• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Rules of Changes in Soil Nutrients and Enzyme Activities of Larix principis-rupprechtii in Different Forest Ages

    2019-05-24 08:14:26
    Asian Agricultural Research 2019年4期

    Institute of Land Engineering and Technology, Shaanxi Provincial Land Engineering Construction Group Co., Ltd., Xi’an 710075, China; Shaanxi Provincial Land Engineering Construction Group Co., Ltd., Xi’an 710075, China; Key Laboratory of Degraded and Unused Land Consolidation Engineering, the Ministry of Land and Resources, Xi’an 710075, China; Shaanxi Provincial Land Consolidation Engineering Technology Research Center, Xi’an 710075, China

    Abstract In this study, three different ages of Larix principis-rupprechtii forests in 5, 10 and 20 years were selected as the research objects, and the changes in soil nutrient and soil enzyme activities in different growth stages were analyzed. The results showed that the contents of organic matter and available phosphorus in the soil of different growth stages showed a significant downward trend with the increase of soil depth. For different forest ages in the same soil layer, the soil available phosphorus content declined with the increase of the forest age. The organic matter content of 40-60 cm in 20 years of forest age was the lowest in July, which was 4.17 g/kg, significantly lower than that in other soil layers. Besides, the soil available phosphorus content of 5 years of forest age reached the maximum in July, with an average of 4.44 mg/kg, which was higher than the available phosphorus content in soil in May and September, but the difference between the three months was not significant. The changes in ammonium nitrogen and nitrate nitrogen content in soil with different forest ages were consistent with the changes in the soil depth, showing a downward trend. In the new leaf stage, the ammonium nitrogen content of the L. principis-rupprechtii forest land in 5 years of age at 20-40 and 40-60 cm of the soil depth was 13.47 and 9.09 mg/kg, respectively, which was 46.9% and 64.2% lower than that at 0-20 cm (25.36 mg/kg) of the soil depth. The soil nitrate nitrogen content of 20 years of forest age was 19.24 mg/kg, which was 25.8% lower than that of 10 years of forest age, showing significant difference (P<0.05). In addition, with the increase of the age of L. principis-rupprechtii, soil catalase (CAT), alkaline phosphatase (ALP) and urease (Ure) decreased, and the decline of ALP was slow, while CAT and Ure decreased significantly. In summary, it is concluded that the soil fertility of forest land declined with the increase of forest age on the basis of change trend of soil nutrient and soil enzyme activity in the surveyed forest age.

    Key words Larix principis-rupprechtii, Forest age, Soil nutrient content, Enzyme activity

    1 Introduction

    With the rapid development of China’s economy, the demand for wood is increasing sharply. At present, the existing natural forest resources have been unable to support such high demand, and the production cycle of plantations is relatively short, and cultivation can be achieved according to demand, and the efficiency is high, so the artificial afforestation industry has risen rapidly, it plays an important role in solving the problems of the shortage of timber and environmental protection in the world[1].LarixgmeliniiRupr. is a deciduous arbor of the genusLarix, and it is widely distributed in high altitude areas of China. The survival rate of special varietyLarixprincipis-rupprechtiiin the high mountains of North China is relatively high.L.principis-rupprechtiiis strong positive tree species with the height up to 30 m. This variety can grow rapidly, the timber quality is excellent, and it has a good effect on the maintenance of water and soil, thus it is one of the main choices for afforestation[2-3]. In 1958, Shaanxi Province started the introduction ofL.principis-rupprechtii. In 1986, the afforestation area reached 3.2×103ha only in Qinling Mountains. In the early stage ofL.principis-rupprechtiiintroduction, the trees grew well, but the growth trend of large-scale artificial afforestation becomes slow in recent years. In this situation, how to manage and maintain a large area ofL.principis-rupprechtiiplantation becomes very important[4-5]. Due to some limitations in the early state of planting, such as dense planting, single species, and no hierarchical structure, the management of plantations is relatively extensive, productivity has been declining from generation to generation, leading to serious problems such as soil fertility decline[6]. Therefore, focusing on how to solve the problem of decline of soil fertility in plantation forest is favorable for the sustainable development of plantations in China[7].

    The soil nutrients complement the growth of the plants. The soil nutrients can effectively protect the growth and development of the plantation forests, while the artificial forests will affect the physical and chemical properties of the soil through the decay of the fallen leaves, root exudates and symbiotic microorganisms[8-9]. Soil enzymes can promote soil metabolic processes by changing physical and chemical properties of the soil[10-11]. In this experiment, we intend to study the decline of soil fertility inL.principis-rupprechtiiforests from the basic soil nutrients and related enzyme activities. We surveyed and analyzed the increase and decrease in the basic soil nutrient and soil related enzyme activities in different forest ages ofL.principis-rupprechtiiforests, to explore the specific forms and stages of the forestland degradation. In this survey, we selected three gradients of forest age, namely 5, 10 and 20 years, analyzed the soil nutrient and soil enzyme activities of forest land, in the hope of revealing the trend of soil fertility and related enzyme activities in different forest ages, to provide important guiding significance for studying the decline ofL.principis-rupprechtiiforest land.

    2 Materials and methods

    2.1 General situation of the study areaIn this survey, we mainly selected Nantan Nursery of Taibai Forestry Bureau Forest Farm in Taibai County, Shaanxi Province. The forest farm is located at the foot of Qinling Mountain, about 4 km southeast of Taibai County. Its climate belongs to the Qinling Gorge microclimate zone, with an average altitude of about 1 660 m. The annual average rainfall is 580-1 020 mm, frost-free period is 155 d, annual average temperature is 7.7℃, and the annual temperature range is -25.3℃-32.9℃. The soil pH of the forest farm is 6.52-6.71, and other basic nutrient conditions are listed in Table 1[12].

