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

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 in5 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 was25. 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.

Nutrients in litterfall,forest floor and mineral soils in two adjacent forest ecosystems in Greece

The fluxes of masses and the nutrients Ca,Mg,K,N,P and S were determined in the litterfall of two adjacent forest ecosystems of Hungarian oak(Quercus frainetto L.)and European beech(Fagus sylvatica L.)in a mountainous area of northeastern Greece in 2010–2015.The foliar litterfall for both species reached about 70%of the total litterfall,and was significantly higher from the other two fractions(woody and rest litterfall).The fluxes of masses and nutrients were compared between ecosystems for each fraction separately.Only one significant statistical difference was found,that of K in the woody litterfall.In addition,the stocks of masses and nutrients were calculated in the forest floors and mineral soils of the two ecosystems.Likewise,the stocks of nutrients in the forest floors and mineral soils were compared between ecosystems.In the L horizon of the forest floors,statistical differences,as a result of species effect,were found for the stocks of Ca and N.In the FH horizons,the masses and all the nutrient stocks differed significantly,as the beech plot had much higher quantities of organic matter and nutrients.These higher quantities were probably due to low soil temperatures(microclimate)and high acidity in the beech plot(species effect)that slowed down decomposition.In the mineral soils,the propagation of random error derived from random errors of the individual soil layers was an important factor in the statistical comparisons.Because of the soil acidity in the beech plot,the stocks of exchangeable base cations were significantly higher in the oak plot,whereas the other nutrient stocks did not differ.

The Effects of Forest Thinning Practices and Altered Nutrient Supply on Soil Trace Gas Fluxes in Colorado

Increases in wildfire activity in the western United States have prompted land managers to reevaluate management practices. In the Colorado Front Range, where population density is high, there is often a great concern regarding wildfire which leads to efforts that will reduce fire hazard. The most common method of achieving this goal is to thin the forest of small diameter trees. Oftentimes these practices are undertaken with little knowledge of the ecological consequences of such treatments. We investigated the effect(s) of three treatments (control, thinning-only and broadcast chipping) on trace gas fluxes (CO2, CH4, and N2O), litter mass, and soil carbon and nitrogen. In a small plot study, we used a 2 × 3 × 3 randomized complete block design to determine the influence of nutrient amendments (woodchips, nitrogen, and phosphorus availability) on trace gas fluxes. The stand-management study revealed that neither thinning-only nor broadcast chipping significantly affected soil carbon or nitrogen, while thinning-only significantly reduced the amount of forest floor litter. Each trace gas flux was significantly affected by the date of sampling (June or August). CO2 and N2O fluxes each had a significant interaction between treatment and sampling date. We attribute this to a difference in moisture availability between the sampling times. In the plot study we found that only the interaction between woodchip addition and phosphorus availability significantly affected CO2 flux. Nitrous oxide fluxes were not significantly affected by any combination, however, methane uptake was found to respond significantly to different nitrogen and phosphorus levels.

Benefit Assessment of Forest Function in Reducing Soil Erosion and Nutrient Loss in Anji County of Taihu Lake Basin

The non-point source pollution arising from soil erosion is one of the main reasons for the deterioration of the water quality of the Taihu Lake Basin. Forest plays an important role in controlling soil erosion and reducing nutrient loss. Based on the survey data on forest resources in Anji County, we estimate the amount of soil erosion and nutrient loss of nitrogen and phosphorus reduced by forest, using soil erosion modulus method and soil nutrient content. In accordance with the degradation coefficient of pollutant and regional compensation standards of environmental resources, we assess the ecological benefits of forest function in reducing nutrient loss of nitrogen and phosphorus in Anji County. The results show that the forest in Anji County can reduce the soil erosion amount at 1.51 million t annually on the average, so as to control the nutrient loss of 1 409 t of total nitrogen and 577 t of total phosphorus in soil, equivalent to annually avoiding the flow of 824 t of total nitrogen and 410 t of total phosphorus into river water; this ecological service function can make forests in Anji County get 92.55 million yuan of ecological compensation funds (about 688 yuan/hm2·a), equivalent to 15 times of the current ecological compensation standard (47 yuan/hm2). The study reveals the importance of forest function in controlling soil erosion and nutrient loss in the upper reaches of Taihu Lake Basin to water environment protection in the basin, conducive to carrying out pollution control and protection work of the water environment in the basin.

