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As a common measure for grassland restoration, the fence for prohibition of grazing is usually applied to the steppe in northern China. A study in Hulunbuir grassland showed the average litter mass in the steppes that enclosed for ten years can reach 70-550g/m2. The excessive accumulation of litter caused by long-term grazing prohibition can intercept more precipitation, which will reduce the water available to grassland plants and hinder the further recovery of plant communities. Therefore, the establishment of a reasonable litter interception model can help estimating the interception of steppes with different litter accumulation and provide some theoretical support for the formulation of fencing policies. Based on the model of litter interception rate change, we established a dynamic interception model of litter: I = I m ( 1 − e − k t ) ( t : time; I : dynamic interception; I m : maximum interception; k : exponential coefficient of litter interception). After testing by an indoor simulated rainfall experiment, we found that this model has high accuracy ( R 2 : 0.908 – 0.992). The litter mass (LM) determines the maximum interception, and the rainfall intensity (RI) determines the speed of interception which reaches its maximum value. After the conversion of coefficients, we established a prediction model of litter interception based on LM and RI: I = ( 0.003 L M + 0.44 ) [ 1 − e − ( 0.33 R I + 3.76 ) t ] , R 2 = 0.86 , P 0.001 . The easily obtainable characteristics of LM and RI data make this model easy to apply.

A plant's foliar uptake of dew can mitigate the adverse effects caused by drought stress. However, in grassland ecosystems, it is inconclusive whether the dew condensation characteristics of plants at different heights are consistent. In this study, we wanted to know whether plant height had a significant effect on the formation of dew. In addition, we wanted to understand the difference of dew formation between C3 plant Leymus chinensis (LC) and C4 plant Cleistogenes squarrosa (CS) which have different heights and can succeed each other in the community. In nine dew nights, we measured the amount of dew formed on simulated condensation surface (different heights) and two plants at the same time. The results showed that in the height range of 5–80 cm, the dew amount increases with the canopy height, but its increase rate gradually slows down and approaches zero. The shorter CS (5–15 cm) has a similar dew amount (0.095 mm) as LC (40–70 cm) due to its compact structure of the leaves with pubescence and the more stable micro-meteorological conditions. The CS can obtain more potential dew per unit organic matter, and this may be one of the potential mechanisms for the succession from LC communities to CS communities under drought stress. HIGHLIGHTS The dew formation on leaves theoretically changes exponentially with steppe plant height: y = a(1 − e−bx).; Both plant height and morphological characteristics affect dew formation.; One of the potential mechanisms of succession from Leymus chinensis (LC) community to Cleistogenes squarrosa (CS) community under drought stress was proposed.

Environmental factors are generally considered to be important factors affecting the release process of phosphorus (P) in sediments. However, little is known about the effect of temperature increased at first and then decreased with the season change on the P flux rate and flux amount at the sediment-water interface in the steppe wetlands. The effects of the temperature variation on P flux at the sediment-water interface in the steppe wetlands during the vegetation growing season under simulated wetland habitat were studied. The results showed that the release of P from sediments to overlying water was greatly affected by temperature changes. When the temperature rose, P was released from the sediment into the overlying water, while P was precipitated from the water into the sediment with the temperature dropped. During simulation period, the total P in water flux rates between sediment and overlying water (FP) was ranged from - 4.51 to 4.99 mg·m

Hulunbuir steppe has flat terrain and wide riparian zone of rivers and lakes on it. Owing to climate change, these riparian zones are often submerged or dried. This not only results in the instability of biodiversity in these regions but also affects the soil biogeochemical cycles. Soil C:N:P ecological stoichiometry plays a vital role in predicting and understanding the balance of multiple chemicals in ecological interactions. However, few studies have examined the soil C:N:P ecological stoichiometry in riparian zones of Hulunbuir steppe under different submergence states. Our objectives were to explore whether submergence frequencies impact soil C:N:P stoichiometry and identify the key factors. Four study sites were selected along the Hui river in Hulunbuir steppe, and three plots of different submergence frequencies, high (HF-sub, 5 to 7 times per year), moderate (MF-sub, 2 to 3 times per year), and low (LF-sub, unflooded or flooded once per year), were selected for each study site. Soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), their ecological stoichiometric ratios (soil C:N, N:P, and C:P), soil ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), available phosphorus (AP), soil pH, electrical conductivity (EC), soil moisture content (SMC), soil bulk density (SBD), porosity, and hardness were measured and analyzed. The results indicated that soil C:N:P ecological stoichiometry was notably affected by submergence frequency across the four study sites (P

