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沙漠公路防护林主要植物种凋落物的分解特征
张雪梅
学位类型博士
导师徐新文 ; 吕光辉
2017-05-01
学位授予单位中国科学院大学
学位授予地点新疆乌鲁木齐
学位专业理学博士
关键词沙漠公路防护林 盐生木本植物 分解速率 养分迁移 控制措施 Tarim Desert Highway Shelterbelt Woody Halophyte Decomposition Rate Nutrients Regulation Treatment
摘要塔里木沙漠公路沿线气候条件极端干旱、水资源匮乏、地下水矿化度高、风沙活动强烈、沙丘流动性极强。塔里木沙漠公路作为联通新疆南北疆的交通要道,是世界上穿越流动沙漠最长的等级公路。沙漠公路两侧建立了就地利用高矿化度地下水滴灌,以高抗逆性的柽柳属(Tamarix Linn.)、沙拐枣属(Calligonum L.)和梭梭属(HaloxylonBunge)灌木和小乔木为主要造林树种的生物防沙体系,即塔里木沙漠公路防护林。塔里木沙漠公路防护林所处的特殊地理环境,使得防护林凋落物分解所释放的养分成为植物营养和土壤肥力的主要来源。本文以塔里木沙漠公路防护林内乔木状沙拐枣(Calligonum arborescens)、梭梭(Haloxylon ammodendron)和多枝柽柳(Tamarix ramosissima)的凋落物为研究对象,于 2012 年~2014 年通过野外定点监测、原位分解试验、定点控制试验和室内凋落物样品分析,研究了塔里木沙漠公路防护林三种主要植物种凋落物的凋落量及其组成随定植年限增加的动态变化特征;分析了不同凋落物类型、不同定植年限防护林地、不同林龄凋落物和不同控制措施对凋落物的质量残留率、分解速率、分解过程中元素(C、N、P、K、Ca、Mg、木质素和纤维素)及元素比值动态变化特征的影响。揭示了塔里木沙漠公路防护林凋落物的凋落动态,探讨了控制措施对凋落物分解的影响;阐明了塔里木沙漠公路防护林凋落物分解过程、养分迁移模式及主要影响因素。主要结论如下:塔里木沙漠公路 1995 年、1998 年、2001 年、2004 年和 2006 年定植防护林的年总凋落量分别为 7.93 t·hm-2、6.19 t·hm-2、10.54 t·hm-2、9.10 t·hm-2、8.31 t·hm-2。各定植年限防护林三种植物的年凋落量均以柽柳最高,且秋季最高。凋落物组成均以梭梭同化枝、柽柳枝和沙拐枣同化枝的凋落量最高,占年总凋落量的 70.58%~88.93%。不同定植年限防护林,总凋落量和主要凋落组分凋落量的月动态趋势皆呈三峰型,峰值出现在 3~5 月、7 月、9~11 月,最高值均出现在 11 月。其余凋落物组成呈不规则变化且峰值出现的时间有所差异,梭梭老枝和柽柳叶为 5~7 月,梭梭果为 9~10月,沙拐枣果为 6~7 月,柽柳花和沙拐枣花凋落在 5~8 月。沙漠公路防护林组成物种的遗传和生态学特性、生理过程和气候条件影响凋落量及其组成的凋落动态。在塔里木沙漠公路不同定植年限防护林地,三种凋落物的分解速率从高到低分别为多枝柽柳枝(0.24~0.32 g·g-1·a-1),乔木状沙拐枣同化枝(0.17~0.23 g·g-1·a-1),梭梭枝(0.13~0.18 g·g-1·a-1)。三种凋落物分解速率最低值均出现在 1995a 防护林地;分解速率最高值,多枝柽柳枝和乔木状沙拐枣同化枝出现在 2004a 防护林地,梭梭枝出现在 2001a 防护林地。防护林定植年限通过凋落物分解的微环境直接或间接影响凋落物分解。凋落物初始 C、P、K 和 Mg 含量是分解前期的主要控制因子;初始木质素、纤维素含量,C/N 和 N/P 比值是分解中期和后期的主导因子。在 720d 的分解过程中,三种凋落物的 C 元素呈净释放模式,N 和 P 元素呈富集−释放模式,K 元素呈释放−富集模式,梭梭枝和乔木状沙拐枣同化枝的 Ca 和 Mg 元素呈净富集模式,多枝柽柳枝的 Ca 和 Mg 元素呈释放−富集模式。木质素和纤维素含量呈先升高后降低的变化趋势,木质素在分解后期低于初始浓度,纤维素始终高于初始浓度。沙漠公路防护林凋落物的元素迁移动态主要受到凋落物基质质量、元素自身特性、分解阶段和分解环境等的综合影响。不同控制措施以及不同林龄凋落物的地表和埋深处理,凋落物分解速率最高为梭梭同化枝,多枝柽柳枝次之,最低为乔木状沙拐枣同化枝。不同控制措施对凋落物分解速率的影响有所差异,对照组乔木状沙拐枣同化枝、梭梭同化枝和多枝柽柳枝凋落物分解速率分别为 0.53 g·g-1·a-1、0.94 g·g-1·a-1、0.55 g·g-1·a-1。各控制措施中,沙埋10cm三种凋落物的分解速率(0.92~1.69 g·g-1·a-1)最高,矿化度 29.7g·L-1 水灌溉的分解速率(0.31~0.54 g·g-1·a-1)最低。沙埋(0.69~1.69 g·g-1·a-1)、灌水周期 7d(0.69~1.34 g·g-1·a-1)、施用磷钾复合肥(0.57~1.25 g·g-1·a-1)和淡水灌溉(0.59~1.12 g·g-1·a-1)显著提高三种凋落物的分解速率。控制措施通过改变凋落物分解的微环境从而影响凋落物分解速率,水分是主要影响因素。凋落物的初始 N 含量和 C/N、木质素/N 比值是不同控制措施下凋落物分解速率的主要控制因素,凋落物初始养分含量能较好的预测初期分解速率,凋落物难分解物质是控制后期分解速率的主要因素,不同控制措施下凋落物分解各阶段主要控制因素有所差异。凋落物 420d 的分解过程中,不同控制措施对凋落物分解过程中元素迁移模式的影响有所异同。其中,淡水灌溉处理下乔木状沙拐枣同化枝和多枝柽柳枝在分解中后期呈现出 P 富集。高矿化度水灌溉处理下梭梭同化枝和多枝柽柳枝在分解中后期呈现出 Ca 富集。沙埋处理下乔木状沙拐枣同化枝在分解前期呈现出 N 富集,沙埋 10cm处理下三种凋落物呈现出 P 富集。施用氮肥处理下三种凋落物呈现出 N 富集,梭梭同化枝呈现出 Ca 富集。施用磷钾复合肥处理下乔木状沙拐枣同化枝在分解前期和中期呈现出 N 富集,三种凋落物皆呈现出 P 和 K 富集。灌水周期处理下乔木状沙拐枣和梭梭同化枝呈现出 Mg 释放。覆膜处理下多枝柽柳枝呈现出 P 释放;梭梭同化枝呈现出 Ca 富集。控制措施在一定程度上促使元素出现了富集现象,增加了凋落物的养分归还量。分解过程中木质素含量呈上升−下降趋势,因凋落物质量和控制措施的作用在不同时间出现下降的拐点,乔木状沙拐枣同化枝和多枝柽柳枝在分解后期低于初始值,梭梭同化枝木质素始终高于初始值;三种凋落物的纤维素含量呈波动上升趋势且始终高于初始值。不同林龄凋落物,7a 乔木状沙拐枣和梭梭同化枝的分解速率最高,15a 多枝柽柳枝凋落物分解速率最高。不同林龄凋落物的分解速率,初始 C 和 N 含量为分解前期主要限制因素,木质素和纤维素为分解后期主导因素。不同林龄三种凋落物的 C、P、K 和 Mg 元素皆呈释放模式,N 元素主要呈释放模式,Ca 元素主要呈富集−释放模式。各林龄三种凋落物的木质素含量呈上升−降低趋势,因凋落物类型的差异,乔木状沙拐枣同化枝在分解 120d 后低于初始值,梭梭同化枝和多枝柽柳枝始终高于初始值;纤维素含量呈波动上升趋势且始终高于初始值。本研究表明,在极端干旱的沙漠人工防护林,凋落物初始化学性质是凋落物分解速率的主要内在决定因素,水分和养分条件影响着凋落物的分解速率和养分归还。本文研究结果不仅对揭示特殊生境下沙漠人工防护林凋落物的凋落动态、分解速率和养分循环等有重要的理论意义,而且为沙漠人工防护林土壤性质的改善、土壤肥力的提高,防护林稳定和可持续发展管护措施的优化提供了数据支撑和科学依据。
