decreased, but diversity and evenness of landscape pattern displayed an increasing trend. With respect to LVI in different periods, the eastern part of the basin was higher than the western part, while the northern part was higher than the southern part. The spatial distribution of LVI was related to topography, layout of landscape types and change of land use. The LVI of Nansihu Lake basin showed a decline trend during 1980-2015. In the eastern part of the basin, higher level of LVI gradually dispersed and was replaced by lower level. In the northwest, the recovery of LVI was obvious. In the south and southwest parts, LVI was consistently low.

Land use change has an important role in hydrological processes and utilization of water resources, and is the main driving force of water yield function of ecosystem. This paper analyzed the change of land use from 1990 to 2013 in Nansi Lake Basin, Shandong Province. The future land use in 2030 was also predicted and simulated by CLUE-S model. Based on land use scenarios, we analyzed the influence of land use change on ecosystem function of water yield in nearly 25 years through InVEST water yield model and spatial mapping. The results showed that the area of construction land increased by 3.5% in 2013 because of burgeoning urbanization process, but farmland area decreased by 2.4% which was conversed to construction land mostly. The simulated result of InVEST model suggested that water yield level of whole basin decreased firstly and increased subsequently during last 25 years and peaked at 232.1 mm in 2013. The construction land area would increase by 6.7% in 2030 based on the land use scenarios of fast urbanization, which would lead to a remarkable growth for water yield and risk of flowing flooding. However, the water yield level of whole basin would decrease by 1.2 % in 2013 if 300 meter-wide forest buffer strips around Nansi Lake were built up.

Seasonal snow cover may change the characteristics of freezing, leaching and freeze-thaw cycles in the scenario of climate change, and then play important roles in the dynamics of water soluble and organic solvent soluble components during foliar litter decomposition in the alpine forest. Therefore, a field litterbag experiment was conducted in an alpine forest in western Sichuan, China. The foliar litterbags of typical tree species (birch, cypress, larch and fir) and shrub species (willow and azalea) were placed on the forest floor under different snow cover thickness (deep snow, medium snow, thin snow and no snow). The litterbags were sampled at snow formation stage, snow cover stage and snow melting stage in winter. The results showed that the content of water soluble components from six foliar litters decreased at snow formation stage and snow melting stage, but increased at snow cover stage as litter decomposition proceeded in the winter. Besides the content of organic solvent soluble components from azalea foliar litter increased at snow cover stage, the content of organic solvent soluble components from the other five foliar litters kept a continue decreasing tendency in the winter. Compared with the content of organic solvent soluble components, the content of water soluble components was affected more strongly by snow cover thickness, especially at snow formation stage and snow cover stage. Compared with the thicker snow covers, the thin snow cover promoted the decrease of water soluble component contents from willow and azalea foliar litter and restrain the decrease of water soluble component content from cypress foliar litter. Few changes in the content of water soluble components from birch, fir and larch foliar litter were observed under the different thicknesses of snow cover. The results suggested that the effects of snow cover on the contents of water soluble and organic solvent soluble components during litter decomposition would be controlled by litter quality.

A field experiment using litterbags was conducted in an alpine forest of western Sichuan in order to understand the effects of snow patches on the dynamics of N and P during decomposition of six representative species foliar litter in different periods of winter. Net N immobilization during foliar litter decomposition was observed in the whole snow cover season regardless of species. In contrast, P mainly released from foliar litter in the snow cover season, with a rapid rate of P release in the snow melt stage. Thick and moderate snow patches showed higher P release rates, but lower N release rates of foliar litter. The rate of N release was negatively related to daily mean temperature regardless of species, but the rate of P release was positively related to daily mean temperature with the exception of fir needle-litter. The decrease of snow cover in the scenario of global warming could inhibit P release but promote N release from foliar litter decomposition in winter in the alpine forest.

