Introduction: The ahuehuete (Taxodium mucronatum Ten.), National Tree of Mexico, is frequently found in urban green areas, in conditions of restricted humidity and compacted soils. These characteristics negatively affect growth and survival. Objective: To evaluate root growth of young ahuehuete trees by the effect of the frequency of irrigation and loosening of the soil surrounding the planting strain. Materials and methods: 24 trees 2 m high were planted in an urban area. The experiment was established as a completely random design with factorial arrangement: a) irrigation frequency (frequent [once weekly] and spaced [once every two weeks]) and b) treatment of the soil surrounding the plantation strain (soil with and without loosening). The growth of the root system was monitored for 12 months through digital photographs, obtained from rhizotrons installed on a side wall of each plantation strain. Results and discussion: The original compaction of the site did not present restrictive levels for growth; therefore, the surrounding loosening did not significantly improve (P > 0.1) short-term root growth. Root length (267.75 to 453.28 cm) showed no statistically significant differences for the irrigation and soil factors and their interaction; however, the number of roots was affected by the interaction of the factors (P ≤ 0.1). Trees with frequent irrigation and soil without loosening developed a higher number of roots (190.5). Conclusion: The interaction of irrigation frequency and soil condition influences the number of roots, but not the length.

Introduction: Land uses associated with anthropogenic activities affect soil quality negatively.

Objective: To determine the effect of regeneration cuts on the physical and hydrological properties of an Umbrisol.

Materials and methods: In each stand (parent trees [PT], clear cutting, selection, regenerated area [post-fire] and reference [R]), in situ tests were performed and four samples composed of soil by depth (0 to 20 cm and 20 to 40 cm) were collected. Data were analyzed by Kruskal-Wallis and ANOVA tests. The physical variables (apparent density [AD], porosity, silt, leaf litter and humus, mechanical resistance to penetration [MRP], sand and clay) and hydrological variables (infiltration, field capacity, permanent wilt point, available water and permeability) were related by means of the Spearman correlation coefficient.

Results and discussion: Differences were significant (P ≤ 0.01) in MRP, sand and clay in the forest stand factor. For the depth factor, all the variables were similar, except for the MRP; its increase in clear cutting was higher than 100 %, with respect to R. The interaction was only significant (P ≤ 0.01) for the sand percentage. The Kruskal-Wallis test (P ≤ 0.05) indicated that infiltration, humus and litter were lower in clear cutting. There is a significant negative correlation (P ≤ 0.01) of AD with permeability, porosity, clay and sand. PT and clear cuttings increased AD (24.28 and 37.58 %) and MRP (32.59 and 222.22 %), with respect to R.

Conclusion: PT and selection cuts did not cause significant variations in properties such as those of a total cut (clear cutting).

Introduction: The increase in the intensity of wood harvesting has a negative influence on ecosystem functions of soils in temperate and boreal forests.

Objective: To understand the impacts of intensive and extensive forest management methods on the physical, chemical and biological properties of soils, and consequences on nutrient availability and stabilization processes in temperate and boreal forests.

Results and discussion: Intensive forest management methods can generate greater imbalance in the processes of availability and stabilization of nutrients, compared to selective methods. The impact is reflected in the deterioration of soil structure and the decrease of nutrient reserves and microbial communities. These damages affect fertility and functionality of soil, decreasing long-term productivity. Affectations depend on the intensity of biomass extracted, environmental conditions and site preparation. This makes evident the need to monitor forest management and its impact on soil ecology in temperate forests, which maintains long-term productivity and ensures the availability of wood volumes.

Conclusion: In Mexico, the impact of forest management has been scarcely analyzed and it is indispensable to understand the functional changes in the processes that determine soil fertility and forest productivity.

Introduction: Native forest reserves in southern Chile are the largest carbon sinks in the country, but the amount and level of grouping of the polygons that form these coverages is unknown.

Objective: to estimate aerial biomass (AB) and carbon content in native forests in the county of Valdivia, Los Rios region, as well as the degree of grouping of polygons containing carbon in aerial biomass.

Materials and methods: 21 land plots of 50 x 10 m were installed. Tree species were identified, and their diameter and height were measured. The AB was calculated using allometric equations, and the carbon content was calculated relating the AB to the factor 0.5. The degree of grouping of polygons with carbon content was calculated using the Getis-Ord G statistic.