其他摘要The Tarim Desert Highway, which was the important transport highway across the Taklimakan Desert from north to south, it was the world's longest highway that through mobile desert. It is extreme arid climate, scarcity of surface water resource, highly salinity groundwater, intensive wind erosion activity and shifting dunes along the Tarim Desert Highway. To build biological sand control system along the highway on both sides of the Tarim Desert Highway, which was drip irrigation with local salinity groundwater, and have the high stress resistance genus of Calligonum L., Haloxylon Bunge and Tamarix Linn. as the main forestation. Because of the special geographic environment of the Tarim Desert Highway Shelterbelt, the nutrients release by litter decomposition was the main source of plant nutrients and soil fertility. This study has selected the main litter components of Calligonum arborescens, Haloxylon ammodendron and Tamarix ramosissima in the Tarim Desert Highway Shelterbelt as object. From 2012 to 2014, through wild fixed point observation, in-situ decomposition experiment, control experiment, and laboratory analysis of litter, we have studied the dynamics of litterfall biomass and components changed with the planting year of shelterbelt. The litter mass remaining, litter decomposition rate, dynamic variation of elements (C, N, P, K, Ca, Mg, lignin, and cellulose) and element ratios on different litter types, planting year of shelterbelt, different stand ages and regulation treatments. To reveal the litterfall biomass dynamics, to discuss the effects of regulatory treatments on litter decomposition; to preliminary understanding the decompos ition and nutrients release and controlling factors to the main litter type for three species in the Tarim Desert Highway Shelterbelt. The main results as following: In the Tarim Desert Highway Shelterbelt, the annual litterfall biomass of shelterbelt planting years for 1995a, 1998a, 2001a, 2004a and 2006a were 7.93 t·hm-2, 6.19 t·hm-2,10.54 t·hm-2, 9.10 t·hm-2 and 8.31 t·hm-2, respectively. The total biomass of litterfall and components among species were decreased in the order of H. ammodendron, T. ramosissima and C. arborescens with different planting years,and the highest litterfall biomass in autumn. The largest litterfall biomass components were assimilative branches of H. ammodendron, branches of T. ramosissima, and assimilative branches of C. arborescens, accounting for 70.58%~88.93% of the total amount. There was similar seasonal dynamic in different planting year’s shelterbelt. Monthly changes in litterfall pattern showed three peaks in the total biomass and biomass for the assimilative branches of C. arborescens and H. ammodendron, and the branches of T. ramosissima, reaching the peaks in March to May, July, and September to November, and the highest amount in November. While no obvious litterfall pattern was found for leaves, seeds and others, they reaching the peaks in different times, branches of H. ammodendron and leaves of T. ramosissima in May to July, seeds of H. ammodendron in September to October, seeds of C. arborescens in June and July, flowers of C. arborescens and T. ramosissima only present from May to August. The genetic and ecological physiological processes and climatic conditions for the species in Tarim Desert Highway Shelterbelt have effect on the dynamics of litterfall biomass and components. The study on litter decomposition in shelterbelt of different planting years showed that litter decomposition rate were decrease as the order of branches of T. ramosissima (0.24~0.32g·g-1·a-1), assimilative branches of C. arborescens (0.17~0.23g·g-1·a-1), and branches of H. ammodendron (0.13~0.18g·g-1·a-1). The lowest decomposition rate was appeared at 1995a planting shelterbelt for three