Effect of land utilization patterns on total and easy-to-use components of soil carbon, nitrogen and phosphorus in the karst area of Pingguo, Guangxi
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摘要: 以广西平果喀斯特生态系统国家野外科学观测研究站及周边地块的三种土地利用方式(退耕林地、退耕草地、耕地(甘蔗地和玉米地))为研究对象,通过采集0~15 cm表层土壤,分析土壤的理化性质和土壤碳、氮、磷全量与易利用组分及其关系,以期能更加准确地理解和把握退耕还林还草、土地利用方式转变对喀斯特地区土壤碳、氮、磷全量及易利用组分的影响。结果表明:(1)与耕地相比,退耕后林地和草地土壤pH值显著升高,大团聚体、速效氮显著增加,微团聚体、速效磷显著减少。(2)退耕后林地和草地土壤有机碳较耕地显著增加,林地和草地分别是甘蔗地的1.98和1.88倍,分别是玉米地的2.15和2.04倍。林地和草地土壤微生物生物量碳、全氮、微生物生物量氮较耕地也明显提高。对于磷,草地全磷(1.04 g·kg−1)最高,其次玉米地(0.81 g·kg−1),且甘蔗地和玉米地的可溶性磷均显著高于林地和草地。在土壤碳氮磷生态化学计量比方面,林地的OC/TP、TN/TP显著高于草地和耕地,而草地和耕地没有显著差异。(3)土壤容重、团聚体结构、pH、速效氮、速效磷都与土壤碳、氮、磷全量与易利用组分有着显著的相关关系。上述结果表明,退耕还林还草、土地利用方式转变显著提高了喀斯特土壤碳、氮水平,提升了土壤质量,退耕还林还草、转变土地利用方式是喀斯特地区石漠化治理、生态环境保护的重要、有效途径。Abstract:
Soil carbon, nitrogen and phosphorus are important factors of soil quality, which play important roles in increasing soil nutrient storage, improving soil fertility and promoting plant growth. A large number of studies have shown that returning cultivated land back to forest and grassland and converting land use patterns will lead to changes in soil nutrient status and stoichiometry. However, systematic studies on total and easy-to-use components of soil carbon, nitrogen, and phosphorus are relatively few in Pingguo karst area of Youjiang River Valley in central Guangxi. In this study, plots of three types of land use (the restored forest and grassland from cultivated land and cultivated land for sugarcane and maize) inside and near Pingguo National Field Observation and Research Station of Karst Ecosystem, Guangxi were taken as research objects, and 0-15 cm surface soil was sampled in March, 2021. The physical and chemical properties of soil, total and easy-to-use components of carbon, nitrogen and phosphorus and their relationships were analysed in order to better understand the effects of returning cultivated land back to forest and grassland and converting land utilization patterns on total and easy-to-use components of carbon, nitrogen and phosphorus of soil in karst areas. The results showed as follows: 1) Compared to cultivated land, the soil pH values of the restored forest and grassland from cultivated land increased significantly. The macro-aggregates of restored forest and grassland (42.82%, 57.11% respectively) were significantly higher than those of cultivated land for sugarcane (16.94%) and maize (5.49%), and their micro-aggregates (4.58%, 1.76% respectivey) were significantly lower than those of cultivated land for sugarcane (12.42%) and maize (16.34%). Meanwhile, compared to cultivated land for sugarcane (103.39 mg·kg−1, 3.22 mg·kg−1) and that for maize (105.02 mg·kg−1, 3.07 mg·kg−1), available nitrogen of restored forest and grassland significantly increased to 156.55 and 166.49 mg·kg−1, repectively, while available phosphorus significantly decreased to 0.41 and 0.30 mg·kg−1, respectively. 