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91.
92.
刺槐林是中国北方丘陵半干旱区典型的生态防护林树种之一。通过自然降雨径流场定位观测试验,本文对辽宁西部地区(1850-12225E,4024-4234N)刺槐生态防护林及其采伐迹地的产流、产沙特征和土壤水分动态变化规律进行了定量研究。采伐迹地与刺槐林地相比二者之间的产流量和产沙量存在显著差异,采伐迹地的产流量和产沙量比刺槐林地分别增加40%-177%和180%-400%。典型降雨产流水文过程线显示,刺槐林地径流峰值比采伐迹地低1.0-2.5?0-3m3穝-1,且径流峰值出现的时间比采伐迹地滞后10-20min。谐波分析表明,刺槐林地与采伐迹地土壤含水量随年内降水量变化分干、湿两季,呈周期性变化,刺槐林地土壤年平均含水量比采伐迹地高2.3%。研究结果表明:刺槐生态防护林具有涵养水源、增加土壤水分、减少地表径流与土壤侵蚀的重要作用。图2表4参12。 相似文献
93.
马尾松木荷混交林林分结构和土壤肥力研究 总被引:10,自引:0,他引:10
对马尾松木荷混交林与马尾松纯林林分生长、径阶分布及土壤理化性质研究表明 :马尾松与木荷以 2∶1比例行状混交 ,马尾松生长快 ,林分各径阶呈正态分布 ,林分生产力高、结构稳定。马尾松木荷混交林不仅提高土壤通透性和蓄水性 ,促进土壤良好结构形成 ,而且增加土壤养分含量 ,改善土壤肥力状况 相似文献
94.
土壤干旱与柿叶片膜脂及脂质过氧化的关系 总被引:3,自引:0,他引:3
在不同灌水条件下,对盆栽柿幼树叶片组织相对含水量,细胞透性,超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性,膜脂脂肪酸组分和脂质过氧化作用产物——丙二醛(MDA)含量进行测定,结果表明:当水势Ψ_S下降时,细胞透性(PERM)增大,SOD和CAT活性下降,脂质过氧化作用增强,膜脂中不饱和脂肪酸含量下降,饱和脂肪酸含量升高。试验证明:土壤水势(?)_S=-3.80±0.47bar,各指标变化最明显。本试验条件下,幼柿叶片SOD活性,CAT活性,MDA含量,PERM,不饱和脂肪酸指数(IUFA)与组织相对含水量(RWC)和土壤水势(Ψ_s)间具显著相关关系。 相似文献
95.
集水措施是干旱半干旱地区解决因降雨少且季节间分配不均带来的水资源短缺的主要措施之一,有关微集水区防渗处理材料及其防渗效果的研究也已广泛开展。本文通过5 年(1992-1996)的野外试验对半干旱黄土高原微集水系统生物结皮覆盖对造林的影响进行了研究。结果表明,结皮接种3 年后,集水区表面大部分为结皮所覆盖,其集水功能已经部分地表现出来。在春季3 个典型时段内浅层土壤含水量与对照相比显著提高(0.05 水平),1m 土层内春季月均含水量均比对照提高了0.9%–6.04%。同时在研究期末(1996 年)结皮处理的样地内树木个体的树高(H)、胸径(DBH)和地径(DGL)均较对照有显著提高(0.05 水平),提高幅度分别为22.38%、17.34%和20.49%。作为一种生物防渗材料,生物结皮具有无污染、自我繁殖、使用期长和投入小等特点,因此很可以作为西部大开发中植被恢复的主要集水材料,进一步的工作应放在干旱环境下当地适宜结皮种类的选择及其快速繁殖技术上。 相似文献
96.
Variation in infiltration with landscape position: Implications for forest productivity and surface water quality 总被引:1,自引:0,他引:1
Thomas J. Sauer Sally D. Logsdon J. Van Brahana John F. Murdoch 《Forest Ecology and Management》2005,220(1-3):118-127
Variation of infiltration rates with landscape position influences the amount, distribution, and routing of overland flow. Knowledge of runoff patterns gives land managers the opportunity to affect changes that optimize water use efficiency and reduce the risk of water quality impacts. The objective of this study was to assess the effect of landscape position and associated soil properties on infiltration in a small (147 ha) forest/pasture watershed in the Ozark Highlands. Three previously reported studies measured infiltration rates using double ring, sprinkling, single ring, and tension infiltrometers on soils at varying landscape positions. Although large variation in infiltration rates was observed among measurement techniques, upland and side slope soils (Nixa and Clarksville) had consistently lower infiltration rates compared to the soil in the valley bottom (Razort). A conceptual understanding of watershed runoff is developed from these data that includes infiltration excess runoff from the Nixa and Clarksville soils and saturation excess runoff on the Razort soil. Management of the soil water regime based on this understanding would focus on increasing infiltration in upland soils and maintaining the Razort soil areas in forest. Forest productivity would be enhanced by increasing plant-available water in upland soils and decreasing flooding on the Razort soil. Surface water quality would be improved by reducing the transport of potential water contaminants from animal manure applied to upland pastures. 相似文献
97.
