Explaining First-Year Seedling Survival from Quality Distributions of Bare-Root Seedlings and Microsites in Industrial Plantations

First-year seedling survival impacts all subsequent management planning in plantation forestry. Descriptive statistics of first-year seedling survival data from the Louisiana Department of Agriculture and Forestry (LDAF) indicated that survival success reaches a plateau at between 79% - 85% under normal weather conditions. We provide an explanation for this plateau based on an analysis of seedling and microsite qualities involved in operational pine plantations by: 1) using a conceptual model demonstrating how variation in seedling quality and microsite quality interact to determine plantation survival, 2) presenting an example to characterize quality distributions of seedling and microsite qualities, and 3) comparing model outcomes based on measured distributions to realistic values of first-year survival. Simulation results indicated that consistent survival could result from random pairings of initial seedling and site quality distributions. LDAF data analysis indicated that 72% of seedlings were associated with the most frequent quality class that comprised seedlings with stem caliper between 3.2 to 4.7 mm and average stem height and volume of 25.75 cm and 3.43 cm3, respectively. Similarly, assessment of microsites at planting sites in Southeast Louisiana indicated that 48% of planted seedlings were associated with the most frequent microsite quality class which supported first-year height increment between 9 to 29 cm. Modelling of current operational practice indicated that using seedlings with larger caliper size would increase first year survival, but would result in higher establishment costs. The conceptual model could be modified to for use in other regions regardless of species types involved.

Synergies between microsites of plant communities and steady-stage alpine meadows on the Qinghai-Tibetan Plateau

Background:Due to the effects of climate change and overgrazing in recent decades,alternative stable states in the alpine Kobresia meadow degradation process have coexisted in the same geographical and climatic environment,with variations occurring among microsites.Methods:We used a space-for-time substitution approach to explore the synergies of microsite variation according to its numerical characteristics and the proportion of each stable state at various stages of succession in alpine Kobresia meadows on the Qinghai-Tibetan Plateau.Results:(1)The highest average aboveground biomass in summer was 196.2±20.3 gm^(-2),with significantly higher levels of biomass in≤3.65 sheep unit ha^(-1) than in other levels of grazing intensity,while the parameters showed no significant differences among grazing intensity levels in>3.65 sheep unit ha^(-1).(2)The importance of plant functional groups,aboveground biomass,and niche breadth of Poaceae and Cyperaceae significantly decreased as the grazing intensity increased.(3)The effects of≥0°C accumulated temperature,total precipitation,altitude,longitude,and latitude cumulatively contributed less than 20%of the variation in the distribution of functional group characteristics across microsites.Conclusions:(1)Overgrazing decreases primary production in alpine Kobresia meadows,but ecosystem responses regulate plant community structure and botanical components so as to partially counteract grazing disturbance.(2)Overgrazing changed the proportion of microsites,which in turn led to regime shift in the plant community and subsequent synergies between the microsites of plant communities and their stable states.

Saxicolous lichen communities in three basins associated with mining activity in northwestern Argentina

Mining activity affects the vegetation and soils of the ecosystems.However,the effects of mining activity on saxicolous lichen communities are less concerned.Thus,the aim of this study was to characterize saxicolous lichen communities in three basins(Vis-Vis River basin,Poteros River basin,and Capillitas River basin)surrounding metalliferous mining projects of different types of operation and at different stages of exploitation.A large-scale mine(Bajo de la Alumbrera)with more than 25 a of open-pit mining located in the Vis-Vis River basin(CRV).A pre-exploitation mine(Agua Rica)located in the Poteros River basin(CRP),and a small-scale mine(Minas Capillitas)with more than 160 a of underground mining located in the Capillitas River basin(CAC).In each basin,species richness,cover,and frequency of lichen communities were measured on 40 rock outcrops.Also,explanatory variables were recorded,i.e.,altitude,slope,aspect,vegetation cover,rock,and soil cover around the rocky area sampled.Richness and total cover of lichen communities were analysed using linear models,and species composition was explored using multivariate ordination analysis.Results showed that a total of 118 lichen species were identified.The species richness differed among basins and the lichen composition present in areas close to mining sites responded mainly to basins,altitude,and microsite variables.The lichen cover showed no difference among basins,but it changed under different rock and vegetation cover.It was not possible to quantify the effects of mining activity on species richness and composition.However,the low richness values found in the downstream of Minera Alumbrera could be associated with the negative impact of open-pit mining.Moreover,the effects of large-scale mining activity on lichen communities needs more investigation.

