Land-use induced soil carbon stabilization at the expense of rock derived nutrients: insights from pristine Andean soils.

Soils contain significantly more carbon than the atmosphere, hence we should understand how best to stabilize it. Unfortunately, the role of human interventions on soil organic carbon (SOC) persistence in the Anthropocene remains vague, lacking adequate sites that allow unbiased direct comparisons of pristine and human influenced soils. Here we present data from a unique study system in the High Andes that guarantees pristineness of the reference sites by physical inaccessibility through vertical cliffs. By comparing the isotopic signatures of SOC, mineral related carbon stabilization, and soil nutrient status across grazed versus pristine soils, we provide counterintuitive evidence that thousands of years of pastoralism increased soil C persistence. Mineral associated organic carbon (MAOC) was significantly higher in pastures. Land use increased poorly crystalline minerals (PCM's), of which aluminum correlated best with MAOC. On the other hand, human's acceleration of weathering led to acidification and higher losses of cations. This highlights a dilemma of lower soil quality but higher persistence of SOC due to millennia of pastoralism. The dynamics of soil genesis in the Anthropocene needs better understanding, but if human-induced weathering proves generally to promote soil carbon persistence it will need to be included in climate-soil feedback projections.

Comparative analysis of the complete plastid genomes in Prunus subgenus Cerasus (Rosaceae): Molecular structures and phylogenetic relationships.

Prunus subgenus Cerasus (cherry) is an economically important group that distributed in temperate regions of the northern hemisphere. However, shared interspecific morphological traits and variability across taxa of Cerasus are among the impediments to taxonomic efforts to correctly delimit taxa. This is further complicated by a lack of genetic information on these taxa, with no focused genomic or phylogenetic studies being done on Cerasus. In this study, we conducted comparative analysis on the complete plastid genomes (plastomes) of 20 Cerasus species to gain a greater understanding of the attributes of the plastome of these taxa while helping resolve their phylogenetic placement in Prunus sensu lato and interspecific relationships within the subgenus. Our results displayed that (1) the plastomes of the 20 Cerasus species studied exhibited a typical quadripartite structure with conversed genome arrangement, structure, and moderate divergence. (2) The average size of complete plastomes for the Cerasus taxa studied was 157,861 bp, ranging from 157,458 to 158,024 bp. A total of 134 genes were annotated, including 86 protein-coding genes, 40 tRNAs, and 8 rRNAs across all species. In simple sequence repeat analysis, we found Cerasus had a comparable number of dispersed and tandem repeats to those identified in other angiosperm taxa, with only P. pseudocerasus found to contain trinucleotide repeats. Nucleotide diversity analysis revealed that the trnG-GCC gene and rpl32-trnL region had the highest Pi value showing potential as phylogenetic markers. (3) Two phylogenetic trees of the plastomes verified the monophyletic relationship of Cerasus and provided a more resolved species-level phylogeny. Our study provides detailed plastome information for exploring the phylogeny of subg. Cerasus taxa. We identified various types of repeats and nucleotide diversity hotspots, which can be a reference for species identification and reconstruction of phylogenetic relationships.

A phylogeny of species near Agrostis supporting the recognition of two new genera, Agrostula and Alpagrostis (Poaceae, Pooideae, Agrostidinae) from Europe.

