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生态化学计量学是基于生态学和化学计量学的基本原理,研究生物系统能量以及多重化学元素平衡的科学,其中以碳、氮、磷元素为主。这一研究领域可将生物学科相关的研究理论有机结合[1-2],已成为生态系统研究的新型工具之一[3]。目前,生态化学计量学的研究集中于水生生态系统、种群动态与森林演替、陆地植物生态系统的碳循环以及全球碳、氮、磷生物地球化学循环等方面[4-5],且多数从植物组织元素的角度展开[6-8]。对土壤养分的生态化学计量学研究却相对较少[9-10]。碳、氮、磷既是土壤中重要的生源要素,也是植物生长的必需养分。土壤碳、氮、磷的生态化学计量特征具有良好的指示作用,不仅可反映植物生长速度(碳氮比和碳磷比)[11],表征营养元素对生产力的限制性作用(氮磷比)[12],同时也可揭示土壤内部碳、氮、磷的循环特征(C∶N∶P)。因此,生态化学计量学特征的研究对揭示土壤养分的可获得性以及碳、氮、磷等营养元素的循环和平衡机制等方面均具有重要的意义[13]。目前,茶Camellia sinensis 园生态系统主要集中于土壤理化性质、微生物生态、团聚体、酸化等方面的探讨[14-15],就退耕植茶后的土壤生态化学计量学特征方面的研究鲜见报道。四川作为中国主要产茶区之一,植茶历史悠久,受国家“退耕还林(草)”和“天然林保护”等工程政策的影响,四川省雅安市名山区中峰乡根据其地理条件和水土、气候等资源特点形成了以“退耕植茶”为主的退耕模式。以往研究表明:随着植茶年限的延长,土壤pH值下降,酸化加剧[16-17],氟、铝逐渐富集,钙、镁等盐基离子相对缺乏[18-19],土壤结构与功能的变化尤为明显[20],影响着土壤供肥能力、茶树生长及茶园生态环境等,而这些变化在土壤碳、氮、磷及其生态化学计量特征方面的反映有待深入研究。因此,本研究选取川西低山丘陵区典型退耕植茶区为研究对象,开展不同退耕植茶年限土壤碳、氮、磷生态化学计量学特征的研究,以期为实现茶园土壤持续利用与退耕植茶工程的有效实施提供科学依据。
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如图 1所示:样地各土层土壤有机碳质量分数均表现为RT16-17>ck>RT9-10>RT2-3。0~10,10~20和20~40 cm土层有机碳质量分数的变化范围分别为20.49~24.84,19.80~23.43和17.15~19.80 g·kg-1。与对照地相比,随着退耕植茶年限的延长,各土层土壤有机碳质量分数均表现为先显著降低、后显著增加的趋势(P<0.05)。退耕植茶地各土层土壤有机碳质量分数均表现为RT16-17显著高于RT2-3和RT9-10,分别增加了35.86%,18.32%,15.48%和29.21%,12.36%,11.78%。16~17 a(RT16-17)以后,与对照地相比,各土层土壤有机碳质量分数分别增加了5.67%,5.67%,0.78%。退耕植茶地及对照地土壤有机碳质量分数,0~10 cm和10~20 cm土层均显著高于20~40 cm土层。
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如图 2所示:样地各土层全氮质量分数的变化范围分别为0.78~1.20,0.71~0.98和0.54~0.85 g·kg-1。与对照地相比,随着退耕植茶年限的延长,土壤全氮质量分数表现为先显著降低,而后显著增加的变化趋势(P<0.05),与土壤有机碳变化趋势相似。0~10 cm和10~20 cm土层,土壤全氮质量分数表现为ck>RT16-17>RT9-10>RT2-3;而20~40 cm土层则表现为RT16-17>ck>RT9-10>RT2-3,对照地及RT16-17土壤全氮质量分数显著高于其他退耕植茶地,且对照地和RT16-17土壤全氮间差异不显著。与RT2-3相比,RT16-17土壤全氮质量分数在各土层分别增加了36.92%,25.49%和57.62%。就土层而言,各样地土壤全氮均随土层的加深呈降低趋势,除RT16-17以外,其余各样地土壤全氮质量分数,0~10 cm和10~20 cm土层均显著高于20~40 cm土层。
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如图 3所示:样地各土层全磷质量分数的变化范围分别为0.51~0.75,0.52~0.57和0.50~0.53 g·kg-1。与对照地相比,10~20 cm 和20~40 cm土层,退耕植茶后土壤全磷质量分数变化较为稳定,无显著变化(P>0.05); 0~10 cm土层,RT16-17土壤全磷质量分数显著高于其他样地(P<0.05),较ck,RT2-3和RT9-10分别增加了45.63%,35.64%和29.31%;就土层而言,RT9-10土壤全磷表现为0~10 cm和10~20 cm土层显著高于20~40 cm土层;RT16-17土壤全磷质量分数却表现为0~10 cm土层显著高于其他土层。
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如图 4所示:退耕植茶地土壤碳、氮、磷间存在极显著的正相关关系(P<0.01)。其中,碳和氮间的变化几乎同步,其线性拟合关系良好(R2=0.730 7,P<0.01);碳和磷(R2=0.327 8)及氮和磷(R2=0.130 9)之间的线性拟合程度较弱。