Nutrient status of Populus euphratica growing in desert riparian forests of northwestern China

Seasonal and microhabitat variations of chemical constituents of foliar organic carbon （C）, total nitrogen （N）, total phosphorus （P）, and total potassium （K）, in Populus euphratica growing in desert riparian forests in northwestern China and their correlations were studied. Results show that ranges of C, N, P and K contents in the leaves ofP. euphratica were 39.08%-46.16%, 0.28%-2.81%, 0.05%-0.18% and 0.35%-2.03%, with means of 43.51%, 1.49%, 0.102% and 1.17%, respectively. The ratio of C/N, C/P and N/P changed from 16.26 to 146.61, from 258.08 to 908.67 and from 2.89 to 26.67; the mean was 37.24, 466.27 and 15.14, respectively. The mean N content was significantly lower than of deciduous trees in China, but the mean P content was nearly equivalent. The ratio of C/N was remarkably higher than of global land plants. The ratio of N/P indicated that growth ofP. euphratica was jointly limited by N and P nutrient deficiency. During the growth season, total trends of leaf C, N, P and K contents decreased. The max- imum appeared in May, and the minimum in September. Among microhabitats, C, N and K contents gradually increased from ri- parian lowland, flatland, sandpile, Gobi and dune, but C/N ratio was opposite, and P content was not apparent. Foliar C content was extremely, significantly and positively correlated with N and K contents, respectively. The relationships of N-K and P-K were both significantly positive.

Variation of SPAD values in uneven-aged leaves of different dominant species in Castanopsis carlessi forest in Lingshishan National Forest Park

The greenness （SPAD） of uneven-aged leaves of dominant species in the Castanopsis carlessi forest at different altitude gradients in Lingshishan National Forest Park, Fujian Province, China were measured by using portable chlorophyll meter SPAD-502. In addition, the correlation between SPAD value and the concentration of chlorophyll and foliar nitrogen was also investigated. Significant variations in SPAD values were found between the uneven-aged leaves of different dominant species and different altitude gradients. Regression analysis showed that SPAD value was significantly correlated with the concentration of chlorophyll and the content of foliar nitrogen, indicating that SPAD value could be indicators for foliar chlorophyll and nitrogen. It is suggested that SPAD meter is a useful tool for forest assessments in decision-making and operational nutrient management programs.

毛竹扩张对幕阜山区森林土壤碳氮磷含量及生态化学计量特征的影响

以幕阜山区同一片毛竹林向两侧杉木林和阔叶林扩张形成的连续生态界面为研究对象,分析不同林型土壤有机碳(SOC)、全氮(TN)、全磷(TP)、硝态氮(NO_(3)^(−)−N)、铵态氮(NH_(4)^(+)−N)含量及其生态化学计量比,探讨毛竹不同扩张模式对森林土壤碳(C)、氮(N)、磷(P)的影响。结果表明:在2种扩张模式下,随土壤层次的增加,除NO_(3)^(−)−N呈不规律变化外,SOC、TN、TP、NH_(4)^(+)−N含量均呈逐渐降低趋势。在毛竹向杉木林扩张过程中,杉木林、竹杉混交林、毛竹林同一土层SOC、TN、TP含量均无显著差异;在毛竹向阔叶林扩张过程中,毛竹林0~10 cm土层SOC和TN含量较阔叶林和竹阔混交林分别降低了27.71%、30.45%和36.67%、31.11%,而在10~20 cm和20~30 cm土层则无显著差异;毛竹扩张对杉木林和阔叶林各土层TP含量无显著影响;毛竹向杉木林扩张增加了0~10 cm和20~30 cm土层NH_(4)^(+)−N含量,毛竹向阔叶林扩张增加了10~20 cm土层NH_(4)^(+)−N含量及20~30 cm土层NO_(3)^(−)−N含量;毛竹向杉木林扩张对土壤C/N、C/P、N/P无显著影响,毛竹向阔叶林扩张导致0~10 cm土层N/P明显降低、10~20 cm土层C/N显著增加。综上,毛竹向杉木林扩张对土壤SOC、TN、TP影响不显著,但提升了表层和深层土壤NH_(4)^(+)−N含量,毛竹向阔叶林扩张造成表层土壤SOC、TN含量显著降低,并导致中层土壤NH_(4)^(+)−N含量和深层土壤NO_(3)^(−)−N含量明显增加。

Nutrient cycling characteristics of Quercus acutissima and Pinus massoniana mixed forest in the Three Gorge Reservoir area, China