    Table 1 Basic soil fertility characteristics of the surveyed forest farm

    Soil depth∥cmSoil water∥%Nitrate nitrogen∥mg/kgAmmonium nitrogen∥mg/kgAvailable phosphorus∥mg/kgOrganic matter∥g/kg0-2013.9630.822.486.4522.8520-4014.5419.312.014.9819.3240-6015.6515.48.244.0116.22

    2.2 Experiment designIn this experiment, we selected theL.principis-rupprechtiiforest land in different ages as the experimental objects, the forest ages are 5, 10 and 20 years, marked as LD-1, LD-2 and LD-3, respectively. All three experimental areas are located in the northeast direction in the middle of the slope with a slope of about 15-25 degrees. In LD-1 forest land, the average tree height is 4.8 m, the diameter at breast height (DBH) is 14.5 cm; in LD-2 forest land, the average tree height is 8.6 m, the diameter at breast height (DBH) is 22.3 cm; in LD-2 forest land, the average tree height is 10.2 m, the diameter at breast height (DBH) is 10.2 cm. The area of the forest plots of different ages is 20 m × 20 m. The sampling time was: May 12, 2014 (new leaf stage), July 15, 2014 (vigorous growth stage) and September 15, 2014 (early defoliation stage). The sampling was carried out by W type five-point sampling method. In each area, we randomly selected three sampling points, and collected the soil at 0-20, 20-40 and 40-60 cm depth respectively at a distance of 45 cm from the forest. We stored the collected soil samples in two parts: one fresh soil for the determination of ammonia nitrogen and nitrate nitrogen was stored at 4℃, and the other soil for determining soil nutrient and soil enzyme activity was naturally dried, ground, screened with 1 mm and 0.149 mm sieves, respectively, and kept for use.

    2.3 Measurement items and methodsSoil organic matter was measured by potassium dichromate volumetric method-external heating method, soil nitrate nitrogen and ammonium nitrogen were determined by AA3 continuous flow analyzer, soil available phosphorus was extracted by 0.5 mol/L NaHCO3and measured by molybdenum antimony colorimetric method[13].

    Soil urease activity: using indophenol colorimetry, urease activity was expressed in milligrams of NH3-N in 1 g soil after 24 h(mg/g); soil phosphatase activity: disodium phenyl phosphate colorimetric method, its activity was expressed using the amount of P2O5mg in the 1 g soil after 2 h (mg/g); the soil catalase activity: potassium permanganate method, and its activity was expressed in milliliters of 0.02 mol/L KMnO4consumed by 1 g of soil (mL/g)[14].

    3 Results and analyses

    3.1 Changes in soil nutrients ofL.principis-rupprechtiiin different forest ages

    3.1.1Changes in soil organic matter content ofL.principis-rupprechtiiland. From Table 1, it can be seen that the changes in soil organic matter content in forest at different stages are consistent, that is, decline with the increase of the soil depth. In the new leaf stage of tree growth, the soil organic matter content of the 20 years old forest land was 24.90, 7.58 and 4.51 g/kg from the surface soil to the bottom, and the latter two layers decreased by 229% and 452% compared with 0-20 cm, and both were significantly lower than 0-20 cm (P<0.05), but the difference between the two was not significant. The organic matter content in surface soil increased with the increase of forest ages. The content of organic matter in other soil layers declined with the increase of forest ages. During the vigorous growth stage, LD-3 had the lowest organic matter content at 40-60 cm soil depth, 4.17 g/kg, which is significantly lower than that in other soil layers. The soil organic matter content in the forest land from LD-1 to LD-3 declined significantly, which is a form of decline of the forest soil quality. Besides, the organic matter of LD-3 surface soil is higher than that of LD-1 and LD-2, possibly influenced by the humus produced by litter decay on the soil surface.

    Table 2 Changes in soil organic matter content ofLarixprincipis-rupprechtiiland in different forest ages

    MonthDepth∥cmOrganic matter∥g/kgLD-1LD-2LD-3May0-2019.72 bA20.96 bA24.90 bA20-4013.05 cB11.57 cB7.58 dB40-607.62 bC9.02 bC4.51 cBJuly0-2018.22 cA18.21 cA23.41 bA20-4013.12 bB13.10 bB5.41 cB40-609.26 bC9.26 bC4.17 cBSeptember0-2023.31 bA18.83 cA19.50 cA20-4015.29 bB12.84 cB9.02 dB40-6012.83 aB12.03 b8.55 cB

    Note: Different lowercase letters in the same row indicate significant difference at 5% level (P<0.05) between forest ages. Different uppercase letters in the same column indicate significant difference at 5% level (P<0.05) between different soil depth or the difference between different months (P<0.05). It is the same as below.

