基于混合像元分解和知识规则的人工刺槐林健康分类

提出一种基于精度较高的Landsat TM数据检测刺槐林枯梢状况的方法,整个过程分为:1)利用监督分类提取出林地分布范围,制作刺槐林地掩膜;2)对刺槐林地利用线性光谱混合模型进行混合像元分解,得到健康刺槐、非光合作用绿色植被(NPV)、土壤的丰度图,定义刺槐林的健康分类等级:健康或轻度枯梢、中度枯梢、重度枯梢或死亡;3)利用决策树分类器对丰度图像、归一化植被指数(NDVI)以及经缨帽变换获取的亮度和绿度成分定义一组规则,进行刺槐林生长健康状况分类,分类结果与实地样方数据具有较好的一致性,利用林冠分级向导进行精度分析,精度达82.2%,Kappa系数为0.752。     

面向对象的刺槐林健康等级分类方法

以高分辨率IKONOS影像为数据源,将呈区域性分布的刺槐林划分为孤岛、军马场和黄河故道3个地区;采用面向对象的方法,结合随机森林算法,筛选出基于J-M距离确定的最佳窗口和方向的8个纹理特征及2个植被指数特征中较为重要的特征。结果表明,孤岛地区的最佳分割尺度为3、军马场地区的最佳分割尺度为12,尺度9和3在黄河故道地区不同健康类型中有不同的优越性;最佳纹理窗口为13×13,最佳纹理方向为45°。结合实地样方数据进行精度评价得到孤岛地区的总精度为91.15%、军马场地区为87.57%、黄河故道地区为91.57%,与实地样方数据具有较好的一致性。该方法可为森林退化监测制图、防护林恢复及区域生态建设提供科学思路。     

黄土丘陵沟壑区不同退耕年限刺槐林地土壤氮素动态特征

土壤无机氮的可利用性是影响植物生长发育和植被演替进程的关键因子之一,尤其在生态系统十分脆弱的黄土丘陵沟壑区更为重要。因此,采用时空代换法,通过选取不同退耕年限（10 a、20 a、30 a、40 a）的刺槐林地及相邻对照草地为研究对象,系统研究刺槐林在生长季（4~9月）土壤无机氮净转化速率的变化情况。结果表明：（1）刺槐林地土壤NO₃^--N平均含量约是对照草地的4.57倍,而NH₄⁺-N在两个样地之间没有显著差异。（2）刺槐林地及对照草地土壤在7~8月以硝化作用为主,在4~5月和8~9月以氨化过程为主,且刺槐林地氮素净转化速率大于对照样地。（3）刺槐林地土壤NO₃^--N在前30 a处于积累状态,随后呈现消耗趋势。总而言之,退耕地刺槐林营造可以减少土壤NO₃^--N的淋失,提高NO₃^--N净转化速率,但刺槐林NO₃^--N的累积状态在30 a后变为消耗状态。所以要采取应对30 a以上林龄的刺槐林采取间伐措施,以促进刺槐林的健康发展。     

植绿排岩场 打造鞍山“绿肺”

10月25日,笔者在鞍山市外环路沿线看到,路南侧的东鞍山铁矿排岩场已被平整成25°倾斜的山坡。今年春天种植的一株株刺槐苗、毛樱桃、山楂树苗、樟子松树苗组成了一块黄绿交织的绒毯,覆盖住了过去灰尘四散的岩体,为近在咫尺的北部市区构筑起一道天然的绿色屏障。这里是东鞍山铁矿排岩场地质环境治理工程的最后一个标段。标段项目经理陈兴源说:"等明年春天你们再来,长高的刺槐映着樱桃、山楂花,别提多美了。"作为鞍山市2012年为群众办的20件实事项目之一,东鞍山铁矿排岩场有1250亩得到治理,眼前山、东鞍山和大孤山铁矿矿山排岩场有500亩得到治理,植下的90.2万株树木让昔日的不毛之地披上绿装。10     

Age-related changes of carbon accumulation and allocation in plants and soil of black locust forest on Loess Plateau in Ansai County,Shaanxi Province of China

The effects of reforestation on carbon(C) sequestration in China′s Loess Plateau ecosystem have attracted much research attention in recent years. Black locust trees(Robinia pseudoacacia L.) are valued for their important use in reforestation and water and soil conservation efforts. This forest type is widespread across the Loess Plateau, and must be an essential component of any planning for C sequestration efforts in this fragile ecological region. The long-term effects of stand age on C accumulation and allocation after reforestation remains uncertain. We examined an age-sequence of black locust forest(5, 9, 20, 30, 38, and 56 yr since planting) on the Loess Plateau to evaluate C accumulation and allocation in plants(trees, shrubs, herbages, and leaf litter) and soil(0–100 cm). Allometric equations were developed for estimating the biomass of tree components(leaf, branch, stem without bark, bark and root) with a destructive sampling method. Our results demonstrated that black locust forest ecosystem accumulated C constantly, from 31.42 Mg C/ ha(1 Mg = 10~6 g) at 5 yr to 79.44 Mg C/ha at 38 yr. At the ′old forest′ stage(38 to 56 yr), the amount of C in plant biomass significantly decreased(from 45.32 to 34.52 Mg C/ha) due to the high mortality of trees. However, old forest was able to accumulate C continuously in soil(from 33.66 to 41.00 Mg C/ha). The C in shrub biomass increased with stand age, while the C stock in the herbage layer and leaf litter was age-independent. Reforestation resulted in C re-allocation in the forest soil. The topsoil(0–20 cm) C stock increased constantly with stand age. However, C storage in sub-top soil, in the 20–30, 30–50, 50–100, and 20–100 cm layers, was age-independent. These results suggest that succession, as a temporal factor, plays a key role in C accumulation and re-allocation in black locust forests and also in regional C dynamics in vegetation.     