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由表 2可知:不同土层各样地土壤碳氮比的变化范围分别为21.97~26.28,22.57~27.84和23.40~32.12,变异系数分别为8.1%,8.7%和15.4%。与对照地相比,随着退耕植茶年限的延长,0~10 cm和10~20 cm土层,土壤碳氮比表现为先显著增加(P<0.05),后逐渐趋于稳定;20~40 cm土层,土壤碳氮比表现为先显著增加,后显著降低的变化趋势。各土层土壤碳氮比均在RT2-3达到最大值,分别较对照地增加了19.64%,23.38%和35.07%。
表 1 样地基本情况
Table 1. Description of the sampling plots
退耕植茶地 坡度/(0) 海拔/m 面积/hm2 植被类型 ck 28 740 0.20 零散的棕叶狗尾草Setaria palmifolia RT2-3 30 742 0.4l 茶树 RT9-l0 30 742 0.75 茶树 RTl6-l7 30 742 0.67 茶树 表 2 退耕植茶地土壤碳氮比的分布特征
Table 2. Distribution of C N ratios in the soils of returning farmland to tea
土层/cm 土壤碳氮比 ck RT2-3 RT9-10 RT16-17 0-10 21.97±0.77 bb 26.28±0.92 ab 25.45±1.94 aa 26.06±1.88 aab 10-20 22.57±0.60 bab 27.84±2.10 ab 25.45±1.09 aa 26.30±2.28 aa 20-40 23.78±0.71 ba 32.12±4.03 aa 25.68±1.90 ba 23.40±1.73 bb 说明: 不同字母表示在相同土层不同退耕年限间差异显著(P<0.05),上标不同字母表示在相同年限不同土层间差异显著(P<0.05)。 -
由表 3可知:退耕植茶地土壤碳磷比的变化范围分别为37.29~51.95,36.79~43.06和34.43~39.14。与对照相比,随着退耕植茶年限的延长,0~10 cm土层,土壤碳磷比表现为先显著降低,再趋于稳定(P<0.05),其变异系数为17.6%;RT2-3,RT9-10,RT16-17较对照地分别降低了28.22%,27.56%和27.76%。10~20 cm和20~40 cm土层,退耕植茶地及对照地间土壤碳磷比均无显著差异。随着土层的加深,对照地碳磷比呈现降低的变化趋势;而退耕植茶地土壤碳磷比却无显著差异。
表 3 退耕植茶地土壤碳磷比的分布特征
Table 3. Distribution of C:P ratios in the soils of returning farmland to tea
土层/cm 土壤碳磷比 ck RT2-3 RT9-10 RT16-17 0-10 51.95±6.44 aa 37.29±1.73 ba 37.63±2.57 ba 37.53±4.96 ba 10-20 43.06±7.03 aab 38.30±4.15 aa 36.79±3.48 aa 42.02±1.66 aa 20-40 39.14±2.63 ab 34.43±7.95 aa 34.47±0.69 aa 37.85±4.38 aa 说明: 不同字母表示在相同土层不同退耕年限间差异显著(P<0.05),上标不同字母表示在相同年限不同土层间差异显著(P<0.05)。 -
由表 4可知:退耕植茶地土壤氮磷比的变化范围分别为1.42~2.37,1.37~1.91和1.10~1.65,变异系数分别为27.5%,14.9%和18.0%。0~10 cm和10~20 cm土层,对照地土壤氮磷比显著高于退耕植茶地。与对照相比,随着退耕植茶年限的延长,土壤氮磷比表现为先显著降低,后逐渐趋于稳定(P<0.05),RT2-3的各土层土壤氮磷比较对照分别降低了40.08%和27.88%。20~40 cm土层,土壤氮磷比表现为先显著降低,而后逐渐增加的变化趋势。随土层深度的加深,对照地及RT2-3土壤氮磷比均有降低趋势,而其他样地无显著变化。
表 4 退耕植茶地土壤氮磷比的分布特征
Table 4. Distribution of N:P ratios in the soils of returning farmland to tea
土层/cm 土壤氮磷比 ck RT2-3 RT9-10 RT16-17 0-10 2.37±0.32 aa 1.42±0.02 ba 1.49±0.15 ba 1.44±0.13 ba 10-20 1.91±0.29 aab 1.37±0.09 bab 1.45±0.14 ba 1.61±0.13 ba 20-40 1.65±0.06 ab 1.10±0.36 bb 1.35±0.11 aba 1.62±0.19 aa 说明: 不同字母表示在相同土层不同退耕年限间差异显著(P<0.05),上标不同字母表示在相同年限不同土层间差异显著(P<0.05)。
Ecological stoichiometry of soil C, N, and P for returning farmland to tea plantations