    3.1.2Changes in ammonium and nitrate nitrogen contents of forest soil in different forest ages. From Table 2, it can be known that the ammonium nitrogen content in the soil gradually declined with the increase of the growing month. At the same growth stage, the ammonium nitrogen content in the soil declined with the deepening of the soil layer, and declined with the increase of forest ages. At the new leaf stage of forest growth, the average ammonium nitrogen content of the forest LD-3 was 6.39 mg/kg, which was significantly lower than that of LD-1 (15.86 mg/kg) and LD-2 (11.22 mg/kg). At the vigorous metabolism stage, the average ammonium nitrogen content of the LD-1, LD-2 and LD-3 in the forest farm was 9.07, 6.32 and 2.31 mg/kg, and the difference between them was significant (P<0.05). At the new leaf stage of forest growth, the ammonium nitrogen content of LD-1 at 20-40 and 40-60 cm soil depth was 13.36 and 8.98 mg/kg, respectively, declined by 88.9% and 181% compared with that at 0-20 cm soil depth (25.24 mg/kg); during the growth stage and defoliation stage, the ammonium nitrogen content in the forest LD-3 declined from soil surface layer to deeper layers, specifically 6.97, 5.43 and 4.37 mg/kg respectively, and the difference in ammonia nitrogen content between the topsoil and the other two layers was significant. From Table 2, it can be seen that the nitrate nitrogen content in the soil ofL.principis-rupprechtiiforest land declined with the increase of soil depth at the new leaf stage and the defoliation stage, but at the vigorous growth stage, the changes in nitrate nitrogen content in the soil were not consistent, that is, first increase then decline. At the vigorous growth stage, the difference in nitrate nitrogen content in the LD-1 and LD-2 forest soil was not significant between different soil layers. However, at the new leaf stage of forest growth, the nitrate nitrogen content in the soil declined first and then increased with the increase of the forest age. The nitrate nitrogen content of LD-3 forest soil was 19.24 mg/kg, which was 34.8% lower than that of LD-2 (25.93 mg/kg), and the difference between the two was significant (P<0.05); in July and September, the nitrate nitrogen content in the soil increased slowly with the increase of the forest age, it was 22.96 mg/L in LD-1 in September and 22.58 mg/kg in LD-2, both were significantly lower than 32.94 mg/kg in LD-3.

    Table 3 Changes in nitrate nitrogen and ammonium nitrogen contents of forest soil in different forest farms

    MonthDepth∥cmLD-1Nitrate nitrogenmg/kgAmmonium nitrogenmg/kgLD-2Nitrate nitrogenmg/kgAmmonium nitrogenmg/kgLD-3Nitrate nitrogenmg/kgAmmonium nitrogenmg/kgMay0-2029.73 cA25.24 aA30.31 cA11.77 cA20.88 cA7.32 dA20-4019.40 cB13.36 aB28.01 bA10.45 bA19.68 dA5.93 cB40-6015.35 cB8.98 bC19.46 cB11.45 aA17.16 cA5.92 cBAverage val-ue21.49 d15.86 a25.93 c11.22 b19.24 d6.39 cJuly0-2040.32 bA17.41 aA40.27 bA6.58 cA43.73 bA2.46 dA20-4043.53 aA5.45 bB42.23 cA6.50 bA49.53 bA2.21 cA40-6043.08 cA4.36 bB41.87 aA5.88 bA25.38 bB2.25 cAAverage val-ue42.31 c9.07 a41.46 c6.32 b48.77 b2.31 cSeptember0-2029.26 cA16.62 aA26.63 cA7.58 cA44.93 bA6.97 cA20-4022.81 cB9.87 aB21.07 cB6.92 bA27.20 bB5.43 bB40-6016.80 dC5.58 bA20.03 cB5.92 bB26.68 bB4.37 cBAverage val-ue22.96 c10.69 a22.58 c6.81 b32.94 a5.59 cOverall mean28.93 c11.92 a30.00 c8.12 b33.66 c4.77 c

    3.1.3Characteristics of changes in available phosphorus content ofL.principis-rupprechtiiland in different forest ages. From Table 3, it can be seen that the available phosphorus content in the soil of different ages ofL.principis-rupprechtiiat different growth stages declined with the increase of soil layer, and the difference in available phosphorus content between different soil layers was significant (P<0.05). For different growth ages in the same soil layer, the soil available phosphorus content declined with the increase of the forest age. Specifically, the available phosphorus content in the soil surface of LD-1 forest age was the highest; in May, July and September, it was 5.53, 5.89 and 5.50 mg/kg, respectively, which were higher than that in other soil layers, but the difference was not significant. In addition, from Table 4, it can be seen that the soil available phosphorus content of LD-1 forest age reached the maximum in July, with an average of 4.44 mg/kg, which was higher than the available phosphorus content in soil in May and September, but the difference between the three was not significant; it was significantly higher than the average available phos-phorus content of LD-2 forest age (3.26 mg/kg), followed by 2.65 mg/kg of LD-3 forest age, and the difference between the three was significant (P<0.05).

    Table 4 Changes in available phosphorus content ofLarixprincipis-rupprechtiiland in different forest ages

    MonthDepth∥cmAvailable phosphorus content∥mg/kgLD-1LD-2LD-3May0-205.53 aA4.71 bA3.52 cA20-404.32 aB3.61 bB2.32 cB40-603.14 aC2.70 bC1.70 dCAverage value4.33 a3.67 b2.51 dJuly0-205.89 aA4.47 bA3.63 cA20-404.17 aB3.10 bB2.52 cB40-603.27 aC2.21 bC1.82 cCAverage value4.44 a3.26 b2.65 cSeptember0-205.50 aA4.42 bA3.29 cA20-404.00 aB3.52 bB2.63 cB40-603.15 aC2.85 bC2.02 cBAverage value4.22 a3.60 b2.65 cOverall mean4.33 a3.51 b2.60 c

    3.2 Changes in soil enzyme activity ofL.principis-rupprechtiiland

    3.2.1Changes in soil catalase activity of different forest farms. From Table 4, it can be seen that the soil catalase activity of different forest farms declined with the deepening of the soil layer, and the catalase activity of the same soil layer declined with the increase of the forest age. For the same forest farm, the catalase activity of the topsoil at the new leaf stage of the forest growth was significantly higher than that of the other two soil layers. Specifically, at the 0-20 cm depth, the soil enzyme activity of LD-1 forest age was 5.37 mL/g; at 40-60 cm depth, the soil enzyme activity dropped to 2.84 mL/g, declining by 47.1%. At the vigorous growth stage, the enzyme activity of surface soil was 4.80 mL/g, and at 40-60 cm depth, the soil catalase activity was 4.51 mL/g, which was 6.0% lower than that at the 0-20 cm depth. For different ages ofL.principis-rupprechtiiforest land, the soil catalase activity showed a declining trend at different stages (May, July and September). The average catalase activity of different forest ages was as follows: LD-1 > LD-2 > LD-3. Specifically, in May, the soil catalase activity of LD-3 had the lowest value of 3.19 mL/g, which was significantly lower than 3.68 mL/g of LD-2 and 4.31 mL/g of LD-1; in September, the soil catalase activity of LD-3 was also the lowest (1.37 mL/g) and the difference with the surface soil was significant (P<0.05).