毁田卖土 国法难容——郑州经济技术开发区司赵村毁地卖土案始末

说来也巧,2005年5月18日,郑州经济技术开发区检察院副院长李俊华一上班,就拿起了办公桌上的一张报纸看了起来,当他看到郑州一家媒体“绿色家园”栏目环保征文其中的一篇文章时,他的目光停住了,文章的题目是《毁林卖砂触目惊心》,文中写道:“爸爸带我到南曹乡司赵村时看到,这里的几百亩林地被人为制造了一个个大峡谷,宛如课本上见到的黄土高原。这里的风沙真大,就像电视上楼兰古城消失前的景观。但这里一年前,却长着浓密的刺槐林……”这篇文章的内容引起了李俊华的注意,因为,早在2005年年初,该院根据群众反映,已就此事向警方发出了《要求说…     

刺槐盛花期预报模式的研究

根据积温学说的原理，研究了刺槐生长发育速度与平均气温的关系。得出了刺槐生长发育的下温度为12℃，达到盛花期需要≥12℃活动积温460℃；并以活动积温460℃作为盛花期预报指标，利用逐步回归的方法对刺槐花期前期大量因子进行筛选，建立了刺槐盛花期的积温预报方法和统计预报模式，应用效果良好。     

Soil carbon stock and flux in plantation forest and grassland ecosystems in Loess Plateau,China

Carbon sequestration occurs when cultivated soils are re-vegetated. In the hilly area of the Loess Plateau, China, black locust(Robinia pseudoacacia) plantation forest and grassland were the two main vegetation types used to mitigate soil and water loss after cultivation abandonment. The purpose of this study was to compare the soil carbon stock and flux of these two types of vegetation which restored for 25 years. The experiment was conducted in Yangjuangou catchment in Yan′an City, Shaanxi Province, China. Two adjacent slopes were chosen for this study. Six sample sites were spaced every 35–45 m from summit to toe slope along the hill slope, and each sample site contained three sampling plots. Soil organic carbon and related physicochemical properties in the surface soil layer(0–10 cm and 10–20 cm) were measured based on soil sampling and laboratory analysis, and the soil carbon dioxide(CO2) emissions and environmental factors were measured in the same sample sites simultaneously. Results indicated that in general, a higher soil carbon stock was found in the black locust plantation forest than that in grassland throughout the hill slope. Meanwhile, significant differences in the soil carbon stock were observed between these two vegetation types in the upper slope at soil depth 0–10 cm and lower slope at soil depth 10–20 cm. The average daily values of the soil CO2 emissions were 1.27 μmol/(m2·s) and 1.39 μmol/(m2·s) for forest and grassland, respectively. The soil carbon flux in forest covered areas was higher in spring and less variation was detected between different seasons, while the highest carbon flux was found in grassland in summer, which was about three times higher than that in autumn and spring. From the carbon sequestration point of view, black locust plantation forest on hill slopes might be better than grassland because of a higher soil carbon stock and lower carbon flux.     

黄土高原刺槐、油松人工幼林生态系统碳汇研究

为定量评价黄土高原人工林的生态效益,采用固定样地法选择研究刺槐、油松主要人工林生态系统有机碳密度、碳储量及碳分配,结果表明:对照荒地生态系统有机碳总储量为51.29 t/hm2,7 a生刺槐人工林为57.76 t//hm2,6 a生油松林为63.05 t/hm2,刺槐与油松林生态系统有机碳密度分别比荒地提高12.62%和22.94%;荒地在0～80cm土层土壤碳储量为50.86 t//hm2,7 a生刺槐林为46.40 t/hm2,与荒地相比降低了8.77%,6 a生油松林为58.40 t/hm2,与荒地相比增加了14.83%;荒地凋落物层碳储量为0.02 t/hm2,7 a生刺槐林为0.16 t/hm2,与荒地相比增加了666.67%,6 a生油松林为0.02 t/hm2,与荒地相比降低了0.95%;荒地灌草层碳储量为0.41 t/,hm2,7 a生刺槐林为0.39 t/hm2,与荒地相比降低了6.37%,6 a生油松林为0.42 t/hm2,与荒地相比增加了2.45%,说明黄土高原营造人工生态林具有明显的碳增汇效应.