氮添加对侵蚀退化红壤化学性质及芒萁叶功能性状的影响

蕨类植物芒萁(Dicranopteris dichotoma)是我国南方红壤侵蚀区重要的水土保持植物,但目前氮添加对芒萁叶功能性状及其基部土壤化学性质以及这二者之间关系的影响尚不清楚.以芒萁作为研究对象,采用盆栽实验,设置CK(0 gm^-2a^-1)、N1(1.1 gm^-2a^-1)、N2(2.3 gm^-2a^-1)、N3(3.4 gm^-2a^-1)、N4(4.5 gm^-2a^-1)、N5(5.6 gm^-2a^-1)共6个梯度的氮添加处理,研究氮添加对芒萁主要叶功能性状及其基部土壤主要理化性质的影响,并分析芒萁叶功能性状与土壤化学性质间的相关关系,为南方红壤侵蚀区生态恢复以及可持续发展提供相关科学依据.结果显示:(1)氮添加显著增加土壤全氮、硝态氮和铵态氮含量(P <0.05),显著降低pH值和全磷含量(P <0.05),表明氮添加能提高氮素有效性及导致红壤酸化.(2)氮添加显著增大芒萁叶面积、叶绿素含量与叶氮含量(P <0.05),但未对比叶面积和叶组织密度产生显著影响.(3)芒萁叶面积与土壤pH及其全磷含量呈极显著负相关(P <0.01),与土壤全氮、铵态氮和硝态氮含量呈显著正相关(P <0.05);叶氮含量与土壤pH呈极显著负相关(P <0.01),与土壤全磷含量呈显著负相关(P <0.05),与土壤全氮、铵态氮和硝态氮含量呈显著正相关(P <0.05);叶磷含量与土壤pH呈显著正相关(P <0.05),与土壤全氮、铵态氮和硝态氮含量呈极显著负相关(P <0.01),与土壤全磷含量相关不明显;叶绿素含量与土壤各化学性质指标均未存在显著相关性.上述结果表明,氮添加会提高退化土壤氮素有效性,促进芒萁对土壤氮素的吸收,导致叶氮含量升高;适度的氮添加会提高叶磷含量,但过量的氮添加则会显著降低叶磷含量.(图1表2参62)

Effects of nitrogen addition on soil chemical properties and leaf functional traits of Dicranopteris dichotoma in the red soil erosion area of southern China

Dicranopteris dichotoma, a fern species, is an important soil and water conservation plant in the red soil erosion area of southern China. However, the effects of nitrogen(N) addition on the chemical properties of red soil and plant leaf functional traits, as well as the relationship between them, are still poorly understood. Taking D. dichotoma seedlings as the research object, we conducted a pot experiment with 6 gradients of N addition, including CK(0 gm^-2a^-1), N1(1.1 gm^-2a^-1), N2(2.3 gm^-2a^-1), N3(3.4 gm^-2a^-1), N4(4.5 gm^-2a^-1), and N5(5.6 gm^-2a^-1). The results indicated that the N addition significantly increased soil total N(STN), nitrate(NO3--N), and ammonium nitrogen(NH4+-N) contents(P < 0.05), and reduced soil pH value and total phosphorus(P) content(STP)(P < 0.05). N deposition could improve N availability and lead to soil acidification. N addition significantly increased leaf area(LA), chlorophyll concentrations(Chl), and leaf N contents(LNC) of D. dichotoma(P < 0.05). However, N addition had no significant effect on specific leaf area(SLA) and leaf tissue density(LTD). The leaf area was extremely significantly negatively correlated with pH and STP(P < 0.01), and significantly positively correlated with STN, NH4+-N, and NO3--N(P < 0.05). The leaf N content was extremely significantly negatively correlated with pH(P < 0.01), significantly negatively correlated with STP(P < 0.05), and significantly positively correlated with STN, NH4+-N, and NO3--N(P < 0.05). The leaf P Content(LPC) was significantly positively correlated with pH(P < 0.05), extremely significantly negatively correlated with STN, NH4+-N and NO3--N(P < 0.01), but had no significant correlation with STP. Chlorophyll concentrations had no significant correlation with soil chemical properties. It appeared manifested that N addition promoted N absorption in D. dichotoma by increasing the soil N availability, which resulted in increased LNC. Moderate N addition would increase LPC, but excessive N addition would significantly reduce LPC. Our results provide a scientific basis for ecological restoration and sustainable development of the red soil erosion area in southern China.