大兴安岭地区森林雷击火与闪电的关系

林火是森林生态系统的重要影响因子.随着全球气候变暖,林火,特别是雷击火有增多的趋势.本文对我国东北大兴安岭地区1966-2007年的林火数据及相应的闪电和气象资料进行分析.结果表明:1966-2007年,该地区雷击火的次数及其过火面积都呈显著增加趋势.影响雷击火的气象条件与研究时间尺度有关,年尺度的雷击火与降水显著相关,相关系数达-0.489;月尺度的雷击火则与气温显著相关,相关系数为0.18.雷击火与闪电的关系也与时间尺度有关,年尺度的雷击火与闪电关系不明显,受降水影响较大;月尺度的雷击火与闪电具有较好的相关性,且受降水的影响;日尺度的雷击火在降水量＞5 mm时与闪电关系不明显,但当降水量＜5 mm时,雷击火与闪电次数呈正相关.据此,发展了基于闪电定位仪数据的火险指数算法以及大兴安岭地区的森林雷击火预报模型.经2005-2007年雷击火验证,该模型的预报准确率＞80％.     

太白山针叶林的Fuzzy分类研究

应用模糊聚类分析法和模糊图论分析对太白山针叶林进行了数量分类比较研究。将２６个样地分为两大类共７个群落类型。研究结果表明,两种方法在植物群落分类研究中,不但是可行的,而且所分类的实际结果是等价的,与实际观测情况也是吻合的。其中的图论法直接依据模糊相似系数得到树状图,简便易行,显示出更大的适用性。     

High and dry: post‐fire tree seedling establishment in subalpine forests decreases with post‐fire drought and large stand‐replacing burn patches

Aim Climate warming and increased wildfire activity are hypothesized to catalyse biogeographical shifts, reducing the resilience of fire‐prone forests world‐wide. Two key mechanisms underpinning hypotheses are: (1) reduced seed availability in large stand‐replacing burn patches, and (2) reduced seedling establishment/survival after post‐fire drought. We tested for regional evidence consistent with these mechanisms in an extensive fire‐prone forest biome by assessing post‐fire tree seedling establishment, a key indicator of forest resilience. Location Subalpine forests, US Rocky Mountains. Methods We analysed post‐fire tree seedling establishment from 184 field plots where stand‐replacing forest fires were followed by varying post‐fire climate conditions. Generalized linear mixed models tested how establishment rates varied with post‐fire drought severity and distance to seed source (among other relevant factors) for tree species with contrasting post‐fire regeneration adaptations. Results Total post‐fire tree seedling establishment (all species combined) declined sharply with greater post‐fire drought severity and with greater distance to seed sources (i.e. the interior of burn patches). Effects varied among key species groups. For conifers that dominate present‐day subalpine forests (Picea engelmannii, Abies lasiocarpa), post‐fire seedling establishment declined sharply with both factors. One exception was serotinous Pinus contorta, which did not vary with either factor. For montane species expected to move upslope under future climate change (Larix occidentalis, Pseudotsuga menziesii, Populus tremuloides) and upper treeline species (Pinus albicaulis), establishment was unrelated to either factor. Greater post‐fire tree seedling establishment on cooler/wetter aspects suggested local topographic refugia during post‐fire droughts. Main conclusions If future drought and wildfire patterns manifest as expected, post‐fire tree seedling establishment of species that currently characterize subalpine forests could be substantially reduced. Compensatory increases from lower montane and upper treeline species may partially offset these reductions, but our data suggest important near‐ to mid‐term shifts in the composition and structure of high‐elevation forests under continued climate warming and increased wildfire activity.     