Phosphorus (P) loss with surface runoff accounts for the P input to and acceleration of eutrophication of the freshwater. Many studies have focused on factors affecting P loss with surface runoff from soils, but rarely on the relationship among these factors. In the present study, rainfall simulation on P loss with surface runoff was conducted in Huihe National Nature Reserve, in Hulunbeier grassland, China, and the relationships between P loss with surface runoff, soil properties, and rainfall conditions were examined. Principal component analysis and path analysis were used to analyze the direct and indirect effects on P loss with surface runoff. The results showed that P loss with surface runoff was closely correlated with soil electrical conductivity, soil pH, soil Olsen P, soil total nitrogen (TN), soil total phosphorus (TP), and soil organic carbon (SOC). The main driving factors which influenced P loss with surface runoff were soil TN, soil pH, soil Olsen P, and soil water content. Path analysis and determination coefficient analysis indicated that the standard multiple regression equation for P loss with surface runoff and each main factor was Y = 7.429 – 0.439 soil TN − 6.834 soil pH + 1.721 soil Olsen-P + 0.183 soil water content (r = 0.487, p

The development of a (layer of) thatch in turfgrass causes important changes to near-surface eco-hydrological processes. In this study, we investigated the effects of turfgrass thatch, specifically Kentucky bluegrass (Poa pratensis L.) and red fescue (Festuca rubra L.) on water infiltration, surface runoff, and soil moisture evaporation. The thatches were collected from the field for controlled experiments using packed soil columns under various rainfall conditions. Results indicated that the presence of thatch delayed the onset of infiltration compared with situations without a thatch at the soil surface. Infiltration was delayed for a longer period in thicker red fescue thatch than thinner Kentucky bluegrass thatch. The presence of a thatch reduced runoff by holding more water locally during the rainfall period and allowing a longer period of time for infiltration. Additionally, evaporative water loss was reduced with the presence of thatch than that of bare soil. Our results highlight that the presence of thatch changes the near-surface hydrological processes, which may help improve turf management practices in terms of thatch control and irrigation scheduling.

The effect of climate warming on soil organic carbon (SOC) of sediment in wetlands is important for accurately projecting SOC content. Thus, understanding the mechanism influencing SOC content under climate warming is necessary. Field investigation and a laboratory incubation experiment were conducted in Hulunbeier steppe wetland during 2016 and 2017. Four types of wetland were selected to incubate with ambient temperature and temperature increased by 2.5 °C. The results showed that SOC content was negatively affected by temperature warming. The SOC content reduction in sediment caused by increasing temperature was ranged from - 2.34 to 39.52%. In addition, the content of sand, silt, total phosphorus (TP), calcium phosphate tribasic (Ca-P), total nitrogen (TN), and sediment moisture (MC) should be considered in models of SOC content in steppe wetland. However, it requires further validation, in particular how SOC content varies with warming temperatures, the duration of incubation, and other abiotic and biotic factors. These findings provide evidence that both climate warming and original characteristics of sediment can control the SOC storage dynamics in the steppe wetland. Graphical abstract.

In order to reveal dynamics changes in phosphorus release from the sediments of wetlands in a mid-temperature steppe without external phosphorus input, the relationship between phosphorus content in the overlying water, sediment, and interstitial water was studied using the variables control method. The results showed that, during the incubation period, the content of total phosphorus in the overlying water and the content of total phosphorus in interstitial water both presented in the order of AugustSeptemberJuly. Furthermore, the correlation relationships between phosphorus content in the overlying water, total phosphorus in the interstitial water, and the ratios of sediment Olsen-P to total phosphorus in the interstitial water, indicated that Olsen-P might be a kind of release form of phosphorus - from the sediment to the overlying water of the wetlands in Hulunbeier steppe, without external phosphorus input. This article is protected by copyright. All rights reserved.