Based on a molecular DNA phylogeny of three plastid (rpl32-trnK, rps16 intron, and rps16-trnK) and nuclear ITS regions investigating 32 species of Agrostidinae, we describe two new genera, Agrostula gen. nov. with a single species and Alpagrostis gen. nov. with four species; provide support for five species in a monophyletic Podagrostis; and include a small sample of 12 species of a monophyletic Agrostis s.s. (including the type and most species of Neoschischkinia), that separates into two clades corresponding to A. subg. Agrostis and A. subg. Vilfa. Agrostula differs from Agrostis in having leaf blades with pillars of sclerenchyma which are continuous between the adaxial and abaxial surface of the blades, dorsally rounded glumes with blunt to truncate and erose to denticulate apices, florets ½ the length of the glumes, lemmas equally wide as long, widest at (or near) apex, apices broadly truncate, irregularly 5 to 7 denticulate to erose, awnless, anthers longer than the lemmas, and rugose-papillose caryopses. Alpagrostis differs from Agrostis in having geniculate basally inserted awns and truncate lemma apices with lateral veins prolonged from the apex in (2)4 setae. The following eight new combinations are made: Agrostula truncatula, Agrostula truncatula subsp. durieui, Alpagrostis alpina, Alpagrostis alpina var. flavescens, Alpagrostis barceloi, Alpagrostis setacea, Alpagrostis setacea var. flava, and Alpagrostis schleicheri. In addition, we provide a key separating Agrostula and Alpagrostis from Agrostis s.s. and other genera previously considered as synonyms of Agrostis; lectotypify Agrostis alpina Scop., A. schleicheri Jord. & Verl., A. truncatula Parl., and A. truncatula var. durieui Henriq.; and neotypify A. setacea Curtis.

ResumenSobre la base de una filogenia molecular de ADN de tres regiones plastidiales (rpl32-trnK, rps16 intrón y rps16-trnK) e ITS nuclear de 32 especies de Agrostidinae, describimos dos nuevos géneros, Agrostula gen. nov. con una sola especie, y Alpagrostis gen. nov. con cuatro especies; mostramos el apoyo para las cinco especies dentro de Podagrostis monofilético; e incluimos una pequeña muestra de 12 especies de Agrostis s.s (que incluye el tipo y la mayoría de las especies de Neoschischkinia), este último dividido en dos subclados que corresponden a A. subg. Agrostis y A. subg. Vilfa. Agrostula se diferencia de otras especies de Agrostis por tener láminas foliares con haces de esclerénquima continuos entre las superficies adaxial y abaxial de los limbos, glumas de dorso redondeado y ápice embotado a truncado y eroso a denticulado, antecios de ½ de la longitud de las glumas, lemas tan anchas como largas, lo más ancho en o cerca del ápice, ápices anchamente truncados, irregularmente 5 a 7 denticulados o erosos, sin arista, anteras más largas que los lemas y cariopsis rugosa-papilosa. Alpagrostis se diferencia de otras especies de Agrostis por tener aristas geniculadas insertas basalmente y ápices de lema truncados con venas laterales que se prolongan en (2)4 arístulas apicales. Presentamos las siguientes ocho nuevas combinaciones: Agrostula truncatula, Agrostula truncatula subsp. durieui, Alpagrostis alpina, Alpagrostis alpina var. flavescens, Alpagrostis barceloi, Alpagrostis setacea, Alpagrostis setacea var. flava y Alpagrostis schleicheri. Además, proporcionamos una clave que separa Agrostula y Alpagrostis de Agrostis s.s. y otros géneros previamente considerados como sinónimos de Agrostis, lectotipificamos Agrostis alpina Scop., A. schleicheri Jord. & Verl., A. truncatula Parl. y A. truncatula var. durieui Henriq. y neotipificamos A. setacea Curtis.

Re-instatement of Sorbus harrowiana (Rosaceae), based on morphometric analysis.

Sorbus harrowiana (≡Pyrus harrowiana), previously considered a synonym of Sorbus insignis (≡Pyrus insignis) in the Flora of China, is re-instated here and shown to be distinct from S. insignis, based on morphometric analysis, coupled with herbarium and field investigation. We also present for the first-time full descriptions, distributional records and notes for S. harrowiana and S. insignis.

New records and key to Poa (Pooideae, Poaceae) from the Flora of Southern Africa region and notes on taxa including a diclinous breeding system in Poa binata.

Four species of Poa L. are newly reported for sub-Saharan Africa and southern Africa, Poa compressa L., P. iconia Azn., P. infirma Kunth and P. nemoralis L. This is the first report of P. iconia from Africa. Vouchers at PRE of P. bulbosa L. all belong to var. vivipara Koeler, those of P. iconia belong to var. iconia and the one of P. trivialis L. belongs to var. trivialis. Two subspecies are recognised in P. pratensis L.: subsp. irrigata (Lindm.) H.Lindb. and subsp. pratensis. We also designate a lectotype for P. iconia and second-step lectotype for P. leptoclada Hochst. ex A.Rich. and report the first recording of a diclinous breeding system in P. binata Nees. Our account updates the treatment in Identification Guide to Southern African Grasses (Fish et al. 2015) including a key to the taxa and notes on infrageneric taxonomy, DNA subtypes, ecology, chromosome numbers and breeding systems.