Isolation and introgression in the Intermountain West: contrasting gene genealogies reveal the complex biogeographic history of the American pika (Ochotona princeps)

Aim We studied the history of colonization, diversification and introgression among major phylogroups in the American pika, Ochotona princeps (Lagomorpha), using comparative and statistical phylogeographic methods. Our goal was to understand how Pleistocene climatic fluctuations have shaped the distribution of diversity at mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) loci in this alpine specialist. Location North America’s Intermountain West. Methods We accumulated mtDNA sequence data (c. 560–1700 bp) from 232 pikas representing 64 localities, and sequenced two nuclear introns (mast cell growth factor, c. 550 bp, n = 148; protein kinase C iota, c. 660 bp, n = 139) from a subset of individuals. To determine the distribution of major mtDNA lineages, we conducted a phylogenetic analysis on the mtDNA sequence data, and we calculated divergence times among the lineages using a Bayesian Markov chain Monte Carlo approach. Relationships among nuclear alleles were explored with minimum spanning networks. Finally, we conducted coalescent simulations of alternative models of population history to test for congruence between nDNA and mtDNA responses to Pleistocene glacial cycles. Results We found that: (1) all individuals could be assigned to one of five allopatric mtDNA lineages; (2) lineages are associated with separate mountain provinces; (3) lineages originated from at least two rounds of differentiation; (4) nDNA and mtDNA markers exhibited overall phylogeographic congruence; and (5) introgression among phylogroups has occurred at nuclear loci since their initial isolation. Main conclusions Pika populations associated with different mountain systems have followed separate but not completely independent evolutionary trajectories through multiple glacial cycles. Range expansion associated with climate cooling (i.e. glaciations) promoted genetic admixture among populations within mountain ranges. It also permitted periodic contact and introgression between phylogroups associated with different mountain systems, the record of which is retained at nDNA but not mtDNA loci. Evidence for different histories at nuclear and mtDNA loci (i.e. periodic introgression versus deep isolation, respectively) emphasizes the importance of multilocus perspectives for reconstructing complete population histories.     

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(...     

Invertebrate community and stream substrate responses to woody debris removal from an ice storm-impacted stream system, NY USA

We assessed the influence of ice-storm-derived debris dams on aquatic macroinvertebrates and stream substrates in a high-gradient watershed in the eastern Adirondack Mountains of New York State. Using a modification of electrofishing techniques, invertebrates were collected once before (June 2000) and once after (June 2001) wood removal from the downstream reach in each of six pairs of reaches (second and third-order streams). Stream substrates were also mapped in 2000 and 2001 to evaluate shifts in dominant substrates within a reach following wood removal. The following metrics were used to compare the invertebrate communities before and after wood removal: genera similarity, Shannon–Weiner equitability, taxa richness, dominant taxon, percent dominance and functional feeding group relative abundance. The changes in removal reaches were evaluated relative to changes in upstream reference reaches using a Before-After Control-Impact (BACI) design and analysis. Stream substrates did not change significantly in response to wood removal, although a trend toward coarser substrates was observed following removal. Following wood removal, the relative proportion of grazers increased upstream and downstream from removed dams in all streams; however, comparisons of other metrics indicated no significant response to removal. Invertebrate responses to wood removal were lower than expected, perhaps due to the presence of abundant boulder-formed pools in this high gradient system. Electronic supplementary material Electronic supplementary material is available for this article at and accessible for authorised users.     

Do rivers function as genetic barriers for the plateau wood frog at high elevations?

Using the plateau wood frog Rana kukunoris from the Hengduan Mountains as a model system, we tested whether rivers form significant genetic barriers (the riverine barrier hypothesis) to high elevation amphibians. Samples were collected from eight sites across three major river drainages, the Min, the Dadu and the Yalong Rivers, and the population genetic structure of these frogs was evaluated with data from eight microsatellite DNA loci. A large amount of genetic structure was found, and the pairwise F _ST ranged from 0.022 to 0.508 and a global F _ST was 0.215. Both analysis of molecular variance and isolation by distance analysis suggested that rivers, mountain ridges and geographic distances all contributed significantly to the population structure. However, no single landscape has prominent barrier effect to the plateau wood frog populations. An assignment analysis using the computer program Structure grouped the eight populations into four population clusters, and no single type of landscape can sufficiently explain the clustering. In conclusion, rivers do not appear to be the leading genetic barriers for the plateau wood frog. The strong population genetic structure is likely the consequence of attributes of the species, as opposed to environmental fragmentation, and the barrier effect of the landscapes is largely swamped by the large amount of intrinsic population structure.     