Effective grassland restoration practices can promote degraded meadows recovery. However, little has been documented regarding the effect of water addition on the restoration of degraded meadows in the Qinghai–Tibetan Plateau (QTP) . A field experiment with five water addition levels was established to identify the interactions between soil bio-physicochemical properties and plant of the degraded alpine meadows in the Sanjiangyuan region, QTP. Soil enzyme activity (α-glucosidase, αG; β-1,4-glucosidase, βG; β-D-cellubiosidase, βDC; β-xylosidase, βX; β-1,4-N-acetylgucosaminidase, NAG; leucine aminopeptidase, LAP; phosphorus, P), microbial biomass C (MBC) and N (MBN), MBC: MBN, physicochemical properties (soil moisture content, SMC; bulk density, SBD; pH; total organic C, TOC; total N, TN; soil C: N; ammoniacal N, NH4+-N; nitrate N, NO3−-N; nitrite N, NO2−-N), and plant diversity and productivity were analyzed throughout the growing season. The results indicated that soil SMC, available N (NH 4 + -N and NO 3 − -N), TOC, the activities of αG, βDC, βX, NAG, MBC and MBN significantly increased with water addition levels, whereas the activity of LAP and P, and MBC: MBN decreased (p 4 + -N, and NO 3 − -N, were significantly related to plant diversity and productivity. The changes in soil enzyme activity (especially βDC, βG, LAP) under water addition might the key drivers affecting soil nutrients such as TOC, NO 3 − -N and NH 4 + -N, which subsequently increased plant coverage and productivity. Our findings suggested that the obviously increase in enzymes activity and nutrients might be beneficial for the vegetation recovery of degraded alpine meadow on the QTP under water addition.

Water shortage is the most critical constraint for alfalfa (Medicago sativa L.) hay production in the arid areas of Northwest China. In this study, we evaluated the effectiveness of partial root-zone drying (PRD) with subsurface drip irrigation (SDI) for alfalfa and compared it with conventional subsurface drip irrigation (CI). Field plot tests were conducted in 2017 and 2018 with three irrigation treatments under partial root-zone drying SDI system. Conventional SDI systems were used as the control. The irrigation quotas were 10 mm, 20 mm, and 30 mm per week for PRD1, PRD2, and PRD3, respectively, and that for CI was 30 mm per week. The number of drip irrigations for alfalfa in the whole growing stage were 13 and 19 in 2017 and 2018, respectively. There were three harvests in 2017 and four harvests in 2018. The results showed that the plant height of PRD was 0.4–11.57 cm higher than that of CI under the same irrigation regime. Moreover, PRD decreased the annual hay yield of one-year-old alfalfa, but increased the annual hay yield of two-year-old alfalfa, while in 2018 the annual hay yield increased by 832.27 kg ha−1 as compared to that of CI. Moreover, PRD has marked effect on alfalfa quality under insufficient amounts of water applied (PRD1), with significantly decreased acid detergent fiber by 7.81–27.02% and neutral detergent fiber by 0.25–15.23%, and increased crude protein by 0.59–12.68%, compared with CI. Crop water productivity (WPC) of one-year-old alfalfa under PRD3 in 2017 increased by 4.15–15.33% relative to CI, while WPC of two-year-old alfalfa under PRD2 in 2018 increased by 1.66–44.32% relative to CI. These results suggest that the proposed PRD could be a promising technique for alfalfa production in the arid area of Northwest China, with improved WPC and positive effect on quality characteristics.

Phosphorus (P) losses from terrestrial soils contribute to eutrophication of surface waters. As priority non-point source pollution ways, rainfall runoff (RS1) and snowmelt runoff (RS2) are the main carrier of P loss from terrestrial ecosystem. The aim of this study was to investigate the similarities and differences between P loss with RS1 and RS2 of the same soil type. Six types of soil were used in this experiment. Results have shown that 1), Different types of soil have different P loss with RS1 and RS2 under different slope, and the changes ranged from 0.003 to 0.370 mg L−1. 2), The effects of soil type, slope and runoff type on P loss with surface runoff was not independent, both individual effects of all factors and their interaction with the other two factors effected the P loss with runoff. 3), In our experiment, some soils showed no significant difference between P content in RS1 and RS2. In some soils, P loss with RS1 was higher than that with RS2 while the opposite conclusion was showed in Bog soil (BS) which with higher soil water content. 4), The P loss with RS1 and RS2 of different soils were both mainly affected by soil water content (SW), Olsen-P content (OP) and soil organic matter content (OM). These results can help us understand the P loss with different patterns of surface runoff better and are expected to provide pertinent opinions on the analysis of P loss with runoff and its influencing factors of grassland soils.

