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Managing Forests for Both Downstream and Downwind Water
Forests and trees are key to solving water availability problems in the face of climate change and to achieving the United Nations Sustainable Development Goals. A recent global assessment of forest and water science posed the question: How do forests matter for water? Here we synthesize science from that assessment, which shows that forests and water are an integrated system. We assert that forests, from the tops of their canopies to the base of the soils in which trees are rooted, must be considered a key component in the complex temporal and spatial dimensions of the hydrologic cycle. While it is clear that forests influence both downstream and downwind water availability, their actual impact depends on where they are located and their processes affected by natural and anthropogenic conditions. A holistic approach is needed to manage the connections between forests, water and people in the face of current governance systems that often ignore these connections. We need policy interventions that will lead to forestation strategies that decrease the dangerous rate of loss in forest cover and that -where appropriate- increase the gain in forest cover. We need collective interventions that will integrate transboundary forest and water management to ensure sustainability of water supplies at local, national and continental scales. The United Nations should continue to show leadership by providing forums in which interventions can be discussed, negotiated and monitored, and national governments must collaborate to sustainably manage forests to ensure secure water supplies and equitable and sustainable outcomes.
Creed, Irena F.-Jones, Julia-Archer, Emma-Claassen, Marius-Ellison, David-Mcnulty, Steven G.-Van Noordwijk, Meine-Vira, Bhaskar-Wei, Xiaohua-Bishop, Kevin-Blanco, Juan A.-Gush, Mark-Gyawali, Dipak-Jobbágy, Esteban-Lara Aguilar, Antonio-Little Cárdenas, Christian-Martin Ortega, Julia-Mukherji, Aditi-Murdiyarso, Daniel-Ovando Pol, Paola-Sullivan, Caroline A.-Xu, Jianchu
2019
Climate response and drought resilience of Nothofagus obliqua secondary forests across a latitudinal gradient in south-central Chile
The climate response and resilience of tree growth to drought events have been widely reported for forests from the Northern Hemisphere. However, studies are much scarcer in the extra-tropical forests of southern South America. Mediterranean and Temperate forests of Chile are suffering from a moderate warming and a sustained precipitation decrease, occurring on top of an unprecedented megadrought since 2010. This study evaluated tree-growth patterns, the climate response and drought resilience of nine secondary Nothofagus obliqua forests across a latitudinal gradient from Mediterranean to Temperate climate in the Andes of Chile (35.7° to 40.3° S). Moreover, to improve the understanding of the spatial variation in productivity patterns, this research assessed trends in the maximum Normalized Difference Vegetation Index (peak in the NDVI) across the gradient for 2001–2018. Tree-growth patterns were highly influenced by stand dynamics, with steep decreasing trends in most of the stands related to a gradual canopy closure. Productivity trends had a flat pattern north of 38oS, but positive trends south of this latitude, which were mostly attributed to stand development. Tree growth was positively related to precipitation in all the sites, with annual and summer rainfall being more important in the north (Mediterranean climate) and south (Temperate climate), respectively. Conversely, maximum temperature had a negative effect on growth in most of the studied forests. This implies that projected warmer and drier conditions may have a detrimental effect on N. obliqua growth during coming decades. The two northern stands, located at the species dry range edge, were among the most resilient to drought and have not been strongly affected by the current megadrought in the area. Overall climate conditions, however, do not define the tolerance of stands to droughts, likely because local environmental and forests conditions play a key role. Although droughts have not strongly impacted the growth of N. obliqua across its distribution so far, future studies should assess the effects of the current long-term megadrought on growth resilience, and physiological studies should address the impacts of droughts and heat waves on forest function beyond what growth can unveil.
Urrutia-Jalabert, Rocío-Barichivich Henríquez, Jonathan Eligio-Rozas, V.-Lara Aguilar, Antonio-Rojas Ponce, Yasna-Bahamóndez V., Carlos-Rojas-Badilla, Moisés-Gipoulou-Zuñiga, T.-Cuq, Emilio
2021
+A 5680-year tree-ring temperature record for southern South America
It is widely documented that the Earth’s surface temperatures have increased in recent decades. However, temperature increment patterns are not uniform around the globe, showing different or even contrasting trends. Here we present a mean maximum summer temperature record, based on tree-ring widths, over the past 5682 years (3672BC – 2009AD) for southern South America (SSA), covering from mid-Holocene to the present. This is the longest such record for the Southern Hemisphere (SH), and expands available annual proxy climate records for this region in more than 2060 years. Our record explains 49% of the temperature variation, and documents two major warm periods between 3140–2800BC and 70BC – 150AD, which coincide with the lack of evidence of glacier advances in SSA. Recent decades in the reconstruction (1959–2009) show a warming trend that is not exceptional in the context of the last five millennia. The long-term relationship between our temperature reconstruction and a reconstructed total solar irradiance record, with coinciding cycles at 293, 372, 432–434, 512 and 746 years, indicate a persistent influence of solar forcing on centennial climate variability in SSA. At interannual to interdecadal scales, reconstructed temperature is mainly related to the internal climate variability of the Pacific Ocean, including El Niño Southern Oscillation (ENSO) and longer oscillations. Our study reveals the need to characterize regional-scale climate variability and its drivers, which in the context of global-scale processes such as anthropogenic warming, interact to modulate local climate affecting humans and ecosystems.
Lara Aguilar, Antonio-Villalba, Ricardo-Urrutia-Jalabert, Rocío-Gonzalez Reyes, Alvaro-Aravena, Juan-Luckman, Brian-Cuq, Emilio-Rodríguez, Carmen Gloria-Wolodarsky-Franke, Alexia
2020
The role of streamside native forests on dissolved organic matter in forested and agricultural watersheds in northwestern Patagonia
Streamside native forests are known for their key role in water provision, commonly referred to as buffers that control the input or output of nutrients from terrestrial to aquatic ecosystems (i.e., nitrogen or carbon cycle). In order to assess the functional role of indigenous forests along streamside channels, we measured 10 parameters associated with DOM (Dissolved Organic Matter) at 42 points in 12 small catchments (15–200 ha) dominated by native forests (reference, WNF), forest plantations (WFP) and agricultural lands (WAL) in which the land cover portion was calculated in the entire watershed and along 30 and 60-m wide buffer strips. We found that watersheds WFP and WAL were statistically different than WNF, according to DIC concentrations (Dissolved Inorganic Carbon) and the intensity of the maximum fluorescence of DOM components. Using linear models, we related streamside native forest coverage in buffer strips with DOM parameters. The increase of streamside native forest coverage in 60 m wide buffer strips (0–100%) was related to lower DIC concentrations (0.89 to 0.28 mg C L−1). In watersheds WFP and WAL, the humic and fulvic-like components (0.42 to 1.42 R.U./mg C L−1) that predominated were related to an increase in streamside native forest coverage in the form of a 60 m wide buffer strip (0–75%). This is evidence that streamside native forests influence outputs of detritus and lowered in-stream processing with concomitant downstream transport, and functional integrity and water quality. We propose that DOM quantity and quality may be a potential tool for the identification of priority areas near streams for conservation and ecological restoration in terms of recovery of water quality as an important ecosystem service. The results of this study are useful to inform policy and regulations about the width of streamside native forests as well as their characteristics and restrictions.
Becerra Rodas, Constanza-Little Cárdenas, Christian-Lara Aguilar, Antonio-Sandoval, Jorge-Osorio, Sebastián-Nimptsch, Jorge
2019

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