Festuca drakensbergensis (Poaceae): A common new species in the F. caprina complex from the Drakensberg Mountain Centre of Floristic Endemism, southern Africa, with key and notes on taxa in the complex including the overlooked F. exaristata.

We present taxonomic notes on the Festuca caprina complex from southern Africa that includes description and illustration of the new species F. drakensbergensis from the Drakensberg Mountain Centre of Floristic Endemism of South Africa and Lesotho. Festuca drakensbergensis can be differentiated from F. caprina s.l. by forming lax short tufts with extravaginally-branching tillers and lateral-tending cataphyllous shoots or rhizomes present, basal foliage reaching < ½ the length of the culms, with generally shorter leaves and shorter anthers, 0.8-1.6(-1.8) mm long. The species also differs from the overlooked species F. exaristata - currently known from two collections from Lesotho - by its fibrous basal sheaths, usually sharp, keel-like leaf blade midrib, drooping panicle with lightly to densely scabrous pendent panicle branches, longer lemmas, 4.5-5.8 mm long, with awns usually present, 0.5-3 mm long, ovary apices sparsely to densely hairy and anthers 0.8-1.6(-1.8) mm long. Taxonomic notes on the different taxa of the F. caprina complex in southern Africa are also provided, including images, key, and lectotypification of F. caprina var. curvula. This research adds a further two endemic species (F. drakensbergensis and F. exaristata) and two endemic varieties (F. caprina var. irrasa and F. caprina var. macra) to the Drakensberg Mountain Centre of Floristic Endemism.

Agrostis and Podagrostis (Agrostidinae, Poaceae) from páramos of Boyacá, Colombia: synoptic taxonomy including a key to Colombian species.

We present taxonomic notes, including updated species descriptions and images, for the nine species of Agrostis and one species of Podagrostis found in páramos of Departamento Boyacá, Colombia (A. boyacensis, A. breviculmis, A. capillaris, A. foliata, A. cf. imberbis, A. mertensii, A. perennans s.l., A. stolonifera, A. tolucensis, Podagrostis trichodes). Agrostis cf. imberbis, previously known from austral South America, is newly recorded for Colombia, A. capillaris is a new regional record for Boyacá, and the name Agrostis stuebelii is lectotypified. We include keys in English and Spanish to distinguish the 15 species of Agrostis and two species of Podagrostis that are cited as occurring in Colombia.

ResumenSe presentan notas taxonómicas, además de descripciones e imágenes actualizadas, para las nueve especies de Agrostis y una especie de Podagrostis encontradas en los páramos del departamento de Boyacá, Colombia (A. boyacensis, A. breviculmis, A. capillaris, A. foliata, A. cf. imberbis, A. mertensii, A. perennans s.l., A. stolonifera, A. tolucensis, Podagrostis trichodes). Agrostis cf. imberbis previamente conocido de Sudamerica austral, se presenta como un nuevo registro para Colombia y A. capillaris se presenta como un nuevo registro regional para Boyacá con el nombre de Agrostis stuebelii también lectotipificado. Se incluyen claves en inglés y español para distinguir las 15 especies de Agrostis y dos especies de Podagrostis citadas para Colombia.

New combinations and updated descriptions in Podagrostis (Agrostidinae, Poaceae) from the Neotropics and Mexico.