The cycling characteristics of nitrogen(N), phosphorus(P) and potassium(K) of the Quercus acutissima and Pinus massoniana mixed forest which is the most common forest type in the Three Gorge Reservoir areas in China, were systematically analyzed. The results showed that N, P and K accumulated in the plant pool and in the litter pool, while total N, P, and K were deficient in the soil pool and in the forest systems. Contents of N in the soil of depth 20—40 cm were the key factor limiting growth of trees. The biological outside cycling coefficients were 878, 725 and 117 times of inside cycling coefficients of N, P and K, respectively. 3392, 1026 and 1588 kg of N, P and K return to the litter pool from branches, leaves and throughfall per year, but, 1431, 132 and 1048 kg of N, P and K return to the soil from litter pool per year respectively. It is clear that 58% of N, 87% of P, and 34% of K are lost by surface runoff per year. 549%, 130%, and 834% of N, P and K withdraw from leaves to branches, 499%, 199% and 730% of N, P and K withdraw from branches to trunks per year, respectively.

Relationship between Leaf Micro- and Macro-Nutrients in Top Canopy Trees in a Mixed Forest in the Upper Rio Negro in the Amazon Region

The mixed forests of the upper Rio Negro at the northern of the Amazon basin grow in oxisol soils that are extremely infertile. These areas exhibit deficiencies in several macro-nutrients, and may also be characterized by the shortage or toxic excess of some micronutrients. The overall goal of this research is to collect more comprehensive information regarding the micronutrient composition of the upper Rio Negro forests as well as discern the relationship between leaf micro- and macro-nutrients that may contribute to the homeostasis and balance of the ionome. Firstly, the nutrient composition within the oxisol soil and leaf tissues of two top canopy tree species from the mixed forests was determined. We then analyzed the relationship between leaf micronutrient composition with N and P levels of the two species and that of species inhabiting the Amazon caatinga. Extractable soil Zn, B, Mn and Cu were very low in the mixed forest. In contrast, Fe and Al levels were potentially toxic. The analysis of leaf N/P ratios revealed for the first time the co-limitation of N and P in the mixed forest. This contrasts with species from the adjacent Amazon caatinga toposequence that are characterized by strong N limitation. All micronutrients within leaves of species inhabiting the mixed forest were also found to have low concentrations. Moreover, Fe and Al were detected at concentrations well below those reported for accumulator species. This suggested that leaf ion homeostasis was maintained under potentially toxic soil Fe and Al conditions. Leaf micronutrient (Fe, Zn and B) contents mirrored that of leaf N and P contents, and comparable Fe/N, Fe/P, Zn/N, Zn/P, B/N as well as B/P ratios were found across species and forest types. Therefore, forest species exhibited the capability to maintain leaf nutrient balances under soil conditions with deficient or toxic levels of micronutrients.

新兴林粮——黄精产业发展战略研究

当前,全球粮食安全形势复杂严峻,与饮食相关的慢性疾病普遍存在,“以健康为中心”“营养多元”“食物即药物”等观点成为普遍共识;利用农业生物多样性来探寻高产且有营养的新一代作物成为国际潮流,黄精具有明显的特色和优势。本文从充分发挥黄精潜能的角度出发,系统总结了黄精食药用历史、黄精林粮营养与功效的物质基础、黄精资源分布与粮食生产潜力。现有研究发现,黄精不含淀粉,富含结构复杂、易降解、有能量的果聚糖等营养功效物质,能够服务生命健康;适合林下栽培或与玉米套种,不占良田、不争林地,产能潜力极大,可用于保障粮食安全;适合广大农户种植和加工,经济效益良好,有利于实现共同富裕。为解决黄精林粮产业存在的基础科学研究薄弱、应用技术支撑不足、文化传承与政策支持滞后等问题,需加强黄精基础科学研究、强化黄精全产业链应用技术研究,同时将黄精生产列入木本粮油政策资金保障体系,将黄精应用纳入医疗保健与人口健康规划,将黄精产业列为乡村振兴和共同富裕的重要举措,构建完备的黄精全产业链创新应用体系。