Seed rain and soil seed bank compensatory roles on Nassella tenuis(Phil.)Barkworth seedling recruitment in ungrazed and grazed sites

In semi-arid lands,vegetation is distributed in shrub patches immersed in a less vegetated interpatch matrix.Grazing affects perennial grass seed bank through a decrease in seed rain and an increase in seed predation and soil compaction.Nevertheless,some species with anchorage mechanisms in their seeds might overcome this,such as Nassella tenuis(Phil.)Barkworth.This is an important species in grazing paddocks because it has an intermediate palatability and its relatively tolerant to grazing.These characteristics allow N.tenuis to increase its abundance in grazed sites.Our objective was to assess how grazing affects the key palatable species from seeds to seedlings:i.e.,seed rain,soil seed bank,and seedling recruitment in different microsites along a windward-leeward transect across shrub canopy.We hypothesized that:(1)the negative effects of grazing on N.tenuis fructification are reflected in its seed rain,soil seed bank,and seedling recruitment,especially in interpatches;(2)Nassella tenuis seed rain reduction,soil compaction by cattle in grazed sites,and removal of seeds by wind decrease its soil seed bank,especially in microsites exposed to the predominant wind;and(3)the decrease in N.tenuis soil seed bank and cover increase in annual species in grazed sites have negative effects on its seedling recruitment,especially in microsites exposed to predominant wind.We placed seed traps,collected soil samples,and monitored seedling recruitment in different locations around shrub canopy to address our hypotheses.Also,we established a manipulative experiment in which we sow N.tenuis seeds and followed its recruitment in different microsites.We compared the seed rain,soil seed bank,natural seedling recruitment,and sown seeds recruitment of N.tenuis between grazed and ungrazed sites.We analyzed differences between microsites along a windward-leeward transect across shrubs patches.Seed rain and soil seed bank had the same density in patches and interpatches both in ungrazed and grazed sites.But seed rain was higher,and soil seed bank was lower in ungrazed sites than in grazed sites.Almost all under-canopy microsites showed greater soil seed bank abundance and natural seedling recruitment in ungrazed sites.Sown seeds recruitment was the same between grazed and ungrazed sites,but it showed protective effects of shrubs in leeward microsites under grazed sites.As a conclusion,seed rain and soil seed bank are complementary under grazed sites.

A dwarf bamboo(Pleioblastus chino) and winter browsing by Japanese hare(Lepus brachyurus) combine to limit establishment of transplanted native tree seedlings in an abandoned agricultural field

Natural forest recovery on abandoned farmland is hindered by a variety of factors and active restoration plays an important role when quick afforestation is desired.We investigated seedling survival of four transplanted native tree species(Quercus myrsinifolia, Quercus serrata,Aphananthe aspera, and Rhus sylvestris) by experimentally manipulating the vegetation cover, which was mainly dominated by dwarf bamboo(Pleioblastus chino), and herbivore access to the planting sites on farmland that had been abandoned for 15 years at the start of the study. Few transplanted seedlings of any species survived under intact vegetation cover, irrespective of herbivore presence. In gaps in the vegetation cover, winter browsing by Japanese hare(Lepus brachyurus) damaged all species. However,lower browsing frequency and higher resprouting ability after grazing of the seedlings enabled both Quercus species to survive better than the other species. These results indicate that dwarf bamboo and the hare jointly limit the establishment of native trees in old fields. If active afforestation by transplanting seedlings at sites dominated by dwarf bamboo is planned, a combination of vegetation removal, selection of suitable species, and temporary seedling protection will be most effective.