Based on morphological study and corroborated by unpublished molecular phylogenetic analyses, five grass species of high-mountain grasslands in Mexico, Central and South America, Agrostis bacillata, A. exserta, A. liebmannii, A. rosei, and A. trichodes, are transferred to Podagrostis and bring the number of species of this genus recognized in the New World to ten. The name Apera liebmannii is lectotypified and epitypified. We provide an updated genus description for Podagrostis, and updated species descriptions, images, and notes on the new combinations. The diagnostic characteristics differentiating Podagrostis from Agrostis are: a) palea that reaches from (2/3) ¾ to almost the apex of the lemma; b) florets that usually almost equal the length of the glumes or are at least ¾ the length of the glumes; c) rachilla extension present and emerging from under the base of the palea as a slender short stub (rudimentary or up to 1.4 mm long, sometimes obscure in most florets in P. rosei), smooth or scaberulous, glabrous or distally pilulose (hairs < 0.3 mm long); d) lemmas usually awnless, sometimes with a short straight awn 0.2-0.6 mm long, inserted medially or in the upper 1/3 of the lemma, not surpassing the glumes (awn well-developed, straight or geniculate and inserted in lower 1/3 of lemma, not or briefly surpassing glumes in P. rosei). We include a generic key to distinguish the species of Podagrostis from other similar genera in Latin America and a key to distinguish the species of Podagrostis now accepted as occurring in these areas.

ResumenBasado en estudios morfológicos y corroborado por datos no publicados de análisis filogenéticos, las cinco gramíneas de alta montaña de los pastizales en México, Centroamérica y Sur América Agrostis bacillata, A. exserta, A. liebmannii, A. rosei, y A. trichodes, son transferidos a Podagrostis incrementando a diez el número de especies en el nuevo mundo de este reconocido género. El nombre de Apera liebmannii también es lectotipificado y epitipicado. Proporcionamos una descripción actualizada del género Podagrostis, y descripciones actualizadas de las especies, imágenes y comentarios sobre las nuevas combinaciones. Las características diagnósticas que diferencian a Podagrostis de Agrostis son: a) pálea de 2/3-¾ hasta casi el ápice de la lemma; b) espiguillas, generalmente casi iguales en longitud a las glumas o de al menos ¾ la longitud de las glumas; c) extensión de la raquilla presente y emergiendo desde debajo de la base de la pálea como un trozo corto y delgado (desde rudimentario hasta de 1.4 mm de largo, a veces oscuro en la mayoría de los flósculos en P. rosei), liso o escabérulo, glabro o piloso distalmente (pelos < 0.3 mm de largo); d) lemmas generalmente sin arista, o a veces con arista corta y recta de 0.2­0.6 mm de largo, insertada medialmente o en el tercio superior de la lemma, sin sobrepasar las glumas (arista bien desarrollada, recta o geniculada e insertada en la parte inferior 1/3 de lemma, no o superando brevemente las glumas en P. rosei). Incluimos una clave para distinguir Podagrostis de otros géneros similares presentes en América Latina y una clave para distinguir las especies de Podagrostis ahora aceptadas por estar presentes en estas áreas.

Páramo Calamagrostis s.l. (Poaceae): An updated list and key to the species known or likely to occur in páramos of NW South America and southern Central America including two new species, one new variety and five new records for Colombia.

