Do rates of litter decomposition tell us anything we really need to know?

Results of several long-term studies of non-woody litter decomposition in forests indicate that we need to rethink why and how we measure rates of litter decomposition. Effects on litter decomposition rates were postulated to explain some of the nutritional effects of factors such as tree species, forest harvesting and fertilization. However, the accumulated experimental evidence indicates that litter decomposition rates do not mediate these responses. Many studies have reported litter mass loss becoming extremely slow at values considerably below 100%, indicating that early decay rates may not accurately foreshadow the entire decay process. Exclusion of soil faunal activities from current measurements of decomposition rates seriously reduces the likelihood that we are properly modeling decomposition. Finally, the use of regression and correlation analyses to determine which climate or initial litter quality factors control decay rate has led to many unwarranted and potentially misleading conclusions. These concerns are illustrated with examples from a suite of litter decomposition studies in British Columbia, Canada. Insights into nutrient cycling and carbon storage in ecosystems are more likely to arise from measuring the mass and nutrient content of annual litter input and determining the maximum decomposition limit and nutrient content at that stage, than by measuring early rates of decay. Improved predictions of relative decay rates of plant litters are likely to arise from a holistic approach based on plant life attributes rather than correlations based on individual initial litter chemistry parameters. Finally, a better understanding of the fate of faecal material of soil fauna is necessary before we can accurately predict and model litter decomposition.     

Behavior of four broad-leaved tree species used to revegetate eroded granite hill slopes

Information on primary growth behavior after planting is required for mixed-plantation revegetation using broad-leaved species. To estimate primary growth, especially from the perspective of crown coverage and changing growth rates, we examined the growth and survival of four broad-leaved species that are frequently used in erosion-control plantations in Japan. The species studied were Myrica rubra Sieb. et Zucc., Alnus pendula Matsum., Quercus glauca Thunb., and Q. serrata Thunb. The survival, height, and basal diameter of planted trees were measured over a 4-year period, and crown area was calculated over a 3-year period. We found a negative relationship between relative growth rate (RGR) and survival rate, suggesting that fast growth may be fatal when resources are severely limited. The relative height growth rate (RHGR) of A. pendula was especially high during the early period of the study (1997–1999) and then drastically declined, whereas the opposite tendency was observed in Q. glauca. The results of stem allometry analyses conformed to the specific relationships between height growth and diameter growth of the four species; increases in stem thickness based on height increments were smaller in the pioneer species A. pendula. Between-species differences in coverage per planted tree (mean crown area multiplied by survival rate) were small as a result of the negative relationship between coverage area and survival rate.     

灌木林对地表风况及空气动力学参数影响的野外调查研究——以丰宁满族自治县小坝子乡为例

通过野外实地调查和定位观测,系统研究了灌木林盖度和高度对地表风况及空气动力学参数的影响。结果表明:风速轮廓线受灌木林覆盖度和高度的影响显著;风蚀率随灌木林覆盖度的减少呈指数增加,灌木林高度对土壤风蚀影响相对较小。空气动力学粗糙度及零风速平面位移高度均与灌木林覆盖度之间呈幂函数关系。灌木林高度对空气动力学粗糙度的影响不明显。     

北美红杉扦插生根的影响因素分析

研究了扦插基质,激素种类、浓度与处理时间,采条部位以及基因型对北美红杉扦插成活率的影响。结果表明:基质配比、激素种类、浓度及处理时间、采条部位等对北美红杉扦插成活率均有显著影响。基质配比以珍珠岩∶草炭=7∶3效果最好;激素以1 000 mg/kg ABT速蘸处理效果为佳;枝条顶部插穗好于下部插穗。不同基因型的扦插成活率差异显著。选取合适的基因型,采集顶部插穗,用1 000 mg/kg的ABT速蘸处理,扦插在珍珠岩∶草炭=7∶3的基质上能获得理想的效果。     

