Modelling biomass of mountainous grasslands by including a species composition map

High mountain grasslands offer multiple goods and services to society but are severely threatened by improper land use practices such as abandonment or rapid intensification. In order to reduce abandonment and strengthen the common extensive agricultural practice a sustainable land use management of high mountain grasslands is needed. A spatially detailed yield assessment helps to identify possible meadows or, on the contrary, areas with a low carrying capacity in a region, making it easier to manage these sites. Such assessments are rarely available for remote and inaccessible areas. Remotely sensed vegetation indices are able to provide valuable information on grassland properties. These indices tend, however, to saturate for high biomass. This affects their applicability to assessments of high-yield grasslands.The main aim of this study was to model a spatially explicit grassland yield map and to test whether saturation issues can be tackled by consideration of plant species composition in the modelling process. The high mountain grassland of the subalpine belt (1800 – 2500 m a.s.l.) in the Kazbegi region, Greater Caucasus, Georgia, was chosen as test site for its strong species composition and yield gradients.We first modelled the species composition of the grassland described as metrically scaled gradients in the form of ordination axes by random forest regression. We then derived vegetation indices from Rapid Eye imagery, and topographic variables from a digital elevation model, which we used together with the multispectral bands as predictive variables. For comparison, we performed two yield models, one excluding the species composition maps and one including the species composition map as predictors. Moreover, we performed a third individual model, with species composition as predictors and a split dataset, to produce the final yield map.Three main grassland types were found in the vegetation analysis: Hordeum violaceum-meadows, Gentianella caucasea-grassland and Astragalus captiosus-grassland. The three random forest regression models for the ordination axes explained 64%, 33% and 46% of the variance in species composition. Independent validation of modelled ordination scores against a validation data set resulted in an R² of 0.64, 0.32 and 0.46 for the first, second and third axes, respectively. The model based on species composition resulted in a R² = 0.55, whereas the benchmark model showed weaker relationships between yield and the multispectral reflectance, vegetation indices, and topographical parameters (R² = 0.42). The final random forest yield model used to derive the yield map resulted in 62% variance explained and an R² = 0.64 between predicted and observed biomass. The results further indicate that high yields are generally difficult to predict with both models.The benefit of including a species composition map as a predictor variable for grassland yield lies in the preservation of ecologically meaningful features, especially the occurrence of high yielding vegetation type of Hordeum violaceum meadows is depicted accurately in the map. Even though we used a gradient based design, sharp boundaries or immediate changes in productivity were visible, especially in small structures such as arable fields or roads (Fig. 6b), making it a valuable tool for sustainable land use management. The saturation effect however, was mitigated by using species composition as predictor variables but is still present at high yields.     

大仓鼠肥满度的研究

本文依公式K=100W/L~3计算了大仓鼠肥满度。统计结果表明,雌性肥满度大于雄性肥满度。肥满度随年龄增长而减小。不同作物类型样地中大仓鼠的肥满度变化不明显。不同季节肥满度有一定的变化,主要与繁殖和气候有关。肥满度与种群密度之间不存在明显的对应关系。     

Dioecy inMikania (Compositae:Eupatorieae)

For the first time dioecy inMikania and in the tribeEupatorieae is described and discussed. The condition is known only in members of theMikania swartziana Griseb. complex, a group of eight species, all endemic to the Greater Antillean Islands of Cuba, Hispaniola, and Jamaica.     

国人坐骨大切迹的测量与性别判别分析

本文对614件(男358件女256件)国人坐骨大切迹进行了八项测算。对坐骨大切迹在性别鉴定上的作用进行了探讨。     

伤害性刺激和非伤害性刺激对大鼠丘脑后核神经元电活动的影响

用微电极细胞外记录的方法,观察内脏痛、躯体痛和触觉刺激对大鼠丘脑后核(PO)中770个神经元电活动的影响,其中305(38.3％)个对伤害性刺激起反应,103(13.4％)个对触觉刺激起反应。对伤害性刺激反应的神经元中多数对躯体痛和内脏痛刺激均起反应且反应形式相同,少数反应不同或相反,对触觉刺激反应的神经元中多数也对两种伤害性刺激均起反应,只对触觉刺激反应的神经元很少。     

The palatability of Arctic willow for greater snow geese: the role of nutrients and deterring factors

Temporary feeding on willow buds and leaves by nesting greater snow geese provided us with an opportunity to test the relative importance of nutrients and deterrents in affecting the palatability for geese of a food plant with a high phenol content. Protein, total phenol and fiber (neutral and acid detergent fiber, and lignin) were analyzed in closed and open buds and in rolled and open leaves. Geese feed on willows at the open-buds and rolled-leaf stages but not at the closed-bud and open-leaf stages. Protein content was higher in open buds and rolled leaves (25–27%) than in closed buds and open leaves (19–21%). Phenol content increased during leaf emergence but was already high (14%) in rolled leaves. All plant fibers were very high in closed buds but declined rapidly during leaf emergence. The increase in phenol: protein ratio appeared to be more important than phenol concentration alone in explaining the cessation of feeding by geese on willow leaves whereas the high fiber content of closed buds may explain why they were not eaten. Our results illustrate the value of a multifactorial approach in the study of the food selection process in herbivores.     