Results and discussion: The total carbon content in AB was estimated at 599.6 Mg C·ha -1 . Carbon is concentrated in three forest types, Evergreen being the most important (63.3 %). The most abundant species was Nothofagus obliqua (Mirb.) Oerst. (18.34 %). There is a clustered spatial dependence on carbon-containing polygons in areas with forest reserves; the rest of the territory showed random distribution. Spatial dependence is related to the physiographic characteristics of the study area.

Conclusions: The use of allometric functions for the estimation of aerial biomass and factors to obtain the carbon content is a valid methodology. The carbon polygons of the native forests in Valdivia have grouped spatial distribution.

Introduction: Basal area increment (BAI) is an indicator of forest productivity that varies with tree age and site factors such as soil and climate.

Objective: To generate tree-ring width index (RWI) and BAI chronologies of Pinus hartwegii Lindl., relate them to climatic variables, and study the variation in BAI at different altitudes and aspects.

Materials and methods: Four observation sites were identified, combining northwest (NW) and southwest (SW) aspects, as well as altitudes of 3 800 and 3 700 m. At each site, the temperature was recorded every four hours for 435 days and 32 growth ring segments were collected using a Pressler´s increment borer. Tree-ring width was measured and BAI was calculated; the correlation index between these indicators and the climatic variables was Pearson’s correlation coefficient.

Results and discussion: The RWI series from the four observation sites had an intercorrelation of 0.33 (P < 0.01). Two low-growth periods were detected, one between 1950 and 1960 and the other between 1990 and 2005. Site SO-3700 had a different growth pattern, due to a second growth phase beginning in 1978, possibly a benefit resulting from increased temperature. The previous autumn temperature, spring temperature and April-September precipitation of the current year explained the variation in BAI (P < 0.05).

Conclusion: The BAI of P. hartwegii could respond favorably to the predicted increases in temperature at an altitude of 3 700 m with southwest aspect.

Introduction: The specific relation between ecosystem services (ES), land use systems productivity and welfare is complex and poorly understood.

Objective: To analyze the relationship between natural capital and welfare in the Agriculture, Forestry and Other Land Use (AFOLU) sector to assess Ecosystem Services contribution to agriculture, forestry and fishing value added (GDP [Gross Domestic Product]) and analyze policy implications.

Materials and methods: Using land use allocation variables, forest transition model and land use GDP for 97 tropical countries, the production function of AFOLU sector was estimated using a linear regression model and a bootstrap method. The properties of the function were analyzed, and the optimal land allocation was calculated.

Results and discussion: There is a direct contribution and an indirect contribution from forest ecosystems to GDP. The direct effect is manifested through the partial elasticity of forestland (P < 0.05). The indirect effect is reflected through the production scale (P < 0.05). Partial elasticity of agriculture is significantly higher than partial elasticity of forestland (P < 0.05) and production scale increases as forestland is depleted (P < 0.05). In addition, optimal land use indicates that 75 countries have forest superavit (13.2 Mkm 2 ) and 22 forest deficit (1.5 Mkm 2 ).

Conclusions: Forest ecosystems in the AFOLU sector in the tropics produce ecosystem services for society. However, these contributions are dwarfed by agricultural land productivity.

Introduction: Understanding the dendroclimatic potential of a species allows us to reconstruct the climate variability in the latitudes and altitudes of its distribution.

Objective: To determine the potential of Pinus montezumae Lamb. to reconstruct climatic variables.

Materials and methods: A total of 80 samples were extracted with a Pressler increment borer and dated, allowing growth rates to be generated. Average monthly rainfall and minimum and maximum temperature were obtained, and a response function analysis between growth rates and climate data was conducted.

Results and discussion: Dated samples represented 75 % of the total. The COFECHA program indicated a correlation between series of r = 0.57 (P < 0.01) and a mean sensitivity of 0.31; P. montezumae is sufficiently sensitive to record climate variability. Three chronologies (standard, residual and arstan) covering 228 years (1790-2017) were generated for each of the three growth rates (total ring, early and latewood). The response function analysis showed that it is possible to reconstruct the spring rainfall and the May-July maximum temperature based on the total ring (r = 0.66; P < 0.01) and latewood (r = 0.35; P < 0.01) indices, respectively.