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摘要: 研究不同退耕植茶年限土壤有机碳、全氮和全磷的质量分数分布及其生态化学计量学特征,以期为退耕植茶地土壤持续利用和茶园持续发展提供理论依据。选取退耕植茶2~3 a(RT2-3), 9~10 a(RT9-10)和16~17 a(RT16-17)的各5个样地为研究对象,以邻近耕地作为对照,采用野外调查与室内分析相结合的方法,按0~10,10~20和20~40 cm土层取样,测定土壤有机碳、全氮、全磷的质量分数,并计算了碳、氮、磷之间的计量比。结果表明:随着退耕植茶年限的延长,土壤有机碳、全氮质量分数表现为先显著降低后增加的趋势(P<0.05),全磷质量分数变化较为稳定。0~10 cm土层,退耕植茶地土壤碳氮比(C/N)显著高于对照地,退耕植茶地土壤碳磷比(C/P)和氮磷比(N/P)显著低于对照地;10~20 cm土层,退耕植茶地土壤碳氮比显著高于对照地,碳磷比在各样地间均无显著差异,氮磷比则表现为对照地土壤显著高于退耕植茶地;20~40 cm土层,碳氮比表现为RT2-3显著高于其他样地,碳磷比和氮磷比在各样地间均无显著差异。退耕植茶后,土壤碳氮比显著增加,有机质分解速率降低。退耕植茶有利于土壤有机碳、全氮的积累;虽有利于提高土壤中磷的有效性,但随着植茶年限的延长,磷素对退耕植茶地限制性逐渐增强。Abstract: To provide a scientific basis for sustainable use of soil and sustainable development of tea plantations, soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) at different ages (2-3, 9-10, and 16-17 years old) were measured in returning farmland to tea with elemental changes in the soil profile of the tea plantations noted. Three tea plantations with different ages located in Zhongfeng Township of Mingshan District were selected as the study plots, and the near cropland was used as contrast. Adopting field investigation and indoor analysis methods, soil samples were collected from 0-10, 10-20, and 20-40 cm depths with SOC, TN, and TP being analyzed and C:N, C:P, and N:P ratios being estimated. ANOVA was performed using the DPS software (7.05). Two-way ANOVA, followed by the least significant difference (LSD) test (P<0.05), was used to compare the sites representing the different tea plantations age and soil layer. Results showed that after returning farmland to tea, SOC content and TN significantly decreased first (P<0.05) and then increased (P<0.05); whereas, changes of TP were relatively stable (P<0.05). In the 0-10 cm soil layer, C:N of returning farmland to tea was significantly higher than the control (P<0.05); whereas C:P and N:P were significantly lower than the control (P<0.05). In the 10-20 cm soil layer, C:N of returning farmland to tea was significantly higher than the control (P<0.05). In the 20-40 cm soil layer, C:N for returning farmland to tea (2-3 years old) was significantly higher than other plots (P<0.05). Also, after returning farmland to tea, the artificial disturbance decreased, which resulted in the degradation of organic matter decomposition rate. Therefore, returning farmland to tea was beneficial to SOC and TN accumulation, improved P efficiency, but limited P on tea plantations which became problematic overtime.
