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生态化学计量学是研究多重元素化学平衡的一门科学,内稳性理论和生长速率理论是生态化学计量学存在的重要基础[1-2]。C(碳)、N(氮)、P(磷)、K(钾)是地球生物圈的生命基本组成元素,尤其是C、N、P作为生态系统最基本的组成元素和植物必需的营养元素,在生物地球化学循环和维持生态系统结构及功能稳定性方面发挥着极其重要的作用[3-4]。研究植物的C、N、P、K化学计量特征,特别是C、N、P含量及C/N、C/P的关系,不但可以了解它们的生长发育过程、群落结构、多样性以及功能等,还能反映它们对环境变化的适应能力[5],有利于研究全球气候变化和国家“双碳”目标下植物的固碳增汇机制[6]。人工柏木林(Cupressus funebris)是川中丘陵区的主要森林类型,在维护该区域生态安全,发挥保持水土、涵养水源以及森林的固碳增汇等生态服务功能方面起着十分重要的作用。对于该区域人工柏木林的生态化学计量,国内专家主要从植物叶片、土壤和枯落物中的C、N、P含量进行了研究[7-10],系统研究柏木各器官的C、N、P、K含量及其比率关系尚未见报道。本文以川中丘陵区人工中龄柏木林作为研究对象,测定不同器官的生态化学计量指标,分析C、N、P、K 含量和比率分布格局,以期揭示该地区植物的生理特征,为人工柏木林质量和固碳增汇能力提升提供理论依据。
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2021年9—10月,在四川盆地中部的金堂县、简阳市设置 20 m×20 m 的标准样地6个。记录标准地的经纬度、郁闭度、海拔、土壤类型、坡度、坡向、坡位、土层厚、枯落物厚等因子。样地基本情况详见表1。
样地号
Plot NO.海拔
Altitude/m坡向
Aspect坡度
Slope/(°)坡位
Slope position平均胸径
DBH/cm平均树高
Height/m林分密度
Density/(株.hm-2)郁闭度
Crown density1 573 S 25 上坡 11.24 8.24 3075 0.72 2 547 SE20 22 中坡 10.48 7.70 3575 0.80 3 637 ES15 26 下坡 12.86 9.70 3350 0.75 4 546 S 23 下坡 12.45 10.62 2700 0.70 5 495 E 22 上坡 12.64 9.55 3075 0.72 6 498 EN30 25 中坡 11.27 8.87 3300 0.75 Table 1. Basic status of sampling sites
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(1)样地调查
乔木调查:每木检尺,测定并记录树种名称、树高、胸径、冠幅等因子;
灌木调查:种名、高度、盖度、株(丛)数等因子;
草本调查:种名、高度、盖度等因子。
(2)样品采集
主要采集乔木的干、枝、叶、皮和根, 其中干和皮分别从树干基部、胸径和梢头 3 个部位进行取样, 枝带皮从粗枝到小枝按比例取样, 叶亦分别从不同部位取样, 根带皮从粗根到小根按比例分别取样。采集的样品野外称鲜质量, 并取样, 标记好带回实验室进行实验测定及实验分析。
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将带回实验室的植物各器官样品置于85℃烘箱烘干至恒重,用粉碎机粉碎后过100目筛,密封以测N、P、K、C等元素。N含量采用凯氏定氮法测定,P含量采用硫酸-高氯酸消煮作目锑抗分光光度法测定,K含量采用硫酸-双氧水消煮-火焰光度法测定,C含量采用重铬酸钾习壳酸氧化法测定[2,13]。
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运用WPS 进行数据录入、基本计算;在 SPSS 20.0 里面进行单因素方差分析(Oneway ANOVA)和多重比较(LSD,显著水平 P<0.05),作图使用 OriginPro 2018[11]。
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不同器官化学计量特征的变异系数相差较大(见表2)。柏木叶片中N、C、P、K含量均高于其他器官,其含量分别在9.34~18.05 g.kg−1、464.96~573.35 g.kg−1、0.46~1.04 g.kg−1、1.12~3.98 g.kg−1。干的N含量较小,在6.33~8.17 g.kg−1,干和根的C含量较小,分别在490.21~500.89 g.kg−1和457.20~500.09 g.kg−1。枝的P和K含量均最小,分别在0.17~0.37 g.kg−1和1.12~3.98 g.kg−1。从变异系数来看[2],C含量在各器官中的变异系数均在7%以下,属弱变异;N含量除干属弱变异外,其余均属于中等变异;P含量除在叶和枝中属于中等变异外,在干、根、皮中属强变异;K含量表现的规律与P含量类似。
参数 N含量(g.kg−1) C含量(g.kg−1) P含量(g.kg−1) K含量(g.kg−1) 最大
Max最小
Min变异系数
CV(%)最大
Max最小
Min变异系数
CV(%)最大
Max最小
Min变异系数
CV(%)最大
Max最小
Min变异系数
CV(%)干 8.17 6.33 9.28 500.89 490.21 0.79 0.79 0.17 89.50 2.46 0.52 93.81 根 11.77 6.32 20.45 500.09 457.20 2.75 0.88 0.10 123.19 2.88 0.52 73.84 皮 15.35 7.97 20.61 540.68 499.74 2.48 0.82 0.31 41.35 2.34 0.58 61.01 叶 18.05 9.34 15.14 573.35 464.96 6.33 1.04 0.46 18.74 3.98 1.12 30.07 枝 8.86 5.63 15.72 515.55 494.00 1.56 0.37 0.17 26.57 1.38 0.64 29.05 Table 2. Stoichiometric characteristics and coefficient of variation of different organs