M.E.?Isaac A.M.?GordonEmail author N.?Thevathasan S.K.?Oppong J.?Quashie-Sam 《Agroforestry Systems》2005,65(1):23-31
The conversion of forests to agroecosystems or agroforests comes with many changes in biological and chemical processes. Agroforestry,
a tree based agroecosystem, has shown promise with respect to enhanced system nutrient accumulation after land conversion
as compared to sole cropping systems. Previous research on tropical agroforestry systems has revealed increases in soil organic
matter and total organic nitrogen in the short term. However, research is lacking on long-term system level sustainability
of nutrient cycles and storage, specifically in traditional multi-strata agroforestry systems, as data on both the scope and
duration of nutrient instability are inconclusive and often conflicting. This study, conducted in Ghana, West Africa, focused
on carbon and nitrogen dynamics in a twenty-five year chronosequence of cacao (Theobroma cacao Linn.) plantations. Three treatments were selected as on-farm research sites: 2, 15 and 25-year-old plantations. Soil carbon
(C, to a depth of 15 cm) varied between treatments (2 years: 22.6 Mg C ha−1; 15 years: 17.6 Mg C ha−1; 25 years: 18.2 Mg C ha−1) with a significant difference between the 2- and 15- and the 2- and 25-year-old treatments (p < 0.05). Total soil nitrogen in the top 15 cm varied between 1.09 and 1.25 Mg N ha−1 but no significant differences were noted between treatments. Soil nitrification rates and litter fall increased significantly
with treatment age. However, photosynthetically active radiation (PAR) and soil temperature showed a significant decrease
with age. No difference was found between decay rates of litter at each treatment age. By 25 years, system carbon sequestration
rates were 3 Mg C ha−1 y−1, although results suggest that even by 15 years, system-level attributes were progressing towards those of a natural system. 相似文献
98.
Arbuscular mycorrhizas and performance of Polylepis australis trees in relation to livestock density
Polylepis australis trees endemic to Argentina dominate the canopy of subtropical high altitude forests. Here, livestock rearing is the main economic activity and is suspect of the low performance of P. australis trees through direct and indirect effects which could include the reduction in arbuscular mycorrhizal fungi (AMF) and their benefit to trees. To elucidate the role of AMF, we compare plant performance indicators, arbuscular mycorrhizal (AM) colonization and AMF communities in 20 trees distributed in two areas of central Argentina which differed in livestock grazing intensity. The area with high livestock density presented more soil degradation and trees with a lower overall plant performance than the area with reduced livestock density. The AM colonization values of P. australis were considerably higher than reported for other tree species and the area with high livestock density had a lower proportion of arbuscules and higher proportion of hyphae, while vesicles and AM colonization – all structure considered together – did not differ between areas. Overall AMF spore number and of most species when considered separately was significantly higher in the area with high livestock density, suggesting a high tolerance and adaptation of AMF to livestock. We conclude that a reduction in livestock improves the performance of P. australis, that this improvement could be mediated by an increase in the proportion of arbuscules, but there does not appear to be any limitation in AM colonization or AMF spore number which could otherwise be limiting forest restoration. 相似文献
99.
100.
Variations in soil chemical properties and microbial biomass in artificial gaps in silver fir stands
Changes in soil chemical and microbiological parameters in small (185 m2) and medium (410 m2) gaps, created in mature silver fir (Abies alba Mill) stands (mean height 30 m) in the Calabrian Apennines (Southern Italy), were studied over 2 years. Medium gaps had high
soil temperature and photosynthetically active radiation (PAR) transmittance and low soil moisture. Within small gaps we detected
a greater amount of organic matter, with respect to under canopy cover sites and medium gaps. Moreover, a different trend
of the organic matter between small and medium gaps was observed. In the medium gaps, with respect to under canopy cover sites
and small gaps, we found a relatively low content of organic matter, associated to a lower amount of humic acid, which suggested
that the organic substrate undergoes a mineralization rather than a humification process. An opposite trend was observed in
small gaps, where the increase of organic matter content, associated to an increase of humic acid and microbial biomass, suggested
a better humification process. Moreover, in small gaps the highest level of urease and the greatest fluorescein diacetate
(FDA) hydrolysis were observed. The different trend of organic matter observed in small and medium gaps may be related to
changes in the environmental conditions. PAR transmittance, significantly higher in medium gaps, contributed to increase soil
temperature and decrease soil moisture, affecting soil microbial populations and organic matter trend. These results suggest
that the creation of small gaps represents the silvicultural practice with minor environmental impact. 相似文献