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Key words:
- forest soil science /
- ecological stoichiometry /
- carbon /
- nitrogen /
- phosphorus /
- returning farmland to tea
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表 1 样地基本情况
Table 1. Description of the sampling plots
退耕植茶地 坡度/(0) 海拔/m 面积/hm2 植被类型 ck 28 740 0.20 零散的棕叶狗尾草Setaria palmifolia RT2-3 30 742 0.4l 茶树 RT9-l0 30 742 0.75 茶树 RTl6-l7 30 742 0.67 茶树 表 2 退耕植茶地土壤碳氮比的分布特征
Table 2. Distribution of C N ratios in the soils of returning farmland to tea
土层/cm 土壤碳氮比 ck RT2-3 RT9-10 RT16-17 0-10 21.97±0.77 bb 26.28±0.92 ab 25.45±1.94 aa 26.06±1.88 aab 10-20 22.57±0.60 bab 27.84±2.10 ab 25.45±1.09 aa 26.30±2.28 aa 20-40 23.78±0.71 ba 32.12±4.03 aa 25.68±1.90 ba 23.40±1.73 bb 说明: 不同字母表示在相同土层不同退耕年限间差异显著(P<0.05),上标不同字母表示在相同年限不同土层间差异显著(P<0.05)。 表 3 退耕植茶地土壤碳磷比的分布特征
Table 3. Distribution of C:P ratios in the soils of returning farmland to tea
土层/cm 土壤碳磷比 ck RT2-3 RT9-10 RT16-17 0-10 51.95±6.44 aa 37.29±1.73 ba 37.63±2.57 ba 37.53±4.96 ba 10-20 43.06±7.03 aab 38.30±4.15 aa 36.79±3.48 aa 42.02±1.66 aa 20-40 39.14±2.63 ab 34.43±7.95 aa 34.47±0.69 aa 37.85±4.38 aa 说明: 不同字母表示在相同土层不同退耕年限间差异显著(P<0.05),上标不同字母表示在相同年限不同土层间差异显著(P<0.05)。 表 4 退耕植茶地土壤氮磷比的分布特征
Table 4. Distribution of N:P ratios in the soils of returning farmland to tea
土层/cm 土壤氮磷比 ck RT2-3 RT9-10 RT16-17 0-10 2.37±0.32 aa 1.42±0.02 ba 1.49±0.15 ba 1.44±0.13 ba 10-20 1.91±0.29 aab 1.37±0.09 bab 1.45±0.14 ba 1.61±0.13 ba 20-40 1.65±0.06 ab 1.10±0.36 bb 1.35±0.11 aba 1.62±0.19 aa 说明: 不同字母表示在相同土层不同退耕年限间差异显著(P<0.05),上标不同字母表示在相同年限不同土层间差异显著(P<0.05)。 -
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https://zlxb.zafu.edu.cn/article/doi/10.11833/j.issn.2095-0756.2016.04.009