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柏木干、根、皮、叶、枝4种元素C、N、P、K的含量及C/N、C/P见图1。不同器官的C含量在491.264~518.996 g.kg−1之间。最高的是叶(518.996±32.791 g.kg−1),最低的是根(491.264±13.527 g.kg−1)各器官C含量按大小排列为叶>皮>枝>干>根。方差分析和多重比较(LSD)表明,叶的C含量与皮、枝差异不显著(P>0.05),与干、根的C含量之间差异显著(P<0.05),干的C含量与根、皮、枝的C含量之间差异不显著(P>0.05),与皮和叶之间差异显著(P<0.05)。各器官的N含量以叶中最高(15.761±2.508 g.kg−1),最低的是干(7.421±0.702 g.kg−1)。按大小排列为叶>皮>根>枝>干。方差分析和多重比较(LSD)表明,叶和皮的N含量与其他器官的N含量之间差异均显著(P<0.05),干、根、枝的N含量之间差异不显著(P>0.05)。各器官的P元素含量以叶占绝对优势,分别为干、根、皮、枝的3.20倍、2.87倍、2.18倍、3.35倍,且除叶的P含量与其他器官之间差异显著外(P<0.05),其余器官之间均差异不显著(P>0.05),各器官的K元素含量表现出类似规律。C/N最高的是枝(69.25±13.09),最小的是叶(34.05±8.41)。方差分析和多重比较表明,皮和叶的C/N与其他器官之间差异均显著(P<0.05),干、根、枝的C/N之间差异均不显著(P>0.05)。各器官的C/P差异较大。其中叶的C/P最小(602.66±208.75),分别为干、根、皮、枝的27.63%、21.97%、46.24%、30.74%。方差分析和多重比较表明,根的C/P与干、枝之间差异不显著(P>0.05),与皮、叶的C/P差异显著(P<0.05)。皮的C/P与叶、枝之间差异不显著(P>0.05),叶的C/P除与皮之间差异不显著外(P>0.05),与其他器官之间均差异显著(P<0.05)。
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通过各器官的N含量、C含量、P含量、K含量、C/N、C/P的相关性分析表明(表3):N与C呈显著正相关(P<0.05),与P、K呈极显著正相关(P<0.01),与C/N、C/P均呈极显著负相关(P<0.01);C含量与K呈显著正相关(P<0.05),与C/N呈显著负相关(P<0.05),与P含量和C/P均没有相关性(P>0.05);P含量与K呈极显著正相关(P<0.01),与C/N、C/P均呈极显著负相关(P<0.01);K含量与C/N、C/P均呈极显著负相关(P<0.01);C/N与C/P呈极显著正相关(P<0.01)。
参数 N C P K C/N C/P N 1 0.513* 0.946** 0.867** −0.977** −0.768** C 1 0.395 0.513* −0.447* −0.328 P 1 0.923** −0.884** −0.801** K 1 −0.772** −0.652** C/N 1 0.782** C/P 1 注:*表示显著相关(P<0.05),**表示极显著相关(P<0.01)。 Table 3. Correlation between water content and stoichiometric ratio
Stoichiometric Characteristics of C, N, P, K in Different Organs of Artificial Cypress Plantation in Hilly Areas of Central Sichuan
doi: 10.12172/202303100001
- Received Date: 2023-03-10
- Available Online: 2023-05-30
- Publish Date: 2023-08-30
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Key words:
- Hilly areas of central Sichuan /
- Artificial cypress plantation /
- Ecological stoichiometry
Abstract: In order to understand the ecological and chemical metrological characteristics of C, N, P, K in various organs of the artificial cypress forest in the hilly area of central Sichuan, master the distribution pattern of nutrient elements in the cypress forest and the nutrient restriction status of various organs, samples were taken from the leaves, branches, trunks, bark, roots and other organs of the artificial cypress forest in this area to analyze their water content, C, N, P, K content, C/N, C/P and