A field plot experiment was conducted to study the effects of seed dressing with imidacloprid at the pesticide/seed mass ratios of 6:10000, 9:10000, and 12:10000 on the seedlings growth and protective enzyme activities of high-yielding summer maize. Seed dressing with an imidacloprid/seed mass ratio of 6:10000 increased the seedlings height, primary root length, secondary root number, aboveground fresh mass, and underground fresh mass by 2.81 cm, 2.31 cm, 1.71, 0.30 g, and 8.28 g, respectively, as compared to the control, and had better effect than the treatments 9:10000 and 12:10000. Comparing with the control, treatment 6:10000 increased the leaf- and root soluble protein content by 12.6% and 27.9% and catalase (CAT) activity by 2.5% and 11.5%, decreased malondialdehyde (MDA) content by 26.3% and 60.9%, improved superoxide dismutase (SOD) activity by 19.7% and 5.6%, enhanced glutathione-S-transferase (GSTs) activity by 11.5% and 13.2%, respectively, and increased the root peroxidase (POD) activity by 31.8%. Seed dressing with imidacloprid at the pesticide/seed mass ratio of 6:10000 could markedly improve maize seedlings protective enzyme activities, but had no promotion effect on leaf peroxidase (POD) activity.

A total of 21 different disease-grading summer maize groups were formed by fixed-point natural infection of maize brown spot in the field, and mass loss estimation models of single ear mass and 100-grain mass were constructed by stepwise regression with DPS software. The mass loss estimation models of single ear and 100-grain were Y = -4.012 + 0.377X1 - 0.228X2 + 0.694X3 - 0.144X4 and Y = -4.536 + 0.173X1 + 0.188X2 + 0.248X3 - 0.034X4, respectively, where Y was yield loss rate, X1 was the disease index at flowering stage, X2 was the disease index at pollination stage, X3 was the disease index at filling stage, and X4 was the disease index at dough stage. The measured relationships between the disease indices at different growth stages and the mass loss for single ear and 100-grain coincided well with the modeling results. Maize brown spot directly affected the net photosynthetic rate of ear height leaf and the activities of RuBP carboxylase and PEP carboxylase. The higher the disease-grade, the lower the net photosynthetic rate and the activities of the two enzymes were.

A field plot experiment was conducted to study the effects of foliar spraying DA-6 at the rates of 10, 20, and 40 mg x L(-1) at jointing stage on the leaf photosynthetic carboxylase and protective enzyme activities and grain yield of high-yielding summer maize cultivar Denghai 661. Comparing with the control (foliar spraying surfactant and water), spraying 10, 20, and 40 mg x L(-1) of DA-6 increased the grain yield of Denghai 661 significantly, with the increment being 10.0%, 8.9%, and 9.4%, respectively, but no significant differences were observed among the DA-6 treatments. Different concentration DA-6 increased the leaf area index, net photosynthetic rate, and RuBPCase and PEPCase activities significantly, and the promotion effects on the net photosynthetic rate and RuBPCase and PEPCase activities increased with increasing concentration of DA-6. After treated with DA-6, the leaf superoxide dismutase, catalase, peroxidase, and glutathione S-transferase activities and the leaf soluble protein content at the stages of silking, grain-filling, milky, and wax maturity all increased significantly, and the leaf malondialdehyde decreased significantly, compared with the control. The catalase activity increased with increasing DA-6 concentration, but the other indices had no significant differences among the DA-6 treatments.

Oyster reef ecosystem is a natural decontamination plant of estuarine environment. This paper analyzed the bioaccumulation of heavy metals by Crassostrea sp. population at the dams of Yangtze River estuary, with its purification capacity and ecological services value assessed. The results indicated that Crassostrea sp. had a high capacity in bio-accumulating Cu, Zn and Cd, with the bio-concentration factor (BCF) and biota-sediment accumulation factor (BSAF) being (14.28 +/- 2.41) x 10(3), (12.75 +/- 2.02) x 10(3) and (14.51 +/- 3.71) x 10(3), and 26.78 +/- 4.53, 23.24 +/- 3.69 and 16.62 +/- 4.25, respectively. The bioaccumulation capacity decreased in the order of Cu > Zn > Cd > As > Pb > Hg. The total weight and fresh meat weight of the oyster at the dams of Yangtze River estuary were about 1.07 x 10(6) t and 1.75 x 10(5) t, respectively, and the total storage of nutrients and heavy metals were 1.462 x 10(6) kg N, 1 x 10(5) kg P, 24 745 kg Cu, 58 257 kg Zn, 609 kg Pb, 254 kg Cd, 0.18 kg Hg and 329 kg As. The total ecological services value of the oyster reef was estimated at about 8.27 x 10(6) RMB x a(-1), including habitat value of about 5.10 x 10(6) RMB x a(-1) and environmental value of about 3.17 x 10(6) RMB x a(-1). Such an environmental value was equivalent to the value of treating about 7.31 x 10(6) t combined sewage each year, and corresponded to a large municipal sewage plant with a treatment capacity about 20 000 t d(-1).