Calamagrostis (syn. Deyeuxia), as traditionally circumscribed, is one of the most speciose genera from páramo grasslands of northwest South America and southern Central America and often dominates these high-elevation habitats. However, it remains difficult for researchers to accurately identify the species due to a lack of floristic treatments for most of the countries containing páramo, with the distribution of many species still very poorly known. In an effort to ameliorate this, we present an updated list and identification keys in English and Spanish (as electronic appendix) to the species of Calamagrostis s.l. known or likely to occur in the páramos of Peru, Ecuador, Colombia, Venezuela, Costa Rica and Panama. Fifty-four species are accepted, constituting 47 species currently circumscribed in Calamagrostis and seven species recently transferred to Deschampsia. Included within this are two new species, Calamagrostiscrispifolius and Deschampsiasantamartensis, which are described and illustrated. Both new species are found in páramos of the Sierra Nevada de Santa Marta (departamento Magdalena), on the northernmost tip of Colombia, with C.crispifolius also found in the Serrania de Perija on the border with Venezuela. Calamagrostiscrispifolius differs from all other species of Calamagrostis s.l. by the presence of strongly curled, readily deciduous leaf blades, amongst numerous other characteristics including open inflorescences with generally patent branches, small spikelets, (3.5-)4-5.5 mm long, with sessile florets and a rachilla prolongation reaching from 2/3 to almost the apex of the lemma, with short hairs (< 1 mm long). Deschampsiasantamartensis is similar to Deschampsiahackelii (=Calamagrostishackelii) from austral South America but differs by its broad, rigid and erect, strongly conduplicate blades, 1.5-2.5 mm wide when folded, ligules of innovations 0.5-1 mm long, truncate or obtuse, ligules of upper flowering culms 3-4 mm long, broadly shouldered with an attenuate central point, ellipsoid spike-like panicle, 3-5.5 long × 1.5-2.5 cm wide, lemma surfaces moderately to lightly scabrous between the veins, lemma apex acute to muticous, entire, rachilla extension often absent and inside of the floret often with hyaline shiny sinuous trichomes to 1 mm long, emerging from the base of the ovary. We also present a broader circumscription of the common species Deschampsiapodophora (=Calamagrostispodophora), with the new variety D.podophoravar.mutica described and illustrated. Deschampsiapodophoravar.mutica principally differs from var. podophora by florets lacking awns and larger habit i.e. multiple taller culms with longer and wider leaf blades forming tussocks, with inflorescences often held within sheaths. Nomenclatural changes are presented, with Deyeuxiamacrostachya newly synonymised under C.macrophylla and C.pittieri, C.pubescens and Deyeuxiapubescens newly synonimised under C.planifolia. Lectotypes are designated for Agrostisantoniana, Calamagrostispisinna, Deyeuxiamacrostachya and Deyeuxiasodiroana. We also document and give notes on five new records of Calamagrostis for Colombia: C.carchiensis, C.guamanensis, C.heterophylla, C.pisinna and C.rigida.

ResumenCalamagrostis (syn. Deyeuxia), como traditionalmente está delimitado, es uno de los géneros con mayor número de especies registradas para las zonas paramunas de Sudamérica y el sur de Centroamérica, en donde a menudo es un elemento dominante en hábitats de alta montaña tropical. Sin embargo, es aun difícil para investigadores identificar con precisión las especies de este género, principalmente por la falta de tratamientos florísticos para la mayoría de países que contienen páramo, con la distribución de muchas especies todavía poca conocida. Con el fin de realizar un aporte al conocimiento de las gramíneas tropicales, se presenta una lista actualizada de nombres y claves de identificación taxonómica en inglés y español (como appendice electrónico) de las especies de Calamagrostis s.l. conocidas o que probablemente se encuentran en los páramos de Perú, Ecuador, Colombia, Venezuela, Costa Rica y Panamá. Como resultado, 54 especies son aceptadas, de las cuales 47 especies están circunscritas en Calamagrostis y siete especies están recientemente transferidas a Deschampsia. Como novedades taxonómicas, se presentan dos nuevas especies, Calamagrostiscrispifolius y Deschampsiasantamartensis, las cuales están descritas e ilustradas. Estas nuevas especies crecen en páramos de la Sierra Nevada de Santa Marta (departamento de Magdalena), en la punta más al norte de Colombia, con C.crispifolius también presente en la Serranía de Perijá en la frontera con Venezuela. Calamagrostiscrispifolius difiere de las otras especies de Calamagrostis s.l. por la presencia de láminas foliares fuertemente crispadas y fácilmente caducas, entre otras características incluyendo inflorescencias abiertas con ramas generalmente patentes, espiguillas pequeñas, (3.5­)4­5.5 mm long., con antecios sésiles y una prolongación de la raquilla llegando desde 2/3 hasta casi el ápice de la lema, con tricomas cortos (< 1 mm long.). Deschampsiasantamartensis es parecida a Deschampsiahackelii (=Calamagrostishackelii) de Sudamérica austral, pero difiere por sus láminas foliares siendo anchas, rígidas y rectas, y fuertemente conduplicadas, 1.5­2.5 mm de ancho cuando plegada, lígulas de las innovaciones 0.5­1 mm long., truncadas u obtusas, lígulas de la parte superior de las cañas floríferas 3­4 mm long., anchas con un punto central atenuado, panojas elipsoides y espiciforme, 3­5.5 long. × 1.5­2.5 cm de ancho, superficies de las lemas moderada a levemente escabroso entre las venas, ápices de las lemas agudas a múticas, enteras, prolongación de la raquilla a menudo ausente, y la presencia de tricomas hialinos, brillantes, y sinuosos de hasta 1 mm long., los cuales salen de la base del ovario. Por último, se presenta una circunscripción más amplia de la especie común Deschampsiapodophora (=Calamagrostispodophora), con la nueva variedad D.podophoravar.mutica, la cual es descrita e ilustrada. Deschampsiapodophoravar.mutica difiere principalmente de la var. podophora porque en sus antecios las aristas están ausentes, y su hábito es más grande i.e. con múltiples cañas largas con láminas foliares más largas y anchas, con inflorescencias a menudo escondidas dentro de las vainas. Los cambios nomenclaturales que se presentan son Deyeuxiamacrostachya sinonimizada bajo C.macrophylla, y C.pittieri, C.pubescens y Deyeuxiapubescens sinonimizada bajo C.planifolia. Designamos los lectotipos para Agrostisantoniana, Calamagrostispisinna, Deyeuxiamacrostachya y Deyeuxiasodiroana. También documentamos y damos notas de cinco nuevos registros de Calamagrostis para la flora de Colombia: C.carchiensis, C.guamanensis, C.heterophylla, C.pisinna, y C.rigida.

