亚热带水产养殖寒灾预警系统的设计与实现

通过对亚热带水产养殖现状的分析，论述了亚热带水产养殖寒灾预警系统建设的必要性、研究的目标和任务，详细介绍了系统的结构和框架，以及亚热带水产养殖寒灾预警的几个关键问题及其解决方法。     

亚热带农业小流域水体氮素及其稳定同位素分布特征

为控制流域氮素养分流失、改善流域水体环境,以亚热带典型农业小流域脱甲河为研究对象,对表层水体铵态氮(NH_4~+-N)、硝态氮(NO_3--N)浓度和水体硝态氮δ~(15)N(δ~(15)N-NO_3-)、沉积物有机质δ~(15)N(δ~(15)N-Org)浓度进行了连续试验观测,分析氮素浓度及其稳定同位素值的时空特征,探讨影响氮素分布的环境因子及水体NO_3-和沉积物有机质氮素的可能来源。结果表明:水体NO_3--N浓度明显高于NH_4~+-N,均值分别为1.62 mg·L~(-1)和0.90mg·L~(-1),并且分别在6月、8月及冬季较高;城镇区和农田区水体NH_4~+-N浓度与其他类型区差异显著(P0.05),并且显著高于其他水体;NO_3--N浓度在城镇区、农田区及山间林地区较高,水库区较低。支流NH_4~+-N浓度高于干流,均表现为冬季春季夏季秋季;干流、支流NO_3--N浓度分别表现为冬季夏季秋季春季、秋季冬季夏季春季。源头和出口处水体均表现为NO_3--N浓度高于NH_4~+-N,源头处氮素浓度低于出口处。水体δ~(15)N-NO_3-及底泥δ~(15)N-Org值分布范围分别为-19.87‰~8.11‰和-0.69‰~6.51‰,水体δ~(15)N-NO_3-最高值在Ⅲ级河段,最低值出现于Ⅳ级河段,各级河段间水体δ~(15)N-NO_3-11月差异较小,而1、2月差异明显;河流底泥δ~(15)N-Org最高值也位于Ⅲ级河段,而最低值则在Ⅰ级河段,Ⅲ、Ⅳ级河段δ~(15)N-Org值随时间变化趋势较为一致,Ⅰ、Ⅱ级河段δ~(15)N-Org最小值出现于1月。总之,脱甲河水体存在氮素污染现象且以外源输入为主,水体氮素来源主要为土壤有机质、人工合成肥料及陆源有机质,开展流域氮素分布及来源研究对认识流域尺度氮污染物的源解析具有一定科学意义。     

Sprouting characteristics of a subtropical evergreen broad-leaved forest following clear-cutting in Okinawa,Japan

This study explores the sprouting characteristics of an evergreen broad-leaved forest after clear-cutting based on a survey of 1,893 stumps of 62 tree species in Okinawa, Japan. The sprouting capabilities of the stumps varied among tree species. The stumps of 60 species could produce sprouts, while those of the other two species could not. In 10 of the sprouting species, the mean sprout-stem number was higher than 4.0 stems per stump; nine sprouting species showed low sprouting capabilities. Additionally, Castanopsis sieboldii and Schima wallichii, the dominant species, exhibited high sprouting capabilities. Further, the sprouting capabilities varied with stump diameter at breast height (DBH). Stumps with a larger DBH tended to have a higher mean number of sprout stems per stump, higher DBH, and higher tree height than the smaller stumps. The forest stands regenerated by sprouting might recover into a tree community similar to that before clear-cutting.     

牧压和肥力对亚热带山地牧草净生产的影响

在亚热带山地湿润环境条件下,研究牧压和土壤肥力对人工草地净生产的影响.三年试验结果表明,绵羊在轮牧下,产草量和磷肥对全年及各月牧草净生产具有显著影响.禁牧时,夏季地上生物量积累到一定程度后,只有很少量的净生产.放牧时,产草量在1000 kg DM/hm2左右时,净生产最大,当产草量低于300 kg DM/hm2以下时,净生产量则降低.每年施一次P2O5 36～60 kg/hm2,可以显著增加牧草净生产,尤以春末夏初时施肥更为显著.最低产草量出现在不施肥处理.     