大兴安岭北部不同海拔天然林土壤胞外酶化学计量特征及其季节动态

研究了大兴安岭北部奥克里堆山不同海拔(750～1420 m)天然林土壤胞外酶活性(EEA)和酶计量比的变化特征及影响机制。结果表明: 海拔、季节及其交互作用对β-葡萄糖苷酶(BG)、N-乙酰-β-氨基葡萄糖苷酶(NAG)、亮氨酸氨基肽酶(LAP)和酸性磷酸酶(AP)活性均存在显著影响。5月,BG和NAG活性随海拔升高呈逐渐增大趋势,AP活性随海拔升高呈先升高后降低的趋势。7月,NAG活性随海拔升高而增大,AP活性则先升高后降低。9月,不同海拔上NAG活性变化幅度较大,在1420 m处活性最高,为124.22 nmol·h^-1·g^-1。随着海拔的升高,酶化学计量比ln(BG)∶ln(NAG+LAP)呈降低的趋势。除海拔830 m外,7月化学计量比值最高。土壤C、N、P转化酶活性对数转换后的比值为1∶1.25∶0.82。海拔和土壤温度是影响土壤胞外酶的主要因素,土壤温度与BG、NAG和AP呈显著正相关。ln(BG)∶ln(NAG+LAP)和ln(NAG+LAP)∶ln(AP)与pH分别呈显著正相关和负相关,与DOC分别呈显著负相关和正相关,而ln(BG)∶ln(AP)受土壤容重的影响较大。     

粤港澳大湾区生态系统服务时空演化及其权衡与协同特征

打造国际一流湾区和世界级城市群的粤港澳大湾区,生态保护、环境优化与城市发展、经济开放具有同等重要地位,掌握其城镇化过程中生态系统及其服务变化状况有助于科学合理、有针对性的制定生态保护修复相关政策。基于2000-2015年粤港澳大湾区生态系统宏观格局变化,分析了大湾区生态系统生产力、水源涵养、土壤保持服务的时空演化特征,进而探讨了供给与调节服务之间的权衡与协同关系。结果表明：（1）森林与农田是大湾区的主体生态系统,面积占大湾区国土面积的54.1%和22.8%,近15年由于城镇面积快速增长（增幅达68.6%）,导致森林、农田、湿地面积不断减少。（2）基于净初级生产力的供给服务量和土壤保持量整体上均呈现轻度增加趋势,特别是江门、肇庆等生态服务主要提供区域;东南部最高、北部次之、中部偏低的水源涵养量,除西北部呈现增加趋势以外,其它区域皆呈现减少趋势;城镇扩张是生态系统供给、调节服务明显减少的主要影响因素。（3）大湾区生态系统供给服务与水源涵养、土壤保持调节服务之间的相关关系均以协同为主,然而,在大湾区东北部和南部的广州、惠州、江门等区域呈现明显的权衡关系,提示大湾区发展过程中,需要在这些呈现权衡关系的区域实施有针对性的生态保护修复措施,优化绿地结构、保护生态空间,减少城镇扩张和不合理的人类活动对生态系统服务的消极影响,建设生态优美、文化繁荣的美丽湾区。     

基于地区GDP和人口空间分布的粤港澳大湾区生境质量时空演变研究

经济发展与人口集聚引起的土地利用变化对一个地区的生态环境影响显著,生境质量评价在一定程度上可以反映区域生物多样性的状况。分析地区生境质量与社会经济、人口密度的关系,能够为区域生态安全及可持续发展提供科学依据。运用InVEST模型,以粤港澳大湾区2005、2010、2015、2018年四期土地利用数据分析生境质量的时空演变特征,结合社会经济及人口分布数据探究各地区城市发展与生境质量的权衡关系,并预测2030年大湾区不同情景下生境质量状况。结果表明：（1）2005-2018年粤港澳大湾区整体生境质量逐年降低,呈现出中部低、四周高的环状分布,生境破碎、建设用地增加是生境质量下降的主要原因。（2）珠三角九市生境质量与地区总GDP呈弱负相关,与第一产业产值呈中等正相关,与第二产业产值呈中等负相关,与第三产业产值呈弱正相关。（3）粤港澳大湾区生境质量与人口密度存在较大的不平衡,最主要的空间为高生境质量-低人口密度、低生境质量-高人口密度两种类型。（4）通过空间管制分区,预测2030年大湾区规划保护情景下大湾区平均生境质量较2018上升0.04,达到0.599,生境质量有明显改善。