氮沉降对城市森林凋落物养分元素含量及其耦合性的影响

目前,氮沉降增加呈现全球化趋势,影响森林生态系统生物地球化学循环过程,已成为生态和环境研究的热点内容之一。为探讨氮沉降增加对城市森林凋落物养分含量的影响,进一步认识城市森林养分循环过程,为区域城市化进程的生态风险评估提供科学依据,本研究以安徽省合肥市蜀山国家森林公园凋落物为研究对象,在连续3年模拟氮沉降实验后(氮添加设置3种水平,分别为对照组:0 kg·hm^(–2)·a^(–1)、CK;低氮:50 kg·hm^(–2)·a^(–1)、LN;高氮:100 kg·hm^(–2)·a^(–1)、HN),研究氮沉降对城市森林凋落物(枝叶果碎)养分元素含量及其耦合性的影响。结果表明:(1)不同施氮水平下,凋落果内CK与HN中C元素含量,凋落叶中CK与LN、碎中LN与HN两组中N元素含量差异显著(P<0.05)。(2)凋落物不同组分间,N沉降显著影响Ca元素含量(P<0.05),对C元素含量无显著影响;凋落枝组分间K含量差异显著(P<0.05),凋落叶与其他各组间N含量差异显著(P<0.05),凋落果与其他各组间P含量差异显著(P<0.05);凋落叶与凋落果间Mg元素差异显著。(3)N沉降对各组分间的C/N、C/P、N/P等生态化学计量比无显著性影响,但对凋落叶、凋落果中C/N值有显著抑制作用(P<0.05)。(4)N沉降显著影响C、N间相关性及Ca、Mg间相关性,且均表现为LN显著增强相关性,HN显著抑制相关性;N沉降显著增强了P、K间的相关性,而显著降低了K与Ca、Mg的相关性。(5)N沉降对C/N与N/P、C/P与N/P间的耦合性有显著影响,且均表现为LN显著增强生态化学计量比间的耦合性,HN显著降低二者耦合性。研究结果为城市森林凋落物养分循环过程对N沉降的响应提供了理论依据。

不同肥料类型对阔叶箬竹修剪后生长及土壤养分含量的影响

选用菌肥(T1)、控释肥(奥绿肥318s,T2)、复合肥(T3)、有机肥(羊粪,T4)4种肥料类型,以不施肥为对照(T5),研究了不同肥料类型对阔叶箬竹地上部分剪除后的竹林生长及土壤养分的影响。结果显示:1)在促进阔叶箬竹生长方面,控释肥(T2)整体表现较好,施用后竹林的母株成活量、出笋量、竹笋地茎、竹笋高度分别比对照增加243.7%、300.0%、55.7%、129.7%,退笋数量较对照减少37.5%;叶片全氮、全磷、全钾、总钙和总镁含量分别比对照提高8.3%、3.2%、18.3%、4.7%和24.9%;5种处理在促进竹林生长的综合效应方面表现为T2>T1>T3>T4>T5。2)在改善土壤养分状况方面,控释肥(T2)的效果最好,施用后土壤碱解氮、有效磷、速效钾含量分别比对照提高50.8%、44.8%、56.7%,土壤EC值提高160%,pH值降低0.7%;5种处理对于改善林地土壤肥力的综合效果表现为T2>T1=T3=T4>T5。阔叶箬竹地上部分剪除后,施用控释肥(奥绿肥318s)为最佳施肥方案。

喀斯特石漠化区林草间作对土壤养分及微生物数量的影响

林草间作具有水源涵养、提高土壤肥力和增加生物多样性等多重优势,是喀斯特石漠化区生态恢复较为理想的模式之一。为了探讨林草间作对喀斯特石漠化区土壤养分和微生物数量的影响,在贵州省关岭县板贵乡选择花椒(Zanthoxylum bungeanum)+拉巴豆(Dolichos lablab)间作、花椒+雀稗(Paspalum thunbergii)间作及单作花椒3种模式开展研究。结果表明:与花椒单作相比,土壤中有机质、全氮、速效钾、碱解氮含量均有所增加,土壤pH降低,土壤微生物数量增加,其中真菌数量显著增加(P<0.05)。0-10 cm土壤中有效磷含量显著降低(P<0.05),而10-20 cm土壤中有效磷增加。相关性分析表明,0-10 cm土壤中细菌数量与有效磷含量显著负相关(P<0.05),真菌数量与有机质含量极显著正相关(P<0.05),与全氮、有效磷含量显著正相关(P<0.05),与pH显著负相关(P<0.05);10-20 cm土壤中细菌数量与速效钾含量显著正相关(P<0.05),真菌数量与pH显著负相关(P<0.05)。说明在喀斯特石漠化地区花椒和牧草构成的林草间作生态恢复模式在提高土壤养分、增加微生物数量方面有积极作用。