涂高效抽枝宝和刻芽对苹果幼树1a生枝条萌芽和新梢生长的影响

以2013年栽植的‘2001’富士苹果幼树为试材,研究了涂高效抽枝宝和刻芽对拉枝后1a生枝条萌芽和新梢生长的影响。结果表明:涂高效抽枝宝、刻芽和自然生长的枝条萌芽率分别为89.95%、89.05%和69.13%;单株抽出新梢量分别为30.74个、18.41个和16.07个。涂高效抽枝宝与刻芽的萌芽物候期基本一致,均比自然生长的提前2d。自然生长枝条上的新梢生长量要显著高于涂高效抽枝宝和刻芽处理,涂高效抽枝宝处理的新梢生长量与刻芽处理无显著差异。     

墨西哥柏幼苗生长和光合生理对氮沉降的响应

选取2年生墨西哥柏幼苗为试验对象,以NH4NO3为外加氮源,通过模拟氮沉降试验,研究其生长和光合生理对氮增加的响应.结果表明:幼苗在高氮水平处理下其生长不断受到抑制,而在中氮水平处理下,幼苗生长不断得到促进.随着施氮浓度增加,墨西哥柏幼苗的根质量和根长均降低,表明氮处理抑制根的生长,分配到根部分的生物量下降.幼苗的净光合速率呈现出随氮处理浓度增加而先增加后降低的趋势,即中氮组的净光合速率最高,而高氮组开始逐渐下降.幼苗的水分利用效率变化趋势与净光合速率一致.幼苗叶片光合色素含量随氮处理水平增加而增加.说明短期内中氮水平对幼苗生长和光合作用影响最显著,而高氮水平对幼苗光合色素影响最显著.     

季铵铜防腐木中有效成分总流失率的动力学分析

以季铵铜防腐剂处理的南方松为试材,参照美国AWPA E11-06标准,分析10、30和50℃3种温度条件下防腐木中有效成分的总流失率,并基于时间-温度叠加原理,运用阿伦尼乌斯方程,进行总流失率的动力学分析.结果表明:3种温度条件下铜和DDAC的流失趋势是一致的.根据铜和DDAC总流失率,得出防腐木表面的活化能为Ea=54.59 kJ/moL,相关系数R2达到0.98以上,拟合性较好,由此证明可以用动力学分析方法预测ACQ防腐材中铜和DDAC在10～50℃温度范围内总流失率变化.     

6种杀菌剂对桑树轮纹病菌的室内毒力测定

在室内培养条件下,采用菌丝生长速率法测定了6种杀菌剂对桑膝节霉的抑制效果。结果显示,6种杀菌剂对桑树轮纹病病原菌桑膝节霉的菌丝生长均有不同程度的抑制作用,其中50％多菌灵、75％百菌清、10％苯醚甲环唑、250 g／L丙环唑、450 g／L咪酰胺和70％甲基硫菌灵的EC50分别为2.45 mg／L、2.51 mg／L、1.68 mg／L、1.31 mg／L、0.46 mg／L和7.99 mg／L。测试药剂中,供试桑树轮纹病菌对450 g／L咪酰胺最为敏感,250 g／L丙环唑次之。450 g／L咪酰胺和250 g／L丙环唑皆可作为防治桑树轮纹病的最佳药剂,用于田间试验。     

7种园林绿化树种蒸腾耗水特性研究

以香樟、桂花、无患子、黄山栾树、沙朴、紫弹朴和珊瑚朴等7种园林绿化树种为研究对象,采用盆栽实验方法,用Li-6400便携式光合测定仪和ACS-D11电子天平等仪器,通过对其在不同天气条件下的瞬时蒸腾速率、日耗水量等进行了测定和研究。结果表明:1在水分充足条件下,7种供试树种在不同天气条件下的耗水速率基本一致,均是早晚低、中午前后高,呈双峰或单峰曲线;2日耗水量在不同天气条件下差异达到了极显著水平,而在不同树种间差异达到了显著水平,其中紫弹朴的日耗水量是极显著高于香樟,且显著高于其他5个树种。     

不同土壤类型对毛竹林生长的影响研究

研究了福建省常见的7种土壤类型（红壤、黄红壤、黄壤、紫色土、红土、黄泥土、水稻土）对毛竹林出笋数、新竹成竹率和新竹胸径的影响。结果显示,毛竹林出笋数及新竹胸径在不同土壤类型间均存在极显著差异,新竹成竹率在不同土壤类型处理间的差异不显著。研究结果认为,在毛竹造林时应优先选择退耕的农地,即耕作土壤黄泥土和红土。