Denitrification and the challenge of scaling microsite knowledge to the globe

Our knowledge of microbial processes—who is responsible for what,the rates at which they occur,and the substrates consumed and products produced—is imperfect for many if not most taxa,but even less is known about how microsite processes scale to the ecosystem and thence the globe.In both natural and managed environments,scaling links fundamental knowledge to application and also allows for global assessments of the importance of microbial processes.But rarely is scaling straightforward:More often than not,process rates in situ are distributed in a highly skewed fashion,under the influence of multiple interacting controls,and thus often difficult to sample,quantify,and predict.To date,quantitative models of many important processes fail to capture daily,seasonal,and annual fluxes with the precision needed to effect meaningful management outcomes.Nitrogen cycle processes are a case in point,and denitrification is a prime example.Statistical models based on machine learning can improve predictability and identify the best environmental predictors but are—by themselves—insufficient for revealing process-level knowledge gaps or predicting outcomes under novel environmental conditions.Hybrid models that incorporate well-calibrated process models as predictors for machine learning algorithms can provide both improved understanding and more reliable forecasts under environmental conditions not yet experienced.Incorporating trait-based models into such efforts promises to improve predictions and understanding still further,but much more development is needed.

Influence of experimental soil disturbances on the diversity of plants in agricultural grasslands

Aims and Methods Disturbance is supposed to play an important role for biodiversity and ecosystem stability as described by the intermediate disturbance hypoth-esis(IDH),which predicts highest species richness at intermediate levels of disturbances.In this study,we tested the effects of artificial soil distur-bances on diversity of annual and perennial vascular plants and bryo-phytes in a field experiment in 86 agricultural grasslands differing in land use in two regions of Germany.On each grassland,we implemented four treatments:three treatments differing in application time of soil dis-turbances and one control.One year after experimental disturbance,we recorded vegetation and measured biomass productivity and bare ground.We analysed the disturbance response taking effects of region and land-use-accompanied disturbance regimes into account.Important Findings Region and land-use type strongly determined plant species rich-ness.Experimental disturbances had small positive effects on the species richness of annuals,but none on perennials or bryophytes.Bare ground was positively related to species richness of bryophytes.However,exceeding the creation of 12%bare ground further distur-bance had a detrimental effect on bryophyte species richness,which corresponds to the IDH.As biomass productivity was unaffected by disturbance our results indicate that the disturbance effect on spe-cies richness of annuals was not due to decreased overall produc-tivity,but rather due to short-term lowered inter-and intraspecific competition at the newly created microsites.Generally,our results highlight the importance of soil disturbances for species richness of annual plants and bryophytes in agricultural grasslands.However,most grasslands were disturbed naturally or by land-use practices and our additional experimental soil dis-turbances only had a small short-term effect.Overall,total plant diversity in grasslands seemed to be more limited by the availabil-ity of propagules rather than by suitable microsites for germination.Thus,nature conservation efforts to increase grassland diversity should focus on overcoming propagule limitation,for instance by additional sowing of seeds,while the creation of additional open patches by disturbance might only be appropriate where natural disturbances are scarce.

Enriching plant diversity in grasslands by large-scale experimental sward disturbance and seed addition along gradients of land-use intensity