the correlation between various elements, The results showed that: (1) The contents of C, N, P, K in leaves were significantly higher than those in other organs; The highest C/N was in branches (69.25 ± 13.09) and the lowest was in leaves (34.05 ± 8.41). The C/P of each organ varies greatly. The C/P of leaves was the lowest (602.66 ± 208.75). There was no significant difference between leaf C content and bark and branch C content (P>0.05), but there was significant difference between leaf C content and stem and root C content (P<0.05). There was significant difference between the N content of leaves and bark and that of other organs (P<0.05), but there was no significant difference between the N content of stems, roots and branches (P>0.05). The P content in leaves was significantly different from that in other organs (P<0.05), but not in other organs (P>0.05). The C/N of bark and leaf were significantly different from that of other organs (P<0.05), while the C/N of trunk, root and branch were not significantly different (P>0.05). There was no significant difference in C/P between root, stem and branch (P>0.05), but significant difference in C/P between root, bark and leaf (P<0.05). There was no significant difference between the C/P of bark and that of leaves and branches (P>0.05). Except that there was no significant difference between the C/P of leaves and bark (P>0.05), there was significant difference between the C/P of leaves and other organs (P<0.05). (2) The coefficient of variation of C content in all organs was below 7%, which belonged to weak variation; Except for the weak variation of stem, the rest of N content belonged to the medium variation; P content was moderate variation in leaves and branches, but strong variation in stems, roots and bark; The law of K content is similar to that of P content. (3) N was positively correlated with C (P<0.05), positively correlated with P and K (P<0.01), and negatively correlated with C/P (P<0.01); C content was positively correlated with K (P<0.05) and negatively correlated with C/N (P<0.05); P content was positively correlated with K (P<0.01) and negatively correlated with C/P (P<0.01); K content was negatively correlated with C/N and C/P (P<0.01); C/N was positively correlated with C/P (P<0.01).(4) The content of N and P in the cypress forest is relatively scarce, so N and P fertilizer should be reasonably increased, or the mixed forest should be formed by thinning and replanting alder and other leguminous plants to improve the soil capacity and promote the nutrient cycle of the forest land.