    Table 5 Changes in soil catalase activity of different forest farms

    MonthDepth∥cmCatalase activity (0.02 mol/L KMnO4)∥mL/gLD-1LD-2LD-3May0-205.37 abA4.67 bA3.99 cA20-404.73 bA3.72 cB3.47 cA40-602.84 cB2.65 cC2.12 dBAverage value4.31 c3.68 c3.19 dJuly0-204.80 cA4.80 cA4.32 dA20-404.80 bA4.36 bA3.35 cB40-604.51 aA3.95 bB2.25 cCAverage value4.70 b4.37 b3.31 cSeptember0-204.61 aA2.34 bA1.45 cA20-402.97 bB2.15 cA1.33 dA40-602.53 aB1.39 cB1.33 cAAverage value3.37 a1.96 c1.37 cOverall mean4.13 b3.34 c2.62 d

    3.2.2Changes in soil phosphatase activity of different forest farms. From Table 5, it can be seen that the soil phosphatase activity ofL.principis-rupprechtiiland declined significantly with the deepening of the soil layer. Specifically, at different growth stages ofL.principis-rupprechtii, the phosphatase activity of surface soil declined slowly with the increase of tree growth years, and the phosphatase activity in other soil layers declined significantly, and the phosphatase activity remained unchanged during the growth years of different forests. The phosphatase activity of LD-3 in the topsoil was the lowest (0.27 mg/g) at the defoliation stage; the phosphatase activity in the surface soil of LD-1 was the highest (0.41 mg/g); at 20-40 and 40-60 cm, it sharply declined to 0.17 and 0.07 mg/g, respectively, which were 58.5% and 82.9% lower than that in the topsoil, and the difference was significant (P<0.05). By comparison, for different ages ofL.principis-rupprechtiiforest land, the average soil phosphatase activity showed a declining trend with the increase of forest age. In May, LD-3 had the lowest soil phosphatase activity (0.16 mg/g), which was significantly lower than that of LD-2 (0.18 mg/g) and LD-1 (0.21 mg/g); in September, the phosphatase activity of LD-3 was the lowest (0.16 mg/g), followed by 0.19 mg/g for LD-2 and 0.20 mg/g for LD-1, respectively. In the same forest farm, the soil phosphatase activity did not change significantly at different growth stages.

    Table 6 Changes in soil phosphatase activity of different forest farms

    MonthDepth∥cmPhosphatase activity (phenol)∥mg/gLD-1LD-2LD-3May0-200.41 cA0.35 cA0.28 dA20-400.17 bB0.12 cB0.12 cB40-600.07 aC0.07 aC0.07 aCAverage value0.21 b0.18 bc0.16 cJuly0-200.32 bA0.31 bA0.28 bA20-400.16 bB0.14 bB0.16 bB40-600.11 bB0.09 bC0.13 abBAverage value0.20 b0.18 b0.19 bSeptember0-200.30 bcA0.30 bcA0.27 cA20-400.18 aB0.17 aB0.15 bB40-600.11 aC0.09 aC0.08 aCAverage value0.20 ab0.19 b0.16 bOverall mean0.20 b0.18 b0.17 b

    3.2.3Characteristics of changes in soil urease activity of different forest farms. From Table 6, it can be can be seen that the soil urease activity ofL.principis-rupprechtiiland declined significantly with the deepening of the soil layer at different stages and in different forest ages. Specifically,L.principis-rupprechtiiin five years old had the highest soil urease activity (0.65 mL/g) at the surface layer, 0.16 mL/g at 20-40 cm soil depth, and declined to 0.10 mL at 40-60 cm soil depth, which were 75.4% and 84.6% lower than the surface layer, respectively, and the urease activity was significantly different from the surface soil (P<0.05), but the difference between the two was not significant. At the new leaf stage of forest growth, the surface soil urease activity of LD-2 was 0.52 mL/g, which was significantly higher than 0.18 mL/g at 20-40 cm soil depth and 0.13 mL/g at 40-60 cm soil depth.

    There were significant differences in the soil urease activity ofL.principis-rupprechtiiin different ages and at different growth stages. The changes of five years old and 20 years old ofL.principis-rupprechtiiat different growth stages were as follows: September > July > May, and that of 10 years old was May > September > July. The soil urease activity ofL.principis-rupprechtiiland increased firstly and then declined at the new leaf stage; at the vigorous growth stage and defoliation stage, the soil urease activity declined with the increase of the forest age. From Table 7, it can be found that the average soil urease activity during the whole growth stage was 0.24 mL/g for 5 and 10 years old, and by the age of 20, the soil urease activity declined to 0.08 mL/g, which was 66.7% lower than that of five years old and 10 years old and the difference was significant (P<0.05).