Conclusion: Statistical parameters indicate that P. montezumae is an adequate proxy source for climate variability reconstruction studies.

Introduction: The primary wood processing industry releases greenhouse gases (GHGs); their mitigation involves measuring the carbon footprint. Objective: To estimate the carbon footprint of two forestry companies dedicated to the primary transformation of wood.

Materials and methods: Companies established as organizational boundaries L1 and L2 have two (Q1 and Q2) and one (D) sawmill, respectively. The operational limits were A1 (direct emissions from fossil fuel consumption), A2 (indirect emissions from electricity consumption) and A3 (emission sources not owned by L1 and L2). GHG emissions were calculated in two annuities with the method of using documented activity data and emission factors level 1. The annuities were compared with the Student’ t-test and Wilcoxon test, and the sawmills with the Kruskal-Wallis test.

Results and discussion: The estimated carbon footprint for L1 was 480.06 tCO 2 e·year - 1 , where A1, A2 and A3 represented 29.32 %, 14.59 % and 56.09 %, respectively. L2 had a footprint of 230.56 tCO 2 e·year -1 of which 9.39 %, 11.78 % and 78.83 % corresponded to the categories A1, A2 and A3, respectively. The cumulative uncertainty was within a fair range of accuracy (±25 %). Only the direct GHG emissions between L1 annuities were statistically different (P < 0.05). Mechanical technology made the difference in GHG emissions among sawmills (P < 0.05).

Conclusions: The carbon footprint is inherent to the energy used; energy management ensures the mitigation of GHG emissions.

Introduction: The choice of sample size is an important decision in the development of volume models and taper functions.

Objective: To calculate the minimum sample size required for fitting compatible taper-volume functions for Pinus arizonica Engelm., P. durangensis Martínez and P. engelmannii Carr. in Chihuahua.

Materials and methods: The methodology was divided into three phases: (i) fitting of a linear regression model to the diameter-height data of 50 trees of each species in the three forest regions; (ii) calculation of the minimum sample size required, and (iii) comparison of the goodness of fit of the taper-volume function using both sample sizes.

Results and discussion: The minimum number of trees calculated ranged from 53 (Pinus durangensis) to 88 (P. engelmannii) and it is located in the interval reported in studies carried out to estimate the optimal sample size for the development of taper functions. No significant differences were observed in the goodness of fit (α = 0.05) in terms of the R 2 and the root mean square error, using the full sample size and the calculated minimum sample size; no significant effect was observed in the stem volume estimates.

Conclusion: The use of small samples in the fit of taper-volume models generates accurate estimates if adequate representation of the study population is ensured.

Introduction: Tropical hurricanes modify composition and structure of ecosystems.

Objective: To analyze the impact of tropical hurricanes on the recovery and resilience of vegetation cover.

Materials and methods: The resilience of the lower basin and estuary of San Jose del Cabo was evaluated by studying the impact of 11 tropical hurricanes (2013-2017) on the vegetation cover. Landsat images were analyzed for each event and two SPOT-6 images for the Hurricane Lidia. The areas of gain, stability, loss and recovery of vegetation types were estimated based on the analysis of changes in the Normalized Difference Vegetation Index (NDVI).

Results and discussion: Average stability of vegetation cover was 90 %; however, in the case of hurricane Odile (2014) and Lidia (2017), stability decreased considerably, with a loss of 35.4 and 20.5 %, respectively, being the perennial herbaceous vegetation the most affected. One year after Odile and Lidia, recovery was 8.4 % and 25.4 %, respectively; the most recovered vegetation type was reed-tree. The analysis of SPOT-6 images allowed the detailed observation of Lidia's effect on palm grove. The main cause of its loss was runoff from the stream, which favored the growth of invasive species (Arundo donax L. and Tamarix sp.); furthermore, it was estimated that 1.4 ha were deforested, and an area of 20 ha affected by fire in 2017.

Conclusion: Vegetation is resilient to tropical hurricanes; however, events that provide more than 50 % of annual precipitation decrease the capacity of vegetation to recover.