海南橡胶林土壤生态化学计量特征及影响因素

探究海南不同地区不同林龄橡胶林土壤碳、氮、磷生态化学计量特征,为揭示橡胶林土壤养分分布规律及养分管理提供理论依据。以海南文昌市、琼中县和东方市3个橡胶种植区土壤为研究对象,对5个林龄段(0~5、6~10、11~15、26~30、31~35 a)橡胶林的6个土层深度(0~10、10~20、20~40、40~60、60~80、80~100 cm)开展研究,分析海南橡胶林土壤养分含量及碳、氮、磷生态化学计量比的时空分布特征及影响因素。结果表明,(1)3个研究区橡胶林土壤养分含量及生态化学计量比差异显著(P<0.05),土壤有机碳、全磷含量均为文昌>东方>琼中,全氮含量为东方>文昌>琼中,土壤碳氮比表现为文昌显著高于琼中和东方(P<0.05),土壤碳磷比和氮磷比则文昌显著低于其他两个地区(P<0.05)。(2)不同林龄橡胶林土壤养分及生态化学计量比差异明显,其中6~10 a橡胶林土壤有机碳含量和碳氮比最高,0~5 a橡胶林土壤全磷含量最高,31~35 a橡胶林土壤全氮含量、碳磷比和氮磷比最高。(3)从土层垂直分布看,橡胶林土壤有机碳、全氮含量、碳磷比及氮磷比随着土层深度的增加整体呈现递减趋势,土壤全磷含量和碳氮比随着土层深度增加无显著差异。(4)冗余分析表明,海拔、坡度、土壤容重、土壤含水量和郁闭度是影响橡胶林土壤碳、氮、磷含量的主要影响因素。

基于随机森林法的山核桃林地土壤速效养分含量空间分布特征研究

土壤氮磷钾是土壤肥力管理的重要元素,是植物生长的必要养分元素。对土壤氮磷钾的空间分布进行特征解译,可为精准管理临安山核桃产区林地土壤肥力,促进山核桃林产业可持续发展提供理论依据。研究以临安山核桃主产区为研究区域,利用随机森林(RF)、普通克里格(OK)和Shapley加性解释(SHAP)方法,结合地形因子、气候因子、土壤因子、遥感因子等环境变量,对山核桃林地土壤碱解氮(AN)、有效磷(AP)、速效钾(AK)的空间分布特征进行分析。研究结果表明:相比于OK模型,基于环境协变量所构建的RF模型对AN、AP和AK含量空间分布预测表现最佳,R^(2)分别为0.68、0.60和0.64,均方根误差(RMSE)分别为20.005、10.287和22.426,平均绝对误差(MAE)分别为15.425、7.709和21.628。RF模型SHAP分析显示,AN和AK含量分布主要受土壤有机质(SOM)的影响,并且SOM与AN和AK存在正相关性;AP主要受pH的影响,其次为色调指数,AP与pH和色调指数均具有负相关性;AK和AP同时受到海拔和坡向的影响。两种模型预测的氮磷钾空间分布趋势总体相似,不同速效养分存在明显的空间异质性。碱解氮高值区域主要分布于研究区东部;有效磷高值区域主要分布于研究区西部,但分散度高;速效钾高值区域则主要分布于研究区中部。总体而言,基于随机森林模型可以高精度模拟山核桃林地土壤氮磷钾含量空间分布特征,并依据主要环境协变量对土壤氮磷钾的影响关系,提出相应改良措施。在有效磷含量低值区域可以施用石灰来缓解土壤酸化,同时补追磷肥;碱解氮含量高值区域可以合理减少氮肥施用;速效钾含量低值区域合理施加钾肥;对于海拔较高及迎风坡多降雨的区域,可以构建林下高效水土保持植被,减轻水土流失;在林地施用有机肥料,改善土壤理化性质,增加土壤养分含量。