2) Compared to cultivated land, the organic carbon, microbial biomass carbon and total nitrogen of soil in restored forest and grassland increased significantly. The values of soil organic carbon of restored forest and grassland (34.12 g·kg−1, 32.45 g·kg−1respectively) were 1.98 and 1.88 times of cultivated land for sugarcane (17.26 g·kg−1), and 2.15 and 2.04 times of cultivated land for maize (15.89 g·kg−1), respectively. The values of microbial biomass carbon of soil in restored forest and grassland (985.35 mg·kg−1, 1,110.04 mg·kg−1repectively) were 2.71 and 3.05 times of cultivated land for sugarcane (364.07 mg·kg−1), and 3.14 and 3.54 times of cultivated land for maize (313.92 mg·kg−1), respectively. The values of total nitrogen of soil in restored forest and grassland (4.14 g·kg−1, 4.10 g·kg−1respectively) were 2.48 and 2.46 times of cultivated land for sugarcane (1.67 g·kg−1), and 2.19 and 2.16 times of cultivated land for maize (1.89 g·kg−1), respectively. The total value of phosphorus in restored grassland was the highest (1.04 g·kg−1), followed by that of cultivated land for maize (0.81 g·kg−1), and the values of dissolved phosphorus of cultivated land for sugarcane and maize were significantly higher than those of restored forest and grassland. The values of stoichiometry of carbon, nitrogen, and phosphorus, OC/TP, TN/TP of soil in restored forest were significantly higher than those of restored grassland and cultivated land, and the values of restored grassland and cultivated land did not show significant difference. 3) Soil bulk density, aggregate structure, pH value, available nitrogen and available phosphorus were significantly correlated with total and easy-to-use components of carbon, nitrogen and phosphorus of soil. Properly speaking, soil pH value, large macro-aggregates, and available nitrogen showed a significantly positive correlation with organic carbon, microbial biomass carbon, total nitrogen and microbial biomass nitrogen of soil, and a significantly negative correlation with dissolved phosphorus. Meanwhile, bulk density, micro-aggregates, and available phosphorus of soil showed a significantly negative correlation with organic carbon, microbial biomass carbon, total nitrogen and microbial biomass nitrogen of soil, and a significantly positive correlation with dissolved phosphorus. The results indicated that the measures of returning cultivated land back to forest and grassland and converting land use patterns significantly improved soil carbon, nitrogen and soil quality in karst areas. These two measures are important and effective ways to control rocky desertification and protect ecological environment in karst areas. -
Key words:
- land utilization patterns /
- Guangxi Pingguo /
- karst /
- carbon /
- nitrogen /
- phosphorus
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表 1 样地概况
Table 1. Plot information
样地 坐标 海拔/m 退耕时间 地形 优势植物 植被高度/m 耕作 施肥 林地 F 23°23′39″ N
107°23′23″ E246.20 2006年 坡地 茶条木(Delavaya toxocarpa Franch.) 3.20 无耕作 无施肥 草地 G 23°23′28″ N
107°23′24″ E196.33 2003年 坡改梯形
平地芒草(Arundinella nepalensis Trin.)、
肾蕨(Nephrolepis auriculata (L.) Trimen)、鬼针草(Bidens pilosa Linn.)0.50 无耕作 无施肥 甘蔗地 S 23°24′29″ N
107°24′28″ E107.36 耕种至今 平地 甘蔗(Saccharum officinarum Linn.) 甘蔗宿根
零星出芽2-3年翻耕1次 甘蔗叶还田,肥料量N:P2O5:K2O=
45:15:28 kg /亩/年玉米地 M 23°22′33″ N
107°23′32″ E329.80 耕种至今 平地 玉米(Zea mays L.) 玉米种子
零星出苗1年翻耕
2次一年两季,肥料量N:P2O5:K2O=
25:10:16 kg /亩/年表 2 不同样地土壤理化性质
Table 2. Soil physicochemical properties of different plots
样地 林地 F 草地 G 甘蔗地 S 玉米地 M 容重/g·cm−3 1.10±0.12 a 1.09±0.05 a 1.20±0.12 a 1.29±0.04 a 团聚体/% 大团聚体 42.82±0.42 a 57.11±10.98 a 16.94±2.74 b 5.49±0.95 b 小团聚体 39.70±3.50 ab 27.14±8.89 b 43.67±6.88 a 48.43±3.58 a 微团聚体 4.58±0.37 b 1.76±1.44 b 12.42±1.85 a 16.34±5.70 a 其他 12.90±3.64 b 13.99±0.94 ab 26.96±8.36 ab 29.74±8.19 a pH 6.87±0.06 b 8.20±0.13 a 5.09±0.85 c 6.00±0.22 c 速效氮 /mg·kg−1 156.55±17.12 a 166.49±28.09 a 103.39±8.20 b 105.02±5.57 b 速效磷 /mg·kg−1 0.41±0.19 b 0.30±0.05 b 3.22±0.67 a 3.07±0.18 a 注:不同字母表示同一指标不同样地在0.05水平差异显著。下同。