litters, the largest decomposition rate was appeared at 2004a planting shelterbelt for branches of T. ramosissima and assimilative branches of C. arborescens, at 2001a planting shelterbelt for branches of H. ammodendron. Shelterbelt planting years mainly through the micro environmental conditions have significant directly or indirectly effects on litter decomposition rates. The initial litter C, P, K and Mg content were the main controlling factors of early decomposition, initial lignin, cellulose and C/N, N/P ratio were the main limiting factors to later decomposition. During the litter decomposition for 720 days, C element for three litters showed net release pattern, N and P element showed enrichment‒release pattern, K element present release‒ enrichment pattern. Ca and Mg element for assimilative branches of C. arborescens and branches of H. ammodendron were showed accumulation pattern, and for the branches of T. ramosissima was showed release‒ enrichment pattern. The concentration of lignin and cellulose was showed the rise to reduce trend, the lignin concentration was lower than initial concentration at the later decomposition stage, while the cellulose concentration was always higher than initial concentration. The dynamics of elements was mainly influenced by litter substrate, the properties of elements, decomposition stage and micro environment. The study on litter decomposition under different regulation treatments and litter of different stand ages showed that litter decomposition rates were decreased in the order of assimilative branches of H. ammodendron, the branches of T. ramosissima and assimilative branches of C. arborescens. The different regulation treatments have significantly effects on litter decomposition rate, the decomposition rate for assimilative branches of C. arborescens, assimilative branches of H. ammodendron and the branches of T. ramosissima in control group were 0.53g·g-1·a-1, 0.94g·g-1·a-1, 0.55g·g-1·a-1. The highest decomposition rate for three litters was under sand buried depth of 10cm treatment (0.92~1.69g·g-1·a-1), lowest under irrigation with 29.7g·L-1 saline water (0.31~0.54g·g-1·a-1). The regulation treatments that have increase the decomposition were the treatments of sand buried (0.69~1.69g·g-1·a-1), irrigation period of 7 days (0.69~1.34g·g-1·a-1), phosphorus and potassium compound fertilizer addition (0.57~1.25g·g-1·a-1), and irrigation with fresh water (0.59~1.12g·g-1·a-1). The regulation measure affected the litter composition rate by changing the micro environment of litter decomposition, while moisture is the main factors. Initial litter N content and ratio of C/N lignin/N were the main factors affecting litter decomposition rates under different regulation treatments. The initial nutrients contents can forecast the initial decomposition rate, and the recalcitrant compounds were the controlling factors for late decomposition rate. The main determining factors for litter decomposition will make changed with the decomposition stage and regulation treatments. During the litter decomposition for 420 days, the influences of regulation treatments on litter element dynamics difference with treatments. The irrigation with fresh water will change assimilative branches of C. arborescens and branches of T. ramosissima to P accumulation at the middle and late decomposition stages. The irrigation with high saline water will change assimilative branches of C. arborescens to Ca accumulation at the middle and late decomposition stages. The sand buried will