蒙古栎低质林改造后2010—2023年林地土壤质量的综合评价及未来6a土壤质量变化趋势预测——以2009年改造的蒙古栎低质林为例

在黑龙江省大兴安岭林区的加格达奇林业局翠峰林场174林班,以蒙古栎(Quercus mongolica)低质林为例,2009年进行不同采伐带宽度的顺山皆伐,每条采伐带设置在近似相同海拔高度,皆伐带带长均为300 m,带宽分别为6、10、14、18 m,采伐后在每种采伐带分别补植了西伯利亚红松(Pinus sibirica)、兴安落叶松(Larix gmelinii)、樟子松(Pinus sylvestris),共设置12个不同改造样地;2010—2023年,测定12个不同改造样地的7个土壤养分指标(有机质质量分数、全氮质量分数、全磷质量分数、全钾质量分数、速效氮质量分数、速效磷质量分数、速效钾质量分数),应用模糊综合评价法、主成分分析法对土壤质量进行综合评价;结合2010—2023年对样地土壤养分质量评价结果,采用非线性自回归外部输入(NARX)神经网络模型预测2024—2029年各样地的土壤养分质量状况,分析未来6 a土壤养分质量变化趋势。结果表明:2023年测定的改造样地的土壤养分质量,91.67%的改造样地满足功能标准。补植樟子松样地中,只有采伐宽度为14 m的样地土壤养分质量相对稳定,其他采伐宽度的样地土壤养分质量状态不稳定。在2024—2029年,除了采伐宽度为10、18 m宽带中补植樟子松的样地以及采伐宽度为14 m宽带中补植西伯利亚红松的样地土壤养分不稳定外,其他样地未来6 a总体看土壤养分质量均较好,为Ⅰ级。构建的评价模型框架,可为低质林改造样地土壤养分质量综合评价及预测提供技术支持,弥补了土壤观测的数据盲区。

晋西黄土区不同密度刺槐人工林叶片-枯落物-土壤化学计量特征

[目的]研究不同林分密度对刺槐人工林叶片、枯落物、土壤C、N、P化学计量特征的影响,为晋西黄土区刺槐人工林的经营管理提供科学参考。[方法]通过野外调查,选择晋西黄土区5种不同密度(500、1000、1500、2000、2500株·hm^(-2))刺槐人工林,测定和分析叶片、枯落物、土壤的养分。用单因素分析法分析密度对三者养分的影响,采用Pearson相关系数,分析刺槐人工林叶片、枯落物、土壤C、N、P及其化学计量比之间的相关性。[结果]随着密度增加,刺槐人工林叶片C、N、P含量先增加后减小,叶片C∶P、N∶P先降低后增加;枯落物的C、C∶N、C∶P、N∶P随着密度先减少后增大,N、P则先增大后减少;土壤C、P、N含量及C∶P、N∶P随密度的增大而降低;C∶N随密度呈先降低后增加的趋势。不同林分密度下,叶片N∶P均大于14,叶片-枯落物-土壤C、N、P及其化学计量比中除了叶片N、C∶N以外,均存在不同的显著差异性(p<0.05)。[结论]不同林分密度下,叶片N∶P均大于14,说明研究区刺槐人工林主要受到P限制;密度在一定程度上影响着刺槐人工林的养分循环及其分配和化学计量特征;在密度为1000~1500株·hm-2的刺槐人工林叶片、枯落物、土壤C、N、P含量最高,养分限制最弱,枯落物分解速率相对较快,为适宜经营密度。

赛罕乌拉林草交错区典型生态系统土壤理化性质对比

为分析退耕林地、自然草地、农田3种植被管理方式对土壤理化性质的影响,识别不同植被修复模式下土壤理化性质的差异,本研究以内蒙古赛罕乌拉林草交错区自然草地、退耕林地、农田3种典型植被类型为研究对象,通过对比分析3种植被类型下0 cm、10 cm、20 cm、40 cm、60 cm深度土壤容重、含水量、粒径比等物理属性以及全氮、全磷、全钾、碱解氮、速效磷、速效钾养分元素含量,结合元素含量之间的相关性分析,结果发现:1)农田土壤存在明显的犁底层,犁底层之下养分元素含量迅速下降;2)草地土壤pH值低、有机碳含量高,农田pH值最高、有机碳含量低,退耕林地浅层土壤有机碳含量少,其土壤理化性质呈现出居于农田与自然草地之间的特征;3)农田土壤除速效磷、全钾等指标高于自然草地外,其他养分含量均低于自然草地。本研究表明,自然草地、退耕林地和农田是在相同土壤母质基础上,因经营管理方式差异而产生的土壤理化性质差异,草地的有机质含量最高、农田最低,土壤有机碳含量对于其他养分元素含量具有关键作用。因此,林草交错区生态系统固碳功能对于防风固沙等其他生态功能发挥具有决定作用,退耕还草有利于土壤养分元素的恢复,退耕还林工程还应注重林冠下方草本灌木生物量及物种多样性的恢复。