Aims The relationship between biodiversity and ecosystem functioning is among the most active areas of ecological research.Furthermore,enhancing the diversity of degraded ecosystems is a major goal in applied restoration ecology.In grasslands,many species may be locally absent due to dispersal or microsite limitation and may therefore profit from mechanical disturbance of the resident vegeta-tion.We established a seed addition and disturbance experiment across several grassland sites of different land use to test whether plant diversity can be increased in these grasslands.Additionally,the experiment will allow us testing the consequences of increased plant diversity for ecosystem processes and for the diversity of other taxa in real-world ecosystems.Here,we present details of the experimen-tal design and report results from the first vegetation survey 1 year after disturbance and seed addition.Moreover,we tested whether the effects of seed addition and disturbance varied among grassland depending on their land use or pre-disturbance plant diversity.Methods A full-factorial experiment was installed in 73 grasslands in three regions across Germany.Grasslands were under regular agricul-tural use,but varied in the type and the intensity of management,thereby representing the range of management typical for large parts of Central Europe.The disturbance treatment consisted of disturbing the top 10 cm of the sward using a rotavator or rotary harrow.Seed addition consisted of sowing a high-diversity seed mixture of regional plant species.These species were all regionally present,but often locally absent,depending on the resident vegetation composi-tion and richness of each grassland.Important Findings Seven months after sward disturbance,respective plots had significantly increased in bare soil,seedling species richness and number of seed-lings.Seed addition had increased plant species richness,but only in combination with sward disturbance.The increase in species richness,when both seed addition and disturbance was applied,was higher at high land-use intensity and low resident diversity.Thus,we show that at least the early recruitment of many species is possible also at high land-use intensity,indicating the potential to restore and enhance bio-diversity of species-poor agricultural grasslands.Our newly established experiment provides a unique platform for broad-scale research on the land-use dependence of future trajectories of vegetation diversity and composition and their effects on ecosystem functioning.

Interactions among dwarf bamboo, litter and consumption by small vertebrates place multiple constraints on the establishment of native tree seedlings in a Japanese agricultural landscape

Aims Faunal assemblage alterations due to anthropogenic impacts have changed herbivore-vegetation relationships in various ecosystems,but the influences of small vertebrates on revegetation processes remain unclear.In a peri-urban agricultural landscape in eastern Japan that lacks large ungulates but supports small generalist herbivores,fewer native seedlings have become established in thickets dominated by native dwarf bamboo,Pleioblastus chino(Franch.et Sav.)Makino.The mechanisms limiting tree seedling establishment are unknown.Our aim here was to evaluate the influence of interactions among the dwarf bamboo,its litter cover and small vertebrate herbivores on the micro-site conditions governing the establishment of native tree seedlings from different successional stages in an old field in temperate Japan.Methods First,seedling emergence and survival of seeded Pinus densiflora Siebold et Zucc.,Celtis sinensis Pers.,Aphananthe aspera(Thunb.)Planch.,Quercus serrata Murray,Quercus myrsinifolia Blume and Castanopsis sieboldii(Makino)Hatus.ex T.Yamaz.et Mashiba were observed in a factorial design that accounted for the presence or absence of dwarf bamboo and its litter cover,as well as the exclu-sion or access of small vertebrate fauna,in 2009 and 2010.To identify small vertebrate herbivores that reduced the emergence or survival of tree seedlings in the first experiment,reseeding experi-ments using P.densiflora,C.sinensis,A.aspera and Q.myrsinifolia were conducted by video trapping in 2011 and video and still-cam-era trapping in 2012.Important Findings The abiotic conditions under the dwarf bamboo were lethal to early-to mid-successional P.densiflora,C.sinensis,A.aspera and Q.serrata but led to better survival-although spindly growth-of late-succes-sional Q.myrsinifolia and C.sieboldii.The main consumers and the plants they found palatable differed between the bamboo thickets and the intervening gaps.Predation by mice appeared to have severely limited the emergence of all species,particularly in the bamboo thick-ets but occasionally in the gaps,whereas litter cover slightly mitigated this limitation.However,bamboo litter cover reduced the emergence of P.densiflora in the gaps.Chinese bamboo partridge(Bambusicola thoracicus Temminck),an introduced game bird,selectively and severely fed on the cotyledons-and probably seeds-of A.aspera and moderately preyed upon those of P.densiflora in the gaps.Apparent consumption of seedlings in the gaps by the Japanese hare(Lepus brachyurus Temminck)suppressed the growth of all species but apparently did not severely affect emergence and survival.Thus,the net balance of positive and negative interactions at the bamboo thicket scale(i.e.the presence of dominant dwarf bamboo cover or intervening gaps and the herbivore behaviours in these two environments)and at the microsite level(i.e.litter cover)shapes the early establishment patterns of native tree seedlings,and this balance differs among tree seedling species.