    Table 7 Changes in soil urease activity of different forest farms

    MonthDepth∥cmUrease activity (0.02 mol/L KMnO4)∥mL/gLD-1LD-2LD-3May0-200.34 cA0.52 bA0.15 dA20-400.16 aB0.18 aB0.04 bB40-600.06 bC0.13 aB0.02 cBAverage value0.18 c0.28 b0.07 dJuly0-200.44 cA0.32 dA0.17 eA20-400.16 bB0.16 bB0.05 cB40-600.07 aC0.05 abC0.02 bBAverage value0.22 b0.17 c0.08 dSeptember0-200.65 bA0.56 cA0.18 dA20-400.16 bB0.18 bB0.06 cB40-600.10 bB0.07 aC0.04 bBAverage value0.30 b0.27 b0.09 cOverall mean0.24 b0.24 b0.08 c

    4 Conclusions

    Through surveying and analyzing the changes in soil nutrient and soil enzyme activities in different forest farms, we found that the soil nutrient and enzyme activity declined most significantly in the 20-year forest age (LD-3) of the forest farm.

    (i) The soil organic matter, ammonium nitrogen and available phosphorus in different forest farms declined with the increase of forest age. These changes in soil fertility indicators can show the changes of soil fertility. In other words, the soil nutrient and enzyme activity declined most significantly in the 20-year forest age (LD-3) of the forest farm. The soil layer indicates that the changes of organic matter with the forest age was inconsistent with that of soil depth, possibly because the accumulation of rot of litter in the forest may increase the organic matter content of the surface soil.

    (ii) The soil catalase, phosphatase and urease declined with the increase of forest age in different forest farms, and declined to the lowest in the forest farm LD-3. However, the decrease in phosphatase was not significant, and the catalase, urease and sucrase activities were significantly declined. In summary, the soil enzyme activity is an essential indicator indicating soil fertility, reflecting that theL.principis-rupprechtiiforest is most likely to decline in the LD-3 forest farm.