米槠天然更新林与人促更新林枯枝落叶层现存量及养分贮量

枯枝落叶层现存量及其养分特征研究对了解枯枝落叶层在森林生态系统碳和养分循环中的作用具有重要的意义。通过对中亚热带米槠天然更新林与人促更新林枯枝落叶层现存量和养分贮量进行研究发现:1)总现存量不受更新方式的影响,而叶现存量天然更新林显著高于人促更新林,天然更新林枝现存量显著小于人促更新林,其他组分不受更新方式影响。2)在未分解层,天然更新林的枝现存量显著高于人促更新林。在半分解层,天然更新林的叶现存量显著高于人促更新林,而人促更新林的枝现存量显著高于天然更新林。3)两个林分同一分解层叶的氮(N)、磷(P)浓度均显著高于枝,而碳(C)浓度则无显著差异。4)2个林分枯枝落叶层的碳氮磷贮量无显著差异。结果表明,天然更新林更有利于养分的维持和循环。因此在未来研究中应更加关注天然更新方式对生态系统养分循环的影响。

异质养分环境下不同家系福建柏光合特性及酶活性的差异

【目的】探究在不同异质养分环境下,福建柏[Fokienia hodginsii(Dunn)Henry et Thomas]不同家系幼苗叶片光合特性和酶活性差异及变化趋势,为福建柏新品种培育提供理论依据和数据支持。【方法】以福建柏9个1年生家系(454,464,467,474,490,493,500,534,541)幼苗为研究对象,采用盆栽试验,设置氮(N)、磷(P)、钾(K)3种不同异质养分环境,以同质养分环境为对照,研究福建柏各家系幼苗叶片的光合特性、荧光参数及酶(超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT))活性和丙二醛(MDA)含量对不同养分斑块的响应差异。在此基础上,计算不同家系福建柏幼苗叶片光合特性、荧光参数及酶活性和MDA含量的表型可塑性指数。【结果】(1)N、P异质斑块下,福建柏幼苗叶片的净光合速率(P_(n))、气孔导度(G_(s))和蒸腾速率(T_(r))均高于同质养分斑块和K异质斑块,493家系在N异质斑块、541家系在P异质斑块中的P_(n)均最高。K异质斑块和同质养分斑块下,福建柏幼苗叶片胞间CO_(2)浓度(C_(i))明显高于N、P异质斑块,N异质斑块下大部分福建柏家系幼苗叶片WUE较高。(2)在N异质斑块中,不同家系福建柏幼苗叶片的初始荧光值(F_(o))和PSⅡ最大光化学量子产量(F_(v)/F_(m))均较高,PSⅡ实际光化学效率(Yield)和光合电子传递速率(ETR)呈极显著正相关,N、P异质斑块中各家系Yield和ETR均较高。各斑块下福建柏家系PSⅡ的潜在活性(F_(v)/F_(o))无明显的变化规律,同一家系的F_(v)/F_(o)峰值在各种斑块间差异较大,其中500家系的F_(v)/F_(o)在各斑块之间差异显著,534家系的F_(v)/F_(o)在各斑块间无显著差异。(3)在P异质斑块中不同家系福建柏幼苗叶片POD活性均最高,在N异质斑块中大部分家系幼苗叶片POD活性较同质养分斑块有一定提升,在K异质斑块下福建柏家系幼苗叶片POD活性较同质养分斑块无明显规律。N、P异质斑块中,各家系福建柏幼苗叶片SOD和CAT活性均高于同质养分斑块,K异质斑块中POD、SOD和CAT 3种酶活性与同质养分斑块差异不大。N、P异质斑块中,福建柏幼苗叶片MDA含量均明显低于同质养分斑块,而K异质斑块中MDA含量则明显高于N、P异质斑块。(4)福建柏家系幼苗叶片荧光参数的表型可塑性指数均值最低,为0.29,光合特性的表型可塑性指数均值为0.52,而酶活性和MDA含量的表型可塑性指数均值为0.57。光合生理整体表型可塑性指数最高的是464家系,最低的是490家系。【结论】福建柏各家系幼苗叶片对N、P异质环境表现出较好的适应性,K异质环境对福建柏幼苗叶片光合作用强度和酶活性有一定的抑制作用;9个家系中,464家系具有较高的光合生理可塑性。