Turfgrasses have been widely utilized by humans to enhance the environment for more than several centuries. Seed germination is of great importance in the development of the turfgrass industry. In this study, the seed germination models of the responses of three types of turfgrasses to water were studied. The results indicated that irrigation water was mainly related to the variation of seed volume rather than a fixed value in this experiment. The maximum k value of tall fescue, Kentucky bluegrass and perennial ryegrass is 1.1548, 1.6946 and 4.0940, respectively. The optimal value of k is 1.0617 for tall fescue, 1.4610 for Kentucky bluegrass, and 1.6614 for perennial ryegrass. Perennial ryegrass seeds are more sensitive to water than those of tall fescue and Kentucky bluegrass, and this turfgrass is the fastest to reach the maximum value of the germination rate. Based on the results from the present experiment, the seed germination function can describe the response of turfgrass seed germination to external water content variation and their sensitivities. The function obtained could be used to perform quantitative studies on the dynamic changes of seed germination under different water conditions that will contribute to improved predictions of the optimal fitting curves of the germination over a range of water.

Alfalfa (Medicago sativa) is one of the major crops grown in Northern China in recent years, however, the current serious water shortage conditions present a challenge to the growth of this crop, especially if efficient use of water is considered in forage production for sustainability. This study aimed to evaluate alfalfa productivity and water use efficiency (WUE) under different sprinkler irrigation levels. This experiment was conducted at Shiyanghe Experimental Station for Water-Saving in Agriculture and Ecology of China Agricultural University in Wuwei, Gansu, China, over a period of two years. There were three irrigation treatments: A1: 100% measured evapotranspiration (ETc) of alfalfa; A2: irrigation amount was 66% of A1; A3: irrigation amount was 33% of A1; and a control of A4: no irrigation during the growing season. A randomized block design with three replications were applied. The results showed that the ETc and forage yield of alfalfa decreased, while WUE and crude protein (CP) increased with the decreasing irrigation amounts. The seasonal average ETc and yield ranged from 412 mm to 809 mm and from 11,577 to 18,636 kg/ha, respectively, under different irrigation levels. The highest yields were obtained from the first growth period in all treatments in both years, due to the winter irrigation and the longest growth period. Alfalfa grown under lesser irrigation treatment conditions had higher variability in ETc and yield, mainly due to the variability in the amount of rainfall during the growth period. The seasonal average WUE of treatments ranged from 22.78 to 26.84 kg/(mm·ha), and the highest WUE was obtained at the first growth period, regardless of treatments. Seasonal average CP content ranged from 18.99% to 22.99%. A significant linear relationship was found between yield and ETc or irrigation amount, and the fitting results varied between growth periods and years. The present results also implied that winter irrigation provided the space for saving water and should be applied at the end of each growing season to fill the soil profile, and to maintain a greater yield in the next growing season. During the growing season, more irrigation should be concentrated in the early growth period, especially in the second growth period.