Relict high-Andean ecosystems challenge our concepts of naturalness and human impact.

What would current ecosystems be like without the impact of mankind? This question, which is critical for ecosystem management, has long remained unanswered due to a lack of present-day data from truly undisturbed ecosystems. Using mountaineering techniques, we accessed pristine relict ecosystems in the Peruvian Andes to provide this baseline data and compared it with the surrounding accessible and disturbed landscape. We show that natural ecosystems and human impact in the high Andes are radically different from preconceived ideas. Vegetation of these 'lost worlds' was dominated by plant species previously unknown to science that have become extinct in nearby human-affected ecosystems. Furthermore, natural vegetation had greater plant biomass with potentially as much as ten times more forest, but lower plant diversity. Contrary to our expectations, soils showed relatively little degradation when compared within a vegetation type, but differed mainly between forest and grassland ecosystems. At the landscape level, a presumed large-scale forest reduction resulted in a nowadays more acidic soilscape with higher carbon storage, partly ameliorating carbon loss through deforestation. Human impact in the high Andes, thus, had mixed effects on biodiversity, while soils and carbon stocks would have been mainly indirectly affected through a suggested large-scale vegetation change.

An updated checklist and key to the open-panicled species of Poa L. (Poaceae) in Peru including three new species, Poa ramoniana, Poa tayacajaensis, and Poa urubambensis.

We provide an updated checklist and key to the 30 Poa species with open panicles from Peru which includes previously circumscribed Dissanthelium and Aphanelytrum species, new taxon records, and three undescribed species. Poa compressa, Poa grisebachii, and Poa leioclada are recorded from Peru for the first time. A number of species are placed in synonymy: Poa carazensis, Poa ferreyrae and Poa tovarii are synonymized under the name Poa fibrifera; Poa adusta (tentatively) and Poa pilgeri are synonymized under Poa candamoana; Poa superata is synonymized under Poa grisebachii; and Poa paramoensis is synonymized under Poa huancavelicae. Included within this treatment are three new species, Poa ramoniana, Poa tayacajaensis and Poa urubambensis, which are described and illustrated. Poa ramoniana, found growing near lakes in high elevation Puna grasslands of Junín, is similar to a small form of Poa glaberrima, but differs in having rhizomes and growing to only 5 cm tall. Poa tayacajaensis, found from shrublands on Andean slopes of Huancavelica and Huánuco, bears similarities to Poa aequatoriensis but differs in having shorter lemmas which are pubescent between the veins, densely scabrous sheaths with smooth, glabrous throats, and shorter ligules. Poa urubambensis, a common element of the undisturbed Polylepis forest understory of the Cordillera Urubamba, Cusco, is distinct from all other members of open-panicled Poa's by having glabrous lemmas with a smooth and glabrous callus, and notably small anthers. The type material for the name Poa adusta is discussed and a lectotype is selected.