    欧美激情国产日韩精品一区| 有码 亚洲区| 毛片一级片免费看久久久久| 日日摸夜夜添夜夜添av毛片| 最后的刺客免费高清国语| 午夜福利在线观看吧| 日日干狠狠操夜夜爽| 乱人视频在线观看| 欧美性猛交╳xxx乱大交人| 亚洲自偷自拍三级| 99热只有精品国产| 国产高清视频在线观看网站| 长腿黑丝高跟| 精品久久国产蜜桃| 女生性感内裤真人,穿戴方法视频| 亚洲无线在线观看| 国产高清视频在线观看网站| 天堂动漫精品| 免费看日本二区| 九九爱精品视频在线观看| 日韩一区二区视频免费看| 国语自产精品视频在线第100页| ponron亚洲| 欧美日本亚洲视频在线播放| 婷婷六月久久综合丁香| 欧美一区二区国产精品久久精品| 久久久久九九精品影院| 成人鲁丝片一二三区免费| 成人欧美大片| 女同久久另类99精品国产91| 国产精品久久久久久亚洲av鲁大| 日韩三级伦理在线观看| 毛片一级片免费看久久久久| 麻豆av噜噜一区二区三区| 久久精品国产鲁丝片午夜精品| 成人欧美大片| 免费人成在线观看视频色| 久久久久久久久中文| 久久久久免费精品人妻一区二区| 日韩精品中文字幕看吧| 国产精品1区2区在线观看.| 亚洲一区二区三区色噜噜| 日韩人妻高清精品专区| 中文字幕av成人在线电影| 色在线成人网| 一a级毛片在线观看| 天堂动漫精品| 日日干狠狠操夜夜爽| 日韩亚洲欧美综合| 欧洲精品卡2卡3卡4卡5卡区| 99久国产av精品国产电影| 亚洲图色成人| 波野结衣二区三区在线| 国产成人91sexporn| 欧美成人a在线观看| 人妻久久中文字幕网| 两性午夜刺激爽爽歪歪视频在线观看| 少妇丰满av| av视频在线观看入口| 91精品国产九色| 尾随美女入室| 人人妻人人澡欧美一区二区| 噜噜噜噜噜久久久久久91| 最近的中文字幕免费完整| 成人欧美大片| 国产精品久久久久久亚洲av鲁大| av在线播放精品| 最新在线观看一区二区三区| 日韩精品中文字幕看吧| 99久久精品热视频| 99riav亚洲国产免费| av黄色大香蕉| 精品一区二区三区视频在线观看免费| 久久久久久久久久黄片| 日韩高清综合在线| 啦啦啦观看免费观看视频高清| 日韩欧美 国产精品| 九色成人免费人妻av| 麻豆国产av国片精品| 免费观看精品视频网站| 日本免费一区二区三区高清不卡| 狂野欧美激情性xxxx在线观看| 在线免费观看不下载黄p国产| 国产在线男女| 亚洲精品成人久久久久久| 一区二区三区四区激情视频 | 日韩亚洲欧美综合| 看片在线看免费视频| 欧美一区二区精品小视频在线| 精品久久久久久久久av| 少妇熟女欧美另类| 欧美+日韩+精品| 久久国产乱子免费精品| 日韩av在线大香蕉| 久久久久久久久久久丰满| 成人亚洲欧美一区二区av| 久久热精品热| 亚洲国产欧美人成| 久久国内精品自在自线图片| 蜜桃久久精品国产亚洲av| 亚洲精品一卡2卡三卡4卡5卡| 亚洲欧美成人综合另类久久久 | 久久久精品欧美日韩精品| 韩国av在线不卡| 亚洲无线观看免费| 日韩中字成人| 日韩成人av中文字幕在线观看 | 五月玫瑰六月丁香| 亚洲国产精品成人久久小说 | 国产精品久久久久久亚洲av鲁大| 午夜亚洲福利在线播放| 亚洲人成网站在线播| 国产视频一区二区在线看| 日韩三级伦理在线观看| 少妇人妻精品综合一区二区 | 免费不卡的大黄色大毛片视频在线观看 | 精品熟女少妇av免费看| 日韩一本色道免费dvd| 一区福利在线观看| 九九久久精品国产亚洲av麻豆| 日本 av在线| 亚洲av免费在线观看| 久久人人爽人人爽人人片va| 日韩成人av中文字幕在线观看 | 全区人妻精品视频| 午夜福利18| 欧美性猛交黑人性爽| 一a级毛片在线观看| 少妇的逼水好多| 看十八女毛片水多多多| 国产精品一区二区性色av| 国产男靠女视频免费网站| 亚洲一级一片aⅴ在线观看| 菩萨蛮人人尽说江南好唐韦庄 | 91在线精品国自产拍蜜月| 99热6这里只有精品| 三级毛片av免费| 老熟妇仑乱视频hdxx| 日韩欧美 国产精品| 国产成年人精品一区二区| 成人特级av手机在线观看| 99riav亚洲国产免费| 久久人人爽人人片av| 九九爱精品视频在线观看| 成人一区二区视频在线观看| 天天一区二区日本电影三级| 国内精品美女久久久久久| www.色视频.com| 久久久精品欧美日韩精品| 99久久精品国产国产毛片| 色av中文字幕| 中国美白少妇内射xxxbb| av在线蜜桃| 精品一区二区免费观看| 一夜夜www| 午夜激情欧美在线| 精品久久久久久久久久久久久| 日日摸夜夜添夜夜添av毛片| 中文亚洲av片在线观看爽| av在线观看视频网站免费| 长腿黑丝高跟| 国产aⅴ精品一区二区三区波| 国产白丝娇喘喷水9色精品| 久久久久久九九精品二区国产| 菩萨蛮人人尽说江南好唐韦庄 | 成人欧美大片| 国产伦精品一区二区三区视频9| 给我免费播放毛片高清在线观看| 欧美日韩国产亚洲二区| 国产精品久久久久久精品电影| 久久九九热精品免费| 亚洲欧美成人精品一区二区| 日日撸夜夜添| 99热全是精品| 免费av不卡在线播放| 哪里可以看免费的av片| 最新在线观看一区二区三区| 我的老师免费观看完整版| 少妇裸体淫交视频免费看高清| 久久精品国产亚洲av天美| 亚洲一区二区三区色噜噜| 俄罗斯特黄特色一大片| 丝袜喷水一区| 亚洲真实伦在线观看| 毛片一级片免费看久久久久| 亚洲国产日韩欧美精品在线观看| 久久精品夜夜夜夜夜久久蜜豆| 99riav亚洲国产免费| 国产精品人妻久久久久久| 久久精品久久久久久噜噜老黄 | 18禁在线无遮挡免费观看视频 | 欧美激情在线99| 国产精品一区二区免费欧美| 日本色播在线视频| 国产亚洲av嫩草精品影院| 日韩欧美在线乱码| 草草在线视频免费看| 国产黄色视频一区二区在线观看 | 国产精品亚洲美女久久久| 免费电影在线观看免费观看| 成年女人毛片免费观看观看9| 成人特级黄色片久久久久久久| 九九热线精品视视频播放| 