贺兰山马鹿冬春季生境的选择

2007年12月～2008年1月和2008年4～5月,在贺兰山利用痕迹检验法和直接观察法对马鹿阿拉善亚种冬春季生境选择进行研究.通过在选定的15条沟段里进行调查,冬春季各测定了131个和181个样方的18种生态因子.结果表明,冬春季贺兰山马鹿在植被类型、优势乔木、灌木密度、灌木高度、灌木距离、坡向、坡位、海拔高度、距裸岩距离和隐蔽级10种生态因子上差异极显著(P ＜ 0.001),其余生态因子无显著差异(P ＜ 0.05),相对于冬季生境而言,马鹿春季更偏爱选择以油松和青海云杉为优势乔木的山地针叶林带,灌木密度大、高度高、距离近,半阴半阳坡的中坡位,海拔较高,距裸岩较近,隐蔽程度高的生境.典则判别系数显示冬春季马鹿在生境选择上存在一定程度的重叠,但春季马鹿的分布范围要比冬季更广一些,Wilk's λ值显示冬春季马鹿的生境选择具有较高的差异性(Wilk's λ = 0.683,x2 = 116.995,df = 13,P ＜ 0.001).逐步判别分析表明在区分冬春季马鹿生境方面有一系列生态因子发挥作用,依照贡献值的大小依次为:乔木密度、灌木距离、坡度、海拔高度、距水源距离、距裸岩距离和隐蔽级,由这7个变量构成的方程对冬春季马鹿生境的正确区分率达到79.9%,其中对春季的误判率为22.1%,对冬季的误判率为20.6%.     

湖北西部山地革螨及恙螨名录

自1989年以来,先后从湖北西部山地6个不同海拔、12个不同类型生境捕获的啮齿、食虫等小型哺乳动物体外采集到一大批革螨、恙螨和吸虱标本,经初步整理,鉴定有革螨l1科32属73种、恙螨有3亚科11属41种和亚种、吸虱3种,其中有中国新纪录1种,籁氏巨刺螨Macronyssus leucippe（Domrow）和湖北新纪录41种。     

长期施肥对黄土高原旱地黑垆土水稳性团聚体的影响

通过27年的长期定位试验,研究了长期施肥对黄土高原旱地黑垆土水稳性团聚体的影响.结果表明：与自然土壤相比,黑垆土开垦后,0～10 cm和10～20 cm土层＞0.25 mm的水稳性团聚体含量分别下降了21.35%和38.82%;0.5 mm以上各粒级的水稳性团聚体含量均呈下降趋势,其中>5 mm和5～2 mm大粒径团聚体的下降幅度最大;而0.5～0.25 mm的水稳性团聚体含量却增加了104.75%和23.13%.0～10 cm土层各粒级水稳性团聚体含量均高于10～20 cm土层.单施有机肥和有机无机肥配施处理5～2 mm粒级的水稳性团聚体含量增加最多,>5 mm粒级次之;增施有机肥、有机无机肥配合施用和秸秆还田处理能显著增加大粒径水稳性团聚体含量,改善土壤团聚体的结构.各处理0～10 cm土壤水稳性团聚体平均质量直径（MMD）均大于10～20 cm土层;自然土壤的团聚体MMD显著高于同层次耕作土壤,长期施肥处理MMD大于无肥对照,有机物质培肥处理明显高于化肥处理.土壤团聚体MMD与＞0,25 mm水稳性团聚体含量呈显著正相关.