Irrigation consumes considerable water to satisfy the current food demand. An improvement in water use efficiency for irrigation is essential. Wind drift and evaporation losses reduce the water use efficiency of center pivot irrigation systems in arid and semi-arid areas. In this paper, a model of water vapor dynamics during and after overhead sprinkler irrigation was developed and validated by experimental data using a center pivot simulator and a water vapor measuring system. The model was represented as an exponential equation during irrigation and a logistic equation after irrigation. The water vapor dynamics measured next to and 2 m from the sprinkler were well-fitted with the developed model. Model performance was good according to evaluations of the Nash—Sutcliffe efficiency coefficient, with values of 0.961 and 0.934 for estimations next to the sprinkler and 2 m from the sprinkler, respectively. Results showed that both modeled and observed water vapor dynamics increased rapidly as irrigation started, and then leveled off to maximum values. After irrigation, the water vapor dynamics started to decrease gradually, and eventually decreased rapidly. The decreasing rate stopped when the water vapor content was restored to the level of the surrounding atmosphere. The model parameters showed that the maximum increases in water vapor content were from 2.506 to 6.476 g m−3 for the area next to the sprinkler, and 1.277 to 3.380 g m−3 for the area 2 m from the sprinkler, under the influence of vapor pressure deficits. The increasing and decreasing rates of the dynamics during and after irrigation were influenced by temperature, relative humidity, and vapor pressure deficits, according to Pearson’s correlations. A period of 2.3 to 4.0 h was required to restore water vapor to the atmospheric level.

Sprinkler selection influences the water distribution uniformity of center pivot irrigation systems. The sprinkling uniformity of the center pivot is crucial for the yield and quality of crops on a large scale. Rotating and fixed spray plate sprinklers (RSPSs and FSPSs) are the two most popular types. However, sprinkler selection is mainly based on price, not on differences in performance between them. Under low-wind field conditions, the water distributions of individual RSPSs and FSPSs with different nozzles (2.78, 4.76, and 6.75 mm in diameter) were measured using a catch can method. Cubic spline interpolation was used for data conversion for FSPS measurements; the nozzle configuration model was used to simulate the water distribution of the same-nozzle-sprinkler pipe section and full circular irrigated areas in a simulated center pivot under three sprinkler intervals of 1.5, 3.0, and 4.5 m respectively. Results showed that (1) individual RSPSs distributed the most water around the sprinkler, whereas individual FSPSs distributed the most water over a ring-shaped region at the periphery of the sprinkler, and the wetted radii for RSPSs and FSPSs ranged from 4.88 to 7.05 m and from 5.02 to 6.85 m, respectively; (2) same-nozzle-sprinkler pipe sections of RSPSs distributed the most water around the central axes of the pipe sections, and their sprinkling uniformities were 44.7%–51.0%, whereas FSPSs distributed the most water over both sides of the axes symmetrically, and less water around the axes, with sprinkling uniformities of 40.3%–58.0%; and (3) the sprinkling uniformities of the full circular irrigated areas were 85.8%–91.7% and 85.8%–86.2% when using RSPSs and FSPSs, respectively, under different sprinkler intervals, and the uniformities were 3.1% and 6.2% higher using RSPSs than FSPSs with sprinkler intervals of 3.0 and 4.5 m, respectively. RSPS accommodated larger sprinkler intervals (>3.0 m) and maintained superior sprinkling performance when compared with FSPS.

Summary Plant leaf can absorb water when the leaf is in contact with water. This happens when the rainfall is intercepted by plant leaves, where the intercepted part of rain remains on the leaf surface. When the intercepted water is either absorbed or subsequently evaporated into the atmosphere, the plant leaves can dissipate water through the desorption process until the plant is dry or rewatered. In this paper, two symptomatic models in the form of exponential functions for leaf water absorption and leaf water desorption were derived and validated by experimental data using leaves of three turfgrasses (Tall fescue, Perennial ryegrass and Kentucky bluegrass). Both the models and measured data showed that the rate of leaf water absorption was high at the low initial leaf water content and then gradually leveled off toward the saturated leaf water content. The rate of leaf water desorption was high at the high initial leaf water content then decreased drastically over time toward zero. The different plant leaves showed different exponents and other parameters of the functions which indicate the difference of plant species. Both the absorption and desorption rates were relatively higher for the Kentucky bluegrass and lower for the Tall fescue and Perennial ryegrass. The concept of specific leaf area (SLA) was used to understand the saturated leaf water content (Cs) of the three turfgrasses. Linear relationships were found between Cs and SLA. The leaf water absorption and desorption functions are useful for deriving physiological parameters of the plant such as permanent wilting leaf water content, naturally irreducible leaf water content, exponential leaf water absorption coefficient, and exponential leaf desorption coefficient, as well as for evaluating the effects of rainfall interception on plant growth and water use efficiency.

Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] is a warm-season grass for low-maintenance lawns. The objective of our study was to assess the genetic variation in 10 accessions of buffalograss obtained from the Chinese Academy of Agricultural Sciences by random amplified polymorphic DNA (RAPD) markers. Fourteen of the 60 primers screened generated 72 highly repeatable polymorphic bands. A dendrogram constructed on the basis of the unweighted pair group method arithmetic average clustering algorithm revealed that nine of 10 accessions formed two distinct clusters. Genetic similarity coefficients calculated from the RAPD data ranged from 0.30 to 0.89 with the lowest value of 0.30 measured between No. 4 and No. 7 from Japan and the United States, respectively. The highest value of 0.89 was measured between No. 6 and No. 8 from the United States and Mexico, respectively. The cophenetic correlation coefficient (r) was 0.92, indicative of a very good fit between the data matrix and the resulting cluster analysis. Principal coordinate analysis (PCO) clearly grouped nine accessions on the two axes with a single accession from the United States that did not cluster with others. The PCO clustering pattern corresponded well with the dendrogram. No. 7 from the United States did not cluster with any other accessions either in the dendrogram or on the basis of the PCO.

In rainfed semiarid areas of northwestern China, alfalfa ( Medicago sativa L.) is usually cultivated in flat fields with spaced rows. The yield of the crop is normally low because of insufficient moisture in the soil. The purpose of this study was to examine the effect of soil ridging and plastic film, covering the ridges, on rainwater harvest and alfalfa yield and to identify the optimal design of the ridge-furrow system. In this system the ridges served as the runoff area and the furrows as the infiltration area, where alfalfa was grown. Three ridge width (RW) measured at the bottom of the ridge, namely 30, 45 and 60 cm, were tested under the condition of the ridge-furrow systems with or without plastic film covering the ridge. These treatments were compared with the flat soil (FS) planting system, having neither ridge nor plastic cover. No matter what RW (or in the case of FS spacing between planting belts), the width of furrow (planting belt) was the same as 0.6 m. Soil moisture was measured at 7–10 day intervals, in 10 cm increments, to soil depth of 2 m. Rainwater harvests were measured from two additional plots without planting, representing the covered ridge (CR) and uncovered ridge (UR) systems, respectively. The results showed that in terms of average alfalfa yield on a total area basis, ridge type and ridge width both had significant effects, with CR being better than UR, and UR in turn being better than FS. The 2-year average annual yield of alfalfa was 5114 kg DM ha −1 for CR, 2531 kg DM ha −1 for UR, and 1927 kg DM ha −1 for FS. For the CR treatments, the ridge width (RW) of 0.3 m resulted in higher yield (5528 kg DM ha −1 ) than RW of 45 cm (5095 kg DM ha −1 ) and 60 cm (4719 kg DM ha −1 ). For the UR treatments, yields with 30 cm RW (3088 kg DM ha −1 ) were higher than with 45 cm RW (2434 kg DM ha −1 ) and 60 cm RW (2071 kg DM ha −1 ). The results also showed that the CR planting system had additional advantage of collecting more rainwater to improve plant effective soil moisture. In conclusion, the CR with a RW of 0.3 m and furrow width of 0.6 m is recommended for improved rainwater utilization and improved alfalfa yield in the semiarid areas where alfalfa production is largely rainfed.

The dynamic changes in sediment nutrients, alkaline phosphatase activity and the relationships between them and wetland in Hulunbeier Grassland in different sites were studied. The results show that with the time change, pH value of wetlands sediment in three sites showed increasing trend. And organic matter of wetlands sediment in three sites showed first decreased slightly first and then gradually increased trend; Total nitrogen of wetlands sediment in three sites presented a slightly decreased trend. Total phosphorus of wetlands sediment in three sites showed a gradually decreased trend. The alkaline phosphatase activity of wetlands sediment in Hulun Lakes and Yimin River had the largest increase in July and then decreased while it was reached maximum in August and then decreased in September in Hui River. Correlation analysis results showed that the alkaline phosphatase activity of wetlands sediment was positively correlated with organic carbon, total phosphorus and pH value while it was significantly positively correlated with total nitrogen.