午夜精品国产一区二区电影 | 日韩欧美 国产精品| 男女啪啪激烈高潮av片| 亚州av有码| 国内精品宾馆在线| 黄色配什么色好看| 久久久久久大精品| 99久久成人亚洲精品观看| 国产乱人视频| 国模一区二区三区四区视频| 欧美高清成人免费视频www| 国产一区二区在线观看日韩| 51国产日韩欧美| 看免费成人av毛片| 亚洲无线在线观看| 久久久久久久亚洲中文字幕| 国产不卡一卡二| 午夜福利视频1000在线观看| 成人永久免费在线观看视频| 亚洲精品粉嫩美女一区| 亚洲av不卡在线观看| 寂寞人妻少妇视频99o| 久久精品综合一区二区三区| 日韩欧美国产在线观看| 亚洲真实伦在线观看| 午夜福利视频1000在线观看| 国产毛片a区久久久久| 天堂√8在线中文| 精品日产1卡2卡| 悠悠久久av| 成人午夜高清在线视频| 人妻丰满熟妇av一区二区三区| 国产不卡一卡二| 最近2019中文字幕mv第一页| 色哟哟哟哟哟哟| 免费观看人在逋| 亚洲三级黄色毛片| 久久精品国产自在天天线| 国产真实乱freesex| 亚洲欧美日韩东京热| 亚洲国产欧美人成| 中文在线观看免费www的网站| 此物有八面人人有两片| 午夜福利视频1000在线观看| 国产黄片美女视频| 欧美日韩乱码在线| 啦啦啦观看免费观看视频高清| 精品国产三级普通话版| 午夜激情福利司机影院| 高清午夜精品一区二区三区 | 非洲黑人性xxxx精品又粗又长| 国产黄片美女视频| 久久综合国产亚洲精品| 免费观看精品视频网站| 草草在线视频免费看| 麻豆乱淫一区二区| 亚洲电影在线观看av| 综合色丁香网| 看片在线看免费视频| 免费电影在线观看免费观看| 内地一区二区视频在线| 婷婷精品国产亚洲av在线| 在线观看午夜福利视频| 欧美人与善性xxx| 亚洲熟妇中文字幕五十中出| 国产久久久一区二区三区| 麻豆久久精品国产亚洲av| 69av精品久久久久久| 成人一区二区视频在线观看| 免费不卡的大黄色大毛片视频在线观看 | 午夜福利在线观看免费完整高清在 | 欧美成人一区二区免费高清观看| 天天一区二区日本电影三级| 免费观看人在逋| 国产激情偷乱视频一区二区| 亚洲熟妇中文字幕五十中出| 国产成人a区在线观看| 亚洲精品日韩av片在线观看| 在线看三级毛片| 变态另类成人亚洲欧美熟女| 嫩草影院入口| 色综合色国产| 亚洲aⅴ乱码一区二区在线播放| 一级毛片aaaaaa免费看小| 男女下面进入的视频免费午夜| 国产视频内射| 国产爱豆传媒在线观看| 老司机影院成人| 国产精品1区2区在线观看.| 观看美女的网站| 免费观看精品视频网站| 亚洲av免费在线观看| 中文字幕免费在线视频6| 国产精品久久久久久亚洲av鲁大| 人妻少妇偷人精品九色| 不卡一级毛片| 亚洲欧美清纯卡通| 久久精品国产亚洲av涩爱 | 秋霞在线观看毛片| 久久人人精品亚洲av| 精品久久久久久久末码| 久久久久国产精品人妻aⅴ院| 听说在线观看完整版免费高清| 人妻丰满熟妇av一区二区三区| 久久精品国产清高在天天线| 99热这里只有精品一区| 日本与韩国留学比较| 亚洲av免费高清在线观看| 国产黄片美女视频| 日日摸夜夜添夜夜爱| 中文资源天堂在线| 成年女人永久免费观看视频| 99精品在免费线老司机午夜| 九色成人免费人妻av| 国产大屁股一区二区在线视频| 日韩中字成人| 精品日产1卡2卡| 无遮挡黄片免费观看| 狂野欧美白嫩少妇大欣赏| 两个人的视频大全免费| 午夜免费激情av| 国产高清不卡午夜福利| 六月丁香七月| 在线观看免费视频日本深夜| 国国产精品蜜臀av免费| 成人av在线播放网站| 综合色av麻豆| 乱系列少妇在线播放| 内射极品少妇av片p| 国产伦精品一区二区三区视频9| 日韩高清综合在线| 人妻制服诱惑在线中文字幕| 亚州av有码| 久久久久国内视频| 久久精品国产亚洲网站| 天堂av国产一区二区熟女人妻| 国产高清不卡午夜福利| 乱人视频在线观看| 精品一区二区三区av网在线观看| 久久热精品热| 91在线精品国自产拍蜜月| 国产精品一区二区免费欧美| 成人亚洲欧美一区二区av| 久久人人爽人人爽人人片va| 麻豆精品久久久久久蜜桃| 国产毛片a区久久久久| 色吧在线观看| 欧美色视频一区免费| 特级一级黄色大片| av免费在线看不卡| 国产久久久一区二区三区| 日韩精品有码人妻一区| 久久草成人影院| 国产av在哪里看| 麻豆精品久久久久久蜜桃| 日韩av不卡免费在线播放| 久久午夜亚洲精品久久| 波野结衣二区三区在线| 亚洲va在线va天堂va国产| 久久久久久久久中文| 久久精品夜夜夜夜夜久久蜜豆| 中文字幕免费在线视频6| 午夜福利高清视频| 天天躁日日操中文字幕| 日韩国内少妇激情av| 免费大片18禁| 不卡视频在线观看欧美| 免费看美女性在线毛片视频| 亚洲,欧美,日韩| 18禁在线播放成人免费| 成人永久免费在线观看视频| 嫩草影院新地址| 内射极品少妇av片p| 狂野欧美激情性xxxx在线观看| 午夜日韩欧美国产| 美女xxoo啪啪120秒动态图| 国产精品人妻久久久久久| 亚洲熟妇熟女久久| 亚洲三级黄色毛片| 亚洲精品国产成人久久av| 精品久久久久久久人妻蜜臀av| 色综合站精品国产| 尾随美女入室| 欧美zozozo另类| h日本视频在线播放| 一个人观看的视频www高清免费观看| 国产精品不卡视频一区二区| 变态另类丝袜制服| 中文字幕精品亚洲无线码一区| 91久久精品国产一区二区成人| 免费看日本二区| 国产伦精品一区二区三区四那| 无遮挡黄片免费观看| 一级毛片久久久久久久久女| 久久久国产成人精品二区| h日本视频在线播放| 久久久久久久久久黄片| 简卡轻食公司| 精品少妇黑人巨大在线播放 | 久久久久久久亚洲中文字幕| 亚洲国产精品sss在线观看| 国产高清有码在线观看视频| 校园春色视频在线观看| 国内少妇人妻偷人精品xxx网站| or卡值多少钱| 亚洲精品456在线播放app| 亚洲人成网站在线播放欧美日韩| 99在线人妻在线中文字幕| 