SWOT框架下的北亚热带人工草地鼠害防控响应浅析

基于SWOT模型,从防控优势、防控劣势、防控机会、防控威胁四个方面浅析了北亚热带人工草地极具代表性的昆明小哨草场的鼠害防控条件。结果表明,防控优势是农牧民生产实践中积累的有效防控鼠害经验;防控劣势是鼠害危害程度大,不易被发现;防控机会是防控方法增多,应该借鉴引用;防控威胁是草场退化滋养了鼠害的发生,资金和研发力度不够。提出了建立健全北亚热带区草地鼠害监控系统,将鼠害控制在萌芽阶段,使鼠害造成的损失降到最低,实现北亚热带区人工草地的健康、持续、稳定发展。     

The impact of marine reserves on nekton diversity and community composition in subtropical eastern Australia

The effectiveness of marine reserve protection on the biodiversity of aquatic assemblages (i.e. nekton) in subtropical eastern Australia was examined within two small (<6 km²) marine reserves and four non-reserve areas. The two marine reserves, and their corresponding non-reserves, were located in different geographical locations within Moreton Bay (north and south) and sites were surveyed with multiple hauls of a seine net. Species richness, evenness, density and mean size of the inshore communities were compared between the reserves and non-reserves. No statistical significant difference was detected in species richness between the areas however species evenness was significantly lower in the only non-reserve site impacted by commercial net fishing. Mean size of nekton was found to be significantly greater in the marine reserves compared to non-reserves but no statistical significant difference was found in the density of nekton between the study sites. Multivariate analysis revealed differences in community composition, particularly between the geographical locations where areas were impacted by different types of fishing pressure (recreational v commercial). These results highlight the impact commercial fishing can have on entire nekton assemblages, not just on targeted species. Our study demonstrates that the small marine reserves in Moreton Bay are protecting marine biodiversity and are thus at least partially achieving their management objective (to enhance the zone’s marine biodiversity).     

Effects of artificial afforestation and successional stage on a lowland forest bird community in southern China

To examine the relationship between forest succession after severe logging forestry practices and the composition of avian communities, we investigated how forest bird composition and guild structure change as a function of structural properties along a successional gradient, including a climax mature forest (>400 years), a rehabilitated mixed forest (50-70 years), and a disturbed Masson pine forest (70 years) of the Dinghushan Nature Reserve, Guangdong Province, China. Of a total of 51 resident species recorded, mixed forests hosted the highest numbers of individuals and species, reflecting the high species richness of both forest and non-forest species. For forest-dependent species, however, mature stands had the highest observed and estimated species richness. Of 6 habitat-use guilds identified, vertical-profile generalists and understory-birds formed the two dominant guilds, accounting for 54.0% and 38.7% of all individuals respectively. The results of canonical correspondence analysis (CCA) clearly showed that most forest-dependent species were associated with high proportions of native canopy cover and the mean density of dead trees and large trees, which are characteristic of old-growth mature forests (horizontal heterogeneity) at stand level. Accordingly, conservation efforts should focus on the specialized requirements of the most habitat-restricted species in the future, especially for understory insectivores (Babblers) and large-tree users in mature subtropical monsoon forests of southern China. Moreover, since regenerating mixed forests are very similar to mature forests in both vegetation structure and bird community composition, we recommend that logging cycles (>50 years) be increased to a minimum of 50 years in southern China, so that a balance between economic and ecological interest can be reestablished.     

亚热带水产养殖寒灾预警系统的设计与实现

通过对亚热带水产养殖现状的分析,论述了亚热带水产养殖寒灾预警系统建设的必要性、研究的目标和任务,详细介绍了系统的结构和框架,以及亚热带水产养殖寒灾预警的几个关键问题及解决方法。     

亚热带山地多年生黑麦草与白三叶混播草地生物量动态研究

本研究对亚热带中山地区多年生黑麦草与白三叶混播人工草地牧草生物量年动态进行监测。通过九年观测,研究结果表明,草地建植初期总生物量呈由低到高的变化趋势,峰值出现在第三年,以后随着生长发育年限的延续,生物量则由高到低逐年降低。草地群落中的多年生黑麦草生物量由高到低,而白三叶生物量则由低到高呈逐年上升的趋势。禾草与豆草的比例,由建植初期3:1下降到九年后的0.47:1。     

增温对亚热带森林土壤呼吸变化的影响

[目的]研究增温条件下亚热带森林土壤呼吸的变化。[方法]以福建省亚热带杉木林为对象,通过埋设加热电缆的方法开展亚热带模拟土壤增温试验,采用13C脉冲标记技术,高效追踪土壤气体的变化情况。[结果]在试验期间,增温后土壤总呼吸、异养呼吸的δ13C均高于对照组,δ13C先下降后上升,然后继续下降,与初始状态持平;增温后土壤总呼吸速率与异养呼吸速率变化趋势基本一致,且异养呼吸速率与其对应的δ13C的相关性大于土壤呼吸与其对应的δ13C的相关性。因而,在气候变暖条件下,增温对土壤中的微生物以及根系造成影响,导致土壤呼吸以及异养呼吸变化会有较大的浮动。[结论]该研究为进一步了解增温后亚热带森林地区土壤呼吸的变化提供了一定的参考依据。