A pressure reducing pipe (PRP), used at the inlet of a lateral in microirrigation systems to improve water application uniformity, is developed. It is composed of an internal spiral and a sleeve pipe and is made of molded polyethylene plastic. It functions to dissipate a pressure head that exceeds the required pressure head of a lateral inlet by directing water flow through the spiral grooved path and creating a certain head loss. An improved design method for submain units using the pressure reducing pipes is based on the hydraulics of the submain unit and the characteristics of the head loss in the PRP. The effects of the PRP on water application uniformity in a submain unit are analyzed by computer simulation. The submain unit with the PRP has higher uniformity than that of the commonly used method. After choosing the PRP, the permissible range of pressure variation in a submain will not need to be considered for the submain length in a layout.

Rising temperature causes a process of phosphorus release, which can be characterized well using phosphorus release rates (VP). The objective of the present study was to investigate the major factors affecting sediment phosphorus release rates through a wetland habitat simulation experiment. The results showed that the VP of different wetland sediments were different and changed with the order of W–R (river wetland) > W–L (lake wetland) > W–M (grassy marsh wetland) > W–A (reservoir wetland). The main driving factors which influenced sediment phosphorus flux velocity in the sediment–water interface were sediment B-SO42−, B-MBN and A-MBP content. Path analysis and determination coefficient analysis indicated the standard multiple regression equation for sediment phosphorus release rates in the sediment–water interface, and each main factor was Y = −0.105 + 0.096X1 + 0.275X2 − 0.010X3 (r = 0.416, p < 0.01, n = 144), where Y is sediment phosphorus release rates; X1 is sediment B-SO42− content; X2 is sediment B-MBN; and X3 is sediment A-MBP content. Sediment B-SO42−, B-MBN and A-MBP content and the interaction between them were the main factors affecting sediment phosphorus release rates in the sediment–water interface. Therefore, these results suggest that soil chemical properties and microbial activities likely play an important role in phosphorus release rates in the sediment–water interface. We hope to provide effective scientific management and control methods for relevant environmental protection departments.

Climate warming generates a tremendous threat to the stability of geographically-isolated wetland (GIW) ecosystems and changes the type of evaporation and atmospheric precipitation in a region. The intrinsic balance of biogeochemical processes and enzyme activity in GIWs may be altered as well. In this paper, we sampled three types of GIWs exhibiting different kinds of flooding periods. With the participation of real-time temperature regulation measures, we assembled a computer-mediated wetland warming micro-system in June 2016 to simulate climate situation of ambient temperature (control group) and two experimental temperature differences (+2.5 °C and +5.0 °C) following a scientific climate change circumstance based on daily and monthly temperature monitoring at a two-minutes scale. Our results demonstrate that the contents of the total organic carbon (TOC), total nitrogen (TN), and total phosphorus (TP) in the warmed showed, roughly, a balance or a slight decrease than the control treatment. Warming obstructed the natural subsidence of sediment, but reinforced the character of the ecological source, and reduced the activity of urease (URE), but promoted the activity of alkaline phosphatase (AKP) and sucrase (SUC). Redundancy analysis showed that sucrase, urease, available phosphorus (AP), and pH were the major correlating factors under warming conditions in our research scope. Total organic carbon, total nitrogen, sucrase, catalase (CAT), and alkaline phosphatase were the principal reference factors to reflect the ambient temperature variations. Nutrient compositions and enzyme activities in GIW ecosystems could be reconstructed under the warming influence.

In order to realize the integration of design and calculation of dripping irrigation pipeline in AutoCAD, this paper developed a set of software which is embedded in AutoCAD and used for pipeline calculation. As an integrated development software, VBA can share and exchange data with other VBA programs directly. This makes connecting with other software and processing data more easy. Using AutoCAD VBA, this paper developed the software for the automatic design of drip irrigation. Under this circumstance, user can complete data analysis and calculation thus makes the design work more efficiency.. The software contains three modules, knowledge module, calculating module and documents managing module. Through these facilities, Not only can the users finish the work of design, but also it produces the Excel to transmit the data, which is necessary for the design or choosing equipments. Further more it is convenient to maintain and upgrade.