change assimilative branches of C. arborescens and branches of T. ramosissima to N accumulation at the initial decomposition stages, and will change assimilative branches of H. ammodendron to P accumulation. The nitrogen fertilizer addition will change three litters to N accumulation, and assimilative branches of H. ammodendron to Ca accumulation. The phosphorus and potassium compound fertilizer addition will change assimilative branches of C. arborescens to N accumulation at the initial and middle decomposition stages, three litters to P and K accumulation. The film will change branches of T. ramosissima to P release, assimilative branches of H. ammodendron to Ca accumulation. The regulation treatments have contributed to the accumulation of some elements, increasing the nutrient return of litter. During the decomposition, the concentration of lignin was showed the rise–reduce trend, because of the litter substrate quality and influence of regulation treatments, the point for declining was different, the lignin concentration for assimilative branches of C. arborescens and branches of T. ramosissima was lower than initial concentration at the later decomposition stage, while assimilative branches of H. ammodendron was always higher than initial concentration. The cellulose concentration was showed rising trend and always higher than initial concentration. The study on litter decomposition with litter of different stand ages showed that the decomposition rate for assimilative branches of H. ammodendron and C. arborescens were highest at stand ages of 7a, for branches of T. ramosissima were highest at stand ages of 15a. The litter decomposition rate for different stand ages litters were significantly correlated with initial content, the initial C and N content were the main limiting factor in early decomposition, initial lignin and cellulose content were the leading factors for late decomposition. The C, P, K, and Mg element of three litters for different stand ages under surface and buried treatments was showed release pattern. The N element was mainly showed release pattern. The Ca element was mainly showed enrichment‒release pattern. During the decomposition process, the lignin concentration was showed rise–downward trend, the lignin concentration was lower than the initial value after decomposition 120 days for assimilative branches of C. arborescens, and always higher than the initial value for assimilative branches of H. ammodendron and branches of T. ramosissima. The cellulose content was always higher than the initial concentration for three litters. In conclusion, the litter initial content was the determine factors on litter decompos ition rate, and moisture and nutrient condition have effect on decompos ition rate and nutrient return in extreme arid shelterbelt. The research on the litterfall biomass and litter decomposition characteristics of Tarim Desert Highway Shelterbelt, not only important in theory for understanding the litterfall biomass dynamics, litter decomposition rate and nutrient cycles under special habitats, but also provides data support and scientific basis for improving soil properties, enhancing soil fertility, and optimizing management treatments for the stability and sustainable development of Tarim Desert Highway Shelterbelt.
学科领域生态学
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14796
专题研究系统_荒漠环境研究室
研究系统_空间对地观测与系统模拟研究室
作者单位中国科学院新疆生态与地理研究所
推荐引用方式
GB/T 7714
张雪梅. 沙漠公路防护林主要植物种凋落物的分解特征[D]. 新疆乌鲁木齐. 中国科学院大学,2017.
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