Note: Different letters indicate significant differences among plots at 0.05 level.The same below。表 3 不同样地土壤易利用碳组分占有机碳比例/%
Table 3. Proportions of soil easy-to-use carbon components to the soil organic carbon in different plots/%
样地 可溶性碳/
有机碳
DC/OC微生物生物
量碳/有机碳
MBC/OC(可溶性碳+微生物
生物量碳)/有机碳
(DC+MBC)/OC林地 F 0.29±0.07 c 2.91±0.49 ab 3.20±0.55 a 草地 G 0.41±0.09 bc 3.54±1.17 a 3.95±1.27 a 甘蔗地 S 1.14±0.22 a 2.09±0.22 b 3.24±0.01 a 玉米地 M 0.70±0.06 b 1.98±0.17 b 2.67±0.13 a 注:DC-可溶性碳,MBC-微生物生物量碳,OC-有机碳。下同。
Note: DC-dissolved carbon,MBC-microbial biomass carbon,OC-organic carbon. The same below.表 4 不同样地土壤易利用氮组分占总氮比例/%
Table 4. Proportions of soil easy-to-use nitrogen components to the total nitrogen in different plots/%
样地 可溶性氮/
全氮
DN/TN微生物生物
量氮/全氮
MBN/TN(可溶性氮+微生物
生物量氮)/全氮
(DN+MBN)/TN林地 F 0.61±0.04 b 2.55±0.52 a 3.15±0.56 b 草地 G 0.81±0.18 b 3.60±0.56 a 4.41±0.74 ab 甘蔗地 S 1.79±0.41 a 3.03±0.48 a 4.82±0.40 a 玉米地 M 1.64±0.35 a 2.30±0.58 a 3.93±0.24 ab 注:DN-可溶性氮,MBN-微生物生物量氮,TN-全氮。下同。
Note: DN-dissolved nitrogen,MBC-microbial biomass nitrogen,TN-total nitrogen. The same below.表 5 不同样地土壤易利用磷组分占总磷比例/%
Table 5. Proportions of soil easy-to-use phorsphorus componentsto the total phosphorus in different plots/%
样地 可溶性磷/
全磷
DP/TP (%)微生物生物
量磷/全磷
MBP/TP(可溶性磷+微生物
生物量磷)/全磷
(DP+MBP)/TP林地 F 0.31±0.14 b 1.23±0.83 ab 1.54±0.82 b 草地 G 0.28±0.09 b 0.45±0.13 bc 0.73±0.08 b 甘蔗地 S 1.18±0.36 a 2.03±0.61 a 3.20±0.24 a 玉米地 M 1.07±0.15 a 0.24±0.09 c 1.31±0.10 b 注:DP-可溶性磷, MBP-微生物生物量磷, TP-全磷。下同。
Note: DP-dissolved phosphorus, MBP-microbial biomass phosphorus, TP- total phosphorus. The same below.表 6 不同样地土壤碳氮磷全量及易利用组分生态化学计量比
Table 6. Stoichiometry of total and easy-to-use components of carbon, nitrogen, and phosphorus of soil in different plots
样地 林地 F 草地 G 甘蔗地 S 玉米地 M OC/TN 8.26±1.30 a 7.91±1.35 a 10.48±1.65 a 8.40±0.10 a OC/TP 67.11±18.74 a 31.02±3.18 b 34.36±5.65 b 19.66±1.88 b TN/TP 8.12±1.84 a 3.95±0.27 b 3.34±0.82 b 2.34±0.21 b DC/DN 3.87±0.16 b 4.03±0.44 b 6.68±0.40 a 3.64±0.47 b DC/DP 68.12±23.19 a 46.16±8.90 ab 34.70±10.29 ab 12.78±0.78 b DN/DP 17.76±6.55 a 11.47±1.88 ab 5.19±1.44 b 3.56±0.60 b MBC/MBN 9.42±0.65 a 7.50±0.32 a 7.26±0.85 a 7.45±1.30 a MBC/MBP 180.97±51.39 ab 261.87±131.81 a 36.59±5.94 b 178.04±57.50 ab MBN/MBP 19.05±4.36 ab 34.51±16.20 a 5.13±1.29 b 23.46±4.00 ab 表 7 不同样地土壤碳氮磷全量及易利用组分与土壤理化性质的相关关系
Table 7. Correlation among total and easy-to-use components of carbon, nitrogen, phosphorus of soil and soil physicochemical properties in different plots
有机碳
OC可溶
性碳
DC微生物
生物量碳
MBC全氮
TN可溶
性氮
DN微生物
生物量氮
MBN全磷
TP可溶
性磷
DP微生物
生物量磷
MBP容重 −0.702* 0.004 −0.707* −0.647* −0.091 −0.678* −0.034 0.584* −0.222 团聚体 大团聚体 0.875** −0.382 0.957** 0.965** −0.028 0.866** 0.149 −0.875** −0.035 小团聚体 0.371 −0.657* 0.193 0.406 −0.757** 0.009 −0.431 −0.452 −0.111 微团聚体 −0.649* −0.117 −0.703* −0.645* −0.451 −0.700* −0.318 0.614* −0.114 其他 −0.204 −0.044 −0.253 −0.274 −0.058 −0.310 −0.287 0.152 0.117 pH 0.754** −0.505 0.826** 0.851** 0.104 0.856** 0.664* −0.659* −0.264 速效氮 0.740** −0.378 0.916** 0.871** 0.085 0.855** 0.239 −0.740** −0.114 速效磷 −0.897** 0.530 −0.922** −0.976** 0.077 −0.860** −0.293 0.827** 0.179 注:*代表在0.05水平上显著相关,**代表在0.01水平上显著相关。
Note: * referring to a significant correlation at 0.05 level; ** referring to a significant correlation at 0.01 level. -
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