91久久精品国产一区二区成人| 男女那种视频在线观看| 亚洲精品一区av在线观看| 插阴视频在线观看视频| 日韩欧美在线乱码| 亚洲av免费在线观看| 国产单亲对白刺激| 日本-黄色视频高清免费观看| 一个人免费在线观看电影| 国产综合懂色| 97人妻精品一区二区三区麻豆| 老司机影院成人| 12—13女人毛片做爰片一| 亚洲成人久久爱视频| 亚洲真实伦在线观看| 女人被狂操c到高潮| 精品人妻视频免费看| 国产单亲对白刺激| 国产伦精品一区二区三区视频9| 真实男女啪啪啪动态图| 久久久成人免费电影| 国产aⅴ精品一区二区三区波| 亚洲av美国av| 在线国产一区二区在线| 最近视频中文字幕2019在线8| 免费看光身美女| 99久久无色码亚洲精品果冻| 亚洲欧美精品自产自拍| 狂野欧美白嫩少妇大欣赏| 91午夜精品亚洲一区二区三区| 在线看三级毛片| 91av网一区二区| 久久精品国产鲁丝片午夜精品| 国产私拍福利视频在线观看| 精品国内亚洲2022精品成人| 中文字幕熟女人妻在线| 久久鲁丝午夜福利片| 18禁在线无遮挡免费观看视频 | 成年免费大片在线观看| 18禁黄网站禁片免费观看直播| 禁无遮挡网站| 日韩人妻高清精品专区| 国产精品伦人一区二区| 久久精品国产清高在天天线| 人妻丰满熟妇av一区二区三区| 噜噜噜噜噜久久久久久91| 欧美激情国产日韩精品一区| 成人无遮挡网站| 成人亚洲欧美一区二区av| 国产片特级美女逼逼视频| 国产精品一区二区性色av| 欧美日韩乱码在线| av天堂中文字幕网| 亚洲成人久久爱视频| 亚洲欧美日韩无卡精品| 老师上课跳d突然被开到最大视频| 免费不卡的大黄色大毛片视频在线观看 | 亚洲精品成人久久久久久| 色av中文字幕| 亚洲熟妇中文字幕五十中出| 亚洲精华国产精华液的使用体验 | 亚洲av不卡在线观看| 精品一区二区免费观看| 真人做人爱边吃奶动态| 久久6这里有精品| 亚洲最大成人中文| 国内精品宾馆在线| av中文乱码字幕在线| 亚洲av电影不卡..在线观看| 亚洲av免费在线观看| 午夜日韩欧美国产| 丝袜美腿在线中文| 国产女主播在线喷水免费视频网站 | 你懂的网址亚洲精品在线观看 | 午夜精品在线福利| 蜜臀久久99精品久久宅男| 国产精品久久久久久久久免| 99久久中文字幕三级久久日本| 欧美潮喷喷水| 岛国在线免费视频观看| 日本-黄色视频高清免费观看| 麻豆乱淫一区二区| 国产精品av视频在线免费观看| 国产探花在线观看一区二区| 免费观看人在逋| 九九在线视频观看精品| 热99re8久久精品国产| 搡老岳熟女国产| 国产在线精品亚洲第一网站| 我要看日韩黄色一级片| 日本成人三级电影网站| 欧美xxxx性猛交bbbb| 美女免费视频网站| 国产在线精品亚洲第一网站| 国产精品女同一区二区软件| 中文亚洲av片在线观看爽| 狂野欧美白嫩少妇大欣赏| 在线观看一区二区三区| 黄色欧美视频在线观看| 免费观看人在逋| 日本成人三级电影网站| 麻豆乱淫一区二区| 精品一区二区免费观看| 欧美高清成人免费视频www| 美女内射精品一级片tv| 精品人妻偷拍中文字幕| 欧洲精品卡2卡3卡4卡5卡区| 少妇的逼好多水| 人妻制服诱惑在线中文字幕| 麻豆成人午夜福利视频| 村上凉子中文字幕在线| 中文字幕人妻熟人妻熟丝袜美| 亚洲熟妇熟女久久| 欧美不卡视频在线免费观看| 午夜精品在线福利| 精华霜和精华液先用哪个| 真实男女啪啪啪动态图| 99九九线精品视频在线观看视频| 在线天堂最新版资源| 免费在线观看成人毛片| 久久精品国产清高在天天线| 国产精品人妻久久久久久| 成人无遮挡网站| av天堂在线播放| 久久精品国产鲁丝片午夜精品| 亚洲无线在线观看| 黄色日韩在线| 日韩 亚洲 欧美在线| 日本色播在线视频| 国产精品电影一区二区三区| 久久韩国三级中文字幕| 日本免费一区二区三区高清不卡| 亚洲图色成人| 综合色av麻豆| 熟女电影av网| 免费看日本二区| 国产成年人精品一区二区| 一个人看视频在线观看www免费| 午夜老司机福利剧场| 欧美日本亚洲视频在线播放| 久久久久久久亚洲中文字幕| 日韩成人av中文字幕在线观看 | 干丝袜人妻中文字幕| 日韩制服骚丝袜av| 日日摸夜夜添夜夜添av毛片| 久久久久九九精品影院| 91av网一区二区| 国内精品久久久久精免费| 日日摸夜夜添夜夜爱| 日韩一本色道免费dvd| 亚洲国产精品久久男人天堂| 久久久精品欧美日韩精品| 网址你懂的国产日韩在线| 秋霞在线观看毛片| 国产精品国产三级国产av玫瑰| 亚洲无线观看免费| 国产精品嫩草影院av在线观看| 一级a爱片免费观看的视频| 亚洲欧美日韩高清在线视频| 亚洲aⅴ乱码一区二区在线播放| 成人毛片a级毛片在线播放| 亚洲av不卡在线观看| 有码 亚洲区| 三级男女做爰猛烈吃奶摸视频| 日韩 亚洲 欧美在线| 久久久久久伊人网av| 国产免费男女视频| 99在线视频只有这里精品首页| 精品国产三级普通话版| 亚洲中文日韩欧美视频| 美女cb高潮喷水在线观看| 国产乱人视频| 精品久久久久久久久久久久久| 日韩欧美免费精品| 国产免费男女视频| 国产精品久久久久久av不卡| 高清午夜精品一区二区三区 | 精品欧美国产一区二区三| 精品熟女少妇av免费看| 熟女人妻精品中文字幕| 免费看a级黄色片| 国内久久婷婷六月综合欲色啪| 色噜噜av男人的天堂激情| av黄色大香蕉| 日本精品一区二区三区蜜桃| 国产探花在线观看一区二区| a级毛片a级免费在线| 久久久久国产精品人妻aⅴ院| 成人无遮挡网站| 久久久久久九九精品二区国产| 久久久久性生活片| 少妇被粗大猛烈的视频| 国产综合懂色| 综合色av麻豆| 日韩国内少妇激情av| 18禁裸乳无遮挡免费网站照片| 99久久久亚洲精品蜜臀av| 美女 人体艺术 gogo| 一级a爱片免费观看的视频| 别揉我奶头 嗯啊视频| 日本精品一区二区三区蜜桃| 亚洲中文日韩欧美视频| 丝袜美腿在线中文| 你懂的网址亚洲精品在线观看 |