ResúmenAportamos una lista actualizada y una clave para las 30 especies de Poa con panículas abiertas de Perú que incluye las especies de Dissanthelium y Aphanelytrum anteriormente circunscritas, nuevos registros de taxones y tres especies no descritas. Poa compressa, Poa grisebachii, y Poa leioclada se registran para Perú por primera vez. Un número de especies son sinonimizadas: Poa carazensis, Poa ferreyrae y Poa tovarii son sinonimizadas bajo el nombre de Poa fibrifera; Poa adusta (tentativamente) y Poa pilgeri son sinonimizadas bajo el nombre de Poa candamoana; Poa superata es sinonimizada bajo Poa grisebachii; y Poa paramoensis es sinonimizada bajo Poa huancavelicae. Dentro de este tratamiento se incluyen dos especies nuevas, Poa ramoniana, Poa tayacajaensis y Poa urubambensis que a continuación se describen e ilustran. Poa ramoniana, que se encuentra creciendo en pastizales de alta elevación cercanos a lagos en la Puna de Junín, es similar a la forma pequeña de Poa glaberrima, pero se diferencia por tener rizomas y crecer hasta sólo 5 cm de altura. Poa tayacajaensis, que se encuentra en matorrales de las laderas andinas de Huancavelica y Huánuco, tiene un parecido a Poa aequatoriensis, pero se diferencia por tener lemas cortas que son pubescentes entre las venas, vainas densamente escabrosas con suaves gargantas glabras, y lígulas cortas. Poa urubambensis, un elemento común de sotobosque no perturbado de los bosques de Polylepis de la Cordillera Urubamba, Cusco, se distingue de todos los otros miembros de Poa con panícula-abierta por tener lemas glabras con un callo suave y glabro, y sus notables anteras pequeñas. El material tipo del nombre Poa adusta es discutido y un lectotipo es seleccionado.

Elevational patterns of Polylepis tree height (Rosaceae) in the high Andes of Peru: role of human impact and climatic conditions.

We studied tree height in stands of high-Andean Polylepis forests in two cordilleras near Cuzco (Peru) with respect to variations in human impact and climatic conditions, and compared air and soil temperatures between qualitatively defined dry and humid slopes. We studied 46 forest plots of 100 m(2) of five Polylepis species at 3560-4680 m. We measured diameter at breast height (dbh) and tree height in the stands (1229 trees in total), as well as air and soil temperatures in a subset of plots. The data was analyzed combining plots of given species from different sites at the same elevation (±100 m). There was no elevational decrease of mean maximum tree height across the entire data set. On humid slopes, tree height decreased continuously with elevation, whereas on dry slopes it peaked at middle elevations. With mean maximum tree heights of 9 m at 4530 m on the humid slopes and of 13 m at 4650 m on the dry slopes, we here document the tallest high-elevation forests found so far worldwide. These highest stands grow under cold mean growing season air temperatures (3.6 and 3.8°C on humid vs. dry slopes) and mean growing season soil temperatures (5.1 vs. 4.6°C). Mean annual air and soil temperature both decreased with elevation. Dry slopes had higher mean and maximum growing season air temperatures than humid slopes. Mean annual soil temperatures did not significantly differ and mean annual air temperatures only slightly differed between slopes. However, maximum air temperatures differed on average by 6.6 K between dry and humid slopes. This suggests that the differences in tree height between the two slopes are most likely due to differences in solar radiation as reflected by maximum air temperatures. Our study furthermore provides evidence that alpine Polylepis treelines grow under lower temperature conditions than global high-elevation treelines on average, suggesting that Polylepis species may have evolved special physiological adaptations to low temperatures.